Influence of Storing Composite Filling Materials in a Low-pH Artificial Saliva on Their Mechanical Properties—An In Vitro Study

Abstract

Restorative composites are subjected to various influences in the oral cavity environment, such as high or low temperatures, the mechanical force generated during mastication, colonization of various microorganisms, and low pH, which may result from ingested food and the influence of microbial flora. This study aimed to investigate the effect of a recently developed commercial artificial saliva (pH = 4, highly acidic) on 17 commercially available restorative materials. After polymerization, the samples were stored in an artificial solution for 3 and 60 days and subjected to crushing resistance and flexural strength tests. The surface additions of the materials were examined in terms of the shapes and sizes of the fillers and elemental composition. When stored in an acidic environment, the resistance of the composite materials was reduced by 2–12%. Larger compressive and flexural strength resistance values were observed for composites that could be bonded to microfilled materials (invented before 2000). This may result from the filler structure taking an irregular form, which results in a faster hydrolysis of silane bonds. All composite materials meet the standard requirements when stored for a long period in an acidic environment. However, storage of the materials in an acid environment has a destructive impact on the materials’ properties.

Properties of Nanohybrid Dental Composites—A Comparative In Vitro Study

“…Un-polished specimens have a significantly lower compression strength than polished samples for each of the tested composites. The compressive strength obtained for CM-polished samples is in good agreement with the data in the literature [32], but the values obtained for HU samples are slightly below the values mentioned in the literature [33]. The wavy structures observed on the composites' unpolished surfaces that embed large micro-particles that are partially exposed on the outermost layer act as tension concentrators during pressing, acting as cracks initiators.…”

“…This compressive effort is concentrated on these initial cracks, promoting in-depth failure, explaining the lower compressive strength obtained on the unpolished samples. The polished surfaces resist as a single monolith under compressive solicitations and uniformly dissipate the effort within the whole microstructure [33].…”

Alterations in Surface Gloss and Hardness of Direct Dental Resin Composites and Indirect CAD/CAM Composite Block after Single Application of Bifluorid 10 Varnish: An In Vitro Study

“…Different storage media could be used, such as distilled water, saline, ethanol, and artificial saliva. Artificial saliva was selected as it has the simplest physiological effect on the specimens to standardize the variables and simulate clinical situations [44,45].…”

Analysis of Resin-Based Dental Materials’ Composition Depending on Their Clinical Applications

“…In recent years, the increasing presence of resin-based dental materials in oral cavity has raised questions about biocompatibility and safety of resin-matrix components [ 1 , 2 ]. Resin-based dental materials are subjected to numerous constraints that may be physical–chemical (thermal variations), mechanical (abrasion linked to oral hygiene measures and functions or parafunctions), chemical (corrosion caused by food and drinks, acid attacks, pH variations or hydrolysis), or even bacteriological (bacterial enzymatic attacks) [ 7 , 8 , 9 , 10 ]. These constraints and the context of the oral environment inevitably lead to their degradation and consequently the release of all or part of their components [ 8 , 9 , 10 ].…”

“…Resin-based dental materials are subjected to numerous constraints that may be physical–chemical (thermal variations), mechanical (abrasion linked to oral hygiene measures and functions or parafunctions), chemical (corrosion caused by food and drinks, acid attacks, pH variations or hydrolysis), or even bacteriological (bacterial enzymatic attacks) [ 7 , 8 , 9 , 10 ]. These constraints and the context of the oral environment inevitably lead to their degradation and consequently the release of all or part of their components [ 8 , 9 , 10 ]. In addition, during the polymerization reaction of resin-based materials, monomers are converted into polymers mostly initiated by the light-curing of the material [ 11 ].…”