Original study - ZZI 01/2010

Clinical results with acid-etched implants in edentulous patients: a prospective multicenter study

S. Heberer, L. Hohl, K. Nelson

The aim of this prospective study was to evaluate the clinical parameters of acid-etched implants up to one year after loading. The study examined 135 wi.tal implants placed in the maxilla and mandible of 27 edentulous patients. The healing time in the maxilla was twelve weeks and in the mandible eight weeks. The implants were checked at defined intervals based on the success criteria of Buser and clinical parameters like mPII, mBI and pocket depths were evaluated. All patients had standardized orthopantomographs for evaluation of peri-implant bone loss after implant placement, at loading, after six months and after twelve months.

69 implants were placed in the maxilla and 66 in the mandible. During the observation period three implants failed, resulting in a success rate of 97.7 % for the maxilla and 100 % for the mandible. The results indicate that success rate of the present study is comparable to that of other studies. The bone level changes over the different time points fulfill the success criteria. Further studies are necessary to assess the long-term outcome.

Keywords: edentulous; reduced healing time; acid-etched implants; bone level

Introduction

The long-term success of dental implants is based on the knowledge that these can be retained in the bone by direct bone-to-implant contact. The concept of osseointegration was described in this connection by Brånemark et al. and its importance was underpinned by numerous scientific studies [1, 38].

Factors that influence the sustenance of osseointegration have been investigated in a number of studies [4, 13, 16, 50]. The surface structure of the implants is a relevant focus [36]. A distinction is made between the macro-, micro- and nano-structure of the implant surfaces. While the macrostructure refers to design elements such as the thread, lacunae or pores, the microstructure refers to the chemical, mechanical and/ or physical structuring of the surface [35]. The nanostructure describes the chemical and biochemical properties of the implant surface and can influence cell orientation and function [40]. Smooth titanium or titanium oxide surfaces are distinguished from conditioned surfaces. The possibilities for conditioning implant surfaces are classified as ablative and additive processes. The ablative processes include ablating techniques such as etching, for example with HCL/H2SO4, blasting with various particles (sand, Al2O3, TiO2) or a combination of the two (sand-blasted and acid-etched). In the additive processes, the implant surface is microstructured by additive techniques such as coating with hydroxyapatite or sintering nanoparticles. It has already been shown that the physical properties of the surfaces initially accelerate tissue reactions and influence processes such as cell adhesion and cell differentiation in the tissue surrounding the implant [18, 19, 46]. Studies have shown that rough implant surfaces promote active locomotion of pre-osteoblasts thus ensuring that they are superior to smooth implant surfaces where intimacy of bone contact and enhancement of biomechanical interaction are concerned [16, 17]. Other investigations have demonstrated differences in bone-implant contact within the group of conditioned and rough implant surfaces. [12, 45]

Buser et al. [12] investigated the influence of the surface structure of different implant systems on bone integration in a study in minipigs. The results showed that additional conditioning of blasted implant surfaces with HCl/H2SO4 has a stimulating influence on bone apposition. A high capacity for osseointegration was also attributed to implants with surfaces that were merely etched [45 47]. Cho et al. showed that dual etched surfaces influence the osteoconductive process during healing by deposition of fibrin and osteogenic cells [15]. In experimental animal studies, Novaes et al. and Papalexiou et al. found greater bone-implant contact rates in dual etched implants compared with TPS-coated implants [45, 47]. In a human split-mouth study by Lazzarra et al., the bone contact rates of dual etched implants were compared with machined implants. After a six-month healing period, the histological results showed greater average implant-bone contact rates with the dual etched surfaces [34].

The objective of this study was to assess clinically the hard and soft tissue situation of etched implants after one year of functional loading in edentulous patients.

Material and methods

The study design was prospective and multicenter. The agreement of the ethics committee of the Charité hospital required for conducting the study was obtained.

Four clinicians (three dentists’ practices and one OMF surgery clinic) were involved in recording the data. There were 27 patients. The average age was 61.11 years (38 to 76 years). Augmentative procedures were not used in any patient prior to placement. The following exclusion criteria were formulated (Tab. 1).

Implant system

135 implants were placed (wi.tal, Wieland Dental Implants Wiernsheim, Germany). The wi.tal implant system is a parallel-walled screw-retained implant designed in two parts, with the same internal connection for all diameters (Fig. 1). The implant body is self-tapping and has an acid-etched surface that extends as far as the implant platform. The surface is called an Osseo-Attract surface. According to the manufacturer, this implant is made of grade 4 titanium (99 % pure titanium), but Wieland did not provide further details on the roughness or etching method.

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