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Lec. 2 4th

class

9-10-2010 Dr.

Samer Ramzi

OCCLUSION

Occlusion: is the static relation between the upper and lower teeth.

Occlusion is a complex phenomenon involving the teeth, the

periodontal ligament, the jaws, the TMJ, the muscles and the

nervous system.

Ideal occlusion:is a hypothetical concept based upon the anatomy

of the teeth and rarely found in nature. Its features are

!" The patient has #$ or %# occluding teeth that are of normal

si&e and shape.#" The teeth are perfectly aligned buccolingually and

occlusogingivally.%" There are no rotations.'" There is no crowding or spacing.(" )ach tooth is at the correct inclination and angulation with

respect to its neighbor.*" The occlusal plane has a smooth curve.+" )ach upper tooth occludes with its opposing lower tooth and

the tooth distal to it, with the exception of the upper third molar.$" The upper teeth occlude buccallabial to the lower teeth.-" The upper and lower centerlines are coincident with each

other and the facial midline.!" The dental arches are symmetrical.

!

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Normal occlusion:is an occlusion within the accepted deviation of

ideal that is with minor variations in the alignment of the teeth which

are not of esthetic or functional importance.

Malocclusion: is an irregularity in the occlusion beyond theaccepted range of normal. /owever, there is wide range of

variations between individuals and races.

Normal Occlusion Malocclusion

Angle's classification of malocclusion (1899):

0ngle1s definition of normal occlusion the mesiobuccal cusp of the

maxillary first permanent molar occluding with the mid"buccal groove

of the opposing mandibular first permanent molar and the teeth are

arranged in a smoothly curving line of occlusion.

Class I malocclusion: the mesiobuccal cusp of the maxillary first

permanent molar occluding with the mid"buccal groove of the

opposing mandibular first permanent molar with irregularity in the

teeth li2e spacing or crowding.

Class IImalocclusion the mesiobuccal cusp of the maxillary first

permanent molar occluding mesial to the mid"buccal groove of the

opposing mandibular first permanent molar by more than half cusp

width.

3lass II may be further subdivided according to the inclination

of the upper central incisors

Division 1:the upper incisors are proclined.

Division 2:the upper central incisors are retroclined.

#

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Class IIImalocclusion the mesiobuccal cusp of the maxillary first

permanent molar occluding distal to the mid"buccal groove of the

opposing mandibular first permanent molar by more than half cusp

width.

3l I 3l II 3l III

British standards institute classification ased on Incisor

relationshi!:

Class I 4 the lower incisor edges occlude with or lieimmediately below the cingulum plateau 5middle third of thepalatal surface6 of the upper central incisors.

Class II4 the lower incisor edges lie posterior to the cingulumplateau of the upper incisors. There are two subdivisions of

this category

o 7ivision ! 4 the upper central incisors are proclined orof average inclination.

o 7ivision # 4 the upper central incisors are retroclined.

Class III4 the lower incisor edges lie anterior to the cingulumplateau of the upper incisors.

3l I 3l II 3l II 3l III

7ivision ! 7ivision #

%

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Canine classification:

Class I 8 the upper permanent canine should occlude into the

embrasure between the lower canine and first premolar.

Class II 8 the embrasure between the lower canine and first

premolar lies distal to the cusp of the upper canine.

Class III " the embrasure between the lower canine and first

premolar lies too far forward to the cusp of the upper canine.

Cl I Cl II Cl III

O"erite: is the vertical distance between the tips of upper and

lower incisors in occlusion, normally it is #"' mm.

O"er#et:is the hori&ontal distance between the tips of the upper and

lower incisors in occlusion, normally it is #"' mm.

'