Long-term stability of curve of Spee depth among orthodontically treated patients: A retrospective longitudinal study.

OBJECTIVE: The curve of Spee is deemed important characteristic of the dentition for a balanced occlusion and distribution of masticatory forces, while orthodontic levelling of an accentuated curve of Spee is generally included as a treatment goal for deepbite correction. However, relapse is often seen and can be problematic. METHODS: A retrospective longitudinal study of predominantly young patients with a deep curve of Spee, who had been treated orthodontically with 0.018"-slot Edgewise fixed appliances, was performed. The depth of the curve of Spee was digitally measured before treatment (T1), at debond (T2), and an average of 7 years post-debond (T3) and analysed statistically at 5%. RESULTS: A total of 157 patients were included (56.7% female; 11.6-year-old at T1), 16.6% of which were treated with premolars extractions. Non-extraction treatment reduced the curve of Spee at the first premolar from 1.87 mm (T1) to 0.22 mm (T2), which relapsed 0.12 mm (T3; P = .04). The respective depths for the second premolar were 2.0 mm (T1), reduced to 0.80 mm (T2). No significant relapse was seen for the second premolar (0.08 mm; P > .05) or the first permanent molar (0.06 mm; P > .05). No overall significant differences in absolute relapse were seen between extraction and non-extraction patients, but premolar extractions were associated with less clinically relevant relapse at the first molar (odds ratio 0.27; 95%-confidence interval 0.08-0.88; P = .003). CONCLUSION: Steep curves of Spee can be satisfactorily levelled orthodontically with satisfactory stability in the long term, while premolar extractions might be associated with less relapse.

Vertical effects of cervical headgear in growing patients with Class II malocclusion: a systematic review and meta-analysis.

BACKGROUND: Cervical headgear (cHG) has been shown to be effective in Class II correction both with dental and orthopaedic effects but has traditionally been associated with vertical adverse effects in terms of posterior mandibular rotation. OBJECTIVE: To assess the treatment effects of cHG treatment in the vertical dimension. SEARCH METHODS: Unrestricted literature search of five databases up to May 2023. SELECTION CRITERIA: Randomized/non-randomized clinical studies comparing cHG to untreated controls, high-pull headgear (hp-HG), cHG adjuncts, or other Class II treatment alternatives (functional appliances or distalisers). DATA COLLECTION AND ANALYSIS: After duplicate study selection, data extraction, and risk-of-bias assessment according to Cochrane, random-effects meta-analyses of mean differences (MD)/standardized mean diffences (SMD) and their 95% confidence intervals (CIs) were performed, followed by meta-regressions, sensitivity analyses, and assessment of certainty on existed evidence. RESULTS: Two randomized/16 non-randomized studies (12 retrospective/4 prospective) involving 1094 patients (mean age 10.9 years and 46% male) were included. Compared to natural growth, cHG treatment was not associated on average with increases in mandibular (eight studies; SMD 0.22; 95% CI -0.06, 0.49; P = 0.11) or maxillary plane angle (seven studies; SMD 0.81; 95% CI -0.34, 1.95; P=0.14). Observed changes translate to MDs of 0.48° (95% CI -0.13, 1.07°) and 1.22° (95% CI -0.51, 2.94°) in the SN-ML and SN-NL angles, respectively. No significant differences were seen in y-axis, facial axis angle, or posterior face height (P > 0.05). Similarly, no significant differences were found between cHG treatment and (i) addition of a lower utility arch, (ii) hp-HG treatment, and (iii) removable functional appliance treatment (P > 0.05 for all). Meta-regressions of patient age, sex, or duration and sensitivity analyses showed relative robustness, while our confidence in these estimates was low to very low due to the risk of bias, inconsistency, and imprecision. CONCLUSIONS: cHG on average is not consistently associated with posterior rotation of the jaws or a consistent increase in vertical facial dimensions among Class II patients. REGISTRATION: PROSPERO registration (CRD42022374603).

Effect of heat treatment and nitrogen atmosphere during post-curing on mechanical properties of 3D-printed orthodontic aligners.

OBJECTIVES: Three-dimensional (3D)-printed aligners present a promising orthodontic treatment modality, whose clinical success largely depends on the material's mechanical properties. The aim of this study was to evaluate the mechanical properties of resin-made 3D-printed aligners and assess the effect of two different post-curing conditions. MATERIALS AND METHODS: Forty dumbbell-shaped specimens and 40 resin aligners were 3D-printed and divided into four equal groups according to post-curing conditions: presence or absence of oxygen during post-curing and water heat treatment at 85°C for 15 s or none. Samples from the central incisor of the aligner (n = 5/group) were studied by Attenuated Total Reflection Fourier-transform infrared spectroscopy (ATR-FTIR). The dumbbell-shaped specimens were loaded up to fracture under tensile mode and yield strength, ultimate tensile strength, elastic and plastic strain were calculated. The first mandibular molar area from 3D-printed aligners (n = 10/group) was cut and embedded in acrylic resin and then underwent metallographic grinding and polishing followed by instrumented indentation testing to determine the following mechanical properties: Martens hardness, indentation modulus, elastic index, and indentation relaxation. After descriptive statistics, differences according to each post-curing protocol, as well as their combination, were analyzed with linear regression modeling at a 5% significance level. RESULTS: All groups showed identical ATR-FTIR spectra, while no statistically significant effects were seen for either post-curing protocol (N2 presence and heat treatment) or their combination (P > .05 in all instances). CONCLUSIONS: The mechanical properties of 3D-printed resin aligners were not considerably affected either by post-curing in N2 atmosphere or heat treatment.

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.

Pain profile during orthodontic levelling and alignment with fixed appliances reported in randomized trials: a systematic review with meta-analyses.

OBJECTIVE: To assess the pain profile of patients in the levelling/alignment phase of orthodontic treatment, as reported from randomized clinical trials. MATERIALS AND METHODS: Five databases were searched in September 2022 for randomized clinical trials assessing pain during levelling/alignment with a visual analogue scale (VAS). After duplicate study selection, data extraction, and risk-of-bias assessment, random effects meta-analyses of mean differences (MDs) and their 95% confidence intervals (CIs) were performed, followed by subgroup/meta-regression, and certainty analyses. RESULTS: A total of 37 randomized trials including 2277 patients (40.3% male; mean age 17.5 years) were identified. Data indicated quick pain initiation after insertion of orthodontic appliances (n = 6; average = 12.4 mm VAS), a quick increase to a peak at day 1 (n = 29; average = 42.4 mm), and gradually daily decrease the first week until its end (n = 23; average = 9.0 mm). Every second patient reported analgesic use at least once this week (n = 8; 54.5%), with peak analgesic use at 6 h post-insertion (n = 2; 62.3%). Patients reported reduced pain in the evening compared to morning (n = 3; MD = - 3.0 mm; 95%CI = - 5.3, - 0.6; P = 0.01) and increased pain during chewing (n = 2; MD = 19.2 mm; 95% CI = 7.9, 30.4; P < 0.001) or occlusion of the back teeth (n = 2; MD = 12.4 mm; 95% CI = 1.4, 23.4; P = 0.3), while non-consistent effects were seen for patient age, sex, irregularity, or analgesic use. Subgroup analyses indicated increased pain among extraction cases and during treatment of the lower (rather than the upper) arch, while certainty around estimates was moderate to high. CONCLUSIONS: Evidence indicated a specific pain profile during orthodontic levelling/alignment, without signs of consistent patient-related influencing factors.

Clinical implementation of axial angulation of incisors in the course of routine fixed appliance treatment - a retrospective cohort study.

PURPOSE: To identify clinically relevant factors for changes in axial angulation of incisors during routine fixed appliance orthodontic treatment. METHODS: A total of 106 patients (grades 1-2 of IOTN, 64 females, 42 males; mean age: 15.5 years) from a private practice and treated with metal or ceramic brackets were included in this retrospective cohort study. The axial angulation of the upper and lower incisors was measured on lateral cephalograms before insertion of the first rectangular 0.016 × 0.022-in NiTi archwire (T0) and at the end of treatment about 8 weeks after insertion of the working 0.019 × 0.025-in stainless steel archwire (T1). Treatment-related changes according to bracket type, initial situation, premolar extraction, angle class, and skeletal vertical configuration were analyzed. RESULTS: Although statistically significant treatment-related changes were seen for both the upper incisors (+ 1.3°) and the lower incisors (- 5.2°), only in ten patients (9.4%) was the prescribed torque value of 17° for the upper incisors and in no patient for the lower incisors achieved. A negative association between the induced change of axial angulation of incisors and the initial values was detected for the upper incisors as well as for the lower incisors. A comparison of the angle classes revealed significant differences in incisor changes. At the end of therapy, only a slight change for the upper central incisors in patients in angle class I cases and a significantly greater change in patients with angle class II/2 was observed. Cases with premolar extraction ended with lower axial angulation of the incisor than cases without extraction. The individual analysis of possible influencing factors also revealed an association with the vertical skeletal configuration. CONCLUSIONS: For the first time, the presented data show clinically relevant influencing factors for incisor axial angulation changes of the upper and lower incisors in relation to the torque value of the applied brackets in the course of routine clinical practice. For the orthodontist, it remains mandatory to decide whether a customized system must be individualized in order to achieve individual therapy goals.

Duration of canine retraction with fixed appliances: A systematic review and meta-analysis.

INTRODUCTION: Space closure is a challenging and time-consuming phase of orthodontic treatment with fixed appliances. This systematic review evaluated canine retraction duration using fixed appliances after maxillary first premolar extraction. METHODS: Unrestricted systematic literature searches were conducted in 8 databases for randomized clinical trials, assessing the duration and rate of maxillary canine retraction using fixed appliances with or without treatment adjuncts published up to July 2021. Study selection, data extraction, and risk of bias evaluation were conducted independently and in duplicate. Random-effects meta-analyses of average rates or mean differences (MD) and 95% confidence intervals (CI) were conducted at α = 5%, followed by sensitivity and Grading of Recommendations Assessment, Development, and Evaluation analysis. RESULTS: Fifty randomized clinical trials (6 parallel and 44 split-mouth designs) covering 811 participants (mean age 19.9 years; 34% male) were included. The estimated average pooled duration to achieve complete canine retraction was 4.98 months (2 trials; 95% CI, -2.9 to 12.88 months). Pooled average canine retraction was 0.97 mm at months 0-1 (23 trials; 95% CI, 0.79-1.16), 1.83 mm at months 0-2 (20 trials; 95% CI, 1.52-2.14), 2.44 mm at months 0-3 (23 trials; 95% CI, 2.10-2.79), 3.49 mm at months 0-4 (6 trials; 95% CI, 1.81-5.17) and 4.25 mm at months 0-5 (2 trials; 95% CI, 0.36-8.14). Surgically-assisted orthodontics was associated with greater canine retraction at all time points: months 0-1 (10 trials; MD, 0.52 mm; P = 0.004), months 0-2 (8 trials; MD, 0.53 mm; P = 0.04), months 0-3 (8 trials; MD, 0.67 mm; P = 0.01), and months 0-4 (3 trials; MD, 1.13 mm; P = 0.01), whereas subgroup analyses indicated significant effects of anchorage reinforcement method and bracket slot size on canine retraction. CONCLUSIONS: The average time to achieve complete retraction of the maxillary canine using fixed appliances was around 5.0 months. Most studies used split-mouth randomization to investigate canine retraction for around 1-3 months, with substantial heterogeneity across studies. At 3 months of treatment, high-quality evidence supported greater canine retraction with surgically-assisted orthodontics.

Palatal shape covariation in extraction versus nonextraction borderline patients: A geometric morphometric study.

INTRODUCTION: This study aimed to evaluate changes in palatal shape after orthodontic treatment from a borderline sample of extraction and nonextraction patients with a Class I relationship. METHODS: A borderline sample regarding premolar extractions was obtained through discriminant analysis and comprised 30 nonextraction and 23 extraction patients. The digital dental casts of these patients were digitized with 3 curves and 239 landmarks placed on the hard palate. Procrustes superimposition and principal component analysis were implemented to assess group shape variability patterns. RESULTS: The success of the discriminant analysis in identifying a borderline sample regarding the extraction modality was validated using geometric morphometrics. Concerning palatal shape, no sexual dimorphism was found (P = 0.78). The first 6 principal components that were statistically significant accounted for 79.2% of the total shape variance. Palatal changes were 61% more pronounced in the extraction group, which exhibited a decrease in palatal length (P = 0.02; 10,000 permutations). In contrast, the nonextraction group showed an increase in the palatal width (P <0.001; 10,000 permutations). Intergroup comparisons indicated that the nonextraction group exhibited longer palates, whereas the extraction group exhibited higher palates (P = 0.02; 10,000 permutations). CONCLUSIONS: Considerable changes in palatal shape were seen for the nonextraction and extraction treatment group, with the latter exhibiting more pronounced changes, mainly in terms of palatal length. Further investigations are needed to clarify the clinical significance of the palatal shape changes in borderline patients after extraction and nonextraction treatment.

Interventions to facilitate the successful eruption of impacted maxillary incisor teeth due to the presence of a supernumerary: A systematic review and meta-analysis.

INTRODUCTION: A failure of maxillary incisor eruption is commonly attributed to the presence of a supernumerary tooth. This systematic review aimed to assess the percentage of impacted maxillary incisors that successfully erupt after surgical removal of supernumerary teeth with or without other interventions. METHODS: Systematic literature searches without restrictions were undertaken in 8 databases for studies reporting any intervention aimed at facilitating incisor eruption, including surgical removal of the supernumerary alone or in conjunction with additional interventions published up to September 2022. After duplicate study selection, data extraction, and risk of bias assessment according to the risk of bias in nonrandomized studies of interventions and Newcastle-Ottawa scale, random-effects meta-analyses of aggregate data were conducted. RESULTS: Fifteen studies (14 retrospective and 1 prospective) were included with 1058 participants (68.9% male; mean age, 9.1 years). The pooled eruption prevalence for removal of the supernumerary tooth with space creation or removal of the supernumerary tooth with orthodontic traction was significantly higher at 82.4% (95% confidence interval [CI], 65.5-93.2) and 96.9% (95% CI, 83.8-99.9) respectively, compared with removal of an associated supernumerary only (57.6%; 95% CI, 47.8-67.0). The odds of successful eruption of an impacted maxillary incisor after removal of a supernumerary were more favorable if the obstruction was removed in the deciduous dentition (odds ratio [OR], 0.42; 95% CI, 0.20-0.90; P = 0.02); if the supernumeraries were conical (OR, 2.91; 95% CI, 1.98-4.28; P <0.001); if the incisor was in the correct position (OR, 2.19; 95% CI, 1.14-4.20; P = 0.02), at the level of the gingival third (OR 0.07; 95% CI, <0.01-0.97; P = 0.04) and had incomplete root formation (OR, 9.02; 95% CI, 2.04-39.78; P = 0.004). Delaying removal of the supernumerary tooth 12 months after the expected eruption time of the maxillary incisor (OR, 0.33; 95% CI, 0.10-1.03; P = 0.05) and waiting >6 months for spontaneous eruption after removal of the obstacle (OR, 0.13; 95% CI, 0.03-0.50; P = 0.003) was associated with worse odds for eruption. CONCLUSIONS: Limited evidence indicated that the adjunctive use of orthodontic measures and removal of supernumerary teeth might be associated with greater odds of successfull impacted incisor eruption than removal of the supernumerary tooth alone. Certain characteristics related to supernumerary type and the position or developmental stage of the incisor may also influence successful eruption after removal of the supernumerary. However, these findings should be viewed with caution as our certainty is very low to low because of bias and heterogeneity. Further well-conducted and reported studies are required. The results of this systematic review have been used to inform and justify the iMAC Trial.

Manual and mechanical stripping-induced enamel roughness and elemental composition in vivo.

OBJECTIVES: Interproximal enamel reduction (IPR) is routinely used in orthodontics to generate small to moderate amounts of space within the dental arch. Aim of this ex vivo study was to evaluate the effect of two different IPR systems on the enamel surface's waviness, roughness, and elemental composition after 6 months of intraoral exposure. MATERIALS AND METHODS: Fifteen orthodontic extraction patients were included in the present study. The 39 healthy premolars, which were scheduled to be extracted, were subjected to IPR at least 6 months before their extraction. IPR was performed on their mesial side with two different methods: (1) instrumented method with the Ortho-Strips system (on handpiece) and (2) manually with the Intensiv ProxoStrip (strips)-each with four different grits for contouring, finishing, and polishing. The distal side of each premolar served as its own internal control. Treated and untreated tooth surfaces were evaluated by optical profilometry, Raman, and scanning electron microscope/X-ray energy-dispersive (EDX) analyses. Data were analysed with descriptive statistics and generalized linear models at alpha = 5%. RESULTS: Both IPR methods significantly reduced the waviness of the enamel surface (P < 0.001), with manual IPR leading to smaller waviness reductions than the instrumented IPR (P ≤ 0.001). On the other side, both IPR methods led to a significant increase in enamel surface roughness (P < 0.001), with no significant differences between IPR methods. EDX and Raman analyses did not demonstrate any alterations on elemental composition of enamel after at least 6 months of intraoral exposure. CONCLUSIONS: Both stripping systems led to a flatter but rougher enamel surface. Further polishing is needed to restore the initial enamel smoothness. The elemental composition of the stripped enamel returns to the baseline level after 6 months of intraoral exposure.

Effects of chlorhexidine use on periodontal health during fixed appliance orthodontic treatment: a systematic review and meta-analysis.

BACKGROUND: Proper oral hygiene and absence of periodontal inflammation is pre-requisite for orthodontic treatment. Chlorhexidine (CHX) is an established oral antiseptic used in the treatment of periodontal disease, but its role in orthodontic therapy is unclear. OBJECTIVES: To assess the efficacy of adjunct use of CHX-containing products in maintaining gingival health among orthodontic patients with fixed appliances. SEARCH METHODS: Five databases were searched without limitations up to August 2021. SELECTION CRITERIA: Randomized clinical trials (RCTs) assessing Gingival Index (GI) (primary outcome), Plaque Index (PI), Bleeding Index (BI), or Pocket Probing Depth (PPD). DATA COLLECTION AND ANALYSIS: Study selection, data extraction, and risk of bias assessment were done independently in duplicate. Random-effects meta-analyses of mean differences (MDs) or standardized mean differences (SMDs) with their 95% confidence intervals (CIs) were conducted, followed by sensitivity and Grades of Recommendations, Assessment, Development and Evaluation analysis. RESULTS: Twenty RCTs (1001 patients) were included assessing CHX-containing mouthwashes (n = 11), toothpastes (n = 2), gels (n = 3), or varnishes (n = 4) compared to placebo/control (n = 19) or sodium fluoride-products (n = 4). In the short-term, CHX-containing mouthwash was associated with lower GI (n = 9; MD = -0.68; 95% CI = -0.97 to -0.38; P < 0.001; high quality), lower PI (n = 9; MD = -0.65; 95% CI = -0.86 to -0.43; P < 0.001; high quality), lower BI (n = 2; SMD = -1.61; 95% CI = -2.99 to -0.22; P = 0.02; low quality), and lower PPD (n = 2; MD = -0.60 mm; 95% CI = -1.06 to -0.14 mm; P = 0.01; low quality). No considerable benefits were found from the use of CHX-gel or CHX-varnish in terms of GI, PI, or PPD (P > 0.05/low quality in all instances). Use of a CHX-containing toothpaste was more effective in lowering PI (Heintze-index) than adjunct use of fluoride-containing mouthwash (n = 2; MD = -5.24; 95% CI = -10.46 to -0.02; P = 0.04), but not GI (P = 0.68) or BI (P = 0.27), while sensitivity analyses indicated robustness. CONCLUSIONS: Adjunct use of CHX mouthwash during fixed-appliance treatment is associated with improved gingival inflammation, plaque control, and pocket depths, but caution is warranted and recommendations about CHX use during orthodontic treatment of children/adults should consider the heterogeneous patient response, cost-effectiveness, and potential adverse effects. REGISTRATION: PROSPERO registration (CRD42021228759).

Periodontal outcomes associated with impacted maxillary central incisor and canine teeth following surgical exposure and orthodontic alignment: a systematic review and meta-analysis.

BACKGROUND: Maxillary incisor and canine teeth are commonly impacted and require multidisciplinary treatment to accommodate them in the dental arch. OBJECTIVES: To assess the periodontal outcomes of impacted maxillary central incisor and canine teeth, which have been successfully aligned in the arch following surgical exposure and orthodontic traction with fixed appliance therapy. SEARCH METHODS: Systematic literature searches without restrictions were undertaken in eight databases. SELECTION CRITERIA: Studies reporting surgical interventions in combination with orthodontic traction with fixed appliance therapy to align impacted maxillary incisors or canines published up to January 2023. DATA COLLECTION: Duplicate independent study selection, data extraction, and risk of bias assessment. ANALYSIS: Random-effects meta-analyses of aggregate data. RESULTS: Twenty-three studies (21 retrospective and 2 prospective) were included in the final analysis. Three studies reported outcomes for maxillary central incisors and 20 reported outcomes for maxillary canines. For maxillary central incisors, all three studies were rated as being at moderate risk of bias. For maxillary canines, 17 studies and 1 study were rated at moderate and high risk of bias, respectively. Both prospective studies were rated at a low risk of bias. Meta-analyses comparing aligned impacted maxillary canines to their non-impacted contralateral counterparts found the former had increased Plaque Index scores (mean difference [MD] 0.19; 95% confidence interval [CI] 0.03, 0.35; P = 0.03), increased clinical attachment loss (MD 0.40 mm; 95% CI 0.17, 0.63; P = 0.01), increased pocket probing depth (MD 0.18 mm; 95% CI 0.07, 0.28; P = 0.001), increased bone loss (MD 0.51 mm; 95% CI 0.31, 0.72; P < 0.001), and reduced keratinized gingival width (MD -0.31 mm; 95% CI -0.61, -0.01; P = 0.04). CONCLUSIONS: Limited evidence suggests that surgical exposure and orthodontic alignment of impacted maxillary central incisor or canine teeth, results in modest adverse effects in the periodontium. These findings should be viewed with caution as our certainty for these outcomes is very low to low due to the bias and heterogeneity. Further well-conducted studies reporting patient centred outcomes are required. REGISTRATION: PROSPERO (CRD42020225639).

Molar-incisor hypomineralisation: Knowledge and perception of Syrian undergraduate and postgraduate dental students.

INTRODUCTION: Dentists' knowledge and expertise, especially in their early career, are primarily shaped during undergraduate studies. This cross-sectional study aimed to assess the knowledge and perception of Syrian under- and postgraduate students regarding diagnosing and managing molar-incisor hypomineralisation (MIH)-affected teeth. MATERIALS AND METHODS: Final-year dental students (FY-students), postgraduates in paediatric dentistry (PD-postgraduates) and postgraduates in other lines of specialty (OS-postgraduates) in all Syrian dental schools were invited to participate in an established web-based survey covering the knowledge and attitudes regarding the prevalence, aetiology, diagnosis and management of MIH. Data were analysed with descriptive statistics and Fisher's exact/chi-squared tests at 5%. RESULTS: In total, 1142 post- and undergraduate students from six public and five private dental schools in Syria participated in this study (867 FY-students, 74 PD-postgraduates and 201 OS-postgraduates). PD-postgraduates were found to present statistically significantly better knowledge regarding MIH compared with the two other groups. Only 19% of FY-students and 54% of OS-postgraduates reported themselves familiar with MIH (compared with 97% of PD-postgraduates). Similarly, 18% of FY-students and 27% of OS-postgraduates were capable of diagnosing MIH (compared with 81% of PD-postgraduates). Stainless-steel crowns and direct composite fillings were chosen as most suitable for treating MIH-affected molars from all responders. CONCLUSIONS: FY-students and even OS-postgraduates in Syria lack knowledge and confidence when confronted with MIH. The university curricula need to include more educational materials to equip the students with the necessary tools to manage MIH clinically.

Effect of periodontal-orthodontic treatment of teeth with pathological tooth flaring, drifting, and elongation in patients with severe periodontitis: A systematic review with meta-analysis.

AIM: To assess the beneficial and adverse effects on the dental and periodontal issues of periodontal-orthodontic treatment of teeth with pathological tooth flaring, drifting, and elongation in patients with severe periodontitis. MATERIALS AND METHODS: Nine databases were searched in April 2020 for randomized/non-randomized clinical studies. After duplicate study selection, data extraction, and risk-of-bias assessment, random-effect meta-analyses of mean differences (MDs) and their 95% confidence intervals (CIs) were performed, followed by subgroup/meta-regression analyses. RESULTS: A total of 30 randomized and non-randomized clinical studies including 914 patients (29.7% male; mean age 43.4 years) were identified. Orthodontic treatment of pathologically migrated teeth was associated with clinical attachment gain (-0.24 mm; seven studies), pocket probing depth reduction (-0.23 mm; seven studies), marginal bone gain (-0.36 mm; seven studies), and papilla height gain (-1.42 mm; two studies) without considerable adverse effects, while patient sex, gingival phenotype, baseline disease severity, interval between periodontal and orthodontic treatment, and orthodontic treatment duration affected the results. Greater marginal bone level gains were seen by additional circumferential fiberotomy (two studies; MD = -0.98 mm; 95% CI = -1.87 to -0.10 mm; p = .03), but the quality of evidence was low. CONCLUSIONS: Limited evidence of poor quality indicates that orthodontic treatment might be associated with small improvements of periodontal parameters, which do not seem to affect prognosis, but more research is needed.

The influence of thin as compared to thick peri-implant soft tissues on aesthetic outcomes: A systematic review and meta-analysis.

OBJECTIVES: In systematically healthy patients with an implant-supported fixed restoration (P), what is the influence of thin (E) as compared to thick (C) peri-implant soft tissues on aesthetic outcomes (O)? METHODS: Following an a priori protocol, a literature search of six databases was conducted up to August 2020 to identify prospective/retrospective clinical studies on healthy patients with an implant-supported fixed reconstruction. Measurement of the buccal soft tissue thickness and an aesthetic outcome was a prerequisite, and sites presenting with a buccal soft tissue thickness of <2 mm or shimmering of a periodontal probe were categorized as a thin phenotype. After study selection, data extraction, and risk of bias assessment, random-effects meta-analysis of Mean Differences (MD) or Odds Ratios (OR) with their corresponding 95% Confidence Intervals (CI) were conducted, followed by sensitivity analyses and assessment of the quality of evidence. RESULTS: Thirty-four unique studies reporting on 1508 patients with 1606 sites were included (9 randomized controlled trials, one controlled trial, 10 prospective cohort studies, 8 cross-sectional studies, and 6 retrospective cohort studies). The mean difference of the pink aesthetic score (PES) after the follow-up was not significantly different between thin (<2.0 mm) or thick soft tissues (≥2.0 mm) or phenotypes (12 studies; MD = 0.15; [95% CI = -0.24, 0.53]; p = .46). PES changes during the follow-up, however, were significantly in favour of thick soft tissues (≥2.0 mm) or phenotypes (p = .05). An increased mean mucosal thickness was associated with an increased papilla index (5 studies; MD = 0.5; [95% CI = 0.1, 0.3]; p = .002) and an increase in papilla presence (5 studies; OR = 1.6; [95% CI = 1.0, 2.3]; p = .03). Thin soft tissues were associated with more recession, -0.62 mm (4 studies; [95% CI = -1.06, -0.18]; p = .006). Patient-reported outcome measures (patient satisfaction) were in favour of thick soft tissues -2.33 (6 studies; [95% CI = -4.70, 0.04]; p = .05). However, the quality of evidence was very low in all instances due to the inclusion of non-randomized studies, high risk of bias and residual confounding. CONCLUSION: Within the limitations of the present study (weak study designs and various soft tissue measurements or time-points), it can be concluded that increased soft tissue thickness at implant sites was associated with more favourable aesthetic outcomes.

Interproximal contact loss at implant sites: a retrospective clinical study with a 10-year follow-up.

AIM: To assess the frequency and quantity of interproximal contact loss (ICL) between implant restorations and adjacent teeth after at least 10 years of follow-up (FU). METHODS: Thirty-nine patients (median age 57.3 years) with 80 implants were re-examined at least 10 years after insertion of final restorations (single crowns or fixed dental prostheses (FDPs)). Baseline (insertion of the restorations) and FU examinations encompassed the following: Stone casts were scanned and superimposed for metric assessment of tooth movements, radiographs, and clinical measurements. Outcome measures at implant sites were as follows: the extent of tooth movement and the frequency of interproximal contact loss [ICL], peri-implant marginal bone levels [MBLs], and clinical measurements (plaque control record [PCR], Bleeding on Probing [BOP], and probing depth [PD]). Data were analyzed statistically with generalized regression modeling with robust standard errors to account for within-patient clustering at 5%. RESULTS: Interproximal contact loss for at least one contact point after 10 years was observed in 50% of all implants (with open interproximal spaces up to 1.64 mm). Mesial contact points were significantly more prone to ICL than distal ones (relative risk [RR] = 1.79; 95% confidence interval [CI] = 1.07-2.99; p = .03). The type of restoration had a significant effect on ICL, with FDPs of 2 implants being significantly more prone to mesial ICL than single crowns (RR = 1.52; 95% CI = 1.02-2.25; p = .04). ICL was also associated with a significant increase in PD (+0.46 mm (95% CI = 0.04-0.88 mm; p = .03)) compared to implant sites without ICL. BOP, MBLs, and PCR were not significantly influenced by ICL. CONCLUSION: Interproximal contact loss was a common finding in 50% of the implant sites and was significantly associated with an increase in PD.

Comparative analysis of mechanical properties of orthodontic aligners produced by different contemporary 3D printers.

OBJECTIVE: The aim of this study was to compare the mechanical properties of orthodontic aligners among different commercially available 3D printing devices. MATERIALS AND METHODS: Five 3D printers (Ka:rv LP 550, Swinwon; "KAR"), (L120, Dazz 3D; "L12"), (MiiCraft 125, Miicraft Jena; "MIC"), (Slash 2, Uniz; "SLS") and (Pro 95, SprintRay; "PRO") were used to prepare orthodontic aligners with dental resin (Tera Harz TC-85DAW, Graphy). The central incisors of each aligner were cut, prepared and evaluated in terms of Martens-Hardness (HM), indentation-modulus (EIT ) and elastic-index (ηIT ) as per ISO14577-1:2002. Force-indentation curves were recorded and differences among printers were checked with generalized linear regressions (alpha=5%). RESULTS: Statistically significant differences were seen for all mechanical properties (P < .05), which were in descending order: HM (N/mm2 ) as median (Interquartile Range [IQR]): SLS 108.5 (106.0-112.0), L12 103.0 (102.0-107.0), KAR 101.5 (97.5-103.0), MIC 100.0 (97.5-101.5) and PRO 94.0 (93.0-96.0); EIT (MPa) as mean (Standard Deviation [SD]): SLS 2696.3 (124.7), L12 2627.8 (73.5), MIC 2566.2 (125.1), KAR 2565.0 (130.2) and PRO 2491.2 (53.3); and ηIT (%) as median (IQR): SLS 32.8 (32.3-33.1), L12 31.6 (30.8-32.3), KAR 31.3 (30.9-31.9), MIC 30.5 (29.9-31.2) and PRO 29.5 (29.1-30.0). Additionally, significant differences existed between liquid crystal display (LCD) and digital light processing (DLP) printers for HM (P < .001), EIT (P = .002) and ηIT (P < .001), with aligners from the former having higher values than aligners from the latter printer. CONCLUSION: Under the limitations of this study, it may be concluded that the mechanical properties of 3D-printed orthodontic aligners are dependent on the 3D printer used, and thus, differences in their clinical efficacy are anticipated.

Prolific authorship in orthodontic scientific publishing.

OBJECTIVES: To identify the 10 most numerically prolific authors publishing in the field of orthodontics for each year over the last decade (2011-2020), describe the characteristics of these outputs and identify trends in the types of study being published. MATERIALS AND METHODS: A Scopus literature search was conducted to identify the 10 most numerically prolific publishing authors in orthodontics for each year during this decade. Number and characteristics of all publications for each author were analysed with descriptive and inferential statistics. RESULTS: Forty-nine different individual authors were identified who were collectively prolific for between 1-8 years within the assessment decade. These authors published a total of 2025 papers, with a median annual output of 18 papers per year; however, half of these authors published between 15-24 papers per year (range 5-200). Amongst authors, 2 or more collaborated on only 7% of the identified papers. The median number of authors per paper was 5 (range 1-27) with significant variation according to study design (P < .001). The majority of authors originated from Brazil (19.3%), Italy (14.1%) and India (12.7%). Most papers described non-prospective clinical studies (38.1%), case reports or case series (11.1%) and narrative reviews (10.8%). Finally, prolific authors had a smaller annual output when publishing in orthodontic journals (P < .001) and when publishing experimental primary research (P = .04). CONCLUSIONS: A cohort of prolific authors in orthodontics between 2011-2020 was identified. Extreme variation was found in annual output between these authors but case reports, non-prospective clinical studies and narrative reviews predominated.

Cytotoxicity and estrogenicity of a novel 3-dimensional printed orthodontic aligner.

INTRODUCTION: Orthodontic aligners printed with in-office 3-dimensional (3D) procedures have been described, but no data on their biocompatibility exist. This study investigates the cytotoxicity and estrogenicity of a 3D-printed orthodontic aligner by assessing its biological and behavioral effects. METHODS: Ten sets of 1 type of aligner were immersed in sterile deionized water for 14 days, and the cytotoxicity and estrogenicity of released factors were assessed via MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assays on human gingival fibroblasts and the estrogen-sensitive MCF-7 and the estrogen-insensitive MDA-MB-231 breast cancer cell lines. 17ß-Estradiol and bisphenol-A were used as positive controls. The statistical analysis of data was performed with generalized linear models at a 0.05 level of significance. RESULTS: No signs of cytotoxicity were seen for the aligner samples for concentrations (v/v) of 20% (P = 0.32), 10% (P = 0.79), or 5% (P = 0.76). The antioxidant activity expressed as the capacity to reduce intracellular levels of reactive oxygen species was not affected in the aligner samples (P = 0.08). No significant estrogenicity was induced by the aligner samples compared with eluents from the negative control for both MCF-7 (P = 0.65) and MDA-MB-231 (P = 0.78). As expected, 17ß-Estradiol and bisphenol-A stimulated MCF-7 cell proliferation, whereas no effect was observed on MDA-MB-231 cells. CONCLUSIONS: In conclusion, if any factors were released during the 14-day aging of 3D-printed aligners in water, these were not found to be cytotoxic for human gingival fibroblasts and did not affect their intracellular reactive oxygen species levels. Moreover, no estrogenic effects of these putative eluates were observed based on an E-screen assay.

Duration of tooth alignment with fixed appliances: A systematic review and meta-analysis.

INTRODUCTION: A key goal of orthodontic treatment with fixed appliances is alignment of the dentition, and this remains a commonly selected outcome in clinical studies investigating orthodontic tooth movement. This systematic review has evaluated treatment duration to achieve alignment of the mandibular dentition using fixed appliances. METHODS: Systematic literature searches without restrictions were undertaken in 9 databases for randomized clinical trials (RCTs) assessing duration and rate of tooth alignment using fixed appliances with or without treatment adjuncts published up to January 2021. After duplicate study selection, data extraction, and risk of bias assessment according to Cochrane, random-effects meta-analyses of aggregate data, and individual patient data were conducted. RESULTS: Thirty-five trials were included with 2258 participants (39% male; mean age 17.8 years), giving a pooled duration to achieve whole-arch alignment of the mandibular dentition of 263.0 days (4 trials; 95% confidence interval [CI], 186.7-339.4 days) and incisor alignment in the mandibular arch of 100.7 days (9 trials; 95% CI, 84.1-117.4 days). Surgical-assisted orthodontics was associated with reduced duration of incisor alignment: mean difference of 44.3 days less (4 trials; 95% CI, 20.0-68.9 days; P <0.001; high quality of evidence), whereas subgroup and meta-regression analyses indicated significant effects of baseline crowding and premolar extractions. Individual patient data analysis from 3 RCTs indicated that for each additional participant age year, whole-arch alignment of the mandibular dentition took 13.7 days longer (3 trials; 95% CI, 7.7-17.7 days; P <0.001) and for each additional mm of irregularity, 17.5 days more were needed (2 trials; 95% CI, 9.8-25.2 days; P <0.001). CONCLUSIONS: Patient and treatment-related characteristics can significantly affect the duration of tooth alignment and should be taken into account both clinically and when designing trial outcomes. Future research studies investigating rates of orthodontic tooth alignment would benefit from adequate sample sizes and a more consistent methodology in outcome assessment. Data in this systematic review provides a basis for appropriate trial design for future RCTs investigating the rate of orthodontic tooth alignment with fixed appliances.