Browsing by Subject "Orthodontics"
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Item Accuracy of Two Indirect Bonding Transfer Methods: A Three-Dimensional, In-vivo analysis(2015-07) Gyllenhaal, KelleyBackground: Recent literature has suggested that indirect bonding results in more accurate bracket placement. However, this more ideal positioning is of no use to the orthodontist unless the indirect bracket set-up is transferred accurately to the patient's dentition. This study aims to investigate the positional integrity of the indirect bonding transfer method of two commercially available tray types. Materials and Methods: Eighteen patients were randomly assigned to either a transparent tray light-cure or an opaque tray chemical-cure indirect bonding system. A total of 129 teeth were analyzed for the transparent tray group and 99 teeth for the opaque tray group. An intraoral scanner was used to generate three-dimension .stl models of each indirect set-up ("pre-transfer"� model) and each corresponding in-vivo bracketed patient arch ("post-transfer"� model). A comparison software was used to superimpose these models based on a surface best-fit algorithm. Bracket position differences were measured in three translational and three rotational planes of space to the nearest 1 �m. Statistical analysis was performed to compare the pre- and post-transfer bracket position, to detect any directional patterns of error, and to compare the transparent and opaque tray systems. Results: The indirect bonding transfer was found to be accurate for the data as a whole and for each tray type individually (p<0.0001). Final bracket position tended to be slightly more buccal and more occlusal for both groups compared to the set-up. This error was clinically insignificant but was more pronounced for the opaque tray group. Conclusions: Both indirect bonding methods transfer bracket position accurately in actual clinical use.Item Comparison of spheno-occipital synchondrosis closure, cervical vertebrae maturation and hand-wrist maturation as skeletal maturation indicators(2018-06) Dillon, MollyAim: To examine the correlation between three skeletal maturation indicators: hand-wrist maturation, cervical vertebrae maturation and the spheno-occipital synchondrosis closure. Methods: The hand-wrist radiographs and images of cervical vertebrae and the spheno-occipital synchondrosis (extracted from CBCTs) of 61 patients were graded for skeletal maturation by three raters on two different dates. Their stages were compared to analyze the agreement between the three skeletal maturation markers. The reliability of the staging of the three analyses was also studied. Results: The hand-wrist maturation analysis had the highest intra-rater (ĸ= 0.895) and inter-rater reliability (Kendall’s coefficient = 0.972), while the spheno-occipital’s reliability was the lowest (intra-rater reliability ĸ = 0.642; inter-rater reliability Kendall’s coefficient = 0.886). The skeletal maturation indicators that agreed most closely were the hand-wrist maturation and the spheno-occipital synchondrosis (ĸ = 0.5079). Conclusions: The three skeletal maturation analyses studied are related but not inter-changeable. More clear definitions of the staging of the analyses and calibrations of the analyses are needed to improve reliability. A clinician should rely on multiple markers to make decisions regarding a patient’s growth potential.Item Debonding and adhesive remnant cleanup: an in vitro comparison of bond quality, adhesive remnant cleanup, and orthodontic acceptance of a flash-free product(2014-06) Sudit, Geoffrey NathanBackground: New orthodontic products are continuously introduced to clinicians seeking more practical and efficient solutions for their practice. One such product is a new flash-free adhesive for orthodontic bracket bonding, which has been introduced to the market recently. This new adhesive needs to be clinically appraised with regard to its efficacy and efficiency, and compared with conventional orthodontic adhesives that are currently in use.Aims: To compare the quality of the bond at the enamel-bracket interface using micro-computed tomography (microCT), the amount of adhesive remaining on the tooth surface after bracket debonding, the time required for adhesive remnant cleanup, and clinical practitioners' preference between the new flash-free and a conventional adhesive. Materials and Methods: A total of 160 bovine incisors were bonded with ceramic orthodontic brackets using the flash-free adhesive (APC Flash-Free Adhesive Coated Appliance System, 3M) on one side and a conventional adhesive (APCII Adhesive Coated Appliance System, 3M) on the other side. Twenty-four teeth were randomly selected and scanned using microCT to analyze microleakage into the adhesive layer. Twenty orthodontists debonded twenty mounted dental arches. The adhesive remnant on the bovine incisors was quantified. The orthodontists then removed the remaining adhesive. The time required for complete removal of adhesive was recorded. Finally, the orthodontists completed a specifically designed survey to evaluate their preference for one of the two adhesives. Results: For both adhesives tested, the microleakage was very minimal with no significant differences between the two adhesives. The amount of adhesive remaining on the tooth after bracket debonding was significantly larger for the flash-free adhesive (P<0.0001). The adhesive cleanup was about 8% faster when using the flash-free adhesive, but the difference was not statistically significant when compared with the conventional adhesive. Fourteen out of 20 orthodontists preferred the flash-free product over the conventional product.Conclusions: With regard to the practicality and efficiency, the new flash-free adhesive performs just as well as the conventional adhesive.Item The Effect of Attachment Flash on Clear Aligner Force Delivery(2022-06) Larson, ZoeIntroduction: Composite attachments are a vital part of clear aligner therapy and crucial to accomplish the intended tooth movements throughout treatment. Due to the necessity and importance of attachments, accurate application is imperative. When attachments are bonded, placing them without excess composite flash going beyond the perimeter is nearly impossible. Recent research has studied certain attachment bonding protocols to investigate which bonding protocol produces the least amount of excess, but no research has been done to demonstrate clinical effects excess composite flash has on clear aligner treatment. Aim: To evaluate the effect attachment flash thickness and surface area has on the force delivered to a maxillary central incisors with a Zendura FLX clear aligner. Methods: The experiment was conducted in a lab setting using 3D printed models of the maxillary arch. Zendura FLX .030 mil clear aligners programmed for 0.25 mm of extrusion will be used on a maxillary central incisor. To evaluate the effect of flash thickness and surface area, a standard rectangular anterior extrusion attachment placed on the midfacial surface of the clinical crown was designed with no flash which served as the control. We tested three different surface areas (7mm2, 14mm2, 21mm2) at three different thicknesses (0.2 mm, 0.35 mm, 0.5 mm), making ten total designs. For each of the ten groups, five aligners were fabricated with margins 0.75 mm apical to the gingival zenith. Extrusive and lingual forces were measured using a force gauge. Means and standard deviations were calculated and presented by group. The one-way analysis of variance (ANOVA) was conducted to compare the means between the groups and Tukey’s method was used to adjust for multiple comparisons. P-values less than 0.05 were considered statistically significant. Results: The intended extrusive force decreases as flash surface area decreases and as flash thickness increases. The main finding to note when examining how the intended extrusive force was affected by flash was looking at the standard deviations for each group. The control group had the smallest standard deviation compared to all the groups with flash. When looking at the mean unintended lingual force, all groups including flash showed higher lingual force than the control group with seven out of the nine groups being statically significant. In general, as the thickness of the flash increases, the lingual force applied to the tooth by a clear aligner (CA) increases. Similarly, as the surface area of the flash increases, the lingual force applied to the tooth by a CA increases. Conclusions: This is the first study in which the effect of attachment flash on force applied by a clear aligner has been studied. In this benchtop study, a few conclusions can be made as to the effect attachment flash has on clear aligner therapy (CAT). CAs exert more lingual force when attachment flash is present compared to attachments without flash. As flash thickness increases and flash surface area increases the CAs exert more lingual force. As flash thickness increases and flash surface area decreases the intended extrusive force applied by CAs decreases. When flash is present, the intended extrusive force is less predictable compared to when no flash is present.Item Effect of the Periodontal Ligament on Clear Aligner Material Surface Strain when Measured In-Vivo(2023-06) Nelson, SamanthaIntroduction: Clear aligner therapy has become increasingly popular as an alternative to traditional braces. Despite advances in technology, the efficacy and efficiency of clear aligner treatment remains challenged. Numerous in-vitro studies into the force systems of clear aligners have been developed. Currently, there are no guidelines for evaluating orthodontic force systems intraorally with clear aligners. The effect of the periodontal ligament and intraoral environment on orthodontic tooth movement with clear aligners remains unknown. Aim: To determine if surface strain can be measured in-vivo with digital image correlation (DIC). And to evaluate the effect of the periodontal ligament and intraoral environment on the surface strain delivered by a clear aligner to a maxillary central incisor during lingual tipping. Methods: Clear aligners were designed with 2.0 degrees of lingual crown tipping about an estimated center of rotation on a maxillary central incisor for 33 subjects. Clear aligners were fabricated using two materials, Essix ACE and Zendura A, in 0.030 mil (0.75 mm) thickness. A dual-camera, three-dimensional DIC system was used to record the transverse strain on the facial surfaces on the subject’s model, in the subject’s mouth, and on the subject’s model after submersion in artificial saliva. The relationships between transverse strain and the predictors, aligner material and environment, were examined using linear mixed effects models, with a random intercept for subject. A statistical model was also fit to test associations between transverse strains and predictors aligner material, gender, and presence of artificial saliva. Estimates are reported as a means with 95% confidence intervals. The passive and active models and aligners were assembled and scanned by micro-CT to measure the gap size between the aligner and model. Displacement at the incisal half of the target tooth was measured with GeoMagic software. Results: Initial forces delivered by clear aligners produced a strain threshold high enough to be detected and captured intraorally by DIC. The strain distribution and contour differed between in-vivo and in-vitro, as well as between material types, but followed the same pattern and peaks. Mean transverse strain increased as the point of focus narrowed to the incisal half of the target tooth. The effects of the environment were statistically significant at the incisal half of the target tooth, with increased transverse strain in-vitro compared to in-vivo. Zendura A expressed significantly less transverse strain than Essix ACE within both environments. The effect of the material was more pronounced in-vitro for the entire dentition, but not at the incisal half of the target tooth. No differences in transverse strain were noted with the presence or absence of artificial saliva, as well as between genders. Strong reproducibility existed between trials, with more similar strain profiles in-vitro compared to in-vivo. Micro-CT images demonstrated a lack of gap between the aligner and passive model on the labial surface of the target tooth, while gap sizes increased at the interproximal contact points and on adjacent teeth. Based on inciso-gingival crown length of tooth, there was no difference in incisor displacement between subjects. Conclusions: This is the first study in which the strain distribution on a clear aligner has been studied in-vivo with DIC. Initial force delivered by clear aligners can be detected and evaluated intraorally. The difference in surface deformation between environments is only significant at the point of greatest tooth displacement, with increased transverse strain in-vitro. Material type influences clear aligner strain, with a more pronounced effect in-vitro. Clear aligners distribute strain to multiple teeth despite efforts to isolate movement to a single target tooth. And the presence of artificial saliva and influence of gender do not affect strain level or surface deformation.Item The findings and natural history of radiographic signs of temporomandibular osseous changes in an orthodontic population(2013-08) Anderson, Brian CraigAIMS: Evaluate the natural history of radiographic temporomandibular joint (TMJ) findings in an orthodontic sample population by interpreting cone-beam CT (CBCT) scans, made before and after comprehensive orthodontic treatment, according to Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) imaging criteria. METHODS: 348 subjects were included in the study. Pre-treatment CBCTs were interpreted and screening diagnoses were given. Subjects were categorized: control (normal), indeterminate (remodeling), and case (degenerative joint disease [DJD]); these were matched for age and gender. The pre-treatment and post-treatment CBCTs of 76 matched subjects (152 joints) were interpreted and definitive diagnoses were given for each joint. RESULTS AND CONCLUSIONS: There was no statistical evidence that, on average, a worse joint diagnosis existed pre-treatment or post-treatment. The likelihood of having a worse diagnosis post-treatment was statistically significant given a pre-treatment diagnosis of DJD or indeterminate. From pre-treatment to post-treatment 52.6% of diagnoses were unchanged, 25% worsened, and 22.4% improved.Item Indirect bonding of orthodontic Brackets: an evaluation of transfer accuracy and reliability(2014-06) Lee, Michael StevenBackground: Indirect bonding of orthodontic brackets has been viewed as a method of achieving greater accuracy and effectiveness in orthodontic treatment. Although the concept of indirect bonding has been widely studied, the accuracy of the transfer between the indirect stone model-set of the brackets to the patient's dentition has not been investigated in a clinical setting. The goal of the present study is to elicit the frequency, directional bias, and magnitude of bracket positioning errors due to this transfer.Methods: A total of 163 brackets were initially placed on indirect stone model set-ups and scanned using a cone-beam computed tomography system to capture 3-D bracket positioning data. These brackets were then transferred to the patient's dentition and later scanned using CBCT to capture the final 3-D bracket positioning on the teeth. Virtual models of the teeth and attached brackets were constructed from the scanned data. Initial and final pairs of models were digitally superimposed. Differences in bracket positioning were measured using customized software. One-tailed t-tests were used to compare measurement data with the pre-determined acceptable ranges of +/- 0.5 mm linearly and 2.0 degrees angularly for differences in each of 6 dimensions studied. Results: The indirect transfer of brackets resulted in accurate positioning (&alpha = 0.05, P < 0.0001). Bracket positioning along mesial-distal, buccal-lingual, and vertical axis most frequently satisfied the accuracy requirements. The indirect bonding transfer of brackets had a modest bias towards the buccal and gingival. The bracket failure (detachment) rate in this study was 9.8%.Conclusions: The indirect bonding transfer is statistically accurate and reliable.Item Loss of Class II HDAC10 Expression on Osteoclastogenesis(2017-07) Spencer, EkaterinaOsteoclasts differentiation is regulated by a complex series of genes. HDACs, histone deacetylases, are a family of proteins that inhibit gene expression in multiple cell types. Class II HDACs are expressed in multiple cell types and found either in the nucleus or the cytoplasm or both cellular compartments of cells. This localization suggests that they have roles in regulating cell differentiation. The Mansky lab and other have demonstrated that the class II HDACs, HDAC7 and HDAC9, act as inhibitors of osteoclast differentiation. The aim of my project was to investigate the role of HDAC10, another class II HDAC, in regulating osteoclast differentiation. Osteoclasts expressing a shRNA against HDAC10 were larger in size and demineralized more of a calcium/phosphate substrate compared to control infected cells. This data suggests that similar to HDAC7 and HDAC9, HDAC10 acts as an inhibitor of osteoclast differentiation.Item Midpalatal suture density ratio as a predictor of skeletal response to rapid maxillary expansion(2015-06) Larson, ChadBackground: During adolescence, increasing interdigitation of the midpalatal suture increases resistance to rapid maxillary expansion (RME), which decreases its skeletal effect. Purpose: To determine if a novel measure of midpalatal suture maturity, the midpalatal suture radiographic density ratio (MPSD), is a predictor of the skeletal response to RME. Research design: Pre-treatment measurements of MPSD ratio, age, and cervical vertebral maturation (CVM) were obtained of 30 patients who underwent RME. Measurements on CBCT scans were used to determine the proportion of prescribed expansion achieved at both the greater palatine foramina (GPFp) and infraorbital foramina (IOFp). Results: There was a statistically significant correlation between the MPSD and both GPFp and IOFp (P<0.05). In contrast, age and CVM were not significantly correlated to the measures of skeletal expansion (P>0.05). Conclusions: The MPSD has the potential to become a useful clinical predictor of skeletal response to RME.Item On the Relationship between Condylar Cortication and Mandibular Growth Activity(2021-07) Sharp, JohnIntroduction: Mandibular growth prediction is central to orthodontics, yet little is known of the condylar bone density that accompanies this growth. Aims: To determine the bilateral symmetry of condylar cortical (CC), condylar trabecular (CT) and otic capsule (OC) grey values (GVs). To determine the relationship between condylar and OC GVs with age. To determine the relationship between three-dimensional mandibular growth and age. To determine the relationship between condylar cortication and mandibular growth activity. Methods: Mandibular growth rate was measured on CBCTs of orthodontically treated adolescents and young adults. OC, CC, and CT GVs were collected, and a bone density ratio calculated. Results: Significant differences exist in bilateral CC and OC GVs. CC, CT, and OC GVs significantly vary with age. Intercondylar width and mandibular growth rate significantly vary with age. Condylar cortication significantly predicts mandibular growth rate. Conclusions: A novel method to assess mandibular growth activity is introduced.Item Optimal head position: A new frame of reference for cephalometric analysis(2013-08) Teeters, Christopher AndrewIntroduction: Facial considerations are important in any contemporary cephalometric analysis based on a soft-tissue paradigm, and head position is often an important component of these soft-tissue measurements. Natural head position (NHP) has long been used as the reference position for craniofacial morphology and it has been subject to great scrutiny due to its inherent variability. This study aims to determine if there is an operator-defined optimal head position (OHP) that is deemed the most pleasant, universal to all skeletal classifications, and parallel to Frankfort Horizontal (FH). Methods: 31 subjects (10 orthodontists, 10 orthodontic residents, and 11 orthodontic staff members) were asked to take an online survey evaluating 9 soft-tissue rendering profile positions (2.5 degrees apart) of 30 different models (N=31, Power = 0.92). They were asked to indicate the most pleasant profile orientation and to disclose whether they were orthodontists, residents, or staff members. Results: Chi-square tests and two one-sided t-test procedure (TOST) tests were performed to test the null hypotheses. All null hypotheses were rejected, therefore: (1) not all profile orientations were chosen with equal frequency. The most commonly chosen angle was 0 (about 30% of the choices, p < 0.0001) corresponding to the Helion-Canthion line (HC line) parallel to the floor and about 70% of the choices were within 2.5 degrees of the angle 0. There was no significant difference in the head orientations chosen by orthodontists, orthodontic residents, and staff members; (2) the three skeletal classes demonstrated a very similar pattern of angle choice, which was most often 0 (p < 0.05); and (3) the soft-tissue HC line and hard-tissue FH deviation resulted in a mean of deviation range of values within the limits of ±0.5° (p< 0.001) denoting very high concordance between HC line and FH. Conclusions: 70% of responders chose the orientation within one standard deviation consistent with HC parallel to the floor (p < 0.001). We noticed that the most commonly chosen angle was 0 for each of the three skeletal groups (p < 0.05), and that their frequency distributions of angle choice had very similar shapes. The suggested OHP reference plane proved to be parallel to FH and it was deemed to be an esthetically pleasing and easily determined soft-tissue head orientation. We believe that OHP can be confidently and meaningfully used in contemporary cephalometric analyses. This head orientation may be obtained prior to taking pictures and radiographs (including CBCTs) or after the exposure, by rotating the picture or soft tissue rendering until the HC line is parallel to the floor.Item The Relationship Between the Amount of Orthodontic Tooth Movement and the Effectiveness of Computer Assisted Treatment(2017-06) Czarnik, ScottAim: To evaluate the effectiveness of SureSmile technology and determine if a correlation exists between discrepancy and overall movement throughout treatment. Methods: Digital pre-treatment models, predicted final treatment models, and actual final treatment models of 30 patients were superimposed to determine both the overall movement each tooth completed throughout treatment, the amount of discrepancy between predicted and actual results, and if any correlation exists between these two findings. Results: Statistically significant correlation between amount of overall tooth movement and discrepancy between predicted and actual final alignment was found in the following instances: Mesial-distal dimension in maxillary canines. Facial-lingual dimension of maxillary central incisors, and lateral incisors. Torque of maxillary central incisors, lateral incisors, 1st molars, and all mandibular teeth. Rotation of maxillary central incisors. Conclusion: The effectiveness of SureSmile is highly variable and dependent on tooth type and dimension of movement.Item Transfer Accuracy of 3D-Printed Trays for Indirect Bonding of Orthodontic Brackets: A Clinical Study(2021-06) Bachour, PetraAim: To evaluate the transfer accuracy of 3D-printed indirect bonding trays constructed using a fully digital workflow in a clinical setting.Methods: Twenty-three consecutive patients had their incisors, canines, and premolars bonded using a fully digital indirect bonding method and 3D-printed transfer trays. Intraoral scans were taken to capture the final bracket positioning on the teeth following bonding. Digital models of the post-bonding scans were superimposed on those of the corresponding virtual bracket setups, and bracket positioning differences were quantified. A total of 363 brackets were evaluated. One tailed t-tests were used to determine whether bracket positioning differences were within limits of 0.5 mm in the mesio-distal, bucco-lingual, and occluso-gingival dimensions, and within 2° for torque, tip, and rotation. Results: Mean bracket positioning differences were 0.10 mm, 0.10 mm, and 0.18 mm for mesio-distal, bucco-lingual, and occluso-gingival measurements, respectively. For the linear dimensions, frequencies of bracket positioning error within the 0.5-mm limit ranged from 96.4–100%. Mean differences were significantly within the acceptable range for these dimensions. Mean differences were 2.55°, 2.01°, and 2.47° for torque, tip, and rotation, respectively. For the angular measurements, frequencies within the 2°-limit ranged from 46.0–57.0%. The mean differences for the angular dimensions were outside the acceptable limit; however, this may have been due to limitations of the scan data. Conclusions: Indirect bonding using 3D-printed trays transfers the planned bracket position from the digital setup to the patient’s dentition with a high positional accuracy in the mesio-distal, bucco-lingual, and occluso-gingival dimensions. Questions remain regarding the transfer accuracy in the angular dimensions.