TY - JOUR
T1 - Three-dimensional fit of lithium disilicate partial crowns in vitro
AU - Schaefer, Oliver
AU - Kuepper, Harald
AU - Sigusch, Bernd W.
AU - Thompson, Geoffrey A.
AU - Hefti, Arthur F.
AU - Guentsch, Arndt
N1 - Funding Information:
The investigation was supported in part by Kettenbach GmbH, Eschenburg, Germany. The authors thank Alexander Drothen of Otto Vision Technology GmbH, Jena, Germany for access to their structure light scanner, and Thilo Böhme of Böhme Zahntechnik, Jena, Germany for fabricating the partial crowns. The authors received no financial support and declare no potential conflicts of interest with respect to the authorship and/or publication of this article.
PY - 2013/3
Y1 - 2013/3
N2 - Objectives: A novel three-dimensional scanning technique was used to investigate the effects a one-step and a two-step impression methods can have on the three-dimensional fit of ceramic partial crowns. Methods: An acrylic model of a mandibular first molar was prepared to receive a partial coverage all-ceramic crown (mesio-occlusal-distal inlay preparation with reduction of all cusps and rounded shoulder finish line of buccal wall). Type IV plaster replicates were cast based on one-step single viscosity (OS/SV), one-step dual viscosity (OS/DV), and two-step dual viscosity (TS/DV) impressions. Five partial crowns were fabricated per impression method using hot-pressed lithium disilicate ceramics. Then, preparation and restorations were digitized using a non-contact, white-light scanner featuring self-calibrating optics (overall measurement uncertainty of <5 μm). Data were entered into quality inspection software which superimposed the records (best-fit-algorithm), calculated fit-discrepancies for every pixel, and colour-coded the results to aid visualization. Furthermore, mean quadratic deviations (RMS) were computed and analyzed statistically with a 1-way ANOVA. Scheffé's procedure was applied for multiple comparisons (α = 0.05). Results: Mean RMS-values for marginal (internal) surfaces were: OS/SV 70 (20) μm, OS/DV 78 (34) μm, and TS/DV 107 (52) μm. Differences among impression techniques were statistically significant at p = 0.006 (0.001). Qualitatively, occlusal ridges and preparation finish lines were over contoured, whereas inner occlusal boxes and the proximal-occlusal isthmus were under contoured. Conclusions: OS/SV and OS/DV impressions resulted in statistically significantly smaller marginal and internal discrepancies than the two-step technique. Clinical significance: Marginal and internal fit of hot-pressed lithium disilicate partial crowns depended on the employed impression technique. One-step impressions are preferred over two-step techniques in many day-to-day clinical situations, especially for the fabrication of partial coverage crown restorations.
AB - Objectives: A novel three-dimensional scanning technique was used to investigate the effects a one-step and a two-step impression methods can have on the three-dimensional fit of ceramic partial crowns. Methods: An acrylic model of a mandibular first molar was prepared to receive a partial coverage all-ceramic crown (mesio-occlusal-distal inlay preparation with reduction of all cusps and rounded shoulder finish line of buccal wall). Type IV plaster replicates were cast based on one-step single viscosity (OS/SV), one-step dual viscosity (OS/DV), and two-step dual viscosity (TS/DV) impressions. Five partial crowns were fabricated per impression method using hot-pressed lithium disilicate ceramics. Then, preparation and restorations were digitized using a non-contact, white-light scanner featuring self-calibrating optics (overall measurement uncertainty of <5 μm). Data were entered into quality inspection software which superimposed the records (best-fit-algorithm), calculated fit-discrepancies for every pixel, and colour-coded the results to aid visualization. Furthermore, mean quadratic deviations (RMS) were computed and analyzed statistically with a 1-way ANOVA. Scheffé's procedure was applied for multiple comparisons (α = 0.05). Results: Mean RMS-values for marginal (internal) surfaces were: OS/SV 70 (20) μm, OS/DV 78 (34) μm, and TS/DV 107 (52) μm. Differences among impression techniques were statistically significant at p = 0.006 (0.001). Qualitatively, occlusal ridges and preparation finish lines were over contoured, whereas inner occlusal boxes and the proximal-occlusal isthmus were under contoured. Conclusions: OS/SV and OS/DV impressions resulted in statistically significantly smaller marginal and internal discrepancies than the two-step technique. Clinical significance: Marginal and internal fit of hot-pressed lithium disilicate partial crowns depended on the employed impression technique. One-step impressions are preferred over two-step techniques in many day-to-day clinical situations, especially for the fabrication of partial coverage crown restorations.
KW - Computer-aided analysis
KW - Dental ceramics
KW - Internal fit
KW - Marginal fit
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U2 - 10.1016/j.jdent.2012.11.014
DO - 10.1016/j.jdent.2012.11.014
M3 - Article
C2 - 23228498
AN - SCOPUS:84875218263
SN - 0300-5712
VL - 41
SP - 271
EP - 277
JO - Journal of Dentistry
JF - Journal of Dentistry
IS - 3
ER -