Marginal fit at cylinder-abutment interface before and after overcasting procedure

Abstract

The aim of this study was to measure marginal fit at cylinder-abutment interface, before and after overcasting procedure. A hexagonal implant was fixed to a stainless steel base and a Estheticone-like abutment used during all the experiment. Before casting procedure, gold (Group I) and Ni-Cr-Be (Group II) premachined cylinders were tightened to the abutment with gold and titanium screws (in both groups), with 10Ncm and 20Ncm torque values for the same screw type. Vertical measures were taken at the light microscope (Mitutoyo 5050, Tokyo, Japan) three times in six different parts along the abutment-cylinder interface for each torque value. Cylinders were overcast with Ag-Pd (Group I) or Ni-Cr-Be (Group II) alloy. After casting, the same measures and torque values were repeated. Intragroup differences (10 or 20Ncm torque values, before and after casting) and intergroup differences (10 and 20Ncm torque values, before or after casting) were analyzed by the Paired t Test; (p<0.05). Intragroup differences were observed for G-I (gold, 20Ncm, titanium screw, p=0.044) and for G-II (Ni-Cr-Be, 10Ncm, gold screw, p=0.002). Intergroup differences only were not observed in the G-II group (Ni-Cr-Be, 10 and 20Ncm, titanium screw, p=0.534). Within the limits of this study, the following conclusions can be drawn: 1) Regardless of screw type, marginal misfit was higher for Ni-Cr-Be cylinders after casting, but within acceptable levels of fit; 2) The combination of gold cylinders with gold or titanium screws was the most effective to reduce marginal misfit; 3) Both screw types did not improve marginal fit of Ni-Cr-Be cylinders after overcastting, and 4) Although a 20Ncm torque improved marginal fit in all situations, its use is not recommended due to the increased risk of prosthesis failure. Ni-Cr-Be alloys may be successfully used in single-tooth implant restorations, with no damage to the fit between abutment and prosthetic cylinder.

Machined and plastic copings in three-element prostheses with different types of implantabutment joints: a strain gauge comparative analysis

“…An implant-supported prosthesis may be under the influence of external (functional or parafunctional) and/or internal (preload) forces. The magnitude of this forces affects the amount of induced strains and stresses in all components of bone-implant-prosthesis complex 6,8-10,15,19,22,23,25,26 .…”

A new portable vibrator for plaster pouring: effect on the marginal fit at cylinder-abutment

“…According to literature 1,4,12 the marginal misfit can be influenced by the technique 1 and by the material 4,12 used to fabricate the frameworks. However, this research suggests that the vibration is also an important factor at this point, reminding that it refers to just one of many steps that are required to get a prosthetic piece.…”

“…However, the variables found in the steps of the clinical and laboratory procedures involved in the fabrication prostheses become an obstacle in the search for a perfect fit 7 , leading to errors that make it impossible to obtain a dental implant with a perfect framework fit 12 .…”

Influence of the difference between implant body and screw materials on abutment screw loosening

“…Yoshida performed a torsional fracture test using M2×0.4 pure titanium micro-screws, and reported that the torsional strength was 54 N•cm 24) . Moraes et al also reported that when two sets of cylinders made of gold and Ni-Cr-Br were tightened onto an abutment with titanium screws at a tightening torque of 10 or 20 N•cm, the group tightened at 20 N•cm showed less of a gap 25) . Based on these reports, the tightening torque in the present study was set to 20 N•cm.…”