A Novel Technique for Bulk-Fill Resin-Based Restorations: Achieving Function and Esthetics in Posterior Teeth

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

OBJECTIVES

The aim was to compare the porosity of different bulk-fill resin-based composites (RBCs) placement techniques to the conventional incremental technique using microcomputed tomography (μ-CT).

MATERIAL AND METHODS

Occlusal cavities were prepared on extracted human molars, divided into five groups based on the placement technique (n = 10/group). Techniques examined were Monoblock-two-step (SureFil SDR flow + Ceram.X), Monoblock-two-step (Tetric EvoFlow Bulk-Fill + Tetric EvoCeram Bulk-Fill), Monoblock-one-step (Tetric EvoCeram Bulk-Fill), Monoblock with sonic activation (SonicFill2), and incremental technique (Filtek Z250). μ-CT scanning (SkyScan, Bruker, Belgium) assessed the number, volume of closed pores, and total porosity. Analysis of variance on ranks was used (Student-Newman-Keuls method and Mann-Whitney rank-sum test), to determine the significance of RBC viscosity and the sonication placement technique. The Spearman correlation method assessed the correlation between porosity characteristics (α = 0.05).

RESULTS

The SonicFill2 presented a higher number of closed pores than the other groups (p < 0.05). The overall porosity within the restoration seemed greater in this order: Filtek Z250 > SonicFill2 > Tetric EvoFlow Bulk-Fill + Tetric EvoCeram Bulk-Fill > Tetric EvoCeram Bulk-Fill > SureFil SDR Flow + Ceram.X. Sonication was associated with increased number (p = 0.005) and volume (p = 0.036) of closed pores. A strong correlation was observed between the number and volume of closed pores (R2 = 0.549, p < 001).

CONCLUSIONS

The monoblock technique with sonic activation showed significantly more internal porosity than the other placement techniques. Sonication during application contributed to the higher number and volume of closed pores than the passive bulk-fill application.

CLINICAL RELEVANCE

Using bulk-fill materials enhances efficiency, yet void formation remains an issue, depending on viscosity and active/passive delivery of materials. Clinicians must familiarize themselves with effective placement techniques to reduce void formation and optimizing treatment outcomes.

Influence of carbonated acid beverage on fracture resistance and marginal gap formation in different restorative approaches to non-carious cervical lesions

OBJECTIVE

This study is to evaluate fracture resistance, failure mode, and gap formation at the restorative interface of unrestored or restored non-carious cervical lesions (NCCLs) submitted to a short-term erosive environment.

MATERIALS AND METHODS

Artificial NCCLs were produced in vitro in bovine incisors, and were randomly divided into four restorative resins groups (n = 22): nanohybrid-NR; bulk-fill-BR; flow with a nanohybrid layer-FNR; bulk-fill with a nanohybrid layer-BNR; and a group unrestored-UR (n = 16). Half of the specimens were submitted to an erosive challenge (per 5 min, 3 × a day for 7 days, before and after restoration), and the other half, was immersed in artificial saliva. After, all teeth undergone thermal (5 ºC, 37 ºC, and 55 ºC, 3600 cycles) and mechanical (50 N, 2 Hz, 300,000 cycles) aging. Eighty teeth were subjected to compressive loading, and resistance and failures were analyzed, while 24 teeth were evaluated for gaps by microcomputed tomography. Statistical tests were performed (p < 0.05).

RESULTS

The restorative approaches affected fracture resistance (η2p = 0.14, p = 0.023), and gap formation (η2 = 0.18, p = 0.012) and so did the immersion medium (fracture η2p = 0.09, p = 0.008; gap η2 = 0.09, p = 0.017). BNR showed the highest resistance, while UR the lowest. FNR showed the highest gaps in both immersion media. Neither the resin groups nor the immersion media were associated with failure mode.

CONCLUSIONS

The erosive immersion medium based in acid beverages has been shown to affect NCCLs with or without restoration, but when Bulk-Fill resin is covered by nanohybrid resin, the performance is good.

CLINICAL RELEVANCE

Erosion negatively affects restorations, but unrestored NCCL shows worse biomechanical performance in stress-bearing situations.

One-Year Clinical Aging of Low Stress Bulk-Fill Flowable Composite in Class II Restorations: A Case Report and Literature Review

Bulk-fill flowable composites provide functional and aesthetic restorations while eliminating incremental composite layering and saving time. The degradation of the adhesive interface with subsequent gap formation is a concern when adhesively luted restorations are placed. Moreover, the number of adhesive interface failures increases when they are exposed to long-term water storage. The aim of the present study was to evaluate the morphological characteristics of the tooth-composite interface in class II cavities restored with a low stress bulk-fill flowable composite after aging in an oral environment. We describe a case of a patient with class II cavities in four premolars restored with a low stress bulk-fill flowable composite Surefil SDR (Dentsply DeTrey GmbH, Konstanz, Germany). The occlusal part was restored with nano-hybrid resin composite Ceram X Mono (Dentsply DeTrey GmbH). After one year of clinical function, the teeth were extracted and examined in a scanning electron microscope (SEM). It can be concluded that the application of bulk-fill covered with conventional composite seems to provide the homogeneous and stable bond to tooth structure after one year of aging in an oral environment. However, some defects within the dentin-resin composite interface were observed.