Orlando Chevitarese

Diffusion of calcium through dentin

The purpose of this research was to investigate whether calcium ions from a paste of calcium hydroxide [Ca(OH)2] and saline introduced into root canals diffuse through the dentin to reach the surface of the root. Six teeth were opened and submitted to a biomechanical process, after which all the smear layer was removed. The experiment was divided into three phases: dissolution, dissolution and diffusion I, and dissolution and diffusion II. Dissolution-each tooth, with no Ca(OH)2 paste in place, was sealed both cervically and apically and stored in 700 ml of deonized water until calcium losses from the tooth into the water were stabilized. Dissolution and diffusion I-each root canal was filled with a paste of Ca(OH)2 and saline, sealed again apically and cervically, and returned to its solution. Dissolution and diffusion II-samples were divided into three parts: the control group or group 1, containing the original paste; group 2, in which the existing paste was diluted and the teeth were resealed and replaced in their solutions; and group 3, in which the existing paste was removed and a fresh paste was introduced. The diffusion was greater in group 3, followed by group 2. In the control group, we found a diffusion of calcium, which is statistically null. The results showed that calcium diffusion was observed, in the first 16 days, in all situations in which there was Ca(OH)2 paste inside the root canals.

Bonding brackets to porcelain: in vitro study

The aim of this research was to verify, in vitro, the effect of various porcelain surface treatment on the shear strength of orthodontic brackets bonded to porcelain and the mode of fracture after debonding. Eighty-eight samples of metallic supported feldspathic porcelain were randomly divided into four groups according to their surface preparation as follows: the porcelain was maintained intact (GI), roughened with a diamond bur (GII), etched with 10% hydrofluoric acid (GIII), or sandblasted with aluminum oxide (GIV). The specimens were treated with silane (Scotchprime) and brackets were bonded with Concise. Each sample was subjected to a shear load at a crosshead speed of 1 mm/min and a recording was made at the point of failure. Bond strengths, adequate to withstand the application of orthodontic forces, were achieved in all groups. The Kruskal-Wallis statistical test showed no significant differences in bond strength between the groups (p > 0.05). However, many more porcelain fractures occurred on deglazed porcelain. This study indicates that with the appropriate material selection, the silane/composite procedure alone may be adequate for bonding.

Ca2+ Diffusion Through Dentin of Ca(OH)2 Associated with Seven Different Vehicles

This investigation measured the diffusion of Ca2+ through dentin by using Ca(OH)2 associated with various vehicles. After mechanical preparation and removal of smear layer, 41 human premolar teeth were stored individually in flasks containing 800 ml of ultra-pure deionized water for 2855 h. The Ca2+ concentration was measured by atomic absorption spectrophotometry as a function of time. These measurements were divided into two phases: dissolution, to check the loss of Ca2+ from the tooth structure itself, for which all canals were kept empty and open in the absence of medication for 1168 h, and diffusion, in which the specimens were divided into 10 groups (3 control groups: group 1 = water control, group 2 = sealing control, and group 3 = open canal dissolution control; 7 experimental groups in which the whose canals were filled with Ca(OH)2 paste associated with the following vehicles: group 4 = saline; group 5 = polyethylene glycol (Calen); group 6 = glycerin and camphorated parachlorophenol group 7 = camphorated paramonochlorophenol; group 8 = glycerin; group 9 = glycerin and tricresol formaldehyde (TCF); and group 10 = anesthetic solution. This phase lasted 1687 h. A total of 1058 measurements of Ca2+ were made. Regression analysis was used for statistical evaluation. We concluded that diffusion occurred differently for each group: the medications used in the root canals interacted with the dentinal structure or among themselves; the medication coated the dentinal tubule, facilitating the diffusion of Ca2+ into the external part of the root.

Diffusion of Ca(OH)2 associated with different vehicles: chromatographic study (high-performance liquid chromatography).

Using high-performance liquid chromatography (HPLC), small amounts of liquid samples in which 25 premolar human teeth were immersed were evaluated. Each tooth was immersed separately in 800-ml flasks with distilled ultra-pure deionized water and remained there for 1678 h after the filling of their canals with Ca(OH)2 associated with different vehicles: group 1: polyethylene glycol and colophon (Calen); group 2: glycerin and camphorated paramonochlorophenol; group 3: camphorated paramonochlorophenol; group 4: glycerin and tricresol formol; and group 5: anesthetic solution (Citanest). Five polyethylene tubes were filled with each of these pastes and placed unsealed in similar flasks. At the end of this period, HPLC analyses of the aqueous medium related to each group were performed to detect other substances that had diffused from the pastes used in the canals of the teeth other than calcium and hydroxyl ions. Although the groups presented different maximum peaks when there was no barrier, they all showed higher values than when the tooth was present. At least 15 substances other than Ca2+ and OH- were detected in the aqueous medium of group 4. Analyzing the HPLC graphs, we concluded that not only Ca2+ and OH-, but also a considerable quantity of other components of the pastes diffused through the dentine and reached the external root surface.

Influência do agente clareador peróxido de carbamida a 10% na resistência mecânica da colagem de braquetes ortodônticos

O proposito deste estudo in vitro foi determinar a influencia do agente clareador peroxido de carbamida a 10% na resistencia mecânica da colagem de braquetes ortodonticos. Foram estudados tres grupos denominados G1 (nao submetido ao clareamento), G2 (com clareamento e colagem realizada 1 semana apos) e G3 (com clareamento e colagem realizada 24h apos). O teste de cisalhamento foi conduzido na maquina de ensaios mecânicos Emic, com a velocidade de deformacao de 0,5 mm/min.A resitencia ao cisalhamento em relacao a area de colagem foi calculada para cada dente e expressa em MPa. Os resultados mostraram aumento estatisticamente significante (p<0,001) da resistencia mecânica da colagem apos clareamento.

The standardized stop: a new concept in endodontics.

This article presents a technique for making and using disposable standardized silicone stops. The stops have several diameters, colors, and thicknesses in order to make nonsurgical endodontics more efficient and improve the quality of therapy.