Ayao Hirashita

Elimination of transverse dental compensation is critical for treatment of patients with severe facial asymmetry

This case report describes the importance of eliminating transverse dental compensation during preoperative orthodontic treatment for a patient with severe facial asymmetry. The patient, a 17-year-old Japanese woman, had severe facial asymmetry involving the maxilla and the mandible, and extreme transverse dental compensation of the anterior and posterior teeth in both arches. Therefore, the main treatment objectives were elimination of the transverse dental compensation by orthodontic treatment and correction of the morphology of the maxilla and the mandible by orthognathic surgery. The preoperative orthodontic treatment resulted in sufficient elimination of the transverse dental compensation and movement of the teeth into their proper positions so that basal bone firmly supported them. LeFort I osteotomy and sagittal split ramus osteotomy were performed to correct the skeletal morphology. Facial asymmetry was dramatically improved, and a favorable occlusion was obtained. At 1 year 8 months after the surgical orthodontic treatment, the facial symmetry and occlusion remained favorable. The results suggest that sufficient elimination of transverse dental compensation in the maxillary and mandibular arches during preoperative orthodontic treatment is requisite for successful treatment of severe facial asymmetry.

Tooth movement limited to periodontal ligament width using interrupted orthodontic force

Abstract A new orthodontic appliance with ratchet mechanism (ratchet bracket) was used in experimental animals and clinically, in order to assess tooth movement limited to periodontal ligament (PDL) width, using interrupted orthodontic force. After experimental tooth movement using two beagle dogs’ third incisors, active bone formation was seen at the tension region on fluorescent images, and blood vessels could be seen in the maximal compressed region. No obvious signs of root resorption were seen on the outline of the roots in micro-CT images. The average distal movement of 10 upper canines in six female patients was 1.9 mm (S.D. 0.21) in a month, and 5.5 mm in 102 days, which was the longest period. No patient complained of spontaneous pain during tooth movement or pain on biting. Dental radiography revealed long and thick lamina dura on the tension side of the canines, suggesting bodily tooth movement and a relatively dense bone formation. There was no obvious sign of root resorption in any canines. These results suggested that an interrupted orthodontic force controlled to a distance of 0.26 mm using ratchet mechanism may cause tooth movement without serious damage or pain.

Orthodontic treatment for oral rehabilitation after multiple maxillofacial bone fractures

We present the orthodontic treatment of a patient with occlusal dysfunction after plastic surgery for multiple maxillofacial bone fractures caused by a traffic accident. The patient had mandibular deviation to the right because of inappropriate repositioning and fixation of the fractured bone and complete avulsion of both mandibular central incisors. The bilateral mandibular incisors, canines, and premolars were also suspected of partial avulsion or alveolar bone fracture. Several tests, including percussion and dental computed tomography, were performed on these teeth to rule out ankylosis and confirm tooth movement. Camouflage orthodontic treatment was carried out with expansion of the maxillary arch, alignment of both arches, and space closure between the mandibular lateral incisors to improve the occlusion. Good occlusion and interdigitation were obtained. Orthodontic treatment is useful for the rehabilitation of occlusal dysfunction caused by multiple maxillofacial bone fractures.

Orthodontic contribution to the periodontal management of a patient with localized aggressive periodontitis (post-juvenile periodontitis)

Abstract In aggressive periodontitis, pathological tooth migration and destruction of occlusion often occur in patients’ younger age, therefore, it is necessary to give a treatment considering their quality of life. A 30-year-old female patient diagnosed as Angle class I upper protrusion associated with post-juvenile periodontitis had diastema of maxillary incisors since she was about 20 years old. She was treated by multidisciplinary approach of a periodontist and an orthodontist and patients obtained esthetical dental arch and functional occlusion. Periodontal tissue was also in good condition and she was very satisfied with the outcome. The patient has obtained periodontal and orthodontic long favorable stability. Good periodontal condition has been maintained for 6 years after active orthodontic treatment.

A study on change of palate form in ages 6–12 years

Mini-screw implant for orthodontics (mini-screw) has recently drawn attention as an external anchorage in orthodontic treatment. The aim of this study was to define correlations between shape and torque property of mini-screws. Surface texture and the shape of six commercially available mini-screws were observed by scanning electron microscope. Additionally, maximum insertion/removal torque of the miniscrews against a hard polyurethane foam was measured by a modified experimental torque meter. Mini-screws were classified as either straight (angle, <18) or tapered type due to their thread angles. The self-tapping miniscrews showed >908 of apex angles whereas self-drilling screws were <608. A large number of defects were observed on the surface of pure titanium mini-screws in the SEM images. The insertion/removal torque of tapered type was remarkably higher than that of straight type. The insertion/ removal torque was apparently influenced by the miniscrews’ shape due to the individual mechanical properties of materials. In particular, pure titanium mini-screws generated relatively lower torque due to their inferior mechanical properties in comparison with stainless steel or titanium alloy mini-screws. These findings suggest that mini-screws should be applied to surgical sites with caution as regards inherent bone quality in clinical practice. doi: 10.1016/j.odw.2009.12.004

Asymmetry of the lips of orthognathic surgery patients

Material andmethods: The 3D finite element model of maxillary 14 teeth, periodontal ligament, alveolar bone, archwire, bracket was created. An appliance with 0.018-in slot brackets with 0.018 0.025-in stainless steel archwire was generated and four power arms were attached at a site mesial and distal to canine onto the archwire bilaterally and perpendicular to the archwire. Assuming that two titanium mini-screw or mini-plate implants, used as orthodontic skeletal anchorage, were inserted at both sides of the buccal region of the posterior teeth, the retraction force of 150 g was applied bilaterally from the implant anchorage to each power arm parallel to the archwire. The height levels on power arm from the bracket slot were 0, 2, 4, 6, 8, 10 and 12 mm. Coefficient of friction between bracket slots and archwire was assumed to be 0.2. We investigated how the archwire is deformed and how the maxillary central incisor will move, consequently. Results: In case the power arm was placed mesial to canine, at a level of 5.5 mm, the bodily movement of the incisor was produced and the archwire was less deformed. Lingual crown tipping of the incisor was observed at the level of retraction force below 5.5 mm and the anterior segment of the archwire was deformed downward. On the other hand, lingual root tipping was observed above 5.5 mm, the anterior segment of the archwire was deformed downward. In case the power arm was placed distal to canine, at a level of 11.2 mm, bodily movement was found. Discussion: At the power arm height of 10 mm, there were remarkable differences in archwire deformation and the resultant incisor movement between the cases in which power arms were attached mesial and distal to the canine. When the power arm was located mesial to canine, the anterior segment of the archwire was raised upward due to a bending moment produced at a portion of archwire between lateral incisor and canine as a cantilever effect of the power arm set mesial to canine. On the other hand, in case the power arm was set distal to canine, the anterior segment of the archwire was less deformed. In fact, the canine is subjected to an intrusive force and the root apex is depressed into its socket, however, the adjacent alveolar bone may strongly resist the intrusive action and will absorb the force and bending moment generated from the archwire deformation. Therefore, an intrusive force caused by archwire deformation is less likely to be transmitted to the central incisor than the case of the power arm set mesial to canine. From a biomechanical viewpoint, the relationship between the line of action of a force and the location of the center of resistance of a tooth determines the type of tooth movement. However, tooth movements analyzed in this study were not in agreement with those based on this biomechanical principle. Knowledge of the biomechanical principles of tooth movement cannot be directly applied in clinical situations in which sliding mechanics is employed. Effect of the archwire deflection on force system acting on a tooth should also be taken into consideration. Conclusions: Placement of the power arm between lateral incisor and canine enables orthodontists to carry out a better control of the anterior teeth in sliding mechanics. Not only the biomechanical principles associated with the location of the center of resistance of a tooth but also the deformation of the archwire should be taken into consideration to speedy and efficient orthodontic tooth movement.

Changes of Serum Biochemical Markers during Bone Repair just after Orthognathic Surgery

Abstract The purpose of this study was to elucidate changes in serum biochemical markers related to bone turnover after orthognathic surgery in skeletal Class III patients. The subjects consisted of 16 healthy, adult men aged 22.1 to 40.3 years, one week before surgery. Samples of venous blood (5–6 mL) were taken at 10 : 00 a. m.–12 : 00 a. m.. The timing of each sample collection was: before-surg, one week before surgery; 3-d, three days after surgery; 10-d, ten days after surgery; 1-m, one month after surgery; 3-m, 3 months after surgery; and 6-m, 6 months after surgery. Serum osteocalcin, bone alkaline phosphatase (BAP), and tartrate-resistant acid phosphatase (TRAP) were measured at each stage. Additionally, serum C-reactive protein (CRP) and other serum components were measured as general examinations of bone metabolism and for health checks. Results: 1. Among all values of serum components during the observation period, only CRP at 3-d was higher than the standard value for Japanese adults. 2. Serum osteocalcin (p

Effects of Exogenous Bone Morphogenetic Protein 2 on the Formation of Mouse Molar Tooth Germ

Abstract The effects of exogenous bone morphogenetic protein 2 (BMP2) in the formation of mouse molar tooth germ were investigated using an organ culture system of mandibles. Mandibles dissected from mouse embryos at Ell were cultured in BGJb medium supplemented with and without 4 μg/ml of BMP2 for 8 days. The mRNA expression of glyceraldehyde-phosphate dehydrogenase (GAPDH), a housekeeping gene, in the mandibles was examined by competitive polymerase chain reaction in com bination with reverse-transcription. Cryosections of the mandibles were prepared and stained with hematoxylin and eosin, and the maximum area of molar tooth germ on the section was measured. The distribution of proliferating cell nuclear antigen (PCNA) was analyzed using immunohistochemistry. Exogenous BMP2 did not induce a significant difference in the amount of mRNA for the GAPDH contained in the mandibles. The maximum area of BMP2 - treated molar tooth germ was 0.0348 ° 0.0027 mm 2 (mean ° SD, n=4), which was 78% greater than that of the control molar tooth germ (0.0195 ° 0.0046 mm 2 ) (p