The Influence of Fluoride Varnish on the Attrition of Dentine

Effect of Galla сhinensis on the Wear Resistance of Dentine

The aim of this study was to investigate the effect of natural herb material Galla Chinensis extraction (GCE) on the wear resistance of dentine in vitro. Forty sound bovine dentine blocks were prepared and randomly divided into two groups. The samples were first treated with 4000 ppm aqueous solution of Galla chinensis and distilled deionized water (DDW) was used as a control. Then the samples were subjected to 5,000 cycles of attrition bathed under artificial saliva with 150 N loads. Wear measurement, scanning electron microscopy (SEM) examination and energy-dispersive X-ray spectrometry (EDX) analysis were utilized to evaluate the effects of GCE on the wear resistance. The depth of the wear scar of DDW-treated surface (mean = 32.5 μm, SD = 11.8 μm) was significantly greater than that of GCE-treated surface (mean = 26.4 μm, SD = 13.9 μm) (p < 0.05). Furthermore, the SEM images showed severe wear on the DDW specimens and less wear on the GCE-treated samples. Finally, from EDX data, GEC group had higher percentage of Ca and P than the control. In conclusion, our study suggested that Galla chinensis could enhance wear resistance of dentine.

Electrochemical induced dissolution of fragments of nickel-titanium endodontic files and their removal from simulated root canals

AIM

To improve the dissolution process of NiTi endodontic rotary files aiming at fragment removal and the recovery of the original path of the root canal during a clinically acceptable period of time.

METHODOLOGY

Anodic polarization curves and redox curves were obtained to determine the conditions necessary for the dissolution of endodontic files. Anodic polarization of K3 files was performed, and analysis of variance (P < 0.05) was used to compare different test times in relation to weight loss, length loss and electrical charge generated in each solution. The polarization of fragments in simulated root canals was undertaken to evaluate the dissolution process. After the tests, a size 10 K-file was used to verify the possibility to bypass the fragment. The total electrical charge of each test was obtained from the corresponding graph area. Radiographic analysis of the simulated canals was used before and after the tests to verify fragment dissolution.

RESULTS

The weight loss values, the length loss values and the total values of electrical charge in each period of time were significantly higher (P < 0.05) in the tests using the selected solution compared with the solution previously proposed. A progressive consumption of the K3 file tip was observed up to 30 min. The anodic polarization of file fragments in simulated root canals for 60 min resulted in their partial dissolution and enabled the recovery of the original canal pathway with size 10 K-files.

CONCLUSIONS

Increasing fluoride concentration resulted in greater active dissolution of NiTi files. The dissolution of fractured files in simulated root canals enabled the recovery of its original path during a clinically acceptable period of time.

An experiment on the attrition of acid demineralized dentine in vitro

BACKGROUND

A laboratory investigation was designed to test the hypothesis that acids increase the rate of wear caused by attrition on dentine.

METHODS

Dentine sections from 10 teeth were polished, cleaned in an ultrasonic bath and divided into 8 equally sized areas. The occlusal tip of a tooth, placed vertically in a wear machine and loaded at 150 N, was moved against each dentine section for 5000 return strokes with artificial saliva acting as a lubricant. Each dentine section was divided into 8 sections and half randomly immersed in a 1% citric acid solution (pH 2.3) for 20 minutes. The wear regime produced 8 wear scars in total per dentine sample. The volume of each wear scar was measured using a contacting digitizing profilometer.

RESULTS

A total of 80 wear scars were produced with 40 treated with acid and 40 acting as controls. The mean for wear volume of the dentine scars with acid was 4.84 μm(3) (1.38) and for the non-acid surface 2.95 μm(3) (0.86). This difference was statistically significant (p < 0.05).

CONCLUSIONS

These results support the hypothesis that acids increase the rate of wear caused by attrition on dentine.

The effect of increasing sodium fluoride concentrations on erosion and attrition of enamel and dentine in vitro

OBJECTIVES

To investigate the effect of an aqueous sodium fluoride solution of increasing concentration on erosion and attrition of enamel and dentine in vitro.

METHODS

Enamel and dentine sections from caries-free human third molars were polished flat and taped (exposing a 3 mm x 3 mm area) before being randomly allocated to 1 of 5 groups per substrate (n=10/gp): G1 (distilled water control); G2 (225 ppm NaF); G3 (1450 ppm NaF); G4 (5000 ppm NaF); G5 (19,000 ppm NaF). All specimens were subjected to 5, 10 and 15 cycles of experimental wear [1 cycle=artificial saliva (2h, pH 7.0)+erosion (0.3% citric acid, pH 3.2, 5 min)+fluoride/control (5 min)+attrition (60 linear strokes in artificial saliva from enamel antagonists loaded to 300 g)]. Following tape removal, step height (SH) in mum was measured using optical profilometry.

RESULTS

When the number of cycles increased the amount of tooth surface loss increased significantly in enamel and dentine after attrition and erosion and for dentine after attrition. Attrition and erosion resulted in greater surface loss than attrition alone after 15 cycles of experimental wear of enamel. 5000 ppm and 19,000 ppm sodium fluoride solutions had a protective effect on erosive and attritional enamel tooth wear in vitro, however no other groups showed significant differences.

CONCLUSIONS

The more intensive the fluoride regime the more protection was afforded to enamel from attrition and erosion. However, in this study no such protective effect was demonstrated for dentine.