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Biomedical subjects

Toshio Hosoi

Publications and source records attributed to Toshio Hosoi.

12 recordsLinked to original sources
PubMed2005

Effect of surface reaction layer on grindability of cast titanium alloys.

OBJECTIVE: The purpose of this study was to investigate the effect of the cast surface reaction layer on the grindability of titanium alloys, including free-machining titanium alloy (DT2F), and to compare the results with the grindability of two dental casting alloys (gold and Co-Cr). METHODS: All titanium specimens (pure Ti, Ti-6Al-4V and DT2F) were cast using a centrifugal casting machine in magnesia-based investment molds. Two specimen sizes were used to cast the titanium metals so that the larger castings would be the same size as the smaller gold and Co-Cr alloy specimens after removal of the surface reaction layer (alpha-case). Grindability was measured as volume loss ground from a specimen for 1 min using a handpiece engine with a SiC abrasive wheel at 0.1 kgf and four circumferential wheel speeds. RESULTS: For the titanium and gold alloys, grindability increased as the rotational speed increased. There was no statistical difference (p>0.05) in grindability for all titanium specimens either with or without the alpha-case. Of the titanium metals tested, Ti-6 Al-4V had the greatest grindability at higher speeds, followed by DT2F and CP Ti. The grindability of the gold alloy was similar to that of Ti-6 Al-4V, whereas the Co-Cr alloy had the lowest grindability. SIGNIFICANCE: The results of this study indicated that the alpha-case did not significantly affect the grindability of the titanium alloys. The free-machining titanium alloy had improved grindability compared to CP Ti.

Alloys↗
PubMed2005

In vitro wear resistance of three types of composite resin denture teeth.

STATEMENT OF PROBLEM: The wear resistance of artificial teeth is important to the life of the removable prosthesis for the edentulous patient. The ability of artificial teeth to maintain a stable occlusal relationship over time may be influenced by this property. PURPOSE: The purpose of this in vitro study was to evaluate the wear resistance of artificial teeth based on composite resin filler content when opposed by a denture tooth antagonist. MATERIAL AND METHODS: The right first molars (both maxillary and mandibular) of 3 composite resin denture teeth (Endura, 47% organic filler; Duradent, 42% organic and inorganic filler; and Duracross, 68% organic filler) were secured in an in vitro 2-body wear-testing apparatus that simulated masticatory function (60 strokes/min, grinding distance of 2 mm, under 37 degrees C flowing water). Wear resistance was assessed as volume loss (mm3) and height loss (mm) at 5 kgf (grinding force) after 50,000 strokes (6 pairs for each type). The Vickers microhardness (VHN) of the occlusal surfaces was measured with a load of 50 g and a loading time of 30 seconds. After testing, the worn surfaces were observed with a scanning electron microscope (SEM). Mean values were analyzed using a 1-way analysis of variance followed by the Fisher test (alpha=.05). RESULTS: The volume loss of Duradent teeth (0.87 +/- 0.03 mm3) was significantly higher than of the 2 other types of teeth tested (P<.001). The Duracross teeth (0.22 +/- 0.08 mm3 and 0.11 +/- 0.04 mm) exhibited the best wear resistance of the denture teeth tested. The wear resistance of the materials tested was consistent with their hardness (Endura 27.54 +/- 0.67 VHN, Duradent 24.00 +/- 0.60 VHN, Duracross 39.64 +/- 3.11 VHN). SEM observation showed that many filler particles were missing from the matrix of Duradent. CONCLUSION: The wear resistance among the 3 types of teeth was significantly different; Duracross and Endura were more wear resistant than Duradent. Although the densities as reported by the manufacturer were similar, hardness and microstructure were the primary factors affecting the wear resistance of artificial teeth. Hardness appears to correlate with wear resistance since the wear resistance of Duradent with a lower VHN of 24 was greater than the other 2 types of teeth with greater hardness.

Analysis of Variance↗
PubMed2005

[A clinical study on the feeling of oral dryness in denture wearers. Part 1. Results of a questionnaire survey].

PURPOSE: We surveyed youths and denture wearers to evaluate the feeling of oral dryness. In the denture wearers group, we evaluated the association between dentures and feeling of oral dryness. MATERIALS AND METHODS: The survey was performed in 100 denture wearers (mean age, 66.2+/-8.6 years) who visited our department from June to October 2003. A similar survey was performed in 50 youths (mean age, 25.6+/-2.4 years, 20-29 year-old group). The survey consisted of a questionnaire and oral and denture examination. The questionnaire asked about oral dryness symptoms, general condition and current medications. The oral and denture examination examined the condition of the remaining teeth, the kinds of prosthesis, materials of dentures and form of the denture base. RESULTS: A feeling of oral dryness was observed in 11 of the 20-29 year-old group (22%) and 48 denture wearers (48%), hence the incidence was significantly higher in the denture wearers group (p<0.01). No association was observed between the oral dryness symptoms and age, sex, general condition, current medications, or number of residual teeth. The kinds of prosthesis (no denture, partial denture, complete denture) and form of the denture base have no relationship with the feeling of oral dryness. CONCLUSIONS: 48% of the denture wearers had the feeling of oral dryness, and the incidence was higher than in the 20-29 year-old group. However, no association was observed between the oral dryness symptoms and dentures. Further studies are necessary to evaluate factors associated with the development of the feeling of oral dryness.

Adult↗
PubMed2005

[A clinical study on the feeling of oral dryness in denture wearers. Part 2. Measurement of the height of the salivary moisture area].

PURPOSE: We surveyed youths and denture wearers to evaluate the feeling of oral dryness. MATERIALS AND METHODS: The survey was performed in 100 denture wearers (mean age, 66.2+/-8.6 years) who visited our department from June to October 2003. A similar survey was performed in 50 20-29 year-old persons (mean age, 25.6+/-2.4 years). Measurement of the height of the salivary moisture area, and detection of Candida were performed. We used Saliva Wet Tester for measuring the height of the salivary moisture area. RESULTS: The mean height of the salivary moisture area was significantly lower in the denture wearers group than in the 20-29 year-old group (p<0.05). No association was observed between the height of the salivary moisture area and general condition, current medications, number of residual teeth, or the denture base. In the denture wearers group, the height of the salivary moisture area was high in patients with bounded saddle dentures or unilateral distal extension dentures in either or both jaws but low in those with dentures covering the entire palatal and lingual mucosa in both the upper and lower jaws. However, the feeling of oral dryness was not always consistent with the height of the salivary moisture area. In the denture wearers group, the height of the salivary moisture area matched the low tendency of detection of Candida of 100 CFU or more in patients. CONCLUSIONS: The mean height of the salivary moisture area was significantly lower in the denture wearers group than in the 20-29 year-old group. However, the feeling of oral dryness was not always consistent with the height of the salivary moisture area. Further study, including a mental factor, is necessary.

Adult↗
PubMed2005

Retentive force of O-ring attachment to use Immediate Provisional Implant (IPI)-retained overdenture.

This study evaluated the retentive force of the O-ring attachment to an Immediate Provisional Implant (IPI)-retained overdenture. Two sizes of O-rings (#1, #2) were placed on the IPI abutment head. As the controls, soft relining material, silicone lining material, and the PMMA resin were used to connect the IPI abutment head. The retentive forces (n=5, N) obtained at a crosshead speed of 40 mm/min were analyzed by ANOVA/Tukey's HSD test (alpha=0.05). O-ring #1 showed the significantly greatest force among all materials tested (p0.05). Appropriate retention was obtained using the smaller O-ring#1 for the IPI-retained overdenture.

Analysis of Variance↗
PubMed2004

O-ring attachments for transitional implant-retained overdentures.

The lack of proper stability and retention is frequently found in mandibular complete dentures. The stability and retention of existing complete dentures may be improved by using transitional implants (TIs) incorporating the O-ring retention system. This article describes the procedures used to convert an existing conventional complete denture to a TI-retained complete overdenture with O-ring.

Dental Abutments↗
PubMed2004

A technique for making a diagnostic and surgical template.

Implant-supported restorations can restore function and esthetics provided that the implants are placed in the predetermined location and properly angulated. This article describes the fabrication of a diagnostic template incorporating a silicone radiopaque marker as a guide for achieving 3-dimensional evaluation of bone without artifacts using computed tomography. The diagnostic template may be easily transformed into a surgical template by removing the silicone marker.

Dental Implantation, Endosseous↗
PubMed2003

A sectional stock tray system for making impressions.

This article describes a sectional stock tray system developed by the authors for making preliminary impressions. It may be used not only for individual dental arches but also for patients with microstomia or constricted oral openings. This system allows many combinations of right and left tray sizes and forms to be assembled into a well-fitted anatomically-conforming tray in spite of individual anatomic discrepancies.

Dental Arch↗
PubMed2003

Application of cast iron-platinum keeper to a collapsible denture for a patient with constricted oral opening: a clinical report.

Insertion of a denture is especially difficult for patents with a constricted oral opening. This report describes the fabrication of a collapsible removable partial denture with a cast iron-platinum attachment for a partially edentulous woman with a constricted oral opening resulting from rheumatoid arthritis and a craniotomy for a subarachnoid hemorrhage.

Aged↗
PubMed2003

Application of thermography in dentistry--visualization of temperature distribution on oral tissues.

The purpose of this study was to devise and propose appropriate conditions for the photographing of thermal images in the oral cavity and to evaluate which thermography techniques can be applied to dentistry by evaluating the differences in temperature among oral tissues. Thermal images of oral cavities of 20 volunteers in normal oral condition were taken according to the guidelines of the Japanese Society of Thermography, with five added items for oral observation. The use of a mirror made it possible to take thermal images of the posterior portion or palate. Teeth, free gingiva, attached gingiva and alveolar mucosa were identified on thermal images. There were differences in temperature between teeth, free gingiva, attached gingiva and alveolar mucosa. These were nearly in agreement with the anatomical view. Thermography need no longer be restricted to the anterior portion using a mirror, and can now be applied to the dental region.

Adult↗
PubMed2002

In vitro wear assessment of titanium alloy teeth.

PURPOSE: Wear of commercially pure (CP) titanium prosthetic teeth has frequently been observed. The greatest wear has been found when the same grades of CP titanium are used for both maxillary and mandibular teeth. This study examined the wear behavior of teeth made with cast titanium alloy and compared these results with those for CP titanium and gold alloy teeth. MATERIALS AND METHODS: All tooth specimens were cast with grade 3 alpha titanium, 3 metastable beta alloys [Ti-15Mo-2.8Nb-0.2Si (Timetal 21 SRx), Ti-13Nb-13Zr, and Ti-15V-3Cr-3Sn-3Al], and 2 alpha+beta alloys (Ti-6Al-7Nb and Ti-6Al-4V). As a control, Type IV gold alloy was also cast conventionally. All teeth (both maxillary and mandibular) were secured in an in vitro 2-body wear testing apparatus that simulated chewing function (60 strokes/min; grinding distance, 2 mm under flowing water). Wear resistance was assessed as volume loss (mm(3)) at 5 kgf (grinding force) after 50,000 strokes. The results (n = 5) were analyzed using analysis of variance or Fisher's exact test (alpha = 0.05). RESULTS: Of the titanium teeth, the wear of 2 of the metastable beta alloys (Timetal 21 SRx and Ti-15V-3Cr-3Sn-3Al) was found to be significantly (p <0.05) higher than that of CP titanium and the 2 alpha+beta alloys. The Type IV gold alloy exhibited better wear resistance than all of the titanium teeth tested. No correlation was found between wear loss and hardness among all the metals tested. CONCLUSIONS: Among the titanium teeth examined, the alpha+beta alloys exhibited significantly less wear than the other types of titanium. The dental casting gold alloy tested exhibited the best wear resistance among all of the metals tested.

Alloys↗