Alexander Dudic

Detection of apical root resorption after orthodontic treatment by using panoramic radiography and cone-beam computed tomography of super-high resolution

INTRODUCTION Apical root resorption is an adverse side effect of orthodontic treatment. We compared panoramic radiography (OPT) with cone-beam computed tomography (CBCT) in evaluating orthodontically induced apical root resorption. METHODS The study sample comprised 275 teeth in 22 patients near the end of orthodontic treatment with fixed appliances. Two calibrated examiners assessed blindly the presence or absence and the severity of apical root resorption on the OPT images after treatment and the corresponding reconstructed CBCT images. Resorption was evaluated as no, mild, moderate, severe, and extreme. RESULTS On the OPT images, 17 teeth (6.2%) could not be evaluated. Statistically significant differences were found between the 2 methods: 56.5% and 31% of the teeth showed no resorption by OPT and CBCT, respectively; 33.5% and 49% of the teeth showed mild resorption, whereas 8% and 19% showed moderate resorption by OPT and CBCT, respectively. Severe resorption was found in only 2 teeth by CBCT. CONCLUSIONS Apical root resorption after orthodontic tooth movement is underestimated when evaluated on OPT. CBCT might be a useful complementary diagnostic method to conventional radiography, to be applied when a decision on continuation or modification of the orthodontic treatment is necessary because of orthodontically induced root resorption.

Diagnostic accuracy of digitized periapical radiographs validated against micro-computed tomography scanning in evaluating orthodontically induced apical root resorption

The aim of this study was to validate the use of digitized periapical radiographs in evaluating orthodontically induced apical root resorption against micro-computed tomography (micro-CT) scanning as a criterion standard test. In a standardized experimental protocol, 29 premolars in 16 subjects were tipped buccally for 8 wk. Nineteen contralateral premolars not subjected to orthodontic movement served as controls. Standardized periapical radiographs were taken before and after the experimental period (Rx method). These teeth were extracted and scanned using a micro-CT technique with a 9 mum resolution. Two calibrated examiners assessed blindly the presence or absence of apical root resorption on digitized radiographs and three-dimensional reconstructions of the scans. Significant differences were detected between the orthodontically moved teeth and controls: 86% of the orthodontically moved teeth and 21% of the control teeth showed apical root resorption when using micro-CT as a validation method. A total of 55% of the experimental teeth and 5% of the control teeth showed resorption when assessed using Rx method. The Rx method showed a specificity of 78% and a sensitivity of 44%, which means that less than half of the cases with root resorption identified using a CT scanner were identified by radiography. Nearly all the orthodontically moved teeth showed apical root resorption. Apical root resorption may be underestimated when evaluated using digitized periapical radiographs.

Factors related to the rate of orthodontically induced tooth movement

INTRODUCTION The purpose of this study was to investigate the variations of orthodontically induced tooth movement in the maxillary and mandibular arches between patients and the factors such as age, sex, and presence of an interference that might influence the amount of tooth displacement. METHODS By using a standardized experimental orthodontic tooth movement in 30 subjects, 57 premolars were moved buccally during 8 weeks with the application of a 1-N force. Forty-four contralateral premolars not subjected to orthodontic tooth movement served as the controls. Plaster models from before and after the experimental tooth movement were digitized and superimposed to evaluate the amounts of tooth movement. Differences in tooth movement between the experimental and control groups were tested by an unpaired t test. For the experimental teeth, subject-related factors (age and sex) and tooth-related factors (location in the maxillary or mandibular dental arch, and the presence or absence of an intra-arch or interarch obstacle such as neighboring touching teeth or teeth interfering with the occlusion) were examined with analysis of variance. Multiple linear regression analysis was performed to determine correlations between tooth displacement, age, sex, tooth location, and presence of an interference. RESULTS Each subject contributed at least 2 experimental premolars and 1 control premolar. The displacement of the orthodontically moved teeth was 2.42 mm (range, 0.3-5.8 mm). Younger subjects (<16 years; n = 19; number of teeth, 36) had significantly greater amounts of tooth displacement compared with older subjects (≥16 years; n = 11; number of teeth, 21): 2.6 ± 1.3 mm vs 1.8 ± 0.8 mm; P <0.01. When an interarch or intra-arch obstacle was present, the amount of tooth movement was significantly less (2.6 ± 1.3 mm vs 1.8 ± 0.8 mm) (P <0.05). Neither sex nor the location of the experimental teeth in the mandible or the maxilla had any effect. CONCLUSIONS Younger patients showed greater tooth movement velocity than did older ones. An interarch or intra-arch obstacle decreased the amount of tooth displacement.

Root-contact evaluation by panoramic radiography and cone-beam computed tomography of super-high resolution.

INTRODUCTION Correct tooth position in the 3 planes of space is a major objective of orthodontic treatment. The aim of this study was to determine whether a panoramic radiograph (OPT) provides a true assessment of the mesiodistal root relationship of adjacent teeth. METHODS OPTs of 22 patients near the end of treatment with fixed appliances in both arches were taken before debonding. When the roots of adjacent teeth were touching on the OPT, cone-beam computed tomography (CBCT) was used to show the true root relationships. RESULTS We evaluated 235 interdental sites by OPT and CBCT; 47 areas showed contact between adjacent roots in the OPT images. However, the CBCT images showed true contact in only 5 of these areas; ie, 11% of the diagnoses based on OPT images were true positive, whereas the rest (89%) was false positive. One hundred eighty-eight sites showed no contact in the OPT images; this was confirmed by CBCT. CONCLUSIONS OPT has high sensitivity and relatively high specificity to detect adjacent roots touching each other. Root contacts are overestimated when evaluated by OPT.

Periodontal parameters and cervical root resorption during orthodontic tooth movement

OBJECTIVES To assess the relationship between periodontal parameters and cervical root resorption in orthodontically moved teeth. MATERIAL AND METHODS In a standardized experimental tooth movement in 16 periodontally healthy subjects, 29 pre-molars were tipped buccally for 8 weeks. Eighteen contralateral pre-molars not subjected to orthodontic movement served as controls. Plaque Index (PI), Gingival Index (GI), probing depth and bleeding on probing were assessed three times before and six times during the experimental phase. Teeth were extracted and scanned in a micro-computed tomography scanner. The presence or absence, and the severity of cervical root resorption were evaluated on the three-dimensional reconstruction of the scans by two calibrated examiners. RESULTS Overall, periodontal parameters were not different between the test and the control teeth. Clear signs of buccal cervical resorption were detected on 27 of 29 orthodontically moved teeth and on one control tooth. Ten subjects had perfect oral hygiene and no gingivitis, whereas six subjects showed a moderate level of plaque and gingivitis (>20% occurrences of PI or GI with >0). No relationship could be demonstrated between resorption and periodontal parameters. CONCLUSIONS Nearly all orthodontically moved teeth showed signs of cervical resorption. Periodontal parameters were unrelated to this important side effect of orthodontic treatment.

Quantitative comparison of 3 enamel-stripping devices in vitro: How precisely can we strip teeth?

INTRODUCTION In this in-vitro study, we aimed to investigate the predictability of the expected amount of stripping using 3 common stripping devices on premolars. METHODS One hundred eighty extracted premolars were mounted and aligned in silicone. Tooth mobility was tested with Periotest (Medizintechnik Gulden, Modautal, Germany) (8.3 ± 2.8 units). The selected methods for interproximal enamel reduction were hand-pulled strips (Horico, Hapf Ringleb & Company, Berlin, Germany), oscillating segmental disks (O-drive-OD 30; KaVo Dental, Biberach, Germany), and motor-driven abrasive strips (Orthofile; SDC Switzerland, Lugano-Grancia, Switzerland). With each device, the operator intended to strip 0.1, 0.2, 0.3, or 0.4 mm on the mesial side of 15 teeth. The teeth were scanned before and after stripping with a 3-dimensional laser scanner. Superposition and measurement of stripped enamel on the most mesial point of the tooth were conducted with Viewbox software (dHal Software, Kifissia, Greece). The Wilcoxon signed rank test and the Kruskal-Wallis test were applied; statistical significance was set at alpha ≤ 0.05. RESULTS Large variations between the intended and the actual amounts of stripped enamel, and between stripping procedures, were observed. Significant differences were found at 0.1 mm of intended stripping (P ≤ 0.05) for the hand-pulled method and at 0.4 mm of intended stripping (P ≤ 0.001 to P = 0.05) for all methods. For all scenarios of enamel reduction, the actual amount of stripping was less than the predetermined and expected amount of stripping. The Kruskal-Wallis analysis showed no significant differences between the 3 methods. CONCLUSIONS There were variations in the stripped amounts of enamel, and the stripping technique did not appear to be a significant predictor of the actual amount of enamel reduction. In most cases, actual stripping was less than the intended amount of enamel reduction.

Slow and fast orthodontic tooth movement: an experimental study on humans

INTRODUCTION The aim of this study was to investigate the variation in the amount of the orthodontically induced tooth movement in humans and potential associations between the amount of tooth movement with age and location in the mandible or maxilla. SUBJECTS AND METHODS This study included 11 participants (7 females, 4 males) with an age range of 11.3-28.6 years. In a standardized experimental orthodontic tooth movement protocol, two premolars of each participant were moved buccally during 8 weeks with the use of 1 N force. No functional or localized obstacles were affecting the displacement. Plaster models before and after the experimental tooth movement were constructed, digitized, and superimposed, to evaluate the amount of tooth movement of each tooth. Random effects linear regression analysis was performed to examine associations between tooth displacement, age, and tooth location. RESULTS The mean displacement of the teeth was 2.7±1.4mm. The range of tooth movement varied substantially between individuals (0.6-5.8mm). The displacement of the teeth within the same individual was highly correlated (R (2) = 0.78, P < 0.001). The tooth displacement decreased with age; however, this finding did not reach statistical significance (β = -0.11, 95% CI: -0.28, 0.05, P = 0.172). The tooth movement was higher in the maxilla than in the mandible (β = 0.47, 95% CI: 0.81, 0.86, P = 0.018). CONCLUSION Wide range of tooth displacement revealed slow and fast movers in this sample. Larger displacements were recorded in the maxilla compared to the mandible and in younger individuals.

Intraobserver Reliability of the 2-Dimensional Analysis of Facial Expressions

PURPOSE The aim of our study was to develop a reliable method to identify certain facial expressions of the lower face that are easy to re-create through proper instruction and with high reproducibility. We wanted to quantitatively evaluate facial expressions in a simple, efficient, and inexpensive manner that is easily applicable in many clinical settings and in a wide variety of patients. MATERIALS AND METHODS We included 40 healthy subjects (20 women [mean age, 25.6 years] and 20 men [mean age, 27.0 years]). A digital camcorder recorded a video sequence (video 1) where the subject was verbally asked to execute several facial expressions (posed smile, spontaneous smile, aggressive smile, lip pucker, and maximum opening). Two weeks later, the video session was repeated (video 2). Frames of each expression were selected from the digitized video sequences. Horizontal and vertical distances were measured in each selected frame. RESULTS We found no statistically significant differences between the 2 videos of the expressions studied (except vertical lip changes for posed smile, lip pucker, and maximum mouth opening expression). The calculated coefficient of reliability was high and varied between 0.994 and 0.996, which confirms the reliability of the method. CONCLUSION This 2-dimensional method is an accurate means to quantitatively evaluate facial expressions in a simple, efficient, and inexpensive manner. The lip pucker, posed smile, spontaneous smile, and aggressive smile were the best and most reproducible expressions of the chosen expressions in this study.

Orthodontically induced cervical root resorption in humans is associated with the amount of tooth movement

Introduction The aim of this study was to investigate the variation in the amount of the orthodontically induced cervical root resorption and the association with several factors, such as the amount of tooth displacement, location of tooth in the maxilla or mandible, and presence of an interference that may influence the amount of root resorption. Subjects and methods This study included 30 subjects (20 females, 10 males) with an age range of 11.3 to 43.0 years. Using a standardized experimental orthodontic tooth movement, 59 premolars were moved buccaly during 8 weeks with application of 1 N force. Fifty-eight contralateral premolars not subjected to orthodontic tooth movement served as controls. At the end of the experimental period the teeth were carefully extracted, scanned in a micro-computed tomography scanner with a resolution of 9 µm, and the reconstructed images were processed for volumetric evaluation of resorption craters at the cervical part of the root surface. Data were analyzed using unpaired t-test and the Pearsons correlation. Results Higher amount of cervical root resorption was detected in the orthodontically moved teeth (0.00055 mm3) compared to controls (0.00003 mm3; P < 0.001). Moderate correlation was found between root resorption in the two experimental teeth within the same individual (R = 0.421, P = 0.023). Teeth located in the mandible presented more resorption than those in the maxilla (P = 0.046). The amount of root resorption was correlated to the amount of tooth movement (R = 0.318, P = 0.016). Conclusion Application of a 1 N force over a 2-month period provokes severe root resorption at the compression cervical sites. Resorption is correlated with the amount of tooth movement and the location of the teeth.