Effectiveness of diamond-impregnated felt wheels for polishing a hybrid composite

The effectiveness of diamond-impregnated felt wheels for polishing the surfaces of a fine-particle hybrid composite was studied in relation to different finishing methods. Standardised composite specimens were finished with one or a series of two or three finishing diamonds (particle size 30, 15 and 8 μm), one or two tungsten carbide finishing burs (12- and 30-fluted) or with a finishing diamond followed by a tungsten carbide bur. The final polishing of all specimens was done with the diamond-impregnated felt wheel Diafix α. Treatment with Sof-Lex discs after the use of a finishing diamond served as a polishing standard for comparison. Evaluation of the final surfaces was done with profilometry and by scanning electron microscopy. The profilometric results showed that the type of pretreatment was decisive for the quality of the final polishing. Nearly all surfaces polished by the diamond-impregnated felt wheels were smoother than those treated by the flexible discs (P<0.01). The lowest roughness data were recorded following a pretreatment with a finishing diamond and a tungsten carbide finishing bur. After appropriate pretreatment, the hybrid composite surface was sufficiently polished with the diamond-impregnated felt wheels.     

渗透技术及抛光对人工早期釉质龋表面粗糙度的影响

目的：研究早期釉质龋形成后,渗透树脂治疗后不同抛光处理对其表面粗糙度的影响,为临床治疗中选择合适的抛光系统提供参考。方法：制取牛下切牙唇面样本54个,随机分为6组,设健康釉质组、早期釉质龋组,其余4组先用部分饱和酸缓冲系统形成早期釉质龋,然后进行渗透树脂治疗,根据抛光与否和抛光工具种类(橡皮杯、抛光碟、矽粒子)进行分组。采用表面粗糙度轮廓仪PGI800测量各组样本的表面粗糙度,表面粗糙度参数取轮廓算术平均偏差(Ra)和轮廓最大高度(Rz)。采用SPSS17.0软件包对数据进行统计学分析。结果：早期釉质龋组较健康釉质组表面粗糙度均值略大,但无显著差异(P>0.05);早期釉质龋渗透树脂治疗后,不抛光组表面粗糙度显著高于早期釉质龋组(P<0.05);渗透树脂治疗后,3种不同工具抛光组之间两两比较,表面粗糙度无显著差异(P>0.05);各抛光组较未抛光组表面粗糙度均减小,差异显著(P<0.05);各抛光组与早期釉质龋组相比,表面粗糙度均无显著差异(P>0.05)。结论：早期龋进行渗透树脂治疗后,表面粗糙度明显升高,需要进行抛光处理,使用橡皮杯和粒度较小的抛光碟抛光,是较有效的表面处理方法。     

两种抛光方法对纯钛和钴铬合金粗糙度的影响

目的：研究两种抛光方法对纯钛和钴铬合金表面粗糙度的影响。方法：将纯钛和钴铬合金各分为3组,除一个对照组外,其余两组分别进行机械法和化学法抛光。记录试件抛光后的减重率（wt%）,测量表面粗糙度Ra值,并用扫描电镜（SEM）观察试件表面形态变化。结果：同种金属经过不同抛光处理后,减重率和表面粗糙度Ra值都有显著差异（P〈0.01）,且纯钛和钴铬合金分别经过同种抛光处理后,减重率和表面粗糙度也均有显著差异（P〈0.01）。扫描电镜观察表明,化学抛光后钴铬合金表面更加光滑,均匀一致。结论：与纯钛相比,钴铬合金更容易抛光,且化学法比机械法更易于获得良好的金属表面。     

EFFECTS OF POLISHING PROCEDURES ON COLOR STABILITY OF COMPOSITE RESINS

The purpose of this study was to investigate the effect of different polishing methods on color stability of posterior, universal and nanohybrid composite resin restorative materials upon exposure to a staining agent. Twenty-five specimens were prepared for each of 5 different composite resins (Filtek Z250, Filtek P60, Quadrant LC, Grandio and Filtek Supreme). Specimens were divided into 5 groups and different polishing procedures, including polishing discs (Pd), polishing discs then diamond polishing paste (PdP), polishing discs then a liquid polishing system (Biscover) (PdB), and combinations of these (PdPB) were used. Unpolished specimens served as the control (C). The specimens were stored for 48 h in a coffee solution. The color of all specimens was measured before and after exposure with a colorimeter, and total color change ∆E*) were calculated. The data were analyzed with a two-way ANOVA and the means were compared by Tukey HSD test (α=0.05). The lowest color difference was observed in the groups PdP and C, while the highest color difference was observed in PdPB, and PdB. When comparing the five different restorative materials, no significant difference was observed between FiltekP60 and FiltekZ250, and these materials demonstrated significantly less color change than Quadrant LC and the nanohybrid materials (Grandio, Filtek Supreme). The posterior (Filtek P60) and universal (Filtek Z250) composite resin restorative materials, which do not contain tetraethyleneglycol dimethacrylate (TEGDMA), were found to be less stainable than the nanohybrid (Grandio, Filtek Supreme) and universal (Quadrant LC) composite resins, which contain TEGDMA. The use of diamond polishing paste after polishing with polishing discs significantly decreased staining when compared to the groups that used polishing discs alone, for all restorative materials tested. The highest color change values were obtained for the specimens that were polished with the Biscover liquid polish system (PdB and PdPB groups).     

抛光材料的粒度对复合树脂表面粗糙度及润湿性的影响

目的：比较抛光材料的粒度对3种复合树脂粗糙度及表面润湿性的影响。方法选择3种复合树脂材料,分别为Filtek Z100（A组）,Charisma（B组）和Clearfil AP-X（C组）,采用不同粒度的抛光材料（Sof-LexTM Extra Thin抛光彩碟）,随机分组抛光,然后,检测表面粗糙度（Ra）及接触角,并进行统计学分析。结果随抛光彩碟粒度减小,3种材料的Ra值均逐渐减小,精细粒度抛光组的接触角显著低于3个较粗粒度抛光组（P〈0.05）;3种材料在相同抛光材料粒度处理后,Ra显著不同（P〈0.05）：A组＜B组＜C组,同时,A组的接触角明显高于B组和C组（P〈0.05）。结论复合树脂的表面粗糙度及润湿性与材料种类和抛光材料的粒度相关。     

牙科陶瓷调磨后不同的抛光上釉方法对其表面性状的影响

目的牙科陶瓷调磨后比较不同的抛光上釉方式其表面的光泽度。方法 用V intage瓷粉制作盘状试件24个,均匀调磨后按不同的处理方式随机分成四组,以粗糙度测试仪测量各组的粗糙度值并进行统计学分析,体视显微镜和电子显微镜观察试件表面形貌。结果抛光和上釉表面粗糙度值无显著性差异（P〉0.05）;镜下观察四组试件表面结构及光滑度无明显差别。结论牙科陶瓷调磨后抛光可以达到与自身上釉相近似的效果。     

Effects of air-polishing powders on color stability of composite resins

Objectives

The purpose of this study was to investigate the effect of different air-polishing powders on the color stability of different types of composite resin restorative materials.

Material and methods

Thirty cylindrical specimens (15×2 mm) were prepared for each of 7 composite resin restorative materials. All specimens were polished with a series of aluminum oxide polishing discs (Sof-Lex). The prepared specimens of each composite resin were randomly divided into 3 groups of 10 specimens each, for control (Group-C) and two air-powder applications (Group-CP: Cavitron Prophy-Jet; Group-PS: Sirona ProSmile prophylaxis powder). A standard air-polishing unit (ProSmile Handly) was used. All specimens were air-powdered for 10 s at 4-bar pressure. The distance of the spray nosel from the specimens was approximately 10 mm and angulation of the nosel was 90º. Specimens were stored in 100 mL of coffee (Nescafe Classic) for 24 h at 37ºC. Color measurement of all specimens was recorded before and after exposure to staining agent with a colorimeter (Minolta CR-300). Color differences (∆E*) between the 2 color measurements (baseline and after 24 h storage) were calculated. The data were analyzed with a 2-way ANOVA test, and mean values were compared by the Tukey HSD test (p≤0.05).

Results

According to the 2-way ANOVA results, composite resin restorative materials, air-polishing powders, and their interaction were statistically significant (p<0.05) For Aelite Aesthetic Enemal, Filtek Z250, Grandio, CeramX Mono, and Quixfil composite resin restorative materials, no significant difference was observed between Group-PS and Group-CP (p>.05) and these groups demonstrated the highest ∆E* values. For Filtek Silorane and IntenS, the highest ∆E* values were observed in Group-PS. The lowest ∆E* values for all composite resin groups were observed in Group-C. When comparing the 7 composite resin restorative materials, Aelite Aesthetic Enemal demonstrated significantly less ∆E* values than the other composite resins tested. The highest ∆E* values were observed in Quixfil.

Conclusion

Except for Quixfil, all control groups of composite resins that were polished Sof-Lex exhibited clinically acceptable ∆E values (<3.7). Air-polishing applications increased the color change for all composite resin restorative materials tested. Composite restorations may require re-polishing after air-polishing.     

不同车针去除正畸粘接剂对牙表面粗糙度的影响

目的 比较不同釉质抛光法去除正畸托槽粘接剂后对牙釉质表面粗糙度的影响,为临床应用提供实验依据。方法 选取24颗因正畸治疗拔除的离体前磨牙,随机分为3组,金刚砂磨头组（A组）、金刚砂车针组（B组）和钨钢车针组（C组）,每组8颗牙,正畸粘接剂粘接后用不同方法去除并记录操作时间,再用橡皮轮抛光20s。表面粗糙度测量仪测量托槽粘接前、橡皮轮抛光前、后颊面正中部位表面粗糙度（Ra⁰、Ra¹、Ra²）,并作扫描电镜观察。结果 单因素方差分析显示：操作时间以及橡皮轮抛光前后表面粗糙度比较,A组与两组比较差异有统计学意义（P<0.05）,B组与C组无显著差异（P>0.05）;配对T检验结果显示3组表面粗糙度Ra²值最小,C组Ra⁰值与Ra¹值比较差异无统计学意义（P>0.05）,其余两组比较差异有统计学意义（P<0.05）;扫描电镜结果显示牙面光洁度C组优于B组优于A组。结论 钨钢车针去除正畸粘接剂效果最佳。     

Comparative effects of tungsten,diamond burs and laser for residual adhesive removal after orthodontic debonding on flexural strength,surface roughness and phase transformation of high-translucent zirconia: An in vitro study

ObjectivesInformation regarding the effects of orthodontic bracket debonding on zirconia restorations, and the preferred method for residual adhesive removal from the zirconia restoration surface is lacking. Thus, this study aimed to assess the effects of different methods of residual adhesive removal after orthodontic bracket debonding on flexural strength, surface roughness, and phase transformation of high-translucent (HT) zirconia.Materials and methodsThis in vitro study evaluated 72 bar-shaped HT zirconia specimens; 18 specimens were assigned to the control group. Metal brackets were bonded to the remaining specimens by resin cement. After bracket debonding, the residual adhesive on the surface of specimens was removed by three methods (n = 18): a 30-flute tungsten-carbide (TC) bur at low speed, an ultrafine diamond bur at high speed, and Er:YAG laser irradiation. The surface roughness (Ra and Rz) was measured. X-ray diffraction (XRD) analysis was carried out, and the flexural strength was measured as well. Data were statistically analyzed (α = 0.05).ResultsBefore polishing, all methods increased the Ra and Rz values (P < 0.05) except for the diamond bur yielding a Rz value comparable to that of the control group. The Ra values of the test groups were comparable after polishing, and still higher than that of the control group (P < 0.05). The flexural strength of all three test groups was comparable (P > 0.05), and significantly lower than that of the control group (P < 0.001). The monoclinic phase was not observed in any group.ConclusionsOrthodontic bracket debonding adversely affects the surface roughness and flexural strength of zirconia despite polishing.     

Current status of zirconia restoration

During the past decade, zirconia-based ceramics have been successfully introduced into the clinic to fabricate fixed dental prostheses (FDPs), along with a dental computer-aided/computer-aided manufacturing (CAD/CAM) system. In this article (1) development of dental ceramics, (2) the current status of dental CAD/CAM systems, (3) CAD/CAM and zirconia restoration, (4) bond between zirconia and veneering ceramics, (5) bond of zirconia with resin-based luting agents, (6) surface finish of zirconia restoration and antagonist enamel wear, and (7) clinical evaluation of zirconia restoration are reviewed.Yttria partially stabilized tetragonal zirconia polycrystalline (Y-TZP) showed better mechanical properties and superior resistance to fracture than other conventional dental ceramics. Furthermore, ceria-stabilized tetragonal zirconia polycrystalline and alumina nanocomposites (Ce-TZP/A) had the highest fracture toughness and had resistance to low-temperature aging degradation. Both zirconia-based ceramics have been clinically available as an alternative to the metal framework for fixed dental prostheses (FDPs). Marginal adaptation of zirconia-based FDPs is acceptable for clinical application. The most frequent clinical complication with zirconia-based FDPs was chipping of the veneering porcelain that was affected by many factors. The mechanism for the bonding between zirconia and veneering ceramics remains unknown. There was no clear evidence of chemical bonding and the bond strength between zirconia and porcelain was lower than that between metal and porcelain.There were two alternatives proposed that might avoid chipping of veneering porcelains. One was hybrid-structured FDPs comprising CAD/CAM-fabricated porcelain parts adhering to a CAD/CAM fabricated zirconia framework. Another option was full-contour zirconia FDPs using high translucent zirconia. Combined application of silica coating and/or silane coupler, and 10-methacryloyloxydecyl dihydrogen phosphate is currently one of the most reliable bonding systems for zirconia. Adhesive treatments could be applied to luting the restorations and fabricating hybrid-structured FDPs. Full-contour zirconia FDPs caused concern about the wear of antagonist enamel, because the hardness of Y-TZP was over double that of porcelain. However, this review demonstrates that highly polished zirconia yielded lower antagonist wear compared with porcelains. Polishing of zirconia is possible, but glazing is not recommended for the surface finish of zirconia.Clinical data since 2010 are included in this review. The zirconia frameworks rarely got damaged in many cases and complications often occurred in the veneering ceramic materials. Further clinical studies with larger sample sizes and longer follow-up periods are required to investigate the possible influencing factors of technical failures.