| Summary: | 碩士 === 高雄醫學大學 === 牙醫學研究所碩士在職專班 === 99 === Abstract
Objective:
It has been a customary or routine standard to produce a multiunit long-span fixed partial denture through the processing of one-piece casting over removable individual dies and inlay wax, where it usually yields distortions, twists and significant gaps on the margins of the fabricated protheses. Subsequently, these tedious laboratory multi-steps will require further re-processing such as sectioning or/and re-soldering of the products to be re-oriented into the patient’s mouths before final delivery, which often end up with more clinical problems. The aim of the present study was to introduce and to assess the feasibility of a revised or re-modified wax-pattern combined with self-cured resin technique (called: pattern resin) featuring one-piece casting over the individual dies with solid cast without soldering prior to producing the multi-unit fixed partial dentures, which is expected to manifestly fulfill ― 50 ?慆 ‖ professional standards set for assessing the ―absolute marginal discrepancy‖(AMD). on the fabricated crown margins as recommended by the ADA (American Dental Association).
Materials & Methods:
For fabricating the multiunit fixed partial denture via one-piece casting on individual dies with solid cast without soldering, each of the five replicates per group was designed as follows: the traditional approach using a wax-pattern method on individual dies and solid casts was ― the control ‖ group (WI/WS, n=5) and our revised/ re-developed wax/pattern resin method was set as ― the experimental ‖ group (MI/MS, n=5), each of which in total of 40 corresponding units were then further processed for subsequent embedment, casting into metal frameworks and the final refinements. The resulting ― maximal ‖ AMD on each of the buccal (B), lingual (L), mesial (M) and distal (D) margins on the abutments, (WI/MI), (WS/MS): 12, 13, 23 & 24 (FDI system) were separately recorded by using the optical stereo-microscope for images, then by using computer through the build-in software for scanning & image analyses. The resulting data sets were analyzed by SPSS13.0
software and the paired-t test was employed for statistical comparisons between both groups where α value was set 0.05.
The results:
Based on the computer images acquired and subsequent analyses obtained from both groups, the results of assessing the ― maximal ‖ absolute marginal discrepancy (AMD) in the four areas: B, L, M & D, a totaling of 320 measurements, showed that: on individual dies, the mean AMD value for WI in the control group (total=80) was 73.18 um with the averaged success rate of 90% (by reaching 50 ?戥m); whereas the mean AMD for MI in the experimental group (total=80) was 33.82 ?慆 with the averaged success rate of 100% (by reaching 50 ?慆). And, on solid casts, the mean AMD value for WS in the control group (total=80) was 433.09 ?慆 with the averaged success rate of 36.25% (by reaching 50 ?慆), whereas the mean AMD for MS in the experimental group (total=80) was 51.65 ?慆 with the averaged success rate of 98.75% (by reaching 50 ?慆). Meanwhile, the results of paired-t test involving all four B, L, M & D areas showed that there were statistically significant differences between WI-MI, WS-MS, WS_B-WS_L, WS_M-WS_D & MS_B-MS_L for comparisons with P<0.05, respectively; while others showed no significant difference, individually.
Conclusion:
Under the experimental conditions studied, our preliminary pilot analyses with each of five replicates per group provided a rationalized support briefly summarized as follows: for the multiunit fixed partial denture fabricated by one-piece casting over the individual dies with solid cast without soldering, our analyses on assessing the resulting feasibility and accuracy indicated that: i) it is very difficult to achieve the satisfactory outcomes without significant marginal gaps or/and distortions(i.e., AMD values) via the traditional fashion of wax-pattern method on the individual dies with solid casts, and ii) our revised/modified mixed wax/pattern resin method demonstrates quite significantly less marginal discrepancy with much higher success rates for satisfactory laboratory results. Therefore, this revised new technique may have the potential to be applied in the modern dental laboratory to
achieve better clinical outcomes and efficacy in the future.
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