Discussion
parafunctional habits, ’ behavior, ’, low caries, fracture, caries, fractures
SECONDARY, POSTERIOR, CAVITY, CARIES
In this study, some clinical parameters of the performance of restorations were influenced by the bulk-fill composite packaging and SEE. After 24 months of clinical use, restorations placed using the bulk-fill composite, mainly in capsules, showed better clinical performance than those placed with the incremental technique. Furthermore, restorations placed with SEE followed by adhesive application showed better performance than those placed using only the SET strategy.Initially, considering the parameters of the FDI criteria for evaluating restorative materials’ functional properties, the main outcome from the point of view of longitudinal evaluation was the restoration fracture and retention. This study showed a few cases of fracture in various groups after 24 months, with no significant difference between them, regardless of the packaging of composite resin (syringe vs. capsule) and the adhesive strategy (SEE vs. SET). Therefore, the first and second null hypotheses were accepted. The reason for fractures of composite restorations in this study could be non-diagnosed parafunctional habits or changes in some patients’ behavior during the follow-up times and should be considered in addition to the restorative material itself. However, the similar satisfactory clinical performance of bulk-fill restorations and those with incremental resin agrees with previous literature.The studied composites’ low fracture rate, as well as the satisfactory anatomic form and proximal contact, could be explained by their larger amount of filler. Moreover, the materials contain additional zirconia filler, and zirconia/silica fillers (2.5 and 5.0 wt%) replace those of glass, improving some mechanical properties such as flexural strength and fracture resistance.In our study, this translucency characteristic of bulk-fill composite resins seems not to affect the restorations’ color match after a 24-month evaluation. Even so, a larger percentage of restorations with color mismatch was observed in the incremental groups (12%) and bulk-fill composite resin in syringe groups (9%) than in the bulk-fill composite resin in capsules (0%). This behavior could be related to several factors. First, composites have different chemical compositions because only the Filtek Supreme Ultra composite resin, which was used in the incremental group, contains the hydrophilic monomer triethyleneglycol dimethacrylate, which makes the composite more prone to incorporate pigments and staining over time due to its higher water absorption capacity.The marginal staining and marginal adaptation were the categories in which bulk-fill composite resin restorations showed better results compared to those made with incremental resin. Therefore, the third null hypothesis was partially rejected. When the composition of Filtek Bulk-Fill (Filtek Bulk-Fill Posterior Restorative or Filtek One Bulk-Fill) was evaluated, some components such as an aromatic dimethacrylate (AUDMA), additional fragmentation molecules (AFM), urethane dimethacrylate (UDMA), and 1,12-dodecane dimethacrylate (DDMA) were found in its resin matrix.However, the most interesting results related to marginal adaptation were observed in the evaluation of the commercial presentation of bulk-fill composite resins. Composites in capsules showed better marginal adaptation after a 24-month recall than composites in syringes. Several factors may be involved in the effective marginal adaptation of a resin composite to the cavity.Regarding the secondary outcomes of the adhesive strategy, our study showed a difference only in the marginal adaptation category, whereas the universal adhesive applied with SEE showed better marginal adaptation than the SET mode. Therefore, the fourth null hypothesis was partially rejected. Studies frequently report that the universal adhesives applied in the SET mode did not properly etch the enamel surface.It was reported that some baseline characteristics of cavities could affect the survival of posterior restorations, such as cavity extensions (class I or II).One of the limitations of this study is that although some significant differences were observed between the groups after 24 months, which is a medium-term clinical follow-up, the defects observed did not impact the patients’ perception and could be easily resolved by repolishing the restorations.Finally, the characteristics of the participants included in our study were good general health and acceptable oral hygiene, which could result in participants with low caries risk; therefore, a caries risk assessment was not conducted. However, a systematic analysis of participants’ caries risk assessment would be important to identify patient factors’ effect on restorations’ clinical performance,