To intrude or not to intrude? A systematic review of the controversy surrounding orthodontic intrusion on reduced periodontium.

OBJECTIVE: The main objective of this review was to evaluate the effects of orthodontic intrusion on patients with reduced periodontium. Additionally, this review aims to explore the potential for attachment gain and tissue regeneration in these patients and identify optimal therapeutic conditions to mitigate any negative effects of intrusion. METHODS: A systematic review was conducted according to the PRISMA 2020 statement. Duplicate electronic searches of the PubMed, Cochrane, EMC Premium, and Science Direct databases were performed by two independent reviewers. Data extraction and quality assessments, including risk of bias evaluation using the Cochrane and ROBINS-I tools were conducted. RESULTS: From an initial pool of 418 articles, 29 were selected after title and abstract screening for full-text review. Following thorough full-text reading, 15 studies were ultimately included in the analysis. The total number of patients included in the studies is 528, who underwent orthodontic intrusion on reduced periodontium. Studies indicated a decrease in periodontal pocket depth and an increase in clinical attachment with ortho-periodontal treatment. Alveolar bone level outcomes varied, showing both increases and losses. Authors generally observed improved papillary regeneration and reduced gingival recessions. CONCLUSION: Clinical studies involving combined ortho-periodontal treatment showed that orthodontic intrusion on a reduced but healthy periodontium can be considered a beneficial treatment for the periodontium, provided that potential adverse effects are carefully monitored.

Prevention and repair of orthodontically induced root resorption using ultrasound: a scoping review.

INTRODUCTION: This review summarizes the available recent literature on different mechanisms and parameters of pulsed ultrasound (US) that have been used during orthodontic treatments to prevent and repair root resorption. AREAS COVERED: A literature search was conducted between January (2002) and September (2022) in the following databases: PubMed, Google-Scholar, Embase, and The-Cochrane-Library. After exclusions, a total of 19 papers were included in the present review. The most used US parameters with positive outcomes were frequency of 1.5 MHz, pulse repetition frequency of 1000 Hz, output intensity of 30 mW/cm2, duration of application of 20 min and total number sessions were 14 with a repetition interval of 1 day. The suggested mechanisms induced by US were alteration of cementoblasts, osteoblasts, osteoclasts, alkaline-phosphatase (ALP), runt-related-gene-2 (Runx2), osteoprotegerin (OPG), type-I-collagen (Col-I), C-telopeptide-type-I-collagen (CTX-I), hepatocyte-growth-factor (HGF), bone morphogenetic protein-2 (BMP-2), cyclooxygenase-2 (Cox-2), calcium (Ca2+), receptor activator of nuclear factor-kappa-B ligand (RANKL), and receptor activator of nuclear factor-kappa-B (RANK). EXPERT OPINION: Understanding mechanisms and deciding which parameters of US that can be used during orthodontic treatment to prevent and repair root resorption is a great challenge. This work summarizes all the available data that can aid this process and suggest that US is an effective noninvasive method not only in prevention and repairing of orthodontic induced root resorption but also in accelerating teeth movement.

Is maxillary arch expansion with Invisalign® efficient and predictable? A systematic review.

BACKGROUND: The main objective of this review is to assess the effectiveness and predictability of the transverse expansion movement performed by Invisalign®. The secondary objectives are to determine whether the expansion is of a dentoalveolar or skeletal nature, and to locate the areas of expansion on the dental arch. METHODS: Two investigators used the PubMed database to search for articles related to the subject. After using a research equation, specific inclusion and exclusion criteria were applied and the final selection of articles was done after being read in full. The ROBINS-I tool for non-randomized studies was applied to assess risk of bias in the results of each included study. RESULTS: After reading the articles in full, 12 articles were included. Regarding effectiveness, most studies showed an increase in all measured interdental distances, with a maximum expansion at the premolar level. As for predictability, significant differences were found between post-treatment models and Clincheck® models, making it generally weak. Concerning the nature and areas of expansion, increase of arch width was due to buccal tipping of the crowns following a decreasing gradient from anterior to posterior. CONCLUSIONS: Invisalign® treatment is effective in achieving a maxillary transverse expansion. However, this expansion is mainly dentoalveolar, with a facial crown tipping of the posterior teeth. Clincheck® software tends to overestimate the expansion movement when compared to the clinical outcome, therefore the predictability of movement is low.

Comparison of the sliding resistance between three models of self-ligating ceramic brackets: An in vitro and micro-morphological study.

OBJECTIVE: The main objective of our study was to compare a new model of self-ligating ceramic bracket (Clarity™ Ultra by 3M™), to its competitors by evaluating their resistance to sliding during an in vitro simulation of canine retraction. MATERIAL AND METHODS: The sample consisted of 120 brackets (30 brackets in each group: Victory Twin Series LP™, Clarity Ultra™ by 3M™, Damon Clear 2™ by Ormco™ and Empower™ 2 Clear by American Orthodontics™). Canine retraction was simulated using a universal testing machine connected to a software that measured the average sliding resistance (ASR) for each group. Five brackets from each group were randomly selected and observed under a digital optical microscope at ×50 magnification. ANOVA test and Tukey's analysis were carried to detect statistically significant differences between the groups' sliding resistance values, at the risk of α=0.05. RESULTS: Measured ASR values of control group (metallic Victory Twin) were the highest ones (70.55g), followed by 3M™ (33.22g) then Damon™ (6.72g) and AO™ (5.49g) (P-value<0.0001). Through microscopic observations, we found that the 3M™ bracket has the lowest percentage of slot chamfering (8%) compared to the other brackets (12%). The 3M™ bracket also has the widest slot followed by AO, and then Damon™. All three bracket types have oversized slots compared to the manufacturer's description, the least oversized being the 3M™ bracket, followed by AO™ and then Damon™. 3M™ and Damon™ brackets have covers that concealed the entire wire in the vertical dimension whereas the AO™ bracket has a curvilinear cover that only shields the gingival part of its slot. Wire-play is zero for the 3M™ group, and 0.1mm for the other two groups. CONCLUSION: Clarity Ultra™ ceramic bracket produced by 3M™ does not perform well against friction forces compared to its competitors and that is due to its micro-morphological characteristics.

Release and toxicity of bisphenol-A (BPA) contained in orthodontic adhesives: A systematic review.

OBJECTIVE: The objectives of this systematic review of the literature are to search for BPA release from biomaterials used in orthodontics and to highlight their possible impact on human health. MATERIALS AND METHODS: Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) model, digital and manual searches were conducted in February 2020 in the database of CENTRAL, MEDLINE and EMBASE. Thirteen parameters relating to the release and biological effects of BPA were identified and analysed. RESULTS: Thirty-one non-randomized clinical trials were included. In general, the level of evidence was low, and the risk of bias ranged from moderate to high. Furthermore, although at different concentrations, most of in vitro and in vivo studies found BPA release from orthodontic adhesives. The lack of standardized protocols and the clinical and methodological heterogeneity of the studies prevented a valid interpretation of the actual results. Concerning the possible toxicity of BPA, no conclusive scientific evidence could be drawn, but it seems that orthodontic biomaterials containing BPA have potential adverse biological effects in humans. DISCUSSION AND CONCLUSION: Until we have solid evidence from clinical trials, clinicians should consider that orthodontic adhesives containing BPA have potential short- and long-term adverse biological effects in humans. Careful consideration should therefore be given to bonding, polymerization and debonding protocols in orthodontics.

Variation of upper lip pressure on upper teeth during non-extraction orthodontic treatment: A prospective clinical study.

OBJECTIVE: The objectives of this prospective clinical study are to quantify the variation of pressure exerted by the upper lip on the upper teeth during the alignment phase and to evaluate its capacity to adapt to changes in dental position. MATERIALS AND METHODS: Thirty young subjects in skeletal Class I relationship requiring non-extraction orthodontic treatment were included in this study. The pressure exerted by the upper lip on the upper central incisors and right canine were measured during rest and swallowing positions using a pressure transducer before bracket placement (T0), after bracket placement (T1), three months (T2) and six months later (T3). Maxillary intercanine width (CC), upper arch length (U) and crowding (C) were measured on stone models at T1, T2 and T3 to determine the existence of a correlation between the variation of lip pressure and these variables. RESULTS: The lip pressure significantly increased after bracket placement and remained relatively stable during the six-month period. The labial pressure on the incisors was the only variable to significantly decrease at T3, though remaining significantly higher than the starting pressure. A positive correlation was found between the variation of the inter-canine distance and the labial pressure on the canine at rest whereas a negative correlation exists between the crowding and the labial pressure on the incisors at rest. CONCLUSION: This study showed that increasing inter-canine width disrupts the muscle equilibrium and therefore is prone to relapse, whereas the upper lip can better adapt to the protrusion of upper incisors.