role of amalgam mix and corrosion upon the edge strength of some dental amalgams

The purpose of the present work was to study the effect of time ofcondensation and corrosion upon the edge strength of some amalgam alloys. Theangle of amalgam margins for all the samples has measured 70C and it wassubjected to a load of 500 gm. Amalgam condensation was made at 1, 2, 4 and 5min. after the end of trituration. Corrosion of amalgam samples was done bystoring the samples in 0.01 M lactic acid buffered with NaCl 0.02% adjusted topH 4. For the corroded samples, it was found that conventional amalgam showeda severe deterioration of the edge strength. While, for the non-gamma II, therewas a decrease in edge strength, but not statistically significant. For allthe investigated amalgam alloys, it was found that a triturated mix when kept5 min in air before condensation showed a marked reduction in the edgestrength

In-vitro study: the effect of plasticity, time of condensation upon surface roughness of some amalgam alloys

The present work was performed to evaluate the role of some variables that mayaffect the surface roughness of dental amalgam. Three different types ofcommercial amalgams were used in this study. The combination of variablesincluded in this work were plasticity of the triturated mix, and time elapsingfrom the end of trituration up to start of condensation. The results showedthat the surface roughness of the investigated amalgams was affected markedlyby the studied variables

Curing contraction of some elastomeric impression materials

The curing contraction in% [%] of seven elastomeric impressionmaterials, available on the Egyptian market, was measured by means of amercury bath technique. Measurements were done at different time intervalsafter mixing for 15 min, 60 min and 24 hr. Four of the elastomeric impressionmaterials tested in the present study [Coltex, Impregum, Brovil and Reproisl]showed a curing contraction of 0.08% after 24 hr. Although the presenttechnique is a simple test compared to ADA No. 19 for measuring thedimensional changes of elastic impression materials, yet the effectivecontraction determined as the accuracy of stone dies produced by dentalimpressions perhaps is more realistic than the free contraction of theimpression by either mercury bath technique or by the ADA No. 19

In-vitro study on dimensional changes of composite cores

Dimensional changes for the composite cores, after using two types ofcomposite resin, caused by water sorption were measured. Three differenttechniques for the retention of composite cores were followed. Thesetechniques were slot technique, T.M.S. pins applied vertically on the dentinefloor and T.M.S. pins as before but were then bended. Measurements ofdimensional changes were done using a stereomicroscope for 1 day, 3 days and 7days after water immersion. The results of the present study showed that forboth types of composite resin investigated, bending the pin after beingapplied vertically on dentine floor showed the least values of dimensionalchanges. For all the variables included in this study, it was found thatafter three days storage in water, there were no dimensional changes. It isadvocated from the findings of this study to delay crown preparation in caseof composite cores a few days later to avoid discrepancy due to hygroscopicexpansion caused by water sorption

role of some cleansing agents upon removal of dentinal-smeared layer: a scanning electron microscope study

The purpose of this paper was to study the role of some cleansing agents uponthe removal of smeared layer formed on the cut dentin surface. The differentcleansers used in the present study were EDTA, phosphoric acid, citric acid,ascorbic acid, sodium chloride and deionized water. The results of thepresent study showed that the application of EDTA, phosphoric acid andascorbic acid for one minute has removed the smeared layer formed onto the cutdentin surface. On the other hand, washing the cut dentin surface withdeionized water or NaCl for one minute did not remove the smeared layer. Theapplication time, upon the removal of the dentinal smeared layer, of thevarious inorganic acids used in the present work was also studied

Bonding strength of ASPA cement filling to hard tooth structure

The purpose of the present study was to determine the role of application time for ferric chloride solution upon bonding strength between ASPA cement filing and dentin, after which dentin was formally washed for one minute by means of phosphoric acid solution 5% [W/W]. Also, it aimed to study the effect of alternative application of phosphoric acid and ferric chloride upon bonding strength between ASPA cement and enamel. For bonding strength between ASPA cement and dentin, it was found that the optimum values of bonding strength were obtained when ferric chloride was applied for one minute. In case of enamel, it was found that ferric chloride seemed to have no effect upon the bonding strength between ASPA cement filling and enamel