In vitro milling accuracy and fit of 'natural inlays'.
OBJECTIVE
This study aimed to investigate the milling behaviour of natural inlays (NI) dental restorations constructed from sound extracted teeth. This was done by comparing the milling accuracy and fit of NI to those of industrial porcelain inlays (PI), milled in the same way.


METHODS
A calibration pro-inlay was used to mill three NI and three PI. These were cemented in six acrylic cavities reproduced from the calibration mould, using composite luting cement. No etching and bonding were done. After storage for 24 h in water at room temperature the specimens were sliced buccolingually in a standardised way. For each specimen, two sections were photographed under a light-microscope, resulting in enlarged pictures of the sections. An acetate matrix with the measurement points was placed over each picture in a standardised way. The interfaces between inlays and moulds were measured at 13 fixed points per section using computerised image analysis software. The mean vertical- and floor-interfaces were calculated for each picture, and the overall means were found for each group. Confidence intervals were used for comparison of the differences. The profiles of the milled materials were examined using scanning electron microscopy.


RESULTS
There were no differences between NI and PI in the mean interfaces (NI, 102 +/- 8 micrometers; PI, 107 +/- 8 micrometers). Electron microscopy revealed no apparent differences in the profiles of the milled surfaces.


CONCLUSIONS
These findings indicate that the milling accuracy and the fit of natural inlays and milled porcelain inlays are comparable.
Department of Occlusal Reconstruction and Oral Function, College of Dental Science, Medical Faculty, University of Nijmegen, The Netherlands. H.MOSCOVICH@dent.kun.NL
H
H
Moscovich
J W
JW
Von den Hoff
N H
NH
Creugers
R J
RJ
De Kanter
D002138:Calibration; D002484:Cementation; D003188:Composite Resins / Q000737:chemistry; D016001:Confidence Intervals; D003743:Dental Enamel / Q000648:ultrastructure*; D003764:Dental Materials / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design; D003804:Dentin / Q000648:ultrastructure*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007284:Inlays; D008855:Microscopy, Electron, Scanning; D010781:Photography; D019904:Polymethyl Methacrylate / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry
D003188:Composite Resins; D003764:Dental Materials; D019279:Resin Cements; D014867:Water; D003776:Dental Porcelain; D019904:Polymethyl Methacrylate