Efeitos dentoesqueléticos do aparelho extrabucal de tração occipital no tratamento da má-oclusão de classe II, divisão 1 / Dentoskeletal effects of the extraoral occipital traction appliance on the treatment of class II, division 1 malocclusion

O objetivo deste estudo foi comparar as alterações dentoesqueléticas decorrentes do tratamento exclusivo com o aparelho extrabucal de tração occipital em pacientes com más-oclusões de Classe II, Divisão I, com um grupo controle com o mesmo tipo de má-oclusão. O grupo experimental compreendeu 25 pacientes (dez meninos e 15 meninas), com média de idade inicial e final de 10,28 e 1 1,82 anos, respectivamente e período médio de tratamento de 1,54 anos. O grupo controle consistiu de 31 indivíduos (22 meninos e nove meninas), com média de idade inicial e final de 9,08 e 12,11 anos, respectivamente. Utilizaram-se telerradiografias de todos os indivíduos, obtidas antes e após a colocação do aparelho e do período de observação. O test "t" pareado foi utilizado na comparação intragrupos e o test "t" na comparação intergrupos. A tendência de deslocamento anterior da maxila foi alterada,'apresentando melhora na relação maxilomandibular e na convexidade facial. O comportamento vertical maxilar foi equilibrado e o desenvolvimento dos molares superiores no sentido vertical e sagital foi restringido. Concluiu-seque o uso do aparelho extrabucal de tração occipital é eficiente na correção das más-oclusões de Classe II, Divisão I, sendo indicado para pacientes meso e dolicofaciais.

The aim of this prospective study was to compare the dentoskeletal alterations resulting from treatment exclusively with the Extraoral occipital fraction appliance in patients with Class II, Division I, malocclusions with a control group with the same type of malocclusion. The Experimental group comprised 25patients (ten boys and 15 girls), with initial and final mean ages of 10.28 and 11.82 years, respectively and a treatment mean period of 1.54 years. The Control group consisted of 31 individuals (22 boys and 9 girls). with initial and final mean ages of 9.08 and 12.11 years, respectively. Lateral cephalometric radiographs were taken before and after placement of the appliance and of the period of observation. The paired t-test was used in the intragroup comparison and the t-test in the intergroup comparison. The trend towards anterior displacement of the maxilla was altered, presenting improvement in the maxillomandibular relationship and in facial convexity. The vertical maxillary behavior was balanced and development of the maxillary molars in the vertical and sagittal directions was restricted. The use of the Extraoral occipital traction appliance is very efficient for correcting Class 11, Division I, malocclusions, being an excellent option of treatment.

A descriptive study of mandibular incisor alignment in untreated subjects.

INTRODUCTION: The development of mandibular incisor crowding appears to be a continuous process throughout life, but more evidence is needed to understand why changes occur. METHODS: In this study, we describe the longitudinal dental changes in untreated children (n = 15) who had records at 3 times and in an untreated adult group (n = 18) (parents) who had records for 2 times. The mean numbers of years between initial and final observations were 29.8 years for the children and 33.7 years for the parents. All subjects were participants in the original Burlington Growth Research Project at the University of Toronto. The following variables were measured to an accuracy of 0.01 mm: overjet, overbite, mandibular intercanine width, mandibular interfirst premolar width, mandibular intermolar width, mandibular arch length, Little's incisor irregularity index, mandibular anterior space analysis, and Carey's space analysis. RESULTS: There were no statistically significant (P >.01) differences between the sexes for the variables measured. Little's irregularity index continued to increase in all groups (P <.01), although this rate appeared to be lower in the parent group. Intercanine and interfirst premolar widths and arch lengths continued to decrease with age. CONCLUSIONS: These results underline the importance of studies showing that untreated dentitions change over time. Orthodontic patient education is imperative about retention protocols and late developmental crowding.

Estudo cefalométrico das alterações dentoesqueléticas da má oclusão de Classe II, divisão 1 tratada com o aparelho de Herbst com cantiléver / Cephalometric study in patients that displayed Class II, division 1 malocclusion treated with herbst appliance

OBJETIVO: Realizou-se um estudo cefalométrico, em telerradiografias, objetivando-se determinar os efeitos no complexo craniofacial de pacientes com más oclusões de Classe II, divisão 1 submetidos ao tratamento com o aparelho de Herbst com cantiléver. METODOLOGIA: Para tanto, utilizou-se uma amostra composta por dois grupos, sendo um experimental e um controle. O grupo experimental originou-se da Faculdade de Odontologia de Bauru - USP, com 25 pacientes tratados com o aparelho ortopédico funcional e a idade inicial média de 12,01 anos. O grupo de controle, pareado cronologicamente ao grupo experimental, foi composto por pacientes não tratados ortodonticamente e/ou ortopedicamente, oriundos do arquivo de documentações denominado Burlington Growth Centre, localizado na Faculdade de Odontologia da Universidade de Toronto, Canadá. Para cada componente dos dois grupos, obtiveram-se as telerradiografias ao início (T1) e ao final (T2) do período de tratamento ou de observação, sendo traçadas manualmente e digitalizadas para um programa de cefalometria. Foram estabelecidas 33 grandezas cefalométricas. RESULTADOS E CONCLUSÕES: A comparação estatística entre o grupo experimental e o grupo controle (teste t de Student, com nível de significância p<0,05) evidenciou que a terapia corrigiu, em curto prazo, a má oclusão inicial, com grandes alterações dentoalveolares, em decorrência da perda substancial de ancoragem dentária, mesializando os molares inferiores e vestibularizando os incisivos inferiores. A terapia restringiu o desenvolvimento normal no sentido vertical dos dentes póstero-superiores, contribuindo decisivamente para a correção da relação molar de Classe II e manutenção do padrão de crescimento craniofacial dos pacientes.

OBJECTIVE: This study investigated the treatment effects on the craniofacial growth of Class II patients treated with Herbst appliance. METHODOLOGY: The sample was comprised of two groups, one experimental and one control group. The experimental group originated from Bauru Dental School, University of São Paulo. This consisted of 25 patients treated by the Herbst appliance, with an initial mean age of 12,01 years. The control group, matched by age with the experimental group, was originated from the Burlington Growth Centre, located at the Faculty of Dentistry, University of Toronto, Canada. All patients were assessed at the beginning (T1) and at the end of the treatment or observation period (T2) and 33 cephalometric variables were established. RESULTS AND CONCLUSIONS: The statistical comparison between the experimental group and the control group (Student t test) showed in short-term fashion, the correction of the initial malocclusion with pronounced dental changes (loss anchorage). The effect in inhibiting the vertical development of the maxillary first molars, essential characteristic to correct the Class II molar relationship and to maintain the craniofacial growth pattern, was shown with the therapy.

Third molar availability in Class II subdivision malocclusion.

INTRODUCTION: In this study, we compared retromolar available space and third molar angulation between the Class I and Class II sides in patients with Class II subdivision malocclusion. METHODS: Two samples were obtained from 46 subjects grouped according to the following characteristics: group 1 comprised 29 subjects (17 male, 12 female) with Class II subdivision malocclusion at a mean age of 14.73 years. Group 2 was the control to assist in the asymmetry evaluation and included 17 subjects (11 female, 6 male) with normal occlusion at a mean age of 21.73 years. Corrected oblique radiographs of each patient side were obtained to evaluate right and left retromolar available space and third molar angulation. The retromolar space and third molar angulations in the Class I and Class II sides in each group were compared with paired t and Wilcoxon tests. Asymmetry between the Class I and Class II sides of the Class II subdivision malocclusion group was compared with asymmetry between the right and left sides of the normal occlusion group with independent t and Mann-Whitney tests. RESULTS: The results demonstrated significant differences between the Class I and Class II retromolar available spaces in the Class II subdivision malocclusion group. Significant angular asymmetry between these sides was observed only for the mandibular third molars. However, when retromolar space asymmetry and third molar angular asymmetry were compared between the Class II subdivision malocclusion and the normal occlusion groups, there were significant differences only for retromolar space asymmetry. CONCLUSIONS: Patients with Class II subdivision malocclusion have asymmetric amounts of maxillary and mandibular retromolar available space and asymmetric angulation of the mandibular third molars between the Class I and Class II sides.

Class II subdivision malocclusion types and evaluation of their asymmetries.

INTRODUCTION: The primary objective of this study was to determine, by means of frontal photographic evaluation, the distribution of the 2 main types of Class II subdivision malocclusions. The secondary objective was to compare the dentoskeletal asymmetries in these 2 types with a group of normal-occlusion subjects by using submentovertex and posteroanterior radiographs. METHODS: The experimental group included 44 untreated Class II subdivision malocclusion subjects with a mean age of 15.3 years. The control group included 30 subjects with normal occlusions with a mean age of 22.4 years. All had full complements of permanent teeth up to the first molars and had not received orthodontic treatment. Type 1 Class II subdivision malocclusion is coincidence of the maxillary dental midline with the facial midline and deviation of the mandibular midline. Type 2 has the opposite characteristics. The frontal photographs were evaluated subjectively by 2 examiners. In the submentovertex and posteroanterior radiographs, symmetry was assessed by measuring the relative difference in the spatial positions of dentoskeletal landmarks between the right and left sides. Independent t tests were used to compare the dentoskeletal asymmetries of types 1 and 2 with the normal-occlusion group. RESULTS AND CONCLUSIONS: The results showed that 61.36% had type 1, 18.18% had type 2 Class II subdivision malocclusion, and 20.45% had mixed characteristics. The predominant asymmetric dentoalveolar characteristics of both types of Class II subdivision malocclusions were evident when individually compared with a normal-occlusion control group. There was a tendency for the type 1 subjects to have greater mandibular asymmetry than type 2, as compared with the control group.

Peri-implant bone response to orthodontic loading: Part 1. A histomorphometric study of the effects of implant surface design.

INTRODUCTION: Bone response to orthodontic loading was compared histomorphometrically around 2 different types of osseointegrated implants (porous surfaced and machined threaded) to determine their suitability for orthodontic anchorage. METHODS: Five beagles each received 3 implants of each design in contralateral mandibular locations. After a 6-week initial healing period, abutments were placed, and, 1 week later, the 2 mesial implants on each side were orthodontically loaded for 22 weeks. All implants remained osseointegrated throughout orthodontic loading except for 1 threaded implant that loosened. Light miscroscopy and back-scattered scanning electron microscopy were used to compare responses around the 2 implant designs. RESULTS: Porous-surfaced implants had higher marginal bone levels (P +/- .025) and less relative implant displacement than threaded implants. CONCLUSIONS: Differences in implant surface design can lead to differences in peri-implant bone height and bone-to-implant contact. Porous-surfaced implants might be successful as orthodontic anchorage units.

Peri-implant bone response to orthodontic loading: Part 2. Implant surface geometry and its effect on regional bone remodeling.

INTRODUCTION: Bone response to orthodontic loading was compared around 2 different types of osseointegrated implants (porous surfaced and machined threaded) to determine the effect of implant surface geometry on regional bone remodeling. METHODS: Five beagles each received 3 implants of each design in contralateral mandibular extraction sites. After a 6-week initial healing period, abutments were placed, and, 1 week later, the 2 mesial implants on each side were orthodontically loaded for 22 weeks. All implants remained osseointegrated throughout orthodontic loading except for 1 threaded implant that loosened. Back-scattered scanning electron microscopy and fluorochrome bone labeling techniques were used to compare responses around the 2 types of implants. RESULTS: The loaded, porous-surfaced implants had significantly higher marginal bone levels and greater bone-to-implant contact than did the machined-threaded implants. CONCLUSIONS: Significant differences in peri-implant bone remodeling and bone formation in response to controlled orthodontic loading were observed for the 2 implant designs. Short, porous-surfaced implants might be more effective for orthodontic applications than machine-threaded implants.

Dentoskeletal treatment changes in Class II subdivision malocclusions in submentovertex and posteroanterior radiographs.

The objective of this study was to evaluate the dentoskeletal changes consequent to orthodontic treatment in subjects with Class II subdivision malocclusions, treated with asymmetric extractions, compared with a normal-occlusion control group. The sample consisted of 3 groups, with 30 subjects in each: normal-occlusion subjects (group 1), untreated Class II subdivision subjects (group 2), and Class II subdivision patients treated with asymmetric extractions (group 3). All subjects had a full complement of permanent teeth at the beginning of treatment. The average ages of the subjects were 22.42, 15.76, and 18.57 years, respectively, in groups 1, 2, and 3. Measurements of relative differences in the spatial position of dental and skeletal bilateral landmarks were obtained from the submentovertex and posteroanterior cephalometric (PA) radiographs. The t test for independent samples was used to compare group 1 with groups 2 and 3 at different times. Results from the submentovertex radiograph showed that asymmetric extractions in Class II subdivision malocclusions will maintain the differences in the anteroposterior positions of right and left, maxillary and mandibular first molars, as would be expected with the treatment protocols used. There were no significant skeletal changes that could be attributed to the treatment approaches investigated or transverse collateral effects with the asymmetric mechanics used. It was also demonstrated that treatment of Class II subdivision malocclusions with asymmetric extractions produced corrections of maxillary and mandibular dental midline deviations with the midsagittal plane, without canting the occlusal plane or any other investigated horizontal plane, as seen in the PA radiograph. Treatment of Class II subdivision malocclusions with asymmetric extractions constitutes a beneficial approach to this problem.

Condyle-fossa modifications and muscle interactions during Herbst treatment, Part 2. Results and conclusions.

Herbst appliances were activated progressively in growing nonhuman primates, and the results were compared with primate and human controls. The methods and materials of this research are explained in Part 1 of this study. The results are discussed here in Part 2. All experimental subjects developed large super Class I malocclusions, the result of many factors including posterior movement of the maxilla and the maxillary teeth, an increased horizontal component of condylar growth, and anterior displacement of the mandible and the mandibular teeth. The growth modification measured in the glenoid fossa was in an inferior and anterior direction. Restriction of the downward and backward growth of the fossa observed in the control subjects might additionally contribute to the overall super Class I malocclusion. Clinically, these combined effects could be significant at the fossa. The restriction of local temporal bone (fossa) growth cannot be observed clinically; thus, these results might also clarify some Class II correction effects that cannot be explained with functional appliances. Differences in the area and maximum thickness of new bone formation in the glenoid fossa and in condylar growth were statistically significant. The bony changes in the condyle and the glenoid fossa were correlated with decreased postural electromyographic activity during the experimental period. Results from permanently implanted electromyographic sensors demonstrated that lateral pterygoid muscle hyperactivity was not associated with condyle-glenoid fossa growth modification with functional appliances, and that other factors, such as reciprocal stretch forces and subsequent transduction along the fibrocartilage between the displaced condyle and fossa, might play a more significant role in new bone formation. These results support the growth relativity concept.

Condyle-fossa modifications and muscle interactions during herbst treatment, part 1. New technological methods.

Changes in the condyle, the glenoid fossa, and the muscles of mastication were investigated in subjects undergoing continuous orthopedic advancement of the mandible with a Herbst-block appliance. The total sample consisted of 56 subjects and included 15 nonhuman primates (in the middle mixed, early permanent, and permanent dentitions), 17 human Herbst patients in the early permanent dentition, and 24 human controls from the Burlington Growth Center. The 8 nonhuman primates in the middle mixed dentition were the focus of this study. Mandibular advancement was obtained progressively in 5 animals by adding stops to the telescopic arms of fixed functional Herbst appliances with occlusal coverage; activations of 5.0 mm, 7.0 mm, and 8.0 mm were achieved. Two primates served as controls, and the third was a sham control. Two experimental animals and the 2 controls also wore surgically implanted electromyographic electrodes in the superior and inferior heads of the lateral pterygoid muscles and in the superficial masseter and anterior digastric muscles. Changes in condylar growth direction and amount were assessed with the Björk method from measurements made on serial cephalometric tracings superimposed on metallic implants. Undecalcified sections, treated with intravenous tetracycline vital staining, were viewed with fluorescence microscopy to examine histologic changes in the condyle and the glenoid fossa. New bone formation in the fossa associated with continuous mandibular protrusion was quantified by using computerized histomorphometric analysis of decalcified histological sections and polarized light. The unique combination of permanently implanted electromyographic electrodes, tetracycline vital staining, and histomorphometry represents a significant technological advancement in methods and materials. Together, they demonstrated different muscle-bone interaction results for functional appliances than those reported in previous studies. In Part 1 of this study, we describe and discuss the techniques used in this research and give a brief overview of the findings; in Part 2 (to be published next month), we offer a more in-depth discussion of the results and the implications of our findings.

Crescimento maxilar e mandibular após alteraçäo do modo respiratório / Mandibular and maxillary growth after changed mode of breathing

Foram estudados a quantidade e a direçäo do crescimento maxilar e mandibular em 38 crianças durante os 5 anos pós-adenoidectomia para correçäo de uma obstruçäo nasofaringeana severa. A quantidade de crescimento mandibular medida entre os pontos gnático inicial e gnático pós-adenoidectomia em radiografias superpostas foi significantemente maior no grupo submetido à adenoidectomia do que no grupo controle pareado. Nos meninos a diferença foi 3,8 mm (p,001) e nas meninas a diferença foi 2,5 mm (p,01). Os meninos também mostraram uma tendência de um crescimento maior na maxila quando os pontos subnasal foram medidos (1,2 mm,p 0,05). Näo detectamos diferença na direçäo do crescimento maxilar entre os indivíduos submetidos à adenoidectomia e o grupo controle