BIOLOGYIC CONSIDRITION FOR OSSEOINTERATION
the discovery of methods to maximize the amount of # bone and implant contact. Osseointegration ‘is a histologic definition meaning “a direct connection between living bone and load-bearing end osseous Implant at the
light microscopic level.” Four main factors are required to achievesuccessful osseointegrated bone-to-implant interface: (1) a biocompatible material, (2) an implant precisely adapted to the prepared bony site, (3) traurnatic surgery to minimize tissue damage, and (4) an Irnrnobile, undisturbed healing phase. A biocompatihle material is necessary to promote healing without a foreign-body rejection reaction by the host tissue:lf biocompatible materials are not used, the body attempts to isolate theforeign-body plant material by surrounding it with granulation and then connective tissue. It has been.
BOX 14-1 .
Generally Accepted Implant Success Criteria
‘l. The individual unattached implant is immobile whentested clinically.
2. No evidence of periimplant radiolucency is present,
as assessed on an undistorted radio graph.
3. The mean vertical bone loss is less than 0.02 mmannually after the first year of service.
4. No persistent pain, discomfort, or infection is attributable to the implant.
5. The ‘implant design does not preclude placement of,a crown or prosthesis with .an appearance that is satisfactory to the patient and the dentist.
From Smith D, Zarb GA: Criteria for success for osseointegrated end osseous implants, J Prosthet Dent 62:567, 1989.
demonstrated that titanium and certain calciurn-phosphate ceramics are both biologically inert. The size of the gap between the implant and the bone immediately after implant placement is critical to achieving
osseointegration. The gap size can be controlled primarily by the preparation of a precise surgical bed into which the Implarrt is placed. Cylindrical preparations are the mostpredictably made in an accurate shape. Precision instrumentation and a technically sound surgical procedure minimize the distance between the implant and host bone.
Atraumatic surgery is required to allow minimal mechanical ‘and thermal injury to occur. Sharp, highquality burs that are run at low speed by high-torque drills are essential to precise atraumatic bed preparation.
Copious irrigation by either internal or, external methods keeps the bone temperatures to Ievels below S6° C, which is the level beyond which irreversible bone damage occurs. It has been also found that bone tissue damage occurs when the bone temperature reaches 47° C for more than 1 minute. If the temperature rises, alkaline phosphatase within the bone is denatured, which prevents alkaline calcium synthesis. If the gap between the implant and the bone can be minimized and surgery isatraumatic, embryonic bone will rapidly be laid down between the implant and the bone and WIll ihen mature into the lamellar load-bearing bone (Fig. 14-6).
Implant immobility during the healing phase is affect-.ed by bone quality and quantity. Areas of the jaws that have a high percentage of cortical
bone, such as the anterior mandible, are more likely to anchor the implant successfully. Areas of the jaws with a high percentage of cancellous bone make initial stability for the implant more difficult to achieve. It is also
advantageous for init ial implant stability if both the superior and inferior cortical plates can be used to stabilize the implant (Fig. 14-7), which is frequently possible in the anterior mandible and the maxilla. However, the
inferior alv, .lar can al prevents this from occurring in theposterior mandible.
Once the initial stability of the implant has been acruevcd. it must be maintained throughout the healing phase. Should the patient desire to continue to wear the removable prosthesis during the healing period, it is
important that a soft liner be placed in the removable denture to further decrease load transfer to the implant. The bone in the mandible is generally denser than the bone inthe maxilla. Therefore because the maxilla is primarily cancellous bone, osseointegration requires a longer healing
period. When placing implants, it is crucial to obtain primary stabilization for successful osseointegration. The achievement of successful sseointegration is first assessed at the second -surgery. Once- the abutment is attached to the implant body, the surgeon should carefully ch eck for any signs Of clinically detectable mobility An immobile implant at this stage indicates successful osseointegration. Detectable mobility at this stage indicates that fibrous connective tissue has encapsulated the implant. If mobility .s detected, the implant should be removed at that time. The failed site is allowed to heal and another implant can be placed at a later time. once – a successful osseointegrated bone-to-implant interface . has been achieved, masticatory function at least equal that of natural dentition is generally possible. The major mechanisms for the destruction of osseointegration are similar to those’ of natural teeth. Disease activity in the periimplant soft tissue environment and biomechanical overload of the individual implant are the two factors most commo~11 associated with the potential breakdown of osseointegration.