Cusp Fracture Research Articles

Do onlays and crowns offer similar outcomes to posterior teeth with mesial-occlusal-distal preparations? A systematic review.

Teeth prepared for mesial-occlusal-distal (MOD) restorations have a significant risk of cusp fracture. Crowns and onlays can provide cusp coverage to reinforce posterior teeth at risk. Onlays are often more conservative of tooth structure which may be an advantage for teeth with large MOD preparations. It remains uncertain how onlays and crowns compare for posterior teeth with MOD tooth structure loss. The purpose of this systematic review was to compare the resistance to fracture, success rate, survival rate, and failure rate of teeth with MOD preparations restored with onlays or crowns. An electronic search queried Medline (PubMed), Embase (Ovid), Scopus, the Cochrane Library, and grey literature (OpenGrey) from database inception through April 29, 2023. After eliminating duplicates and irrelevant records, 32 manuscripts were assessed. Only three publications met the criteria for inclusion. Most exclusions were due to poor reporting of restorative design and the amount of tooth structure remaining, or due to combining various restorative designs. Due to the limited sample size and high heterogeneity, no meta-analysis was conducted. One study observed a better outcome for onlays and two observed no difference. All three studies reported the mode of failure for crowns as more catastrophic whereas teeth with onlays could be salvaged. Onlays may be an advantageous alternative to crowns for teeth with MOD preparations, but the level of evidence is insufficient to draw meaningful conclusions. Current evidence is insufficient to determine whether onlays or crowns are providing a different outcome when used to restore posterior teeth with MOD tooth structure loss. However, the fracture of teeth with MOD tooth structure loss restored with onlays appears to be less catastrophic than when restored with crowns.

Evaluating the efficacy of endodontic microsurgery for teeth with an undeveloped root apex and periapical periodontitis after nonsurgical treatment failure

AimTo determine the efficacy of endodontic microsurgery for teeth with an undeveloped root apex and periapical periodontitis caused by an abnormal central cusp fracture after failed nonsurgical treatment.MethodologyEighty teeth in 78 patients were subjected to endodontic microsurgery. All patients were clinically and radiologically examined 1 year postoperatively. The data were statistically analyzed using SPSS 27.0 software.ResultsOf the 80 teeth in 78 patients, periapical lesions had disappeared in 77 teeth at 1-year postoperative follow-up, with a success rate of approximately 96.3% (77/80). The efficacy of endodontic microsurgery was not affected by sex, age, extent of periapical lesions, and presence of the sinus tract. Between-group differences were not statistically significant (P > 0.05).ConclusionsEndodontic microsurgery can be an effective alternative treatment option for teeth with an undeveloped root apex and periapical periodontitis caused by an abnormal central cusp fracture after nonsurgical treatment failure.

Managing a Deep Subgingival Cusp Fracture: Case Reports

Cuspal fractures are relatively common. Fortunately for esthetics, when a cuspal fracture occurs in a maxillary premolar, it most commonly involves the palatal cusp. Fractures with a favorable prognosis may be approached with a minimally invasive treatment to successfully retain the natural tooth. This report describes 3 cases of “cuspidization” to treat maxillary premolars with cuspal fractures. After identifying a palatal cusp fracture, the fractured segment was removed, resulting in a tooth that closely resembles a cuspid. Depending on the extent and location of the fracture, root canal treatment was indicated. Subsequently, conservative restorations sealed the access and covered exposed dentin. Full coverage restorations were neither required nor indicated. The resulting treatment provided practical and functional treatment with a good esthetic outcome. When indicated, the described cuspidization technique can conservatively manage patients with subgingival cuspal fractures. The procedure is minimally invasive and cost-effective and can be done conveniently in routine practice.

Fracture resistance of defective amalgam restorations repaired with a resin-based composite material

BackgroundRepair is used to increase the longevity of defective restorations, such as large amalgams. The aim of this study was to investigate the fracture resistance and fracture modes of mesio-occlusodistal (MOD) amalgam molar restorations with extensive cuspal fracture repaired or replaced using a bulk-fill resin-based composite material. MethodsAmalgam restorations were placed in 84 permanent extracted molars and randomly assigned (n = 14) to groups: (1) MOD amalgam, (2) composite repair of 1-cusp fracture and adjacent proximal box, (3) composite repair of 1-cusp fracture, (4) composite repair of 2-cusp fracture, (5) replacement of 1-cusp defect and existing MOD amalgam, (6) replacement of 2-cusp defect and MOD amalgam. Each molar was prepared to simulate the assigned fracture and either repaired or replaced. Specimens were aged and then loaded to fracture. Fracture resistance and fracture modes were recorded. ResultsThe authors found significant differences (P < .001) between group 4 (1,652.3 N) and groups 5 (3,095.0 N), 1 (2,669.8 N), 6 (2,658.6 N), and 2 (2,442.9 N) as well as between group 3 (2,133.5 N) and group 5 (3,095.0 N). The results of the Fisher exact test showed differences among groups (P < .001), with group 5 having the highest number of nonrestorable fractures as well as higher fracture resistance on average. ConclusionsComposite material is a viable option for the repair and replacement of cuspal defects, especially in the case of a 1-cusp fracture and 1-cusp fracture involving the adjacent proximal box. Practical ImplicationsWithin the limitations of this study, the repair of cusp fractures in existing MOD amalgam–restored molars is an appropriate treatment option, although replacement of the defect and existing restoration with resin-based composite will withstand higher forces.

Cuspal Deflection and Fracture Resistance of Maxillary Premolars with Complex Class II and Restored with Contemporary Bulk-Fill Resin Composite

Cuspal Deflection and Fracture Resistance of Maxillary Premolars with Complex Class II and Restored with Contemporary Bulk-Fill Resin Composite

Cuspal Deflection and Fracture Resistance of Maxillary Premolars with Complex Class II and Restored with Contemporary Bulk-Fill Resin Composite

Cuspal Deflection and Fracture Resistance of Maxillary Premolars with Complex Class II and Restored with Contemporary Bulk-Fill Resin Composite

Risk Factors Associated with Cusp Fractures in Posterior Permanent Teeth—A Cross-Sectional Study

Objectives: This cross-sectional study aimed to evaluate the frequency and risk factors associated with cusp fractures in posterior permanent teeth. Methods: Patients presented cusp fractures on posterior permanent teeth, clinically assessed in up to 7 days after the event, and requesting dental treatment at two public services were included in this cross-sectional study. Fractured teeth already treated, with antagonist absence, or with prosthesis (total or removable) were excluded. Demographic and clinical data were collected to draw the patient profiles and establish how teeth were affected individually. Statistical analysis was performed by the Fisher exact test, and uni- and multivariate logistic regression (α = 0.05). Results: One hundred and seventy-seven (177) patients from 16 to 66 years old (±41.56), from 1998 to 2016, were included in this study. Non-functional and lingual cusps presented a higher fracture than functional and buccal cusps, respectively. Fractures were more common in teeth with isthmus wider than 1/3 of the intercuspid distance and/or more than three restored surfaces. Teeth with endodontic treatment presented a higher subgingival fracture. On lingual cusps, fracture type and location were significantly associated, being that total fractures were 3.2 times more likely to occur than partial fractures, and subgingival were 3.62 times more likely to occur than supragingival fractures. Conclusion: Indications of classic protection on functional cusps (LUBL) was refuted since, generally, nonfunctional cusps fractured more than the functional cusps. However, upper pre-molars showed more fractures in functional cusps and lower molars presented more fractures on the nonfunctional cusps. In general, lingual cusps were the most fractured and were associated with a higher prevalence of severe fractures (total fractures at the subgingival level). Fractures were more common in teeth where the restoration had an isthmus wider than 1/3 of the intercuspid distance and/or involved more than three restored surfaces. Most of the patients did not show previous symptoms and signs. Overall, teeth with endodontic treatment presented a higher subgingival fracture.

RECENT ADVANCES IN POST SYSTEMS -A REVIEW

Preservation of natural tooth in dental arch is ultimate objective of dental treatment. After endodontic treatment, tooth becomes brittle and prone to fracture which results in reduction of strength of crown causing fracture of cusp or sometimes weakness of the roots. In order to strengthen crown some anchorage within teeth has to be made and that anchorage and support is gained by rigid structure which is known as post. This article focuses on recent advances in post systems and their application, merits and demerits in endodontics.

Measuring fracture toughness of human dental enamel at small scale using notched microcantilever beams

Dental enamel is the most mineralised hard tissue with a complex hierarchically organised anisotropic structure and it protects human teeth from mechanical damage during the dental function. Due to the sample size constraints, the available data for quantitative evaluation of the fracture toughness of human enamel is very limited. Here, on the basis of microstructural characterisation, the fracture toughness of human dental enamel at small scale with respect to orientation was measured using notched microcantilever beams fabricated by focussed ion beam. The fracture toughness of human enamel with perpendicular orientation was measured to be 1.244 ± 0.12 MPa · m1/2, 80% tougher than that of in-plane parallel orientation (0.698 ± 0.18 MPa · m1/2). The present results are expected to provide deep insights into cusp fractures and the synthesis of enamel-like restorative materials.

Influence of Preparation Design and Restorative Material on Fatigue and Fracture Strength of Restored Maxillary Premolars.

Extensive carious lesions and/or large preexisting restorations possibly contribute to crack formation, ultimately resulting in a fracture that may lead to the loss of a tooth cusp. Hence, preparation design strategy in conjunction with the restorative material selected could be influential in the occurrence of a cuspal fracture. The purpose of this in vitro study was to evaluate the fatigue behavior and fracture strength of maxillary premolars restored with direct composite and indirect ceramic inlays and overlays, with different preparation depths in the presence or absence of cuspal coverage, and analyze their failure types. Sound maxillary premolars (N=90; n=10) were divided into nine groups: group C: control; group DCI3: direct composite inlay 3 mm; group DCI5: direct composite inlay 5 mm; group ICI3: indirect ceramic inlay 3 mm; group ICI5: indirect ceramic inlay 5 mm; group DCO3: direct composite overlay 3 mm; group DCO5: direct composite overlay 5 mm; group ICO3: indirect ceramic overlay 3 mm; group ICO5: indirect ceramic overlay 5 mm. In indirect ceramic, lithium disilicate restoration groups, immediate dentin sealing was applied. After restoration, all specimens were tested in fatigue (1,200,000 cycles, 50 N, 1.7 Hz). Samples were critically appraised, and the specimens without failure were subjected to a load to failure test. Failure types were classified and the data analyzed. Zero failures were observed in the fatigue testing. The following mean load to failure strengths (N) were recorded: group ICO5: 858 N; group DCI3: 829 N; group ICO3: 816 N; group C: 804 N; group ICI3: 681 N; group DCO5: 635 N; group DCI5: 528 N; group DCO3: 507 N; group ICI5: 482 N. Zero interaction was found between design-depth-material (p=0.468). However, significant interactions were found for the design-depth (p=0.012) and design-material (p=0.006). Within restorations at preparation depth of 3 mm, direct composite overlays obtained a significantly lower fracture strength in comparison to indirect ceramic onlays (p=0.013) and direct composite inlays (p=0.028). In restorations at depth 5 mm, significantly higher fracture load values were observed in indirect ceramic overlays compared with the inlays (p=0.018). Indirect ceramic overlays on 3 mm were significantly stronger than the deep inlays in ceramic (p=0.002) and tended to be stronger than the deep direct composite inlays. Severe, nonreparable fractures were observed with preparation depth of 5 mm within ceramic groups. The preparation depth significantly affected the fracture strength of tooth when restored with either composite or ceramic materials. Upon deep cavity preparations, cuspal coverage proved to be beneficial when a glass ceramic was used as the restorative material. Upon shallow cavity preparations, a minimally invasive approach regarding preparation design used in conjunction with a direct composite material was favorable.

Trends in Resin Composite Restoration Repair Teaching in Dental Colleges in Pakistan

Abstract Objective The paradigm shift from replacement to repair of defective resin composite restorations to implement minimal intervention approaches has been popular. Therefore, the teaching of composite repair strategies is included in contemporary dental curricula across the globe. Methods A validated 18-item questionnaire pertaining to existing educational practices related to the teaching of defective composite restorations repair was acquired form dental colleges in Pakistan. Results The response rate was 63% and the majority of dental colleges (67%) reported that they have included the teaching of composite restorations repair in the curricula, where four colleges (33%) implemented only didactic teaching and eight colleges (66%) reported a combination of didactic teaching and clinical training. The composite repair indications taught included tooth substance conservation 100% (12), reduced cost to patient 84.3% (10) and dentist 100% (12), reduced iatrogenic pulpal damage 100% (12), and reduced chair side treatment time 91.3% (11), restoration-related defects (66% preferred repair), anterior tooth fracture from incisal/proximal margin (80% teach repair), and in case of posterior tooth cusp fracture (20% teach repair). Our results revealed that the choice of mechanical and adhesive substrate surface conditioning depended on case selection. Conclusion The teaching of defective composite restorations repair was less widespread and certain variations in teaching were identified. Nearly all dental colleges reported to incorporate current evidence of minimum invasive strategies of composite repair in curricula in future.

Assessment of outcome of root canal treatment performed on an incomplete fracture non vital permanent first molar

Tooth infraction is usually of three types 1) confined to enamel (craze lines) and usually do not require treatment 2) related to cuspal fracture that typically do not involve pulp 3) more centrally located that do involve the pulp. Vertical root fracture (VRF) are longitudinal fracture that originate in root of teeth in contrast to tooth infraction that originate in the crown. VRF occurs usually in endodontically treated teeth. This case report represent tooth infraction originating in the tooth crown on the distal marginal ridge and propagating into the pulp chamber and DEJ(dentino enamel junction). Root canal treatment was performed and in a 7 month follow up period, there was a remarkable improvement in the supporting periodontal structures with bone deposition/remodelling in the crestal and furcation area/region and patient was quite satisfied with the treatment outcome.

Association between longitudinal tooth fractures and visual detection methods in diagnosis

ObjectivesThis study investigated the distribution of longitudinal tooth fractures (LTFs) according to the patient’s age and analyzed the association between visual detection methods and the types of LTFs. MethodsPatients with symptomatic teeth with LTFs were examined at the department of conservative dentistry in a dental hospital from September 1, 2009 to March 31, 2014. Naked eye examination, staining with a dye, operating microscopy, transillunimation, and periapical radiography were used to identify the fracture lines. Diagnostic surgery was performed to visualize the fracture line in some cases with vertical root fractures. The final diagnosis was based on the American Association of Endodontists (AAE) classification: cracked tooth, fractured cusp, split tooth, and vertical root facture. The probability density function for each type of LTF was calculated to assess the risks of LTF development according to age. The association between the detection methods and types of LTFs was identified using the association plot. ResultsA total of 245 teeth with LTFs were enrolled. Overall, 71.8% of LTFs was observed in patients aged 40–69 years, and 65.7% of LTFs were diagnosed as cracked teeth. The mean age in patients with cracked teeth was 49.3 years, while the mean age in patients with fractured cusps was 59.1 years. A significant association was observed between the detection method and type of LTF (p < 0.001). ConclusionsCracked tooth was the most common type of LTF. The probability of occurrence of cracked teeth peaked in patients aged approximately 50 years, while the probability of occurrence of fractured cusps peaked in patients aged approximately 60 years. Cracked teeth were detected most often using transillumination. Clinical significanceLTFs occurred mostly in patients aged 40 years and older. Transillumination is useful for the diagnosis of cracked teeth.

Treatment of Deep Cusp Fractures: A New Technique.

Cusp fractures occur frequently in endodontically treated teeth with large restorations and no cusp protection. These fractures often lead to challenging clinical decisions, such as whether to undertake complex restorative management or extraction of the affected teeth. This article reports the surgical and restorative management of two teeth with fractures exceeding the biologic width to juxtacrestal and subcrestal levels, respectively, and describes a new technique for such treatment.

Clinical performance and SEM marginal quality of extended posterior resin composite restorations after 12 years

ObjectiveTo investigate the clinical behavior of two different resin-based restorative systems in extended Class II cavities in a controlled prospective split-mouth study over 12 years and to assess marginal quality under a SEM using epoxy replicas. MethodsThirty patients received 68 resin composite restorations (Solobond M+Grandio: n=36; Syntac+Tetric Ceram: n=32) by one dentist in a private practice. 35% of cavities revealed no enamel at the bottom of the proximal box, 48% of cavities provided <0.5mm remaining proximal enamel. Restorations were examined according to modified USPHS criteria at baseline, and after six months, one, two, four, six, eight, 10, and 12 years. Expoxy replicas of 21 restoration pairs were analysed under a SEM at 200× magnification regarding marginal quality. ResultsAt the 12-years recall, 59 of the original 68 restorations in 27 of 30 patients were available (drop out 13%). Two restorations failed due to cusp fracture (Tetric Ceram) and marginal fracture (Grandio). The overall success rate of all restorations was 97.1% (Kaplan–Meier survival algorithm) with no differences between the two materials (p=0.923). After 144 months of clinical service, restorations in molars performed worse than in premolars regarding the integrity of restoration and tooth (p<0.05) being detected as wear, chippings, and cracks. Beyond the 4-year recall, marginal staining significantly increased. SEM evaluation of replicas revealed that perfect margin (49% baseline vs. 10% after 12 years), overhang (13% at baseline vs. 3% after 12 years), negative step formation (34% at baseline vs. 75% after 12 years), and marginal fractures (0% at baseline vs. 6% after 12 years) significantly changed during the evaluation period (p<0.001). SignificanceExtended direct resin composite restorations performed satisfactorily over 12 years of clinical service. SEM analysis delivered qualitative data regarding marginal deterioration over time.

Primary diffuse large B-cell lymphoma of mandible masquerading as toothache

Background Diffuse large B-cell lymphoma (DLBL) is an aggressive, fast-growing form of non-Hodgkin disease, with rare manifestation in the mandible as the primary site. The absence of pathognomonic features in this localization often leads to misdiagnosis as an odontogenic process or to delayed diagnosis. We report here a case where nonodontogenic jaw pain mimicked toothache, prompting multiple dental interventions before the persistence of pain and atypical findings led to the consideration of a malignant etiology. Case Summary A 54-year-old male presented to our oral medicine service for dental clearance before radiation for mandibular lymphoma. He had presented to his dentist for evaluation of right-sided jaw pain a few months earlier. On presentation, he had no lymphadenopathy or paresthesia, and his oral evaluation was within normal limits. Radiographic examination showed a deep restoration with pulpal proximity in tooth #31, widened periodontal ligament, loss of lamina dura, and diffuse periapical rarefaction. Tooth #31 was diagnosed with pulpitis, and the patient underwent root canal treatment. After a brief period of quiescence, the jaw pain returned, and the fractured cusp of tooth #30 was bonded to address the symptoms. Despite these measures, the jaw pain persisted, and tooth #31 gradually developed extreme compressive mobility. Imaging revealed extensive alveolar bone loss, furcation involvement, and floating molars. While extracting #31, a large osseous defect was visualized. This raised suspicion of a nonodontogenic etiology for the patient's pain and prompted referral for bone biopsy. Microscopic examination of the jaw specimen showed a tumor composed of neoplastic lymphocytes with large nuclei, prominent nucleoli, and scattered mitotic figures. Immunohistochemical staining was positive for CD45, CD20, CD79 a, and BCL-6. Positron emission tomography/computed tomography showed a solitary lytic lesion measuring 3.5 cm in length, with intense metabolic activity in the right mandibular body. Oncologic workup confirmed primary extranodal DLBL, and the patient was started on chemotherapy. Follow-up imaging showed marked reduction in metabolic activity (3.8 compared with previous 44.4). The patient subsequently received low-dose radiotherapy for residual disease in the mandible and achieved remission. Conclusions Dental providers should consider malignancy, including lymphoma, although uncommon, in the differential diagnosis of jaw pain, particularly when thorough evaluation fails to disclose a dental etiology, routine dental interventions fail to control symptoms, or there are atypical clinical or radiographic findings.

A Combined Amalgam-Composite Filling Technique to Resist Cuspal Fracture

This study was carried out to study a restorative technique of 2 mm thickness of composite resin filling material that bonded, by adhesive (4-META), to MOD cavities (Mesial, Occlusal and Distal surfaces of a tooth) partially filled with amalgam filling materials in upper premolars on the fracture resistance when compared to a sound tooth. Forty freshly sound extracted upper premolars were divided into four groups: the first group of ten sound premolars is subjected to fracture resistance test, the second group of ten premolars with a MOD of half intercuspal distance cavities, which was prepared with long bevel at the cavosurface angle and the teeth were filled with composite resin following incremental technique. The third group of ten teeth were prepared with a box form and butt joint of the same MOD cavities dimension and filled with non-gamma II amalgam. The fourth group of ten premolars with the same MOD cavities dimension are filled with amalgam, a 2 mm thickness of amalgam was removed of the occlusal surface after 24 hours, extended proximally mesially and distally, etch of the exposed enamel, dentin and amalgam was performed, and 4-META adhesive was applied to amalgam and exposed dentin and enamel followed by posterior composite bonded to tooth and amalgam, and cured with light for 40 seconds. The teeth of all groups were tested for fracture resistance. The group I showed the highest resistance to fracture followed by group IV followed by group II and lastly, group III. This study concluded that the use of combined bonded amalgam-composite and tooth structure provided the best technique for filling than cavity only filled with composite or amalgam.

Long-term clinical evaluation of direct resin composite restorations in vital vs. endodontically treated posterior teeth — Retrospective study up to 13 years

ObjectivesThis retrospective study evaluated and compared the survival rate of Class II posterior direct resin based composite (RBC) restorations made in vital teeth (VT) and endodontically treated teeth (ETT). The influence of risk factors on the long-term performance of restorations was also investigated. MethodsPatients (n=245) receiving RBC posterior restorations between 2004 and 2012 were selected. A total of 597 restorations (485 in VT, 112 in ETT) with minimum 2.5–3mm remaining cusp thickness, made with the same brand of RBC and adhesive, were evaluated using the USPHS criteria. Data were analyzed with Mann–Whitney, Chi-square and Fisher’s Exact Test, Extended Cox-regression and Kaplan–Meier analysis (p<0.05). Relative risk ratio was estimated for each evaluated parameter. ResultsThe mean observation period was 8.6±2.3 years. An annual failure rate in VT and ETT of 0.08% and 1.78%, respectively, was detected. The reasons of failures included restoration fracture, secondary caries in VT; vertical root fracture, cusp fracture, restoration fracture, secondary caries and loss of adhesion in ETT. Significantly better performance was observed in RBCs of VT for each evaluated parameter. Among the evaluated risk factors only occlusal stress affected negatively the survival of RBC in ETT (Hazard Ratio 37.1; CI95% 8.4–163.7). SignificanceAlthough, there is significant difference in the success rate of RBCs in VT (98.97%) and ETT (76.8%), the long-term (6–13 years) durability of Class II RBCs with 2.5–3mm cusp thickness in ETT is also clinically acceptable. The presence of occlusal stress decreases the survival of RBCs in ETT.

Effect of Preparation Design on Fracture Resistance and Failure Mode of Root Canal Treated Maxillary Premolars Restored with Onlay Restorations

Purpose: Cusp fractures are among the major reasons for the extractions of root-treated teeth. With the intention of increasing information about the mechanical behavior of minimally invasive cusp coverage restorations, the aim of current study was to evaluate the fracture resistance and failure modes of endodontically treated maxillary premolars restored with onlays employing various cusp reduction designs (anatomic, horizontal and beveled) to identify the optimum design and to assess whether these designs influence the restorable fracture rate.Materials and methods: Fifty defect-free maxillary premolar teeth were divided into 5 groups: onlay with anatomic occlusal reduction design (OA), onlay with horizontal occlusal reduction design (OH), onlay with beveled occlusal reduction design (OB), full-coverage crown (CR) and non-restored sound teeth (NR). In OA, OH, OB and CR groups, the access cavities were sealed using bonded composite after endodontic treatment. For OA, OH and OB groups, cusps were prepared with anatomic, horizontal and beveled designs. Except for NR group, all teeth were restored with resin-infiltrated ceramic restorations. After thermal aging for 10000 cycles between 5°C and 50 °C, all specimens were submitted to compressive axial load at a crosshead speed of 1 mm min-1 till failure. The data were analyzed using ANOVA test.Results: The highest load to fracture values (N) was recorded in control non-restored group (1657±167.7N), followed by CR, OA, OB and OH groups where the mean values were 887.5±40.3, 789.4±54.8, 722.2±46.2 and 634.8±74.2N respectively. Significant differences were found among fracture values of test groups (p<.05). The intact teeth predominantly fractured with favorable fracture patterns followed by CR group; while both OB and OH groups showed the heights non-favorable pattern of fracture. Group OA represented moderate percentage of favorable fracture.Conclusions: Root treated teeth restored with anatomic cusp reduction design displayed greater fracture resistance and greater rates of restorable fractures than root treated teeth submitted to horizontal and beveled reduction deigns.

Effect of Load Cycling on the Fracture Strength/Mode of Teeth Restored with FRC Posts or a FRC Liner and a Resin Composite.

The aim of the study was to comparatively evaluate the fracture strength and mode of root canal treated teeth restored with resin composites with and without posts. The lingual cusps of root canal treated first upper premolars (n = 10/group) were removed down to cervical enamel and restored with the following: group A: glass-fiber post (Glassix) followed by a particulate-filled composite resin (PFC, G-aenial posterior, 3 × 2 mm layers); group B: glass-fiber reinforced composite bulk fill liner (EverX posterior, 4 mm layer) with the PFC (2 mm layer). Specimens were immersed in H2O (1 w/37°C), then subjected to load cycling (50 N/0.2 Hz/200k cycles), and fractured under compressive loading. Failure mode was characterized by stereomicroscopy. Statistical analysis was performed by Mann-Whitney (load) and Chi-square (mode) at a = 0.05. No statistically significant differences (p = 0.273) were found in fracture load between median values of groups A (860 N) and B (1059 N). In group A, 60% of the specimens demonstrated catastrophic root fractures and 40% mixed crown fractures (tooth cusp and restoration), whereas in group B, no root fractures were found, and the failure modes were equally distributed between mixed fractures as above and fracture of the buccal cusp. These differences were statistically significant (p = 0.004). The combination of the glass-FRC bulk fill liner with the PFC diminished the catastrophic root fractures induced by FRC posts, at a similar or higher fracture load.