published_or_final_version / Dentistry / Master / Master of Dental Surgery

published_or_final_version / Dentistry / Master / Master of Dental Surgery

AIM: To assess root parallelism after Invisalign® treatment. MATERIALS AND METHODS: The sample consisted of 101 patients (mean age: 22.7 years, 29 males, 72 females) treated non-extraction with Invisalign® by one orthodontist. Root angulations were assessed using the 4-point angulation tool (Dolphin imaging©); the long axes of adjacent teeth were traced, yielding a convergence/divergence angle. Acceptable root parallelism was assessed if the root angulation did not converge/diverge more than 7 degrees. Sites evaluated: between 1st molars and 2nd premolars, 2nd and 1st premolars, lateral and central incisors, and between central incisors in all four quadrants. The average change in mesio-distal root angulation was assessed between pre- and post-treatment panoramic radiographs. RESULTS: Paired t-tests were used to analyze the average change in mesiodistal root angulation. Statistically significant differences were obtained indicating a reduction in the convergence/divergence angles between teeth #16-15, #15-14, #11-21, #24-25, #25-26, #45-44, #42-41, #41-31, #31-32, and #34-35 (at p-value <0.05). The average change in root angulation was not affected (p>0.05) by age (Pearson correlation coefficient), gender, occlusion type (I, II, or III), or elastic use (unpaired, 2 sample t-test at p<0.05). Intra and inter-rater reliability for 20% of the studied sample was assessed using the interclass correlation coefficient 3 test. All measured areas except teeth #16-15, #26-25, and #36-35 yielded good ICC reliability scores above 0.7. CONCLUSION: Root parallelism was improved post-Invisalign® treatment in ten of the fourteen areas evaluated. Thus, Invisalign® may be an effective treatment modality in controlling root angulation in non-extraction cases. / May 2016

Thesis (MSD) --Boston University (Periodontics). / Includes bibliographic references: leaves 84-89. / Twenty-two male patients from 12-14 years of age were selected prior to active orthodontic therapy at Boston University School of Graduate Dentistry's Departmant of Orthodontics. These patients were projected to undergo full-banded orthodontic treatnent. The objective of this investigation was designed as a long tenn project to document the quantitative and qualitative changes occurring in the periodontium during and following orthodontic therapy. The patients were examined for the first 9 month period by Dr. Stuart Sears and Dr. Sergio Tejedor-Leon. Relocation of two families reduced the number of patients to twenty which were examined for the second 9 nonth period by Dr. Robert E. Roe and Dr. Robert P. Rubins. [TRUNCATED]

OBJECTIVE: To evaluate the predictability of virtual orthodontic setup technology by comparing it with posttreatment models in terms of ABO Model Grading System (ABO OGS) scores. MATERIALS AND METHODS: Posttreatment models and printed virtual setups made from the corresponding initial casts of 26 cases were used. The initial models were scanned and virtual setups were fabricated using a proprietary virtual setup software program. Evaluation of the printed models of the virtual setups and final mode ls was performed using the ABO OGS. RESULTS: We found statistically significant differences (p<0.001) between the posttreatment plaster models and the printed virtual setup models in total scores, marginal ridges (MR), buccolingual inclination (BLI), occlusal contacts (OC), occlusal relationship (OR), and interproximal contacts (IPC) (p<0.05). The only statistically significant correlations found were in alignment (A) and marginal ridges (MR) measurements although they were low positive correlations. CONCLUSIONS: The greatest difference between final treatment models and virtual setup models was in the OC due to overlapping of the occlusal surfaces in the virtual setup software. Printed models of virtual setups can be predictive in A and MR measurements. Overall, the 3-dimensional printed virtual setup models had better MR, BLI, and IPC, worse OC, OR, and total score, and equivalent A and OJ when compared to the posttreatment plaster models.

Thesis (M.D.S.)--University of Hong Kong, 1996. / Includes bibliographical references (leaves [193]-247) Also available in print.

Thesis (M.D.S.)--University of Hong Kong, 1994. / Includes bibliographical references. Also available in print.

No description available.

Nitric oxide (NO) is a short lived free radical regulating bone turnover and bone cell function (1, 2). Osteoclasts are multinucleated bone resorbing cells which form by fusion of pre-osteoclasts. In addition, NO is a signaling molecule in mechanical loading of the bone (3), and in orthodontic tooth movement (OTM) (4). In OTM, force is applied to the tooth and transferred to the bone resulting in bone remodeling leading to tooth movement. This project has two parts: 1) NO in osteoclastogenesis: a) An intense NO signal was observed in pre-osteoclasts preceding cell fusion. b) Osteoclastogenesis increased when cells were exposed to the NOS inhibitor, L-NMMA, during their differentiation phase. c) In contrast, pre-osteoclast fusion decreased in presence of to L-NMMA during the fusion phase. d) NOS inhibitors, decreased osteoclast formation. e) The inhibitory effect of L-NMMA on osteoclast formation was abolished with increasing concentrations of sRANKL. f) NO donors increased osteoclast formation. g) An increase in NO production coincided with pre-osteoclasts fusion. h) Inhibiting fusion decreased osteoclast formation and NO production. i) L-NMMA decreased, while NO donors increased actin free barbed ends. Conclusion: While NO initially negatively regulates pre-osteoclast differentiation, it later facilitates the fusion of mononuclear pre-osteoclasts, possibly by up regulating actin remodeling. 2) Involvement of NO in OTM: Differential expression of NOS isoforms was investigated in periodontal ligament (PDL) and bone in tension and pressure sides using immunohistochemistry with NOS isoforms in a rat model of OTM. a) Expression of all isoforms was increased in the tension side. b) iNOS and nNOS expressions in the pressure side with the cell free zone were decreased while in the pressure side without the cell free zone were increased. c) The intensity of eNOS staining was increased in the tension side. d) Duration of force only changed the pattern of nNOS expression. e) Osteocyte NOS expression did not change. Conclusion: All NOS isoforms are involved in OTM with different expression patterns between the tension and pressure with nNOS being more involved in early OTM. PDL cells, rather than osteocytes are the mechanosensors in early OTM with regards to NO signaling.

The purpose of this study was to determine the impact of insertion angle of orthodontic mini screws on the stability and resistance to movement of the mini screw, and on the peri-implant interface. Three orthodontic mini screws were placed in each tibia of six New Zealand white rabbits bilaterally (N=36), with randomized angulation (65° away, 65° toward, or 90° to the direction of applied force). After two weeks, two orthodontic mini screws within each tibia were loaded with a 200g Nitinol closed-coil spring for up to 14 days. No statistically significant differences were found among the variably angulated loaded and unloaded orthodontic mini screws in the amount of movement or change in angulation demonstrated over the experimental period. Micro CT analysis revealed no clinically significant differences in the amount of cortical bone-to-implant contact. Mini screw placement angulation seems to have minimal impact on stability and migration of orthodontic mini screws over time.