Introduction
infection, fracture, caries
INFECTION, SECONDARY, RECURRENCE, CARIES
For many years, the incremental technique has been the most suitable method for restoring teeth using composite resin, with increments of up to 2 mm in thickness. This technique facilitates a proper light curing of the composite and reduces the stress generated by polymerization shrinkage.To minimize these problems and simplify the restorative technique, bulk-fill composite resins have been introduced to the market. Modifications to this material allow for the use of increments of 4-5 mm in thickness, without negatively affecting the light curing of the deeper layers. Due to the low polymerization shrinkage, it is possible to insert increments joining more than two walls, unlike with conventional composite resins.The first bulk-fill composite resins introduced to the market were flowable bulk-fill or low-viscosity bulk composite resins, whose effectiveness has been evaluated and approved in long-term studies.On the other hand, several commercial composite resins were recently launched in single doses (capsules) in addition to the traditional presentation in syringes. According to the manufacturers, this new presentation seems to help clinicians with infection control during restorative procedures, apart from being easily handled with a dispenser and being less time-consuming because it does not require using a spatula to pick a portion of the material from the syringe, which is necessary in some cases. However, a recently published studyUniversal adhesive systems are another group of materials that have been developed aiming to facilitate and speed up the performance of adhesive restorative procedures due to their versatility.Therefore, this randomized clinical trial aims to evaluate, after 24 months of clinical evaluation, the clinical performance of class I and class II restorations performed with universal adhesives applied either in the SEE or in the self-etch (SET) mode and to determine if bulk-fill composite resins packaged either in syringes or in capsules are reliable substitutes for composite resins inserted using the incremental technique.The null hypotheses tested were: i) there is no significant difference in the fracture and retention rates of class I and class II restorations made with different composite packaging (syringe vs. capsule) and the incremental technique when evaluated using FDI criteria, ii) there is no statistical difference in the fracture and retention rates of class I and class II bulk-fill restorations made with SEE compared to SET adhesive strategy when evaluated using FDI criteria, iii) there is no statistical difference in the secondary outcomes (recurrence of caries, anatomic form, proximal contact quality, color match, marginal staining, marginal adaptation, postoperative sensitivity, and patient perception) of class I and class II bulk-fill restorations made with different composite packaging (syringe vs. capsule) compared to the incremental technique when evaluated using FDI criteria, and iv) there is no statistical difference in the secondary outcomes of class I and class II bulk-fill restorations made with the SEE compared to SET adhesive strategy when evaluated using FDI criteria.