Surface Of Mandibular Bone Research Articles

A hybrid registration method using the mandibular bone surface for electromagnetic navigation in mandibular surgery.

To utilize navigated mandibular (reconstructive) surgery, accurate registration of the preoperative CT scan with the actual patient in the operating room (OR) is required. In this phantom study, the feasibility of a noninvasive hybrid registration method is assessed. This method consists of a point registration with anatomic landmarks for initialization and a surface registration using the bare mandibular bone surface for optimization. Three mandible phantoms with reference notches on two osteotomy planes were 3D printed. An electromagnetic tracking system in combination with 3D Slicer software was used for navigation. Different configurations, i.e., different surface point areas and number and configuration of surface points, were tested with a dentate phantom (A) in a metal-free environment. To simulate the intraoperative environment and different anatomies, the registration procedure was also performed with an OR bed using the dentate phantom and two (partially) edentulous phantoms with atypical anatomy (B and C). The accuracy of the registration was calculated using the notches on the osteotomy planes and was expressed as the target registration error (TRE). TRE values of less than 2.0mm were considered as clinically acceptable. In all experiments, the mean TRE was less than 2.0mm. No differences were found using different surface point areas or number or configurations of surface points. Registration accuracy in the simulated intraoperative setting was-mean (SD)-0.96 (0.22), 0.93 (0.26), and 1.50 (0.28) mm for phantom A, phantom B, and phantom C. Hybrid registration is a noninvasive method that requires only a small area of the bare mandibular bone surface to obtain high accuracy in phantom setting. Future studies should test this method in clinical setting during actual surgery.

LARGE IRREGULAR PIGMENTED MACULE IN THE POSTERIOR EDENTULOUS MANDIBULAR ALVEOLAR RIDGE

We report an unusual case of a 1.5-cm dark macule on the edentulous posterior mandibular alveolar ridge. The lesion affected a 62-year-old woman referred by a clinician to the oral medicine service with suspect of melanoma. Clinical investigation found no signs of pain and discomfort. The patient stated she had not noticed the lesion previously. An excisional biopsy was performed and during the excision a loose brownish granular material within the submucosa and over the mandibular bone surface was seen. This material was curetted and submitted for microscopic evaluation. The histopathologic report described a loosely organized connective tissue with blackened granular agglomerates that also stained the elastic collagen fibers dispersed in the matrix and in the vessel wall leading to a foreign body–type granuloma with focal argyrosis (amalgam tattoo). Postsurgical follow-up of 11 months was uneventful. We report an unusual case of a 1.5-cm dark macule on the edentulous posterior mandibular alveolar ridge. The lesion affected a 62-year-old woman referred by a clinician to the oral medicine service with suspect of melanoma. Clinical investigation found no signs of pain and discomfort. The patient stated she had not noticed the lesion previously. An excisional biopsy was performed and during the excision a loose brownish granular material within the submucosa and over the mandibular bone surface was seen. This material was curetted and submitted for microscopic evaluation. The histopathologic report described a loosely organized connective tissue with blackened granular agglomerates that also stained the elastic collagen fibers dispersed in the matrix and in the vessel wall leading to a foreign body–type granuloma with focal argyrosis (amalgam tattoo). Postsurgical follow-up of 11 months was uneventful.

The Role of Collagen Membrane as a Scaffold of Etchant for Regional Acceleratory Phenomenon

Purpose: The goal of this research is to find the role of collagen membrane, which can reduce physical damage, as a scaffold for possible alternative to the corticotomy which causes Regional Acceleratory Phenomenon (RAP). Materials and Methods: The experiments were carried out on 12 New Zealand white rabbits, approximately 3.5 kg in bodyweight. We made an incision on the skin of the mandibular border and applied 37% phosphoric acid and collagen membrane to the mandibular bone surface of the first group (experimental group), and only phosphoric acid to the second group (control group). After 3 days, 1 week, and 2 weeks, 4 rabbits each were sacrificed and specimens were obtained. Each specimen was stained by H&E and Tartrate-resistant acid phosphatase (TRAP), and histological changes were observed by light microscope. Results: The demineralization of the experimental group was weak compared to the control group. It also showed a gradual increase of demineralization (after 3 days, 1 week, and 2 weeks) and the control group showed more extensive demineralization than the experimental group. Conclusion: This study demonstrates the amount of demineralization as a result of using phosphoric acid, and as time went by, demineralization increased. The absorbable collagen membrane was used as a scaffold to increase bone demineralization effect and prevent dispersion to adjacent tissues, but rather the amount of bone demineralization decreased. Therefore, the role of collagen membrane as a scaffold for RAP was weak.

Extremely high expression of beta-actin mRNA in osteoclasts resorbing alveolar bone located at the distal area of the developing molar tooth germ in newborn rats.

Expression of beta-actin is widely utilized as an internal control of mRNA expression in various cells. Here we show evidence that the expression level of beta-actin mRNA in osteoclasts significantly differs in its intensity according to the position in bone tissues. By use of in situ hybridization, we obtained clear data showing that osteoclasts facing the distal part of a developing molar tooth germ expressed extremely high levels of beta-actin mRNA in comparison with other osteoclasts observed in the mandibular bone surface. No signal was detected when beta-nerve growth factor transcripts were observed. Electron microscopic analysis revealed that osteoclasts localized in these areas were functionally active, estimated from the expression of high levels of the osteoclast membrane antigen, Kat1 antigen, which associated with active osteoclasts. These data suggest that osteoclasts expressing extremely high levels of beta-actin are highly related to active osteoclasts induced by the mechanical stress caused by physiological movement of molar tooth germ towards distal directions in the developing mandible.

Measurement of mechanical strain on mandibular surface with mastication robot: influence of muscle loading direction and magnitude.

To investigate the mechanical effects of mastication on the mandible, we developed computational controlled mastication robot system with human dry skull and analyzed the strain distribution on the mandibular bone surface. In the mastication robot, the mandible was suspended by eight wires, which simulated masticatory muscles. A non-linear spring damper generated viscoelastic properties, and tension sensors for simulation of jaw reflection to avoid unusual biting force were applied as a biological feedback mechanism. By using this robot system, various patterns of muscle loading (change of wire direction and magnitude) were performed. From the results, significant differences in the amount of principal strain and its distribution were demonstrated in each condition (ANOVA, post hoc test, and p < 0.05). The value of maximum principal strain ranged from 79.66 x 10(-6) [at anterior border of ramus (Buccal side), 128 N] to -1.42 x 10(-6) [at foramen mentale (Buccal side), 32 N]. These results suggested that the muscle loading generated the mechanical strain on the mandibular bone surface and it was affected by the changes in loading direction and magnitude.

メカトロニクス・ロボティクスを用いたそしゃく時の下顎骨歪に関する研究

The purpose of this study was to investigate the mechanical behavior of the human mandible in mastication for basic knowledge in order to understand the interrelationship between malocclusion and bone deformation.For reproduction of accurate mechanical conditions, mechanical mastication robotics with viscous-elastic actuator controlled by a 32-bit computer system was used. Dry skulls were placed on this robotics, and muscle loading direction, forces and attachment area were determined from the information of Computed Tomographic data of living subjects. The mechanical strain generated on the surface of mandibular bone during mastication was measured by three axial electric strain gages.The results were as follows:1) On the application of light loading forces (Totalamount of 24N), the mandibular bone was bent from the anterior to the posterior part in the gonial region. Only two-dimensional distribution of strain around the loading area was demonstrated.2) As for heavy force (Total 96N), a large amount of tension was generated from the anterior to the posterior part, the alveolar bone was inclined towards the lingual side, and inferior region of the rami was bent to the outside.From the results, three-dimensional changes of strain and dynamics during mastication were demonstrated. These findings suggested that various biomechanical situations occurred in the mandible during mastication, and skeletal growth and/or bone formation might be affected by the mechanical behavior of muscle loading.Therefore, the clinical diagnosis of dentomaxillofacial deformities should include careful consideration of the muscular performance and mechanical conditions.

Effects of neonatal sympathectomy and capsaicin treatment on bone remodeling in rats

Bone metabolism may be influenced by the innervation of skeletal tissues. Neuropeptides such as vasoactive intestinal peptide, from sympathetic nerves, and calcitonin gene-related peptide, from sensory nerves, have been implicated as local modulators of bone metabolism. The effect of neonatal sympathectomy and of capsaicin-induced sensory denervation in rats was studied on the following: (i) the radial bone growth and apposition rate in tibiae (normal growth and modeling) and (ii) the percentage of periosteal surface of the mandible occupied by osteoclasts during induced remodeling. Neonate rats were treated with guanethidine, capsaicin, or appropriate vehicle. At seven weeks, maxillary molars were removed to induce remodeling on the buccal surface of the mandible. Animals were killed four days after surgery. Cross-sectional cortical area, medullary area, and periosteal apposition rate were measured by histomorphometry in ground sections of tibiae. The percentage of periosteal surface at the remodeling site occupied by osteoclasts (stained for acid phosphatase) was measured in frozen, undecalcified sections. There was no significant difference in cortical or medullary area or periosteal apposition rate in tibiae between each drug treatment and its control. However, the mandibular bone surface occupied by osteoclasts was increased 45.5% ( P ⩽ 0.005) in animals treated neonatally with guanethidine compared to controls. In contrast, the mandibular surface occupied by osteoclasts was decreased 21.2% ( P ⩽ 0.04) in animals treated neonatally with capsaicin compared to controls. The alteration of bone remodeling (osteoclast surface) by both treatments indicates that sensory and sympathetic nerves play a role in focal metabolism of bone.

Metal release from plates used in jaw fracture treatment. A pilot study

This study investigated the occurrence of corrosion associated with the use of metallic implants to stabilize jaw fractures. Three different types of plates, Co-Cr and Ni-Cr alloys and Titanium, were connected in vivo to the mandibular bone surface of monkeys ( Cercopithecus aethiops). The animals were killed after 3 and 6 months. The mucous membrane and bone tissue were analysed for concentrations of Co, Cr, Ni, Mo, Al, and Ti by atomic absorption spectrophotometry and a radiochemical neutron activation technique. With the exception of Ti, higher concentrations of all the above elements were found in the tissue near the implants when compared with contralateral controls. However, no signs of corrosion, macroscopic or microscopic, were observed on the surface of the implants.