Apical root resorption due to orthodontic treatment detected by cone beam computed tomography

Objective:To determine the frequency of apical root resorption (ARR) due to orthodontic treatment using cone beam computed tomography (CBCT) in a sample of 1256 roots from 30 patients.Materials and Methods:All patients had Class I malocclusion with crowding. Of the 30 patients evaluated, 11 were boys and 19 were girls; their mean age was 13 years (11 to 16 years). Orthodontic treatment followed the nonextraction treatment. CBCT images were obtained before and after orthodontic treatment, and ARR was determined using Axial Guided Navigation of CBCT images.Results:All patients had ARR. No statistically significant association was found between resorption frequency, gender, and age. ARR was detected using CBCT in 46% of all roots that underwent orthodontic treatment.Conclusions:CBCT was effective for detecting in vivo even minimal degrees of ARR due to orthodontic treatment and allowed three-dimensional evaluation of dental roots and visualization of palatine roots of maxillary molars. The highest frequencies and the most significant ARR occurred in incisors and distal roots of first maxillary and mandibular molars.     

Comparison of Orthodontic Root Resorption of Root-filled and Vital Teeth Using Micro–computed Tomography

ObjectiveTo evaluate the difference in orthodontic root resorption between root-filled and vital teeth.Material and MethodsSixteen individuals who required bilateral premolar tooth extraction due to orthodontic treatment and had a previously root-filled premolar tooth on one side were included in the study. The experimental group consisted of root-filled premolar teeth, and the control group consisted of contralateral vital premolar teeth. A 150-g buccally directed force was applied to these teeth using 0.017 × 0.025-inch TMA cantilever springs. The premolars were extracted 8 weeks after the application of force. Images were obtained using micro–computed tomography. Resorption measurements were obtained using the Image J program.ResultsThe mean values for resorption were 0.08869 mm³ for the root-filled teeth and 0.14077 mm³ for the contralateral teeth, indicating significantly less resorption for the root-filled teeth compared with the contralateral teeth after the application of orthodontic force (P = .003). In both groups, the most resorption was seen on the cervical-buccal and apical-lingual surfaces. The mean resorption value of the cervical region was 0.06305 mm³ in the control group and 0.0291 mm³ in the experimental group, and the difference was statistically significant (P = .002).ConclusionsRoot-filled teeth showed significantly less orthodontic root resorption than vital teeth.     

正畸矫治对根管治疗牙齿牙根吸收程度影响的CBCT研究

目的利用CBCT评价正畸治疗对根管治疗牙齿牙根吸收程度的影响。方法选择上下颌牙齿轻中度拥挤的成年患者16例,患者上颌前牙中至少有一颗已行根管治疗。使用0.558 8 mm槽沟的MBT托槽进行非拔牙矫治。于治疗前、后分别拍摄头颅CBCT,并分别测量根管治疗牙齿以及对侧同名牙齿的长度。采用配对t检验进行统计分析。结果 16例患者一共有18颗上颌前牙接受过根管治疗,其中包括6颗中切牙,8颗侧切牙,4颗尖牙。平均治疗时间为(18.3±2.6)个月。治疗前,已行根管治疗牙齿牙根平均长度(22.68±2.14)mm;治疗后,牙根平均长度为(21.98±2.05)mm。治疗前,对侧同名活髓牙牙根平均长度(22.61±2.01)mm;治疗后,牙根平均长度为(22.01±2.37)mm。两组差别无统计学意义。按照牙位单独分析,亦无统计学差异。结论利用CBCT能够很好地观察正畸治疗后牙根吸收的情况。在轻中度拥挤非拔牙的病例中,正畸治疗并不会增加上颌前牙已行根管治疗牙齿牙根吸收的风险。     

Cone beam computed tomography evaluation of distance from cementoenamel junction to alveolar crest before and after nonextraction orthodontic treatment

Objective:To evaluate the distance between the cementoenamel junction and the alveolar bone crest before and after orthodontic treatment using cone beam computed tomography (CBCT).Materials and Methods:The sample comprised 30 patients with Angle Class I malocclusion and mild to moderate crowding. The study database comprised dental CBCT scans obtained before and after orthodontic treatment. The distance between the cementoenamel junction to the bone crest of the buccal (n  =  720) and lingual (n  =  720) surfaces was measured in 24 teeth for each patient using a specific software tool (Xoran version 3.1.62). The Wilcoxon test was used for statistical analysis, and the level of significance was set at P < .05.Results:The distance between the cementoenamel junction and the bone crest increased in 822 (57%) of the 1440 surfaces after orthodontic treatment. The buccal surface of the lower central incisors had the greatest frequency of increased distance (75%), and the lingual surface of lateral incisors had the lowest (40%). The distance between the cementoenamel junction and the alveolar bone crest was greater than 2 mm (alveolar bone dehiscence) in 162 (11%) of the 1440 surfaces before orthodontic treatment and in 279 (19%) after treatment.Conclusions:The distance from the cementoenamel junction to the bone crest changed after orthodontic treatment; the distance was greater than 2 mm in 11% of the surfaces before treatment and in 19% after treatment.     

Comparison of root resorption between self-ligating and conventional preadjusted brackets using cone beam computed tomography

Objective:To compare the magnitude of external apical root resorption (EARR) of incisors in patients undergoing the initial phase of orthodontic treatment with two sets of brackets.Materials and Methods:According to the results of the power analysis for sample size calculation, 19 Angle Class I patients (anterior crowding: 3 to 5 mm; mean age: 20.6 years) were included in the study and randomly divided into two groups: group I (n  =  11, self-ligating brackets) and group II (n  =  8, conventional preadjusted brackets). The degree of EARR was detected in 152 upper and lower incisors by using cone-beam computed tomography (CBCT) scans and a three-dimensional program (Dolphin 11.5, Dolphin Imaging & Management Solutions, Chatsworth, Calif) with 25% level of sensitivity. The CBCT scans were obtained before (T1) and 6 months after initiation of treatment (T2). Differences between and within groups were analyzed by nonpaired and paired t-test, respectively, with 5% significance level.Results:Significant differences were found for both groups between T1 and T2. However, no differences in the degree of EARR were detected between the groups studied.Conclusions:Although EARR has occurred in all teeth evaluated, the bracket design (self-ligating or conventional) did not demonstrate any influence on the results observed.     

External apical root resorption in maxillary root-filled incisors after orthodontic treatment: a split-mouth design study

Introduction: The purpose of this study was to compare, in a split mouth design, the external apical root resorption (EARR) associated with orthodontic treatment in root-filled maxillary incisors and their contralateral teeth with vital pulps. Methodology: The study sample consisted of 38 patients (14 males and 24 females), who had one root-filled incisor before completion of multiband/bracket orthodontic therapy for at least 1 year. For each patient, digital panoramic radiographs taken before and after orthodontic treatment were used to determine the root resortion and the proportion of external root resorption (PRR), defined as the ratio between the root resorption in the endodontically treated incisor and that in its contralateral incisor with a vital pulp. The student’s t-test, chi-square test and logistic regression analysis were used to determine statistical significance. Results: There was no statistically significant difference (p > 0.05) between EARR in vital teeth (1.1 ± 1.0 mm) and endodontically treated incisors (1.1 ± 0.8 mm). Twenty-six patients (68.4%) showed greater resorption of the endodontically treated incisor than its homolog vital tooth (p > 0.05). The mean and standard deviation of PPR were 1.0 ± 0.2. Multivariate logistic regression suggested that PRR does not correlate with any of the variables analyzed. Conclusions: There was no significant difference in the amount or severity of external root resorption during orthodontic movement between root-filled incisors and their contralateral teeth with vital pulps. Key words:Endodontics, orthodontics, root canal treatment, root resorption.     

Mutagenicity and cytotoxicity in patients submitted to ionizing radiation: A comparison between cone beam computed tomography and radiographs for orthodontic treatment

Objectives:To evaluate and compare mutagenicity (micronucleus) and cytotoxicity (karyorrhexis, pyknosis, and karyolysis) in exfoliated buccal mucosa cells of children following cone beam computed tomography (CBCT) or conventional radiograph exposure necessary for orthodontic planning.Materials and Methods:A total of 49 healthy children were submitted to CBCT or a conventional orthodontic radiographic protocol; they were divided into two groups based on exam: CBCT (n  =  24) and Radiographic Set (n  =  25) groups. The micronucleus test in the exfoliated buccal mucosa cells was applied.Results:There was not a statistically significant difference (P > .05) found between the number of micronucleated buccal mucosa cells (MNC) before and after exposure to radiation in either group, showing that neither group experienced a mutagenic effect. However, radiation did cause other nuclear alterations closely related to cytotoxicity, including karyorrhexis, pyknosis, and karyolysis, in both groups (P < .05). The CBCT group presented a greater increase in cell death than was noted in the Radiographic Set group (P < .044).Conclusion:According to the micronucleus test, mutagenicity was not induced by the CBCT or the conventional radiographs, but cytotoxicity was verified after these exams, especially after CBCT. That might have happened once the CBCT group received a greater radiation dose than the Radiographic Set group as a result of the protocols used in orthodontic planning for this study.     

A Study of the Root Canal Morphology of Mandibular Anterior Teeth Using Cone-beam Computed Tomography in a Chinese Subpopulation

IntroductionThe purpose of this study was to investigate the root canal configuration of the mandibular anterior teeth using cone-beam computed tomographic (CBCT) imaging in a Chinese subpopulation.MethodsA total of 3,871 CBCT images of mandibular anterior teeth were collected from 648 patients who accepted CBCT projection as a preoperative assessment for implants or orthodontic treatment. The following items were recorded and evaluated: tooth position, root number, canal number, root canal type, the distance between the anatomic apex and the point at which the canal divided into 2 for mandibular anterior teeth with 2 root canals (excluding canines with 2 roots), and the distance between the 2 root canal orifices. The Fisher exact test was used to analyze the correlation between the number of root canals and tooth position.ResultsAll of the incisors in this study had 1 root, and 1.32% of the canines had 2 roots. The prevalence of 2 root canals in the lateral incisors (354, 27.36%) was higher than that in the central incisors (202, 15.71%) (P < .05) and the canines (81, 6.27%) (P < .05).ConclusionsThere is a high prevalence of 2 root canals in the mandibular anterior teeth of the studied Chinese subpopulation. This study provides detailed information about the root canal morphology of mandibular anterior teeth in a Chinese subpopulation.     

Three-dimensional analysis of molar compensation in patients with facial asymmetry and mandibular prognathism

Objective:To evaluate the characteristic transverse dental compensations in patients with facial asymmetry and mandibular prognathism and to compare features of dental compensations between two types of mandibular asymmetry using 3-dimensional (3D) cone-beam computed tomography (CBCT).Materials and Methods:Seventy-eight adult patients with skeletal Class I (control group; n  =  33; 19 men and 14 women) or skeletal Class III with facial asymmetry (experimental group; n  =  45; 23 men and 22 women) were included. The experimental group was subdivided into two groups according to the type of mandibular asymmetry: translation type (T-type; n  =  20) and roll type (R-type; n  =  19). CBCT images were acquired before orthodontic treatment and 3D analyses were performed.Results:The transverse dental distance was significantly different between the two groups only at the palatal root apex of the maxillary first molar (P < .05). In the experimental group, the first molar axes were compensated significantly on both arches except the maxillary nondeviated side. The vertical molar heights were different between the two groups only on the maxillary arch (P < .001). The R-type showed greater mandibular ramal length difference and menton deviation than the T-type (P < .001). In the R-type, transverse compensation of the maxillary first molars was more obvious than with the T-type, which resulted in canting in the maxillary occlusal plane.Conclusions:Mandibular asymmetry with prognathism showed a characteristic transverse dental compensation pattern. The mandibular asymmetry type influenced the amount and direction of molar compensation on the maxillary arch.     

Change in dental pulp parameters in response to different modes of orthodontic force application

Objectives:(1) To evaluate dental pulp sensitivity by electrical pulp testing and measure aspartate aminotransferase activity in the pulp after 14 days of orthodontic intrusion, and (2) to compare those measurements with measurements obtained in teeth after 7 days of intrusion and 7 days of rest.Materials and Methods:The study sample included 13 subjects (mean age  =  16.5 ± 2.7 years). For every subject, before extraction, two contralateral premolars were included in a spring and loaded by a force. Two study groups were formed: Group A, teeth with 14 days of mechanical load, and Group B, teeth with 7 days of mechanical load plus 7 days of rest. Electrical pulp testing and aspartate aminotransferase activity measurements were performed after 14 days in all tested teeth. After extraction, aspartate aminotransferase activity in the pulp was determined spectrophotometrically at 20°C.Results:Mean aspartate aminotransferase activity values were 0.21 U/mg (SD  =  0.15) in Group A and 0.27 U/mg (SD  =  0.17) in Group B. Mean electrical pulp testing readings were 38.92 µA (SD  =  24.61) in Group A and 36.77 µA (SD  =  26.84) in Group B. Mean values of the intrusive force magnitude did not differ in both groups.Conclusions:Different durations of orthodontic intrusion, defined as 14 days of load and 7 days of load followed by 7 resting days, were not reflected by electrical pulp testing or by aspartate aminotransferase activity levels in the pulp of the affected teeth. However, the response threshold to electrical pulp stimulation was elevated in all tested teeth.     

Effect of 980-nm diode laser–aided circumferential supracrestal fiberotomy on fluorosed root surfaces

Objective:To evaluate and compare the root surface morphological changes after 980-nm diode laser–aided circumferential supracrestal fiberotomy (CSF) on fluorosed and non-fluorosed teeth.Materials and Methods:The sample comprised 27 orthodontic patients (14 males and 13 females; mean age  =  17.3 years) with and without fluorosis, from whom 40 fluorosed and 40 non-fluorosed premolar teeth were extracted for orthodontic reasons. Conventional (control group) and laser-aided (experimental group) CSF was performed on fluorosed and non-fluorosed teeth indicated for orthodontic extraction, using a scalpel and a 980-nm diode laser at 2.5 W power, respectively. Subsequently, teeth were extracted, sectioned, and examined by scanning electron microscope to assess the ultrastructural changes.Results:There were differences in surface morphology among fluorosed and non-fluorosed roots in the control group. The root specimens of both fluorosed and non-fluorosed teeth irradiated by diode laser exhibited no evidence of smear layer, laser-induced pitting or cavitation, linear cuts/markings, carbonization of surface, and heat-induced surface cracking. However, a glazed or slightly melted appearance was observed in root specimens of fluorosed teeth after diode laser irradiation.Conclusions:These findings suggest that the diode laser–aided CSF procedure is free from thermal hazard on non-fluorosed root surfaces but may provoke some thermal changes on fluorosed root surfaces.     

Patient attitudes toward retention and perceptions of treatment success

Objective:To discern patients'' opinions regarding responsibility for orthodontic retention and to determine whether patient attitudes toward retention are related to perceptions of treatment success.Materials and Methods:Questionnaires regarding orthodontic retention were distributed to first-year undergraduate college students (n  =  158), first-year dental students (n  =  183), and retention patients at orthodontic offices (n  =  214). Items included treatment satisfaction, perceived responsibility for retention, type of retainer prescribed, reasons for discontinuing use of retainers, and relapse experienced.Results:Four hundred twenty-eight of 555 participants indicated that they had received orthodontic treatment. Most indicated they were either “satisfied” or “very satisfied” with their teeth, both at the end of treatment (96%) and currently (84%). There was a strong relationship between the perception of stability of tooth position and current satisfaction level (P < .0001). Most individuals (88%) indicated that they themselves were responsible for maintaining the alignment and fit of their teeth. Those who indicated that someone else was responsible were nearly twice as likely to be dissatisfied with their teeth (P  =  .0496). Patients who had been prescribed clear, invisible retainers were significantly more likely to be “very satisfied” currently (50%) compared to those with Hawley (35%) or permanently bonded (36%) retainers (P  =  .0002). Patients with Hawley retainers were significantly less likely to be wearing them currently as prescribed (45%) than those with invisible (65%) or bonded (68%) retainers (P < .0001).Conclusions:Satisfaction with orthodontic results after treatment is related to patient perceptions of responsibility for retention and perceived stability of tooth position. Patients should play a contributory role in formulating orthodontic retention plans.     

Evaluation and comparison of root resorption between tooth-borne and tooth-tissue borne rapid maxillary expansion appliances: A CBCT study

Objective:To compare volumetric root resorption after rapid maxillary expansion (RME) between tooth-borne and tissue-borne appliances using CBCT. Repair in resorption cavities after 6 months of fixed retention was also compared.Materials and Methods:A sample of 33 subjects were randomly divided into two groups: Hyrax (n  = 16) and Haas (n = 17). CBCT scans were taken 6 months before expansion, immediately after expansion, and 6 months after fixed retention. Mimics Innovation V 16.0 software was used for segmentation and volumetric measurement of 198 teeth. Bland-Altman plots, independent samples t test, repeated measures analysis of variance, and the Friedman test were used for statistical analysis.Results:Differences in root resorption after RME and repair after retention were not significant between the hyrax and Haas appliances or between male and female. Significant differences were found between preexpansion and postexpansion root volumes in the first premolars and molars—even in unattached second premolars. When the percentage of root volume loss is considered, no significant difference was found between the first premolar, second premolar, and first molar. Volumetric changes after 6 months of retention were not statistically significant.Conclusions:More resorption was observed in the Hyrax expander group. But it was not statistically significant. Repair was observed after 6 months of retention. Heavy RME forces affected premolars and molar similarly.     

Failure of treatment of impacted canines associated with invasive cervical root resorption

Objectives:To propose invasive cervical root resorption (ICRR) as an unrecognized and/or overlooked etiologic factor in the failure of response of an impacted tooth to orthodontic traction and to underline the importance of cone beam computerized tomography (CBCT) for early and accurate diagnosis of ICRR.Materials and Methods:Fourteen patients (age 13–21 years) with impacted canines (15 canines) that had failed to respond to orthodontic forces and that exhibited ICRR formed the case series for this investigation. The initial diagnosis, treatment, clinical and radiographic expression of failure, and adverse effects on adjacent teeth were analyzed.Results:Initial diagnosis had been performed on plane radiographs. The orthodontist was absent during surgery in 11 patients. Nine canines had been exposed by open procedures. ICRR was not related to the severity of impaction. Its diagnosis was made on existing radiographs, new films, and/or new CBCT. The severity of the lesions was Class 3 or 4, and the teeth were finally extracted. Loss of anchorage characterized 11 patients. Apical resorption of the roots of adjacent teeth was diagnosed in 9 patients.Conclusions:ICRR is a frequently undiagnosed or unrecognized cause of failure of orthodontic resolution of impacted canines and should be distinguished from replacement resorption. CBCT should be used for its early detection and accurate assessment of potential damage to adjacent anchor teeth.     

Cone Beam Computed Tomography for Assessment of Root Length and Marginal Bone Level during Orthodontic Treatment

Objective:To evaluate the accuracy and precision of cone beam computed tomography (CBCT) with regard to measurements of root length and marginal bone level in vitro and in vivo during the course of orthodontic treatment.Materials and Methods:Thirteen patients (aged 12–18 years) from an ongoing study and a dry skull were examined with CBCT using multiplanar reformatting for measurements of root length and marginal bone level. For in vivo evaluation of changes in root length, an index according to Malmgren et al was used, along with a modification of this method.Results:The in vitro mean difference between physical and radiographic measurements was 0.05 mm (SD 0.75) for root length and −0.04 mm (SD 0.54) for marginal bone level. In vivo the error was <0.35 mm for root length determinations and <0.40 mm for marginal bone level assessments.Conclusion:Despite changes in tooth positions, the CBCT technique yields a high level of reproducibility, enhancing its usefulness in orthodontic research.     

Influence of unilateral maxillary first molar extraction treatment on second and third molar inclination in Class II subdivision patients

Objective:To assess the maxillary second molar (M2) and third molar (M3) inclination following orthodontic treatment of Class II subdivision malocclusion with unilateral maxillary first molar (M1) extraction.Materials and Methods:Panoramic radiographs of 21 Class II subdivision adolescents (eight boys, 13 girls; mean age, 12.8 years; standard deviation, 1.7 years) before treatment, after treatment with extraction of one maxillary first molar and Begg appliances and after at least 1.8 years in retention were retrospectively collected from a private practice. M2 and M3 inclination angles (M2/ITP, M2/IOP, M3/ITP, M3/IOP), constructed by intertuberosity (ITP) and interorbital planes (IOP), were calculated for the extracted and nonextracted segments. Random effects regression analysis was performed to evaluate the effect on the molar angulation of extraction, time, and gender after adjusting for baseline measurements.Results:Time and extraction status were significant predictors for M2 angulation. M2/ITP and M2/IOP decreased by 4.04 (95% confidence interval [CI]: −6.93, 1.16; P  =  .001) and 3.67 (95% CI: −6.76, −0.58; P  =  .020) in the extraction group compared to the nonextraction group after adjusting for time and gender. The adjusted analysis showed that extraction was the only predictor for M3 angulation that reached statistical significance. M3 mesial inclination increased by 7.38° (95% CI: −11.2, −3.54; P < .001) and 7.33° (95% CI: −11.48, −3.19; P  =  .001).Conclusions:M2 and M3 uprighting significantly improved in the extraction side after orthodontic treatment with unilateral maxillary M1 extraction. There was a significant increase in mesial tipping of maxillary second molar crowns over time.     

Bone mineral density: Methods of measurement and its influence on primary stability of miniscrews

Objective:To verify whether bone mineral density (BMD) of cortical bone, trabecular bone, and total bone influence the primary stability of orthodontic miniscrews and to verify whether there is a correlation between the measurement of BMD by cone-beam computed tomography (CBCT) and central dual-energy x-ray absorptiometry (DEXA).Materials and Methods:Twenty bovine bone sections were extracted from the pubic and iliac bones from regions with cortical thicknesses of approximately 1 mm. The BMD of the total bone block was evaluated using two methods: CBCT and DEXA. The BMD of cortical, trabecular, and total bone in the region of interest (ROI) were also evaluated by CBCT. After scanning the bone blocks, 20 self-drilling miniscrews (INP®) 1.4 mm in diameter and 6 mm long were inserted into them. The peak implant insertion torque (IT) was registered. After this, the pull-out test (PS) was performed and the maximum force registered. The Pearson correlation test was applied to verify the correlations between variables.Results:The BMD of the total bone block verified by CBCT and DEXA showed a positive and strong correlation (r  =  0.866, P  =  .000). The BMD of the ROI for cortical bone influenced the IT (r  =  0.518, P  =  .40) and the PS of miniscrews (r  =  0.713, P  =  .001, Table 2). However, the total bone BMD (verified by CBCT and DEXA) and trabecular bone BMD presented weak and not statistically significant correlations with primary stability.Conclusions:There was a positive correlation between total bone block BMD measured by DEXA and CBCT. The cortical BMD influenced the IT and PS.     

Characteristics of Cracked Teeth with Reversible Pulpitis After Orthodontic Banding—A Prospective Cohort Study

IntroductionCracked teeth with reversible pulpitis can be managed with orthodontic bands in the interim before definitive restorations. The aim of this study was to determine short-term outcomes of these teeth following orthodontic band placement. The time taken for definitive pulp diagnoses after orthodontic band placement and associated prognostic factors was also analyzed.MethodsOne hundred twenty-five patients with a cracked tooth with reversible pulpitis each were recruited. Preoperative data including patient and tooth factors were collected. Cracked teeth were banded and reviewed until symptoms resolved before referral for coronal coverage. Kaplan-Meier and Cox analyses were performed to analyze pulp survival of these teeth. Prognostic factors were investigated using Pearson's chi-square and Student's t-test.ResultsOne hundred twenty-two cracked teeth were analyzed. One hundred thirteen (92.6%) teeth had the pulpitis resolved within 2 months (median 40.0; interquartile range 28–61). The median time taken for progression to irreversible pulpitis or pulp necrosis for teeth that required root canal treatment was 3 months (median 90.0; interquartile range 68–110). No prognostic factors were associated with the resolution of pulpal symptoms. However, higher preoperative triggered pain scores (P < .05, hazards ratio 1.547) and absence of a distal marginal ridge crack (P < .05, hazards ratio 0.638) were correlated with a longer duration before definitive pulp diagnoses.ConclusionFollowing orthodontic band placement, a normal pulp diagnosis was achieved in 92.6% of cracked teeth with preoperative reversible pulpitis. Definitive pulp diagnoses could be determined in approximately 2 months. Teeth with higher preoperative triggered pain scores may require a longer review period.     

Influence of cone-beam computed tomography image artifacts on the determination of dental arch measurements

Objective:To compare dental plaster model (DPM) and cone-beam computed tomography (CBCT) in the measurement of the dental arches, and investigate whether CBCT image artifacts compromise the reliability of such measurements.Materials and Methods:Twenty patients were divided into two groups based on the presence or absence of metallic restorations in the posterior teeth. Both dental arches of the patients were scanned with the CBCT unit i-CAT, and DPMs were obtained. Two examiners obtained eight arch measurements on the CBCT images and DPMs and repeated this procedure 15 days later. The arch measurements of each patient group were compared separately by the Wilcoxon rank sum (Mann-Whitney U) test, with a significance level of 5% (α  =  .05). Intraclass correlation measured the level of intraobserver agreement.Results:Patients with healthy teeth showed no significant difference between all DPM and CBCT arch measurements (P > .05). Patients with metallic restoration showed significant difference between DPM and CBCT for the majority of the arch measurements (P > .05). The two examiners showed excellent intraobserver agreement for both measuring methods with intraclass correlation coefficient higher than 0.95.Conclusion:CBCT provided the same accuracy as DPM in the measurement of the dental arches, and was negatively influenced by the presence of image artifacts.     

A comparative study of the effect of the intrusion arch and straight wire mechanics on incisor root resorption: A randomized,controlled trial

Objective:To analyze and compare external apical root resorption (EARR) of maxillary incisors treated by intrusion arch or continuous archwire mechanics.Materials and Methods:This cone-beam computed tomography (CBCT) study analyzed 28 deep bite patients in the permanent dentition who were randomly divided into two groups: Group 1, 12 patients with initial mean age of 15.1 ± 1.6 years and mean overbite of 4.6 ± 1.2 mm treated with the Connecticut intrusion arch (CIA) in the upper arch (Ortho Organizers, Carlsbad, Calif) for a mean period of 5.8 ± 1.27 months. Group 2, 16 patients with initial mean age of 22.1 ± 5.7 years and mean overbite of 4.1 ± 1.1 mm treated with conventional leveling and alignment using continuous archwire mechanics for 6.1 ± 0.81 months. The degree of EARR was detected in 112 maxillary incisors by using CBCT scans and a three-dimensional program (Dolphin 11.7, Dolphin Imaging & Management Solutions, Chatsworth, Calif). The CBCT scans were obtained before (T1) and 6 months after initiation of treatment (T2). Differences between and within groups were assessed by nonpaired and paired t-tests, respectively, with a 5% significance level.Results:Significant differences were found for both groups between T1 and T2 (P < .05) indicating that EARR occurred in both groups. However, there were no significant differences when EARR was compared between group 1 (−0.76 mm) and group 2 (−0.59 mm).Conclusions:The Connecticut intrusion arch did not lead to greater EARR of maxillary incisors when compared with conventional orthodontic mechanics.