Effect of human saliva on surface degradation of composite resins

Abstract

– The amount of methacrylic acid produced by incubation of the dimethacrylate ester TEGDMA in human whole saliva was measured. The conversion rate of TEGDMA was determined in stimulated saliva from dental students and in unstimulated saliva from both dental students and patients. The differences in mean conversion rate measured in the three groups were not statistically significant (P= 0.346). The mean conversion rate ± SD for all saliva samples was 4.54 ± 3.24 μmol MAA/L. h. The surface of BISGMA/TEGDMA‐polymer specimens treated with porcine liver esterase in activities equivalent to those found in human saliva exhibited a lower Wallace microhardness than the surface of untreated specimens. Polymer specimens incubated in human saliva exhibited a similar reduction in the microhardness. The results demonstrated that enzymes in human saliva are capable of softening the surface of dimethaerylate polymers presumably by inducing a hydrolysis of methacrylate ester bonds. The mechanical removal of a surface layer softened by hydrolases will expose a new surface layer to enzymatic attack. The enzymatic softening may thus contribute to the in vivo wear of composite restorations.

Hydrogel properties influence ECM production by chondrocytes photoencapsulated in poly(ethylene glycol) hydrogels

“…These gels did not degrade under the in vitro conditions used and on the time-scale studied; however, the ester linkage has been shown to degrade slowly in vivo. 32 The photocrosslinked PEG hydrogels had varying degrees of crosslinking and spanned a range of properties (Table I). Bovine articular cartilage is comprised of ∼80% water, which corresponds to a q of ∼5, and has a compressive modulus of 500-1000 kPa.…”

The influence of mouthrinses and simulated toothbrushing on the surface roughness of a nanofilled composite resin

“…These changes have been attributed to the degradation of the polymer matrix, or the resin-filler interface, and loss of inorganic filler particles. 11,13,14 In non-stressbearing areas, the main causal factors of texture changes are the relationship between biodegradation and oral hygiene procedures. 15 Thus, regular prophylactic procedures, such as toothbrushing, the use of mouthrinses, or a combination of these, may produce deleterious side- effects on the surface and physical properties of restorative materials.…”

Biodegradation and Abrasive Wear of Nano Restorative Materials

“…The chemical challenges can be caused by acids produced by cariogenic biofilm, 7 acidic diet, 8,9 and salivary enzymes, 10,11 leading to softening and increased surface roughness of resin-based materials. [11][12][13] When brushed with dentifrice daily, these damaged surfaces gradually would lose softened material (matrix and filler), causing loss of contour, change of color, and roughening of the restoration surface again, influencing its esthetic and clinical longevity.…”