Browsing by Subject "root resorption"

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    Biology of biomechanics: Finite Element Analysis of a Statically Determinate System to Rotate the Occlusal Plane for Correction of Skeletal Class III Openbite Malocclusion
    (Elsevier, 2015-12) Roberts, W. Eugene; Viecilli, Rodrigo F.; Chang, Chris; Katona, Thomas R.; Paydar, Nasser H.; Department of Orthodontics and Oral Facial Genetics, IU School of Dentistry
    Introduction In the absence of adequate animal or in-vitro models, the biomechanics of human malocclusion must be studied indirectly. Finite element analysis (FEA) is emerging as a clinical technology to assist in diagnosis, treatment planning, and retrospective analysis. The hypothesis tested is that instantaneous FEA can retrospectively simulate long-term mandibular arch retraction and occlusal plane rotation for the correction of a skeletal Class III malocclusion. Methods Seventeen published case reports were selected of patients treated with statically determinate mechanics using posterior mandible or infrazygomatic crest bone screw anchorage to retract the mandibular arch. Two-dimensional measurements were made for incisor and molar movements, mandibular arch rotation, and retraction relative to the maxillary arch. A patient with cone-beam computed tomography imaging was selected for a retrospective FEA. Results The mean age for the sample was 23.3 ± 3.3 years; there were 7 men and 10 women. Mean incisor movements were 3.35 ± 1.55 mm of retraction and 2.18 ± 2.51 mm of extrusion. Corresponding molar movements were retractions of 4.85 ± 1.78 mm and intrusions of 0.85 ± 2.22 mm. Retraction of the mandibular arch relative to the maxillary arch was 4.88 ± 1.41 mm. Mean posterior rotation of the mandibular arch was –5.76° ± 4.77° (counterclockwise). The mean treatment time (n = 16) was 36.2 ± 15.3 months. Bone screws in the posterior mandibular region were more efficient for intruding molars and decreasing the vertical dimension of the occlusion to close an open bite. The full-cusp, skeletal Class III patient selected for FEA was treated to an American Board of Orthodontics Cast-Radiograph Evaluation score of 24 points in about 36 months by en-masse retraction and posterior rotation of the mandibular arch: the bilateral load on the mandibular segment was about 200 cN. The mandibular arch was retracted by about 5 mm, posterior rotation was about 16.5°, and molar intrusion was about 3 mm. There was a 4° decrease in the mandibular plane angle to close the skeletal open bite. Retrospective sequential iterations (FEA animation) simulated the clinical response, as documented with longitudinal cephalometrics. The level of periodontal ligament stress was relatively uniform (<5 kPa) for all teeth in the mandibular arch segment. Conclusions En-masse retraction of the mandibular arch is efficient for conservatively treating a skeletal Class III malocclusion. Posterior mandibular anchorage causes intrusion of the molars to close the vertical dimension of the occlusion and the mandibular plane angle. Instantaneous FEA as modeled here could be used to reasonably predict the clinical results of an applied load.
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    Canine-Lateral Incisor Transposition: Controlling Root Resorption with a Bone- Anchored T-Loop Retraction
    (Elsevier, 2016-12) Hsu, Yu Lin; Chang, Chris H.; Roberts, W. Eugene; Department of Orthodontics and Oral Facial Genetics, School of Dentistry
    Introduction: A 12-yr old female presented with a Class II division 1 malocclusion, complicated by a complete transposition of the maxillary left canine, into the position normally occupied by the left lateral incisor. Dental and medical histories were noncontributory. Methods: Brackets were bonded on all maxillary teeth, from first molar to first molar, except for the left lateral incisor. Because the lateral incisor was not engaged on the archwire, the tooth was free to physiologically move out of the path of canine root movement. To prepare the site for canine retraction, a coil spring was used to open space between the left central incisor and first premolar. A 2X12mm stainless steel miniscrew was placed in the infrazygomatic crest (IZC), labial to the mesiodistal cusp of the left maxillary first molar. Results: A 0.019 X 0.025” titanium-molybdenum alloy (TMA) T-loop, anchored by the miniscrew, was used to retract the canine root over the labial surface of the root of the distally positioned lateral incisor. Conclusions: In 24 months, this difficult malocclusion with a Discrepancy Index (DI) of 18 was treated to a cast-radiograph evaluation (CRE) score of 26.
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    Decreased alveolar bone turnover is related to the occurrence of root resorption during experimental tooth movement in dogs
    (2015) Deguchi, Toru; Seiryu, Masahiro; Daimaruya, Takayoshi; Garetto, Lawrence P.; Takana-Yamamoto, Teruko; Roberts, W. Eugene; Department of Oral Pathology, Medicine and Radiology, IU School of Dentistry
    Objective:  To investigate the relationship between root resorption (RR) and bone turnover in two different types of tooth movement in dogs. Materials and Methods:  A total of 16 dogs in two different groups were used. Tooth movement of dog premolars resulted from approximately 200 g of force. Histomorphometric analysis of premolar roots was assessed after 4 and 12 weeks of tooth movement by comparing nonresorptive to resorptive surfaces. Results:  Histomorphometric analysis indicated a significant decrease in the bone formation rate in the root resorptive areas, which resulted in decreased bone volume after 12 weeks. The threshold to detect RR in periapical radiographs was about 1.0 mm2. Conclusions:  A sustained mechanical load, due to the prolonged stress and strain of continuous mechanics, induces elevated bone metabolic activity, such as the bone turnover (remodeling) and change in bone volume (modeling). Therefore, our data support the hypothesis that increased RR is related to decreased bone formation (turnover) in high stress areas exposed to prolonged orthodontic tooth movement.
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    Histomorphometric and Histopathologic Evaluation of the Effects of Systemic Fluoride Intake on Orthodontic Tooth Movement
    (Thieme, 2019) Zorlu, Fatma Yalcin; Darici, Hakan; Turkkahraman, Hakan; Orthodontics and Oral Facial Genetics, School of Dentistry
    Objectives The aim of this study was to determine the effects of systemic fluoride intake on orthodontic tooth movement with histomorphometric and histopathologic methods. Materials and Methods Forty-eight Wistar albino rats were randomly divided into four groups of 12 rats each. Group I received fluoridated water and underwent orthodontic tooth movement. Group II received fluoridated water and did not undergo orthodontic tooth movement. Group III received nonfluoridated water and underwent orthodontic tooth movement. Group IV received nonfluoridated water and did not undergo orthodontic tooth movement. At the beginning of the experiment (T1), impressions were taken from the maxilla of the rats in groups I and III under general anesthesia, and a NiTi closed coil spring appliance was ligated between the left maxillary central incisors and maxillary first molar. The orthodontic force applied was approximately 75 g, and the duration of the experimental period was 18 days. During the experimental period, appliances were controlled daily. At the end of the experimental period (T2), the rats were sacrificed with an overdose of a ketamine/xylasine combination, and their impressions were obtained. The upper first molars were subsequently dissected for histological examination. Incisor–molar distance, number of osteoblasts, number of osteoclasts and periodontal ligament (PDL) space widths on the compression and tension sides were measured. Statistical Analysis All measurements were statistically analyzed with SPSS for Windows version 18.0 (SPSS Inc., Chicago, IL, USA). Repeated measures ANOVA and posthoc Tukey tests were used to compare the groups. Results No statistically significant difference was found with respect to the amount of tooth movement between the fluoridated and nonfluoridated groups (p > 0.05). Orthodontic force application increased the number of osteoblasts at the tension sides and reduced it at the compression sides (p < 0.001). An increased number of osteoclasts was observed in the nonfluoridated group relative to the fluoridated group (p < 0.01). Conclusions No difference was observed with respect to the amount of tooth movement between the fluoridated and nonfluoridated groups. Fluoride significantly reduced the number of osteoclasts in the experimental groups.