09/25/2009 The six keys to normal occlusion

Resident: Hencler
Date: 09/25/2009

Article title: The Six keys To Normal Occlusion
Author(s): Lawrence F. Andrews, DDS
Journal: Am. J. Orthod.
Volume #62; Number 3; Page 296-309
Year: 09/1972

Major topic: Occlusion
Type of Article: Observational Study

Main Purpose: Identify and explore significant characteristics in non-orthodontic patients that constitute a normal occlusion.

Overview of method of research: Examine 120 study models of non-orthodontic patients to identify key characteristics that make up a normal occlusion. 120 study models were selected from patients which, have never had orthodontic treatment , had teeth that were straight and pleasing in appearance, and had a bite which looked generally correct, and would not benefit from orthodontic treatment.

Findings: The 6 keys to a normal occlusion were found to include 1) molar relationship 2) crown angulation 3) crown inclination 4) rotations 5) spaces 6) occlusal plane.

Key points in the article discussion:

• Key 1 molar relationship: The mesiobuccal cusp of the maxillary 1st molar occludes in the mesiobuccal groove of the mandibular 1st molar. The distal surface of the of the distobuccal cusp of the maxillary 1st molar occludes with the measial surface of the mesiobuccal cusp of the mandibular 2nd molar

• Key 2 crown angulation (tip): The gingival portion of the long axes of all crowns was more distal than the incisal portions. Normal occlusion is dependent upon proper distal crown tip.

• Key 3 crown inclination (labiolingual or buccolingual inclination): Properly inclined anterior crowns contribute to normal overbite and posterior occlusion. Anterior teeth have a slight labial inclination. Maxillary posterior teeth have a lingual crown inclination that is similar from the canines through the 2nd molars. Mandibular posterior teeth have a lingual inclination that increases from the canines through the second molars.

• Key 4 rotations: Teeth should be free of undesirable rotations.

• Key 5 tight contacts: Tooth contact points should be tight with no spaces.

• Key 6 occlusal plane: Normal models ranged from flat to slight curves of Spee. The author claims that a flat plane of occlusion should be a goal of orthodontic treatment because there is a natural tendency for the curve of Spee to deepen with time.

Summary of conclusions: The 6 keys to normal occlusion contribute individually and collectively to the total scheme of occlusion and are essential to successful orthodontic treatment.

Assessment of article: I thought this was an interesting article because this information is still relevant today. Occlusion is important in every aspect of clinical dentistry so it’s never a bad time for a little review.