Biomaterial and Biofilm Interactions with the Pulp-Dentin Complex-on-a-Chip.

Calcium silicate cements (CSCs) are the choice materials for vital pulp therapy because of their bioactive properties, promotion of pulp repair, and dentin bridge formation. Despite the significant progress made in understanding CSCs' mechanisms of action, the key events that characterize the early interplay between CSC-dentin-pulp are still poorly understood. To address this gap, a microfluidic device, the "tooth-on-a-chip," which was developed to emulate the biomaterial-dentin-pulp interface, was used to test 1) the effect of CSCs (ProRoot, Biodentine, and TheraCal) on the viability and proliferation of human dental pulp stem cells, 2) variations of pH, and 3) release within the pulp chamber of transforming growth factor-ß (TGFß) as a surrogate of the bioactive dentin matrix molecules. ProRoot significantly increased the extraction of TGFß (P < 0.05) within 24 to 72 h and, along with Biodentine, induced higher cell proliferation (P > 0.05), while TheraCal decreased cell viability and provoked atypical changes in cell morphology. No correlation between TGFß levels and pH was observed. Further, we established a biofilm of Streptococcus mutans on-chip to model the biomaterial-biofilm-dentin interface and conducted a live and dead assay to test the antimicrobial capability of ProRoot in real time. In conclusion, the device allows for direct characterization of the interaction of bioactive dental materials with the dentin-pulp complex on a model of restored tooth while enabling assessment of antibiofilm properties at the interface in real time that was previously unattainable.

Two-year clinical evaluation of chlorhexidine incorporation in two-step self-etch adhesive.

OBJECTIVES: The aim of this 24-month double-blind randomized paired-tooth clinical study was to evaluate the 2-year clinical performance of two self-etch adhesives containing or not chlorhexidine digluconate (CHX) in non-carious cervical lesions (NCCLs). METHODS: Twenty-two patients, with at least four NCCLs, participated in this study. After sample size calculation, 126 restorations were assigned to one of the following groups: CSE--Clearfil SE Bond (Kuraray); CSE/CHX--Clearfil SE Bond+CHX; ADS--AdheSE (Ivoclar Vivadent); and ADS/CHX--AdheSE+CHX. The composite resin Filtek Z-250 composite (3M ESPE) was placed incrementally by one expert operator. The restorations were evaluated at baseline and after 2 years using the modified USPHS criteria. Statistical analyses were performed with Friedman repeated measures ANOVA by rank and Fisher exact test for significance in each pair (α=0.05). RESULTS: No significant difference was observed between baseline and 2-year for any criteria when adhesives with and without the addition of CHX were compared (p>0.05). ADS and ADS/CHX resulted in lower retention rates (82% on average) than CSE and CSE/CHX (97%) (p=0.02). CONCLUSIONS: The inclusion of CHX into the primer of both self-etch systems did not add clinical advantages over the 2-year period. Clearfil SE Bond resulted in better retention rate than AdheSE. CLINICAL SIGNIFICANCE: It is more important to choose a gold standard self-etch adhesive, like a Clearfil SE Bond, than to consider the inclusion of CHX in the self-etch adhesives.

Carbodiimide inactivation of MMPs and effect on dentin bonding.

The use of protein cross-linking agents during bonding procedures has been recently proposed to improve bond durability. This study aimed to use zymography and in situ zymography techniques to evaluate the ability of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) cross-linker to inhibit matrix metalloproteinase (MMP) activity. The hypotheses tested were that: (1) bonding procedures increase dentin gelatinolytic activity and (2) EDC pre-treatment prevents this enzymatic activity. The zymographic assay was performed on protein extracts obtained from dentin powder treated with Optibond FL or Scotchbond 1XT with or without 0.3M EDC pre-treatment. For in situ zymography, adhesive/dentin interfaces were created with the same adhesives applied to acid-etched dentin slabs pre-treated or not with EDC conditioner. Zymograms revealed increased expression of dentin endogenous MMP-2 and -9 after adhesive application, while the use of EDC as a primer inactivated dentin gelatinases. Results of in situ zymograpy showed that hybrid layers of tested adhesives exhibited intense collagenolytic activity, while almost no fluorescence signal was detected when specimens were pre-treated with EDC. The correlative analysis used in this study demonstrated that EDC could contribute to inactivate endogenous dentin MMPs within the hybrid layer created by etch-and-rinse adhesives.