ANATOMICAL LANDMARKS OF DENTURE BEARING

AREA OFMAXILLA AND MANDIBLE

PRESENTED BY: Dr. BRAJENDRA SINGH TOMAR PG 1ST YEAR DEPT. OF PROSTHODONTICS

GUIDED BY:Dr. G. S. CHANDU

• THE ANATOMY OF EDENTULOUS RIDGES IN THE MAXILLA AND MANDIBLE IS VERY IMPORTANT FOR THE DESIGN OF THE COMPLETE DENTURE

• THE TOTAL AREA OF SUPPORT FROM THE MANDIBLE IS SIGNIFICANTLY LESS THAN FROM THE MAXILLA.

• THE AVERAGE AVAILABLE DENTURE BEARING AREA FOR AN EDENTULOUS MANDIBLE IS 14cm2 , WHEREAS FOR EDENTULOS MAXILLA IT IS 24cm2. THEREFORE THE MANDIBLE IS LESS CAPABLE OF RESISTING OCCLUSAL FORCES THAN THE MAXILLA.

INTRODUCTION

• THE CONSISTENCY OF THE MUCOSA AND THE UNDERLYING BONE IS DIFFERENT IN VARIOUS PARTS OF THE EDENTULOUS RIDGE

• SOME PARTS OF THE RIDGE ARE CAPABLE OF WITHSTANDING MORE FORCE THAN OTHER AREARS

THE MUCOUS MEMBRANE

SERVES AS A CUSHION BETWEEN THE DENTURE BASE AND THE SUPPORTING BONE.

MUCOUS MEMBRANE IS COMPOSED OF MUCOSA AND SUB MUCOSA.

SUBMUCOSA IS FORMED BY CONNECTIVE TISSUE THAT VARIES FROM DENSE TO LOOSE AREOLAR TISSUE

MUCOSA COVERING THE HARD PALATE AND THE CREST OF THE RIDGE IS CLASSIFIED AS MASTICATORY MUCOSA

CHARECTERIZED BY ITS WELL –DEFINED KERATINIZED EPITHELIUM AND LACK OF TISSUE MOVEMENTS.

ANATOMICAL LANDMARKS OF THE MAXILLA

LIMITING STRUCTURES SUPPORTING STRUCTURES RELIEF AREAS

LIMITING STRUCTURES

LABIAL FRENUM LABIAL VESTIBULE BUCCAL FRENUM BUCCAL VESTIBULE HAMULAR NOTCH POSTERIOR PALATAL SEAL AREA

LABIAL FRENUM

FOLD OF MUCOUS MEMBRANE

NO MUSCLE NO ACTION OF ITS OWN A “V” SHAPED NOTCH

SHOULD BE RECORDED DURING IMPRESSION MAKING

LABIAL NOTCH OF THE LABIAL FLANGE OF THE DENTURE MUST BE JUST WIDE ENOUGH AND JUST DEEP ENOUGH TO ACCOMMODATE THE LABIAL FRENUM

LABIAL VESTIBULE IT IS DIVIDED LEFT AND

RIGHT BY THE LABIAL FRENUM

ORBICULARIS ORIS IS THE MAIN MUSCLE WHICH FORMS THE OUTER SURFACE OF THE LABIAL VESTIBULE

ORBICULARIS ORIS MUSCLE HAS ONLY AN INDIRECT EFFECT ON THE LABIAL VESTIBULE BECAUSE ITS FIBERS RUN IN HORIZONTAL DIRECTION

BUCCAL FRENUM DIVIDING LINE BETWEEN

THE LABIAL AND BUCCAL VESTIBULE.

FRENUM MAY BE SINGLE OR DOUBLE.

LEVETOR ANGULI ORIS MUSCLE ATTACHES BENEATH THE FRENUM.

ORBICULARIS MUSCLE PULLS THE FRENUM FORWARD.

BUCCINATOR MUSCLE PULLS IT BACKWARD.

REQUIRE MORE CLEARENCE FOR ITS ACTION

BUCCAL VESTIBULE

EXTEND FROM BUCCAL FRENUM TO HAMULAR NOTCH

BOUNDED LATERALLY BY THE CHEEKS AND MEDIALLY BY THE RIDGE.

SIZE OF THE VESTIBULE VARIES WITH THE CNTRACTION OF BUCCINATOR MUSCLE, POSITION OF THE MANDIBLE, AND AMOUNT OF BONE LOST FROM MAXILLA.

ADEQUATE DEPTH/WIDTH SHOULD BE RECORDED

HAMULAR NOTCH

DISTAL LIMIT OF THE BUCCAL VESTINULE.

SITUATED BETWEEN THE TUBROSITY AND HAMULUS OF THE MEDIAL PTERYGOID BONE.

TENSOR VELI PALATINI MUSCLE RUNS HORIZONTALLY THROUGH THIS NOTCH.

AIDS IN ACHIEVING POSTERIOR PALATAL SEAL.

POSTERIOR PALATAL SEAL “THE SOFT TISSUE AT OR ALONG THE JUNCTION OF THE HARD

AND SOFT PALATE ON WHICH PRESSURE WITHIN THE PHYSIOLOGICAL LIMITS OF THE TISSUE S CAN BE APPLIED BY A DENTURE TO AID IN THE RETENSION OF THE DENTURE” -GPT.

PARTS:•POSTPALATAL SEAL•PTERYGOMAXILLARY SEAL

EXTENSIONS:•ANTERIORLY- ANTERIOR VIBRATING LINE•POSTERIORLY- POSTERIOR VIBRATING LINE•LATERALLY- 3-4 MM ANTERIOLATERAL TO HAMULAR NOTCH

VIBRATING LINE

“THE IMAGINARY LINE ACROSS THE POSTERIOR PART OF THE PALATE MAKING THE DIVISION BETWEEN THE MOVABLE AND IMMOVABLE TISSUES OF THE SOFT PALATE WHICH CAN BE IDENTIFIED WHEN THE MOVABLE TISSUES ARE MOVING”-GPT

Anterior &Posterior Vibrating line

SUPPORTING STRUCTURES

PRIMARY STRESS BEARING AREA

SECONDRY STRESS BEARING AREA

HARD PALATE MAXILLARY

TUBEROSITY RESIDUAL ALVEOLAR

RIDGE

HARD PALATE

COVERED BY KERATINIZED SQUAMOUS EPITHELIUM.

ANTERIOLATERALLY, THE SUBMUCOSA CONTAINS ADIPOSE TISSUE.

POSTEROLATERALLY IT CONTAINS GLANDULAR TISSUE.

THE HORIZONTAL PORTION OF THE HARD PALATE PROVIDES THE PRIMARY STRESS-BEARING AREA

MAXILLARY TUBEROSITY

IT IS THE POSTERIOR CONVEXITY OF THE MAXILLARY BODY.

THE MEDIAL AND LATERAL WALLS RESIST THE HORIZONTAL AND TORQUING FORCES WHICH WOULD MOVE THE DENTURE BASE IN LATERAL OR PALATAL DIRECTION.

THEREFORE MAXILLARY DENTURE BASE SHOULD COVER THE TUBEROSITY AND FILL THE HAMULAR NOTCHES.

RESIDUAL ALVEOLAR RIDGE

COVERED BY KERATINIZED SRATIFIED SQUAMOUS EPITHELIUM.

THE SUB MUCOSA IS CHARECTERIZED BY DENSE COLLAGENOUS FIBERS THAT ARE CONTIGUOUS WITH LAMINA PROPRIA

CONSIDERED AS A SECONDRY STRESS BEARING AREA BECAUSE IT IS SUBJECTED TO RESORPTION TO HORIZONTAL PORTION OF HARD PALATE

RELIEF AREAS

INCISIVE PAPILLA MEDIAN PALATAL RAPHE

FOVEA PALATINE

INCISIVE PAPILLA

SITUATED ON A LINE IMMEDIATELY BEHIND AND BETWEEN THE CENTRAL INCISORS

THE INCISIVE FORAMEN IS LOCATED BENEATH THE INCISIVE PAPILLA.

LOCATION OF THE INCISIVE PAPILLA GIVES AN INDICATION AS TO THE AMOUNT OF RESORPTION THAT HAS TAKEN PLACE.

THE NASOPALATINE NERVES AND VESSELS PASS THROUGH THE INCISIVE FORAMEN.

MEDIAN PALATAL RAPHE

THE SUBMUCOSA IS EXTREMELY THIN IN THE REGION OF MEDIAL PALATAL SUTURE, SO THE MUCOSAL LAYER IS IN CLOSE CONTACT WITH THE UNDERLYING BONE.

FOR THIS REGION, THE SOFT TISSUE COVERING THE MEDIAN PALATAL TISSUE IS NONRESILIENT IN NATURE & MAY NEED TO BE RELIEVED.

FOVEA PALATINA

BILATERAL INDENTATION NEAR THE MIDLINE OF PALATE

FORMED BY COALESCENCE OF SEVERAL MUCOSAL GLAND DUCT

POSTERIOR TO JUNCTION OF HARD AND SOFT PALATE

ALWAYS ON SOFT PALATE

ANATOMICAL LANDMARKS OF MADIBUALR DENTURE BEARING AREA

LIMITING STRUCTURES SUPPORTING STRUCTURES RELIEF AREAS

Limiting structures

Labial frenum Labial vestibule Buccal frenum Buccal vestibule Lingual frenum Alveolingual sulcus Retromolar pad Pterygomandibular raphe

Labial frenum

It is a fold of mucous membrane at the median line.

It divids the labial vestibule into left and right labial vestibule

Recorded as a notch in the impression made

Frenum contains fiber of Orbicularis oris and Mentalis muscle

Therefore the frenum is quite sensitive and active, and the denture must be fitted carefully around it to maintain a seal without causing soreness

Labial vestibule

The labial vestibule extend from the labial frenum to the buccal frenum

Muscle attachment close to the crest of the ridge –limits the denture flange extension

Buccal frenum

The buccal frenum forms the dividing line between the labial and buccal vestibule.

It overlies the depressor anguli oris muscle.

Fibers of buccinator muscle attached to the frenum.

Frenum may be single or double, broad U shaped or sharp V shaped.

It should be relieved to prevent displacement of the denture during function.

Buccal vestibule

Extend from buccal frenum to retromolar pad

The extent of buccal vestibule is influenced by the buccinator muscle,

which extends from the modiolus anteriorly to the pterygomandibular raphe posteriorly

The impression is widest in this region.

Lingual frenum

Fold of mucous membrane.

•Base of tongue to supragenial tubercle.

The anterior region of the lingual flange is called sub-lingual crescent area

A high frenum is called as Tongue tie.it should be corrected if it affects the stability of the denture.

Alveololingual sulcus

· Space between the residual ridge & tongue .

· Extends from lingual frenum to retromylohyoid curtain .

· 3 regions (anterior, middle & posterior)

· The anterior region extends from the lingual f. back to where mylohyoid muscle curves above the level of the sulcus (premylohyoid fossa) .

· The middle region extends from premylohyoid fossa to the distal end of the mylohyoid ridge, curving medially from the body of the mandible. This curvature is caused by the prominance of mylohyoid ridge & the action of mylohyoid muscle.

· The posterior region: here the flange passes into the retromylohyoid fossa & completes the typical S form of the correctly shaped lingual flange.

Retromylohyoid space

· The retromylohyoid space lies at the distal end of the alveololingual sulcus.

· Bounded by Anterior tonsillar

pillar,posteriorly by the retromylohyoid curtain.

Retromylohyoid curtain

Formed posteriorly by the

superior constrictor muscle,

Laterally by the mandible & pterygomandibular raphe,

Anteriorly by lingual tuberosity, and

Inferiorly by the mylohyoid muscle.

Retromolar pad

The retromolar pad is a pear shaped area containing glandular tissue, loose areolar connective tissue,the lower margin of the pterygomandibular raphe,fibers of buccinator and superior constrictor, along with the fibers of temporal tendon. The retromolar papilla is a pear shaped area just anterior to the retromolar pad, it is dense, fibrous connective tissue.

SUPPORTING STRUCTURES

Buccal shelf area

Residual alveolar ridge

Buccal shelf area Extend from the

buccal frenum to the anterior edge of the masseter muscle.

Boundries :Medially- crest of the

ridgeLaterally- external

oblique ridge.Distally –retromolar pad

· The mucous membrane covering the buccal shelf area is loosely attached, less keratinized & contains thick submucosal layer.

· Considered as a primary stress-bearing area because it is covered by a layer of cortical bone, & it lies at right angles to vertical occlusal forces

Residual alveolar ridge

The crest of the residual alveolar ridge is covered by fibrous connective tissue,

But in many mouths the underlying bone is cancellous and without a good cortical bony plate covering it.

Residual alveolar ridge The mucous membrane covering the crest

of the residual ridge is covered by keratinized layer and is attached by its submucosa to the periosteum of the mandible.

The extent of this attachment varies considerably. In some people, the submucosa is loosely attached to the bone over the entire crest of the residual ridge, and the soft tissue is quite movable.

RESIDUAL ALVEOLAR RIDGE

In others, the submucosa is firmly attached to the bone on both the crest and the slopes of the lower residual ridge.

However, because underlying bone is often cancellous (bony spicules and nutrient canals), the crest of the residual ridge may not be favorable as the primary stress-bearing area for a lower denture.

Relief area

Mental foramen Genial tubercle Mylohyoid ridge Mandibular tori.

Mental foramen

As resorption takes place, the mental foramen will come to lie closer to the crest of ridge.

In these circumstances, the mental nerve and blood vessels may be compressed by denture base unless relief is provided.

Pressure on mental nerve can cause numbness of lower lip.

Genial tubercle The genial tubercle are a

pair of dense prominences at the inferior border of the mandible at the lingual midline.

They represents the muscle attachment of the genioglossus and geniohyoid muscle.

They only become relevant in the denture when there is excessive resorption of the residual ridge.

Mylohyoid ridge The mylohyoid ridge is a boney

prominence along the lingual aspect of the mandible

Soft tissue usually hides the sharpness of mylohyoid ridge.

Anteriorly, this ridge with mylohyoid muscle is close to inferior surface of mandible.

Posteriorly, after resorption, it often flushes with the residual ridge.

The mucous membrane overlying the sharp or irregular mylohyoid ridge needs to be relieved.

Mandibular tori

Mandibular tori are lingual bilateral prominences of cortical bone in the premolar area.but they may extend posteriorly to the molar area.

small tori may only require relief in the denture.

Large tori reguire removal before a denture can be fabricated

References

Boucher's Prosthodontics Treatment for Edentulous Patients.

13th Edition. Chapter 8. Winkler’s –Essentials of Complete

Denture Prosthodontics.Chapter-7.

Heartwell’s syllabus of complete denture.4th edition.

Chapter 6.

THANK YOUYOU

MAXILLARY RUGAE

THESE ARE THE MUCOSAL FOLDS IN THE ANTERIOR REGION OF THE HARD PALATE.

IN THE AREA OF THE RUGAE , THE PALATE IS SET AT AN ANGLE TO THE RESIDUAL RIDGE & COVERED BY THIN SOFT TISSUE.

PALY AN IMPORTANT ROLE IN SPEECH