Effect of five commercial mouth rinses on the microhardness of a nanofilled resin composite restorative material: An in vitro study

Abstract

Aim and Objectives:This in vitro study was designed to comparatively evaluate the effect of five commercial mouth rinses on the micro hardness of a nanofilled resin based restorative material.Materials and Methods:Fifty specimens of resin composite material (Filtek Z350XT, 3M ESPE, St.Paul, MN USA) were prepared and immersed in artificial saliva for 24 h. The base line micro hardness of specimens was recorded using Vicker's micro hardness tester (MMT – X7 Matsuzawa, Japan). The specimens were randomly distributed into five groups, each containing 10 specimens (n=10) as follows – Group I Listerine (alcohol based), Group II Periogard (alcohol based), Group III Colgate plax (alcohol based), Group IV C- prev (alcohol free), Group V Hiora(alcohol free). The specimens were immersed in 20 ml of mouth rinses and incubated for 24 h at 37°C. The post immersion micro hardness values of the specimens were recorded and the data was tabulated for statistical analysis. Kruskal–Wallis test was used for inter group comparison followed by pair wise comparison of groups using Mann–Whitney U test. The level of significance was set at P=0.05.Results:Significant reduction in the mean VHN (Vicker's micro hardness number) was observed in all the groups after exposure to the tested mouth rinses (P<0.01) and the reduction in mean VHN values were as follows: Group I 12.09, Group II 3.42, Group II 1.51, Group IV 1.03, Group V 0.57. Inter group comparison showed statistically significant reduction in micro hardness in Groups I and II compared to all other groups with P<0.001. There was no significant difference between Groups III, IV and V.Conclusion:All the mouth rinses showed a reduction in the microhardness of nanofilled resin composite material with listerine (Group I) containing maximum amount of alcohol, showing highest reduction in micro hardness value.

Effect of a novel commercial potassium-oxalate containing tooth-desensitizing mouthrinse on the microhardness of resin composite restorative materials with different monomer compositions

“…This slight difference may be attributed to the lower pH of the mouthrinse (pH:4.2) compared to the artificial saliva (pH:7.0). ‘The low pH’ of essential oil mouthrinses may have the potential for erosion (1,6). This phenomenon is a complex process that might result in composite polymer matrix collapse, causing several problems such as filler-polymer matrix debonding, release of residual monomers, and wear and erosion (21).…”

“…They have mentioned that the formulation of commercially available mouthrinses contains various substances, such as water, antimicrobial agents, salts, preservatives and, in some cases, alcohol (2,4,5). ‘Alcohol’ in the mouthrinses and low pH may soften the resin composite restorative materials (5,6). According to Jyothi et al (6) the ‘low pH’ of mouthrinses may act in the polymeric matrix of the resin composite, through catalysis of ester groups from dimethacrylate monomers present in the composition (Bis GMA, Bis EMA, UDMA and TEGDMA) and the hydrolysis of these ester groups may form alcohol and carboxylic acid molecules that may accelerate the degradation of the resin composite.…”

“…‘Alcohol’ in the mouthrinses and low pH may soften the resin composite restorative materials (5,6). According to Jyothi et al (6) the ‘low pH’ of mouthrinses may act in the polymeric matrix of the resin composite, through catalysis of ester groups from dimethacrylate monomers present in the composition (Bis GMA, Bis EMA, UDMA and TEGDMA) and the hydrolysis of these ester groups may form alcohol and carboxylic acid molecules that may accelerate the degradation of the resin composite. ‘Water’ is also directly related to the composite organic matrix deterioration; the absorption of this liquid results in a widespread process within the composite ‘resin matrix’ that causes its degradation and results in lower physical and mechanical properties such as resin hardness (7).…”

“…A decrease in the hardness of a material may result in premature failure of a restoration requiring its replacement (6). …”

“…The effects of mouthrinses on dental resin composites have been investigated extensively (2-5,6,9-11). However, there is little information available, to our knowledge, regarding the effects of ‘newly developed mouthrinse’ formulations on the microhardness of different monomer based composite systems.…”