Biomedical Engineering Reference
In-Depth Information
most referenced insertion technique includes the implant coverage with the epithelial tissue
originally present at the insertion site Branemark (1983); Branemark et al. (1969); Fragiskos &
Alexandridis (2007); Gapski et al. (2003); Leckholm (2003); Lindhe et al. (2003).
The use of this technique reduces the wound healing time by the temporally isolation of the
implant from an environment full of microorganism as the oral cavity and increases the bone
formation at the implant surface reducing the bacterial contamination risk Branemark (1983);
Gapski et al. (2003); Hansson et al. (1983). In general terms, this technique known as
two-stages
needs for two surgical interventions to complete the prosthesis placement Branemark et al.
(1969). During the first intervention the implant is inserted in the placement site and covered
by the epithelial tissue. 4 to 6 week later, a second intervention is carried out to remove the
epithelium cover, expose the cortical side of the implant and attach the abutment and the
prosthesis Fragiskos & Alexandridis (2007).
However, there is another type of insertion technique in which the implant, the abutment and
the prosthesis are placed at the same time during a single surgical intervention. This technique
known as
single-stage
avoids the epithelium coverage but reduces the healing time increasing
then the patient benefit Heydenrijk et al. (2002). Nevertheless, this technique is less used due
to bacterial contamination problems present during wound healing and an increased damage
on growing tissues by micromovements caused during the earlier loading of the prosthesis
and the implant Gapski et al. (2003); Heydenrijk et al. (2002).
2.2 Osseointegration
Although the evaluation of the anatomic characteristics of the host alveolar bone, the selection
of the implant and the use of an adequate insertion protocol are conditions related to the
bone-dental implant interface successfully healing, the implant osseointegration depends
more on the bone formation directly over the implant surface Albrektsson & Johansson
(2001); Branemark (1983). A successful osseointegration requires the action of two previous
processes:
osteoinduction
and
osteoconduction
Albrektsson & Johansson (2001). Osteoinduction
is the process by which stem cells are somehow stimulated to differentiate at the bone-dental
implant interface into osteogenic cells that synthesize bone tissue (Figure 2a). New bone
deposition by this cells is known as
osteogenesis
(Figure 2b) Albrektsson & Johansson (2001).
There are two kinds of osteogenesis. A first
distant osteogenesis
where bone tissue is formed
from the host bone border towards the implant surface Davies (2003), and a second
contact
osteogenesis
where bone tissue is formed from the implant surface towards the host bone
border (Figure 2b) Davies (2003); Puleo & Nanci (1999).
Contact osteogenesis implies the implant surface to be colonized by the osteogenic cells Davies
(2003). This cell colonization or osteoconduction allows the bone growth over a biomaterial
surface (Figure 2c) Albrektsson & Johansson (2001); Davies (2003). This process essentially
depends on the material biocompatibility and the implant surface characteristics Huang et al.
(2005); Wennerberg et al. (2003). Osteoconduction creates a direct contact between the implant
and the surrounding growing tissues forming a contact interface that after the complete
wound healing process conduces to the implant osseointegration (Figure 2d).
The canalled body of the screw-type dental implant allows it to support stresses and provide
stability, while the deep surface irregularities provide the implant surface with a surface patter
similar to that left behind by the osteoclasts after bone resorption during bone remodeling
MartÃnez et al. (2002); Stanford & Schneider (2004). This surface pattern allows the osteogenic
cells front to synthesize the first new bone line or
cementation line
interlaced with the
