Attachment and proliferation of dental pulp stem cells on dentine treated with different regenerative endodontic protocols.

AIM: To investigate the attachment and proliferation of dental pulp stem cells (DPSC) on dentine treated with various endodontic regeneration protocols. METHODOLOGY: Standardized dentine samples were irrigated with sodium hypochlorite (1.5% NaOCl) and ethylenediaminetetraacetic acid (17% EDTA) and randomized into four treatment groups and two control groups. The treatment groups were treated with a clinically used concentration of triple antibiotic paste (TAP), double antibiotic paste (DAP), calcium hydroxide (Ca(OH)2 ) or diluted TAP in a methylcellulose system (DTAP) for 1 week. Each sample in the treatment groups was then irrigated with EDTA. The two control groups were treated with EDTA or received no treatment. Dental pulp stem cells were seeded on each dentine specimen (10 000 cells). Lactate dehydrogenase activity assays were then performed to evaluate the attached DPSC after 1 day of incubation. Water-soluble tetrazolium assays were used to determine DPSC proliferation after three additional days of incubation. Friedman's test followed by least significant difference were used for statistical analyses (α = 0.05). RESULTS: Triple antibiotic paste and DTAP regeneration protocols, as well as EDTA-treated dentine, caused significant increases in DPSC attachment to dentine. Triple antibiotic paste, DAP and Ca(OH)2 regeneration protocols caused significant reductions in DPSC proliferation on dentine. However, the DTAP regeneration protocol did not have any significant negative effects on DPSC proliferation. CONCLUSIONS: The clinically used endodontic regeneration protocols that include the use of TAP, DAP or Ca(OH)2 medicament negatively affected DPSC proliferation on dentine. However, the use of DTAP medicament during regenerative endodontic treatment may not adversely affect the proliferation of DPSC.

Doxycycline-encapsulated nanotube-modified dentin adhesives.

This article presents details of fabrication, biological activity (i.e., anti-matrix metalloproteinase [anti-MMP] inhibition), cytocompatibility, and bonding characteristics to dentin of a unique doxycycline (DOX)-encapsulated halloysite nanotube (HNT)-modified adhesive. We tested the hypothesis that the release of DOX from the DOX-encapsulated nanotube-modified adhesive can effectively inhibit MMP activity. We incorporated nanotubes, encapsulated or not with DOX, into the adhesive resin of a commercially available bonding system (Scotchbond Multi-Purpose [SBMP]). The following groups were tested: unmodified SBMP (control), SBMP with nanotubes (HNT), and DOX-encapsulated nanotube-modified adhesive (HNT+DOX). Changes in degree of conversion (DC) and microtensile bond strength were evaluated. Cytotoxicity was examined on human dental pulp stem cells (hDPSCs). To prove the successful encapsulation of DOX within the adhesives-but, more important, to support the hypothesis that the HNT+DOX adhesive would release DOX at subantimicrobial levels-we tested the antimicrobial activity of synthesized adhesives and the DOX-containing eluates against Streptococcus mutans through agar diffusion assays. Anti-MMP properties were assessed via ß-casein cleavage assays. Increasing curing times (10, 20, 40 sec) led to increased DC values. There were no statistically significant differences (p > .05) in DC within each increasing curing time between the modified adhesives compared to SBMP. No statistically significant differences in microtensile bond strength were noted. None of the adhesives eluates were cytotoxic to the human dental pulp stem cells. A significant growth inhibition of S. mutans by direct contact illustrates successful encapsulation of DOX into the experimental adhesive. More important, DOX-containing eluates promoted inhibition of MMP-1 activity when compared to the control. Collectively, our findings provide a solid background for further testing of encapsulated MMP inhibitors into the synthesis of therapeutic adhesives that may enhance the longevity of hybrid layers and the overall clinical performance of adhesively bonded resin composite restorations.

Effect of surface treatments on microtensile bond strength of repaired aged silorane resin composite.

OBJECTIVE: This laboratory study compared the repaired microtensile bond strengths of aged silorane resin composite using different surface treatments and either silorane or methacrylate resin composite. METHODS: One hundred eight silorane resin composite blocks (Filtek LS) were fabricated and aged by thermocycling between 8°C and 48°C (5000 cycles). A control (solid resin composite) and four surface treatment groups (no treatment, acid treatment, aluminum oxide sandblasting, and diamond bur abrasion) were tested (N=12 blocks, 108 beams/group). Each treatment group was randomly divided in half and repaired with either silorane resin composite (LS adhesive) or methacrylate resin composite (Filtek Z250/Single Bond Plus). After 24 hours in 37°C distilled water, microtensile bond strength testing was performed using a non-trimming technique. Surface topography after surface treatment was analyzed using scanning electron microscopy (SEM). Failure mode was examined using optical microscopy (50×). RESULTS: Weibull-distribution survival analysis revealed that aluminum oxide sandblasting followed by silorane or methacrylate resin composite and acid treatment with methacrylate resin composite provided insignificant differences from the control (p>0.05). All other groups were significantly lower than the control. Failure was primarily adhesive in all groups. CONCLUSION: Aluminum oxide sandblasting produced microtensile bond strength not different from the cohesive strength of silorane resin composite. After aluminum oxide sandblasting, aged silorane resin composite can be repaired with either silorane resin composite with LS system adhesive or methacrylate resin composite with methacrylate dental adhesive.