ABSTRACT
Purpose: This study investigated the effect of three types of cement materials on the retention of cast post and core and examined the effect of core preparation on the retention of cemented posts
Materials and Methods: Sixty extracted teeth were subjected to root canal therapy instrumentation and were left unobturated. Post spaces were prepared by Peeso reamers followed by no. 6 parallel-sided Parapost twist drill to a depth of 10 mm. Post and core patterns were fabricated, sprued, invested and cast. The specimens were divided into 3 groups of 20 each. The posts were cemented with zinc-phosphate [Cement Type I], glass-ionomer [Ketac-Cem] or composite resin cements [C and B cement]. The specimens were stored in water at 37°C for 24 hours. The specimens were further divided into two subgroups of 10 each used for the prepared and unprepared cores respectively. The core preparation carried out by using a diamond instrument. The post retention was tested using a universal testing machine. A 2-way ANOVA and the Tukey's multiple range test were used to determine the mean differences.
Results: The mean forces required to remove posts from unprepared groups were 482 +/- 102 N for zinc-phosphate, 283 +/- 88 N for glass-ionomer and 442±98 N for composite resin. The zinc-phosphate and composite resin cements specimens exhibited significantly greater retention forces compared to the glass-ionomer cement specimens [P 0=003]. The core preparation only significantly influenced the retention forces for the glass-ionomer cement [P=0.038].
Conclusions: Retention forces of Cement Type I and C and B composite resin cements were significantly greater than those of Ketac-Cem cement after 24 hours of cementation. High-speed preparation 24 hours after cementation had a significant negative effect on the retentive strengfhs of cast posts cemented with Ketac-Cem, but not posts cemented with Cement Type I or C and B cements
ABSTRACT
Purpose: The techniques used to enhance the titanium-ceramic bonding can be factors that may affect the color of dental porcelain. The purpose of this study was to investigate the effects of bonding agents, sandblasting, and hydrochloric acid on the final shade of low-fusing porcelain bonded to commercially pure cast titanium
Materials and Methods: Sixty specimens of commercially pure titanium were equally divided into 6 groups. The first group received no surface treatment and served as control, the second group was subjected to sandblasting, and the third one was treated with hydrochloric acid. The remaining 3 groups were treated similarly but with application of a bonding agent. Low-fusing porcelain [Nor-itake] was fired onto the surface of the titanium specimens. The CIE Lab color parameters of the specimens were measured with spectrophotometer
Results: The color difference [AE] between the control group and the other groups was in the range of 1.12 to 2.24 units. There were no significant differences among the AE for all the groups. Furthermore, there were no significant differences for the L and a color parameters among different surface treatments. However, the significant difference was found between the b color parameter
Conclusions: The bonding agents and the surface treatment using sandblasting or hydrochloric acid have minimal effects on the final shade of low fusing porcelain-commercially pure titanium system
ABSTRACT
Purpose: Titanium metal's affinity for gaseous element such as oxygen may affect the titanium-ceramic bonding. The purpose of this study was to evaluate the bonding potential between a low fusing porcelain and commercially pure titanium and titanium alloy, and to compare the bond strength with those of two conventional metal-ceramic systems
Materials and Methods: Forty specimens were fabricated, 10 specimens for each group. Titanium casting unit was used to cast the commercially pure titanium and titanium alloy [T1-6A1-4V] specimens and Noritake low fusing porcelain was applied to them. The gold-based and the Ni-Cr alloys were melted and cast with an automatic centrifugal casting machine and Vita VMK 95 conventional porcelain material was applied to them. A universal testing machine was used to perform the . 3-poinl bending test. The metal-ceramic interfaces were subjected to scanning electron microscopic examination
Results: The mean bond strength values obtained with the four different metals were 33.12 +/- 6.16 MPa for the commercially pure titanium, 14.01 +/- 5.63 MPa for the titanium alloy, 44.73 +/- 5.63 MPa for the gold-based alloy and 40.76 +/- 7.62 MPa for the Ni-Cr alloy. The gold-based alloy exhibited significantly greater bond strengths compared to the commercially pure titanium [P<.001]. Furthermore, the commercially pure titanium group showed significantly greater bond strength than the titanium alloy group [P<.0001]. There was no significant difference in the bond strength between the gold-based and the Ni-Cr groups [P=.503]
Conclusions: The bond strength of the conventional metal-ceramic combination was significantly greater than the bond strengths of the cast commercially pure titanium-Noritake ceramic combinations. Noritake porcelain showed significantly higher bonding strength to commercially pure titanium than to titanium alloy
ABSTRACT
A total of 439 Saudi patients were examined to determine if there is a correlation between the width of the maxillary anterior teeth and four anatomical facial references [the bizygomatic width, interpupillary distance, intraalar width and the width of the mouth]. All measurements done by using a modified Boley gauge, except the bizygomatic which was done by using a face bow. No correlation was found between the measurements for the population as whole, nor when the population was divided accordingly to sex