Vertical control: a multifactorial problem and its clinical implications

Redirecting mandibular growth through orthodontic dentoalveolar height development in growing patients with Class III malocclusion undergoing maxillary orthopedic protraction

INTRODUCTION

To control mandibular growth could be the determining factor for any growing patients with Class III malocclusion undergoing maxillary orthopedics. It has been reported that orthodontic dentoalveolar height development (ODHD) through orthodontic total arch extrusion might redirect mandibular growth backward and downward in growing patients with Class III malocclusion. We hypothesized bimaxillary-ODHD (bimax-ODHD) should be equal to or exceed the mandibular condylar growth to redirect the mandible to grow downward and backward in growing patients with Class III malocclusion.

METHODS

Twenty-seven consecutive growing patients with Class III malocclusion who underwent maxillary orthopedics (MO) were recruited in this study, including 13 control patients (aged 12.70 ± 2.09 years) who underwent treatment of MO with no ODHD and another 14 patients who underwent MO and ODHD (ODHD group; aged 12.75 ± 1.40 years). The pretreatment (T1) and posttreatment (T2) CBCT images were superimposed and measured for the amount of ODHD and maxillary downward growth (ODHD-Mx), ODHD in the mandible (ODHD-Mn), T2 - T1 changes on facial convexity, y-axis, maxillary and condylar growth, and mandibular posture. The data were analyzed statistically.

RESULTS

The T2 - T1 treatment duration was 7.5 months, significantly (P = 0.028) shorter in the ODHD group. The maxillary and condylar growth were similar among the groups. The mandible grew forward and downward in the control group, the ODHD-Mx and ODHD-Mn were significantly (P = 0.011) more in the ODHD group, and the mandible significantly (P = 0.001) grew backward and downward. The mandible grew backward and downward when the bimax-ODHD (ODHD-Mx + ODHD-Mn) exceeded the condylar growth (r = 0.715; P <0.001).

CONCLUSIONS

The bimax-ODHD, including the downward growth of the maxilla, should be equal to or exceed the mandibular condylar growth to redirect the mandible to grow downward and backward and improve the skeletal facial convexity in growing patients with Class III malocclusion.

Does muscular activity related to vertical facial divergence influence the time needed for orthodontic extrusion of palatally impacted maxillary canines? A retrospective study

Background

The aim of the present study was to evaluate if the different muscular activity correlated to different degrees of facial divergence has an effect on the time needed to extrude a palatally impacted maxillary canine.

Material and Methods

Twenty-six patients were retrospectively selected, all treated with a specific cantilever appliance that allows extrusion of the impacted canine applying a physiologic amount of force below 0.6 N in a predictable way. For all the patients, pre-treatment cephalometric tracings were used to evaluate facial divergence through the FMA angle, the angle between the maxillary and mandibular plane, and the angles between the occlusal plane and either the maxillary and mandibular plane. Linear bivariate regression was calculated to evaluate if facial divergence can predict the time needed for canine extrusion.

Results

The linear regression model was not able to predict extrusion time from variables explaining the facial divergence.

Conclusions

Palatally impacted maxillary canines can be treated with the application of physiologic extrusion force regardless of patients’ facial divergence and muscular activity.

Key words:Impacted canines, cantilever, facial divergence, muscular activity.

Má oclusão Classe I de Angle, com mordida aberta anterior, tratada com extração de dentes permanentes

A mordida aberta é uma anomalia com características distintas que, além da complexidade dos múltiplos fatores etiológicos, traz consequências estéticas e funcionais. Muitas alternativas têm sido utilizadas em seu tratamento, entre elas a grade palatina, forças ortopédicas, ajuste oclusal, camuflagem com ou sem exodontias, mini-implantes ou miniplacas e cirurgia ortognática. O diagnóstico preciso e a determinação da etiologia permitem estabelecer os objetivos e o plano de tratamento ideal para essa má oclusão. O presente relato descreve o tratamento de uma má oclusão Classe I de Angle, com padrão esquelético de Classe II e mordida aberta anterior, realizado em duas fases e que foi apresentado à diretoria do Board Brasileiro de Ortodontia e Ortopedia Facial (BBO), representando a categoria 2, como parte dos requisitos para a obtenção do título de Diplomado pelo BBO.

The mandibular muscles and their importance in orthodontics: a contemporary review

It is widely accepted that the orthodontist should have a thorough understanding of the craniofacial musculature and its association with the growth and development of the dentofacial complex. There is still much controversy regarding the influence of the mandibular muscles on normal growth and development, and on orthodontic treatment and stability. This review presents an outline of the mandibular muscles and the vertical facial pattern. The different methods by which the mandibular muscles have been investigated are discussed. The potential influence of these muscles on normal morphologic variation in different people is also discussed, along with the implications for contemporary orthodontic treatment and stability.

Orthodontics and temporomandibular disorders: a review of the literature (1966-1988)

The orthodontist has been both accused of causing and complimented for curing temporomandibular dysfunction. To better understand the origins of these conflicting opinions, a review of the orthodontic and temporomandibular joint journals was performed for articles published since 1966. A total of 91 publications that discussed the relationship between orthodontics and temporomandibular disorders was found, and these articles were divided in three categories: viewpoint publications, case reports, and sample studies. Among the areas scrutinized in each category was the method that has led to the diversity of viewpoints. From this analysis, the following conclusions were drawn: (1) viewpoint publications and case reports were excessively represented in comparison with the number of sample studies; (2) viewpoint publications and case reports described a wide variety of conflicting opinions on the relationship between orthodontics and temporomandibular disorders; (3) unlike sample studies, viewpoint publications and case reports have little or no value in assessment of the relationship between orthodontics and temporomandibular disorders; (4) sample studies indicate that orthodontic treatment is not responsible for creating temporomandibular disorders, regardless of the orthodontic technique; and (5) sample studies indicate that orthodontic treatment is not specific or necessary to cure signs and symptoms of temporomandibular dysfunction.

A growth-related concept for skeletal class II treatment

The use of a combined activator--high-pull headgear appliance for treatment of Class II, Division 1 malocclusion is presented as a preliminary report. The activator itself is equipped with a palatal bar, lower lip pads, and torque-control auxiliaries for the upper incisors. The face-bow is mounted directly on the activator, and the extraoral force vector is equivalent to that of an anterior high-pull vector. During bite registration the veritcal displacement of the mandible is restricted to a minimum, and the anterior displacement should not exceed 6 mm. On the basis of current knowledge of the growth of the bony facial structures, treatment objectives and a specific approach for skeletal Class II correction are defined. Following these objectives, the therapy aims at correcting the malocclusion without diverting the anterior landmarks of the bony face from their specific lines of growth. This is brought about by the corresponding mechanics of the activator-headgear combination. The corrective effect of this appliance may be assumed to be the result of several different factors. The maxillary dentition is restrained in a posterior cranial direction, and an inhibitory effect on the maxilla counter to its line of development is attained. The mandibular dentition is influenced in an anterior downward direction by means of the bite registration, and the occlusion is unlocked during treatment. Any transfer of distally directed headgear forces from the maxilla to the mandible is prevented. Temporary stimulation of condylar growth, possibly combined with temporary posterior deflection of condylar growth, may also be induced. In this way it is possible to take maximum advantage of condylar growth in the sagittal dimension. Thus, not only is the malocclusion corrected but, at the same time, decisive profile improvement is achieved by anterior development of the mandible. From the experience gained so far with a Class II, Division 1 sample undergoing treatment with the activator-headgear combination, it would appear that skeletal control of the direction of facial growth during treatment is possible. A quantitative report on this group of approximately forty patients, some of whom are still receiving treatment, is in preparation.