Original study - ZZI 03/2017

A pilot study for evaluating interfaces by OCT: loading of a Resin Nano Ceramic on one-piece ZrO2 implants

Max Seidemann1, Rainer Haak2, Constanze Olms3

Introduction: The prosthetic treatment of one-piece ZrO2 implants is a challenge because of the scarce long-term data available. In order to achieve a physiological rehabilitation on rigid, one-piece implant systems, a certain resilience is desired according to the natural tooth. The best way to achieve this, is with the restoration and a suitable bonding procedure to secure a stable and durable bond. The aim of this study was to visualize changes at interfaces before and after dynamic loading of adhesively bonded Resin Nano Ceramic (RNC) crowns on one-piece ZrO2 implants by optical coherence tomography (OCT).

Material and Method: A total of 20 one-piece ZrO2 trial implants were produced and 20 crowns from LAVA Ultimate (LU, 3M ESPE, Seefeld, Germany) were made using CAD/CAM procedures. After tribochemical pretreatment (SB) of all crowns, as well as half of the implant abutments (CoJet, 30 ?m, 2 bar), the crowns were bonded to the implants with Scotchbond Universal (SU) and RelyX Ultimate (RU) according to the manufacturer’s instructions. Subsequently, OCT images (Telesto II, Thorlabs GmbH) of the attached crowns were recorded before and after chewing simulation (CS, 1.2 million cycles with 50 N at 5–55 °C for 60 sec each, SD Mechatronik GmbH). The changes in the signal lines visible in the OCT-B scans were assessed visually as “indistinct”, “equal” or “more pronounced”.

Results: An evaluation of the visible changes to the signal lines in the OCT-B scan was performed according to a visual classification into “indistinct”, “equal” or “more pronounced”. For all samples in the OCT-B scan a signal was visible along the SU+RU/ZrO2 interface not only before, but also after the CS. This signal was “more pronounced” for non-SB before CS than for samples that received pretreatment (SB). The signal intensity on the SU+RU/ZrO2 interface did not increase after CS for non-SB, whereas in SB samples it was “more pronounced”. In the occlusal B-scans, a second signal line was visible only in non-SB test samples after dynamic loading.

Conclusion: The pilot study shows that non-invasive imaging of changes in RNC interfaces by OCT is possible and thereby additional visual information on the bond can be attained.

Keywords: Resin Nano Ceramics; one-piece ZrO2 implants; optical coherence tomography (OCT); interface

Cite as:

Seidemann M-R, Haak R, Olms C: A pilot study for evaluating interfaces by OCT: loading of a Resin Nano Ceramic on one-piece ZrO2 implants. Z Zahnärztl Implantol 2017; 33: 202–211

DOI 10.3238/ZZI.2017.0202–0211

Introduction

Numerous studies document the successful clinical application of zirconium oxide implants [5]. In particular one-piece ZrO2 implants represent a promising alternative to two-piece titanium implants in the esthetical zone [2]. The advantage of one-piece systems is that there is no gap between implant and abutment, thus preventing any form of uncontrolled micro-movement as well as bacterial infestation of the gap and leading to less crestal bone loss [6]. The system is rigid.

There are repeatedly intentional aims of creating a resilience based on the natural tooth in the implant system. The development of resilient implant elements is designed to avoid an unbuffered transfer of forces and thus unfavourable tension peaks and overexertion within the sense of an occlusal trauma leading to peri-implant bone deterioration [9]. To increase resilience besides the many complex technical constructions [7, 12] there are also approaches using resilient base materials for abutments and implants [15]. In this examination the prosthetic restoration and the suitable bonding procedure as resilient components are at the focus, as besides the surgical also the prosthetic evaluation is decisive for a long-term clinical success. With the introduction of the Resin Nano Ceramic Lava Ultimate on the dental market (2012, 3M ESPE, Seefeld, Germany), a restoration material with an e-module resembling natural dentine and a thus associated resilience to absorb impacting forces is available [1]. The „shock-absorbing“ properties of this material class [8] and the high flexural resistance speak in favour of a durable restoration material on one-piece implants which corresponds to physiological biomechanical properties. In order to benefit from a clinical application of appropriate restoration material and its advantages also on one-piece implants, it is necessary to guarantee a long-term bonding. The examination of the existing interfaces and possible changes following dynamic stress between restoration, bonding material and implant is of interest. To date there are no published examinations which have described a non-invasive method and which are able to demonstrate possible changes to interfaces of intact crowns bonded on implants following dynamic stress between restoration, bonding and implant material.

As a result of the special composition of Lava Ultimate as cross-linked polymer with a carrier material percentage of 80 %, new possibilities are now also available to examine this in contrast to products with similar resilient properties (e.g. VITA Enamic, VITA Zahnfabrik, Bad Säckingen, Germany). In addition to the conventional methods of materials examination, additional visual information on the compound situation of this material could be derived by means of Optical Coherence Tomography (OCT) and thus contribute to evaluating a possible clinical application.

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