Antibacterial dental restorative materials: A review.

PURPOSE: To provide updated summary information about antibacterial dental materials, primarily covering the literature from 2012 through 2017. METHODS: A key-worded search was conducted of peer-reviewed literature (Titles/Abstracts) indexed by PubMed databases, constrained to "English" and " dental" publications between the years 2012 and 2017. Key words applied to the search included: antimicrobial, antibacterial, primer, bonding agent, adhesive, cement, composite, liner, sealant, etchant, and core-build-up. Titles and abstracts of the articles returned by the search were reviewed and evaluated for appropriateness for inclusion in this review. RESULTS: A variety of antibacterial agents have been incorporated into experimental and commercial dental restorative materials to provide antibacterial activity in dental applications. No new antibacterial compounds were introduced in this review period (2012-2017), since the last review of period of 1980-2012. Antibacterial agents include leachable compounds (e.g. benzalkonium chloride, chlorhexidine), polymerizable monomers (e.g. quaternary ammonium methacrylates), and filler particles (e.g. silver nanoparticle). During the 2012-2017 review period, many antibacterial agents were tested in experimental formulations, but only four agents (benzalkonium chloride, chlorhexidine, glutaraldehyde, and MDPB) were used in commercial products. CLINICAL SIGNIFICANCE: Leachable antibacterial agents are the most frequently used type of antibacterial dental materials, but their efficacy may be short-lived due to their characteristic burst effect. Solid filler particles appear to be effective antibacterial agents, especially given their ability to reduce biofilm formation, but the color stability of their component metal particles is unfavorable for use in a commercial product. Polymerizable antibacterial agents (MDPB) are theoretically a good choice of material because they are very effective at killing any residual bacteria in a cavity preparation prior to polymerization, however, apart from their proven effect on reduction of biofilm formation, their long-term clinical performance is still questionable.

Effect of silane contamination on dentin bond strength.

STATEMENT OF PROBLEM: Intraoral repair of porcelain or other silica-based ceramics typically requires the use of silane in the repair protocol. Some porcelain intraoral repairs also involve bonding to exposed or involved tooth tissues including dentin. A study is needed to evaluate whether the cross-contamination of dentin with silane affects bond strength to this tissue. PURPOSE: The purpose of this in vitro study was to investigate the effect of silane cross-contamination on dentin bond strength. MATERIAL AND METHODS: Flat surfaces of human dentin specimens were created, followed by wet polishing with 320-grit silicon carbide paper. The dentin specimens were divided into 4 groups: group SE (All-Bond Universal Adhesive used in self-etching mode); group SiSE (silane applied to dentin followed by All-Bond Universal Adhesive used in self-etching mode); group ER (All-Bond Universal Adhesive used in total-etch (etch-and-rinse) mode); and group ERSi (Etch and rinse and silane applied to dentin followed by All-Bond Universal Adhesive). The dentin specimens were treated with a universal adhesive (All-Bond Universal) and bonded with a composite resin, using an Ultradent jig mold. Shear bond strength (n=10) was measured after 24 hours of water storage at 37°C. After the shear bond strength test, the dentin sides of fractured specimens in each group were examined with a stereomicroscope at ×15 magnification to determine failure modes. Data were statistically analyzed by 2-way and a 1-way ANOVA followed by post hoc Tukey honest significant difference test (α=.05). Scanning electron microscopy examination was used to evaluate the dentin surface morphology before and after bonding. RESULTS: The shear bond strength of composite resin to dentin was not affected adversely when the dentin was contaminated with silane prior to using All-Bond Universal in the self-etch or total- etch (phosphoric acid) mode. SE, 30.3 ±3.8 MPa; SiSE, 32.9 ±3.9 MPa; ER, 34.9 ±3.1 MPa; ERSi: 35.2 ±4.9 MPa (P>.05) CONCLUSIONS: Under the conditions of this study, cross-contamination of dentin with silane before the use of All-Bond Universal in the self-etch or total-etch with phosphoric acid mode did not adversely affect composite resin bond strength to dentin.

Effects of light-, self-, and tack-curing on degree of conversion and physical strength of dual-cure resin cements.

PURPOSE: To evaluate the polymerization degree of conversion (DC) and physical strength of dual-cure cements with tack-curing, and compare them to those with light-curing and self-curing resins. METHODS: Four dual-cure resin cements were evaluated by DC and diametral tensile strength (DTS) tests with three different polymerization methods: Light-cure (photo-polymerization 40 seconds, self-curing 30 minutes); Self-cure (self-curing 30 minutes); and Tack-cure (photo-polymerization 3 seconds, self-curing 30 minutes). Polymerization degree of conversion was determined using Fourier transform infrared spectroscopy, and calculated based on the ratio changes of aliphatic-to-aromatic C=C IR absorption peaks before and after polymerized. Specimens for DTS (n = 10) were prepared using circular molds (6.0 mm in diameter and 3.0 mm in height) and tested after 24-hour water storage. Data were analyzed by two-way ANOVA. Multiple post-hoc pairwise comparisons were performed by t-test when significant effects were found across the factors (α = 0.05). Results: The Self-cure groups had slow initial curing rate, resulting in the lower DC than both the Light-cure and Tack-cure groups. After 30 minutes of polymerization, only in the RelyX Ultimate group, light-curing resulted in higher DC than tack-curing, which resulted in higher DC than self-curing (P < 0.05). The self-cure of resin cements resulted in a significantly lower DTS only for RelyX Ultimate cement (P < 0.05). There was no significantly different DTS between the Tack-cure and Light-cure groups for all of the resin cements. For all of the three curing modes, RelyX Ultimate cements had the lowest DTS among the four cements tested in this study.

Effect of hydrophilicity on the compatibility between a dual-curing resin cement and one-bottle simplified adhesives.

PURPOSE: To evaluate the effect of the hydrophilicity of adhesives on the compatibility between one-bottle simplified adhesives and a dual-curing resin cement. MATERIALS AND METHODS: Three experimental and two commercial adhesives (All-Bond Universal, OptiBond Allin- One) with the same or similar pH and various degrees of hydrophilicity were tested in this study. Extracted human dentin was treated with each adhesive and bonded with a dual-curing resin cement (Duolink), which was either light cured or chemically (self) cured (n = 10). Shear bond strength was tested using the Ultradent jig method, and failure modes were determined using a stereomicroscope. Water contact angle (as a measure of hydrophilicity/-phobicity) was measured on a fully cured adhesive (n = 10). The data were analyzed statistically by ANOVA and Tukey's test. The quantitative relationship between the hydrophilicity and bond strength differences was analyzed (confidence level 95%). RESULTS: Among the experimental adhesives, differences in bond strengths between light-curing and self-curing modes were larger for the more hydrophilic adhesives. For the commercial adhesives, Optibond All-in-One had a lower contact angle than All-bond Universal (p < 0.05). Bond strength (MPa) values for Optibond All-in-One and All-bond Universal were 29.6 and 31.5, respectively (light cured), and 1.9 and 30.0, respectively (self-cured). Adhesive failure was a predominant mode for all adhesives except for All-Bond Universal. Regression analysis indicated a linear correlation between adhesives' hydrophilicity and bond strength differences (p < 0.05). CONCLUSION: The more hydrophilic adhesives were less compatible (larger bond strength differences between different curing modes) with this dual-curing resin cement. All-bond Universal is more hydrophobic than Optibond All-in-One and it is compatible with this self-/dual-curing resin cement.

Bioactive dental restorative materials: a review.

PURPOSE: To present an updated knowledge on the remineralizing dental restorative materials and their performance in vivo and/or in vitro. METHODS: A search of English peer-reviewed dental literature over the last 30 years from PubMed and MEDLINE databases was conducted, and the key words included: remineralization, pulp capping, restoration, composite, cement, primer, bonding, adhesive, liner and sealant. Titles and abstracts of the articles listed from search results were reviewed and evaluated for appropriateness. RESULTS: A variety of dental restorative materials are able to promote tooth remineralization and/or inhibit tooth demineralization. These remineralizing materials include fluoride- and/or calcium-containing pulp capping materials, bonding agents, resin composites, resin cements, glass-ionomer cements, and sealants.

Effect of incorporating BisGMA resin on the bonding properties of silane and zirconia primers.

STATEMENT OF PROBLEM: Some silane primers and some zirconia primers contain extra resins such as bisphenol A glycol dimethacrylate (BisGMA) in their formulations for better wetting. No studies exist on the bonding properties of zirconia and silane primers, which contain extra resins. PURPOSE: The purpose of this study was to investigate the effect of incorporating BisGMA resin on the bonding properties of silane and zirconia primers. MATERIAL AND METHODS: Silica-base lithium disilicate was etched and treated with BisGMA-incorporated Porcelain Primer, unmodified Porcelain Primer, or resin-containing Kerr Silane. Zirconia ceramic was airborne-particle abraded and treated with BisGMA-incorporated Monobond Plus, unmodified Monobond Plus, or BisGMA-containing ZPrime Plus. After primer treatment and cleaning with ethanol, the contact angles were measured to determine surface change (n=10). Shear bond strength tests were also performed to measure the adhesion strength between resin cements and ceramic surfaces (n=10). Data were statistically analyzed by 1-way ANOVA followed by the Tukey multiple comparison as a post hoc test (significance level .05). RESULTS: The incorporation of BisGMA resin did not significantly influence the bond strength or contact angle of the zirconia primer (P>.05), but it did significantly reduce those of the silane primer (P<.05). Resin-containing Kerr Silane (22 degrees, 23 MPa) had a similar contact angle and higher bond strength than the control (21 degrees, 18 MPa), but lower than Porcelain Primer (88 degrees, 34 MPa). Resin-containing ZPrime Plus (75 degrees, 29 MPa) had a similar contact angle and higher bond strength than both Monobond Plus (74 degrees, 18 MPa) and the control (15 degrees, 4 MPa). CONCLUSIONS: The addition of BisGMA resin significantly inhibited the efficacy of silane-containing porcelain primers but did not affect that of phosphate-containing zirconia primers.

Antibacterial dental restorative materials: a state-of-the-art review.

This review presents an updated knowledge on the antibacterial dental restorative materials and their performance clinically and in the laboratory. A search of English peer-reviewed dental literature over the last 30 years from PubMed and MEDLINE databases was conducted, and the key words included antibacterial, antimicrobial, dental, primer, adhesive, bonding agent, cement, and composite. Titles and abstracts of the articles listed from search results were reviewed and evaluated for relevancy. In summary, the incorporation of an appropriate amount of antibacterial agent provided dental restorative materials (dental bonding agents, resin composites, resin cements, glass-ionomer cements) antibacterial activity without significantly influencing mechanical properties.

Bonding of primed zirconia ceramics: evidence of chemical bonding and improved bond strengths.

PURPOSE: To investigate changes of zirconia surface hydrophobicity (contact angle) following the application of a zirconia primer as a function of post-priming storage period and after exposure to harsh conditions and to analyze whether there is a chemical bond formation between a zirconia primer and zirconia ceramics. METHODS: Zirconia ceramics were treated with a zirconia primer (ZPrime Plus, Bisco), left undisturbed for specific times (reaction time), followed by ultrasonic cleansing in ethanol or acetone bath, and then contact angles were measured (n = 10). The primed zirconia ceramics were also subjected to harsh conditions (strong acid or boiling water) prior to contact angle testing. The chemical change of zirconia surface with and without being primed was analyzed by time-of-flight secondary ion mass spectroscopy (TOF-SIMS). Shear bond strength (Ultradent jig method) on zirconia surface was tested using different zirconia primers. The data were statistically analyzed using one-way ANOVA and Tukey's post-hoc test with 95% confidence level. RESULTS: The contact angle on the primed zirconia surface (from 56 degrees to 72 degrees for different primers) was significantly higher than that of unprimed zirconia (15 degrees) (P < 0.05). Contact angles were maximized as the reaction time increased within 5 minutes (increased from 58 degree at 10 seconds, to 72 degrees at 5 minutes). Exposure to harsh conditions (i.e. strong acid or boiling water) exhibited no significant change in contact angle values (P > 0.05). The TOF-SIMS detected fragmentations with mass of 549 and 411, indicating that a chemical group of phosphate monomer(P)-O-Zr existed, which indicated a chemical bond was formed between zirconia and ZPrime Plus. All of the zirconia primers tested in the study significantly improved zirconia bond strengths (4 MPa for unprimed zirconia, and 17-23 MPa for primed zirconia, P < 0.05).

Evaluation of silica-coating techniques for zirconia bonding.

PURPOSE: To evaluate silica-coating/silane treatment techniques for zirconia bonding. METHODS: 19 groups of zirconia disks were subjected to different surface treatments: polished or sandblasted by CoJet or alumina, and treatment with silane or zirconia primers (containing phosphate- or phosphonate-monomer). After surface treatments, the zirconia disks were cemented with resin cements and stored in deionized water for 2 hours at 370 degrees C prior to shear bond strength testing. Zirconia surface (polished and unpolished), CoJet sand, Cojet-treated zirconia surface (before and after water rinsing) and representative debonded surfaces were examined by scanning electron microscopy (SEM). The zirconia surface after silica-coating was examined by Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy. RESULTS: A non-phosphate-containing resin cement (Choice 2) had almost no bond strength on polished zirconia, while MDP-containing cements (Panavia F2.0) had mild bond strength. After zirconia was sandblasted with CoJet or alumina, bond strengths were slightly increased. Silane treatment did not increase bond strength, while phosphate/carboxylate-based primer (i.e. Exp Z-Prime) doubled the bond strengths. Silica nanoparticles identified by FTIR-ATR spectra, were observed by SEM on the zirconia surface after CoJet treatment. However, these nanoparticles were removed by forceful water stream.

Cytotoxicity and biocompatibility of resin-free and resin-modified direct pulp capping materials: A state-of-the-art review.

Direct pulp capping is the placement of a dental material directly over exposed pulp to prevent dental pulp from dying and avoid the need for root canal treatments. Calcium hydroxide and calcium silicates/mineral trioxide aggregates (MTA) have been commonly used for direct pulp capping with great success clinically. In recent years, resin-modified calcium hydroxide and calcium silicates have been developed with the advantages of precise placement, command set, and superior physical strength. As pulp capping materials would be in direct contact with the pulp, the cytotoxicity and biocompatibility is of particular importance in order to avoid pulp irritation and maintain pulp vitality. Therefore, this review article will summarize the cytotoxicity and biocompatibility of direct pulp capping materials, particularly resin-modified materials.

Translucent quartz-fiber post luted in vivo with self-curing composite cement: case report and microscopic examination at a two-year clinical follow-up.

A maxillary central incisor with mild periodontitis and extensive loss of coronal tooth structure was endodontically treated and restored with a translucent quartz-fiber post and a composite core. Treatment was completed with the cementation of full-ceramic crowns on teeth 11 and 21. Informed consent was obtained from the patient. Due to the extent of the periodontal disease, tooth 11 was extracted two years later. With the patient's consent, the tooth was used for research. The tooth was sectioned at 11 levels perpendicularly to the long axis and investigated by means of optical microscopy and scanning electron microscope (SEM). The visual examination showed perfect adhesion between the various interfaces (restoration-dentin-post) at both the coronal and root levels. The adhesion between the post and dentin appeared to be free of gaps, and even where the composite cement showed a nonhomogeneous thickness, voids were not apparent. The tooth under examination allowed the authors to check the effectiveness of the adhesion and the integrity of the hybrid layer after exposure to the oral cavity for two years. The results of this investigation show that there were no gaps between the adhesive resin and dentin and no hydrolysis of the adhesive bond. This case suggests that it is possible to obtain good results in the short term from the cementation of quartz-fiber posts with composite resin cements.

Comparison of the Physical and Mechanical Properties of Resin Matrix with Two Photoinitiator Systems in Dental Adhesives.

This study evaluated the physical and mechanical properties of resin matrices in dental adhesives with two photoinitiator systems. Resin matrix specimens were made with five different kinds of photoinitiators. Neat resin consisted of 60% 2,2-bis[4-2(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (Bis-GMA) and 40% hydroxyethyl methacrylate (HEMA) by weight, along with camphorquinone (CQ, 1 mol %) and additional components (1 mol % each) as follows: Group 1, 2-(dimethylamino)ethyl methacrylate (DMAEMA); Group 2, ethyl-4-(dimethylamino) benzoate (EDMAB); Group 3, diphenyliodonium hexafluorphosphate (DPIHFP); Group 4, DMAEMA+DPIHFP; Group 5, EDMAB+DPIHFP. The degree of conversion (DC), flexural strength, flexural modulus, microhardness, and ultimate tensile strength were tested. The contribution of each photoinitiator to the DC in a selected group was analyzed with contour plots. One-way ANOVA and Tukey tests (p < 0.05) were used for statistical analyses. The DC of Groups 2, 4, and 5 was similar. The flexural strength was similar in all groups, but flexural modulus was significantly different. Group 3 had the lowest values for all physical and mechanical properties. Among all methods, the microhardness test revealed the greatest degree of difference among the five specimens. CQ, EDMAB, and DPIHFP were the most effective photoinitiators and CQ was the most influential factor for the DC rate.

The anti-MMP activity of benzalkonium chloride.

OBJECTIVE: This study evaluated the ability of benzalkonium chloride (BAC) to bind to dentine and to inhibit soluble recombinant MMPs and bound dentine matrix metalloproteinases (MMPs). METHODS: Dentine powder was prepared from extracted human molars. Half was left mineralized; the other half was completely demineralized. The binding of BAC to dentine powder was followed by measuring changes in the supernatant concentration using UV spectrometry. The inhibitory effects of BAC on rhMMP-2, -8 and -9 were followed using a commercially available in vitro proteolytic assay. Matrix-bound endogenous MMP-activity was evaluated in completely demineralized beams. Each beam was either dipped into BAC and then dropped into 1 mL of a complete medium (CM) or they were placed in 1 mL of CM containing BAC for 30 days. After 30 days, changes in the dry mass of the beams or in the hydroxyproline (HYP) content of hydrolysates of the media were quantitated as indirect measures of matrix collagen hydrolysis by MMPs. RESULTS: Demineralized dentine powder took up 10-times more BAC than did mineralized powder. Water rinsing removed about 50% of the bound BAC, whilst rinsing with 0.5M NaCl removed more than 90% of the bound BAC. BAC concentrations 0.5wt% produced 100% inhibition of soluble recombinant MMP-2, -8 or -9, and inhibited matrix-bound MMPs between 55 and 66% when measured as mass loss or 76-81% when measured as solubilization of collagen peptide fragments. CONCLUSIONS: BAC is effective at inhibiting both soluble recombinant MMPs and matrix-bound dentine MMPs in the absence of resins.

Oxygen-inhibited layer in adhesion dentistry.

PURPOSE: Characteristics of the oxygen-inhibited layer, including bond strength, photoinitiator decomposition, and post-curing degree of conversion, were investigated. MATERIALS AND METHODS: To investigate shear bond strength, BisCover (Bisco, Inc., Schaumburg, IL, USA) and D/E Resin (Bisco, Inc.) were placed on disks of Renew composite (Bisco, Inc.) and cured both with and without an oxygen-inhibited layer. Light-Bond composite (Reliance Orthodontic, Itasca, IL, USA) was placed in a gelatin capsule and light cured over the cured resin. After soaking in water for 2 hours at 37 degrees C, specimens were sheared to failure using a universal testing machine (Model 4466, Instron Inc., Canton, MA, USA). To investigate microtensile bond strength, composite substrates prepared using Renew A2 composite were light cured either in air or under nitrogen. Light-Core (Bisco, Inc.) was placed on each substrate and light cured. The resulting specimens were sectioned into composite beams and stressed to failure using a microtensile tester (built by Bisco, Inc.). To determine camphorquinone (CQ) decomposition, an experimental CQ resin was placed between two glass plates and irradiated for different time intervals. The absorption spectrum was obtained using a Cary 50 Bio UV-Visible Spectrometer (Varian, Mulgrave, Australia). To explore the degree of conversion, polyester film strips (Mylar, DuPont, Wilmington, DE, USA) coated with the CQ resin were pre-cured in air for different time periods, and then post-cured at low intensity for 5 minutes under nitrogen. A Spectrum 1000FTIR Spectrometer (Perkin Elmer, Norwalk, CT, USA) was used to measure the degree of conversion. RESULTS: Bond strength tests resulted in no significant difference between samples with or without an oxygen-inhibited layer. The oxygen-inhibited layer contained reduced amounts of photoinitiator. The degree of conversion of post-cured oxygen-inhibited layers was lower than that for the control. CONCLUSION: An oxygen-inhibited layer is not necessary for bonding with composite resin. CLINICAL SIGNIFICANCE: It was believed that an oxygen-inhibited layer was required for bonding of composite resin. Studies show that composites bond even in the absence of an oxygen-inhibited layer, including recent products that cure without an oxygen-inhibited layer. With many simplified adhesives, especially self-etching, all-in-one adhesives, the oxygen-inhibited layer is acidic. This acidity interferes with self-curing reactions, making these adhesives incompatible with self-cured composites.