Orofacial Orthopedics / Fortschritte der Kieferorthopädie

Influence of the three-dimensional printing technique and printing layer thickness on model accuracy Abstract Objective The accuracies of three-dimensional (3D) printed dental models using various digital light processing (DLP) and stereolithography (SLA) printers at different thicknesses were compared. Materials and methods Based on digital dental models (originally digitized using R700; 3Shape, Copenhagen, Denmark), physical dental models were printed using three types of DLP printers: (1) EvoDent (UnionTec, Shanghai, China) with layer thicknesses of 50 μm and 100 μm; (2) EncaDent (Encashape, WuXi, China) with layer thicknesses of 20, 30, 50 and 100 μm; (3) Vida HD (Envisioned, Dearborn, MI, USA) with layer thicknesses of 50 and 100 μm. Models with the SLA printer Form 2 (Formlabs, Somerville, MA, USA) were printed with layer thicknesses of 25, 50 and 100 μm. All 22 printed models were converted to digital dental models using a D2000 model scanner (3 Shape, Copenhagen, Denmark) and compared three-dimensionally to the source files using Geomagic Qualify 12.0 (3D Systems, Rock Hill, SC, USA). Results The printing accuracy of all printers was higher at 50 μm. When the layer thickness was set at 100 μm, the printing speed and printing accuracy of DLP printer were both superior to those of the SLA printer. In all groups, the EvoDent 50 μm group had the highest consistency with the source files (mean absolute deviation of 0.0233 mm in the maxilla and 0.0301 mm in the mandible). While the accuracy of Form 2 100 μm group was the lowest (mean absolute deviation of 0.0511 mm in the maxilla and 0.0570 mm in the mandible). Conclusion For the 3D printers studied, 50 μm was the optimum layer thickness for DLP technology, and the printing accuracy using SLA technology increased with decreasing layer thickness. The DLP technology also had higher printing accuracy at a layer thickness of 100 μm. EvoDent 50 μm had the highest and Form 2 100 μm the lowest printing accuracy.

Gender-dependent impact of aging on facial proportions Abstract Purpose Facial proportions in younger people have been evaluated in several studies. However, the number of older people who need orthognathic surgery is growing steadily. The aim of this study was to evaluate facial morphology in Caucasians accounting for age and gender. Methods Three-dimensional facial scans of 240 healthy volunteers were taken. The subjects were divided into males and females, then into three groups by age (21–35, 36–50 and 51–65 years). Landmarks and artificial planes were placed in the scans. Distances, relations and angles between them and the artificial frontal plane were recorded. Results Nearly all distances between the tragion and the landmarks in the middle of the face increased with the age of the volunteers. Therefore, the soft tissue of the face grows horizontally with increasing age. Also, the length of the upper lip increased with age. The percentage of subnasale-stomion and stomion-menton distances of the total subnasale-stomion-menton measurement changed significantly (men: p = 0.149; women: p < 0.001) during aging in females but not in males. The landmarks in the upper and middle third of the face were closer to the frontal plane in women than in men. Conclusion Using the created frontal plane for evaluating landmarks in the sagittal plane facilitates measuring positions of soft tissue. There are significant changes in distances, angles and relations during aging which can be very important for planning orthognathic surgery.

Mitteilungen der DGKFO

Biomechanical analysis of initial incisor crowding alignment in the periodontally reduced mandible using the finite element method Abstract Aims To reduce remaining plaque niches due to dental malocclusion after periodontal treatment and to avoid reinflammation of periodontitis, severe anterior crowding can be treated orthodontically. The treatment indication is motivated by aesthetic and functional needs. In this study the biomechanical behaviour of crowded lower front teeth in reduced periodontium is analysed. Methods Using the finite element (FE) method, a model of the mandible was constructed with an anterior crowding of 4 mm and a vertical bone loss of 4 mm in the front tooth area. A 0.3 mm (0.012″) round superelastic nickel titanium (NiTi) arch wire was fitted to an ideal positioned teeth set-up and was inserted into the brackets of teeth 34 to 44 in the crowded model. The premolars were used as the anchorage unit. Material parameters were adopted from previous investigations, including bone (homogenous, isotropic, E = 2 GPa), teeth (E = 20 GPa) and healthy periodontal ligament (PDL, bilinear elastic; E1 = 0.05 MPa; E2 = 0.2 MPa; ε12 = 7%). All simulations were compared to simulations with a physiological periodontal model to assess the effect of bone loss at teeth 42 to 32. Additionally, the influence of three arch wire materials (nonsuperelastic NiTi, superelastic NiTi and stainless steel) were analysed in a reduced model, including only brackets in position of the crowded front teeth, wire and ligatures. Wire force levels and stresses were determined to assess the influence of material variation. Results Initial tooth mobility is increased by a factor of 2.5 in case of a moderate periodontal defect. Front teeth with reduced attachment display increased strains in the periodontal ligament up to a factor of 2. Forces in the model with reduced periodontium were decreased by a factor of 2. Comparing different aligning arch wires, stainless steel appears to have the highest force and stress levels. Force levels of this alloy were 7.5 times higher than with the superelastic NiTi wire. Force levels of nonsuperelastic NiTi appeared to be 1.8 times higher than superelastic NiTi. Calculated stresses with stainless steel were 5 times higher than with the nonsuperelastic NiTi and 10 times higher than with superelastic NiTi. Conclusion Periodontally reduced incisors 42 to 32 are associated with an increased load on periodontal tissue and increased level of tooth mobility during fixed orthodontic treatment. This has to be considered by reducing orthodontic force levels and by selecting mechanics that reduce the load to the tissue.

Impact of specific orthodontic parameters on the oral health-related quality of life in children and adolescents Abstract Purpose The aim of the present study was to analyse the impact of specific orthodontic findings on oral health-related quality of life (OHRQoL) when taking into consideration age and psychological factors in children and adolescents. Methods In all, 250 children and adolescents with an indication for orthodontic diagnostics were recruited using a multicentre study design. Using validated and internationally acknowledged questionnaires, we assessed OHRQoL, health-related quality of life (HRQoL), self-esteem and behavioural problems. We also examined a selection of specific orthodontic findings using photos, model casts and cephalometric analyses, and investigated the impact of these parameters on OHRQoL using simple linear regression analyses. Thereafter, we added all the significant specific orthodontic and psychological parameters to a multiple linear regression model using a stepwise forwards selection procedure. Results We were able to identify different specific orthodontic findings that have a significant impact on OHRQoL. These were the type of lip closure, the position of the chin, the Little-index of the upper jaw, the overjet, the overbite and the ANB angle. Moreover, we were able to demonstrate that psychological and some specific orthodontic parameters have a significant impact on OHRQoL. Conclusion Specific orthodontic findings have a significant impact on patients' perceived OHRQoL. Further longitudinal studies are required to investigate whether the treatment and correction of these malocclusions also improve the OHRQoL of children and adolescents.

Dimensional changes of the alveolar ridge contour of the premolar extraction site in adolescents Abstract Purpose Premolar extraction in orthodontic therapy is common in adolescent patients. Knowledge of the tissue reaction in an extraction site is mainly based on studies with animal and adults. Thus, we aim to describe the time-dependent dimensional changes of the alveolar ridge contour of the premolar extraction site in adolescents. Methods Clinical data were obtained from a randomized controlled clinical trial (Universal Trial Number U1111-1132-6655), comparing treatment modalities with orthodontic space closure was initiated after 2–4 weeks (group A) and ≥ 12 weeks after tooth extraction (group B). Dental casts taken before the tooth extraction (T1) and before initiation of the space closure (T2) were digitalized with a 3D scanner and superimposed to analyze the dimensional changes of the alveolar ridge in early and later stage of wound healing. Linear mixed models were used for statistical analysis. Results Plaster models of 25 patients (mean age 15.2 years, 11 male and 14 female) with 66 extraction sites were enrolled. The average atrophic changes from tooth extraction to the early stage of wound healing (group A, n = 41) were in total 27.5% ± 11.8; labially 31.3% ± 15.1 and orally 23.6% ± 13.4. In group B (n = 25) the average atrophic changes were in total 38.6% ± 12.1; labially 46.2% ± 16.7; orally 31.3% ± 18.9. The atrophic changes between the groups in total (p = 0.031) and at the labial side (p = 0.012) were significant. The jaw affiliation was a significant parameter for all examined areas in regard to all cases (labial p = 0.019; oral p = 0.020; total p = 0.001). Atrophic changes between genders were not statistically different. Conclusions Alveolar atrophy increased over time after extraction primarily in the lower jaw at the labial side. The main atrophy occurred in the first healing phase of the extraction socket. Thus, timely coordination is important to preserve sufficient bone levels. The atrophic changes of the alveolar ridge in adolescents parallel those reported for adults.

Relationship between alveolar bone thickness, tooth root morphology, and sagittal skeletal pattern Abstract Purpose The goal of this work was to examine the relationship between sagittal facial pattern and thickness of alveolar bone in conjunction with root morphology of teeth by using cone beam computed tomography (CBCT). Methods The study was carried out on the CBCT scans from 3 group of patients (n = 20 in each group). The first group involved skeletal class 1, the second group involved skeletal class 2, and the third group involved skeletal class 3 patients. In all, 14 permanent teeth and interdental regions in the maxilla and mandible were evaluated. Root length and root width were measured on each tooth. Buccal cortical bone thickness, cancellous bone thickness, and lingual cortical bone thicknesses were measured in each interdental region. Analysis of variance, Kruskall–Wallis H and Mann–Whitney U tests were used for statistical comparisons. Results No significant difference was found between the groups for root length, root width, buccal cortical bone and lingual cortical bone thickness. A significant difference was observed between the groups for cancellous bone thickness as it was thicker in skeletal class 2 group. Cortical bone was thicker in the mandible compared to maxilla on both buccal and lingual sides and it was thicker in the posterior region compared to the anterior region on the buccal side. Conclusions Differences in cancellous bone thickness between different sagittal facial patterns and differences in cortical bone thickness between different alveolar regions should be taken into consideration when planning orthodontic tooth movements and anchorage mechanics.

Expression of lubricin in rat posterior mandibular condylar cartilage following functional mandibular forward repositioning Abstract Purpose The aim of the present study was to investigate the effects of mandibular forward repositioning on expression of lubricin in rat posterior condylar cartilage. Methods In total, fifty 5‑week-old female Sprague Dawley rats were divided randomly into experimental groups and control groups. The animals in the experimental groups were fitted with modified acrylic inclined planes to advance the mandible, whereas rats in the normal control groups were left intact. Rats were sacrificed on days 3, 7, 14, 21, and 30, and temporomandibular joint (TMJ) samples were collected. The expression of lubricin of the posterior mandibular condylar cartilage was evaluated by immunohistochemistry. Results In the control groups, higher expression of lubricin was observed in the proliferative zone of the posterior mandibular condylar cartilage compared with the hypertrophic zone during the experimental period. Compared with the control group, the positive signals for lubricin of the posterior mandibular condylar cartilage in the experimental animals were significantly higher on days 7, 14, and 21; however, no statistical difference was found on day 3 or 30. Conclusions Data analyses suggest that the bite jumping appliance temporarily enhanced lubricin expression, providing a good mechanical environment for the physiologic growth of the condyle and mandible, and contributes to TMJ remodeling by the regulation of condylar chondrocyte proliferation.

Mitteilungen der DGKFO

Influence of enamel sealing with a light-cured filled sealant before bracket bonding on the bond failure rate during fixed orthodontic therapy Abstract Purpose Fluoride-containing adhesives for enamel sealing are commonly used for the prevention of white spot lesions during fixed orthodontic treatment. Thus, we examined whether enamel sealing with L.E.D. ProSeal® (Reliance Orthodontic Products Inc., Itasca, IL, USA) before bracket bonding increases the rate of bond failure during orthodontic treatment. Methods In 20 adolescents (11–16 years, 10 male/10 female) at the start of fixed therapy, self-ligating SmartClip™SL3 metal brackets (3M Unitek, Monovia, CA, USA) were bonded to cleaned and conditioned (40% H3PO4, 30 s) buccal enamel surfaces of all permanent teeth except molars using Transbond™ XT (3M Unitek). In a split-mouth design, either L.E.D. ProSeal® (1st/3rd quadrant) or Clinpro™ XT Varnish (2nd/4th quadrant; 3M Unitek) was applied to enamel surfaces before (ProSeal®) or after (Clinpro™ XT Varnish) bracket bonding (200 teeth each; light curing: 20 s, Ortholux™ Luminous, 3M Unitek). Cumulative bond failure as total number of teeth with bracket detachment since start of therapy was documented every 3 months for a total of 12 months. Results Cumulative bond failure was higher for enamel sealing before bonding from 6 months onward reaching significance at 12 months (34/200) compared to sealing after bonding (24/200): p = 0.038; Cramér's V = 0.488; odds ratio (OR) = 1.5; relative risk (RR) = 1.4. The higher loss rate was limited to the lower arch, but evident within 3 months reaching significance at 9 and 12 months (p = 0.019/0.011, V = 0.636/0.630; OR = 1.7/1.75, RR = 1.5/1.6). In general, cumulative bond failure at 12 months was higher in the lower arch, but this was only significant for teeth sealed before bonding (p = 0.001, V = 0.303, OR = 3.4, RR = 2.8). Conclusions Enamel sealing with L.E.D. ProSeal® should be performed after bracket bonding to prevent increased bond failure and bracket loss in the lower dental arch.

Alexandros Sfakianakis
Anapafseos 5 . Agios Nikolaos
Crete.Greece.72100
2841026182

6948891480

alsfakia@gmail.com