Originalarbeit englisch - ZZI 03/2014

A retrospective cohort study to compare narrow-diameter implants of Roxolid and of pure titanium with regard to the peri-implant soft and hard tissues

V. Oberhoff1, P. Tetsch1

Introduction: Implants with a diameter ? 3.5 mm are called narrow-diameter implants. They extend the treatment options and reduce the necessity for bone augmentation. Their disadvantage is the high risk of fracture. Therefore the Institut Straumann developed a new implant material with improved mechanical properties called Roxolid. Compared with pure titanium the titanium-zirconium alloy is characterized by significantly higher fatigue strength. Only a limited number of clinical studies have compared the performance of Roxolid versus titanium with regard to the peri-implant soft and hard tissues. The present study should provide more evidence.

Material and methods: All bone level implants (Institut Straumann AG) with a diameter of 3.3 mm which were inserted in our dental clinic between May 2010 and October 2011 were included in the study. Patients referred for implantation and patients who did not appear for the recall visit in a selected period of time were excluded. All implants were investigated clinically and in 33 patients also radiographically. Bleeding on probing, the maximum probing depth and the peri-implant bone loss were evaluated. A total of 78 patients with 198 implants (159 of Roxolid and 39 of pure titanium) were investigated.

Results: After a period of 21.8 months an average of 34.8 % implants showed bleeding on probing. The mean maximum probing depth of each implant was 3.1 mm. The average peri-implant bone loss amounted to 0.5 mm. Statistically significant differences were not observed. Irrespective of the implant material the narrow-diameter implants did not show fractures but did show significantly higher peri-implant bone loss when positioned in the posterior jaws.

Conclusion: The present study demonstrates that narrow-diameter bone level implants of Roxolid and of pure titanium do not differ with regard to implant survival or with regard to the peri-implant hard and soft tissues. Further clinical studies are needed to investigate the long-term performance of the new titanium-zirconium alloy.

Keywords: Roxolid; titanium-zirconium; narrow-diameter; bone level; implant; peri-implant; tissue

Cite as:

Oberhoff V, Tetsch P: A retrospective cohort study to compare narrow-diameter implants of Roxolid and of pure titanium with regard to the peri-implant soft and hard tissues. Z Zahnärztl Implantol 2014;30:190–203

DOI 10.3238/ZZI.2014.0190–0203

Introduction

Endosteal implants are available in various diameters. The choice of suitable diameter is influenced by the residual bone volume [39] and the type of dentition, as well as by the available space, the emergence profile and the occlusion [12]. Implants with a diameter ? 3.5 mm are described as narrow-diameter implants [3, 12, 41]. Their use reduces the need for or extent of augmentation procedures and enables implantation to be performed where little space is available [11–13, 50]. The indications are single tooth gaps with a reduced mesiodistal distance [50] and a narrow alveolar ridge [12, 13]. Narrow-diameter implants can avoid damage to adjacent teeth, the need for orthodontic widening of the gap or replacement with a conventional prosthetic restoration [12]. They are particularly suitable in the lower incisor and upper lateral incisor regions [30, 39, 50] and for tooth agenesis [12] (fig. 1). The problems with these implants become apparent in biomechanical studies [5, 20, 22, 33, 37, 38]. With the reduction in diameter, there is not only a drop in stability [22, 38], but the stress on the crestal bone [20, 33, 37] and the fracture risk [3, 50] also increase. In clinical studies, survival rates of at least 89 %, and usually 95 to 100 % [4, 13, 31, 32, 39, 41, 48–50] were observed, similar to those of standard implants [8, 13, 41, 50]. Some authors found implant fractures [49, 50]. To lower the fracture risk of narrow-diameter implants, the Straumann company developed the new implant material Roxolid [42]. The binary titanium-zirconium alloy consists of about 85 % titanium and 15 % zirconium [42]. Compared with pure titanium, it exhibits improved biocompatibility [21] besides significantly higher fatigue and tensile strength [27] (fig. 2). Roxolid was introduced on the European market in October 2009 [42]. All narrow-diameter implants from Straumann were available in titanium and Roxolid from then on [42]. Since 2014 they have been available only in Roxolid [42].

The osseointegration behavior of both materials was compared in various animal studies [17, 24, 40, 44, 47]. While there were no differences with regard to bone-implant contact [17, 40, 44, 47], significantly increased removal torque was observed for the Roxolid implants [17, 47]. Kämmerer et al. published a report on initially delayed osteoconductivity of Roxolid, but this was no longer found after the twentieth postoperative day [24].

Because the new material has been available only recently, the number of clinical studies of narrow-diameter Roxolid implants is relatively small [1, 6, 9,45]. In prospectively designed case control studies, Barter and Chiapasco studied Roxolid implants after 2 years of follow-up. They observed success rates and survival rates similar to those obtained with standard implants and assessed the narrow-diameter Roxolid implants as reliable and safe [6, 9]. Al-Nawas and Tolentino concentrated on comparing narrow-diameter implants made of Roxolid and of titanium in prospective controlled studies [1, 45]. In the multicenter study by Al-Nawas et al. each study participant underwent insertion of one narrow-diameter Roxolid bone level implant and one narrow-diameter titanium bone level implant using the split-mouth principle [1]. Tolentino et al. studied patients with single tooth implants of either Roxolid or titanium [45]. While Al-Nawas et al. considered peri-implant bone loss after 12 months [1], Tolentino et al. studied the peri-implant soft tissue after one year of loading [45]. In both studies, no significant differences were found between narrow-diameter Roxolid and titanium implants [1, 45].

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