AFM study of the effects of collagenase and its inhibitors on dentine collagen fibrils

Captopril inhibits matrix metalloproteinase activity and improves dentin bonding durability

OBJECTIVES

We investigated the inhibitory effects of captopril on matrix metalloproteinases (MMPs) and its effect as a primer on dentin bonding durability.

MATERIALS AND METHODS

One hundred fifty human third molars were selected. Flat surfaces of the middle dentin were exposed, etched 15 s, and followed by pretreatment with a primer for 60 s, including distilled water (control, the negative control primer), 2% chlorhexidine digluconate (CHD, the positive control primer), and captopril solution. Inhibitory effects of primers on MMPs were evaluated by hydroxyproline and gelatinase activity tests. All primers were applied on dentin followed by bonding. Some of the samples were sliced into slabs, placed in a fluorescent solution containing gelatin, and incubated for in situ zymography. Some were cut into sticks, and after aging for 1 day, 12 months, or 24 months, microtensile bonding strength was tested. Some were cut into slabs, aged for 1 day, 12 months, or 24 months, and taken out for nanoleakage tests to reveal interface defects.

RESULTS

Hydroxyproline and gelatinase activity analyses showed that captopril exerted better inhibitory effects on MMPs, relative to 2% CHD (p < 0.05). A 0.2% captopril aqueous solution (0.2% CapW) was chosen to apply to the dentin. In situ zymography showed that inhibitory effects of captopril on gelatinase were significantly higher compared to 2% CHD (p < 0.01). Microtensile strength revealed that the bonding effects of the 0.2% CapW group lasted longer, compared to the control and 2% CHD groups (p < 0.05). Interface defects, detected by nanoleakage, were significantly reduced in the 0.2% CapW group, compared to the control and 2% CHD groups (p < 0.05).

CONCLUSIONS

Captopril inhibits dentin MMP activities and effectively improves dentin bonding durability.

CLINICAL RELEVANCE

Captopril is a promising dentin bonding primer for improving bonding durability.

Atomic force microscopy analysis of the surface alterations of enamel, dentin, composite and ceramic materials exposed to low oral pH in GERD

Dental erosion is a significant topic in medical literature, both for gastroenterology and dental medicine. Dental structure loss has a psychosocial and functional significance. The pathogenesis of dental erosion in patients diagnosed with gastroesophageal reflux disease (GERD) characterized by the presence of an acidic oral environment after reflux episodes, is not well understood. The present study was designed to observe the effect of low oral pH in time on natural surfaces including enamel and dentine, but also on materials used in treating these dental destructions such as composites and ceramics. The acidic oral environment was estimated in relation to salivary pH. In the dental laboratory, 5-mm2 and 1-mm composite pieces of thick enamel, dentine, Emax Ceramic and Nexco Ivoclar were cut in order to be analyzed using atomic force microscopy (AFM) and to observe the surface alterations. Gastric acid was collected and mixed with saliva until a pH value of 6.0 was obtained, in which the pieces were immersed for 24, 120, 240 h. Roughness of each surface was calculated at a microstructure and nanostructure level. The results showed significant alterations in enamel and dentine exposed to a lower pH level beginning even at a short immersion time, in comparison with composites and ceramics which had no alterations. In conclusion, multidisciplinary attention should be given to detect and manage acidity of the oral cavity caused by GERD, in order to prevent dental erosion.

Demineralization-remineralization dynamics in teeth and bone

Biomineralization is a dynamic, complex, lifelong process by which living organisms control precipitations of inorganic nanocrystals within organic matrices to form unique hybrid biological tissues, for example, enamel, dentin, cementum, and bone. Understanding the process of mineral deposition is important for the development of treatments for mineralization-related diseases and also for the innovation and development of scaffolds. This review provides a thorough overview of the up-to-date information on the theories describing the possible mechanisms and the factors implicated as agonists and antagonists of mineralization. Then, the role of calcium and phosphate ions in the maintenance of teeth and bone health is described. Throughout the life, teeth and bone are at risk of demineralization, with particular emphasis on teeth, due to their anatomical arrangement and location. Teeth are exposed to food, drink, and the microbiota of the mouth; therefore, they have developed a high resistance to localized demineralization that is unmatched by bone. The mechanisms by which demineralization-remineralization process occurs in both teeth and bone and the new therapies/technologies that reverse demineralization or boost remineralization are also scrupulously discussed. Technologies discussed include composites with nano- and micron-sized inorganic minerals that can mimic mechanical properties of the tooth and bone in addition to promoting more natural repair of surrounding tissues. Turning these new technologies to products and practices would improve health care worldwide.

Cytotoxicity and effect on protease activity of copolymer extracts containing catechin

OBJECTIVE

To evaluate cytotoxicity and effect on protease activity of epigallocatechin-gallate extracted from experimental restorative dental copolymers in comparison to the control compound chlorhexidine.

METHODS

Copolymer disks were prepared from bis-GMA/TEGDMA (70/30 mol%) containing no compound (control) or 1% w/w of either epigallocatechin-gallate or chlorhexidine. MDPC-23 odontoblast-like cells were seeded with the copolymer extracts leached out into deionized water. Cell metabolic activity was quantified by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay at 24, 48, 72 h. Inhibition of protease activity by resin extracts was measured by a collagenolytic/genatinolytic enzyme activity assay and gelatin zymography. Data for MTT and protease inhibition were analyzed using two-way ANOVA followed by Tukey or Bonferroni post hoc tests (α=0.05).

RESULTS

The MTT revealed that at 72 h, extracts from control (16.7%) and chlorhexidine (22.3%) copolymers induced significant reduction in cell metabolism (p<0.05). All copolymer extracts caused enzymatic inhibition in a dose dependent manner (p<0.01). Even when highly diluted, epigallocatechin-gallate extract had a significant antiproteolytic activity (p<0.05). Zymograms showed that all extracts reduced activity of MMP-2 and MMP-9 (pro- and active forms), with MMP-9 exhibiting the highest percentage inhibition revealed by densitometry.

CONCLUSIONS

Epigallocatechin-gallate and chlorhexidine extracts did not exert cytotoxicity on evaluated cells when compared to control extracts. Both compounds retained antiproteolytic activity after extraction from a dental copolymer.

CLINICAL SIGNIFICANCE

Once extracted from a dental copolymer, epigallocatechin-gallate is not cytotoxic and retains antiproteolytic activity. These results may allow incorporation of epigallocatechin-gallate as a natural-safe alternative to chlorhexidine in functionalized restorative materials.

Immunohistochemical analysis of matrix metalloproteinase-13 in human caries dentin

The immunoexpression profile of matrix metalloproteinase-13 was investigated for the first time in dentin of human caries and healthy teeth. Twelve permanent premolars (10 caries and 2 sound) were decalcified in ethylenediaminetetraacetic acid and processed for embedding in paraffin wax. Sections 3-4 µm in thickness were cut and processed for immunohistochemistry. A mouse monoclonal anti-metalloproteinase-13 antibody was used for localisation using an immunoperoxidase technique. Dentinal immunoreactivity was detected in all teeth; it was weak in sound teeth and strong close to the caries area. These in vivo findings suggest a role for metalloproteinase-13 in the development and progression of adult human dental tissue disorders.