OCCLUSION

OCCLUSION

> may mean the contact relationship of the teeth in function or parafunction.

> It refers not only to contact of the arches at an occlusal interface but also to all those factors concerned with the development & stability of the masticatory system & with the use of the teeth in oral motor behavior.

SUGGESTED TOPICS FOR THE STUDY OF OCCLUSION:1. Development of

Occlusion

Primary Dentition

– development of occlusion begins with the occlusion of the deciduous teeth.

Permanent Dentition

– there are significant differences in the eruption sequences between the maxillary arch & the mandibular arch that do not appear in the eruption of the primary dentition.

Sequence of eruption in the maxillary arch:

6 – 1 – 2 – 4 – 3 – 5 – 7 – 8

Sequence of eruption in the mandibular arch:

6 – 1 – 2 – 3 – 4 – 5 – 7 – 8

2. Dental Arch Form

- the basic pattern of tooth position is the arch.

- The form is largely determined by the shape of the underlying basal bone.

3. Compensating Curvatures of the Dental Arches

Curved Occlusal Plane – mandibular arch conforms generally to one or more curved planes which appear concave, & the opposing maxillary arch appears convex.

Von Spee noted that the cusps & incisal ridges of the teeth tended to display a curved alignment when the arches were observed from a point opposite the first molars.

This alignment is within the sagittal plane only & is known as the Curve of Spee.

4. Angulation of the Individual Teeth in Relation to Various Planes

Root form – each tooth must be placed at an angle that best withstands the lines of forces brought against its function.

5. Functional Form of the Teeth at their Incisal & Occlusal Thirds

- the incisal & occlusal thirds of the tooth crown present a convex & concave surface at all contacting occlusal areas.

- a convex surface, representing a segment of the occlusal third of one tooth may come into contact with a concave segment of another tooth.

6. Facial & Lingual Relations of Each Tooth in one Arch to its Antagonists in the Opposing Arch in Centric Occlusion

- Each tooth has two antagonists, the loss of one still leaves one antagonist remaining.

- This will keep the tooth in occlusal contact with the opposing arch & keep it in its own arch relation at the same time by preventing elongation & displacement through the lack of antagonism.

7. Occlusal Contact & Intercusp Relations of all the Teeth of one Arch with those in the Opposing Arch in Centric Occlusion

- Centric occlusion is frequently the position of the jaw for bracing during swallowing & the terminal position of the masticatory stroke.

- When the teeth of both jaws come together in centric occlusion, forces should be equalized so that the teeth are stabilized by all forces acting on them.

ARTICULATION

- used to describe contacts between the teeth in opposing dental arches during mandibular movements.

Articulators – mechanical device by which the occlusal relationship during mandibular movements may be copied.

POSITION

- the relationship of the maxilla & the mandible when the teeth are in occlusion.

Five Positions in which occlusion takes place:

1. Intercuspal occlusion2. Protruded occlusion3. Retruded occlusion4. Left lateral occlusion5. Right lateral occlusion

POSTURAL OR MANDIBULAR REST POSITION- teeth not in function, mouth is closed by the tonic contraction of the muscles of mastication & facial expression & the teeth are not in contact.- there is intercuspal or freeway space of 2-5mm between teeth.

REST VERTICAL DIMENSION

- the face is in an involuntary relaxed state.

- a distance measured from the inferior border of the nose to the point of the chin.

OCCLUSAL VERTICAL DIMENSION

- teeth are in intercuspal occlusion.

(* The difference between the RVD & OVD represents the freeway space.)

DISTURBANCE

- alteration in the established form of the teeth or in occlusal function.

Example:1. overcrowding2. rotation/displacement of teeth from

the dental arches3. increase overbite/overjet4. posterior open bite5. anterior open bite6. missing, painful, sharp teeth

DISORDER

- disturbances that cause pathological alterations in the masticatory system.

Example:1. bruxism2. attrition3. cracked tooth syndrome4. mandibular pain dysfunction

syndrome

IDEAL OCCLUSION

- is a perfect dentition which can be rarely found.

NORMAL OCCLUSION

- takes into account the ability of the masticatory system to adapt or compensate for some deviations within the range of acceptable variation without producing disturbances or disorders

ANGLE’S CLASSIFICATION OF OCCLUSION

Normal Occlusion/ Ideal Occlusion- the MB cusp of the maxillary first molars occlude with the MB groove of the mandibular first molars.

- the DB cusp of the maxillary first molar occlude with the distal cusp of the mandibular first molar & with the MB cusp of the mandibular second molar.

- each tooth occludes with 2 teeth in the opposing dental arch with exception to the mandibular central incisors & the maxillary third molars.

OVERBITE

- vertical relation between the upper and lower incisors.

OVERJET

- horizontal relation between the upper and lower incisors.

OCCLUSAL PLANE

- imaginary plane that passes through the incisal edges of the mandibular central incisors & curves gently upwards through the tips of the buccal cusps of the premolar & molar teeth to the tip of the DB cusps of mandibular second molars.

Slope of the Curve – Compensating Curve

CLASSIFICATION OF MALOCCLUSION:

1. NEUTROCCLUSION /ANGLE’S CLASS I

- antero-posterior relationship of dental arches are normal.

- malocclusion found is due to discrepancies between the length of the two dental arches & tooth size.

- spacing/ crowding/ crossbite may be present.

2. DISTOCCLUSION/ ANGLE’S CLASS II

- mandibular first molars lie in distal relationship to the maxillary molars.

Division I - maxillary incisors proclined - increase overjet

Division II - maxillary incisors are retroclined and crowded maxillary incisors are proclined & overlap the central incisors.

3. MESIOCCLUSION / ANGLE’S CLASS III

- mandibular molars lie mesial to the maxillary molars

- negative overjet

Pseudo – Class III

- the incisors have negative overjet but the molar relationship is Class I.

Treatment for Malocclusion:

1. Orthodontic treatment2. Surgery

Functional Movement of the Mandible

1. Bilateral Movement- bilaterally symmetrical, both

head and condyle are involved- example:

a. depressionb. elevationc. protrusion d. retrusion

2. Unilateral Asymmetrical Movement- one head of the condyle

moves in one direction while the other head stays in position as seen during the chewing cycle of mastication.

3. Balancing Bite / Position- static relationship of the

mandibular & maxillary teeth to one another on one side of the dental arch when closure is made and the mandible moved laterally to the opposite side.

4. Balancing Occlusion- dynamic relationship of

mandibular & maxillary teeth to one another during the excursion of the mandible for balancing position to centric occlusion.

5. Working Bite / Position- static relationship of the

mandible & maxillary teeth to one another on one side of the dental arch when closure is made with the mandible moved laterally to that side.

6. Working Occlusion - dynamic relationship of

mandibular & maxillary teeth to one another during the excursion of the mandible for working position to centric occlusion.