Classification of Occlusion and Malocclusion

Question 1

Andrew’s 6 keys

Answer 1

1. Correct molar relationship (distobuccal cusp of upper 6 lies within embrasure between lower 6 and 7)
2. Correct incisor relationship (class 1 correct OJ and OB)
3. Correct crown inclination
4. Correct angulation of teeth
5. Tight contact points and no rotations
6. Flat occlusal plane (or slight curve of Speed)

Question 2

BSI classification of occlusion - incisor relationship

Answer 2

based on the incisor relationship:
- Class I. The lower incisor edges occlude with or lie immediately below the cingulum plateau of the upper central incisors.
- Class II. The lower incisor edges lie posteriorly to the cingulum plateau of the upper central incisors.
• Division 1. The upper incisors are proclined or of an average inclination.
• Division 2. The upper central incisors are retroclined.
- Class III. The incisal edges of the lower incisors lie anterior to the cingulum plateau of the upper incisors.
(The overjet is reduced or reversed. i.e. 1 mm or less including negative values.)

Question 3

Angle’s classification of occlusion - molar relationship

Answer 3

• Class I - the mesiobuccal cusp of the upper first molar occludes with the mesiobuccal groove of the lower first molar.
• Class II - the upper first molar occludes mesial to the Class I position.
• Class III - the upper first molar occludes distal to the Class I position.

Question 4

How do you assess the Dental Health Component of the IOTN?

Answer 4

The single worst feature of a malocclusion is noted (the index is not cumulative) and categorised into one of five grades reflecting need for treatment.  
Grade 1-no need, 
Grade 2- little need, 
Grade 3 -moderate need, 
Grade 4 -great need, 
Grade 5 - very great need

Question 5

How do you assess the Aesthetic Component of the IOTN? And what is the disadvantage of the Aesthetic component?

Answer 5

• Developed in an attempt to assess the aesthetic handicap posed by a malocclusion and thus the likely psychosocial impact upon the patient. The aesthetic component comprises a set of ten standard photographs which also grade from score 1, the most aesthetically pleasing to score 10, the least aesthetically pleasing.
• Aesthetic component score 1 or 2 = none, 3 or 4 = slight, 5= borderline, 6, or 7 = moderate, 8,9,10 = definite need.
• Disadvantage- subjective and no Class III or open bite photographs

Question 6

How do you evaluate the quality of treatment provided?

Answer 6

• Peer Assessment Rating Index (PAR)
• Scores are listed for a number of parameters before and at the end of treatment, using study models
• (i) great improvement; (ii) moderate improvement; (iii) no change