Background: It has been suggested that host matrix metalloproteinase-2 (MMP-2) present in dentin may be involved in caries progression, however, its response to caries is not known. Bone sialoprotein (BSP) has been implicated in dentin mineralization and MMP-2 modulation. Objective: To identify and compare the distribution of MMP-2 and BSP in healthy human coronal dentin and those with early caries. Methods: Freshly extracted 3rd molars and premolars with and without early caries were fixed, demineralized and subjected to immunohistochemistry using a monoclonal anti-MMP-2 antibody and monoclonal anti-BSP antibody with an avidin-biotin complex method. Immunoreactivity was visualized with 3,3′-diaminobenzidine substrate and observed under light microscopy. Results: Immunohistochemical analysis revealed that MMP-2 and BSP are not detected in the tubule lumens of healthy dentin. However, intense immunoreactivity for MMP-2 and BSP was detected in association with the full length of the caries-affected dentinal tubules. The MMP-2 and BSP at the dentino-enamel junction appeared unaltered. Conclusion: The results indicate that MMP-2 and BSP may be actively secreted by odontoblasts in response to carious insult. MMP-2 and BSP accumulation in the caries-affected dentinal tubules may indicate their potential involvement in the host defense mechanism which results in calcification of regions affected by the carious process.
The silorane-based composite resin Filtek LS and the conventional methacrylate-based composite resin Tetric EvoCeram performed similarly well in posterior restorations over at least 36 months of clinical service.
Use of ceramic inlays to restore defects in posterior teeth requires careful attention to detail. Placement of ceramic inlay materials in high-stress areas may result in less predictable long-term performance. Ceramic inlays are advantageous for restoring moderately sized defects when optimal control of restoration contours and esthetics is desired.
To evaluate the survival rate (fatigue resistance), bonding efficiency and marginal integrity of monolithic zirconia partial and full coverage single restorations adhesively bonded to the tooth structure using air‐particle abrasion, a primer with 10‐methacryloyloxydecyl dihydrogen phosphate and a composite‐resin cement (APC) protocol.
Materials and Methods
Extracted human premolars (N = 32) were randomly divided into four groups of eight specimens each. Premolars were prepared for the following restorations: full crown (group 1, control), mesial‐occlusal‐distal‐facial onlay (MODF, group 2) preserving 2 mm facio‐lingual functional cusp width, mesial‐occlusal‐distal‐lingual onlay (MODL, group 3) preserving 2 mm facio‐lingual nonfunctional cusp width, mesial‐occlusal‐distal‐buccal‐lingual onlay (MODBL, group 4), overlay preparation. All restorations were milled from monolithic 3 mol% yttria (3Y) zirconia blocks (ZirCad, A1 LT, Ivoclar Vivadent) with CAD/CAM software presets at minimum occlusal and axial thicknesses of 1 mm. The intaglio surface of the restorations was air‐particle abraded (50 µm Al2O3, 2‐Bar pressure, 15 s, 10 mm distance) and primed. An adhesive cement system was used to bond the restorations. Each group was subjected to thermomechanical loading for 1.2 million cycles (force = 70 N, 1.4 Hz) with simultaneous thermocycling (5‐55°C, 30 s dwell time) using a mastication simulator. All specimens were examined under scanning electron microscope (SEM) analysis (30, 100, and 150×) to evaluate cracks and marginal defects. Fracture of restoration and/or fracture within tooth structure, and debonding were considered modes of failure.
One specimen from group 2 debonded at 632,000 cycles. None of the specimens failed due to fracture. SEM analysis at 30× indicated marginal integrity issue of the remaining seven intact specimens of group 2 in the area of antagonist contact. No specimens from group 1, 3, and 4 demonstrated marginal integrity issue at 30×. None of the specimens demonstrated any microcrack at 100× and150×.
Due to its fatigue resistance, 3Y‐zirconia is a viable option for partial and full coverage single restorations. Following a strict bonding protocol, zirconia demonstrated durable adhesion to the tooth structure. Occlusal contact on restoration margins should be avoided.
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