Maki Hosoki

Assessment of allergic hypersensitivity to dental materials

Some metallic materials in dental prostheses may cause allergic hypersensitivity. Symptoms appear not only in the oral cavity, but also on hands, feet or the entire body. Release of metal ions is thought to cause the allergic reactions; micro-particles of the corrosion products of the metal and/or ionic metal hydroxides/oxides may be the allergens. The study purpose was to review clinical surveillance of dental allergic hypersensitivity in our dental hospital. From July 2000 to June 2005, 212 patients with suspected dental metal allergy were patch tested with 26 reagents, including 19 ready-made patch test reagents (Patch test reagents, Torii Pharmaceutical Corporation, Tokyo, Japan) and 9 custom-made reagents. One-hundred-and-sixty-seven patients were females (78.8%) and 45 patients were males (21.2%). A total of 148 patients (69.8%) had one or more positive patch test reactions. The most common allergens were nickel (25.0%), palladium (24.4%), chromium (16.7%), cobalt (15.9%) and stannum (12.5%). Typical allergic symptoms and diagnoses were Pustulosis palmaris et plantaris, lichen planus, stomatitis and contact dermatitis. This study indicates that dentists and dental researchers should be concerned about the allergenic potential of dental metal materials.

Clinical application of removable partial dentures using thermoplastic resin. Part II: Material properties and clinical features of non-metal clasp dentures

This position paper reviews physical and mechanical properties of thermoplastic resin used for non-metal clasp dentures, and describes feature of each thermoplastic resin in clinical application of non-metal clasp dentures and complications based on clinical experience of expert panels. Since products of thermoplastic resin have great variability in physical and mechanical properties, clinicians should utilize them with careful consideration of the specific properties of each product. In general, thermoplastic resin has lower color-stability and higher risk for fracture than polymethyl methacrylate. Additionally, the surface of thermoplastic resin becomes roughened more easily than polymethyl methacrylate. Studies related to material properties of thermoplastic resin, treatment efficacy and follow-up are insufficient to provide definitive conclusions at this time. Therefore, this position paper should be revised based on future studies and a clinical guideline should be provided.

Allergic contact dermatitis caused by titanium screws and dental implants

PATIENTS Titanium has been considered to be a non-allergenic material. However, several studies have reported cases of metal allergy caused by titanium-containing materials. We describe a 69-year-old male for whom significant pathologic findings around dental implants had never been observed. He exhibited allergic symptoms (eczema) after orthopedic surgery. The titanium screws used in the orthopedic surgery that he underwent were removed 1 year later, but the eczema remained. After removal of dental implants, the eczema disappeared completely. DISCUSSION Titanium is used not only for medical applications such as plastic surgery and/or dental implants, but also for paints, white pigments, photocatalysts, and various types of everyday goods. Most of the usage of titanium is in the form of titanium dioxide. This rapid expansion of titanium-containing products has increased percutaneous and permucosal exposure of titanium to the population. CONCLUSIONS In general, allergic risk of titanium material is smaller than that of other metal materials. However, we suggest that pre-implant patients should be asked about a history of hypersensitivity reactions to metals, and patch testing should be recommended to patients who have experienced such reactions.

Effect of different head positions on the jaw closing point during tapping movements

This study aimed to investigate the effects of different head positions on jaw closing points during tapping movements. The jaw movements of 20 adult volunteers were assessed using a new jaw-tracking device. All subjects had stable maximal intercuspation with their natural dentitions. The subjects were asked to seat on a dental chair with their head upright, and tapping movements were recorded for 5 s without any further instructions. After the chair was reclined to the horizontal position, tapping movements were also recorded with the head in the supine position. The location of the tapping point was defined as the jaw position which was the most closed to the maximum intercuspal position during each tapping stroke. Fifteen tapping points were obtained from the upright and supine head positions of each subject. Six-hundred tapping points were compared to evaluate the effects of different head positions. With the head upright, tapping points were relatively stable and close to the jaw position at the maximum intercuspation. However, in the supine position, tapping points varied widely and shifted forward. The average distance between the positions of the incisal point at the maximum intercuspation and at the tapping points was 0.11 mm (SD, 0.10) in the upright position and 0.30 mm (SD, 0.08) in the supine position. A Wilcoxon signed rank test showed a significant difference (P < 0.01) between these distances. We conclude that tapping points shift anteriorly in the supine position.

Comparison between flipped classroom and team-based learning in fixed prosthodontic education

PURPOSE We previously investigated the effects of team-based learning (TBL) on fixed prosthodontic education and reported that TBL could have higher efficiency with high student satisfaction than traditional lecture. In the current report, we introduced flipped classroom to the fixed prosthodontic education and compared their effectiveness based on the final examination score in addition to TBL. METHODS Participants were 41 students from Tokushima University School of Dentistry who attended a fixed prosthodontics course. The first six classes adopted the flipped classroom style while the latter eight classes adopted TBL. To evaluate the relationship between learning styles and their effectiveness, we compared results from the term-end examination between the curriculum covered by flipped classroom and TBL-style classes. To draw comparisons, a referential examination with the same questions was conducted to eight faculty members who had not attended any of these classes. RESULTS Term-end examination results showed that TBL classes had slightly higher scores than flipped classroom classes. Referential examination results also showed higher scores for the same curriculum and no significant interaction was found between class formats and the term-end and referential examination scores. Analysis revealed no noticeable difference in the effectiveness of the class formats. CONCLUSION Our previous study reported that TBL had higher efficiency than traditional style lecture. In the current study, there was no statistical difference in the examination score between flipped classroom and TBL. Therefore, we conclude that both styles are highly effective than traditional style lecture and constitute valid formats for clinical dental education.

Dental Metal Allergy

Dental metal allergy is the general term used to describe allergic diseases caused by reactions to dental metal materials. Recently, allergic symptoms involving other dental materials, such as organic compounds, have been reported, and these allergic diseases need to be referred to as either a dental allergy or dental material allergy. When safety evaluations involving biomaterials are performed, various kinds of risk factors, including the potential for cytotoxicity and/or allergization, need to be taken into consideration (Geurtsen, 2002, Wataha, 2000).

Cross-sectional observational study exploring clinical risk of titanium allergy caused by dental implants

PURPOSE Studies have reported cases of metal allergy caused by titanium-containing materials. We wished to clarify the relationship between titanium allergy and dental implants by describing patients who suffered allergic symptoms after they had received such implants. METHODS A total of 270 patients who visited a Dental Metal Allergy Clinic at Tokushima University Hospital from April 2010 to March 2014 were the study cohort. Patch testing with 28 types of metal allergens (including four titanium allergens) was undertaken for patients. RESULTS A total of 217 patients (80.4 %) exhibited allergy-positive reactions to at least one type of metal allergen. Mercury, palladium, chromium and nickel exhibited a higher prevalence of allergy-positive reactions than other metals. Sixteen patients visited our clinic suffering allergic symptoms after receiving dental implants. Eleven of those patients exhibited allergy-positive reactions for any of the metal allergens, and 4 of these patients had allergy-positive reactions against titanium allergens. The total number of allergy-positive reactions for titanium allergens among all 270 patients was 17 (6.3 %). No patient exhibited a positive reaction only for the titanium allergen. CONCLUSIONS The prevalence of allergy-positive reactions for titanium allergens was lower than for other metal allergens. We suggest examination of pre-implant patients who have a history of hypersensitivity reactions to metals.

Metal allergy patient treated by titanium implant denture: A case report with at least 4‐year follow‐up

Patch testing with metal reagents was positive on female patient with history of metal hypersensitivity after dental treatment. All of the dental restorations with metal components were removed, and subsequent oral rehabilitation utilizing dental implants and metal‐free prostheses was carried out. The treatments alleviate the presenting signs and symptoms.

Validity of Peer Evaluation for Team-Based Learning in a Dental School in Japan

The aim of this study was to determine the validity of peer evaluation for team-based learning (TBL) classes in dental education in comparison with the term-end examination records and TBL class scores. Examination and TBL class records of 256 third- and fourth-year dental students in six fixed prosthodontics courses from 2013 to 2015 in one dental school in Japan were investigated. Results of the term-end examination during those courses, individual readiness assurance test (IRAT), group readiness assurance test (GRAT), group assignment projects (GAP), and peer evaluation of group members in TBL classes were collected. Significant positive correlations were found between all combinations of peer evaluation, IRAT, and term-end examination. Individual scores also showed a positive correlation with group score (total of GRAT and GAP). From the investigation of the correlations in the six courses, significant positive correlations between peer evaluation and individual score were found in four of the six courses. In this study, peer evaluation seemed to be a valid index for learning performance in TBL classes. To verify the effectiveness of peer evaluation, all students have to realize the significance of scoring the team members performance. Clear criteria and detailed instruction for appropriate evaluation are also required.