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Am J Orthod. 1972 Sep;62(3):296-309
•The of the upper first molar should occlude in the groove between the mesial and medial buccal cusp of the lower first molar.
•The crown of the upper first molar must be angulated so that its occludes with the mesial marginal ridge of the lower second molar.
•The of the upper first molar should occlude in the central fossa of the lower first molar.
distal marginal ridge
Molar interarch relationship
Mesio-distal crown angulation
Labio-lingual crown inclination
No rotations
Tight proximal contacts
Flat occlusal plane(curve of Spee)
Class I Molar relationship
(Andrews,1972)
mesiobuccal cusp
mesiolingual cusp
(Andrews,1972)
Mesio-distal crown angulation
•The gingival part of the long
axis of the crown must be distal
to the occlusal part of the axis.
Molar interarch relationship
Mesio-distal crown angulation
Labio-lingual crown inclination
No rotations
Tight proximal contacts
Flat occlusal plane(curve of Spee)
Anterior:
•The interincisal angle between the crown tangents of the upper and lower incisors is 132o for normal occlusions
Posterior:
•The gingival portions of the teeth are
more pronounced buccally than the
occlusal portions.
(Andrews,1972)
Labio-lingual crown inclinationMolar interarch relationship
Mesio-distal crown angulation
Labio-lingual crown inclination
No rotations
Tight proximal contacts
Flat occlusal plane(curve of Spee)
•In order to achieve correct occlusion, none of the
teeth should be rotated.
•Rotated molars and premolars occupy more space in
the dental arch than normal.
•Rotated incisors may occupy less space than those
correctly aligned.
•Rotated canines adversely affect esthetics and may
lead to occlusal interferences.
(Andrews,1972)
RotationsMolar interarch relationship
Mesio-distal crown angulation
Labio-lingual crown inclination
No rotations
Tight proximal contacts
Flat occlusal plane(curve of Spee)
•If there are no anomalies in the shape of the teeth,
or intermaxillary discrepancies in the mesiodistal
tooth size, the contact points should abut in normal
occlusion.
(Andrews,1972)
Tight proximal contacts
(no spacing)Molar interarch relationship
Mesio-distal crown angulation
Labio-lingual crown inclination
No rotations
Tight proximal contacts
Flat occlusal plane(curve of Spee)
•A normal occlusion has a flat occlusal plane (the
mandibular curve of Spee should not be deeper than
1.5mm).
(Andrews,1972)
Flat occlusal plane
(curve of Spee)Molar interarch relationship
Mesio-distal crown angulation
Labio-lingual crown inclination
No rotations
Tight proximal contacts
Flat occlusal plane(curve of Spee)
