Evaluation of dentin desensitization protocols on the dentinal surface and their effects on the dentin bond interface

Effect of irrigation acid solutions on cleaning and bond strength to post-space dentin

This study evaluated the effects of irrigating solutions containing 5% boric acid + 1% citric acid or 1% peracetic acid + high concentration hydrogen peroxide on root cleaning and bond strength of cementation systems after 24 h and 6 months of glass fiber post cementation. One hundred and twenty roots were endodontically treated. The specimens were randomized into one of four treatments (n = 10): DW (distilled water); NaOCl2.5% + EDTA17% (2.5% sodium hypochlorite solution + 17% EDTA); PA1% + HP (1% peracetic acid solution + high concentration of hydrogen peroxide); BA5% + CA1% (5% boric acid associated with 1% citric acid). The cleaning efficacy in the cervical, middle, and apical thirds of the post-space, and the push-out bond strength at 24 h and 6 months after post cementation were evaluated by Kruskal-Wallis and two-way ANOVA tests, respectively. BA5% + CA1% showed statistically significantly superior cleaning efficacy compared to the other solutions. This irrigation protocol also resulted in higher bond strength at 24 h and 6 months, regardless of the root third considered, and this was statistically significantly higher than those seen for DW and PA1% + HP. For BA5% + CA1% irrigation protocol, type 1 adhesive failure was the most prevalent. Post-space irrigation with BA5% + CA1% provided both higher cleaning efficacy and better bond strength.

Effect of Remineralization Pretreatments on Human Dentin Permeability and Bond Strength

This study aimed to evaluate Nd:YAG laser, calcium phosphate, and adhesive system effect as different pretreatments in different protocols on dentin permeability (DP) and bond strength (BS). Fifty human dentin discs were used (4 mm in diameter and 1,5 mm in height). Specimens were divided into five groups (n = 10): (A): adhesive system (control); (AL): adhesive system + Nd:YAG laser; (LAL): Nd:YAG laser + adhesive system + Nd:YAG laser; (PAL): calcium phosphate-based dentin desensitizer TeethMate + adhesive system + Nd:YAG laser; and group (PLAL): Nd:YAG laser + calcium phosphate-based dentin desensitizer + adhesive system + Nd:YAG laser. All materials were used according to the manufacturers' instructions. The specimens were submitted to artificial aging (5,000 thermal cycles and 12 × 10⁴ mechanical cycles) then a bond test was performed. DP was measured using the split chamber model. Data were submitted to one-way analysis of variance (ANOVA), paired t-test, RM ANOVA, and Tukey test (p < 0.05). All treatments were effective in DP reduction. For BS, the groups PAL and PLAL had improved BS with a statistically significant difference of the control group (A). Nd:Yag laser irradiation and calcium phosphate-based desensitizing agents significantly reduced DP, and the association between them could improve the BS on resin-human dentin interface.

Influence of calcium-based desensitizing toothpastes on the bonding performance of universal adhesive

The study evaluated the effect of calcium-based desensitizing toothpastes on the dentinal tubule occlusion and its influence on the dentin bond strength of universal adhesive. Mid-coronal dentin samples were prepared for hypersensitivity model and treated by the following calcium-based desensitizing toothpastes: no treatment (Control), Clinpro (fTCP), Pro-Relief (Pro-Argin), and Repair & Protect (Novamin). Single Bond Universal adhesive was applied in self-etch or etch-and-rinse mode. The dentinal tubule occlusion and adhesion interface were evaluated under scanning electron microscope (SEM). A double-fluorescence technique was used to examine interfacial permeability under confocal laser scanning microscopy (CLSM). The micro-tensile bond strength (μTBS) was employed, followed by the fracture interface observation. SEM showed the toothpastes occluded dentinal tubules, and the occlusion exhibited stability against acid and abrasion. Hindered resin infiltration was observed in the adhesion interface after desensitization. CLSM showed more water permeation within or under the adhesion interface in etch-and-rinse mode than self-etch mode. Desensitization decreased the μTBS in self-etch mode. When using etch-and-rinse mode, the desensitized samples presented similar μTBS to the control group. No difference in μTBS was found between the two bonding modes, except for the control group. Calcium-based desensitizing toothpastes can effectively occlude the exposed dentinal tubules with acid-resistant and abrasion-resistant stability. The desensitization reduced the dentin bond strength of the universal adhesive system in self-etch mode but did not affect the bond strength of etch-and-rinse mode.

The effect of desensitizing agents on the bond strength of dentin bonding agents: A systematic review

Background

Dentinal hypersensitivity (DH) is a common dental problem and is treated non-invasively using topical application of various desensitizing agents. When there is loss of tooth structure or tooth preparation is to be followed by a bonded restoration, it requires application of dentin bonding agent. However, the effect of desensitizers on bond strength is still controversial.

Aim and Objective

To evaluate the influence of different desensitizing agents on the bond strength of the dentin bonding agents.

Methods and Materials

PICO strategy was used to formulate the research question. In-vitro studies conducted on human teeth to evaluate the bond strength of dentin bonding agent following the application of desensitizing agent were included. Electronic databases PubMed and Cochrane and google scholar were searched using search terms alone or in combination from the year 2010 till 2020. Search was conducted using the key words and MeSH terms (hypersensitivity, bond strength, dental adhesives, dentin bonding agents). The title and abstract were read to verify the inclusion and exclusion criteria and if further any details required, full article was accessed to check the criteria and then included or excluded. Data extraction was done using a customized data extraction form. The risk of bias was evaluated using modified Cochrane Collaboration Quality Assessment tool.

Results

Total no of studies identified in the search were 146, after scrutiny 23 articles were eligible to be included in this study. Out of 23 articles, 17 articles were of medium bias and 6 articles were of high risk after risk of bias assessment.

Conclusion

According to the various articles included in this study, GLUMA and 8.0%Arginine and CaCO3 when used as desensitizing agents along with different bonding agents, were found to be highly compatible without interfering with the bond strength of the dentin adhesives.

Cleaning and microstructural effects of amyl acetate on pulp chamber dentin impregnated with epoxy resin-based endodontic sealer

OBJECTIVE

To evaluate the cleaning potential of 95% ethanol, acetone, and amyl acetate solutions used solely or in association, to remove epoxy resin-based sealer residues from pulp chamber dentin and their microstructural effects.

MATERIALS AND METHODS

One hundred and eighty bovine incisor specimens were divided into nine groups according to the cleaning protocol: ET (ethanol); AC (acetone); AA (amyl acetate); E1: AA+AC; E2: AA+ET; E3: AC+ET; E4: AA+AC+ET; PC (positive control), and NC (negative control). All groups were impregnated with epoxy resin-sealer, except NC. Ninety specimens were divided into groups (n = 10) for evaluation of persistence of residues and amount of open dentinal tubules by SEM analysis and evaluation of chemical compounds on the dentin surface after cleaning with electron dispersive spectroscopy. The others 90 specimens were submitted to Knoop microhardness evaluation. Persistence of residues data were submitted to the Kruskal Wallis and Dunn tests (α = 0.05). Open dentinal tubules and microhardness data were submitted to one-way ANOVA and Mann Whitney tests (α = 0.05).

RESULTS

AA and E4 protocols showed the lowest persistence of residues. E4 group had the highest incidence of open dentinal tubules. E3 and E4 groups showed no changes in the atomic ratio Ca/P, which was similar to NC group. E4 group did not present W, an element presents in all the other groups. ET and E4 protocols showed the smallest reduction in dentin microhardness.

CONCLUSIONS

The combination of amyl acetate, acetone and ethanol is the most effective and safe protocol to remove epoxy sealer residues on pulp chamber dentin. Moreover, it has the lowest microhardness reduction.

CLINICAL SIGNIFICANCE

The combined use of amyl acetate, acetone, and ethanol enhanced the cleaning of pulp chamber dentin with minimal microstructural damage.

Effect of irrigation protocols on chemical smear layer formation over the post-space dentin

This study evaluated the effect of irrigation protocols using 95% ethanol (ET) or 1% peracetic acid (PA) prior the use of 2% chlorhexidine (CHX) compared to distilled water (DW) on the chemical smear layer (CSL) formation and incidence of open dentin tubules at the apical, medium, and cervical third of the post-space dentin. Scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS) images were used. Forty bovine roots were endodontically treated. After, post-space preparation was performed and the roots were randomized in four groups (n = 10) according to the irrigation protocol: DW, CHX, CHX-ET and CHX-PA. The chemical composition of CSL and the incidence of open dentin tubules at the post-space thirds were evaluated by EDS (500× magnification) and SEM (2000× magnification) images, respectively. Data from chemical composition of CSL were descriptively analyzed, while the incidence of open dentin tubules was evaluated by scores and submitted to Kruskal-Wallis and Dunn test (p = .05). Cl, Bi, and Si were the chemical elements most found over the dentin after the irrigation with CHX and CHX-ET. Moreover, CHX and CHX-ET showed the highest incidence of CSL (p < .05), but without difference between them (p > .05), regardless of the post-space third. DW and CHX-PA showed similar incidence of CSL (p > .05). No difference on the incidence of open dentin tubules was found for any irrigation protocol and post-space third (p > .05). The use of 1% PA prior the post-space irrigation with CHX decrease the incidence of CSL. RESEARCH HIGHLIGHTS: The post-space irrigation with chlorhexidine results in the formation of chemical smear layer. Ethanol is not capable to remove the chemical smear layer. Peracetic acid is more effective to remove the chemical smear layer.

Applications of scanning electron microscopy and focused ion beam milling in dental research

The abilities of scanning electron microscopy (SEM) and focused ion beam (FIB) milling for obtaining high-resolution images from top surfaces, cross-sectional surfaces, and even in three dimensions, are becoming increasingly important for imaging and analyzing tooth structures such as enamel and dentin. FIB was originally developed for material research in the semiconductor industry. However, use of SEM/FIB has been growing recently in dental research due to the versatility of dual platform instruments that can be used as a milling device to obtain low-artifact cross-sections of samples combined with high-resolution images. The advent of the SEM/FIB system and accessories may offer access to previously inaccessible length scales for characterizing tooth structures for dental research, opening exciting opportunities to address many central questions in dental research. New discoveries and fundamental breakthroughs in understanding are likely to follow. This review covers the applications, key findings, and future direction of SEM/FIB in dental research in morphology imaging, specimen preparation for transmission electron microscopy (TEM) analysis, and three-dimensional volume imaging using SEM/FIB tomography.

Effect of mechanical cleaning protocols in the fiber post space on the adhesive interface between universal adhesive and root dentin

The aim of this study was to evaluate the effects of cleaning protocols on the presence of residues, open dentinal tubules, and bond strength of a self-etch adhesive plus a dual-cure resin cement to dentin in the fiber-post space. The methods for cleaning utilized were conventional irrigation (CI), rotary brush with continuous rotary movement (RB), and continuous ultrasonic irrigation (CUI). Sixty bovine incisors were used for fiber-post space preparation. Thirty roots were divided into three groups (n = 10) according to the cleaning protocols and submitted to scanning electron microscope to evaluate presence of residues and relative quantity of open dentinal tubules on dentin surface. Similar protocols were performed in the other thirty roots (n = 10) using a self-etching adhesive system (Scotchbond Universal) and a dual-cure resin cement (Relyx Unicem 2). After 6 months cervical, middle, and apical thirds sections of fiber-post space were submitted to push-out testing. To data ANOVA and Tukey's test were employed (α = 5%). RB and CUI showed the lowest presence of residues on dentin surface (p = .015) and the highest bond strength values (p < .001), regardless of the dentin third. CUI presented the highest quantity of open dentinal tubules in middle and apical thirds (p < .001). CI presented the lowest bond strength value of resin cement, regardless of dentin third (p < .001). Mechanical cleaning protocols, such as RB and CUI, presented better surface cleaning capabilities and higher bond strength than CI with dual-cure resin cement employed. The use of a mechanical cleaning protocol seems to cause appropriate condition on the root dentin surface. Mechanical cleaning of root dentin provided greater bond strength of the self-etching system with dual resin cement. Conventional irrigation did not provide adequate root dentin cleaning.

The Effect of Dentin Treated with Calcium Phosphate Desensitizer on Shear Bond Strength with Different Resin Cement: An In Vitro Study

Aim:

The aim of this study was to evaluate the effect of calcium phosphate based desensitizing agent on shear bond strength of self-etch/adhesive resin cements to dentin.

Materials and Methods:

Eighty dentin specimens were prepared from freshly extracted human third molar teeth and were classified, randomly ( n = 20). Half of groups were treated with calcium phosphate based Teethmate Desensitizer and then Panavia V5, RelyX Ultimate (containing self-etch primer), Panavia SA, and RelyX U200 self-adhesive resin cements were luted to all dentin surfaces. All specimens were stored in an incubator at 37°C for 24 h. Shear bond strength was tested by a universal test machine at a 0.5 mm/min crosshead speed. The data were analyzed with a statistical program. Two-way ANOVA was used for statistical differences ( P <.05). Dentin surfaces were examined with scanning electron microscopy (SEM) at x5000 and x10000 magnifications.

Results:

The higher shear bond values were observed in the groups with Teethmate Desensitizer applied and cemented with self-etch (16.05 ± 6.24 and 14.73 ± 4.75), whereas the lowest bonding values were observed in the groups with self-adhesive resin cement without Teethmate Desensitizer (3.73 ± 0.77 and 5.85 ± 4.19; P <.001). As the main effect of the treatment, the bond strength was 9.39 ± 6.04 in the control group, whereas it was 13.49 ± 5.44 in the Teethmate applied groups ( P <.05)

Conclusions:

Calcium phosphate desensitizer did not adversely effected shear bond strength of self-etch/adhesive resin cements to dentin. It even significantly increased the shear bond strength of self-adhesive resin cements.

Effects of Remineralizing Agents Based on Calcium Phosphate, Sodium Phosphate, or Sodium Fluoride on Eroded Cervical Dentin

OBJECTIVES

To evaluate the effect of remineralizing agents on collagen matrix pattern, precipitate formation, and dentinal tubule obliteration in eroded cervical dentin.

METHODS AND MATERIALS

One hundred bovine cervical dentin specimens were previously eroded (0.6% hydrochloric acid, pH 2.3, 5 minutes) and then randomized into five groups (n=20): G1, control (without treatment); G2, Desensibilize Nano P (FGM); G3, MI Paste Plus (Recaldent); G4, Regenerate (NR-5); and G5, Desensibilize KF 2% (FGM). These treatments were applied in four sessions with 7-day intervals. During this period, the samples were subjected to an erosive challenge with orange juice (pH 3.8, 5 minutes). The specimens were analyzed by polarized light microscopy with picrosirius red staining, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX).

RESULTS

The G3 showed a higher concentration of type I collagen than G2 and G5 (p<0.05). The G3 showed greater formation of surface precipitates than that of G1 and G5 (p<0.05). In addition, G4 and G5 showed a greater number of open dentinal tubules than that of G3 (p<0.05).

CONCLUSIONS

Calcium phosphate-based remineralizing agents have shown to be a promising alternative treatment for preventing deleterious effects on the eroded dentin collagen matrix. In addition, they promoted precipitate formation and dentinal tubule obliteration on the eroded dentin.

Bonding Performance of Universal Adhesives Applied to Nano-Hydroxyapatite Desensitized Dentin Using Etch-and-Rinse or Self-Etch Mode

The study assessed the bonding performance of three universal adhesives on desensitized dentin with etch-and-rinse mode or self-etch mode after nano-hydroxyapatite (nHAp)-based desensitizers application. Simulated sensitive dentin specimens were prepared and separated into four groups: no treatment as the negative control, groups desensitized by Biorepair toothpaste, Dontodent toothpaste, or nHAp paste. Three universal adhesives of All-Bond Universal, Single Bond Universal, and Clearfil Universal Bond with etch-and-rinse or self-etch mode were bonded to the desensitized dentin specimens separately, followed by resin composite build-ups. Micro-tensile bond strength was measured using a micro-tensile tester. The wettability of desensitized dentin was evaluated by the contact angle of the adhesives. Resin infiltration was observed by confocal laser scanning microscopy. Dentin tubular occlusion and nanoleakage were observed by scanning electron microscope. The results showed that the etch-and-rinse or self-etch mode of each adhesive showed similar bond strength when bonding to nHAp-based desensitized dentin. The dentin surface was partially covered by desensitizers after desensitization. Compared with the self-etch mode, stronger demineralization and more reopened dentin tubules were observed in the etch-and-rinse mode after acid etching; longer resin tags and more nanoleakage in the resin-dentin interface were observed when using the etch-and-rinse mode. When bonding to nHAp-based desensitized dentin with universal adhesives, no significant difference in bond strength was found between self-etch mode or etch-and-rinse mode; while the latter produced more nanoleakage in the resin-dentin interfaces.

Analysis of permeability and biological properties of dentin treated with experimental bioactive glasses

OBJECTIVES

To evaluate obliterating capability and biological performance of desensitizing agents.

METHODS

50 dentin blocks were distributed according to the desensitizing agent used (n = 10): Control (Artificial saliva); Ultra EZ (Ultradent); Desensibilize Nano P (FGM); T5-OH Bioactive Glass (Experimental solution); F18 Bioactive Glass (Experimental solution). Desensitizing treatments were performed for 15 days. In addition, specimens were subjected to acid challenge to simulate oral environment demineralizing conditions. Samples were subjected to permeability analysis before and after desensitizing procedures and acid challenge. Cytotoxicity analysis was performed by using Alamar Blue assay and complemented by total protein quantification by Pierce Bicinchoninic Acid assay at 15 min, 24-h and 48-h time points. Scanning electron microscopy and energy dispersion X-ray spectroscopy were performed for qualitative analysis. Data of dentin permeability was analyzed by two-way repeated measures ANOVA and Tukey's test. For cytotoxicity, Kruskal-Wallis and Newman-Keuls tests.

RESULTS

for dentin permeability there was no significant difference among desensitizing agents after treatment, but control group presented highest values (0.131 ± 0.076 Lp). After acid challenge, control group maintained highest values (0.044 ± 0.014 Lp) with significant difference to other groups, except for Desensibilize Nano P (0.037 ± 0.019 Lp). For cytotoxicity, there were no significant differences among groups.

CONCLUSION

Bioglass-based desensitizers caused similar effects to commercially available products, regarding permeability and dentin biological properties.

CLINICAL SIGNIFICANCE

There is no gold standard protocol for dentin sensitivity. The study of novel desensitizing agents that can obliterate dentinal tubules in a faster-acting and long-lasting way may help meet this clinical need.

Effect of irrigation protocol during post space preparation on the dentin adhesive interface: An in vitro study

STATEMENT OF PROBLEM

The post space must be prepared with techniques that do not interfere with the bond strength. These techniques are related to the availability of opened dentinal tubules and incidence of residue among the dentin, the adhesive, and the cement. Nevertheless, the effect of different irrigants during endodontic instrumentation is unclear.

PURPOSE

The purpose of this in vitro study was to assess the incidence of residue, the number of opened dentinal tubules, and the bond strength of the cementation system to root dentin of post space after 3 different irrigation protocols.

MATERIAL AND METHODS

The roots of bovine incisors were obturated, prepared to receive a fiber post, and divided into 3 groups as per the irrigation protocol: without irrigation, with alternating irrigation, and with continuous irrigation. Thirty roots (n=10) were evaluated by using scanning electron microscopy to assess the incidence of residue (×100 magnification) and the number of opened dentinal tubules (×2000 magnification). The fiber posts were cemented, and the remaining specimens (n=10) were subjected to pushout testing and failure mode evaluation.

RESULTS

All protocols presented a similar incidence of residue, regardless of the post space third (P>.05). The irrigation protocol without irrigation had the lowest number of opened dentinal tubules in the cervical and middle thirds (P<.05). The number of opened dentinal tubules was similar in all protocols in the apical third of the post space (P>.05). The irrigation protocol without irrigation had the lowest bond strength values in the cervical and middle thirds (P<.05). The irrigation protocol with continuous irrigation had the highest bond strength values in the apical third (P<.05).

CONCLUSIONS

Post space preparation without irrigation negatively affected the bond strength of the resin cementation system to root dentin.