Surface roughness, gloss and sequential polishing times of various chairside computer aided design/manufacturing restorative materials / 北京大学学报(医学版)

OBJECTIVE@#To investigate the effect of polishing on surface roughness, gloss and optimum polishing time of various computer aided design/computer aided manufacturing (CAD/CAM) restorative materials and to provide a proper polishing procedure for dental clinicians.@*METHODS@#Five CAD/CAM restorative materials including vita mark Ⅱ (VM), vita enamic (VE), lava ultimate (LU), shofu block HC (SB) and brilliant crios (BC) were selected. Six specimens were prepared for each material. The specimen was fixed on a custom-made polishing apparatus and sequentially polished with Sof-Lex poli-shing disk system including medium disk (with abrasive particle sizes of 10-40 μm), fine disk (with abrasive particle sizes of 3-9 μm) and superfine disk (with abrasive particle sizes of 1-7 μm). Surface roughness (Ra value) and gloss value were measured every 10 seconds until the numerical values were no longer changed. Then the surface roughness, gloss value and polishing time were recorded and the specimen was moved to the next sequence of polishing. Finally, statistical analysis was performed using SPSS 24.0.@*RESULTS@#For all the restorative materials, the Ra values were significantly reduced (P < 0.05) and the gloss values were significantly increased (P < 0.05) after sequentially polishing with Sof-Lex disks. No significant difference was detected among Ra values of all the tested materials (P>0.05) after sequential polishing. The gloss values of LU [(68.1±4.5) GU] and BC [(68.2±5.8) GU] were significantly higher than those of VE [(48.1±8.1) GU] and BC [(53.2±5.8) GU], P < 0.05. To obtain optimal surface smoothness, VM cost the shortest polishing time [40 (30, 55) s] among all the restorative materials (P < 0.05). No significant differences in the total polishing time were observed among VE [140 (135, 145) s], LU [130 (120, 140) s], SB [140 (130, 150) s] and BC [130 (120, 140) s], P>0.05.@*CONCLUSION@#The surface roughness of all CAD/CAM restorative materials were decreased after sequentially polishing with Sof-Lex disk system. To obtain the smoothest surface, different types of restorative materials might need different polishing times using Sof-Lex polishing disk system. For ceramic restorative material VM, we recommend polishing only with medium disk for 40 s. For hybrid restorative material VE and composite restorative material LU, SB and BC, we recommend polishing with medium disk, fine disk and superfine disk in sequence for 130-140 s in total.

Evaluation of wear property of Giomer and universal composite in vivo / 北京大学学报(医学版)

OBJECTIVE@#To observe the wear performance of Giomer and universal composite for posterior restorations by 3D laser scan method, in order to guide the material selection in clinic.@*METHODS@#In this study, 48 patients (108 teeth) were selected according to the inclusion and exclusion criteria. All the patients in need of a minimum of 2 Class Ⅰ and/or Class Ⅱ restorations were invited to join the study. The teeth were restored with Giomer (Beautifil Ⅱ, BF) and universal composite (Filtek Z350, Z350) randomly. The restorations were evaluated at baseline and after 6-, 18-, 48-month using the modified United States Public Health Service (USPHS) criteria for clinical performance. The in vivo images and gypsum replicas were taken at each recall. A 3D-laser scanner and Geomagic Studio 12 were used to analyze the wear depth quantitatively. Statistical analysis was performed with SPSS 20.0.@*RESULTS@#After 4 years, 89.6% patients were recalled. The survival rate of both materials was 95.8% (Kaplan-Meier survival analysis). Seven restorations of the two materials failed due to loss of restoration, bulk fracture, secondary caries and pulp necrosis. The wear patterns of restorations were divided into 2 classes. Pattern Ⅰ: occlusal contact areas showed the deepest and fastest wear depth; pattern Ⅱ: the wear depth was slow and uniform. Both materials showed a rapid wear in the first 6 months. Then the wear rate was decreased. The occlusal wear depth after 4 years were (58±22) μm and (54±16) μm for BF group and Z350 group respectively, which were in accordance with the American Dental Association (ADA) guidelines (wear depth for 3 years < 100 μm). No significant differences (P>0.05) were observed between the two groups. Regarding the restorations with wear pattern Ⅰ, the wear depth of BF group was higher than Z350 group at 6- and 48-month (P < 0.05), while there was no significant difference between restorations with wear pattern Ⅱ (P>0.05).@*CONCLUSION@#Within the limitation of the study, after 4 years, the survival rate and wear resistance of Giomer met ADA guidelines for tooth-colored restorative materials for posterior teeth. When the two materials were applied in occlusal contact areas, wear resistance of Giomer was slightly lower than universal composite resin. No significant difference was found when they were applied in none of the occlusal contact areas.

Effect of intrapulpal pressure on the bonding strength of resin cement to dentin / 北京大学学报(医学版)

OBJECTIVE@#To evaluate the effect of intrapulpal pressure simulation on the micro-tensile bond strength (μTBS) of resin cement to dentin.@*METHODS@#Thirty extracted human third molars were selected. Occlusal enamel was removed to expose dentine surface and teeth with residual dentin thickness of 0.5-2.5 mm were selected. Dye permeation through dentin tubules with or without intrapulpal pressure (IPP) simulation, or after Single Bond Universal (SBU) application on dentin surface with IPP simulation were observed at the end of 0 min, 5 min, 30 min and 2 h. The teeth with residual dentin thickness of (1.0±0.1) mm were divided into 2 groups with IPP simulation of 15 or 0 cmH2O (1 cmH2O=0.098 kPa), which was maintained for 30 min before bonding procedure. SBU was applied on the dentin surface and light cured, then RelyX Ultimate (RLX) cement was heaped on the dentin surface (diameter=10 mm, height=4 mm) and light-cured. After the dentin-resin cement samples were stored in distilled water for 24 h at 37 °C, the samples were cut into beams with cross sectional area of 0.9 mm×0.9 mm for μTSB testing (n=100). The data were analyzed with two independent samples t-test (α=0.05). The fracture mode was observed using scanning electron microscopy (SEM). The results were analyzed with Fisher exact test (α=0.05). The rest of dentin-resin cement samples (five samples for each group) were cut perpendicular to the bonding interface and the morphology of the bonding interface was observed using SEM.@*RESULTS@#The dye permeation through dentin tubules with IPP simulation was faster than those without IPP simulation. The μTSB of RLX to dentin with and without IPP simulation were (26.26±9.78) MPa and (28.70±9.0) MPa, respectively. The most frequent fracture mode was mixed-fracture mode. There was no significant difference between the two groups for neither bond strength nor fracture types distribution (P>0.05). Regarding the morphology of dentin-resin cement bonding interface, both groups showed 4-8 μm finger-like resin tags.@*CONCLUSION@#With SBU pretreatment, the IPP simulation had no influence on the immediate bond strength of RLX to dentin.

Influence of setting time on bond strength of different bioactive pulp capping materials with dental adhesive / 北京大学学报(医学版)

OBJECTIVE@#To investigate influence of setting time on bond strength of different bioactive pulp capping materials with self-etch or etch-and-rinse adhesive.@*METHODS@#Sixty specimens were prepared for each of the three tested capping materials, namely mineral trioxide aggregate (MTA), iRoot BP Plus (BP) and iRoot FS (FS). Specimens of each material were divided into three groups and bonded at three setting time points of the materials respectively: initial setting time (4 h for MTA, 2 h for BP and 20 min for FS), 24 h after application and 7 d after application. The specimen surfaces of each group were treated with self-etch mode or etch-and-rinse mode of one universal adhesive (Single Bond Universal, SBU) (n=10). The bonding area was restricted to a round area with 3 mm diameter, on which composite cylinders were build up with flowable composite and light cured completely. The shear bond strength was tested immediately with a shear strength tester and fracture mode was observed under stereo microscope and recorded. The mean shear bond strength for each group was analyzed with SPSS 19.0 software ANOVA method. The surface morphology of each material was observed after setting and acid treatment under scanning electron microscope.@*RESULTS@#There was no significant difference among the three tested materials at either initial setting point or 7 d after application (P<0.05). The bond strength of MTA was significantly higher than those of BP and FS 24 h after application in both bonding modes (P<0.05). For all the three tested materials, shear bond strength was significantly higher for complete setting group than for initial setting group of the same material (P<0.05). Under scanning electron microscope, the characteristic crystal patterns could be observed on the three bioactive materials surfaces after complete setting, the size of which was bigger for MTA than for BP and FS. These features were lost to some extent after self-etch primer application or phosphoric acid etching.@*CONCLUSION@#Based on the present results, adequate bond strength can be obtained for FS at initial setting time, which is comparable with BP and MTA. This implies that clinically composite restoration can be placed over bioactive direct capping materials after shortened initial setting process in one visit.

The durability of three self-etch adhesives bonded to dentin / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the durability of self-etch adhesives bonded to dentin in vitro.</p><p><b>METHODS</b>Forty-two extracted human molars were selected and occlusal dentin surfaces were exposed. The teeth were randomly distributed into three groups based on adhesives applied. The one-step self-etch adhesive B(Adper Prompt) and C(G-Bond) and two-step self-etch adhesive A (Clearfil SE bond) were used. After application of the adhesives to the dentin surfaces, composite crowns were built up, after 24 h water storage, the teeth were sectioned longitudinally into sticks (1.0 mm×1.0 mm bonding area) for microtensile testing or slabs (1 mm thick) for scanning electron microscopec (SEM) observation. Bonding strength (mTBS) and nano-leakage were evaluated immediately after cutting or after 6 months in water. The mTBS was analyzed using one-way ANOVA (SPSS 13.0). The nanoleakage was observed by SEM with a backscattered electron detector.</p><p><b>RESULTS</b>Both adhesives and water storage time affected the mTBS. All adhesives showed decreased bond strength after six-month water aging [A dropped from (40.60 ± 5.76) MPa to (36.04 ± 3.15) MPa; B dropped from (19.06 ± 1.50) MPa to (11.19 ± 1.97) MPa; C dropped from (17.75 ± 1.10) MPa to (9.14 ± 1.15) MPa] (P < 0.05). B and C showed lower mTBS than A after aging (P < 0.05). Compared to A, nanoleakage was more obvious after aging for B and C.</p><p><b>CONCLUSIONS</b>All self-etch adhesives tested were probably influenced by water aging, however, the two-step adhesive showed better durability than the one-step adhesives.</p>

Effects of application methods of self-etching adhesives on resin-dentin bonding / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of application time and rubbing action of self-etching adhesives on resin-dentin bond strength and interface morphology in vitro.</p><p><b>METHODS</b>Caries-free human third molars were wet ground to expose dentin surface. Three self-etching bonding agents were applied with varying application time and with/without rubbing. The microtensile bond strength and interface morphology were evaluated.</p><p><b>RESULTS</b>When etching time was shortened, normal and prolonged, the bond strength was bonding agent 1 (Adper Prompt): (16.30 +/- 2.59), (23.13 +/- 2.56), (22.28 +/- 2.83) MPa, bonding agent 2 (Xeno III): (15.17 +/- 6.07), (34.50 +/- 3.64), (24.87 +/- 7.01) MPa, bonding agent 3 (Clearfil SE Bond): (29.92 +/- 3.32), (42.21 +/- 6.28), (41.07 +/- 3.93) MPa. When etching was applied with and without rubbing, the bond strength was bonding agent 1 (23.13 +/- 2.56), (12.53 +/- 3.73) MPa, bonding agent 2 (23.98 +/- 3.86), (34.50 +/- 3.64) MPa, bonding agent 3 (48.37 +/- 4.95), (42.21 +/- 6.28) MPa.</p><p><b>CONCLUSIONS</b>Shortening application time decreased bond strength of self-etching adhesives, while prolonging application time did not increase bond strength of self-etching adhesives. Not all self-etching adhesives applied with rubbing showed increased bond strength to dentin, which is product-dependent. Manufactures' instructions should be followed to achieve optimum bonding.</p>

Microtensile bond strengths of one-step self-etching adhesive systems / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the microtensile bond strength of one-step self-etching adhesives to dentin in vitro.</p><p><b>METHODS</b>Three commercially available one-step self-etching bonding systems (group A: Adper Prompt, group B: Clearfil S(3) Bond, group C: Xeno III) were compared with two-step self-etching adhesive (group D: Clearfil SE Bond) in this study. The microtensile bond strength was determined with microtensile tester and the fractured bonding surfaces were observed under stereomicroscope and scanning electronic microscope (SEM). The mean bond strengths were analyzed using one-way ANOVA test (P < 0.05).</p><p><b>RESULTS</b>Mean microtensile bond strengths of group C, B, A and D were (34.59 +/- 3.46), (30.46 +/- 3.82), (23.36 +/- 2.55) and (45.06 +/- 5.29) MPa, respectively. Group D showed the highest bond strength (P < 0.01).</p><p><b>CONCLUSIONS</b>Two-step self-etching adhesive had a higher bond strength than one-step self-etching adhesive systems, although all of them can satisfy the clinical requirements.</p>