Effect of plastic-covered ultrasonic scalers on titanium implant surfaces.

OBJECTIVES: Maintaining oral health around titanium implants is essential. The formation of a biofilm on the titanium surface will influence the continuing success of the implant. These concerns have led to modified ultrasonic scaler instruments that look to reduce implant damage while maximising the cleaning effect. This study aimed to assess the effect of instrumentation, with traditional and modified ultrasonic scalers, on titanium implant surfaces and to correlate this with the oscillations of the instruments. MATERIALS AND METHODS: Two ultrasonic insert designs (metallic TFI-10 and a plastic-tipped implant insert) were selected. Each scaler probe was scanned using a scanning laser vibrometer, under loaded and unloaded conditions, to determine their oscillation characteristics. Loads were applied against a titanium implant (100g and 200 g) for 10 s. The resulting implant surfaces were then scanned using laser profilometry and scanning electron microscopy (SEM). RESULTS: Insert probes oscillated with an elliptical motion with the maximum amplitude at the probe tip. Laser profilometry detected defects in the titanium surface only for the metallic scaler insert. Defect widths at 200 g high power were significantly larger than all other load/power conditions (P<0.02). Using SEM, it was observed that modifications to the implant surface had occurred following instrumentation with the plastic-tipped insert. Debris was also visible around the defects. CONCLUSIONS: Metal scalers produce defects in titanium implant surfaces and load and power are important factors in the damage caused. Plastic-coated scaler probes cause minimal damage to implant surfaces and have a polishing action but can leave plastic deposits behind on the implant surface.

Reconstruction of dental ultrasonic scaler 3D vibration patterns from phase-related data.

Ultrasonic scalers are used in dentistry for removing mineralised plaque, known as calculus, from tooth surfaces. Though there is much information relating to the longitudinal vibrations of scaler probes, corresponding lateral data is limited. Understanding the lateral motion of ultrasonic probes is essential as, when used correctly, this motion will contribute to the cleaning process as well as to any damage caused to tooth surfaces. In this work we demonstrate the use of a single-axis scanning laser vibrometer, in conjunction with a mirror, to evaluate simultaneously the longitudinal and lateral motion of dental scaler probes oscillating at ultrasonic frequencies (approximately 30 kHz). Node/antinode patterns along the probe length were observed, as was an elliptical motion along the length of the probe. Application of a load to the tip of the instrument modified the vibration pattern of the whole probe. This technique seems an important step towards better characterisation of the three-dimensional movement of oscillating ultrasonic scaler probes, particularly when probes are contacted against teeth. Understanding the three-dimensional probe motion and how this is affected by contact with tooth surfaces may lead to future instrument designs with improved cleaning efficiency whilst minimising potential tooth damage.

Ultrasonic scaler oscillations and tooth-surface defects.

Damage to tooth root surfaces may occur during ultrasonic cleaning with both piezoelectric and magnetostrictive ultrasonic scalers. It is unclear which mechanism causes more damage or how their mechanism of action leads to such damage. Our null hypothesis is that tooth-surface defect dimensions, resulting from instrumentation with ultrasonic scalers, are independent of whether the scaler probe is magnetostrictive or piezoelectric. Piezoelectric and magnetostrictive ultrasonic scaler probes were placed into contact against polished dentin samples (100 g/200 g). Resulting tooth surfaces were evaluated with a laser metrology system. Ultrasonic instrumentation produced an indentation directly related to the bodily movement of the probe as it made an impact on the surface. Load, generator power, and probe cross-section significantly affected probe vibration and defect depth/volume. Defect dimensions were independent of generator type. Magnetostrictive probes oscillated with greater displacement amplitudes than piezoelectric probes, but produced similar defects. This may be due to the cross-sectional shape of the probes.

VEGF and odontoblast-like cells: stimulation by low frequency ultrasound.

OBJECTIVE: Vascular endothelial growth factor (VEGF) has been implicated in the regulation of dental pulp and dentine repair. Therapeutic ultrasound was shown to be effective for fracture repair. We investigated whether low frequency ultrasound influences the production of VEGF by odontoblast-like cells. Moreover, we examined the direct effects of VEGF on odontoblast-like cell proliferation. DESIGN: MDPC-23, an established odontoblast-like cell line, was exposed to increasing intensities of 30kHz ultrasound using an ultrasonic tip probe. RESULTS: After 24h cell culture, WST-1 analysis of cell viability and number showed a dose-dependent decrease in the number of viable cells with increasing ultrasound power. However, the relative concentration of VEGF as analysed by ELISA and normalised to cell number was significantly increased in the culture supernatants indicating an ultrasound-induced stimulation of odontoblastic VEGF secretion. Analysis of VEGF gene expression by sqRT-PCR revealed the expression of the main VEGF isoforms in the MDPC-23 cells, i.e. VEGF(120) and VEGF(164) as well as to a minor extent VEGF(188). Low power ultrasound increased gene expression of all VEGF isoforms. Addition of recombinant VEGF to the cell cultures significantly stimulated cell proliferation. Gene expression of the VEGF receptors Flt1/VEGFR1 and KDR/VEGFR2 was detected in the MDPC-23, suggesting the possibility that VEGF may act on the odontoblast-like cells in an autocrine manner. CONCLUSIONS: Our results indicate that ultrasound promoted VEGF expression and production by odontoblast-like cells and that VEGF may have autocrine effects on these cells. It is proposed that ultrasound may influence odontoblast activity and dentine repair by modulating production of endogenous growth factors in the dentine-pulp complex.

A study to determine whether cavitation occurs around dental ultrasonic scaling instruments.

The aim of this investigation was to determine if cavitation occurred around dental ultrasonic scalers and to estimate the amount of cavitation occurring. Three styles of tip (3 x TFI-10, 3 x TFI-3, 3 x TFI-1) were used, in conjunction with a Cavitron SPS ultrasonic generator (Dentsply, USA), to insonate terephthalic acid solution. The hydroxyl radical, [*OH], concentration, produced due to cavitation from the scaler tips, was monitored by fluorescence spectroscopy. Cavitational activity was enhanced at higher power settings and at longer operating times. The tip dimensions and geometry as well as the generator power setting are both important factors that affect the production of cavitation.

A new insight into the oscillation characteristics of endosonic files used in dentistry.

The aim of this study was to assess the oscillation characteristics of unconstrained endosonic files using a scanning laser vibrometer (SLV). Factors investigated included file vibration frequency and node/antinode location as well as the variation in file displacement amplitude due to increasing generator power setting. A 30 kHz Mini Piezon generator (Electro-Medical Systems, Switzerland) was used in conjunction with a #15 and #35 K-file. Each file was fixed in position with the long axis of the file perpendicular to the SLV camera head. The laser from the SLV was scanned over the length of the oscillating file for generator power settings 1 to 5 (minimum to half power). Measurements were repeated ten times. The fundamental vibration frequency for both files was 27.50 kHz. Scans of each file showed the positions of nodes/anti-nodes along the file length. The #15 file demonstrated no significant variation in its mean maximum displacement amplitude with increasing generator power, except at power setting 5, where a decrease in displacement amplitude was observed. The #35 file showed a general increase in mean maximum displacement amplitude with increasing power setting, except at power setting 4 where a 65% decrease in displacement amplitude occurred. In conclusion, scanning laser vibrometry is an effective method for assessing endosonic file vibration characteristics. The SLV was able to demonstrate that (unloaded) file vibration displacement amplitude does not increase linearly with increasing generator power. Further work is being performed on a greater variety of files and generators. Vibration characteristics of files under various loads and varying degrees of constraint should also be investigated.

Does cavitation occur around powered toothbrushes?

AIMS/OBJECTIVES: The aim of this investigation was to determine if cavitational activity occurred around powered toothbrushes using a chemical dosimeter system based on terephthalic acid (TA). MATERIAL AND METHODS: Five powered toothbrushes were used in this investigation: Braun Plaque Remover D8, Braun Oral-B 3D, Philips Jordan Sensiflex HX2520, Sonicare PS-1 and Sonicare Elite HX 7351/02. Each brush head was inserted into a conical flask containing 50 cm3 of aqueous TA solution. Brushes were operated for 10 and 20 min and a cuvette of the solution was placed in a fluorescence spectrometer (Perkin Elmer 3000). The fluorescence emitted at wavelength 425 nm, which is proportional to *OH radical concentration, was monitored. RESULTS: Any cavitational activity that may have been produced by the powered toothbrushes was below the limit of detection of the system (<10(-8) M) for the timescales investigated. CONCLUSIONS: This work has demonstrated that cavitational activity does not occur around powered toothbrushes. Operating the toothbrushes for periods up to 20 min resulted in no cavitational activity being detected.

Ultrasonic scaler tip performance under various load conditions.

OBJECTIVES: The aim of this investigation was to assess the effect of loading on ultrasonic scaler tip displacement amplitude, using a scanning laser vibrometer. MATERIAL AND METHODS: Four generators were selected for this investigation including: Cavitron Select (Dentsply), Cavitron SPS (Dentsply), Piezon Master 400 (EMS) and Mini Piezon (EMS). The insert designs used with these generators included the TFI-10 and TFI-3 (with the Dentsply generators) and P-tip (with the EMS generators). The insert tips were contacted against tooth surfaces with loads of 0.25, 0.5 and 1.0 N. The scanning laser vibrometer was then used to scan the vibrating scalers at various generator power settings. RESULTS: The tips generally showed an increase in displacement amplitude with increasing power setting, although this increase was often nonlinear. Displacement amplitudes of like tips were generally found to be significantly different from each other at all loads. For individual inserts, loading caused a significant difference in tip response from the unloaded situation and also between loads. CONCLUSIONS: This investigation has demonstrated that there is a high variability associated with dental ultrasonic scaler inserts. Clinicians and researchers should be aware of this variability as it may affect both clinical procedures and future research.

Displacement amplitude of ultrasonic scaler inserts.

OBJECTIVES: Scanning laser vibrometry is a noninvasive method of measuring the velocity, displacement amplitude and oscillation frequency of vibrating objects. The purpose of this study was to assess, using a scanning laser vibrometer (SLV), the performance of different designs of commercially available ultrasonic scaler generators by measuring the oscillatory characteristics of various scaler tips. METHODS: Four ultrasonic generators were tested (Cavitron SPS and Cavitron Select (Dentsply, York, PA, USA) and Piezon Master 400 and Mini Piezon (Electro-Medical Systems, Switzerland)) with various designs of scaler tip. The tips were positioned with their anterior surface perpendicular to the direction of the laser. A graduated scale, placed over the manufacturer's power dial, enabled incremental power setting selection. For each power setting, the laser beam from the SLV was scanned over the surface of the oscillating tip. RESULTS: The ranges of longitudinal displacement amplitudes (in micrometres) were as follows: Mini Piezon (P-tip): 12.90+/-1.44 to 44.03+/-7.80; Piezon Master 400 (P-tip): 16.02+/-2.66 to 35.85+/-5.29; Cavitron SPS (TFI-10 tip): 7.81+/-0.51 to 29.70+/-1.12; Cavitron Select (TFI-10 tip): 13.13+/-1.44 to 33.77+/-4.27; Cavitron SPS (TFI-3 tip): 5.50+/-0.46 to 31.35+/-3.62. CONCLUSIONS: This study shows that there are differences between commercially available generators and that tip movement varies between tips of the same style as well as between the generator and tip design. Users of ultrasonic scalers should be made aware of this inherent variability that may influence clinical procedures.

Vibration characteristics of ultrasonic scalers assessed with scanning laser vibrometry.

OBJECTIVES: Scanning laser vibrometry is a non-invasive method of accurately measuring the vibratory characteristics of oscillating objects. The aim of this study was to observe, using a scanning laser vibrometer (SLV), the vibration patterns of dental ultrasonic scaler tips and to assess the effects of water flow rate and power setting on these patterns whilst operating the tips in an unloaded environment. METHODS: A 30kHz ultrasonic scaler (TFI-10, Dentsply) was fixed in position and a laser beam from the SLV was focused onto the tip. The laser, guided by a virtual measurement grid, was scanned over the oscillating tip surface. Scans were taken with the laser beam perpendicular to the long axis of the front face of the tip. RESULTS: Oscillation frequencies and the displacement amplitude at the unconstrained end of the tip were measured for various power/water settings. Vibration nodal positions were recorded for the various settings and were found to occur approximately 4mm from the free end of the tip. At low and medium power settings, tip displacement amplitude was reduced by increased water flow. At high power settings, combined with a high flow rate, the water leaves the body of the instrument as a jet. This left the tip relatively unconstrained, allowing it to oscillate at increased displacement amplitudes. CONCLUSIONS: This study shows that the SLV is able to accurately characterise the movement of oscillating ultrasonic scaler tips. The tips are affected by power setting and water flow rates.