Background: Osteocompatibility of dressing collagen sponge is crucial for successful socket preservation before implant placement. Recently, adverse effects of implantable devices and materials were found to be associated with an excessive generation of reactive oxygen species (ROS). N-acetyl cysteine (NAC) can detoxify such cytotoxic materials.
Objectives: This study determined whether commercially available collagen dressing sponge shows any cytotoxic effects on osteoblasts, and if so, whether treating the material with NAC diminishes the cytotoxicity.
Methods:Rat calvarial osteoblasts were seeded on culture-grade polystyrene dishes or on a bovine-driven atelocollagen dressing sponge (TERUPLUG^® , Olympus Terumo Biomaterial Corp., Tokyo) soaked in saline or NAC solution. Cytotoxicity of the materials was evaluated by a cell viability analysis, attached cell quantification, an intracellular ROS fluorescent quantification and a confocal laser microscopic observation with anti-ROS and cytoskeletal fluorescent staining after 24-h incubation. Cell function on collagen sponge was assessed by ALP staining at day 5 of culture.
Results:The percentage of viable cells was below 50% on the collagen dressing sponge tested. However, pretreating the collagen sponge with NAC increased the percentage of viable cells up to 70% on material. The collagen sponge induced osteoblastic functional disorders as shown by small attached cell number, impaired cellular adhesion and suppressed alkaline phosphatase activity on materials, which was restored by pretreating the material with NAC. NAC prevented extraordinary generation of intracellular reactive oxygen species on the collagen sponge.
Conclusion:Culturing rat calvarial osteoblasts on commercial collagen dressing sponge resulted in devastating damage to cell viability and function. Application of NAC greatly reduced the cytotoxicity for the collagen dressing sponge tested, suggesting that this molecule is useful for improving the biocompatibility of biomaterials.

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The purpose of this study was to investigate the buccolingual and mesiodistal cervical diameters of each tooth in Japanese males and females to establish reference values for selecting suitable implants. The study examined the skulls of 110 cadavers belonging to the First Department of Anatomy of the Jikei University School of Medicine. The age and gender of each skull were known, and the skulls retained most of their dentition. The skulls were of 71 Japanese male and 39 Japanese female with an average age of 29 years. The gender difference for each tooth type was ascertained, then the maximum buccolingual and mesiodistal diameters of each tooth were measured at the cement-enamel junction and analyzed with respect to difference between the sexes and tooth type. The results were as follows:
1. The buccolingual diameters of the maxillary canine, mandibular canine, mandibular lateral incisor, and mandibular central incisor in males were significantly greater than those in females.
2. Mesiodistal diameters for males were significantly greater than for females, except for the maxillary first molar, mandibular central incisor, and mandibular second molar.
3. Judging from the mesiodistal cervical diameter of natural teeth, implants for selection should be increased from 3.0 mm to 8.0 mm in diameter and the difference in tooth cervical width by sex should be considered. Therefore, smaller steps in implant diameter are necessary for implant selection.

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Objective: Recently, regenerative medicine has been introduced in implant treatment; however, there is no anatomical evidence for the influence of alveolar mucosal incisions on the success or failure of treatment. In this study, we carried out an anatomical investigation of the vasculature; in particular, we investigated the arterial network in the lower alveolar mucosa and its nutrient artery and discussed the method of alveolar mucosal incision based on the anatomy.
Methods: Seven fresh cadavers were systemically injected with a lead oxide-gelatin mixture, and the stereographic vasculature of the lower alveolar mucosa was observed both macroscopically and radiographically. In addition, the facial artery and sublingual artery were macroscopically investigated in 15 embalmed cadavers.
Results: Blood was supplied to the lingual alveolar mucosa and the buccal alveolar mucosa by the sublingual artery and the facial artery, respectively. In the superficial layer of the alveolar mucosa, the arterial network was observed in a random pattern, while in the deeper layer of the alveolar mucosa, axial arteries were observed toward the crest of the alveolus. There was poor artery communication between the left and right arteries in the central regions of the buccal and lingual alveolar mucosa. Furthermore, there was negligible artery connection between the buccal and lingual alveolar mucosa in the crest of toothless jaws, and an avascular zone of approximately 2 mm was observed on angiographic study. The sublingual artery was derived from the submental artery in 67% of the cases.
Conclusion: The arterial network of the buccal and lingual alveolar mucosa forms the axial artery. It is desirable to use the alveolar mucosal flap for all the layers, considering the vascular anatomy. After making an incision in the crest of the alveolus in the toothless jaw, a flap margin of width 1 mm should be cut off in order to avoid necrosis of the margin. In cases involving bleeding of the floor of the mouth, the submental artery or facial artery should first be ligated.

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In dental radiographs, the effects of digital regulation on the conversion from the irregular tone of excessively bright or excessively dark to the standard tone was investigated with seven stages of hydroxyapatite phantom (HA phantom) made of 20 mL of polyvinyl silicone (PS) containing 15 g of hydroxyapatite crystal powder (HA) (HA 750 mg/PS mL).
Three kinds of HA phantom radiographs; standard (ST), excessively bright (EB), and excessively dark (ED) were used, and three images were made by scanning the radiographs of ST, EB and ED with a GT-500 scanner (SEIKO-EPSON) at 720 dpi. Also, two images that were regulated from EB and ED to the standard by digital regulation of TCD (tone curve dialogue) were prepared. A total of five scanned images were used to evaluate the accuracy of the digital regulation of TCD with gray scale values and hydroxyapatite contents (GSV/HA mg). The error range of the digital regulation compared with HA mg of theoretical value was narrow as follows; average -18.8 mg and standard deviation 30.5 mg in the regulated EB. Average -5 mg and standard deviation 61.5 mg in the regulated ED. From these findings, the digital regulation by TCD for irregular tones of dental radiographs is reliable for tracing the chronological change of the mineral content in alveolar bone.

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Several techniques have been suggested for the reconstruction of a severely atrophic mandible before implant placement. Autogenous bone graft with titanium mesh has become an acceptable treatment modality for partially edentulous regions.
This report describes autogenous bone graft with titanium mesh for reconstructing the mandible and investigates its stability for long-term success.
A 50-year-old male was diagnosed with bone resorption in the right side of the mandible. Radiographic examinations were carried out on the bone resorption area and we planned to reconstruct the mandible using autogenous bone. Tibial bone was used as an alternative source for obtaining sufficient bone. As a result, 6 g of autogenous bone, including cancellous bone and cortical bone, were collected. An autogenous bone graft with titanium mesh was used to reconstruct the mandible. Implant placement was performed in the mandible after 3 months. The patient was clinically and radiographically examined 3 months after the bone graft and thereafter annually for 5 years. Resorption of autogenous bone graft reached 16% after 5 years. Long-term stability of the bone morphology is an important factor for implant success.

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Purpose: The keeper surface of a conventional manufactured magnetic attachment for implants normally faces perpendicularly toward the long axis of the implant. Hence, the keeper surface is not parallel to the occlusal plane if the implant is placed at an angle. In such cases, the keeper makes a large undercut and thus, the retentive force decreases. A trial magnetic keeper cap that can be connected to an angled abutment on the implant has been developed. The attractive force of the angled magnetic attachment was compared to that of the conventional keeper.
Methods: In order to fit the Multi-Unit Abutment (Replace RP, Nobel Biocare, Sweden), a trial magnetic keeper (4.8 mm dia., 3 mm high) was milled with stainless steel (72.0%Fe-26.0%Cr-2%other). The trial keeper was connected to a 17- or 30-degree angled Multi-Unit Abutment with a screw. As a control, a Physio Magnet keeper #40 (Hitachi Metals, Japan) was prepared. After a magnet assembly (Physio Magnet #40, Hitachi Metals) was attached to each keeper, they were mounted on a screw-driven tensile machine with a Digital Force Gauge (Nidec-Shimpo Corp., Japan). The attractive force (N) was measured as the maximum tensile force needed to separate the magnet assembly from the keeper. The data (n=5) were analyzed using a t-test at a significance level of α=0.05.
Results: The trial keeper could be easily connected to the manufactured angled abutment using the screw for implant overdentures. There was no significant difference in the attractive force between the trial magnetic keeper and the control (p＞0.05).
Conclusions: The attractive force of the trial keeper was comparable to that of the conventional commercial keeper. This novel keeper has appropriate retention and can be used as a suitable retainer for implant overdentures.

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Purpose:Implant hole preparation using conventional drilling instruments is sometimes unsatisfactory due to the need to apply undue pressure. A recent study reported that an Er:YAG laser proved better with little constraint on the positioning of the laser tip. There have been reports on histological evaluation of osseointegration in comparable sites prepared with an Er:YAG laser and with traditional drills. The aim of this study was to assess the feasibility of an Er:YAG laser (Lite Touch™, Syneron, Israel) and its effectiveness by comparing laser exposure time with depth of bone hole in an experiment using the mandible of a beagle dog.
Materials and methods:A postmenopausal beagle dog was used. The laser was irradiated at three sites of the buccal bone surface of the mandible. Point A:a site over the mandibular canal;point B:the corresponding site under the mandibular canal;and point C:the buccal bone surface at the inferior margin of the mandible. The irradiation output was 8.4 W (700 mJ ×12 Hz) on the chip. The volume of spraying water was about 30 mL/min. The sapphire laser tip was 19 mm by 1.3 mm. The exposure time at points A and B was 5 sec and that at point C was 1,2,3,5 and 10 sec (n=5).
Results and discussion:The average depth of bone hole made by 5-sec laser irradiation at points A and B was 4.7±1.4 mm and 5.6±0.4 mm, respectively. It was surmised that at both points the drilling speed was 1.4 or 1.5 mm/sec for the first 3 sec through cortical bone, increasing to 1.8 mm/sec through cancellous bone. At point C, the speed increased gradually with an average of 0.7±0.1 mm at 1 sec, 1.0±0.1 mm at 2 sec, and 1.5±0.2 mm at 3 sec (with a 3-sec average speed of 0.5 mm/sec). The average speed at 5 sec and 10 sec was 1.7±0.2mm and 1.6±0.1 mm, respectively. The nature of cortical bone seems to prevent the speed from increasing.
Conclusion:The Er:YAG laser in the study required no pressure application, giving precise results with little constraint on the positioning of the laser tip. Bone holes were formed in a straight line. The preparation speed of a bone hole relative to laser irradiation time was slow and the depth seemed limited in cortical bone, whereas the speed increased through cancellous bone. The Er:YAG laser was shown to be useful for preparing implant holes with almost no technical constraints.

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