INTRODUCTION

In the Chinese population, the prevalence of Class III malocclusion is comparatively high, involving one of 20 individuals. Of these, more than half have pseudo Class III malocclusion.1 The diagnosis of pseudo Class III malocclusion differs from that of skeletal Class III malocclusion because it is defined as functional forward displacement of the mandible as a result of retroclined maxillary incisors.2–6 Because the major underlying cause of pseudo Class III malocclusion is the inclination of the maxillary incisors, the treatment objectives aim to change the inclination of those incisors.

In general terms, the goal of interceptive orthodontics is to prevent an existing problem from getting worse. Specifically for pseudo Class III, the goals of early treatment are to correct the anterior displacement of the mandible before the eruption of the canines and premolars so that they can be guided into Class I in the proper mandibular position, to provide space for the eruption of the buccal segments as a result of proclination of the upper incisor, and to provide a normal environment for the growth of the maxilla, eliminating the anterior crossbite.147

Various appliances have been devised for early treatment of a pseudo Class III, such as removable plates with springs, fixed or removable inclined planes, functional appliances, chin-cups, and simple fixed appliances.589 One popular type of simple fixed appliance is the 2 × 4 appliance, which is composed of bands on the first permanent maxillary molars, brackets on the maxillary incisors, and a wire with advancing loops.9

Most clinical studies seemingly are based on retrospectively selected samples with favorable results, and this is likely to result in biased results.10–12 To better evaluate a success rate, it is necessary to follow consecutively treated cases for a reasonable time and also to describe the inevitable dropout. Ideally, one would like to follow patients treated at a young age until growth ceases. However, because pseudo Class III is characterized by dental problems and the early treatment is aimed at correcting the angulation of the upper incisors, the follow-up period should be extended until the eruption of all the permanent dentition except the third molars. Accordingly, we decided to follow- up all consecutively treated patients for a period of five years.

Previously, we reported a series of consecutive young patients with pseudo Class III malocclusion, in whom the simple 2 × 4 appliance efficiently corrected the malocclusion. In that sample, the selection criteria were a Class III incisor relationship (at least two incisors in crossbite) in centric occlusion, in the early mixed dentition, without exfoliation of the second primary molars, exhibiting mandibular displacement and the patients did not have orthodontic therapy before the treatment related to the study.7 These patients were successfully treated with the simple 2 × 4 appliance13 and were followed-up for one year.7 Subsequently, this study aims to present the long-term follow-up of consecutive young patients with pseudo Class III malocclusion treated with the simple fixed 2 × 4 appliance.

MATERIALS AND METHODS

The original sample of 27 consecutive young patients (12 female and 15 male patients) with pseudo Class III malocclusion6 treated with a simple 2 × 4 appliance9 was selected using the criteria described earlier by Rabie and Gu.6 At the 5-year follow-up, 25 patients (15 male and 10 female patients) participated (Table 1). Two patients dropped out soon after the successful completion of 2 × 4 appliance treatment.

TABLE 1. Age (y) at Start of Treatment (T0), End of Treatment (T1), and Five-y Follow-up (T2); and Duration of the Treatment/Observation Period (y) of 27 Patients Treated by Simple 2 × 4 Fixed Appliance

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Twenty patients had the 2 × 4 appliance treatment only, whereas the other five patients also underwent comprehensive upper and lower fixed appliance treatment (extended treatment group) because of crowding. Among these five patients, only one of them had all first premolars extracted during the orthodontic treatment, whereas the other four patients had nonextraction fixed appliance treatment (Table 2). In this study, the lateral cephalograms obtained at the start of treatment (T0), at the end of the 2 × 4 appliance treatment (T1), and at the five-year follow-up (T2) were analyzed according to Pancherz's method (Figures 1 and 2).1415 This analyzes dentofacial morphology at the start of treatment (Table 3), treatment changes (T0-T1), posttreatment changes (T1-T2), and total changes (T0-T2) (Tables 4 and 5; Figure 3).

TABLE 2. Description of Five Patients who had 2 × 4 Appliance Treatment Followed by Comprehensive Fixed Appliance (FA) Treatment (Extended Treatment Group) During the Five-y Follow-up. Age (y) at Start of Treatment (T0), End of 2 × 4 Appliance Treatment (T1), and at Follow-up (T2)

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TABLE 3. Dentofacial Morphology of the Pseudo Class III Subjects at the Start of Treatment (T0), End of Treatment (T1), and Five-y Follow- up (T2)

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TABLE 4. Sagittal Treatment Changes (T0-T1), Posttreatment Changes (T1-T2), and Total Changes (T0-T2) in 2 × 4 Appliance Only Group (n = 20) and Extended Treatment Group (n = 5)

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TABLE 5. Vertical Treatment Changes (T0-T1), Posttreatment Changes (T1-T2), and Total Changes (T0-T2) in 2 × 4 Appliance Only Group (n = 20) and Extended Treatment Group (n = 5)

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RESULTS

DISCUSSION

This study describes the follow-up changes in a sample of consecutively treated patients followed for more than five years after active treatment with a simple 2 × 4 fixed appliance. The original sample consisted of 27 consecutive young patients with pseudo Class III malocclusions due to retroclined upper incisors, who were treated with 2 × 4 appliance according to a prospective protocol.71316 The immediate treatment changes and short-term follow-up results have been reported previously.716 During the five-year follow-up, there was a dropout of two patients (Table 1). Among the five patients who had undergone comprehensive fixed appliance therapy during the follow-up period, ie, after the 2 × 4 appliance treatment, the main reason for the fixed appliance treatment was malalignment, and none of those patients were treated because of a relapse of the reverse overjet (Table 2).

A commonly used method to assess success rate and stability of overjet correction has been to report the status of the overjet.1718–20 In the present study, all patients achieved a positive and often slightly overcorrected overjet during the active treatment after an average of eight months of treatment. This positive overjet was maintained in all subjects who were followed for five years after active treatment. The overjet remained stable because the corrected upper incisors were kept in place by normalizing the overjet and overbite in the phase 1 treatment. In addition, the proclination of the upper incisors before the eruption of the buccal segment allowed the canines and premolars to erupt into a Class I in centric relations, which also may have contributed to the stability of the occlusion (Table 4; Figure 3b). In this study, the dentofacial changes were assessed mainly by linear1516 rather than angular measurements.21 Bookstein22 has shown that linear measurements are more accurate than angular measurements to describe dentofacial changes. Using Pancherz's analysis,1516 all measurements are made in relation to the occlusal plane, ie, close to the “problem area.” Pancherz's method has also been reported to be a more suitable method for assessing dentofacial changes as compared with other superimposition methods.23

One of the benefits claimed for early treatment with 2 × 4 appliance is that space will be provided for the eruption of the canines and premolars in the upper arch, allowing the erupting dentition to be guided into a Class I relationship in centric relation.17 In this five-year follow up, 75% of the original patients who had 2 × 4 appliance treatment seemingly did not need to have comprehensive treatment. A further study will address the need for second-phase treatment objectively.

Among the five patients with extended treatment, which was offered without additional charge, only one patient had extraction therapy. Thus, early intervention with 2 × 4 appliances in subjects with pseudo Class III required no further orthodontic intervention in the vast majority of the patients treated. Thus, the treatment seems to have served as a good interceptive measure.

During the five-year follow-up, A point moved forward significantly (3.2 mm, P< .001) in the 2 × 4 appliance– treated group, which was similar to the reported longitudinal growth changes of the maxilla.24 This indicated that early treatment with 2 × 4 appliance could provide an environment for normal maxillary growth after active treatment to correct the reverse overjet. The forward mandibular growth during the five-year follow-up was about twice that of the maxillary forward growth, which is similar to that reported for cases with stable results after reverse headgear treatment25 and similar to that observed after functional appliances therapy of Class II cases.24

At the five-year follow up, the patients were on average 16.5 years of age, ie, when the majority of the patients were still growing, but usually at a slower rate.26 This supports the success of the treatment because patients showing unfavorable posttreatment changes would be revealed by 16.5 years of age after a five-year follow-up.1418

The purpose of the current study was to follow-up the cases that received early treatment and to verify the benefits of early treatment with simple fixed appliances. Therefore, there was no direct need for an untreated matched control group. The five-year follow-up showed that by subjective assessment, 75% of the cases treated in the young permanent dentition required no further orthodontic treatment after the initial period of eight months of treatment in the mixed dentition with the 2 × 4 appliance. The remaining 25% that received further comprehensive fixed appliance therapy were all corrected by nonextraction, with the exception of one case who had extraction therapy.

Treatment of pseudo Class III in the mixed dentition in this study has fulfilled the expected objectives of interceptive treatment by either eliminating the need for further treatment or simplifying the second phase of comprehensive treatment. It is important to highlight the fact that the objective of early treatment of a pseudo Class III is not necessary to eliminate the need for second phase of treatment but rather to reduce the difficulty of treatment of phase II if it is needed.

At least two studies1920 have reported that self-correction of anterior crossbite during the transition from primary to early mixed dentition was potentially high. This seems to indicate that very early treatment of anterior crossbite should be implemented with great caution to avoid unnecessary clinical procedures.

CONCLUSIONS

This prospective longitudinal study showed that treatment of pseudo Class III in the mixed dentition, with a simple fixed (2 × 4) appliance as a first-phase treatment, resulted in a positive overjet, which was maintained in the long-term. In a minority of patients, a second-phase treatment with fixed appliance was needed.