Journal of Orofacial Orthopedics-Fortschritte Der Kieferorthopadie最新文献

Purpose: This study aimed to investigate the association between skeletal malocclusions and dental maturity in a German population.

Methods: A retrospective cross-sectional study was conducted with 542 patients (274 males, 268 females) aged 6-16 years from Germany. Skeletal sagittal malocclusions were classified as class I, II, or III according to the ANB, and vertical growth patterns of the mandible were determined using the Articulare-Gonion-Menton angle. Dental maturity was estimated using the Demirjian method on panoramic radiographs, and the deviation between dental age and chronological age (delta) was calculated.

Results: Among the sample, 43.9% presented skeletal class I, 41.5% class II, and 14.6% class III malocclusions. In our study population, mandibular vertical growth patterns were distributed as 53.5% normodivergent, 43.4% hyperdivergent (vertical), and 3.1% hypodivergent (horizontal). The mean chronological age was 11.6 years, while the mean dental age was 11.7 years, with an average delta of 0.08 (standard deviation = 1.2) years. No significant correlations were found between dental age deviation and the chosen cephalometric variables (p > 0.05). No significant associations were found between dental age deviation and sagittal and vertical malocclusions (p > 0.05).

Conclusion: Skeletal malocclusions were not associated with deviations in dental maturity in this German sample. These findings indicate that dental development occurs independently of skeletal discrepancies, supporting the reliability of the Demirjian method across clinical and research contexts.

Purpose: This study aimed to compare the distorotation of the upper first molars (U6) and the expansion of the upper dental arch achieved using clear aligners (CA), Leaf Expander® (LE; Leone, Sesto Fiorentino, Italy), and rapid maxillary expander (RME), all anchored to the second primary molars.

Materials and methods: The research was structured as a superiority randomized controlled trial conducted in two academic medical centers in Italy. Participants included children in growth phase presenting transverse maxillary deficiency with intermolar width less than 30 mm, early mixed dentition with fully erupted upper first molars, and a cervical vertebral maturation stage (CVMS) 1 or 2, without systemic diseases or syndromes. Subjects were randomly assigned to one of the three treatment groups: CA, LE, or RME. The main variable measured was the distorotation of U6, with secondary variables including the width between canines, first molars, and second primary molars.

Results: In all, 60 subjects were randomized equally into the three groups. Average treatment time was 8 ± 3 months for the LE group and 9 ± 1 months for the RME group (p = 0.089). Mean treatment time for the CA group was 15 months with a standard deviation of 2 months. A significant difference was observed in the number of clinical visits: 6 ± 2 for LE and 8 ± 1 for RME (p < 0.001). The RME group completed the active treatment phase in 10 ± 2 days, which was notably shorter than the 3.5 ± 0.71 months required for the LE group (p < 0.001). Analysis of variance (ANOVA) revealed statistically significant differences among the groups in terms of U6 distorotation (p < 0.05), whereas no significant differences were found for the expansion of the upper arch. Overall molar distorotation was highest in the LE group (11.73°), surpassing the RME group (6.22°), and was similar to the result observed in the CA group (11.89°).

Conclusion: Both CA and maxillary expanders fixed to upper primary molars produced comparable levels of dentoalveolar expansion. The spontaneous distorotation of the U6 obtained with LE was similar to the planned distorotation achieved with CA and significantly higher than that observed with RME.

Purpose: We explored the association between the 6‑n-propylthiouracil (PROP) taste phenotypes and the incidence and severity of initial caries lesions (ICL) during fixed orthodontic treatment.

Methods: The participants were a prospective cohort of 44 fixed orthodontic patients (16 males, 28 females, 18.7 ± 5.5 years) classified as non-tasters (n = 19) and tasters (n = 25) based on their bitter taste perception of PROP. The primary outcome was the cumulative incidence (C_in) of ICL at the facial surfaces of the anterior teeth and premolars at 1, 3, 6, 9 and 12 months in treatment. The severity of ICL (Enamel Decalcification Index, EDI) was the secondary outcome. Baseline age, sex, caries status, dietary habits, oral hygiene practice, type of treatment (non-extraction/extraction), oral hygiene, and salivary flow during treatment were the confounders/covariates explored.

Results: Non-tasters had a higher relative risk (RR) of a tooth developing ICL than tasters at 9 months (C_in = 8.6 vs 0.6%, RR = 13.4 [4.1-43.7]), and 1 year (C_in = 18 vs 7.2%, RR = 2.5 [4.1-43.7]) in univariate analysis. The EDI scores were marginally higher in non-tasters than in tasters at 6, 9, and 12 months, although the differences were not clinically significant. In the generalized linear models, the teeth in non-tasters had higher odds of developing ICL (OR = 2.8 [1.2-6.3]) than tasters, but the effect on its severity was only modest (b = 0.04).

Conclusion: The results suggest a possible role of the individual's taste phenotype in the development and severity of ICL during fixed orthodontic treatment.

Purpose: To assess the effects of attachment design and location on derotation of mandibular second premolars through the finite element method.

Materials and methods: A mandibular model consisting of teeth, periodontal ligament (PDL), trabecular/compact bones, attachment, and clear aligner was created. Tooth 35 was positioned with 30° mesial rotation. Seven treatment scenarios were planned to analyze the derotation movement, i.e., Model 1: no attachment; Model 2: buccal vertical rectangular attachment (VRA); Model 3: buccal beveled VRA (bVRA); Model 4: lingual VRA: Model 5: lingual bVRA; Model 6: buccal and lingual VRAs; and Model 7: buccal and lingual bVRAs. Derotation activation was 1.2° for each aligner. Tooth displacement, aligner deformation, and stresses produced in the PDL and the aligner were analyzed.

Results: The highest value for tooth displacement (0.087 mm, 0.51°) was detected in Model 7, while Model 1 exhibited the lowest value (0.067 mm, 0.39°). Model 7 created the least deformation of the clear aligner (0.469 mm) and the highest stresses in the PDL (6.780 MPa) and the clear aligner (101.258 MPa), whereas Model 1 induced the highest deformation of the clear aligner (0.523 mm) and the lowest stresses in the PDL (6.253 MPa) and the clear aligner (62.667 MPa). Greater derotations were observed in models with bVRA than in those with VRA in the same placement and in models with attachments on both surfaces than in those with attachment on one surface.

Conclusion: bVRAs placed on both the buccal and lingual surfaces provided the most controlled and predictable derotation movement. Aligner deformation and stresses produced in the PDL and the clear aligner showed biomechanical harmony with the movement.

Objective: To evaluate the in vivo accuracy of guided palatal miniscrew insertion, focusing on the effect of insertion side, frontal insertion angle, and miniscrew length.

Materials and methods: In all, 52 palatal miniscrews were inserted using computer-aided design/computer-aided manufacturing (CAD/CAM) surgical guides in 20 patients (average age: 19.74 years ± 6.83). Digital models were acquired after miniscrew insertion and scanbody application. Then, linear and angular discrepancies between planned and realized miniscrew positions were evaluated by superimposing the reference model with the final postinsertion model. Discrepancies are recorded and compared to absolute precision (hypothetical). The effect of side, frontal insertion angle, and miniscrew length on accuracy were investigated.

Results: Mean linear total discrepancies were 1.10 ± 1.01 mm and 1.71 ± 1.10 mm at the miniscrew head and tip points, respectively. Mean angular discrepancies were 5.90 ± 6.06° in the transverse (XY), 2.65 ± 2.47° in the sagittal (YZ), and 3.02 ± 2.65° in the coronal (XZ) plane. All discrepancies were significantly different to absolute precision (p < 0.001), although not to an extent considered clinically relevant. Neither side nor frontal insertion angle (clinical factors), or miniscrew length (structural factor) significantly impacted accuracy.

Conclusion: CAD/CAM surgical guides ensured clinically acceptable accuracy despite significant deviations from absolute precision. The insertion side, frontal insertion angle, and miniscrew length had minimal influence on accuracy, and therefore on outcome. Further studies should explore the effects of additional clinical, procedural, anatomical, and structural variables.

Purpose: Complications of bonded lingual retainers in terms of unexpected tooth movements have been reported with increasing frequency during the last decade, but the vast majority of the literature comprises case reports. The purpose of the present retrospective case-control study was to analyze the amount and direction of unwanted tooth movements despite lower bonded retainers, to analyze possible predisposing pretreatment- and treatment-related factors, and to seek for movement thresholds which could enhance the rapid and objective identification of critical cases.

Methods: Plaster casts of 1026 patients who completed orthodontic treatment and a subsequent retention phase of 2 years were screened for unintentional tooth movements. The study group comprised 39 patients with tooth movements in the lower jaw, while 39 randomly selected patients without visible tooth movements served as the control group. For all patients, plaster casts after debonding of multibracket appliances (T1) and after supervised retention (T2) were digitized, and a three-dimensional (3D) digital superimposition based on the best fit of premolars and molars was undertaken. Thereafter, translational as well as rotational movements were measured in all three planes of space. Pretreatment- and treatment-related factors of the study and control groups were compared. A severity classification based on rotational movement thresholds was applied to seek a critical amount of translational movements.

Results: The mean translational movements ranged between 0 and 0.4 mm and the average rotational movements between 0 and 1.6°. Large individual movements up to 1.9 mm translation and 16° rotation were seen. A twist-effect with opposite movements of the canines along the Y‑axis could be confirmed. Compared to the control group, patients of the study group had a smaller intercanine distance at all timepoints. In addition, study group patients presented a slightly larger intercanine expansion during treatment and were more often affected by retainer bonding site detachments. Applying the severity classification based on rotational thresholds, translational movements of 0.5-1.0 mm along the X‑ and Y‑axis could serve as a critical threshold. It can be assumed that extrusive translational movements along the Z‑axis seem to be of specific nature and perhaps do not reflect a retainer complication in terms of unwanted tooth movements.

Conclusions: Patients with a larger intercanine distance after active treatment and those with more frequent retainer bonding site detachments could be at higher risk for unwanted tooth movements during fixed retention. Sagittal and transverse movements of 0.5-1.0 mm should sensitize the practitioner for further measures.

Purpose: Advancements in computer-aided design and manufacturing (CAD/CAM), such as intraoral scanners, digital treatment planning, and 3D printers, offer digital alternatives to conventional orthodontics. For transforming digital data into a traditional model, precise 3D printing technologies are necessary. With numerous settings available on each 3D printer, selecting the most precise one is challenging. Therefore, the impact of layer height, printing temperature, print speed, and infill density on the accuracy of dental models was analyzed in this study.

Methods: A 3D file of a right upper central incisor was designed and printed 275 times in total with different settings for temperature, layer height, print speed, and infill density by using polylactic acid (PLA) filament on an industrial 3D printer. After scanning the models, root mean square error was calculated for analysis of precision. For each group, R² value was calculated and linear regression as well as an ANOVA was performed for the factors influencing accuracy.

Results: Printing temperature as well as layer height had statistically significant impacts on printing 3D tooth models (p < 0.05). R² values of 0.43 for printing temperature as well as of 0.11 for layer height were detected. The infill density as well as the print speed had no statistically significant impacts on accuracy (p > 0.05).

Conclusion: This study confirms that choosing the correct printing temperature and layer height for printing dental models with PLA is important for obtaining good accuracy, whereas print speed and infill density have less of an impact.

Purpose: This study aimed to evaluate the effects of the use of class III elastics with fixed appliances and the Alt-RAMEC procedure on dentofacial structures in patients diagnosed with skeletal class III malocclusion.

Methods: The retrospective cohort study was performed on lateral cephalometric radiographs of 20 individuals (7 girls, 13 boys; mean chronological age 12.41 years) with skeletal class III malocclusion because of maxillary deficiency or maxillary deficiency and mandibular excess which were treated by using the Alt-RAMEC protocol and class III elastics. The patients were chosen from the archive of Gazi University Faculty of Dentistry, Department of Orthodontics. In order to distinguish between growth-related changes and the effects of treatment, results were compared with a control group consisting of 20 individuals (8 girls, 12 boys; mean chronological age 12 years) with similar skeletal characteristics.

Results: In the treatment group, there were significant increases of 2.2°, 4.2° and 1° in the SNA, ANB and SN/GoGN angles, respectively, in contrast to the control group (p < 0.001). There was also a significant decrease of 1.9° in the SNB angle within the treatment group in contrast to the control group (p < 0.001). While the U1/SN angle increased by 1.4° in the treatment group, the L1-NB distance decreased by 0.7 mm (p < 0.01).

Conclusions: The results of this study showed that application of the Alt-RAMEC protocol and class III elastics with fixed appliances showed successful results in the management of skeletal class III malocclusions, while avoiding undesirable dental effects, such as excessive lingual tipping of the lower incisors.