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Objective: To test the null hypotheses that at clinically relevant amounts of applied moment, there are no differences in the amount of resistance to sliding (RS) between self-ligating (SL) and conventionally ligated (CL) brackets on both stainless steel (SS) and nickel-titanium (NT) archwire. Materials and Methods: Three different SL brackets and one CL bracket, all 0.0220 slot, were tested on a custom-built device to simulate canine retraction mechanics in the second-order dimension. The setup allowed for simultaneous and continuous measurement of RS and applied moment at the bracket-archwire interface. The brackets tested were Damon3, In-Ovation R, Smartclip, and Victory, all of which were tested with 0.0190 3 0.0250 SS and NT archwires. The RS at calculated moments of 2000 g-mm and 4000 g-mm was determined and compared between the various brackets and both archwire types. Descriptive measures, analysis of variance, and TukeyKramer post-test comparisons were used to calculate results. Results: All brackets displayed a greater amount of RS with NT than with SS archwires. At the higher moment levels (4000 g-mm), no significant reduction in RS was found between CL and SL brackets on both SS and NT archwires. At lower levels of applied moment (2000 g-mm), reductions in RS of 18% (42.7 g) and 18% (38.5 g) were found between the CL bracket and the best performing SL bracket on NT and SS, respectively. Conclusion: At low values of applied moment, some statistical differences were found; however, in general, the differences in RS amongst the various SL and CL brackets tested may not be clinically relevant. (Angle Orthod. 2011;81:794-799.)

Objective: To determine the effect of mode of ligation and bracket material on resistance to sliding (RS) by comparing various esthetic brackets of conventionally ligated and self-ligating (SL) designs under an increasing applied moment in the second-order dimension. Materials and Methods: Eight different commercially available esthetic brackets of SL and conventional elastomeric-ligated (CL) designs were mounted on a testing apparatus to simulate canine retraction using sliding mechanics and the application of a moment on 0. . The RS at calculated moments of 2000 g-mm and 4000 g-mm was determined and compared between the various brackets. Descriptive measures and one-way analysis of variance were used to calculate means and statistical differences among the bracket types. Results: The CL monocrystalline bracket displayed significantly greater (P , .05) RS than all other brackets tested. Among the other brackets, the range of RS values was 145.8-191.7 g and 291.9-389.2 g at moments of 2000 g-mm and 4000 g-mm, respectfully, though these differences were not significant (P , .05). All brackets tested displayed greater levels of RS (P , .05) at 4000 g-mm than at 2000 g-mm.Conclusion: With the exception of the CL monocrystalline bracket, all brackets displayed comparable amounts of RS regardless of mode of ligation or bracket slot material. (Angle Orthod. 2014;84:134-139.)

Objectives To assess factors that may be associated with buccal bone changes adjacent to maxillary first molars after rapid maxillary expansion (RME) and fixed appliance therapy. Materials and Methods Pretreatment (T1) and posttreatment (T2) cone-beam computed tomography scans were obtained from 45 patients treated with RME and preadjusted edgewise appliances. Buccal alveolar bone thickness was measured adjacent to the mesiobuccal root of the maxillary first molar 4 mm, 6 mm, and 8 mm apical to the cementoenamel junction, and anatomic defects were recorded. Paired and unpaired t-tests were used to compare alveolar bone thickness at T1 and T2 and to determine whether teeth with posttreatment anatomic defects had thinner initial bone. Correlation analyses were used to examine relationships between buccal alveolar bone thickness changes and amount of expansion, initial bone thickness, age at T1, postexpansion retention time, and treatment time. Results There was a statistically significant reduction in buccal alveolar bone thickness from T1 to T2. Approximately half (47.7%) of the teeth developed anatomic defects from T1 to T2. These teeth had significantly thinner buccal bone at T1. Reduction in alveolar bone thickness was correlated with only one tested variable: initial bone thickness. Conclusions RME and fixed-appliance therapy can be associated with significant reduction in buccal alveolar bone thickness and an increase in anatomic defects adjacent to the expander anchor teeth. Anchor teeth with greater initial buccal bone thickness have less reduction in buccal bone thickness and are less likely to develop posttreatment anatomic defects of buccal bone.

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Background: Orthodontic treatment with fixed appliances involves sliding of brackets along archwires. These movements involve friction, which causes resistance to sliding. In addition, moments cause teeth to tip until binding occurs between the bracket and archwire. The manufacturer of a new TiMolium®Titanium archwire claims material properties superior to β-Titanium, potentially leading to reduced resistance to sliding. Objective: To compare TiMolium archwires with β-Titanium and stainless steel archwires as the current gold standard for sliding mechanics under application of an increasing moment. Materials and methods: A total of 120 stainless steel (Smartclip, 3M, Monrovia, CA) and ceramic self-ligating 0.022″-slot brackets (Clarity SL, 3M) were divided into six equal-sized groups. Resistance to sliding was tested with 0.019″ × 0.025″ TiMolium (TP Orthodontics, La Porte, IN), β-Titanium (3M), and stainless steel (3M) archwires using a custom-designed apparatus to simulate sliding mechanics and application of moments of 1000, 2000, and 3000 g-mm. Results: Using stainless steel brackets, the TiMolium archwires had significantly higher resistance to sliding than stainless steel archwires at all moments tested while there was no difference between TiMolium and β-Titanium. Using ceramic brackets, the resistance to sliding with TiMolium archwires was no different than with stainless steel archwires. Both TiMolium and stainless steel archwires showed significantly lower resistance to sliding than β-Titanium. Conclusion: TiMolium archwires have resistance to sliding intermediary to stainless steel and β-Titanium archwires when clinically relevant moments are applied. Used with the stainless steel brackets, they behave like β-Titanium, whereas used with the ceramic brackets, they behave more like stainless steel.

A system recently developed for measuring wear in dental restorative materials may have applications in the field of physical anthropology. The method, computerized profilometry, uses a computer guided stylus to digitize a tooth surface directly or via epoxy replicas. The digital information is manipulated using customized computer graphic software programs which include the following features: three-dimensional measurement, comparison of surfaces using "goodness of fit" algorithms, and color graphic representations of anatomic surfaces. The system has been calibrated to an accuracy of 0.0006 mm3The advantages offered by mensurational and descriptive studies of the dentition are well recognized. The detailed morphologic structure of teeth reflect the results of isolation, inbreeding, hybridization, drift, and other phenomena responsible for the genetic compositions of populations (Kraus and Furr, 1953). To adequately study these characteristics, subtle measurement techniques are required. Because of the complex shape of human tooth crowns, many investigators have concentrated on simple measurements of tooth size, including length, breadth, and computed area of the crown. But these simple indicators do not reveal all the morphological information which tooth crowns provide (Wood and Abbott, 1983).Detailed digitizations of tooth occlusal surfaces are now possible (DeLong et al., 1985). Primarily used in wear studies of dental restorative materials, the method can also be used to provide highly accurate qualitative and quantitative measurements of the tooth surface. At its most basic, absolute distances between two points on the tooth surface can be measured. What follows is a description of the technique, together with a report of an in vivo study which compared the interobserver error of digitizer-based and traditional caliper-based measurements of intercuspal distances. Twenty pairs (n = 40) of newly erupted and caries-free premolar teeth were measured. The teeth were impressioned with a vinylpolysiloxane material and epoxy replicas made. Surfaces of each replica were profiled and digitized using a displacement stylus and programmable data retrieval system. A logic diagram (Fig 1.) gives an overview of the method. The graphic images of each tooth were viewed on a high resolution computer screen and threedimensional point measurements were made using the image processing software.' The program identified the highest point coordinates corresponding to cusp tips on each tooth and then calculated the intercuspal distance. All measurements were done by the same two independent investigators in a blind manner. All data generated were stored on magnetic disk for reference and further manipulation. Each tooth required 60 kilobytes of computer memory and the time required to digitize and analyze each tooth was approximately 40 minutes. The replicas were then measured by the two investigators using a dial caliper readable to 0.05 mm.The computer method proved superior. A repeat-measures ANOVA tested for systematic error be...