Arne Mordenfeld
610418-5654
Gävle, Sweden
15 June 2008-05-22
Research Plan
On healing of deproteinized bovine bone grafts for the reconstruction of the
resorbed maxilla
Background
Edentulous people have a social and functional problem. Implant supported prosthesis is a
treatment that successfully has been used in the past 30 years with good results 1.
Rehabilitation of the posterior maxilla with implants is often a problem due to inadequate
bone volume caused by pneumatised sinuses and resorption of the alveolar crest2. When there
is a lack of bone height or bone width, autogenous bone can be harvested from the jaws or the
iliac crest and grafted to the maxillary sinuses. After a period of healing implants can be
installed in the grafted area3. This procedure is associated with problems from the donor site4
and the degree of graft resorptions is difficult to predict5,6.
In order to reduce morbidity and to simplify the procedure bone substitutes have been used
instead of or in combination with autogenous bone.
Some authors suggest that the ideal bone substitute should be biocompatible, completely
replaced by new bone, osteoinductive and osteoconductive7.
One of the most documented bone substitutes for augmentation of the sinus floor is Bio-Oss®
(Geistlich, Wolhusen, Switzerland) which is a deproteinised and sterile bovine bone8,9,10.
There are different opinions whether Bio-Oss® is resorbed or not. Some authors have
reported that the material is resorbed fast and replaced by bone11 wheras others have observed
only a few resorption lacunas indicating slow resorption12,7. There are also researchers who
could not see any resorption at all13,8,9.
Further clinical and histological studies are necessary to investigate the fate of Bio-oss grafts
in the long-term.
With the material from Hallman´s studies8,9 we have a unique possibility to analyze changes
in 6- month, 3-year and 10-year biopsies.
In addition we it is not known if the combination of Bio-Oss® and autogenous bone
contributes or not to a better healing of the graft.
Hyphothesis
The hypothesis of my project work is that deproteinized bovine bone grafted to the maxilla
does not resorb or has a very low resorption rate and is well integrated in the host bone.
Aims


To study the long-term stability of deproteinized bovine bone grafted to the maxillary
sinus
To study the long-term success of dental implants in grafted maxillary sinus

To study the healing of deproteinized bovine bone with or without autogenous bone
used as onlay graft in the maxilla
Subprojects
1. Meta-analysis on long-term evaluation of deprotenized bovine bone as a grafting
material in the maxilla.
2. Histologic analysis of biopsies harvested 10 years after maxillary sinus floor
augmentation with an 80:20 mixture of deprotenized bovine bone and autogenous bone
Bone biopsies are to be harvested from the grafted area in 9 patients using a 3,5 mm trephine
under sterile saline solution irrigation with the guide of ICAT CT-scan to localize the most
representative area of the graft. The samples will be fixed in 4% formalin, dehydrated with
ethanol and embedded in hexamethylmethacrylate resin. Resin blocks containing the bone
samples will then be sectioned under water irrigation with a band saw to expose the layer of
the bone/deprotenized bovine bone fragment. Sections from half of each block are to be
processed for histology and stained with toluidine blue. Histomorhometric analyses will be
made of the sections measuring deprotenized bovine bone area and bone area. The results will
be compared with results of histomorhometric analysis performed from biopsies harvested in
the same study group at 6 months and 3 years.
The study was approved by the local ethics committee in Uppsala and informed written
consent was obtained from all patients.
3. A prospective 10-year clinical and radiographic study of implants placed after
maxillary sinus floor augmentation with an 80:20 mixture of deprotenized bovine bone
and autogenous bone.
A prospective study based on 20 consecutive patients from Hallman et al9 study with 14
women and 6 men, age range of 48-69 years at the time of grafting. In 1996-1997 thirty
maxillary sinuses were augmented with a mixture of 80% deproteinized bovine bone, 20%
autogenous bone from the mental region and fibrin glue.
Fourteen of the patients will be followed throughout the study period. Three patients are
diseased, 2 are too ill to participate and one patient could not be reached.
All bridges will be removed, intra oral radiographs and ICAT CT-scan will be taken and the
following parameters are to be measured; pocket depth, bleeding on probing, mobility,
resonance frequency analysis, marginal bone level and volume of the grafting material.
The study is approved by the local ethics committee in Uppsala.
4. Back-scattered electron imaging and elemental microanalysis of biopsies retrieved 6
months, 3 years and 10 years after maxillary sinus floor augmentation with an 80:20
mixture of deprotenized bovine bone and autogenous bone.
Microscopy and analysis were carried out at the Centre for Electron Microscopy, University
of Birmingham, UK.
The unused half of each block in study 1 will be processed for scanning electron microscopy
and elemental analysis of the tissues. The surface of each resin block containing the bone
fragment will be polished using a manual grinder with 800 grit silicone carbide paper. The
blocks will then mounted on an aluminium stub and carbon coated (Polaron sputter coater).
Samples will be examined using a field emission environmental scanning electron microscope
(Philips bXL 30 FEG ESEM) operating in high vacuum mode at working distance of 10 mm
and accelerating voltage of 15kV. Back-scattered electron imaging will be used to provide
contrast between resin, bone and biomaterial.
Energy dispersive X-ray spectroscopy (EDS) is used to identify and evaluate the relative
concentrations of all the chemical elements present in the tissues and is carried out using
Oxford INCATM EDS system, using point analysis, line-scan and mapping facilities.
5. A prospective, controlled and randomized clinical study on deprotenized bovine bone
as buccal onlay grafts in the resorbed maxilla with or without autogenous bone.
Twenty consecutive patients referred to the Oral&Maxillofacial department, Gävle county
hospital with the need for widening of the alveolar crest will be randomized for buccal
grafting with deprotenized bovine bone alone (10 patients) or in combination with 20% bone
(10 patients). After a healing period of 8 months, at the time of fixture installation, biopsies
will be harvested from the grafted area. The biopsies will be analysed and histomorhometry
performed.
The clinical outcome of the graft and fixtures will be investigated by the means of x-rays and
clinical evaluation. Pocket depth, bleeding on probing, mobility, resonance frequency
analysis and marginal bone level will be measured at 1-year follow up..
Significance
Since several million patients have been treated with Bio-Oss® it is of great importance to
understand the long-term changes in the graft especially if used in the aesthetic zone.
Resorption of the the material in these areas could lead to complications with the need of
additional treatment.
References
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