Adhesion between the resin-based materials and the tooth substrate is the foundation of restorative dentistry. Despite all the improvements in adhesive systems, the hybrid layer, which is the interface of the bonding between the tooth substrate and adhesive materials, remains the weakest area in adhesive dentistry. [1] In general, it is accepted that the resin-dentin bond created by adhesives deteriorates over time. Degradation of the hybrid layer is the main cause of this phenomenon. Decreased resin monomer diffusion within the acid-etched creates incompletely infiltrated zones along the bottom of the hybrid layer that contains denuded collagen fibrils. These denuded collagen fibrils are vulnerable to degradation by endogenous matrix metalloproteinases (MMPs). [2] MMPs are a group of calcium-and zinc-dependent host-derived enzymes that are trapped within the mineralized dentin matrix during tooth development. They can hydrolyze components of the extracellular matrix.Dentinogenesis is a complicated developmental phenomenon that requires the active extra-cellular enzymatic function of several different proteinases, mainly of the MMP family. Recent studies revealed the contributions of host-derived proteinases to the breakdown of the collagen matrices in the pathogenesis of dentin and periodontal disease. [3] The existence of an acidic environment due to caries leads to the activation of different MMPs and degradation of the collagen fibrils, hence weakening the bond between the adhesive and dentin interface occurs. [4] During bonding procedures with etch-and-rinse or self-etch systems, demineralization of dentin activates proteolytic enzymes (MMPs), which degrades unprotected

Objectives. Although early childhood dental caries (ECC) have the same general etiology as other types of caries, predisposing factors are not well elucidated. This study aimed to investigate the effect of salivary alpha-amylase (sAA) activity, body mass index (BMI), dietary habits, and oral hygiene on ECC. Methods. This cross-sectional study was performed on 38 ECC-affected and 41 caries-free children, aged 36 to 72 months. Upon the parents’ consent, 3 mL of non-stimulated saliva was collected from the participants to measure the level of sAA activity through spectrophotometry. Additionally, parents/caretakers completed a structured questionnaire about demographic factors, oral hygiene, and consumption of sugar-containing foods. BMI, BMI z-scores, and percentile data were calculated by using an online calculator. The independent variables were dichotomized and tested through chi-square test, followed by a stepwise logistic regression, by using SPSS software (α = 0.05). Results. The sAA activity was significantly higher in caries-free children ( P ≤ 0.001 ). However, the mean BMI was not significantly different between the two groups ( P = 0.49 ). Brushing and other measured dietary habits were significantly associated with the development of ECC ( P ≤ 0.001 ). According to the results of the logistic regression, sAA activity was shown to be a predictor for ECC development (Odds ratio (95% confidence interval): 0.9 (0.95–0.98)). Conclusion. Children with inherently lower levels of sAA activity were more susceptible to dental caries. Improper nutritional habits and poor oral health care could exacerbate the risk of ECC.

Objectives The present study aimed to investigate the effect of casein phosphopeptide–amorphous calcium phosphate (CPP-ACP) complex and the type of flowable composite (conventional or self-adhesive bioactive) on the fracture resistance of fractured incisors restored through reattachment technique. Materials and Methods In this experimental in vitro study, 60 extracted bovine central mandibular incisors were randomly divided into six groups (n = 10) according to the reattachment technique. Their incisal edges were cut off to represent an enamel–dentin fracture. The fragment edges were reattached as follows: Group 1—selective etching and bonding followed by conventional flowable composite; Group 2—selective etching and bonding followed by bioactive flowable composite; Group 3 was like Group 2 but without applying bonding; Groups 4, 5, and 6 were similar to Groups 1, 2, and 3, respectively, but both tooth fragments were pretreated with CPP-ACP-containing paste for 3 minutes. Fracture resistance was assessed by a universal testing machine. Statistical Analysis Data were analyzed by SPSS—Statistical Package for the Social Sciences—software using one-way analysis of variance and Tukey post-hoc tests (α= 0.05). Results The highest and lowest fracture resistance was recorded in Groups 5 (15.96 MPa) and Group 6 (1.95 MPa), respectively, being significantly different from the other groups. The mean fracture resistance of Groups 3 and 6 was significantly lower than the other groups (p < 0.05). However, Groups 1, 2, and 4 showed no difference in fracture resistance. Conclusion Bioactive composite was not superior to conventional composite for fragment reattachment, but using it in self-adhesive mode reduced the fracture strength significantly. Yet, pretreatment with CPP-ACP, followed by application of adhesive, improved the fracture resistance of bioactive composite.

Objective: The purpose of this study was to evaluate the effect of pretreatment with of matrix metalloproteinase inhibitors on the shear bond strength (SBS) of Adper Single Bond 2 total etch adhesive to the primary teeth dentin following 6 months of storage in artificial saliva. Materials and Methods: One hundred and twenty primary anterior teeth extracted for orthodontic reasons were selected. After etching, dentin blocks from each tooth were pretreated for 60 s with: (i) phosphate-buffered saline (0.01 M, pH 7.2) as the control group, (ii) 17% ethylenediaminetetraacetic acid (EDTA), (iii) 2% doxycycline (DO) solution, and (iv) 2% chlorhexidine (CHX) solution, with subsequent application of an etch-and-rinse adhesive system (Adper Single Bond 2). The composite was placed in clear Teflon cylinders. The SBS values were determined immediately and following 6 months of aging with a universal testing machine. Failure mode was evaluated using the stereomicroscope and scanning electron microscope. Data were analyzed by the SPSS software using the one-way analysis of variance and post hoc tests (P = 0.05). Results: At baseline, no significant difference was observed between control, EDTA, CHX, and DO groups (P = 0.554). Following 6 months of aging, the SBS of the CHX group was significantly higher than the control group (P = 0.013). However, the SBS of the control, EDTA, and DO groups was not statistically different (P < 0.05). Conclusions: Following 6 months of aging, among different groups of the study, only CHX significantly preserved the SBS of composite resin to primary teeth dentin using Adper Single Bond 2 adhesive.