The document discusses residual ridge resorption (RRR), which is the progressive loss of jaw bone after tooth extraction. It defines RRR and provides classifications. RRR is considered a pathological process due to its variability between individuals. The document covers the epidemiology, etiology, and risk factors of RRR, including anatomical, mechanical, metabolic and prosthetic factors. Treatment aims to prevent or reduce RRR through denture design and patient education.

2.  Definitions
 Pathology
 classification
 Pathogenesis
 Epidemiology
 Etiology
 Prevention
 Treatment
 Summary and conclusion

3. DEFINITIONS :
 “Bone - a highly vascularised, living, constantly
changing, mineralized connective tissue”. [Gray’s
Anatomy-40th edition]
 “Alveolar process -- that part of the maxilla and
mandible that forms and supports the sockets of the
teeth”. [Orban’s]

4.  “Alveolar bone is the bony portion of the maxilla and
the mandible in which roots of the teeth are held by
fibers of periodontal ligament”. [GPT-8]

5.  “Residual alveolar ridge is the portion of the
alveolar ridge and its soft tissue covering
which remains following the removal of or loss
of teeth.
[GPT-8]

6.  The residual bony architecture of the maxilla and
mandible undergoes a life-long catabolic remodelling.
 The rate of reduction in size of the residual ridge is
maximum in the first 3-6 months and then
gradually tapers off.
 However, bone resorption activity continues
throughout life at a slower rate, resulting in loss of
varying amount of jaw structure, ultimately leaving
the patient a ‘dental cripple’.

7. classification

8. According to Atwood’s :
(JPD 1971 Vol.26)
 Order 1 : Pre-extraction
 Order 2 : Post-
extraction
 Order 3 : High, well
rounded
 Order 4 : Knife-edge
 Order 5 : Low, well
rounded
 Order 6 : Depressed
Pre
extraction Post ext High well rounded
Knife edge Low well rounded Depressed

10.  Immediately following the extraction (Order II), any sharp
edges remaining are rounded off by external osteoclastic
resorption leaving a high well rounded ridge (Order III).
 As resorption continues from the labial and lingual
aspects ,the crest of the ridge becomes increasingly narrow,
ultimately becoming knife edged (Order IV).
 As the process continues, the knife-edge becomes shorter
and eventually disappears leaving a low well-rounded or flat
ridge (Order V). Eventually this too resorbs, leaving a
depressed ridge (Order VI).

11.  Class I : Upto one third of the original vertical
height lost.
 Class II : From one third to two thirds of the
vertical height lost.
 Class III : Two third or more of the mandibular
height lost.

12. Based on Bone Height (Mandible only)
 Type I : Residual bone height of 21 mm or greater
measured at the least vertical height of the mandible.
 Type II : Residual bone height of 16 - 20 mm measured
at least vertical height of the mandible.

 Type III : Residual alveolar bone height of 11 - 15 mm
measured at the least vertical height of the mandible.
 Type IV : Residual vertical bone height of 10 mm or less
measured at the least vertical height of the mandible.

13.  Some clinicians feel that RRR is not a disease but a
normal physiological process.
 However there is wide variation in the rate of RRR
in different individuals- depending on multiple
factors.
 The need to elucidate these major differences
warrants labeling this process a “ disease” or
“pathology”

14.  “Until a process is recognized as a disease entity,
little progress is made in understanding its
etiology and in developing adequate treatment
and prevention.”
 - Douglas Allen
Atwood


15. Based on the clinical fact that :
•RRR is not inevitable
• Its rate varies
• The rate of resorption is greater that the rate of
formation in some patients ,
….RRR should be considered a pathologic process.

19.  Epithelial tissues begin its proliferation and migration
within the first week and the disrupted tissue integrity
is quickly restored.
 Histologic evidence of active bone formation is seen
as early as 2 weeks after the extraction and the
socket is progressively filled with newly formed bone
in about 6 months..
 The most striking feature of the extraction wound
healing is that even after the healing of wounds, the
residual ridge undergoes a lifelong catabolic
remodeling.

20. • This unique phenomenon has been described as
RESIDUAL RIDGE RESORPTION (RRR).
• The rate of RRR is different among persons and
even at different sites in the same person.

21.  Coupled process between:
1. Bone deposition by osteoblasts
2. Bone resorption by osteoclasts
 5-7% of bone mass recycled weekly
 All spongy bone replaced every 3-4 years.
 All compact bone replaced every 10 years.
Prevents mineral salts from crystallizing; protecting
against brittle bones and fractures

22. Gross Microscopic

23.  Patient has an expression “ My gums have
shrunken”
 RRR Is primarily a localized loss of bone structure.
 In some cases it may leave excessive and redundant
overlying mucoperiosteum and in some cases it may
not.

25. In dry specimens
*External cortical surface of maxilla and mandible are
uniformly smooth & crestal area of residual ridge
shows porosities and imperfections.
*Bones with more severe RRR display gross porosities
of medullary bone on the crest of ridge.

26.  Panoramic radiograph showing severe RRR in both
maxilla and mandible in contrast to dentulous
area that support three mandibular teeth.

27. Osteoclastic activity occurs on
the external surface of crest of
ridges .
Scalloped margins of
Howships lacunae sometimes
contain visible osteoclasts.
Frequently the scalloped
external surface seems
inactive without bone
resorbing cells.

28. The sequence of resorptive events is
considered to be
Attachment of osteoclasts to mineralized surface of bone
Creation of a ruffled border and a sealed acidic
environment through action of the proton pump
Dissolution of the Hydroxyapatite
Fall in pH to 2.5-3 in the osteoclast resorption space
Digestion of the organic components of the matrix by
proteolytic enzymes

29. 1. Serial Examination of
diagnostic casts.
2. Lateral cephalometric
radiographs
◦ Most accurate
◦ Measures RRR over a period
of time.

30. {Kenneth E. Wical and Charles C. Swoope. Studies of
residual ridge resorption. Uses panaromic radiographs for
evaluation and classification of mandibular resorption.
JPD;1974;32;7}

31. EPIDEMIOLOGY OF RRR:
•To date, it appears that RRR world-wide, occurs in
males and females, young and old, sickness and in
health, with and without dentures and is unrelated to
the primary reason for the extraction of the teeth
(Caries / periodontal disease).
• Rate of RRR is variable
-between persons.
-within the same person at different times.
-within the same person at different sites.

32.  According to Boucher,
 During the first year after tooth extraction, the
reduction in residual ridge height in the
midsagittal plane is
 2-3 mm for maxilla
4-5 mm for mandible
 Annual rate of reduction in height
0.1-0.2 mm for mandible
4 times less in the maxilla

33.  Maxilla resorbs upward and
inward to become progressively
smaller because of the direction
and inclination of the roots of the
teeth and the alveolar process.
 The opposite is true of the
mandible, which inclines outward
and becomes progressively wider.
 This progressive change of the
edentulous mandible and maxilla
makes many patients appear
prognathic.

34. •Thus, RRR is centripetal in maxilla and
centrifugal in mandible.

35.  In the Mandible, large proportions of bone loss
occurs in the
 labial side of anterior residual ridge,
 equally on the buccal and lingual side in premolar
region and
 lingually in the posterior or molar region.
 In the Maxilla bone loss primarily occurs on the
labial or buccal aspect.

36.  While teeth arrangement we should try to restore
the natural position of the teeth before they were
lost, Hence teeth in the maxillary arch are arranged
slightly labially and buccally .
 While in the mandible, teeth in the anterior region
are arranged labially, on the centre of the ridge in
the premolar region and slightly lingually in the
molar region.

37.  It is a clinically acknowledged fact that the anterior
mandible resorbs 4 times faster than the anterior
maxilla.
 Woelfel et al have cited the projected maxillary denture
area to be 4.2 sq in and 2.3 sq in for the mandible;
which is in the ratio of 1.8:1.
 If a patient bites with a pressure of 50 lbs, this is
calculated to be 12 lbs/sq in under the maxillary
denture and 21 lbs/sq under the mandibular
denture. The significant difference in the two forces
may be a causative factor to cause a difference in the
rates of resorption.
Maxilla V/s Mandible

38.  Cancellous bone is ideally designed to absorb and
dissipate the forces it is subjected to.
 The maxillary residual ridge is often broader,
flatter, and more cancellous than the mandibular
ridge.
 Trabeculae in maxilla are oriented parallel to the
direction of compression deformation, allowing for
maximal resistance to deformation.
 The stronger these trabeculae are, the greater is
the resistance.

39. ◦ Generally more in mandible than in maxilla but the
reverse may also occur….
◦ So one must treat every patient as a “PARTICULAR
PATIENT, NOT THE AVERAGE PATIENT!”!
•RRR is chronic, progressive, irreversible, and
cumulative.
•Autonomous regrowth has not been reported.

40.  Acc. To Atwood… {Some clinical factors related to
rate of resorption of residual ridges JPD Vol 12,issue
3, pages 441-450.
 RRR is a multifactorial biomechanical disease
caused by a combination of
◦ ANATOMIC FACTORS
◦ MECHANICAL FACTORS
◦ METABOLIC FACTORS

41.  It is postulated that RRR varies with the quantity and
quality of the bone of residual ridges..
ie, the more bone there is, the more RRR will
ultimately be.
But this cannot be considered a good prognostic
factor, because in some cases large ridges resorb
rapidly and some knife-edge ridges may remain with
little change for long periods of time.
RRR α Anatomic factors

42.  We should always try to evaluate the present status
of the residual ridge to determine what has gone on
before.
 If a ridge has existed as high and well rounded
(order III) for several years, it will likely to continue
to do so.
 But if a ridge has gone from an order II to order IV
in just two years it will probably continue to resorb
rapidly.

43.  RRR varies directly with certain systemic or
localized bone resorptive factors and inversely with
certain bone formation factors.
RRR  BONE RESORPTION FACTORS
BONE FORMATION FACTORS

44. BONE RESORPTION FACTORS
LOCAL SYSTEMIC
-Endotoxins from dental plaque
-Osteoclast activating factor(OAF)
-Prostaglandins
-Human gingival bone resorption
factor
-Trauma due to ill fitting dentures
which leads to increased or
decreased vascularity and changes
in oxygen tension.
-Correct amount of circulating
estrogen, thyroxine, growth
hormone, calcium,
phosphorus,
-vitamin D ,
-Osteoporosis
- Hypophosphetemia
- Parathormone
- Calcitonin

45.  Osteoporosis is defined by the WHO as bone
mineral density (BMD) greater than 2.5
standard deviations below that of the young
adult BMD.
 Osteoporosis is common in aging individuals,
especially post menopausal women when the
estrogenic blood level is low.
 In elderly men and women, osteoporosis is caused
by a variety of factors such as calcium loss,
calcium deficiency, hormonal deficiency, change in
protein nutrition and decreased physical activity.

46. osteoporosis
Primary
(no known cause)
Type 1
Post
menopausal
Type 2
Age related
secondary
Traceable
etiology

47. Normal Bone Osteoporosis

48.  Residual ridge resorption of the jaws is also more
rapid in increasing age group, depleted bone being
prone to the injurious impact of mechanical forces.

49.  The most popular theory of how osteoporosis occur
in females is based on the central role of oestrogen
in bone remodelling.

50. Decreased oestrogen levels leads to
increased pro-inflammatory cytokine
levels like IL1 and TNF leading to
increased osteoclast formation and
hence increased bone loss.
Oestrogen acts through two
receptors: oestrogen receptor a (ERa)
and ERb, ERa appears to be the
primary mediator of the actions of
oestrogen on the skeleton.
Another line of action is the decreased
antagonistic action of oestrogen on
parathyroid leads to more
parathormone secretion and
consequently increased bone
resorption.

52. One
• loss and/or mobility of teeth
Two
• edentulism,
Three
• excessive residual ridge resorption
Four
• dentures which require repeated
revision or remakes

53. Mandibular and maxillary radiographs are suggested
in screening patients for osteoporosis for two reasons
 potential frequency of dental radiographs
compared to the rest of the body
 the prosthodontic implications of osteoporosis.
 Bone density may be assessed by a prosthodontist
using linear measurements (morphometric
analysis) or by measuring optical density of bone
(densitometric analysis).

54.  Bone that is used by regular physical activity will tend
to strengthen within certain limits, than the bone that
is in “disuse atrophy”, while others postulated that
due to denture wearing RRR is caused due to an
“abuse” bone resorption.
 Perhaps there is truth in both the hypotheses.
 The fact is that with or without dentures some patients
have little or no RRR and some have severe RRR.

55.  When force is considered one must be concerned not
only about the amount of force but also with the
frequency of force, the duration, the area over which the
force is distributed and the damping effect of underlying
tissue.
 The amount of force applied to the bone may be affected
inversely by the damping effect or energy absorption.
RRR α Force
1
RRR α ———————-
Damping effect

56.  The damping effect is due to the viscoelastic
property of the mucoperiosteum and may vary
from patient to patient and also from maxilla to
mandible.
 Cancellous bone helps in the absorption and
dissipation of forces and is more in maxilla than
mandible, which could be a reason in the
difference in RRR between them.

57.  Excessive stress resulting from artificial environment.
 Abuse of tissues from lack of rest-
Bone is moldable. It can tolerate masticatory forces
within the limits of physiologic tolerance.
• But exceeding that it causes damaging forces which will
result in resorption of the alveolar bone.
PROSTHETIC FACTORS

58.  Long continued use of ill fitting dentures:
• may be due to : Long use, Loss of bone, Incorrect
occlusion, Incorrect jaw relation
 Lack of freeway space due to increased vertical
dimension of occlusion:
• Freeway space is present in the teeth in the
physiologic rest position. It is normally around
2mm.
• At times, due to lack of freeway space the bone
resorbs because of increased vertical height in an
attempt to create the space.

59.  Incorrect Centric relation record:
• If the Centric relation is not recorded properly, the
mandibular teeth will not occlude properly with those on
the maxillary arch. This proper occlusion is essential to
the health of bony support.
• Otherwise, during eccentric movement, it causes pressure
on bone due to failure of denture stability. Hence
resorption of base occurs.

60.  If occlusal corrections are not done:
• These errors which may be caused due to processing
techniques if not corrected causes premature contacts
resulting in increased stress.
• Selective grinding should be done to minimize lateral
stress and resulting tissue trauma.

61.  Kelly first described the “combination syndrome”
wherein patients with remaining mandibular natural
teeth against a maxillary complete denture were
shown to have an exaggerated loss of anterior
segment of maxillary residual ridge.

62.  In addition to the 3 major categories of factors
(anatomic, metabolic and mechanical) the
importance of time since extraction is also
important. This can be added to the formula by an
inverse relation.
Bone resorption factors Force
factors
RRR α anatomic factors + ———————————— + ————
——— +
Bone formation factors Damping
effect
1
——
Time

63.  Apparent loss of sulcus width
and depth.
 Displacement of muscle
attachment close to the ridge.
 Loss of vertical dimension of
occlusion.
 Reduction of the lower face
height.
 Increase in relative
prognathia

64.  Changes in inter alveolar relationship.
 Morphological changes of the alveolar bone such as
sharp, spiny uneven residual ridges.
 Location of mental formina close to the ridge crest.

65.  “Treatment of RRR is ideally by preventing it.”
a. Prevention of loss of natural teeth:
 Alveolar bone supporting natural teeth receives
tensile loads through a large area of periodontal
ligament.
 While the edentulous residual ridge receives
vertical, diagonal and horizontal loads applied by a
denture with a surface area much smaller than the
total area of the periodontal ligament of all the
natural teeth that had been present.

66.  Optimal tissue health prior to making impression.
 Impression procedures
Minimal pressure impression technique.
Selective pressure impression technique: places
stress on those areas that best resist functional
forces
Adequate relief of non stress bearing areas eg.
Crest of mandibular ridge.
 Broad area of coverage helps in reducing the
force /unit area(Snow Shoe Effect)

67.  Avoidance of inclined planes to minimize dislodgment of
dentures and shear forces.
 Centralization of occlusal contacts to increase stability and
maximize compressive forces.
 Provision of adequate tongue room to improve stability of
denture in speech and mastication.
 Adequate interocclusal distance during jaw rest to decrease
the frequency and duration of tooth contact.
 Occlusal table should be narrow
The concept and arrangement of teeth in neutral zone helps
the teeth to occupy a space determined by the functional
balance of the oro- facial and tongue musculature.

68.  It has been seen that one of the cofactor in RRR is
low calcium and vitamin D metabolism.
 Diet counseling for prosthodontic patients is
necessary to correct imbalances in nutrient
intake.
 Denture patients with excessive RRR report lower
calcium intake and poorer calcium phosphorus
ratio, along with less vitamin D.

69.  Excessive RRR leads to loss of sulcus width and
depth with displacement of muscle attachment more
to the crest of residual ridge.
 Osseous reconstruction surgeries, removal of high
frenal attachments, augmentation procedures,
vestibuloplasties etc may be required to correct
these conditions.

70.  Inferior Border Augmentation
 Superior Border Augmentation
 Interpositional Grafts

71. e. Immediate dentures:
Some authors claim that extraction followed by
immediate dentures reduces the ridge resorption.

72. f. Overdentures
 Tooth supported over dentures
help in improved stress
distribution there by maintaining
the integrity of residual ridge.
 The occlusal and parafunctional
stresses are distributed through
the abutment teeth.
 A study was conducted with overdentures supported
by canines and it was seen that, the bone loss was
0.6mm where as 5mm in conventional complete
dentures.

73. 1. The denture bearing mucosa of the residual ridges
are spared abuse.
2. Maintenance of the alveolar bone.
3. Sensory feedback.
4. Tactile sensitivity discrimination.
5. Masticatory performance.
6. Reduction of Psychological trauma.

74.  The introduction of osseointegrated implants has
eclipsed traditional preprosthetic surgical techniques.
The use of implant-supported overdentures resembles
the same clinical situation of teeth supported
overdentures.

75.  Metal based denture with soft liner is advocated
in patients with severely atrophic residual ridges.
 Metal base provides-
◦ Weight necessary to facilitate retention
◦ Maintain Adequate strength with modest extensions
 The soft liner accomodates ridge irregularities
and changes.
Metal based dentures {JPD 1987 ;57:6 }

76.  Precautions during extraction to
reduce RRR
◦ When a tooth is removed the labial plate should be
preserved.
◦ The labial periosteal covering should remain intact as
its inner layer is responsible for remodeling of bone.
◦ If a bone has to be removed it must be the palatal plate.

77.  The ultimate aim of a successful prosthesis is
stability in function and excellent esthetics.
 The expectations of edentulous patients are highly
variable therefore the outcome of patient treatment
varies significantly.
 Patients should be educated regarding the type and
extent of treatment that is ideal for them, the
prognosis of the treatment outcomes with various
types of removable or fixed prostheses and the
alternatives that are available.