Assessment of internal porosities for different placement techniques of bulk-fill resin-based composites: a micro-computed tomography study

The effect of contouring instruments on immediate quality and porosity of direct restorations

OBJECTIVE

The study aims to evaluate the effect of contouring instruments on the porosity and immediate quality of direct dental restorations.

MATERIALS AND METHODS

Fifteen human molars with 30 Class II and 10 Class V cavities were restored by five voluntary dentists using three contouring instruments (conventional steel, silicone-tipped and diamond-like carbon coated-instruments) and three filling materials (Admira Fusion, Filtek Supreme XTE and Fuji II LC). The restorations were evaluated for immediate quality, porosity and number of pores using stereomicroscope and micro-computed tomography. Statistical analysis included the Shapiro‒Wilk test for normality, one-way ANOVA with Holm‒Sidak post hoc test for normal data, Kruskal‒Wallis ANOVA and Dunn's test for non-normal data, and Fisher's exact test for restoration quality comparisons. Statistical significance level was set at p < 0.05.

RESULTS

The proportion of restorations with acceptable immediate quality was higher for the restorations that had been contoured using a diamond-coated non-stick contouring instrument compared to the restorations that had been contoured using a conventional steel instrument (p = 0.033). The number of pores and porosity were similar for restorations that had been contoured with different contouring instruments. However, the number of pores and porosity were lowest in the restorations made of Filtek Supreme XTE followed by Admira Fusion and Fuji II LC.

CONCLUSION

The use of diamond-like carbon-coated contouring instruments increased the proportion of acceptable composite restorations compared to conventional steel instruments.

CLINICAL RELEVANCE

Non-stick contouring instruments should be considered for wider use.

Efficiency of bulk-fill versus conventional resin-based composite in class II restorations: A dental student perspective

Purpose/objectives

The aim of the study was to evaluate the effect of two distinct light-polymerization protocols, used by dental students, on the placement time and polymerization efficiency of bulk-fill (BF) and conventional (CRC) resin-based composites (RBCs).

Methods

Thirty dental students participated in this study. Each student was asked to complete four Class II RBC restorations using two different types of RBCs (BF and CRC) paired with two distinct light-polymerization protocols: one using 1200 mW/cm2 irradiance (P1200) and one using 800 mW/cm2 irradiance (P800). Manufacturer instructions for curing times relative to these irradiance levels were adhered to. The restorations were retrieved, sectioned and Vickers microhardness (VMH) was measured at specific reading points. The placement time was recorded for each procedure. Multivariate analysis of variance and Bonferroni post hoc test were used for data analysis.

Results

Bulk-fill RBCs were associated with significantly shortened placement times (P < 0.001). VMH values of CRC-P800 were significantly higher compared to all other groups (P < 0.02). Across all groups tested, the VMH values at the deepest reading points exceeded those at the occlusal surfaces by over 80 %.

Conclusions

The use of BF RBCs with a P1200 light-polymerization protocol reduced students' procedural times while maintaining effective polymerization of the restorations.

Bonding performance and interfacial adaptation of modern bulk-fill restorative composites after aging in artificial saliva: an in vitro study

OBJECTIVES

This study aimed at comparing the microtensile bond strength (MTBS) and interfacial adaptation of a modern self-curing and a light-curing restorative bulk-fill composite to a conventional composite applied with the layering technique.

METHODS

Forty-eight occlusal cavities were divided in three main groups (16/group) based on tested materials: (i) STELA, bulk-fill self-curing restorative (STELA, SDI Ltd.); (ii) 3 M-BULK, bulk-fill composite (Filtek One Bulk-Fill, 3 M Oral Care); and (iii) 3 M-CTR, a conventional composite (Filtek Supreme XTE, 3 M Oral Care). These were used in combination with their adhesives in self-etch (SE) or etch-and-rinse (ER) mode. Specimens stored in artificial saliva (24 h or 12 months) were evaluated for MTBS and fractography. The interfacial analysis was performed through confocal microscopy. ANOVA and Fisher's LSD post hoc tests were performed with a level of significance of 5%.

RESULTS

All the tested materials applied in ER mode presented (24 h) greater bond strength than in SE mode. Although all materials showed a significant drop in the bond strength after prolonged storage, STELA showed the highest bonding performance and interfaces with few gaps. 3 M-BULK had the lowest bond strength and an interface with several voids and gaps.

CONCLUSIONS

All materials were affected by interface degradation and bonding reduction over prolonged aging. However, their use in combination with adhesives applied in ER mode may offer greater immediate bonding performance.

CLINICAL RELEVANCE

The use of restorative light-curing bulk-fill composites may generate gaps at the bonding interface and voids. STELA may represent a suitable alternative to avoid such issues.