1365 Effect of Preparation Taper on Fit of E4D CAD/CAM Crowns

Saturday, March 24, 2012: 9:45 a.m. - 11 a.m.
Presentation Type: Poster Session
J. PLOURDE, J. STEIN, M. HARSONO, M. FINKELMAN, and G. KUGEL, Tufts University, Boston, MA

Objectives: To determine if variation in preparation taper affected the in vitro marginal and internal fit of all-ceramic crowns produced using the CAD/CAM scanning and milling system E4D DentistTM (D4D Technologies).

Methods: Typodont tooth #14 was prepared to receive all-ceramic crown for previously reported fit study. Control preparation had total occlusal convergence (TOC) of 10.72░ in buccolingual plane. Preparation was modified to a TOC of 20.85░. Both preparations had well-defined rounded shoulder, ~2 mm occlusal reduction, and rounded internal angles. Small indentations were made on root of preparation as a plane of sectioning. Fifty-six impressions of prepared typodont tooth were taken using VPS and 56 die stone models poured. Dies were placed in full-dentate typodont and scanned with E4D laser. IPS e.max« CAD LT A1/C14 crowns (Ivoclar Vivadent) were fabricated per manufacturer's instructions. Crowns were cemented using Multilink« Automix (Ivoclar Vivadent) under constant pressure of 100 N. Samples were embedded in clear acrylic resin and sectioned buccolingually in a consistent plane using the root indentations as guidance (Isomet 1000, Buehler). Sections were evaluated under digital microscope with 50X objective (Olympus) and measured using OmniMet software (Buehler) on 3 locations per buccal and lingual side of section: marginal-edge, mid-axial wall, and cusp-tip. One measurement was made on occlusal table. Mean thicknesses at each location were calculated and compared to results previously obtained from the un-modified preparation. Data analyzed by independent samples t-test using Holm-Bonferroni correction adjusting for multiple comparisons.

Results: Comparison of mean fits at various locations of initial and modified preparations are shown in Table 1.


Table 1: Cement thicknesses measured at marginal and internal locations of preps (n=28).

Measurement Location







Occlusal Table




Modified Prep

Mean Thickness

(Ám ▒ SD)

72.05 ▒ 61.66

74.76 ▒ 35.65

138.79 ▒ 61.55

290.64 ▒ 74.54


+ 68.62

112.00 ▒ 34.35

90.23 ▒ 88.65

Control Prep

Mean Thickness

(Ám ▒ SD)

67.44 ▒ 45.46

116.22 ▒ 45.56

78.56 ▒ 52.54

151.34 ▒ 31.58


+ 34.05

146.78 ▒ 57.18

45.62 ▒ 30.89

p Value


< 0.001

< 0.001

< 0.001




Conclusions: Six of seven fit measurements were significantly different between modified and control preparations.

This abstract is based on research that was funded entirely or partially by an outside source: Ivoclar Vivadent

Keywords: CAD/CAM, Dental materials, Effectiveness and Taper
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