Biomechanics of edentulous state 1/ oral surgery courses

BIOMECHANICSBIOMECHANICS
OFOF
EDENTULOUS STATEEDENTULOUS STATE
INDIAN DENTAL ACADEMY
Leader in Continuing Dental Education
www.indiandentalacademy.comwww.indiandentalacademy.com

contents
 Introduction
 Mechanism of support
Natural dentition
Complete denture
 Function and Para function
 Morphologic changes in
Face height
TMJ
Cosmetic changes
 Psychological changes
 Adaptive response
 Summary
 Bibliography

INTRODUCTIONINTRODUCTION
The edentulous state represents aThe edentulous state represents a
compromise in the integrity of masticatorycompromise in the integrity of masticatory
system. It is frequently accompanied bysystem. It is frequently accompanied by
adverse function and cosmetic problemsadverse function and cosmetic problems
which are varyingly perceived by affectedwhich are varyingly perceived by affected
patient.patient.
Perception of edentulous state may rangePerception of edentulous state may range
from feelings of inconvenience to feelings offrom feelings of inconvenience to feelings of
severe handicap as some regard total toothsevere handicap as some regard total tooth
loss as equivalent to loss of a body part.loss as equivalent to loss of a body part.www.indiandentalacademy.comwww.indiandentalacademy.com

DEFINITIONSDEFINITIONS
BIOMECHANICS:BIOMECHANICS:
 The application of mechanical laws to livingThe application of mechanical laws to living
structures, specifically the locomotor systemsstructures, specifically the locomotor systems
of the body.of the body.
The study of biology from the functional viewThe study of biology from the functional view
point.point.
An application of principles of engineeringAn application of principles of engineering
design as implemented in living organisms.design as implemented in living organisms.

DENTALDENTAL BIOMECHANICS:BIOMECHANICS:
The relationship between the biologicThe relationship between the biologic
behavior of oral structures and the physicalbehavior of oral structures and the physical
influence of a dental restoration.influence of a dental restoration.

 The treatment of edentulous state present aThe treatment of edentulous state present a
range of biomechanical problems that involverange of biomechanical problems that involve
individual tolerances and perceptions.individual tolerances and perceptions.

The clinical implications of the biomechanicalThe clinical implications of the biomechanical
differences can be considered under thedifferences can be considered under the
following:following:
1. Modifications in area of support.1. Modifications in area of support.
2.Functional and Para functional2.Functional and Para functional
considerations.considerations.
3. Changes in morphologic face height.3. Changes in morphologic face height.
4. Cosmetic changes.4. Cosmetic changes.
5. Adaptive responses.5. Adaptive responses.

MODIFICATIONS IN AREA OFMODIFICATIONS IN AREA OF
SUPPORTSUPPORT
DefinitionsDefinitions
Mechanism of tooth supportMechanism of tooth support
Mechanism of denture supportMechanism of denture support

DEFINITIONSDEFINITIONS
SUPPORT:SUPPORT:
To hold up ,serve as a foundation, or propTo hold up ,serve as a foundation, or prop
for.for.
The foundation area on which a dentalThe foundation area on which a dental
prosthesis rests. With respect to dentalprosthesis rests. With respect to dental
prostheses, the resistance to displacementprostheses, the resistance to displacement
away from the basal tissue or underlyingaway from the basal tissue or underlying
structures.structures.

SUPPORTING AREA:SUPPORTING AREA:
The surface of the mouth available forThe surface of the mouth available for
support of a denture[ GPT1].support of a denture[ GPT1].
Those areas of maxillary and mandibularThose areas of maxillary and mandibular
edentulous ridges that are considered bestedentulous ridges that are considered best
suited to carry the forces of masticationsuited to carry the forces of mastication
when the dentures are in function. [ GPT 1].when the dentures are in function. [ GPT 1].

MECHANISM OF TOOTHMECHANISM OF TOOTH
SUPPORTSUPPORT
The whole masticatory apparatus isThe whole masticatory apparatus is
involved in the process of trituration ofinvolved in the process of trituration of
food.the direct responsibility of this tasksfood.the direct responsibility of this tasks
falls on the teeth and their supportingfalls on the teeth and their supporting
structures .structures .
The attachment of teeth in their sockets isThe attachment of teeth in their sockets is
but one of the many important modificationsbut one of the many important modifications
that took place during the period when thethat took place during the period when the
earliest mammals were evolving from theearliest mammals were evolving from the
reptilians predecessors.reptilians predecessors.www.indiandentalacademy.comwww.indiandentalacademy.com

Teeth functions properly only if adequatelyTeeth functions properly only if adequately
supported .supported .
Periodontium is the connective tissuePeriodontium is the connective tissue
support mechanism for teeth .support mechanism for teeth .
It is composed of hard connective tissueIt is composed of hard connective tissue
[cementum and bone] soft connective tissue[[cementum and bone] soft connective tissue[
lamina propria of the gingiva and periodontallamina propria of the gingiva and periodontal
ligament].ligament].

Periodontium is regarded as a functional
unit and is attached to dentin by cementum
and to the jaw bone by the alveolar
processes. The periodontal ligament and
lamina propria maintains the continuity
between these hard and soft tissue
components.

PERIODONTIUMPERIODONTIUM

PERIODONTAL LIGAMENTPERIODONTAL LIGAMENT
The periodontal ligament is the connectiveThe periodontal ligament is the connective
tissue that surrounds the root and connectstissue that surrounds the root and connects
it to the bone .it to the bone .
It is composed of:It is composed of:
 Fibers.Fibers.
 Cellular elements.Cellular elements.
 Ground substance.Ground substance.

FIBERSFIBERS
Principal fibers :Principal fibers :
Collagenous.Collagenous.
Arranged in bundles.Arranged in bundles.
Follow wavy course.Follow wavy course.
Insert into cementum and bone [sharpey’sInsert into cementum and bone [sharpey’s
fibers].fibers].

Principal fibers are arranged in six groups thatPrincipal fibers are arranged in six groups that
develop sequentially in the developing rootdevelop sequentially in the developing root
1. Transseptal group1. Transseptal group
2. Alveolar crestal group2. Alveolar crestal group
3. Horizontal group3. Horizontal group
4. Oblique group4. Oblique group
5. Apical group5. Apical group
6. Inter radicular group6. Inter radicular group

Periodontal ligament fibersPeriodontal ligament fibers

CELLULAR ELEMENTSCELLULAR ELEMENTS
Types Of Cells:Types Of Cells:
1.Connective tissue cells- fibroblasts,1.Connective tissue cells- fibroblasts,
cementoblasts, and osteoblasts.cementoblasts, and osteoblasts.
2. Epithelial cell rests- remnants of hertwigs2. Epithelial cell rests- remnants of hertwigs
root sheath[ cell rests of malassez].root sheath[ cell rests of malassez].
3.Immune system cells-neutrophils,3.Immune system cells-neutrophils,
lymphocytes, macrophages, mast cells andlymphocytes, macrophages, mast cells and
eosinophils.eosinophils. www.indiandentalacademy.comwww.indiandentalacademy.com

GROUND SUBSTANCEGROUND SUBSTANCE
Glycosaminoglycans-hyaluronic acid andGlycosaminoglycans-hyaluronic acid and
proteoglycans.proteoglycans.
 Glycoprotiens-fibronectin and laminin. 70% isGlycoprotiens-fibronectin and laminin. 70% is
composed of water.composed of water.
The ground substances fills the spacesThe ground substances fills the spaces
between fibers and cells.between fibers and cells.
Cementicles which may be free or attached toCementicles which may be free or attached to
root surfaces may be present.root surfaces may be present.

FUNCTIONSFUNCTIONS
Physical function.Physical function.
Formative and remodelling function.Formative and remodelling function.
Nutritional function.Nutritional function.
sensory function.sensory function.

1.Resistance to impact of occlusal forces1.Resistance to impact of occlusal forces
[shock absorption]. Two theories relative to[shock absorption]. Two theories relative to
mechanism of tooth support have beenmechanism of tooth support have been
considered.considered.
a.Tentional theory:a.Tentional theory: According to this theoryAccording to this theory
when force is applied to the crown principalwhen force is applied to the crown principal
fibers first unfold and straightened and thenfibers first unfold and straightened and then
transmit the forces to alveolar bone causingtransmit the forces to alveolar bone causing
elastic deformation of the bony socket. Whenelastic deformation of the bony socket. When
alveolar bone has reached its limit load isalveolar bone has reached its limit load is
transmitted to basal bone .transmitted to basal bone .
PHYSICAL FUNCTIONPHYSICAL FUNCTION

 b. Viscoelastic system theory-b. Viscoelastic system theory- According to thisAccording to this
theory fluids move out of the PDL into marrowtheory fluids move out of the PDL into marrow
spaces through foramina when forces arespaces through foramina when forces are
applied. The fibers slack and tighten. Arteryapplied. The fibers slack and tighten. Artery
stenosis causes back pressure and ballooningstenosis causes back pressure and ballooning
of vessels to replenish the tissue fluids.of vessels to replenish the tissue fluids.

2. transmission of occlusal forces to bone2. transmission of occlusal forces to bone
The principal fibers are arranged similar toThe principal fibers are arranged similar to
suspension bridge or hammock.suspension bridge or hammock.
 Axial forces – oblique fibers.Axial forces – oblique fibers.
 Horizontal forces-primary tooth movementHorizontal forces-primary tooth movement
within the confines of PDL and secondary toothwithin the confines of PDL and secondary tooth
movement by displacement of facial and lingualmovement by displacement of facial and lingual
bony plates.bony plates.
 Axis of rotation - PDL is shaped as an hourAxis of rotation - PDL is shaped as an hour
glass and thinnest at the axis of rotation.glass and thinnest at the axis of rotation.

FORMATIVE AND REMODELLINGFORMATIVE AND REMODELLING
The cells of the PDL are responsible forThe cells of the PDL are responsible for
continues remodelling of bone and cementumcontinues remodelling of bone and cementum
which occur to accommodatewhich occur to accommodate
Physiological tooth movement.Physiological tooth movement.
Response to occlusal forces.Response to occlusal forces.
Repair of injuries.Repair of injuries.

NUTRITION AND SENSORYNUTRITION AND SENSORY
FUNCTIONFUNCTION
The PDL supplies nutrition to laminaThe PDL supplies nutrition to lamina
propria, bone and cementum .propria, bone and cementum .
Nerve bundles pass into PDL divide intoNerve bundles pass into PDL divide into
single myelinated fibers, loose theresingle myelinated fibers, loose there
myelin sheaths and end in one of the fourmyelin sheaths and end in one of the four
types of neural termination.types of neural termination.
1.Free endings-tree like and carry pain1.Free endings-tree like and carry pain
sensation.sensation.
2.Ruffini’s corpuscles- mechanoreceptors2.Ruffini’s corpuscles- mechanoreceptors
[apical area][apical area]

3.Meissnerscorpuscles-mechanoreceptors3.Meissnerscorpuscles-mechanoreceptors
[midroot area].[midroot area].
4.Spindles-pressure and vibration endings4.Spindles-pressure and vibration endings
[apical area].[apical area].

Nerve corpusclesNerve corpuscles

As soon as the teeth erupt into the oral cavityAs soon as the teeth erupt into the oral cavity
and occlusal contact is established, the nonand occlusal contact is established, the non
functional orientation of PDL fibers changesfunctional orientation of PDL fibers changes
into functional arrangement.into functional arrangement.
The occlusal forces exerted by teeth areThe occlusal forces exerted by teeth are
controlled by neuromuscular mechanism ofcontrolled by neuromuscular mechanism of
masticatory systems.masticatory systems.
The propioceptors in the PDL muscles andThe propioceptors in the PDL muscles and
TMJ have specific memory patternsTMJ have specific memory patterns
[engrams] which guide the jaw to the correct[engrams] which guide the jaw to the correct
closing pattern.closing pattern.

FORCES ACTING ON THE TEETHFORCES ACTING ON THE TEETH
The greatest forces acting on teeth areThe greatest forces acting on teeth are
produced during mastication deglutition, areproduced during mastication deglutition, are
essentially vertical in direction.essentially vertical in direction.
Loads of lower order but of longer durationLoads of lower order but of longer duration
are produced through out the day by tongueare produced through out the day by tongue
and perioral musculature .these forces areand perioral musculature .these forces are
predominantly in horizontal direction.predominantly in horizontal direction.

Graf [1969] calculated the total time duringGraf [1969] calculated the total time during
which teeth are subjected to functionalwhich teeth are subjected to functional
forces . He concluded that this total timeforces . He concluded that this total time
and range seemed to be well withinand range seemed to be well within
tolerance level of healthy periodontaltolerance level of healthy periodontal
tissues.tissues.

Actual chewingActual chewing
time per mealtime per meal
450 sec450 sec
Four meals per dayFour meals per day 1800 sec1800 sec
Each second 1Each second 1
chewing strokechewing stroke
1800 stroke1800 stroke
Duration of eachDuration of each
strokestroke
0.3 sec0.3 sec
Total chewingTotal chewing
forcesforces
540 sec= 9 min540 sec= 9 min
CHEWINGCHEWING

SWALLOWINGSWALLOWING
MealsMeals
Duration of one deglutitionDuration of one deglutition
movementmovement
1 sec1 sec
During chewing 3* perDuring chewing 3* per
min1/3 of movements withmin1/3 of movements with
occlusal force onlyocclusal force only
30 sec 0.5 min30 sec 0.5 min
Between mealsBetween meals
Day time -25 per hour [16Day time -25 per hour [16
hours]hours]
400 sec, 6.6400 sec, 6.6
minmin
Sleep -10 per hour[8 hours]Sleep -10 per hour[8 hours] 80 sec , 1.380 sec , 1.3
minminwww.indiandentalacademy.comwww.indiandentalacademy.com

Total 1050 seconds= 17.5 minTotal 1050 seconds= 17.5 min

MECHANISM OF COMPLETEMECHANISM OF COMPLETE
DENTURE SUPPORTDENTURE SUPPORT
The basic problem in treatment of edentulousThe basic problem in treatment of edentulous
patients lies in the nature of differencepatients lies in the nature of difference
between the ways natural and their artificialbetween the ways natural and their artificial
replacements are attached to supportingreplacements are attached to supporting
bone.bone.
The complete dentures are not a substituteThe complete dentures are not a substitute
for natural teeth, but only a prosthetic solutionfor natural teeth, but only a prosthetic solution
for no teeth.for no teeth.

The factors which differ in supporting theThe factors which differ in supporting the
natural teeth and complete dentures are:natural teeth and complete dentures are:
1. Nature of support.1. Nature of support.
2. Area of support.2. Area of support.
3. Masticatory loads.3. Masticatory loads.

 PDLPDL  Edentulous ridgeEdentulous ridge

NATURE OF SUPPORTNATURE OF SUPPORT
The unsuitability of tissue supporting completeThe unsuitability of tissue supporting complete
denture for load bearing function must bedenture for load bearing function must be
immediately recognized.immediately recognized.
In normal function in dentulous state light loadsIn normal function in dentulous state light loads
are placed on the mucous membrane.are placed on the mucous membrane.
With complete dentures the mucousWith complete dentures the mucous
membrane is forced to serve the samemembrane is forced to serve the same
purpose as PDL, that provides support forpurpose as PDL, that provides support for
natural teeth.natural teeth. www.indiandentalacademy.comwww.indiandentalacademy.com

ORAL MUCOSAORAL MUCOSA
The oral mucous membrane is the lining ofThe oral mucous membrane is the lining of
the oral cavity. At the lips it is continuousthe oral cavity. At the lips it is continuous
with the skin & at the pharynx continuouswith the skin & at the pharynx continuous
with the intestinal mucosa .Its structurewith the intestinal mucosa .Its structure
varies in an apparent adaptation to functionvaries in an apparent adaptation to function
in different areas of the oral cavity.in different areas of the oral cavity.

CLASSIFICATIONCLASSIFICATION
 BASED ON THE FUNCTIONAL CRITERIABASED ON THE FUNCTIONAL CRITERIA
 Masticatory mucosa.Masticatory mucosa.
 Lining or reflecting mucosa.Lining or reflecting mucosa.
 Specialized mucosa.Specialized mucosa.
 BASED HISTOLOGICALLY ON KERATINIZATIONBASED HISTOLOGICALLY ON KERATINIZATION
 Keratinized mucosa.Keratinized mucosa.
 Non keratinized mucosa.Non keratinized mucosa.

Oral mucous membraneOral mucous membrane

MASTICATORY MUCOSAMASTICATORY MUCOSA
Seen on the gingiva and hard palateSeen on the gingiva and hard palate
 Gingiva –Gingiva –
1. Epithelium is ortho or Para keratinized1. Epithelium is ortho or Para keratinized
with stippling, lamina propria shows longwith stippling, lamina propria shows long
narrow papillae with dense collagenousnarrow papillae with dense collagenous
connective tissue .connective tissue .
2. Sub mucosa - is not distinct as mucosa2. Sub mucosa - is not distinct as mucosa
attaches by collagen fibers into cementumattaches by collagen fibers into cementum
and bone(mucoperiostium).and bone(mucoperiostium).

HARD PALATEHARD PALATE
EpitheliumEpithelium – orthokeratinized, Parakeratinized– orthokeratinized, Parakeratinized
in parts with transverse palatal ridges into C.T.in parts with transverse palatal ridges into C.T.
Lamina propriaLamina propria – long papillae with dense– long papillae with dense
collagenous tissue especially under rugae.collagenous tissue especially under rugae.
Sub mucosaSub mucosa – dense collagenous tissue– dense collagenous tissue
attaching the mucosa to periosteumattaching the mucosa to periosteum
(mucoperiostium) .anteriorly adipose tissue and(mucoperiostium) .anteriorly adipose tissue and
posteriorly minor salivary glands are packedposteriorly minor salivary glands are packed
into the C.T.into the C.T.

LINING MUCOSALINING MUCOSA
It is found on the lip, cheek, vestibular fornix,It is found on the lip, cheek, vestibular fornix,
ventral surface of the tongue, floor of theventral surface of the tongue, floor of the
mouth and soft palate. It is nonkeratinizedmouth and soft palate. It is nonkeratinized
stratified squamous variety.stratified squamous variety.

LIPSLIPS
Vermilion border – thin ortho or ParaVermilion border – thin ortho or Para
keratinized epithelium.keratinized epithelium.
Lamina propria – has numerous long narrowLamina propria – has numerous long narrow
papillae with capillary loops close to thepapillae with capillary loops close to the
epithelium .epithelium .
Submucosa – is firmly attached to unde4rSubmucosa – is firmly attached to unde4r
lying muscle ;some sebaceous glands in thelying muscle ;some sebaceous glands in the
vermilion border. Intermediate zone showsvermilion border. Intermediate zone shows
minor salivary glands & fatminor salivary glands & fat

LABIAL AND BUCCAL MUCOSALABIAL AND BUCCAL MUCOSA
Epithelium is very thick. Lamina propria –hasEpithelium is very thick. Lamina propria –has
long slender papillae ,dense fibrous C.Tlong slender papillae ,dense fibrous C.T
containing elastic and collagen fibers.containing elastic and collagen fibers.
Submucosa is firmly attached to underlyingSubmucosa is firmly attached to underlying
muscle. Few minor salivary glands andmuscle. Few minor salivary glands and
sebaceous glands are seen. it prevents thesebaceous glands are seen. it prevents the
mucosa from folding. .mucosa from folding. .

FLOOR OF THE MOUTHFLOOR OF THE MOUTH
Epithelium very thin nonkeratinized variety.Epithelium very thin nonkeratinized variety.
Lamina propria –has short papillae, elasticLamina propria –has short papillae, elastic
fibers & capillary anastomoses .allows forfibers & capillary anastomoses .allows for
tongue movements.tongue movements.
Submucosa – has loose C.T & minor salivarySubmucosa – has loose C.T & minor salivary
glands.glands.

VENTRAL SURFACE OF TONGUEVENTRAL SURFACE OF TONGUE
Epithelium – thin nonkeratinized variety.Epithelium – thin nonkeratinized variety.
Lamina propria – thin with short papillaeLamina propria – thin with short papillae
elastic fibers & minor salivary glandselastic fibers & minor salivary glands
.papillary network in sub papillary layer..papillary network in sub papillary layer.
Submucosa – no distinct layer ,mucosa isSubmucosa – no distinct layer ,mucosa is
bound to tongue musculature .bound to tongue musculature .

SOFT PALATESOFT PALATE
Epithelium – thick non keratinized with tasteEpithelium – thick non keratinized with taste
buds .buds .
Lamina propria –thick with numerous shortLamina propria –thick with numerous short
papillae; elastic fibers forming an elasticpapillae; elastic fibers forming an elastic
lamina.lamina.
Submucosa –diffuse containing numerousSubmucosa –diffuse containing numerous
minor salivary glands .minor salivary glands .

ALVEOLAR MUCOSAALVEOLAR MUCOSA
Epithelium -thin non keratinized variety.Epithelium -thin non keratinized variety.
Lamina propria –short papillae C.T showsLamina propria –short papillae C.T shows
many elastic fibers & capillary loops close tomany elastic fibers & capillary loops close to
surface.surface.
Submucosa –loose C.T containing elasticSubmucosa –loose C.T containing elastic
fibers attaching it to periosteum of alveolarfibers attaching it to periosteum of alveolar
bone & minor salivary glands.bone & minor salivary glands.

SPECIALIZED MUCOSASPECIALIZED MUCOSA
Dorsal surface of the tongue is divided by V –Dorsal surface of the tongue is divided by V –
shaped sulcus terminalis into 2 parts.shaped sulcus terminalis into 2 parts.
Anterior 2/3 [papillary] portion.Anterior 2/3 [papillary] portion.
Posterior 1/3 [lymphoid] portion.Posterior 1/3 [lymphoid] portion.

Anterior 2/3 of tongue shows “Anterior 2/3 of tongue shows “SS” cone shaped” cone shaped
filliform papillae which gives velvettefilliform papillae which gives velvette
appearance. Interspersed between them areappearance. Interspersed between them are
mushroom shaped fungi form papillae withmushroom shaped fungi form papillae with
taste buds. In front of the sulcus are 8 to 10taste buds. In front of the sulcus are 8 to 10
circumvalate papillae .circumvalate papillae .
They have a trough into which von ebnersThey have a trough into which von ebners
glands open & have taste buds. On the lateralglands open & have taste buds. On the lateral
border of the posterior part of the tongue areborder of the posterior part of the tongue are
parallel clefts of varying length they areparallel clefts of varying length they are
vestige of large foliate papillae ,they containvestige of large foliate papillae ,they contain
taste buds.taste buds.

EPITHELIUMEPITHELIUM
Oral epithelium is of stratified squamousOral epithelium is of stratified squamous
variety. It may be keratinized or nonvariety. It may be keratinized or non
keratinized. Cells with ultimately keratinizekeratinized. Cells with ultimately keratinize
are called keratocytes or keratinocytes.are called keratocytes or keratinocytes.
Keratinizing oral epithelium has 4 cellKeratinizing oral epithelium has 4 cell
layerslayers..
Stratum basale.Stratum basale.
Stratum spinosum.Stratum spinosum.
Stratum granulosum.Stratum granulosum.
Stratum corneum.Stratum corneum.

LAMINA PROPRIALAMINA PROPRIA
For descriptive reasons it is divided into 2 partsFor descriptive reasons it is divided into 2 parts
Papillary portion & Reticular portion.Papillary portion & Reticular portion.
The lamina propria contains fine immatureThe lamina propria contains fine immature
collagen fibers termed reticular fibers. Itcollagen fibers termed reticular fibers. It
contains, fibroblasts,histocytes, collagen fibercontains, fibroblasts,histocytes, collagen fiber
bundle & vasculature. The interlockingbundle & vasculature. The interlocking
arrangement of CT papillae & epithelial ridgesarrangement of CT papillae & epithelial ridges
& even finer undulation & projection found at& even finer undulation & projection found at
the base of each epithelial cell increases thethe base of each epithelial cell increases the
area of contact between epithelium & CT.area of contact between epithelium & CT.www.indiandentalacademy.comwww.indiandentalacademy.com

SUBMUCOSASUBMUCOSA
It attaches the overlying mucosa toIt attaches the overlying mucosa to
periosteum. Its composition varies inperiosteum. Its composition varies in
different areas of the oral mucosa. Itdifferent areas of the oral mucosa. It
contains glands, adipose tissue musclescontains glands, adipose tissue muscles
,blood vessels, nerves & lymph vessels.,blood vessels, nerves & lymph vessels.

RESIDUAL RIDGERESIDUAL RIDGE
When the alveolar process is madeWhen the alveolar process is made
edentulous,by loss of teeth,the alveoli thatedentulous,by loss of teeth,the alveoli that
contained the roots of the teeth fill in withcontained the roots of the teeth fill in with
new bone.new bone.
This alveolar process becomes the residualThis alveolar process becomes the residual
ridge ,which is the foundation for dentures.ridge ,which is the foundation for dentures.
Residual ridge is that bone of the alveolarResidual ridge is that bone of the alveolar
process that remains after the teeth are lostprocess that remains after the teeth are lost
Residual ridge consists of denture bearingResidual ridge consists of denture bearing
mucosa ,the submucosa ,periosteum andmucosa ,the submucosa ,periosteum and
underlying residual alveolar bone.underlying residual alveolar bone.www.indiandentalacademy.comwww.indiandentalacademy.com

 Alveolar ridge vary greatly in size andAlveolar ridge vary greatly in size and
shape and their ultimate form is dependentshape and their ultimate form is dependent
on following factors.on following factors.
1.Developmental structure.1.Developmental structure.
2.Size of natural teeth.2.Size of natural teeth.
3.Amount of bone lost prior to extraction-3.Amount of bone lost prior to extraction-
Periodontitis.Periodontitis.
4.Amount of alveolar process removed4.Amount of alveolar process removed
during extraction.during extraction.
5.Rate and degree of resorption.5.Rate and degree of resorption.
6.Effect of previous dentures.6.Effect of previous dentures.

RR may be said to have 2 forms:RR may be said to have 2 forms:
 Anatomic formAnatomic form – surface contour of ridge– surface contour of ridge
when it is not supporting an occlusal load.when it is not supporting an occlusal load.
Functional formFunctional form - surface contour of ridge- surface contour of ridge
when it is supporting an occlusal load.when it is supporting an occlusal load.

When the alveolar process is madeWhen the alveolar process is made
edentulous,by loss of teeth, the alveoli thatedentulous,by loss of teeth, the alveoli that
contained the roots of the teeth fill in with newcontained the roots of the teeth fill in with new
bone.bone.
This alveolar process becomes the residualThis alveolar process becomes the residual
ridge , which is the foundation for dentures.ridge , which is the foundation for dentures.
Residual ridge is that bone of the alveolarResidual ridge is that bone of the alveolar
process that remains after the teeth are lost.process that remains after the teeth are lost.
Residual ridge consists of denture bearingResidual ridge consists of denture bearing
mucosa ,the submucosa ,periosteum andmucosa ,the submucosa ,periosteum and
underlying residual alveolar bone.underlying residual alveolar bone.

Residual ridgeResidual ridge

CONTOUR & QUALITY OFCONTOUR & QUALITY OF
Ideal residual ridge is to support a dentureIdeal residual ridge is to support a denture
base would consist of cortical bone thatbase would consist of cortical bone that
covers relatively dense cancellous bonecovers relatively dense cancellous bone
with a broad rounded crest with high verticalwith a broad rounded crest with high vertical
slopes & covered by firm dense fibrousslopes & covered by firm dense fibrous
connective tissue. such a residual ridgeconnective tissue. such a residual ridge
would optimally support vertical &would optimally support vertical &
horizontal stresses placed on it by denturehorizontal stresses placed on it by denture
base.base.

PATHOLOGY OF RESIDUALPATHOLOGY OF RESIDUAL
RIDGE RESORPTIONRIDGE RESORPTION
Gross Pathology.Gross Pathology.
Microscopic pathology.Microscopic pathology.

GROSS PATHOLOGYGROSS PATHOLOGY
Reduction in the size of the bony ridge.Reduction in the size of the bony ridge.
It is primarily a localized loss of boneIt is primarily a localized loss of bone
structure.structure.
In clinical examination, usually ,one canIn clinical examination, usually ,one can
visualize the residual ridge form.however thisvisualize the residual ridge form.however this
may be masked with redundant or inflamedmay be masked with redundant or inflamed
soft tissue.soft tissue.
This can be accurately determined byThis can be accurately determined by
palpation.palpation.

Lateral cephalometric radiographs provide theLateral cephalometric radiographs provide the
most accurate method for determining themost accurate method for determining the
amount of residual ridge and rate of RRR overamount of residual ridge and rate of RRR over
a period of time.a period of time.
Numerous longitudinal radiographic studiesNumerous longitudinal radiographic studies
have provided excellent visualization of thehave provided excellent visualization of the
gross patterns of bone loss.gross patterns of bone loss.
Superimposition of portions of tracings ofSuperimposition of portions of tracings of
lateral cephalograms has clearly shown thelateral cephalograms has clearly shown the
gross reduction of bone in size and shapegross reduction of bone in size and shape
that occurs on the external surface on thethat occurs on the external surface on the
labial ,crestal and lingual aspects of residuallabial ,crestal and lingual aspects of residual
ridge.ridge.

Order – IOrder – I pre-extractionpre-extraction
Order –IIOrder –II post-extractionpost-extraction
Order –IIIOrder –III high well roundedhigh well rounded
Order-IVOrder-IV knife edgeknife edge
Order-VOrder-V low well roundedlow well rounded
Order –VIOrder –VI depresseddepressed

MICROSCOPIC PATHOLOGYMICROSCOPIC PATHOLOGY
Studies have revealed evidence ofStudies have revealed evidence of
osteoclastic activity on the external surfaceosteoclastic activity on the external surface
of the crest of residual ridges, where visibleof the crest of residual ridges, where visible
osteoclasts are seen.osteoclasts are seen.

PATHOPHYSIOLOGY OFPATHOPHYSIOLOGY OF
RESORPTIONRESORPTION
During growth ,bone formation exceedsDuring growth ,bone formation exceeds
bone resorption.bone resorption.
Osteoporosis- generalized disease ofOsteoporosis- generalized disease of
bone ,where bone resorption exceeds bonebone ,where bone resorption exceeds bone
formation.formation.
RRR is a localized physiologic loss of bone.RRR is a localized physiologic loss of bone.

Physiologic process of internal bonePhysiologic process of internal bone
remodelling goes on, even in the presence ofremodelling goes on, even in the presence of
this pathologic external osteoclastic activitythis pathologic external osteoclastic activity
that is responsible for the loss of so muchthat is responsible for the loss of so much
bone substance.bone substance.
Three types of endosteal bone on the crest ofThree types of endosteal bone on the crest of
the residual ridge are;the residual ridge are;
A well-rounded compact cortical layerA well-rounded compact cortical layer
consisting of a whorled,convoluted type ofconsisting of a whorled,convoluted type of
bone.bone.

A knife edge ridge that shows a lingual plateA knife edge ridge that shows a lingual plate
of whorled convoluted bone & a labial plateof whorled convoluted bone & a labial plate
of uninterrupted circumferential lamellae onof uninterrupted circumferential lamellae on
its endosteal side.its endosteal side.
A low depressed ridge that has no crestalA low depressed ridge that has no crestal
cortical layer but only trabecular bone,cortical layer but only trabecular bone,
which is actually medullary bone.which is actually medullary bone.

RRR is chronic, progressive, irreversible &RRR is chronic, progressive, irreversible &
cumulative, usually RRR proceeds slowly overcumulative, usually RRR proceeds slowly over
a long period of time flowing from one stagea long period of time flowing from one stage
imperceptibly to the next.imperceptibly to the next.
The patient with the most RRR in the earlyThe patient with the most RRR in the early
post extraction period continued to have thepost extraction period continued to have the
highest rate of RRR in the later stages.highest rate of RRR in the later stages.

RATE OF RESORPTION OFRATE OF RESORPTION OF
RESIDUAL ALVEOLAR RIDGESRESIDUAL ALVEOLAR RIDGES
Depends on;Depends on;
The size, shape, density of the alveolarThe size, shape, density of the alveolar
ridge.ridge.
The cellular activity of the osteoblast andThe cellular activity of the osteoblast and
osteoclasts.osteoclasts.
The duration, frequency and direction ofThe duration, frequency and direction of
any previous occlusal forces to the bone.any previous occlusal forces to the bone.
Forces generated from the presentForces generated from the present
appliance.appliance.
The patient’s resistance to these forces.The patient’s resistance to these forces.www.indiandentalacademy.comwww.indiandentalacademy.com

PATTERNS OF BONE LOSSPATTERNS OF BONE LOSS
Tallgren in 1972,has stated that most ofTallgren in 1972,has stated that most of
the bone loss occurs in the first year ofthe bone loss occurs in the first year of
denture wearing and it is ten timesdenture wearing and it is ten times
greater,than the loss seen in the followinggreater,than the loss seen in the following
years.years.
He also demonstrated four times moreHe also demonstrated four times more
bone loss in the mandible,than in maxillabone loss in the mandible,than in maxilla
over the years.over the years.
(maxilla distributes the compressive forces(maxilla distributes the compressive forces
over a wider surface area)over a wider surface area)

 The direction of resorption in the maxilla differsThe direction of resorption in the maxilla differs
from the mandibular bone resorption.from the mandibular bone resorption.
 The usual resorption of the maxilla is on the buccalThe usual resorption of the maxilla is on the buccal
and inferior portion of the alveolar ridge.the patternand inferior portion of the alveolar ridge.the pattern
of edentulous bone loss results in upward andof edentulous bone loss results in upward and
inward loss of structures.inward loss of structures.
 In the anterior maxilla, there is less horizontalIn the anterior maxilla, there is less horizontal
bone loss and posterior drift of the anterior crest isbone loss and posterior drift of the anterior crest is
seen more than in the edentulous mandible.seen more than in the edentulous mandible. IIn then the
posterior maxilla, there is inward drift of theposterior maxilla, there is inward drift of the
posterior crest, the width of the maxilla is reduced.posterior crest, the width of the maxilla is reduced.

Because of the progressive resorption overBecause of the progressive resorption over
the years, the depth of the palatal vaultthe years, the depth of the palatal vault
decreases and a very thin bone may bedecreases and a very thin bone may be
present between the floor of the maxillarypresent between the floor of the maxillary
sinus and the nasal cavity.sinus and the nasal cavity.
The mandible resorbs downwards andThe mandible resorbs downwards and
outwards causing rapid flattening of theoutwards causing rapid flattening of the
ridge.ridge.
Tallgren has estimated that the edentulousTallgren has estimated that the edentulous
bone loss is up to 1mm per year,with thebone loss is up to 1mm per year,with the
greatest loss occurring within 12-18 monthsgreatest loss occurring within 12-18 months
after extractions.after extractions.

Extractions of teeth done at different timesExtractions of teeth done at different times
with long time gaps will exhibit irregular bonywith long time gaps will exhibit irregular bony
ridge pattern.ridge pattern.
Skeletal morphology has got definite role onSkeletal morphology has got definite role on
the resorption pattern of the edentulousthe resorption pattern of the edentulous
maxilla. People with long faces have moremaxilla. People with long faces have more
alveolar height than those with short faces.alveolar height than those with short faces.
Short face patients have greater biting force,Short face patients have greater biting force,
therefore are predisposed to greater bonetherefore are predisposed to greater bone
loss.loss.

RESORPTIVE PATTERN OF THERESORPTIVE PATTERN OF THE
EDENTULOUS RIDGEEDENTULOUS RIDGE
(MERCIER1995)(MERCIER1995)
 The ridge is wideThe ridge is wide
enough at its crest toenough at its crest to
accommodate theaccommodate the
recently extracted teeth.recently extracted teeth.
 The ridge becomes thinThe ridge becomes thin
and pointed.and pointed.
 The pointed ridgeThe pointed ridge
flattens to the level offlattens to the level of
basal bone.basal bone.
 The flattened ridgeThe flattened ridge
becomes concave as thebecomes concave as the
basal bone resorbs.basal bone resorbs.
Type I –minor ridgeType I –minor ridge
modellingmodelling
Type II –sharpType II –sharp
atrophic residualatrophic residual
ridgeridge
Type III –basalType III –basal
bone ridgebone ridge
Type IV –basalType IV –basal
bone resorptionbone resorption

ETIOLOGY OF RRRETIOLOGY OF RRR
RRR is directly proportional to AnatomicRRR is directly proportional to Anatomic
factors -It varies with the quality,quantityfactors -It varies with the quality,quantity
and density of bone of residual ridges.and density of bone of residual ridges.
RRR varies directly with certain systemic orRRR varies directly with certain systemic or
localized bone resorption factors andlocalized bone resorption factors and
inversely with bone formation factors.inversely with bone formation factors.

Local bone resorbing factors –include localLocal bone resorbing factors –include local
biochemical factors, such as endotoxin,biochemical factors, such as endotoxin,
osteoclast activating factor (OAF),osteoclast activating factor (OAF),
prostaglandin's, human gingival boneprostaglandin's, human gingival bone
resorption stimulating factor, heparinresorption stimulating factor, heparin
(which is a cofactor in bone resorption)(which is a cofactor in bone resorption)
trauma (ill-fitting denture) resultingtrauma (ill-fitting denture) resulting
increased or decreased vascularity andincreased or decreased vascularity and
changes in oxygen tension.changes in oxygen tension.

Systemic factorsSystemic factors
 Some individuals may already be in aSome individuals may already be in a
negative bone balance owing to some formnegative bone balance owing to some form
of osteoporosis and may therefore be moreof osteoporosis and may therefore be more
vulnerable to unfavorable local factors.vulnerable to unfavorable local factors.

MECHANICAL FACTORSMECHANICAL FACTORS
Some postulate that RRR- ‘disuse atrophy’Some postulate that RRR- ‘disuse atrophy’
others postulate that RRR is an ‘abuse’others postulate that RRR is an ‘abuse’
bone resorption due to excessive forcesbone resorption due to excessive forces
transmitted through dentures.transmitted through dentures.
 The fact is that with or without denturesThe fact is that with or without dentures
some patients have little or no RRR & somesome patients have little or no RRR & some
have severe RRR.have severe RRR.
Force is a co-factor in RRR can beForce is a co-factor in RRR can be
expressed asexpressed as
RRR is directly proportional to force.RRR is directly proportional to force.

Design of dentures is to reduce the amount ofDesign of dentures is to reduce the amount of
force to the ridge & thereby to reduce RRR.force to the ridge & thereby to reduce RRR.
These prosthetic factors include;These prosthetic factors include;
Broad-area coverage.Broad-area coverage.
Decreased number of dental units.Decreased number of dental units.
Decreased buccolingual width of teeth.Decreased buccolingual width of teeth.
Improved tooth form.Improved tooth form.
Avoidance of inclined planes.Avoidance of inclined planes.
Centralization of occlusal contacts.Centralization of occlusal contacts.

FORMULA RELATING TO RRRFORMULA RELATING TO RRR
 RRRRRR anatomic factors +anatomic factors + Bone resorption factorsBone resorption factors
Bone formation factorsBone formation factors
Force factorsForce factors
++ Damping effect factorsDamping effect factors

CLINICAL APPLICATIONCLINICAL APPLICATION
Consequences of residual ridgeConsequences of residual ridge
resorption.resorption.
Apparent loss of sulcus width & depth,withApparent loss of sulcus width & depth,with
displacement of the muscle attachment closerdisplacement of the muscle attachment closer
to the crest of the residual ridge.to the crest of the residual ridge.
Loss of the vertical dimension of occlusion.Loss of the vertical dimension of occlusion.
Reduction of the lower face height.Reduction of the lower face height.

CONTOUR & QUALITY OFCONTOUR & QUALITY OF
Ideal residual ridge is to support a dentureIdeal residual ridge is to support a denture
base would consist of cortical bone thatbase would consist of cortical bone that
covers relatively dense cancellous bonecovers relatively dense cancellous bone
with a broad rounded crest with high verticalwith a broad rounded crest with high vertical
slopes & covered by firm dense fibrousslopes & covered by firm dense fibrous
connective tissue. such a residual ridgeconnective tissue. such a residual ridge
would optimally support vertical &would optimally support vertical &
horizontal stresses placed on it by denturehorizontal stresses placed on it by denture
base.base. www.indiandentalacademy.comwww.indiandentalacademy.com

MASTICATORY LOADSMASTICATORY LOADS
Natural teeth exert 44lb [20Natural teeth exert 44lb [20 kg].kg].
Complete dentures exert 13 – 16 lb [ 6 – 8 Kg ].Complete dentures exert 13 – 16 lb [ 6 – 8 Kg ].
Edentulous patients decrease the amount ofEdentulous patients decrease the amount of
forces on the tissues by selecting softer foods.forces on the tissues by selecting softer foods.

AREA OF SUPPORTAREA OF SUPPORT
Watt in 1961 computed the mean dentureWatt in 1961 computed the mean denture
bearing area to be;bearing area to be;
 22.96 cm sq in edentulous maxilla.22.96 cm sq in edentulous maxilla.
12.25 cm sq in edentulous mandible.12.25 cm sq in edentulous mandible.
45 cm sq is the average periodontal45 cm sq is the average periodontal
membrane area in each jaw with naturalmembrane area in each jaw with natural
teeth.teeth.
Further more the basal seat becomesFurther more the basal seat becomes
progressively smaller as residual ridgesprogressively smaller as residual ridges
resorb.resorb.

Functional and parafunctionalFunctional and parafunctional
considerationsconsiderations
 Masticatory system seems to function bestMasticatory system seems to function best
in an environment of continuing functionalin an environment of continuing functional
equilibrium .[Moyer's 1969}.equilibrium .[Moyer's 1969}.
 Primary components of human dentalPrimary components of human dental
occlusion are;occlusion are;
 1.The dentition.1.The dentition.
 2.The neuromuscular system and2.The neuromuscular system and
 3. Craniofacial structures.3. Craniofacial structures.

The dentition develops in a milieu that isThe dentition develops in a milieu that is
characterized by a period of dental alveolarcharacterized by a period of dental alveolar
and craniofacial adaptability which is also aand craniofacial adaptability which is also a
time when motor skills and neuromusculartime when motor skills and neuromuscular
learning are developed.learning are developed.

DentitionDentition

Complete denture service is characterized byComplete denture service is characterized by
an integration of biologic information withan integration of biologic information with
instrumentation, techniques, and use ofinstrumentation, techniques, and use of
materials.materials.
Complete dentures are designed so that theirComplete dentures are designed so that their
occlusal surfaces permit both functional andocclusal surfaces permit both functional and
Para functional movements of the mandible.Para functional movements of the mandible.
Orofacial and tongue muscles play anOrofacial and tongue muscles play an
important role in retaining and stabilizingimportant role in retaining and stabilizing
complete dentures.complete dentures.

This is accomplished by arrangement of theThis is accomplished by arrangement of the
artificial teeth to occupy a “neutral zone“ inartificial teeth to occupy a “neutral zone“ in
the edentulous mouth so that the teeth willthe edentulous mouth so that the teeth will
occupy a space determined by the functionaloccupy a space determined by the functional
balance of the orofacial and tonguebalance of the orofacial and tongue
musculature. Thus the teeth in the dental archmusculature. Thus the teeth in the dental arch
need not necessarily be placed directly overneed not necessarily be placed directly over
the residual ridges.the residual ridges.

Neutral zoneNeutral zone

FUNCTIONFUNCTION
Mastication and swallowingMastication and swallowing
During masticatory movements theDuring masticatory movements the
tongue and cheek muscles play antongue and cheek muscles play an
essential role in keeping the food bolusessential role in keeping the food bolus
between the occlusal surface of thebetween the occlusal surface of the
teeth.teeth.

Deviation from the normal path ofDeviation from the normal path of
mandibular movements can injure themandibular movements can injure the
tongue, buccal mucosa and even the teethtongue, buccal mucosa and even the teeth
and their supporting tissues . so the dentistand their supporting tissues . so the dentist
must place teeth with in the confines ofmust place teeth with in the confines of
functional balance of the musculaturefunctional balance of the musculature
involved in controlling the food bolusinvolved in controlling the food bolus
between the occlusal surface of the teeth.between the occlusal surface of the teeth.

The maximal bite force in denture wearers isThe maximal bite force in denture wearers is
five to six times less than in dentulousfive to six times less than in dentulous
subjects.subjects.
Edentulous patient are clearly handicapped inEdentulous patient are clearly handicapped in
masticatory function and even clinicallymasticatory function and even clinically
satisfactory complete dentures are poorsatisfactory complete dentures are poor
substitutes for natural teeth.substitutes for natural teeth.

Mandibular movementsMandibular movements
The dentulous person usually demonstrateThe dentulous person usually demonstrate
smooth jaw motion during mastication. It issmooth jaw motion during mastication. It is
shaped some what like a tear drop, whenshaped some what like a tear drop, when
viewed in the frontal plane. On the otherviewed in the frontal plane. On the other
hand, the edentulous patient will often havehand, the edentulous patient will often have
a distortion of this movement with thea distortion of this movement with the
process becoming more random and inprocess becoming more random and in
discriminate.discriminate.

During the closing part of the cycle, theDuring the closing part of the cycle, the
dentulous subjects, will decelerate, thedentulous subjects, will decelerate, the
movement just before tooth contact tomovement just before tooth contact to
dampen the effect of closure on thedampen the effect of closure on the
dentition, but edentulous person will seemsdentition, but edentulous person will seems
to elevate the jaw at a constant velocity withto elevate the jaw at a constant velocity with
no deceleration near the end of the closure.no deceleration near the end of the closure.

The edentulous patient will not develop theThe edentulous patient will not develop the
same isometric tension on artificial denturesame isometric tension on artificial denture
that is attained by people closing withthat is attained by people closing with
natural teeth.natural teeth.
Recent evidences indicates that jawRecent evidences indicates that jaw
movement is controlled and coordinated bymovement is controlled and coordinated by
central pattern generator or “ chewingcentral pattern generator or “ chewing
center”.center”.

Which is activated by impulse from cerebralWhich is activated by impulse from cerebral
cortex or from peripheral sensory receptors.cortex or from peripheral sensory receptors.
At one time , it was believed that masticationAt one time , it was believed that mastication
was the result of the alteration of the simplewas the result of the alteration of the simple
brain stem reflexes.brain stem reflexes.
This concept has been replaced by the ideaThis concept has been replaced by the idea
that central pattern generator , once initiated,that central pattern generator , once initiated,
that produce rhythmic alternation of openingthat produce rhythmic alternation of opening
and closing movements that constituteand closing movements that constitute
mastication.mastication.

This rhythmic act, how ever can be modifiedThis rhythmic act, how ever can be modified
by the shape, size and consistency of theby the shape, size and consistency of the
bolus as well as by other variables.bolus as well as by other variables.
Since neurosensory input, such as fromSince neurosensory input, such as from
periodontal and other receptors can influenceperiodontal and other receptors can influence
the central pattern generator and the chewingthe central pattern generator and the chewing
cycle, it is reasonable to consider that a statecycle, it is reasonable to consider that a state
of edentulism will provide some what differentof edentulism will provide some what different
neurosensory information to the neurologicalneurosensory information to the neurological
control mechanism.control mechanism.

For example.For example.
Anesthesia experiment have demonstratedAnesthesia experiment have demonstrated
that coordinated chewing can occur afterthat coordinated chewing can occur after
sensory deprivation , how ever absence ofsensory deprivation , how ever absence of
sensory information appears to affect thesensory information appears to affect the
preciseness of occlusal contacts during jawpreciseness of occlusal contacts during jaw
function.function.

 The use of centric relation has its physiologicThe use of centric relation has its physiologic
justification.justification.
 In vast majority unconscious swallowing is carriedIn vast majority unconscious swallowing is carried
out with mandible or at near centric relation. Thisout with mandible or at near centric relation. This
unconscious reflex swallow is important inunconscious reflex swallow is important in
developing dentition, as it influences thedeveloping dentition, as it influences the
movement of teeth within the muscle matrix andmovement of teeth within the muscle matrix and
this movement determines tooth position andthis movement determines tooth position and
occlusal relations.occlusal relations.

 The occlusion of complete denture is designed toThe occlusion of complete denture is designed to
harmonize with this primitive reflex of patientsharmonize with this primitive reflex of patients
unconscious swallow.unconscious swallow.
 Tooth contacts and mandibular bracing againstTooth contacts and mandibular bracing against
maxilla occurred during swallowing by C.Dmaxilla occurred during swallowing by C.D
patients. This suggest that C.D occlusion must bepatients. This suggest that C.D occlusion must be
compatible with forces developed duringcompatible with forces developed during
deglutition to prevent disharmonious occlusaldeglutition to prevent disharmonious occlusal
contact that can be caused to the basal seat .contact that can be caused to the basal seat .

This factor is an important consideration inThis factor is an important consideration in
treating edentulous patient, since thetreating edentulous patient, since the
occlusal scheme to develop on completeocclusal scheme to develop on complete
dentures should attempt to account for anydentures should attempt to account for any
loss of ability to close to precise position.loss of ability to close to precise position.

Temporomandibular jointsTemporomandibular joints
changeschanges

Although the relationship between occlusionAlthough the relationship between occlusion
and degenerative joint disease is notand degenerative joint disease is not
completely clear, the dentist is tempted tocompletely clear, the dentist is tempted to
believe that a depleted or in adequately caredbelieve that a depleted or in adequately cared
for dentition , obviously loads the TMJ .for dentition , obviously loads the TMJ .
Denture wearers have been shown to sufferDenture wearers have been shown to suffer
from degenerative changes of joints morefrom degenerative changes of joints more
frequently than person with a complete naturalfrequently than person with a complete natural
dentition , but this may be age related ratherdentition , but this may be age related rather
than due to state of dentition.than due to state of dentition.

Research strongly suggest that purely dentalResearch strongly suggest that purely dental
factors may be important in etiology offactors may be important in etiology of
degenerative joint disease of mandibulardegenerative joint disease of mandibular
condyles.condyles.
Clinical experience indicates that theClinical experience indicates that the
application of sound prosthodontic principles,application of sound prosthodontic principles,
accompanied by appropriate systemic careaccompanied by appropriate systemic care
by a physician ,is usually adequate toby a physician ,is usually adequate to
provide the patient with comfort.provide the patient with comfort.

Tongue changesTongue changes
The tongue is a highly mobile muscularThe tongue is a highly mobile muscular
organ that merits careful attention during theorgan that merits careful attention during the
construction of complete dentures. Inconstruction of complete dentures. In
coordination with lips , cheek , palate , andcoordination with lips , cheek , palate , and
pharynx, the tongue functions in speech,pharynx, the tongue functions in speech,
mastication, and swallowing.mastication, and swallowing.

The tongue is in intimate contact with aThe tongue is in intimate contact with a
complete lower denture and its position incomplete lower denture and its position in
relationship must be considered veryrelationship must be considered very
carefully in each particular patient.carefully in each particular patient.
In those patients in whom the genial tubercleIn those patients in whom the genial tubercle
become extremely prominent due tobecome extremely prominent due to
excessive resorption of the alveolar process,excessive resorption of the alveolar process,
special attention must be paid in contouringspecial attention must be paid in contouring
the lingual flange of a lower denture in orderthe lingual flange of a lower denture in order
that the denture is not displaced every timethat the denture is not displaced every time
the genioglossus muscle contracts.the genioglossus muscle contracts.

The size of the tongue does not vary withThe size of the tongue does not vary with
age. how ever, tooth loss can lead to widerage. how ever, tooth loss can lead to wider
tongue morphology by virtue of antongue morphology by virtue of an
overdevelopment of some parts of tongue’soverdevelopment of some parts of tongue’s
intrinsic musculature.intrinsic musculature.
Constant and habitual attempts to keep aConstant and habitual attempts to keep a
loose maxillary denture in place can causeloose maxillary denture in place can cause
these changes. The effect of this onthese changes. The effect of this on
subsequent wearing must not be over looked.subsequent wearing must not be over looked.

STRESS DISTRIBUTION TOSTRESS DISTRIBUTION TO
DENTURE SUPPORTING TISSUESDENTURE SUPPORTING TISSUES
The need to full filling fundamental objectiveThe need to full filling fundamental objective
of good prosthodontic treatment is underof good prosthodontic treatment is under
scored by the preceding information.scored by the preceding information.
All possible methods to ensure continueAll possible methods to ensure continue
tissue health by minimizing potentialtissue health by minimizing potential
traumatic effect by complete denture weartraumatic effect by complete denture wear
should be undertaken.should be undertaken.

The capability of supporting tissues shouldThe capability of supporting tissues should
be improved when ever possible bybe improved when ever possible by
adequate preparation of both hard and softadequate preparation of both hard and soft
tissues.tissues.

Mucosal health may be promoted byMucosal health may be promoted by
hygienic and therapeutic measures, andhygienic and therapeutic measures, and
tissue conditioning techniques may betissue conditioning techniques may be
applied when appropriate.applied when appropriate.
 Complete denture base extension withinComplete denture base extension within
morphologic and functional limits canmorphologic and functional limits can
reduce considerably the occlusal load onreduce considerably the occlusal load on
the unit area of mucosa.the unit area of mucosa.
Resilient denture base lining materials mayResilient denture base lining materials may
be used.be used.
The masticatory loading may be decreasedThe masticatory loading may be decreased
by reduction of the area of the occlusalby reduction of the area of the occlusal
table.table. www.indiandentalacademy.comwww.indiandentalacademy.com

Currently, for practical purposes, denture basesCurrently, for practical purposes, denture bases
are made of rigid materials. These may be oneare made of rigid materials. These may be one
of various types of resins, metals, orof various types of resins, metals, or
combinations of them the dentist mustcombinations of them the dentist must
recognize that the prolonged contact of theserecognize that the prolonged contact of these
vases with their underlying tissues.vases with their underlying tissues.
 Furthermore, the tissues are susceptible toFurthermore, the tissues are susceptible to
changes caused by the increased longevity ofchanges caused by the increased longevity of
patients with the effects of aging on tissues , aspatients with the effects of aging on tissues , as
well as the functional and para functionalwell as the functional and para functional
demands that patients make on their denturedemands that patients make on their denture
supporting tissues .supporting tissues .

Many dentists have been tempted to equateMany dentists have been tempted to equate
the prevalent residual ridge reduction in thethe prevalent residual ridge reduction in the
edentulous population with excessiveedentulous population with excessive
stresses that are imposed on these ridges.stresses that are imposed on these ridges.
Up to now there is no specific evidence toUp to now there is no specific evidence to
indicate any one factor as causing advancedindicate any one factor as causing advanced
ridge reduction.ridge reduction.
However, strong theoretical evidence exists toHowever, strong theoretical evidence exists to
justify the development of permanentlyjustify the development of permanently
resilient lining materials in complete dentures.resilient lining materials in complete dentures.

These materials could permit a widerThese materials could permit a wider
dispersion of forces and result in a lowerdispersion of forces and result in a lower
force per unit area being transmitted toforce per unit area being transmitted to
supporting tissues.supporting tissues.
Such a soft denture lining material couldSuch a soft denture lining material could
effectively increase the thickness of the oraleffectively increase the thickness of the oral
tissue by serving as a analog of thetissue by serving as a analog of the
mucoperiostium with its relatively low elasticmucoperiostium with its relatively low elastic
modulus [kydd and mandley, 1967]modulus [kydd and mandley, 1967]

The distance increment between the hardThe distance increment between the hard
denture base and the non-resilient bonydenture base and the non-resilient bony
support would be increased withsupport would be increased with
hypothetical salutary long tern results. Thehypothetical salutary long tern results. The
academy of denture prosthetics listed ideasacademy of denture prosthetics listed ideas
for the improvement of denture basefor the improvement of denture base
materials and cites the following desirablematerials and cites the following desirable
properties;properties;
1. Possessing variable consistency under1. Possessing variable consistency under
varying mouth conditions.varying mouth conditions.
2. Selectively resilient, compatible with2. Selectively resilient, compatible with
resiliency of the tissues.resiliency of the tissues.
3. Resilient with quick recovery able to3. Resilient with quick recovery able to
recover shape quickly after deformingrecover shape quickly after deforming
forces are removed.forces are removed.www.indiandentalacademy.comwww.indiandentalacademy.com

4. Compressible on tissue side but rigid on4. Compressible on tissue side but rigid on
occlusal side.occlusal side.
5. Shock absorbing.5. Shock absorbing.
6. Controlling or reducing forces transmitted6. Controlling or reducing forces transmitted
through the base to the underlying tissue.through the base to the underlying tissue.
7. Possessing flexibility that can be controlled7. Possessing flexibility that can be controlled
and varied in processing as desired.and varied in processing as desired.

The work of kydd and associates [1971] onThe work of kydd and associates [1971] on
pressures in the oral cavity has posed anpressures in the oral cavity has posed an
excellent argument favoring the employmentexcellent argument favoring the employment
of soft lining materials.of soft lining materials.
They argue that during function andThey argue that during function and
parafunction, pressures are applied by theparafunction, pressures are applied by the
dentures, which will displace the soft tissues.dentures, which will displace the soft tissues.
These pressures deform the mucoperiostiumThese pressures deform the mucoperiostium
and interfere with circulation of blood,and interfere with circulation of blood,
nutrients, and metabolites.nutrients, and metabolites.
Several studies have demonstrated changesSeveral studies have demonstrated changes
in soft-tissue contour as a result of mechanicalin soft-tissue contour as a result of mechanical
stress.stress.

Kydd and associates describes theKydd and associates describes the
viscoelastic character of denture supportingviscoelastic character of denture supporting
tissue.tissue.
There is an initial elastic compression of softThere is an initial elastic compression of soft
tissues that takes place instantly ontissues that takes place instantly on
application of load.application of load.
After the elastic phase there is delayed elasticAfter the elastic phase there is delayed elastic
deformation of the tissue that takes placedeformation of the tissue that takes place
slowly and continues to diminish in rate ofslowly and continues to diminish in rate of
changes as duration of load is extended .changes as duration of load is extended .
An instantaneous elastic decompressionAn instantaneous elastic decompression
occurs when the pressure is removed. Thisoccurs when the pressure is removed. This
is followed by a continuing delayed elasticis followed by a continuing delayed elastic
recovery.recovery. www.indiandentalacademy.comwww.indiandentalacademy.com

Histological, the stressed oral mucosa hasHistological, the stressed oral mucosa has
an altered morphologic pattern. The loadedan altered morphologic pattern. The loaded
epithelium demonstrates a decease in theepithelium demonstrates a decease in the
depth of the epithelial ridges, and thedepth of the epithelial ridges, and the
connective tissues papillae are obliteratedconnective tissues papillae are obliterated
the extent of these alterations varies withthe extent of these alterations varies with
the force and duration of the applied force.the force and duration of the applied force.
Human soft tissues take as long as 4 hoursHuman soft tissues take as long as 4 hours
to recover after moderate loading for 10to recover after moderate loading for 10
minutes.minutes.

 A Change in tissue displaceability can alsoA Change in tissue displaceability can also
be demonstrated as being a function of age.be demonstrated as being a function of age.
A longer period of time is needed for theA longer period of time is needed for the
recovery of displaced mucosa in elderlyrecovery of displaced mucosa in elderly
people (68 to 70 years) when compared withpeople (68 to 70 years) when compared with
young adults (21 to 27 years).young adults (21 to 27 years).
It appears that any Intraoral prosthesis canIt appears that any Intraoral prosthesis can
be intruded into the denture-supporting oralbe intruded into the denture-supporting oral
mucosa by up to 20% of its resting thicknessmucosa by up to 20% of its resting thickness
with relatively small occluding forces (0.2with relatively small occluding forces (0.2
gmmsq) .gmmsq) .
Lindan (1961) has shown that pressures asLindan (1961) has shown that pressures as
small as 0.13 gmmsq will displace humansmall as 0.13 gmmsq will displace human
soft tissues to 95% of their resting thickness.soft tissues to 95% of their resting thickness.www.indiandentalacademy.comwww.indiandentalacademy.com

This indicates that impression materials, forThis indicates that impression materials, for
example, must flow readily and with minimalexample, must flow readily and with minimal
pressure when an impression is made.pressure when an impression is made.

Cutright and associates( 1976) recordedCutright and associates( 1976) recorded
pressures under complete maxillary dentures.pressures under complete maxillary dentures.
They used a closed fluid system connected toThey used a closed fluid system connected to
a pressure transducer and recorder to registera pressure transducer and recorder to register
positive and negative pressures in fourpositive and negative pressures in four
subjects at four locations. Each subjectsubjects at four locations. Each subject
performed a number of controlled masticatoryperformed a number of controlled masticatory
and non-masticatory activities.and non-masticatory activities.
Their findings indicate that a number of non-Their findings indicate that a number of non-
masticatory activities (smoking, swallowing,masticatory activities (smoking, swallowing,
speaking) created as much, or more, positivespeaking) created as much, or more, positive
and negative pressures on the supportingand negative pressures on the supporting
tissues as the masticatory activities.tissues as the masticatory activities.

IT is tempting to suggest that theseIT is tempting to suggest that these
pressures could affect the soft tissue andpressures could affect the soft tissue and
the blood and lymph vessels, perhapsthe blood and lymph vessels, perhaps
causing sclerosis, diminished blood supply,causing sclerosis, diminished blood supply,
and the many morphologic variants weand the many morphologic variants we
encounter in our edentulous patients.encounter in our edentulous patients.
 Cutright and associates concluded that theCutright and associates concluded that the
effect of these continually occurring, non –effect of these continually occurring, non –
masticatory induced pressure changes andmasticatory induced pressure changes and
waves may well be of greater significancewaves may well be of greater significance
than that of mastication.than that of mastication.

The amount of force generated by a patientsThe amount of force generated by a patients
masticatory system is not controlled by themasticatory system is not controlled by the
dentist.dentist.
The dentist can seek to minimize forceThe dentist can seek to minimize force
distribution by maximizing denture basedistribution by maximizing denture base
coverage and developing an optimal denturecoverage and developing an optimal denture
occlusion.occlusion.
Occlusal surfaces of the artificial teeth canOcclusal surfaces of the artificial teeth can
be smaller, and the patient can be instructedbe smaller, and the patient can be instructed
to handle parafunctional habits throughto handle parafunctional habits through
education and understanding.education and understanding.

Forces can also be reduced or diluted by useForces can also be reduced or diluted by use
of a permanently resilient liner if suchof a permanently resilient liner if such
materials are readily available.materials are readily available.
The time factor can be controlled to a largeThe time factor can be controlled to a large
extent by frequent rest periods for the denture-extent by frequent rest periods for the denture-
supporting tissues, Leaving the dentures out ofsupporting tissues, Leaving the dentures out of
the mouth during sleeping hours isthe mouth during sleeping hours is
recommended.recommended.
Oral tissues were designed to be exposed toOral tissues were designed to be exposed to
oral fluids and to be stimulated by the action oforal fluids and to be stimulated by the action of
tongue, lips, and cheeks. Nocturnal rest cantongue, lips, and cheeks. Nocturnal rest can
achieve this objective, along with a quantitativeachieve this objective, along with a quantitative
diminution in the duration of exposure of thesediminution in the duration of exposure of these
tissues to stress.tissues to stress.

The efficiency of temporary soft or treatmentThe efficiency of temporary soft or treatment
liners in routine prosthodontic practice hasliners in routine prosthodontic practice has
proved the value of such an approach inproved the value of such an approach in
treating soft-tissue problems.treating soft-tissue problems.
The contribution of permanent liners towardThe contribution of permanent liners toward
the maintenance of supporting tissuethe maintenance of supporting tissue
integrity and morphology is still hypothetical.integrity and morphology is still hypothetical.

The most frequently used liners are usuallyThe most frequently used liners are usually
produced from silicone rubbers or acrylicproduced from silicone rubbers or acrylic
resins. Recent reports also suggests theresins. Recent reports also suggests the
possible employment of hydrophilic polymerspossible employment of hydrophilic polymers
and fluoropolymers .and fluoropolymers .
The silicone rubber resilient liners, whenThe silicone rubber resilient liners, when
properly used, are the most appropriate ofproperly used, are the most appropriate of
the various types available, but they too arethe various types available, but they too are
only temporary expedients. These materialsonly temporary expedients. These materials
may support yeast growth( e.g., Candidamay support yeast growth( e.g., Candida
Albicans).Albicans).

They must be observed regularly by theThey must be observed regularly by the
dentist and replaced when unsatisfactory.dentist and replaced when unsatisfactory.
 The use of proper cleansers and homeThe use of proper cleansers and home
care habits have contributed to thecare habits have contributed to the
employment of these materials withemployment of these materials with
significantly beneficial results.significantly beneficial results.
It must be emphasized that the use of theseIt must be emphasized that the use of these
materials does not preclude adherence tomaterials does not preclude adherence to
the fundamental principles of completethe fundamental principles of complete
denture construction. When useddenture construction. When used
intelligently, resilient liners can be anintelligently, resilient liners can be an
excellent adjunct in prosthodontics.excellent adjunct in prosthodontics.

Posselt (1952) showed that the borderPosselt (1952) showed that the border
movements of the mandible weremovements of the mandible were
reproducible and that all other movementsreproducible and that all other movements
took place within the confines of his classictook place within the confines of his classic
“envelopes of motion.”“envelopes of motion.”
These researchers concluded that theThese researchers concluded that the
passive hinge movement has a constantpassive hinge movement has a constant
and definite rotational and posterior borderand definite rotational and posterior border
path is of tremendous practical significancepath is of tremendous practical significance
in the treatment ofin the treatment of Prosthodontic patients.Prosthodontic patients.

However, this reproducibility has beenHowever, this reproducibility has been
established in healthy young persons only.established in healthy young persons only.
Tallgren (1957) has shown that morphologicTallgren (1957) has shown that morphologic
face height increased with age in personsface height increased with age in persons
possessing an intact or relatively definition.possessing an intact or relatively definition.
 However, a premature reduction inHowever, a premature reduction in
morphologic face height occurs with attritionmorphologic face height occurs with attrition
or abrasion of teeth. This reduction is evenor abrasion of teeth. This reduction is even
more conspicuous in edentulous Andmore conspicuous in edentulous And
complete denture-wearing patients.complete denture-wearing patients.

Maxillomandibular morphologic changesMaxillomandibular morphologic changes
take place slowly over a period of years andtake place slowly over a period of years and
depend on the balance of osteoblastic anddepend on the balance of osteoblastic and
osteoblastic activity.osteoblastic activity.
The articular surfaces of theThe articular surfaces of the
temperomandibular joints are also involved,temperomandibular joints are also involved,
and at these sites growth and remodelingand at these sites growth and remodeling
are mediated through the proliferativeare mediated through the proliferative
activity of the articular cartilages.activity of the articular cartilages.

Tallgren(1972) has shown that in completeTallgren(1972) has shown that in complete
denture wearers the mean reduction isdenture wearers the mean reduction is
height of the mandibular process, asheight of the mandibular process, as
measured in the anterior region was 6.6measured in the anterior region was 6.6
mm, approximately four times greater thanmm, approximately four times greater than
the mean reduction occurring in thethe mean reduction occurring in the
maxillary process.maxillary process.

The unconscious or reflex swallow isThe unconscious or reflex swallow is
important in the developing dentition. Theimportant in the developing dentition. The
act and frequency of swallowing areact and frequency of swallowing are
important influences in the movement ofimportant influences in the movement of
teeth within the muscle matrix, and thisteeth within the muscle matrix, and this
movement determines the tooth positionmovement determines the tooth position
and occlusal relations (Moyers).and occlusal relations (Moyers).

Temporomandibular joints changesTemporomandibular joints changes
Several authors claim that impaired dentalSeveral authors claim that impaired dental
efficiency resulting from partial tooth loss andefficiency resulting from partial tooth loss and
absence of, or incorrect, prosthodonticabsence of, or incorrect, prosthodontic
treatment can bring about TMJ pain andtreatment can bring about TMJ pain and
dysfunction or even degenerative changes indysfunction or even degenerative changes in
the joint.the joint.

COSMETIC CHANGES ANDCOSMETIC CHANGES AND
INDIVIDUAL ADAPTIVEINDIVIDUAL ADAPTIVE
RESPONSESRESPONSES
Morphological changes associated with theMorphological changes associated with the
edentulous state.edentulous state.
1. Deepening of the nasolabial groove.1. Deepening of the nasolabial groove.
2. Loss of labio dental angle.2. Loss of labio dental angle.
3. Decrease in horizontal labial angle.3. Decrease in horizontal labial angle.
4. Narrowing of lips.4. Narrowing of lips.
5. Increase in columella philtral angle.5. Increase in columella philtral angle.
6. Prognathic appearance.6. Prognathic appearance.

ADAPTIVE RESPONSE TOADAPTIVE RESPONSE TO
COMPLETE DENTURESCOMPLETE DENTURES
It requires adaptation related to learning,It requires adaptation related to learning,
muscular skill and motivation.muscular skill and motivation.
Helping a patient adapt to completeHelping a patient adapt to complete
dentures can be one of the most difficult butdentures can be one of the most difficult but
one of the most rewarding aspect of clinicalone of the most rewarding aspect of clinical
dentistry.dentistry.
The patient who has worn a complete upperThe patient who has worn a complete upper
denture opposing a few natural anteriordenture opposing a few natural anterior
mandibular teeth will usually find a completemandibular teeth will usually find a complete
lower denture difficult to adapt to.lower denture difficult to adapt to.

Such a patient has to contend with anSuch a patient has to contend with an
alteration in size and orientation of thealteration in size and orientation of the
tongue.tongue.
It must be realized that edentulous patientsIt must be realized that edentulous patients
expect and are expected to adapt to theexpect and are expected to adapt to the
dentures more or less instantaneously anddentures more or less instantaneously and
that the adaptation must take place in thethat the adaptation must take place in the
context of the patients oral , systemic ,context of the patients oral , systemic ,
emotional and psychologic states .emotional and psychologic states .

Facility for learning and co-ordinationFacility for learning and co-ordination
appears to diminish with age. Advancingappears to diminish with age. Advancing
age tends to be accompanied byage tends to be accompanied by
progressive atrophy of elements of cerebralprogressive atrophy of elements of cerebral
cortex and a consequent loss in the facilitycortex and a consequent loss in the facility
of co-ordination occurs.of co-ordination occurs.

CONCLUSIONCONCLUSION
The success of prosthetic treatment isThe success of prosthetic treatment is
predicated not only on manual dexterity ,predicated not only on manual dexterity ,
but also on the ability of the dentist to relatebut also on the ability of the dentist to relate
to patients and to understand their needs.to patients and to understand their needs.
The ability to understand and recognize theThe ability to understand and recognize the
problems of edentulous patients and toproblems of edentulous patients and to
reassure them has proved to be of greatreassure them has proved to be of great
clinical value.clinical value.

BibliographyBibliography
 Essentials of complete denture-WinklerEssentials of complete denture-Winkler
 Syllabus of Complete Denture-HeartwellSyllabus of Complete Denture-Heartwell
 Prosthodontic treatment for edentulousProsthodontic treatment for edentulous
patient-Boucherpatient-Boucher
 Clinical Dental Prosthetics-FennClinical Dental Prosthetics-Fenn
 Removable Partial Prsothodontics-Removable Partial Prsothodontics-
McCrackenMcCracken

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