Fabrication of direct fiber-reinforced posts: a structural design concept

A comparative evaluation of fracture resistance of endodontically treated premolar teeth reinforced with different prefabricated and custom-made fiber-reinforced post system with two different post lengths: An in vitro study

Aims

The aim of this study is to determine the mean failure load for each postsystem and the relationship between post lengths with the mean failure loads.

Materials and Methods

Ninety single-rooted decoronated mandibular premolar teeth were endodontically treated and randomly assigned to three groups with respect to their post length (2/3^rd and ½ of the root length). The first two groups were randomly divided into four subgroups, restored with the following postsystem: polyethylene-woven fiber posts, glass fiber tape, prefabricated carbon, and glass fiber posts. A composite core with no post served as control. All posts were cemented using dual-cure resin cement, and the same was used for core buildup. The standard cores were formed in each group. All the specimens were tested in a universal testing machine, and the load was calculated.

Results

One-way analysis of variance (ANOVA) showed that prefabricated glass fiber post had significantly highest fracture resistance when compared to other prefabricated and custom fiber-reinforced composite posts. Two-way ANOVA demonstrated no significant difference among the post lengths.

Conclusion

The results of this study showed that glass fiber posts showed higher fracture load, but post length did not significantly increase the fracture resistance of endodontically treated teeth.

Effect of fibre posts, bone losses and fibre content on the biomechanical behaviour of endodontically treated teeth: 3D-finite element analysis

The aim of this work was to evaluate the stress distribution inside endodontically treated teeth restored with different posts (glass fibre, carbon fibre and steel posts) under different loading conditions by using a 3D-finite element analysis. The effect of masticatory and impact forces on teeth with different degrees of bone loss was analysed. The model consists of: dentine, post, cement, gutta-percha, core and crown. Four simulations were conducted with two static forces (170N horizontal and 100N oblique) and two sections constrained: 1mm (alveolar bone position in a normal periodontium) and 6mm (middle of root) below the crown. Von Mises and the principal stresses were evaluated and analysed with a 3-way ANOVA and Tukey test (α=0.05) and the effect of fibre percentage analysed. Significant differences were found among the stress values for all conditions (p<0.05). Impact load was always responsible for the most critical situation especially when the bone loss was more evident. The system with steel posts showed the highest principal stresses at the post-cement interface with horizontal load and top constraints (compressive stress of 121MPa and tensile stress of 115MPa). The use of glass posts provides a more homogeneous behaviour of the system with lower stresses. Higher fibre percentages gave higher stress in the posts. Moreover, larger bone losses are responsible for important increase in stress. Thus, this work demonstrated that periodontal disease has an important role in the success of tooth restoration after endodontic therapy, influencing the choice of post material and depth.

Finite element analysis and fracture resistance testing of a new intraradicular post

Objectives

The objective of the present study was to evaluate a prefabricated intraradicular threaded pure titanium post, designed and developed at the São José dos Campos School of Dentistry - UNESP, Brazil. This new post was designed to minimize stresses observed with prefabricated post systems and to improve cost-benefits.

Material and methods

Fracture resistance testing of the post/core/root complex, fracture analysis by microscopy and stress analysis by the finite element method were used for post evaluation. The following four prefabricated metal post systems were analyzed: group 1, experimental post; group 2, modification of the experimental post; group 3, Flexi Post, and group 4, Para Post. For the analysis of fracture resistance, 40 bovine teeth were randomly assigned to the four groups (n=10) and used for the fabrication of test specimens simulating the situation in the mouth. The test specimens were subjected to compressive strength testing until fracture in an EMIC universal testing machine. After fracture of the test specimens, their roots were sectioned and analyzed by microscopy. For the finite element method, specimens of the fracture resistance test were simulated by computer modeling to determine the stress distribution pattern in the post systems studied.

Results

The fracture test presented the following averages and standard deviation: G1 (45.63±8.77), G2 (49.98±7.08), G3 (43.84±5.52), G4 (47.61±7.23). Stress was homogenously distributed along the body of the intraradicular post in group 1, whereas high stress concentrations in certain regions were observed in the other groups. These stress concentrations in the body of the post induced the same stress concentration in root dentin.

Conclusions

The experimental post (original and modified versions) presented similar fracture resistance and better results in the stress analysis when compared with the commercial post systems tested (08/2008-PA/CEP).

Fracture resistance of teeth restored with cast post and core: An in vitro study

CONTEXT

Influence of luting agent, design of tooth preparation for cast posts on tooth resistance to fracture.

AIM

To evaluate fracture resistance of teeth restored with cast posts and cores with or without cervical ferrule and cemented with zinc phosphate, glass ionomer, or resin cement.

MATERIALS AND METHODS

Sixty single-rooted maxillary first premolars of similar sizes were selected. Biomechanical preparation and post space preparation for cast post was done for all samples and then they were divided into two groups (n=30). Cervical ferrule preparation was done for Group A, and Group B was prepared without any cervical ferrule. Both groups were further divided into three subgroups (1, 2, and 3; n=10) Cast posts for subgroups 1, 2, and 3 were cemented with zinc phosphate, glass ionomer, and resin cement, respectively. A shearing load was applied to indented buccal cusp of specimens at an angle of 45° in universal testing machine at a cross-head speed of 1 mm/min until fracture.

RESULTS

Specimens with ferrule (Group A) had significantly higher shear bond strength values (mean 1503.37 N) than specimens without ferrule (Group B) (mean 1052.09 N).

CONCLUSION

Inclusion of ferrule in tooth preparations for posts increased the fracture resistance regardless of the luting agent.

An ex vivo comparative study on the retention of custom and prefabricated posts

Aim:

This study was designed to comparatively evaluate the effect of cyclic loading on the retention of custom-fabricated fiber-reinforced composite (CF-FRC), prefabricated metal, and glass fiber posts.

Materials and Methods:

Thirty mandibular first premolars decoronated at the CE junction were divided into three groups (n=10). Groups A, B, and C were restored using Para Post (Whale dent), Reforpost (Angelus), and CF-FRC post (Ribbond-THM), respectively. Five specimens from each group were subjected to cyclic loading. Tensile bond strength (TBS) was evaluated.

Results:

Pre-loading TBS values were statistically, significantly higher for all posts (P<0.05). Before and after loading, there was a significant difference between group C as compared to groups A and B.

Conclusions:

Cyclic loading reduced the retention of all posts but was comparatively lesser for the CF-FRC post. This system provides sufficient retention required for clinical success.

Influence of modification in core building procedure on fracture strength and failure patterns of premolars restored with fiber post and composite core

PURPOSE

The influence of the modified process in the fiber-reinforced post and resin core foundation treatment on the fracture resistance and failure pattern of premolar was tested in this study.

MATERIALS AND METHODS

Thirty-six human mandibular premolars were divided into 4 groups (n = 9). In group DCT, the quartz fibre post (D.T. Light-post) was cemented with resin cement (DUO-LINK) and a core foundation was formed with composite resin (LIGHT-CORE). In group DMO and DMT, resin cement (DUO-LINK) was used for post (D.T. Light-post) cementation and core foundation; in group DMO, these procedures were performed simultaneously in one step, while DMT group was accomplished in separated two steps. In group LCT, the glass fiber post (LuxaPost) cementation and core foundation was accomplished with composite resin (LuxaCore-Dual) in separated procedures. Tooth were prepared with 2 mm ferrule and restored with nickel-chromium crowns. A static loading test was carried out and loads were applied to the buccal surface of the buccal cusp at a 45 degree inclination to the long axis of the tooth until failure occurred. The data were analyzed with MANOVA (α = .05). The failure pattern was observed and classified as either favorable (allowing repair) or unfavorable (not allowing repair).

RESULTS

The mean fracture strength was highest in group DCT followed in descending order by groups DMO, DMT, and LCT. However, there were no significant differences in fracture strength between the groups. A higher prevalence of favorable fractures was detected in group DMT but there were no significant differences between the groups.

CONCLUSION

The change of post or core foundation method does not appear to influence the fracture strength and failure patterns.

Three-year clinical evaluation of endodontically treated anterior teeth restored with a polyethylene fibre-reinforced composite

BACKGROUND

Polyethylene fibre-reinforced composites (FRCs) have been under development for some time. However, there is a lack of data on the clinical performance of these restorations. The purpose of this descriptive study was to evaluate the clinical performance of endodontically treated anterior teeth restored using polyethylene FRCs.

METHODS

Eighty-seven endodontically treated anterior teeth in 65 patients were restored with polyethylene FRCs. The restorations were placed by three operators. The patients were recalled for examinations every year for up to three years. The restorations were evaluated using modified Ryge and USPHS criteria.

RESULTS

A statistical analysis showed no significant difference in marginal irregularity, marginal discolouration, surface texture, wear/anatomic form, fracture and retention, radiographic appearance, or debonding between the baseline and three-year results.

CONCLUSIONS

Based on our three-year examination results, polyethylene FRC restorations appear to be clinically successful.

Resistance to fracture and structural characteristics of different fiber reinforced post systems

OBJECTIVES

The aim of this study was to investigate the ultrastructure and resistance to fracture of eight different types of fiber post, and to verify the existence of a correlation between structural characteristics and flexural strength.

METHODS

Eight types of fiber post were selected for this study. Fiber Kor (Jeneric-Pentron), Para Post Fiber White (Colténe), Luscent Anchor (Dentatus), Twin-Luscent Anchor (Dentatus), Style Post (Metalor), DT White-Post (VDW), DT Light-Post (VDW) and ER Dentin Post (Brasseler). Ten posts of each experimental group were selected for a three-point bending test, and one was processed for SEM evaluation. A universal testing machine loading at an angle of 90 degrees was employed for the three-point bending test. The test was carried out until fracturing of the post. After fracture testing, the posts with the highest and the lowest values of flexural strength of each system were additionally processed for SEM analysis. SEM evaluation was performed using a PC-measurement program to assess the fiber/matrix ratio and fiber dimensions.

RESULTS

The fracture load of the tested systems ranged from 60 to 96 N and the flexural strength from 565 to 898 MPa. DT White-Post and DT Light-Post (898 and 842 MPa, respectively) had significantly higher flexural strengths than the other posts. Style Post (565 MPa) showed a significantly lower flexural strength than all other posts. The differences in fiber diameter ranged from 8.2 to 21 microm and for the fiber/matrix ratio from 41 to 76%. Of the various structural characteristics investigated, only the fiber/matrix ratio showed a significant correlation to the flexural strength (r=0.922, p=0.003).

SIGNIFICANCE

The FRC-posts investigated displayed significant differences with regard to fracture load and flexural strength. A strong and significant linear correlation between the fiber/matrix ratio and the flexural strength was found.

Conservative aesthetic solutions for the adolescent and young adult utilizing composite resins

The demand for aesthetic procedures in today's dental arena is increasing exponentially, yet these desires often call for conservative restorative options, especially for the adolescent patient. The use of direct composite resin restorations offers the dentist the most sim-ple and cost-effective manner in which to create an aesthetic change in the anterior portion of the mouth. The combination of improved materials and innovative delivery techniques allows clinicians to reach these aesthetic goals by creating conservative and functional restorations that have excellent longevity. This article demonstrates five direct composite approaches for solving aesthetic dilemmas in the adolescent and young adult patient.

Two-Year Clinical Evaluation of Nonvital Tooth Whitening and Resin Composite Restorations

BACKGROUND

Adhesive systems, resin composites, and light curing systems underwent continuous improvement in the past decade. The number of patients asking for ultraconservative treatments is increasing; clinicians are starting to reevaluate the dogma of traditional restorative dentistry and look for alternative methods to build up severely destroyed teeth.

PURPOSE

The purpose of this study was to evaluate the efficacy of nonvital tooth whitening and the clinical performance of direct composite restorations used to reconstruct extensive restorations on endodontically bleached teeth.

MATERIALS AND METHODS

Twenty-one patients 18 years or older were included in this clinical trial, and 26 endodontically treated and bleached maxillary and mandibular teeth were restored using a microhybrid resin composite. Patients with severe internal (tetracycline stains) and external discoloration (fluorosis), smokers, and pregnant and nursing women were excluded from the study. Only patients with A3 or darker shades were included. Teeth having endodontic access opening only to be restored were excluded; conversely, teeth having a combination of endodontic access and Class III/IV cavities were included in the study. A Vita shade guide (Vita Zahnfabrik, Bad Säckingen, Germany) arranged by value order was used to record the shade for each patient. Temporary or existing restorations were removed, along with a 1 mm gutta-percha below the cementoenamel junction (CEJ), and a resin-modified glass ionomer barrier was placed at the CEJ. Bleaching treatment was performed using a combination of in-office (OpalescenceXtra, Ultradent Products, South Jordan, UT, USA) and at-home (Opalescence 10% PF, Ultradent Products) applications. Two weeks after completion of the bleaching, the teeth were restored using a combination of PQ1 adhesive system and Vit-l-escence microhybrid resin composite (Ultradent Products). Wedge-shaped increments were placed and cured using the VIP Light (Bisco, Inc Schaumburg, IL, USA) through a combination of pulse and progressive curing techniques.

RESULTS

All but one restoration were evaluated by two independent evaluators every 6 months during a 2-year period using modified US Public Health Service criteria. No restoration failed and "alpha" scores were recorded for all parameters but color stability, which was scored "bravo." Analysis of variance showed a significant shade change between baseline (mean=14.4+/-1.9) versus 2 weeks (mean=1.6+/-0.7) and 2 years (mean=2.8+/-1.7) (p<.0001). Although a significant shade change was observed between 2 weeks and the 2-year follow-up (p=.008), no significant difference was reported between the baseline and 2 weeks (12.9+/-2) versus baseline and 2 years (11.9+/-2.3).

CONCLUSIONS

Significant tooth lightening was reported after the completion of whitening therapy on devitalized teeth; shade rebound was reported in less than 50% of the treated teeth and was limited to a maximum of four shades. A microhybrid resin composite demonstrated excellent clinical performance in the restoration of all endodontically treated and bleached teeth after a 2-year evaluation period.

CLINICAL SIGNIFICANCE

Nonvital tooth whitening is responsible for a significant change in color of endodontically stained teeth. Successful nonvital tooth-whitening therapy allows for conservative tooth preparation, preserving and reinforcing sound tooth structure. The proper use of modern adhesive systems along with resin composite restorations precludes the use of more extensive restorative treatment, delaying expensive crown and bridge procedures.

Dentinal Bonding Reaches the Root Canal System

Several factors can contribute to the achievement of success with endodontic therapy. After an effective microbial-control phase, an adequate canal and coronal filling will guarantee a high probability of success. Gutta-percha has for many years been widely used as a solid material in root fillings associated with different types of sealers. Even associated with a sealer, this material it is not capable of preventing leakage, as has been shown in many studies. In fact, because of gutta-percha's limitations, the seal of a coronal restoration may be as important as the gutta-percha fill in preventing reinfection of the root canal. Although sealers can form close adhesion to the root canal wall, none is able to bond to the gutta-percha core material. Upon setting, the sealer pulls away from the gutta-percha core, leaving a gap through which bacteria may pass. This article describes a new thermoplastic, synthetic root canal filling material, whose design is based on polyester chemistry, that looks and handles like gutta-percha. It is used in the same manner as most bonding systems. After the usual preparation of the root canal, a self-etch primer is used to condition the canal walls and prepare them for bonding to the resin. The resin sealant is introduced in the root canal. It bonds to the primer and to the resin core material; thus, a "monoblock" is formed without the gaps typical in gutta-percha fillings. Studies have shown that leakage of bacteria with this material is significantly reduced compared with gutta-percha.