In-Vitro: Reproducibility of Periotest and Resonance Frequency Analysis

Objective: An in-vitro assessment of reproducibility of the Periotest and Ostell (RFA) instruments. Assessing the stability of endosseous dental implants provides some indication of the "health/status of the bone-implant complex" at any given time. There are two common errors which may occur when attempting to assess this status in clinical studies -- 1) poor reproducibility of instrument and 2) incorrect use by untrained evaluators. Currently two instruments are used, A) Periotest and B) Ostell (Resonance Requency Analysis). Methods: Five evaluators were trained in their use, each evaluator was required to demonstrate the correct use of each instrument before participating in this study. Two standardization methods were used: #1: A Metal Standardization Cylinder, (hollow metal cylinder with a thin metal disk covering the hollowed portion of the cylinder), #2: calibrating device provided with the Ostell instrument -- two out of three reproducible readings were required. Three wood blocks of different densities (Balsa wood, Poplar, Euro-Beech with epoxy) received ASTRA (5X13mm) implants. Each implant was tested three times by each evaluator, the range and mean values determined. Results: Balsa wood: PTV mean = +21(range 18 to 24), RFA = 32(30 to 35); Poplar: PTV mean = -3 (-1 to -4), RFA 65(63 to 69); Euro-Beech with Epoxy: PTV mean = -7 (-6 to -7), RFA = 68 (65 to 70). Discussion: A new approach was used to train and standardize evaluators prior to activation of a clinical study. The results demonstrated minimal variation in the data recorded for both instruments. Conclusion: while utilizing different "scales", each instrument provided very reproducible readings when used properly by trained/standardized evaluators. This in-vitro assessment of training methods used and the reproducibiliy of these instruments, will improve data reliabity for a future in-vivo/clinical study that is being planned.