Accuracy of three corrective techniques for implant bar fabrication.
BACKGROUND
Numerous articles emphasize the importance of passivity of implant-prosthetic component interfaces. Nonpassive interfaces can lead to bone loss, abutment fracture, and connecting screw breakage.


OBJECTIVE
The purpose of this study was to evaluate 3 postcasting techniques for the correction of non-passive fit between a cast bar superstructure and its interface with an implant abutment.


METHODS
Thirty implant Hader bars were fabricated based on a metal model composed of two 3.8/4.5 HL PME titanium implant abutments. Initial measurements were collected on the y-axis of the left implant abutment-bar interface by using a M2001ARS toolmaker microscope. Means were calculated from buccal, distal, and lingual measurements on each specimen. Ten specimens were sectioned, indexed, and corrected by casting the same alloy (group 1). Ten specimens were sectioned, indexed, and corrected by soldering (group 2). The last 10 specimens were submitted to 2 cycles of electrical discharge machining on a MedArc M-2 EDM machine (group 3). Postcorrection measurements were collected on the 3 groups. A 1-way ANOVA and a Tukey-Kramer test at a 0.05 significance level were performed on the 3 groups after the corrective techniques.


RESULTS
Initial gap means were 192 microm for group 1, 190 microm for group 2, and 198 microm for group 3. There was a significant difference (P<0.05) in gap means between group 1 (15 microm) and group 2 (72 microm) as well as between group 2 and group 3 (7.5 microm) after each correction technique. No difference was detected between group 1 and group 3.


CONCLUSIONS
The electrical discharge machining group resulted in the smallest mean gap distance of 7.5 microm, thus meeting the criteria of passive fit (within 10 microm) described in the literature.
Romero
G G
GG
University of Texas-Houston Dental Branch, Houston, Texas 77030, USA.
Engelmeier
R
R
Powers
J M
JM
Canterbury
A A
AA
D000704:Analysis of Variance; D000044:Dental Abutments / Q000706:statistics & numerical data; D003735:Dental Casting Technique / Q000592:standards / Q000706:statistics & numerical data; D003761:Dental Impression Technique; D019094:Dental Prosthesis, Implant-Supported / Q000295:instrumentation* / Q000379:methods / Q000592:standards / Q000706:statistics & numerical data; D012994:Dental Soldering / Q000379:methods; D003779:Denture Design / Q000379:methods / Q000592:standards / Q000706:statistics & numerical data; D003832:Denture, Partial, Removable / Q000592:standards / Q000706:statistics & numerical data; D006047:Gold Alloys; D006801:Humans; D014025:Titanium
D006047:Gold Alloys; D014025:Titanium