Esterase like activity of Enterococcus faecalis and Lactobacillus casei on microhardness and weight loss of resin luting cements.

INTRODUCTION: Gap-free/continuous cement margins have been considered important for the longevity of indirect dental restorations. Bacterial species have demonstrated esterase-like activity that can cause biodegradation of resin composites. AIM: The aim of this study was to evaluate the effect of the esterase-like activity of E. faecalis and L. casei on three resin luting cements. SETTINGS AND DESIGN: In-vitro study materials and three resin luting cements tested were: Variolink N, Rely X U200 and Panavia F2.0. E. faecalis and L. casei suspensions and supernatants were assessed for enzymatic activity by bacterial esterase activity assay. Circular samples of resin luting cements were exposed to suspensions of E. faecalis and L. casei for 7 and 28 days followed by testing for solubility, microhardness and bishydroxy propoxy phenyl propane (BisHPPP) release. RESULTS: E. faecalis and L. casei both demonstrated esterase-like activity. Bacterial suspensions had significantly increased enzymatic activity than supernatant solutions (P < 0.05). There was no significant reduction in microhardness or increased weight loss in all three cements after incubation in E. faecalis and L. casei for 7 and 28 days. BisHPPP release signifying resin degradation was seen after 7 and 28 days of incubation in E. faecalis and L. casei. CONCLUSION: Within the limitations of this in vitro study, E. faecalis and L. casei demonstrated esterase-like activity. BisHPPP release was evident in all three cements after 7 and 28 days. However, the bacterial strains did not significantly reduce the microhardness or cause weight loss of the tested resin luting cements (Variolink N, Panavia F2.0 and Rely X U200) after 7 and 28 days of incubation.

Remineralization ability of sodium fluoride on the microhardness of enamel, dentin, and dentinoenamel junction: An in vitro study.

AIM: Dental tissues such as enamel, dentinoenamel junction (DEJ), dentin, and root dentin can react differently to demineralization and remineralization. The aim of this study was to evaluate the remineralization ability of sodium fluoride on the microhardness of enamel, dentin, and dentinoenamel junction. MATERIALS AND METHODS: Ten extracted third molar teeth were sectioned mesiodistally to form control and test groups. For the test group, initial demineralization was done with acetic acid for 24 h followed by remineralization for 28 days by application of sodium fluoride (226 ppm) for 2 min twice a day. Vickers microhardness test was done to control and test groups at different sites after initial demineralization and on the 3rd, 5th, 7th, 14th, and 28th day of remineralization. STATISTICAL ANALYSIS USED: Data were analyzed with one-way analysis of variance and post hoc test with a significance level of P < 0.001 with SPSS (21) software. RESULTS: Microhardness values in the demineralization group were significantly lower than controls (P < 0.001). Evaluation of remineralization samples showed that microhardness similar to control values were achieved at the 3rd day in root predentin and on the 5th day in coronal dentin and coronal predentin. On the 7th day, remineralization coronal predentin was significantly higher than the control (P < 0.001). On the 14th day, DEJ axial zone and root dentin were similar to control and coronal dentin was significantly higher than the control (P < 0.001). Enamel was similar to control on the 28th day. Microhardness of DEJ-cusp tip and DEJ-center of the fissure was significantly lower than control even at the 28th day (P < 0.001). CONCLUSION: Long-term repeated application of sodium fluoride (226 ppm) can improve the microhardness of demineralized dental tissues on enamel, dentin, and DEJ-axial zone, except in the DEJ-cusp tip and DEJ-center of fissure.

Dentinal defects before and after rotary root canal instrumentation with three different obturation techniques and two obturating materials.

AIM: To evaluate the role of rotary root canal instrumentation followed by obturation with three different techniques and two different materials on the incidence of dentinal defects. MATERIALS AND METHODS: One hundred and sixty mandibular premolars were divided into eight groups (n = 20). Group I was left untreated and served as control. The other seven groups were prepared with profile rotary instruments till #40.06 taper. After preparation, group II was left unfilled, groups III, IV, and V were obturated with Gutta-percha and AH Plus sealer using passive technique, lateral compaction and warm vertical compaction, respectively. Groups VI, VII, and VIII were obturated with Resilon and Realseal sealer using passive technique, lateral compaction, and warm vertical compaction, respectively. Roots were then sectioned at 3, 6, and 9 mm from the apex and inspected under a stereomicroscope (50×) for dentinal defects. Chi-square test was performed to compare the incidence of dentinal defects between the groups (P < 0.05). RESULTS: The unprepared control group had no dentinal defects. The instrumentation group (group II) and the obturation group (groups III-VIII) showed significantly more defects than the uninstrumented control group (group I) (P < 0.001). There was no significant difference between the root canal obturating techniques (group III-VIII) when compared with the instrumentation group (group II). On inter group comparison among the obturation groups the number of defects after lateral compaction with Gutta-percha (group IV) was significantly larger than passive Gutta-percha obturation (group III) (P < 0.05). CONCLUSIONS: The results suggest that root canal instrumentation significantly influenced the incidence of dentinal defects or fracture. Dentinal defects were more significantly attributed to the role of root canal instrumentation rather than the type of obturation technique or material. Lateral compaction with Gutta-percha significantly produces more defects than passive Gutta-percha obturation.