Interaction of different concentrations of 10-MDP and GPDM on the zirconia bonding.

OBJECTIVES: To analyze the influence of different concentrations of 10-MDP and GPDM used, combined or not, on the bonding to zirconia. METHODS: Specimens of zirconia and a resin-composite (7 mm length, 1 mm width, and 1 mm thick) were obtained. The experimental groups were obtained according to the functional monomer (10-MDP and GPDM) and the concentrations (3 %, 5 %, and 8 %). For the groups with combined 10-MDP and GPDM, the agents were used with a proportion of 50 %/50 % wt until reaching the 3 %, 5 % and 8 % concentrations. All monomers were diluted in ethanol to obtain the primers. Two control groups were established: ethanol (negative control) and a commercial reference Monobond N (positive control). The zirconia surface treatment was performed with the primer application followed by the bonding to a resin-composite sample with a light-curing resin cement. Twenty-four hours after the adhesive procedure, a microtensile test was performed and the failure pattern of each sample was analysed with a stereoscopic magnifying glass. Data were analysed by a two-way ANOVA and Dunnet test. RESULTS: All experimental primers presented a higher bond strength than the negative control (ethanol). Excepting the 8 % GPDM primer, all groups presented statistically similar bond strength compared to the positive control, with a predominance of adhesive failure. SIGNIFICANCE: 10-MDP, GPDM, and the combination of both for the concentrations tested promote an effective chemical bonding to zirconia. However, using 10-MDP and GPDM in the same primer has no synergistic effect.

Physicochemical properties of dental resins formulated with amine-free photoinitiation systems.

OBJECTIVE: To assess the mechanical properties of two different dimethacrylate resin blends containing the photosensitizer camphorquinone (CQ) alone or in combination with one or more synergists including an amine and/or an iodonium. METHODS: Two co-monomer resin blends were formulated using Bis-GMA/TEGDMA and UDMA/TEGDMA, both at 1:1 mass ratio. Each resin blend was divided into four groups, comprising the following four photoinitiation systems: (1) CQ + 2-(dimethylamino)ethyl methacrylate (DMAEMA); (2) CQ + DMAEMA + bis(4-methyl phenyl)iodonium hexafluorophosphate (BPI); (3) CQ; and (4) CQ + BPI. Materials were evaluated for polymerisation kinetics, water sorption, solubility, flexural strength and modulus. RESULTS: BisGMA/TEGDMA with CQ showed minimal and insignificant degree of conversion and was not tested for water sorption/solubility and mechanical properties. The ternary system (i.e., CQ + DMAEMA + BPI), promoted the highest degree of conversion for each monomer blend. The resins containing amine had higher mechanical properties than the amine free. However, the UDMA amine free resins exhibited greater flexural strength and modulus than the corresponding amine free BisGMA resins. BisGMA/TEGDMA containing CQ + DMAEMA or CQ + BPI had significantly higher water sorption and solubility than the other groups. SIGNIFICANCE: Resins containing amine presented better properties than the amine-free systems. The addition of iodonium salt (BPI) improved the degree of conversion of the resins, even without an amine co-initiator. The amine-free initiator system (CQ + BPI) was more effective when used with UDMA versus BisGMA based-resins respectively.

Effectiveness of XP-Endo Finisher in the reduction of bacterial load in oval-shaped root canals.

This study investigated the effectiveness of XP-Endo Finisher (XPF) associated with XP-Endo Shaper (XPS) or Reciproc Blue (RB) files in reducing bacterial load in oval-shaped root canals (RC) during chemomechanical preparation (CMP) using 0.9% saline solution (NaCl) or 2.5% sodium hypochlorite (NaOCl). Eighty mandibular incisors with single oval-shaped RC were contaminated with Enterococcus faecalis. The teeth were randomly assigned to eight experimental groups (n = 10) according to the CMP, as follows: G1: XPS, G2: XPS + XPF, G3: RB, and G4: RB + XPF. CMP was performed with NaCl or NaOCl. The reduction of bacterial load was assessed by colony-forming unit count before (S1) and after (S2) CMP. Data normality was verified by using Shapiro-Wilk test. ANOVA, Tukey's test, and Bonferroni post-hoc test were used at a 5% significance level. Culturable bacteria were present in all S1 samples (p>0.05). All instrumentation techniques were effective in reducing bacterial load, irrespective of the irrigating solution (p < 0.05). With the use of NaCl, RB was more effective than XPS (p = 0.035). With the use of NaOCl, XPS and RB presented similar effectiveness (p = 0.779). XPF enhanced the bacterial reduction of both systems tested (p < 0.05). The use of NaOCl improved the CMP, irrespective of the instrumentation technique used (p < 0.05). In conclusion, XPS and RB files are effective in reducing bacterial levels in oval-shaped RC. The use of XPF as a method of agitation of the irrigating solution improved the cleaning efficiency of both file systems tested. Mechanical preparation performed with saline solution decreased culturable bacteria from the root canal, but antimicrobial substances such as NaOCl should be used to achieve a significantly better disinfection.

Effectiveness of XP-Endo Finisher in the reduction of bacterial load in oval-shaped root canals

Abstract: This study investigated the effectiveness of XP-Endo Finisher (XPF) associated with XP-Endo Shaper (XPS) or Reciproc Blue (RB) files in reducing bacterial load in oval-shaped root canals (RC) during chemomechanical preparation (CMP) using 0.9% saline solution (NaCl) or 2.5% sodium hypochlorite (NaOCl). Eighty mandibular incisors with single oval-shaped RC were contaminated with Enterococcus faecalis. The teeth were randomly assigned to eight experimental groups (n = 10) according to the CMP, as follows: G1: XPS, G2: XPS + XPF, G3: RB, and G4: RB + XPF. CMP was performed with NaCl or NaOCl. The reduction of bacterial load was assessed by colony-forming unit count before (S1) and after (S2) CMP. Data normality was verified by using Shapiro-Wilk test. ANOVA, Tukey's test, and Bonferroni post-hoc test were used at a 5% significance level. Culturable bacteria were present in all S1 samples (p>0.05). All instrumentation techniques were effective in reducing bacterial load, irrespective of the irrigating solution (p < 0.05). With the use of NaCl, RB was more effective than XPS (p = 0.035). With the use of NaOCl, XPS and RB presented similar effectiveness (p = 0.779). XPF enhanced the bacterial reduction of both systems tested (p < 0.05). The use of NaOCl improved the CMP, irrespective of the instrumentation technique used (p < 0.05). In conclusion, XPS and RB files are effective in reducing bacterial levels in oval-shaped RC. The use of XPF as a method of agitation of the irrigating solution improved the cleaning efficiency of both file systems tested. Mechanical preparation performed with saline solution decreased culturable bacteria from the root canal, but antimicrobial substances such as NaOCl should be used to achieve a significantly better disinfection.

Resveratrol Reverts Epigenetic and Transcription Changes Caused by Smoke Inhalation on Bone-Related Genes in Rats.

We investigated the effects of cigarette smoke (CS) and resveratrol intake on the modulation of bone repair-related genes through epigenetic mechanisms at the global and gene-specific levels, after 30 days of calvarial defects were created, in rats. The samples were assigned to three groups as follows: no CS, CS, and CS/resveratrol. After evaluation of global (5 hmC) changes and epigenetic and transcription regulation at gene-specific levels, CS group showed increased 5 hmC and Tets transcripts with demethylation at Rankl and Trap promoters (p ≤ 0.01), linked to their increased gene expression (p ≤ 0.001). These modifications were reverted in the CS/resveratrol group. Opposite patterns were observed among CS and CS/resveratrol for epigenetic enzyme transcripts with higher levels of Dnmts in the CS/resveratrol (p ≤ 0.01). No CS and CS/resveratrol demonstrated similar gene expression levels for all Tets and bone-related genes. Resveratrol reverts epigenetic and transcription changes caused by CS at both global and gene-specific levels in bone-related and epigenetic machinery genes, emphasizing the resveratrol as biological modulator for CS in rats.

Effect of Fiber Post Cementation Timing on the Bond Strength of Resin Cements in Epoxy Resin-Obturated Canals.

This study evaluated the influence of timing after endodontic treatment and type of resin cement used on the bond strength of fiber posts to epoxy resin-obturated canals. A total of 80 bovine incisor roots were divided into four groups (n = 20). Glass fiber posts were cemented at two different times, immediately or 7 days after endodontic treatment, using either a dual-curing resin cement (RelyX ARC, 3M ESPE) or a self-adhesive resin cement (RelyX U200, 3M ESPE). Following post cementation, the samples were cross-sectioned into slices containing root dentin, cement, and fiber post at the cervical, mid, and apical root thirds. The push-out test was performed on a universal testing machine. Three-way analysis of variance for randomized blocks showed no significant effect within the triple interaction (P = .394) or between the double interactions cement-timing (P = .395), cement-root thirds (P = .996), and timing-root thirds (P = .331). The main factor cement revealed a significant effect, showing that regardless of the timing and root third, RelyX ARC provided significantly higher bond strength values than U200. Regardless of root third and timing, the dual-curing resin cement showed higher bond strength to root dentin when the canals were filled with epoxy resin-based cement.

Effect of rotatory instrument speed on its capacity to remove demineralized and sound dentin.

OBJECTIVES: The aim of this study was to evaluate the capacity of two rotatory instruments (controlled speed electric motor [CSEM] - 300 rpm; conventional slow handpiece [CSHP] - 18,000 rpm) to remove sound and demineralized dentin, by examining prepared cavity walls using the scanning electron microscopy (SEM) and assessing loss of mass. MATERIALS AND METHODS: A total of 40 blocks of human occlusal dentin, measuring 5 mm × 5 mm × 4 mm (L × W × H), were divided into two groups according to the substrate type in which the cavity preparation was performed: D - demineralized dentin; and S - sound dentin (control group). The groups were subdivided according to the rotatory instrument used for cavity preparation (n = 10): CSEM (300 rpm); and CSHP (18,000 rpm). In half of the dentin blocks, caries lesion induction was performed for 6 weeks. The preparation of the cavities was performed on a standardizing machine, using a cylindrical tungsten carbide burr. Before and after the preparation, specimens were dehydrated in an incubator at 60°C for 30 min. The initial and final mass (in mg) of each dentin block was measured 3 times using the digital precision balance to obtain the mean weight Following cavity preparation, all specimens were hemisected and SEM was used to blindly assess each half so that the lateral walls of the prepared cavity were measured in µm, accepting the average of two measurements as the total depth of the preparation. Non-parametric Mann-Whitney analysis was performed with a 5% of significance level. RESULTS: Regarding the weight difference (mg), no significance was detected between the groups. Regarding depth (µm), a significant difference was found between the groups, so that the CSRM showed lower cavity depth when compared with CSHP, both in sound and demineralized dentin. CONCLUSIONS: Controlled speed rotatory instruments were found to be more conservative in removing both sound and demineralized dentin, in terms of preparation and depth.