Journal of Orofacial Orthopedics-Fortschritte Der Kieferorthopadie最新文献

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.

Purpose: The aim was to investigate the influence of three different three-dimensional (3D)-printed bonding tray designs and professional experience on accuracy of indirect bracket placement.

Methods: Virtual bracket placement was performed on a scanned dental model using OnyxCeph software (Image Instruments, Chemnitz, Germany). Three different designs for indirect bonding trays (open, semi-open, and closed design) were created and produced using a 3D printer. To analyze the influence of professional experience, one of the three tray designs was produced twice. In this case, bracket placement was performed by an inexperienced dentist. Bracket positions were scanned after the indirect bonding procedure. Linear and angular transfer errors were measured. Significant differences between the target and actual situation were analyzed using the Kruskal-Wallis and χ² test.

Results: All bonding tray designs resulted in comparable results. The results of the unexperienced dentist showed significantly higher deviations than those for the experienced orthodontist in the torque direction. However, the mean values were comparable. The open tray design exceeded the clinically acceptable limits of 0.25 mm and 1° more often. The inexperienced dentist exceeded these limits significantly more often than the experienced orthodontist in the vertical and torque direction. The immediate bracket loss rate showed no significant differences between the different tray designs. Significantly more bracket losses were observed for the inexperienced dentist during the procedure compared to the experienced orthodontist.

Conclusions: The bonding tray design and professional experience had an influence on the exceedance of clinically relevant limits of positioning accuracy and on the bracket loss rate.

Purpose: The aim of this study was to investigate the influence of mechanical strain on clock gene function in periodontal ligament (PDL) cells. Furthermore, we wanted to analyze whether effects induced by mechanical stress vary in relation to the circadian rhythm.

Methods: Human PDL fibroblasts were synchronized in their circadian rhythm with dexamethasone and stretched over 24 h. Unstretched cells served as controls. Gene expression of the core clock genes were analyzed at 4 h intervals by quantitative real-time polymerase chain reaction (qRT-PCR). Time points 0 h (group SI1) and 12 h (group SI2) after synchronization served as starting points of a 4 h force application period. Collagen-1α (COL-1α/Col-1α), interleukin-1β (IL1-β), and runt-related transcription factor 2 (RUNX2/Runx2) were assessed by qRT-PCR and enzyme-linked immunosorbent assay (ELISA) after 2 and 4 h. Statistical analysis comprised one-way analysis of variance (ANOVA) and post hoc tests.

Results: After synchronization, the typical pattern for clock genes was visible in control cells over the 24 h period. This pattern was significantly altered by mechanical strain. Under tensile stress, ARNTL gene expression was reduced, while Per1 and 2 gene expression were upregulated. In addition, mechanical stress had a differential effect on the expression of Col-1α and IL1‑β depending on its initiation within the circadian rhythm (group SI1 vs group SI2). For RUNX2, no significant differences in the two groups were observed.

Conclusion: Our results suggest that mechanical stress affects the molecular peripheral oscillator of PDL cells. Vice versa, the circadian rhythm also seems to partially influence the effects that mechanical stress exerts on PDL cells.

Objectives: Aligned teeth commonly convey a positive impression to other people. This study aimed to examine the effect of malocclusion on adult facial perceptions using self-reported and quantitative measures.

Materials and methods: Facial photographs of 15 adult patients (11 women; 47.73 years, standard deviation [SD] = 8.86; 12 periodontally compromised) with malocclusion were acquired before (MT0) and after treatment (MT1). The control group (CG) comprised 15 age-matched adults (12 women; 42.93 years, SD = 7.50) without malocclusion. In all, 37 laypersons (18 women; 41.06 years) viewed all pictures. Self-report: Participants rated each face regarding dental condition, smile valence, and friendliness. Eye-tracking: Visual attention was analyzed by entry time and fixation time on predefined face areas.

Results: MT0 pictures received significantly (p < 0.001) more negative ratings regarding dental condition, smile valence, and friendliness. Ratings for MT1 were comparable to those of the control group. Compared with the CG, MT0 faces showed faster first fixations on the mouth (p = 0.005) and had longer fixation durations (36.15%, p < 0.001). After treatment, the difference to the CG decreased significantly (12.38%, p = 0.014).

Conclusion: Malocclusions have a negative effect on the perception of individuals in terms of gaze behavior and self-reported ratings. These effects decrease after treatment, underlining the effect of orthodontic correction.

Clinical relevance: Orthodontic treatment improves facial perception and the assessment of oral regions, highlighting the psychosocial significance of orthodontic treatment.

Aim: To investigate the agreement between palatal bone thickness (PBT) measurements performed on lateral cephalograms and cone-beam computed tomography (CBCT) images in a group of white patients considering different facial patterns.

Materials and methods: Measurements performed on lateral cephalograms and CBCT images from 60 white patients (39 females and 21 males; 24.1 ± 6.4 years) were retrospectively compared. On lateral cephalograms, PBT values were measured by drawing lines perpendicular to the maxillary occlusal plane (MOP) at the point of contact between the first and second premolar (P1-P2), second premolar and first molar (P2-M1), and first and second molar (M1-M2), as well as at the buccal cusps of the second premolar (P2) and first molar (M1). On CBCT images, they were measured at the same landmarks at 2 mm, 4 mm, 6 mm and 8 mm off-centre to the midpalatal suture. Vertical facial pattern of the patients was determined using the Frankfort-mandibular plane angle (FMA). Analysis of variance (ANOVA) and Tukey post hoc tests were used to ascertain the degree of agreement between the two measurement sets (p < 0.05), subsequently quantified by intraclass correlation coefficient (ICC) tests.

Results: Good agreement was found at all investigated sites regardless of vertical facial pattern, except at sites P1-P2 and P2 (8 mm off-centre) and M1 and M1-M2 (2 mm off-centre; p < 0.05). The two measurement sets displayed excellent agreement (ICC > 0.8) at P1-P2 (4 mm off-centre), at P2 (2, 4 and 6 mm off-centre), and all P2-M1 sites.

Conclusion: The lateral cephalogram can be a viable option for digital planning of palatal miniscrews insertion, with the preferred sites being P1-P2 at 4 mm off-centre and P2 at 4 and 6 mm off-centre in selected cases for adolescents and young adults. No significant differences in the degree of agreement between the two sets of PBT measurements were found among the different vertical facial patterns.