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ABSTRACT
Background: Sinus augmentation is a common procedure to increase bone volume and allow for proper implant placement
in the atrophic posterior maxilla. Although the patient’s own bone is considered the best grafting material, various
synthetic or bovine-derived alternatives are used to simplify the grafting procedure.
Purpose: The overall objective of this review was to assess the efficacy of different graft materials used in sinus augmentation
procedures as demonstrated in animal studies.
Materials and Methods: A specific and sensitive database was initially created via PUBMED, focusing on studies published
in English peer-reviewed journals between 1995 and 2004 and kept updated until 2006.
Results: Twenty-six articles were available for comparison and discussion; none concerned the use of alloplastic materials;
24 were comparative histomorphometric; and two were biomechanical studies. Because of a great variability in study
designs, different implant types, great range in follow-up, and lack of specific integration or loading period, a comparison
of the studies and the biomaterials used was difficult.
Conclusions: In general, autogenous bone is the most predictable material of choice for augmentation procedures, despite
a 40% resorption, because it is highly osteoconductive and less dependent on sinus floor endosteal bone migration. The
addition of bovine bone mineral to autogenous bone can be beneficial for graft success because it acts as a slowly resorbing
space maintainer. Porous hydroxyapatite is suitable when mixed with autogenous bone because it enhances bone
formation and bone-to-implant contact in augmented sinuses. Histological evaluation showed that demineralized freezedried
bone is inferior to other materials. Within the limitation of the animal studies examined in this review and only
based on histological examination, the initial osseointegration of implants seems independent of the biomaterial used in
grafting procedures.
INTRODUCTION
The placement of dental implants in the atrophic posterior
maxilla is challenging in implant surgery.1 The
overall long-term failure rate is higher in the posterior
maxilla than in the mandible,2,3 which has been related to bone quality and quantity.4,5 Several procedures and
materials for augmenting bone height have been developed
to overcome the problem of reduced amount of
bone.6 Sinus augmentation has become a standard procedure
to increase bone height in the posterior maxilla,
allowing placement of long dental implants.7 In general,
the implants are inserted after a healing time of 4 to
6 months.8
Although the sinus lifting can be performed under
local anesthesia, harvesting of graft material from the
chin, retromolar region, iliac crest, or calvarium complicates
the treatment, because it often requires general
anaesthesia and hospitalization. It is, therefore, an additional
barrier for patient selection. To overcome extensive
bone grafting, correlated to donor site morbidity,
several artificial materials have been used.
summarizes the most commonly used materials and the
abbreviations used in the article. The biomaterials used
are divided into four categories:
1. Autogenous grafts are transferred from one location
to another within the same individual and are
harvested either from intraoral or from extraoral
donor sites. Calvarium bone is still considered
the most predictable material for sinus grafting
procedures.9,10
2. Allogenic grafts are transferred between genetically
dissimilar members of the same species. A commonly
used material is demineralized freeze-dried
bone (DFDB). The process of freeze drying reduces
the antigenicity of the material,11 and the decalcifi-
cation stresses the osteogenic potential by exposing
bone morphogenetic proteins, inducing host cells to
differentiate into osteoblasts.12 The Sinus Conference
in 1996 concluded that DFDB is not an appropriate
bone substitute because of the risk for disease
transmission and pronounced resorption.13
3. The xenogenic grafts are taken from a donor of
another species. Commonly used are bovine bone
mineral (BBM) and porous hydroxyapatite (pHA),
derived from coral skeletons. The mineral structure
and surface of BBM resembles autogenous bone.
One gram of BBM has a surface of 80 m14 and can
therefore act as a suitable osteoconductive material.
4. The alloplastic materials are inorganic, synthetic
biocompatible bone graft substitutes, such as
hydroxyapatite (HA), beta-tricalcium phosphate
(β-TCP), polymers, and bioactive glasses.
The incorporation of platelet-rich plasma (a PRP),
platelet-derived growth factors (PDGF), and transforming
growth factor (TGF-β) into the sinus graft is often
clinically performed as a method to reduce the healing
time and enhance bone formation within the subantral
environment. Growth factors can be added to all grafting
materials. Platelets are a known source of growth
factors such as PDGF and TGF-β.
15 PRP is a platelet concentrate
derived from blood. Platelet gel allows access
to autologous growth factors, which by definition are
neither toxic nor immunogenic and are capable of accelerating
the normal processes of bone regeneration. PRP
has been proposed as a useful instrument for increasing
the quality and final quantity of regenerated bone in oral
and maxillo-facial surgery. However, the literature is
conflicting with respect to the adjuvant use of PRP in
sinus augmentation. Factors that may contribute to this
conclusion are the variability in study designs, differing
platelet yields, and differing methods of quantifying
bone regeneration and wound healing. The use of PRP
is based on the theoretical premise that by concentrating
platelets, the effects of the released growth factors
(PDGF, TGF-β, IGF-I, and IGF-II) will increase.
Another well-known growth factor is bone morphogenetic
protein (BMP-7), which is osteoinductive and
may have the potential to stimulate mesenchymal cells
to differentiate into bone-forming cells.16 BMP-7 has
been found to be osseoinductive and osseopromotive for
osseointegration. The supplementation of autogenous
bone-derived cells (ABC) to a cell-free grafting material
such as BBM has also been reported.17 The reason for
adding a small amount of autogenous bone is to add
osteoblasts, combined with PRP, with the purpose of
using the osteoinductive capacity of bone.
The aim of this article was to assess the efficacy of
different graft materials used in sinus augmentation
procedures based on histological examination, thus limiting
the investigation to a review of animal studies.
MATERIALS AND METHODS
Search Protocol and Selection of Articles
The search protocol used the electronic database
PUBMED, with a time limit from 1995 to 2004. The
search strategy utilized a combination of MeSH terms
and text words as indicated in Table 2 and kept updated
until 2006. The reference lists of each article completed
the database. We decided not to use any inclusion or exclusion criteria to ensure the sensitivity of our database.
Only peer-reviewed articles written in English were
selected.
In the selected articles, a great variation in the
number (range 8–72) of sinuses, treated with grafting
material, was observed, and factors such as grafting
material, simultaneous versus delayed implant placement,
length of direct bone-to-implant contact in millimeters
(BIB), percentage of bone in direct contact with
implant surface (BIC), mean proportion of new bone,
and height of newly mineralized bone were investigated.
The biomaterials used as graft material were DFDB,
human demineralized freeze-dried bone (hDFDB),
sheep demineralized freeze-dried bone (sDFDB), BBM,
pHA, PRP, BMP-7, and ABC.