Jeffrey C. Posnick, DMD, MD

Functional Aspects

Clinical Characteristics

Dental Findings

Radiographic Findings

Treatment Indications and Objectives

The individual’s immediate aesthetic concerns often center on 1) unfavorable lower-lip contours (e.g., a curled and everted lower lip with an accentuated labiomental fold) 2) a lack of prominence of the chin (e.g., a weak profile) and 3) an unattractive neck (e.g., a soft-tissue double-chin tendency).27,38,39,42,48,47,50,59 Functional issues are also to be expected. For example, when the anterior bite is “deep,” it will cause irritation of the gingival tissues of the palate just behind the maxillary incisors. Partial obstruction of the upper airway as a result of a retropositioned tongue is also common (i.e., heavy snoring, restless sleep, daytime fatigue, and documented or undiagnosed sleep apnea; see Chapter 26).^11,62 Complaints of an uncomfortable “dual” bite, chewing difficulties, masticatory muscle discomfort, and audible speech articulation errors are frequent. The individual with a Class II deep bite may have a greater tendency toward clicking (i.e., anterior disc displacement) in each temporomandibular joint.^25,51 Interestingly, there is little scientific evidence to support the notion that the signs of clicking will into more significant temporomandibular joint pathology (see Chapter 9).

When the mandible is deficient, with significant overjet, and when the anterior facial height is short, the lower lip tends to “get caught” behind the maxillary incisors. During growth, if the lower lip stays behind the upper teeth, then the upper teeth will adapt by tipping forward, thus creating a Class II, Division 1 malocclusion with varied degrees of maxillary incisor spacing. When the mandibular deficiency and the protrusive lower incisors are combined with procumbent maxillary incisors, the individual tends to be concerned with both the lack of chin prominence and the protruding maxillary anterior teeth (i.e., a toothy smile). Alternatively, if the lower lip remains in front of the maxillary incisors, there is an adaptive tendency for the maxillary incisors to tip lingually (i.e. Class II, Division 2).

The Role of Growth Modification in the Preadolescent Child

When the preadolescent child with mandibular deficiency is identified, a growth modification approach to treatment is frequently considered by the evaluating orthodontist.13,33,32 Cozza and colleagues completed a systematic review of the literature to assess the efficacy of functional appliance use for enhancing mandibular growth in subjects with Class II malocclusions.¹⁴ With the use of the Medline database, the survey covered the period from January 1966 to January 2005. A review of 704 articles confirmed only 22 that qualified for the final analysis. Of these 22 articles, only four randomized clinical trials were retrieved and found to be worthy of inclusion. Interestingly, none of these four trials reported a clinically significant change in mandibular length to be induced by functional appliances in the patients with Class II deformities. According to Proffit, the only concrete indications for the treatment of the preadolescent mixed dentition child with a mandibular deficiency who presents without an anterior open bite are the following⁴⁴:

Despite the review by Cozza and colleagues and Proffit’s stated limited indications for early mixed dentition treatment in the child with a mandibular deficiency, a growth modification approach is often carried out by the evaluating orthodontist. The goals are frequently stated to be the restraining of forward maxillary growth while encouraging the mandible to grow downward and forward. In accordance with this rationale, mixed dentition growth modification treatment frequently incorporates the following steps:

Orthodontic Camouflage Approach

When the orthodontist proceeds with growth modification maneuvers and a less than favorable biologic response is realized, it is apparently tempting to proceed with a camouflage (dental compensation) approach (Figs. 19-1 through 19-5).^{34,35,37,36,42} This would be carried out to “neutralize” the occlusion rather than to position the teeth solidly into the alveolar process in combination with orthognathic surgery. Current evidence-based medical standards recommend that the treating orthodontist have a “timeout” (i.e., a sit-down discussion and reassessment with the parents and the patient) that includes a review of the records (e.g., photos, models, radiographs) and a discussion of the biologic effects on the airway, the facial aesthetics, the occlusal stability, and the periodontium that may result from the various treatment options. A referral to an experienced orthognathic surgeon for the discussion of possible future surgical aspects is highly recommended.

An orthodontic camouflage approach for the individual with mandibular deficiency may take the form of maxillary premolar extractions so that the upper incisors can be retracted. This is generally combined with the flaring of the mandibular incisors. When this is carried out in the individual with a mandibular deficiency, the short-term objective of a neutralized occlusion may be achieved, but the following are potential sequelae: 1) unfavorable long-term facial aging 2) the risk for obstructive sleep apnea later in life 3) long-term periodontal deterioration 4) lower anterior crowding with recurrent malocclusion and 5) an inconsistent occlusion (i.e., a dual bite) (see Figs. 19-1 through 19-5). The orthodontist may feel favorable toward a camouflage approach on the basis of the belief that the patient can always have a “chin implant” to improve his or her facial aesthetics. Unfortunately, this approach will rarely achieve a pleasing aesthetic outcome. A chin implant tends to result in 1) an accentuated labiomental fold 2) an overly prominent pogonion and 3) a residual obtuse neck–jaw angle (Fig. 19-4). Furthermore, it does nothing for any baseline masticatory and airway dysfunction (see Chapter 37).

Definitive Reconstruction