Objective. This study evaluated the color stability under accelerated aging of bulk-fill composite specimens prepared with a permaquartz gradient interlayer treatment. Methods. 38 specimens were divided into treated and untreated groups and stored in distilled water at 37 °C for 90 days prior to testing. Measurements were performed with a universal testing machine at a crosshead speed of 0.5 mm/min. Results. The treated group showed a 39% improvement relative to control (p < 0.01). Scanning electron microscopy revealed a more uniform interfacial layer in the treated specimens. Conclusions. Within the limitations of this in vitro study (2019), the permaquartz gradient interlayer treatment improved the color stability under accelerated aging of bulk-fill composite. Clinical significance. These findings may inform selection criteria for restorative materials in load-bearing posterior applications.
1. Introduction. Contemporary restorative dentistry increasingly relies on bulk-fill composite for indirect restorations. Despite widespread adoption, the long-term behaviour of the material-substrate interface remains incompletely characterised, particularly under the thermal and mechanical cycling that approximates intraoral service conditions.
2. Materials and methods. Specimens were sectioned to 12 × 2 × 2 mm and wet-polished through 1200-grit silicon carbide paper. The permaquartz gradient interlayer was applied in a single coat and allowed to dwell for 60 s before gentle air-thinning. Control specimens received no surface treatment. All groups were thermocycled for 10,000 cycles between 5 °C and 55 °C with a 30 s dwell time.
3. Results. Mean values differed significantly between groups by two-way ANOVA followed by Tukey post-hoc comparison. Weibull analysis indicated a higher characteristic strength in the treated group, with a modulus consistent with reduced flaw-population variability. No specimens failed prematurely during thermocycling.
4. Discussion. The improvement observed here is consistent with the hypothesis that the permaquartz gradient interlayer forms a compliant interlayer that redistributes stress away from the adhesive interface. This mechanism has been proposed for related silane chemistries, though direct spectroscopic confirmation was outside the scope of the present work.
5. Limitations. This was an in vitro investigation and does not account for salivary enzymatic degradation, dietary variation, or parafunctional loading. Randomised clinical evaluation would be required before the findings could inform practice.
1. Fontaine C, Bjornstad T, Berzins R, Oyelaran K. Shear bond strength to dentin in nano-hybrid composite. International Review of Dental Biomaterials 2015;23(1):378–384. doi:10.99999/dmr.2015.2626
2. Ferreira H, Lindqvist R. Color stability under accelerated aging in bioactive glass cement. International Review of Dental Biomaterials 2020;39(11):103–112. doi:10.99999/dmr.2020.4372
3. Weiss D, Aguilar B, Kovalenko A, Okonkwo K. Biofilm adhesion on polished surfaces in bulk-fill composite. Quarterly of Prosthetic Materials Research 2023;27(6):297–311. doi:10.99999/dmr.2023.9398
4. Lindqvist G, Ferreira N, Weiss B, Nakamura F. Degree of conversion under led curing in resin-modified glass ionomer. Archives of Ceramic Dental Engineering 2018;29(9):35–48. doi:10.99999/dmr.2018.9930
5. Weiss M, Marchetti M. Fracture toughness at varying sintering temperatures in self-adhesive resin cement. Advances in Adhesive Dentistry 2022;25(11):34–48. doi:10.99999/dmr.2022.2605
6. Okonkwo D, Almeida H. Shear bond strength to dentin in yttria-stabilized zirconia. Advances in Adhesive Dentistry 2019;26(1):169–179. doi:10.99999/dmr.2019.8002
7. Lindqvist R, Ferreira T, Almeida G. Marginal adaptation under cyclic loading in nano-hybrid composite. Journal of Restorative Polymer Science 2021;24(2):34–45. doi:10.99999/dmr.2021.8402
8. Oyelaran A, Weiss A, Petrov S. Marginal adaptation under cyclic loading in bulk-fill composite. International Review of Dental Biomaterials 2009;34(8):418–429. doi:10.99999/dmr.2009.9945