occlusion in orthodontics - harvard...

OCCLUSION IN ORTHODONTICS

Veerasathpurush Allareddy, BDS MBA MHA MMSc PhD

Department of Developmental Biology

Boston Children’s Hospital

Harvard School of Dental Medicine

04/23/2013

OUTLINE

• History

• Terminology

• Occlusion – definition

• Angle’s Classification

• Andrew’s Six Keys to Occlusion

• Clinical Scenarios

History

• Dr. Edward H. Angle

• First dental specialty: Orthodontics

Terminology

Orientations

Buccal

Lingual

Mesial Distal

Overjet

Overbite

OB

Curve of Wilson

Transverse Occlusal Deviations

Midline Deviation

Midline Deviation

Midline Deviation

Functional Shift

Curve of Spee

Curve of spee is 3.5 mm

OCCLUSION

DEFINITION

“The relationship of the mandibular and maxillary teeth as they are brought into functional contact”

COMPLEXITY OF OCCLUSION

• Teeth (morphology and angulation)

• Masticatory muscles

• Skeletal structures

• Temporomandibular joints

• Functional jaw movements

ANGLE’S CLASSIFICATION

Mesiobuccal cusp of maxillary first molar rests on the buccal groove of the mandibular first molar

CLASS II

Class II Division I Class II Division II

CANINE CLASSIFICATION

CANINE CLASSIFICATION

A. Class I - Maxillary canine fits in the embrasure between the mandibular canine and first premolar

B. Class II - Maxillary canine occludes mesial to Class I

C. Class III - Maxillary canine occludes distal to Class I

ANDREW’S SIX KEYS OF NORMAL

OCCLUSION

SIX KEYS OF NORMAL OCCLUSION

• Molar interarch relationship

• Mesiodistal crown angulation

• Labiolingual crown inclination

• Rotations

• Tight contacts

• Occlusal plane (curve of spee)

MOLAR INTERARCH RELATIONSHIP • Mesiobuccal cusp of maxillary first molar occludes in

the buccal groove of mandibular first molar

• Mesiolingual cusps of the maxillary first molar occludes in the central fossa of the mandibular first molar

• Distal marginal ridge of the maxillary first molar occludes with the mesial marginal ridge of the mandibular second molar

MOLAR INTERARCH RELATIONSHIP

MOLAR INTERARCH RELATIONSHIP

YES

MESIODISTAL CROWN ANGULATION

Gingival part of the long axis of the crown must be distal to the occlusal part of the axis

LABIOLINGUAL CROWN INCLINATION BETWEEN MAXILLARY AND MANDIBULAR INCISORS

LABIOLINGUAL CROWN INCLINATION OF POSTERIOR TEETH

NO ROTATIONS

TIGHT CONTACTS – NO SPACING

CURVE OF SPEE

A. Excessive

B. Normal

C. Reverse

REFERENCES Casko J et al. "Objective grading system for dental casts and panoramic radiograph," The American Journal of Orthodontics and

Dentofacial Orthopedics, 114:590-599, 1998.

Cangialosi TJ. “The ABO discrepancy index: A measure of case complexity.” American Journal of Orthodontics and Dentofacial Orthopedics, 125(3):270-278, Mar 2004.

Riolo et al. "ABO Resident Clinical Outcomes Study: Case Complexity as Measured by the Discrepancy Index.” American Journal of Orthodontics and Dentofacial Orthopedics, pp. 161-163, Feb 2005.

Andrews LF. "The Six Keys to Normal Occlusion." American Journal of Orthodontics, 62:296-309, 1972.

Proffit WR et al. “Contemporary Orthdontics”. Fourth edition. Mosby.

English JD et al. “Mosby’s Orthodontic Review”. Mosby.

Rakosi T et al. “Color Atlas of Dental Medicine - Orthodontic Diagnosis”. Thieme.

CLINICAL SCENARIOS