Development of nanobiosilicate, tricalcium phosphate and chlorhexidine materials for biomineralization with crystallographic similarity to hydroxyapatite and biomodified collagen.

OBJECTIVES: The aim of this work is to test experimental cements, doped with a silicate based bioactive nanoparticle (NanoBiosilicate). Methods, we synthesized a glass nanoparticle by Sol-Gel Stöber method, used to be incorporated in a dental material for endodontic uses. MATERIALS AND METHODS: We assess the mineralizing properties and biocompatibility. Besides the crystallography characterization of the resultant new crystals. Results, After analysis, and comparison with commercial materials, the material tested was similar in mechanical properties required by ISO, The ion release was effective after 2 hr. of setting and the novel material was cell compatible accepted by ISO. RESULTS: We found new formed Calcium Phosphate peaks in the spectroscopic analysis (FTIR), remarkably the crystals formed were comparable to hydroxyapatite when analyzed with a Selected Area Electron Diffractometer, with rings of 2.84 Å for 002, and the 2.77 Å is also visible for 210. The 6.83 Å and 6.88 Å, for respective 222 and 004. The incorporation of Chlorhexidine was not detrimental for this property, Significance, the features mentioned represented a progress in biomineralization field that was associated to an improved mineral structure formation with increased crystallographic similarity to natural hydroxyapatite. When chlorhexidine was added a favorable biomodification of the remaining collagen in dentinal walls and antimicrobial activity potential were also observed.

Effect of Er: YAG laser irradiation with additional low energy on resin-dentin bonding and morphology of bonded interface.

OBJECTIVES: To examine the micro tensile bond strength (µTBS) and the resin-dentin interface on a laser-irradiated dentin surface using two different irradiation methods, with or without additional low-energy irradiation. METHODS: The flat bovine dentin surface was divided into three groups: i). control group (C group, no irradiation), ii) 80 mJ/pulse Er: YAG laser group (80 group), iii) 80 + 30 mJ/pulse Er: YAG laser group (80 + 30 group, with an additional 30 mJ/pulse). After the roughness of the dentin surface was recorded, Clearfil SE Bond 2 or Clearfil Universal Bond Quick (Kuraray Noritake Dental Inc., Tokyo, Japan) was applied. After the µTBS testing, the failure mode was observed. The bonded interface was assessed using Rhodamine-dye incorporated adhesives and observed by optical coherence tomography. RESULTS: The dentin surface showed opened dentinal tubules without a smear layer after irradiation. For both adhesives, the µTBS was significantly higher in 80 + 30 group than in the 80 group (p < 0.05). In the 80 group, the thickness of the adhesive layer was not uniform, and the dentin surface was occasionally in direct contact with the composite resin. The failure mode images showed that most of the fractures in the 80 group were at the sub-surface of irradiated dentin. The adhesive layers of the 80 + 30 groups were homogeneous. CONCLUSIONS: The dentin surface was rough and irregular by 80 mJ irradiation, which might result in an inadequate resin-dentin interface and the weak µTBS. The bonded integrity was mitigated by additional irradiation.

Tunable Release of Calcium from Chitosan-Coated Bioglass.

Bioglass presents a standard biomaterial for regeneration of hard tissues in orthopedics and dentistry. The notable osteo-inductive properties of bioglass are largely due to the release of calcium ions from it. However, this release is not easily controllable and can often be excessive, especially during the initial interaction of the biomaterial with the surrounding tissues. Consequently, this excessive release can deplete the calcium content of the bioglass, ultimately reducing its overall bioactivity. In this study, we have tested if applying biopolymer chitosan coatings of different thicknesses would be able to mitigate and regulate the calcium ion release from monodisperse bioglass nanoparticles. Calcium release was assessed for four different chitosan coating thicknesses at different time points over the period of 28 days using a fluorescence quencher. Expectedly, chitosan-coated particles released less calcium as the concentration of chitosan in the coating solution increased, presumably due to the increased thickness of the chitosan coating around the bioglass particles. The mechanism of release remained constant for each coating thickness, corresponding to anomalous, non-Fickian diffusion, but the degree of anomalousness increased with the deposition of chitosan. Zeta potential testing showed an expected increase in the positive double layer charge following the deposition of the chitosan coating due to the surface exposure of the amine groups of chitosan. Less intuitively, the zeta potential became less positive as thickness of the chitosan coating increased, attesting to the lower density of the surface charges within thicker coatings than within the thinner ones. Overall, the findings of this study demonstrate that chitosan coating efficiently prevents the early release of calcium from bioglass. This coating procedure also allows for the tuning of the calcium release kinetics by controlling the chitosan concentration in the parent solution.

Effect of an elastomeric urethane monomer on BisGMA-free resin composites containing different co-initiators.

OBJECTIVES: The aim of this study was to investigate the mechanical, chemical, optical, and adhesive properties of BisGMA-free experimental resin composites containing Exothane-24-an elastomeric urethane monomer-and different co-initiators. MATERIALS AND METHODS: A blend of urethane dimethacrylate (UDMA), extended dimethacrylate urethane (PEG 400), triethylene glycol dimethacrylate (TEGDMA), and camphorquinone was prepared. Two different co-initiators-dimethyl aminoethyl methacrylate (DMAEMA) or 4-N alcohol, N-dimethylamine phenylethyl (DMPOH)-were added to the blend. Exothane-24 monomer was added to the blend for each co-initiator and four groups were established as follows: DMAEMA; DMAEMA + Exothane; DMPOH; and DMPOH + Exothane. Specimens were photo-activated using a multi-wave LED light-curing unit (VALO; 954 mW/cm2 of irradiance). Mechanical (ultimate tensile strength, flexural strength, flexural modulus and hardness), chemical (degree of conversion, hardness reduction, water sorption and solubility), optical (color change), and adhesive (microtensile bond strength) properties were analyzed. Data were submitted to two-way ANOVA and Tukey's test (α = 0.05). RESULTS: The resin composite containing DMPOH and Exothane-24 showed similar or superior performance to those of the other experimental composites for mechanical and chemical properties, except for flexural strength. It also showed less color change and greater micro-tensile bond strength. CONCLUSIONS: Among the combinations tested, the BisGMA-free resin composite containing Exothane-24 combined with the DMPOH co-initiator showed the best mechanical, chemical, optical, and adhesive properties. Clinical relevance Exothane-24 monomer and DMPOH co-initiator could be useful in the formulation of BisGMA-free resin composites in order to minimize exposure to BPA.

Development and characterization of experimental ZnO cement containing niobophosphate bioactive glass as filling temporary material.

AIMS: The aim of this study was to develop and characterize a temporary restorative material based on a zinc oxide matrix containing niobophosphate bioactive glass (NbG) for the caries-affected dentin treatment. MATERIAL AND METHODS: NbG was added to a ZnO2 matrix in different concentrations (wt%). EDS-SEM, ATR-FTIR and XRD analyses were performed to characterize the cement. Calcium release was evaluated in TRIS solution after 1, 7 and 14 days by colorimetric method (A650). Compressive strengths and setting times were performed to analyze mechanical properties. RESULTS: EDS spectra confirmed the presence of Ca, P and Nb in the groups containing NbG. EDS mapping exhibit the ZnO2 homogeneous distribution, and NbG immersed in this matrix. Peaks suggesting interaction between matrix and NbG were not detected in Ftir spectra. Calcium releasing showed to be time-dependent for experimental groups containing 10, 20, 30 and 40%. The NbG incorporation progressively increased the compressive strength values in the experimental groups. NbG incorporation seemed to influence the ZnO2 matrix early setting reaction. No statistical difference was observed in the final setting time. CONCLUSION: The addition of NbG particles into zinc oxide matrix could work as a mechanical reinforcement. It is suggested that the calcium released by the cement containing at least 10% NbG could induce apatite formation.

Cytocompatibility and Synergy of EGCG and Cationic Peptides Against Bacteria Related to Endodontic Infections, in Planktonic and Biofilm Conditions.

This study evaluated the cytocompatibility and antimicrobial/antibiofilm effects of epigallocatechin-3-gallate (EGCG) associated with peptide LL-37 and its analogue KR-12-a5 against oral pathogens. The effect of the compounds on metabolism of fibroblasts was evaluated by methyltetrazolium assays. Antimicrobial activity of the compounds was evaluated on Streptococcus mutans, Enterococcus faecalis, Actinomyces israelii, and Fusobacterium nucleatum under planktonic conditions, on single- and dual-species biofilms and E. faecalis biofilms in dentinal tubules and analyzed by bacterial counts and confocal microscopy. Data were statistically analyzed considering p < 0.05. EGCG and peptide combinations were not toxic to fibroblasts. KR-12-a5 showed synergistic or addictive effects with EGCG and LL-37 against all bacteria tested. However, EGCG associated with KR-12-a5 demonstrated the highest bactericidal activity on all bacteria tested, at lower concentrations. In single-species biofilms, EGCG + KR-12-a5 eliminated S. mutans and A. israelii and reduced E. faecalis and F. nucleatum counts around 5 log CFU/mL. EGCG + KR-12-a5 reduced E. faecalis (-3.93 log CFU/mL) and eliminated S. mutans in dual-species biofilms. No growth of E. faecalis and significant reduction in A. israelii (-6.24 log CFU/mL) and F. nucleatum (-4.62 log CFU/mL) counts were detected in dual-species biofilms. The combination of EGCG and KR-12-a5 led to 88% of E. faecalis dead cells inside dentin tubules. The association of EGCG and KR-12-a5 was cytocompatible and promoted synergistic effect against biofilms of bacteria associated with endodontic infections.

Cytotoxicity and effects of curcumin and cinnamaldehyde hybrids on biofilms of oral pathogens.

The objective of the study was to evaluate the cytotoxicity and effect of curcumin-cinnamaldehyde hybrids (CCHs) on the biofilm of oral pathogens. Of the 18 hybrids tested, nine had an inhibitory effect on at least one of the bacterial species tested, with minimal inhibitory and bactericidal concentrations ranging from 9 to 625 µg ml-1. CCH 7 promoted a potent inhibitory effect against all the bacterial species tested and better compatibility than chlorhexidine (CHX). CCH 7 also presented a similar or improved effect over that of CHX, causing a reduction in bacterial metabolism and viability in single and dual-species biofilms. CCH 7 reduced by 86% and 34% the viability of multispecies biofilms formed by collection and clinical strains. It can be concluded that CCH 7 was cytocompatible at the minimal inhibitory concentration, presented anti-biofilm action against oral pathogens, and could act as an antimicrobial agent for application in endodontics.

Effect of different adhesive strategies and storage time on bond strength of bi-functional monomers to simulated endodontically-treated dentin.

Adhesive strategies were evaluated on the bond strength of bi-functional monomers bonded to endodontically-treated-dentin (ETD). Superficial dentin was removed on human molars. Teeth were immersed in 5 mL 2.5% NaOCl, followed by immersion in 5 mL 17% EDTA. Dentin surface impregnated with epoxy resin-based sealer was then divided four groups (n=10): Scotchbond Multi-Purpose (SBMP); Single Bond Universal (SBU); Optibond All-in-One (OPB); and Tetric-N-Bond Universal (TBU). After 24-h or 1-year-of-storage specimens were submitted to microtensile bond strength (µTBS) and failure classification. A confocal laser scanning microscope (CLSM) evaluated the hybrid layer formation. Two-way ANOVA and Tukey-HSD test were performed (α=5%). The µTBS did not present statistical differences among adhesive strategies after 24-h. Significant differences were found after 1-year-of-storage. CLSM analysis showed water infiltration and consequently degradation of the hybrid layer after 1-year-of-storage. The use of SBU universal adhesive on the self-etching mode on ETD produced more stable bond over the 1-year-of-storage.

Electric current effects on bond strength, nanoleakage, degree of conversion and dentinal infiltration of adhesive systems.

To evaluate the effect of three adhesive systems applied under electric current on microtensile bond strength (µTBS) and degree of conversion (DC). Molar teeth were restored with the aid of three adhesive systems (Adper Single Bond 2-SB2; Clearfil SE Bond-CSE; and Single Bond Universal-SBU) under different electric current intensities (0 µA; 25 µA; and 50 µA). Composite resin blocks were built up in increments (2 mm) and sectioned into 1 × 1 mm beams. The µTBS was tested after 24 h and 1 y distilled water storages. Samples (n = 10) from 24 h to 1 y storages were immersed in a 50% ammoniacal silver nitrate solution and submitted to scanning electron microscopy. The silver nitrate in the hybrid layer was quantified (ImageJ software). The adhesive systems' dentinal infiltration was analyzed using confocal laser scanning microscopy. Fourier transform near infrared spectroscopy was used to measure the DC. The µTBS data were submitted to two-way ANOVA (time vs. electric current) and Bonferroni's test (α = 0.05). Quantitative nanoleakage data were submitted to two-way ANOVA (electric current vs. adhesive) and Bonferroni's test (α = 0.05). DC data were submitted to one-way ANOVA and Tukey's test (α = 0.05) for each adhesive system. The electric current statistically increased the µTBS for SB2 and CSE in 24 h storage, as well as for SB2, CSE and SBU in 1 y storage. No significant difference was observed between storage time for CSE and SBU. When compared to the control, electric currents (25 µA and 50 µA) showed significantly higher DC mean values for SB2 and SBU, and had no effect on CSE. The electric currents (25 µA and 50 µA) reduced the adhesive system's nanoleakage after 1-year storage, and improved the infiltration of SB2 and CSE. Both electric current intensities improved dentinal interface stability.

Resin composite adhesion to dentin using different curing lights and adhesive systems applied under electric current.

OBJECTIVES: To evaluate the effect of electric current application on the resin composite-tooth bond strength and hybrid layer of three adhesive systems light-cured by two light-curing units (LCUs). MATERIALS AND METHODS: Human molar teeth were distributed into 12 groups (n=6). Three adhesive systems were used: two-step etch-and-rinse (SB2; Adper Single Bond 2, 3M ESPE); two-step self-etch (CSE; Clearfil SE Bond, Kuraray); and one-step self-etch (SBU; Single Bond Universal, 3M ESPE) applied with (50µA) and without (control; conventional application) electric current, and light-cured with different LCUs. Resin composite blocks (Filtek Z350XT, 3M ESPE) were produced and cut into sticks (~1mm2) for microtensile bond strength (µTBS). Fracture patterns were analyzed on stereomicroscope and classified as cohesive-dentin, cohesive-resin, adhesive, or mixed. Specimens were prepared for scanning electron microscope observation. The hybrid layer analysis was carried out using a confocal laser scanning microscopy (n=2). Data were submitted to three-way ANOVA followed by Tukey's post hoc test (α=0.05). RESULTS: The electric current increased the µTBS for all adhesive systems light-cured with single-emission peak and multiple-emission peak LCUs. Both LCUs presented similar µTBS values. CSE applied under electric current showed the highest µTBS mean values. The adhesive failure pattern was more frequently observed in all groups. The electric current formed long resin tags for all adhesive systems. CONCLUSIONS: The adhesive systems applied under electric current increased the bond strength using single-emission peak and multiple-emission peak LCUs. CLINICAL RELEVANCE: Electric current at 50µA applied throughout the dentin is a safe mode and results in better impregnation of the adhesive systems.

Do intracanal medications used in regenerative endodontics affect the bond strength of powder-to-liquid and ready-to-use cervical sealing materials?

Aim: This study evaluated the effect of four intracanal medications commonly used in regenerative endodontic procedures on the bond strength of four calcium silicate-based materials, in which two are powder-to-liquid products (MTA and MTA-HP) and the other are ready-to-use materials (EndoSequence Root Repair Material Fast Set Putty [ERRM] and Bioceramic Repair [BIO-C Repair]). Methods: Ten bovine central incisors were selected and 4 slices (1.0 ± 0.1 mm) were prepared from each root. Next, four 0.8-mm wide holes were drilled in each slice and specimens were filled with one of the following intracanal medications: triple antibiotic paste, double antibiotic paste, calcium hydroxide with distilled water, and calcium hydroxide with 2% chlorhexidine gel. After 21 days, holes were filled with one of the materials: MTA, MTA-HP, ERRM, or BIO-C Repair. After storage, push-out test and failure analysis were performed. Data were submitted to analysis of variance in a 4 × 4 factorial scheme. Tukey's test was used for multiple comparisons. Results: The use of different interappointment dressings did not influence the results (P > 0.05). ERRM and BIO-C Repair presented significantly higher values than MTA and MTA-HP (P < 0.0001). Specimens showed a 100% occurrence of adhesive failures. Conclusion: The use of different intracanal medications presented similar impact on bond strength of calcium silicate-based materials. Ready-to-use ERRM and BIO-C Repair materials presented the best push-out values to dentine, whereas powder-to-liquid MTA and MTA-HP cements showed the lowest results.

Is it possible for a simultaneous biomodification during acid etching on naturally caries-affected dentin bonding?

OBJECTIVES: This study investigated the ability of modified phosphoric acids containing chlorhexidine (CHX) or grape seed extract (GSE) for promoting simultaneous biomodification during acid etching on bonding properties in caries-affected dentin (CAD). MATERIALS AND METHODS: Thirty-two human molars (8 with sound dentin [SD] and 24 naturally CAD) were selected for the study. The SD and CAD were initially exposed, then randomized and etched according to the following groups: (1) SD (SD-CT) and CAD (CAD-CT) both with 37% phosphoric acid, (2) CAD with 2% CHX containing 37% phosphoric acid (CAD-CHX), and (3) CAD with 2% GSE containing 10% phosphoric acid (CAD-GSE). The bonding procedure and composite build-ups were performed after acid etching. Subsequently, they were sectioned in resin-dentin specimens. The specimens were submitted for chemical profiling by micro-Raman, microtensile bond strength (µTBS), failure mode with chemical characterization by FEG/SEM-EDX, and in situ zymography by CLSM. The data from µTBS and CLSM were statistically analyzed (1-way ANOVA and Tukey's test; α = 0.05). RESULTS: The highest µTBS results were shown for SD-CT in comparison with all CAD groups (p < 0.001), and the lowest for CAD-CT and CAD-CHX (p < 0.001). The etching with CHX did not increase the µTBS for CAD when compared with CT (p = 0.52). However, the etching with GSE improved significantly the µTBS for CAD when compared with CT and CHX (p < 0.001). The chemical profile detected chemical and structural changes in collagen peaks for CAD-CT, which were not detected when the CAD was etched by modified acids. Also, the poorest hybridization ability was detected in CAD for CT, which was significantly improved with modified acids, especially the GSE, as evaluated by chemical profile and failure mode. A significant reduction of MMP activity on CAD was promoted by modified acids in comparison with CT (both p < 0.001). CONCLUSIONS: The GSE-containing acid was able to promote biomodification during the acid etching, increasing the bonding properties and reducing the activity of the MMPs within the hybrid layer. CLINICAL RELEVANCE: The use of GSE-containing phosphoric acid can be a promising alternative to improve the bonding performance on caries-affected dentin, since it is capable of biomodifying the dentin during the acid etching, without adding any extra step in bonding procedures.

The ability of a nanobioglass-doped self-etching adhesive to re-mineralize and bond to artificially demineralized dentin.

OBJECTIVE: To a self-etch adhesive doped with nano-bioglass and evaluate its ability to bond and re-mineralize artificially demineralized dentin. METHODS: Experimental Si, Ca, Na and PO4 based nanobioglass particles were synthesized, doped into experimental self-etch adhesives, and divided into 3 groups: Clearfi SE2 (CSE2), experimental (EXC), and experimental doped with 10% of nanobioglass (ExNB). The adhesives were applied onto the caries-affected dentin (chemically simulated), and evaluated after 24 h and 28 days of immersion in simulated body fluid. The remineralization process was assessed using optical coherence tomography, nanoindentation, in situ zymography, transmission electron microscopy, confocal laser scanning microscopy, µ-tensile bond strength, and pH buffer. RESULTS: The addition of nanobioglass particles into the experimental self-etch adhesives altered the µTBS in the short-term jeopardizing dentin bonding properties, when compared to the non-doped self-etch adhesive. The remineralization recovered the nanohardness, and volume lost by caries lesion (p = 0.02). Moreover, reduced the enzymatic activity (p = 1.24E-4) and formed new crystals within of the hybrid layer. CONCLUSION: The use of nanobioglass was efficient to recover the properties of a caries affected dentin. Furthermore, the adhesive properties were not hampered and the probabilistic reliability increased.

Effect of Electric Current-assisted Application of Adhesives on their Bond Strength and Quality.

PURPOSE: To assess the effect of the application of different electric currents on dentin bonding and resin infiltration of self-etching and etch-and-rinse adhesives. MATERIALS AND METHODS: Two hundred four sound third molars were selected and divided in groups according to the adhesive (self-etch [CSE, Clearfil SE Bond, Kuraray Noritake], universal [SBU, Single Bond Universal, 3M Oral Care], and etch-and-rinse [SB2, Adper Single Bond 2 (SB2), 3M Oral Care]) and electrical current used (0, 5, 10, 15, 20, 25, 30, and 35 µA). Light curing was performed for 10 s with an LED-curing unit at 1000 mW/cm2. Composite blocks were constructed of nanofilled composite in increments of 2 mm, which were light cured for 20 s. Specimens were sectioned into sticks with a cross-sectional area of ~1 mm2 and stored in distilled water at 37°C for 24 h. Microtensile bond strength (µTBS) testing (n = 8) was performed using a universal testing machine at a crosshead speed of 0.5 mm/min until failure. The bonding quality (n = 2) of adhesives applied with or without 35-µA electric current was evaluated using confocal laser scanning microscopy. Bond strengths were analyzed with two-way ANOVA and Tukey's test (α = 0.05). RESULTS: CSE presented the highest µTBS for all electrical currents tested. For CSE and SBU, electrical currents from 0-20 µA showed the lowest µTBS. Electrical currents from 0-10 and 20-25 µA yielded the lowest µTBS for SB2. CSE and SB2 applied under 35 µA showed a greater number of resin tags in dentin tubules. Fluorescein penetration into the hybrid layer was found for SBU applied without electric current. CONCLUSION: The application of adhesives using 35-µA electric current improved the bond strength and quality of the adhesive interface.

Simplified ethanol wet-bonding technique: an alternative strategy for resin-dentin bonding in root canals.

The objective of this study was to evaluate the effect of the simplified ethanol wet-bonding technique on luting of posts to intraradicular dentin. The effect was assessed by push-out bond strength testing and confocal laser scanning microscopic analysis. Thirty endodontically treated roots were distributed into 3 groups (n = 10): water wet-bonding; stepwise ethanol wet-bonding; and simplified ethanol wet-bonding. After cementation of the posts, the roots were sectioned. Specimens were stored for 24 hours or 1 year before they were stressed to failure. Specimens from each group were processed for microscopic analysis. Data were analyzed using a 2-way analysis of variance and the Tukey test (α = 0.05). Statistically significant differences in push-out bond strength values were observed between the technique groups (P < 0.001) and between the storage periods (P = 0.009). The bond strength results in the group bonded using the simplified ethanol wet-dehydration approach did not differ from those in the group bonded using the stepwise ethanol technique at either storage time interval (P > 0.05). From 24 hours to 1 year, there was a similar decrease in bond strength for specimens prepared with the simplified and stepwise techniques. The microscopic results confirmed that ethanol wet-bonding technique improved the quality of the interface. The simplified ethanol wet-dehydration protocol achieved bond strengths and stability over time that were similar to those obtained with the stepwise ethanol technique and may be considered an alternative strategy to accomplish resin cement-root dentin bonding.

Isolation and characterization of a human cementocyte-like cell line, HCY-23.

Cementum is the mineralized tissue covering the tooth root that functions in tooth attachment and post-eruptive adjustment of tooth position. It has been reported to be highly similar to bone in several respects but remains poorly understood in terms of development and regeneration. Here, we investigate whether cementocytes, the residing cells in cellular cementum, have the potential to be protagonist in cementum homeostasis, responding to endocrine signals and directing local cementum metabolism. Cells from healthy erupted human teeth were isolated using sequential collagenase/EDTA digestions, and maintained in standard cell culture conditions. A cementocyte-like cell line was cloned (HCY-23, for human cementocyte clone 23), which presented a cementocyte compatible gene expression signature, including the expression of dentin matrix protein 1 ( DMP1 ), sclerostin ( SOST ), and E11/gp38/podoplanin ( E11 ). In contrast, these cells did not express the odontoblast/dentin marker dentin sialoprotein ( DSPP ). HCY-23 cells produced mineral-like nodules in vitro under differentiation conditions, and were highly responsive to inorganic phosphate (Pi). Within the limits of the present study, it can be concluded that cementocytes are phosphate-responsive cells, and have the potential do play a key role in periodontal homeostasis and regeneration.

Solvent Degradation and Polymerization Shrinkage Reduction of Resin Composites Using Isobornyl Methacrylate.

The aim of this study was to use the isobornyl methacrylate (IBOMA) as a combining or substituent diluent monomer in the resin matrix of dental resin composites. Thus, the resin matrix was formulated with 60 wt% of BisGMA and 40 wt% of diluent monomers. TEGDMA as the only diluent monomer was used as control with 40 wt%, while total substitution of TEGDMA was done with 40 wt% of IBOMA. The combination of IBOMA and TEGDMA was done with 20 wt% of each monomer. To the resin matrix, 65 wt% of filler particles was added. Degree of conversion (DC) using FT-IR, flexural strength (FS), flexural modulus (FM), polymerization shrinkage by gap formation (GF), Knoop hardness (KH) and solvent degradation (SD) were evaluated. Data were analyzed using ANOVA and Tukey's test (α=0.05; b=0.2). The results showed that reducing or substituting TEGDMA using IBOMA did not affect the DC (0.085), FS (p=0.886) or FM (p=0.414). Also, when IBOMA was used, lower GF was found in comparison to the control containing only TEGDMA as the diluent monomer (p=0.032). However, even though all composites presented reduction in KH during the SD test, the combination of IBOMA and TEGDMA showed similar reduction in KHN in comparison to the control group (p=0.001), while the total substitution of TEGDMA with IBOMA decreased KHN after SD (p=0.041). Thus, the combination of IBOMA and TEGDMA seem to reduce SD and GF without affecting the properties of resin composites.

Degradation of Adhesive-Dentin Interfaces Created Using Different Bonding Strategies after Five-year Simulated Pulpal Pressure.

PURPOSE: To compare after five-year simulated pulpal pressure (SPP) the degradation of adhesive-dentin interfaces created using two simplified adhesives applied with different bonding strategies. MATERIALS AND METHODS: A two-step self-etch (CSE: Clearfil SE Bond) adhesive was used as a control multistep adhesive. The tested experimental materials were two simplified adhesives, a one-step self-etch (CS3: Clearfil S3 Bond) and a self-priming etch-and-rinse adhesive (SB2: Adper Single-Bond 2). Half of the bonded specimens were submitted to microtensile bond strength (µTBS) testing after 24 h. The other half submitted to SPP for five years before µTBS testing. Nonfractured sticks were evaluated using transmission electron microscopy (TEM). Scanning electron microscopy (SEM) was used to evaluate silver-nitrate nanoleakage within the interface. Data were statistically analyzed by two-way ANOVA and Tukey's test (p < 0.05). RESULTS: Prolonged SPP induced bond-strength reduction for both SB2 and CS3. All bonding approaches showed increased nanoleakage after aging. The two simplified adhesives showed severe degradation at the resin-dentin interface. TEM revealed that the main degradation patterns for the etch-and-rinse adhesive SB2 was collagen breakdown, while polymer hydrolysis along with filler debonding was mainly observed in CS3. CONCLUSIONS: Simplified adhesives applied in etch-and-rinse mode are mainly characterized by hydrolysis and collagen degradation. In self-etch mode, simplified adhesives may principally show hydrolysis of the polymeric matrix and/or at the interface of fillers and coupling agent. The use of multistep self-etching adhesives may guarantee greater dentin bond durability compared to simplified adhesives.

Isolation and characterization of a human cementocyte-like cell line, HCY-23

Abstract Cementum is the mineralized tissue covering the tooth root that functions in tooth attachment and post-eruptive adjustment of tooth position. It has been reported to be highly similar to bone in several respects but remains poorly understood in terms of development and regeneration. Here, we investigate whether cementocytes, the residing cells in cellular cementum, have the potential to be protagonist in cementum homeostasis, responding to endocrine signals and directing local cementum metabolism. Cells from healthy erupted human teeth were isolated using sequential collagenase/EDTA digestions, and maintained in standard cell culture conditions. A cementocyte-like cell line was cloned (HCY-23, for human cementocyte clone 23), which presented a cementocyte compatible gene expression signature, including the expression of dentin matrix protein 1 ( DMP1 ), sclerostin ( SOST ), and E11/gp38/podoplanin ( E11 ). In contrast, these cells did not express the odontoblast/dentin marker dentin sialoprotein ( DSPP ). HCY-23 cells produced mineral-like nodules in vitro under differentiation conditions, and were highly responsive to inorganic phosphate (Pi). Within the limits of the present study, it can be concluded that cementocytes are phosphate-responsive cells, and have the potential do play a key role in periodontal homeostasis and regeneration.

A novel dry-bonding approach to reduce collagen degradation and optimize resin-dentin interfaces.

In dentistry, the wet-bonding approach relies on water to maintain demineralized collagen expanded for proper resin infiltration; nevertheless, hydrolytic instability of the resin-dentin interface is inevitable with current bonding techniques. Considering dimethyl sulfoxide's (DMSO) ability to "biomodify" collagen and precipitate enzymes, the aim was to test whether the use of DMSO would permit adequate resin bonding to H3PO4-etched dehydrated dentin and assess its impact on collagen degradation by host-derived enzymes. Etched dentin surfaces from extracted sound human molars were randomly bonded in wet or dry conditions using aqueous or ethanolic DMSO solutions as pretreatments and bonding resins with or without DMSO. Bonded teeth were sectioned into resin-dentin slabs for confocal in situ zymography and beams for microtensile bond strength test. Demineralized powdered dentin was incubated in the tested DMSO -media and a hydroxyproline assay evaluated dissolution of collagen peptides. Zymography was performed on protein extracts obtained from dry and wet H3PO4-ecthed dentin powder treated with the DMSO- media. The correlative biochemical analysis demonstrated that reduction of water content during dentin hybridization by the innovative dry-bonding approaches with DMSO is effective to inactivate host-derived MMP-2 and MMP-9 and thus reduce collagen degradation while simultaneously optimizing resin-dentin bonding.