1 What are the components of a Class II malocclusion?

Utilizing cephalometrics and computer-based statistical evaluation, Moyers et al.⁴ determined that Class II patients were divided into six separate horizontal types and five vertical types based upon various skeletal and dentoalveolar characteristics. The six horizontal types are described in Table 13-1.

TABLE 13-1 The Six Horizontal Class II Types Determined by Moyers et al.

DIAGRAMMATIC REPRESENTATION	DESCRIPTION
	Normal
	Type A: Maxillary dental protraction
	Type B: Maxillary prognathism, dental protraction
	Type C: Maxillary retrognathism with flared or upright incisors, mandibular severe retrognathism with flared lower incisors
	Type D: Maxillary retrognathism with dental protraction, severe mandibular retrognathism
	Type E: Maxillary prognathism and dental protraction + mandibular dental flaring
	Type F: Mandibular retrognathism

Adapted from Moyers RE, Riolo MS, Guire KE, et al: Am J Orthod 1980;78(5):477-494.

The five vertical types (Table 13-2) were defined by an assessment of the following four facial planes relative to their normal position:

TABLE 13-2 The Five Vertical Class II Types Determined by Moyers et al.

DIAGRAMMATIC REPRESENTATION	DESCRIPTION
	Type 1: Mandibular plane steeper than normal, steeper functional occlusal plane, palate tipped somewhat downward, anterior cranial base tipped upward
	Type 2: Mandibular plane, functional occlusal plane and palatal plane are all flatter than normal and are nearly parallel
	Type 3: Palatal plane tipped upward anteriorly
	Type 4: Mandibular plane, the functional occlusal plane, and the palatal plane are all tipped markedly downward
	Type 5: Palatal plane is tipped downward, cranial base tipped downward

Adapted from Moyers RE, Riolo MS, Guire KE, et al: Am J Orthod 1980;78(5):477-494.

In the transverse dimension, the buccal segments of Class II patients often appear normal. A 3 to 4 mm transverse discrepancy, however, usually exists at the level of the first molar due to a narrow maxillary arch. This is readily observable if the mandible is moved into the Class I relationship at the molar. Further assessment of components of Class II malocclusion in an adolescent population indicated that in a sample of 277 children with a Class II malocclusion, mandibular skeletal retrusion was the most common characteristic. The maxilla was generally either retrusive or well positioned.

2 How can Moyers’ differential diagnosis of Class II horizontal and vertical types be used to help us with treatment planning of Class II patients?

Moyers’ differential diagnosis of Class II malocclusions allows us to more easily determine the components of the Class II malocclusion problem. It identifies the skeletal problem and the dentoalveolar problem and thus directs our treatment thinking to these specific areas. Treatment planning considerations using Moyers’ differential Class II horizontal analysis is summarized, at least in part, in Table 13-3.

TABLE 13-3 Summarization of Moyers’ Differential Class II Horizontal Analysis

TYPE	TREATMENT CONSIDERATIONS
Type A	1. Extraction of upper bicuspids + orthodontic retraction and uprighting 2. Distalization of upper dentition into Class I (i.e., headgear, molar distalizers) 3. Surgery: Anterior maxillary alveolar osteotomy setback and uprighting of upper centrals and laterals after extraction of upper bicuspids and orthodontic retraction of canines
Type B	1. Headgear (growing patient) 2. Surgery: maxillary anterior alveolar setback (non-growing patient) with extractions of upper bicuspids
Type C	1. Complex skeletal and dentoalveolar considerations 2. Extraction of upper and lower bicuspids, orthodontics + functional appliance 3. Extraction of upper 5/lower 4’s, orthodontics to close spaces and upright incisors + surgery: maxillary and mandibular differential advancement
Type D	1. Orthodontic + functional appliance (growing patient) 2. Surgery: mandibular advancement (non-growing patient)
Type E	1. Headgear 2. Bimaxillary protrusion-extraction of upper and lower bicuspids 3. Extractions + surgery (non-growing patient)
Type F	1. Functional appliance (growing patient) 2. Surgery: mandibular advancement (non-growing patient)

Adapted from Moyers RE, Riolo MS, Guire KE, et al: Am J Orthod 1980;78(5):477-494.

In addition to the horizontal considerations addressed in Table 13-3, proper patient treatment also requires assessment of the vertical components. Treatment options for vertical correction in growing patients would include biteblocks and various types of headgear. In non-growing patients, surgical correction options such as LeFort I maxillary impaction and alveolar procedures may be required.

3 What is the prevalence of Class II malocclusions?^3,5

According to the NHANES III Study, 15% of the U.S. population have an overjet of greater than 4 mm, 38% an overjet of 3 to 4 mm, and 33% Class II occlusal discrepancies. The same frequency for Class II dental characteristics was found in Caucasians, African-Americans and Hispanics. According to McNamara1, 75% of Class II skeletal discrepancies are the result of mandibular retrognathia.

4 What is the etiology of Class II malocclusion?^6–10

Class II malocclusion is usually an aberration of normal development and not caused by a pathologic process. It is usually the result of multiple factors that influence growth and development and not from one specific factor. The development of Class II malocclusion, however, may be related to some specific causes, genetic influences, and environmental factors. Such specific causes as the effect of teratogens on mandibular growth, mandibular deficient syndromes (Pierre-Robin and Treacher-Collins), fetal molding, trauma to the transmandibular junction (TMJ) area during the birth process, childhood fractures of the jaw, and mandibular arthritic problems may all contribute to the development of a Class II skeletal pattern. Less than 1% of orthodontic patients, however, have a disruption in embryological development that can be attributed as the major cause of malocclusion. Genetic influences have been shown to be associated with Class II malocclusions.

Local and environmental factors may also be an issue in the development of Class II malocclusions because of their alteration of the normal physiologic pressures and forces associated with craniofacial growth. These pressures and forces may be disrupted or imbalanced by the effects of abnormal function of the soft tissues. Disruption of normal lip balance such as that associated with lip incompetency may lead to flaring of the upper incisors from an imbalance of labial and lingual musculature. The need to achieve lip–tongue contact for an oral seal during swallowing can cause the lip to retrocline lower incisors and the protruding tongue to flare upper incisors, thus increasing overjet. It has also been speculated that mouth-breathing can cause the opening muscles to place a distal force on the mandible, retarding its growth and rotating the mandible clockwise. In addition, it is thought that finger-sucking habits can produce a Class II division 1 incisal relationship within a Class II or Class I skeletal pattern (Fig. 13-1).

FIG 13-1 Vertical and anteroposterior distortion of maxilla caused by thumb-sucking habit.

5 What treatment protocols are used to correct Class II malocclusions?

Treatment for Class II malocclusions may involve the following:

The appropriate protocol for each patient depends upon patient desires and doctor assessment of the exact nature of the Class II problem as well as the orthodontist’s treatment protocol preferences.

6 What is extra-oral traction?^3,5,11

Extra-oral traction is the application of force to the dentition and maxilla through the use of headgears (cervical, occipital, combination) fitted to the skull and attached facebows through which force is directly applied to the dentition, usually through the permanent maxillary first molars. Headgear wear is required for at least 12 to 14 hours per day for 6 to 18 months at a force level of 12 to 16 ounces per side for skeletal modification. Three types of headgear are commonly used depending upon the vertical craniofacial growth pattern: cervical pull headgear for low vertical dimension (Frankfort mandibular plane angle [FMA] ≤25), occipital pull headgear (FMA >30) and combination (combi) headgear for cases in which the vector of force application needs to be altered depending upon the desired effect for a specific patient. The various types of headgear and attached facebows are useful in applying forces of appropriate magnitude and direction to the maxilla via the maxillary dentition. The effect of the applied force has an orthopedic effect. It modifies maxillary position by altering its normal downward and forward growth pattern, thus normalizing the Class II to a Class I skeletal pattern (Fig. 13-2).

FIG 13-2 Headgear treatment of Class II division 1 malocclusion. A-D, Initial photos: facial photos (A and B), intraoral photo (C), and cephalometric radiograph (D). E-H, Post-cervical headgear: facial photos (E and F), intraoral photo (G), and cephalometric radiograph (H). I and J, Orthodontic treatment with extractions: facial photo (I) and cephalometric radiograph (J).

7 What is the distalizing protocol for the correction of Class II?^3,5,11,12

Molar distalization is used when the Class II problem is dentoalveolar in nature. Molar distalization corrects a dental Class II by moving the maxillary first molar distally into a Class I relationship. Such treatment has no orthopedic effect. D/>