Displacement of Implant Abutments Following Initial and Repeated Torqueing.

PURPOSE: To measure and compare the three-dimensional (3D) position of nine different abutments manufactured by different manufacturers after repeated torqueing on an internal-hexagon implant. MATERIALS AND METHODS: Nine tapered implants were placed into an acrylic resin block. Five specimens each of nine different abutments (n = 45) were placed into one of nine implants. The abutments were handtightened and then torqued to the manufacturer-recommended torque of 30 Ncm. After 10 minutes, 30 Ncm of torque was reapplied. Another 10 minutes elapsed before testing was completed. Images were recorded in 12-second intervals. The spatial relationship of the abutments to the resin block was determined using 3D digital image correlation. Commercial image correlation software was used to analyze the displacements. Mean displacements for the abutments were calculated in three dimensions and overall for both torque applications. Statistical comparisons were done with a t test and a step-down Bonferroni correction. RESULTS: The overall 3D displacement of the Atlantis Titanium abutment after the second applied torque was significantly greater than that of two of the eight other abutments. Displacement in all three dimensions for the Atlantis Titanium abutment changed direction between the first and second torque applications. All abutments moved further in the same direction except for the Atlantis Titanium abutment, which moved back toward its original hand-tightened position horizontally after the second torque application. CONCLUSION: Re-torqueing of abutments after a 10-minute interval leads to minor displacement of varying degrees between the abutment and a tapered implant. A potential effect of embedment relaxation and/or manufacturing errors should be taken into consideration when selecting an abutment for a cement-retained crown on a tapered implant. Accordingly, clinicians may benefit from adjusting cement-retained implant crowns after re-torqueing the abutments to prevent potential occlusal and interproximal contact problems.

Three-Dimensional Displacement of Nine Different Abutments for an Implant with an Internal Hexagon Platform.

PURPOSE: Clinicians need to know whether there are any differences among the many abutment options available for restoring a particular implant. This study aims to compare nine abutments for one implant system for positional changes between hand tightening and torqueing. MATERIALS AND METHODS: Nine Tapered Screw-Vent (TSV) implants were placed into a resin block. Five specimens of nine different abutments (n = 45) were tried in one of the nine implants. Initially, the abutments were torqued to 20 Ncm to represent hand tightening. Abutments were tightened to 30 Ncm using a torque driver as recommended by the manufacturer for final seating. Images were recorded in 12-second intervals for approximately 10 minutes after the torque was applied. The spatial relationship of the abutments to the resin block was determined using three-dimensional digital image correlation. Commercial image correlation software was used to analyze the displacements. Mean displacements for the nine different abutments were calculated in all three dimensions and for overall displacement in space. A t test with a step-down Bonferroni correction was used for a pairwise comparison of each abutment's mean displacements to the other abutments to determine statistical differences (α = .05). RESULTS: The Atlantis titanium, Inclusive titanium, and Legacy zirconia abutments showed mean displacements that were statistically significantly higher than other abutments in the horizontal direction. The overall three-dimensional displacement of the Atlantis titanium abutment after an applied 30-Ncm torque was significantly higher than that of six of the other eight abutments (P < .0144). CONCLUSION: Within the limitations of this in vitro study, the Zimmer PSA demonstrated less displacement between hand tightening and torqueing than the Atlantis titanium or Inclusive titanium abutments when used to restore a TSV implant.

Interfacial corrections of maxillofacial elastomers for Kubelka-Munk theory using non-contact measurements.

OBJECTIVE: Reflectance measurements using a 45 degrees/0 degrees non-contact measuring system provide accurate data for translucent materials, yet the interfacial reflection corrections (IRCs) for Kubelka-Munk theory have not been evaluated using this system. The objective is to determine which IRC method for Kubelka-Munk theory (K-MT) models the spectral reflectance of pigmented maxillofacial elastomer (MFE) with least error. METHOD: Samples at varying thicknesses of each of 19 shades of skin-colored maxillofacial elastomer were measured using this system on each of three backings. Reflectance values within the visible wavelength range for each shade were fit by non-linear regression to K-MT using different IRC methods: no IRC correction (No), IRC for opaque materials (Op) and IRC for translucent materials (Tr). Errors associated with each method were analyzed using repeated-measures ANOVA and a Bonferroni-corrected t-test. RESULTS: Average error mean square values over all wavelengths were 0.00038 for K-MT with no IRC, 0.00023 with Op IRC, and 0.00015 with Tr IRC. The No method gave a statistically higher error than either the Op or Tr method at all analyzed wavelengths, and the Tr gave a lower error than the OP at all analyzed wavelengths between 450 and 600 nm. The predicted CIELAB values of all the shades tested fell into the range of human skin color space. SIGNIFICANCE: Corrected Kubelka-Munk theory with the IRC for translucent materials proposed by Richmond provides higher accuracy on maxillofacial elastomer over the more important visible wavelengths. Color and translucency of maxillofacial elastomer can be predicted using corrected K-M theory.