Color stability of Lucirin-photo-activated resin composite after immersion in different staining solutions: a spectrophotometric study

Residual TPO Content of Photopolymerized Additively Manufactured Dental Occlusal Splint Materials

Background/Objectives: Diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO) is widely used in the dental industry as a photoinitiator for resin-based materials, while its use may be further limited given its toxicological risks. The aim of this study was, therefore, to analyze the residual TPO content of 3D-printed resin-based dental splint materials. Methods: Six resin-based splint materials were analyzed: LuxaPrint Ortho Plus (DMG), FREEPRINT splint 2.0 (Detax), optiprint splint (Dentona), KeySplint Soft (KeyPrint), FREEPRINT ortho (Detax), V-Print splint comfort (Voco). Grid-shaped specimens were fabricated using the recommended workflow of each manufacturer (n = 18). TPO extraction was conducted using a maximum of eight extraction cycles of 72 h at a temperature of 37 °C until no more TPO eluates were detected by high-performance liquid chromatography (HPLC). The margin of safety (MoS) was calculated as the ratio between the Derived No-Effect Level (DNEL) and the estimated exposure based on the amount of TPO extracted. Results: The total amount of extracted TPO was the lowest for LuxaPrint Ortho Plus (Mean ± SD; 44.0 ± 17.1 ng/mL), followed by optiprint splint (80.6 ± 21.1 ng/mL), FREEPRINT splint 2.0 (127.4 ± 25.3 ng/mL), FREEPRINT ortho (2813.2 ± 348.0 ng/mL), V-Print splint comfort (33,424.6 ± 8357.9 ng/mL) and KeySplint Soft (42,083.5 ± 3175.2 ng/mL). For all tested materials, the calculated MoS was above the critical value of 1, demonstrating toxicological safety in the cured, clinically relevant state. Conclusions: Large differences in the residual TPO content were observed between the materials. Although the TPO content in the uncured state may exceed toxicological safety limits, appropriate curing of the investigated materials resulted in a significant reduction in TPO elution and, thus, in products with a very low toxicological risk for the patient.

Color stability of nanohybrid and microhybrid composites after immersion in common coloring beverages at different times: a laboratory study

OBJECTIVE/AIM

This in vitro study aimed to evaluate the color stability of microhybrid and nanohybrid restorative composites after exposure to immersion media common in Yemen for different periods.

MATERIALS AND METHODS

Two composite materials, nanohybrid Tetric N-Ceram and microhybrid Te-Econom Plus, were investigated. Six groups of 30 cylindrical specimens (n = 5/group; diameter, 10 mm; thickness, 2 mm; shade A2) of each restorative material were immersed for 1 week in distilled water, qat solution, Yemeni coffee, traditional Yemeni coffee (qishr), red tea, and Dilsi cola. Color changes were evaluated by colorimetry. The color data and pH were measured before and 1, 3, and 7 days after immersion. The data were statistically analyzed.

RESULTS

Tetric N-Ceram showed lesser discoloration than did Te-Econom Plus. Qat, coffee, and red tea caused highly significant discoloration than did Dilsi cola and distilled water (p < 0.05). The role of low pH in discoloration depended on the colorant.

DISCUSSION

Nanohybrid Tetric N-Ceram composites are more resistant to discoloration than are microhybrid Te-Econom Plus composites. Qat and coffee have the highest effect on composite discoloration.

CONCLUSIONS

These findings will aid in selecting composite materials and patient instruction.

Can TPO as Photoinitiator Replace "Golden Mean" Camphorquinone and Tertiary Amines in Dental Composites? Testing Experimental Composites Containing Different Concentration of Diphenyl(2,4,6-trimethylbenzoyl)phosphine Oxide

The aim of this research was to compare the biomechanical properties of experimental composites containing a classic photoinitiating system (camphorquinone and 2-(dimethylami-no)ethyl methacrylate) or diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) as a photoinitiator. The produced light-cured composites consisted of an organic matrix-Bis-GMA (60 wt.%), TEGDMA (40 wt.%) and silanized silica filler (45 wt.%). Composites contained 0.27; 0.5; 0.75 or 1 wt.% TPO. Vickers hardness, microhardness (in the nanoindentation test), diametral tensile strength, resistance to three-point bending and the CIE L* a* b* colorimetric analysis was performed with each composite produced. The highest average Vickers hardness values were obtained for the composite containing 1 wt.% TPO (43.18 ± 1.7HV). The diametral tensile strength remains on regardless of the type and amount of photoinitiator statistically the same level, except for the composite containing 0.5 wt.% TPO for which DTS = 22.70 ± 4.7 MPa and is the lowest recorded value. The highest average diametral tensile strength was obtained for the composite containing 0.75 wt.% TPO (29.73 ± 4.8 MPa). The highest modulus of elasticity characterized the composite containing 0.75 wt.% TPO (5383.33 ± 1067.1 MPa). Composite containing 0.75 wt.% TPO has optimal results in terms of Vickers hardness, diametral tensile strength, flexural strength and modulus of elasticity. Moreover, these results are better than the parameters characterizing the composite containing the CQ/DMAEMA system. In terms of an aesthetic composite containing 0.75 wt.%. TPO is less yellow in color than the composite containing CQ/DMAEMA. This conclusion was objectively confirmed by test CIE L* a* b*.

Spectrophotometric study determining staining tendency in different restorative materials (longitudinal in vitro study)

Aim

Our aim was to measure the discolouration degrees in a packable composite, zircon, ceramic, a flowable composite, and GIC (glass isomer cement) and to determine their tendencies to discolour to provide guidance to dentists and prosthodontist for choosing proper materials for cases in which aesthetics is the main treatment goal.

Materials and methods

Sixty discs were fabricated from the composite, zircon, ceramic, the flowable composite, and GIC, and natural teeth were the control group. The shades were recorded using the Ivoclar Vivadent Shade Guide, and readings were recorded from a Vita Easyshade 4.0 spectrophotometer before immersion, after 1 week, 2 weeks, 3 weeks, and 24 weeks of immersion in coffee. The analysis was performed using a SPSS paired t-test and CIE 76 formula.

Results

The ceramic had a starting shade of B1 and kept the same colour throughout the testing period. Zircon had a starting shade of A3 and transitioned to B3 by the second week. The composite had a shade of A1, and after the first week, it was A4; in the second week and afterwards, it was C4. The flowable composite had a starting shade of A1, and after one week, the shade was B3, and then after one more week A3.5; after five months, it was A4.

Conclusion

The ceramic showed no change, making it ideal for aesthetic regions and anterior replacements. Zircon had the second-highest colour stability, whereas all the other materials showed variable degrees of colour and surface changes, making them not ideal choices for anterior restorations. Thus, this information can aid choices for aesthetic regions to provide the highest longevity.

The Photoinitiators Used in Resin Based Dental Composite-A Review and Future Perspectives

The presented paper concerns current knowledge of commercial and alternative photoinitiator systems used in dentistry. It discusses alternative and commercial photoinitiators and focuses on mechanisms of polymerization process, in vitro measurement methods and factors influencing the degree of conversion and hardness of dental resins. PubMed, Academia.edu, Google Scholar, Elsevier, ResearchGate and Mendeley, analysis from 1985 to 2020 were searched electronically with appropriate keywords. Over 60 articles were chosen based on relevance to this review. Dental light-cured composites are the most common filling used in dentistry, but every photoinitiator system requires proper light-curing system with suitable spectrum of light. Alternation of photoinitiator might cause changing the values of biomechanical properties such as: degree of conversion, hardness, biocompatibility. This review contains comparison of biomechanical properties of dental composites including different photosensitizers among other: camphorquinone, phenanthrenequinone, benzophenone and 1-phenyl-1,2 propanedione, trimethylbenzoyl-diphenylphosphine oxide, benzoyl peroxide. The major aim of this article was to point out alternative photoinitiators which would compensate the disadvantages of camphorquinone such as: yellow staining or poor biocompatibility and also would have mechanical properties as satisfactory as camphorquinone. Research showed there is not an adequate photoinitiator which can be as sufficient as camphorquinone (CQ), but alternative photosensitizers like: benzoyl germanium or novel acylphosphine oxide photoinitiators used synergistically with CQ are able to improve aesthetic properties and degree of conversion of dental resin.