The Six Keys to Normal Occlusion 2

The Six Keys To Normal Occlusion

Dentists had a classic guideline in orthodontic diagnosis for half a century set by ANGLE , but it was not enough.

During 1960 1964 , 120 models were studied having these characteristics :

1 No orthodontic treatment. 2 Straight pleasing in appearance. 3 Had a bite generally looked correct. 4 Would not benefit from orthodontic

treatment.

Crowns were studied intensively

Six characteristics were identified

To validate them , these 6 characteristics were compared with 1150 cases from the complementary bank of information of orthodontists in America.

Lack of any of the six characteristics would result in defect.

Characteristics shared by all non orthodontic normals :

1- Molar relationship :

2- Crown angulation {mesiodistal tip}

3-Crown inclination:a- Anterior teeth.b- Upper posterior teeth. c- Lower posterior teeth.

4-Rotation

no rotations.

5-Spaces

no spaces.

6-Occlusal plane varied from flat to curve of spee.

THE SIX KEYS

KEY I

Molar relationship

Key II

Crown angulation

The degree of the crown tip is expressed in degrees , plus or minusPlus reading

Minus reading

Determine : The mesiodistal space. Posterior occlusion Anterior asthetics

Key III Crown inclination

The degree of the crown inclination is expressed in degrees , plus or minus Plus reading Minus reading

A- Anterior teeth 1 overbite. 2 posterior occlusion 3 spaces

B- Upper posterior teeth. Minus crown inclination

C- Lower posterior teeth. Progressively minus crown inclination

Tip and TorqueAs the anterior portion of an upper rectangular arch wire is lingually torqued , a proportional amount of mesial tip of the anterior crowns occurs.

For every 4 degrees of lingual crown torque , there is 1 degree of mesial convergence of the gingival portion.

Key IV Rotations

Key V

Tight contacts

Key VI : Occlusal planeA Deep curve of spee B Flat occlusal plane C Reverse curve of spee

CONCLUSIONThese Six Keys are considered as guidelines which should be shared in normal and treated teeth if no compromise treatment was done due to limitations.

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