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Dental Implant Interview with Dr. Clark Stanford
We recently had a chance to talk with Dr. Clark Stanford about various clinical data points and studies, specifically as they relate to measuring osseointegration and bone quality, fluoride-modified surfaces and more. It´s a very interesting piece. You can read the whole interview by clicking here. Please feel free to add your comments below.
A quick excerpt:
ON: How did you measure the osseointegration and bone quality?
Dr. Stanford: We used resonance frequency analysis. This is a non-invasive technique for assessing implant stability. The device generates harmonic sound waves which are directed to the implant and surrounding bone and a transducer measures the dampening of the waves. This provides a quantitative assessment. The scale of measurement is the Implant Stability Quotient (ISQ) and the Osstell Device (Integration Diagnostics, Savedalen, Sweden). Increases in ISQ measurements are a measure of improved bone stiffness and thus healing around the implant.
Read the whole interview by clicking here. Please feel free to add your comments below.
November 15, 2005 in Techniques and Procedures | Permalink
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Comments
Question for Dr. Stanford:
Are The ISQ values just a measure of bone quality? Does bone quantity also play role,ie %of actual bone contact to implant surface.
Also if the Fluoride ion stimulates bone growth are you able to consider this as osseoinductive? Is it then a bioactive surface treatment?
Thanks
Posted by: Steven Silberg | Nov 16, 2005 4:33:35 PM
ISQ is a global measure of stiffness. This includes the relative stiffness of the surrounding bone, the bone to implant interface as well as the stiffness of the implant stack itself. The real value of ISQ is longitudinally following an individual implant's changes in stiffness. Dr. Silberg is correct in that it is more a reflection of changes in bone quality (although long-term it would include a change in bone quantity, too.)
There are a number of basic science studies in the published literature that indicates the fluoride modification preferentially increases bone differentiation.
Posted by: Clark Stanford | Nov 17, 2005 2:04:43 PM
Do you feel stiffness is an indication of a healthy implant?
If so, how do you explain the failure of implants that have passed the RFA even when properly restored by world class GP's/Prosthodontists?
Posted by: | Nov 22, 2005 2:50:20 PM
Great Question. RFA measurements are really only valid for longitudinal measurements of an implant. Cross sectional data using a number of implant RFA values at any one time point is not as informative.
"Stiffness" is one measure of implant health and is probably more representative of implant bone health when the interface is primarily cancellous in nature.
Posted by: Clark Stanford | Nov 22, 2005 3:26:14 PM
Are you then saying that the RFA is useless in the maxilla?
Posted by: | Nov 22, 2005 4:02:41 PM
No. Sorry for the confusion. I'm saying RFA may be of minimal usefulness in areas of significant pre-existing cortical bone, such as found in the mandible. The maxilla and especially the posterior maxilla following augmentation procedures such as open or indirect sinus lift procedures may be just the place to use this technology. The technology is one more tool in our armantarium to prove the best patient-tailored care possible.
Posted by: Clark Stanford | Nov 22, 2005 8:21:14 PM
I was under the impression that the concept ISQ was to replace the "periotest" device which also sent a signal out to the implant and sounded back a value correlated to "acceptability " of integration. The periotest was used in place of the mirror handle. Seriously, I thought that the ISQ concept was used origionally to qualify whether an implant could be placed into function at the time of surgical placement. Values between say 60-85 was very good. However, higher values than that was not correlated with enhanced success. Therefore, the higher the value does not always mean better.
Does this relate to energy loss disapation and the so called safe range of ISQ values. There has to be a certain point where too stiff is not favorable. Example: Non segmented implant with a high strength ceramic core ie. al oxide or even zircona.Perhaps, in this type of situation there would be a very high ISQ especially if the bone was of type 1 or 2. This may not show up as an early failure. As the restoration functioned the bone could be further minerializing due toload. Then the bone could be getting stiffer over time. The high ISQ value could be associated with less blood supply and over time even several years out lose the interface between the bone and the oxide layer? Are you there Clark? There was something like this in the orthpedic literature with the hip.
Posted by: Steven Silberg | Nov 25, 2005 6:36:48 PM
The Resonance Frequency Analysis (RFA) technique was not developed to replace the Periotest technique. The Periotest is an impact accelerometer designed to test the resilience of a natural teeth to a micro-hammer impact percussed on the lateral aspect of the tooth. Its application was primarily to assess periodontal bone loss. When it was applied to implants the problem is implants only move 5-10 micrometer versus 150-250 micrometers wit teeth.
The RFA approach measures not the response to an impact blow but the harmonic response to a far lower full frequency load to the implant interface. As discussed in the previous submissions this measures the stiffness of the surrounding bone, the interface and the implant body itself. Downside to this approach is that one can have a portion of the interface still firmly connected and this will convey a high level of “stiffness” even though the implant itself displays other signs of pathology (mobility, inflammation, etc.). Thus, it is only one measure of an implant status and it’s greatest asset is NOT the absolute value but a change in values sequentially measured over time. Clinically this means if a patient presents with an implant demonstrating a rapid decline in ISQ interventional procedures such as removal of a provisional or definitive crown may allow remodeling of bone to establish a definitive implant interface.
As Dr. Silberg states, the absolute ISQ value is not as important as the change in the ISQ over time. The objective assessment of implant stability has been an ongoing challenge for clinicians to monitor the outcomes of implant therapy. I’ll paraphrase from a recent article I wrote in order to assist the audience in understanding the issues with this discussion:
“Conventional clinical measures of implant success entails obvious signs of visual and tactile mobility, pain on percussion and palpation, obvious signs of infection, peri-apical radiolucency or ongoing marginal bone loss(26). One approach to improve the objectivity of implant outcomes is the use dynamic vibration analysis. This relatively non-invasive technique has been proposed by a number of investigators in which a pulsed oscillation waveform is applied to the implant (27-40).
In the device developed by Neil Meredith and colleagues (Osstell; Integration Diagnostics, Göteborgsvägen, Sweden), a peizoceramic transducer is used to measure Resonance Frequency Analysis (RFA) by delivering a sinusoidal excitation wave of increasing frequency to the implant and surrounding bone. The damping response of the peak amplitude response of the implant and surrounding bone is then measured by a second transducer and the harmonic frequency displayed as an Implant Stability Quotient (ISQ), an ordinal scale of 1-100 units (36).
The RFA approach may have value in predicting implant outcomes, especially on an individual implant basis, since the measure of ISQ is sensitive to changes in implant stability during healing, supracrestal osseous bone loss and may be a longitudinal predictor of implant failure (with a progressive decrease in sequential readings of ISQ)(32, 33, 36). Friberg et al., (1999) followed 75 external hexed machined surface implants (NobelBiocare Mark II, III and IV series) and demonstrated a significant decrease in bone stiffness (ISQ) for any of the three designs after 3-4 months post-placement. Barewal et al., (2003), longitudinally followed 20 patients using a large grit, acid etched moderate roughened implant for 10 weeks. Patients were monitored based on bone type 1-4 (Lekholm and Zarb, 1985(4)) at implant placement. Changes in RFA values were specific to the pre-operative bone quality in the region. She reported that ISQ values significantly dropped by 9% in type 4 bone situations at 3 weeks post-placement and then increased by 26.9% (from the lowest point at 3 weeks) by the end of the recording period at ten weeks(33). ISQ values did not change for implants in type 2 or 3 bone situations.
In the porcine animal study performed by Büchter et al., (2005), RFA measurements were compared to reverse torque tests of implants placed for either 7 or 28 days. His studies indicate there was no correlation between implant stability as measured with the RFA technique in the tibial condyle and reverse torque tests.(25). These results probably reflect more the type 2/3 bone observed in this region of the porcine tibial plateau and therefore a lack of change in ISQ (ISQ) would follow the human clinical results demonstrated by Barewal et al., (2003).(33). This suggested that the measurement of changes in ISQ may be of value for monitoring the integration of implants placed in primarily type 4 bone (thin cortical and cancellous bone) and may provide a means to follow the effects of bone adaptation on relative stiffness due to secondary remodeling(41-43). “
26. Albrektsson T, Zarb G, Worthington P, Eriksson AR. The long-term efficacy of currently used dental implants: a review and proposed criteria of success. International Journal of Oral & Maxillofacial Implants 1986;1(1):11-25.
27. Elias JJ, Brunski JB, Scarton HA. A dynamic modal testing technique for noninvasive assessment of bone-dental implant interfaces. International Journal of Oral & Maxillofacial Implants 1996;11(6):728-34.
28. Kaneko T. Pulsed oscillation technique for assessing the mechanical state of the dental implant-bone interface. Biomaterials 1991;12(6):555-60.
29. Huang H-M, Chiu C-L, Yeh C-Y, Lee S-Y. Factors influencing the resonance frequency of dental implants. Journal of Oral & Maxillofacial Surgery 2003;61(10):1184-8.
30. O'Sullivan D, Sennerby L, Jagger D, Meredith N. A comparison of two methods of enhancing implant primary stability. Clinical Implant Dentistry & Related Research 2004;6(1):48-57.
31. O'Sullivan D, Sennerby L, Meredith N. Influence of implant taper on the primary and secondary stability of osseointegrated titanium implants. Clinical Oral Implants Research 2004;15(4):474-80.
32. Glauser R, Sennerby L, Meredith N, Ree A, Lundgren A, Gottlow J, et al. Resonance frequency analysis of implants subjected to immediate or early functional occlusal loading. Successful vs. failing implants. Clinical Oral Implants Research 2004;15(4):428-34.
33. Barewal RM, Oates TW, Meredith N, Cochran DL. Resonance frequency measurement of implant stability in vivo on implants with a sandblasted and acid-etched surface. International Journal of Oral & Maxillofacial Implants 2003;18(5):641-51.
34. O'Sullivan D, Sennerby L, Meredith N. Measurements comparing the initial stability of five designs of dental implants: a human cadaver study. Clinical Implant Dentistry & Related Research 2000;2(2):85-92.
35. Meredith N. A review of nondestructive test methods and their application to measure the stability and osseointegration of bone anchored endosseous implants. Critical Reviews in Biomedical Engineering 1998;26(4):275-91.
36. Meredith N. Assessment of implant stability as a prognostic determinant. International Journal of Prosthodontics 1998;11(5):491-501.
37. Rasmusson L, Meredith N, Kahnberg KE, Sennerby L. Stability assessments and histology of titanium implants placed simultaneously with autogenous onlay bone in the rabbit tibia. International Journal of Oral & Maxillofacial Surgery 1998;27(3):229-35.
38. Sennerby L, Meredith N. Resonance frequency analysis: measuring implant stability and osseointegration. Compendium of Continuing Education in Dentistry (Jamesburg, NJ) 1998;19(5):493-8, 500, 502; quiz 504.
39. Meredith N, Book K, Friberg B, Jemt T, Sennerby L. Resonance frequency measurements of implant stability in vivo. A cross-sectional and longitudinal study of resonance frequency measurements on implants in the edentulous and partially dentate maxilla. Clinical Oral Implants Research 1997;8(3):226-33.
40. Meredith N, Alleyne D, Cawley P. Quantitative determination of the stability of the implant-tissue interface using resonance frequency analysis. Clinical Oral Implants Research 1996;7(3):261-7.
41. Stanford CM, Solursh M, Keller JC. Significant role of adhesion properties of primary osteoblast-like cells in early adhesion events for chondroitin sulfate and dermatan sulfate surface molecules. Journal of Biomedical Materials Research 1999;47(3):345-52.
42. Stanford CM. Biomechanical and functional behavior of implants. Advances in Dental Research 1999;13:88-92.
Posted by: Clark Stanford | Nov 29, 2005 8:16:05 PM
Great interview. Thanks for posting the material for further research.
Posted by: gf | May 30, 2006 10:10:56 AM
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