Purpose: The purpose of this study was histological examination for bioactive glass (RKKP) by using human epithelial gingival cells (HGE-15) through SEM and TEM in vitro.
Methods: Commercial titanium alloy (CT), RKKP, Plastic culture dishes (F) were used in this experiment. 10×10⁵ HGE-15 cells were inoculated on the each samples, and cultured for 30 minutes, 1 hour, 2 hours, and 24 hours for SEM. For TEM, HGE-15 cells were cultured for 24 hours and 1 week. The cells were fixed in 2.5% glutaraldehyde, dehydrated conventionally, and subjected to critical point drying. The cells were then coated with gold and examined by SEM. For TEM, HGE-15 cells were fixed in 2.5% glutaraldehyde, postfixed in 1% osmium tetroxide, dehydrated, and embedded in Epon 812. The materials were removed with liquid nitrogen and re-embedded and double-stained, and examined.
Results: SEM findings: On RKKP, though increase and spreading of cells were delayed compared with F and CT after 30 minutes, 1 hour and 2 hours, however, samples were mostly covered with polygonal-shaped cells conclusively 24 hours after incubation. TEM findings: We have observed the double-layer structure on F and CT at the interface. On RKKP, recognized the density layer near the interface. HGE-15 cells were bonded directly to the RKKP.
Conclusion: We have concluded that the RKKP indicated biocompatibility and bioactive property to HGE-15 cells morphologically from SEM and TEM findings in vitro

View full abstract

Purpose: The purpose of this study was to reduce the number of food items for ease of use, and to eliminate the influence of food preferences (likes and/or dislikes) on an earlier version of the food intake questionnaire method for evaluating the ability of mastication in complete denture wearers which had been previously developed by the authors.
Methods: The subjects were 262 complete denture wearers (average age: 76.7±6.1 years old, male: 128 persons, female: 134 persons). The food intake questionnaire composed of a list of 35 food items which were used in the study. All subjects were asked to assign a mark to each type of food according to one of five categories (easily eaten, eaten with difficulty, cannot be eaten, do not eat because of dislike, have not eaten since starting to wear dentures). In order to reduce the number of the initial 35 food items in the questionnaire, the correlation coefficient of the masticatory score, representing the masticatory ability before and after elimination of foods, was examined in all the subjects. The masticatory performance (MP) was also evaluated by a sieving method in all subjects.
Results: In the questionnaire with 5 categories composed of 25 foods, the reliability coefficient (Cronbach’s α) was 0.939. There was significant correlation between the masticatory score using the 35 food item list and the new masticatory score using the new 25 food item list (r=0.95, P<0.01). There was significant correlation between the MP using the sieving method and the N-MS using the 25 food item list (r=0.62, P<0.01).
Conclusion: It was confirmed that the new food intake questionnaire method, with a revised 25 food item list, was both valid and reliable.

View full abstract

Purpose: The brush-on technique has frequently been used when dentures are repaired with autopolymerized acrylic resins. This study evaluated the fluidity and hardening time of autopolymerized acrylic resin applied using this technique.
Methods: Five autopolymerized acrylic resins were tested: Unifast II (GC, Japan), Unifast Trad (GC), Provinice (Shofu, Japan), Metafast (SunMedical, Japan), and Miky (Nissin, Japan). Using both the brush-on and the conventional (L/P: 0.5 ml/g) mixing techniques, all slurry resins were applied on the platform of a rheometer (Seiki, Japan). Fluidity was measured until hardening occurred at room temperature (23±1°C, humidity: 40-50%). To measure the hardening time, the five resins were also poured into silicone tubes (8 mm internal diam., 5 mm long) using the brush-on and the conventional techniques. A thermocouple was placed in the center of each tube to measure the temperature. Hardening time was assessed as the time when the temperature reached the maximum. The data (n=5) were analyzed by ANOVA/Tukey’s test (α=0.05).
Results: Similar fluidity was found for the brush-on and conventional mixing techniques although the onset of hardening was different. Excluding Provinice, there were significant differences in hardening time between both techniques (P<0.05). The hardening time of Metafast was the significantly longest among the resins tested (P<0.05).
Conclusion: The hardening time for the brush-on technique was shorter than for the conventional mixing technique. Because there were great differences in the hardening time of the autopolymerized acrylic resins tested, attention should be paid to handling time during denture repair.

View full abstract

Purpose: Radiotherapy influences bone formation at the surfaces of endosseous implants used for maxillofacial prosthetic rehabilitation in patients with oral tumors. We hypothesize that ionizing irradiation affects the differentiation and cellular physiology of osteoblasts, and thereby impairs matrix formation and mineralization during bone wound healing. The aim of this study was to investigate how the dosage of ionizing radiation affects differentiation of osteoblasts in vitro.
Methods: Osteoblasts were isolated from the bone marrow of Wistar rats. They were exposed to 0, 40, 400, or 4000 mGy of gamma-radiation (using cobalt-60) and cultured for 5, 7, 10, or 14 days. Assays were performed for cell adhesion and alkaline phosphatase activity. Electron probe microanalysis was used to monitor bone matrix mineralization. The reverse transcription-polymerase chain reaction was used to determine mRNA expression for alkaline phosphatase, bone sialoprotein, collagen I, osteocalcin, heat shock protein 47, and β-actin.
Results: Irradiation of less than 400 mGy induced no significant changes in cell adhesion, alkaline phosphatase activity, or osteoblastic gene expression, compared to controls. Electron probe microanalysis indicated that P and Ca signals were more evident throughout the culture period at doses of up to 400 mGy than at 4000 mGy. Bone matrix mineralization was reduced at 4000 mGy.
Conclusion: These results suggest that the phenotypic and molecular changes induced in osteoblasts by higher doses of ionizing radiation interfere with differentiation and delay the mineralization of bone matrix.

View full abstract

Purpose: As for commercially pure titanium (CP-Ti) and titanium alloys (Ti-6Al-4V, Ti-6Al-7Nb), when fluoride exists in an acidic environment, it is known to corrode from recent research. However, it is also reported that the corrosion resistance improves when small amount of platinum is added to pure titanium. The purpose of this study is to examine the corrosion behavior of CP-Ti, Ti-6Al-4V, Ti-6Al-7Nb, and high corrosion Ti-0.5Pt alloy when a fluoride added to the acidic environment produced by streptococcus mutans.
Methods: The specimen (CP-Ti, Ti-6Al-4V, Ti-6Al-7Nb, and experimentally produced Ti-0.5Pt alloy) were polished like a mirror. Streptococcus mutans was cultured for 24 hours with brain heart infusion (BHI) medium adding sucrose on the specimen, and then 1000ppm fluoride solution of same medium volume was added (that is, fluoride concentration becomes 500 ppm). After 10 min, all the solutions were removed and new culture for 24 hours started again. These cycles of 3, 5, 7, and 10 times were repeated and the surfaces of the specimens were observed by scanning electron microscope (SEM).
Results: The CP-Ti and Ti-6Al-4V, Ti-6AL-7Nb alloys were observed the typically metallographical structure by adding fluoride solution repeatedly. The surface of Ti-0.5Pt alloy was no change by adding fluoride solution.
Conclusion: When a fluoride with less than 500 ppm concentration was added to the acid biofilm which was produced by Streptococcus mutans, as for CP-Ti, Ti-6Al-4V and Ti-6Al-7Nb alloys the possibility to corrode was suggested. The Ti-0.5Pt alloy had a high corrosion resistance in the same condition.

View full abstract

Purpose: The purpose of this study was to clarify the effects of covering the palate with a palatal plate on tongue pressure during swallowing.
Methods: We investigated 21 subjects (12 males and 9 females; mean age: 25±2 years). Maximum voluntary tongue pressure and tongue pressure during swallowing were measured with and without the application of an experimental palatal plate. The subjects were asked to compress a pressure probe with a small balloon between the tongue and anterior area of the palate with maximum force, and the peak pressure recorded was regarded as the maximum voluntary tongue pressure. They were also asked to swallow a gelatin drink, and the maximum pressure recorded was regarded as tongue pressure during swallowing. Maximum voluntary tongue pressure and tongue pressure during swallowing recorded with and without the palatal plate were compared. Statistical analysis was performed with the paired-sample t- test. Perceived difficulty in swallowing with the palatal plate was evaluated using a 100-mm visual analog scale (VAS).
Results: No significant difference was noted in maximum voluntary tongue pressure or tongue pressure during swallowing between with and without the palatal plate. The mean ± SD of the VAS score for difficulty in swallowing with the palatal plate was 49.3±26.5.
Conclusion: Perceived difficulty in swallowing with a palatal plate showed wide individual variation. Covering the palate with a denture showed no effect on tongue pressure.

View full abstract

Purpose: The purpose of this study was to consider the possibility of undergraduate dental education improvement by comparing the dental courses in a Japanese dental school with a UK dental school using the speciality of removable prosthodontics.
Methods: Two dental schools, the University of Tokushima in Japan and the University of Birmingham in the United Kingdom, were compared. We compared both dental schools on the curriculum, lectures in removable prosthodontics, phantom head practice in removable prosthodontics, and clinical practice.
Results: There are large differences in undergraduate dental education courses between the two dental schools, especially in clinical practice. Clinical practice exposure in the University of Birmingham is more than three times as long as the University of Tokushima. The number of patients available for treatment in Birmingham is much more than Tokushima and the minimum requirements in removable prosthodontics in Birmingham is more than eight times as many as Tokushima.
Conclusion: Large differences in the undergraduate dental education courses between the two dental schools, including the number of patients for students, may be caused by the dental policy, the economy, religion and customs. It is important to execute education methods such as virtual reality simulation, Problem-Based Learning (PBL), Web-based courseware and Video-based self learning because of the lack of available patients in Japan.

View full abstract

Purpose: The role of occlusion in the progression of periodontal disease has long been discussed, and occlusal trauma is considered a cofactor that allows absorption of the alveolar bone, which might temporarily or permanently increase tooth mobility. In general practice, occlusion has been evaluated during border and tapping movements to detect and remove premature and non-working contacts. Since previous studies have compared occlusion with periodontal tissue that might have a periodontal problem, it has been difficult to differentiate primary and secondary occlusal trauma. This study focused on primary occlusal trauma and evaluates the relationship between tooth contact during lateral excursions and periodontal status.
Methods: Teeth without periodontal disease were studied in 50 men and 50 women and classified into two groups according to the presence or absence of non-working contacts. Probing depth, clinical attachment levels, and tooth mobility were compared between the two groups.
Results: There was no significant difference in the Periotest value, probing depths and clinical attachment levels of the first and the second molars between teeth with and without non-working contacts.
Conclusion: The results of this study pose questions regarding the importance of examinations of tooth contact during lateral excursion and occlusal adjustment based on this examination. Since the significance of non-working contact as a causative factor of occlusal trauma was not proved, the validity of occlusal adjustment for eliminating non-working contact is questionable.

View full abstract

Purpose: The purpose of this experiment was to clarify the effect of amount of masticatory movement on variation of path of mandibular incisor point.
Methods: Forty healthy subjects were asked to chew softened chewing gum on their habitual side. For the 10 cycles from the fifth cycle of mastication, the opening distance (amount of vertical movement) and the masticatory width (amount of lateral movement) as the indicators representing the amount of masticatory movement, and the standard deviations of the lateral opening, lateral closing, and vertical compoments as indicators representing the variations of the masticatory path were calculated. The relationship between the indicators for the amount of movement and indicators for variations of the masticatory path were investigated.
Results: The values of indicators for variations of the masticatory path were large when the opening distance was large, and there was a significant positive correlation between the two (r=0.508-0.685, P<0.01). There was no correlation between the masticatory width and the indicators for variations of the masticatory path.
Conclusion: From these results it was concluded that variations of the masticatory path of the incisor point was not related to the amount of lateral movement, but was closely and proportionally related to the amount of vertical movement.

View full abstract

Patient: A 73-year-old male patient was introduced by his plastic surgeon to the Kyushu Dental College Hospital. Numerous surgical excisions resulted in a defect in the region of the right upper palate. He also had a skin defect on the right cheek due. Although he had worn a removable partial denture and a facial prosthese, he had been complaining of mastication, articulation, and esthetic problems. Seven inner crowns with keeper of magnetic attachment were fixed to the abutment teeth. Metal welding was done between the outer crowns and metal frame. Magnetic assemblies were fixed into the outer crowns. Four magnetic attachments were applied to connect the partial denture and the obtulator. Two magnetic attachments were also applied to connect the facial prosthese and the obtulator.
Discussion: Although the new maxillofacial prosthese was heavier than the old one, the VAS score of the patient’s satisfaction was 100. An articulation, masticatory function, and mealtime were improved.
Conclusion: This clinical report describes the fabrication method for a maxillofacial prosthese by applying dental magnetic attachments for retention and connection. The evaluation of mastication and articulation was done before and after wearing the new prosthese and his complaining improved.

View full abstract