Showing papers on "Post and core published in 2001"

In vitro comparison of the fracture resistance and failure mode of fiber, ceramic, and conventional post systems at various stages of restoration.

Abstract: Purpose This in vitro study evaluated 6 post systems over 4 simulated clinical stages of tooth restoration to (1) determine quantitatively the fracture resistance strength at each stage when a static loading force is applied to cause failure; (2) determine the failure mode for each post system at each simulated clinical stage; and (3) determine the feasibility of removing failed post systems. Materials and methods Ten post systems made with various materials and designs were tested at the following 4 stages of simulated clinical treatment: stage #1: posts only, loaded using a 3-point loading model to failure, to determine transverse strengths and failure modes for each post system; stage #2: posts alone, bonded into teeth; stage #3: posts bonded into teeth with core build up; stage #4: post and core build up and full veneer restoration. For stages #2 through #4, the coronal portion of 60 mandibular premolars was amputated at the cemento-enamel junction, the canals were treated endodontically, and the specimens were mounted in acrylic blocks. A testing force was applied to the posts at 90 degrees to the long axis of the tooth, 4 mm from the cemento-enamel junction. The O'Brien test for constant variance was performed over the treatment groups. For nonconstant variance, the Welsh analysis of variance was used to test for equalities of treatment means. The Tukey Kramer procedure determined which treatment procedures differed. Results The failure thresholds for each post system were significantly different at each stage of testing, but the order of test results by post type remained generally consistent from one stage to the next. ParaPosts (Coltene, Whaledent Int, New York, NY) and core build up resulted in significantly higher failure thresholds through all 4 stages of testing. This post system also consistently displayed a high number of nonfavorable tooth fractures. FibreKor post and cores (Jeneric Pentron Inc, Wallingford, CT) resulted in significantly lower failure threshold values in stages #2 through #4. This post system displayed no tooth fractures in stages #2 and #3 and a similar number of nonfavorable tooth fractures in stage #4 when compared with the other systems. C-Post (Bisco Dental Products, Schaumburg, IL), CosmoPost (Ivoclar Vivadent North America Inc, Amherst, NY), and AesthetiPost (Bisco Dental Products) grouped in descending order through stages #2 to #4. These systems displayed intermediate fracture resistance strengths, as well as a moderate number of nonfavorable tooth fractures. CosmoPost exhibited a significant number of brittle post fractures with fragments left in the root canal at all stages. The fracture resistance of the cast metal post varied from stage to stage. No teeth fractured at stage #2. At stage #3, 9 of 10 teeth fractured nonfavorably, and all teeth fractured nonfavorably in stage #4. Conclusions The fiber posts evaluated provided an advantage over a conventional post that showed a higher number of irretrievable post and unrestorable root fractures. At the stage of final restoration insertion, there was no difference in force to failure for all but the FibreKor material, which continued to be weaker than all other tested materials. The fiber posts were readily retrievable after failure, whereas the remaining post systems tested were nonretrievable. J Prosthodont 2001;10:26-36.

Survival rate and fracture strength of endodontically treated maxillary incisors with moderate defects restored with different post-and-core systems: an in vitro study.

Abstract: Purpose This study compares the survival rate and fracture strength of endodontically treated maxillary incisors with moderate coronal defects restored with different post-and-core systems after exposure to an artificial mouth. Materials and methods Sixty-four caries-free human maxillary central incisors were selected for standardized size and quality, endodontically treated, and decoronated 2 mm coronal to the cementoenamel junction. Group 1 was restored with titanium posts and composite cores, group 2 received zirconia posts and a composite core, and in group 3 zirconia posts with a heat-pressed ceramic core were used. Teeth restored with cast posts and cores served as controls. All teeth were prepared and restored with complete cast crowns. All samples were exposed to 1.2 million cycles in a computer-controlled chewing simulator with simultaneous thermocycling. In addition, the samples were loaded until fracture in a static testing device. Results The survival rates of the different groups were: 94% for titanium/composite, 63% for zirconia/composite, 100% for the all-ceramic post and core, and 94% for the cast post and core. The following mean fracture strengths were obtained: titanium/composite = 425 +/- 155 N, zirconia/composite = 202 +/- 212 N, zirconia/ceramic = 378 +/- 64 N, cast post and core = 426 +/- 178 N. The lower fracture load in the group with zirconia posts and composite cores was statistically significant. The use of zirconia posts resulted in fewer oblique root fractures. Conclusion Prefabricated titanium posts with composite cores, zirconia posts with heat-pressed ceramic cores, and cast posts and cores yield comparable survival rates and fracture strengths for the restoration of crowned maxillary incisors with moderate coronal defects. Survival rates and fracture strengths for zirconia posts with composite cores are significantly lower, so this combination cannot be recommended for clinical use.

Survival rate and fracture strength of incisors restored with different post and core systems after exposure in the artificial mouth.

Abstract: The survival rate and fracture resistance of 40 decapitated endodontically treated maxillary central incisors using four different post and core systems covered with all-ceramic copings was evaluated after exposure in the artificial mouth. Ten samples of the following post and core systems were investigated: high precious metal post (Permador) and core (Olympia) (A), zirconia post (Cerapost) with a pre-fabricated bonded ceramic core (Ceracap) (B), resin-ceramic post (experimental) with a pre-fabricated bonded ceramic core (Ceracap(R)) (C) and a zirconia post (Cerapost) with a custom made ceramic core (Cosmo Ingots) (D). The all-ceramic copings (Procera) were cemented using Panavia TC. The survival rates after 1 200 000 cycles in the artificial mouth are as follows: 90% (A), 80% (B), 60% (C) and 100% (D). The results of the means and standard deviations (s.d.) of the fracture resistance during static loading are: 1270 +/- 312.5 (A), 1494.5 +/- 333.5 (B), 1146.7 +/- 182.6 (C) and 463.3 +/- 46.2 (D). There are statistically significant differences between all groups with the exception of A and B, and A and C (Wilcoxon test). None of the zirconia posts with custom made ceramic cores covered with all-ceramic copings fractured during dynamic loading in the artificial mouth. The mean fracture strength during static loading was less favourable than that of groups A, B and C but above the clinical necessary level.

Anatomical post design meets quartz fiber technology: rationale and case report.

Abstract: Endodontically treated teeth frequently require a post and core to serve as a foundation for the coronal restoration Remaining tooth structure, physical properties of the post material, post shape, and cement type all contribute to the success of the restoration Post adaptation to the canal walls also represents an important element in the biomechanical performance of the prosthetic restoration A double taper post system made of quartz fiber and epoxy was developed to conform more precisely to the shape of endodontically treated canals Immediate benefits of this post system include minimal tooth structure removal during canal reshaping, greater post-to-canal adaptation in the apical and coronal half of the canal, and good post retention The use of a quartz fiber/epoxy material with a lower modulus of elasticity also reduces the incidence of root fracture Furthermore, the esthetic nature of the colors offered with this post system (translucent and off-white) provide a favorable foundation for eliminating discoloration caused by a metallic post placed under all-ceramic crown systems

Fabrication of a functionally graded dental composite resin post and core by laser lithography and finite element analysis of its stress relaxation effect on tooth root.

Abstract: Laser lithography was applied for Computer Aided Design and Computer Aided Manufacturing (CAD/CAM) fabrication of dental prostheses made of composite resin. First, the conditions to obtain the optimum resolution for photo-curing were determined, and then a composite resin full crown was fabricated by laser lithography. Second, a functionally graded composite resin post and core which had gradient elasticity in the post, was manufactured by the gradual change in the filler contents of the composite resin. Finally, stress analysis of the functionally graded post and core was performed by a two-dimensional finite element method. This demonstrated the effects of reducing the stress concentration around the apex of the post.

Fracture strength of different core build-up designs.

Abstract: Purpose To investigate the resistance to fracture of three crown and core combinations, made with different core build-up systems on human teeth, using a standardized test method. Materials and methods The anatomic crowns were removed from six groups (n = 8) of endodontically treated, human premolars in conformity with a brass master dye, using the Celay duplicating device. Three of these groups were provided with a core build-up with-out an endodontic post (Ti-Core, Photo-Core and Ketac-Molar); two other groups were provided with a core build-up with an endodontic post (a cast post and core, and a composite with a silica post), and one group was not provided with a core. All groups were then prepared in conformity with a master dye. This preparation ended in axial dentin, 2 mm apical from the core build-up. Thus in the sixth group (premolars without a core build-up), this preparation only affected the 2 mm axial dentin (ferrule), which resulted in a small retention area (2 mm axial dentine) for the crown. Finally, a standard crown was cemented and 24 hrs afterwards loaded until fracture in an Instron testing machine at an angle of 45 degrees. For comparison with the standardized procedures, a seventh group (Photo-core without post) was prepared manually, with dimensions similar to the standardized groups. Results Within the standardized test set-up no significant difference in strength between the 6 groups could be demonstrated. Only in the case of the hand-made Photo-Core and the cast core was the fracture load significantly different (P= 0.01). In addition, this hand-made group displayed a larger standard deviation than the standardized groups. Taking into consideration the fact that the maximum bite force in the bicuspid region is about 580 N, these tests showed that within the limitations of the standardized test set-up, where the samples had no history of fatiguing, a core build-up without a post is an alternative for the conventional cast core. In this study, the fabrication of the standardized samples proved to be accurate, fast and economical. This method also enables the evaluation of the performance of core and crown design combinations in relationship to the amount of remaining tooth structure by using different master dies and, moreover, to reduce the high standard deviation in this kind of research.

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

Abstract: 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.

The relationship of post design to the long-term success of endodontically restored teeth.

Abstract: Artificial cores replace missing tooth structure and contribute to the retention and stability of the subsequent restoration. The post is the anchoring mechanism for the core, which supports the final restoration. Stability of the post and core is the most important factor concerning the long-term success of the post-and-core restoration. The amount of insertional and functional stresses produced and distributed by a post are also associated with retention. An optimal way of maximizing retention, minimizing insertional stresses, and distributing functional stresses may be through the use of a multi-tiered parallel threaded split-shanked post.

[The preprosthetic preparation of the endodontically treated abutment tooth. Post and core technique: a questionnaire analysis].

Abstract: The goal of the questionnaire was to determine the materials and methods that general dentists in Switzerland at present use for the treatment of non-vital abutment teeth. Questionnaires were sent to 1000 dentists from a computer generated random sample of the list of members of the SSO (Swiss Dental Society). The return ratio was 36%. The responses provided information on the current philosophies and prevailing techniques used to restore endodontically treated abutment teeth. Most of the answering dentists believed it was necessary to stabilize a root treated tooth with a post. The preferred restoration in anterior teeth was the cast post and core, while composite resin build-up with a prefabricated post was predominantly made for posterior teeth. Conical or combined cylindrical-conical posts, which had a sand-blasted surface, were predominantly used. Most of the answering dentists strove to stabilize the remaining tooth structure by circular enclosure of the tooth structure by the later crown (ferrule effect). Zinc phosphate cement was still preferred for cementation of metal posts and ceramic posts were most often fixed with the help of the acid etching technique. The most frequently described failures were retention loss or root fractures.