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The purpose of this review is to search for complications of dental implant superstructures and consider the issues involved. This narrative review was performed by searching through PubMed databases and review articles that were published after 1990. Misfitting of the superstructure can result in loosening of screws, reduced preload, and in some cases, significant stress around the implant. External connection modalities and single implant prostheses have been reported to have more loose or broken abutment screws. In addition, when zirconia abutment was used for platform shifting, the rate of fracture of the abutment was considered to be high. Additionally, it was reported that men were significantly at an increased risk of abutment fracture. As for the retention mechanism of implant overdenture, stud attachment (Locator type) should receive more attention to wear and damage of retention parts than other attachments. The causes of the complications of implant superstructures have not been clarified in some cases, and further verification is required. Verification of complications is considered important to obtain a long-term prognosis for superstructures of implants. It will be necessary to further verify complications of implants in the future.

Collagenous biomaterials that are clinically applied in dentistry have dermis-type and membrane-type, both of which are materials for promoting bone and soft tissue formation. The properties of materials supplied with different types could affect their biodegradation periods. The purpose of this study was to characterize five of these products by four different methods: scanning electron microscopy (SEM) observation, thermogravimetry-differential thermal analysis (TG-DTA), 0.01 wt% collagenase dissolution test, and subcutaneous implantation test in vivo. SEM micrographs revealed that both dermis and membranous materials were fibrous and porous. The membranous materials had higher specific derivative thermal gravimetry (DTG) peak temperatures in TG-DTA at around 320 °C, longer collagenase dissolution time ranging from about 300 to 500 min, and more longevity in mice exceeding 9 weeks than the dermis materials. There existed a correlation between the peak temperature in TG-DTA and the collagenase dissolution time. It was considered that higher cross-link degree among collagen fibrils of the membrane-type collagenous materials might account for these phenomena. The experimental protocol and numerical results obtained could be helpful for selection and future development of fibrous collagenous biomaterials in clinical use.

Background The purpose of this study was to evaluate the accuracy of intraoral scanners by comparing the trueness and precision of several types of scanners in measuring the distance between the ball abutments on pairs of multiple implants. Methods Seven implants were placed on a fully edentulous upper jaw model. After ball abutments were attached to the implants on the master model, the three-dimensional (3D) shape of the model was evaluated using a computer numerical control 3D coordinate-measuring machine. Subsequently, the 3D shape-related data of the model were obtained using two types of intraoral scanners (3M True Definition Scanner [TDS] and 3Shape Trios3 [TR3]) and two types of laboratory scanners (KaVo ARCTICA Auto Scan [KA] and Identica Hybrid [IH]). Using the obtained 3D shape-related data, the trueness and precision in measuring the distance between the balls within seven pairs of ball abutments were compared among the scanners using 3D analysis software. Results Intraoral scanners produced significantly greater errors in trueness and precision than laboratory scanners in measuring the distances between the ball abutments in all the dental regions. Between the intraoral scanners, powder-requiring TDS produced significantly lower errors at inflection points than powder-free TR3. Conclusions These results indicate that an optical impression technique using an intraoral scanner is suitable for dental implant treatment in patients with a few missing teeth.

Titanium is often used in the medical field and in dental implants due to its biocompatibility, but it has a high rate of leading to peri-implantitis, which progresses faster than periodontitis. Therefore, in the present study, the expression of cytokines from gingival epithelial cells by nanotitania was investigated, which is derived from titanium in the oral cavity, and the additional effect of Porphyromonas gingivalis (periodontopathic bacteria) lipopolysaccharide (PgLPS) was investigated. Ca9-22 cells were used as a gingival epithelial cell model and were cultured with nanotitania alone or with PgLPS. Cytokine expression was examined by reverse transcription-quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. In addition, cellular uptake of nanotitania was observed in scanning electron microscopy images. The expression of interleukin (IL)-6 and IL-8 significantly increased in Ca9-22 cells by nanotitania treatment alone, and the expression was further increased by the presence of PgLPS. Nanotitania was observed to phagocytose Ca9-22 cells in a dose- and time-dependent manner. Furthermore, when the expression of IL-11, related to bone resorption, was investigated, a significant increase was confirmed by stimulation with nanotitania alone. Therefore, nanotitania could be associated with the onset and exacerbation of peri-implantitis, and the presence of periodontal pathogens may worsen the condition. Further clinical reports are needed to confirm these preliminary results.

Titanium is often used in the medical field and in dental implants due to its biocompatibility, but it has a high rate of leading to peri-implantitis, which progresses faster than periodontitis. Therefore, in the present study, the expression of cytokines from gingival epithelial cells by nanotitania was investigated, which is derived from titanium in the oral cavity, and the additional effect of Porphyromonasgingivalis (periodontopathic bacteria) lipopolysaccharide (PgLPS) was investigated. Ca9-22 cells were used as a gingival epithelial cell model and were cultured with nanotitania alone or with PgLPS. Cytokine expression was examined by reverse transcription-quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. In addition, cellular uptake of nanotitania was observed in scanning electron microscopy images. The expression of interleukin (IL)-6 and IL-8 significantly increased in Ca9-22 cells by nanotitania treatment alone, and the expression was further increased by the presence of PgLPS. Nanotitania was observed to phagocytose Ca9-22 cells in a dose- and time-dependent manner. Furthermore, when the expression of IL-11, related to bone resorption, was investigated, a significant increase was confirmed by stimulation with nanotitania alone. Therefore, nanotitania could be associated with the onset and exacerbation of peri-implantitis, and the presence of periodontal pathogens may worsen the condition. Further clinical reports are needed to confirm these preliminary results.

Purpose To reveal effects of improvement of masseter muscle activity on brain function in elderly people wearing complete dentures.Methods Subjects were 14 edentulous patients with a chief complaint of the inconvenience of their complete dentures. The surface electromyographic (EMG) activity of the masseter muscles was measured. Brain activities were analyzed with functional magnetic resonance imaging (fMRI), employing chewing gum as the task program. Cognitive functions were evaluated with Trail Making Test Part A (TMT-A), Rey Auditory Verbal Learning Test (RAVLT) and Rey-Osterrieth Complex Figure Test (R-OCFT). Those evaluations were performed in which subjects wore their old dentures (OD) or newly fabricated dentures (ND).Results We compared ND condition with OD condition. The masseter muscle activity significantly increased in ND condition (p0.05, Wilcoxon signed rank test). The brain activity increased significantly in the superior frontal gyrus, precentral gyrus, putamen, inferior parietal lobule, cerebellum, inferior frontal lobe, and middle frontal gyrus under the ND condition than under the OD condition (p0.01, uncorrected, cluster size10 voxels). Results of TMT-A, RAVLT, and R-OCFT were also significantly improved (p0.05, Wilcoxon signed rank test).Conclusions In the edentulous elderly, the brain activity was increased following the improvement of the masseter muscle activity. Consequently, it is possible that the improvement of the masseter muscle activity might influence on the attention, verbal skills, and visual memory.

Osteo-conductive bone substitute materials are required in dentistry. In this study, highly pressed nano-hydroxyapatite/collagen (P-nHAP/COL) composites were formed by a hydraulic press. Critical-size bone defects (Φ = 6 mm) were made in the cranial bones of 10-week-old Wistar rats, in which P-nHAP/COL and pressed collagen (P-COL) specimens were implanted. Defect-only samples (DEF) were also prepared. After the rats had been nourished for 3 days, 4 weeks, or 8 weeks, ossification of the cranial defects of the rats was evaluated by micro-computed tomography (micro-CT) (n = 6 each). Animals were sacrificed at 8 weeks, followed by histological examination. On micro-CT, the opacity of the defect significantly increased with time after P-nHAP/COL implantation (between 3 days and 8 weeks, p < 0.05) due to active bone regeneration. In contrast, with P-COL and DEF, the opacity increased only slightly with time after implantation, indicating sluggish bone regeneration. Histological inspections of the defect zone implanted with P-nHAP/COL indicated the adherence of multinucleated giant cells (osteoclasts) to the implant with phagocytosis and fragmentation of P-nHAP/COL, whereas active bone formation occurred nearby. Fluorescent double staining indicated dynamic bone-formation activities. P-nHAP/COL is strongly osteo-conductive and could serve as a useful novel bone substitute material for future dental implant treatments.

This narrative review aims to provide an overview of recent studies and case reports on three-dimensional (3D) printing, and to verify the applicability of 3D printers in the field of dental prostheses. This review was performed by conducting a search of PubMed. The clinical application of fabricating a prosthesis made with cobalt-chromium is considered possible depending on the material and hardware of the 3D printer. However, it is currently difficult to assess the clinical use of 3D-printed zirconia crowns. Further research is required, such as verification of materials used, margin morphology, and hardware. Clinically acceptable results have been reported for patterns using 3D printers. Interim restorations made using a 3D printer have been reported with good results that are considered clinically usable. Dentures made with 3D printers need further verification in terms of strength and deformation. Custom trays made with 3D printers are clinically useful, however, issues remain with design time and effort. Although several studies have reported the usefulness of 3D printers, further verification is required since 3D printers are still considered new technology.

Purpose To determine the effects of titanium nanoparticles, that may have been scattered after dental implant placement, on gene and promoter expression, and gingival tissue. Methods Ca9-22 cell lines were used as gingival epithelial cells to assess the effects of titanium dioxide nanomaterials as titanium nanoparticles. Cells were cocultured with or without titanium dioxide nanomaterials prior to gene and promoter expression analysis. Expression of interleukin-13α2 receptor was investigated using real-time quantitative reverse-transcription polymerase chain reaction and immunofluorescence staining. Additionally, the enhanced messenger ribonucleic acid (mRNA) expression of transforming growth factor β1 was analyzed using the same method. Results Titanium dioxide nanomaterials affected gene and promoter expression in Ca9-22 cells: among the 160 upregulated genes, the upregulation of IL13RA2, which encodes interleukin-13α2 receptor, was the highest (8.625 log2 fold change). Immunofluorescence staining confirmed the increased expression of interleukin-13α2 receptor, which enhanced transforming growth factor β1 expression by stimulation with interleukin-13. Conclusion Titanium dioxide nanomaterials applied on the gingival epithelium around the dental implant may increase interleukin-13α2 receptor expression. In turn, this can enhance the secretion of transforming growth factor β1, which is known to promote the differentiation of osteoclasts involved in bone resorption, and potentially affect gingival tissue.

PURPOSE The purpose of this study was to examine morphological changes in the superstructure of implants in relation to the degree of attrition of the implant superstructure and its antagonists. METHODS Thirty-three patients participated. The implant superstructures of the first molar and its antagonists were scanned with an intraoral scanner every 3 months. The amount of attrition was calculated in relation to the various materials used for the superstructure, and differences were analyzed statistically (P < 0.05). RESULTS Attrition of the implant superstructure was 110 ± 30 µm for monolithic zirconia and 105 ± 27 µm for resin-veneered metal after 12 months. No statistically significant difference was found between the two groups. In contrast, attrition of the antagonists was 75 ± 25 µm for zirconia and 105 ± 20 µm for resin-veneered metal after 12 months. A statistically significant difference in the attrition levels between the two groups was observed after 9 and 12 months. CONCLUSION During the 12-month observation period, there was no difference in superstructure attrition between zirconia and resin-veneered metal. Attrition of the antagonists was higher for hybrid composite resin-veneered metal than for zirconia, suggesting that surface roughness affected the degree of attrition.

When the sinus is enlarged, it may be necessary to elevate the floor of the maxillary sinus using the crestal or lateral approach. This report presents a case where sinus floor elevation was performed using tricalcium phosphate (TCP) plates supported by implant bodies, and only the blood clot was present around the implant bodies. Cone-beam computed tomography images, taken one year after the lateral approach, revealed the presence of a TCP-like radio-opacity, which almost disappeared after two years. About seven years after the surgery, the patient's superstructure and occlusion were stable. Furthermore, the grafted TCP was completely absorbed, and the implant body appeared to be in good condition, with no signs of bone resorption around the implant.

The purpose of this study was to assess the knowledge, practice, confidence, and perceived barriers to oral cancer screening among teaching faculty in Japan. Results were compared by specialist as well as years of clinical experience. A 25-question survey was used to assess the oral cancer screening practices of faculty dentists at Iwate Medical University, School of Dental Medicine, the only dental school located in the northeast (Tohoku) region of Japan. The study was approved by the Institutional Review Board of Iwate Medical University. The response rate was 83% (n = 110, 71.8% were male). This survey revealed that only 43.6% of the dentists performed oral cancer screening frequently (always or usually) at the initial appointment, and there was no significant differences between specialists and clinical experience. Visual inspection of the oral cavity was the primary screening method, but the frequency and content of the examination (TMJ and tonsil) was significantly different between specialties. A history of cancer and tobacco use motivated providers to perform an examination and was significantly different between various specialists and clinically experienced providers. In contrast, HPV and alcohol consumption were a weak motivator. The confidence level of providers on their examination knowledge/skills was poor, especially among junior faculty. More than 80% of junior faculty indicated a lack of knowledge/skills as a major barrier.

Purpose The digitization of the dental field has been vigorously promoted in recent years. An impression using an intraoral scanner is considered to significantly change future dental treatment. The purpose of this review is to evaluate accuracy and practicality of various intraoral scanners and verification method of intraoral scanners. Study selection This review was based on articles searched through the MEDLINE and PubMed databases. The main keywords that were employed during the search were “Oral Scanner, Intraoral Scanners, Desktop Scanner, and Digital Impression”. Result It was reported that illuminance and color temperature affected trueness and precision of intraoral scanners. The repeatability of intraoral scanners indicated the possibility of producing fixed prostheses within the range of being partially edentulous. It is considered difficult to use intraoral scanners in fabricating cross-arch fixed prostheses. However, with intraoral scanners, it may be considered possible to fabricate mouth guards and dentures equivalent to those of desktop scanners. Current intraoral scanner scans are considered more comfortable than traditional impressions that use irreversible hydrocolloid and elastomeric impression materials. Conclusion Since the intraoral scanner is an evolving device, further improvement in accuracy is expected in the future. In addition, verification of the accuracy of intraoral scanners must be conducted accordingly.

Purpose To determine the appropriate attachment and design of a denture base for mandibular implant overdenture (IOD), the oral mucosa pressure caused by mandibular implant overdentures was measured using edentulous jaw models with various attachments. Methods An experimental edentulous mandibular model with a 1.5-mm thick artificial oral mucosa was used. Two implants were placed at the area equivalent to the bilateral canines of an experimental jaw model. Locator attachments (LA), ball attachments (BA), magnetic attachments (MA), and round-bar attachments (R-BA) were fabricated. Six miniature pressure sensors were placed at the bilateral buccal premolar regions, bilateral buccal shelves, and bilateral lingual molar regions. A precision universal testing machine was used to apply dynamic repetitive loads of 50 N. The load points were the center of the model, which should represent bilateral mastication on both sides (bilateral load), and were equivalent to the left first molar, which should represent unilateral mastication (unilateral load). Statistical analysis was performed using one-way analysis of variance. Multiple comparisons were then performed using the Bonferroni post hoc test. P Results Under the bilateral load condition, the lower oral mucosa pressure value with BA was measured, compared to other attachments at all measurement sites. Under the unilateral load condition, the oral mucosa pressure value of BA was smaller than the other attachments at the measurement site on the loading side. Conclusions BA has exerted the greatest effects on support and bracing, suggesting that, BA is suitable for reducing oral mucosa pressure during mastication.

OBJECTIVES: The purpose of this study was to assess the diagnostic property of intraoral bitewing radiographs (BTW) for early stage interproximal caries, and to compare them with periapical radiographs (PA) at different levels of caries progression. METHODS: A total of 241 interproximal surfaces of BTW and corresponding PAs were used. Seven teaching faculty consisting of three oral and maxillofacial radiologists, two operative faculty, and two prosthodontists evaluated the images. The observers graded images as either “intact”, “enamel caries 1/2 width”, or “caries into dentin”. The gold-standard was established by consensus of two experienced faculty with 35 years and 27 years of experience. Specificity, sensitivity, positive-predictive value, and negative-predictive value were calculated for the different level of caries progression. Furthermore, receiver operating curves) of BTW and PAs of each evaluator were made and the area under the curve of BTW and PAs were compared. RESULTS: There was no significant difference in the specificity of BTW and PAs. BTW showed significantly higher sensitivity than PAs in all levels of caries progression (p

Epithelial attachment via the basal lamina on the tooth surface provides an important structural defence mechanism against bacterial invasion in combating periodontal disease. However, when considering dental implants, strong epithelial attachment does not exist throughout the titanium-soft tissue interface, making soft tissues more susceptible to peri-implant disease. This study introduced a novel synthetic peptide (A10) to enhance epithelial attachment. A10 was identified from a bacterial peptide display library and synthesized. A10 and protease-activated receptor 4-activating peptide (PAR4-AP, positive control) were immobilized on commercially pure titanium. The peptide-treated titanium showed high epithelial cell migration ability during incubation in platelet-rich plasma. We confirmed the development of dense and expanded BL (stained by Ln5) with pericellular junctions (stained by ZO1) on the peptide-treated titanium surface. In an adhesion assay of epithelial cells on A10-treated titanium, PAR4-AP-treated titanium, bovine root and non-treated titanium, A10-treated titanium and PAR4-AP-treated titanium showed significantly stronger adhesion than non-treated titanium. PAR4-AP-treated titanium showed significantly higher inflammatory cytokine release than non-treated titanium. There was no significant difference in inflammatory cytokine release between A10-treated and non-treated titanium. These results indicated that A10 could induce the adhesion and migration of epithelial cells with low inflammatory cytokine release. This novel peptide has a potentially useful application that could improve clinical outcomes with titanium implants and abutments by reducing or preventing peri-implant disease.

The development of new osteoconductive bone substitute materials is expected in medicine. In this study, we attempted to produce new hydroxylapatite (HAP)/collagen (Col) composites using two HAP particles of different sizes and porcine type I collagen. The two HAP particles were either nano-sized (40 nm in average diameter; n-HAP) or had macro-pore sizes of 0.5–1.0 mm in length with fully interconnected pores (m-HAP). The aim of this study was to investigate the effects of apatite particle size in two HAP/Col composites on the osteogenic differentiation profile in osteoblast-like cells (SaOS-2). We created a collagen control sponge (Col) and two HAP/Col composite sponges (n-HAP/Col and m-HAP/Col) using freeze-drying and dehydrothermal cross-linking techniques, and then punched out samples of 6 mm in diameter and 1 mm in height. The SaOS-2 cells were cultured on three test materials for 1, 2, 3 and 4 weeks. Total RNA was extracted from the cultured cells and the expression of osteogenic differentiation-related genes was evaluated by reverse transcription PCR (RT-PCR) using primer sets of alkaline phosphatase (ALP), type 1 collagen (COL1), bone sialoprotein (BSP) and osteocalcin precursor [bone gamma-carboxyglutamate (gla) protein (BGLAP)] genes, as well as the β-actin gene. The cells were also cultured on Col, n-HAP/Col and m-HAP/Col specimens for 1 and 4 weeks, and were then observed under a scanning electron microscope (SEM). The experimental results were as follows: RT-PCR indicated that osteogenic differentiation, particularly the gene expression of BSP, was most accelerated when the cells were cultured on n-HAP/Col specimens, followed by m-HAP/Col, whilst the weakest accelaeration was observed when the cells were cultured on Col specimens. As shown by the SEM images, the SaOS-2 cells were fibroblastic when cultured on Col specimens for up to 4 weeks; they were fibroblastic when cultured on n-HAP/Col specimens for 1 week, but appeared as spheroids, while actively phagocytizing n-HAP particles at 4 weeks; however, they appeared as deformed fibroblasts when cultured on m-HAP/Col specimens, detached from the particles. Despite limited experimental results, our study suggests that n-HAP/Col may be employed as a new osteoconductive bone substitute material.

The aim of this study was to evaluate the barrier function of platelet-induced epithelial sheets on titanium surfaces. The lack of functional peri-implant epithelial sealing with basal lamina (BL) attachment at the interface of the implant and the adjacent epithelium allows for bacterial invasion, which may lead to peri-implantitis. Although various approaches have been reported to combat bacterial infection by surface modifications to titanium, none of these have been successful in a clinical application. In our previous study, surface modification with protease-activated receptor 4–activating peptide (PAR4-AP), which induced platelet activation and aggregation, was successful in demonstrating epithelial attachment via BL and epithelial sheet formation on the titanium surface. We hypothesized that the platelet-induced epithelial sheet on PAR4-AP–modified titanium surfaces would reduce bacterial attachment, penetration, and invasion. Titanium surface was modified with PAR4-AP and incubated with platelet-rich plasma (PRP). The aggregated platelets released collagen IV, a critical BL component, onto the PAR4-AP–modified titanium surface. Then, human gingival epithelial cells were seeded on the modified titanium surface and formed epithelial sheets. Green fluorescent protein (GFP)–expressing Escherichia coli was cultured onto PAR4-AP–modified titanium with and without epithelial sheet formation. While Escherichia coli accumulated densely onto the PAR4-AP titanium lacking epithelial sheet, few Escherichia coli were observed on the epithelial sheet on the PAR4-AP surface. No bacterial invasion into the interface of the epithelial sheet and the titanium surface was observed. These in vitro results indicate the efficacy of a platelet-induced epithelial barrier that functions to prevent bacterial attachment, penetration, and invasion on PAR4-AP–modified titanium.

The aim of this study was to investigate the extent and forms of predoctoral implant dentistry instruction in North American dental schools and to identify future directions and challenges. The survey collected data on curriculum content, departmental oversight, techniques, and materials, as well as current problems to be solved. The 30-question survey was sent in 2012 to the dean or administrator in charge of the predoctoral curriculum of all 73 dental schools in the U.S. and Canada at the time; four reminders were sent. Forty-seven schools responded, for a response rate of 64%. Of the 47 responding schools, 46 (98%) offered didactic instruction (mean of 17 hours); 87% had a laboratory component (mean of 14.46 hours); and 57% had a clinical requirement. In the responding schools, students had an average of 1.85 implant restorative cases and 0.61 surgical cases. Forty-two of the schools (89%) had implemented observation of implant surgery and/or assisting with implant surgery in their curricula. Major challenges reported in implementing a comprehensive predoctoral implant curriculum included expense of implant systems to the schools and to patients, shortage of predoctoral cases, and lack of curriculum time and trained faculty. These results show that implant education for predoctoral dental students continues to expand, with a trend towards more preclinical exercises and clinical experiences and fewer didactic courses.

An impression technique called optical impression using intraoral scanner has attracted attention in digital dentistry. This study aimed to evaluate the accuracy of the optical impression, comparing a virtual model reproduced by an intraoral scanner to a working cast made by conventional silicone impression technique. Two implants were placed on a master model. Working casts made of plaster were fabricated from the master model by silicone impression. The distance between the ball abutments and the angulation between the healing abutments of 5 mm and 7 mm height at master model were measured using Computer Numerical Control Coordinate Measuring Machine (CNCCMM) as control. Working casts were then measured using CNCCMM, and virtual models via stereo lithography data of master model were measured by a three-dimensional analyzing software. The distance between ball abutments of the master model was 9634.9 ± 1.2 μm. The mean values of trueness of the Lava COS and working casts were 64.5 μm and 22.5 μm, respectively, greater than that of control. The mean of precision values of the Lava COS and working casts were 15.6 μm and 13.5 μm, respectively. In the case of a 5-mm-height healing abutment, mean angulation error of the Lava COS was greater than that of the working cast, resulting in significant differences in trueness and precision. However, in the case of a 7-mm-height abutment, mean angulation errors of the Lava COS and the working cast were not significantly different in trueness and precision. Therefore, distance errors of the optical impression were slightly greater than those of conventional impression. Moreover, the trueness and precision of angulation error could be improved in the optical impression using longer healing abutments. In the near future, the development of information technology could enable improvement in the accuracy of the optical impression with intraoral scanners.

Purpose We examined safety issues related to the presence of various metallic dental materials in magnetic resonance (MR) imaging at 7 tesla. Methods A 7T MR imaging scanner was used to examine 18 kinds of materials, including 8 metals used in dental restorations, 6 osseointegrated dental implants, 2 abutments for dental implants, and 2 magnetic attachment keepers. We assessed translational attraction forces between the static magnetic field and materials via deflection angles read on a tailor-made instrument and compared with those at 3T. Heating effects from radiofrequency during image acquisitions using 6 different sequences were examined by measuring associated temperature changes in agarose-gel phantoms with a fiber-optic thermometer. Results Deflection angles of the metallic dental materials were significantly larger at 7T than 3T. Among full metal crowns (FMCs), deflection angles were 18.0° for cobalt-chromium (Co-Cr) alloys, 13.5° for nickel-chromium (Ni-Cr) alloys, and 0° for other materials. Deflection angles of the dental implants and abutments were minimal, ranging from 5.0 to 6.5°, whereas the magnetic attachment keepers were strongly attracted to the field, having deflection angles of 90° or more. Increases in temperature of the FMCs were significant but less than 1°C in every sequence. The dental implant of 50-mm length showed significant but mild temperature increases (up to 1.5°C) when compared with other dental implants and abutments, particularly on sequences with high specific absorption rate values. Conclusion Although most metallic dental materials showed no apparent translational attraction or heating at 7T, substantial attraction forces on the magnetic attachment keepers suggested potential risks to patients and research participants undergoing MR imaging examinations.

The purpose of the present study was to observe the biodegradation process of pure alpha-tricalcium phosphate (alpha-TCP) particles and to determine the efficacy of alpha-TCP as a space maintainer in a bone defect. We used 14 rabbits and prepared two cranial bone defects in each rabbit. One defect was left empty as a control, whereas the other was filled with alpha-TCP particles about 300 mum in diameter. Animals were sacrificed at 1 week, 4 weeks, and 8 weeks. The cranial bone was then embedded either in paraffin wax for the preparation of decalcified specimens, or in polyester resin for the preparation of nondecalcified specimens. All specimens were evaluated histologically and histomorphometrically. As a consequence of the degradation of alpha-TCP, a "reticulate structure" appeared in the particles at 1 week and new bone was observed in this structure at 8 weeks. The amount of new bone between the control and experimental groups was not significantly different at any of the time points. However, in the experimental group, new bone at the surface of alpha-TCP was evident even in the center of the defect whereas fibrous connective tissue was dominant in the control group. These results indicate that alpha-TCP is a degradable osteoconductive material that is able to act as a space maintainer for bone regeneration when applied to a bone defect. While there was no significant difference in total bone formation between the experimental and negative control groups, the space-maintaining and osteoconductive properties of the particles may result in more complete bone formation in longer-term studies.

A surgical guiding system with simulation software has recently been used for safe implant treatment. We report a clinical case in which we successfully used this system for implant treatment of a congenital tooth missing region with severely restricted mesiodistal space. The patient was a 19-year-old female whose mandibular right deciduous canine was wobbling without a successional permanent tooth and who desired implant treatment. CT images showed that this site was narrow buccal-lingually and only five millimeters in mesiodistal width. The implant position was planned using simulation software (SimPlant : Materialise Dental) based on CT data and a surgical guide template (SurgiGuide : Materialise Dental) was fabricated prior to the implant surgery. During the implant surgery, the deciduous canine was extracted under local anesthesia. The implant bed was prepared with the surgical guide template and an implant was installed. One month after surgery, the position of the implant was examined with a cone-beam CT, which demonstrated that the implant position was exactly the same as planned. At 5 months, a provisional prosthesis was delivered and optimal soft-tissue condition was formed by modifying the provisional prosthesis. Then, the final impression was taken and a ceramo-metal implant-supported crown was delivered. In this case of a congenital tooth missing region with narrow space, implant treatment with simulation software and the surgical guide system provided excellent clinical results.

Background Although local application of statins stimulates bone formation, high dose of simvastatin induces inflammation. Objective A study was conducted to test the hypothesis that maximum bone regeneration with less inflammation would be achieved by combining an optimal dose of simvastatin with alpha-tricalcium phosphate (alpha-TCP), which is an osteoconductive biomaterial capable of releasing the drug gradually. Material and methods Bilateral 5-mm-diameter calvarial defects were created in adult Wistar rats and filled with preparations of different doses of simvastatin (0, 0.01, 0.1, 0.25 and 0.5 mg) combined with alpha-TCP particles or left empty. The animals were sacrificed at 2, 4 and 8 weeks and analyzed radiologically and histologically. Half of the animals of 4 and 8 weeks were labeled with fluorescence dyes and histomorphometrically analyzed. Results Simvastatin doses of 0.25 and 0.5 mg caused inflammation of the soft tissue at the graft site whereas control and other doses did not. The micro-CT analysis revealed that the alpha-TCP with 0.1 mg simvastatin (TCP-0.1) group yielded significantly higher bone volumes than untreated control group at all three time points (249%, 227% and 266% at 2, 4 and 8 weeks, respectively). The percentage of defect closure, bone mineral content and bone mineral density were also higher in the TCP-0.1 group than in the other groups. Conclusion When combined with alpha-TCP particles, 0.1 mg simvastatin is the optimal dose for stimulation of the maximum bone regeneration in rat calvarial defects without inducing inflammation and it could be applied as an effective bone graft material.