BACKGROUND: The purpose of this study was to evaluate and compare the incidence of orthodontically induced inflammatory root resorption (OIIRR) after en masse maxillary incisors intrusion and retraction with controlled tipping versus bodily movement using cone beam computed tomography (CBCT).
METHODS: This study is a retrospective study performed on CBCT scans of 36 adult females who had their maxillary first premolars extracted followed by en masse anterior retraction and intrusion using labial biocreative therapy type II. Subjects were divided into two groups of 18 subjects each based on the type of tooth movement required during en masse retraction: Group I; the controlled tipping group, and Group II; the bodily movement group. The amount of intrusion, crown and root retraction, change in incisor inclination, and difference in tooth length was measured from the CBCT scans. Independent t tests were used to compare the measurements between the two groups. Pearson rank correlation analysis was applied to identify the relationship between the mean dental changes and the mean changes in tooth length for all four upper incisors.
RESULTS: OIIRR was found in all four maxillary incisors in both groups. No significant differences were found between the two groups. OIIRR was positively correlated to the amount of root apex retraction and negatively correlated to the change in incisor inclination.
CONCLUSIONS: Anterior retraction and intrusion lead to obvious root resorption affecting all maxillary incisors. No significant differences were found between the two groups. Careful clinical monitoring is needed for patients requiring anterior retraction with intrusion with maximum anchorage.

BACKGROUND: Mesial tipping of posterior teeth occurs frequently during space closure with clear aligners (CAs). In this study, we proposed a new modification of CA by localized thickening of the aligner to form the enhanced structure and investigate its biomechanical effect during anterior retraction.
METHODS: Two methods were employed in this study. First, a finite element (FE) model was constructed, which included alveolar bone, the first premolars extracted maxillary dentition, periodontal ligaments (PDL), attachments and aligners. The second method involved an experimental model-a measuring device using multi-axis transducers and vacuum thermoforming aligners. Two groups were formed: (1) The control group used common CAs and (2) the enhanced structure group used partially thickened CAs.
RESULTS: FE model revealed that the enhanced structure improved the biomechanics during anterior retraction. Specifically, the second premolar, which had a smaller PDL area, experienced a smaller protraction force and moment, making it less likely to tip mesially. In the same vein, the molars could resist movement due to their larger PDL area even though they were applied larger forces. The resultant force of the posterior tooth was closer to the center of resistance, reducing the tipping moment. The canine was applied a larger retraction force and moment, resulting in sufficient retraction of anterior teeth. The experimental model demonstrated a similar trend in force variation as the FE model.
CONCLUSIONS: Enhanced structure allowed force distribution more in accordance with optimal principles of biomechanics during the extraction space closure while permitting less mesial tipping and anchorage loss of posterior teeth and better retraction of anterior teeth. Thus, enhanced structure alleviated the roller coaster effect associated with extraction cases and offered a new possibility for anchorage reinforcement in clear aligner therapy.

BACKGROUND: The aim of this study is to conduct a comparative evaluation of different designs of clear aligners and examine the disparities between clear aligners and fixed appliances.
METHODS: 3D digital models were created, consisting of a maxillary dentition without first premolars, maxilla, periodontal ligaments, attachments, micro-implant, 3D printed lingual retractor, brackets, archwire and clear aligner. The study involved the creation of five design models for clear aligner maxillary anterior internal retraction and one design model for fixed appliance maxillary anterior internal retraction, which were subsequently subjected to finite element analysis. These design models included: (1) Model C0 Control, (2) Model C1 Posterior Micro-implant, (3) Model C2 Anterior Micro-implant, (4) Model C3 Palatal Plate, (5) Model C4 Lingual Retractor, and (6) Model F0 Fixed Appliance.
RESULTS: In the clear aligner models, a consistent pattern of tooth movement was observed. Notably, among all tested models, the modified clear aligner Model C3 exhibited the smallest differences in sagittal displacement of the crown-root of the central incisor, vertical displacement of the central incisor, sagittal displacement of the second premolar and second molar, as well as vertical displacement of posterior teeth. However, distinct variations in tooth movement trends were observed between the clear aligner models and the fixed appliance model. Furthermore, compared to the fixed appliance model, significant increases in tooth displacement were achieved with the use of clear aligner models.
CONCLUSIONS: In the clear aligner models, the movement trend of the teeth remained consistent, but there were variations in the amount of tooth displacement. Overall, the Model C3 exhibited better torque control and provided greater protection for posterior anchorage teeth compared to the other four clear aligner models. On the other hand, the fixed appliance model provides superior anterior torque control and better protection of the posterior anchorage teeth compared to clear aligner models. The clear aligner approach and the fixed appliance approach still exhibit a disparity; nevertheless, this study offers a developmental direction and establishes a theoretical foundation for future non-invasive, aesthetically pleasing, comfortable, and efficient modalities of clear aligner treatment.

This article reviews and critically analyzes the literature on mini-implants (temporary anchorage devices) for anterior en masse retraction in orthodontics. The search methods used were an E-database search, a secondary computerized search of orthodontics journals, and a reference list of selected studies. Eligibility criteria included individuals who underwent orthodontic treatment for correction of malocclusion with premolar extraction. Data were taken from PubMed and Scopus as well as the Cochrane Central Register of Controlled Trials and the Cochrane Database of Systematic Reviews. Keywords used for searching the article were temporary anchorage devices, premolar extraction, orthodontics, and anterior en masse retraction, Anterior en masse retraction with sliding mechanics in pre-adjusted edgewise appliances was considered for the study. Data collection and analysis involved three different researchers performing three steps of selection. All titles were initially filtered for irrelevant review articles. In the first step, all summaries from the selected studies were reviewed, and in the second, the entire content of the papers was read. The study was then discarded based on qualifying standards. A chart was created using the data from the final chosen research as well as the findings. The following information was evaluated for the final table: author, publication year, research structure, study group, sample size, methods/measures, study findings, and conclusion about frictionless mechanics. Results showed that a meta-analysis was not feasible due to clinical and statistical variability, as well as variations in study design, sample selection, and sample size. Thus, it was concluded that sliding mechanisms are widely employed in orthodontic treatment, but temporary anchorage devices and sliding mechanisms deliver great results. There is a need to raise awareness about these devices and use them with care.

OBJECTIVE: To compare the effect of maxillary incisor intrusion and retraction with controlled tipping (CT) versus bodily movement (BM) in extraction cases on alveolar bone height and thickness, using cone-beam computed tomography (CBCT). Correlations between changes in alveolar dimensions and crown or root retraction, incisor inclination, and intrusion were also investigated.
METHODS: In all, 144 incisors of 36 women were retrospectively evaluated. All patients were treated with anterior intrusion and retraction with either controlled tipping (CT) (group 1) or bodily movement (BM) (group 2). CBCT scans were taken before and after retraction and intrusion and measurements of alveolar bone height and thickness at the level of mid-root and root apex were measured. The prevalence of dehiscence was also calculated.
RESULTS: Labial bone thickness (BT) increased at the level of the root apex with increased total BT in the CT group (p < 0.05). The BM group showed decreased palatal BT. Significant vertical bone loss with an increased incidence of dehiscences occurred on the palatal side in both groups. Changes in palatal bone area was negatively correlated with the amount of root apex retraction, while the total BT at the level of root apex was positively correlated with amount of intrusion.
CONCLUSIONS: Bodily retraction can result in reduced palatal bone dimensions and an increase risk of iatrogenic sequelae following anterior retraction in extraction cases. Vertical bone loss and an increased incidence of dehiscences is to be expected following anterior retraction. Careful attention must be paid to the bone boundary conditions to avoid moving the incisors out of the alveolar housing.
UNASSIGNED: ZIELSETZUNG: Vergleich der Auswirkungen der Intrusion und Retraktion des oberen Schneidezahns mit kontrolliertem Kippen („controlled tipping“, CT) und körperlicher Bewegung („bodily movement“, BM) bei Extraktionen auf die Höhe und Dicke des Alveolarknochens mithilfe digitaler Volumentomographie (DVT). Ferner wurden Korrelationen zwischen Veränderungen der Alveolardimensionen und Kronen- bzw. Wurzelretraktion, Schneidezahnneigung und Intrusion untersucht.
UNASSIGNED: Insgesamt wurden 144 Schneidezähne von 36 Frauen retrospektiv ausgewertet. Alle Patientinnen wurden mit anteriorer Intrusion und Retraktion entweder mit CT (Gruppe 1) oder BM (Gruppe 2) behandelt. Vor und nach der Retraktion und Intrusion wurden DVT-Aufnahmen angefertigt sowie Höhe und Dicke des Alveolarknochens auf der Höhe der mittleren Wurzel und der Wurzelspitze gemessen. Zudem wurde die Prävalenz der Dehiszenz berechnet.
UNASSIGNED: Die labiale Knochendicke (BT) nahm auf Höhe der Wurzelspitze zu, wobei die Gesamt-BT in der CT-Gruppe zunahm (p < 0,05). In der BM-Gruppe war die palatinale BT verringert. Auf der palatinalen Seite kam es in beiden Gruppen zu einem signifikanten vertikalen Knochenverlust mit einer erhöhten Inzidenz von Dehiszenzen. Die Veränderungen der palatinalen Knochenfläche waren negativ mit dem Ausmaß der Wurzelspitzenretraktion korreliert, die Gesamt-BT auf Höhe der Wurzelspitze dagegen positiv mit dem Ausmaß der Intrusion.
UNASSIGNED: Körperliche Retraktion kann zu einer Verringerung der palatinalen Knochendimensionen und zu einem erhöhten Risiko iatrogener Folgeerscheinungen nach anteriorer Retraktion bei Extraktionen führen. Nach einer anterioren Retraktion ist mit einem vertikalen Knochenverlust und einer erhöhten Inzidenz von Dehiszenzen zu rechnen. Um eine Verschiebung der Inzisiven aus ihrem alveolären Umfeld zu vermeiden, ist eine sorgfältige Berücksichtigung der Knochenrandbedingungen erforderlich.

OBJECTIVE: To elucidate the relationships and factors affecting the proximity between the incisive canal (IC) and maxillary central incisors and to predict the probable outcomes after anterior tooth retraction using cone beam computed tomography (CBCT).
METHODS: Retrospective CBCT data taken before and after maxillary anterior retraction in 36 patients were used in this study. The incisive canal length (ICL), maxillary central incisor length (TL), angles between the palatal plane and axes of the maxillary alveolar border (θ1), IC (θ2), and maxillary central incisor (θ3), retraction distance (TDE), distance from the maxillary central incisors to the IC (D), cross-sectional area of the IC (CSA), and volume of the IC were evaluated. Comparison of the parameters between contact and noncontact groups were examined. Logistic regression was performed to analyze the probable outcome prediction.
RESULTS: All parameters significantly decreased after anterior retraction, except for the ICL. Eighteen roots in 12 patients contacted the IC. The θ1, θ2, θ3, and D values at all levels were significantly lower, whereas the TDE, midlevel and oral opening CSA, and volume were significantly higher in the contact group compared with the noncontact group. The larger the pretreatment θ1 and θ3 were, the higher was the chance of incisors not contacting the IC.
CONCLUSIONS: Maxillary central incisors not contacting the IC after anterior retraction was positively associated with larger degrees of pretreatment maxillary alveolar bone angle and maxillary central incisor angle.

To evaluate the effect of friction vs frictionless mechanics on the rate of anterior segment retraction (ASR) in patients with bimaxillary protrusion.
Thirty females (18.3 ± 3.7 years) with bimaxillary protrusion were randomly allocated into the friction group, using elastomeric power chains, and the frictionless group, using T-loop springs for ASR. Eligibility criteria included absence of skeletal discrepancies and any systemic diseases or medications, among others. Randomization in a 1:1 ratio was generated by Microsoft Excel. Opaque sealed envelopes were sequentially numbered for allocation concealment. Only blinding of the outcome assessor was applicable. Activations were done every 4 weeks until completion of ASR. The primary outcome was the rate of ASR measured on digital models. Anchorage loss, molar rotation, and pain experienced were also assessed.
Two patients were lost to follow-up. The rate of ASR was 0.68 ± 0.18 mm/mo in the friction group vs 0.88 ± 0.27 mm/mo in the frictionless group, with no significant difference. A significant difference in anchorage loss of 1.63 mm and molar rotation of 7.06° was observed, being higher in the frictionless group. A comparable pain experience associated with both mechanics was reported.
No difference in the rate of ASR or pain experience was observed between friction and frictionless mechanics. However, extra anchorage measures should be considered when using frictionless mechanics as greater anchorage loss and molar rotations are anticipated.

OBJECTIVE: To analyze the biomechanical system of anterior retraction with clear aligner therapy (CAT) with and without an anterior mini-screw and elastics.
METHODS: Models including a maxillary dentition (without first premolars), maxilla, periodontal ligaments (PDLs), attachments, and aligners were constructed and imported to finite element software. Three model groups were created: (1) control (CAT alone), (2) labial elastics (CAT with elastics between the anterior mini-screw and buttons on central incisors), and (3) linguoincisal elastics (CAT with elastics between the anterior mini-screw and precision cuts on the lingual sides of the aligner). Elastic forces (0-300 g, in 50 g increments) were applied.
RESULTS: CAT alone caused lingual tipping and extrusion of the incisors. Labial elastics caused palatal root torquing and intrusion and mesial tipping of the central incisors, while linguoincisal elastics produced palatal root torquing and intrusion of both central and lateral incisors. Second premolars were intruded in all three groups, with less intrusion in the linguoincisal elastics group. For the control group, stress was concentrated on both labial and lingual root surfaces, alveolar ridge, and cervical and apical PDLs. Stress was more concentrated in the labial elastics group and less concentrated in the linguoincisal elastics group.
CONCLUSIONS: CAT produced lingual tipping and extrusion of incisors during anterior retraction. Anterior mini-screws and elastics can achieve incisor intrusion and palatal root torquing. Linguoincisal elastics are superior to labial elastics with a lower likelihood of buccal open bite. Root resorption and alveolar defects may occur in CAT, more likely for labial elastics and less likely for linguoincisal elastics.

BACKGROUND: The objectives were to visualize the incisive canal (IC) remodelling following maximum incisor retraction and to evaluate its impact on canal-invasion-associated apical root resorption.
METHODS: Pre- and post-treatment CBCT images of 34 adult orthodontic patients (age 18-47 years) with a large amount of maxillary incisor retraction (>4 mm) using temporary anchorage devices (TADs) were retrospectively evaluated. Maxillary regional superimpositions and 3D models of the IC along with central incisors were used to measure the changes in IC dimension, IC invasion by the roots and IC remodelling. In addition, the association of the amount of apical root resorption with the root-IC relationship and IC remodelling were evaluated.
RESULTS: IC invasion by the incisor roots following maximum retraction was seen in 53% (18 out of 34) of the cases. IC with larger volume and area showed more invasions compared with those with smaller volume and area (P < .01). The amount of root resorption was significantly higher with IC invasion than without invasion (2.39 mm vs 0.82 mm, P < .0001). IC remodelling following maximum retraction was seen in 24% of the subjects. IC remodelling group demonstrated less apical root resorption than the non-remodelling group (0.98 mm vs 3.27 mm, P < .0001).
CONCLUSIONS: IC with larger volume and surface area before treatment were more likely to show canal invasion by the incisor roots after maximum retraction. IC invasion resulted in apical root resorption. However, approximately one-fourth of cases showed remodelling of the IC, which reduced the amount of root resorption.