Journal of Orofacial Orthopedics-Fortschritte Der Kieferorthopadie最新文献

Objectives: An in vitro experimental study was performed to evaluate the torsional strength and torque released by esthetic coated archwires.

Materials and methods: A total of 52 coated (study group) and 52 stainless steel (control group) rectangular archwires from two manufacturers (brand I: Gestenco International AB, Gothenburg, Sweden and brand II: Ortho Technology, Lutz, FL, USA) in two sizes (0.019 × 0.025 and 0.017 × 0.0250-inch) were evaluated. The straight parts on both ends of each preformed archwire were cut in 30 mm segments. A specially designed experimental device was attached to the universal testing machine (Model Z020, Zwick Roell, Ulm, Germany) to measure torsional strength and to calculate the clinically significant torque interval. The groups were compared based on their brand, presence of coating and size using three-way analysis of variance (ANOVA) test at a significance level of 5%.

Results: The results revealed that coating of the wires of brand 1 resulted in a significant reduction of torsional strength in both wire sizes (P-value = 0.0001). For the wires of brand 2, coating of the 0.017 × 0.025-in wire resulted in a significant reduction in torsional strength. However, for the 0.019 × 0.025 in wire size, the presence of coating significantly increased the torsional strength (P-value = 0.0001). Coating did not affect the measured clinical torque interval of the analyzed wires when a torque between 5 and 20 Nmm was applied (P-value = 0.062).

Conclusions: Mechanical behavior of coated archwires depends mainly on the thickness of their inner core alloy. Reduction in the diameter of the inner alloy resulted in reduced torsional strength. Despite lower mean torsional strength, in the settings of this study, coated and conventional wires demonstrated comparable torque angles if loaded in the typical range of activation.

Purpose: Total mandibular arch mesialization using mini-implants is challenging due to anatomic limitations. The aim of this study was to introduce a mini-implant-supported device for total mesialization of the mandibular dentition and to analyze the biomechanical properties of the device.

Methods: Finite element models were constructed to explore the effect of friction and force direction on the force transmission efficiency of the device. In addition, the three-dimensional displacement of each tooth was evaluated with two force application points (2 or 8 mm hooks) under three force conditions (symmetric: 150 g of force on both sides, or asymmetric: 100 and 200 g of force on each side).

Results: The force transmission efficiency was 66.7% under a friction coefficient of 0.15 and parallel pushing and pulling forces. The force transmission efficiency was 65.90 and 66.63% when the pushing force was 15° away from the pulling force on the sagittal and horizontal planes, respectively. The mandibular dentition moved mesially with a greater tendency for incisor labial crown tipping, mesial molar rotation and buccal second molar crown tipping when using the 8 mm hook compared to that when using the 2 mm hook. Rigid archwires resulted in more consistent tooth mesialization than stainless steel archwires. Asymmetric forces resulted in asymmetric dental arch mesialization.

Conclusion: The forces transmitted by the presented mini-implant-supported device varied depending on the friction level and force direction. The device should be able to achieve symmetric or asymmetric total mesialization of the mandibular dentition.

Purpose: To assess magnetic resonance imaging (MRI) artefacts caused by different computer-aided design/computer-aided manufacturing (CAD/CAM) retainers in comparison with conventional hand bent stainless steel twistflex retainers in vivo.

Materials and methods: MRI scans (3 Tesla) were performed on a male volunteer with different CAD/CAM retainers (cobalt-chromium, CoCr; nickel-titanium, NiTi; grade 5 titanium, Ti5) and twistflex retainers inserted. A total of 126 landmarks inside and outside the retainer area (RA; from canine to canine) were evaluated by two blinded radiologists using an established five-point visibility scoring (1: excellent, 2: good, 3: moderate, 4: poor, 5: not visible). Friedman and two-tailed Wilcoxon tests were used for statistical analysis (significance level: p < 0.05).

Results: Twistflex retainers had the strongest impact on the visibility of all landmarks inside (4.0 ± 1.5) and outside the RA (1.7 ± 1.2). In contrast, artefacts caused by CAD/CAM retainers were limited to the dental area inside the RA (CoCr: 2.2 ± 1.2) or did not impair MRI-based diagnostics in a clinically relevant way (NiTi: 1.0 ± 0.1; Ti5: 1.4 ± 0.6).

Conclusion: The present study on a single test person demonstrates that conventional stainless steel twistflex retainers can severely impair the diagnostic value in head/neck and dental MRI. By contrast, CoCr CAD/CAM retainers can cause artefacts which only slightly impair dental MRI but not head/neck MRI, whereas NiTi and Ti5 CAD/CAM might be fully compatible with both head/neck and dental MRI.

Purpose: We evaluated the changes in the strain energy density (SED) in the temporomandibular joint (TMJ) disk after sagittal split ramus osteotomy (SSRO) at three time points. A finite element model (FEM) based on real patient-based computed tomography (CT) data was used to examine the effect of SSRO on the TMJ.

Methods: Measurements of the condylar position and angulation in CT images and FEM analyses were performed for 17 patients scheduled to undergo SSROs at the following time points: before surgery, immediately after surgery, and 1 year after surgery. SED on the entire disk was calculated at each of the three time points using FEM. Furthermore, the relationship between individual SED values and the corresponding condylar position was also evaluated.

Results: No significant change was observed in the condylar position at the three time points. The FEM analysis showed that SED was the highest and lowest immediately after and 1 year after surgery, respectively. A possible SED distribution imbalance between the left and right joints was improved 1 year after SSRO. Concerning the effect of fossa morphometry and condylar position, wide and deep glenoid fossae and a more posterior condylar position tended to show lower SED.

Conclusion: SED in the articular disk temporarily increased after surgery and significantly decreased 1 year after surgery compared with that before surgery. SSRO generally improved the imbalance between the left and right joints. Thus, SSRO, which improves maxillofacial morphology, may also improve components of temporomandibular disorders.

Background: Cleft lip and/or palate (CL ± P) or isolated cleft palate (CP) are the most common congenital malformations of the face. Although there have been advances in prenatal diagnosis and the discovery of genetic markers, there has been no breakthrough in the identification of parents at risk of giving birth to a child with a cleft.

Aims: To determine a possible phenotypic difference in the craniofacial morphology of parents of children with CL ± P and to investigate whether cephalometric analysis can help identify parents at risk of giving birth to a child with a cleft.

Methods: Cephalometric data of 25 sets of parents having children with CL ± P were compared with that of 25 sets of parents of children without CL ± P. The study population was indigenous to North Karnataka. In all, 10 linear, 2 angular, and 5 triangular measurements were made on lateral cephalograms and compared using an unpaired t‑test.

Results: The length of the posterior cranial base (S-Ba) in mothers was smaller in the study compared to the control group. Total facial height (N-Me) both in fathers and in the group with both parents, upper facial height in the group with both parents, and lower facial height (ANS-Me) in fathers was smaller in the study than in the control group. The area of the nasopharyngeal triangle (S-PNS-Ba) in mothers and that of the anterior maxillary triangle (S-N-A) in fathers was smaller in the study group than in the control group.

Conclusion: Parents of children with CL ± P showed variations in craniofacial morphology. Future research correlating cephalometric findings with genetic studies may indicate whether cephalometric analysis can be an adjunct to genetic tests for risk prediction among susceptible parents.

Purpose: To compare the long-term outcome quality (≥ 15 years) of Class II:1 treatment using either a bionator (BIO) or a Herbst-multibracket appliance (HMB).

Methods: Patients who underwent functional treatment during the ideal treatment period for the respective approach (prepuberty vs. peak/postpeak) were assessed. Inclusion criteria were overjet ≥ 4 mm, skeletal Class II and availability of study casts from before, after and ≥ 15 years after treatment. The study casts were assessed using the Peer Assessment Rating (PAR) index and standard orthodontic cast measurements.

Results: During treatment, PAR score, overjet and sagittal occlusal relationship improved significantly in all groups. Long-term, there was a significant increase of incisor irregularity in the upper (HMB) and lower (BIO) arch and a significant decrease of lower arch width 3 - 3 (BIO). PAR score, overjet, and sagittal occlusal relationship remained stable long-term. Intergroup comparisons revealed significant differences between the BIO and HMB groups in terms of lower arch width (6 - 6), upper and lower arch width (3 + 3/3 - 3) as well as sagittal molar relationship.

Conclusions: The achieved improvement in PAR score, overjet, and sagittal occlusion remained comparably stable long-term in all groups. The long-term changes are probably a consequence of natural aging.

Purpose: The purpose of this cross-sectional study was to use multiple regression analysis to evaluate the relationship between the mandibular curve of Spee (COS) and the maxillary compensating curve with dentoskeletal morphology in young Chinese adults with normal occlusion.

Methods: This study comprised 62 young adults (31 males, mean age: 24.1 ± 2.2 years; 31 females, mean age: 23.3 ± 3.3 years) with Angle class I normal occlusion. For every subject, intraoral scan models of the maxillary and mandibular arches and lateral cephalograms were acquired. The depth of the COS and compensating curve were assessed on the intraoral scan models. Multiple dental arch dimensional and cephalometric variables were screened by univariate analysis. Subsequently, a multiple linear regression model (forward stepwise selection) was constructed to determine which variables were significantly correlated with the two curve depths.

Results: In the mandible, the COS depth was deepest at the mesiobuccal cusp of the first molar. Overjet, mandibular arch width and mandibular-occlusal plane angle significantly correlated with the COS depth (P < 0.05), accounting for 33.1% of the variation in the mandibular COS. In the maxilla, the deepest point of the compensating curve was at the distobuccal cusp of the first molar. Mandibular arch perimeter and overbite significantly correlated with the maxillary compensating curve (P < 0.05), explaining 23.3% of the variation.

Conclusions: Overjet, overbite, mandibular-occlusal plane angle, mandibular arch width and perimeter should be considered when reconstructing occlusal curves in clinical orthodontic treatment and in prosthetic restoration.

Background: The present study aimed to assess the frequency and variation of 13 nonmetric dental crown traits (NDCT) in permanent and primary molars in German orthodontic patients.

Methods: Dental records from orthodontic patients were screened and evaluated. First and second permanent and primary upper and lower molars (from left and right sides) were assessed. Teeth with cavitated dental caries, occlusal wear, restorations and obvious dental deformities were not evaluated. The NDCT for permanent molars were identified and scored according to the odontoscopic system developed by Arizona State University Dental Anthropology System (ASUDAS). The NDCT for primary molars were identified and scored according to ASUDAS, Hanihara's method and Sciulli's method. The χ² test was used to investigate side preference and sexual dimorphism at a significance level of p ≤ 0.050.

Results: A total of 163 orthodontic patients (82 males and 81 females) aged 8-14 years were included. A sexual dimorphism was observed for the hypocone in first upper permanent molar (p = 0.041). The protostylid was observed in lower permanent molars (range 2.1-10%). Males presented more hypoconulid than females (p = 0.019). Only females presented the distal trigonid crest in lower first permanent molars (p = 0.002). The most common groove pattern in primary molars was Y; male presented more Y grade than females in the lower second primary molar (p = 0.039). Asymmetry was observed in some traits, ranging from 0 to 100%.

Conclusion: The present study showed the frequency of NDCT of molars in German orthodontic patients and demonstrated that some traits present sexual dimorphism.