Are posts necessary for the restoration of root filled teeth with limited tissue loss? A structured review of laboratory and clinical studies

Stress Behaviour of an Immature Maxillary Central Incisor: A 3D Finite Element Analysis

BACKGROUND AND OBJECTIVE

Immature maxillary incisors (IMIs) are especially susceptible to failure due to their thin dentinal walls and compromised structural integrity following endodontic treatment. This study aims to evaluate the stress distribution within the root dentin after various post-endodontic treatments.

MATERIALS AND METHODS

A personalized finite element analysis model of IMI was created using cone beam computed tomography (CBCT) data. Based on data from the literature, five stages of root development were reconstructed: half root development (S1), three-quarter development (S2), more than three-quarter development (S3), fully developed root with open apex (S4), and fully developed root with closed apex (S5). Six experimental groups were analyzed: GC Fiber Post (PS1); RelyX Post (PS2); metal post Unimetric 1.0 (PS3); everStick Post (PS4); positive control group with only the gutta-percha filling (PC), and intact maxillary incisor as negative control group (NC). The resulting equivalent stresses were evaluated using the Hencky-von Mises (HMH) strength theory.

RESULTS

The mean HMH stress within the root dentin was statistically significantly higher at the cervical level in all stages, except in stage S1 and models PS2 and PS3 in stage S2, where it was significantly higher at the apical level (p < 0.001 for all models, except stage S3 [PC model p < 0.005; NC model p < 0.008]). The PS4 model showed the lowest stress values at the cervical level in stages S1, S2, and S3 (55.19 MPa, 58.78 MPa, 58.84 MPa) and the PS1 model in stages S4 and S5 (57.48 MPa, 58.81 MPa). At the apical level, model PS3 showed the lowest stress values in stage S1 (69.60 MPa), model PS1 in stages S2, S3, and S5 (35.99 MPa, 44.30 MPa, 12.51 MPa) and model PC in stage S4 (17.85 MPa).

CONCLUSIONS

The results showed that the greatest stress in an immature maxillary central incisor occurred at the cervical level, except during the early stage of root development. Post placement did not reduce root dentin stress.

Chinese dentists' restorative preferences and choices for endodontically treated teeth: a representative survey

BACKGROUND

The optimal restoration protocol for endodontically treated teeth (ETT) remains a subject of debate. This survey aims to assess the current level of awareness, knowledge, and prevailing opinions among dental practitioners in China regarding the application of endocrown versus the post/core/crown ensemble for post-endodontic restoration strategies.

METHODS

A validated questionnaire, encompassing three sections, was distributed electronically to dentists practicing in China. The initial section collected demographic characteristics of the participants, while the subsequent sections assessed their knowledge and preferences regarding ETT restoration techniques in various clinical scenarios. Distribution of the survey was facilitated through the social media platform WeChat, with a total of 600 invitations sent out. Data analysis was conducted using SPSS Statistical Software, employing frequency and Chi-square tests to determine statistical significance at the P < 0.05 threshold.

RESULTS

A total of 400 valid questionnaires were collected. The amount of remaining tooth structure was identified as the most influential factor in determining the restoration strategies, contributing to 26.1%. Over 72.8% of the surveyed dentists acknowledged the reinforcing effect of intraradicular posts on ETT. More than half of the participants reported the application of endocrowns within their post-endodontics management. The preference for endocrowns was pronounced in cases where more than 50% of the tooth's structure remained or when occlusal space limitations were present. The Chi-Square test revealed that the participants' knowledge regarding endocrown restoration was significantly influenced by their age, educational background, and experience (p < 0.05).

CONCLUSIONS

The clinical decision-making process for the restoration of endodontically treated teeth (ETT) by dental practitioners primarily relies on the amount of remaining tooth structure. Most surveyed dentists believe that the presence of a post can reinforce ETT. A majority of participants consider the Endocrown as a viable alternative restorative treatment for ETT.

Mechanical Performance of Direct Restorative Techniques Utilizing Long Fibers for “Horizontal Splinting” to Reinforce Deep MOD Cavities—An Updated Literature Review

Excessive cavity preparation and root canal treatment leads to a weakened tooth structure with a lower resistance to fracture. Fiber reinforcement is frequently used to reinforce such teeth, and multiple fiber types and possible applications exist. Various methods for utilizing long fibers to internally splint the remaining cavity walls in the case of large mesio-occluso-distal (MOD) cavities have been proposed; however, no summary of their performance has been written up to now. Our study aims to review the available literature to evaluate and compare the mechanical performance of the different materials and methods utilized for horizontal splinting in large MOD cavities. Three independent authors performed a thorough literature search using PubMed, ScienceDirect, and Google Scholar up until January 2022. The authors selected in vitro studies that used long fibers placed horizontally in posterior teeth with large MOD cavities to reinforce these teeth. From 1683 potentially relevant articles, 11 publications met our inclusion criteria. Seven out of eleven studies showed that horizontal splinting with long fibers improved the fracture resistance of the restored teeth. Three articles showed no significant difference between the fracture resistance of the restored groups. Only one article reported a lower fracture resistance to the horizontally splinted group, compared to conventional direct composite restoration. Within the limitations of this review, evidence suggests that long fiber reinforcement could be used to improve the fracture resistance of heavily restored teeth.

Monolithic Endocrown Vs. Hybrid Intraradicular Post/Core/Crown Restorations for Endodontically Treated Teeth; Cross-sectional Study

The gold standard for restoring Endodontically Treated Teeth (ETT) with successful clinical longevity requires having minimal invasive preparations and maximal tissue conservation. Many dentists still consider hybrid post/core/crown to be the first choice for restoring ETT. Endocrown is a viable alternative treatment modality to hybrid post/core/crown. This study aims to assess the proper judgment of dentists working in Riyadh, Saudi Arabia on the use of monolithic endocrown versus hybrid post/core/crown for restoring ETT. The IRB of Princess Nourah Bint Abdulrahman University (PNU) Institutional Review Board reviewed this study. The questionnaire was validated and electronically distributed. The participants were pre-informed that their responses are completely anonymous and used for professional purposes only. The questionnaire surveyed dentists working in Riyadh, Saudi Arabia, about their preference for different ETT restorative modalities at various clinical scenarios. Data were analyzed using One-way ANOVA and t-test. All P-values of < 0.05 were considered statistically significant. A total of 275 responses were collected; 61.45% were females and 38.55% males. 56% of them were general practitioners, while 16% were consultants. Prefabricated post/core was the most preferred technique among the participants (18.55%), followed by endocrown (12.36%), and lastly, cast post/core (8.73%). The amount of remaining tooth structure was the most influential in the treatment selection (30.18%), followed by the presence or absence of 1–2 mm ferrule (17.82%). Interocclusal space (12.36%) was the least influential factor. Endocrown recorded 63.27% as the most preferred line of treatment in case of insufficient inter-occlusal space. 40.36% preferred endocrown for patients with occlusal risk factors. The amount of the remaining tooth structure and the tooth position significantly affect the treatment options of the participants. Endocrown was the most preferred treatment modality for restoring ETT for patients with occlusal consideration.

Fracture Resistance of Titanium and Fiber Dental Posts: A Systematic Review and Meta-Analysis

PURPOSE

The fracture resistance of dental post systems is influenced by the material of the post. The purpose of this systematic review and meta-analysis was to assess if there is a difference in fracture resistance between prefabricated dental titanium posts and fiber posts.

METHODS

An online electronic search was performed using the PubMed, Scopus, and Web of Science databases for in vitro studies published from 2010 to 2020 in English. The retrieved eligible studies that compared the fracture resistance of titanium and fiber posts on human teeth were selected. The pooled standardized mean difference (SMD) with a 95% confidence interval was calculated. In addition, the trial sequential analysis (TSA) was performed to test if the available studies are sufficient to make conclusive evidence.

RESULTS

Of the 1165 retrieved studies, 17 studies were included in the qualitative analysis, while 16 studies were included in the quantitative analysis. Because of the high heterogeneity among studies, data from 10 studies were pooled and submitted to TSA. A total of 852 teeth were evaluated for fracture of the posts in 27 independent comparison groups. The pooled effect of the residual studies revealed no significant difference between titanium and fiber posts (SMD = -0.12; 95% CI = -0.30, 0.06; p = 0.20). Results of the TSA revealed no conclusive evidence.

CONCLUSIONS

The results of the current evidence revealed no significant difference between fiber and titanium posts. The evidence is insufficient, and more standardized in vitro studies are required.

Prognostic validity of the Periapical and Endodontic Status Scale for the radiographically assessed 2-year treatment outcomes in teeth with apical periodontitis: a prospective clinical study

Background

Endodontic treatment planning and treatment success evaluation are largely based on radiographic assessment of anatomical and treatment-related parameters of teeth with apical periodontitis (AP). This prospective clinical study aimed to assess radiographically the 2-year endodontic treatment outcomes for teeth with AP, and to evaluate prognostic validity of Periapical and Endodontic Status Scale (PESS).

Methods

A total of 128 patients, representing 176 teeth with AP were examined by cone-beam computed tomography at baseline and at 24 months after endodontic treatment. Treatment outcome was evaluated using estimates of periapical radiolucency and the relationship between anatomical structures and location. The strength of the associations between these and treatment-related parameters was tested by logistic regression analysis. PESS sensitivity and specificity were calculated for every treatment risk group (low, moderate, high) of teeth.

Results

One hundred and fifty-seven teeth, representing 350 root canals had a positive treatment outcome, while 19 teeth, representing 53 root canals had a negative treatment outcome at 24 months. The probability of negative outcome was 25 times higher in the moderate/high-risk group than in the mild-risk group of teeth (OR = 25.1; 95%CI [12.2–51.5]). Pre-treatment complications and retreatment cases with radiolucency were associated with negative outcomes (OR = 35.9; 95%CI [12.6–102.4]; OR = 26.437; 95%CI [10.9–64.1], respectively). PESS sensitivity and specificity was over 80% in all risk groups except for high risk group, due to very low number of cases.

Conclusions

Endodontic treatment outcome depends on the severity of periapical changes. The presence of complications and retreatment cases with periapical lesions are associated with negative treatment outcome. The PESS is a valid instrument to predict outcome of teeth with low-moderate treatment risk of AP.

Influence of remaining tooth substance and post-endodontic restoration on fracture strength of endodontically treated maxillary incisors

The aim is to evaluate the influence of remaining tooth substance and post-endodontic restoration on fracture strength of endodontically treated maxillary incisors. 150 maxillary central incisors were divided into three groups, Group 0, intact teeth; Group 1, removal of distal wall; Group 2, removal of mesial and distal walls, and further into two subgroups A₀,A₁,A₂ and B₀,B₁,B₂ according to post-endodontic restoration (post/no-post), then loaded to fracture. Interactions among variables and intergroup significance were tested with two-way ANOVA and Kruskal Wallis's tests (p≤0.05). Tukey's test was applied for multiple comparisons. Statistically significant differences were found between groups B₁-A₁, and B₂-A₂, but they were not found between B₀-A₀. Intragroup analysis showed statistically significant differences in both groups post/no-post with decreasing dental substance. Fiber post placement causes an increase in fracture strength and a reduction of irreparable fractures in endodontically treated maxillary central incisors that lost at least one wall.

Fracture strength of endodontically treated premolars restored with different post systems and metal-ceramic or monolithic zirconia crowns

The purpose of this study was to investigate the fracture strength of endodontically treated human maxillary premolars (ETP) restored with posts and metal ceramic (MC) or monolithic zirconia (MZ) crowns. Sixty ETP were randomly divided into 3 groups. Teeth in control group (C) received a resin filling. ETP in the MC group were restored with prefabricated metal posts, composite cores and MC crowns while in the MZ group with glass-fiber posts, composite cores and MZ crowns. Half of the specimens were loaded at a 135° angle and half under axial loading until fracture. The fracture modes were divided in repairable and irreparable using optical microscopy. Mean fracture strength was significantly higher for MC than for MZ crowns and control group only under axial loading. The distribution of repairable and irreparable failures presented no significant differences. Crown placement significantly improved the fracture strength of ETP irrespectively of post and crown type.

The restoration of root filled teeth: a review of the clinical literature

Clinicians often face dilemmas regarding the most appropriate way to restore a tooth following root canal treatment. Whilst there is established consensus on the importance of the ferrule effect on the predictable restoration of root filled teeth, other factors, such as residual tooth volume, tooth location, number of proximal contacts, timing of the definitive restoration and the presence of cracks, have been reported to influence restoration and tooth survival. The continued evolution of dental materials and techniques, combined with a trend towards more conservative endodontic-restorative procedures, prompts re-evaluation of the scientific literature. The aim of this literature review was to provide an updated overview of the existing clinical literature relating to the restoration of root filled teeth. An electronic literature search of the PubMed, Ovid (via EMBASE) and MEDLINE (via EMBASE) databases up to July 2020 was performed to identify articles that related the survival of root filled teeth and/or restoration type. The following and other terms were searched: restoration, crown, onlay, root canal, root filled, post, clinical, survival, success. Wherever possible, only clinical studies were selected for the literature review. Full texts of the identified articles were independently screened by two reviewers according to pre-defined criteria. This review identifies the main clinical factors influencing the survival of teeth and restorations following root canal treatment in vivo and discusses the data related to specific restoration type on clinical survival.

Microtomographic Analysis of Resin Composite Core Material Porosity

PURPOSE

To nondestructively evaluate the porosity of ten contemporary resin composite core materials using microtomographic (microCT) analysis.

MATERIAL AND METHODS

Resin composite core material samples (n = 12) including dual-cure, visible light cure only, and a self-cure material were fabricated using a standardized mold following manufacturer's recommendations. After storage in phosphate buffered saline for one week, specimens were analyzed using a microCT unit at 5.3-µm resolution over a rotational range of 360°. Image 3D recombination and analysis was accomplished using microCT software. Evaluated parameters included material volume investigated, closed pore number and volume, as well as closed pore percentage. Parameter mean values were evaluated with Kruskal-Wallis/Dunn at a 95% confidence level (α = 0.05).

RESULTS

Mean percent total porosity with standard deviation identified significant differences in decreasing order as Ti-Core: 2.2 (0.4) > Ti-Core Auto E: 1.3 (0.3) = Ti-Core Flow Plus: 1.1 (0.02) > Clearfil Photo Core: 0.94 (0.5) = Clearfil DC Core Plus: 0.6 (0.18) = MultiCore Flow: 0.58 (0.1) > Fluorocore 2+: 0.14 (0.2) = Build-It FR: 0.068 (0.02) = Gradia Core: 0.03 (0.02) = Rebilda DC: 0.02 (0.01). A pilot microCT evaluation evaluating a mixing tip revealed incomplete mixture between the two resins with porosity introduced from turbulence as the materials are forced through the tip during preparation.

CONCLUSIONS

A wide range of porosity was identified between the ten materials evaluated. These preliminary results warrant more investigation evaluating additional resin composite core materials, the preparation capabilities of automix tips, and porosity presence in the unmixed materials.

Fracture resistance and marginal gap formation of post-core restorations: influence of different fiber-reinforced composites

OBJECTIVES

The aim was to explore the fracture behavior and marginal gap within the root canal of endodontically treated (ET) premolars restored with different fiber-reinforced post-core composites (FRCs). Further aim was to evaluate the composite curing at different depths in the canal.

MATERIALS AND METHODS

Eighty-seven intact upper premolars were collected and randomly divided into six groups. After endodontic procedure, standard MOD cavities were prepared and restored with their respective fiber-reinforced post-core materials: group 1: prefabricated unidirectional FRC-post + conventional composite core; group 2: prefabricated unidirectional FRC-post + short fiber composite (SFRC) core; group 3: individually formed unidirectional FRC-post + conventional composite core; group 4: randomly oriented SFRC directly layered as post and core; group 5: individually formed unidirectional FRC + randomly oriented SFRC as post and core. After restorations were completed, teeth (n = 3/group) were sectioned and then stained. Specimens were viewed under a stereo microscope and the percentage of microgaps within the root canal was calculated. Fracture load was measured using universal testing machine.

RESULTS

SFRC application in the root canal (groups 4 and 5) showed significantly higher fracture load (876.7 N) compared to the other tested groups (512-613 N) (p < 0.05). Post/core restorations made from prefabricated FRC-post (group 1) exhibited the highest number of microgaps (35.1%) at the examined interphase in the root canal.

CONCLUSIONS

The restoration of ET premolars with the use of SFRC as post-core material displayed promising performance in matter of microgap and load-bearing capacity.

CLINICAL SIGNIFICANCE

Fracture resistance of ET premolar restored by bilayered composite restoration that includes both SFRC as post-core material and surface conventional resin seems to be beneficial.

Pino de fibra de vidro anatômico: relato de caso

Introdução: Pinos pré-fabricados de fibra de vidro possuem boas propriedades mecânicas e estéticas. Porém, estes podem não se adaptar bem em canais amplos ou excessivamente cônicos, prejudicando sua retenção ao canal radicular. Uma alternativa para esta desvantagem é a utilização da técnica de pino anatômico. Objetivo: O objetivo do relato de caso foi apresentar a técnica de confecção de um pino fibra de vidro anatômico em dente anterior, com reduzido remanescente coronário e ampla embocadura do canal radicular. Relato de Caso: Paciente masculino, 49 anos, procurou atendimento odontológico com queixa da aparência estética de seus dentes anteriores superiores. Após remoção de uma coroa metalocerâmica e um pino-núcleo metálico fundido do elemento 12, foram confeccionados um pino de fibra de vidro anatômico, núcleo de preenchimento e coroa provisória. Foram realizadas as facetas em resina composta nos elementos 13, 11, 21, 22 e 23. Uma coroa de cerâmica reforçada por dissilicato de lítio (IPS e.max CAD, Ivoclar Vivadent) foi cimentada no elemento 12. Conclusões: Através da técnica pino de fibra de vidro anatômico, é possível reabilitar dentes anteriores tratados endodonticamente sem a utilização de pinos metálicos, apresentando bons resultados estéticos. Entretanto, uma condição oclusal dentro dos princípios de uma oclusão mutuamente protegida deve ser almejada para garantir longevidade da restauração.

Fractographical Analysis and Biomechanical Considerations of a Tooth Restored With Intracanal Fiber Post: Report of the Fracture and Importance of the Fiber Arrangements

OBJECTIVE

This article aims to present a fractographic analysis of an anterior tooth restored with a glass fiber post with parallel fiber arrangement, taking into account force vectors, finite element analysis, and scanning electron microscopy (SEM).

METHODS

A patient presented at the Faculty of Dentistry (Federal University of Santa Maria, Brazil) with an endodontically treated tooth (ETT), a lateral incisor that had a restorable fracture. The treatment was performed, and the fractured piece was analyzed using stereomicroscopy, SEM, and finite element analysis.

RESULTS

The absence of remaining coronal tooth structure might have been the main factor for the clinical failure. We observed different stresses actuating in an ETT restored with a fiber post as well as their relationship with the ultimate fracture. Tensile, compression, and shear stresses presented at different levels inside the restored tooth. Tensile and compressive stresses acted together and were at a maximum in the outer portions and a minimum in the inner portions. In contrast, shear stresses acted concomitantly with tensile and compressive stresses. Shear was higher in the inner portions (center of the post), and lower in the outer portions. This was confirmed by finite element analysis. The SEM analysis showed tensile and compression areas in the fiber post (exposed fibers=tensile areas=lingual surface; nonexposed fibers=compression areas=buccal surface) and shear areas inside the post (scallops and hackle lines). Stereomicroscopic analysis showed brown stains in the crown/root interface, indicating the presence of microleakage (tensile area=lingual surface).

CONCLUSION

We concluded that glass fiber posts with parallel fibers (0°), when restoring anterior teeth, present a greater fracture potential by shear stress because parallel fibers are not mechanically resistant to support oblique occlusal loads. Factors such as the presence of remaining coronal tooth structure and occlusal stability assist in the biomechanical equilibrium of stresses that act upon anterior teeth.