Stress Distribution and Displacement of Craniofacial Structures Following Rapid Maxillary Expansion in Different Types of Cleft Palate: A Three-Dimensional FEM Study

Objective: To evaluate displacements and stress distributions in finite element models (FEMs) of the craniofacial complex of 13-yearold male patient with complete unilateral cleft palate (UCP), a 15-year-old female patient with complete bilateral cleft palate (BCP), and a 15-year-old female patient with isolated cleft palate (ICP), which may respond differently to expansive forces.Methods: The FEMs were based on computed tomography scans of patients with UCP, BCP, and ICP who needed maxillary expansion. Von Mises stress distribution after 0.2 mm of expansion and displacements after 5 mm of expansion were investigated.Results: The highest amount of stress was observed in the ICP model. Surprisingly, no stress was noted around the nose in the BCP model. The amount of dentoalveolar expansion decreased from anterior to posterior on the cleft side of the UCP, BCP, and ICP models. In contrast, on the non-cleft side of the UCP model, the maximum dentoalveolar expansion occurred at the molar area, decreasing toward the anterior parts. Anatomical structures expressed posterior displacement in the UCP model. In the ICP model, structures close to midline showed anterior displacement, while structures in the lateral parts showed posterior displacement. In contrast with the other 2 models, the structures in the BCP model showed anterior displacement. Vertically, all the anatomic structures in the BCP model showed inferior displacement, while in the ICP and UCP models, only the structures close to the midline showed inferior displacement.Conclusion: Maxillary expansion caused different patterns of stress distribution and displacement in different types of clefts. Clinicians should consider the type of the cleft, and may expect differing patterns of widening following maxillary expansion

Evaluation of Initial Stress Distribution and Displacement Pattern of Craniofacial Structures with 3 Different Rapid Maxillary Expansion Appliance Models: A 3-dimensional Finite Element Analysis

Objective: This study aimed to describe the displacement of anatomical structures and the stress distributions caused by the Hyrax, fan-type, and double-hinged expansion screws via the 3-dimensional (3D) finite element method (FEM).Methods: The 3D FEM was based on the computed tomography data of a 12-year-old patient with a constricted maxilla. The Hyrax model included 1,800,981 tetrahedral elements with 2,758,217 nodes. The fan-type model included 1,787,558 tetrahedral elements with 2,737,358 nodes. The double-hinged model included 1,777,080 tetrahedral elements with 2,722,771 nodes. The von Mises stress distributions after 0.2 mm of expansion and displacement patterns after 5 mm of expansion were evaluated.Results: The highest stress accumulation was observed in the sutura zygomatico maxillaris area with all 3 appliances. An increase in stress was noted at the pterygomaxillary fissure, the medial and lateral pterygoid process of the sphenoid bone, and the nasal areas. The wedge-shaped skeletal opening was observed with all 3 appliances. In the transverse plane, maximum posterior expansion was achieved with the Hyrax appliance, whereas the maximum anterior expansion was observed with the double-hinged appliance. The maxilla moved inferiorly and anteriorly with all the 3 appliances. The greatest inferior displacement of the maxilla was recorded with the Hyrax appliance, whereas anterior maxillary displacement was the greatest with the double-hinged appliance.Conclusion: All the appliances showed similar stress distributions. The use of double-hinged screw caused a slight anterior displacement of point A. The fan-type and double-hinged appliances were shown to be more effective on anterior maxillary constriction, whereas the Hyrax appliance might be chosen for resolving maxillary posterior constriction

Shear Bond Strength Evaluation of Different Composites Used As Lingual Retainer Adhesives

The aim of this study was to determine the shear bond strength (SBS) levels and fracture modes of different composites used as lingual retainer adhesives. Sixty human mandibular incisors were used, that mounted in acrylic resin leaving the buccal surface of the crowns parallel to the base of the moulds. Randomly three groups were constructed, each containing 20 teeth. Transbond-LR (3M-Uni-tek), Transbond-XT (3M-Unitek) and Venus Flow (Heraeus Kulzer) were tested. Materials were applied to the teeth surface by packing the material into the cylindrical plastic matrices with a 2.34 mm internal diameter and a 3 mm height (Ultradent) to simulate the lingual retainer bonding. For SBS testing, the specimens were mounted in a universal testing machine, and an apparatus (Ultradent) attached to a compression load cell was applied to each of the specimen until the failure occurred. The SBS data were analyzed using analysis of variance and Tukey tests, and chi-square test was used to analyze the fracture modes. The statistical tests indicated that Transbond-LR shows statistically significant higher SBS (24.7±9.25 MPa) then Transbond-XT (12.01±4.98 MPa) and Venus Flow (14.07±5.25 MPa) (P<0.001) whereas the difference between Transbond-XT and Venus Flow was not significant. In general, a greater percentage of the fractures were adhesive at the tooth-composite interface (60%% for Transbond-LR and Venus Flow and 90°% for Transbond-XT) and no statistically significant difference was found between the groups. According to the results of this study, Transbond LR was found to be most appropriate material for the tested specification

Orthodontic Treatment of a Case with Maxillary Impacted Canines and Congenitally Missing First Premolars

Depending on their roles in oral functions and smile and face esthetic, impaction of maxillary canines is an important problem that should be treated by a conservative approach. In this case report, orthodontic treatment of a patient (9-year 5- months) with congenitally missing one maxillary premolar on both side and impacted two maxillary canines were introduced. The canines were impacted in different depth and angulations; right canine was almost parallel to occlusal plane. Following the determination of the teeth were not erupting by a panoramic radiograph taken in the sixth month after first application, patient was accepted to fixed orthodontic therapy. Primary canines were extracted. Rotations of upper premolars and molars were corrected and spaces were organized. However no traction was applied to maxillary canines, it was determined that they were erupting in the following panoramic radiograph. When they are fully erupted they were bonded. The treatment finished in three years and seven months time. This case shows the importance of early diagnose of impacted maxillary canines and their ability to erupt by uprighting when their spaces are prepared

Reliability Assessment of Orthodontic Apps for Cephalometrics

Objective:The aim of this study was to evaluate the accuracy and reliability of cephalometric measurements using iPad apps called CephNinja and SmartCeph Pro. The measurements were compared with the measurements obtained using Dolphin Imaging computer software.Methods:Twenty digital cephalometric radiographs were randomly selected from the archives and traced using the CephNinja app, SmartCeph Pro app, and Dolphin Imaging software. Twenty-one landmarks and 16 measurements were performed in each program. The statistical analysis was conducted using the Bland-Altman analysis at a significance level of 0.05.Results:For the CephNinja app, there were seven measurements that were in accordance with Dolphin Imaging software. For the SmartCeph Pro app, six measurements were in accordance with Dolphin software. Both apps gave better results for angular measurements than linear ones.Conclusion:These findings indicate that, although they are user-friendly, orthodontic apps for cephalometrics are not equal with Dolphin software now and need to be developed to be more reliable for most of the measurements

Effect of Xylitol Lozenge on Remineralization of Artificial Carious Lesions - In Situ

The purpose of this study was to evaluate the effect of lozenges containing xylitol on in situ remineralization of artificial carious lesions. Eleven patients (aged between 12 and 15 years old) treated by fixed orthodontic therapy with bilateral maxillary first premolar extractions were included into this study. Each subject wore a modified transpalatal arch that was prepared by adding an acrylic resin to the U region for positioning of the enamel blocks (4X4X3 mm) on it. Three enamel blocks were prepared from the extracted tooth of each patient for both control and experimental groups. Artificial caries lesions were prepared by a low pH solution. This was a two stages study of 14 day periods: no-lozenge and xylitol lozenge (5 times/day, after meals). After each stage, the surface enamel microhardness testing was performed using a Vickers Hardness Tester. Three penetrations were made with a load of 300 g for 15 seconds into the enamel. Friedman's test was used for statistical analyses. The microhardness values were 197.5±127.3, 185.2±106.7, 193.2± 103.4 kgf/mm2 for control, no-lozenge and xylitol groups, respectively. Microhardness results demonstrated that there were no statistically significant differences between amount of remineralization in the control and experimental groups. The results showed that xylitol lozenge was not effective on in situ remineralization of artificial carious lesions but at least non-cariogenic

Evaluation of Fit between Tooth and Band Surfaces when Different Orthodontic Cements are Used

The aim of this in vitro study was to compare three orthodontic band cements for gaps remained between tooth and band surfaces, at the cervical margin, which possibly caused after banding procedure. Sixty freshly extracted human mandibular third molars were randomly divided into 3 equal groups. Micro-etched molar bands were cemented to the teeth using each of the orthodontic band cements (Ketac Cem®, 3M Multi-Cure® and Transbond Plus®). The teeth were placed in preformed boxes (2.5X2.5X2.5 cm); crowns were on the bottom and perpendicular to the ground. Samples were capped with black colored plaster on a vibration machine. After hardening of the plasters, samples were removed from the boxes and were trimmed in the bucco-lingual dimension for evaluation. The mean of four parallel sections examined under a stere-omicroscope was noted as the score of that sample, for buccal and lingual sides, separately. Statistically analyses were performed by using analysis of variance and paired-samples t-test. When buccal and lingual gap formations were compared, Transbond Plus® and Ketac Cem® groups were found to have larger gaps in the lingual side than buccal at p<0.05 and p<0.01 level, respectively. Thus, buccal and lingual gaps of three cements were compared separately, and no statistically significant difference was determined among three investigated cement types at buccal and lingual sides. However no differences were found among different types of band cements, it is clear that large gaps were observed under molar bands at cervical margin; where it is not easily possible to clean. Further studies should be conducted to determine a favorable strategy to eliminate these gaps and maintain a gap-free adaptation and cementation between band and tooth structure

Effects of Functional Anterior Shifting On Skeletal and Airway Structures

To compare the maxillary and mandibular skeletal structures and airway dimensions between anterior functional shifting and Class I control patients. This study was composed of 48 patients. The first group was consisted of 24 patients (male: 11, female: 13). Mean ANB value was 0.31 ± 3.49 and mean age is 13.52 ± 2.95. The second group was a skeletal Class I group, and consisted of 24 patients (male: 7, female: 17) and served as the control group. Mean ANB was 2.47 ± 2.27 and mean age was 13.99 ± 1.79. Eighteen cephalometric measurements were used to evaluate skeletal differences, and 14 measurements were used for airway dimensions. Two groups were compared with independent t test. Position and size of the mandible were not affected with anterior functional shifting. S-Go distance was smaller in anterior functional shifting patients (p<0.05). Hard palate - soft palate angle was statistically lower (p< 0.01) and soft palate length (pns-spt) was higher (p<0.01) in anterior functional shifting group. Inferior airway measurement (sbti-phwl) represented higher values in functional anterior shifting group (p< 0.05). There were statistically significant differences in Pns-ppw1 (p< 0.05), spl/sps (p< 0.01) and spl/Ips (p< 0.01) measurements. Patients with anterior functional shifting showed wider airway than Class I control group. Postnatal maxillary development deficiency may be observed in functional anterior shifting cases

Comparison of laser and piezo incisions to accelerate orthodontic tooth movement - A pilot rat model study

Aim: The aim of this study was to determine changes in bone structure after laser and piezo incisions evaluated with micro-computed tomography (micro-CT). Materials and Methods: Forty-eight adult male Sprague Dawley rats were randomly divided into 4 groups: no additional intervention to accelerate tooth movement (n=15), laser incision (n=15), piezocision (n=15), and control (n=3). These groups were divided into subgroups based on duration of applied force: 0, 3, 7, 14, 21, and 28 days. Piezo and laser incisions were made vertically on the mesial palatal side of the left maxillary molar without flap elevation. Tooth movement, bone volume, and bone mineral density were evaluated with micro-CT. P values less than 0.05 were considered statistically significant. Results: There were no significant differences in bone mineral density, bone volume, or amount of tooth movement between time points in any of the groups. The amount of tooth movement was significantly different between the groups at day 21. Conclusion: These findings provide some initial basic understanding of changes in the bone following tooth movement alone and with piezocision and laser incisions. Larger sample sizes are needed to better elucidate their effects