Retention of cast posts cemented with zinc phosphate cement using different cementing techniques.

PURPOSE: This study compares the effect of different cementation techniques on the retention of cast posts and cores. MATERIALS AND METHODS: Twenty-four extracted single rooted human teeth were used in this study. After routine preparation of the root canals, the canal space was enlarged with reamers. Direct post patterns were made with acrylic resin. Castings were fabricated using Ni-Cr-Mb alloy. Zinc phosphate cement was used as a luting agent using 4 different methods of cement introduction to the root canal space. This created 4 treatment groups consisting of 6 teeth in each group. In Group A, the cement was applied over the posts only. For the specimens in Group B, the cement was introduced into the root canals with a spiral filler and applied over the posts. In Group C, cement was injected into the root canals and then applied over the posts. Finally, for the specimens in Group D, cement was injected into the root canals and a spiral was used to spread it into the root canals, and cement was also applied over the posts. After cementation, teeth were stored in saline solution. The tensile retentive force of cast posts was evaluated using the Instron testing machine (Instron, Canton, MA). RESULTS: The retention obtained by the 4 techniques differed significantly (p <.05). The highest tensile force to post dislodgment was observed in Group D, and the least was in Group A. Analysis of variance test revealed a highly significant difference between groups (p <.0001). According to the Fisher exact test, there was a significant increase in retention from Group A to Group D (p <.05). CONCLUSIONS: Under the conditions of this study, the injection of cement into a root canal space followed by the use of a spiral resulted in the highest level of post retention. Retention was reduced when cement was placed using a Lentulo spiral alone (Kerr/Sybron Corp, Romulus, MI), a Jiffy tube (Teledyne Water Pik, Allegheny Teledyne Co, Fort Collins, CO) alone, or by application to the post only. J Prosthodont 2001;10:37-41.

Dental fluorosis in 12-15-year-old rural children exposed to fluorides from well drinking water in the Hail region of Saudi Arabia.

To investigate the relationship between fluoride levels in well drinking water, severity of dental fluorosis and dental caries in the Hail region of Saudi Arabia, 2355 rural children aged 12-15 years were examined. Over 90% of the children had fluorosed teeth and chi-square tests showed a strong association (P < 0.001) between fluoride level (0.5-2.8 ppm) in well drinking water and severity of dental fluorosis. Although regression analysis showed a statistically significant relationship (P < 0.001) between fluoride concentration and caries experience, the amount of variation explained was very low (R2 = 0.9%). Since fluoride in well water had little influence on caries experience and is causing dental fluorosis, it should be removed by defluoridation or the rural population should be provided with an alternative source of drinking water with lower fluoride concentration.

Rapid mixing of zinc phosphate cement for fixed prosthodontic procedures.

This study was done to determine the efficacy of rapidly mixing zinc phosphate cement in conjunction with fixed prosthodontic procedures. Properties measured included rate of pH change and temperature increase, film thickness, and setting time. The rapid mix technique in conjunction with the frozen glass slab resulted in a faster elevation of the pH but slightly greater temperature rise and film thickness. As was expected, the rapid mixing procedure resulted in an increased working time but decreased setting. On the basis of this study, it appears that the rapid mixing technique in conjunction with a frozen glass slab is an acceptable technique for preparing zinc phosphate cement for fixed prosthodontic procedures.