Original study - ZZI 01/2011

Sinus floor elevation using a sintered, natural bone mineral
A histological case report study

A histological case report study

D. Rothamel1, F. Schwarz2, R. Smeets3, A. Happe1, 4, T. Fienitz2, Z. Mazor5, J. Zöller1

Background: Implantological rehabilitation of the posterior maxilla often requires cranialization of the sinus floor to allow for long-term stability and permit the placement of sufficiently long implants. Well known as sinus floor elevation or sinus lift, this operation is one of the most common therapies for vertical deficits of the upper jaw.

Aim: The aim of the present study was the histological and clinical evaluation of the xenogeneic bone substitute material (BEGO OSS, Bego Implant Systems, Bremen) for the indications one-stage and two-stage sinus floor elevation.

Materials and method: Twelve patients were included in the study, undergoing 15 simultaneous or staged sinuslift operations. Data were evaluated clinically and, for two-stage approaches, histologically and histomorphometrically after trephine harvesting during implant bed preparation.

Results: Healing was uneventful in all cases. All patients showed good hard tissue regeneration of the lateral window of the sinus. Neither resorption nor dislocation of the granular bone substitute material was observed. Radiologically, good volume stability of the graft was observed. Histologically, bone substitute particles displayed complete osseous integration in newly formed bone matrix. The proportion of newly formed bone within the graft was 25.8–49.6 %, whereas the proportion of remaining bone substitute material varied from 28.6–38.5 %.

Conclusion: It was concluded that BEGO OSS acts as an osteoconductive material to support hard tissue regeneration after sinus floor elevation. Showing excellent volume stability, it is integrated into newly formed bone matrix within a six-month healing period.

Keywords: augmentation; bone substitute material; sinus floor elevation; hard tissue management; bovine; hydroxyapatite

Introduction

Sinus floor elevation is today one of the most frequently performed regenerative procedures in dental implantology. It is based on the principle of elevation of the basal sinus mucosa and introduction of a matrix, which undergoes bony regeneration in the course of the further healing process [18, 21].

While autogenous bone unreservedly represented the gold standard a few years ago, good results have also been achieved with bone substitute materials in the more recent past, particularly when the height of the residual bone is moderately or extensively diminished. It should be noted that only an autogenous bone graft contains vital bone cells and is therefore capable of direct osteogenesis [12, 16, 25]. However, the availability of autogenous bone is not unlimited and must usually be obtained from other operation sites. This leads to increased patient morbidity [4, 13].

Various bone substitute materials have been available for many years; these can be classified according to different aspects. A widely used classification is according to their origin, which distinguishes natural bone matrix from synthetically produced materials. Among the natural materials, human (allogenic) and animal (xenogenic) bone minerals are established. Plant (phycogentic) tissues play a special role. From the chemical aspect, the natural materials consist predominantly of hydroxyapatite. Tricalcium phosphate, synthetically produced hydroxyapatite and the bioactive glasses are synthetically manufactured materials. The beta-form of tricalcium phosphate has demonstrated complete degradability [24]. However, the biodegradation was also associated with a volume loss, even though regeneration hardly differs from that of autogenous material [19, 25].

In principle a body can react to a non-vital, ceramic bone augmentation material in four different ways: conversion to vital bone tissue with complete absorption of the bone substitute material is called osseous organization. This contrasts with the formation of ceramic-osseous regenerated tissue, in which the substitute is first ensheathed in bone and is absorbed very slowly in the course of natural remodeling. Depending on the absorption kinetics, some bone substitute materials can therefore still be detected histologically even after many years. These usually appear blandly embedded in the newly produced hard substance. A fibrous sheath around the material in the form of a foreign body reaction must be regarded as a failure, as is infection with subsequent loss of the augmentation.

Which of these four possibilities actually takes place depends on the choice of material employed, along with a number of other factors [14]. It should also be noted that all the aforementioned materials have only an osteoconductive effect, unless they are combined with growth factors, so that they only act as a scaffold for bone formation [3, 10].

The aim of the present study was the clinical and histological evaluation of BEGO OSS, a natural xenogeneic bone substitute material (BEGO Implant Systems GmbH & Co. KG, Bremen, Germany) for the indications one- or two-stage sinus floor elevation.

Material and methods

Twelve healthy patients were included in the study (n = 12; average age 54.4 years). All patients had good oral hygiene but had at least one free-end or gap situation in the posterior maxilla requiring implantological rehabilitation. The boundary between a one-stage and two-stage sinus lift was set at a residual bone height of 5 mm, based on the expected primary stability of the implants that would be inserted. Some of the procedures included augmentation of other regions. Nine simultaneous and six two-stage sinus lifts took place in total.

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