Functional appliances and arch width

Transverse maxillary and mandibular growth during and after Bionator therapy: study with metallic implants

INTRODUCTION: This study evaluated posteroanterior cephalograms before and after treatment and long term follow-up of Class II division 1 patients treated with bionator. OBJECTIVE: The objective was to demonstrate the transverse growth of maxilla and mandible during and after bionator therapy. METHODS: Measurement of transverse dimensions between posterior maxillary and mandibular implants, as well as the distances between the buccal, gonial and antegonial points were recorded. Measurements were analyzed at three periods: T1 = before bionator therapy, T2 = after bionator therapy and T3 = 5.74 years after T2. RESULTS: There was statistically significant transverse increase due to growth and/or treatment for all variables, except for the distance between the anterior maxillary implants. CONCLUSIONS: During the study period only the anterior maxillary area did not show transverse growth.

Comparison of arch dimension changes in 1-phase vs 2-phase treatment of Class II malocclusion

INTRODUCTION

We compared arch dimension changes in 1-phase and 2-phase treatment of Class II malocclusion. This was a prospective randomized clinical trial conducted in the Department of Orthodontics at the University of Florida between 1990 and 2003.

METHODS

During phase 1 treatment, 86 subjects were treated with a bionator, 93 were treated with headgear/biteplane, and 81 served as the observation group. For phase 2, all subjects were then treated with full orthodontic appliances. Arch dimensions were followed; maxillary and mandibular alginate impressions were taken at baseline, end of early Class II treatment or observation, beginning of fixed appliance treatment, end of orthodontic treatment, and approximately 3 years posttreatment. Alginate impressions were taken of each dental arch at each data collection point. These were poured in orthodontic stone, trimmed, and photocopied from the occlusal aspect. These images were then scanned and measured.

RESULTS

Although differences between the treatment groups were found in both the maxillary and mandibular arches after phase 1, these differences were no longer evident by the end of full orthodontic treatment or after posttreatment retention.

CONCLUSIONS

There were no differences in arch dimensions after 1-phase or 2-phase treatment of Class II malocclusion.

Do we really want a quick fix?

Dental practitioners have been encouraged recently to take a more structured long term view of their continuing professional development, in particular being wary of any 'weekend' courses apparently offering 'quick fix' solutions to their clinical problems.

Expansion with vestibular shields: an experimental test of the periosteal-pull hypothesis

Two mechanisms are said to be responsible for the expansion commonly produced by buccal shields: (1) unbalanced tongue pressure and (2) periosteal pull; that is, periosteal traction on the bone overlying the molar roots. The present study used 44 young albino rats to examine these two alternatives. Half the rats wore buccal shields to produce molar expansion, and half had their maxillary molar crowns ground down to the gingiva to eliminate the effect of the tongue. In the resulting 2 x 2 design, four experimental groups were formed: (1) SM, shields and intact molars; (2) Sm, shields and reduced molars; (3) sM, no shields and intact molars; and (4) sm, no shields and reduced molars. It was hypothesized that if vestibular shields produce expansion through periosteal traction, the presence or absence of molar crowns should make no difference. Conversely, if the expansion is caused by unbalanced tongue pressure, shields should have an effect only in conjunction with intact maxillary molars. Palatal amalgam implants and dorsoventral cephalograms were used to measure the maxillary basal and dental expansion that occurred during the 6 weeks of the experiment. Analysis of variance showed the presence of highly significant interaction between shields and molars: the shields produced an increase in posterior dental expansion, but only when molar crowns were present. In contrast, basal expansion was unaffected by any combination of treatments. At least for the rat, it may be concluded that unbalanced tongue pressure, rather than periosteal traction, is probably responsible for the expansion produced by buccal shields.

Long-term effects of the Herbst appliance on the dental arches and arch relationships: a biometric study

The purpose of this study was to evaluate biometrically the treatment and post-treatment effects of the Herbst appliance on the dental arches and arch relationships. The sample consisted of 53 Class II, division 1 malocclusion patients (33 boys and 20 girls) treated with the Herbst appliance. The mean age of the patients before treatment was 12.5 years (SD = 1.2 years). Dental casts were analysed before treatment, after treatment, 6 months post-treatment and at the end of the growth period (5-10 years post-treatment). The following variables were assessed: sagittal molar and canine relationships, overjet, overbite, maxillary and mandibular arch perimeters, and inter-molar and inter-canine dental arch widths. During treatment, the overjet, overbite, and sagittal molar relationship were overcorrected in most of the cases, while the sagittal canine relationship was normalized. The maxillary and mandibular arch perimeters increased during treatment, as did dental arch widths (molar and canine). In the long-term (mean = 6.7 years after treatment), Herbst appliance treatment resulted in a normal or over-corrected sagittal molar relationship in 79 per cent and a normal canine relationship in 68 per cent of the cases. Eighty-three per cent of the subjects had an overjet of 4.5 mm or less. In the long-term, the arch perimeters seemed to follow a normal dental development pattern. The increase of the upper molar and canine dental arch widths during treatment remained virtually stable whilst the lower intermolar arch widths seemed unaffected by treatment.

The burden of proof: a critical review of orthodontic claims made by some general practitioners

The increased demand for orthodontic treatment in the developed countries has led to a recent proliferation of "motel courses" that are specifically designed for general practitioners. Most of the techniques presented are only those that have long been available for selection by discerning orthodontists. However, when they are applied exclusively and indiscriminately by inexperienced clinicians, this may result in either prolonged, unnecessary treatment or failure through instability. Therefore some of the claims that are made will be examined and discussed with a review of the literature.