Journal of Orofacial Orthopedics-Fortschritte Der Kieferorthopadie最新文献

Purpose: External apical root resorption is an undesirable outcome of orthodontic treatment. Patients with already existing root resorption who require orthodontic treatment should be carefully evaluated. The objective of this study was to evaluate the effect of apical root resorption and different orthodontic forces on stress and displacement in the tooth and periodontium using a three-dimensional (3D) finite element analysis method.

Methods: Two 3D models of an upper central incisor were constructed based on tomographic images. Two models (original tooth length and an apical resorption of 3 mm) and four types of force application (intrusion, extrusion, tipping, and translation) resulted in eight variations from the two original study factors (apical resorption and orthodontic movement). The mechanical properties, mesh, boundary conditions, and loading were added to the specific finite element analysis software (Ansys, Houston, PA, USA). Orthodontic forces (0.6 N) were applied to the brackets to simulate orthodontic movements.

Results: Quantitative analysis showed that the highest von Mises tension values were found in the models subjected to translational movement, regardless of the root condition. The values obtained for the displacement of the studied structures did not differ significantly. In a qualitative analysis comparing teeth with and without apical resorption, teeth with apical resorption showed higher stress concentrations in the cortical bone and periodontal ligament.

Conclusion: Apical resorption did not significantly influence maximum displacement of the involved structures but influenced stress in the periodontal tissues. The translational movement resulted in the highest stress values in the tooth and periodontal tissues.

Purpose: To evaluate the skeletal, dentoalveolar and soft tissue changes in patients treated with the Forsus fatigue resistance device (FRD) appliance in combination with a full slot labially pretorqued mandibular archwire in class II patients and compare it with applying a conventional plain mandibular archwire.

Methods: The total sample of 31 individuals was divided into three groups: group 1 (G1) with 11 patients (Forsus appliance therapy combined with an 8° labially pretorqued full slot 0.021″ × 0.028″ stainless steel archwire in mandible), G2 with 10 patients (Forsus appliance therapy combined with a plain 0.021″ × 0.025″ stainless steel archwire in mandible), and an untreated control group (GC) with 10 patients. Lateral cephalograms before placement of the Forsus appliance and at end of class II correction with an average time of 6 ± 2 months were analyzed.

Results: The paired students t test revealed that class I molar relation, overjet and overbite correction were achieved in the G1 and G2 individuals. Both G1 individuals (IMPA: 7.18°; L1-NB: 1.64 mm, 7.73°) and G2 individuals (IMPA: 8.40°; L1-NB: 2.00 mm, 7.70°) exhibited lower incisor proclination. However, there was no statistically significant difference in the lower incisor position in the two treatment groups. N to point A and SNA values decreased in G1, while the Wits value decreased in G2. The post hoc test showed significant changes in incisor inclination, molar position, and overjet between the treated groups and the GC.

Conclusion: A Forsus appliance combined with a 0.022″ × 0.028″ labially pretorqued archwire in the mandibular arch showed favorable improvements that were similar to those with a plain 0.021″ × 0.025″ stainless steel archwire with no significant difference in terms of mandibular incisor position (i.e., proclination) and maxillary point A position. However, a Forsus appliance combined with a 0.022″ × 0.028″ labially pretorqued archwire in the mandibular arch showed better distal positioning of maxillary point A , although statistically insignificant.

Background: This research aimed to study whether bracket bonding using guided bonding devices (GBDs) is accurate enough for crowded dentitions in vitro.

Methods: Fifteen three-dimensionally (3D) printed resin model sets were included and divided into three groups: mild, moderate, and severe crowding. The resin models were scanned and virtually bonded with brackets. Corresponding GBDs were generated and 3D printed. Subsequently, the brackets were bonded to the resin models on a dental mannequin using the GBDs. The models with bonded brackets were scanned, and comparisons were made between the positions of the actually bonded and the planned ones to evaluate possible deviations.

Results: There was no immediate bonding failure in any group. The bonding duration tended to increase with crowding severity (P > 0.05). Almost all linear and angular deviations in all groups were below 0.5 mm and 2°, respectively, and no statistically significant difference was found among the different crowding degrees (P > 0.05). In all groups, the brackets tended to deviate lingually and had buccal crown torque. Brackets in the groups with mild and severe crowding showed a tendency for mesiobuccal rotation.

Conclusion: GBDs provide high bracket bonding accuracy for dentitions with different crowding degrees and, thus, could hopefully be applied to uncrowded and crowded dentitions alike.

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 and aim: In Germany, the reimbursement of orthodontic treatment costs within the framework of the statutory health insurance (GKV) was restricted on 01 January 2002 by the introduction of the orthodontic indication groups (KIG). The aim of this study was to evaluate the prevalence of findings requiring treatment in a specialist practice over a 20-year period. The results were then compared with data from existing older studies.

Patients and methods: The distribution of treatment-eligible KIG (KIG classifications grades 3-5) among patients with statutory health insurance in an orthodontic practice in North Rhine was determined over a 20-year period (2002-2021) after the introduction of the KIG system. This period was additionally scrutinized in four 5‑year periods according to the operating cycles of the practice. Findings were classified into the highest of 19 possible KIG treatment needs levels. Multiple classifications were not made.

Results: Orthodontic treatment was indicated in a total of 4537 (2393 female, 2144 male) patients according to current statutory health insurance guidelines. The KIG classification "D" (increased overjet) was the most frequent within the observed 20 years with 24.3%. Among 11 KIG classifications, 86.1% of the 6 most frequent and 13.9% of the 5 rarest findings were observed constantly over all periods. Of 19 possible indications, "D4" was the most frequent with 19.6%. Of 4537 patients, 20.7% had KIG grade 3, 63.6% KIG grade 4 and 15.7% KIG grade 5. The prevalence of sagittal deviations "D" and "M" was 35.0%, transverse "B" and "K" 17.9% and vertical "O" and "T" 3.7%. Tooth position anomalies "E" and "P" had a share of 24.6%.

Conclusions: The present study confirms existing findings as well as the nationwide data of the National Association of Statutory Health Insurance Dentists (KZBV) from 2020: The sagittal deviations "D" (increased overjet) and "M" (negative overjet) represented the most frequent findings with KIG D4 as the most common classification. The prevalence and age distribution of KIG grades 3-5 requiring treatment corresponded to nationwide comparative data.

Objective: Precise root torque adjustment of anterior teeth is indispensable for optimizing dental esthetics and occlusal stability in orthodontics. The efficiency of traditional rectangular archwire manipulation within bracket slots seems to be limited. The crimpable gate spring, a novel device, has emerged as a promising alternative. Yet, there is a paucity of guidelines for its optimal clinical application. This study used finite element analysis (FEA) to investigate the biomechanical impact of the gate spring on torque adjustment of individual anterior teeth and to elucidate the most effective application strategy.

Methods: A FEA model was constructed by a maxillary central incisor affixed with an edgewise bracket featuring a 0.022 × 0.028 inch (in) slot. A range of stainless steel rectangular archwires, in conjunction with a gate spring, were modeled and simulated within the bracket slots. A control group utilized a conventional rectangular wire devoid of a gate spring. Palatal root moments were standardized to 9, 18, and 36 Nmm for both experimental and control groups.

Results: The gate spring significantly amplified palatal root movement, notably with the 0.019 × 0.025 in archwire. However, this was accompanied by an increase in stress on the tooth and periodontal ligament, particularly in the cervical regions. The synergistic use of a 0.019 × 0.025 in rectangular archwire with a gate spring in a 0.022 × 0.028 in bracket slot was identified as most efficacious for torque control of individual anterior teeth.

Conclusions: The gate spring is a viable auxiliary device for enhancing torque adjustment on individual teeth. However, caution is advised as excessive initial stress may concentrate in the cervical and apical regions of the periodontal ligament and tooth.

Purpose: Anterior arch length (AL) and the alterations in its dimension following incisor movements were shown to be predictable for an individual patient using a mathematical-geometrical model based on a third-degree parabola. Although the model has been validated previously, it is hard to apply in daily orthodontic routine. Thus, the aim of this study was to modify the model using different approaches to allow its establishment in daily routine.

Methods: This retrospective study was based on a study collective, which was described previously and consisted of 50 randomly chosen dental casts and lateral cephalograms taken before (T0) and after (T1) orthodontic treatment with fixed appliances. A JAVA computer program (Oracle, Austin, TX, USA) was developed to predict AL changes following therapeutic changes of arch width, depth or incisor inclination/position, taking the type of tooth movement into account. Performing exemplary AL calculations with the computer program, general rules and nomograms were set up, followed by multiple linear regression analyses to establish easy-to-use regression equations.

Results: The JAVA computer program is available for download. Sagittal changes showed more effect on AL than transverse modifications. Protruding incisors increased AL, but also reduced overbite. The extent of alteration in AL depended on the initial depth, width, incisor inclination, tooth movement type and distance between the incisal edge and the centre of rotation.

Conclusions: The computer program precisely predicts individual changes in AL but is time-consuming. The presented regression equations and nomograms, considering metric variables, are easier to apply clinically and the differences compared to the AL calculated by the computer program are negligible.