The present study evaluated the effectiveness of a dicalcium and tetracalcium phosphate-based desensitizer in reducing dentin permeability in vitro. Dentin fluid flow was measured before and after ...treatment of dentin with patent dentinal tubules using 1 or 3 applications of the dicalcium and tetracalcium phosphate containing agent TeethmateTM (TM) and comparing the results with two sodium fluoride varnishes VellaTM (VLA) and VanishTM (VAN), after storage in artificial saliva for 24 h, 48 h and 7 days. Significant differences were observed among the 4 methods employed for reducing dentin permeability (p < 0.001) and the 3 post-treatment times (p < 0.001). VLA and VAN never achieved 50% permeability reductions consistently in any of the 3 time periods. Only the calcium phosphate-based desensitizer applied for 3 times consistently reduced dentin permeability by 50% after 24 h. When applied once, the permeability reduction of TM increased progressively over the 3 time periods. After 7 days, only one and three applications of the calcium phosphate-based desensitizer consistently reduced dentin permeability by more than 50%. Permeability reductions corresponded well with scanning electron microscopy examination of dentinal tubule orifice occlusion in dentin specimens treated with the agents. Overall, the dicalcium and tetracalcium phosphate-based desensitizer is effective in reducing dentin permeability via a tubule occlusion mechanism. The ability of the agent to reduce dentin permeability renders it to be potentially useful as a clinical dentin desensitizing agent, which has to be confirmed in future clinical studies. By contrast, the two sodium fluoride varnishes are not effective in dentin permeability reduction and should be considered as topical fluoride delivering agents rather than tubular orifice-blocking agents.
Abstract Objective This work measured the amount of bound versus unbound water in completely-demineralized dentin. Methods Dentin beams prepared from extracted human teeth were completely ...demineralized, rinsed and dried to constant mass. They were rehydrated in 41% relative humidity (RH), while gravimetrically measuring their mass increase until the first plateau was reached at 0.064 (vacuum) or 0.116 g H2 O/g dry mass (Drierite). The specimens were then exposed to 60% RH until attaining the second plateau at 0.220 (vacuum) or 0.191 g H2 O/g dry mass (Drierite), and subsequently exposed to 99% RH until attaining the third plateau at 0.493 (vacuum) or 0.401 g H2 O/g dry mass (Drierite). Results Exposure of the first layer of bound water to 0% RH for 5 min produced a −0.3% loss of bound water; in the second layer of bound water it caused a −3.3% loss of bound water; in the third layer it caused a −6% loss of bound water. Immersion in 100% ethanol or acetone for 5 min produced a 2.8 and 1.9% loss of bound water from the first layer, respectively; it caused a −4 and −7% loss of bound water in the second layer, respectively; and a −17 and −23% loss of bound water in the third layer. Bound water represented 21–25% of total dentin water. Chemical dehydration of water-saturated dentin with ethanol/acetone for 1 min only removed between 25 and 35% of unbound water, respectively. Significance Attempts to remove bound water by evaporation were not very successful. Chemical dehydration with 100% acetone was more successful than 100% ethanol especially the third layer of bound water. Since unbound water represents between 75 and 79% of total matrix water, the more such water can be removed, the more resin can be infiltrated.
Abstract Objective To determine if acid-etched, cross-linked dentin can be dehydrated without lowering bond strength below that of cross-linked wet-bonded dentin in vitro. Methods Using extracted ...human third molars, control acid-etched dentin was bonded with Single Bond Plus, using either the wet- or dry-bonding technique. Experimental acid-etched dentin was treated with 5 mass% grape seed extract (GSE) in different solvents for 1 min before undergoing wet vs dry resin-dentin bonding with Single Bond Plus. Completely demineralized dentin beams were treated with 5% GSE for 0, 1 or 10 min, before measuring stiffness by 3-point flexure. Other completely demineralized beams were treated similarly and then incubated in buffer for 1 week to measure the collagen solubilization by endogenous dentin proteases. Results 24 h microtensile bond strengths (μTBS) in wet and dry controls were 53.5 ± 3.6 and 9.4 ± 1.8 MPa, respectively ( p < 0.05). 5% GSE in water gave μTBS of 53.7 ± 3.4 and 39.1 ± 9.7 MPa ( p < 0.05), respectively, while 5% GSE in ethanol gave μTBS of 51.2 ± 2.3 and 35.3 ± 2.0 MPa ( p < 0.05). 5% GSE in 5% EtOH/95% water gave wet and dry μTBS of 53.0 ± 2.3 and 55.7 ± 5.1 MPa ( p > 0.05). Cross-linking demineralized dentin with 5% GSE increased stiffness of dentin and decreased collagen degradation ( p < 0.05). Significance 5% GSE pretreatment of acid-etched dentin for 1 min permits the dentin to be completely air-dried without lowering bond strength.
Abstract Objective The general aim of this article is to describe the state-of-the-art of biocompatibility testing for dental materials, and present new strategies for improving operative dentistry ...techniques and the biocompatibility of dental materials as they relate to their interaction with the dentin–pulp complex. Methods The literature was reviewed focusing on articles related to biocompatibilty testing, the dentin–pulp complex and new strategies and materials for operative dentistry. For this purpose, the PubMed database as well as 118 articles published in English from 1939 to 2014 were searched. Data concerning types of biological tests and standardization of in vitro and in vivo protocols employed to evaluate the cytotoxicity and biocompatibility of dental materials were also searched from the US Food and Drug Administration (FDA), International Standards Organization (ISO) and American National Standards Institute (ANSI). Results While there is an ongoing search for feasible strategies in the molecular approach to direct the repair or regeneration of structures that form the oral tissues, it is necessary for professionals to master the clinical therapies available at present. In turn, these techniques must be applied based on knowledge of the morphological and physiological characteristics of the tissues involved, as well as the physical, mechanical and biologic properties of the biomaterials recommended for each specific situation. Thus, particularly within modern esthetic restorative dentistry, the use of minimally invasive operative techniques associated with the use of dental materials with excellent properties and scientifically proved by means of clinical and laboratory studies must be a routine for dentists. This professional and responsible attitude will certainly result in greater possibility of achieving clinical success, benefiting patients and dentists themselves. Significance This article provides a general and critical view of the relations that permeate the interaction between dental materials and the dentin–pulp complex, and establish real possibilities and strategies that favor biocompatibility of the present and new products used in Dentistry, which will certainly benefit clinicians and their patients.
Abstract Objectives To evaluate the effect of EDC on elastic modulus (E), MMPs activity, hydroxyproline (HYP) release and thermal denaturation temperature of demineralized dentin collagen. Methods ...Dentin beams were obtained from human molars and completely demineralized in 10 wt% H3 PO4 for 18 h. The initial E and MMP activity were determined with three-point bending and microcolorimetric assay, respectively. Extra demineralized beams were dehydrated and the initial dry mass (DM) was determined. All the beams were distributed into groups ( n = 10) and treated for 30 s or 60 s with: water, 0.5 M, 1 M or 2 M EDC or 10% glutaraldehyde (GA). After treatment, the new E and MMP activity were redetermined. The beams submitted to DM measurements were storage for 1 week in artificial saliva, after that the mass loss and HYP release were evaluated. The collagen thermal denaturation temperature (TDT) was determined by DSC analysis. Data for E, MMP activity and HYP release were submitted to Wilcoxon and Kruskal–Wallis or Mann–Whitney tests. Mass loss and TDT data were submitted to ANOVA and Tukey tests at the 5% of significance. Results EDC was able to significantly increase collagen stiffness in 60 s. 10% GA groups obtained the highest E values after both 30 and 60 s. All cross-linking agents decreased MMP activity and HYP release and increased TDT temperature. Significant differences were identified among EDC groups after 30 or 60 s of cross-linking, 1 M or 2 M EDC showed the lowest MMP activity. Significance Cross-linking agents are capable of preventing dentin collagen degradation. EDC treatment may be clinically useful to increase resin-dentin stability.
Abstract Objective The objective of this study was to determine if Gluma dentin desensitizer (5.0% glutaraldehyde and 35% HEMA in water) can inhibit the endogenous MMPs of dentin matrices in 60 s and ...to evaluate its effect on dentin matrix stiffness and dry mass weight. Methods Dentin beams of 2 mm × 1 mm × 6 mm were obtained from extracted human third molars coronal dentin. To measure the influence of Gluma treatment time on total MMP activity of dentin, beams were dipped in 37% phosphoric acid (PA) for 15 s and rinsed in water. The acid-etched beams were then dipped in Gluma for 5, 15, 30 or 60 s, rinsed in water and incubated into SensoLyte generic MMP substrate (AnaSpec, Inc.) for 60 min. Controls were dipped in water for 60 s. Additional beams of 1 mm × 1 mm × 6 mm were completely demineralized in 37% PA for 18 h, rinsed and used to evaluate changes on the dry weight and modulus of elasticity ( E ) after 60 s of Gluma treatment followed by incubation in simulated body fluid buffer for 0, 1 or 4 weeks. E was measured by 3-pt flexure. Results Gluma treatment inhibited total MMP activity of acid-etched dentin by 44, 50, 84, 86% after 5, 15, 30 or 60 s of exposure, respectively. All completely demineralized dentin beams lost stiffness after 1 and 4 weeks, with no significant differences between the control and Gluma-treated dentin. Gluma treatment for 60 s yielded significantly less dry mass loss than the control after 4 weeks. Significance The use of Gluma may contribute to the preservation of adhesive interfaces by its cross-linking and inhibitory properties of endogenous dentin MMPs.
Improved stability of the adhesive interface can be obtained using crosslinkers. However, research on the use of crosslinkers in root dentin is lacking.
The purpose of this in vitro study was to ...evaluate the effect of crosslinkers on the proteolytic activity of root dentin and on the bond strength of resin-cemented fiber posts.
Single root canals were obtained from premolars (n=48) and endodontically treated before being divided into 4 groups: deionized water (control), 0.5 mol/L carbodiimide, 5% proanthocyanidin, or 5% glutaraldehyde. After removing the canal sealer, the dentin was etched with phosphoric acid, followed by water rinsing and the application of the crosslinkers for 60 seconds. Fiber posts were cemented using an adhesive (Single Bond 2) and resin cement (RelyX ARC). The roots were then transversally sectioned to obtain 1 mm thick specimens from the cervical, middle, and apical thirds and then aged for 24 hours or 9 months. Nine roots per group were used for the push-out test and 3 for determining the proteolytic activity of the root dentin by in situ zymography. Bond strength data were submitted to a mixed-model ANOVA and Bonferroni tests (α=.05).
Only proanthocyanidin negatively affected the 24-hour bond strength. After 9 months, a significant decrease in bond strength was seen for all groups, except for the crosslinked treated specimens from the cervical third of the root canal. Intense gelatinolytic activity was detected in the control group after 24 hours but was inhibited in the crosslinker-treated groups. Proteolytic activity was also not detected after 9 months for the groups treated with the crosslinkers, irrespective of the root canal third. Conversely, proteolytic activity increased for the specimens from the control group.
Although no proteolytic activity was detected in the hybrid layers along the entire root canal, dentin biomodification with crosslinkers was effective in preventing bond strength loss only in the cervical third.
To evaluate the transdentinal cytotoxicity of three different concentrations of carbodiimide (EDC) or 5% glutaraldehyde (GA) on MDPC-23 cells.
Seventy 0.4-mm-thick dentin disks obtained from human ...molars were adapted to artificial pulp chambers. MDPC-23 cells were seeded on the pulpal surface of the disks. After 48 hours, the occlusal dentin was acid-etched and treated for 60 seconds with one of the following solutions (n=10): no treatment (negative control); 0.1 M, 0.3 M, or 0.5 M EDC; 5% GA; Sorensen buffer; or 29% hydrogen peroxide (positive control). Cell viability and morphology were assessed by methyltetrazolium assay and scanning electron microscopy (SEM), respectively. The eluates were collected after the treatments and applied on MDPC-23 seeded in a 24-well plate to analyze cell death, total protein (TP), and collagen production. The last two tests were performed 24 hours and seven days after the challenge. Data were analyzed by Kruskal-Wallis and Mann-Whitney tests (p<0.05).
EDC at all test concentrations did not reduce cell viability, while 5% GA did increase cell metabolism. Cell death by necrosis was not elicited by EDC or 5% GA. At the 24-hour period, 0.3 M and 0.5 M EDC reduced TP production by 18% and 36.8%, respectively. At seven days, increased TP production was observed in all groups. Collagen production at the 24-hour period was reduced when 0.5 M EDC was used. After seven days, no difference was observed among the groups. SEM showed no alteration in cell morphology or number, except in the hydrogen peroxide group.
Treatment of acid-etched dentin with EDC or GA did not cause transdentinal cytotoxic effects on odontoblast-like cells.
This study evaluated the long-term effect of carbodiimide treatments of acid-etched dentin on resin-dentin bond strength of a simplified etch-and-rinse adhesive system.
Forty-eight sound third molars ...were divided into three groups (n=16) according to the dentin treatment: G1: deionized water; G2: 0.5 mol/L 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) applied for 30 seconds; and G3: 0.5 mol/L EDC applied for 60 seconds. Flat dentin surfaces were produced, etched with 37% phosphoric acid for 15 seconds, and then treated with deionized water for 60 seconds or with 0.5 mol/L EDC for 30 or 60 seconds prior to the application of Single Bond 2. Crowns were restored with resin composite, and beam specimens were prepared for microtensile testing. The beams from each group were tested 24 hours or 6 or 12 months after the adhesive procedures. One slab from each tooth was prepared and analyzed for nanoleakage. Bond strength (MPa) data were submitted to analysis of variance and Tukey test (α=0.05).
The treatment of dentin with 0.5 mol/L EDC for 30 seconds (24.1±6.2 MPa) and 60 seconds (25.5±5.1 MPa) did not negatively affect the immediate bond strength of Single Bond 2 when compared to the control group (24.6±7.3 MPa). Additionally, EDC prevented resin-dentin bond degradation after 12 months in artificial saliva for both periods of treatment. An increased accumulation of silver ions was seen for the control group over time, while a much lower amount of silver grains was observed for the EDC-treated groups.
0.5 mol/L EDC was able to prevent resin-dentin bond degradation after 12 months, especially when applied for 60 seconds.
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