Author/Authors :
Ghanbarzadeh، Jalil نويسنده Dental Research Center, Department of Prosthodontics, Faculty of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran , , Dashti، Hossin Dashti نويسنده Department of Prosthodontics, School of Dentistry , , Karamad، Reza نويسنده Department of Prosthodontics, School of Dentistry , , AliKhasi، Marzieh نويسنده Department of Dental Prosthesis and Implants, Laser Research Center of Dentistry, School of Dentistry, Tehran University of Medical Sciences, Tehran, , , Nakhaei، Mohammadreza نويسنده Dental Research Center, Faculty of Dentistry, Mashhad University of Medical Sciences, ,
Abstract :
Background: The fi nal position of the abutment changes with the amount of tightening torque.
This could eventually lead to loss of passivity and marginal misfi t of prostheses. The aim of this
study was to evaluate the effect of three different tightening torques on the marginal adaptation
of 3-unit cement-retained implant-supported fi xed dental prostheses (FDPs).
Materials and Methods: Two implants (Straumann) were inserted in an acrylic block so that one
of the implants was placed vertically and the other at a 15° vertical angle. A straight abutment and a
15° angulated abutment were connected to the vertically and obliquely installed implants, respectively,
so that the two abutments were parallel. Then, 10 cement-retained FDPs were waxed and cast.
Abutments were tightened with 10, 20, and 35 Ncm torques, respectively. Following each tightening
torque, FDPs were luted on respective abutments with temporary cement. The marginal adaptation
of the retainers was evaluated using stereomicroscope. FDPs were then removed from the
abutments and were sectioned at the connector sites. The retainers were luted again on their
respective abutments. Luting procedures and marginal adaptation measurement were repeated.
Data were analyzed by ANOVA and least signifi cant difference tests (? = 0.05). After cutting the
FDP connectors, the independent samples t-test was used to compare misfi t values (? = 0.05).
Results: Following 10, 20, and 35 Ncm tightening torques, the marginal discrepancy of the retainers
of FDPs signifi cantly increased (P < 0.05). There was no signifi cant difference between the marginal
discrepancies of these two retainers (P > 0.05). The marginal gap values of angulated abutment
retainers (ANRs) were signifi cantly higher than those of the straight abutment after cutting the
connectors (P = 0.026).
Conclusion: Within the limitations of this study, the marginal misfi t of cement-retained FDPs
increased continuously when the tightening torque increased. After cutting the connectors, the
marginal misfi t of the ANRs was higher than those of the straight abutment retainers.
