Retrospective study of fracture survival in endodontically treated molars: the effect of single-unit crowns versus direct-resin composite restorations

In Vitro Bond Strength of Dentin Treated with Sodium Hypochlorite: Effects of Antioxidant Solutions

This systematic review aims to evaluate whether the application of antioxidant solutions can enhance the bond strength of resin-based materials to sodium hypochlorite (NaOCl)-treated dentin. This study follows the PICOT strategy: population (sodium hypochlorite-treated dentin), intervention (application of antioxidants), control (distilled water), outcome (bond strength), and type of studies (in vitro studies). The systematic review and meta-analysis were conducted following PRISMA guidelines. Electronic databases were searched for in vitro studies evaluating the effects of antioxidants on bond strength to sodium hypochlorite-treated dentin. Two independent reviewers screened articles, extracted data, and assessed risk of bias. Meta-analyses were performed using a random-effects model to compare standardized mean differences in bond strength between antioxidant pretreatment and control groups. Inclusion criteria consisted of in vitro studies that examined the bond strength of resin-based materials to NaOCl-treated dentin with antioxidant application, while exclusion criteria included studies with incomplete data, those not using a control group, or those that did not directly measure bond strength. From 3041 initial records, 29 studies were included in the qualitative analysis and 25 in the meta-analysis. Ascorbic acid, sodium ascorbate, grape seed extract, green tea, and rosmarinic acid significantly improved bond strength to sodium hypochlorite-treated dentin (p < 0.05). The effectiveness of grape seed extract varied with adhesive system type. Hesperidin, p-toluene sulfonic acid, and sodium thiosulfate did not significantly improve bond strength. Most studies had a high risk of bias. This suggests that the conclusions drawn from these studies should be interpreted with caution, and further research with more robust methodologies may be needed to confirm the findings. In conclusion, this systematic review implies that certain antioxidants can improve bond strength to sodium hypochlorite-treated dentin, with efficacy depending on the specific agent and adhesive system used. Further standardized studies are needed to optimize protocols and confirm these findings.

Performance of Bonded Lithium Disilicate Partial-coverage Crowns in the Restoration of Endodontically Treated Posterior Teeth: An Up to Seven-Year Retrospective Study

OBJECTIVES

To evaluate the clinical performance of adhesively bonded lithium disilicate glass-ceramic (LDG) partial-coverage crowns in restoring posterior endodontically treated teeth (ETT).

METHODS AND MATERIALS

A total of 121 morphologically compromised posterior ETT were restored with LDG partial-coverage crowns between October 2015 and January 2018. The restorations were fabricated in the laboratory or at the chairside. Two adhesive systems and resin cements were used to cement the restorations. Tooth and restoration survival rates were calculated. The restorations were evaluated clinically using the modified United States Public Health Service (USPHS) criteria for an observation period of 5-7 years. The Cox proportional hazards model was used to estimate relative failure risks such as tooth type, resin cements, gender, and sleep bruxism. The standard chi-squared test was used to compare the survival of different tooth types for significant differences (α=0.05). In addition, survival probability was calculated using the Kaplan-Meier algorithm.

RESULTS

Among seven failed cases, one was a tooth fracture, and six were restoration fractures. According to the Kaplan-Meier analysis, the estimated survival rate of the teeth was 99% for seven years, while the estimated survival rate of the restorations was 94.8% for 5 years and 92.8% for 7 years. Tooth type and resin cements did not influence restoration survival rates (p>0.05), while sleep bruxism and male patients might increase the risk of failure (p<0.05).

CONCLUSIONS

The indirect adhesively bonded LDG partial-coverage crowns of posterior ETT exhibited favorable clinical outcomes. Ceramic fracture was the most common failure pattern.

Stress Analysis on Mesiolingual Cavity of Endodontically Treated Molar Restored Using Bidirectional Fiber-Reinforced Composite (Wallpapering Technique)

Introduction

Endodontically treated teeth (ETT) undergo extensive structure change and experience high stress during biomechanical function. Stress distribution is influenced by the restoration material and the type of bond between material and tooth structure. The selection of materials that can distribute stress will affect the resistance and retention of ETT to mastication forces, thus biomechanical functions were achieved. Composite has mechanical properties similar to dentin, it can transmit and distribute stresses throughout the tooth surface. The disadvantage of composites in large cavities is their lack of toughness. The addition of fiber to composites can increase their toughness.

Purpose

This research is to determine the stress distribution of a fiber-reinforced composite made of polyethylene and e-glass on the mesiolingual cavity of ETT.

Materials and Methods

A three-dimensional model of the mandibular molar was prepared for cavity preparation and the formation of restorations using SolidWorks 2021. The models were analyzed with Abaqus 2020 to determine stress concentrations after given vertical and oblique loading.

Results

The maximum and minimum principal stress data were obtained to assess material resistance and interfacial damage criterion. Polyethylene fiber shows a more homogeneous stress distribution because the modulus of elasticity is close to the dentin and has a thickness that can reduce the volume of the composite. The E-glass shows the stress concentration on the circumferential fiber and cavity floor.

Conclusion

The stress distribution of fiber-reinforced composite on the buccolingual cavity of ETT using the finite element method did not show structural failure in the polyethylene group because the maximum and minimum principal stresses were lower than the strength of the material. Interfacial bond failure occurs at the enamel portion. The maximum and minimum principal values of e-glass indicate structural failure in the circumferential fiber and the base fiber because the stress exceeds the strength of the material. Interfacial bond failure occurred on the circumferential and the cavity floor.

Tooth Fracture and Associated Risk Factors in Permanent Molars Treated with Vital Pulp Therapy and Restored with Direct Resin Composites: A Retrospective Survival Analysis in Young Patients

OBJECTIVE

This study aimed to evaluate the survival from fractures and risk factors of VPT-treated permanent molars restored with direct resin composites in young patients.

METHODS

The dental records of patients aged 6 to 18 years with VPT-treated permanent molars restored with resin composites were retrospectively evaluated for the presence of fractures on these teeth. Kaplan-Meier methods were used to estimate the survival probabilities. The potential risk factors were assessed using the multivariable Cox proportional hazard model.

RESULTS

A total of 234 treated molars from 189 patients were included. An overall average follow-up time was 33.34+-20.54 months (ranging from 6 to 83 months). At the end of the study, 21.8% of molars had fractures with the majority of them (92.2%) were restorable. Radiographically, only 3.9% of the fractured molars had periapical lesions and considered VPT failures. The percentages of the fracture types are as follows: 54.9% natural tooth structure fracture, 27.5% restoration fracture, and 17.6% combination fracture. The most common fracture location among the 37 molars with natural tooth fracture (either alone or in combination with restoration fracture) was at the marginal ridge (59.5%), followed by the marginal ridge extending to cusp (21.6%), and the cusp itself (18.9%). The cumulative survival probabilities of these teeth decreased over time, reaching 66.02% (95% CI: 55.89-74.36) after 5 years. VPT-treated molars in the mandible had a 2.1 times higher risk of fracture than those in the maxilla. Furthermore, the molars treated with partial and coronal pulpotomy had 2.4 times and 4.6 times higher risks of fracture when compared to those with indirect pulp capping, respectively.

CONCLUSION

In VPT-treated permanent molars in young patients, more fractures were seen in mandibular teeth and in teeth with pulp roof removal (partial and coronal pulpotomy). Clinicians should plan for proper restoration on these teeth. (EEJ-2022-08-097).

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.