Dental Implant Integration
What is osseointegration? Is the term used to describe the formation of bone around a dental implant. Successful osseointegration is ideal to ensure a dental implant is strong, sturdy and ready for a permanent restoration.
Successful osseointegration is a prerequisite for functional dental implants. Thus the continual monitoring in an objective and quantitative manner is significant to determine the status of implant stability. Originally, the best method to evaluate osseointegration was microscopically or via histological analysis; however, due to the invasiveness of such procedures various other methods have been developed. These methods include: radiographs, cutting torque resistance, reverse torque, modal analysis, resonance frequency analysis, and patient factors.
Defininition: Successful osseointegration has been viewed as a direct structural and functional connection existing between ordered living bone and the surface of a load carrying implant.
- Under microscope histologic appearance resembled a functional ankylosis with no intervention of fibrous or connective tissue between bone and implant surface.
- Osseointegration can occur at two different stages, primary and secondary. Primary stability is defined as that stability attained through mechanical engagement with cortical bone. Secondary stability is biological stability through bone regeneration and remodelling. The former is a requirement for successful stability (secondary also dictates time of functional loading)
- Is an indirect indication of osseointegration, is a measure of the clinical immobility of an implants. It is achieved at 2 levels, cortical bone (primary) and cancellous bone (secondary). Secondary stability has been shown to begin to increase at 4 weeks. (Branemark protocol suggested 3-6 month non-loading healing period). However, osseointegration is a patient-dependent wound healing process affected by various factors. Therefore, quantification at various times may provide significant information as the individualized optimal healing time.
- Radiographic evaluation is a noninvasive method that can be performed at any stage of healing. Crestal bone levels, is frequently the mode of choice to analyse for signs in integration. It has been reported that 1.5mm of radiographic crestal bone loss can be expected in the first year of loading, with 0.1mm subsequent annual bone loss.
Cutting Torque Resistance analysis
- Determines the energy required (via a current fed electric motor) in cutting off a unit volume of bone; this is significant as the energy required is significantly correlated with bone density (an important factor in assessing for osseointegration). Further CRA can be used to identify areas of low bone density and to quantify bone hardness. Moreover, values of Ncm can be indirectly represented in J/mm3. Finally, although CRA can be beneficial in assessing bone density and bone quality, its primary disadvantage is that is can only be used during surgery.
Reverse Torque Test
- Unlike CRA, which measures bone density and the resistance to cutting torque, the reverse torque test, measures the critical torque threshold where bone-implant contact was destroyed. Sullivan reasoned that can RTV greater than 20 Ncm may be acceptable as a criterion for successful osseointegration, since none of the implants in their study could be removed during abutment connection at 20Ncm. Caution must be emphasised however, as this method has been criticized as being destructive with potential for irreversible plastic deformation.
- Modal analysis measures the natural frequency or displacement signal of a system in resonance, which is initiated by an external steady-state waves or a transient impulse force. Thus, modal analysis can be vied as a vibration analysis. Through this technique modelling can be used to calculate the anticipated stress and strain in various stimulated peri-implant bone levels. Thus, frequency and vibrational tests are currently being tested for evaluating implant mobility.
- Is one of the simplest tests that can be used; this test is based upon vibrational-acoustic science and impact-response theory. Then a clinical judgement based on the outcomes of these measures is made to assess osseointegration. Further, a clearing ringing “crystal” sound indicates successful osseointegration; whereas a dull sound may indicate no osseointegration. The short comings of this method is that is relies on the clinician’s experience level and subjective belief.
Impact Hammer Method
- This method is similar to the percussion test, however the sound generated from a contact between a hammer and an object is process for analysis of transfer characteristics.
Dental Mobility Checker – Percussion – sound wave analysis
Periotest – uses electromagnetic and electronically controlled tapping, sound wave analysis (advocated as more safe, no impact force like the DMC)
Pulse Oscillation Waveform
A waveform is used to analyse the mechanical vibrational characteristics of the implant-bone interface.
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