Disinfection procedures: their effect on the dimensional accuracy and surface quality of irreversible hydrocolloid impression materials and gypsum casts.

OBJECTIVES: This study primarily investigated the effect of disinfection procedures (Perform and sodium hypochlorite) on the dimensional accuracy and surface quality of four irreversible hydrocolloid impression materials and the resultant gypsum casts. The antibacterial efficacy of the procedures was also studied. METHODS: Dimensional accuracy was determined from the mean percentage deviation of six measurements taken from casts made from disinfected impressions compared with corresponding measurements from the master model and controls. Statistical analysis of data was determined by analysis of variance. Surface quality was determined using a stainless steel test block in accordance with ISO 1563. RESULTS: The dimensional accuracy of the impression materials tested were of a comparable standard following disinfection. The surface quality of casts taken from Blueprint Cremix impressions were unaffected by the disinfection procedures. The remaining impression materials studied showed greater surface deterioration on casts following disinfection with sodium hypochlorite than immersion in Perform. All disinfection procedures selected proved appropriate for antibacterial purposes. SIGNIFICANCE: Individual analysis of impression materials is required to determine their suitability to a given disinfection protocol.     

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目的评估藻酸盐印模浸泡消毒对所灌注超硬石膏模型尺寸精度和表面质量的影响。方法2006年2月至5月于南昌大学附属口腔医院修复科选用2种藻酸盐印模材料(Jeltrate和Heraplast NF)制取原始模型和不锈钢模具的印模,分别用2戊二醛、2.5三氯异氰尿酸、碘伏消毒液对以上2种藻酸盐印模材料浸泡消毒30min,灌注超硬石膏模型。测量原始模型及其所翻制的超硬石膏模型尺寸,计算其偏离原始模型的百分数;测量超硬石膏块表面粗糙度Ra值;用SPSS11.5统计软件进行方差分析和q检验(SNK法)。结果超硬石膏模型的长度和宽度变化率都不超过0.1,绝对数值均小于60μm;在所有样本中仅2.5三氯异氰尿酸浸泡消毒处理组表现为膨胀,其余各组均为收缩。2戊二醛浸泡消毒处理组与未消毒处理组的超硬石膏块的表面光滑程度接近,差别无统计意义;2.5三氯异氰尿酸处理组的表面光洁度最差,粗糙度Ra值最大。结论用2戊二醛、2.5三氯异氰尿酸、碘伏消毒液分别对2种藻酸盐印模(Jeltrate,HeraplastNF)浸泡30min,对模型的尺寸稳定性不会造成影响;藻酸盐印模材料的品牌不同和所用的消毒液的不同对超硬石膏块的表面粗糙度的影响不同,Jeltrate印模材料用2戊二醛或碘伏浸泡消毒均能获得很好的表面光洁度;2.5三氯异氰尿酸浸泡消毒对2种藻酸盐印模材料均会导致表面质量的降低。     

In situ effect of an erosive challenge on different restorative materials and on enamel adjacent to these materials

OBJECTIVES: This in situ study evaluated the effect of an erosive challenge on different restorative materials and on enamel restored with these materials, as well as the ability of these materials to protect the adjacent enamel against erosion. METHODS: Ten volunteers wore palatal devices with eight bovine enamel blocks, randomly selected and distributed into two vertical rows, corresponding to the following groups: GI/GV, resin-modified glass ionomer; GII/GVI, conventional glass ionomer; GIII/GVII, composite resin; GIV/GVIII, amalgam. One row (corresponding to groups I-IV) was immersed in a cola drink and the other row (corresponding to groups V-VIII) was subjected to saliva only. The palatal device was continuously worn for 7 days and only half of the appliance (groups I-IV) was immersed in the soft drink (Coca-Cola), 150 mL) for 5 min, three times a day. The study variables comprised the wear (profilometry, microm) and the percentage of surface microhardness change (%SMHC). Data were tested for significant differences by two-way ANOVA and Tukey's tests (p<0.05). RESULTS: Considering the restorative materials, for %SMHC and wear, there were no differences among the materials and between the saliva and the erosive challenge. For enamel analyses, the erosive challenge promoted a higher wear and %SMHC of the enamel than did the saliva. There were no significant differences in wear and %SMHC of the enamel adjacent to the different restorative materials. CONCLUSION: This research data suggest that there is little %SMHC and wear of the studied restorative materials and none of them had a preventive effect against erosion on adjacent enamel, which showed a pronounced wear.     

Effects of intracanal mineral trioxide aggregate and calcium hydroxide during four weeks on pH changes in simulated root surface resorption defects: an in vitro study using matched pairs of human teeth

Introduction

Diffusion of hydroxyl ions from intracanal calcium hydroxide (CH) through dentin is used to arrest external inflammatory root resorption. However, long-term and short-term CH placement has been associated with an increased risk of root fracture. Intracanal mineral trioxide aggregate (MTA) might provide an alternative to CH as a source of hydroxyl ions. This in vitro study compared the effects of intracanal MTA and CH on hydroxyl ion diffusion through dentin by measuring pH changes over time in simulated root surface resorption defects prepared in matched pairs of teeth; the null hypothesis tested was that there is no difference.

Methods

Root surface cavities were prepared 5 mm from the apex in extracted human permanent anterior teeth (21 matched pairs) and 7 additional teeth (controls). Root canals were instrumented to size 50/.04 and filled with either tooth-colored MTA (ProRoot) or CH (UltraCal XS); control teeth were filled with saline. The pH in root surface cavities was measured at 3 hours, 24 hours, 1 week, 2 weeks, 3 weeks, and 4 weeks.

Results

In controls, pH readings did not differ significantly during the 4 weeks (P > .05, repeated-measures analysis of variance [ANOVA]). For the experimental intragroup effects, significant pH changes occurred over time in the MTA group (P = .005, repeated-measures ANOVA) and the CH group (P < .0001). For the experimental intergroup effects, the overall mean pH was higher in the MTA group (8.66; standard error [SE], 0.07) compared with the CH group (8.46; SE, 0.07) (P = .014, paired t test). At 4 weeks pH was higher in the MTA group (8.30; SE, 0.16) compared with the CH group (7.90; SE, 0.11) (P = .011); at all other time points intergroup differences were insignificant. The null hypothesis was rejected.

Conclusions

Intracanal MTA and CH groups differed in their overall effect on pH measured in simulated root surface resorption defects. At 4 weeks intracanal placement of MTA compared with CH resulted in a small but significantly higher pH.