Cavitation in a periodontal pocket by an ultrasonic dental scaler: A numerical investigation.

Periodontal pockets are spaces or holes surrounded by teeth under the gum line. These pockets can become filled with infection-causing bacteria resulting in tissue, bone, and tooth loss. Cavitation produced by the oscillating tip of dental ultrasonic scalers plays a significant role in routine periodontal therapy to clean these areas. Numerical studies were conducted for a scaler vibrating in a periodontal pocket which was simplified to a hole, using ABAQUS based on the finite element method. The simulations consider the three-dimensional, nonlinear, and transient interaction between the vibration and deformation of the scaler tip, the water flow around the scaler and the cavitation formation. The numerical model was validated by comparing results with experimental data for a scaler vibrating in an unbounded liquid, the displacement at the free end of the scaler and the cavitation pattern near the scaler tip displaying excellent agreement. A parametric study for a scaler vibrating in a hole has been carried out in terms of the volume of the hole, the taper ratio (the radius ratio between the circular opening and bottom of the hole), and the immersion depth of the scaler tip in the hole. The amount of cavitation generated is evaluated by the cavitation density (or the void fraction) which is the ratio of the volume of the cavitation occupied in the hole to the total volume of the hole. Numerical results indicate that the cavitation density in the hole increases with the decreasing hole volume and the increasing taper ratio. It is inferred that cleaning effects could be increased if some modifications to the scaler design could be made to increase the blocking effect of the hole during the cleaning process. Cavitation is observed in the hole even if the scaler is placed above the hole and increases with the immersion depth.

Training Plates: A Solution for Patients Unable to Tolerate a Removable Prosthesis.

Dealing with patients who are unable to tolerate dentures can present a challenge to the general dental practitioner (GDP). Careful assessment of patients and their dentures will identify any causes of the intolerance to dentures. Training plates are a useful technique that can be used to allow patients to become accustomed to removable prosthesis but will inevitably lengthen the treatment process. CPD/Clinical Relevance: Training plates offer a possible solution to general dental practitioners who treat patients who are struggling to tolerate dentures.

Cavitation occurrence around ultrasonic dental scalers.

Ultrasonic scalers are used in dentistry to remove calculus and other contaminants from teeth. One mechanism which may assist in the cleaning is cavitation generated in cooling water around the scaler. The vibratory motion of three designs of scaler tip in a water bath has been characterised by laser vibrometry, and compared with the spatial distribution of cavitation around the scaler tips observed using sonochemiluminescence from a luminol solution. The type of cavitation was confirmed by acoustic emission analysed by a 'Cavimeter' supplied by NPL. A node/antinode vibration pattern was observed, with the maximum displacement of each type of tip occurring at the free end. High levels of cavitation activity occurred in areas surrounding the vibration antinodes, although minimal levels were observed at the free end of the tip. There was also good correlation between vibration amplitude and sonochemiluminescence at other points along the scaler tip. 'Cavimeter' analysis correlated well with luminol observations, suggesting the presence of primarily transient cavitation.

Quality of trials in a systematic review of powered toothbrushes: suggestions for future clinical trials.

BACKGROUND: This study aimed to assess the quality of reports of randomized controlled trials (RCTs) comparing manual and powered toothbrushes and provide advice on how future trials might be improved. METHODS: Studies were identified in the Cochrane systematic review of RCTs comparing powered versus manual toothbrushes. Reports were assessed against predefined criteria on the design of the studies to determine the effectiveness of the brushes in everyday home use and on their methodological quality. RESULTS: Only 42 of 297 identified studies satisfied the inclusion criteria and were eligible for inclusion in the review. Many studies were excluded for more than one reason. Fifteen studies employed split-mouth designs that may have changed toothbrushing behavior. Of 42 included RCTs, the generation of randomization sequence was adequate in 15 trials and concealment of allocation was adequate in 16 trials. Intention-to-treat analysis was reported in only five studies. Plaque data were reported using 10 different indices and gingivitis with nine indices. Only 12 trials lasted 3 months or longer, and there were no data on the benefits of powered toothbrushes for periodontal attachment. CONCLUSIONS: Some designs created an artificial research environment that may have undermined the findings. Authors of toothbrush trials should consider the Consolidated Standards of Reporting Trials statement. Greater standardization of the indices used is required. Trials of longer duration would enhance the evaluation of powered toothbrushes. Data on thresholds for clinically significant differences in plaque and gingivitis levels would help to determine whether oral hygiene aids provide important health benefits.