Effect of Loading on the Vibration Characteristics of Thin Magnetostrictive Ultrasonic Scaler Inserts

Assessing the effect of piezoelectric ultrasonic scaler tip wear on root surface roughness under influence of various working parameters: A profilometric and atomic force microscopic study

Background

Assessing the effect of scaler tip wear on the root surface roughness using piezoelectric ultrasonic scaling device under influence of various working parameters, i.e. power setting, lateral force, and instrumentation time.

Materials and Methods

An experimental study was conducted using 160 single-rooted tooth samples divided into two groups of new (n = 80) and worn tips (n = 80). Samples were prepared to examine the root surface roughness after being instrumented by new and worn piezoelectric ultrasonic tips (8 new/8 worn) at different parameters. The erosion ratio (ER) of the new/worn tip was examined under an atomic force microscope and roughness over root surface was measured by a contact surface profilometer. One-way analysis of variance test, post hoc Tukey's test, and independent t-test were used for intragroup, pair-wise multiple comparisons and intergroup comparison of average roughness (Ra) value.

Results

A statistically significant difference was found between the ER of new and worn scaler tips (P < 0.001). Intragroup comparison between subgroups 1 and 8 showed a higher Ra value in both the groups (P < 0.005). There was a significantly higher Ra value of worn tips compared to new tips (P < 0.05). Significantly higher mean Ra value was shown when lateral force changed from 50 g to 100 g (P < 0.005).

Conclusions

Increasing value of power setting, lateral force, and instrumentation time caused more surface roughness in worn-out scaler tips compared to new scaler tips. Lateral force and instrumentation time proved to be a major factor influencing surface roughness.

Influence of tip wear of piezoelectric ultrasonic scalers on root surface roughness at different working parameters. A profilometric and atomic force microscopy study

Roughness on tooth surfaces is reported to facilitate the reestablishment of microbial dental plaque. Hence, the main goal of dental scaling is to remove bacterial plaque and obtain smoother tooth surfaces. This study was aimed to assess the influence of tip wear of ultrasonic scaler inserts on root surface roughness at different working parameters. Twenty piezoelectric ultrasonic scaler inserts (10 worn/10 new) were selected to examine the erosion ratio (ER) on the scaler tips and to assess the influence of tip wear on root surface roughness. Erosion on the tip surfaces was evaluated under atomic force microscopy (AFM). Root samples were prepared and instrumented by new (Group I) and worn (Group II) inserts at different working parameters. Roughness change (Rc) on root surfaces after instrumentation was examined under profilometer and compared between and within the groups. Statistically significant differences were found between the mean ERs of new and worn tips (P < 0.01). The results of this study showed that tip angulation and instrument power strongly influenced the Rc values on instrumented samples (P < 0.05). It was also revealed that tip wear influenced the Rc values on root surfaces especially at 45° tip angulation (P < 0.05). Therefore, tip wear should also be considered as much as the other parameters to minimize the surface roughness during ultrasonic treatment.

The effect of wear on ultrasonic scaler tip displacement amplitude

AIM

During clinical usage, scaler tips may become worn and reduced in length. It is unknown what effect wear has on the magnitude of scaler tip vibrations when they are utilized under typical clinical loads. The aim of this investigation was to assess the effect of simulated wear on ultrasonic scaler tip displacement amplitude, using a scanning laser vibrometer.

MATERIALS AND METHODS

A Cavitron SPS (Dentsply) ultrasonic generator and three scaler insert designs (FSI-100, FSI-1000 and FSI-SLI-10S) were selected for the investigation. Tip vibration displacement amplitude was assessed unloaded and then contacting against tooth surfaces with loads of 0.5 and 1.0 N. Tips were then ground down by 1 mm and then 2 mm and scans were repeated.

RESULTS

For all tips, load and length were found to be significant variables (p<0.0001). The scaler tips showed a fall in displacement amplitude with a reduction in tip length. However, all scaler tips showed variability in the amount oscillation that occurred. This was most pronounced with FSI-SLI-10S.

CONCLUSIONS

This investigation demonstrated that tip wear could affect the performance of dental ultrasonic scaler inserts by reducing their vibration displacement amplitude. Clinicians should be aware of this variability, which may be significant enough to affect clinical procedures.