Determinents of occlusion morphology /certified fixed orthodontic courses by Indian dental academy

Determinants of occlusal

morphologyINDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

www.indiandentalacademy.com

• Posterior controlling factors. (condylar guidance)

• Anterior controlling factors. (anterior guidance)








Effect of plane of occlusion on cusp height


Effect of curve of spee on cusp height






HORIZONTAL DETERMINANTS OF OCCLUSAL MORPHOLOGY

DIRECTION OF GROOVES AND RIDGES








Gnathological Objectives

• To obtain a stable centric relation of the mandible and have the teeth intercusp maximally at this mandibular position

• All centric stops should hit equally and simultaneously and the stress of closure should be directed, as nearly as possible, down the long axis of the posterior teeth.


• To have a harmonious glide path of anterior teeth working against each other to separate or disclude the posterior teeth immediately, but gently , as soon as the mandible moves out of centric closure.


• The glide path provided by the anterior teeth must be in harmony with the way in which the mandible moves through border excursions. If there is immediate shift of the mandible, there must be a concavity in the lingual surfaces of the maxillary anterior teeth to accommodate the side shift movement , or the anterior teeth will be stressed.


• The cuspids should be the main gliding inclines on lateral excursion and the six maxillary anterior teeth should articulate with the six mandibular anterior teeth and the mandibular bicuspids(first bicuspid in non-extraction cases)so that the protrusive load is spread over 14 teeth.


Ideal tooth positioning

Lower incisors at the cephalometric goal- +1 to A-Po

Tips of the upper incisors 2-2.5mm below the lip embrasure of the upper and lower lips , when the lips are closed with no lip strain

No more than 1mm of attached gingiva showing upon full smile


• Approx. a 2.5mm overjet-overbite relationship to the lower incisor(the lower incisor has .0005” clearance with the lingual surface of the upper incisor

• A level or nearly level occlusal plane at the end of appliance therapy that would return to a 1-1.5mm curve at its deepest point after appliance removal and setting of the occlusion


• The curve of Wilson that would allow seating of centric cusps but clearance upon excursions

• As much divergence as possible of the occlusal plane from the angle of the eminence for excursive clearance.


• Lower incisors aligned contact point-to-contact point with the roots in the same plane , when observed from the occlusal , and a mesioaxial inclination of 2 degrees

• Lower cuspid crowns angulated mesially 5 deg with the incisal tip 1mm higher than the incisal edge of the lateral incisors.


• The lower bicuspids should be up righted 1 deg from their normal mesial inclination and should have a slight distal rotation

• The lower molars should be up righted 1deg from their normal 2 deg mesial inclination and should have a slight distal rotation.


• The lower buccal segment should have progressive torque close to Andrew’s measurements for establishing the curve of wilson and there should be no rotations or spaces

• The upper six year molars should have sufficient distal rotation,mesio axial inclination,and buccal root torque; the same would follow for the upper second molars.


• The upper bicuspids should be uprighted to 0 deg from their normal 2 deg mesial inclination with no rotation.

• The upper cuspid must have its contact points adjacent to the contact points of the upper bicuspid and lateral incisor ; it should have 11- 13 deg of mesial crown tip and mesial rotation of 4 deg on an extraction case.


• The upper lateral and central incisors should be almost equal in incisal edge length ,with no more than 0.5mm height differential; they should have 9 deg and 5deg mesioaxial inclination resp. and there should be sufficient torque.

• There should be no rotations ( other than those of overcorrection ) or spaces in the upper arch and the buccal segments from the cuspids distally should have 14 deg nonprogressive buccal root torque.


• The arch form should be a modified catenary curve consisting of five separate radii- one for front of the arch form, one for each cuspid bicuspid area, and one each for buccal segment from the first bicuspid distally


• The widest point of the lower arch would be at the mesiobuccal cusp of the mand. First molars and at the first bicuspids

• The widest point of the maxillary arch would be at the mesiobuccal cusps of the first molars.


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Determinents of occlusion morphology /certified fixed orthodontic courses by Indian dental academy

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