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BACKGROUND Clear aligners are orthodontic devices that are transparent, a plastic used to correct malaligned teeth. Here patient wears a series of customized clear, removable aligners that gradually move the teeth to the desired position. The clear aligner system is a modern adaptation of the systems described since the middle of the 20th century, therefore there were different devices and philosophies that have led to its creation and the system has evolved a lot over the decades. Clear aligner therapy has been a part of the orthodontic practice for years, but, popularity was increased since the introduction of Invisalign appliances (Align Technology) in 1998. There are almost 27 different clear aligner products currently on offer for orthodontic treatment. Nowadays, more people prefer clear aligner treatment because it is aesthetically superior to brackets and lingual orthodontics. The superiority of clear aligners lies in their aesthetics. The optical properties of the clear aligner material play a major role in aesthetics. The rising demand among adult patients for “invisible” orthodontic treatment has led to an exponential growth in the clear aligner market. Indeed, these aligners have a low aesthetic impact, as well as being able to effectively and progressively guide the teeth into their programmed positions. They are also removable and therefore do not hamper oral hygiene maintenance, in turn reducing the risk of white spots, caries, gingivitis and periodontal disease. All the materials do not possess the same chemical composition. The properties change before and after wear. In this article, we bring out the different materials used for the manufacture of clear aligners and their various properties. KEY WORDS Clear Aligners, Optical Properties, Thermoplastic Material, Mechanical Properties

Introduction: It has been suggested that human errors during manual tracing of linear/angular cephalometric parameters can be eliminated by using computer-aided analysis. The landmarks, however, are located manually and the computer system completes the analysis. With the advent of Artificial Intelligence in the field of Dentistry, automatic location of the landmarks has become a promising tool in digital Orthodontics. Methods: Fifty pretreatment lateral cephalograms obtained from the Orthodontic department of SRM dental college (India) were used. Analysis were done by the same investigator using the following methods: WebCeph™, AutoCEPH© for Windows or manual tracing. Landmark identification was carried out automatically by Artificial Intelligence in WebCeph™ and with a mouse driven cursor in AutoCEPH©, and manually using acetate sheet and 0.3-mm pencil, ruler and a protractor. The mean differences of the cephalometric parameters obtained between the three methods were calculated using ANOVA with statistical significance set at p<0.05. Intraclass correlation coefficient (ICC) was used to determine both reproducibility and agreement between linear and angular measurements obtained from the three methods and intrarater reliability of repeated measurements. ICC value of >0.75 indicated good agreement. Results: Intraclass correlation coefficient between the three groups was >0.830, showing good level of agreement, and the value within each group was >0.950, indicating high intrarater reliability. Conclusion: Artificial Intelligence assisted software showed good agreement with AutoCEPH© and manual tracing for all the cephalometric measurements.

Introduction: Number of occlusal contacts and uniform bite force distribution during maximum intercuspation are determinants of a good functional occlusion. Distribution of posterior contacts in the three malocclusion groups along with force distribution has been a topic of research. Aim: To quantify the number of occlusal contacts and areas, bite force distribution in Angle’s Class I, II, III subjects using T-scan and to identify the centre of force trajectory. Materials and Methods: This cross-sectional, observational study was conducted in the Department of Orthodontics, SRM College, Chennai, Tamil Nadu, India, from June 2018 to December 2018. Total 45 subjects in the age group of 18 to 24 years were divided into three groups of 15 subjects each based on Angle’s classification of malocclusion with teeth in normal line of occlusion. T-Scan system sensor and software were used to record and store data. The collected data were analysed with IBM Statistical Package for the Social Sciences (SPSS) software version 23.0. The descriptive statistics were performed, followed by Analysis of Variance (ANOVA). Post hoc Tukey test was done to find the difference between the groups. Chi-square test was done for the categorical data and the Paired t-test for determining the significant difference between the bivariate samples in paired groups. Level of significance was set at p<0.05. Results: Out of three study groups, mean contact points (p<0.001), contact areas (p<0.001) and bite forces (p=0.0032) were statistically highly significant in Angle’s class I group when compared to the other groups. Statistically, the right and the left side differences in force distribution of the three groups were significant with the forces predominantly being higher on the right side. Conclusion: Subjects with Angle’s Class I molar relation had greater contacts, contact area and better bite force distribution. There was preference to the right side in bite force distribution in all the three groups. Centre of force trajectory was concentrated between first and second molars in all the groups

Objectives: This clinical trial was conducted to evaluate the stability and failure rate of surface-treated orthodontic mini-implants and determine whether they differ from those of non-surface-treated orthodontic mini-implants. Trial Design: Randomized clinical trial with a split-mouth study design. Setting: Department of Orthodontics, SRM Dental College, Chennai. Participants: Patients who required orthodontic mini-implants for anterior retraction in both arches. Methods: Self-drilling, tapered, titanium orthodontic mini-implants with and without surface treatment were placed in each patient following a split-mouth design. The maximum insertion and removal torques were measured for each implant using a digital torque driver. The failure rates were calculated for each type of mini-implant. Results: The mean maximum insertion torque was 17.9 ± 5.6 Ncm for surface-treated mini-implants and 16.4 ± 9.0 Ncm for non-surface-treated mini-implants. The mean maximum removal torque was 8.1 ± 2.9 Ncm for surface-treated mini-implants and 3.3 ± 1.9 Ncm for non-surface-treated mini-implants. Among the failed implants, 71.4% were non-surface-treated mini-implants and 28.6% were surface-treated mini-implants. Conclusion: The insertion torque and failure rate did not differ significantly between the groups, whereas the removal torque was significantly higher in the surface-treated group. Thus, surface treatment using sandblasting and acid etching may improve the secondary stability of self-drilling orthodontic mini-implants. Trial registration: The trial was registered in the Clinical Trials Registry, India (ICMR NIMS). Registration number: CTRI/2019/10/021718