Proposal for a gingival shade guide based on in vivo spectrophotometric measurements

PURPOSE: The purpose of this study was to propose and assess a shade guide for pink gingival aesthetics using a Spanish population sample. MATERIALS AND METHODS: The L*, C*, h, a* and b* coordinates of 259 participants were measured using a spectrophotometer in 3 standardized points along the attached gingiva of the maxillary central incisors. A hierarchical clustering analysis was applied to obtain separate solutions regarding the number of shade tabs. For each of the solutions obtained, color differences (ΔE*) were calculated using the CIELab and CIEDE2000 formulas, and the proposed shade guide was selected considering (1) the color differences between tabs and (2) the coverage error of each of the solutions. RESULTS: The proposed shade guide consisted of 8 gingival shade tabs and achieved CIELab and CIEDE2000 coverage errors of less than the respective 50:50% acceptability thresholds (ΔE*=4.6 units and ΔE₀₀=4.1). The coordinates for the various gingival shade tabs were as follows: Tab 1: L*43.3, a*21.9, b*12.3 (1.6); Tab 2: L*42.9, a*34.1, b*19.1; Tab 3: L*46.5, a*25.8, b*10.9; Tab 4: L*46.5, a*27.3, b*15.1; Tab 5: L*49.6, a*23.5, b*16.8; Tab 6: L*51.5, a*19.7, b*13.6; Tab 7: L*55.9, a*22.0, b* 15.0; and Tab 8: L*56.0, a*19.9, b*18.8. CONCLUSION: The CIELab and CIEDE2000 coverage errors for the 8 shade tabs of the proposed gingival shade guide were significantly lower than those of other guides. Therefore, despite the limitations of this study, the proposed guide is more appropriate for matching gingival shade in the Spanish general population.

effect of femtosecond laser treatment on the effectiveness of resin-zirconia adhesive: an in vitro study

Introduction: when aesthetics is compromised, dental ceramics are excellent materials for dental restorations; owing to their optical properties and biocompatibility, zirconia ceramics are particularly interesting. Self-adhesive resin cements are the most suitable for bonding to zirconia ceramics, but traditional adhesive chemistry is ineffective and surface treatments are required to improve the adhesive bonding between resin and zirconia. The aim of this study was to evaluate the effect of femtosecond laser treatment on the shear bond strength [SBS] of self-adhesive resin cement on zirconia surfaces and to contrast it with other different surface conditioning methods

Methods: sixty square-shaped zirconia samples were divided randomly into four groups [n = 15] according to their surface conditioning method: the NT group - no surface treatment; the APA25 group - airborne abrasion with 25 micro m alumina particles; the TSC group - tribochemical silica coating, and the FS group - femtosecond laser irradiation [800 nm, 4 mJ, 40 fs/pulse, 1 kHz]. Self-adhesive resin cements were bonded at the centre of samples, and after 72 hours, they were tested for SBS with a universal testing machine at a crosshead speed of 0.5 mm/min, until fracture. Five zirconia surfaces for each group were subjected to a surface morphology analysis by scanning electron microscopy [SEM]. The failure modes were noted and a third of the specimens were prepared to morphological analysis

Results: the NT group showed lower SBS values than the other groups. Femtosecond laser treatment demonstrated higher values than the control and APA25 groups and similar values to those of the TSC group. In the APA25 group, the surface conditioning method had values close to those of the TSC group, but lower than those obtained with femtosecond laser treatment

Conclusion: the treatment of zirconia with femtosecond laser irradiation created a consistent and profound surface roughness, improving the adhesive effectiveness of the zirconia-resin interfaceIntroduction: when aesthetics is compromised, dental ceramics are excellent materials for dental restorations; owing to their optical properties and biocompatibility, zirconia ceramics are particularly interesting. Self-adhesive resin cements are the most suitable for bonding to zirconia ceramics, but traditional adhesive chemistry is ineffective and surface treatments are required to improve the adhesive bonding between resin and zirconia. The aim of this study was to evaluate the effect of femtosecond laser treatment on the shear bond strength [SBS] of self-adhesive resin cement on zirconia surfaces and to contrast it with other different surface conditioning methods