Restorative Materials Exposed to Acid Challenge: Influence of Temperature on In Vitro Weight Loss

The effect of beverage temperature on the surface roughness, microhardness, and color stability of the monoshade composite resin: An in vitro study

Objective

This study assessed the impact of beverage temperature on the surface roughness, microhardness, and color stability of monoshade composite resin.

Materials and Methods

A batch of 70 monoshade composite resin specimens manufactured by Charisma Diamond ONE (Kulzer, Hanau, Germany) was prepared. Initial readings for surface roughness, microhardness, and color were recorded. The specimens were then divided into seven groupings of ten each: Distilled water (control group), Nescafe coffee at 70 °C and 5 °C, Arabic coffee at 70 °C and 37 °C, and cola at 7 °C and 24 °C. These samples underwent 30-min daily immersion in their respective beverages for a duration of 30 days. Final measurements were then taken. A non-contact profilometer was used for measuring surface roughness, a Vickers microhardness machine from Contour GT-I (Bruker Nano GmbH, Berlin, Germany) for microhardness, and a Color-Eye 7000A Spectrophotometer (X-Rite, GretagMacbeth, Michigan USA) for color stability. Statistical analyses, including repeated measure ANOVA for microhardness, roughness, and color, were executed using SPSS version 23.

Results

All beverages led to changes in composite color and properties. Notably, coffee at 70 °C resulted in significant discoloration of the composite resin surface (p < 0.0001). The beverage that most affected the surface hardness and roughness of the monoshade composite resin was cola at 7 °C (p = 0.008).

Conclusion

The inherent chemicals in beverages, coupled with their temperatures, can influence the composite properties of resin, specifically surface discoloration, hardness, and roughness. Clinicians may, therefore, consider instructing patients about the potential negative effects of these beverages.

Deterioration of direct restorative materials under erosive conditions with impact of abrasion and attrition in vitro

Objective

To compare the cumulative impact of sequential wear on mechanical properties and appearance of a composite resin (CR), Filtek Z250^®, a glass ionomer GI, Fuji IX GP^®, and a glass hybrid (GH), Equia Forte^®.

Material and Methods

Six equally sized specimens of each material were subjected to wear tests, i.e., simulation of brushing, chewing and acidic liquid exposure, mimicking at least 6 months of clinical exposure. Surface roughness, hardness, substance loss and degree of shade lightness were determined.

Results

Following wear tests, significant increase in surface roughness and decrease in hardness values were observed for all materials (p < .05). Significantly larger substance loss was found in Equia Forte^® specimens compared to Filtek Z250^® (p < .05), while that of Fuji IX^® exceeded the measurement capacity of the instrument. Opposite to the two other materials, the shade of Filtek Z250^® became darker.

Conclusions

Sequential wear exposure mimicking abrasion, erosion and attrition to products representing CR, GI and GH, caused weakening and change in appearance of the materials. The composite resin was the most mechanically resistant to the sequential wear.

The Effect of a Green Smoothie on Microhardness, Profile Roughness and Color Change of Dental Restorative Materials

Acidic drinks are known to exert negative effects on the surface properties of dental restorative materials. However, the effect of increasingly popular green smoothie drinks has not been addressed so far. The present study investigated the effect of cyclic immersions (5 min daily over 30 days) in a green smoothie drink on the surface properties of contemporary dental restorative materials, including resin composites, an alkasite, and a glass hybrid. Vickers microhardness, profile roughness, and perceptible color change in the CIE L* a* b* color space were evaluated as clinically relevant properties of the material surface. After 30-day green smoothie immersion, microhardness values either decreased by 8–28% (for resin composites) or increased by up to 91% (for glass hybrid). The increase in profile roughness (Ra parameter) of smoothie-immersed specimens was 7–26 times higher compared to the control group. The perceptible color change (ΔE*) in the smoothie group was 3–8 times higher compared to the control group. Overall, this study demonstrated that daily exposure of dental restorations made from resin composites, alkasites, and glass hybrid materials to a green smoothie drink can significantly accelerate material degradation, which is reflected as surface softening, as well as higher roughness and higher perceptible color change.