From practitioner to practitioner - ZZI 03/2010

Survival rate of immediately loaded implants

L. Ricken, S. Vogel

The demands of our patients regarding an implantological treatment are continuously increasing. Not least the widespread idea of “theeth in an hour” sets the implantologist under pressure. Regardless of the individual prepositions it is suggested that this concept is always practicable. Such statements are wrong in the same way as a generaly denegation of an immediate loading. The aim of our investigation was to find out the survival rate of immediately loaded implants under clearly defined conditions. 256 immediately loaded implants in 56 patients were observed during an average period of 34.7 months. With a survival rate of 99.21 % it is shown that this protocol of loading is successful under restrict adherence to the indication.

Keywords: immediate loading; survival rate; dental implants; provisional prostodontics

Introduction

The patient’s desire for an immediately fixed dental restoration is understandable and is increasingly aroused by corresponding publications in the mass media.

However, this wish is often diametrically opposed by anatomical conditions and biological principles. For instance, bone of adequate quality and quantity must be present at the implant site as an anatomic precondition for lasting stable incorporation of dental implants [1, 5, 8, 10].

When this condition is met, osseointegration of the implant takes place after a sufficiently long healing period [2]. The classical unloaded healing periods of three months in the mandible and six months in the maxilla apply today only in compromised initial situations compensated by means of augmentation techniques [10]. These healing times have been drastically reduced with the introduction of rough implant surfaces [3, 6, 14].

Nevertheless, the biologically determined principles of osseointegration, which require the implant to heal free from micromovements, continue to apply. Transmission of forces to an implant that is not yet osseointegrated therefore always signifies a risk for its osseointegration [9,15].

If forces are to be transmitted to the implant directly after implantation, it is essential to avoid micromovements despite these forces. These torsional and rotational forces, that cause micromovements can be avoided by stable splinting of at least three implants inserted in tripod fashion.

Numerous studies confirm the high likelihood of success of such a procedure. In a systematic review article in 2007 on the immediate loading of dental implants in randomized and controlled clinical studies, Esposito et al. found a similar rate of success with immediate, early and late implant loading [4]. The article by Nkenke and Schliephake, only published after the end of our investigations, arrives at the same result [13].

The study by Wentaschek et al. from 2007, which deals with the minimum stability requirements for implants intended for immediate loading, had a decisive influence on our procedure [16]. The outcome of this study was, firstly, that the insertion torque was the most reliable criterion, compared with resonance frequency analysis and the Periotest result.

Secondly, it was found that no implant was lost in the study period if it had a torque of > 13 Ncm during insertion and was treated with an immediate screw-retained bridge.

The aim of this retrospective analysis was to determine the survival rate of implants placed according to the following mode. A further analysis with regard to the success rate will follow.

Material and method

When the patient is examined for the first time and subsequent treatment is planned, it is often difficult to assess the feasibility of an immediately fixed restoration.

The anterior region of the maxilla, where immediate implant loading is possible because of the often good bone supply, is difficult to assess on orthopantomograph because of the vertebral shadowing, and allows conclusions, if any, only with regard to the vertical bone supply. The horizontal bone supply can be confirmed only by measuring the mucosal thickness and model analysis. This preoperative investigation requires anesthesia of the mucosa and is less accurate than DVT with regard to the vertical dimension, as it is performed as a supplement to the OPG.

For this reason, all patients underwent preoperative radiographic examination by means of DVT (New Tom) (Fig. 1); this allows us to inform the patient of the possibility of an immediately fixed dental prosthesis even during the first discussion.

DVT allows reliable assessment of the quantitative bone supply. However, the definitive feasibility of immediate loading also depends on the quality of the bone, which cannot be fully assessed on DVT as classification in Hounsfield units is not possible. The final decision on whether an implant can be loaded immediately can therefore be made only after insertion and measurement of the insertion torque.

Based on the study by Ledermann in 1979 four abutments were splinted to one another in quadrangular position in the jaw [11].

Restoration was carried out on temporary abutments (PEEK Abutment, Camlog) (Fig. 2) with an acrylic temporary produced during operation (Fig. 3), which was fabricated using a previously vacuum-formed template.

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