ORAL PHYSIOLOGY

It is the branch of dentistry that deals with the normal functions of teeth and all its related structures in the oral cavity.

PHYSIOLOGIC MORPHOLOGY of the TEETH and the PERIODONTIUM

A. There is a definite form related to purpose and function.

B. There are 3 major functions of human teeth to which their form, contour and alignment are directly related:

1. Mastication 2. Esthetics 3. Phonetics (speech)Periodontium- supporting

tissues, both hard and soft may suffer the consequences of dentist-induced imperfection of form.

COMPARATIVE DENTAL ANATOMY

A. Most primitive type of tooth - conical in shape -composed of a single cone or

lobe -common in primitive vertebrates -in modern times is exhibited by

lower vertebrates including rep- tiles -mainly homodonts with similarly

shaped teeth differing in size

-hinge action of jaw, no lateral movement for grasping prey and combat.

B. The dental systems of mammals have evolved to much greater diversity.

-development of tritubercular form of the tooth or 3 lobed (cusped tooth).

-mammals are heterodont in nature bec.of different tooth form, displays more than a single root per tooth.

-dogs are mammal that is fully heterodont but lacks lateral jaw movements due to interlocking cusps.

C. The most highly developed and complex teeth, normally with 4 or more lobes belongs to the PRIMATE (APES AND MONKEYS).

- basically herbivorous diet of fruits. - anthropod ape have dental

formulae identical to man however these animals retained their

elongated canines hence, do not have lateral jaw movement like in man.

D. Man has the most complex dental mechanism of all animals.-being omnivorous, homosapiens has

developed teeth to function both in the mastication of meat and plant foods.The elongated and interlocking canines are reduced in size so that they function with rest of the teeth in lateral movements and the individual teeth differ in both size and development from other primates. All teeth in human dentition are comprised of four or more lobes.

-the ungulates (deer,cow,horse etc.) displays a great range of jaw movement being entirely herviborous, exhibit relatively great latitude of jaw movement.

CROWN SURFACE FORMThe geometric configuration of all

tooth crown surfaces (except incisal and occlusal) can be placed in one of three general categories: triangular, trapezoidal or rhomboidal.

A. FACIAL and LINGUAL SURFACES- Labial, buccal and lingual aspects, all teeth are in the dental arches can be roughly described as trapezoidal.

-incisal or occlusal side forms the base of the trapezoid.

- the cervical represents the shorter parallel side to allow adequate bony support around the root of each tooth as well as abundant circulatory capability.

Viewed from facial

Observe the pronounce

trapezoidal configuration with the base at the incisal or occlusal.

B. MESIAL and DISTAL SURFACES a. Anterior Teeth The crowns of anterior teeth as

viewed from their proximal surfaces, exhibit a triangular shape, with the base of triangle at the cervical and the apex at the incisal. This shape readily fits into the prescribed function of the anterior teeth, since the apex at the functions as a wedge in tearing, biting and incising food material, while the wider cervical base provides strength for the crown form.

b. Maxillary Posterior Teeth The crowns of maxillary posterior

teeth have proximal surfaces which are roughly trapezoidal in shape, with the base at the cervical and the buccal and lingual sides constricting toward the occlusal. This general form aids in the distribution of forces during mastication, as well as serving as an aid to the tooth’s self-cleansing process.

+c. Mandibular Posterior Teeth From the proximal aspect,

mandibular posterior teeth are roughly rhom-boidal in their outline, with the crowns inclined toward the lingual. This form and inclination allows for proper interlocking of the mandibular and maxillary posteriors during mastication.

VIEWED FROM PROXIMAL

A. Triangular with the base at the

gingival.B. Trapezoidal with

the base at the gingival

C. Rhomboidal

GENERAL CONSIDERATIONS IN THE PHYSIOLOGY OF THE PERMANENT DENTITION

A. TOOTH FORM and FUNCTION -are directly related -shapes of incisal/occlusal

surfaces of the teeth are related to their functions.

-movements of the mandible -functions

B. OCCLUSION - when maxillary teeth comes in contact

with mandibular teeth -used to designate the anatomic

alignment of the teeth and their relationship to the rest of the masticatory system.

MALOCCLUSION - any deviation in intermaxillary and/or

intermaxillary relations of the teeth and/or jaw.

ALIGNMENT -teeth are arranged in arches in

each jaw and place in strong contact with adjacent teeth.

-line of forces must be parallel to the long axis of the tooth.

- importance, to withstand forces.

C. CONTACTS -each tooth has contact areas

except 3rd molars (distal) -increase in size with age because

of 1. due to abrading action of the

teeth against each other over a long period of time.

2. brading action between proximal spaces.

-the actual mesio-distal length of dental arches is continuously becoming shorter moving towards the midline or mesially.

-importance, stabilizes the teeth in the dental arch and prevention of food material from packing between teeth resulting to gingivitis.

-there must be tight and proper location of contact areas towards incisocervically/occlusocervically and faciolingually.

GENERAL RULES 1. Contact areas become more

cervically located from anterior to posterior in each quadrant.

2. On individual teeth, the distal contact area normally has a more cervical location than the mesial contact area.

3. The relative size of the contact areas increases from anterior to posterior in each dental arch.

4. Anterior teeth have contact areas which are, in general, centered in the faciolingual dimension.

5. Posterior teeth have contact areas which are, in general, located slightly to the buccal center in the faciolingual dimension.

CONTACTS

A schematic representation of the left quadrant of the mandibular arch. Note how the contact areas asssume a more gingival location as they progress distally.

D. INTERPROXIMAL SPACES-is the triangular shaped area

between adjacent teeth in the same arch normally filled with interdental papilla.

-the triangle is formed by alveolar bone at its cervical base, proximal surfaces of the adjacent teeth on each sides and contact area of the adjacent teeth at its apex.

-importance, the triangular shape is important in the health of the entire periodontium by allowing its proper stimulation and aids in the self-cleansing process of the dentition.

INTERPROXIMAL SPACE

The interproximal space related structures with components labeled.

E. EMBRASURES -open space between the proximal

surfaces of 2 adjacent teeth in the same arch where they diverge facially, lingually and incisally (occlusally) or cervically from the contact area.

-they are named according to location depending from what aspect the teeth are viewed.

-importance, serve as spillway for the food material during mastication and serve as integral part of the self-cleansing process of the tooth. Improper embrasure restoration will result into overstimulation of the periodontium.

GENERAL RULES1. From the facial or lingual aspect,

incisal (occlusal) embrasures increase in relative size from the anterior teeth toward the posterior.

2. From the facial or lingual aspect, cervical (gingival) embrasures decrease in relative size from anterior to posterior.

3. From the incisal aspect, the labial and lingual embrasures are nearly equal in size in anterior teeth.

4. From the occlusal aspect, the lingual embrasure is normally larger than the buccal embrasure in posterior teeth.

5. When one side of an embrasure (tooth outline) has a certain contour (example-convex), the other side of the embrasure will normally have a similar contour.

EMBRASURESF10- anterior teeth

have approximately same size on labial and lingual embrasures.

F11- as the arch progresses distally, buccal embrasures constrict and lingual embrasures enlarge slightly.

F12-shows gingival (cervical) and occlusal embrasure.

F. CONTACT AREAS AND INCISAL AND OCCLUSAL EMBRASURES FRoM THE LABIAL AND BUCCAL ASPECT

A. Central Incisors- contact areas mesially on both central incisors are located at the incisal third crowns.

B. Central and Lateral incisors- distal outline of central incisor crown is rounded, the lateral has a shorter crown and has a more rounded mesioincisal angle than central incisor.

C. Lateral and Canine- distal contact area on the lateral incisor is at the middle third.

- mesial contact area on the canine is at the junction of the incisal and middle thirds.

- creates a more open embrasure than between two central and distal of central and mesial of lateral.

D. Canine and First Premolar - canine has a long distal slope

to its cusp which puts the distal crest of curvature at the center of the middle third of the crown

- premolar, has a long cusp form also, which puts its mesial contact area rather high up on the crown.

-embrasure between these teeth has a wide angle.

G. ROOT SHAPE, LENGTH, NUMBERS

-related to form and function -canine has the longest and

strongest root for tearing -molars are multirooted for

grinding

GENERAL RULES 1. Roots are widest at the cervical

and taper toward the apex. 2.Anterior teeth and premolars

normally have single roots. An exception is the maxillary first premolar which normally exhibits the root branches, or buccal and a lingual.

3.Maxillary molars normally have 3 roots, one lingual and two buccal roots.

4.Mandibular molars normally have 2 roots one mesial and one distal root.

ROOT SHAPE, LENGTH AND NUMBERS

a. Labial view of maxillary incisor shows single root.

b. Buccal view of max.molar shows 2 roots (1 mesial and 1 distal root.

c. Buccal view of max.molar shows 3 roots- 1MB,1DB,1L

H. FACIAL AND LINGUAL HEIGHTS OF CONTOUR (CREST

OF CURVATURE)

-is the greatest area of contour on the facial and lingual surfaces, and best viewed from proximal.

-proximal surface also have heights of contour which are normally located at the contact areas.

-aid in proper protection and stimulation of the gingival tissue.

-if the contour is excessive, the flow of food material will be deflected from the gingival and improper stimulation of these tissues may result in their breakdown.

-inadequate contour allows inadequate protection, and the overstimulation to the gingival tissues may also result in their destruction.

GENERAL RULES1. The height of contour on both the

labial and lingual surfaces of all the anterior teeth is located in the cervical third.

2. The height of contour of the buccal surfaces of all posterior teeth is located in the cervical third.

3. The height of contour of the lingual surfaces of posterior teeth is located in the middle or occlusal third.

CREST OF CURVATURE (PROXIMAL OF M1)

A. Correct contour.B. Overcontoured

max.M1C. M1 with less

than normal contour.

a. ant.tooth showing labial and lingual crest of cur-vature which are both in the cervical third.

b. Mand.post tooth with buccal crest of curva-ture in the cervical 3rd and the lingual height of contour in the occlusal third.

c. Max.post.tooth with the buccal crest of curvature in cervical 3rd and lingual crest of curvature in the middle 3rd.

I. CERVICAL LINE CURVATURES GENERAL RULES1. The amount (depth) of cervical

line curvature on any individual tooth is normally greater on the mesial than on distal.

2. Cervical lines adjacent proximal surfaces of adjacent teeth have approximately the same depth of curvature.

3. The cervical line is normally curved (convex) toward the apical on the facial and lingual surfaces of teeth.

4. The cervical line is normally curved (convex) toward the incisal (occlusal) on the proximal surfaces of teeth.

5. The depth of the curvature on all surfaces is greater on anterior teeth and decreases toward the posterior.

CERVICAL LINEThe cervical line

curvatures as seen from mesial and distal views on a C,PM and M. Note the greater incisal or occlusal cervical line curvature on the mesial surfaces. Note the more distally located the tooth is in the arch, the less pronounced the cervical line curvature.

The cervical line curvatures as seen from the buccal (labial) and lingual.

CERVICAL LINE OR CEJ- a line around the tooth where enamel and cementum meet. This is stable.

GINGIVAL LINE/GINGIVAL MARGIN/GINGIVAL CREST- line which marks the level of termination of the soft tissue surrounding the tooth. The gingival level is variable

and usually above the cervical line early in life, often receding to a lo-wer level as the individual becomes older.

ANATOMICAL CROWN- portion of tooth covered by enamel.

CLINICAL CROWN- portion of tooth which is visible in the mouth.

ANATOMICAL ROOT- portion of the tooth covered by cementum.

CLINICAL ROOT- portion of the tooth not visible in the mouth.

J. AXIAL POSITION- inclination of a tooth from a vertical axis.

Importance- for proper occlusal function of the dentition.

Maxillary anterior• faciolingual dimension- toward

lingual • Mesiodistal- incisors roots slightly

toward mesial; canine-distal

Maxillary Premolar• faciolingual- towards lingual• Mesiodistal- distal

Maxillary Molar• roots- lingual inclination and

moderate distal inclination

Mandibular Anterior• Faciolingual- great root inclination• Mesiodistal- nearly straight with

only minor mesial root inclination• Canine- slight distal root

inclination

Mandibular Premolar• Mesiodistal- distal root inclination• Faciolingual- premolar 1 towards

lingual • Premolar 2 towards buccalMandibular Molar• moderate to great buccal and

distal root angulations

K. GENERAL OCCLUSAL CURVATURES and AXIAL POSITION

IMPORTANCE 1. Allow the most efficient use of

the forces of mastication. 2. Stabilizing and protecting the

dental arches.

CURVE OF SPEE- curve line begins at the tip of the canines and follows the buccal cusp tips of the premolar and molars posteriorly viewed buccally.2 dimensional.

Curve of Spee

Lateral view of maxillary and mandibular left quadrants demons-trating the Curve of Spee.

CURVE OF WILSON- the medio-lateral curvature of the occlusal plane of posterior teeth.

-2 dimensional but in opposite direction to the curve of Spee.

- crowns of mandibular posterior teeth inclines lingually while crowns of maxillary posterior teeth inclines buccally.

- this curve becomes deeper posteriorly, so that the molar’s inclination is greater than that of the premolar.

Importance- to complement the paths of the condyles of the mandible in its movements.

CURVE OF WILSONCurve of Wilson as

seen in a 1st molar cross-sectional view of the maxilla and mandible. Note that to conform to this curve, the lingual cusps of max. molars and the buccal cusps of mandibular molars appear to be longer.

COMPENSATING OCCLUSAL CURVATURE (SPHERE OF MONSOON)

• 3 dimensional curvature of the occlusal plane combination of curve of Spee and Wilson.

• It is in the form of ball and sphere.• Concave on mandibular

arch/convex maxillary

SPHERE OF MONSOON

A Segment of a large sphere super-imposed on the mandible illus-trating compen-sating occlusal curvature.