Accuracy of implant plastic transfer impression copings techniques has not been reported. The 3-D accuracy of plastic transfer copings of 3 systems (NobelBiocare Branemark (NB), Biomet-3i (3i) and ITI-Straumann (STR)) was compared to direct implant-level impression copings at 3 inter-implant bucco-lingual angulations (0°, 8° and 15°).
Methods:
Two-implant master-models, simulating a 3-unit implant-FPD, incorporated gauge blocks that defined the local coordinate reference system. Test-models were made from Impregum® impressions using direct fixture-level impression copings (DR). Abutments were connected to the master-models for the plastic indirect abutment-level (INDR) impressions for a total of 18 test groups, (n=5). A Coordinate Measuring Machine measured linear distortions (dX, dY, dZ), global distortions (dR), actual and absolute angular distortions (dθX, dθY, ABSdθX, ABSdθY) between the Master and Test-models.
Results:
Mean dR ranged from 0.024±0.011mm to 0.109±0.039mm; ABSdθX and ABSdθY ranged from 0.058±0.036° to 0.777±0.307° and from 0.069±0.025° to 0.503±0.233° respectively. The lowest dR was in 3iDR8 and the highest in STRDR15. The lowest ABSdθX was in NBDR15, the highest in STRDR0. The lowest ABSdθY was in NBDR0, the highest in NBINDR15. Three-way ANOVA (p<0.05) showed that SYSTEM had a significant effect on dR, ABSdθX and ABSdθY. ANGLE had a significant effect on dR and ABSdθY. TECHNIQUE had a significant effect on ABSdθY.
Conclusions:
3-D accuracy of implant impressions was dependent on SYSTEM, ANGLE and TECHNIQUE. For DR, NB and 3i systems were not significantly different, while STR showed higher distortions. For INDR, 3i appeared to have lower distortions than the other systems. Inter-implant angulations did not significantly affect accuracy of NBDR, 3iINDR and STRINDR. The accuracy of INDR was comparable to DR at the 3 inter-implant angulations tested for 3i and STR systems. For NB, INDR were comparable to the DR copings at 0° and 8°, but were less accurate at 15° inter-implant angulation.