Factors affecting forced eruption duration of impacted and labially displaced canines

Treatment duration by morphology and location of impacted maxillary canines: A cone-beam computed tomography investigation

INTRODUCTION

This study aimed to identify whether patients with impacted maxillary canines take longer to treat than orthodontic patients without an impacted canine. We also sought to identify factors that are predictive of increased treatment duration in patients with impacted maxillary canines and treated by surgical exposure.

METHODS

A retrospective investigation of 37 patients with an impacted maxillary canine, treated by surgical exposure and fixed appliance therapy, was undertaken. In addition, an age- and sex-matched control group of 39 patients (without impacted canines) was also collected. Patient age, sex, and total treatment duration were recorded. For patients with an impacted canine, patient records and pretreatment cone-beam computed tomography datasets were assessed. Point coordinates identifying relevant landmarks were recorded, and a geometric method was used to calculate variables describing canine location, orientation, and apical morphology.

RESULTS

Controlling for age and sex, linear regression identified a statistically significant increase in treatment duration of 46.7 and 41.5 weeks for palatal and labial/midalveolar impacted canines, respectively, vs controls (P <0.002). Age and sex of patients with impacted canines collectively affected treatment duration (P = 0.04), with females of increased age being treated faster than younger males. Rotation of the impacted canine crown had a highly significant effect on treatment duration, with every degree of rotation increasing treatment duration by 0.32 weeks (P <0.001). There was a significant degree of multicollinearity between the other radiographic variables. Collectively, radiographic variables describing canine displacement significantly prolonged treatment duration (P <0.001) and explained 29.8% of the variability in total treatment time. The apical morphology of impacted maxillary canines was significantly associated with increased treatment duration (P = 0.01) and explained 11.3% of the overall treatment variability (P = 0.01).

CONCLUSIONS

Increased total treatment duration of surgically exposed impacted maxillary canines is associated with increasing mesiopalatal canine crown rotation, worsening displacement, and hooked apical morphology.

Forced eruption in impacted teeth: analysis of failed cases and outcome of re-operation

BACKGROUND

Forced eruption of an impacted tooth usually requires surgical and orthodontic interventions to successfully bring the tooth into the dental arch. The clinical time required for a forced eruption is difficult to predict before treatment begins and success rates are affected by several factors before and after an eruption. This study was conducted to identify factors that affect the success of forced eruption, the duration of orthodontic treatment of impacted teeth, and the reasons for re-operation and forced eruption failure in a various teeth and cases.

METHODS

In this retrospective study, the records regarding the forced eruption of 468 teeth in 371 patients from June 2006 to May 2020 at the Advanced General Dentistry Department of Yonsei University Dental Hospital were initially examined. The records of 214 teeth in 178 patients who completed orthodontic treatment were included in the analysis. Data on patient demographics, tooth characteristics, orthodontic treatment duration, re-operations, and failures were collected from electronic medical records.

RESULTS

There was a significant difference in age between the success and failure forced eruption. Factors significantly affecting treatment duration were apex formation, position, rotation, and re-operation. Re-operation had a 96% success rate. The average orthodontic treatment duration was 29.99 ± 16.93 months, but the average orthodontic treatment duration for teeth that undergone re-operation was 20.36 ± 11.05 months, which was approximately 9 months shorter. Additionally, there was an interaction effect between rotation and re-operation on the duration of orthodontic treatment. The causes for failure of forced eruption in 6 cases were ankyloses (3 cases), incomplete alignment with the normal dental arch (2 cases), and a significant deviation in the impacted tooth's location (1 case).

CONCLUSIONS

To increase the success rate of forced eruption, age should be considered as a priority, and in order to predict the treatment period, the apex formation status, position in the arch, and rotation should be considered in addition to age. When determining re-operation, considering factors such as ankylosis, root curvature, and apex formation can help in the success of orthodontic treatment.

Three-Dimensional Postoperative Results Prediction for Orthognathic Surgery through Deep Learning-Based Alignment Network

To date, for the diagnosis of dentofacial dysmorphosis, we have relied almost entirely on reference points, planes, and angles. This is time consuming, and it is also greatly influenced by the skill level of the practitioner. To solve this problem, we wanted to know if deep neural networks could predict postoperative results of orthognathic surgery without relying on reference points, planes, and angles. We use three-dimensional point cloud data of the skull of 269 patients. The proposed method has two main stages for prediction. In step 1, the skull is divided into six parts through the segmentation network. In step 2, three-dimensional transformation parameters are predicted through the alignment network. The ground truth values of transformation parameters are calculated through the iterative closest points (ICP), which align the preoperative part of skull to the corresponding postoperative part of skull. We compare pointnet, pointnet++ and pointconv for the feature extractor of the alignment network. Moreover, we design a new loss function, which considers the distance error of transformed points for a better accuracy. The accuracy, mean intersection over union (mIoU), and dice coefficient (DC) of the first segmentation network, which divides the upper and lower part of skull, are 0.9998, 0.9994, and 0.9998, respectively. For the second segmentation network, which divides the lower part of skull into 5 parts, they were 0.9949, 0.9900, 0.9949, respectively. The mean absolute error of transverse, anterior-posterior, and vertical distance of part 2 (maxilla) are 0.765 mm, 1.455 mm, and 1.392 mm, respectively. For part 3 (mandible), they were 1.069 mm, 1.831 mm, and 1.375 mm, respectively, and for part 4 (chin), they were 1.913 mm, 2.340 mm, and 1.257 mm, respectively. From this study, postoperative results can now be easily predicted by simply entering the point cloud data of computed tomography.

Decision-Making Criteria of Odontectomy or Surgical Exposure in Impacted Maxillary Canine Based on Treatment Difficulty Index Modification

OBJECTIVE

 Canine impaction is a difficult condition to treat, and it usually necessitates a combination of surgical exposure and orthodontic traction or surgical extraction. An accurate assessment of the maxillary canine's position can help determine the severity of the impaction, the difficulty of therapy, and the treatment's prognosis.

MATERIALS AND METHODS

 A total of 55 impacted canines were studied and selected retrospectively. Difficulty indexes were used to measure the severity of impaction with pretreatment panoramic radiographs.

STATISTICAL ANALYSIS

 Pearson correlation was used to test the validity of the difficulty index modification score. Regression statistical analysis was used to evaluate any correlation between total scoring from each index with surgical treatment.

RESULTS

 The validity test on the variable modification index score showed a valid value (p = 0.000). According to both treatment difficulty and modification index, odontectomy group showed higher mean of total scoring than surgical exposure group. Treatment difficulty and modification index showed a significant correlation with surgical treatment (p = 0.003 and p = 0.001).

CONCLUSIONS

 The higher the severity of canine impaction, the greater is the possibility of odontectomy than surgical exposure. Both indexes can consider to be used in determining surgical treatment planning.

Gray value measurement for the evaluation of local alveolar bone density around impacted maxillary canine teeth using cone beam computed tomography

Background

To investigate whether any relationship between local alveolar bone density and maxillary canine impaction using gray values from cone beam computed tomography.

Material and Methods

The cone beam computed tomography images of 151 patients were retrospectively evaluated. Maxillary canine was defined as an impacted tooth when root formation was complete and the patient’s age older than 13 or the other side of the maxillary canine has completely erupted. Similarly, complete eruption was defined as the tooth in its expected occlusion and position. Using the cone beam computed tomography software, the region of interest which was 5 mm2 in area, was placed in the trabecular bone on cross sectional cone beam computed tomography images and the gray value measurements were recorded. After measuring the gray values of all the teeth, the images were grouped according to the field of view size. Comparison of the gray values of impacted and non-impacted teeth was made between images with the same field of view size.

Results

A total of 151 patients, 101 (66.9%) female and 50 (33.1%) male, were included in the study. The mean age of the patients was 24.94 ±13.9. In images with a 40X40 field of view, the gray values of the impacted canine teeth were higher than the gray values of the non-impacted ones and statistically significant difference was found between them (p=0.003). However no statistically significant difference was found between the gray values of impacted and non-impacted canine teeth in 60x60 and 100x50 field of view (p=0.197, p=0.170, respectively).

Conclusions

We suggest using the smallest field of view size when evaluating bone density using gray values from cone beam computed tomography images and we support the idea that the local increased bone density may influence on impaction.

Key words:Cone-beam computed tomography, tooth, impacted, bone density, maxilla, image processing, computer-assisted.

Three-dimensional changes in root angulation of buccal versus palatal maxillary impacted canines after orthodontic traction: A retrospective before and after study

INTRODUCTION

The aim of this study was to three-dimensionally compare the root angulation changes after orthodontic traction of buccally versus palatally maxillary impacted canines (MICs).

MATERIAL AND METHODS

This retrospective study included patients from a private dental office of both sexes, older than 12 years, with at least one unilateral or bilateral buccal or palatal MIC, no loss of permanent teeth, with complete apical closure at the beginning of traction, and with CBCTs taken at pretreatment (T₀) and after orthodontic traction (T₁). The sample was divided in two groups according to their impaction site: buccal versus palatal. In all the scans, the MIC was segmented and the root angulation changes after traction were evaluated. The assessment included the sigma angle (projected on the XZ plane or coronal tomographic view), the delta angle (projected on the XY plane or axial view) and the epsilon angle (projected on the YZ plane, or sagittal view). Intragroup comparisons were performed with Wilcoxon signed-rank tests. Intergroup comparisons were performed with t-tests or Mann-Whitney U tests. Finally, the influence of MIC characteristics on the measured angles were evaluated with multiple linear regression analyses (α=0.05).

RESULTS

Thirty-three patients (16 men, mean age: 20.38; 17 women, mean age 18.37) with forty-five orthodontically treated MIC (19 buccal versus 26 palatal) were finally included. The palatal MICs showed greater mediolateral uprighting than the buccal MICs, root displacement towards the midsagittal plane, as demonstrated by the sigma angle (palatal group: 37.58±15.08°; buccal group: 29.17±31.15°; P=0.164) and delta (palatal group: -76.90±26.55°; buccal group: -30.56±41.67°; P<0.001)angle changes. The buccal MICs showed greater anteroposterior uprighting, anterior root displacement, as demonstrated by the epsilon angle (palatal group: -4.63±12.37°; buccal group: -25.96±17.79°; P<0.001).

CONCLUSIONS

Mediolateral and anteroposterior root angulation show significant differences after traction between buccal and palatal MICs. Palatal MICs showed greater medial root displacement while buccal MICs showed greater anterior root displacement. This condition should be considered for better planning of traction and orthodontic finishing.

Deep-Learning-Based Detection of Cranio-Spinal Differences between Skeletal Classification Using Cephalometric Radiography

The aim of this study was to reveal cranio-spinal differences between skeletal classification using convolutional neural networks (CNNs). Transverse and longitudinal cephalometric images of 832 patients were used for training and testing of CNNs (365 males and 467 females). Labeling was performed such that the jawbone was sufficiently masked, while the parts other than the jawbone were minimally masked. DenseNet was used as the feature extractor. Five random sampling crossvalidations were performed for two datasets. The average and maximum accuracy of the five crossvalidations were 90.43% and 92.54% for test 1 (evaluation of the entire posterior-anterior (PA) and lateral cephalometric images) and 88.17% and 88.70% for test 2 (evaluation of the PA and lateral cephalometric images obscuring the mandible). In this study, we found that even when jawbones of class I (normal mandible), class II (retrognathism), and class III (prognathism) are masked, their identification is possible through deep learning applied only in the cranio-spinal area. This suggests that cranio-spinal differences between each class exist.