Tooth brush abrasion of paint-on resins for shade modification of crown and bridge resins

The purpose of this study was to evaluate the surface roughness and resistance to toothbrush abrasion of three experimental paint-on composite resins developed for the shade modification of crown and bridge resins. The paint-on resins had less filler volume fraction than restorative composites or the crown and bridge resins and consequently were of low viscosity. The maximum surface roughness (Rmax) and the maximum depth loss by abrasion for the paint-on resins following 40,000 cycles of brushing ranged from 2.45 to 4.07 microm and 8.63 to 13.67 microm, respectively. Rmax values were 37.7-67.5% lower than that for the crown and bridge resin subjected to the same test. Wear depth was 19.9-49.4% lower than for the crown and bridge resin. These results suggest that the paint-on resins are expected to have adequate resistance to toothbrush abrasion and may therefore be suitable for clinical use.     

Morphometric analysis of digital radiographic bone images for trabecular bone structure

A morphometric analysis system of digital radiographic images was constructed for the clinical evaluation of bone trabecular structural change. This system consisted of computed radiography, a mathematical morphological filter, skeletal morphometric measurements, star volume analysis, and node-strut analysis. The computed radiographic data were morphologically processed, and the trabecular structure was extracted as binary skeletal images. Analyses were made with regard to the skeletal number, separation, perimeter, complexity, continuity, and connectivity. A trial study of this system was used to evaluate the therapeutic efficacy of vitamin K₂ in the osteoporotic patients. The system enabled the quantitative evaluation of bone trabecular structural change. Significant differences were observed in the parameters of the skeletal perimeter, skeletal number, and skeletal connectivity in the femur, and improvements in the trabecular structure were indicated. In the lumbar vertebra, significant differences were observed in nearly the same parameters as the femur, although the trabecular structure had deteriorated. These results suggest that the system for bone morphometric analysis of digital radiographic images is useful for the evaluation of structural change in bone trabeculation. Source of support This work was performed at Kanagawa Dental College, Research Center of Advanced Technology for Craniomandibular Function and was supported by a grant-in-aid for Bioventure Research from the Japanese Ministry of Education, Culture, Sports, Science, and Technology.     

A custom mandibular distraction device for the rat

In the last several years, the rat model has been used as a reliable means of studying distraction osteogenesis (DO). This model has several benefits, including lower cost, the availability of molecular reagents for the rat, and the ability to perform a large number of operations in a short time. We have recently developed an external device that is custom-made for the rat mandible and secured at the mandibular ramus. The device consists of a Leone (Florence, Italy) jackscrew distraction assembly (0.2 mm per one-quarter turn), 2 Luhr L-shaped 0.8-mm five-hole microplates, and four 0.8-mm x 3-mm microscrews (Stryker-Leibinger Corp., Kalamazoo, MI) for fixation. Additionally, there is a methylmethacrylate block that is placed on the lingual surface of the angle of the mandible to support the posterior screws. Sterile surgical technique was used, and the same two surgeons performed all operations. To date, we have operated on 153 Sprague-Dawley rats. The procedure has been well tolerated by the animals. We had 17 postoperative deaths (11% mortality), largely as a result of anesthetic complications. There were no wound infections or dehiscence. A mandible fracture was noted in 6 rats (4%), which occurred at the time of device placement. There were no device dislodgments. Postmortem examination showed the device to be well positioned in all rats, with good callous formation at the distraction site. The rats surpassed their preoperative weight after an average of 9.2 days. These results compare favorably with those of other models currently in use. We have developed a device that is currently being used in the study of DO in the rat mandible. Our device is small in size, does not require wide undermining for its placement, and has had a low incidence of device dislodgment or infection. This model has shown great reproducibility and thus should be effective in its application for the histologic and biochemical investigation of DO in the rat.     

Reimpianto dentale in soggetto affetto da paralisi cerebrale infantile: problemi di valutazione medico-legale del danno

Objectives

Analysis of the parameters used for the medicolegal assessment of damages in a case of tooth avulsion and replantation in a child with cerebral palsy.

Materials and methods

The authors report a case of traumatic tooth avulsion in a child with cerebral palsy. During recess at school, the girl fell out of her wheelchair, which was being pushed by her schoolmates, and suffered maxillofacial trauma associated with superior incisor avulsion. The tooth was replanted within 60 minutes, but it fell out 6 years later. Because the traumatic event leading to the avulsion had occurred at school, the parents filed a claim for damages with the school's insurance company.

Discussion

The authors review the procedure for arriving at a fair assessment of the damage, based on the child's condition before the trauma and data in the literature on life expectancy in subjects with cerebral palsy and factors affecting the duration of the tooth replants.     

Characteristics of 40 primary extranodal non-Hodgkin lymphomas of the oral cavity in perspective of the new WHO classification and the International Prognostic Index

Non-Hodgkin lymphomas (NHLs) are often present outside the lymph nodes. Although primary extranodal NHLs (PE-NHL) form a substantial part of all NHLs, reports on oral PE-NHLs are rare. Forty patients with PE-NHL of the oral cavity have been studied for the distribution of gender, age, oral subsite and presenting complaint, histological subtype according to the WHO classification, clinical stage, treatment, and follow-up. The data are reviewed against the background of the literature. Furthermore, the International Prognostic Index has been taken into consideration. All patients had a lymphoma of B-cell lineage. Two-thirds of patients presented with locoregional disease. Mean survival time was 38 months, with a mean recurrence-free survival time of 31 months. There was no statistically significant difference in survival time between patients with bone versus soft tissue localisation of the PE-NHL. In view of the rarity of PE-NHL involving the oral region multicenter studies are needed for evaluation of the usefulness of the International Prognostic Index for non-Hodgkin lymphoma in this particular part of the body.