Introduction: There are currently limited diagnostic tools available to assess the integrity of the cement/adhesive interface beneath fixed restorations. The characteristics of the cement interface beneath ceramic restorations are of particular interest since they are believed to reinforce the ceramic.
Objective: The purpose of this investigation was to determine the feasibility of using Angle Beam Ultrasonic Spectroscopy (ABUS) to assess elastic properties of the cement interface beneath dental ceramics.
Methods: In this set of experiments glass plates (1/2" x 2" x 1/8") were used as dental ceramic analogs and cemented with composite resin containing 77, 53 and 30 wt% filler (F) and 0.1 or 0.2 mm thickness (T). ABUS methods were used to determine density (ρ), cement thickness (h), longitudinal modulus (l+2µ), and shear modulus (µ). The results of two independent measurements on six samples with 3 filler loads and 2 cement thicknesses are reported in the table below.
Sample
| ρ (g/cm3)
| h (mm)
| λ+2μ (GPa)
| μ (GPa)
| ||||||||
1st
| 2nd
| diff%*
| 1st
| 2nd
| diff%
| 1st
| 2nd
| diff%
| 1st
| 2nd
| diff%
| |
T.2F77
| 2.06
| 2.03
| 1.5%
| 0.295
| 0.303
| 2.7%
| 21.9
| 22.2
| 1.4%
| 6.69
| 6.82
| 1.9%
|
T.2F53
| 1.69
| 1.71
| 1.2%
| 0.200
| 0.199
| 0.5%
| 16.0
| 16.2
| 1.3%
| 4.52
| 4.60
| 1.8%
|
T.2F30
| 1.47
| 1.45
| 1.4%
| 0.168
| 0.168
| 0.0%
| 12.6
| 12.7
| 0.8%
| 3.08
| 3.27
| 6.2%
|
T.1F77
| 2.00
| 1.96
| 2.0%
| 0.283
| 0.300
| 6.0%
| 21.0
| 21.9
| 4.3%
| 6.37
| 6.73
| 5.7%
|
T.1F53
| 1.73
| 1.68
| 2.9%
| 0.142
| 0.149
| 4.9%
| 16.6
| 16.3
| 1.8%
| 4.80
| 4.89
| 1.9%
|
T.1F3o
| 1.47
| 1.52
| 3.4%
| 0.158
| 0.151
| 4.4%
| 13.2
| 12.7
| 3.8%
| 3.42
| 3.30
| 3.5%
|
Results: The results indicate that the ABUS method can be used to assess the cement thickness and effective cement modulus below glass plates. Thickness measurements by micrometer indicate good agreement with ultrasonic measurements.
Conclusions: The ABUS technique has potential to be developed as a noninvasive method to determine properties of the cement layer beneath dental crowns.