All about Dowels - A Review Part I. Considerations before Cementation

An Evaluation of the Fracture Resistance of Endodontically Treated Teeth Restored With Two Types of Posts (Diamond Posts and Fiber Posts): An In Vitro Study

OBJECTIVES

The aim of this study is to compare the fracture resistance and the mode of failure of endodontically treated permanent mandibular premolars restored with two types of posts: diamond posts and glass-fiber posts.

MATERIALS AND METHODS

Forty human mandibular premolars indicated for orthodontic extraction were collected for this study and were similar in shape, size, and length. The teeth were sectioned horizontally, 1 mm above the cementoenamel junction. Root canal treatment was carried out on all specimens, and obturation was done by lateral condensation. The teeth were randomly divided into two groups. The post space was prepared in the first group to receive the diamond posts and in the second group to receive the fiber posts. A dual-cure resin material was used for cementing the posts and building up the cores. Then, they were subjected to a compressive load at a cross-head speed of 1 mm per minute and at an angle of 135 degrees to the long axis of the tooth until a fracture occurred using a universal testing machine. Fracture resistance and the mode of failure were assessed. The fracture above the acrylic block level was considered favorable, and the fracture below the acrylic block level was considered unfavorable. The data were analyzed statistically. The statistical analysis of fracture resistance between the two groups was carried out with a t-test. The statistical analysis for the failure mode of the teeth was carried out with a chi-square test.

RESULTS

There was a statistically significant difference showing that the diamond posts had better fracture resistance when compared with glass-fiber posts, while there was no statistically significant difference in terms of the failure mode between the two posts.

CONCLUSION

Within the limitations of this study, it can be concluded that diamond posts showed higher fracture resistance than glass-fiber posts. Glass-fiber posts showed more favorable failure modes but were statistically insignificant compared to diamond posts.

Immediate and Delayed Post Space Preparations in Endodontically Treated Teeth: A Scoping Review

BACKGROUND

The aim of the present review was to identify the effect of the post-space preparation (PSP) timing (immediate or delayed) on endodontically treated teeth.

METHODS

All studies in any language that compared the effect of immediate versus delayed PSP on the outcomes of an endodontically treated tooth were searched in PubMed, Scopus, Web of Science, Cochrane, ProQuest, WorldCat, and Google Scholar databases by two independent researchers until February 12, 2022. Studies assessing merely the immediate or delayed PSP were excluded. A descriptive analysis was performed to evaluate the study design and the characteristics of the included studies.

RESULTS

The initial search yielded 2612 records, of which 68 were included. Except for one randomized controlled trial, all were in vitro. The evaluated variables were apical/coronal microleakage (n = 48/n = 1), post-bond strength (n = 8), bacterial infiltration (n = 7), presence of voids (n = 3), apical extrusion and residual of filling material (n = 1), and post-operative pain (n = 1). The number of publications had steady growth per year and fast growth per decade. "Post-space preparation" was the most popular keywords.

CONCLUSIONS

The present review highlights the need for further investigations due to the various design of studies, controversial results, and an inadequate number of randomized controlled trials.

TRIAL REGISTRATION

Retrospectively registered. Open Science ( https://doi.org/10.17605/OSF.IO/2YTM6 ).

An In Vitro Study Comparing the Diametral Tensile Strength of Composite Core Build-Up Material With Three Different Prefabricated Post Systems

Statement of problem

Dental restorations are subjected to tensile stresses from oblique or transverse loading of their complex geometric forms, making tensile strength a fundamental mechanical property. Since composite core build-up materials are brittle, the integrity of the post and core depends on their tensile strength and resistance to fracture when utilized with various prefabricated post systems. Therefore, it is essential to determine the tensile strength of the prefabricated metallic and nonmetallic posts used to reinforce the composite resin core.

Purpose

This study compared the diametral tensile strength (DTS) of three prefabricated post systems with composite core build-up material.

Material and methodology

Ten composite resin cores from four different groups were formed. The control group was the composite resin core without a post (group 1). Group 2 was composed of composites with metal posts, group 3 was composed of composites with glass fiber posts, and group 4 was composed of composites with carbon fiber posts. All the samples were kept in a humid place for seven days to mimic the conditions in the mouth. DTS was determined by recording the tensile force required to fracture the core material by performing a diametral compression test for tension after a week. The observations were analyzed using a one-way analysis of variance (ANOVA), followed by a post-hoc test.

Results

The tensile strength of the resin core material was decreased by 28.1%, 20.8%, and 10.4% by using posts made of stainless steel, carbon fiber, and glass fiber, respectively. Among the three post systems, stainless steel had the lowest mean DTS values, while glass fiber had the highest mean DTS values.

Conclusion

Composite core glass fiber post systems showed higher tensile strength than other post systems.

Cement selection criteria for different types of intracanal posts

BACKGROUND

To consciously select an appropriate dental cement for each type of intracanal post.

MATERIALS AND METHODS

An electronic search was carried out (1970 to 2020) through Medline, PubMed, Scopus, and Google Scholar. The following keywords were searched in title, abstract, or keywords with different combinations: endodontically treated tooth, root canal therapy, dental posts, post and core, prefabricated posts, custom posts, dental cement, resin cements, cement selection, cement, and adhesive resin cement.

RESULTS

Evaluating full texts, 146 articles were selected to review the types of posts and cements, selection criteria of appropriate cement for each type of post, and compare the results obtained by different cements.

CONCLUSION

Dental cements affect the survival rate, durability, and success rate of postbased treatments. Considering special characteristics and application of each type of intracanal post, conscious selection of cement is an important determining factor in long-lasting success. Choosing an appropriate cement has a key role in success and durability of dowel posts-based fixed restorations.

Customized Post and Cores Fabricated with CAD/CAM Technology: A Literature Review

Post and core restorations are a widely accepted method to restore endodontically treated teeth with compromised tooth structure. The use of computerized technology to fabricate customized post and cores is a simple and quick alternative to conventional methods. A literature search was conducted, and a summary of articles describing fabrication techniques and materials used to fabricate post and cores with computer-aided design and computer-aided manufacturing (CAD/CAM) has been provided. Several techniques have been reported to restore endodontically treated teeth with CAD/CAM post and cores, including direct and indirect methods. Zirconia, composite resin, and hybrid ceramic were the most commonly reported materials. Published reports on CAD/CAM post and core are limited; however, further studies are needed to investigate the long-term outcome of this treatment.

Effect of Luting Cement Film Thickness on the Pull-Out Bond Strength of Endodontic Post Systems

Optimal bond strength between the prefabricated post/dowel to the surrounding dentin is essential. The present study aimed to analyze and compare the effect of three different cement film thicknesses on the pull-out bond strength of three different prefabricated post systems. Extracted natural teeth (N = 90) with similar root dimensions were acquired. Teeth were mounted in resin blocks, endodontically treated, sectioned at cemento-enamel junction, divided into three groups (A: Parapost Fiber Lux plus; B: 3M ESPE Relyx fiber post; and C: Parapost XP), and stored. Uniform post spaces were prepared for the groups (A and C: Length = 8 mm, Width = 1.5 mm; B: Length = 8 mm, Width = 1.6 mm). Each group (N = 30) was further subdivided into three subgroups (n = 10) based on the size (4, 5, and 6) of the post and cemented with resin cement (MultiLink-N, Ivoclar Vivadent). After thermocycling, the specimens were subjected to a pull-out test using a universal testing machine, and tensile force was recorded (MPa). Digital microscopic evaluations were performed for modes of failure. ANOVA and Tukey-HSD tests were used for statistics. Significant differences were observed for each tested material (p = 0.000). The lowest and highest bond strength values were recorded for Group C (Titanium post) and Group A (000), respectively. Multiple comparisons showed significance (p < 0.05) among all the groups, except for space 1 and space 2 (p = 0.316) for Group A. Most of the failures occurred within the cement-dentin and post-cement interface (Adhesive failures, 73.5%). An increase in the luting cement film thickness results in the decrease in pull-out bond strength of prefabricated posts luted with resin cement, irrespective of the type/material/shape of the post. The serrated fiber posts showed the highest pull-out bond strength compared to the smooth surfaced fiber posts or serrated metal posts. Increased pull-out bond strengths were observed when appropriate post space was created with the same sized drill as the post size.

Evaluation of Fracture Resistance and Sites of Failure of Different Dowel Core Restorations: An In-Vitro Study

Background:

Dowel Cores are often required in endodontically treated tooth to aid retention and resistance for a final prosthetic crown. Studies concerning the role of post-core systems on the fracture resistance with different dowel material remain controversial.

Aim:

This experimental study aimed to investigate the fracture resistance strength and failure mode of 3 dowel systems (glass fiber, indirect resin, and prefabricated metal with resin core).

Methods:

Twenty-one extracted human maxillary central incisors were first endodontically treated and then separated into 3 equal groups randomly;1st group consisted of glass fiber dowel, 2nd group consisted of indirect resin dowel, and 3rd group consisted of the prefabricated metal dowel. All specimens were restored with resin core and indirect resin crown. A testing force was applied with a universal testing machine (at 135 o angle) at 3 mm from the incisal edge of crown and forces were measured. Statistical tests were done using One-way ANOVA and Chi-square Test.

Results:

There was no significant difference (P-value >0.05) of the fracture resistance among glass fiber dowel, indirect resin dowel and pre-fabricated dowel with indirect resin crown. The prefabricated metal dowel had maximum fracture resistance (566 ±157.771 N) followed by Glass fiber dowel (541.047 ±199.571 N) and indirect resin dowel and post (444.550 ±139.788 N).

Conclusion:

Glass fiber dowel, indirect resin dowel and prefabricated metal dowel with resin core and indirect resin crown systems showed statistically insignificant fracture strength values and mode of failure.