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At least 127 records · Page 7Linked to original sources
PubMed2001

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.

Acrylic Resins↗
PubMed2000

Retention of a core material supported by three post head designs.

STATEMENT OF PROBLEM: There are few studies on the retention of core build-up materials to prefabricated post head designs, especially for a new ceramic post design. PURPOSE: This in vitro study compared the retention of 2 types of core build-up materials (Ti-Core titanium-reinforced composite and a GC Miracle Mix silver-reinforced glass ionomer) supported by 3 post head designs (Flexi-Post, AccessPost, and Cerapost dowel). For all test groups, heads of the posts were placed into the core material at a 90-degree angle to the surface. Test specimens (unloaded) were then placed into a special jig and retention test was performed using an 810 MTS testing machine. MATERIAL AND METHODS: This study consisted of 6 groups with 10 specimens per group. A 3 x 2 factorial design was used to test for statistical significance and results were considered significant when P <.05. RESULTS: Results of the retention test were as follows: group 1, Flexi-Post/Ti-Core 220.0 lb (982.1 N), group 2, AccessPost/Ti-Core 212.7 lb (949.6 N), group 3, Cerapost/Ti-Core 41. 8 lb (186.6 N), group 4, Flexi-Post/Miracle Mix 43.4 lb (193.8 N), group 5, AccessPost/Miracle Mix 61.6 lb (275 N), and group 6, Cerapost/Miracle Mix 7.5 lb (33.5 N). Results of the ANOVA revealed a highly significant difference between posts and cores (P <.0001). CONCLUSION: Post head designs of the stainless steel AccessPost and Flexi-Post dowels offers greater retention then the smooth ceramic head design of the Cerapost dowel. In addition, the composite core material (Ti-Core) offers greater retentive strength values than the glass ionomer material (Miracle Mix).

Analysis of Variance↗
PubMed1999

Fatigue testing and microscopic evaluation of post and core restorations under artificial crowns.

STATEMENT OF PROBLEM: Coronoradicular reconstruction techniques of pulpless teeth include prefabricated post systems that retain a core material such as silver amalgam, composite, glass ionomer, or modified glass ionomer cement. Mechanical properties of these materials are critical to sustain masticatory forces. PURPOSE: This in vitro study compared the mechanical resistance of 3 core materials (silver amalgam, composite, and silver-reinforced glass ionomer) under masticatory conditions. MATERIAL AND METHODS: Industrially fabricated teeth were used and a total of 75 specimens were divided into 3 groups of 25 specimens. Titanium canal posts were placed, followed by core buildups in amalgam, composite, or glass ionomer. Teeth were prepared for full cast crowns and the crowns were fabricated and cemented with glass ionomer cement. Twenty specimens from each group were placed in a mastication simulator cyclically loading the teeth with a 400 N force for 1.5 million cycles. The 5 remaining specimens were used as controls. Teeth were sectioned and observed macroscopically and microscopically to determine the rate of defects for each material. Observed defects were verified with the Kruskal-Wallis test. The 3 core materials were ranked with the Tukey multiple comparison test. RESULTS: Significant differences of mechanical behavior were found for the 3 materials. At P <.01, silver amalgam was significantly superior to composite and glass ionomer. Composite was significantly superior to glass ionomer. CONCLUSION: Cores fabricated with amalgam had the lowest rate of defects when tested under artificial crowns. Glass ionomer, when used as a core material under artificial crowns, showed the highest rate of defects after an instantaneous load of 400 N for a 1,500,000 repetition cycle.

Biomechanical Phenomena↗
PubMed1986

A cast core system with interlocking posts.

Endodontically treated multirooted posterior teeth can be predictably and conservatively restored by using a combination of cast cores and multiple narrow-diameter, parallel serrated stainless steel posts.

Crowns↗
PubMed1982

Casting and microstructure of post and core at different mold temperatures.

In the present investigation the microstructure and bonding between the wrought and cast elements of the post and core specimens were evaluated with respect to the preheating temperature of the investment. Clinically sized specimens were produced from one type III gold casting alloy in combination with two different wrought wire precious alloys. Preheating temperatures of 500 degrees, 600 degrees, 700 degrees, 800 degrees and 900 degrees C were employed. Microscopic evaluation of polished and etched transverse and longitudinal sections of the specimens indicated that recrystallization of the wrought wire was initiated at 700 degrees C for one type of specimen. The best reproduction of the wax pattern was obtained at 800 degrees C for post and core combinations. The union between the wrought and cast elements was, regardless of wire type, better in the core portion than in the post. The best union between cast and wrought structures was obtained with a non-oxidizing wire at 700 degrees C.

Chemical Phenomena↗
PubMed1997

The effect of eugenol-containing temporary cement on the bond strength of two resin composite core materials to dentin.

PURPOSE: This study investigated the effect of eugenol-containing temporary cement on the bond strength of two resin composite core materials (FluoroCore and Ti-Core) to dentin. MATERIALS AND METHODS: Dentin was exposed in three groups of extracted teeth (20 specimens each). In group one, dentin was covered with eugenol-containing temporary cement; the second group was covered with eugenol-free temporary cement; and the third group was left uncovered and served as a control group. All specimens were stored for 1 week at 37 degrees C and 100% humidity. The dentin surfaces were cleaned and treated using the GLUMA adhesive system, followed by placement of composite core build-ups. Debonding of the core material was accomplished using the Accuforce Elite test system. RESULTS: There was a significant reduction in bond strength for the specimens covered with eugenol temporary cement (p < .0001), but no significant difference was found between the control group and the group treated with eugenol-free temporary cement. Bond strength of the Ti-Core material to dentin was significantly higher than that of FluoroCore (p < .0001). CONCLUSION: Pretreatment of the dentin with eugenol-based temporary cement adversely affects the bond strength of resin composite core material to dentin.

Analysis of Variance↗
PubMed1983

An investigation of the process of casting cores on to preformed wrought dental posts.

The casting of gold on to wrought "Wiptam" and "G.T." posts has been investigated. Notching of "Wiptam" posts gave rise to grain structure rearrangement; carbon deposits from the wax burn were retained in the notches and prevented complete filling by the gold. Serious cracks developed from these notches when the core was cast on centrifugally but only slightly when Solbrig's method was used. These cracks explain why "Wiptam" posts occasionally fracture. The above problems were not encountered with the "G.T." post, which has inbuilt retention channels, and allows a more complete burn out of the wax pattern.

Crowns↗
PubMed2006

Fracture strength of teeth restored with all-ceramic posts and cores.

OBJECTIVE: The purpose of this in vitro investigation was to evaluate the fracture strength of endodontically treated teeth restored with different all-ceramic posts and cores. METHOD AND MATERIALS: Seventy-two endodontically treated human maxillary central incisors were divided into 3 groups with 24 teeth each and restored with 1 of the following methods: prefabricated zirconia ceramic posts and resin composite buildups; zirconia ceramic posts and copy-milled alumina ceramic cores (2-piece technique), or copy-milled all-ceramic posts and cores made from a zirconia-reinforced glass-infiltrated alumina ceramic (1-piece technique). Each group was divided into 3 subgroups of 8 samples each, consisting of teeth that did not receive crown restorations and were stored for 60 days, teeth restored with all-ceramic crowns and stored for 60 days, and teeth restored with all-ceramic crowns and subjected to 1.2 million loading cycles with 30 N in a chewing simulator. RESULTS: The mean fracture strengths ranged from 205 to 522 N. Prefabricated zirconia posts and resin composite buildups showed a statistically significantly lower fracture strength after chewing simulation than teeth restored with prefabricated zirconia posts and alumina ceramic cores. CONCLUSION: All-ceramic posts and cores made with the 2-piece technique showed promising fracture strengths under the tested conditions.

Acrylic Resins↗
PubMed1998

Leakage associated with load fatigue-induced preliminary failure of full crowns placed over three different post and core systems.

Thirty-six maxillary central incisors were endodontically treated and restored with a post and core and cast crown. Three different post and core systems were evaluated. Restored teeth were fatigue-loaded until preliminary failure of the casting occurred as detected by a strain gauge bonded across the lingual margin of the cast crown. After preliminary failure, fatigue loading was continued for 100,000 load cycles with the crown margin exposed to basic fuschin dye. Teeth were then immersed in dye for 24 h, sectioned, and evaluated for leakage. There was no significant difference in the number of load cycles required to cause preliminary failure among the three post and core systems. Leakage occurred in all three groups, with no significant difference between groups. The occurrence of preliminary failure is clinically undetectable, yet it allows leakage between the restoration and tooth that may extend down the prepared post space.

Crowns↗
PubMed2000

In vitro comparison of fluoride release of six direct core materials.

STATEMENT OF PROBLEM: Fluoride has been shown to deter caries and has been incorporated into core build-up materials. However, there is considerable variation in the formulation and release of fluoride from core build-up materials. PURPOSE: This in vitro study compared the fluoride released by 6 commercially available fluoride-releasing core materials over time. METHODS AND MATERIAL: Ten specimen disks (9 for Corestore) of each of the 6 core materials were fabricated, finished, measured, and immersed in deionized water in individual polystyrene jars. The jars were stored in a humidor at 37 degrees C between test periods. At the same time each day for 7 consecutive days, then at days 14, 22, 28, 59, and 89, the fluoride release was measured from each specimen disk in parts per million by testing the storage medium. The data were analyzed using 1-way ANOVA and Tukey-Kramer multiple comparison tests (P <.05). RESULTS: Five of the 6 core build-up materials tested showed an initial high concentration of fluoride release during the first day and gradually tapered over the study period. Fuji II LC consistently released more fluoride than any other material throughout the 89-day testing period. CONCLUSION: Fuji II LC released the most fluoride and was significantly different from the other materials tested. The maximum amount of fluoride was released by 5 of the 6 materials during the first 24 hours and gradually tapered over the 89-day testing period.

Analysis of Variance↗
PubMed1985

Indirect post and core fabrication using a die-investment stone.

A technique has been presented for indirect fabrication of a cast post and core with the refractory material DVP. This method eliminates the need for developing full contoured patterns and their removal from the working cast for investment. Less time is required and the accuracy of the castings is improved.

Calcium Sulfate↗