This in vitro study was conducted to evaluate the effect of Pekkton and zirconia primary crowns on the stresses induced on the supporting structures of Pekkton telescopic mandibular partial denture using strain gauge stress analysis method
Methdology: A mandibular Kennedy class I scanned educational model with second premolars bilaterally were the last abutments. In software, designing and preparing the last 2 abutments bilaterally was done to receive primary coping of telescope. The modified virtual model was 3D printed using into two identical 3 D casts Thus, two groups were defined with Pekkton® RPD frameworks(secondary crowns) Group 1:Pekkton primary crowns,, Group 2: Zirconia primary crowns. The STL file was imported into the 3D system, sending to the milling machine to fabricate both type of primary crowns .Designing and milling of The telescopic Pekkton partial denture framework were done .installations of strain gauge sensors were done and a universal testing machine were used to apply load of bilaterally and unilaterally.
Result: The result revealed that under bilateral loading, the mean values of the stresses distal to the last abutment and in second molar area for (Pekkton primary crown) were (124.70), (49.00) respectively while in ( zirconia primary crown) the mean values were (347.10), (79.30) and the results showed statistically significance difference. During unilateral loading, the results showed higher strain values in zirconia group with statistically significance.
Conclusion: In telescopic RPDs, during bilateral and unilateral loading, Zirconia induces higher strain at the abutments and the distal aspect of the ridge than Pekkton.