Original study - ZZI 01/2012

Sinus lift and simultaneous insertion of dental implants
with a residual bone height less than 5 mm
– a 10-year retrospective clinical evaluation

F.E. Preusse1 , F.A. Preusse1, H. Eymer2, Ph. Streckbein3

Introduction: Sinus lift with simultaneous placement of dental implants is commonly performed on residual maxillary sinus floors with more than 5 mm vertical height. There is a risk of implant failure in situations with less residual bone (< 5 mm) due to initial mobility during healing.

Objectives: The aim of this retrospective study is to present the surgical procedure of simultaneous sinus lift and implant placement in a sandwich technique in patients with less than 5 mm residual vertical bone height and to assess the risk of implant failure.

Material and methods: In the period between 1998 and 2005 39 patients underwent 55 sinus lift procedures with simultaneous placement of 78 dental implants (Semados S and RI implants, BEGO Implant Systems GmbH & Co. KG, Bremen, Germany) in residual maxillary sinus floors below 5 mm. To increase primary stability, additional lateral bone condensation was performed with osteotomes. The subantral space was filled with bone substitutes. Autogenous bone enriched with platelet-rich plasma (PRP) was applied through the implant cavity next to the implant site. Finally a PRP wetted implant was placed. Clinical examination and follow-up x-rays were performed in 2010.

Results: After exposure, 75 of 78 implants withstood a torque of 30 Ncm, which equates to an initial survival rate of 96.2 %. One patient with one implant was lost to follow-

up and another two implants had to be removed due to bisphosphonate-related osteonecrosis. All other implants were bland in situ and satisfactorily integrated in the prosthetic reconstruction. This leads to a survival rate of 92.3 % after a follow-up of up to 12 years (median 8 years, mean 8.12 years; n = 78).

Conclusion: This study shows that simultaneous insertion of dental implants and augmentation in the vertically reduced sinus floor following the described surgical protocol leads to predictable and good results. The simultaneous approach allows considerable acceleration of the implant treatment and spares the patient a further surgical procedure, thus reducing the cost of treatment.

Keywords: lateral sinus floor elevation; simultaneous implantation; sandwich technique; platelet-rich plasma (PRP); lateral condensation; reduced residual bone

Introduction

Simultaneous insertion of endosseous implants and sinus lift are usually performed when the vertical height of the residual bone of the sinus floor is more than 5 mm. If the residual bone height is less than 5 mm, there is a risk of connective tissue healing with subsequent implant loss due to increased initial mobility [2, 29]. Various measures can be undertaken during surgery to counteract this risk. Lateral bone condensation with osteotomes according to Summers can improve the primary stability of inserted implants [20, 25]. Various procedures (e.g. bone substitutes, particulate autogenous bone with and without platelet-rich plasma [PRP]) for filling the subantral space have been discussed in the literature [3, 13].

The aim of this retrospective study is to present an overview of up to ten years clinical experience with sinus lift performed in patients with a residual bone height less than 5 mm using platelet-rich plasma (PRP). Implants were placed simul-taneously in all patients, using a combination of PRP enriched autogenous bone and different bone substitutes in a sandwich technique (Fig. 1).

 

PRP literature and facts

Knowledge of the improvement in wound healing produced by the growth factors contained in PRP has become widespread in other areas of medicine but entered oral and maxillofacial surgery relatively late in 1997 [33]. Marx et al. [14, 15] conducted the first controlled clinical studies in defects of mandibular continuity in 1998. Compared with a control group, the bone density was significantly increased in particulate pelvic cancellous bone grafts with added PRP. In German-speaking countries, the use of PRP in implantology has been discussed increasingly since 1998. Initial clinical experiences were published in 1999 [4]. The industry sometimes gave the impression that implant healing times might be dramatically shortened by accelerated osseointegration and bone augmentation maturation. However, the initially posited hypothesis that PRP would have a beneficial effect on the growth of augmentations performed with bone substitutes was not confirmed [12, 26]. According to current knowledge, the growth factors released into the fresh clot following platelet activation and degranulation have a proliferative effect only on vital cells. Autogenous bone grafts contain differentiated bone cells capable of division, which can be stimulated by endogenous growth factors in the PRP [26]. A bone-inductive effect, as with rhBMP-7, can-
not be detected with PRP in Wistar rats [19]. Healing of standardized mandibular defects in mini pigs did not show platelet concentrate (PC) to have a statistically significant positive effect [10]. However, a positive tendency in new bone formation is reported for the addition of PRP to particulate autogenous bone [4]. It has been shown in different studies that the use of PRP accelerates bone regeneration and healing in the first few weeks [6, 7, 23, 28, 34]. Authors from the Vienna School [5, 35] report an improvement of initial osseointegration in local bone with PRP. In-vitro studies have shown that PRP stimulates the proliferation of osteoblasts and fibro-blasts in the first few days [8, 24, 30]. It has also been shown that PRP stimulates
capillary regeneration and improves wound healing [11, 18]. In ophthalmology, macular defects heal markedly faster and more completely with platelet concentrates [35]. Tetsch et al. observed lower analgesia following surgical procedures when platelet-rich plasma was used [27]. Weibrich et al. provide an overview of the current literature and the most common procedures [31, 32].

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