Fracture toughness and hardness of in-office, 3D-printed ceramic brackets.

OBJECTIVES: Three-dimensional (3D) printing technology is a promising manufacturing technique for fabricating ceramic brackets. The aim of this research was to assess fundamental mechanical properties of in-office, 3D printed ceramic brackets. MATERIALS AND METHODS: 3D-printed zirconia brackets, commercially available polycrystalline alumina ceramic brackets (Clarity, 3 M St. Paul, MN) and 3D-printed customized polycrystalline alumina ceramic ones (LightForce™, Burlington, Massachusetts) were included in this study. Seven 3D printed zirconia brackets and equal number of ceramic ones from each manufacturer underwent metallographic grinding and polishing followed by Vickers indentation testing. Hardness (HV) and fracture toughness (K1c) were estimated by measuring impression average diagonal length and crack length, respectively. After descriptive statistics calculation, group differences were analysed with 1 Way ANOVA and Holm Sidak post hoc multiple comparison test at significance level α = .05. RESULTS: Statistically significant differences were found among the materials tested with respect to hardness and fracture toughness. The 3D-printed zirconia proved to be less hard (1261 ± 39 vs 2000 ± 49 vs 1840 ± 38) but more resistant to crack propagation (K1c = 6.62 ± 0.61 vs 5.30 ± 0.48 vs 4.44 ± 0.30 MPa m1/2 ) than the alumina brackets (Clarity and Light Force respectivelty). Significant differences were observed between the 3D printed and the commercially available polycrystalline alumina ceramic brackets but to a lesser extent. CONCLUSIONS: Under the limitations of this study, the 3D printed zirconia bracket tested is characterized by mechanical properties associated with advantageous orthodontic fixed appliances traits regarding clinically relevant parameters.

The effects of a clinically feasible application of low-level laser therapy on the rate of orthodontic tooth movement: A triple-blind, split-mouth, randomized controlled trial.

INTRODUCTION: This split-mouth trial aimed to investigate the effect of low-level laser therapy (LLLT) on the amount of maxillary canine distalization when applied every 4 weeks over 12 weeks. METHODS: Twenty-two adolescents and young adults (15 female, 7 male; aged 13-25 years; n = 22) requiring bilateral maxillary first premolar extractions were recruited. After extractions and leveling-alignment, canines were retracted using closed-coil nickel-titanium springs delivering 150 g of force. LLLT was applied to 8 intraoral points on the buccal and palatal sides around the canine root for 10 seconds per point, on day 0, 28, and 56 with the control side receiving sham application. Alginate impressions were taken every 4 weeks on day 0, 28, 56, and 84. The amount of tooth movement, anchorage loss, and canine rotation were measured digitally. Randomization was generated using www.randomisation.com and allocation concealment through sequentially numbered, opaque, sealed envelopes. Participants, operator, and statistic assessor were blinded. Linear regression modeling accounting for clustering within each patient was used to identify differences between LLLT and control sides. RESULTS: Twenty-one patients completed the study. The total amount of tooth movement was similar in the LLLT (2.55 ± 0.73 mm) and control group (2.30 ± 0.86 mm), whereas 0.25 mm (95% confidence interval, -0.21, 0.71 mm) of difference was insignificant (P = 0.27). No significant differences were found for anchorage loss (P = 0.22) or canine rotation (P = 0.25). No harms were reported. CONCLUSIONS: Application of LLLT every 4 weeks did not result in differences in the amount of tooth movement, anchorage loss, and canine rotation during extraction space closure.

What evidence exists for myofunctional therapy with prefabricated appliances? A systematic review with meta-analyses of randomised trials.

OBJECTIVE: To assess the treatment efficacy/efficiency with prefabricated myofunctional appliances (PMA) for children with malocclusion. DATA SOURCES: Nine databases searched without limitations till July 2019. DATA SELECTION: Randomised trials comparing PMAs to functional appliance treatment or no treatment. DATA EXTRACTION: Study selection, data extraction and risk of bias assessment were done in duplicate. DATA SYNTHESIS: Random-effects meta-analyses of mean differences (MDs) or relative risks (RRs) with their 95% confidence intervals (CIs) were conducted on seven publications (three published and one unpublished trials; 232 patients; 53% male; mean age 10.2 years). Compared to no treatment, one trial indicated that PMAs were somewhat effective in reducing overjet (MD -2.4; 95% CI -3.3 to -1.5), reducing overbite (MD -2.5; 95% CI -3.2 to -1.8), reducing mandibular crowding (RR 0.4; 95% CI 0.2-0.8) and establishing Class I canine relationship (RR = 2.3; 95% CI 1.1-4.9). However, compared to custom-made functional appliances, three trials indicated that PMAs were less effective in reducing the ANB angle (MD 0.9; 95% CI 0.5-1.4), increasing mandibular ramus length (MD -2.2; 95% CI -2.9 to -1.51), reducing overjet (MD 1.5; 95% CI 0.9-2.1), establishing a solid Class I molar relationship (RR 0.3; 95% CI 0.2-0.7), reducing the nasolabial angle (MD 5.8; 95% CI 0.8-10.8) and reducing facial convexity (MD -2.6; 95% CI -4.3 to -0.9). Finally, the quality of evidence was moderate to low due to risk of bias. CONCLUSIONS: PMAs are more effective in reducing overjet, overbite, mandibular crowding and establishing Class I canine relationship than no treatment. However, compared to custom-made functional appliances, PMAs are less effective in producing dental, skeletal or soft-tissue changes, even though they are less costly.

Interventions for orthodontically induced white spot lesions: a systematic review and meta-analysis.

Background: Although orthodontic white spot lesions (WSLs) are one of the most often and most evident adverse effects of comprehensive fixed appliance treatment, the efficacy of interventions for WSLs has not yet been adequately assessed in an evidence-based manner. Objective: Aim of this systematic review was to assess the therapeutic and adverse effects of interventions to treat post-orthodontic WSLs from randomized trials in human patients. Search methods: An unrestricted electronic search of eight databases from inception to May 2016. Selection criteria: Randomized controlled trials assessing any interventions for post-orthodontic WSLs on human patients. Data collection and analysis: After duplicate study selection, data extraction, and risk of bias assessment according to the Cochrane guidelines, random-effects meta-analyses of mean differences (MDs), standardized mean differences (SMDs), and odds ratios (ORs), including their 95% confidence intervals (CIs) were performed, followed by subgroup and sensitivity analyses. Results: A total of 20 unique studies and a total of 942 (42 per cent male and 58% per cent female) patients were included, with an average age of 16.2 years and a mean number of 8.2 WSLs (range 2.2 to 45.4) per patient. These were allocated to adjunct treatment with casein phosphopeptide-stabilized amorphous calcium phosphate creams, external tooth bleaching, low- or high-concentration fluoride films, gels, mouthrinses or varnishes, resin infiltration, miswak chewing sticks, bioactive glass toothpastse, or to no adjunct treatment (i.e. conventional oral hygiene). The monthly use of fluoride varnish was the best supplement to improve WSLs in terms of lesion area (1 trial; MD = -0.80 mm2; 95% CI = -1.10, -0.50 mm2; P < 0.05; high quality) and enamel fluorescence (3 trials; SMD = -0.92; 95% CI = -1.32, -0.52; P < 0.05; high quality), followed by the use of fluoride film. WSL treatment did not provide a considerable improvement in their clinical evaluation (3 trials; OR = 0.97; 95% CI = 0.60, 1.56; P > 0.05; moderate quality), with imprecision due to small sample size being the main limitation of existing evidence. Conclusions: Based on the existing trials, interventions for post-orthodontic WSLs, mainly fluoride varnish, seem to be effective, but further research is needed to elucidate their clinical relevance. Registration: PROSPERO (CRD42016037538).