柠檬酸致牙釉质脱矿的研究

目的 观察10%柠檬酸酸蚀牙釉质不同时间的效果,以获得研究早期釉质龋的可靠体外实验模型,探索更高效的牙釉质脱矿实验方法.方法 选取离体人恒前磨牙切割制成牙釉质块,经10%柠檬酸及部分饱和酸缓冲脱矿系统脱矿,扫描电镜观察牙釉质表面经柠檬酸酸蚀不同时间(90 s、120 s、150 s)及部分饱和酸缓冲脱矿系统脱矿1周后的形态学特征,并用显微硬度计检测标本脱矿前后表面显微硬度.结果 牙釉质进行脱矿处理后,釉质表面呈现酸蚀状外观.酸蚀90 s时,仅见小部分釉柱晶格脱矿溶解,脱矿牙釉质的能力有限;酸蚀120 s时,与早期自然龋损近似,呈蜂窝状;酸蚀150 s时,牙釉质表面呈酸蚀样破坏形貌,属于过度酸蚀;而部分饱和酸缓冲脱矿系统脱矿效果相对较差.结论 柠檬酸具有较强的酸蚀作用,其脱矿牙釉质的能力随着时间的延长而增强,10%的柠檬酸酸蚀120 s可获得早期釉质龋模型.     

人牙釉质酸蚀过程中三维形貌的原子力显微镜观察

目的 比较不同酸蚀时间处理后牙釉质表面的三维形貌并分析粗糙度的改变,探讨酸蚀对牙釉质微观形貌的影响.方法 将15颗新鲜前磨牙包埋、切割、打磨后得到光滑牙釉质切片,按单纯随机法分为5组,用37％磷酸凝胶分别酸蚀0(对照组)、5、10、20和30s,原子力显微镜观察釉质表面形貌,分析轮廓改变,计算图像的算术平均粗糙度(Ra)、均方根粗糙度(Rq)、十点高度平均差(Rz)值及表面积、容积并对5组的结果数据进行单因素方差分析,用Turkey's法进行组间两两比较,以P＜0.05为差异有统计学意义.结果 镜下形貌观察显示,0～20 s内釉质的釉柱结构逐渐明显,釉质表面由较光滑逐渐变为典型鱼鳞状;20 s后表面形态变化不明显.表面轮廓观察显示,随着酸蚀时间由0s增加至30 s,釉柱间隙首先被溶解,酸蚀深度逐渐增加到2.8μm,30 s后釉柱顶部宽度减小至1.8μm,且高度略降低.从0s到30 s,Ra值由(19.69±3.42) nm增加到(359.51±75.79)nm,Rq值由(22.02±5.57) nm增加到(431.02±83.09) nm,Rz值由(0.24±0.08) μm增加到(2.38±0.26) μm;组间比较显示,Ra和Rq值的20s组与30 s组和Rz值的10、20和30 s组差异无统计学意义(P＞0.05),其余各组间差异均有统计学意义(P＜0.05).同时釉质表面积由(406.77±3.88) μm2 (0 s)增大到(546.69±84.02) μm2 (30 s),容积由(65.73±14.46) μm3 (0 s)增大到(474.63±52.50)μm3(30 s).结论 随着酸蚀时间的增加,釉质表面酸蚀深度不断增大,表面粗糙度增加,表面积及容积增大,酸蚀会造成釉质微观形貌的明显改变.     

酸蚀时间、再矿化时间对乳牙釉质再矿化的影响

目的 本研究采用激光共聚焦显微镜来观测不同酸蚀时间、不同矿化时间对乳牙釉质再矿化的影响。方法 采用随机区组设计,将28枚离体乳切牙的唇面分别开4个窗,随机分到酸蚀30 s、60 s、90 s、120 s 4个处理组中,采用32%磷酸凝胶对标本进行酸蚀处理,而后采用人工唾液进行再矿化,分别于脱矿后、再矿化处理2 h,再矿化处理24 h进行激光共聚焦显微镜扫描,记录其平均荧光量(AF),采用重复测量的方差分析对数据进行分析,显著性水平为0.05。结果 多变量方差分析(MANOVA)结果 显示:再矿化时间、酸蚀时间对再矿化后AF有显著影响(分别F=357.74,P<0.0001;F=51.62,P<0.0001);Bonferroni法多重比较显示:酸蚀时间对再矿化效果影响中,除90 s组与120 s组之间的差异没有显著性,其余各组AF两两比较差异均有显著性;矿化时间对再矿化的影响中,两两比较AF差异均有显著性。结论 在进行乳牙抗酸能力及再矿化潜能检测时,酸蚀时间不可超过60 s,再矿化时间可以为24 h。?     

不同饮料对SD大鼠牙釉质脱矿影响的激光共聚焦扫描电镜观察

目的通过激光共聚焦扫描电镜了解饮料对釉质脱矿的影响。方法80d龄SD大鼠42只,每只单笼饲养,喂饲致龋饲料15天后检测无牙釉质脱矿。余鼠随机分为去离子水组(阴性对照,A组)、雪碧组(碳酸类,B组)、伊力纯牛奶组(牛奶类,C组)、农夫山泉矿泉水组(矿泉水类,D组)、统一鲜橙多组(果汁类,E组)和康师傅鲜c组(果汁类,F组),每组6只,喂饲饮料3个月,用激光共聚焦扫描显微镜观察磨牙釉质的脱矿情况。结果雪碧、统一鲜橙多和康师傅鲜c组的荧光面积、总荧光面积及平均荧光量分别是12.75×10-3μm2、19.83×10-3及1.56;8.90×10-3μm2、14.52×10-3及1.63;15.05×10-3μm2、24.04×10-3及1.60,明显高于对照组(P<0.05),其值为6.03×10-3μm2、9.73×10-3及1.55,其中又以康师傅鲜c组为最高。矿泉水和牛奶类的荧光面积和总荧光量都较低,分别为3.45×10-3μm2、5.41×10-3和3.87×10-3μm2、6.14×10-3,与对照组相比没有显著性差异(P>0.05),与酸性饮料(包括碳酸类和果汁类)比较有显著差异(P<0.01)。结论酸性饮料具有较强的酸蚀性,牛奶和矿泉水对釉质脱矿没有明显的影响。     

氟化泡沫防止正畸固定矫治患者釉质脱矿的实验研究

目的观察氟化泡沫在酸性环境下抑制牙釉质脱矿的作用。方法样本制备后,实验组样本用氟化泡沫处理,对照组藻酸盐印模封闭处理。显微硬度计分别测定人工龋蚀前后样本釉质表面显微硬度,甲基麝香草酚蓝法测定样本酸蚀钙溶出量。结果实验组钙溶出量和釉质显微硬度变化与对照组比较有统计学差异(P<0.01)。结论氟化泡沫能抑制酸性环境下的牙釉质脱矿,能防止正畸固定矫治患者釉质脱矿。     

激光和磷酸处理牙釉质表面的体外对比研究

目前,临床上粘结托槽常规采用磷酸酸蚀技术,但其有以下不足:①引起牙釉质表面的不可逆脱矿(深度约10μm);②残余磷酸可能造成牙体硬组织和局部软组织的损伤;③去托槽时有可能造成釉质折裂。为了克服这些不足,部分学者尝试弱酸或采用牙科激光技术。本研究选用两种常用的牙科激光与磷酸酸蚀技术进行对比研究。     

釉质酸蚀后牙面脱矿与再矿化的扫描电镜观察

目的:观察牙釉质酸蚀后在离体状态下和一段时间内在口腔环境中的结构变化,探讨牙釉质脱矿与再矿化的形态学改变.方法:选择因正畸需要拔除健康第一前磨牙病例10例,40个牙,使用YY0269-1995型酸蚀剂对拟拔除的第一前磨牙颊侧釉质酸蚀60 8,左侧上、下颌第一前磨牙为A组,A组再分为A1、A2组,A1组酸蚀后即刻拔除,制作扫描电镜观察标本,A2组,第一前磨牙酸蚀后即刻拔除,置37℃恒温蒸馏水中浸泡1个月后制作电镜标本观察.右侧上、下颌第一前磨牙为B组,第一前磨牙酸蚀后在口内存留1个月后拔除,用相同的方法进行观察,并比较A、B两组牙釉质形态学变化.结果:A组的牙釉质表面松软,不规则,多孔隙,表面呈蜂窝状改变;B组的牙釉质表面有大量矿物质沉积,孔隙变小,矿化物颗粒细小,沉积不均匀.结论:牙釉质脱矿后,在口腔环境中可发生再矿化,但矿化程度是有限的,提示在临床上应注意酸蚀时间及酸蚀范围.     

��ͬʱ����ʴ������������ʱ�����̬ɨ��羵�۲��о�

目的探讨正畸临床牙釉质的最佳酸处理时间。方法从2005年大连市口腔医院外科门诊200颗正畸减数拔除的双尖牙中挑选出13颗作为样本,随机抽取其中3颗作为对照,未作酸处理。10颗进行酸处理的实验牙用约1mm宽的蜡条沿牙冠颊轴嵴作分界线,蜡条覆盖部分作为对照区。扫描电镜下观察未酸蚀的对照牙、实验牙对照区和经过15s和60s酸蚀处理后的实验牙釉质表面形态。结果镜下观察结果显示:酸蚀前釉质表面多较为光滑,似云片、积雪状外观;酸蚀后在小部分样本釉质表面中看到典型的蜂窝样和鹅卵石样形态。构成比显示60s酸蚀组较15s酸蚀组釉质丢失量多。结论60s酸蚀组较15s酸蚀组釉质丢失更严重,为了尽可能地减少酸蚀粘接对牙釉质的损害,正畸临床可将酸蚀时间适当减少。     

固定矫治术后牙釉质脱矿及其防范措施的临床研究

目的 研究固定矫治术后牙釉质脱矿的发病情况及其影响因素,并分析探讨对其防范措施的有效性。方法 200例固定正畸患者随机分成二组,对照组常规处理;试验组采用综合预防措施。治疗结束后即刻观察患者牙面釉质脱矿斑情况。结果 对照组釉质脱矿率为16.7％,试验组为9.6％,有显著差异性。脱矿好发牙位是上颌侧切牙和下颌第一磨牙,好发部位是牙颈部,不同年龄组釉质脱矿率明显不同。结论 固定矫治器对牙釉质的脱矿损害是值得引起重视的问题。矫治前对其可能的危害因素的充分预测和控制酸蚀时间、牙面氟化处理、治疗中的口腔卫生、定期的洁牙等综合预防措施对减少固定正畸患者牙釉质脱矿是行之有效的方法。     

自酸蚀和酸蚀剂正畸牙面处理效果的临床与扫描电镜研究

目的 比较自酸蚀偶联剂和磷酸凝胶酸蚀剂作为正畸牙面处理剂的粘结效果和釉质脱矿情况.方法 选取临床26例病人,左侧采用37%磷酸凝胶酸蚀剂,右侧使用自酸蚀偶联剂处理牙面,观察3个月内托槽脱落情况,比较临床脱落率.采用扫描电镜分别观察对照组、酸蚀组、自酸蚀组样本树脂突和粘结剂边缘牙釉质的脱矿情况.结果 酸蚀组的托槽脱落率2.44%,自酸蚀组为2.02%,经χ2检验无显著性差异.扫描电镜下自酸蚀较酸蚀组树脂突数量多、粗短且较规则,釉质表面脱矿程度较弱.结论 两种牙面处理剂的临床粘结效果差异不大,自酸蚀偶联剂对釉质脱矿作用更小.     

瓷面处理对金属托槽与瓷面粘接性能的影响

目的　研究瓷表面不同处理方法对金属托槽与瓷修复体的粘接强度及去粘接后瓷面完整性的影响。方 法　根据使用粘接剂和表面处理方法的不同,将80个瓷面随机分为8组,每组10个瓷面。分别用京津釉质粘接剂 和光固化复合树脂粘接,表面处理分别行37%磷酸酸蚀、9·6%氢氟酸酸蚀、打磨去釉、瓷面涂硅烷偶联剂4种表面 处理法。试件粘接托槽后经37℃恒温水浴24 h后测定抗剪切强度,记录去粘接后的瓷面破裂情况。对磷酸酸蚀, 氢氟酸酸蚀、打磨去釉的瓷面进行扫描电镜观察。结果　采用氢氟酸酸蚀、打磨去釉、硅烷偶联剂组的粘接抗剪切 强度明显高于磷酸酸蚀组(P<0·01)。打磨去釉后用光固化复合树脂粘接及氢氟酸酸蚀或瓷表面涂硅烷处理后使 用任意一种粘接材料粘接均取得有效的粘接强度。各组去粘接后的瓷破裂率无显著性差异(P>0·05)。结论　氢 氟酸酸蚀、打磨去釉、瓷面涂硅烷偶联剂均可以明显增加金属托槽与瓷面之间的粘接抗剪切强度。瓷面涂硅烷偶 联剂是金属托槽与瓷面粘接时良好的表面处理剂。     

Effect of etching and light-curing time on the shear bond strength of a resin-modified glass ionomer cement

The aim of this study was to assess the influence of etching and light-curing time on the shear bond strength (SBS) and adhesive remnant index (ARI) of a resin-modified glass ionomer cement (RMGIC) upon debonding of orthodontic brackets. Sixty-eight bovine permanent incisors were obtained and embedded in acrylic resin. Edgewise metallic brackets were bonded to the teeth with Fuji Ortho LC RMGIC. The specimens were randomly assigned to 4 groups, using the following etching and light-curing times: G1: 10% polyacrylic acid and 40 s (control); G2: 37% phosphoric acid and 40 s; G3: 10% polyacrylic acid and 50 s; and G4: 37% phosphoric acid and 50 s. Shear test was performed at 0.5 mm/min and the ARI was assessed. G2 (3.6 ± 0.98 MPa) presented significantly higher (p<0.05) SBS than G1 (2.76 ± 0.86 MPa) and G4 (2.86 ± 0.68 MPa), and there was no statistically significant difference (p>0.05) between G2 and G3 (2.94 ± 0.67 MPa). ARI presented prevalence of scores 2 and 3 in all groups. RMGIC SBS enhanced with 37% phosphoric acid etching and 40 s light-curing time, but this did not occur when the light-curing time was increased, regardless of the acid used. RMGIC presented prevalence of failures at the adhesive/bracket interface.     

Effect of hydrofluoric acid etching duration on the roughness and flexural strength of a lithium disilicate-based glass ceramic

The aim of this study was to examine the effect of different acid etching times on the surface roughness and flexural strength of a lithium disilicate-based glass ceramic. Ceramic bar-shaped specimens (16 mm x 2 mm x 2 mm) were produced from ceramic blocks. All specimens were polished and sonically cleaned in distilled water. Specimens were randomly divided into 5 groups (n=15). Group A (control) no treatment. Groups B-E were etched with 4.9% hydrofluoric acid (HF) for 4 different etching periods: 20 s, 60 s, 90 s and 180 s, respectively. Etched surfaces were observed under scanning electron microscopy. Surface profilometry was used to examine the roughness of the etched ceramic surfaces, and the specimens were loaded to failure using a 3-point bending test to determine the flexural strength. Data were analyzed using one-way ANOVA and Tukey's test (?=0.05). All etching periods produced significantly rougher surfaces than the control group (p<0.05). Roughness values increased with the increase of the etching time. The mean flexural strength values were (MPa): A=417 ± 55; B=367 ± 68; C=363 ± 84; D=329 ± 70; and E=314 ± 62. HF etching significantly reduced the mean flexural strength as the etching time increased (p=0.003). In conclusion, the findings of this study showed that the increase of HF etching time affected the surface roughness and the flexural strength of a lithium disilicate-based glass ceramic, confirming the study hypothesis.     

Effects of etching time of primary dentin on interface morphology and microtensile bond strength

OBJECTIVES: To determine the influence of different etching times (5, 15 or 30 s) on the morphology and micro-tensile bond strength (muTBS) of primary dentin. METHODS: For muTBS study, nine primary molars were randomly distributed in three experimental groups. Three Class I cavities per tooth were drilled and etched (37% orthophosphoric acid gel for 5, 15 or 30 s). Excite adhesive was applied and cavities restored with a resin composite (Tetric Ceram). Composite/dentin bars (ca. 1 mm2 section) were obtained from teeth and tested in tension until debonding. Means of muTBS results were compared with ANOVA and Student-Neuman-Keuls post hoc tests. Morphology: Three occlusal cavities were prepared in five primary molars. Each cavity was etched and restored as described for previous groups and teeth were sectioned mesio-distally. One half of each tooth was prepared for using under optical microscopy using Masson's trichromic dye technique and the other half was examined by SEM. RESULTS: muTBS mean (S.D.) results (in MPa) were 5 s etch: 6.20 (2.81), 15 s: 13.43 (5.91), 30 s: 13.04 (5.67). muTBS groups were Excite 5 s < Excite 15 s = Excite 30 s. Masson's trichromic technique stained the demineralized dentin layer red in all specimens. The mean (S.D.) thickness of the demineralized layers (in mu) were 5 s: 3.28 (1.23), 15 s: 3.83 (1.26), 30 s: 4.44 (1.70). There is a statistically significant linear relationship between time of application of etching and mean depth of demineralized layer. This relationship was established as depth (in mu) = 3.08 + 0.05 time (in s). SIGNIFICANCE: The minimum adequate etching time for primary dentin is 15s.     

The impact of hydrofluoric acid etching followed by unfilled resin on the biaxial strength of a glass-ceramic

Objectives

To evaluate the null hypotheses that hydrofluoric (HF) acid etching time would neither decrease the biaxial flexural strength of a glass-based veneering ceramic nor enhance it after silane and unfilled resin (UR) applications.

Methods

Disc-shaped IPS e.max ZirPress specimens were allocated into 12 groups: G1-control (no-etching), G2-30 s, G3-60 s, G4-90 s, G5-120 s, G6-60 s + 60 s. Groups (G7–G12) were treated in the same fashion as G1–G6, but followed by silane and UR applications. Surface morphology and roughness (Ra and Rq) of the ceramics were assessed by means of scanning electron microscopy (SEM) and profilometry, respectively. Flexural strength was determined by biaxial testing. Data were analyzed by two-way ANOVA and the Sidak test (α = 0.05). Weibull statistics were estimated and finite element analysis (FEA) was carried out to verify the stress concentration end areas of fracture.

Results

The interaction (etching time vs. surface treatment) was significant for Ra (p = 0.008) and Rq (0.0075). Resin-treated groups presented significantly lower Ra and Rq than non-treated groups, except for the 60 s group (p < 0.005). SEM revealed that etching affected the ceramic microstructure and that the UR was able to penetrate into the irregularities. A significant effect of etching time (p = 0.029) on flexural strength was seen. G7–G12 presented higher strength than G1–G6 (p < 0.0001). None of experimental groups failed to show 95% confidence intervals of σ₀ and m overlapped. FEA showed lower stress concentration after resin treatment.

Significance

HF acid etching time did not show a damaging effect on the ceramic flexural strength. Moreover, the flexural strength could be enhanced after UR treatment.     

Effect of acid etching time and a self-etching adhesive on the shear bond strength of composite resin to porcelain

PURPOSE The purpose of this study was to evaluate the effect of different acid etching times with 9.6% hydrofluoric acid gel and two adhesive systems on shear bond strengths of resin composite to porcelain. MATERIALS AND METHODS: Ninety-eight 7 x 7 x 2 mm feldspathic porcelain blocks (VMK 95, Vita) were prepared. The specimens were divided into 7 groups: 1 control (no surface treatment) and 6 groups acid etched with 9.6% hydrofluoric acid gel for different etching times, including 30 s, 30+30 s, 60 s, 60+60 s, 120 s, and 180 s. Each of the etching time groups was divided into two bonding agent (Single Bond, AdheSE) subgroups (n = 7). Microhybrid composite (Filtek Z250) was condensed using a teflon mold and light polymerized for 20 s on the porcelain specimens. The prepared specimens were then stored in distilled water at 37 degrees C for 24 h before mechanical testing. Shear testing of all groups was performed on a universal testing machine (Lloyd LRX) at a crosshead speed of 0.5 mm/min. The bond strength data were analyzed with two-way ANOVA. The means were compared using the Tukey HSD test (alpha = 0.05). RESULTS: Acid etching time and bonding agent statistically significantly influenced bond strength (p < 0.05). In the Single Bond group, the bond strengths between group 0 (10.48 MPa) and Group 30 (11.17 MPa) did not differ significantly, with these groups exhibiting the lowest bond strength values. The highest bond strength in Single Bond group was observed in group 120 (15.07 MPa) and group 60+60 (15.42 MPa), which did not differ significantly from each other. In the AdheSE group, the bond strengths of group 0 (9.33 MPa) and group 30 (9.49 MPa) did not differ significantly, and these groups exhibited the lowest bond strength values. The highest bond strengths in the AdheSE subgroup were observed in group 120 (14.84 MPa) and group 60+60 (14.96 MPa), which were not significantly different. Comparing the two different adhesive systems, Single Bond exhibited higher bond strength values than did the self-etching adhesive AdheSE. CONCLUSIONS: Acid etching of porcelain with 9.6% hydrofluoric acid gel for 120 s provided adequate bond strength for composite repair with a microhybrid composite. When a porcelain restoration is repaired with composite, Single Bond adhesive should be preferred to the AdheSE self-etching adhesive system.     

Effect of surface treatment on the shear bond strength of a resin-based cement to porcelain

The purpose of this in vitro study was to evaluate the effect of different surface treatments on the shear bond strength of a resin-based cement to porcelain. Sixty pairs of 50% aluminous porcelain discs were fabricated. In each pair, one disc measured 6 mm in diameter X 3 mm thickness (A) and the other measured 3 mm in diameter X 3mm thickness (B). The specimens were randomly assigned to 6 groups (n=10 pairs of discs), according to the surface treatment: etching with 10% hydrofluoric acid for 2 or 4 min (G1 and G2); 50-microm particle aluminum oxide sandblasting for 5 s (G3); sandblasting followed by etching for 2 or 4 min (G4 and G5) and control--no treatment (G6). A silane agent was applied to the treated surface of both discs of each pair. Bistite II DC dual-cure resin cement was applied and the B discs were bonded to their respective A discs. Specimens were stored in distilled water at 37 degrees C for 24 h and were tested in shear strength at a crosshead speed of 2 mm/min. Means in MPa were: G1: 14.21 +/- 4.68; G2: 8.92 +/- 3.02; G3: 10.04 +/- 2.37; G4: 12.74 +/- 5.15; G5: 10.99 +/- 3.35; G6: 6.09 +/- 1.84. Data were compared by one-way ANOVA and Tukey's test at 5% significance level. Bond strength recorded after 2-min acid etching was significantly higher than 4-min etching (p<0.05) and control (p<0.05), but did not differ significantly from sandblasting alone (p>0.05) or followed by etching for 2 or 4 min (p>0.05). Within the limitations of an in vitro study, it may be concluded that 2-min hydrofluoric acid etching produced a favorable micromechanical retention that enhanced resin cement bond strength to porcelain.     

Effects of ceramic surface treatments on the bond strength of an adhesive luting agent to CAD-CAM ceramic

OBJECTIVES: The objective of this study was to evaluate the effect of different surface treatments on the micro-tensile bond strength (microTBS) of an adhesive luting agent to CAD-CAM ceramic. The hypothesis tested was that neither of the surface treatments would produce higher bond strength of the adhesive luting agent to CAD-CAM ceramic. METHODS: Ceramic specimens of two different sizes (6 mm x 8 mm x 3 mm; 13 mm x 8 mm x 4 mm) were fabricated from ProCAD ceramic blocs (Ivoclar-Vivadent) with a low-speed diamond saw. The ceramic blocks were divided into seven groups and submitted to the following surface treatments: group 1: no treatment; group 2: etching with 37% H(3)PO(4); group 3: etching with 37% H(3)PO(4)+silane; group 4: etching with 37% H(3)PO(4)+silane+adhesive resin; group 5: etching with 4.9% HF acid; group 6: etching with 4.9% HF acid+silane; group 7: etching with HF acid+silane+adhesive resin. After surface treatment, two differently sized porcelain disks were bonded together with a composite luting agent (Variolink II, Ivoclar-Vivadent). The specimens were stored for 24h in distilled water at 37 degrees C prior to microTBS testing. One-way analysis of variance was used to test the influence of surface treatment and Scheffe multiple comparisons test determined pair-wise statistical differences (p<0.05) in microTBS between the experimental groups. RESULTS: The mean microTBSs (standard deviation) are: group 1: 12.8 (+/-4.6)MPa; group 2: 19.1 (+/-5.0)MPa; group 3: 27.4 (+/-11.1)MPa; group 4: 34.0 (+/-8.9)MPa; group 5: 37.6 (+/-8.4) MPa; group 6: 34.6 (+/-12.8)MPa; group 7: 34.5 (+/-5.1)MPa. Statistical significant differences were found between group 1 and groups 3-7, and between group 2 and groups 4-7. All specimens of groups 1-4 exhibited adhesive failures, while a combination of adhesive and mixed (adhesive and cohesive) failures was observed in the specimens of groups 5-7. CONCLUSIONS: The results show that surface treatment is important to bond to ceramic and suggests that etching is needed preferably with hydrofluoric acid than with phosphoric acid.     

Effect of etching time and light source on the bond strength of metallic brackets to ceramic

This study evaluated the bond strength of brackets to ceramic testing different etching times and light sources for photo-activation of the bonding agent. Cylinders of feldspathic ceramic were etched with 10% hydrofluoric acid for 20 or 60 s. After application of silane on the ceramic surface, metallic brackets were bonded to the cylinders using Transbond XT (3M Unitek). The specimens for each etching time were assigned to 4 groups (n=15), according to the light source: XL2500 halogen light, UltraLume 5 LED, AccuCure 3000 argon laser, and Apollo 95E plasma arc. Light-activation was carried out with total exposure times of 40, 40, 20 and 12 s, respectively. Shear strength testing was carried out after 24 h. The adhesive remnant index (ARI) was evaluated under magnification. Data were subjected to two-way ANOVA and Tukey's test (α=0.05). Specimens etched for 20 s presented significantly lower bond strength (p<0.05) compared with those etched for 60 s. No significant differences (p>0.05) were detected among the light sources. The ARI showed a predominance of scores 0 in all groups, with an increase in scores 1, 2 and 3 for the 60 s time. In conclusion, only the etching time had significant influence on the bond strength of brackets to ceramic.