Clinical validation of robot simulation of toothbrushing--comparative plaque removal efficacy

Abstract

Background: Clinical validation of laboratory toothbrushing tests has important advantages. It was, therefore, the aim to demonstrate correlation of tooth cleaning efficiency of a new robot brushing simulation technique with clinical plaque removal.

Methods: Clinical programme: 27 subjects received dental cleaning prior to 3-day-plaque-regrowth-interval. Plaque was stained, photographically documented and scored using planimetrical index. Subjects brushed teeth 33-47 with three techniques (horizontal, rotating, vertical), each for 20s buccally and for 20s orally in 3 consecutive intervals. The force was calibrated, the brushing technique was video supported. Two different brushes were randomly assigned to the subject. Robot programme: Clinical brushing programmes were transfered to a 6-axis-robot. Artificial teeth 33-47 were covered with plaque-simulating substrate. All brushing techniques were repeated 7 times, results were scored according to clinical planimetry. All data underwent statistical analysis by t-test, U-test and multivariate analysis.

Results: The individual clinical cleaning patterns are well reproduced by the robot programmes. Differences in plaque removal are statistically significant for the two brushes, reproduced in clinical and robot data. Multivariate analysis confirms the higher cleaning efficiency for anterior teeth and for the buccal sites.

Conclusions: The robot tooth brushing simulation programme showed good correlation with clinically standardized tooth brushing.This new robot brushing simulation programme can be used for rapid, reproducible laboratory testing of tooth cleaning.

Figure 1

Example of photographic documentation of the clinical programme (A-F) and the robot programme (G-I). A-C: stained plaque after 3-day plaque regrowth. D-F: same teeth, stained plaque after 20s of toothbrushing. G-I: typodont with simulated plaque after toothbrushing.

Figure 2

Tested toothbrushes. A: Dr.Best® plus medium. B: Dr.Best® Interdent medium (GlaxoSmithKline, Buehl, Germany).

Figure 3

Toothbrushing simulation unit. A: six-axis robot, B: calibrating graticule. C: two shields for calibrating the brushing force. D: mounting plate for mandibular typodont dentition 33–48.

Figure 4

Comparison of different brushing techniques between the robot and the subjects. Cumulative number of not completely cleaned planimetrical fields of teeth 32–47, both toothbrushes and all subjects and robot cycles (total number of fields 9x9 = 81). Explanation: Number of observations: n = 27 subjects; n = 14 robot runs. The mean of a series is depicted using a black point, while the median is drawn as a line through the center of the box. The box represents the middle 50 percent of the data. At both sides it is connected with the last data point within the 1.5* interquartile range from the first resp. third quartile. Data points outside are defined as (°) outliers.

Figure 5

Correlation of not cleaned planimetrical fields (range of 0–9 fields) in clinical versus robot tests. Cleaning patterns tooth by tooth 32 to 47, toothbrush A (Plus) versus toothbrush B (Interdent). Robot cleaning efficacy is slightly higher compared to the cleaning efficacy of the subjects (except for tooth 46 and 47 orally), mean values of number of oral (left) and buccal fields (right) with residual plaque. Number of observations: n = 27 clinical study; n = 14 robot study. Spearman rank correlation coefficients: Oral: B(hor) vs. B(rot): r = 0.62 (0.05 < p < 0.10). B(hor) vs. A(hor): r = 0.68 (0.01 < p < 0.05). B(hor) vs. A(rot): r = 0.80 (p < 0.01). B(rot) vs. A(hor): r = 0.73 (0.01 < p < 0.05). B(rot) vs. A(rot): r = 0.87 (p < 0.01). A(hor) vs. A(rot): r = 0.83 (p < 0.01). Buccal: B(hor) vs. B(rot): r = 0.80 (p < 0.01). B(hor) vs. A(hor): r = 0.48 (p > 0.10). B(hor) vs. A(rot): r = 0.73 (0.01 < p < 0.05). B(rot) vs. A(hor): r = 0.45 (p > 0.10). B(rot) vs. A(rot): r = 0.77 (p < 0.01). A(hor) vs. A(rot): r = 0.60 (0.05 < p < 0.10).