Direct core buildup using a preformed crown and prefabricated zirconium oxide post

Scientific mapping of hotspots and trends of post and core research based on the Web of Science: A bibliometric analysis

Statement of problem

Post and core (PC) restoration has been widely used to restore endodontically treated teeth. Nevertheless, bibliometric studies focusing on PC research are lacking.

Purpose

The purpose of this bibliometric analysis was to review the general situation and determine the research direction of PC restoration by means of visualization, including the time development, countries, institutions, authors, journals, research categories, and the information of references with the strongest citation burst.

Material and methods

The search was carried out within the topic field of the Web of Science (WoS) database. CiteSpace, VOSviewer, and R language were used to analyze the literature. Bibliometric indicators in terms of title, keyword, reference, publication time, institution, country and citation information were analyzed.

Results

Between 1966 and 2022, dental research on PC trended upward, especially in 2011 and up to 2022. Scholars in Brazil, the United States, and Italy actively participated in PC research. The country that published the most was Brazil. Italy both ranked first in the H-index and average citations per item and had cooperative relations with several countries. The United States ranked first in the world in total citation count. The University of Siena published the most articles. The Journal of Prosthetic Dentistry (JPD) was the major contributing journal. The top three authors in this field were Ferrari M, Goracci C and Naumann M. The largest cooperative network of authors consisted of four Italian scholars. There were six main clusters of research topics on PC through CiteSpace co-citations. In addition, CiteSpace co-citations, CiteSpace Burst detection and VOSviewer keyword analysis showed the most important research interests, such as bond strength, fiber post, fracture resistance, and finite element analysis. Photodynamic therapy is the latest research hotspot. Finally, there were the top 25 references with the strongest citation bursts, which mainly focused on four aspects, namely, studies related to fiber posts, PC bonding strength, finite element analysis, and residual teeth and the ferrule effect.

Conclusions

This bibliometric analysis provides a comprehensive overview of PC research, including the research time, country, institution, author, journal, article clustering, article keywords, and important literature analysis, so that researchers can have a clear understanding of the research situation in this field.

Stress Distribution of Post–Core Applications in Maxillary Central Incisors

The purpose of this study was to evaluate the stress distribution in a maxillary central incisor restored with various post–core applications.

The study used a three-dimensional finite element method. The tooth was assumed to be endodontically treated with a porcelain crown. Two different sizes of Flexi-post, Cera-post, and Composipost were compared for 200 N palatal and incisal loads.

It was determined that, purely from the point of view of strength considerations, core material was determined to be of greater importance than post material or size. Higher elastic moduli of the posts resulted in lower stresses throughout the tooth.

Fracture resistance of structurally compromised and normal endodontically treated teeth restored with different post systems: An in vitro study

BACKGROUND

With the aim of developing methods that could increase the fracture resistance of structurally compromised endodontically treated teeth, this study was conducted to compare the effect of three esthetic post systems on the fracture resistance and failure modes of structurally compromised and normal roots.

MATERIALS AND METHODS

Forty five extracted and endodontically treated maxillary central teeth were assigned to 5 experimental groups (n=9). In two groups, the post spaces were prepared with the corresponding drills of the post systems to be restored with double taper light posts (DT.Light-Post) (group DT.N) and zirconia posts (Cosmopost) (group Zr.N). In other 3 groups thin wall canals were simulated to be restored with Double taper Light posts (DT.W), double taper Light posts and Ribbond fibers (DT+R.W) and Zirconia posts (Zr.W). After access cavity restoration and thermocycling, compressive load was applied and the fracture strength values and failure modes were evaluated. Data were analyzed using two-way ANOVA, Tukey and Fisher exact tests (P<0.05).

RESULTS

The mean failure loads (N) were 678.56, 638.22, 732.44, 603.44 and 573.67 for groups DT.N, Zr.N, DT.W, DT+R.W and Zr.w respectively. Group DT+R.W exhibited significantly higher resistance to fracture compared to groups Zr.N, DT.W and Zr.w (P<0.05). A significant difference was detected between groups DT.N and Zr.W (P=0.027). Zirconia posts showed significantly higher root fracture compared to fiber posts (P=0.004).

CONCLUSION

The structurally compromised teeth restored with double taper light posts and Ribbond fibers showed the most fracture resistance and their strengths were comparable to those of normal roots restored with double taper light posts. More desirable fracture patterns were observed in teeth restored with fiber posts.

Shear bond strength of four resin cements used to lute ceramic core material to human dentin

PURPOSE

This study evaluated the effect of four resin cements on the shear bond strength of a ceramic core material to dentin.

MATERIALS AND METHODS

One hundred twenty molar teeth were embedded in a self-curing acrylic resin. The occlusal third of the crowns were sectioned under water cooling. All specimens were randomly divided into four groups of 30 teeth each according to the resin cement used. One hundred twenty cylindrical-shaped, 2.7-mm wide, 3-mm high ceramic core materials were heat-pressed. The core cylinders were then luted with one of the four resin systems to dentin (Super-Bond C&B, Chemiace II, Variolink II, and Panavia F). Half of the specimens (n = 15) were tested after 24 hours; the other half (n = 15) were stored in distilled water at 37 degrees C for 1 day and then thermocycled 1000 times between 5 degrees C and 55 degrees C prior to testing. Shear bond strength of each specimen was measured using a universal testing machine at a crosshead speed of 1 mm/min. The bond strength values were calculated in MPa, and the results were statistically analyzed using a two-way analysis of variance (ANOVA) and Tukey HSD tests.

RESULTS

The shear bond strength varied significantly depending on the resin cement used (p < 0.05). The differences in the bond strengths after thermocycling were not remarkable as compared with the corresponding prethermal cycling groups (p > 0.05). Significant interactions were present between resin cement and thermocycling (p < 0.05). After 24 hours, the specimens luted with Variolink II (5.3 +/- 2.2 MPa) showed the highest shear bond strength, whereas the specimens luted with Chemiace II (1.6 +/- 0.4 MPa) showed the lowest. After thermocycling, the bond strength values of specimens luted with Chemiace II (1.1 +/- 0.1 MPa) and Super-Bond C&B (1.7 +/- 0.4 MPa) decreased; however, this was not statistically significant (p > 0.05). The increase in the shear bond strength values in the Panavia F (4.5 +/- 0.7 MPa) and Variolink II (5.5 +/- 2.1 MPa) groups after thermocycling was also not statistically significant (p > 0.05).

CONCLUSION

Variolink II and Panavia F systems showed higher shear bond strength values than Chemiace II and Super-Bond C&B. They can be recommended for luting ceramic cores to dentin surfaces.

Structural resistance in immature teeth using root reinforcements in vitro

The purpose of this study was to evaluate in vitro the efficacy of root reinforcements by light-cured composite resin or zirconium fiber post in simulated immature non-vital teeth. Fifty-six bovine incisors teeth were used for this study. The crown of each tooth was removed in the medium third to obtain a standard length of 30 mm. The specimens were divided into four groups (n = 14): G1) the root canals were instrumented and enlarged to simulate immature non-vital teeth and were reinforced with a light-cured composite resin using a translucent curing post (Luminex system); (G2) the specimens were instrumented, enlarged and they received root reinforcement with zirconium fiber post; G3 (positive control): they received similar treatment to the G1 and G2 groups, but did not receive root reinforcement; G4 (negative control): the roots were not weakened and did not receive reinforcement. Every tooth was submitted to compressive force using an Instron testing machine with an angle of 45 degrees at a speed of 1 mm min(-1) until the fracture. The results showed a markedly increased resistance to fracture in the G1 and G2 (122.38 and 122.08 kg f, respectively). Among the results of G1 and G2 there was not any significant difference (P > 0.05) but they were significantly different from the control groups (P < 0.05). The conclusion is that the use of root reinforcements with zirconium fiber post or composite resin can increase significantly the structural resistance of the weakened teeth, decreasing the risk of the fracture.

Esthetic enhancement of ceramic crowns with zirconia dowels and cores: a clinical report

There has been an increase in the use of esthetic metal-free ceramic crowns in restoring endodontically treated teeth or teeth with severe coronal destruction. Tooth-colored dowels and cores are used to enhance the esthetic result. This report describes the treatment of a patient with bilateral maxillary supernumerary lateral incisors, a severe malocclusion, and maxillary anterior tooth discoloration. Treatment included heat-pressed, metal-free ceramic crowns supported by zirconia ceramic dowel-and-core foundations.

Restoration of endodontically treated teeth

Endodontically treated teeth have lost substantial tooth structure as a result of previous restorations, dental caries, and the access preparation for the endodontic therapy. The topic of restoring these teeth is complex and controversial, and their long-term prognosis is directly connected to the quality of the final restoration. This article describes contemporary knowledge of the biomechanical principles related to the restoration of pulpless teeth and provides a critical review of currently available materials and methods.

Fracture strength after dynamic loading of endodontically treated teeth restored with different post-and-core systems

STATEMENT OF PROBLEM

Prefabricated metal and ceramic posts can be used with direct or indirect cores as an alternative to the conventional cast post and core. It is unclear how the fracture strength of zirconia posts with composite or ceramic cores and titanium posts with composite cores compares to the fracture strength of gold posts and cores after dynamic loading.

PURPOSE

This study compared the fracture strength of endodontically treated, crowned maxillary incisors with limited ferrule length and different post-and-core systems after fatigue loading.

MATERIAL AND METHODS

Sixty-four caries-free, human maxillary central incisors were divided into 4 groups. After root canal treatment, Group 1 was restored with titanium posts and composite cores, Group 2 with zirconia posts and composite cores, and Group 3 with zirconia posts and heat-pressed ceramic cores. Teeth restored with cast-on gold posts and cores served as the controls (Group 4). Teeth were prepared with a circumferential shoulder including a 1 to 2 mm ferrule; all posts were cemented with an adhesive resin cement, restored with complete-coverage crowns, and exposed to 1.2 million load cycles (30 N) in a computer-controlled chewing simulator. Simultaneous thermocycling between 5 degrees C and 55 degrees C was applied for 60 seconds with an intermediate pause of 12 seconds. All specimens that did not fracture during dynamic loading were loaded until fracture in a universal testing machine at a crosshead speed of 1.5 mm/min; loads were applied at an angle of 130 degrees at the incisal edge. Fracture loads (N) and modes (repairable or catastrophic) were recorded. The Kruskal-Wallis test was used to compare fracture loads among the 4 test groups. Analyses were conducted both with and without the specimens that failed during the chewing simulation. A Fisher exact test was performed to detect group differences in fracture modes. A significance level of P<.05 was used for all comparisons.

RESULTS

The following survival rates were recorded after the chewing simulation: 93.8% (Group 1), 93.8% (Group 2), 100% (Group 3), and 87.5% (Group 4). The median fracture strengths for Groups 1 to 4 were 450 N, 503 N, 521 N, and 408 N, respectively. No significant differences were detected among the groups. The use of zirconia posts resulted in a nonsignificant lower number of catastrophic root fractures.

CONCLUSION

Within the limitations of this study, the results suggest that zirconia posts with ceramic cores can be recommended as an alternative to cast posts and cores. If a chairside procedure is preferred, zirconia or titanium posts with composite cores can be used. Clinical trials are required to verify these in vitro results.

Foundation restorations in fixed prosthodontics: current knowledge and future needs

PURPOSE

The Ad Hoc Committee on Research in Fixed Prosthodontics established by the Academy of Fixed Prosthodontics publishes a yearly comprehensive literature review on a selected topic. The subject for this year is foundation restorations.

METHODS

Literature of various in vitro and in vivo investigations that included technical and clinical articles was reviewed to provide clinical guidelines for the dentist when selecting methods and materials for restoration of structurally compromised teeth. Topics discussed and critically reviewed include: (1) desirable features of foundation restorations, (2) foundations for pulpless teeth, (3) historic perspectives, (4) cast posts and cores, (5) role of the ferrule effect, (6) prefabricated posts, (7) direct cores, (8) foundation restorations for severely compromised teeth, (9) problems and limitations, (10) future needs, and (11) directions for future research.

CONCLUSION

This comprehensive review brings together literature from a variety of in vitro and in vivo studies, along with technique articles and clinical reports to provide meaningful guidelines for the dentist when selecting methods and materials for the restoration of structurally compromised teeth.