Scanning electron microscopy and roughness study of dental composite degradation

Antimicrobial activity of Curcuma xanthorrhiza nanoemulsions on Streptococcus mutans biofilms

In this study, an optimal nanoemulsion formulation for Curcuma xanthorrhiza oil (Xan) was investigated using different sonication times. The antimicrobial effects of the nanoemulsion, the original emulsion, distilled water (DW), and Listerine, on Streptococcus mutans biofilms were compared. The optimum ultrasonic time, determined in terms of droplet size and stability, was found to be 10 min. Cell viability was the lowest on exposure to the nanoemulsion, and significantly different compared with exposure to DW or Listerine. The emulsion's effect was similar to that of the nanoemulsion, but was non-uniform with a high interquartile range. Confocal microscope analysis revealed that the live/dead cell ratio in the nanoemulsion was 50% and 40% less than those in DW and Listerine, respectively. Biofilm treated with the nanoemulsion was thinner than biofilms exposed to the other treatments. Xan nanoemulsions exhibited stable and strong antimicrobial effects due to nano-sized particles, highlighting their potential use in oral health treatment.

Recent advances in understanding the fatigue and wear behavior of dental composites and ceramics

Dental composite and ceramic restorative materials are designed to closely mimic the aesthetics and function of natural tooth tissue, and their longevity in the oral environment depends to a large degree on their fatigue and wear properties. The purpose of this review is to highlight some recent advances in our understanding of fatigue and wear mechanisms, and how they contribute to restoration failures in the complex oral environment. Overall, fatigue and wear processes are found to be closely related, with wear of dental ceramic occlusal surfaces providing initiation sites for fatigue failures, and subsurface fatigue crack propagation driving key wear mechanisms for composites, ceramics, and enamel. Furthermore, both fatigue and wear of composite restorations may be important in enabling secondary caries formation, which is the leading cause of composite restoration failures. Overall, developing a mechanistic description of fatigue, wear, and secondary caries formation, along with understanding the interconnectivity of all three processes, are together seen as essential keys to successfully using in vitro studies to predict in vivo outcomes and develop improved dental restorative materials.

Caries management by risk assessment (CAMBRA) and its effect on the surface roughness of various restorative materials

STATEMENT OF PROBLEM

Whether topical anticaries medicaments used in the oral environment will affect the surface integrity of restorative materials is uncertain.

PURPOSE

The purpose of this in vitro study was to investigate the effect of various anticaries agents on the surface roughness of 3 different restorative materials.

MATERIAL AND METHODS

Sixty-four specimens of each restorative material (feldspathic porcelain, Ni-Cr metal ceramic alloy, and Ti-6Al-4V titanium alloy) were prepared and separated into 4 equal groups for soaking in anticaries agents (Prevident Dental Rinse, ACT mouth wash, chlorhexidine gluconate, and water). A profilometer was used to measure surface roughness before and after soaking the materials for 2 years of simulated usage. The mean change in surface roughness for each specimen was calculated. Statistical analysis was performed with a 2-way ANOVA, followed by the Tukey HSD test (α=.05).

RESULTS

A significant interaction was found between the materials and anticaries agents (F=2.64, P=.02). The significant interaction was between Prevident and chlorhexidine gluconate. Porcelain specimens soaked in Prevident produced a negative change (-0.072 ±0.35 μm) in surface roughness (smoother surface), while chlorhexidine gluconate produced a positive change (0.094 ±0.42 μm) in surface roughness (rougher surface).

CONCLUSION

Within the limitations of this in vitro study, it can be concluded that Prevident Dental Rinse and chlorhexidine gluconate may cause a change in the surface roughness of feldspathic porcelain.

Effect of Toothbrushing-mouthrinse-cycling on Surface Roughness and Topography of Nanofilled, Microfilled, and Microhybrid Resin Composites

The purpose of this study was to evaluate the influence of toothbrushing-mouthrinse-cycling (TMC) on the surface roughness and topography of three resin composites with different filler particle systems (Z350, nanofilled [Nf]; Durafill, microfilled [Mf], and Empress Direct, microhybrid [Mh]). Twenty specimens of each resin composite (8.0 mm diameter and 2 mm height) were randomly divided into four groups (n=5) according to the mouthrinses: alcohol-free (Plax – P) and alcohol-containing (Listerine – L and Plax Fresh Mint – PM) and artificial saliva (control – AS). The specimens were submitted to TMC for nine weeks. A surface roughness tester and a three-dimensional profilometer were used to measure the roughness (Ra) and the topography (Sa) before and after TMC. The data were analyzed by multifactor analysis of variance and Tukey post hoc test (α=0.05). In all media, Mh presented greater roughness than Mf (p<0.05). The highest value of roughness was presented by Mh immersed in L (p<0.05). The lowest values of roughness were presented by Mf (p<0.05). The three resin composites presented the highest roughness after immersion in mouthrinses containing alcohol (PM and L) (p<0.05). For the three resin composites, the increase in roughness was noticeable after the fifth week. Topographic analysis showed that the smoothest surfaces were present after immersion in AS.

FT-Raman spectroscopy study of organic matrix degradation in nanofilled resin composite

This in vitro study evaluated the effect of light curing unit (LCU) type, mouthwashes, and soft drink on chemical degradation of a nanofilled resin composite. Samples (80) were divided into eight groups: halogen LCU, HS--saliva (control); HPT--Pepsi Twist®; HLC--Listerine®; HCP--Colgate Plax®; LED LCU, LS--saliva (control); LPT--Pepsi Twist®; LLC--Listerine®; LCP--Colgate Plax®. The degree of conversion analysis and the measure of the peak area at 2,930 cm-1 (organic matrix) of resin composite were done by Fourier-transform Raman spectroscopy (baseline, after 7 and 14 days). The data were subjected to multifactor analysis of variance (ANOVA) at a 95% confidence followed by Tukey's HSD post-hoc test. The DC ranged from 58.0% (Halogen) to 59.3% (LED) without significance. Differences in the peak area between LCUs were found after 7 days of storage in S and PT. A marked increase in the peak intensity of HLC and LLC groups was found. The soft-start light-activation may influence the chemical degradation of organic matrix in resin composite. Ethanol contained in Listerine® Cool Mint mouthwash had the most significant degradation effect. Raman spectroscopy is shown to be a useful tool to investigate resin composite degradation.

Micro energy-dispersive X-ray fluoresence mapping of enamel and dental materials after chemical erosion

Energy-dispersive X-ray fluorescence was employed to test the hypothesis that beverage consumption or mouthwash utilization will change the chemical properties of dental materials and enamel mineral content. Bovine enamel samples (n = 45) each received two cavity preparations (n = 90), each pair filled with one of three dental materials (R: nanofilled composite resin; GIC: glass-ionomer cement; RMGIC: resin-modified GIC). Furthermore, they were treated with three different solutions (S: saliva; E: erosion/Pepsi Twist®; or EM: erosion+mouthwash/Colgate Plax®). It was found that mineral loss in enamel was greater in GICE samples than in RE > RMGICE > RMGICEM > REM > GICEM. An increased percentage of Zr was found in REM indicating organic matrix degradation. Dental materials tested (R, GIC, and RMGIC) were not able to protect adjacent enamel from acid erosion by the soft drink tested. The use of mouthwash promoted protection of enamel after erosion by the soft drink. To avoid chemical dissolution by mouthwashes, protection by resin composites with surface sealants is recommended.

Potential effects of tooth-brushing on human dentin wear following exposure to acidic soft drinks

This study used scanning electron microscopy and atomic force microscopy to examine the short-term potential effects of brushing time and the start-time of tooth-brushing after demineralization on primary dentin wear in vitro. Thirty-six noncarious primary central incisors were assigned to 12 experimental groups. Exposure to cola drinks was used to initiate the demineralization process. Three brushing times (5, 15 and 30 s) and four start-times of brushing (0, 30, 60 and 120 min) after an erosive attack were used for the abrasion process. Tooth-brushing the softened dentin surface led to increases in the open tubular fraction and microstructural changes on the dentin surface. Brushing immediately after exposure to cola resulted in the greatest irreversible dentin loss, whereas brushing 60 or 120 min after pretreatment resulted in the least irreversible dentin loss. However, brushing time had no effect on the irreversible loss of dentin wear. Based on these experimental results, tooth-brushing should be performed at least 60 min after consuming a cola drink to achieve the desired tooth cleaning and avoid the introduction of surface lesions on dentin.