Malocclusions in Orthodontics

Question 1

What is malocclusion?

Answer 1

An appreciable deviation from normal occlusion.

Question 2

What percentage of malocclusions are due to a variation of normal development?

Answer 2

95%

Question 3

What percentage of malocclusions have an identifiable cause?

Answer 3

5%

Question 4

What are the genetic influences?

Answer 4

Skeletal pattern
Some syndromes such as muscular dystrophy
Tooth morphology

Question 5

What are the environmental influences?

Answer 5

Soft tissues (forces created by lips, tongue, PDL)
Habits
Local factors (retained deciduous teeth, missing teeth)
Pathology (cleft lip and palate)
Trauma

Question 6

What is a class I incisor relationship?

Answer 6

The lower incised edge lies on or below the cingulum plateau of the palate surface of the upper incisors.

Question 7

Features of a class I?

Answer 7

Usually skeletal 1 but may be mild C2 or C3
AOB
Crossbites

Question 8

Dental issues of a class I?

Answer 8

Crowding
Spacing
Bimaxillary proclination
Vertical anomalies - AOB
Transverse anomalies - Crossbites, scissorbites

Question 9

How is crowding managed in a class I?

Answer 9

Creation of space from extractions or arch extension

Question 10

How is spacing managed in a class I?

Answer 10

Open space and place prosthesis

Close space with appliances

Question 11

How are scissorbites managed in class I?

Answer 11

Mandibular expansion and maxillary contraction

If severe may need surgery

Question 12

How are crossbites managed in class I?

Answer 12

Maxillary expansion but before planning treatment, consider if there is a displacement or true asymmetry and manage appropriately. 
Can be treated with:
URA with midline screw/coffin spring
Quadhelix
RME
AW expansion in FA
Expansion arch (attached to molar tubes)
Surgical assisted expansion

Question 13

What is the definition of a Class II DIV 1 incisor relationship?

Answer 13

The lower incisor edges lie palatal to the cingulum plateau of the upper incisors
Upper incisors are proclined or of average inclination with an upper overjet.
Or
The upper incisors are slightly retroclined with an upper overjet.

Question 14

What are the features of a class II?

Answer 14

76% usually have a skeletal 2 base
If skeletal 1, incisor relationship is usually due to a habit
Class II incisor relationship with proclined or average upper incisors
Average or lower face height
Increased overjet
Overbite is usually deep and often incomplete
Buccal segments may have crossbites buccal/lingual

Question 15

Treatment options for Class II div 1

Answer 15

URA (simple tipping)
Functional appliances (in growing patients)
Fixed appliances (if skeletal problem allows camouflage)
Orthognathic surgery (when too severe for orthodontics alone)

Question 16

What is the definition of a Class II div 2?

Answer 16

The lower incisor edges lie palatal to the cingulum plateau of the upper incisors.
Upper incisors (and usually lowers) are retroclined with minimal OJ

Question 17

What are the features of a Class II Div 2?

Answer 17

Usually skeletal 2 base, although could be skeletal 1, or skeletal 3.
Tendency for scissor bite
Retroclined upper and lower incisors
Overbite is usually deep
Overjet is reduced usually
Extruded upper incisors
Scissorbite common in premolar region
Crown-root angle may be decreased
Lower face height
lower MMP angle
lower gonial angle

Question 18

Treatment options for Class II div 2?

Answer 18

URA (to reduce OB with anterior bite plane)
Modified functional appliance (cantilever springs behind the upper incisors to proline the maxillary incisors)
Fixed appliances (likely to need torque to upper incisors)
Avoid extractions in low MMP angle cases as space closure can be difficult
Carefully consider extraction decision, if necessary take 5’s rather than 4s to minimise lingual movement of LLS.
Orthognathic surgery

Question 19

What is the definition of a Class III incisor?

Answer 19

Lower incisor edge lie anterior to cingulum plateau of the palatal surface of the upper incisors.

Question 20

What can a Class III be due to?

Answer 20

Genetics - skeletal pattern

Patients with CLP may present with a III Malocclusion

Question 21

Features of a Class III?

Answer 21

Lower cranial base angle, forwards position of mandible
Normal or lower MMP angle and lower face height
Class III Molar relationship
Reverse Overjet
Reduced Overbite
Incisors compensate for skeletal base ie proclined maxillary, retroclined mandibular incisors
Can have displacements to obtain posterior occlusion due edge to edge incisor contact or unsatisfactory transverse buccal segment relationship

Question 22

Treatment options for a class III?

Answer 22

Growth modification
Orthodontic camouflage
Orthognathic surgery
Anterior cross elastics 
Protraction headgear