The effect of esterase enzyme on aging dental composites

Abstract

We measured the push-out and diametral tensile strength of dental restorative composites following aging under environmental conditions relevant to the oral cavity; air (A), artificial saliva (AS), acidified (50 mM CH 3 COOH, pH = 4.7) artificial saliva (AS + HAc), and AS with esterase enzyme (AS + ENZ). Cylindrical test specimens (6.3 mm diameter by 5.1 mm long) were prepared by placing 0.3 g of nanofilled composite in an epoxy ring and cured. Twenty samples were aged in each environment for 163-186 days at 37 C. The push-out strengths (mean AE standard error of the mean [SEM], in MPa) for specimens were: A-2.4 AE 0.2, AS-7.3 AE 0.5, AS + HAc-7.2 AE 0.9, and AS + ENZ-6.0 AE 0.6. Following the push-out test, the diametral tensile strength and elasticity were immediately determined. The diametral tensile strengths (mean AE SEM, in MPa) for specimens were: A-54.0 AE 1.6, AS-31.4 AE 1.3, AS + HAc-34.3 AE 1.2, and AS + ENZ-22.5 AE 0.7. The push-out strength was lowest for the A environment due to shrinkage of the composite. The push-out strength increased significantly as water diffused into the specimens (AS and AS + HAc) but decreased significantly in the enzyme environment (AS + ENZ). The diametral tensile strength was highest for specimens in the A environment, which was significantly higher than both the AS and AS + HAc specimens and > 2× higher than the AS + ENZ specimens. The results indicated that a water environment (with or without acid) caused a significant decrease in the mechanical properties of this composite, but the greatest decrease was seen in water with esterase. This is the first study to demonstrate that esterase enzymes affect the bulk strength of a commonly used commercial dental composite.

Influences of Different Air-Inhibition Coatings on Monomer Release, Microhardness, and Color Stability of Two Composite Materials

“…The ester-linkages in Bis-GMA and TEGDMA composites are subjected to hydrolysis when exposed to enzymes and an esterase, produced by Streptococcus mutans , seems to be partly responsible for this intraoral degradation [32]. After exposure to esterase enzyme, a nanofilled composite, Filtek supreme plus, showed 57% reduction in the tensile diametral strength and 46% in elasticity [33].…”

Biodegradation of Dental Resin-Based Composite—A Potential Factor Affecting the Bonding Effect: A Narrative Review

“…The presence of esterase in saliva has an adverse impact on the mechanical properties of the resin. After aging for 180 days in an environment containing artificial saliva and esterase, the radial tensile strength and elasticity of resin composite dramatically declined [ 32 ], and the composite also showed the lowest fracture toughness [ 23 ]. On the 12th day alone, the hardness of the thermally polymerized acrylic resin in saliva decreased, and the roughness began to increase on the 24th day [ 33 ].…”

A novel methacrylate derivative polymer that resists bacterial cell‐mediated biodegradation

“…Biodegradation can lead to the destruction of the tooth‐resin composite interface and may contribute to secondary caries being the main cause of restoration failure 1‐4 . Cholesterol esterase‐like (CE), pseudocholinesterase (PCE), 5‐7 and esterase enzymes extracted from Streptococcus mutans 8 have been found in saliva and may have a causative role in secondary caries development. While the expression of lactic acid and insoluble biofilm matrix enzymes plays a clear role in caries etiology, there is now evidence that esterases from S. mutans may inadvertently bind to and hydrolyze ester bonds within polymers of methacrylates in composite materials 8‐11 .…”

“…Current evidence suggests that S. mutans has a multi‐factorial role in the destruction of the tooth‐resin composite interface since ester bond degradation can be pronounced during periods of higher pH (before and during early sucrose exposure) and tooth interfacial demineralization occurs during low pH, where bacterial esterases are less active 8,16 . A cycle of ester bond hydrolysis within the polymer and tooth demineralization may affect the mechanical integrity of both the tooth and resin polymers, thus affecting the overall interfacial adhesive properties 7 . Bacterial degradation may contribute to the low (~65%)‐clinical success rate of resin composites after 10 years in high caries risk patients 17 …”

“…8,16 A cycle of ester bond hydrolysis within the polymer and tooth demineralization may affect the mechanical integrity of both the tooth and resin polymers, thus affecting the overall interfacial adhesive properties. 7 Bacterial degradation may contribute to the low (~65%)-clinical success rate of resin composites after 10 years in high caries risk patients. 17 The catalytic promiscuity of S. mutans' esterases can profoundly degrade the main vulnerable region of methacrylate polymers, which are the internal ester bonds.…”