A comparison of the fracture resistance of premolars without a ferrule with different post systems

Influence of remaining coronal tooth morphology with resin abutment and fiber post on static and dynamic fracture resistances

This study aimed to clarify the fracture resistance of resin abutments built on endodontically treated roots with the remaining coronal teeth via static and cyclic loading tests. Endodontically treated bovine roots, which had a remaining coronal tooth covered with an occupied area for a quarter and half of the circumference at the tensile side or covered the circumference at both the tensile and compressive sides, were fabricated to build up to the resin abutment. Fracture resistance was evaluated via static and cyclic loading tests by applying a load of 30° to the tooth axis. Half of the circumference of the remaining coronal tooth showed a significantly higher static fracture load and survival rate. The remaining coronal tooth on the compressive side improved the dynamic fracture resistance associated with severe fractures. The occupied area and location of the remaining coronal tooth affected the static and dynamic fracture resistances.

Advanced Material Strategy for Restoring Damaged Endodontically Treated Teeth: A Comprehensive Review

The restoration of endodontically treated teeth (ETT) remains a significant challenge in modern dentistry. These teeth often suffer from substantial structural damage due to both the original pathology and the invasive nature of endodontic procedures. Consequently, ETT are more susceptible to fractures compared to vital teeth, necessitating restorative strategies that can effectively restore both function and aesthetics while minimizing the risk of failure. In recent years, advances in adhesive dentistry and the development of high-strength ceramics have further expanded the restorative options for ETT. Bonded restorations have gained popularity as they preserve more tooth structure and enhance the overall strenght of the tooth-restoration complex. The choice of restorative material and technique is influenced by numerous factors, including the amount of remaining tooth structure, the functional requirements of the tooth, and the aesthetic demands of the patient. Despite the plethora of available materials and techniques, the optimal approach to restoring ETT remains a topic of ongoing research and debate. In this comprehensive review, the current state of and recent advances in restoring damaged endodontically treated teeth are explored. Numerous therapeutic options exist, involving a wide range of materials. This article aims to present the biomaterial advancements of the past decade and their applications, offering alternative approaches to treating damaged ETT with the goal of prolonging their retention on the dental arch and serving as a valuable resource for dental practitioners who face this issue daily.

Influence of post material and ferrule thickness on the fracture resistance of endodontically treated premolars: A laboratory study

STATEMENT OF PROBLEM

The influence of the ferrule thickness and post materials on the fracture resistance of endodontically treated teeth remains unclear.

PURPOSE

The purpose of this laboratory study was to evaluate the influence of post material and ferrule thickness on the fracture resistance of endodontically treated mandibular premolars.

MATERIAL AND METHODS

Sixty-four extracted and endodontically treated mandibular first premolars were used and divided into 4 test groups (n=16) depending on the ferrule thickness: F-0: without a ferrule, F-0.5: with a 0.5-mm ferrule thickness, F-1: with a 1-mm ferrule thickness, and F-1.5: with a 1.5-mm ferrule thickness. In groups with ferrules, the height ranged from 2 mm buccally/lingually to 1 mm proximally. Teeth in subgroups (n=8) were restored with either prefabricated glass fiber (FF) or titanium posts (FT) (ISO size 70 and length of 7.5 mm) and then adhesively restored with composite resin foundation materials. After foundation procedures, each specimen was restored with a cobalt chromium crown which was cemented with glass-ionomer cement. All specimens were subjected to dynamic loading in a masticatory simulator for 1 200 000 loading cycles with a nominal load of 5 Kg at 1.2 Hz and simultaneous thermocycling (5 to 55 °C). Specimens were then quasistatically loaded at 30 degrees in a universal testing machine until fracture. Fracture loads were analyzed by using 2-way ANOVA followed by the Tukey honestly significant difference test (α=.05).

RESULTS

Fracture loads ranged from 610 ±45 N (no ferrule - glass fiber post) to 1216 ±169 N (1.5 mm ferrule thickness - glass fiber post). A statistically significant increase in fracture resistance was observed with increasing ferrule thickness (P<.001). However, post materials did not show a statistically significant influence (P=.977).

CONCLUSIONS

Under the conditions of this laboratory study, increasing the ferrule thickness had a significant effect on the fracture resistance of endodontically treated teeth after thermomechanical fatigue, irrespective of post materials.

Fracture resistance of endodontically treated teeth, restored with two post-core systems in different post space diameters (in vitro study)

BACKGROUND

Fracture resistance of post-core restoration depends on the design of the post, post diameter, post length, the type of adhesive cement used along with material of the core. Despite the different studies concerning the effect of post space diameter on the fracture resistance of endodontically treated teeth, more information regarding fracture resistance and the effect of different post space systems/materials and diameters is required.

AIM OF THE STUDY

This study aimed to evaluate fracture resistance of endodontically treated teeth, restored with two post-core systems in different post space diameters.

MATERIALS AND METHODS

Twenty freshly extracted maxillary central incisors were collected for this study. They were randomly divided into four groups according to intracanal post and its diameter. Group GN (glass-fiber post of 10-mm length and 1.3-mm diameter with composite core), group GW (glass-fiber post of 10-mm length and 1.75-mm diameter with composite core), group ZN (custom-made zirconia one-piece post-core of 10-mm length and 1.3-mm diameter) and group ZW(custom-made zirconia one-piece post-core of 10-mm length and 1.75-mm diameter). Fracture resistance for all samples was evaluated using the universal testing machine under a static load. The data was collected and statistically analyzed using One-Way ANOVA test. Modes of failure were assessed using stereomicroscope for each group.

RESULTS

The highest mean fracture resistance was recorded in group GW (638.7 ± 285.1 N), followed by group ZW (598.5 ± 127.6 N), then GN group (442.8 ± 65.38 N). The lowest mean fracture resistance was recorded in group ZN (435.3 ± 117.3 N). One-Way ANOVA test revealed that there was no statistically significant difference in fracture resistance values among the groups.

CONCLUSION

Post space diameter had an impact over the fracture resistance of endodontically treated teeth. Modulus of elasticity of post material had a major effect on the fracture resistance and mode of failure along with the restorability of the restored tooth. However, there was no statistically significant difference among the tested groups.

Internal adaptation and mechanical properties of CAD/CAM glass fiber post-cores in molars: An in vitro study

OBJECTIVE

The purpose of this in vitro study was to evaluate the internal adaptation, fracture resistance, and fracture pattern of the residual roots and crowns of molars restored with computer-aided design/computer-aided manufacturing (CAD/CAM) glass fiber post-cores, and compare them with three other post-core restorations.

MATERIALS AND METHODS

We selected 32 extracted maxillary first molars and divided them into four groups according to the post-core system: traditional casting titanium (Ti) post-cores (TC group); Ti post-cores fabricated with selective laser melting (SLM group); CAD/CAM glass fiber post-cores of the split type (CCS group); and prefabricated glass fiber posts and composite resin cores (PF group). The internal adaptation was analyzed with microcomputed tomography. Teeth were restored with monolithic zirconia crowns and subjected to thermocycling and cyclic loading. A load was applied consistently along the long axis of the tooth until fracture to record the fracture resistance and pattern. For the statistical analysis, one- and two-way analyses of variance, Tukey's post hoc and chi-square tests were performed to compare the differences among the groups.

RESULTS

The CCS, TC, and SLM groups exhibited similar internal adaptations across all sections (P < 0.05). The FP group showed good fit with the root canals in the apical and middle sections but a poor fit with those in the cervical section. The fracture resistance was higher in the CCS, TC, and SLM groups compared to the PF group (P < 0.05). The proportions of restorable fractures in the CCS and PF groups were 62.5% and 50%, respectively. Unrestorable fractures were more frequent in the TC and SLM groups at frequencies of 100% and 87.5%, respectively.

CONCLUSION

The internal adaptation and fracture resistance of the CCS group were similar to those of the TC and SLM groups, and the fracture pattern was mostly restorable, thus meeting the clinical requirements for molar post-core restorations.

CLINICAL SIGNIFICANCE

CCS can be used to restore residual roots and crowns of molars and exhibit high efficacy in terms of adaptability and mechanical properties. More studies are required to evaluate the effectiveness of CCS.

Probability of survival and failure mode of endodontically treated incisors without ferrule restored with CAD/CAM fiber-reinforced composite (FRC) post-cores

PURPOSE

This study evaluated the probability of survival and failure mode of endodontically treated incisors without ferrule restored with CAD/CAM FRC post-cores.

METHODS

Root canals of bovine incisors were treated, leaving post preparations of ∼10 mm. Teeth were allocated into three groups: (i) cast metal post-core, (ii) FRC prefabricated post with a direct resin core build-up, and (iii) CAD/CAM FRC post-core. Posts and zirconia crowns were cemented using resin cement. Specimens were subjected to step-stress accelerated-life fatigue testing in water. Use level probability Weibull curves, probability of survival for a mission of 100,000 cycles at 25, 50, and 100 N, Weibull modulus, and characteristic strength were calculated and plotted. Failure mode was examined under a stereomicroscope.

RESULTS

Restored incisors demonstrated high probability of survival (93-100%) for missions estimated at 25 and 50 N, irrespective of post-core foundation. At 100 N, incisors restored with metal posts presented significantly higher probability of survival (99%) relative to CAD/CAM posts (79%), whereas FRC groups demonstrated no significant difference. Weibull analysis indicated no significant difference on the Weibull modulus (m = 3.38-5.92). Incisors reconstructed with metal post-cores (431 N) presented significantly higher characteristic strength relative to prefabricated (200 N) and CAD/CAM (202 N) FRC post-cores. While post fracture was the chief failure mode for prefabricated and CAD/CAM FRC post-cores, post and/or root fracture were the main event for metal post-cores.

CONCLUSION

Endodontically treated incisors without ferrule restored with CAD/CAM FRC post-cores presented promising probability of survival for loads compatible with anterior masticatory forces and favorable failure modes.

Present status and future directions: The restoration of root filled teeth

This narrative review will focus on a number of contemporary considerations relating to the restoration of root filled teeth and future directions for research. Clinicians are now more than ever, aware of the interdependence of the endodontic and restorative aspects of managing root filled teeth, and how these aspects of treatment are fundamental to obtaining the best long-term survival. To obtain the optimal outcomes for patients, clinicians carrying out endodontic treatment should have a vested interest in the restorative phase of the treatment process, as well as an appreciation for the structural and biomechanical effects of endodontic-restorative procedures on restoration and tooth longevity. Furthermore, the currently available research, largely lacks appreciation of occlusal factors in the longevity of root filled teeth, despite surrogate outcomes demonstrating the considerable influence this variable has. Controversies regarding the clinical relevance of minimally invasive endodontic and restorative concepts are largely unanswered with respect to clinical data, and it is therefore, all too easy to dismiss these ideas due to the lack of scientific evidence. However, conceptually, minimally invasive endodontic-restorative philosophies appear to be valid, and therefore, in the pursuit of improved clinical outcomes, it is important that the efficacies of these treatment protocols are determined. Alongside an increased awareness of the preservation of tooth structure, developments in adhesive bonding, ceramic materials and the inevitable integration of digital dentistry, there is also a need to evaluate the efficacy of new treatment philosophies and techniques with well-designed prospective clinical studies.

Outcome of teeth restored with CAD/CAM zirconium dioxide post-cores: a retrospective study with a follow-up period of 3-6 years

Statement of problem

Computer aided design/computer aided manufacturing (CAD/CAM) zirconia post-cores is one of the options of post crown restoration materials due to their esthetic properties and superior mechanical strength. However, the clinical effect on aesthetics and strength properties is unclear due to the lack of results of their long-term follow-up.

Purpose

This retrospective clinical study aims to analyze the survival rate, clinical manifestations, and failure factors after CAD/CAM zirconia post-core restoration.

Material and methods

Clinical and radiographic examinations were performed on 342 patients with 400 teeth for 3–6 years postsurgical follow-up examination. The patients were all received CAD/CAM zirconia post-cores and all-ceramic crowns at the Department of Prosthodontics in the public hospital. The retrospective outcomes were conducted after zirconia post restoration, including survival rate by Kaplan–Meier analysis and findings of manifestations and failure factors. The effects of gender and dental position on survival rate were analyzed by Cox–Mantel Test.

Results

This study retrospectively evaluated 261 teeth from 229 patients with a 35% drop-out rate. The survival rate was 96.0%, and the success rate was 92.4%. According to the tooth position classification, the survival rate was 100% for 101 anterior teeth, 95.4% for 69 premolars, and 88.3% for 91 molars. According to gender, the survival rate of the male group was 92.3%, while that of the female group was 98.0%, with a significant difference (P < 0.01). The complications included crown fracture (1.9%) periapical inflammation (1.9%), crown debonding (1.1%), percussion abnormal (1.9%) and root fracture (0.8%).

Conclusions

Within the limitations of this retrospective study, it can be concluded that CAD/CAM zirconia post-cores are clinically promising. Compared with the posterior teeth, CAD/CAM zirconia post-cores are more suitable for anterior teeth.

Influence of one-wall remaining coronal tooth with resin abutment and fiber post on static and dynamic fracture resistance

The objective of this study was to determine the influence of height and thickness of the one wall remaining coronal tooth structure on the fracture resistance of an endodontically treated root with resin abutment build-up using resin composite and fiber-reinforced resin composite post. Static and dynamic fracture tests were performed by placing the remaining tooth wall on the tensile side and applying loads at an angle of 30° from the tooth axis. Superior static fracture resistance was observed when the wall remaining on the tooth had a height and thickness greater than 1.0 mm. The dynamic fatigue test showed high loading capacity or fracture resistance in specimens with large height and thickness. The dynamic fatigue test showed the influence of the remaining tooth structure on fracture resistance clearly. In conclusion, the static and dynamic fracture resistances increased with the height and thickness of the one wall remaining tooth structure.

Fracture resistance of maxillary premolars restored with different endocrown designs and materials after artificial ageing

PURPOSE

To evaluate the effect of three different designs and two monolithic ceramic materials on the durability and fracture resistance of endocrowns on maxillary first premolars, in comparison to post-and-core crowns.

METHODS

Fifty-six maxillary premolars were endodontically treated and shortened to a level of 2 mm from the cervical line, and randomly categorized into six endocrown groups and post-and-core crown control group (n=8); E1; endocrowns with flat occlusal table (without ferrule), E2; endocrowns with 1.5 mm circumferential ferrule, E3; endocrowns with 1.5 mm buccal ferrule preparation. Two materials were used for endocrowns: zirconia (4YSZ; Z), and lithium disilicate (L). The control group was restored with zirconia posts, and lithium disilicate crowns. All restorations were bonded using Panavia V5 and its respective primers and underwent thermo-mechanical fatigue with a 10 kg dynamic load for 1,200,000 cycles and thermocycling between 5 and 55 °C. Thereafter all survived specimens were loaded to fracture. The results were statistically analyzed using ANOVA and T-Test.

RESULTS

None of the specimens showed any signs of debonding or fracture caused by the fatigue test. The PC control group showed no statistically significant difference in comparison to groups ZE1, ZE2 and LE2 ( p > 0.05 ). However, it was significantly different from groups LE1, LE3, and ZE3 ( p ≤ 0.05 ).

CONCLUSIONS

Preparation designs and materials affected the fracture resistance of endocrowns. The results showed a superiority of the post-and-core crowns,zirconia/lithium disilicate endocrowns with 1.5 mm circumferential ferrule, and zirconia endocrowns with the flat occlusal table.

Evaluation of shade correspondence between current monolithic CAD/CAM blocks and target shade tab by considering the influence of cement shade and restorative material thickness

It was aimed to evaluate shade matching between novel CAD/CAM blocks and the A2 target shade tab by considering the influence of cement shade and restorative material thickness on the chromatic background. A total number of 120 rectangular-shaped specimens were subtracted from four different prefabricated CAD/CAM blocks [Vita Enamic (VE), Lava Ultimate (LU), GC Cerasmart (GC), and Vita Mark II (VMII)]. These specimens had thicknesses of 0.5 mm and 1.0 mm. Three different shades (A2, opaque, and translucent) of dual-polymerized resin cement were chosen. The dentin shade (A3.5) restorative composite foundation was incrementally fabricated in a silicon mold. For control group, the A2 shade tab of the Vitapan classical shade guide was used. Different restorative material-cement-foundation assemblies were generated with optic gel. Color readings were performed by using a clinical spectrophotometer, and CIEDE2000 (ΔE₀₀) formula was used to assess color differences. Data were statistically analyzed (α = 0.05). With increasing thickness, color difference values decreased. Higher mean ΔE₀₀ units were observed in all restorative material sub-groups for 0.5 mm thickness. In TR shade, no statistically significant difference was detected among the mean ΔE₀₀ values of 0.5 mm-thick restorative materials. Color differences in groups 1.0 mm-opaque-LU and 1.0 mm-opaque-GC indicated perceptible but clinically acceptable values (0.8˂ΔE₀₀ ≤ 1.8). The highest and lowest ΔE₀₀ units were observed in the 0.5 mm-A2-VE group (ΔE₀₀ = 7.07) and 1 mm-opaque-GC group (ΔE₀₀ = 1.46), respectively. Luting cement shade, restorative material type, and thickness significantly influenced the resultant color of restoration. Opaque cement on dentin foundation exhibited lower color differences.