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Adhesion to dentin remains challenging due to its complex nature that prevents complete infiltration of hydrophobic monomer to hydrophilic dentinal substrate. Recently, Er:YAG laser has been used in dentin pretreatment to enhance the bond strength. A deficient hybrid layer is formed following laser etching as it causes thermal damage and collagen denaturation of dentinal substrate. As the results are controversial, attempts are made to modify laser etching technique with respect to energy density, pulse duration and water spray. Thus, the present study aimed to evaluate the influence of Er:YAG laser conditioning of dentin by activation of Chlorhexidine collagen stabilising agent on the bond strength. Samples included 60 freshly extracted premolar which were divided into three groups (n=20) based on the protocol of dentin pretreatment done: Group 1 (Control) - Phosphoric acid etching followed by universal adhesive; Group 2 (Experimental) - Conventional Er:YAG laser dentioning; Group3 (Experimental) - Er:YAG laser dentin conditioning with coronal reservoir of 0.12% Chlorhexidine. Occlusal class 1 cavity was prepared on the samples followed by which dentin conditioning protocol was carried out for the respective groups. Universal adhesive was applied followed by Composite resin restoration. 1000 cycles of Thermocycling was done and the samples were sectioned to obtain microsections. Microtensile bond strength values were obtained by subjecting the specimens to Universal testing machine. Highest microtensile bond strength value was obtained for group 1 followed by group 3 with least value obtained for Group2 with statistically significant values between the groups. (p<0.0001). Within the limitations of the present invitro study, it can be concluded that preetching with phosphoric acid increases the bond strength of universal adhesive to dentin. Laser conditioning of dentin through activation of chlorhexidine provided better bond strength value of universal adhesive when compared to conventional laser dentin conditioning. [ABSTRACT FROM AUTHOR]

Background: Transforming growth factor-beta 1 (TGF-β1) is a key morphogen in regenerative endodontics that plays a central role in regulating cellular functions. Various chelating agents have been shown to release this growth factor upon conditioning. The objective of the study was to evaluate TGF-β1 release from the dentin matrix upon conditioning with ethylene diamine tetra-acetate (EDTA), doxycycline hydrochloride, and propolis. Materials and Methods: Forty-two human 3rd molar teeth were collected and coronal portion of the teeth was sectioned to obtain dentin blocks with dimensions 2 mm × 2 mm × 2 mm. The blocks were then randomly divided into three groups depending on the conditioning agent used; Group 1: 17% EDTA, Group 2: doxycycline hydrochloride (100 mg/mL), and Group 3: propolis (250 μg/mL). Conditioned blocks were placed in 0.5 mL of phosphate buffered saline and incubated for 1 week for quantification. Results: Highest TGF-β1 release was noted for propolis (0.21 ng/mL), followed by doxycycline hydrochloride (0.18 ng/mL) and 17% EDTA (0.14 ng/mL). Conclusion: Doxycycline hydrochloride and propolis significantly enhanced the release of TGF-β1 from the dentin matrix compared to EDTA (P < 0.05). No significant difference was observed between doxycycline hydrochloride and propolis (P > 0.05). Doxycycline and propolis can be used as effective alternatives to EDTA during regenerative endodontic procedures. [ABSTRACT FROM AUTHOR]