An Evaluation of Retentive Ability and Deformation of Acetal Resin and Cobalt-Chromium Clasps

Abstract

Aim: To compare the retentive ability and deformation of Acetal resin with Cobalt-Chromium clasps via Insertion Removal apparatus after subjecting them to stimulate clinical use. Materials and Methods:Materials used for this study are commercially available Cobalt-Chromium alloy namely Wironit, Bego, Germany and Acetal resin namely Biodentaplast, Bredent, Germany. The test samples were divided into two major groups based on the type of materials used in the study. Each major group is further subdivided into two sub groups based on the retentive undercut depths used to engage the clasps. So a total of 20 specimens were prepared, comprising of 5 specimens in each sub group. Then the specimens were tested for retention force and deformation. Results:The results of this study indicate that acetal resin clasps are resistant to deformation and may offer a clinical advantage over the conventional metal clasps. The retentive force of acetal resin clasps did not decrease over the cycling periods. This would be attributed to the resilient nature of acetal resin. Under the conditions of the present study cobalt chromium clasps lost retentive force within 730 cycles of placement and removal and continued to lose retentive force during the remaining test period. Conclusion:This invitro study demonstrated that retentive force of cobalt chromium clasp is superior to that of Acetal resin for removable partial dentures. As acetal resin clasps exhibits greater flexibility and long term retentive resiliency, it can be used for removable partial dentures where aesthetics or periodontal health is a primary concern.A. Meenakshi et al.,

Evaluation of Acetal Resin and Cobalt–chromium Clasp Deformation and Fatigue Resistance in Removable Partial Denture Clasps an in-Vitro Study

“…Also the results of the present study were at variance with Meenakshi et.al (15) who showed increase in the distance between the tips of the Co-Cr clasps more than that occurred with acetal resin clasps but without significant deformation after 12 months test period.…”

“…Others reported that the thermoplastic resin direct retainer is more flexible than the conventional Co-Cr direct retainer. (13)(14)(15)(16)(17)(18) There is controversy in the literatures (19)(20)(21)(22) and also little data available regarding the long-term performance of such direct retainers. Therefore this study was aimed to evaluate the fatigue resistance (amount of clasp deformation) of acetal resin clasps and Co-Cr clasps after attachment/detachment cycles on abutment teeth with two different undercuts.…”

Retention and Fatigue Resistance of Peek and Acetal Thermoplastic Resin Clasps

“…Loss of retention of the clasps due to fatigue resistance test was considered as a good indicator of permanent deformation of the clasps (3) . These agreed with Helal, et al who reported that the clasp may lose its retention force as a result of multiple deflections (12) , and contradict with Meenakshi, et al who showed that the retention force of acetal clasps did not decrease after cycling intervals while the Co-Cr clasps lost retention force within 730 cycles of insertion/removal and continued to lose retention force during the remaining intervals (23) .This may be explained by the method which is used to carry out the test.…”

Examination of inter-rater and intra-rater reliability during retentive force measurement of different clasps using the developed small-sized retentive force measurement device

“…To date, the retentive force of a clasp has been reported in many laboratory studies [6][7][8][9][10][11][12][18][19][20][21][22][23][24][25][26]. Ahmad et al [18] mentioned that the mean retentive force for a framework engaging an undercut of 0.25 mm with Akers clasp was 4.77 N. Meenakshi et al [10] showed the clasp required 7.24 N for 0.25 mm undercut and 8.37 N for 0.50 mm undercut. Frank and Nicholls [19] concluded that 300 to 750 g (2.94 to 7.35 N) represented an acceptable amount of retention for a bilateral distal extension RPD.…”

“…Regarding the measurement of the retentive force of the clasp for RPD, there are also several studies on clasps using the finite element method [ 6 ], on measuring the retentive force using a universal testing machine with a crosshead speed [ 7 ], on weighing the retentive force of removal and insertion cycling of clasp [ 8 ], on cyclic fatigue properties of alloy cast clasps [ 9 ], on an evaluation of retentive ability and deformation [ 10 ], on the comparison of buccal and lingual retention [ 11 ], and on clasps compared with the metal materials used [ 12 ]. These are all studies using large-scale experimental equipment, and until now, there was no equipment in the dental field that could easily measure the retentive force of a clasp of RPD.…”