An evaluation of the effect of blood and human serum on the surface microhardness and surface microstructure of mineral trioxide aggregate.

AIM: Short-term and long-term evaluation of the effect of whole human blood or serum contamination on the surface microhardness value and microstructure of white and grey mineral trioxide aggregate (MTA). METHODOLOGY: Three groups of 10 samples for each type of MTA were prepared. The first group was mixed with and exposed to fresh whole human blood. The second and third groups were mixed with distilled water and exposed to fresh whole human blood or human serum, respectively. The control group samples were mixed with and exposed to distilled water. During preparation, 1 g of MTA was triturated with 0.33 g of the selected liquid using an amalgamator and placed inside borosilicate cylindrical moulds. The samples were treated with ultrasonic energy. Vickers surface microhardness values were compared after 4 and 180 days. Scanning electron microscopy (SEM) analysis was performed after 4 days. RESULTS: White MTA had a greater microhardness value than grey MTA in all groups. There was a significant difference between the control and the experimental groups (P < 0.00001). There was no significant difference between the microhardness values obtained after 4 and 180 days, apart from grey MTA mixed with blood or exposed to serum (P < 0.00001). SEM analysis showed the contaminated samples were devoid of acicular crystals that were prominent in the control groups. CONCLUSION: Blood contamination had a detrimental effect on the surface microhardness of MTA in the short and long term. If blood or serum contamination is unavoidable under clinical conditions, it might be preferable to use white MTA.

pH of pus collected from periapical abscesses.

AIM: To determine the pH of pus collected from periapical abscesses. METHODOLOGY: Forty patients (Male = 17/Female = 23) between the ages 17 and 37 years, each with a periapical abscess and with no relevant medical history, were recruited. All the participants had moderate-to-severe pain on percussion accompanied by localized or generalized swelling. At least 1 mL of pus was aspirated from each participant using a No 20 gauge needle. A pH meter was used to define the pH of the pus immediately following aspiration. RESULT: The mean pH of pus from the periapical abscesses of patients was 6.68 +/- 0.324 with a range between 6.0 and 7.3. There was no statistically significant difference in pH by gender or age. CONCLUSION: The mean pH of pus from periapical abscesses was generally acidic, but some samples (two female and three male) were neutral and some samples (four female and one male) were alkaline.

The effect of pH on surface hardness and microstructure of mineral trioxide aggregate.

AIM: To evaluate the surface microhardness of mineral trioxide aggregate (MTA) specimens following exposure of their surface to a range of acidic environments during hydration. In addition, the morphological microstructure features of samples were studied by scanning electron microscopy (SEM). METHODOLOGY: White ProRoot MTA (Dentsply Tulsa Dental, Johnson City, TN, USA) was mixed and packed into cylindrical polycarbonate tubes. Four groups, each of 10 specimens, were formed using a pressure of 3.22 MPa and exposed to pH 4.4, 5.4, 6.4 and 7.4, respectively, for 4 days. Vickers microhardness of the surface of each specimen was measured after exposure. Four groups of two specimens were prepared and treated in the same way prior to qualitative examination by SEM. Data were subjected to one-way anova and post hoc Tukey's test. RESULT: The greatest mean surface hardness values (53.19 +/- 4.124) were observed following exposure to pH 7.4 with the values decreasing to 14.34 +/- 6.477 following exposure to pH 4.4. The difference between these values at the 95% CI (33.39-44.30) was statistically significant (P < 0.0001). There were no distinct morphological differences between groups in terms of the internal microstructure. However, a trend was observed that the more acidic the solution, the more extensive the porosity of the specimens. CONCLUSION: Under the conditions of this study, surface hardness of MTA was impaired in an acidic environment.

The effect of condensation pressure on selected physical properties of mineral trioxide aggregate.

AIM: To examine the effect of condensation pressure on surface hardness, microstructure and compressive strength of mineral trioxide aggregate (MTA). METHODOLOGY: White ProRoot MTA (Dentsply Tulsa Dental, Johnson City, TN, USA) was mixed and packed into cylindrical polycarbonate tubes. Six groups each of 10 specimens were subjected to pressures of 0.06, 0.44, 1.68, 3.22, 4.46 and 8.88 MPa respectively. The surface hardness of each specimen was measured using Vickers microhardness. Cylindrical specimens of 4 mm in diameter and 6 mm in height were prepared in polycarbonate cylindrical moulds for testing the compressive strength. Five groups of 10 specimens were prepared using pressures of 0.06, 0.44, 1.68, 3.22 or 4.46 MPa. Data were subjected to one-way anova. The microstructure was analysed using a scanning electron microscope (SEM) after sectioning specimens with a scalpel. RESULT: A trend was observed for higher condensation pressures to produce lower surface hardness values. A condensation pressure of 8.88 MPa produced specimens with significantly lower values in terms of surface hardness than other groups (P<0.001). A condensation pressure of 1.68 MPa conferred the maximum compressive strength; however, it was not statistically different. Higher condensation pressures resulted in fewer voids and microchannels when analysed with SEM. In specimens prepared with lower condensation pressures distinctive crystalline structures were observed. They tended to appear around microchannels. CONCLUSION: Condensation pressure may affect the strength and hardness of MTA. Use of controlled condensation pressure in sample preparation for future studies is suggested.