2.anatomy of the denture foundation areas

2. Anatomy of the Denture 2. Anatomy of the Denture Foundation AreasFoundation Areas

Eleni Roumanas, DDSEleni Roumanas, DDSDivision of Advanced Prosthodontics, Biomaterials and Hospital Division of Advanced Prosthodontics, Biomaterials and Hospital

DentistryDentistryUCLA School of DentistryUCLA School of Dentistry

andandFrank Lauciello DDSFrank Lauciello DDS

Ivoclar VivadentIvoclar Vivadent

This program of instruction is protected by copyright ©. No portion of This program of instruction is protected by copyright ©. No portion of this program of instruction may be reproduced, recorded or transferred this program of instruction may be reproduced, recorded or transferred by any means electronic, digital, photographic, mechanical etc., or by by any means electronic, digital, photographic, mechanical etc., or by any information storage or retrieval system, without prior permission.any information storage or retrieval system, without prior permission.

EDENTULOUS ANATOMYEDENTULOUS ANATOMY

In order to properly construct a denture, one must In order to properly construct a denture, one must understand the anatomy and physiology of the edentulous understand the anatomy and physiology of the edentulous patient. A thorough knowledge of the origins and kinetics patient. A thorough knowledge of the origins and kinetics of the muscles of mastication, facial expression, tongue of the muscles of mastication, facial expression, tongue and floor of the mouth is essential.and floor of the mouth is essential.

Key Concepts in ProsthodonticsKey Concepts in ProsthodonticsRetentionRetention:: Resistance to vertical displacement Resistance to vertical displacement

away from the bearing surfaces away from the bearing surfacesStabilityStability:: Resistance to lateral displacement Resistance to lateral displacementSupportSupport:: Factors of the bearing surfaces that Factors of the bearing surfaces that

absorb or resist forces of occlusionabsorb or resist forces of occlusion

When the key anatomic landmarks and their role with respect to When the key anatomic landmarks and their role with respect to retention, stability, support, preservation and esthetics are retention, stability, support, preservation and esthetics are mastered, dentures can be fabricated as integral parts of each mastered, dentures can be fabricated as integral parts of each patient’s oral cavity and not just mechanical artificial substitutes.patient’s oral cavity and not just mechanical artificial substitutes.

Factors that impact the above:Factors that impact the above:The nature of the bearing The nature of the bearing mucosamucosa--attached vs. unattachedattached vs. unattached-degree of keratinization-degree of keratinizationBoneBone contours and retromolar pad contours and retromolar pad--height and contour of alveolar ridgeheight and contour of alveolar ridge-presence of tori-presence of tori-resorption patterns-resorption patternsMuscleMuscle attachments attachments--frenumfrenum-floor of mouth, mylohyoid, retromylohyoid space-floor of mouth, mylohyoid, retromylohyoid space-tongue posture-tongue postureSalivaSaliva--flow ratesflow rates-palatal glands and posterior palatal seal-palatal glands and posterior palatal seal-effect on retention-effect on retentionDisease factorsDisease factors--candida, angular cheilitis, epulis fissuratumcandida, angular cheilitis, epulis fissuratum

Labial frenumLabial frenum

Buccal vestibuleBuccal vestibule

Buccal frenumBuccal frenum

Maxilla-Anatomic LandmarksMaxilla-Anatomic Landmarks

Frenum-Frenum- are folds of are folds of mucous membranemucous membrane and do not contain significant and do not contain significant muscle fibers. High frenum attachments will compromise denture muscle fibers. High frenum attachments will compromise denture retentionretention and may require surgical excision (frenectomy). and may require surgical excision (frenectomy).

Buccal vestibuleBuccal vestibule-when properly filled with the denture flange greatly -when properly filled with the denture flange greatly enhances enhances stabilitystability and and retentionretention..

Incisive papillaIncisive papillaCanine eminenceCanine eminence


Canine eminanceCanine eminance- This prominent bone provides denture- This prominent bone provides denture support support. A . A square arch prevents a denture from rotating and is thus the best for square arch prevents a denture from rotating and is thus the best for denture denture stabilitystability..Incisive papillaIncisive papilla- Is a pad of fibrous connective tissue overlying the - Is a pad of fibrous connective tissue overlying the orifice of the orifice of the nasopalatine canalnasopalatine canal. Pressure in this area will cause a . Pressure in this area will cause a disruption of blood flow and impingement on the nerve, causing the disruption of blood flow and impingement on the nerve, causing the patient to complain of pain or a burning sensation. The denture patient to complain of pain or a burning sensation. The denture should be relieved over this area.should be relieved over this area.

Post. Palatal Post. Palatal Seal AreaSeal Area

TuberosityTuberosity


TuberosityTuberosity- is an important - is an important primary denture support areaprimary denture support area. It also . It also provides resistance to horizontal movements of the denture.provides resistance to horizontal movements of the denture.

Posterior Palatal Seal AreaPosterior Palatal Seal Area- Is distal to the junction of the hard and - Is distal to the junction of the hard and soft palate at the soft palate at the vibrating linevibrating line..


RugaeRugae

Rugae-Rugae-raised areas of raised areas of dense connective tissuedense connective tissue in the anterior 1/3 of the palate. in the anterior 1/3 of the palate. This area This area resists anterior displacement of the dentureresists anterior displacement of the denture and is a and is a secondary secondary support area. support area.

Hamular Notch-Hamular Notch- this narrow cleft extends from the tuberosity to the pterygoid this narrow cleft extends from the tuberosity to the pterygoid muscles. The muscles. The pterygomandibular ligamentpterygomandibular ligament attaches to the pterygoid hamulus attaches to the pterygoid hamulus which is a thin curved process at the terminal end of the medial pterygoid plate which is a thin curved process at the terminal end of the medial pterygoid plate of the sphenoid bone. The hamular notch is critical to the design of the of the sphenoid bone. The hamular notch is critical to the design of the maxillary denture. Improper molding of this area could lead to soreness and maxillary denture. Improper molding of this area could lead to soreness and loss of retention.loss of retention.

Hamular NotchHamular Notch

CoronoidCoronoidprocessprocess


Fovea palatinaFovea palatina

Coronoid processCoronoid process- the patient is allowed to open wide, protrude and go into - the patient is allowed to open wide, protrude and go into lateral movements. The lateral movements. The width of the distobuccal flangewidth of the distobuccal flange will then be will then be contoured by the anterior border of the coronoid process.contoured by the anterior border of the coronoid process.Fovea palatinaFovea palatina- usually two, slightly posterior to the junction of the hard and - usually two, slightly posterior to the junction of the hard and soft palates.soft palates.Minor salivary glandsMinor salivary glands- in the - in the posterior third of the hard palateposterior third of the hard palate the tissue is the tissue is very glandular and displaceable. The impression surface may appear very glandular and displaceable. The impression surface may appear irregular as the glandular secretions will adhere to the impression material.irregular as the glandular secretions will adhere to the impression material.

Minor salivary glandsMinor salivary glands


Zygomatico-alveolar crest

Zygomatico-alveolar crestZygomatico-alveolar crest- the crest has been likened to the buccal - the crest has been likened to the buccal shelf in the mandible as a stress bearing area. However, the mucosal shelf in the mandible as a stress bearing area. However, the mucosal coverage is usually very thin and although the bone is in good position coverage is usually very thin and although the bone is in good position for stress bearing, the mucosa is not considered desirable for this for stress bearing, the mucosa is not considered desirable for this purpose (thin mucosa). purpose (thin mucosa).

Hard palate- consists of the two horizontal palatine processes and appears to resist resorption. For this reason it is a primary support area for the maxillary denture. The configuration of a high palate is not conducive to the stability and support of a denture due to the inclined planes.Midline palatal suture- extends from the incisive papilla to the distal end of the hard palate. The overlying mucosa is tightly attached and thin, relief is usually required to prevent soreness. The underlying bone is dense and often raised forming a torus palatinus.Major palatine foramen- the orifice of the anterior palatine nerve and blood vessels. Relief in this area is usually not required due to the abundant overlying tissues.

Maxilla-Anatomic LandmarksMaxilla-Anatomic LandmarksMidline palatalsuture

Major palatineforamen

Hard palate

Ideal Maxillary RidgeIdeal Maxillary Ridge

Abundant Abundant keratinizedkeratinized attachedattached tissuetissueSquare archSquare archU-shaped in cross-sectionU-shaped in cross-sectionModerate palatal vaultModerate palatal vaultAbsence of undercutsAbsence of undercutsFrenal attachments distal from Frenal attachments distal from crestal ridges as much as possiblecrestal ridges as much as possibleWell defined hamular notchesWell defined hamular notches

Excellent prognosisExcellent prognosis Good prognosisGood prognosis

Poor prognosisPoor prognosis Very poor prognosisVery poor prognosis

Denture prognosis based on anatomic findings:Denture prognosis based on anatomic findings:

Mandible-Anatomic LandmarksMandible-Anatomic LandmarksFrenaFrena

Buccal shelfBuccal shelf

Mylohyoid ridgeMylohyoid ridge

Retromolar padRetromolar pad

Sublingual crescentSublingual crescent

Labial vestibuleLabial vestibule

Buccal VestibuleBuccal Vestibule

Masseter grooveMasseter groove

RetromylohyoidRetromylohyoid

Lingual sulcusLingual sulcus

Mandible-Anatomic LandmarksMandible-Anatomic Landmarks

Labial frenumLabial frenum- histologically and functionally the same as in the maxilla, - histologically and functionally the same as in the maxilla, mucous membranemucous membrane without significant muscle fibers. without significant muscle fibers.

Labial flange spaceLabial flange space

Labial FrenumLabial Frenum


Labial vestibuleLabial vestibule

Labial vestibuleLabial vestibule- limited inferiorly by the mentallis muscle, - limited inferiorly by the mentallis muscle, internally by the residual ridge and labially by the lip.internally by the residual ridge and labially by the lip.MentalisMentalis- - elevates the skin of the chin and turns the lower lip elevates the skin of the chin and turns the lower lip outward. dictates the length and thickness outward. dictates the length and thickness of the labial flange of the labial flange extensionextension of the lower denture. of the lower denture.

MENTALIS MUSCLEOrigin – crest of ridgeInsertion – chinAction – raises the lower lip


Alveolar ridgeAlveolar ridge- is a - is a secondary support areasecondary support area. High rate of resorption . High rate of resorption when excessive pressure is applied to this area.when excessive pressure is applied to this area.

Buccal frenumBuccal frenum- histologically and functionally the same as in the maxilla.- histologically and functionally the same as in the maxilla.

Buccal Frenum

Buccal Buccal FrenumFrenum

Alveolar RidgeAlveolar Ridge


Buccal ShelfBuccal Shelf- bordered externally by the external oblique line and - bordered externally by the external oblique line and internally by the slope of the residual ridge. This region is a internally by the slope of the residual ridge. This region is a primary primary stress bearing area in the mandibular archstress bearing area in the mandibular arch.

Buccal Buccal shelfshelf

The buccal shelf is a prime support area because it is parallel to the The buccal shelf is a prime support area because it is parallel to the occlusal plane and the bone is very dense. These two factors make occlusal plane and the bone is very dense. These two factors make it relatively resistant to resorptionit relatively resistant to resorption..

Buccal shelf area (area within the dotted lines). The greater the Buccal shelf area (area within the dotted lines). The greater the access to the buccal shelf the more support there is available for the access to the buccal shelf the more support there is available for the denture. Access is determined by the attachment of the buccinator.denture. Access is determined by the attachment of the buccinator.

Buccal ShelfBuccal Shelf

Buccal ShelfBuccal Shelf

The size and position of the buccal shelf The size and position of the buccal shelf varies relative to the degree of alveolar varies relative to the degree of alveolar ridge resorptionridge resorption.

Moderate resorptionModerate resorption

Severe resorptionSevere resorption

Dentate Mandible-No resorptionDentate Mandible-No resorption


External Oblique LineExternal Oblique Line- a ridge of dense bone from the mental foramen, - a ridge of dense bone from the mental foramen, coursing superiorly and distally to become continuous with the anterior coursing superiorly and distally to become continuous with the anterior region of the ramus. Is the region of the ramus. Is the attachment site of the buccinator muscleattachment site of the buccinator muscle and and an an anatomic guide for the lateral termination of the buccal flange of the anatomic guide for the lateral termination of the buccal flange of the mandibular denturemandibular denture..

External External ObliqueObliqueLineLine


Mental ForamenMental Foramen- the anterior exit of the mandibular canal and the - the anterior exit of the mandibular canal and the inferior alveolar nerve. In cases of severe residual ridge resorption, the inferior alveolar nerve. In cases of severe residual ridge resorption, the foramen occupies a more superior position and the denture base must foramen occupies a more superior position and the denture base must be be relievedrelieved to prevent nerve compression and pain. to prevent nerve compression and pain.

One constant, relatively unchanging structure on the mandibular denture One constant, relatively unchanging structure on the mandibular denture bearing surface is the retromolar pad (dotted line).bearing surface is the retromolar pad (dotted line).

The pad contains glandular tissue, loose areolar connective tissue, the The pad contains glandular tissue, loose areolar connective tissue, the lower margin of the pterygomandibular raphe, fibers of the buccinator, and lower margin of the pterygomandibular raphe, fibers of the buccinator, and superior constrictor and fibers of the temporal tendon. The bone beneath superior constrictor and fibers of the temporal tendon. The bone beneath does not resorbdoes not resorb secondary to the pressure associated with denture use. It secondary to the pressure associated with denture use. It is is one of the primary support areas.one of the primary support areas.

Retromolar PadRetromolar Pad

Mandibular-Anatomic LandmarksMandibular-Anatomic Landmarks

Masseter GrooveMasseter Groove- the action of the - the action of the masseter masseter muscle reflects the buccinator muscle in a muscle reflects the buccinator muscle in a superior and medial directionsuperior and medial direction. The . The distobuccal flange of the denture should be distobuccal flange of the denture should be contoured to allow freedom for this action contoured to allow freedom for this action otherwise the denture will be displaced or otherwise the denture will be displaced or the pt. will experience soreness in this area.the pt. will experience soreness in this area.

MasseterMasseterGrooveGroove

MasseterMasseterGrooveGroove

Suprahyoid MusclesSuprahyoid MusclesFunction in elevation of the Function in elevation of the hyoid bone and the larynx and hyoid bone and the larynx and depression of the mandible.depression of the mandible.•DigastricDigastric•StylohyoidStylohyoid•MylohyoidMylohyoid•GeniohyoidGeniohyoid

Mylohyoid muscleMylohyoid muscle- forms the - forms the muscular floor of the mouthmuscular floor of the mouth. Arises from . Arises from the mylohyoid ridge of the mandible. Determines the lingual flange the mylohyoid ridge of the mandible. Determines the lingual flange extension of the denture.extension of the denture.

Mandibular-Anatomic Landmarks

Mylohyoid RidgeMylohyoid Ridge

Note the position of the mylohyoid ridge Note the position of the mylohyoid ridge as it varies relative to the degree of as it varies relative to the degree of alveolar ridge resorptionalveolar ridge resorption..

Moderate resorptionModerate resorption

Severe resorptionSevere resorption

Dentate Mandible-No resorption

Mylohyoid RidgeMylohyoid Ridge

Palpate the mylohyoid ridge to Palpate the mylohyoid ridge to determine its contour, sharpness determine its contour, sharpness and degree ofand degree ofundercutundercut.

Geniotubercle(Mental Spines)-Geniotubercle(Mental Spines)- present on the anterior surface of the present on the anterior surface of the mandible and serve as the mandible and serve as the attachment sites of the genioglossus and attachment sites of the genioglossus and geniohyoid musclesgeniohyoid muscles. In pts. with severe ridge resorption the . In pts. with severe ridge resorption the geniotubercles may cause discomfort if they are exposed to the denture geniotubercles may cause discomfort if they are exposed to the denture base.base.


Genial TuberclesGenial Tubercles

Lingual frenumLingual frenum- overlies the genioglossus muscle, which takes origin - overlies the genioglossus muscle, which takes origin from the superior genial spinefrom the superior genial spine

Sublingual Folds-Sublingual Folds- formed by the superior surface of the sublingual formed by the superior surface of the sublingual glands and the ducts of the submandibularglands and the ducts of the submandibular glands


Sublingual foldsSublingual folds

Lingual FrenumLingual Frenum


Retromylohyoid space- lies at the distal end of the alveolingual sulcus. Bounded medially by the anterior tonsilar pillar, posteriorly by the retromylohyoid curtain which is formed posteriorly by the superior constrictor muscle, laterally by the mandible and pterygomandibular raphe, anteriorly by the lingual tuberosity of the mandible and inferiorly by the mylohyoid muscle.***The retromylohyoid space is very important for denture stability and retention.

Ideal Mandibular RidgeIdeal Mandibular Ridge

Well defined retromolar padWell defined retromolar padBlunt mylohyoid ridge Blunt mylohyoid ridge Deep retromylohyoid spaceDeep retromylohyoid spaceLow frenum attachmentsLow frenum attachmentsAbsence of undercutsAbsence of undercutsAbundant attached keratinized mucosaAbundant attached keratinized mucosaAdequate alveolar heightAdequate alveolar height

MandibleMandible –Note the varying degrees of ridge width and height –Note the varying degrees of ridge width and height

Mandibular Ridge QualityMandibular Ridge Quality

Support and retention will be affectedSupport and retention will be affected

TongueTongueIntrinsic MusclesIntrinsic Muscles-originate and insert within the -originate and insert within the tongue. Produce changes in the tongue. Produce changes in the shape of the tongueshape of the tongueExtrinsic MusclesExtrinsic Muscles-originate in structures outside the -originate in structures outside the tongue and can move the tongue tongue and can move the tongue and alter its shapeand alter its shape

GenioglossusGenioglossusStyloglossusStyloglossusHyoglossusHyoglossusPalatoglossusPalatoglossus

******The denture flanges must be contoured to allow the tongue to have its The denture flanges must be contoured to allow the tongue to have its normal range of functional movements. normal range of functional movements.

Retruded tongue postureRetruded tongue posture

***Approximately 35% of tongues are abnormal in either size, position or shape.***Approximately 35% of tongues are abnormal in either size, position or shape.***A ***A retruded tongueretruded tongue position is very unfavorable for denture retention and position is very unfavorable for denture retention and function.function.

MyologyMyologyMuscles of Facial ExpressionMuscles of Facial Expression -Generally do not insert in bone and need -Generally do not insert in bone and need

support from the teeth for proper support from the teeth for proper function.function.ModiolusModiolusMentalisMentalisBuccinatorBuccinatorOrbicularis OrisOrbicularis OrisIncisivus Labii SuperiorusIncisivus Labii Superiorus& Inferiorus& Inferiorus

ModiolusModiolus- situated - situated laterally and slightly superiorly to the corner of the mouthlaterally and slightly superiorly to the corner of the mouth is is a concentration of many fibers of this muscle group. This is an area where a concentration of many fibers of this muscle group. This is an area where extrinsic perioral muscles decussate to join intrinsic fibers of the orbicularis extrinsic perioral muscles decussate to join intrinsic fibers of the orbicularis oris muscleoris muscle. It is a very forceful area which can influence the labial flange . It is a very forceful area which can influence the labial flange thickness of the maxillary denture.thickness of the maxillary denture.

BuccinatorBuccinator- provides support and mobility of the soft tissues of the cheek. The - provides support and mobility of the soft tissues of the cheek. The muscle muscle fibers contract in a line parallel to the plane of occlusionfibers contract in a line parallel to the plane of occlusion. As a . As a person person ages, tension is lost in this muscle and predisposes them to cheek biting.ages, tension is lost in this muscle and predisposes them to cheek biting.

MyologyMyologyMuscles of Facial ExpressionMuscles of Facial Expression --Generally do not insert in bone and Generally do not insert in bone and

need support from the teeth and need support from the teeth and denture flanges for proper function.denture flanges for proper function.ModiolusModiolusBuccinatorBuccinatorMentalisMentalisIncisivus Labii SuperiorusIncisivus Labii Superiorus&Inferiorus&InferiorusOrbicularis OrisOrbicularis Oris

MentalisMentalis- - elevates the skin of the chin and turns the lower lip outward. Dictates elevates the skin of the chin and turns the lower lip outward. Dictates the length and thickness the length and thickness of the labial flange extensionof the labial flange extension of the lower denture. of the lower denture.Incisivus Labii Superioris & InferiorusIncisivus Labii Superioris & Inferiorus- their action on the vestibular fornix are - their action on the vestibular fornix are similar to that of the mentalis muscle.similar to that of the mentalis muscle.Orbicularis OrisOrbicularis Oris- is the - is the sphincter musclesphincter muscle of the mouth. Has no skeletal of the mouth. Has no skeletal attachments, is a composite muscle, composed not only of intrinsic fibers but attachments, is a composite muscle, composed not only of intrinsic fibers but also of extrinsic fibers of many muscles that converge at the modiolus.also of extrinsic fibers of many muscles that converge at the modiolus.

Generally do not insert in bone and need support from the Generally do not insert in bone and need support from the teeth and denture flanges for proper support and functionteeth and denture flanges for proper support and function

Improper lip supportImproper lip support

Proper lip support provided Proper lip support provided by the pts. new dentureby the pts. new denture

BeforeBefore

AfterAfter

Muscles of Facial Expression:Muscles of Facial Expression:

Post Palatal RegionPost Palatal RegionMuscles of the soft palate:Muscles of the soft palate:

Tensor veli palatiniTensor veli palatiniLevator veli palatiniLevator veli palatiniMusculus uvulaeMusculus uvulaePalatoglossusPalatoglossusPalatopharyngeousPalatopharyngeous

Soft Palate Classification:Soft Palate Classification:Class 1-Class 1-Minimal elevation required to Minimal elevation required to achieve velopharyngeal closureachieve velopharyngeal closure. . Most Most favorable palate for placing an favorable palate for placing an adequate posteriorpalatal seal.adequate posteriorpalatal seal.

Class 2-Class 2-Would require more muscle Would require more muscle activity to achieve closure.activity to achieve closure.

Class 3-Class 3-Least favorable, requires Least favorable, requires considerable muscle activity for considerable muscle activity for closure of the nasopharynx and this closure of the nasopharynx and this action makes placing a posterior action makes placing a posterior palatal seal difficultpalatal seal difficult

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Velopharyngeal Closure

The House Palatal ClassificationThe House Palatal Classification

The greater the functional movement of the soft palate the less favorable the House ClassificationThe greater the functional movement of the soft palate the less favorable the House Classification

2.anatomy of the denture foundation areas

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