Occlusion: Classification, Curves & Guidance

Angle classification (permanent first molars)

Class	Mesiobuccal cusp of the maxillary first molar	Profile and notes
Class I	Sits in the buccal groove of the mandibular first molar	Straight profile; crowding or spacing can still be present
Class II division 1	Mesial to the buccal groove (mandibular molar is distal)	Convex profile; proclined maxillary incisors, large overjet
Class II division 2	Mesial to the buccal groove	Retroclined maxillary central incisors, flared laterals, deep bite
Class III	Distal to the buccal groove (mandibular molar is mesial)	Concave profile; anterior crossbite or edge-to-edge incisors

Canine relationship (Class I): the maxillary canine cusp sits in the embrasure between the mandibular canine and first premolar.
Overjet is horizontal overlap and overbite is vertical overlap; roughly 2–3 mm of each is commonly described as normal.

Curve	Plane	Description
Curve of Spee	Anteroposterior (seen from the side)	Mandibular cusp tips form an upward-concave curve from canine to last molar
Curve of Wilson	Mediolateral (seen from the front)	Mandibular posteriors incline lingually, so the curve is concave upward across the arch
Curve of Monson	Three-dimensional	Combines Spee and Wilson into a sphere (classically about a 4-inch radius) centered near the glabella

Centric relation (CR): a maxillomandibular relationship with the condyles in the anterior-superior position against the articular eminences and the discs properly placed; it does not depend on tooth contact and is reproducible.
Maximum intercuspation (MI, also called centric occlusion): the tooth-determined position of fullest interdigitation; often slightly anterior to CR.
Supporting (centric holding) cusps: maxillary lingual and mandibular buccal. Guiding (nonsupporting) cusps: maxillary buccal and mandibular lingual.
Working side = the side the mandible moves toward; nonworking (balancing) side = the opposite side. Nonworking-side contacts are the most harmful interferences.
Mutually protected occlusion: posterior teeth protect the anteriors in MI; anterior teeth disclude the posteriors in protrusion; canines disclude in lateral movement (canine guidance). Group function shares lateral guidance among canine and premolars (sometimes molars).
Every tooth occludes with two opposing teeth except the mandibular central incisors and maxillary third molars.

Using the canine or the DISTObuccal cusp for Angle's class: Angle uses the maxillary MESIObuccal cusp and the mandibular buccal groove.
Mixing up Class II division 1 (proclined incisors) and division 2 (retroclined centrals, deep bite).
Treating CR as a tooth position: CR is a joint position; MI is the tooth position.
Calling the curve of Wilson anteroposterior: Spee is front-to-back, Wilson is side-to-side.

BULL rule: when adjusting lateral interferences, reduce the Buccal of Upper and Lingual of Lower (the guiding cusps) and spare the supporting cusps (maxillary lingual, mandibular buccal).

Pick an answer to see right away whether it is correct and why.

The maxillary first molar's mesiobuccal cusp occludes distal to the mandibular first molar's buccal groove. The molar relationship is:
A patient has a deep bite, retroclined maxillary central incisors and flared lateral incisors. The most likely classification is:
Which curve describes the lingual inclination of mandibular posterior teeth seen from the front?
During a right lateral excursion, which contacts are considered the most damaging?
Which tooth normally occludes with only ONE opposing tooth?

0 of 5 answered

Answer key: 1 C · 2 B · 3 C · 4 B · 5 D

Dental School Map · Original study material, written and checked by our team; always confirm clinical decisions against current guidelines.