Effect of pH variations in a cycling model on the properties of restorative materials

This study evaluated the effect of cycling various pH demineralizing solutions on the surface hardness, fluoride release and surface properties of restorative materials (Ketac-Fil Plus, Vitremer, Fuji II LC, Freedom and Fluorofil). Thirty specimens of each material were made and the surface hardness measured. The specimens were randomized into five groups according to the pH (4.3; 4.6; 5.0; 5.5 and 6.2) of the demineralizing solution. The specimens were submitted to pH-cycling for 15 days. The specimens remained in the demineralizing solution for six hours and in the remineralizing solution for 18 hours. Then, the surface hardness (SH) was remeasured and the surface properties were assessed. Fluoride release was determined daily. Data from SH and the percentage of alteration in surface hardness were analyzed by analysis of variance (p < 0.05); the Kruskal-Wallis test was performed for the fluoride release results. When hardness was compared, the variation in pH led to a positive correlation for glass ionomer cements and a negative correlation for fluoride release. For polyacid-modified resin composites, a negative correlation was found with regards to fluoride release; no significant correlation was observed for hardness. Surface properties were influenced: an acidic pH led to a greater alteration, except for polyacid-modified resin composites. The pH of the demineralizing solution influenced fluoride release from the tested materials. The pH variation altered hardness and surface properties of glass ionomer cements but did not influence polyacid-modified resin composites.

COLOR STABILITY of SEALED COMPOSITE RESIN RESTORATIVE MATERIALS AFTER ULTRAVIOLET ARTIFICIAL AGING and IMMERSION IN STAINING SOLUTIONS

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Surface Roughness Analysis of Four Restorative Materials Exposed to 10% and 15% Carbamide Peroxide

The aim of this study was to evaluate the effects of carbamide peroxide (CP) on surfaces of different restorative materials. Porcelain, composite resin, glass ionomer, and amalgam were analyzed in this study. Surface roughness (Ra) was measured before and after treatment with 10% and 15% CP. Fifteen percent CP increased Ra values in both the glass ionomer and amalgam subgroups, while 10% CP increased Ra values in the glass ionomer subgroup only. Changes in restorative material surfaces can be more severe when bleaching is completed without a clinician's supervision. Hence, thorough patient examinations must be done before, during, and after bleaching treatment. Int J Prosthodont 2011;24:155-157

In Vitro Evaluation of Surface Roughness and Microhardness of Restorative Materials Submitted to Erosive Challenges

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Fluoride release/recharge from restorative materials: effect of fluoride gels and time

This study examined the differences in fluoride release and recharge among four restorative materials following treatment with APF or neutral fluoride gel for one or four minutes. Specimens were immersed in 2 mL of deionized water, while fluoride release was measured at 24-hour intervals for 15 days using an ion-selective electrode and analyzer. The materials were then treated with the fluoride gels. The fluoride release was measured for 15 days. ANOVA (p<0.05) showed higher fluoride release for Ketac-Fil before fluoride application and for Vitremer and Fuji 11 LC after application of APF gel. APF gel yielded higher fluoride release when compared to neutral gel, regardless of the material. Fluoride recharge and release was greater after the four-minute APF gel application, with no difference between the times of application for the neutral gel (p>0.05), except for Ketac-Fil. The pattern of release before and after application of the gels was similar and was higher at day 16 compared to day one for the APF gel for resin materials, with higher release at day 15 compared to the initial for Fuji 11 LC and Vitremer. Et was concluded that RM-GICs were the most effective materials with regards to fluoride release after application of APF gel for four minutes.

Effect of prolonged erosive pH cycling on different restorative materials

This in vitro study evaluated the effect of a prolonged erosive pH cycling on the superficial microhardness change (SMHC) and the erosive wear of different restorative materials. Eighty enamel specimens with prepared cavities of 1.5 x 1.5 mm were randomly divided into eight groups according to the restorative materials used for the fillings (RMGI - resin-modified glass-ionomer, CGI - conventional glass-ionomer, CR- composite resin, A - amalgam) and immersion media used (ERO - erosive medium or SAL - artificial saliva). During 35 days, half of the specimens were immersed in a cola drink (ERO), for 5 min, three times a day, and they remained in SAL between the erosive cycles. The other half of the specimens was immersed in SAL only, for the entire experimental period (control). Data were tested for significant differences by anova and Tukey's tests (P < 0.05). Scanning electron microscopy images were made to illustrate the enamel erosive wear and restorative materials alterations. The mean SMHC (%) and mean erosive wear (mu m) of the materials were: RMGI-ERO (30/0.5); CGI-ERO (37/0.5); CR-ERO (-0.3/0.3); A-ERO (-4/0.3); RMGI-SAL (4/0.4); CGI-SAL (-6/0.4); CR-SAL (-3/0.2) and A-SAL (2/0.4). Scanning electron microscopy images showed pronounced enamel erosive wear on groups submitted to erosive pH cycling when compared with groups maintained in saliva. In conclusion, the prolonged pH cycling promoted significantly higher alterations (SMHC and erosive wear) on the glass-ionomer cements than the CR and amalgam.

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 (R), 150 mL) for 5 min, three times a day. The study variables comprised the wear (profilometry, mu m) 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. (c) 2007 Elsevier Ltd. All rights reserved.

Effect of erosive pH cycling on different restorative materials and on enamel restored with these materials

This in vitro study evaluated the effect of erosive pH cycling on the percentage of surface micro-hardness change (%SMHC) and wear of different restorative materials and bovine enamel restored with these materials. Eighty enamel specimens were randomly divided into eight groups according to the restorative materials and immersion media used: GI/GV-resin-modifled glass-ionomer, GII/GVI-conventional glass-ionomer, GIII/GVII-resin composite and GIV/GVIII-amalgam. Over a period of seven days, groups GI to GIV were immersed in a cola drink (ERO) for 5 minutes, 3x/day and kept in artificial saliva between erosive cycles. Groups GV to GVIII were immersed in artificial saliva (SAL) throughout the entire experimental period (control). Data were tested for significant differences using ANOVA and Tukey's tests (p < 0.05). For %SMHC, considering the restorative materials, no significant differences were detected among the materials and immersion media. Mean wear was higher for the resin modified glass ionomer cement when compared to conventional cement, but those materials did not significantly differ from the others. For enamel analyses, erosive pH cycling promoted higher wear and %SMHC compared to saliva. There were no significant differences in wear and %SMHC of enamel around the different restorative materials, regardless of the distance from the restorative material (50, 150 or 300 mu m). In conclusion, there were only subtle differences among the materials, and these differences were not able to protect the surrounding enamel from erosion.

Ability of different restorative materials to prevent in situ secondary caries: analysis by polarized light-microscopy and energy-dispersive X-ray

Secondary caries is the main cause of direct restoration replacement. The purpose of this study was to analyze enamel adjacent to different restorative materials after in situ cariogenic challenge using polarized-light microscopy (PLM), scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDS). Twelve volunteers, with a low level of dental plaque, a low level of mutans streptococci, and normal salivary flow, wore removable palatal acrylic appliances containing enamel specimens restored with Z250 composite, Freedom composite, Fuji IX glass-ionomer cement, or Vitremer resin-modified glass-ionomer for 14 days. Volunteers dripped one drop of 20% sucrose solution (n = 10) or distilled water (control group) onto each specimen 8 times per day. Specimens were removed from the appliances and submitted to PLM for examination of the lesion area (in mm(2)), followed by dehydration, gold-sputtering, and submission to SEM and EDS. The calcium (Ca) and phosphorus (P) contents were evaluated in weight per cent (%wt). Differences were found between Z250 and Vitremer, and between Z250 and FujiIX, when analyzed using PLM. Energy-dispersive X-ray analysis results showed differences between the studied materials regarding Ca %wt. In conclusion, enamel adjacent to glass-ionomer cement presented a higher Ca %wt, but this material did not completely prevent enamel secondary caries under in situ cariogenic challenge.