Evaluation of the Retentive Forces from Removable Partial Denture Clasps Manufactured by the Digital Method

Abstract

The purpose of this study was to evaluate the retentive forces over time of removable partial denture clasps fabricated by the digital method. Occlusal rest seats were fabricated on three premolar teeth fixed in acrylic blocks (9 × 20 × 40 mm). Digitization of the teeth was performed using a laboratory scanner (Zirkonzahn Scanner S600 GmbH, Gais, Italy). After the analysis and determination of the insertion axis, two types of clasps with mesial occlusal rests were designed per tooth: the back-action and the reverse back-action clasps, using the Partial Planner Zirkonzahn program. The file was sent for fabrication of six metal clasps from a cobalt-chromium SP2 alloy in the EOSINT M270 system by a direct laser sintering process. The Instron 5544 universal testing machine was used to perform 20,000 cycles of clasp insertion and removal in the corresponding tooth with a load cell of 100 N and a speed of 2.5 mm/s. The retentive force was recorded for each of the 1000 cycles, and the change in retention over time was calculated. Statistical analysis was performed using the nonparametric Mann–Whitney test and a significance level of 5%. At 16,000 cycles, a maximum change in retention of 3.74 N was recorded for the back-action clasps and a minimum of −24.28 N at 1000 cycles for the reverse back-action clasps. The reverse back-action clasps exhibited statistically significant lower change in retention than the reverse-action clasps at 4000 and 5000 cycles. No differences were observed in the remaining cycles. During the 20,000 cycles, the change in retention was low regardless of the type of clasp. For most cycles, there were no differences in the change in retention between the two types of clasps.

Deformation and retentive forces variations of the additively manufactured cobalt-chromium and titanium alloys dental clasps

“…1 k). A total of 5000 cycles of vertical movements repetition, parallel to the longest axis of the tooth and to the axis of insertion of the clasps, were performed to simulate 3.5 years of usage of the RPD, as if the patient performs four cycles of insertion and removal of the RPD per day ( Anes et al, 2023 ).…”

Special Issue on New Techniques, Materials and Technologies in Dentistry

“…Also, building a bridge with the digital area, Anes et al [19] evaluated the retentive forces from removable partial denture clasps manufactured using the digital method. The objective of this study was to evaluate retentive forces and the change in clasps with digitally manufactured different designs over time.…”

Evaluation of Removable Partial Denture Metal Frameworks Produced by Digital Methods—A Systematic Review

“…This conventional protocol initiates with a clinical impression, followed by laboratory steps, including diagnostic cast production and surveying, refractory cast acquisition, waxing, casting, metal framework fabrication, and finishing [8]. Cobalt-chromium is usually the metal alloy used due to its good biocompatibility, appropriate wear and corrosion resistance, high fatigue strength, and low cost [7,[9][10][11][12]. Titanium can also be used, but, despite the advantages of lower weight and lower modulus of elasticity, it has the disadvantage of lower yield strength [13][14][15].…”