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December 2011. A thesis submitted to the College of Dental Medicine of Nova Southeastern University of the degree of Master of Science in Dentistry. Background: Temporary anchorage devices (TADs) provide a versatile means by which orthodontic anchorage can be established without the need for patient compliance and complex force systems. Their use is predicated on their ability to remain stable throughout the course of treatment in which they are needed. This has been shown to be the result of "primary stability" which is achieved through mechanical interlocking of the screw threads with the surrounding bone immediately upon placement. Therefore, evaluating the factors that can either enhance or detract from the primary stability of TADs can serve to improve the predictability of their success. Objectives: The objectives of this study were to describe how variations in synthetic cortical bone thickness and the angle of force applied in relation to the long axis of TADs affects their stability in terms of pull-out strength, and to ascertain the perspectives of practicing orthodontists in the state of Florida on their experiences with temporary anchorage devices with regards to success and failure. Methods: For the bench top study, 90 1.5x8mm long neck Orthotechnology Spider Screws were randomly allocated to 9 groups of 10 TADs each. The 9 groups were established based on both the thickness of synthetic cortical bone (1.0, 1.5, and 2.0mm) and the angle of force vector applied relative to the long axis of the TADs (45, 90, and 1800). Pull-out testing was carried out by applying a force to the TADs via a universal testing machine (Instron, Canton, MA) at a rate of 2.0mm/minute. Real-time graphical and digital readings were recorded, with the forces being recorded in Newtons (N). Each miniscrew was subjected to the pull force until peak force values were obtained. For the 450 and 1800 tests, the force registered at the time-point of pull-out, or screw head movement of 1.5mm within the synthetic bone blocks. The determination of 1.5mm of movement was made due the dramatically erratic deflection observed by the digital and graphical readouts at precisely this point. For the survey portion of this study, A customized survey was developed for this study. The survey was composed of 12 questions, some of which were obtained from a questionnaire that was created by Buschang et al.54 The additional questions were devised by the members of this research project, with the aim of answering questions regarding the clinical experiences that practicing orthodontists experienced with TADs. Results: For the bench top study: Implants placed in 2.0mm of synthetic cortical bone and pulled at an angle of 1800 had the highest pull-out strength among all groups (258.38N), while those placed in 1.0mm of synthetic cortical bone and pulled at an angle of 900 exhibited the lowest (67.11N). When evaluated separately, a cortical bone thickness of 2.0 mm displayed the highest pull-out forces for the three angles of force application, and 1800 angle of force displayed the highest-pull-out forces for the three cortical bone thicknesses. Conversely, 1.0mm of cortical bone thickness displayed the lowest pull-out forces for the three angles of force application, and 900 angle of force displayed the highest-pull-out forces for the three cortical bone thicknesses. For the survey: The most important factor associated with TAD failure was cited as placement location by 45.7% (n=16) of respondents, while root proximity was cited as the least important factor by 35.3% (n=12) of respondents. For the site from which practitioners indicated that they experience the greatest success, 81.8% cited the palate, while 51.9% responded that they experience the highest failure rates for the posterior maxilla (distal to the cuspids). Conclusions: A synthetic cortical bone thickness of 2mm and pull forces applied parallel to the long axis of TADs resulted in the greatest resistance to pull-out.

A thesis submitted to the College of Dental Medicine of Nova Southeastern University of the degree of Master of Science in Dentistry. Objectives. The purpose of this study was to determine the effect of pitch and thread depth of orthodontic miniscrew implants(MSI's) on stress generation. Methods. Quasi-three dimensional photoelastic models were created with MSI's embedded and then loaded with 60 and 104 grams respectively and evaluated under a full field reflection polariscope. The control MSI's (1.0mm pitch / 0.25mm thread depth) were compared to 3 experimental groups (n=10) which varied with only one design characteristic: Group 1 (0.75mm pitch), Group 2 (1.25mm pitch) and Group 3 (0.40 thread depth). The maximum shear stress (τmax) was calculated at 5 predetermined and standardized points. A two-way ANOVA was conducted to compare the means of τmax followed by a Tukey's post hoc (p<0.05). Results. No statistical differences were found for τmax between the control group and each of the 3 experimental groups except at point 4. At point 4, the control group was higher by an average of 5.05 and 7.1 MPa for the 60 and 104 gram loads respectively (p<0.05). No statistically significant differences were found for points 1, 2, and 5 for the 60 gram load and for points 1, 2, 3, and 5 for the 104 gram load. The mean τ max from highest to lowest was located at points 5<1< 2<4 <3 in both the 60 and 104 load steps. The variability in τmax at point 4 may have been due to its proximity to the neutral zone of the present loading conditions. Conclusions. As the orthodontic load was increased, maximum shear stress also increased for each of the four MSI designs used in this study. The results of this study suggest that, within limits, variation of pitch and thread depth of MSI's may not have a significant influence on the stress generation when loaded for orthodontic purposes. Photoelastic analysis has shown to be a viable option to evaluate mechanical properties of MSI'S.

Os dispositivos de ancoragem temporária têm sido amplamente utilizados como auxiliares de ancoragem esquelética no tratamento de má oclusões mais severas. Para a instalação de mini parafusos na crista infrazigomática é necessário o conhecimento anatômico desta região e suas possíveis variações. Na literatura são descritos diferentes tipos faciais que diferem na predominância em relação ao padrão de crescimento facial vertical ou horizontal configurando conformações ósseas distintas. Com isso o objetivo deste estudo é avaliar se há diferença na espessura óssea na região de crista infrazigomática em cada o tipo facial. Para este estudo retrospectivo foi selecionada uma amostra composta por 86 tomografias computadorizadas por feixe cônico de indivíduos dos gêneros masculino e feminino, adultos, com idade entre 18 e 40 anos. As imagens foram avaliadas no software Dolphin® (versão 11.0, Dolphin Imaging and Manegement Solutions, Chatsworth, CA - EUA). As tomografias foram divididas em três grupos de acordo com o tipo facial, sendo: 24 do tipo facial Hiperdivergente, 30 do tipo facial Neutro e 32 do tipo facial Hipodivergente. Para atender aos objetivos do estudo, as medidas foram realizadas nas regiões entre segundo pré-molar e primeiro molar superior até região de raiz distal de segundo molar superior em alturas de 5 7, 9 e 11 mm a partir da crista alveolar. Os resultados mostraram que no grupo hiperdivergente os locais considerados seguros para a instalação dos mini parafusos foram entre primeiros e segundos molares superiores em 11 mm da crista alveolar, na região das raizes mesiais dos segundos molares superiores a partir de 9 mm da crista alveolar e em região das raizes distais dos segundos molares superiores em 11 mm da crista alveolar. No grupo neutro os locais considerados seguros para a instalação dos mini parafusos foram entre primeiro e segundo molar em 11 mm da crista alveolar do lado direito e em região das raizes mesiais dos segundos molares superiores em 11 mm da crista alveolar. Para o grupo hipodivergente observou-se como locais considerados seguros, entre primeiros e segundos molares superiores em 11 mm da crista alveolar e em região das raizes mesiais dos segundos molares superiores em 11 mm da crista alveolar. Baseados nos resultados obtidos consideramos que existe uma diferença de espessura entre os tipos faciais e que este fator deve ser considerado durante o planejamento para instalação de mini parafusos de ancoragem ortodôntica, no entanto para todos os grupos o local mais adequado é na região de raiz mesial dos segundos molares superiores em 11 mm da crista alveolar. / Temporary anchoring devices have been widely used as skeletal Anchorage in treatment of more severe malocclusions. The anatomical knowledge of this region and its possible variation are necessary for the installation of mini screws in the infrazygomatic crest. In the literature diferente facial types are described that differ in the predominance in relation to the vertical or horizontal facial growth pattern configuring different bone conformations. Therefore, the purpose os this study is to evaluate if there is difference in bone thickness in the region os the infrazigomatic crest in each facial type. For this retropective study, a sample composed fo 86 computed tomography scans of individuals of the masculine and feminine adults aged between 18 and 40 years, was selected. The images were evaluated in Dolphin® software (version 11.0, Dolphin Imaging and Manegement Solution, Chastworth, CA - USA). The CT scans were divided into three groups according to the facial type: 24 of the facial type Hyperdivergent, 30 of the facial type Neutral and 32 of the facial type Hipodivergent. To meet the study objectives, the measurements were performed in the regions between the second pre-molar and the first molar superior to the region of the upper second molar distal root at heights of 5, 7, 9 and 11 mm from the alveolar crest. The results showed that in the hyperdivergent group the sites that was considered safe for the installation of the mini screws were between the first and second maxillary molars in 11 mm of the alveolar crest, in the region of the mesial roots of the second maxillary molars from 9 mm of the alveolar crest and in the region of the distal roots of the second maxillary molars 11 mm from the alveolar crest. In the neutral group, the sites considered safe for the installation of mini screws were between the first and second molars in 11 mm of the alveolar ridge on the right side and in the region of the mesial roots of the maxillary second molars in 11 mm of the alveolar ridge. For the hypodivergent group, were considered safe places between the first and second maxillary molars were observed in 11 mm of the alveolar crest and in the region of the mesial roots of the maxillary second molars in 11 mm of the alveolar crest. Based on the results obtained, we consider that there is a difference in thickness between facial types and that this factor should be considered during planning for installation of mini orthodontic anchor bolts, however for all groups the most appropriate place is in the mesial root region of the upper second molars.

A ancoragem ortodôntica tem sido motivo de preocupação para os ortodontistas desde o inicio da prática ortodôntica. Os dispositivos transitórios de ancoragem esquelética (miniparafuso) definiram um novo conceito de ancoragem em Ortodontia. A colocação dos dispositivos em uma região extra-alveolar mandibular permite o uso de parafusos de maior diâmetro que podem ser inseridos paralelamente à inclinação axial de molares inferiores sem interferir com as raízes dos dentes que serão movimentados. Na literatura são descritos diferentes tipos faciais que diferem na predominância em relação ao padrão de crescimento facial vertical ou horizontal configurando conformações ósseas mandibulares distintas entre os tipos faciais. Desta forma, o objetivo deste estudo é avaliar se há diferença na espessura do osso vestibular na região do shelf mandibular entre os tipos faciais. Para este estudo retrospectivo foi selecionada uma amostra composta por 84 tomografias computadorizadas por feixe cônico (TCFC) de indivíduos dos gêneros masculino e feminino, adultos, com idade entre 18 e 40 anos. As imagens foram avaliadas no software Dolphin® (versão 11.0, Dolphin Imaging and Management Solutions, Chatsworth, CA - EUA). As tomografias foram divididas em três grupos de acordo com o tipo facial, determinado por meio de reconstruções bidimensionais em norma lateral para realização do traçado da análise cafalométrica proposta por Bjork-Jarabak, sendo: 28 do tipo facial hiperdivergente (Grupo1), 28 do tipo facial neutro (Grupo 2) e 28 do tipo facial hipodivergente (Grupo 3). Para atender aos objetivos do estudo, as medidas foram realizadas nas seguintes regiões: 1- Vestibular da raiz mesial do primeiro molar inferior dos lados esquerdo e direito; 2 - Vestibular da raiz distal do primeiro molar inferior dos lados esquerdo e direito; 3 - Vestibular entre o primeiro e segundo molar inferior dos lados esquerdo e direito; 4 - Vestibular da raiz mesial do segundo molar inferior dos lados esquerdo e direito; 5 - Vestibular da raiz distal do segundo molar inferior dos lados esquerdo e direito. As medidas foram realizadas a 3, 6 e 9 milímetros a partir da junção amelocementária (JAC) dos primeiros e segundos molares, em direção apical, no corte axial, estendendo-se do ponto médio das raízes mesial e distal até a borda mais externa da cortical óssea alveolar adjacente. Os resultados mostraram que, com relação à idade e gênero, não houve diferença estatisticamente significativa entre os grupos. As medidas do Grupo 1 mostraram que na vestibular da raiz distal do 2º molar a 9mm da JAC apresentaram, em média, valores maiores de 5mm, sendo considerada possível de instação de miniparafuso nesta região, em ambos os lados. No grupo 2 observou-se espaço suficiente para instalação de miniparafuso na vestibular da raiz distal do 2º molar a 6 mm e 9 mm da JAC. Para o Grupo 3 observou-se medidas acima de 5 mm na vestibular da raiz mesial dos segundos molares a 9 mm da JAC e na vestibular da raiz distal a 6 mm e 9 mm da JAC. Baseados nos resultados obtidos, consideramos que existe uma diferença de espessura entre os tipos faciais e que este fator deve ser considerado durante o planejamento para instalação de miniparafusos de ancoragem ortodôntica, no entando para todos os grupos a região mais adequada é na vestibular da raiz distal dos segundos molares inferiores. / Orthodontic anchorage has been of concern to orthodontists since the beginning of orthodontic practice. The transitory anchorage devices (miniscrew) have defined a new concept of anchorage in Orthodontics. Placement of the devices in a mandibular extra alveolar region allows the use of larger diameter screws that can be inserted parallel to the axial inclination of lower molars without interfering with the roots of the teeth that will be moved. The literature describes different facial types that differ in the predominance in relation to the vertical or horizontal facial growth pattern, configuring different mandibular bone conformations between the facial types. Thus, the objective of this study is to evaluate if there is difference in the thickness of the buccal bone in the MBS region between the facial types. For this retrospective study, a sample composed of 84 Cone Beam Computed Tomography (CBCT) of males and females adults, aged between 18 and 40 years, was selected. The images were evaluated in Dolphin® software (version 11.0, Dolphin Imaging and Manegement Solutions, Chatsworth, CA - USA). CT scans were divided into three groups according to the facial type, pre-determined by two-dimensional reconstructions in lateral norm for tracing cephalometric analysis proposed for Bjork-Jarabak\'s: 28 of the hyperdivergent facial type (Group 1), 28 of the neutral facial type (Group 2) and 28 of the hypodivergent facial type (Group 3). To respond the objectives of the study, the measurements were performed in the following regions: 1- Mesial root vestibular of the first lower molar of the left and right sides; 2 - Vestibular of the distal root of the first lower molar of the left and right sides; 3 - Vestibular between the first and second lower molars of the left and right sides; 4 - Vestibular mesial root of the second lower molar of the left and right sides; 5 - Vestibular of the distal root of the second lower molar of the left and right sides. Measurements were made at 3, 6 and 9 millimeters from the amelocemental junction of the first and second molars, apically in the axial cut, extending from the midpoint of the mesial and distal roots to the external border of the alveolar cortical bone adjacent. The results showed that, regarding age and gender, there was no significant statistical difference between the groups. The measurements of Group 1 showed that in the distal root of the 2nd molar to 9mm of the JAC presented, in average, values greater than 5mm, being considered possible of insertion of miniscrew in this region, in both sides. In group 2, sufficient space was observed for the installation of a miniscrew in the distal root of the 2nd molar to 6 mm and 9 mm of the JAC. For Group 3, measurements above 5 mm in the mesial root of the 2nd molars were observed at 9 mm from the JAC and in the distal root of 2nd to 6 mm and 9 mm of the JAC. Based on the results obtained, we consider that there is a difference in thickness between the facial types and that this factor should be considered during the planning for installation of orthodontic miniscrew, whereas for all groups the most suitable region is the vestibular of the distal root of second molars.