Influence of paper mixing pads thickness on the compressive strength of glass ionomer cement / 北京大学学报(医学版)

OBJECTIVE@#To explore the influence of the thickness of mixed cardboard on the compressive strength of glass ionomer cement and the associated factors.@*METHODS@#Three different types of glass ionomer cements were mixed on the top of 60, 40, 20 and 1 pieces of paper (P60, P40, P20 and P1), respectively. The compressive strength of the materials was tested after solidification, and the bubble rate was calculated with the assistance of scanning electron microscope.@*RESULTS@#(1) Compressive strength: ① ChemFil Superior glass ionomer (CF): The average compressive strength of P1 group was the highest, which was significantly different from that of P40 and P60 groups (P values were 0.041 and 0.032 respectively); ② To Fuji IX GP glass ionomer (IX): The average compressive strength of P1 group was the highest, which was statistically different from that of P40 and P60 groups (P values were 0.042 and 0.038 respectively); ③ Glaslonomer FX-Ⅱ glass ionomer cement (FX): The average compressive strength of P1 group was the highest, which was statistically different from that of P20, P40 and P60 groups (P values were 0.031, 0.040 and 0.041 respectively), but there was no statistical difference among the other groups. All the three materials showed that the compressive strength of glass ions gradually increased with the decrease of the thickness of the blended paperboard, and the two materials had a highly linear negative correlation, the correlation coefficients of which were CF-0.927, IX-0.989, FX-0.892, respectively. (2) Scanning electron microscope: P1 group had the least bubbles among the three materials.@*CONCLUSION@#It indicates that the thickness of mixed cardboard has a negative correlation with the compressive strength of glass ions. The thicker the mixed cardboard is, the greater the elasticity is. Excessive elasticity will accelerate the mixing speed when the grinding glass ions. Studies have shown that the faster the speed of artificial mixing is, the more bubbles is produced.The thicker ther mixed cardboard is, the more bubblesn are generated by glass ionomer cement, and the higher the compressive strength is. Using one piece of paper board to mix glass ionomer cement has the least bubbles and can obtain higher compressive strength.

Influence of different mixing pads on physical and mechanical properties of glass ionomer cement / 北京大学学报(医学版)

OBJECTIVE@#To analyze the influence of different mixing pads on the physical and mechanical properties of glass ionomer cement.@*METHODS@#Three different glass ionomer base cements were mixed with a plastic spatula on three different mixing pads including paper pad, glass pad and silicon pad whose HS were 40, 60 and 80. The GIC was packed into stainless steel molds to get specimens. Surface roughness, surface hardness and compressive strength were evaluated.@*RESULTS@#As for compressive strength, CF: There was the highest mean compressive strength that was significantly higher than those of silicon pad 60 group, paper 60 group and paper 20 group in silicon pad 40 group, the differences P values were 0.002, 0.027, and 0.036, statistically significant difference between the above groups (P<0.05). IX: there was the highest mean compressive strength that was significantly higher than those of silicon pad 60 group in paper pad 20 group,the differences P value was 0.008, statistically significant (P<0.05). FX: there was the highest mean compressive strength that was no significantly higher than those of paper pad 20 group in silicon pad 40 group, but was significantly higher than those of the other groups. As for surface hardness, CF: there was the highest mean surface hardness that was significantly higher than those of silicon pad 60 and 80 group, paper 60 group in silicon pad 40 group, the differences P value was 0.021, 0.001, 0.032, 0.008 and 0.016, statistically significant difference between the above groups (P<0.05). IX and FX: there was no statistical significance between any two groups in surface hardness. As for surface roughness, CF: there was no statistical significance between any two groups in surface roughness. IX: there was the lowest mean surface roughness that was significantly lower than those of paper pad 40 and 60 group in glass pad group, the differences P values were 0.003 and 0.027, statistically significant difference between the above groups (P<0.05). FX: there was the lowest mean surface roughness that was significantly lower than those of paper pad 60 group in glass pad group, the differences P value was 0.018, showing a statistical difference (P<0.05).@*CONCLUSION@#Mixing glass ionomer cement on silicon pad 40 results in higher compressive strength and lower surface roughness, worthy of clinical popularization.

Comparative study of resosolv and chloroform in retreatment of canal obturated with resinifying agent / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the possibility for removal of resinifying agent, time required for removal and the working length loss by Resosolv or Chloroform.</p><p><b>METHODS</b>40 human teeth (80 root canals) obturated with FR phenolaldehyde agent were divided into four groups, 20 root canals per group. Group A: Resosolv with K file; group B: chloroform with K file; group C: Resosolv with Ultrasonic K file; group D: Chloroform with ultrasonic K file. Calculating the pereentage for removal of resinifying agent, time required for removal and the working length loss.</p><p><b>RESULTS</b>The effectiveness of Resosolv for removing resinifying agent was better than chloroform. 87.5% of canals could be negotiated by Resosolv; 45% of canals be negotiated by chloroform.</p><p><b>CONCLUSION</b>Resosolv is an effective solvent for canals obturated with resinifying agent.</p>

Location and negotiation of second mesiobuccal canals in maxillary molars / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate prevalence, location, negotiation and the effect of operating microscope (OM) in the treatment of the second mesiobuccal canal (MB2) in maxillary molars.</p><p><b>METHODS</b>113 maxillary molars were studied. The crowns of the teeth were removed 1 mm above the chamber bottom for searching MB2 canal. Initially location and negotiation of MB2 canal were attempted without OM. Teeth in which MB2 canal were not located or negotiated were further explored under OM. Canal orifices including MB orifice, MB2 orifice and palatal orifice were filled by red gutta-percha cones, then the teeth were scanned by scanner. The images were analyzed by Image-Proplus 4.0 software to measure the relationship between MB2 canal and other canals.</p><p><b>RESULTS</b>The MB-MB2 distance is (1.47 +/- 0.54) mm, MB-P distance is (5.77 +/- 0.66) mm, the vertical distance from MB2 to MB-P line is (0.53 +/- 0.28) mm, the angle between MB-P line and MB-MB2 line is 23.07 degrees +/- 13.08 degrees. MB2 orifices were located in 70 teeth (61.9%) and negotiated in 53 teeth (46.9%) without OM. With OM, additional MB2 orifices were located in other 6 teeth, 4 were negotiated; and 2 were negotiated in which MB2 canal were not negotiated without OM.</p><p><b>CONCLUSIONS</b>MB2 canal can be located in 67.3% and negotiated in 52.2% of maxillary molars. Ability to locate and negotiate MB2 canal is facilitated by OM. The MB2 canal was located less than 1 mm mesially to the MB-P line and 2 mm palatally from the MB orifice.</p>