Takayoshi Daimaruya

The Influences of Molar Intrusion on the Inferior Alveolar Neurovascular Bundle and Root Using the Skeletal Anchorage System in Dogs

The skeletal anchorage system (SAS) was developed as intraoral rigid anchors for open-bite correction by intrusion of molars. Since the application of SAS is a new modality in orthodontic treatment, the influences of radical molar intrusion on the root and the inferior alveolar neurovascular bundle were unknown. The purpose of this research is to verify the effect of molar intrusion on the neurovascular bundle, the level of osseointegration of bone screws, and root resorption. The results of this study showed mandibular molars were intruded 3.4 mm on the average over 7 months in dogs. The miniplates were well stabilized with osseointegrated bone screws and the peri-implant soft tissues showed slight inflammatory changes. Neither nerves nor blood vessels were damaged. Root resorption was observed but was repaired with new cementum. We concluded that the SAS utilizing transmucosal titanium miniplates as an immovable orthodontic anchorage could provide a new modality for molar intrusions without serious iatrogenic problems.

Effects of Maxillary Molar Intrusion on the Nasal Floor and Tooth Root Using the Skeletal Anchorage System in Dogs

The skeletal anchorage system (SAS) was developed to provide intraoral absolute anchorage for the intrusion or distalization of molars. The purpose of this study was to verify the effects of remarkable molar intrusion on the tooth root and the maxillary sinus floor. Six adult female beagles with fully erupted dentition were used. Titanium miniplates were implanted bilaterally above the maxillary second premolar root apices using pentobarbital anesthesia. The second premolars were intruded for four or seven months after three months of healing after implantation. Standardized dental radiographs were taken periodically to evaluate the amount of tooth movement and root resorption. After the experimental animals were fixed by perfusion at the end of each experimental period, the second premolars were dissected along with the surrounding alveolar bone. Undecalcified (60 microm thick) and decalcified (five microm thick) sections were prepared. The average extent of intrusion was 1.8 mm after four months and 4.2 mm after seven months. The root apices of the intruded molars penetrated into the nasal cavity. Remodeled bone around the intruded molar toots was rich in woven bone on the buccal side, whereas that on the palatal side was rich in lamellar bone. Nasal floor membrane and a thin layer of newly formed bone, which lifted intranasally, covered the intruded molar root. Root resorption partly reached into the dentine without the formation of reparative cementum, and little or no serious pathological changes were seen in the pulp of the intruded molars. SAS effectively intruded maxillary molars, but some moderate root resorption was observed.

Accuracy of intraoral radiography, multidetector helical CT, and limited cone-beam CT for the detection of horizontal tooth root fracture.

OBJECTIVE The accuracies of intraoral radiography (IOR), multidetector helical computerized tomography (MDHCT) at slice thicknesses 0.63 mm and 1.25 mm, and limited cone-beam computerized tomography (LCBCT) were compared for detection of horizontal tooth root fracture. STUDY DESIGN In 7 beagle dogs, 28 maxillary anterior teeth were used, of which 13 had artificially induced horizontal root fracture. The specimens were examined by the above-mentioned 4 modalities. Diagnosis of root fracture was based on direct visualization of radiolucent line in each image by 6 radiologists. RESULTS Sensitivity, negative predictive value, and diagnostic accuracy (true positives + true negatives) for detecting fracture lines in LCBCT (0.96 +/- 0.04, 0.97 +/- 0.03, 0.93 +/- 0.04, respectively) were significantly higher than MDHCT at 0.63 mm (0.76 +/- 0.09, 0.8 +/- 0.05, 0.8 +/- 0.05, respectively), MDHCT at 1.25 mm (0.49 +/- 0.09, 0.66 +/- 0.04, 0.69 +/- 0.05, respectively), and IOR (0.51 +/- 0.18, 0.67 +/- 0.08, 0.69 +/- 0.08, respectively). Specificity and positive predictive value showed no significant intermethod difference among the 4 modalities. CONCLUSION Limited cone-beam CT is more useful than the other 3 radiographic modalities for diagnostic imaging of horizontal tooth root fracture.

Midfacial Changes Through Distraction Osteogenesis Using a Rigid External Distraction System With Retention Plates in Cleft Lip and Palate Patients

PURPOSE The purpose of this study was to investigate the changes in and stability of the maxilla and soft tissue profile achieved after the application of distraction osteogenesis (DO) by use of rigid external distraction (RED) with a retention plate system in unilateral cleft lip and palate (UCLP) adult patients. We compared 2 treatment methods in the management of maxillary hypoplasia: Le Fort I osteotomy and DO. MATERIALS AND METHODS Six UCLP adult patients who underwent treatment with the RED retention plate system were examined (DO group). Changes in the positions of soft and hard tissue landmarks were calculated from lateral cephalograms taken before distraction, at the removal of the halo, and 1 year after surgery and were compared with those in 7 other UCLP patients who underwent Le Fort I osteotomy (LF1 group). RESULTS The mean maxillary advancement was significantly larger in the DO group than in the LF1 group after distraction. During the follow-up period, the relapse rate of the maxilla was significantly smaller in the DO group. An undesirable labial inclination of the upper incisors was found in the LF1 group, which may have been due to relapse. The DO group tended to have a higher soft tissue-to-hard tissue anterior movement ratio from the time of distraction to follow-up. CONCLUSIONS The RED retention plate system improved the midfacial profile by advancement of soft and hard tissue and minimized the risk of injury to the upper lip. Using the RED system with retention plates prevented the undesirable labial inclination of upper incisors that was found in the LF1 group.

Improvement of asymmetric stomatognathic functions, unilateral crossbite, and facial esthetics in a patient with skeletal Class III malocclusion and mandibular asymmetry, treated with orthognathic surgery

Patients with a dentofacial skeletal deformity have not only esthetic and morphologic problems related to facial proportions and dentition, but also problems of stomatognathic functions. Therefore, in addition to morphologic analysis, functional analysis is important for the diagnosis and evaluation of treatment in these patients. However, no reports have described longitudinal simultaneous evaluations of stomatognathic functions, and the comprehensive effects of surgical orthodontics on the stomatognathic functions are unclear. A patient was diagnosed as having a skeletal Class III jaw-base relationship, mandibular asymmetry, unilateral crossbite, asymmetric stomatognathic functions, and a temporomandibular disorder. She was treated with a combination of surgery and orthodontic therapy. As a result, facial proportions and occlusion improved; in particular, asymmetric stomatognathic functions, including masticatory muscle activity, condylar movement, and occlusal force, became symmetric between the left and right sides. Moreover, after 2 years of retention, the activity of the masticatory muscles and the values of occlusal force and occlusal contact area exceeded those at pretreatment. These results suggest that improvement of asymmetric stomatognathic functions can be achieved by correction of dentofacial morphology by surgical orthodontic treatment in patients with mandibular asymmetry.

Effects of CO2 Laser Irradiation of the Gingiva during Tooth Movement

Patients often feel pain or discomfort in response to orthodontic force. It was hypothesized that CO2 laser irradiation may reduce the early responses to nociceptive stimuli during tooth movement. The distribution of Fos-immunoreactive (Fos-IR) neurons in the medullary dorsal horn of rats was evaluated. Two hrs after tooth movement, Fos-IR neurons in the ipsilateral part of the medullary dorsal horn increased significantly. CO2 laser irradiation to the gingiva just after tooth movement caused a significant decrease of Fos-IR neurons. PGP 9.5- and CGRP-positive nerve fibers were observed in the PDL of all study groups. The maximum temperature below the mucosa during CO2 laser irradiation was less than 40°C. It was suggested that CO2 laser irradiation reduced the early responses to nociceptive stimuli during tooth movement and might not have adverse effects on periodontal tissue.

Effects of CO 2 Laser Irradiation of the Gingiva During Tooth Movement

It was hypothesized that CO 2 laser irradiation may reduce the early responses to nociceptive stimuli during tooth movement. The distribution of Fos- immunoreactive (Fos-IR) neurons in the medullary dorsal horn of rats was evalu- ated. Two hours after tooth movement, Fos-IR neurons in the ipsilateral part of the medullary dorsal horn increased significantly. CO 2 laser irradiation to the gingiva just after tooth movement caused a significant decrease of Fos-IR neurons. PGP 9.5- and CGRP-positive nerve fibers were observed in the PDL of all study groups. It was suggested that CO 2 laser irradiation reduced the early responses to nocicep- tive stimuli during tooth movement and might not have adverse effects on periodon- tal tissue.

Midfacial Changes Through Anterior Maxillary Distraction Osteogenesis in Patients With Cleft Lip and Palate

Abstract Maxillary hypoplasia is a major issue in cleft lip and palate patients, and predictable surgical maxillary advancement is required. In the present study, the changes and stability of the maxilla and soft tissue profile achieved after the application of anterior maxillary distraction osteogenesis (AMDO) using intraoral expander in unilateral cleft lip and palate and isolated cleft palate patients were investigated by comparing to the Le Fort I osteotomy (LFI) and maxillary distraction osteogenesis (DO) with rigid external distraction (RED) system. Ten patients who underwent orthognathic treatment with AMDO were examined (AMDO group). Changes in the positions of soft and hard tissue landmarks were calculated from the lateral cephalograms taken before the distraction, at the end of the distraction, and 1 year after the surgery. They were compared with the changes in 7 other unilateral cleft lip and palate patients who underwent LFI (LFI group) and 6 others who underwent DO with RED (RED group). The mean maxillary advancement of the AMDO group was similar to that of the RED group, judged by the change of point A. During DO, the AMDO group showed less clockwise rotation of mandible compared to the RED group. The soft tissue advancement of the upper lip and nose in the AMDO group was similar to that in the RED group, which was significantly larger than that in the LFI group. Our results indicate that AMDO can be surgical option to cleft lip and palate patients with less invasive but excellent improvement in both midfacial skeletal and soft tissue similar to DO–RED.

Decreased alveolar bone turnover is related to the occurrence of root resorption during experimental tooth movement in dogs

OBJECTIVE To investigate the relationship between root resorption (RR) and bone turnover in two different types of tooth movement in dogs. MATERIALS AND METHODS A total of 16 dogs in two different groups were used. Tooth movement of dog premolars resulted from approximately 200 g of force. Histomorphometric analysis of premolar roots was assessed after 4 and 12 weeks of tooth movement by comparing nonresorptive to resorptive surfaces. RESULTS Histomorphometric analysis indicated a significant decrease in the bone formation rate in the root resorptive areas, which resulted in decreased bone volume after 12 weeks. The threshold to detect RR in periapical radiographs was about 1.0 mm(2). CONCLUSIONS A sustained mechanical load, due to the prolonged stress and strain of continuous mechanics, induces elevated bone metabolic activity, such as the bone turnover (remodeling) and change in bone volume (modeling). Therefore, our data support the hypothesis that increased RR is related to decreased bone formation (turnover) in high stress areas exposed to prolonged orthodontic tooth movement.

Decreases of occlusal vertical dimension induce changes in masticatory muscle fiber composition

Abstract Objectives To evaluate the effects of artificially decreased occlusal vertical dimension on the fiber phenotypes of the masseter muscle in the rat. Materials and methods The experimental animals were divided into two groups: A decreased occlusal vertical dimension (DOVD) group and a sham-operated control group. Five rats from each group were sacrificed on days 0, 3, 7, and 14 after the operation. The extent of DOVD, the masseter muscle fiber composition, and fiber diameter were analyzed. Results The average decrease in the vertical dimension was 1.1 ± 0.5 mm. The masseter muscle fiber composition of Type IIA and Type IIB muscle fibers shifted significantly in favor of Type IIA fibers on day 3 in the DOVD group. Toward the end of the observation period, shifting occurred back to the original composition. A significant decrease in the diameter of muscle fibers was seen on day 3 in the DOVD group. Conclusion In this experiment, when the occlusal vertical dimension was artificially reduced, the masseter muscle atrophied and the muscle fiber type changed temporarily while adapting to the new position of the mandible.