Dynamic behavior of implants as a measure of osseointegration.

Research into the formation, destruction, and adaptation of bone around implants would benefit from a sensitive, nondestructive, noninvasive, and quantitative technique to assess the bone-implant interface. It is hypothesized that osseointegration can be quantified by sensing the mechanical impedance (or micromobility) of the implant when it is subjected to minute vibratory forces superimposed upon a quasi-static preload. To test this hypothesis, a total of 24 identical threaded, titanium root-form implants (10 x 3.75 mm, Osteo-Implant, New Castle, PA) were placed in the mandibles of 4 Walker hounds and allowed to heal submerged for 3 months. The implants were exposed and characterized for osseointegration using clinical observations, quantitative radiography, and a custom-designed impedance instrument. Subsequently, arbitrarily selected implants were ligated to induce bone loss and examined monthly over a 6-month study period. Following the terminal examination and euthanasia, quantitative histologic measurements were made of bone adjacent to the implant, including estimates of both crestal bone height and the percent bone (bone fraction). Linearized dynamic parameters (effective stiffness and effective damping) correlated well with radiographic and histologic measures of bony support (r2 values ranged from 0.70 to 0.89). Moreover, the presence of nonlinear stiffness was clearly associated with a bimodal "clinical impression" of osseointegration (P < .0003, 1-way analysis of variance). These results confirm that, in this animal model, mechanical impedance can be used as a measure of implant osseointegration.

Periodontal disease progression.

BACKGROUND: The objective of this investigation is to use noninvasive, state-of-the-art, diagnostic techniques to measure periodontal disease progression and model periodontal disease activity over time. In this investigation, digital subtraction radiography and an electronic controlled force periodontal probe capable of attachment level measurement were used to measure bone loss and attachment loss, respectively. The use of these nearly continuous measures of attachment and bone loss allowed detection of small amounts of disease activity and provided data to be used in modeling of the disease process over time. METHODS: Forty-four patients were studied for 18 months. Examinations used clinical attachment level measures at 1-month intervals and quantitative radiology at 6-month intervals. The sites were analyzed by regression for statistically significant changes. These data were used to determine sites of periodontal disease activity for testing various models of periodontal disease progression. RESULTS: Overall 22.8% of sites lost attachment, 5.4% gained, and 71.7% demonstrated no statistically significant change. The mean time to lose 1 mm of attachment was 8.4 +/- 0.6 months. In the first model tested a step-wise discriminant analysis was used to determine whether or not baseline measurements of plaque (PI), gingival inflammation (GI), attachment loss, and probing depth (PD) could be used to derive a satisfactory model for disease progression. Although the overall model was statistically significant with PI, PD, and GI contributing to the model (Wilks' lambda = 0.859, F = 5.71, P <0.0012), its predictive power was relatively weak. A considerably stronger significant model resulted when the rate of attachment loss over the first 6 months, baseline PI, and baseline GI were included (Wilks' lambda = 0.712, F = 14.17, P<0.00001). A significant model also resulted when bone loss during the first 6 months and baseline probing depth were included (Wilks' lambda = 0.438, F = 61.48, P<0.00001). When the last model was applied to each site, the sensitivity in predicting disease progression was 80.0% and the specificity in ruling out progressive disease was 93.9%. CONCLUSIONS: This study indicates that clinically significant progression of attachment loss in posterior tooth sites occurs as a frequent event in adult periodontitis. The modeling data also suggest that short-term (6 month) measures of periodontal disease progression greatly improve the ability to model attachment loss over a longer period in untreated periodontitis patients.

Assessment of osseointegration by nonlinear dynamic response.

Quantitative assessment of osseointegration remains a goal of researchers and clinicians alike. In this study, an instrument was designed for this purpose and tested in an animal model. Effective mechanical impedance, linearized for quasi-static force, was measured in 22 implants placed in the hind tibiae of 2 large hounds. The results demonstrate that in this animal long-bone model, the effective impedance of titanium root-form implants exhibits a degree of nonlinear behavior correlated with their state of osseointegration. This observation may be the basis for useful clinical instrumentation.

Planning interactive implant treatment with 3-D computed tomography.

Treatment planning for dental implants presents special challenges to the dentist. The authors review the conventional radiographic and non-radiographic methods for the assessment of the implant site. A new dental interactive treatment planning program under development at the University of Alabama School of Dentistry Department of Periodontics is described.

A periodontal probe with automated cemento--enamel junction detection-design and clinical trials.

An automated periodontal probe has been developed to measure pocket depth and attachment loss in a single measurement under controlled force conditions. A natural anatomic landmark, the cemento-enamel junction (CEJ), is used as a reference for attachment level measurements. The CEJ is detected automatically by immediate digital postprocessing of simultaneous measurements of probe tip acceleration and displacement during probing. Clinical trials in the beagle dog model for naturally occurring periodontitis have shown that the automated probe, when used with 35 g probing force, has a repeatability of 0.16 mm and a bias of 0.09 mm. These results indicate that the automated periodontal probe is capable of attachment level measurements with a high degree of repeatability and validity.

A new periodontal probe with automated cemento-enamel junction detection.

A new automated periodontal probe has been developed which measures attachment level relative to the cemento-enamel junction in a single measurement. The probe tip automatically enters the periodontal pocket and retracts under controlled force. As the probe tip transverses the cemento-enamel junction, the electronics detect an alteration in the acceleration of the probe tip. Thus, the location of the cemento-enamel junction is determined automatically. The repeatability and accuracy of the probe was assessed in vitro. Measurements of attachment level were repeatable to 0.03 mm, and the probe had a net accuracy of 0.04 mm.