Evandro Piva

Bond strength of universal adhesives: A systematic review and meta-analysis.

OBJECTIVES A systematic review was conducted to determine whether the etch-and-rinse or self-etching mode is the best protocol for dentin and enamel adhesion by universal adhesives. DATA This report followed the PRISMA Statement. A total of 10 articles were included in the meta-analysis. SOURCES Two reviewers performed a literature search up to October 2014 in eight databases: PubMed, Web of Science, Scopus, BBO, SciELO, LILACS, IBECS and The Cochrane Library. STUDY SELECTION In vitro studies evaluating the bond strength of universal adhesives to dentin and/or enamel by the etch-and-rinse and self-etch strategies were eligible to be selected. Statistical analyses were conducted using RevMan 5.1 (The Cochrane Collaboration, Copenhagen, Denmark). A global comparison was performed with random-effects models at a significance level of p<0.05. RESULTS The analysis of dentin micro-tensile bond strength showed no statistically significant difference between the etch-and-rinse and self-etch strategies for mild universal adhesives (p≥0.05). However, for the ultra-mild All-Bond Universal adhesive, the etch-and-rinse strategy was significantly different than the self-etch mode in terms of dentin micro-tensile bond strength, as well as in the global analysis of enamel micro-tensile and micro-shear bond strength (p≤0.05). CONCLUSIONS The enamel bond strength of universal adhesives is improved with prior phosphoric acid etching. However, this effect was not evident for dentin with the use of mild universal adhesives with the etch-and-rinse strategy. CLINICAL SIGNIFICANCE Selective enamel etching prior to the application of a mild universal adhesive is an advisable strategy for optimizing bonding.

Impact of immediate and delayed light activation on self-polymerization of dual-cured dental resin luting agents.

This study investigated the impact of immediate and delayed light activation on self-polymerization of a model dual-cured luting agent. The material presented the following components: base paste - 2,2-bis[4-(2-hydroxy-3-methacryloxyprop-1-oxy)phenyl]propane/triethylene glycol dimethacrylate (TEGDMA), camphorquinone, dimethyl-p-toluidine, butylated hydroxytoluene (BHT), glass fillers; catalyst paste - bisphenol-A ethoxylated dimethacrylate/TEGDMA, benzoyl peroxide, BHT, fillers. The pastes were mixed and seven polymerization scenarios tested: immediate light activation using low (5Jcm(-2)) or high (20Jcm(-2)) energy dose; delayed light activation (after 2min - short delay) using low or high dose; delayed light activation (after 10min - long delay) using low or high dose; and self-polymerization only. The degree of conversion (DC) and rate of polymerization (R(p)) were evaluated for 30min by real-time infrared spectroscopy. The lowest DC was detected for the self-polymerized and immediate-low dose groups, whereas the immediate-high dose and short delay-high dose groups showed the highest values. For the self-polymerized and immediate-high dose samples, R(p)(max) was detected after approximately 7s, whereas this took approximately 14s for the immediate-low dose group. R(p)(max) for the immediate-high dose group was higher than for the self-polymerized sample, which in turn was higher than for the immediate-low dose group. R(p)(max) for the short delay groups was higher than for the long delay groups. In conclusion, the extent of self-polymerization was influenced by the light dose reaching the material, which was dependent on high radiant exposure for optimal polymerization and the moment at which the light was applied; the short delay increased the DC for lower doses, while also generally decreasing the R(p) for all scenarios.

A systematic review about antibacterial monomers used in dental adhesive systems: Current status and further prospects.

OBJECTIVES This study systematically review the literature to assess the effectiveness of antibacterial monomers incorporated into dental adhesive systems against major oral bacteria; as well as the research advances and the future prospects of this technology. METHODS The following seven databases were screened: MedLine (PubMed), Lilacs, Ibecs, Web of Science, Scopus, Scielo, and The Cochrane Library. Furthermore, the online system Questel Orbit (Paris, France) was accessed to obtain patent data. The inclusion criteria were articles and patents that investigated the antimicrobial activity of antibacterial monomers in dental adhesive systems. Only documents written in English, Spanish or Portuguese were included. RESULTS After screening, 33 studies and eight patents fulfilled all the criteria and were included. Antibacterial agents, such as QA, MDPB, DMAHM and DMADDM were found in patents, which claimed their incorporation into adhesive compositions, dental cements, composite resins. MDPB was the only antimicrobial monomer incorporated into a commercially available adhesive system, Clearfil Protect Bond™ (Kuraray Co. Ltd., Japan). All studies reported the inclusion of antimicrobial monomers in adhesive systems to be an effective dental treatment strategy. SIGNIFICANCE There are potential areas to be explored with antibacterial monomers for dentistry, and their use could have important implications for future more conservative dental treatments. Although there is evidence of antibacterial activity from in vitro studies, clinical studies must be conducted to confirm the effectiveness of these materials in the prevention of dental pathologies.

Light- and time-dependent polymerization of dual-cured resin luting agent beneath ceramic

Objective. In this study we investigated the degree of conversion (DC) of a dual-cured resin luting agent beneath a ceramic of different thickness. Material and Methods. The luting material (RelyX) was photo-activated for 40s through ceramic disks (Empress Esthetic, 0.7, 1.4, or 2mm thick). Dual (DUC) and chemically cured (CC) control groups were obtained. A delayed exposure (DE) procedure was tested in which the material was light-activated after 5 min without using ceramic. DC (%) was measured using infrared spectroscopy at 40 s, 1, 2, 4, 6, 8, and 10min. Light irradiance and spectrum transmitted through ceramic were measured using a power meter and a spectrometer. Results. A decrease in irradiance was detected with increasing ceramic thickness, but no alteration in the emission profile was observed. At 10min, all groups showed DC higher than at 40s. No significant differences were detected for DUC compared with the groups indirectly activated through the ceramic disks. Generally, CC showed the lowest DC values. No significant effect in DC was detected for DE after 10min. A significant increase in DC was generally detected only up to 4min. Conclusions. The luting agent was dependent on light exposure and time to obtain improved DC. Neither the indirect activation nor the DE procedure significantly influenced the final DC.

Influence of 2-hydroxyethyl methacrylate concentration on polymer network of adhesive resin.

PURPOSE To evaluate the effect of variations in 2-hydroxyethyl methacrylate (HEMA) concentrations in an experimental comonomer blend on degree of conversion, water sorption, solubility, and ultimate tensile strength of adhesive resin. MATERIALS AND METHODS The effect of HEMA content (0, 15, 30, and 50%wt - control, G15, G30, and G50 groups, respectively) was tested in an experimental comonomer blend of bis-GMA, bis-EMA, TEG-DMA, and HEMA. The degree of conversion, polymerization rate, ultimate tensile strength, water sorption, and solubility of the adhesive resin blends were determined. RESULTS At 40 s of light activation time, groups G30 and G50 showed a decrease of 30% and 61%, respectively, in degree of conversion compared to control. Water sorption and solubility differed for all groups, and was statistically higher in G50. For ultimate tensile strength, the control and G15 groups showed statistically higher values than the other groups (p < 0.05). CONCLUSION Higher HEMA content increases dental adhesive resin degradation.

Nanofiller loading level: Influence on selected properties of an adhesive resin.

OBJECTIVES To evaluate the effect of the filler content in the cohesive strength (sigma), Weibull modulus (m) and degree of conversion (DC) of an experimental adhesive system. METHODS A HEMA/Bis-GMA/TEGDMA-based adhesive was formulated and filled with silica nanofillers in the following weight percentages (wt%): R0=0%; R1=1%; R3=3%; R5=5% and R10=10%. The adhesive of Adper Scotchbond Multi-Purpose (SBMP) system was used as a commercial reference. Twenty dumbbell-shaped specimens with cross-sectional area of 0.5mm(2) were made per group and tensile tested with a crosshead speed of 0.5mm/min until fracture. The cohesive strength was calculated in MPa. DC was obtained through FTIR after light curing for 25s. Data were submitted to one-way ANOVA and Tukeys test (alpha=0.05) and to Weibull analysis. RESULTS Mean sigma results were: R0=65.4+/-8.4; R1=73.2+/-8.8; R3=72.0+/-8.4; R5=73.1+/-9.7; R10=85.5+/-13.1 and SBMP=79.0+/-11.0MPa. R10 presented the highest sigma, while R0 showed the lowest. R5 and SBMP did not differ significantly (p<0.05). Weibull analysis revealed no significant difference in structural reliability between groups. The experimental adhesives presented similar results of DC, which, in turn, were significantly higher than the SBMP. CONCLUSIONS The addition of 10% filler in weight improves the cohesive strength of the adhesive, not interfering in the structural reliability or the degree of conversion.

Functionalized Scaffolds to Control Dental Pulp Stem Cell Fate

Emerging understanding about interactions between stem cells, scaffolds, and morphogenic factors has accelerated translational research in the field of dental pulp tissue engineering. Dental pulp stem cells constitute a subpopulation of cells endowed with self-renewal and multipotency. Dental pulp stem cells seeded in biodegradable scaffolds and exposed to dentin-derived morphogenic factors give rise to a pulplike tissue capable of generating new dentin. Notably, dentin-derived proteins are sufficient to induce dental pulp stem cell differentiation into odontoblasts. Ongoing work is focused on developing ways of mobilizing dentin-derived proteins and disinfecting the root canal of necrotic teeth without compromising the morphogenic potential of these signaling molecules. On the other hand, dentin by itself does not appear to be capable of inducing endothelial differentiation of dental pulp stem cells despite the well-known presence of angiogenic factors in dentin. This is particularly relevant in the context of dental pulp tissue engineering in full root canals in which access to blood supply is limited to the apical foramina. To address this challenge, scientists are looking at ways to use the scaffold as a controlled-release device for angiogenic factors. The aim of this article was to present and discuss current strategies to functionalize injectable scaffolds and customize them for dental pulp tissue engineering. The long-term goal of this work is to develop stem cell-based therapies that enable the engineering of functional dental pulps capable of generating new tubular dentin in humans.

Degree of Conversion of Etch-and-Rinse and Self-etch Adhesives Light-cured Using QTH or LED

In the current study, the degree of conversion (DC) of bonding agents photoactivated using QTH or LED light-curing units (LCUs) was evaluated by Fourier Transform infrared spectroscopy with an attenuated total reflectance (ATR) device. Four LCUs were evaluated: one QTH (Optilux 501; Demetron Kerr) and three LEDs: Radii Cal (SDI), Elipar FreeLight 2 (3M ESPE) and Bluephase (Ivoclar Vivadent). Two etch-and-rinse (Scotchbond Multi-Purpose-SBMP and Single Bond 2-SB2) and two self-etch adhesives (Clearfil SE Bond-CSE, and Clearfil S3 Bond-CS3) were tested. For SBMP and CSE, the primer was not used. The irradiance and spectral emission of the LCUs were obtained with a radiometer and spectrometer. The materials were placed onto the ATR cell as thin films, the solvent was evaporated (when necessary) and photoactivation was carried out for 20 seconds. The DC (%) was evaluated after five minutes (n = 5). The data were statistically analyzed (p < 0.05). The irradiance for Optilux, Radii, FreeLight 2 and Bluephase was 760, 600, 1000 and 1100 mW.cm(-2), respectively. The wavelength of emission for Optilux was between 375 and 520 nm (peak at 496 nm), while for Radii, it was between 420 and 520 nm (peak at 467 nm). Freelight 2 presented an emission spectrum between 415 and 520 nm, and for Bluephase, it was between 410 and 530 nm, both having a peak at 454 nm. SB2 generally showed higher DC compared with the other bonding agents. When cured using the QTH unit, the DC results were SB2 = CS3 > CSE > SBMP; for all LEDs, the DC results showed SB2 > CSE > SBMP > CS3. For SB2, the highest DC was observed when the material was cured with Radii, while there were no significant differences among the other LCUs. CSE and CS3 showed higher DC when cured using the QTH unit, but similar results were observed among the LEDs. For SBMP, no significant differences among the LCUs were detected. In conclusion, the combination bonding agent vs curing unit had a significant effect on DC, mainly for the self-etch adhesives.

BAPO as an alternative photoinitiator for the radical polymerization of dental resins

OBJECTIVES This study evaluated the performance of phenylbis (2,4,6-trimethylbenzoyl)-phosphine oxide (BAPO) as an alternative photoinitiator in the polymerization kinetics (PK), flexural strength (σ) and elastic modulus (E) of a model dental resin. METHODS A monomer mixture based on Bis-GMA and TEGDMA was used as model dental resin. Initially a screening was performed to evaluate BAPO concentrations (0.125, 0.25, 0.50, 1, 2, and 4 mol%). Photoinitiator systems were formed with the combination of camphorquinone (CQ), ethyl-dimethylamino benzoate (EDAB), diphenyliodonium hexafluorophosphate (DPIHFP), and BAPO. Groups with unitary photoinitiator systems (BAPO and CQ), binary (BAPO+EDAB, BAPO+DPIHFP and CQ+EDAB), ternary (BAPO+CQ+EDAB, BAPO+CQ+DPIHFP, BAPO+EDAB+DPIHFP and CQ+EDAB+DPIHFP) and quaternary (BAPO+CQ+EDAB+DPIHFP) were formulated for evaluation. Real-time Fourier transform infrared spectroscopy was used to investigate the PK and test mini-bending to evaluate σ and E. RESULTS When only CQ was used, a slow polymerization reaction was observed and a lower monomer conversion. When only BAPO was used as photoinitiator an increase in the polymerization rate was observed and conversion was higher than CQ+EDAB. The ternary system (BAPO+EDAB+DPIHFP) showed the highest polymerization and conversion rate, in short photo-activation time. SIGNIFICANCE BAPO it is a potential photoinitiator for the photopolymerization of dental materials.

The Effect of Polishing Techniques and Time on the Surface Characteristics and Sealing Ability of Resin Composite Restorations After One-year Storage

Since there is a lack of information on the surface properties of composite restorations achieved with standard polishing procedures after aging processes, this study evaluated the effects of immediate (IM) and delayed (DE) polishing on the surface roughness (Ra), microhardness (KHN) and microleakage (ML) of microfilled (Filtek A110) and hybrid (Filtek Z250) resin composites after one-year storage. Standardized preparations were made on the buccal surface of 256 bovine teeth, where half were restored with each composite. For each composite, the specimens were randomly allocated to two subgroups. The first group (IM) was polished immediately after gross finishing using three different systems/techniques (n=16): Sof-Lex, Flexicups and Flexicups + Jiffy Polishing Brush + Flexibuffs (sequential), then stored for three weeks in saline. The DE group was stored for two weeks, polished with the same systems and stored for one week. From each subgroup, eight specimens were assessed after three weeks regarding Ra, KHN and ML (baseline), andthe eight remaining specimens were stored for one year before analysis. The data were analyzed (alpha=0.05) with ANOVA, paired Students t-test (Ra and KHN) or Kruskal-Wallis and Signed Rank tests (microleakage). After one year, microfilled resin composite specimens showed the lowest Ra and KHN (p<0.05). N o differencein microleakage was observed among the different groups (p>0.05). The sequential technique provided the lowest roughness and Sof-Lex the lowest hardness (p<0.05). IM showed similar or better performance than DE for ML and Ra (p<0.05). In conclusion, aging increased the composites Ra and ML in all experimental conditions (p<0.05).