3. INTRODUCTION
A thorough knowledge of orofacial anatomy is necessary
for making impressions, recording jaw relations, adjusting
dentures, etc.
It helps the clinician in identifying enough landmarks that
in turn act as positive guides in treatment planning.
The anatomical significance and the anatomy of the
edentulous ridge in the maxilla and mandible is very
important for the design of a complete denture.
5. The Extra Oral Landmarks are:
Philtrum: is a midline shallow depression of
the upper lip, which starts at the labial
tubercle and ends at the nose.
Labial Tubercle: is a little swelling in the mid
portion of the vermillion border of the upper
lip.
6. Vermillion Borders: the lip is covered
by the skin at its facial surface and the
mucous membrane at its inner surface.
The transitional area between the skin
and the mucous membrane of the upper
and lower lips is a pink or red zone of
thinner epithelium, which is called the
vermillion border.
Labial Commissure: is a junction of
upper and lower lips lateral to the angle
of the mouth.
7. Nasolabial Groove: is a
furrow of variable depth that
extends from the ala of nose
to end at some distance from
the corner of the mouth.
Angle of the Mouth: is the
lateral limit of the oral
fissure.
Mentolabial Groove: is a
sharp or deep groove that lies
between the lower lip and the
chin.
8. Nasolabial Angle: is an angle between
columella of nose and philtrum of lip,
normally, approximately 90˚ as viewed
in profile.
Modiolus: This muscular knot is at the
angle of the mouth. Modiolus may lie
laterally to the lower premolars so it
will displace a lower denture if those
teeth are set too far buccally.
9. Maxillary and mandibular dentures transfer occlusal loads to
supporting structures. Denture supporting areas comprises of:
1.UNDERLYING BONE: The
nature of bone and its site of location plays an
important role in determining the areas of
stress distribution.
Maxillary denture is supported by two pairs of
bones i.e.. Maxillae and palatine bone.
Mandibular denture is supported by Mandible.
There are two types of bone seen:
1) Compact or Cortical Bone
2) Trabecular or Cancellous Bone
10. 2. OVERLYING MUCOSA:
Denture bases rest on the mucous membrane, which serve
as a cushion between denture base and supporting bone.
Mucous membrane is composed of Mucosa and Submucosa.
The oral mucosa is the mucous membrane lining the inside
of the mouth. It comprises of stratified squamous
epithelium, termed "oral epithelium", and an underlying
connective tissue termed “lamina propria”. Submucosa is
formed by connective tissue that varies from dense to loose
areolar tissue and varies in thickness.
11. Masticatory mucosa: keratinized stratified squamous
epithelium, found on the dorsum of the tongue, hard palate, and
attached gingiva.
Oral mucosa can be divided into three main categories based on
function and histology:
12. Lining mucosa: non-keratinized stratified
squamous epithelium, found almost
everywhere else in the oral cavity, including
the:
Alveolar mucosa: the lining between the
buccal and labial mucosae. It is a brighter
red, smooth, and shiny with many blood
vessels, and is not connected to underlying
tissue by rete pegs.
Buccal mucosa: the inside lining of the
cheeks and floor of the mouth; part of the
lining mucosa.
Labial mucosa: the inside lining of the
lips; part of the lining mucosa.
13. Specialized mucosa: specifically in the regions of the taste buds
on lingual papillae on the dorsal surface of the tongue; contains
nerve endings for general sensory reception and taste perception.
17. Limiting Structures
The limiting structures guide us in having an optimum extension of
the denture so as to engage maximum surface area without
encroaching upon the muscle actions.
Encroaching upon these structures will lead to dislodgement of the
denture and/or soreness of the area while failure to cover the areas
up to the limiting structure will imply decreased retention stability
and support.
They are as follows:
18. Labial Frenum: It is normally a single band of
fibrous connective tissue and may consist of two or
more fibrous bands.
It appears as a fold of mucous membrane extending
from the mucous lining of the lip to or towards the
crest of residual ridge on the labial surface.
It may be single / multiple. It may be narrow / broad.
It contains no muscle fibres of significance.
Clinical Considerations: Sufficient relief should be given during final impression
procedure and in completed prosthesis because overriding of function of frenum will cause
pain and dislodgement of denture. During impression procedure the lip should be stretched
horizontal outwards for the proper recording of frenum. If frenum is attached close to the
crest frenectomy is done, failure of which will lead to the denture border being placed on
the bone tissue which will cause decreased border seal.
19. Clinical Consideration: For effective border contact between denture
and tissue, vestibule should be completely filled with impression material.
The major muscle of the lip is the orbicularis oris, whose fibres are
horizontal, so careful border molding is necessary because it is easy to
overextend the impression.
Labial Vestibule: The labial vestibule
extends between the right and left buccal
frenums or between the area of the right and
left first premolars if the frenums are absent.
It is bounded laterally by the labial mucosa
medially by maxillary residual alveolar ridge.
20. Clinical Consideration: During final impression procedure and in final
prosthesis sufficient relief should be given for the movement of frenum
because overriding of function of frenum will cause pain and dislodgement of
denture. During impression procedure the cheek should be reflected laterally
and posteriorly. If frenum is attached close to the crest of alveolar ridge,
frenectomy can be done.
Buccal Frenum: It consists of one or more
bands, may be totally absent or may be in an
entirely different location.
Most of the muscles of expression converge at the
corner of the mouth to form a nodule called the
Modiolus.
The major muscles in this area are the Buccinator,
Levator anguli oris and Zygomticus.
21. Clinical Consideration: During impression procedure the vestibule should be completely
filled with impression material for proper border contact between denture and tissues. When
the vestibular space that is distal and lateral to the alveolar tubercles is properly filled with
denture flange the stability and retention of the maxillary denture is greatly enhanced. To
effectively record the maxillary buccal sulcus the mouth should be half way closed because
wide opening of the mouth narrows the space and does not allow proper contouring of sulcus
because the coronoid process of mandible comes closer to the sulcus.
Buccal Vestibule: It extends from buccal frenum or
from the first premolar area to the hamular notch.
It is bounded anteriorly by the buccal frenum, laterally
by the buccal mucosa and medially by residual
alveolar ridge.
It is influenced mainly by the modiolus and buccinator
muscle, and distally by the coronoid process.
22. Clinical Considerations: Overextending distal to the notch will usually cause
extreme discomfort and soarness due to interference with the ascending ramus of the
mandible. Under extension will lead to poor retention. It aids in achieving posterior
palatal seal area. Discomfort and loss of seal in posterior border will occur if dentist is
incapable of identifying and marking this critical area.
Hamular Notch: Also called as
Pterygomandibular Notch is a displaceable area ,
about 2mm wide, between the tuberosity of the
maxilla and the hamulus of the medial pterygoid
plate.
It is necessary to locate this area because it identifies
the important distal end of the denture.
23. Clinical Considerations: They are used by dental technicians to determine
the posterior border of denture but they are not so reliable. There are no clinical
significance.
Fovea Palatini: They are two small indentations
that are on each side of the midline usually on the
distal end of the hard palate.
They are the remnants of ducts coalescence.
They indicate the vicinity of posterior palatine seal
area.
24. Posterior Palatal Seal Area/ Post Dam Area: PPS area
lies between the anterior and posterior vibrating lines.
It is the soft tissue at or along the juntion of soft and hard palate
on which the pressure within physiological limits of the tissue
can be applied by a denture to aid in the retention of the denture.
It consists of:
1. Pterygomaxillary seal- The part of the PPSA that
extends across the hamular notch. It extends 3-4mm
anterolaterally to end in the mucogingival junction on the
posterior part of the maxillary ridge.
2. Posterior Palatal Seal- This is a part of PPSA that
extends between the two maxillary tuberosity.
25. Clinical Considerations: It reduces the tendency of gag reflex. It
maintains contact of the denture with the soft tissue and decreases food
accumulation with adequate tissue compressibility. It increases retention
and stability by creating partial vacuum.
Vibrating Lines: Also called “Ah” line is an area at, or
distal to the junction of hard and soft palate where the
movement occurs when the patient says “ah”.
The Anterior vibrating line is an imaginary line located at the
junction of attached tissue overlying the hard palate and
adjacent movable tissue overlying the soft palate.
The Posterior vibrating line is an imaginary line at the junction
of the aponeurosis of the Tensor veli palatini muscle and the
muscular portion of the soft palate.
26. HOUSE CLASSIFICATION
Class I : More than 5mm of movable tissue
available for post-damming; Ideal for retention.
The posterior border and the posterior palatal seal are two of the most
critical areas for maxillary denture retention. In most instances , the
denture should end distal to the hard palate, it should not extend too far
or there will be irritation to the muscles of the soft palate
27. Class II : 1-5mm of movable tissue
available for post-damming; good
retention is usually possible.
Class III : Less than 1mm movable tissue
available for post-damming; retention is
usually poor.
28. Stress Bearing Areas:
Primary Stress Bearing Area-
The areas that are most capable of bearing the masticatory
load providing a proper support to the denture.
The Primary Stress Bearing area are:
1. Hard Palate: The shape of the hard palate in cross
section is either flat , rounded U-shaped or V-shaped.
It is covered by Keratinized squamous epithelium.
Anterolaterally the mucosa contains adipose tissue and
posterolaterally it contains glandular tissue.
Clinical Significance: The horizontal portion of the hard
palate provides the primary denture stress bearing area.
29. Clinical Considerations: It is the foundation of the denture.
2.Posterior Residual Alveolar Ridges : They are
the residual bone left after removal of all the teeth.
They are considered as the most important areas of
support because the ridges are considered least likely to
resorb under pressure.
The residual ridge consists of mucosa , submucosa,
periosteum and residual alveolar bone.
30. Secondary Stress Bearing Area-
Anterior Residual Ridge: The anterior alveolar ridge
is considered as a secondary area of support as the anterior
ridge seems to be more susceptible to resorption
Rugae: They are raised areas of dense connective tissue
radiating from the midline in the anterior one-third of the
palate.
Clinical Considerations: Both acts as Secondary stress bearing areas. Rugae are
concerned with phonetics. It increases the surface area of the foundation and thus
supplement the values of retention. It is the denture stabilizing area in the maxillary
foundation. They are often compressed or distorted from an ill fitting denture and should
be allowed to return to their normal form prior to impression making.
31. Clinical Considerations: Often there is lateral and vertical growth of tuberosity and the
area assumes importance when maxillary antrum extends laterally with undercuts at the
tuberosity region. It is important to prevent oro-antral fistula so it is important to have
radiograph before resection of the tuberosity. It can be used for the retention of the denture.
Tuberosity should be resected on one side only i.e. if patient is right side chewer we should
retain that sided tuberosity.
Maxillary Tuberosity: It is the distal most part
of the residual alveolar ridge and presents the hard
tissue landmarks.
It is the bulbous extension of the residual ridge in
the 2nd and 3rd molar region.
32. Relief Areas:
Incisive Papilla: It is a pad of
fibrous connective tissue overlying the
bony exit of the nasopalatine vessels
and nerves.
Clinical Considerations: It should not be displaced or compressed while
impression making. Denture pressure on the papilla can cause parasthesia, pain, a
burning sensation, other vague complaints, so some relief should be provided. It is a
biometric guide giving information on positional relation to central incisors which
are about 8-10 mm anterior to incisive papilla. Biometric guide which gives us
information about location of maxillary canines.
33. Clinical Considerations: During final impression procedure this raphe is
relieved in order to create equilibrium between the resilient and non-resilient
tissues.
Median Palatine Raphe/ Mid Palatine
Suture: The junction of palatine processes of
the maxillae are often raised and covered with
only a thin layer of mucosa.
It is the area extending from the incisive
papilla to the distal end of the hard palate .
34. Clinical Considerations: The area of the torus can be cut out of the centre of the
denture and the use of 1.5mm wide and 1mm deep bead on the inside of the denture around
the torus may suffice adequate retention. A roofless denture is indicated when the ridges are
large and the opposing arch is a denture. The patient should be informed that the retention
may be compromised in cased where surgery is not performed.
Maxillary Torus/ Torus Palatinus:
It is often found near the centre of hard
palate.
It can be of small size that can be relieved
using pressure-indicating paste or a very
large growth that should be surgically
removed.
37. Clinical Consideration: During final impression procedure the lip has to be
reflected anteriorly and horizontally. During final impression procedure and in final
prosthesis provision should be made in the form of notch to prevent overriding of
function which may result in laceration. The activity in this area seems to be vertical
thus notch in denture should be narrow.
Limiting Structures:
Labial Frenum: It is usually a single narrow band
but may consists of two or more bands.
The mandibular frenum is usually shorter and often
wider than maxillary labial frenum.
38. Clinical Consideration: For effective border contact between denture and tissue,
the vestibule should be completely filled with impression material during impression
procedure. Due to orbicularis oris the impression should not be overextended. Careful
Border Molding is required.
Labial Vestibule: It is the sulcus between the
buccal frenums, or between the first premolars if
the frenums are absent or in an unusual location.
The major muscle in this area is the orbicularis
oris whose fibres are mainly horizontal.
The mentalis muscle originates from the mental
tubercles and inserts in the lower lip. It is vertical
muscle and may be very active in some patients.
39. Clinical Consideration: During final impression procedure and final prosthesis
sufficient relief should be given to prevent overriding of function of frenum which
may result in laceration. The contour of the denture will be a little narrower in this
area due to activity of depressor anguli oris muscle.
Buccal Frenum: They are usually in the area of
the first premolar.
It may be single band but it is often two or more
bands .
The oral activities in this area are horizontal as
well as vertical.
Movements such as puckering and grinning etc.
are seen.
40. Clinical Consideration: This space constitutes an area to be completely filled by
impression material during impression procedure. It is necessary to limit the lateral content
of buccal flange in the region where the masseter muscle is in function (anterior fibers) may
push against the distal part of buccinator muscle, failure of which may cause soreness of
tissue when heavy pressure is applied.
Buccal Vestibule: It is bounded anteriorly by the buccal
frenum, posteriorly by the massetric notch area, medially by
residual alveolar ridge and laterally by buccal mucosa.
It is an area of esthetic consideration. The buccal flange covers
about 5 mm or more of fibers of buccinator in this area but since
it runs in a horizontal manner in the anteroposterior direction, it
is not a dislodging factor.
Anatomically the buccinator muscle is three muscles with
separate innervations. The middle fibres are primarily active in
food bolus formation. The upper and lower fibres are relatively
flaccid especially at area of origin.
41. Clinical Consideration: Sufficient relief should be given in the final impression and
the final denture to prevent overriding of function of frenum. During impression procedure
touch the tip of the tongue to the incisive papilla region. Careful clearance is required as
inadequate clearance may result in pain and displacement of the denture.
Lingual Frenum: It is a fibrous band of tissue that
overlies the centre of the genioglossus muscle.
It is usually a narrow single band of tissue but may be
broad and exist as two or more frenums.
It is the mucobuccal fold that joins the alveolar
mucosa to the tongue.
42. Clinical Considerations: It is quite prominent in some patients and may even
require a notch-like clearance. A simple wide-open visual and digital inspection will
usually determine whether or not clearance is necessary.
Pterygomandibular Raphe: It originates
from the pterygoid hamulus of the medial
pterygoid lamina and attaches to the distal end
of the mylohyoid ridge.
It is partly the origin of the buccinator muscle
laterally and the superior constrictor muscle
medially
43. Alveolingual Sulcus/ The Lingual Vestibule:
The space between the residual ridge and the tongue.
It extends from the lingual frenum to the
retromylohyoid curtain.
It is divided into:
1. Anterior vestibule / the sublingual crescent area / premylohyoid / anterior sublingual
fold.
2. Middle vestibule/the alveolingual sulcus/ mylohyoid area.
3. Distolingual vestibule / lateral throat form / retromylohyoid fossa / lingual pouch.
44. Clinical Considerations: If the mandibular ridge is highly resorbed the attachment of the
genioglossus lies almost at the level of the crest of the alveolar ridge. Surgical sulcus deepening
may be required in such scenarios. The width of the border of the denture in this region is
usually about 2mm.But the width depends on the tonicity of the genioglossus.The genioglossus
and the lingual frenum are recorded by asking the patient to moderately protrude the tongue as
these tissues do not tolerate impingement.
Anterior Lingual Vestibule: Also known as
sublingual crescent area or anterior sublingual fold.
It extends from the lingual foramen to the point where
the mylohyoid ridge curves down below the level of the
sulcus.
Lingual frenum is superimposed over the genioglossus
which raises the tongue
45. Clinical Considerations: The length and width of the mylohyoid flange is
determined by the membranous attachment of the tongue to the mylohyoid ridge and the
width of the hypoglossus muscle and can only be determined by skillful border molding
and impression procedures.
Middle Vestibule: Also known as mylohyoid vestibule.
Forms the largest part of the alveololingual sulcus
Influenced by:
Mylohyoid muscle
Sublingual glands
46. Distolingual Vestibule :Also known as lateral throat form or
retromylohyoid fossa.
Boundaries -
Anteriorly– Mylohyoid Muscle
Laterally– Pear Shaped Pad
Postero-laterally– Superior Constrictor Muscle
Postero-medially– Palatoglossus
Medially– Tongue
47. NEIL CLASSIFICATION
•Class I: Low -1/2 inch or more from the
mylohyoid ridge to the bottom of the retro-
mylohyoid fold, visible when the tongue is
in a slightly protruded position. Most
favorable.
•Class II:Medium -Less than 1/2 inch under
the same conditions as above.
•Class III: High -Retromylohyoid fold at
same level as mylohyoid ridge. Least
favorable.
48. Retromylohyoid Curtain: It is a wall of mucous
membrane which limits distolingual part of denture
flange.
It overlies the superior constrictor muscle in the postero-
lateral portion and covers the palatoglossus and the
lateral surface of the tongue in the postero-medial
portion.
The medial pterygoid muscle lies just posterior to it.
Contraction of medial pterygoid can cause a bulge in the
wall of Retromylohyoid curtain.
49. The “S” curve of the mandibular denture, results from the stronger
intrinsic and extrinsic tongue muscles, which usually places the
retromylohyoid borders more laterally and toward the retromolar fossa than in
the mylohyoid area.
The proper extension of the mandibular denture into the lingual sulcus, within
their anatomical and functional limits, ensure a proper peripheral seal.
Also, these flanges present favorable inclined planes to the tongue resulting in
vectors of forces that help maintaing the mandibular denture in place.
50. Clinical Consideration: When mouth is opened widely the borders cut into the tissue
so it should be recorded. During impression procedure in the area of massetric notch
downward pressure is applied and the patient is asked to close the mouth against the
pressure. Overextension of denture causes dislodgement of denture and laceration
Massetric Notch : It is immediately
lateral to retromolar pad and continuous
anteriorly to buccal vestibular sulcus..
It is due to the contraction of masseter
that a depression is formed at the
distobuccal corner of retromolar pad.
51. Clinical Considerations: It presents an area of compact bone which by virtue of its
deposition is horizontal and therefore is best suited to receive masticatory stresses in the
vertical direction. It is the primary stress bearing area in the mandibular foundation. It is
advisable to extend the impression beyond the external oblique ridge failures may be due to:
Inadequate selection of impression tray. Involuntary effort on part of the operator.
Primary Stress Bearing Area:
Buccal Shelf Area: It can range from 4-6mm wide
on an average mandible to 2-3mm or less in a narrow
mandible.
Area of compact bone which is bounded laterally by
external oblique ridge and medially by crest of
mandibular ridge.
52. Clinical Consideration: Helps in maintaining the occlusal plane. Divide retromolar pad
into anterior 2/3rd and posterior 1/3rd. Posterior height of occlusal rim should not cross
anterior 2/3rd. Helps in arranging mandibular posterior teeth. Draw a line from highest point
in canine region to the apex of the retro molar triangle extending it to the land of the cast.
The central fossa of all posterior teeth should lie on this crestal line. Teeth should not be
placed on the retro molar pad. Because of muscular tendinous elements the area should not
be subjected to pressure
Retromolar Pad/ Retromolar Triangle: It is pear
shaped body at the distal end of the residual alveolar ridge.
It represents distal limit of mandibular denture.
It has muscular and tendinous elements. Few fibers of
temporalis. Few fibers of masseter. Few fibers of
buccinator. Fibers of superior constrictor muscles of
pharynx. Tendinous mandibular raphe.
53. Retromolar Papilla
1. Termed by Craddock .
2. Refers to the area formed by the
residual scar of 3rd molar and
retromolar papilla. The mucosa is
usually attached gingiva.
3. Mucosa:
Firm.
Stippled.
Dull appearance.
Pear Shaped Pad
1. Termed by Sicher.
2. A soft elevation of mucosa that
lies distal to the 3rd molar. It
contains loose connective tissue
with an aggregation of mucous
glands. It is covered by a
smoother, less hornified epithelium
than that seen over the gingiva.
3. Mucosa:
Soft.
Non stippled.
Shiny appearance.
54. Clinical Considerations: It is used as stress bearing area.
Secondary Stress Bearing Area:
Residual Alveolar Ridge: The alveolar process is
the process of the mandible that surrounds the roots of
the natural teeth.
The right and left alveolar processes combine to form the
mandibular arch.
After natural teeth are extracted, the remnant of the
alveolar process is called the residual ridge. As time goes
on, a residual ridge usually resorbs.
As the ridge is often poor so it is considered as secondary
stress bearing area.
55. Clinical Consideration: It is best to cover the torus to the height of contour and finish
the denture borders around the torus as thick as tongue will tolerate. If surgical correction is
contraindicated then the patient should be informed that the results will be compromised.
Lingual Tori/ Torus Mandibularis: They are bony
protuberances that are ordinarily located in the premolar
area.
They are usually bilateral and sometimes may be on one
side only.
The tori rarely increases in size but the mucosal covering
tends to be very thin and any settling will cause pain and
discomfort.
Relief Areas:
56. Clinical Considerations: It should be relieved with the wax spacer, failure of which
lead to ulceration. In severly resorbed ridge it is seen above the residual alveolar ridge
and hence it should be relieved.
Genial Tubercle: Usually seen below the crest of
the ridge.
Mucosa covering the genial tubercles is thin and
tightly adherent to the underlying bone.
57. Clinical Considerations: In these cases, relief of the denture is necessary to avoid
excessive pressure on the nerve fibers which exit from this foramen, compression results in
loss of sensation in the lower lip.Relief in this case is defined as space provided between the
undersurface of the denture and the soft tissue to reduce or eliminate pressure on certain
anatomical structures.
Mental Foramen: They are the foramina in bone
normally found on the buccal surface of the alveolar
ridge.
It is located between and slightly below the root tips
of the first and second premolar teeth.
When resorption of the alveolar ridge is drastic, the
mental foramen is found below the oral mucosa on the
crest of the alveolar process.
58. CONCLUSION
It is necessary to review the important structures that are directly related to
impression making.
It is also important to know their function and to be aware of anatomical variations.
Successful accomplishment of complete denture treatment constitutes a joint
responsibility of both the operator and the patient by way of correctly participating in
the treatment procedures.
It is imperative that apart from the knowledge of all the above factors of anatomical
and physiological relevance in treatment procedures, execution of the factors, digital
dexterity and communication skills of the operator are of paramount importance.
Thus, the diagnostic and clinical acumen of the operator constitute important
considerations in the application of above knowledge.
59. REFERENCES
Impressions for complete denture, Bernard Levin
Zarb,Bolender,Carlson Boucher’s prosthodontic treatment for edentulous patients,13th
edition ,9th edition
Sheldon Winkler Essentials of complete denture Prosthodontics,ed.2
Heartwell Charles syllabus for complete dentures Ed.4,Philadelphia
B D Chaurasia Human Anatomy Fifth Edition
Orban’s Oral histology and embryology
Anatomic landmarks in a maxillary and mandibular ridge - A clinical perspective by
Mohd. Azeem, Ashraf Mujtaba, Shrestha Subodh, Ahmad Naeem, Gaur Abhishek and
Pandey Kaushik Kumar