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

Buccal

 

Lingual

Margin

Mid-Axial

Cusp

Occlusal Table

Cusp

Mid-Axial

Margin

Modified Prep

Mean Thickness

(µm ± SD)

72.05 ± 61.66

74.76 ± 35.65

138.79 ± 61.55

290.64 ± 74.54

135.61

+ 68.62

112.00 ± 34.35

90.23 ± 88.65

Control Prep

Mean Thickness

(µm ± SD)

67.44 ± 45.46

116.22 ± 45.56

78.56 ± 52.54

151.34 ± 31.58

85.02

+ 34.05

146.78 ± 57.18

45.62 ± 30.89

p Value

0.751*

< 0.001

< 0.001

< 0.001

<0.001

0.008

0.017

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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