In Vitro Analysis of Shear Stress: CAD Milled vs Printed Denture Base Resins with Bonded Denture Tooth

Abstract

As the fabrication of computer-aided design (CAD) milled and 3D printed denture base resins with bonded denture teeth increase in popularity, there is a need for research comparing the shear bond stress of milled and printed denture base resins with bonded denture teeth to that of a conventional heat processed denture base. Materials and methods: Denture base resin specimens (n = 9) were fabricated according to manufacturers' instructions using a novel test design. Two milled (Ivobase CAD PMMA, Ivoclar Vivadent and Polident PMMA, Polident Dental) and two 3D printed (Denture Base LP Resin, Formlabs and Lucitone Digital Print, Dentsply Sirona) materials were used. Conventional heat processed polymethylmethacrylate was used as the control (Lucitone 199, Dentsply Sirona). Denture teeth (VITA Vitapan XL T44, #8, VITA Zahnfabrik) were bonded to their respective bases using denture tooth bonding agent (Ivobase CAD bonding system, Ivoclar). Specimens were aged in water for 600 hours at 37 • C and loaded until failure in a Universal testing machine. Shear bond stress was calculated. All specimens were evaluated for mode of failure and select specimens under scanning electron microscope and vertical scanning interferometry. Data were analyzed with one-way ANOVA followed by Tukey test (IBM SPSS) and fracture analysis performed. Results: Shear stress was highest for the heat processed control (mean = 180 N ±26.76) and Polident test groups (mean = 180 N ± 34.90). Milled specimens were not significantly different from the control (p = 0.076 for IvoBase CAD and 1.00 for Polident), while the printed groups were significantly different from the control (p = 0.012 for Formlabs Denture Base Resin and p = 0.00 for Carbon Lucitone Digital Print). Milled denture base resins performed similarly to heat processed denture base resin and better than 3D printed denture bases. Conclusion: For complete denture wearers, all resin materials used in this study may be clinically acceptable, as the sheer stress for all groups was higher than the reported maximum biting force of complete denture patients. However, for implant retained prostheses, the incorporation of additional retentive features should be considered when bonding denture teeth to printed bases. More research is needed to evaluate methods to increase the bond strength of denture teeth to printed denture base resins.

A discussion of “In vitro analysis of shear stress: CAD milled vs printed denture base resins with bonded denture tooth”

“…When this specimen was submitted to testing, the six teeth (100%) showed a cohesive fracture, suggesting, albeit indirectly, a much higher bond strength than that reported by Kane & Shah. 1 These results and this inference find support in the work of Alfadhli, who conducted an in vitro evaluation on the SBS and MoF of denture teeth materials bonded to denture base materials, with and without thermocycling. A closer look at the study methodology reveals that the author did use the DS 3-Step Fuse System to bond LDP to Lucitone Digital Value™.…”

“…Shear bond strength (SBS) and mode of failure (MoF) were the outcomes assessed. 1 Their results showed LDP's SBS to be statistically lower than that of the other four materials tested, and 100% of fractures (of all materials) to be both adhesive and cohesive. 1 The latter is in stark contrast to Dentsply Sirona's (DS) internal tests and to Alfadhli's findings, with both showing all fractures to be cohesive.…”

“…1 Their results showed LDP's SBS to be statistically lower than that of the other four materials tested, and 100% of fractures (of all materials) to be both adhesive and cohesive. 1 The latter is in stark contrast to Dentsply Sirona's (DS) internal tests and to Alfadhli's findings, with both showing all fractures to be cohesive. 2 Alfadhli goes even further to show that, of all denture base materials tested (very much the same as Kane and Shah, 1 with the exception of PoliDent, as detailed below), LDP was the only one to present 100% of cohesive fractures with and without thermocycling.…”

“…Speaking of ways to try to optimize tooth bonding, Kane and Shah suggest that for implant-retained prostheses, additional retentive features should be considered when bonding denture teeth to printed bases. 1 LDP has been validated for implant-retained dentures with attachments over the implants in combination with any of the following pick-up materials: EZ PickUp ® (Sterngold Dental, LLC, Attleboro, MA); Quick Up ® (VOCO GmbH, Cuxhaven, Germany); and Chairside ® Attachment Processing Material (Zest Dental Solutions, Carlsbad, CA). However, there are no differences in the tooth bonding protocol; this is the same regardless of the type of support to the prosthesis.…”

“…Regarding differences in test methods between DS's and those of Kane and Shah, 1 Dentistry-Artificial teeth for dental prostheses. 6 Both ISOs reference each other for the exact same test for tooth bond testing, as both base and teeth are required for testing.…”