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Dental India newsletter dated 9th March 2008
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Evaluation of apical surface roughness after root resection: a scanning electron microscopic study

Marco Antonio Hungaro Duarte PhD a, , Rubens Domingues MS a, Marisa Akemi Matsumoto PhD a, Luis Eduardo Marques Padovan PhD a and Milton Carlos Kuga PhD b
aBauru, Sagrado Cora? University, Bauru, S?Paulo, Brazil.
bFISA/FUNEC, Sagrado Cora? University, Bauru, S?Paulo, Brazil.
Received 3 May 2007;  revised 27 June 2007;  accepted 10 July 2007.  Available online 18 October 2007.

Objectives

The objective of this study was to compare, by scanning electron microscopy, the smoothness of the resected apical root surface after preparation with high-speed #699 bur, #699 bur plus Shofu finishing and Zekrya bur, and with an erbium:YAG laser.

Study design

Thirty-nine extracted human premolars were instrumented and obturated and their root apices were resected. The roots were divided into 4 groups according to the root resection method. The teeth were dried, metallized, and analyzed at ?00 by scanning electron microscopy. Scores ranging from 0 to 3 were attributed to surface smoothness. The data were analyzed by the Kruskal-Wallis test for overall comparison, and by Dunn's test for individual comparisons.

Results

Smoother surfaces were observed for the groups treated with the #699 bur and the #699 bur plus Shofu point finishing, while rougher surfaces were obtained with the laser, which differed significantly from the other 2 methods (P < .05).

Conclusions

Treatment with the #699 bur plus Shofu finishing yielded better results in terms of surface smoothness, whereas the laser treatment produced more irregular and rougher surfaces after root resection.

Interaction between Sodium Hypochlorite and Chlorhexidine Gluconate

  Bettina R. Basrani , DDS? , Sheela Manek, BSc ?, Rana N.S. Sodhi, PhD?, Edward Fillery, BSc, PhD?, Aldo Manzur, DDS, MSc?

published online 21 May 2007.

Abstract

The combination of sodium hypochlorite (NaOCl) and chlorhexidine (CHX) results in the formation of a precipitate. The aim of this study was to determine the minimum concentration of NaOCl required to form a precipitate with 2.0% CHX. This was accomplished with a serial dilution technique. X-ray photon spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) were used to qualify and quantify the precipitate. A color change and precipitate were induced in 2.0% CHX by 0.023 % and 0.19 % NaOCl, respectively. Both XPS and TOF-SIMS showed the presence of para-chloroaniline in an amount directly related to the concentration of NaOCl used. Until this precipitate is studied further, its formation should be avoided by removing the NaOCl before placing CHX into the canal.

RESEARCH REPORT
Biomaterials & Bioengineering

Micromechanical Property Recovery of Human Carious Dentin Achieved with Colloidal Nano-?-tricalcium Phosphate

Y. Shibata1,*, L.H. He2, Y. Kataoka1, T. Miyazaki1, and M.V. Swain2

1 Department of Oral Biomaterials and Technology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan; and
2 Biomaterials Science Research Unit, Faculty of Dentistry, University of Sydney, Sydney Dental Hospital, Surry Hills, NSW 2010, Australia

* corresponding author, yookun@dent.showa-u.ac.jp

Reconstitution of carious dentin has been recognized as difficult, because it progresses by loss of collagen polymerization and by demineralization under acidic conditions. Recently, colloidal alkaline nano-calcium phosphate, prepared by electrical discharge in a buffered physiological saline solution, has been shown to be effective in the formulation of a bone-like biocomposite by simply being mixed with acidic collagen solution. It was hypothesized that colloidal calcium phosphate was suitable for the reconstitution of carious dentin. Natural caries lesions in dentin from permanent teeth were exposed to colloidal hydroxyapatite and ?-tricalcium phosphate for 10 days. The micromechanical properties of these tissues were evaluated by nano-indentation. The elastic modulus of human carious dentin improved after samples were immersed in colloida? ?-tricalcium phosphate. The mineral density of carious dentin exposed to ?-tricalcium phosphate increased more than that immersed in hydroxyapatite. However, since it was not directly proportional to micromechanical recovery, mineral density alone was not a sufficient indicator of mechanical behavior.

KEY WORDS: Nanoindentation ? dentin ? calcium phosphate ? collagen