Improvement of Total Etching Dentin Bonding with Subpressure.

This study aimed to investigate the effects of subpressure on the bond properties of total-etching adhesive to dentin. Thirty-six caries-free premolars were sectioned parallel to the occlusal plane and randomly divided into four groups (n = 9): a control group (C, no treatment) and three subpressure groups, which were treated under 0.8, 0.6 or 0.4 bar after applying adhesives, named S8, S6 and S4, respectively. Afterward, resin was bonded to the dentin surface, and 27 beams (1.0 mm × 1.0 mm) of each group were sectioned. One was selected to observe the bonding interface from each group by SEM. Each group was divided into two subgroups (n = 13): 24 hours of water storage (I) and 10,000 thermocycling (A). The microtensile bond strength (µTBS), failure modes and nanoleakage expression were evaluated. SEM results showed that the subpressure groups had longer and denser resin tags. The µTBS of the subpressure groups was higher than that of the control group (p < 0.05). The subpressure groups were dominated by mixed failure, whereas main interfacial failure appeared in group C. The subpressure groups showed less silver deposition than the control group (p < 0.05). The subpressure technique may remarkably improve bonding strength and decrease nanoleakage on total-etching bonding.

Effects of clasp retention forces and abrasion on different cast crowns.

STATEMENT OF PROBLEM: Dental alloys have different mechanical properties compared with enamel. However, few studies have been conducted to determine the effects of the retention forces of clasps when applied on different cast crowns. PURPOSE: The purpose of this study was to evaluate the retention forces of cast circumferential clasps made of cobalt-chromium alloy on complete cast crowns made of cobalt-chromium (CC group) and gold-silver-palladium (AC group) alloys, and to observe their abrasion patterns. MATERIAL AND METHODS: Two groups of specimens were fabricated (n=5) and subjected to repeated insertion-removal tests (100 to 15,000 cycles). The mean values of removal forces at 100, 400, 800, 1500, 4500, 7500, 10,000, and 15,000 cycles, and their corresponding change rates compared with the initial 100 cycles' retention were determined. The differences between the 2 groups were analyzed by 2-way repeated measures analysis of variance at 100, 7500, and 15,000 cycles. The surfaces of specimens were observed with scanning electron microscopy. RESULTS: There were significant differences between the CC and AC groups in retention forces (P<.05). Clasp retention showed a descending trend for cobalt-chromium alloy crowns from the initial value, which decreased by 29.9% after 15,000 insertion-removal cycles. A sharp increase in retention could be observed in the AC group, which rose by 99.7% ultimately. The worn surfaces of the gold-silver-palladium crowns showed different wear patterns compared with the cobalt-chromium alloy crowns. CONCLUSIONS: The results indicate that cobalt-chromium alloy crowns and gold-silver-palladium alloy crowns perform differently when cobalt-chromium alloy clasps are designed as retainers for partial removable dental prostheses. Crown designs should be changed, depending on the retainer and clasp materials for partial removable dental prostheses abutment teeth.

[Influence of reducing buccolingual width of artificial crown of implant prosthesis on distribution of biting force and masticatory efficiency].

OBJECTIVE: To discuss the influence of reducing buccolingual width of artificial crown on distribution of biting force and masticatory efficiency in unilateral distal-extension implant denture and provide valuable information for the design of buccolingual width. To find a design that the biting force of implant prothesis was less evident than those on the contralateral natural teeth without compromising masticatory efficiency. METHODS: T-Scan II occlusal analyzer and 722 grating spectrophotometer were used to analyze the distribution of biting force and masticatory efficiency in unilateral distal-extension implant denture. Heat-cured resin crowns with three different buccolingual width (group A: standard buccolingual width; group B: the buccolingual width was reduced by 1/4; group C: the buccolingual width was reduced by 1/3) were designed as follow, one was contoured with standard buccolingual width, the other two were made with reducd buccolingual width by 1/4 and 1/3. RESULTS: The ratio of biting force (ROF) of group C was 16.25%, which was significantly lower than group A (27.38%) and B (22.60%) (P < 0.0083). The X axis displacement of center of occlusal force (COF) of group C was 2.0 mm, which was significantly difference with group A (1.5 mm, P = 0.004). The masticatory efficiency absorbance A value (MEA) of group C was 0.217, which was significantly lower than group A (0.345, P = 0.005) and B (0.289, P = 0.004). CONCLUSIONS: According to the study, the buccolingual width of the crown reduced by 1/4 was a more ideal design for unilateral distal-extension implant denture.

[Clinical application and follow-up evaluation of attachments in partial edentulous jaw prosthodontics].

OBJECTIVE: To evaluate the outcomes of attachments prosthesis in patients with complicated intraoral situation. METHODS: Thirty-eight patients provided with fixed-removable partial denture were followed up for 1 to 5 years. A total of 51 attachments restoration supported by 139 abutments were included. RESULTS: Good retention and stability of the restoration were achieved; masticatory function and esthetic effects were recovered satisfactorily. CONCLUSIONS: Fixed-removable partial denture is an effective method for patients with complicated intraoral situation.