Occlusion recording device for dental implant-supported restorations.
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Acrylic Resins↗
Biomedical subjects
Chikahiro Ohkubo
Publications and source records attributed to Chikahiro Ohkubo.
Clinical marginal gap of porcelain fused to electro-formed gold coping crowns.
This study evaluated the marginal and internal gaps of Auro Galvano Crowns (AGC) in vivo. One hundred AGC crowns were examined using white and black silicone materials; the thickness of the silicone layer was measured at 16 reference points using a microscope. The mean marginal gaps among anterior, premolar and molar teeth, and the mean gaps within the groups were compared by analysis of variance and Dunnett T3 test. The results showed that at the margins, there were no significant differences among the four measuring points within each group, and there were no significant differences in the mean marginal gaps among the three groups. The mean marginal gaps in all groups were within the limits of clinical acceptability.
Analysis of Variance↗
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↗
Shear bond strength of resin composite to magnetic Fe-Pt alloy.
STATEMENT OF PROBLEM: It is important to obtain strong adhesion between resin composite material and magnetic Fe-Pt alloy for fabrication of an indirect veneered crown. However, little is known about the bond strength between these materials. PURPOSE: This study evaluated the bond strength of resin composite to magnetic Fe-Pt alloy, using 4 adhesive metal primers. MATERIAL AND METHODS: Seventy disk-shaped patterns (7.5 mm in diameter, 2.0 mm thick) were cast from a custom-made Fe-Pt ingot using a high-frequency centrifugal casting machine. After the bonding surfaces were airborne-particle abraded with 50 microm Al2O3, specimens were divided into groups (n=7) and primed with either Metal Primer II (MP), Meta Fast Bonding Liner (BL), New Meta Color INFIS Opaque Primer (IN), or Epricord Opaque Primer (EP). Nonprimed specimens served as controls (n=7). A resin composite (New Meta Color INFIS) was then applied to all specimens and polymerized. After the specimens were immersed in 37 degrees C water for 24 hours or thermal cycled at 4 degrees C to 60 degrees C with a 1-minute dwell time of up to 10,000 cycles, the shear bond strengths (MPa) were measured using a universal testing machine at a crosshead speed of 0.5 mm/min. The data were statistically analyzed by a 2-way analysis of variance and the Scheffe test (alpha=.05). RESULTS: Although IN had the lowest strength, there were no significant differences in bond strengths of the other 3 primers (MP, BL, and EP) before thermal cycling. The bond strengths of MP and EP were slightly altered by thermal cycling (P >.05); however, BL and IN underwent a significant decrease (P <.05). CONCLUSION: The results of this in vitro study indicate that MP and EP provide superior long-term shear strength when bonding the resin composite evaluated to Fe-Pt alloy.
Composite Resins↗
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↗
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↗
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↗
Titanium removable partial denture clasp repair using laser welding: a clinical report.
This clinical report describes repair of a fractured removable partial denture clasp using laser welding rather than a conventional torch soldering technique.
Aged↗
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↗
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↗
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↗
Application of cast magnetic attachments to sectional complete dentures for a patient with microstomia: a clinical report.
Patients with microstomia who must wear removable dental prostheses often state that they are unable to insert or remove the prosthesis because of the constricted opening of the oral cavity. This article presents a cast iron-platinum magnetic attachment system applied to sectional collapsed complete dentures for an edentulous patient with microstomia. With the use of lingual and palatal midline hinges and a cast iron-platinum magnetic attachment, the sectional prosthesis was successfully and easily inserted and provided adequate function in the patient's mouth.
Aged↗