Orthodontic root resorption.

External apical root resorption (EARR) is one of the most frequently reported iatrogenic side effects of orthodontic movement. Nevertheless, no robust and unequivocal scientific evidence is yet available in the literature regarding the clinical and biological factors that trigger EARR. The purpose of the present position paper is to provide clinicians, residents, and investigators a summary of our current understanding about root resorption caused by orthodontic tooth movement, based on up-to-date available scientific evidence. Morphological, structural, biomechanical, and biological differences account for predisposing the apical third to EARR compared to other root surfaces during orthodontic treatment. In addition, a relevant number of patient and treatment-related factors increase risk of EARR. The main patient-related factors are reviewed and discussed: genetic factors, tooth anatomy, demographic factors, malocclusion factors, previous endodontic treatment, medical history, short root anomaly. Similarly, the influence of treatment-related factors are analyzed with regard to the effect of: biomechanical factors, type of orthodontic appliance, adjunctive therapies to accelerate tooth movement, early treatment, maxillary expansion, teeth extractions, the duration of treatment and the amount of apical displacement. Clinical management of EARR from pre-treatment records to the monitoring strategy as well as recommendations for the post orthodontic-treatment period are presented as a guide for the clinician. Despite years of studies, we still do not fully understand EARR, but the future is promising. True three-dimensional imaging with higher resolution and low radiation, and predictive tools towards an earlier detection without radiographs, will mark future developments in the field of EARR in orthodontics.

Three-dimensional assessment of virtual bracket removal for orthodontic retainers: A prospective clinical study.

INTRODUCTION: Computer-aided design and manufacturing of orthodontic retainers from digitally debonded models can be used to facilitate same-day delivery. The purpose of this prospective clinical study was to validate a novel technique for virtual bracket removal (VBR) in-office, comparing the accuracy with 2 orthodontic laboratories that use VBR for retainer fabrication in the digital workflow. METHODS: The sample consisted of 40 intraoral scans of 20 patients. Four groups were compared. The scans without brackets were used as a control group. VBR was performed by 3 groups: In-office VBR (Software Meshmixer, version 3.5.474; Autodesk, San Rafael, Calif), Orthodent Laboratory (ODL; Buffalo, NY), and New England Orthodontic Laboratory (NEOLab; Andover, Mass). The virtually debonded models were superimposed onto the control models using surface-based registration. Regional 3-dimensional Euclidean distances between surface points of superimposed models were calculated for comparative analysis of surface changes after VBR using Vector Analysis Module (Canfield Scientific, Fairfield, NJ) software. RESULTS: The accuracy of VBR using the Meshmixer did not differ significantly from the VBR protocols used by the 2 laboratories. However, there was a statistically significant difference between the 2 laboratories, with ODL showing lower accuracy than NEOLab. Although some differences were statistically significant, they were very small and not considered clinically relevant. There was also a statistically significant difference between the 3 tooth segments (incisors, canines/premolars, and first molars), with VBR of the first molars and second premolars showing the least accuracy. CONCLUSIONS: The VBR techniques using the in-office Meshmixer, ODL, and NEOLab were considered accurate enough for the clinical use of orthodontic retainers fabricated from printed models.

Evaluating the treatment effectiveness and efficiency of Carriere Distalizer: a cephalometric and study model comparison of Class II appliances.

BACKGROUND: The purpose of this study was to evaluate the treatment effectiveness of Carriere Distalizer in comparison to Class II intermaxillary elastics and Forsus. METHODS: Three groups of patients treated with Class II intermaxillary elastics (n = 18), Carriere Distalizer (n = 18), and Forsus appliance (n = 18) were collected from three private orthodontic practices. Inclusion criteria were as follows: (1) 10-14 years old of start age with permanent dentition, (2) no history of previous orthodontic treatment, (3) complete pre- and post-treatment records, (4) dental Class II division 1 (end-to-end or more), (5) no pre-treatment transverse discrepancy, (6) non-extraction treatment plan, and (7) Class I post-treatment occlusal relationship. The data consisted of cephalometric and study model measurements from pre- and post-treatment records and treatment time. Two-tail Student t test was used to analyze the differences in cephalometric changes and dental corrections between Carriere Distalizer group and Class II elastics/Forsus group. RESULTS: All three groups of patients showed no differences in the age of treatment initiation, pre-treatment cephalometric measurements and discrepancy index (DI). The time of Class II correction for Carriere Distalizer was significantly shorter than that for Class II elastics; there was no difference in the length of Class II correction between Carriere Distalizer and Forsus groups. The amount of Class II correction (canine/molar relationship) was significantly lower for Carriere Distalizer when compared with Forsus appliance. Carriere Distalizer, similarly to Class II elastics, did not induce any statistically significant correction in skeletal component (ANB and Wits appraisal). CONCLUSIONS: There is no clinically significant skeletal correction induced by Carriere Distalizer in growing patients. Carriere Distalizer can be applied to treatment of mild to moderate Class II dental malocclusion over 6 months on average, although the total treatment time may be prolonged due to various side effects. Overall, the Carriere Distalizer appears to be no more effective or efficient than alternatives in the treatment of Class II malocclusion.

Cone-beam computed tomography evaluation of bone plate and root length after maxillary expansion using tooth-borne and tooth-tissue-borne banded expanders.

INTRODUCTION: The objective of this research was to evaluate the buccal bone plate and root length of maxillary permanent first molars using cone-beam computed tomography after maxillary expansion with different activation protocols. METHODS: Cone-beam computed tomography images of growing patients were obtained from the orthodontic department of Pontifical Catholic University of Rio Grande do Sul in Brazil. The groups were Haas-type 2/4 turns, Haas-type 4/4 turns, hyrax-type 2/4 turns, and hyrax-type with alternate rapid maxillary expansions and constrictions (alt-RAMEC) 4/4 turns a day. Tooth length, periodontal insertion, alveolar bone thickness, and intermolar distances were evaluated. The data at the start of treatment and 6 months later were compared using generalized linear models. The intergroup differences were determined by univariate analysis of variance with the Bonferroni adjustment. RESULTS: Tooth length was significantly shortened after expansion in all groups (-0.28 to -0.51 mm), except for the alt-RAMEC group. Bone level variables (bone level and bone level at the tooth tip) changed statistically in all groups, except for the Haas 4/4 turns group. There was significant periodontal attachment loss after rapid maxillary expansion with the hyrax/alt-RAMEC (5.09 mm). The hyrax/alt-RAMEC and hyrax groups had more dehiscences, fenestrations, and exposures of the root. CONCLUSIONS: The consequence of rapid maxillary expansion using the hyrax was alveolar bone resorption, especially in the hyrax/alt-RAMEC group, whereas the Haas expander caused mild root resorption.

Three-dimensional monitoring of root movement during orthodontic treatment.

INTRODUCTION: A significant objective of orthodontic treatment is to achieve proper and stable tooth positions that involve not only the crowns, but also their roots. However, the current methods of clinically monitoring root alignment are unreliable and inaccurate. Therefore, the purpose of this study was to develop a methodology that can accurately identify root position in a clinical situation. METHODS: Pretreatment and posttreatment cone-beam computed tomography (CBCT) and extraoral laser scans of study models of a patient were obtained. Threshold segmentation of the CBCT scans was performed, resulting in 3-dimensional surface models. The pretreatment CBCT teeth were isolated from their respective arches for individual tooth manipulation. These isolated pretreatment CBCT teeth were superimposed onto the posttreatment surface scan depicting the expected root position setup. To validate the accuracy of the expected root position setup, it was compared with the true root position represented by the posttreatment CBCT scan. Color displacement maps were generated to measure any differences between the expected and true root positions. RESULTS: Color map analysis through crown superimposition showed displacement differences of 0.148 ± 0.411 mm for the maxillary roots and 0.065 ± 0.364 mm for the mandibular roots. CONCLUSIONS: This methodology has been demonstrated to be an accurate and reliable approach to visualize the 3-dimensional positions of all teeth, including the roots, with no additional radiation applied.

Monitoring of typodont root movement via crown superimposition of single cone-beam computed tomography and consecutive intraoral scans.

INTRODUCTION: The purpose of this study was to develop a new methodology to visualize in 3 dimensions whole teeth, including the roots, at any moment during orthodontic treatment without the need for multiple cone-beam computed tomography (CBCT) scans. METHODS: An extraoral typodont model was created using extracted teeth placed in a wax base. These teeth were arranged to represent a typical malocclusion. Initial records of the malocclusion, including CBCT and intraoral surface scans, were taken. Threshold segmentation of the CBCT was performed to generate a 3-dimensional virtual model. This model and the intraoral surface scan model were superimposed to generate a complete set of digital composite teeth composed of high-resolution surface scan crowns sutured to the CBCT roots. These composite teeth were individually isolated from their respective arches for single-tooth manipulations. Orthodontic treatment for the malocclusion typodont model was performed, and posttreatment intraoral surface scans before and after bracket removal were taken. A CBCT scan after bracket removal was also obtained. The isolated composite teeth were individually superimposed onto the posttreatment surface scan, creating the expected root position setup. To validate this setup, it was compared with the posttreatment CBCT scan, which showed the true positions of the roots. Color displacement maps were generated to confirm accurate crown superimpositions and to measure the discrepancies between the expected and the true root positions. RESULTS: Color displacement maps through crown superimpositions showed differences between the expected and true root positions of 0.1678 ± 0.3178 mm for the maxillary teeth and 0.1140 ± 0.1587 mm for the mandibular teeth with brackets. Once the brackets were removed, differences of 0.1634 ± 0.3204 mm for the maxillary teeth and 0.0902 ± 0.2505 mm for the mandibular teeth were found. CONCLUSIONS: A new reliable approach was demonstrated in an ex-vivo typdont model to have the potential to track the 3-dimensional positions of whole teeth including the roots, with only the initial CBCT scan and consecutive intraoral scans. Since the presence of brackets in the intraoral scan had a minimal influence in the analysis, this method can be applied at any stage of orthodontic treatment.

Evaluation of dental and basal arch forms using cone-beam CT and 3D virtual models of normal occlusion.

UNLABELLED: OBIECTIVES: To evaluate the relationship between the mandibular dental and basal arches using CBCT, and to assess the correlation between basal arch dimensions derived from CBCT and 3-dimensional (3D) virtual models in a cohort sample exhibiting normal occlusions. METHODS: The facial axis (FA) and root centre (RC) points of mandibular teeth were identified on 32 CBCT images. FA and WALA points were digitised on 3D models of 28 mandibular casts from the same sample. The relationships between dental and basal arch dimensions, and between the two basal depth dimensions derived from RC and WALA points were statistically assessed by Pearson's correlation. RESULTS: Strong correlations were found between dental and basal intercanine and intermolar arch widths. Also, the basal intercanine width showed a moderate correlation with dental intermolar width and depth. The basal intercanine and intermolar widths measured on 3D models showed moderate correlations with those measurements on CBCT, whereas the basal canine and molar depths showed no correlations. CONCLUSIONS: The dental and basal anterior and posterior arch widths were strongly correlated in normal occlusion. No correlations were found between the arch depths measured from WALA points and RC points. Hence, RC points may represent more useable landmarks compared to WALA points in the evaluation of basal arch forms. It is recommended that the relationship between the dental and basal arches is evaluated during treatment planning in order to improve arch co-ordination.

Comparison between dental and basal arch forms in normal occlusion and Class III malocclusions utilizing cone-beam computed tomography.

OBJECTIVE: The purpose of this study was to investigate the relationship between the mandibular dental and basal arch forms in subjects with normal occlusion and compare them with those of Class III malocclusion using cone-beam computed tomography (CBCT). METHODS: CBCT images of 32 normal occlusion (19 males, 13 females; 24.3 years) and 33 Class III malocclusion subjects (20 males, 13 females, 22.2 years) were selected. Facial axis and root center points were identified from the left to right mandibular first molars. Distances between the facial axis and root center points for each tooth were calculated, and 4 linear and 2 ratio variables were measured and calculated for each arch form. The variables were compared between groups by independent t-test. Pearson correlation coefficient was applied to assess the relationships between dental and basal variables within each group. RESULTS: The mandibular dental and basal intercanine widths were significantly greater in the Class III group than in normal occlusion subjects (p < 0.05). The dental and basal intercanine widths as well as the dental and basal intermolar widths were strongly correlated in normal occlusion and moderately correlated in Class III malocclusion. CONCLUSIONS: The dental arch form demon strated a strong positive correlation with the basal arch form in the normal occlusion group and moderate correlation in the Class III malocclusion group. These results might be helpful for clinicians to have a better understanding of the importance of basal arch form in the alveolar bone.

Imaging software accuracy for 3-dimensional analysis of the upper airway.

INTRODUCTION: The aim of this study was to compare the precision and accuracy of 6 imaging software programs for measuring upper airway volumes in cone-beam computed tomography data. METHODS: The sample consisted of 33 growing patients and an oropharynx acrylic phantom, scanned with an i-CAT scanner (Imaging Sciences International, Hatfield, Pa). The known oropharynx acrylic phantom volume was used as the gold standard. Semi-automatic segmentations with interactive and fixed threshold protocols of the patients' oropharynx and oropharynx acrylic phantom were performed by using Mimics (Materialise, Leuven, Belgium), ITK-Snap (www.itksnap.org), OsiriX (Pixmeo, Geneva, Switzerland), Dolphin3D (Dolphin Imaging & Management Solutions, Chatsworth, Calif), InVivo Dental (Anatomage, San Jose, Calif), and Ondemand3D (CyberMed, Seoul, Korea) software programs. The intraclass correlation coefficient was used for the reliability tests. A repeated measurements analysis of variance (ANOVA) test and post-hoc tests (Bonferroni) were used to compare the software programs. RESULTS: The reliability was high for all programs. With the interactive threshold protocol, the oropharynx acrylic phantom segmentations with Mimics, Dolphin3D, OsiriX, and ITK-Snap showed less than 2% errors in volumes compared with the gold standard. Ondemand3D and InVivo Dental had more than 5% errors compared with the gold standard. With the fixed threshold protocol, the volume errors were similar (-11.1% to -11.7%) among the programs. In the oropharynx segmentation with the interactive protocol, ITK-Snap, Mimics, OsiriX, and Dolphin3D were statistically significantly different (P <0.05) from InVivo Dental. No statistical difference (P >0.05) was found between InVivo Dental and OnDemand3D. CONCLUSIONS: All 6 imaging software programs were reliable but had errors in the volume segmentations of the oropharynx. Mimics, Dolphin3D, ITK-Snap, and OsiriX were similar and more accurate than InVivo Dental and Ondemand3D for upper airway assessment.

A new method to measure mesiodistal angulation and faciolingual inclination of each whole tooth with volumetric cone-beam computed tomography images.

INTRODUCTION: The purpose of this study was to develop a methodology to measure the mesiodistal angulation and the faciolingual inclination of each whole tooth (including the root) by using 3-dimensional volumetric images generated from cone-beam computed tomography scans. METHODS: A plastic typodont with 28 teeth in ideal occlusion was fixed in position in a dry human skull. Stainless steel balls were fixed to the occlusal centers of the crowns and to the apices or bifurcation or trifurcation centers of the roots. Cone-beam computed tomography images were taken and rendered in Dolphin 3D (Dolphin, Chatsworth, Calif). The University of Southern California root vector analysis program was developed and customized to digitize the crown and root centers that define the long axis of each whole tooth. Special algorithms were used to automatically calculate the mesiodistal angulation and the faciolingual inclination of each whole tooth. Angulation measurements repeated 5 times by using this new method were compared with the true values from the coordinate measuring machine measurements. Next, the root points of 8 selected typodont teeth were modified to generate known angulation and inclination values, and 5-time repeated measurements of these teeth were compared with the known values. RESULTS: Intraclass correlation coefficients for the repeated mesiodistal angulation and faciolingual inclination measurements were close to 1. Comparisons between our 5-time repeated angulation measurements and the coordinate measuring machine's true angulation values showed 5 teeth with statistically significant differences. However, only the maxillary right lateral incisor showed a mean difference that might exceed 2.5° for clinical significance. Comparisons between the 5-repeated measurements of 8 teeth with known mesiodistal angulation and faciolingual inclination values showed no statistically significant differences between the measured and the known values, and no measurement had a 95% confidence interval beyond 1°. CONCLUSIONS: We have developed the novel University of Southern California root vector analysis program to accurately measure each whole tooth mesiodistal angulation and faciolingual inclination, in a clinically significant level, directly from the cone-beam computed tomography volumetric images.

Mesiodistal angulation and faciolingual inclination of each whole tooth in 3-dimensional space in patients with near-normal occlusion.

INTRODUCTION: An important objective of orthodontic treatment is to obtain the correct mesiodistal angulation and faciolingual inclination for all teeth. Current techniques are based on crown angulation and inclination standards, and not enough attention has been given to the roots. In this study, we report the mesiodistal angulation and faciolingual inclination of each whole tooth including the root in patients with near-normal occlusion. METHODS: We screened 1840 patients who had cone-beam computed tomography scans taken before treatment to obtain a sample of 76 patients with near-normal occlusion. Using our custom University of Sourthern California root vector analysis software program, we digitized the crown and root centers to determine the "true" long axis of each tooth from where the mesiodistal angulation and the faciolingual inclination were measured. RESULTS: The means and standard deviations for the mesiodistal angulation and the faciolingual inclination of each whole tooth were calculated. The maxillary angulations of the teeth started from approximately 6° for the central incisors, slightly increased for the lateral incisors, and peaked at 11° for the canines; then it gradually decreased to just above 0° for the first molars and eventually reached -6° for the second molars. The mandibular angulations started from about 0° for the incisors and increased to 17.5° for the second molars. The maxillary inclination was the highest at 33.5° for the central incisors, decreased to about 0° at the second premolars, and then increased for the 2 molars. The mandibular inclination also was the highest at 26.5° for the central incisors, decreased also to about 0° at the second premolars, and continued to decrease for the 2 molars. For the opposing tooth pairs, the interdental mesiodistal angulations always remained within 10° from one another, whereas the interdental faciolingual inclination increased from about 120° for the incisors to about 180° for the second premolars and the 2 molars. CONCLUSIONS: We obtained the average mesiodistal angulation and faciolingual inclination for each whole tooth measured from its long axis digitized on the cone-beam computed tomography volumetric images of 76 patients with near-normal occlusion. We found distinctive angulation and inclination relationships between the neighboring and opposing teeth. This information can be used in addition to the crown standards for positioning each whole tooth properly in the arches.

Measurements of the torque moment in various archwire-bracket-ligation combinations.

The torque moment generated by third-order bends is important for tooth movement. The purpose of this study was to measure the torque moment that can be delivered by various archwire and bracket combinations at the targeted tooth. Stainless steel (SS) upper brackets with 0.018 and 0.022 inch slots, two sizes of nickel-titanium (Ni-Ti) alloy wires, and three sizes of SS wires for each bracket were used. The wire was ligated with elastics or wire. The torque moment delivered by the various archwire-bracket-ligation combinations was measured using a torque gauge. Statistical analysis was undertaken using analysis of variance (multiple comparison tests and post hoc using Tukey's honestly significant difference test. The torque moment increased as the degree of torque and wire size increased. There was no significant difference in torque moment between the SS and Ni-Ti wires at lower or higher than 40 degrees torque. The torque moment with wire ligation was significantly larger than that with elastic ligation with 0.016 × 0.022 and 0.017 × 0.025 inch Ni-Ti wires in the 0.018 inch slot brackets and the 0.017 × 0.025 and 0.019 × 0.025 inch SS and Ni-Ti wires in the 0.022 inch slot brackets. However, there was no significant difference in torque moment between either ligation method when using the full slot size wires.

Comparison of Australian and American orthodontic clinical approaches towards root resorption.

AIMS: As part of The Rocky Mountain Travelling Fellowship, a pilot survey was conducted to assess current diagnostic and clinical approaches to the management of orthodontic patients in relation to root resorption. METHODS: Groups comprising Australians (Sydney, New South Wales) and North Americans (Los Angeles, California), in two stages of their orthodontic careers (post-graduate orthodontic students from the University of Sydney and University of Southern California and qualified practising orthodontists) were asked to complete a questionnaire. The questions examined diagnosis and management approaches related to root resorption used in their clinical practice. RESULTS: Replies demonstrated that there were differences in management depending on operator experience and the country of clinical practice. However, a summarised common approach to orthodontic root resorption comprised (1) the use of an orthopantomogram as a screening diagnostic tool, followed by periapical radiographs for those perceived as 'higher risk' patients, particularly individuals with a history of root resorption; (2) a six monthly radiographic review during treatment; (3) the use of light forces and/or rest periods (discontinuous forces) every two to three months; (4) the extraction of deciduous teeth if permanent successors were erupting ectopically and causing damage to adjacent root structures; and (5) the use of fixed retention after treatment. CONCLUSION: This project was intended to initiate discussion and form a basis for further investigation into the clinical management of orthodontic root resorption.

Comparison of arch forms between Egyptian and North American white populations.

INTRODUCTION: The aim of this study was to evaluate the morphologic differences in the mandibular arches of Egyptian and North American white subjects. METHODS: The sample included 94 Egyptian subjects (35 Class I, 32 Class II, and 27 Class III) and 92 white subjects (37 Class I, 29 Class II, and 26 Class III). The subjects were grouped according to arch form types (tapered, ovoid, and square) to compare their frequency distribution between ethnic groups in each Angle classification. The most facial portions of 13 proximal contact areas were digitized on scanned images of mandibular casts to estimate the corresponding clinical bracket point for each tooth. Four linear and 2 proportional measurements were taken. RESULTS: In comparing arch dimensions, intermolar width was narrower in Egyptians than in the whites (P = 0.001). There was an even frequency distribution of the 3 arch forms in the Egyptian group. On the other hand, the most frequent arch form was ovoid followed by tapered and square in the white group; the square arch form was significantly less frequent than the tapered and ovoid arch forms (P = 0.029). CONCLUSIONS: The arch forms of Egyptians are narrower than those of whites. The distribution of the arch form types in Egyptians showed similar frequency, but the square arch form was less frequent in whites. It is recommended to select narrower archwires from the available variations to suit many Egyptian patients.

Oropharyngeal airway changes after rapid palatal expansion evaluated with cone-beam computed tomography.

INTRODUCTION: The aims of this retrospective study were to use cone-beam computed tomography (CBCT) to assess changes in the volume of the oropharynx in growing patients with maxillary constriction treated by rapid palatal expansion (RPE) and to compare them with changes in age- and sex-matched orthodontic patients. METHODS: The experimental group consisted of 24 patients (mean age, 12.8+/-1.88 years) with maxillary constriction who were treated with hyrax palatal expanders; the control group comprised 24 age- and sex-matched patients (mean age, 12.8+/-1.85 years) who were just starting regular orthodontic treatment. Beginning and progress CBCT scans, taken in the supine position, were analyzed with software to measure volume, length, and minimal cross-sectional area of the oropharyngeal airway. The 2 groups were compared with paired t tests. RESULTS: Only retropalatal airway volume was found to be significantly different between groups before treatment (P = 0.011), and this difference remained after treatment (P = 0.024). No other statistically significant differences were found relative to changes in volume, length, or minimum cross-sectional area of the oropharyngeal airway between the groups, but the molar-to-molar width after RPE increased significantly compared with the controls (P <0.001). CONCLUSIONS: Narrow oropharyngeal airways in growing patients with maxillary constriction was demonstrated. But there was no evidence to support the hypothesis that RPE could enlarge oropharyngeal airway volume.

Stress distribution in mandible and temporomandibular joint by mandibular distraction: a 3-dimensional finite-element analysis.

The effects of mandibular distraction on the mandible and its surrounding tissue remain to be clarified. Here, we used a 3-dimensional finite-element method to investigate the effects of unilateral horizontal lengthening of the mandibular body and vertical lengthening of the mandibular ramus on the mandible and temporomandibular joint (TMJ). With horizontal loading that assumed mandibular body lengthening, tensile and compressive stresses were great near the anterior region of the mandibular angle (the loading area). With vertical loading that assumed mandibular ramus lengthening, tensile and compressive stresses were great at the center of the mandibular ramus (the loading area). Under both loading conditions, stress distribution in the TMJ was greater on the loading side than on the non-loading side. With mandibular body lengthening, the center of the mandible deviated in the direction of the non-lengthened side to widen the mandible in the lateral direction. With mandibular ramus lengthening, the occlusal plane tilted in the inferior direction on the lengthened side. In the TMJ, stress was greatest on the affected side during mandibular ramus lengthening, suggesting the need to consider the mandibular condyle on the affected side during this procedure.

Mesiodistal root angulation using panoramic and cone beam CT.

OBJECTIVE: To determine if the panoramic projection can accurately determine mesiodistal root angulations. MATERIALS AND METHODS: A plaster study model of the dentition of each of five patients was prepared. A radiographic stent containing radiopaque markers was fabricated for each of the models. Panoramic and cone beam computed tomography (CBCT) scans were taken on each patient with the radiographic stent seated on the dentition. Root angulations for each of the radiographic images were measured and compared. RESULTS: Root angulation was measured by three independent individuals and good reliability between measurements was demonstrated. Compared to plaster model measurements (the gold standard), the CBCT scan produced very accurate measurements of root angulation. Compared to CBCT images, panoramic projections did not provide reliable data on root angulation. CONCLUSION: Panoramic images did not accurately represent the mesiodistal root angulations on clinical patients.

Development of three-dimensional FE modeling system from the limited cone beam CT images for orthodontic tipping tooth movement.

Previously, numerous three-dimensional finite element (FE) models of the dentoalveolar complex have been developed and stress analyses of orthodontic tooth movements were reported. Most of the models were, however, developed based on average anatomical data, but not on individual data. The aim of this study, therefore, was to investigate dentoalveolar stress distribution by lingual and distal tipping tooth movements using FE models of individual teeth based on the limited cone beam CT (3DX) images. Three extracted teeth (lower canine, upper molar, and lower molar) were used to test the three-dimensional reconstruction procedure in terms of accuracy and reproducibility in linear dimensions and sizes. From the stress analysis of the three different models, the equivalent stress in tipping movement concentrated at the cervical region of the PDL and bone crest in all teeth. It was suggested that the FE modeling technique based on 3DX in this study is recommended for the individual determination of optimal orthodontic force for effective tooth movement.