Original study - ZZI 01/2013

Analysis of the precision of implant templates

This study was designed to investigate how accurately holes can be drilled with the twist drills and sleeves provided by the industry and how accurately the position of the implant can then be established. So far there have been no studies in the literature of the possibility of precise and reproducible drilling with one and the same template with the assistance of drilling sleeves. This question is addressed with the data obtained here.

The measurement process was defined. The “treating dentists”, that is, the persons who drilled the holes, all worked under the same conditions with the same material and with the same established calibrated procedure. The analyst was the dental technician. He produced a reproducible report of the results, which was checked by the first author.

The numbers give secure information. Template-guided drilling in the submillimeter range with an operating template produced according to three-dimensional analysis is possible. It was shown that this reproducibility even provides such high precision, thus assisting the work, that even inexperienced persons unfamiliar with drilling in bone can achieve exact drilling geometry. It was not shown clearly that the experienced dentist familiar with dental surgery can achieve better results.

Average error sources of up to 0.5 mm have been discussed in previous publications [3, 5, 7, 9, 16, 17, 19, 20, 21, 22]. Lower errors on average arose with the question of the precision of the sleeve-drill relationship analyzed here.

Many authors have already dealt with the validity of CBCT, transfer of data to planning software, with differences in these programs, with the possibility of transferring the planning to the oral situation and with similar potential sources of error
[1, 2, 7, 16, 17, 19]. These studies are the basis for the precision of template-guided implantology. A new study of the deviations, as shown here, shows the mounting of the drills in the template sleeves.

The digital workflow is easy to manage [15]. However, the operation itself is still performed by human hands. Although guided, inaccuracies, which have not been presented hitherto, cannot be circumvented despite the extremely precise drilling possibilities.

89 % of the total of 86 drilled holes in the study did not deviate in the vertical dimension. About 10 % have a small deviation, all of which occurred with the Med3D-assisted template. The ExpertEase-assisted template with its sleeves exhibits clear advantages. No inaccuracies were identified. No differences were found between the dental nurse and the experienced dentist. These findings were suspected before now but were not yet demonstrated in any study.

Guiding the drilling in the horizontal plane was exact in about half while the other half resulted in a deviation of 0.1 mm to 2 mm. In this case too, no differences were found between the experienced and inexperienced surgeon. However, it should be noted that there was a trend for the precision to increase with each person after several drilling procedures, that is, towards the end of the series of tests. It can be assumed that a learning curve must be overcome and experience leads to better results. In the literature, routine use of implantological measures is frequently evaluated [13, 14].

In the comparison of the numbers, an advantage was found in the precision of the ExpertEase template and the corresponding sleeve system.

A serious difference between the dental nurse and the experienced implantologist was not found in the horizontal dimension when drilling with Med3D and ExpertEase template guidance was compared.

However, a clear trend was noted with advancing practice. Nearly all errors occurred with earlier drillings, while the inaccuracies diminished markedly with the later drillings by both persons. It appears that a learning curve must be overcome in navigated drilling.

In this in vitro study, the difficulties that occur during use in the mouth are absent. Restricted mouth opening, contact between the handpiece and the antagonist teeth, saliva, mucosa and many other factors make procedures in the oral cavity more difficult. With template-guided drilling, particular attention should be paid to the completely submerged precise seating of the individual sleeves in the parent sleeve. With this procedure, the results obtained in vitro are quite applicable to the real situation and provide valid data on drilling precision.

The precision values in our study are confirmed by the literature, which has hitherto analyzed other parameters.

The use of CT or CBCT data allows a precise position in all three dimensions because of the precise determination of the actual bone quantity in the submillimeter range. Precise values can be obtained, especially in the vertical document, where drills with fixed depth stops confer major advantages.

Summary

The aim of this study was to evaluate the precision of holes drilled in implant templates, which were analyzed with digital volume tomography (CBCT) using suitable planning software. 40 templates that had been used clinically to enable successful treatment were studied. 17 of the analyzed templates were fabricated with the Med3D program (C. Hafner GmbH, Pforzheim) and 23 templates were made with the ExpertEase software of Dentsply Friadent GmbH. The Scanora Soredex was used for imaging. Comparative measurements were made on a plaster model with silicone key using a specially fabricated appliance. 3 holes were drilled in each template by 3 different persons. The resulting data were compared to within less than a millimeter.

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