A pilot study on the fitness of a zirconia keeper coping fabricated byCAM system̶Application of a high-precision scanner
D. MATSUMOTO, M. SONE, N. KOYAMA, Y. TANIUCHI, K. AOKI, T. MATSUKAWA, F.
NARUMI, K. OKAMOTO and M. FUJISAWA1）
Division of Removable Prosthodontics, Department of Restorative and Biomaterials Sciences,
Meikai University School of Dentistry1)Division of Fixed Prosthodontics, Department of Restorative and Biomaterials Sciences,
Meikai University School of Dentistry
Abstract

In this study, we report on the accuracy of matching of zirconia root plates fabricated usinga high-precision laboratory scanner.
The abutment tooth was a preformed root plate‒type epoxy artificial tooth (A50-359,NISSIN). The manufacturing procedure involves scanning the work model using a laboratory
scanner (E3, 3Shape), modeling it using design software (Dental System, 3Shape), and thencutting it with a milling machine (CORiTEC 350i, Imes-Icore). Five specimens were tested,
and the fitting accuracy of the zirconia root plates was evaluated using the cement replica
method.
The measurement points are the labial margin at point a, the labial cervix at point b, thelabial post at point c, the tip of the post at point d, the lingual post at point e, the lingual cervix
at point f, and the lingual margin set as point g. The average gaps were 61.5±32.2 μm at
point a, 73.5±32.4 μm at point b, 41.5±11.6 μm at point c, 148.5±19.1 μm at point d,45.0±11.6 μm at point e, 81.5±27.8 μm at point f, and 46.0±13.3μm at point g.
It was suggested that the zirconia root plate manufactured using a high-precision laboratory
scanner could be applied clinically.
Introduction

The progress of dental CAD/CAM systems in recent years has been remarkable, and thefurther simplification of workflow and improvement in the compatibility of prosthetic devices
are expected. At the 26th Annual Scientific Meeting, we examined the suitability of a zirconia
root plate manufactured by supplementing the deep part of the model that was difficult toscan using a supplementary scanning post, and we reported that it was acceptable for clinicalapplication. This time, we attempted to fabricate a zirconia root plate with a single systemusing a dental scanner for laboratory use, which has become more sophisticated and precise
in recent years.
Materials and Methods

The abutment was an epoxy artificial tooth (A50-359, NISSIN) with a post part five mmdeep, as recommended by this society. As for the manufacturing procedure, after taking animpression according to the standard method, a working model was made, it was scanned
using a dental scanner for laboratory use (E3, 3Shape), and it was then scanned using design
software (Dental System, 3Shape). After modeling, we cut it out using a milling machine(Figs. 1 and 2). The cement space was the specified value of the software, and the numberof test samples was five.

Fig. 1 Scanned model and designed keeper coping

Fig. 2 Fabricated zirconia keeper coping
The fitting accuracy was evaluated using the cement replica method, which quantifies thegap between the model and the root plate based on the thickness of the silicone rubber
coating (Fig. 3). In addition, the gap distance was measured by capturing a digital image ofthe cut surface of the silicone rubber together with a scale used as a reference and measuring
it on a PC. In addition, seven measurement points were set as shown in Fig. 4.

Fig. 3 Fabrication procedure of specimens (Cement-replica technique)Fig. 4 Measuring points(a:labial margin b:labial cervical c:labial center of post d: tip of thepost e: lingual center of post f: lingual cervical g: lingual margin)
Results

The average gaps are 61.5±32.2 μm at point a, 73.5±32.4 μm at point b, 41.5±11.6μm at point c, 148.5±19.1 μm at point d, 45.0±11.6 μm at point e, 81.5±27.8 μm at
point f, and 46.0±13.3 μm at the g point (Fig. 5). Measurement points a, b, c, e, f, and gshowed good compatibility as compared with the allowable range of compatibility for
CAD/CAM prostheses reported by Suto et al.,1⁾ which is 100 μm.

Fig. 5 Average gap volumeConclusion

The reason compatibility was generally good was thought to be the influence of smooth andhighly accurate modeling of the model due to the improved measurement accuracy of thecamera and the corresponding software. In addition, the reason the value of point d did notmeet the standard was considered to be that the setting value of the cement space was highas compared to those of other points, and that scanning and milling were somewhat difficult
due to the morphology.
In the future, we plan to verify the fitting accuracy with a post length of 5 mm or more andalso to investigate whether it is possible to set the anti-rotation groove and the keeper
housing.
References

1. N. Suto, S. Miura, R. Inagaki, Y. Kaneta, M. Yoda and K. Kimura: A Basic Study on
Fitness of All-ceramic Crown Fabricated by CAD/CAM System, Ann Jpn Prosthodont
Soc, 1, 21‒28, 2009.