[Study on interface compatibility and fracture resistance of polyglycidyl methacrylate pre-impregnated quartz fiber reinforced polymethyl methacrylate denture base resin].

OBJECTIVE: To explore the reinforcement of polyglycidyl methacrylate (PGMA) pre-impregnated quartz fiber mesh in denture base materials by investigation of interface compatibility and fracture resistance. METHODS: 1-layer, 2-layer, 3-layer PGMA pre-impregnated quartz fiber meshes, electrolyzed cobalt-chromium alloy mesh and cobalt-chromium alloy mesh conditioned by metal primer were integrated in polymethyl methacrylate (PMMA) resin by sandwich embedding method. Block samples of 5 groups were prepared (40 mm×15 mm×2 mm). Fracture resistance was determined in a 3-point bending test at 2 mm/min. Scanning electron microscope (SEM), micrographs were taken from the fractured surfaces to analyze the bonding interface compatibility. RESULTS: The group of 3-layer PGMA pre-impregnated quartz fiber mesh presented the highest elastic modulus of 6 406 MPa and flexural strength of 227 MPa among the five groups, while the 1-layer and 2-layer expressed the similar elastic modulus and flexural strength to the pure PMMA group. The metal groups demonstrated better mechanical properties, while the metal surface conditioner played much better. The metal surface conditioner pre-impregnated cobalt-chromium alloy and PGMA pre-impregnated quartz fiber mesh showed compatible interface with PMMA. CONCLUSION: The mechanical properties were improved by the increasing of the fiber by adding the more meshed. Although the benign interface did help the compatibility, the quantity of the fibers played an important role in the strength.

[The primary evaluation of minimal prepared ceramic veneer in anterior teeth for clinical application].

OBJECTIVE: To evaluate the clinical application value of minimal prepared ceramic veneer in anterior teeth, by analyzing the esthetic effects and success rates. METHODS: Forty-four anterior teeth in 30 patients with minor esthetic defect were included in this study. Less than 0.5 mm preparation or no preparaion technique was used in the clinical procedure. Glass ceramics veneers were delivered and 3M Relyx Veneer were used as the adhesive. The final appearance of each restoration was evaluated by patients on visual analogue scales (VAS) and by professional prosthodontists. Evaluation criteria included margin effects, color, shape and translucency. The success rate of all the restoration were analyzed in 6, 12 and 24 month after the treatment. RESULTS: The patients' degree of satisfaction was 9.2 ± 0.4, while the excellent rate of esthetic effect of margin effect, color, shape and translucency was 89% (39/44), 91% (40/44), 98% (43/44) and 93% (41/44) by professional prosthodontist. The success rate of 6, 12 and 24 month were 100% (44/44), 98% (43/44) and 91% (40/44). CONCLUSIONS: The minimal prepared venneers have a good esthetic effect and a satisfactory success rate, and is a suitable technique in esthetic treatment under the critical indications.

[In vivo model to evaluate the accuracy of complete-tooth spectrophotometer for dental clinics].

OBJECTIVE: To test ΔE between measured value and right value from the Crystaleye complete-tooth spectrophotometer, and to evaluate the accuracy rate of the spectrophotometer. METHODS: Twenty prosthodontists participated in the study. Each of them used Vita 3D-Master shadeguide to do the shade matching, and used Crystaleye complete-tooth spectrophotometer (before and after the test training) tested the middle of eight fixed tabs from shadeguide in the dark box. The results of shade matching and spectrophotometer were recorded. The accuracy rate of shade matching and the spectrophotometer before and after training were calculated. RESULTS: The average accuracy rate of shade matching was 49%. The average accuracy rate of the spectrophotometer before and after training was 83% and 99%. CONCLUSIONS: The accuracy of the spectrophotometer was significant higher than that in shade matching, and training can improve the accuracy rate.

[Comparison of color and translucency between resin and try-in paste with same number].

OBJECTIVE: To test and compare the color and translucency between the mono-component light-cure adhesive resin and try-in paste with same number for porcelain veneer restorations, and evaluate the consistency of the materials. METHODS: Variolink Veneer and Relyx Veneer were involved in the study. The adhesive resins and try-in pastes were added into a model of diameter of 10 mm and thick of 2 mm with white background and covered with filtered cover glass, and then the resins was cured with light. The color (L(*), a(*), b(*)) of these samples was test and ΔE was also calculated to evaluate the color consistency of samples. The resins and try-in pastes were made into a thin layer of 0.15 mm, and their translucency was tested under the light from 380 µm to 780 µm. Average translucency was calculated. Tukey t-test for multiple comparisons was used to analysis the differences of ΔE. Paired t-test was used to analysis the differences of translucency of them. RESULTS: Tukey's t-test shows that the evaluation of ΔE of TR (1.11 ± 0.18) was a; those of LV-1 (6.38 ± 0.45), LV-2 (5.94 ± 0.19), A1 (7.54 ± 0.20), WO (4.24 ± 1.14) were b; those of HV + 2 (10.90 ± 0.41), HV + 1 (11.48 ± 0.17), LV-3 (10.69 ± 0.13), B0.5 (13.26 ± 0.21) were c; and those of HV + 3 (21.94 ± 0.21), MV0 (29.78 ± 0.14), A3 (32.67 ± 0.19) were d (a, b, c, d meaned that the consistency of resin and try-in paste became lower and lower). There were significant differences between resin and tray-in paste in 7 colors (A1, TR, HV + 3, HV + 2, HV + 1, LV-2, LV-3) of 12 colors (P < 0.01). CONCLUSIONS: The consistency of color and translucency between most adhesive resin and try-in paste with same number is low. This kind of materials should be used with caution in demanding cases.

[Application and comparison of two shade guide training systems].

OBJECTIVES: To evaluate the effect of shade guide training box and shade guide training software on shade matching ability of observers when used separately. To find out the difference between two training plans when the two training methods were used in combination, and to provide information on shade matching training system. METHODS: Sixty-two postgraduate dental students who specialized in prosthodontics with 1 to 5 year clinical experience were enrolled in this study. At base line, each participant were asked to match 7 standard shade tabs which have been randomly chosen from Vita 3D-Master shade guide and 7 intermediate shade tabs from Vita bleached guide 3D-Master. Then the subjects were allocated to 2 groups [Toothguide Training Box (TTB) group and Toothguide Training (TT) group] according to the baseline data. Participants in group TTB received training session once a week for 3 weeks, while those in group TT received TT training session once a week for 3 weeks. All participants took a middle term shade-matching test. Then the two groups exchange the training methods and repeat the whole process, a final test was given to each participant. The elapsed time and number of accurate shade matching were recorded for each training session. Wilcoxon signed ranks test and ANOVA were used in data analysis. RESULTS: There were no significant differences in the number of accurate shade matching (standard shade tab and the sum) between group TTB (4.4 +/- 1.3 and 5.3 +/- 1.6) and TT (4.0 +/- 1.4 and 4.9 +/- 1.5) in the middle term test with higher value found in group TTB. In the final test, the number of accurate shade matching (standard shade tab and the sum) in group TT (4.9 +/- 0.8 and 6.4 +/- 0.8) was higher than that in group TTB (4.7 +/- 1.1 and 5.8 +/- 0.9), but significant difference was found only when the sum number of accurate shade matching was compared between the two groups (P < 0.05). There was no significant difference between data from middle term test and from final test in group TTB; while in group TT, the number of accurate shade matching in the final test was significantly increased compared with that in the middle term test (P < 0.05). CONCLUSIONS: When used in combination, TT training followed by TTB training is recommended.

[Comparison of shade matching accuracy of tabs of shadeguide and tabs out of shadeguide].

OBJECTIVE: To compare the shade matching accuracy between tabs of shade guide and tabs out of shade guide by prosthodontists. METHODS: Sixty-two graduate students who had 1 to 5 years clinical experience without color blindness were included in this study. Twenty-nine tabs from Vita 3D-Master shadeguide and 7 tabs out of Vita 3D-Master shade guide but from Vita Bleachedguide 3D-Master were taken as the targets of shade matching and observed under the standard light. Subjects' shade matching accuracy on tabs of shadeguide and tabs out of shadeguide was recorded. Frequency of right match was analyzed using Monte Carlo exact probability-test. Wilcoxin test was used to analyze the difference between each group on ranked data of value, chroma and hue. RESULTS: The shade matching accuracy of tabs of shade guide [45.9% (199/434)] was significantly higher than that of tabs out of shade guide [9.0% (39/434)]. There was significant difference between the two kinds of tabs of ranked data of value [0.2 (0.1 - 0.3), 0.4 (0.4 - 0.5)] and chroma [0.2 (0.1 - 0.4), 0.5 (0.4 - 0.6), P < 0.01, but there was no significant difference in hue data [0.3 (0.1 - 0.4), 0.3 (0.1 - 0.4)]. CONCLUSIONS: The shade matching ability of prosthodontists on tabs out of shade guide is lower than that on tabs of shadeguide. To fulfill clinical need, more training is necessary.

[The influence of toothguide training box on shade matching veracity].

PURPOSE: The aim of the study was to evaluate the influence of toothguide training box(TTB) on shade matching veracity, and compare the differences of influence on shade matching veracity of tabs of shadeguide and on that of tabs out of shadeguide. METHODS: 31 graduated students who had 1 to 5-year clinical experience without color blindness were trained by TTB once a week for 3 weeks. Elapsed time and scores from the training system were recorded each time. And everyone was tested by 29 tabs of Vita 3D-Master shadeguide and 7 tabs out of Vita 3D-Master shadeguide before the first training as the base line and tested again after the last training as the test after training. SPSS 10.0 software package was used for analysis. The variances of scores and elapsed time were analyzed by ANOVA, and the differences of veracity between tabs of shadeguide and that of tabs out of shadeguide by Wilcoxon signed ranks test. RESULTS: The scores of the tests were rising via training. There was significant difference (P<0.01) between the first (900.29+/-51.68) and the third training (933.81+/-32.94). The elapsed time was turning shorter via training. There is significant difference (P<0.01) between the first [(46.29+/-13.29)min] and the second training [(32.68+/-8.81)min], and also between the first and the third training (30.00+/-7.07)min. The veracity of test after training was higher than the veracity of base line. A significant difference (P<0.01) of shade matching veracity was demonstrated between base line and test after training in both tabs of shadeguide (60.37%+/-18.33%,46.08%+/-22.04%) and the total (37.10%+/-11.58%,28.34%+/-11.73%), but that difference in tabs out of shadeguide (13.82+/-14.98%,10.60%+/-11.65%) was not significant(P>0.01). CONCLUSION: TTB can improve the shade matching ability of prosthodontists, but has limited influence on the shade matching ability of tabs out of shadeguide.

[Relationship between resin bonding strength and time on deep enamel after bleaching treatment].

OBJECTIVE: To study the effect of pre-restoration bleaching treatment on tensile strength of resin bonding agents to deep enamel and its duration, and to estimate the optimal timing of porcelain veneers bonding operation after bleaching treatment. METHODS: A total of 96 extracted human permanent teeth were allocated into 6 groups, 16 teeth for each. In 5 study groups, 80 teeth were bleached using 35% hydrogen peroxide activated by cold light. Right after bleaching and at 1, 4, 7, and 14 days after bleaching, the teeth were prepared with removal of 0.6 to 0.8 mm depth of enamel respectively. And then each study group was divided into two subgroups and bonded with resin bonding agents A (One-step plus) and B (Single bond). In the control group, 16 unbleached teeth were divided into two subgroups and bonded with the two bonding agents respectively. The tensile bonding strength was measured. RESULTS: The tensile strength was [(17.79 +/- 3.53) and (19.41 +/- 3.37) MPa], [(17.50 +/- 4.29) and (19.66 +/- 3.48) MPa], and [(18.39 +/- 3.58) and (19.53 +/- 3.21) MPa] right after bleaching 0 day, 1 day, and 4 days, which were significantly smaller (about 30%) than that of the control group [(25.94 +/- 4.88) and (28.02 +/- 4.36) MPa] (P < 0.001). At 7 days after bleaching the tensile strength [(22.46 +/- 3.98) and (23.74 +/- 5.04) MPa] reached 87% and 85% of that in the control(P > 0.01). At 14 days after bleaching treatment, the strength [(26.03 +/- 4.47) and (27.88 +/- 4.78) MPa] reached the same level as that in the control (P > 0.01). There was no significant difference in bonding tensile strength between the two resin bonding agents. CONCLUSIONS: The bonding strength of resin bonding agents to deep enamel was low during 2 weeks after bleaching treatment. It is suggested that porcelain veneer bonding operation should be performed till 2 weeks after bleaching treatment.

[Comparison of accuracy between visual and spectrophotometric shade matching].

OBJECTIVE: To compare visual and spectrophotometric shade matching using Vita Easyshade and to evaluate its accuracy. METHODS: One hundred and twenty participants with single anterior full ceramic restorations were included in this study. Subjects were randomly assigned to 2 groups, the visual shade matching group (Group V) and the spectrophotometric shade matching (Vita Easyshade) group (Group S). In each group, subjects were allocated into 2 subgroups, those matched with shade tabs (V1, S1) and those out of shade tabs (V2, S2). Following the treatment, the Commission International de I'Eclairage Lab parameters were tested using the spectrophotometric, and the DeltaEab* between the restoration and contrast teeth was calculated. RESULTS: There were significant differences between DeltaEab*V (3.92 +/- 1.59) and DeltaEab*S (2.23 +/- 0.96), and also between DeltaEab*V2 (4.42 +/- 1.42) and DeltaEab*S2 (2.27 +/- 1.01), DeltaEab*V1 (2.29 +/- 0.88) and DeltaEab*V2 (P < 0.01). There was no significant difference between DeltaEab*V1 and DeltaEab*S1 (2.12 +/- 0.84) (P = 0.698), nor between DeltaEab*S1 and DeltaEab*S2 (P = 0.014). CONCLUSIONS: Spectrophotometric (Vita Easyshade) shade matching method is more accurate than visual shade matching when used on tooth that has out-of-shade-tab colour expression. It provides better colour reappearance, than does visual colour matching.