Original study - ZZI 01/2012

Morphological evaluation of circular osteotomies by two different
trephine bur systems in vitro

F.G. Draenert1, E. Schiegnitz1, S. Telkes1, E. Stender2, P.W. Kämmerer1

Introduction: The harvesting of bone grafts with trephine burs plays an important role in oral and maxillofacial surgery. The integrity of the bone graft and the local donor site should be preserved as much as possible. The aim of this study was therefore a comparative in vitro study of the bone donor site after cylindrical osteotomy with a standard trephine and a diamond hollow drill.

Material and Methods: Bovine pelvic bone was drilled using a standard trephine and a diamond hollow drill at different rotational speeds (20, 40, 60, 80, 100 %). Impressions of the drill holes were prepared and the bone samples were processed for histomorphometrical analysis.

Results: In this study the diamond hollow drill demonstrated a better quality of the drill hole and gentler bone removal with fewer artifacts in both the impressions and the histological studies.

Conclusion: For gentle and atraumatic bone graft harvesting, the diamond hollow drill shows advantages compared with the standard trephine.

Keywords: trephine burs; diamond hollow drill

Introduction

Various trephine systems are used in oral surgery. Removal of cylindrical bone grafts with a trephine bur for bone augmentation of defects in the jaw prior to implant insertion is a standard procedure [2, 6, 16]. Removal of bone structures with a trephine in vivo or in vitro for histological examination is also a routine experimental procedure [18, 22, 24]. Common to all methods is the desire to interfere as little as possible with the bony integrity of the donor site and bone graft. Mechanical injuries, such as fractures and abrasions during the removal of bone grafts from the donor sites, are associated with a risk of delayed or even entirely absent healing [19, 20]. For exact examination and orientation of the histology and microtopography, the surface of the donor site and bone trephine should be as intact as possible, without bony artifacts [6]. Bone removal using appropriate instruments should be as precise as possible [17, 21, 23]. Accordingly, instruments have been developed that cause only minimal damage on the bone surface during removal [4, 6, 14].

A technical investigation of the cutting behavior of different drills used in the orthopedic DCT trephine system has already shown the advantages of the diamond drill. The principle of the diamond hollow drill for cutting material derives from stone working and has been used successfully in numerous clinical applications [8, 10–13]. These Diamond Cutting Tools (MedArtis AG, Altnau, CH; Cerres Orthopedics GmbH, Munich, Germany) (Fig 1) work with an attachment on an AO pneumatic drill. In contrast to macroscopic rasping rotary instruments, cutting and rasping take place on a micro level. This leads primarily to a more exact and atraumatic result, which was confirmed in an in-vitro model using 8 different drills and rasps [7]. The diamond hollow drill was the only instrument that could also be used for obtaining a graft with an acceptable ground surface. The standard drill with threaded blades also demonstrated good results in the ground bearing, confirming its dissemination for the preparation of dental implant beds also [7]. However, a histological assessment of any bone damage at the donor sites produced by current dental trephine systems compared with a diamond hollow drill has not so far been performed.

The aim of the present study therefore was an in-vitro evaluation of the bone donor sites after cylindrical osteotomy with a commercially available standard trephine system as compared with a diamond hollow drill. The quality of the drill hole was evaluated with regard to its structure and form by
means of a polyether impression. In addition, the extent of damage to compact and cancellous bone caused by the drilling process was examined histologically, and the sharpness and precision of the drill holes were evaluated. The results were analyzed descriptively.

 

Materials and methods

Removal of the trephine samples

The cutting characteristics of a standard trephine system (T1; Meisinger, Neuss, Germany) (Fig. 1) and a diamond hollow drill (T2; Meisinger, Neuss, Germany) were compared under standardized conditions on fresh bovine pelvic bone obtained from a local butcher. The drilling was performed by hand using a conventional dental treatment unit (Siemens Sirona M1, Sirona Dental Systems GmbH, Bensheim, Germany). Drilling was performed with each drill type at rotational speeds of 20 %, 40 %, 60 %, 80 % and 100 %. All drilling procedures were performed twice for each rotational speed.

 

Drill hole impression

The drill holes were then photographed and an impression of the holes was made with a commercially available polyether impression material (Impregum Penta, 3M ESPE, Seefeld, Germany) (Fig. 2 and 3). On each impression, the quality and form of five randomly selected areas were examined descriptively under magnification (x 20).

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