Introduction of a new periodontal probe: the pressure probe

Abstract. A new periodontal probe has been developed: the pressure probe. The probe consists of a cylinder and piston assembly connected to a variable air pressure system. The working end is a metal tube in which a plunger can move freely. By means of air pressure the plunger is constantly fully extruded. During probing the plunger will intrude from the position of maximum extrusion only as the probing force exceeds the predetemined force acting on the plunger. The difference by which the plunger is intruded can be read on a millimeter scale within the handle of the probe. The purpose of the present investigation was to determine whether probing force is constant during probing, to study the reliability of reading pocket depth measurements in vitro, and to investigate the relationship between pocket depth and applied force in man. In order to evaluate whether the probing force is constant during probing, measurements were performed on a force transducer. Results show that the device makes probing possible with a constant and adjustable pressure. The influence of the reading of the calibration on pocket depth assessment in vitro was studied in an in vitro model. Results show that pocket depths of 1 mm to 8 mm ± 0.25 mm were read correctly in about 90 % of instances. Generally about 45 % of the half millimeter values were recorded as the lower whole millimeter. To investigate the relationship between pocket depth and applied force, 173 pocket depth measurements were performed in eight patients. Patients selected for this study had, in some part of the upper anterior segment, loss of alveolar bone support up to two-thirds of the root length, visible on periapical radiographs. All patients received preliminary treatment consisting of plaque control and removal of subgingival deposits. The mean Sulcus Bleeding index score was 0.2. Pocket depth measurements were carried out with forces of 0.15, 0.25, 0.50 and 0.75 N. Both approximal and vestibular pocket depths were recorded. In this study 0.75 N was chosen as the maximal force since in a pilot study a force of 1.0 N appeared too painful for patients. Results show an increasing pocket depth with increasing probing force. The mean pocket depths increased from 2.08 mm at 0.15 N to 3.71 mm at 0.75 N. Testing showed it to be statistically significant. At 0.75 N, 72 out of the 173 pockets examined were equal to or deeper than 4 mm. The percentages were calculated of differences equal to or more than 2 mm between pocket depth measurements carried out with 0.75 N and lower forces. It was found that 63.3 % of pocket depths measured with 0.15 N were, when measured with 0.75 N, 2 mm or more deeper. This was 43.1 % when 0.25 N and 0.75 N were compared and 9.7 % when 0.50 N and 0.75 N were compared. The maximal differences varied from 5 mm to 7 mm.