Visual and digital comparative tooth colour assessment methods and atomic force microscopy surface roughness.

This study compared digital and visual colour tooth colour assessment methods in a sample of 99 teeth consisting of incisors, canines and pre-molars. The teeth were equally divided between Control, Ozicure Oxygen Activator bleach and Opalescence Quick bleach and subjected to three treatments. Colour readings were recorded at nine intervals by two assessment methods, VITA Easyshade and VITAPAN 3D MASTER TOOTH GUIDE, giving a total of 1782 colour readings. Descriptive and statistical analysis was undertaken using a GLM test for Analysis of Variance for a Fractional Design set at a significance of P < 0.05. Atomic force micros copy was used to examine treated ename surfaces and establish surface roughness. Visual tooth colour assessment showed significance for the independent variables of treatment, number of treatments, tooth type and the combination tooth type and treatment. Digital colour assessment indicated treatment and tooth type to be of significance in tooth colour change. Poor agreement was found between visual and digital colour assessment methods for Control and Ozicure Oxygen Activator treatments. Surface roughness values increased two-fold for Opalescence Quick specimens over the two other treatments, implying that increased light scattering improved digital colour reading. Both digital and visual colour matching methods should be used in tooth bleaching studies to complement each other and to compensate for deficiencies.

Tooth colour change with Ozicure Oxygen Activator: a comparative in vitro tooth bleaching study.

INTRODUCTION: This in vitro study compared a new tooth bleaching product, Ozicure Oxygen Activator (O3, RSA) with Opalescence Quick (Ultradent, USA) using a randomised block design to assess tooth colour change. AIM: Colour change, stability and relapse in canine, incisor and premolar teeth was assessed following three bleach treatments and subsequent tooth colour assessment. METHODS: Ninety nine teeth (canines, incisors and premolars), which were caries free, had no surface defects and were within the colour range 1M2 and 5M3 were selected. Teeth were randomly divided into the three experimental groups: Opalescence Quick, Ozicure Oxygen Activator and control. The three experimental groups received three treatments of one hour each over three consecutive days. Tooth colour was assessed using the Vitapan 3D Master Tooth Guide (VITA, Germany). A General Linear Models test for analysis of variance for a fractional design with significance set at P < 0.05 was used to test for significance. RESULTS: Both bleaching methods significantly lightened the teeth (P < 0.0001). Tooth colour change was mainly after the first hour of tooth bleaching. The tooth type was significant in tooth colour change (P = 0.0416). Tooth colour relapse and resistance to colour change were observed. CONCLUSIONS: Ozicure Oxygen Activator bleached teeth in a manner and to an extent similar to Opalescence Quick.

WO3 nano-spheres into W18O49 one-dimensional nano-structures through thermal annealing.

We elaborate the size controlled synthesis of nano-spheres and nano-crystals of WO3 by ultrasonic spray pyrolysis. The as-deposited particles are predominantly spherical in shape and tend to exhibit less agglomeration and a decrease in diameter as the process temperature is increased. Characterization was carried out using transmission (TEM) and scanning (SEM) electron microscopy, energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). One-dimensional nano-structures with the highest yield of WOx nano-wires were observed in a sample synthesized at 500 degrees C but only after thermal annealing of this sample at 500 degrees C for 17 hour in flowing argon. XRD revealed a high deficiency in oxygen in all samples suggesting that the nano-structures are transformed to sub-oxides of tungsten. Micro-diffraction patterns of a typical nano-wire reveal the monoclinic phase of W18O49.

Formation of palladium nanoparticles in poly (o-methoxyaniline) macromolecule fibers: an in-situ chemical synthesis method.

We report here a novel in-situ synthetic method for the preparation of poly (o-methoxyaniline) and palladium nanoparticle composite material. Ortho-Methoxyaniline and palladium acetate were used as the precursors; during the reaction o-methoxyaniline was oxidized and forms poly (o-methoxyaniline) and palladium acetate is reduced forming palladium nanoparticles. IR and Raman spectra provide information on the structure of the polymer. The TEM and SEM analysis are used to determine the size of the nanoparticles and the morphology of the polymer respectively.

Marginal seal composition in amalgam restored teeth of varying marginal leakage.

An in vitro study was performed to ascertain the marginal seal elemental composition of amalgam restored extracted teeth of known marginal leakage. Occlusal cavities were cut in 400 caries free extracted teeth and left unlined or lined with one of 5 bases. A varnish was applied to half the cavities followed by restoration with a low copper or high copper amalgam to produce 20 restoration combinations. The teeth were stored in 1 per cent NaCl and thymol for 3 and 12 months at 20 degrees C whereafter a standard fluorescent dye marginal leakage test was performed on 320 specimens (eight teeth per treatment). Restoration combinations were grouped into 4 seal classes depending on percentage marginal seal achieved for each combination: 0-25 per cent; 26-50 per cent; 51-75 per cent and 76-100 per cent. The 80 remaining teeth (2 teeth per treatment) were fractured to expose the restoration and cavity surface, covered with marginal seal material and this was analysed by energy dispersive X-ray analysis. Elemental seal composition was compared to percentage marginal seal achieved using ANOVA and Tukey's test with significance set at p < 0.05. Numbers of elemental analysis specimens falling into each marginal seal class was 0-25 per cent = 48; 26-50 per cent = 18; 51-75 per cent = 10; 76-100 per cent = 4. Of the 16 elements detected, nine were significantly linked to sealing/leakage: Ca, Cl, Cu, Mg, Hg, P, Ag, Sn and Zn. The findings have a bearing on the improved longevity of amalgam restorations.

Method for jet polishing two-phase materials.

A two-stage jet polishing technique is described which, utilising the effects of the characteristic current-voltage behaviour of electropolishing solutions, can produce excellent TEM foils of relatively coarse two-phase materials.

Influence of amalgams, bases, and varnish on seal composition at restoration tooth interfaces.

Eighty extracted, noncarious premolars were restored with one of 20 different combinations of restorative materials: a high- or low-copper amalgam, unlined or lined with one of five bases, and varnished or unvarnished. The teeth were aged in 1% NaCl and after 3 months and 1 year the seal material deposited on the cut tooth cavity surface and the surface of the amalgam restoration was analyzed by use of energy dispersive x-ray analysis. Atomic weight percentages of marginal seal elements were statistically examined with ANOVA and Tukey's test with significance set at p < 0.05. The results indicated that only one type of seal was formed centered around tin. More marginal seal material was present in the 1-year specimens. Restoration materials used affected the deposition rate of marginal seal material. Low-copper amalgam-restored teeth formed more seal material with significantly greater amounts of chlorine and tin. Less marginal seal material was found in varnished cavities. A calcium hydroxide base produced a thick marginal seal with a significantly different composition of elements compared with the unlined and zinc-based specimens. Tin in Poly-F Plus polycarboxylate cement did not significantly increase the tin content of the marginal seal. Base materials can play a role in determining crevice pH. The findings have bearing on improved longevity of amalgam restorations.

The use of extraction replicas in scanning electron microscopy for the elemental analysis of marginal seals.

Elemental analysis of marginal seal material on 20 bulk samples of occlusally restored teeth have shown that, generally, more elements were detected in the seal material analyzed on the bulk restoration or fractured tooth surfaces than when such material was extracted using a nitrocellulose replica prior to analysis. No mercury was detected in any of the extracted seal material and only three of the replica specimens contained silver. This implies that the technique of using extraction replicas to remove material from the amalgam-tooth interface for subsequent x-ray microanalysis can provide an accurate elemental composition. The details of fabrication and the advantages of using high resolution nitrocellulose replicas for extracting marginal seal material from teeth for subsequent x-ray microanalysis are described.

Elements in marginal seals at amalgam-tooth interfaces.

X-ray micro-analysis was used to determine the elemental composition of the tooth, amalgam, and base material of ten aged, amalgam-restored, posterior teeth after they had been fractured across the amalgam-tooth interface. Subsequently, replicas were used to remove marginal seal material from each interface for examination by x-ray micro-analysis. The results show that P and Sn were present in all marginal seal material analyzed. Ca, Cl, Cu, Fe, S, and Zn were present in the marginal seals of various numbers of specimens.

The suitability of various adhesives as mounting media for scanning electron microscopy. I. Epoxies, sprays and tapes.

Fifty-six relatively commonly used epoxies, sprays and tapes have been tested with respect to properties that are, or may be, important if they were to be used as scanning electron microscopy sample mounting adhesives. Recommendations are made as to the most appropriate adhesive for each type of mounting media.