Evaluation of Antimicrobial Properties, Cell Viability, and Metalloproteinase Activity of Bioceramic Endodontic Materials Used in Vital Pulp Therapy.

This study aimed to evaluate the antimicrobial properties, cell viability, and matrix metalloproteinase (MMP) inhibition capacity of several endodontic materials aimed at vital pulp therapy: Pro Root MTA®, EndoSequence®, Biodentine®, MTA Angelus®, TheraCal LC®, and BioC Repair®. The materials were prepared according to the manufacturer's instructions. Antimicrobial tests were conducted using a microcosm biofilm model, cell viability was assessed using murine fibroblasts (L929), and MMP activity was analyzed through electrophoresis. The results showed that BioC Repair®, Biodentine®, and EndoSequence® exhibited similar antimicrobial properties, while MTA Angelus® and ProRoot MTA® had inferior results but were comparable to each other. In terms of cell viability, no significant differences were observed among the materials. EndoSequence® demonstrated the highest MMP inhibition capacity. In conclusion, BioC Repair®, Biodentine®, EndoSequence®, and TheraCal® showed better antimicrobial properties among the tested materials. The materials did not exhibit significant differences in terms of cytotoxicity. However, EndoSequence® displayed superior MMP inhibition capacity.

Bioactivity Potential of Bioceramic-Based Root Canal Sealers: A Scoping Review.

INTRODUCTION: Bioceramic-based root canal sealers are novel materials with a bioactivity potential that stands out compared with conventional root canal sealers. However, the term bioactivity may be overused and is often misunderstood. Hence, the objective of this study was to synthesize and map key concepts related to the bioactivity analysis of bioceramic-based root canal sealers. METHODS: The present scoping review is reported in accordance with the PRISMA-ScR Statement and is registered in the Open Science Framework. Two blinded reviewers carried out a comprehensive search in six databases up to January 10th, 2022: MEDLINE, Scopus, Embase, Web of Science, Cochrane Library, and Lilacs/BBO. Eligibility was considered for in vitro and in vivo studies that evaluated the bioactivity potential of bioceramic-based root canal sealers. RESULTS: A total of 53 studies were included in the qualitative synthesis. In vitro bioactivity was evaluated through the mineralization potential, formation of carbonated apatite on the surface, and the gene expression related to proteins involved in the mineralization process. Meanwhile, for in vivo studies, staining techniques associated with immunohistochemical tests were mainly used to detect mineralization on the material-host tissue interface. CONCLUSIONS: According to the methodology used, the most prevalent methods to assess bioactivity in acellular form were the immersion of the material in Hank's balanced salt solution, followed by surface observation with scanning electron microscopy and energy dispersive X-ray. In cell cultures, the chosen method was usually Alizarin Red staining, followed by the evaluation of alkaline phosphatase enzymatic activity and the use of molecular biology tests.

Dihydropyrimidinones Against Multiresistant Bacteria.

The increase in bacterial resistance to antimicrobials has led to high morbidity and mortality rates, posing a major public health problem, requiring the discovery of novel antimicrobial substances. The biological samples were identified as the Gram-negative bacilli Acinetobacter baumannii, Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Morganella morgannii, Pseudomonas aeruginosa and Serratia marcescens and the Gram-positive cocci Enterococcus faecium, and Staphylococcus aureus, all of them resistant to at least three classes of antimicrobials. The antibacterial activity of the compounds was checked in vitro by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) by the broth microdilution method and plating in brain heart infusion (BHI) agar, respectively. The chemical characterization of the compounds was performed by measuring the melting point and gas chromatography coupled with mass spectrometry (GC-MS) on a Shimadzu GC-MS-QP system 2010SE. Synthetic compounds showed antimicrobial activity against Gram-positive cocci at MIC concentrations 0.16-80 µg/ml and Gram-negative bacilli at MIC concentrations 23.2-80 µg/ml. Enterococcus faecium and S. aureus had the best MIC values. The results of the cytotoxicity test indicated that the synthetic compounds showed no significant difference in three concentrations tested (5, 20, and 80 µg/ml), allowing cell viability not different from that assigned to the control, without the tested compounds. In this context, the development of DHPM derivatives brings an alternative and perspective on effectiveness of drugs as potential future antimicrobial agents.

Experimental resin-based dual-cured calcium aluminate and calcium titanate materials for vital pulp therapy.

This paper evaluates the physicochemical and biological properties of experimental resin-based dual-cured calcium aluminate (CA) and calcium titanate (CTi) materials for vital pulp therapy (VPT). The experimental dual-cured materials were obtained as two pastes: a) Bis-EMA 10, PEG 400, DHEPT, EDAB, camphorquinone, and butylated hydroxytoluene; and b) fluoride ytterbium, Bis-EMA 10, Bis-EMA 30, benzoyl peroxide, and butylated hydroxytoluene. The materials were divided into six groups based on the added calcium component: MTA (MTA®, Angelus); CLQ (Clinker-Fillapex®, Angelus); CA (calcined at ,1200°C in pastes a and b); CA800 (calcined at 800°C in paste a); CA1200 (calcined at 1,200°C in paste a); and CTi (paste a). The real-time degree of conversion and rate of polymerization (n = 3), diametral tensile strength (n = 10), hydrogen potential (n = 15), calcium ion release (n = 10), water sorption and solubility (n = 10), and cell viability (n = 6) were evaluated. One- and two-way ANOVA and Tukey's post hoc test were used in the analysis of the parametric data, and Kruskal-Wallis and Dunn's multiple tests were used to analyze the nonparametric data (α = 0.05). CLQ, CA800 and CA1200 had the highest diametral tensile strength. The water solubility of MTA was similar to that of CA800, CA1200 and CTi. CA800 and CA1200 resulted in cell viabilities similar to those of MTA and CLQ. The experimental dual-cured CA-based material that calcined at 800°C showed physicochemical and biological properties suitable for VPT, and similar to those of MTA.

Effect of an Intraorifice Barrier on Endodontically Treated Teeth: A Systematic Review and Meta-Analysis of In Vitro Studies.

The main cause of unsuccess in endodontically treated teeth (ETT) is due to bacterial recontamination. The placement of an intraorifice barrier (IOB) has been proposed for preventing this event in cases that the restoration is in an inadequate condition, enhancing the possibilities for predictable long-term success in endodontic therapy. Objectives. To evaluate through a systematic review and meta-analysis if it would be necessary to place an IOB in ETT. Materials and Methods. The present review is in accordance with the PRISMA 2020 Statement and is registered in the Open Science Framework. Two blinded reviewers carried out a comprehensive search in four databases up to July 10th, 2021: MEDLINE, Scopus, Embase, and Web of Science. Eligible studies were the ones which evaluated the use of an IOB in ETT in reducing microleakage with any material of choice and with any methods employed. Only in vitro studies published in English were included. Results. A total of thirty in vitro studies were included in the qualitative synthesis, and seven of those were included in the quantitative analyses evaluating the following materials: bioceramic cement, glass-ionomer cement (GIC), and resin-based composite (RBC). Most of the included studies placed an IOB at a 3 mm depth. Reduction in microleakage was observed when an IOB was placed, regardless of the material employed (p ≤ 0.01). Among the materials, GIC and RBC performed similarly (p > 0.05), with the bioceramic subgroup being statistically superior to the GIC subgroup (p ≤ 0.05). Conclusions. Although well-designed randomized clinical trials are required, the placement of an intraorifice barrier can significantly reduce microleakage in endodontically treated teeth, and the use of bioceramics as IOB seems to be the best available material for this purpose.

Experimental resin-based dual-cured calcium aluminate and calcium titanate materials for vital pulp therapy

Abstract: This paper evaluates the physicochemical and biological properties of experimental resin-based dual-cured calcium aluminate (CA) and calcium titanate (CTi) materials for vital pulp therapy (VPT). The experimental dual-cured materials were obtained as two pastes: a) Bis-EMA 10, PEG 400, DHEPT, EDAB, camphorquinone, and butylated hydroxytoluene; and b) fluoride ytterbium, Bis-EMA 10, Bis-EMA 30, benzoyl peroxide, and butylated hydroxytoluene. The materials were divided into six groups based on the added calcium component: MTA (MTA®, Angelus); CLQ (Clinker-Fillapex®, Angelus); CA (calcined at ,1200°C in pastes a and b); CA800 (calcined at 800°C in paste a); CA1200 (calcined at 1,200°C in paste a); and CTi (paste a). The real-time degree of conversion and rate of polymerization (n = 3), diametral tensile strength (n = 10), hydrogen potential (n = 15), calcium ion release (n = 10), water sorption and solubility (n = 10), and cell viability (n = 6) were evaluated. One- and two-way ANOVA and Tukey's post hoc test were used in the analysis of the parametric data, and Kruskal-Wallis and Dunn's multiple tests were used to analyze the nonparametric data (α = 0.05). CLQ, CA800 and CA1200 had the highest diametral tensile strength. The water solubility of MTA was similar to that of CA800, CA1200 and CTi. CA800 and CA1200 resulted in cell viabilities similar to those of MTA and CLQ. The experimental dual-cured CA-based material that calcined at 800°C showed physicochemical and biological properties suitable for VPT, and similar to those of MTA.

The Effect of Deproteinizing Agents on Bond Strength of Resin-based Materials to Enamel: A Systematic Review and Meta-Analysis of In Vitro Studies.

PURPOSE: To systematically review the literature to evaluate whether the bond strength of resin-based materials to enamel is affected by deproteinizing agents. MATERIALS AND METHODS: This systematic review and meta-analysis was conducted according to the PRISMA statement. PubMed, ISI Web of Science, Cochrane Library, SciELO, Scopus, LILACS, IBECS, and BVS databases were screened up to December 2020. Eligibility criteria included in vitro studies that reported the effect of a deproteinizing agent applied before or after acid etching on the immediate or long-term bond strength of resin-based materials to enamel. The meta-analysis was carried out using Review Manager (version 5.3.5). A global comparison was performed with the standardized mean difference based on random-effect models at a significance level of α = 0.05. RESULTS: A total of 23 studies were included in the meta-analysis. In all the studies, only the immediate bond strength was evaluated. The bond strength of the materials was improved by the application of NaOCl or papain prior to enamel etching with phosphoric acid (p ≤ 0.006). None of the deproteinizing agents had a significant effect when applied after etching with phosphoric acid (p ≥ 0.27). CONCLUSIONS: Based on in vitro studies, deproteinization with sodium hypochlorite or papain-based agents increases the immediate bond strength of resin-based materials to enamel only when used prior to phosphoric-acid etching.

Salivary characteristics may be associated with burning mouth syndrome?

BACKGROUND: Burning mouth syndrome (BMS) it is characterized by burning and uncomfortable sensations with no clinical alterations or laboratory findings. The evaluation of the salivary characteristics of people with BMS can help the understanding of the pathogenesis of this condition. This case-control study aimed to trace the salivary profile of women with burning mouth syndrome (BMS). MATERIAL AND METHODS: 40 women with BMS and 40 control women were recruited. Unstimulated salivary flow rate (uSFR), pH, salivary cortisol levels, salivary viscosity, and oral health impact profile (OHIP-14 questioner) were determined. P< 0.05 was considered statistically significant. RESULTS: For uSFR, mean values obtained for BMS and for control group respectively were 0.35 and 0.61 mL/min; for pH, 7.23 and 7.34; for cortisol levels, 0.36 and 0.15 µg/dL; for viscosity values, 31.1 and 45.01 mPas and for OHIP-14 scores, 21.7 and 5.7. To uSFR, cortisol levels, viscosity values and OHIP-14 scores, differences were statistically significant. Salivary cortisol levels and OHIP-14 scores were correlated positively (rho = 0.624; p< 0.05). CONCLUSIONS: BMS women have lower uSFR and salivary viscosity and higher salivary cortisol levels that were associated with worse quality of life, compared with the control group. Key words:Xerostomia, Burning mouth syndrome, Viscosity.

Local delivery therapies as adjuvants to non-surgical periodontal treatment of periodontitis grade C: a systematic review.

OBJECTIVES: The aim of this article was to perform a systematic review on the effectiveness of local adjuvant therapies in the treatment of aggressive periodontitis (AgP), now reported as periodontitis grade C. MATERIALS AND METHODS: The authors selected randomized clinical trials of AgP patients who received local therapy as adjuvants to non-surgical periodontal with a duration of at least 90 days. Seven databases were searched up to January 2020. The gain in clinical attachment level (CAL) and reduction of probing depth (PD) were the outcomes of interest. RESULTS: Of the 3583 studies found, only five articles were included in the qualitative analysis. Among the substances analyzed, only 1.2 mg of simvastatin gel (SMV) (1.2 mg/0.1 ml), 1% of alendronate gel (ALN) (10 mg/ml), and 25% metronidazole gel (MTZ) (Elyzol@) showed a significant decrease in the probing depth when compared with their respective control groups. The gain CAL was shown using 1.2 mg SMV gel (1.2 mg/0.1 ml) and 1% ALN gel (10 mg/ml). CONCLUSION: Although 1.2 mg SMV gel (1.2 mg/0.1 ml), 1% ALN gel (10 mg/ml), and 25% MTZ gel (Elyzol) have shown better results, local therapies adjuvant to SRP the data found were limited. Future clinical studies with appreciable methodological quality should be conducted. CLINICAL RELEVANCE: Despite some benefits of local delivery therapy, up to now, it has not been possible to prove the efficacy of local therapy as an adjunct to standard treatment of AgP (periodontitis grade C).

Novel in-office peroxide-free tooth-whitening gels: bleaching effectiveness, enamel surface alterations, and cell viability.

To evaluate the bleaching ability, the effect on enamel surface and cytotoxicity of novel tooth-whitening formulations containing papain, ficin, or bromelain. Forty bovine dental discs (6 cm ×4 cm) were pigmentated and randomly allocated into the following groups (n = 10): Group 1, 20 wt% carbamide peroxide (control); group 2, 1% papain-based whitening; group 3, 1% ficin-based whitening; and group 4, 1% bromelain-based whitening. The whitening gels were prepared and applied on the enamel three times per day once a week, for 4 weeks. Color measurement was obtained by CIEDE2000. Enamel Knoop microhardness and roughness were evaluated. The WST-1 assay was used to evaluate the cell viability of mouse fibroblast cells (L929). Data were statistically analyzed by one-way analysis of variance (ANOVA) and Student Newman Keuls's post hoc test at α = 0.05 significance level. Bromelain, ficin-based, and carbamide peroxide bleaching gels showed a similar color change (p < 0.001). Higher enamel hardness decrease and higher enamel roughness were caused by the carbamide peroxide (p < 0.05). The experimental whitening gels did not affect cell viability. Tooth bleaching gels containing bromelain, papain, or ficin have substantial clinical potential to be used in the development of peroxide-free tooth whitening gels.

Bonding Strength of Universal Adhesives to Indirect Substrates: A Meta-Analysis of in Vitro Studies.

PURPOSE: To evaluate the in vitro bond strength of universal adhesive systems to indirect substrates. MATERIAL AND METHODS: Two reviewers performed a literature search up to March 2018 in seven databases: PubMed, Web of Science, SciELO, Scopus, LILACS, IBECS, and BBO. The review included studies that compared the bond strength of universal adhesives and well-established material-specific primers to indirect substrates: lithium disilicate ceramic, yttrium-stabilized zirconium dioxide ceramic, leucite-reinforced ceramic, feldspathic porcelain, polymer infiltrated ceramic material, resin composite or metal alloys. Analyses were carried out using RevMan 5.3.5. A global comparison was performed with the standardized mean difference using a random-effects models at a significance level of p < 0.05. RESULTS: A total of 45 studies were included in the qualitative analysis, and the meta-analysis was performed with 42 studies. Bond strength to glass-based ceramics and alloys was improved with the use of a specific-primer as separate step before the bonding procedures (lithium disilicate, p < 0.001; alloys, p < 0.001). The bond strength to zirconium substrates was improved with the use of universal adhesives (p < 0.001). For bond strength to composite resin as indirect substrate, universal adhesives performed in a manner similar to that of the material-specific primer (p = 0.11). CONCLUSIONS: The clinical procedure of luting zirconia and resin composite restorations could be simplified by using single-bottle universal adhesives. However, the ability of universal adhesives to achieve an adequate and durable bond to glass-based ceramics and alloys appears to be limited.

Efficacy of natural, peroxide-free tooth-bleaching agents: A systematic review, meta-analysis, and technological prospecting.

The aim of this study is to analyze the efficacy of natural bleaching agents and the current technological development in this research field. Two reviewers performed a literature search up to July 2019 in 15 databases. Five laboratory studies and 25 patents were included. Data regarding natural bleaching agent used, application protocol, and the main findings of studies were analyzed. Laboratory studies that evaluated natural bleaching agents' peroxide-free or associated to peroxides and patents related to natural bleaching agents were included. The studies evaluated papain, bromelain, chlorine dioxide, sodium chloride plus vinegar and sodium bicarbonate as peroxide-free agents; and sweet potato extract, lactoperoxidase, and peroxidase associated to peroxide used were included. Twenty-five patents were included; among the most cited are the papain and the chlorine. The addition of non-peroxide agents into peroxide showed improvement in bleaching effect with the incorporation of these non-peroxide agents (p < .05). On the other hand, peroxide-free agents did not show an improvement in bleaching effect (p < .05). The evidence in literature suggested that natural bleaching agents incorporated to peroxide may improve the bleaching. Therefore, the current literature does not support the use of natural agents as dental bleaching.

Impact of shelf-life simulation on bonding performance of universal adhesive systems.

OBJECTIVES: To evaluate the micro-tensile bond strength to dentin (µTBS), the degree of conversion (DC) and nanoleakage expression (NL) of eight dental adhesives considering their expiry date (as-received, half-life and or end of shelf-life) after shelf-life simulation. METHODS: Five universal adhesives (Single Bond Universal, SBU; Tetric Bond Universal, TBU; OneCoat Universal, OCU; OptiBond Universal, OBU; and Prime&Bond Elect, P&B), two two-step self-etch adhesives (Clearfil SE, CSE; and AdheSE, ASE) and one two-step etch-and-rinse adhesive (Adper Singlebond 2, ASB) were evaluated. Shelf-life was simulated by storing the materials in an acclimatization chamber for different periods of time. The µTBS was tested in accordance with ISO/TS 11,405. DC was evaluated by means of FTIR spectroscopy. NL was evaluated after ammoniacal silver challenge. The significance level of α=0.05 was used for all statistical analyses. RESULTS: The µTBS to dentin of TBU, P&B, ASE, and ASB adhesive systems remained stable throughout the shelf-life periods evaluated, while for SBU, OCU, OBU, and CSE, decreased significantly after evaluation in the 'half-life' or 'end of shelf-life' condition (p<0.05). Except for P&B, ASE and OBU, the degree of conversion significantly decreased after the shelf-life simulation (p<0.05). OCU, ASE, and CSE showed significantly increased percentage of silver deposition within the adhesive layer (p<0.05). SIGNIFICANCE: Storing conditions and progressively longer storage time affect the performance of universal adhesives systems.

Bonding Performance of Universal Adhesives: An Updated Systematic Review and Meta-Analysis.

PURPOSE: To evaluate through a systematic review and meta-analysis whether the immediate and long-term bonding performance of universal adhesives would be improved by prior acid etching. MATERIALS AND METHODS: Two reviewers performed a literature search up to April 2018 in eight databases: PubMed, Web of Science, Cochrane Library, SciELO, Scopus, LILACS, IBECS, and BBO. Only studies that evaluated the dentin or enamel bond strength of universal adhesives using a self-etch or etch-and-rinse strategy were included. Analyses were carried out using RevMan 5.3.5 (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark). A global analysis comparing self-etch or etch-and-rinse strategies and the influence of aging on bonding performance was performed with random-effects models at a significance level of p < 0.05. RESULTS: A total of 59 in vitro studies were included in the meta-analysis. The enamel bond strength of universal adhesives was improved by the etch-and-rinse approach (p < 0.05). In dentin, this effect was observed for ultra-mild and intermediately strong universal adhesives (p < 0.05). Irrespective of the strategy employed, intermediately strong adhesives showed a decrease in bond strength after all types of aging. This effect was also observed for ultra--mild universal adhesives used in the etch-and-rinse approach (p < 0.05). Mild universal adhesives showed bond strength stability in both strategies (p > 0.05). CONCLUSIONS: The in vitro evidence suggests that bonding performance of mild universal adhesives can be improved by using the selective enamel-etch strategy. Mild universal adhesives seem to be the more stable materials, in both etch-and-rinse or self-etch strategies.

Does laser therapy improve the wound healing process after tooth extraction? A systematic review.

Laser therapy could amplify the oral wound healing process by stimulating cell regeneration after injury, attenuating pain, and modulating the immune system. The purpose of this systematic review was to evaluate whether the application of laser therapy improved alveolar healing after tooth extractions. Eight electronic databases were screened: MedLine (PubMed), The Cochrane Library, Web of Science, Scopus, Lilacs, Ibecs, Scielo, and BBO. Three reviewers independently assessed the title and abstracts of potentially relevant studies. Only clinical trials and animal experiments that evaluated the wound healing effect of laser therapy after tooth extraction were included. A total of 16 studies fulfilled all criteria, thus 8 animal experiments and 8 clinical trials were included. Different types of laser were evaluated, such as CO2 , GaAlAs, Nd:YAG, Diode Laser, HeNe, and High-frequency Pulsed Diode Laser. Although HF, Diode and GaAs lasers were able to enhance wound healing process in clinical studies, four trials and one animal experiment showed no improvement in wound healing with laser therapy after tooth extractions. In general, the current available evidence in the literature showed that laser therapy improved the wound healing process, but these findings were limited to the type of laser applied and its specific settings. Further well-designed and randomized controlled trials are needed to support a benefit effect of using laser therapy after tooth extraction. PROSPERO registration number: CRD42014007509 (2014).

Efficacy of rhBMP-2 in Cleft Lip and Palate Defects: Systematic Review and Meta-analysis.

The aim of this study was to analyze the efficacy of using rhBMP-2 (recombinant human morphogenetic protein-2) in the treatment of patients with cleft lip and palate defects (CLPD). Seven databases were screened: PubMed (Medline), Lilacs, Ibecs, Web of Science, BBO, Scopus, and The Cochrane Library. Clinical trials that evaluated the use of bioactive treatment with rhBMP-2 in the treatment of patients with CLPD were included. Statistical analyses were performed by comparing the standardized mean difference of bone formation volume and bone filling percentage (p = 0.05). Ten studies compared the use of rhBMP-2 and iliac crest bone graft (ICBG). The global analysis for bone formation volume and bone filling percentage showed that bioactive materials were similar to ICBG with a standardized mean difference of respectively 0.07 (95% CI - 0.41 to 0.56) and 0.24 (95% CI - 0.32 to 0.80). The available literature suggested that use of rhBMP-2 presented similar bone formation results to those of ICBG in secondary alveolar bone grafting for patients with CLPD.

Synthesis of an allyl carbonate monomer as alternative to TEGDMA in the formulation of dental composite resins.

Over the past years, significant effort has been dedicated to synthesizing low-shrinking formulations, however, development of dental composites with low volumetric shrinkage continues to be challenging. The purpose of this study was to synthesize a bisphenol allylic derivate (BPhADAC) and evaluate its inclusion in the formulation of a photopolymerizable dental composite resin, as a BisGMA diluent. Experimental (BisGMA/BPhADAC) and control (BisGMA/TEGDMA) photopolymerizable composites were prepared. Double bond conversion, polymerization kinetics, volumetric shrinkage, water sorption, solubility, and flexural properties were investigated. The experimental composite showed higher degree of conversion values, less volumetric shrinkage and less water sorption than the control composite (p < 0.05). In addition, flexural strength between the materials was found to be similar. The overall properties prove that the allylic monomer BPhADAC could be potentially useful in the formulation of low-shrinking dental composite resins.

Polymerization shrinkage stress of resin-based dental materials: A systematic review and meta-analyses of composition strategies.

PURPOSE: A systematic review was conducted to determine whether there were composition strategies available to reduce and control polymerization shrinkage stress development in resin-based restorative dental materials. DATA SOURCES: This report was reported in accordance with the PRISMA Statement. Two reviewers performed a literature search up to December 2016, without restriction of the year of publication, in seven databases: PubMed, Web of Science, Scopus, SciELO, LILACS, IBECS, and BBO. STUDY SELECTION: Only laboratory studies that evaluated polymerization shrinkage stress by direct testing were included. Pilot studies, reviews and in vitro studies that evaluated polymerization shrinkage stress by indirect methods (e.g., microleakage or cuspal deflection measurements), finite elemental analysis, or theoretical and mathematical models were excluded. Of the 6113 eligible articles, 62 studies were included in the qualitative analysis, and the meta-analysis was performed with 58 studies. The composition strategy was subdivided according to the modified part of the material: filler phase, coupling agent, or resin matrix. A global comparison was performed with random-effects models (α = 0.05). The only subgroup that did not show a statistical difference between the alternative strategy and the control was 'the use of alternative photo-initiators' (p = 0.29). CONCLUSION: Modification of the resin matrix made the largest contribution to minimizing stress development. The technology used for decreasing stress in the formulation of low-shrinkage and bulk-fill materials was shown to be a promising application for reducing and controlling stress development.

Polymerization shrinkage stress of resin-based dental materials: A systematic review and meta-analyses of technique protocol and photo-activation strategies.

PURPOSE: A systematic review was conducted to determine whether there were any alternative technique or additional step strategies available to reduce and control polymerization shrinkage stress development in dental resin-based restorative materials. DATA SOURCES: This report followed the PRISMA Statement. A total of 36 studies were included in this review. Two reviewers performed a literature search up to December 2016, without restriction of the year of publication, in seven databases: PubMed, Web of Science, Scopus, SciELO, LILACS, IBECS, and BBO. STUDY SELECTION: Only in vitro studies that evaluated polymerization shrinkage stress by direct testing were included. Pilot studies, reviews and in vitro studies that evaluated polymerization shrinkage stress by indirect methods (e.g., microleakage or cuspal deflection measurements), finite elemental analysis or mathematical models were excluded. Of the 6.113 eligible articles, 36 studies were included in the qualitative analysis, and the meta-analysis was performed with 25 studies. A global comparison was performed with random-effects models (α = 0.05). The strategies were subdivided as follows: the use of an alternative technique protocol of placing the material inside the tooth cavity; the modification of the irradiation intensity or total energy delivered to the material; the use of an alternative light-curing source; or the use of an alternative photo-activation mode. All alternative strategies showed statistically significant differences when compared with their respective controls (p < 0.05). CONCLUSION: The use of alternative light-curing sources contributed more to minimizing stress development than placing the material by means of an alternative technique protocol or by modifying the irradiant intensity or total energy delivered to the material during photo-activation. Moreover, the use of an alternative photo-activation mode (intermittent light, exponential, soft-start or pulse delay modes) was shown to be an effective strategy for reducing and controlling stress development in resin-based dental materials.