The relationship between local alveolar bone housing and size of canine in maxillary canine-lateral incisor transposition: A retrospective cone-beam computed tomography-based study.

INTRODUCTION: This study aimed to use 3-dimensional data to analyze the relationship between local alveolar bone housing and canine size in maxillary canine-lateral incisor transposition. METHODS: Cone-beam computed tomography study data from 31 patients with maxillary canine-lateral incisor transposition were imported into Dolphin Imaging software (version 11.8; Dolphin Imaging and Management Solutions, Chatsworth, Calif) for measurement. The buccal and palatal alveolar thickness of lateral incisor roots at different heights, the maximal thickness of displaced canine, and canine height were measured. Alveolar height-thickness variation curves at the lateral incisor region and maximal thickness of displaced canine were plotted to calculate the appropriate theoretical minimum alveolar heights of total alveolar housing, buccal alveolar housing after concentrating the bone buccally (TMAH-B1), and original buccal alveolar housing (TMAH-B2) required for correcting the transposition of 2 teeth. RESULTS: Canines could only be moved distally above lateral incisors in 5 patients. The mean value of theoretical minimum alveolar heights of total alveolar housing was 14.57 ± 1.75 mm. It was possible to reposition canines distally by concentrating the alveolar bone buccally in the remaining 26 patients. The mean value of TMAH-B1 was 10.86 ± 3.70 mm. Canines could be repositioned distally directly over the buccal aspect of the lateral incisor in 17 patients. The mean value of TMAH-B2 was 9.30 ± 2.35 mm. Canine height was greater than TMAH-B1 in 18 patients; however, only 10 patients were greater than TMAH-B2. CONCLUSIONS: Correction of transposition was difficult in some patients because of the lack of alveolar bone housing. Repositioning was possible when the height of the canine was higher than a certain height. An accurate assessment of the relationship between alveolar housing and tooth size is recommended.

The differences of root morphology and root length between different types of impacted maxillary central incisors: A retrospective cone-beam computed tomography study.

INTRODUCTION: The purpose of this trial was to use 3-dimensional data to analyze the differences of root morphology and root length between 3 different types of impacted maxillary central incisors. METHODS: Cone-beam computed tomography images of 126 patients with impacted maxillary central incisors were included in this retrospective study. On the basis of the angle of the impacted incisor to the palatal plane, we categorized the tooth as labial inversely impacted, labially positioned, or palatal impacted incisor. In each category, the early and late dental age groups were classified according to the method of Nolla. The total root length of both impacted and homonym teeth, length of the nondilacerated part of the root, length of the dilacerated part of the root, the angle between the crown and root, and root direction, were measured in the sagittal-view sections using Dolphin Imaging software (version 11.9; Dolphin Imaging and Management Solutions, Chatsworth, Calif). RESULTS: Compared with the early dental age groups, the length of the dilacerated portion of the root and rate of dilaceration for inverse labial and labially positioned impactions increases, and crown-root angle decreases (P <0.05). The dilacerated part of the root bent labially, and the root morphology shows an obvious L-shaped curve. The length of the nondilacerated part of the root for palatal impactions is greater(P <0.05). The dilacerated part of the root bends palatally, and the root morphology shows a continuous C-shaped curve. CONCLUSIONS: Obstruction from the alveolar bone will cause different root morphology. Root morphology of labial impactions shows an obvious L-shaped curve; palatal impactions show a continuous C-shaped curve.

Association between palatally displaced maxillary central incisors and lateral incisors: A retrospective cone-beam computed tomographic study.

INTRODUCTION: The objective of this study was to investigate the location, orientation and root development of maxillary lateral incisors in patients with palatally impacted central incisors. Comparison was made between the lateral incisor on the affected side and that on the normally erupted side. METHODS: Cone-beam computed tomographic images from 20 patients (10 boys, 10 girls, mean age (9.01 ± 1.52 years old) with unilateral palatally impacted maxillary central incisors were imported into Dolphin imaging software 11.8 for 3-dimensional reconstruction and reorientation. Software measurement tools were used to measure the root length, crown distance, angle to palatal plane, distance to midline, and angle to midsagittal plane of the maxillary lateral incisors on both the impacted and unaffected sides. RESULTS: The Wilcoxon signed rank test indicated that lateral incisors on the impacted side were more proclined, at a mean angle difference of 29.47° in the sagittal plane (P < 0.001). The mean length of the roots of the lateral incisors was 1.21 mm shorter (P < 0.05) on the affected side compared with the normal side, and the lateral incisor crowns on the impacted side were located at an average of 4.57 mm closer to the palatal plane than on the normally erupted side (P < 0.001). The angle of long axis of the lateral incisors on the affected side had a greater angulation to the midsagittal plane compared with the unaffected side, with a mean difference of 30.27° (P < 0.001). CONCLUSIONS: Maxillary lateral incisors adjacent to palatally impacted maxillary central incisors side had abnormal root development and demonstrated angulation and position change compared with those adjacent to normally erupted central incisors.

Factors affecting treatment duration of labial inversely impacted maxillary central incisors.

INTRODUCTION: A labial inversely impacted maxillary central incisor is a relatively rare occurrence. The crown of the tooth is directed upward, and its palatal aspect is facing labially. This typical orientation can be the result of trauma to the deciduous incisor transmitted to the palatal side of the crown of the permanent incisor. Labial inversely impacted maxillary central incisors are most commonly combined with labial-lingual root dilacerations. The aim of this study was to examine factors that affect the surgical-orthodontic treatment duration of labial inversely impacted maxillary central incisors. METHOD: The records of 35 consecutively treated patients were retrospectively evaluated. Cone-beam computed tomography images were taken before treatment, and factors affecting treatment time, including age, length, crown-root angle, crown height and depth, angle of inversion, rotation to axial plane, and distance and angle to midline, were measured using Dolphin Imaging software (version 11.8; Patterson Supply, St Paul, Minn). Treatment duration was evaluated for each patient, and logistic regression analyses were applied. RESULTS: The 15 boys and 20 girls had a mean age 8.36 ± 1.36 years. The mean orthodontic traction duration was 11.28 ± 3.08 months. Multiple regression analyses indicated that factors resulting in a longer duration were age (ß = 0.779; P = 0.043), crown height (ß = 0.344; P = 0.007), crown-root angle (ß = -0.037; P = 0.018), and tooth length (ß = -0.623; P = 0.038). CONCLUSIONS: Surgical-orthodontic correction of labial inversely impacted maxillary incisors requires an average of 1 year. Assessments of age, crown height, root dilaceration, and length of incisor can help the orthodontist to better predict treatment duration during consultations with patients and parents.

Impact of fixed orthodontic appliance or clear-aligner on daily performance, in adult patients with moderate need for treatment.

OBJECTIVE: To assess the impact of wearing fixed orthodontic appliance (FOA) or clear-aligner, on daily performance in adult patients. METHODS: The Oral Impacts on Daily Performance (OIDP) index was assessed in 152 adults aged 25-35 years at baseline (T0), 6 months after bonding (T1), and 12 months after bonding (T2). Participants were randomly divided into two groups: CA group (participants treated with clear-aligner) and a control group (FOA group; participants treated with FOA). Baseline malocclusion severity was assessed using the Index of Orthodontic Treatment Need. RESULTS: There were no significant differences in sociodemographic variables and OIDP scores at baseline between the two groups. Significant changes in OIDP total and subscale scores were observed while wearing FOA: OIDP total score and subscale scores of eating, cleaning teeth, smiling, and social relation at T1 and T2 were significantly higher than at baseline (P<0.05 or P<0.01). However, only OIDP total score was significantly increased at T1 compared to the baseline in the CA group. OIDP total score and subscale scores of eating, cleaning teeth, smiling, and social relation were significantly higher in patients wearing FOA than in patients wearing clear-aligner at T1 and T2 (P<0.05 or P<0.01). CONCLUSION: Patients wearing clear-aligner have fewer impacts on daily life than those wearing FOA during treatment, and have no significant changes in OIPD subscale scores at 12 months. FOA therapy significantly impacts daily performance in adult patients during treatment.