Clinical longevity of metallic versus fiberglass intraradicular posts: a systematic review / Longevidade clínica de pinos intraradiculares metálicos versus de fibra de vidro: uma revisão sistemática

Objective: This systematic review aims to compare the clinical longevity of metallic and fiberglass intraradicular posts in teeth with severely compromised crowns, utilizing randomized clinical trials and case reports published in the last eleven years. Material and Methods: The research was conducted on PubMed, Medline, Lilacs, and BBO databases using the first search strategy with the descriptors 'dental posts,' 'longevity,' 'fiberglass-reinforced posts' or 'metallic posts.' The second search strategy involved analyzing the references of articles identified by the first search. Both studies were carried out with stringent inclusion and exclusion criteria. Results: No statistically significant and clinically relevant differences in longevity were observed between metallic and fiberglass posts. Conclusion: The clinical success and durability of the restorative procedure using intraradicular posts primarily depend on the remaining amount around the post (ferrule), the type and position of the tooth in the arch (impacting the masticatory forces exerted on the restored tooth), and the correct application of the cementation technique. It is noteworthy that fiberglass posts offer substantial advantages by presenting a modulus of elasticity similar to dental structure, ensuring a more homogeneous distribution of masticatory forces and reducing the risk of fractures. These findings have practical implications for material selection in restorative procedures involving intraradicular posts.(AU)

Objetivo: Esta revisão sistemática visa comparar a longevidade clínica de pinos intrarradiculares metálicos e de fibra de vidro em dentes com coroas severamente comprometidas, através de estudos clínicos randomizados e relatos de casos, publicados nos últimos onze anos. Material e Métodos: A pesquisa foi conduzida nas bases de dados PubMed, Medline, Lilacs e BBO, utilizando a primeira estratégia de busca com os s 'pinos dentais' e 'longevidade' e 'pinos reforçados com fibra de vidro' ou 'pinos metálicos'. A segunda estratégia de busca consistiu na análise das referências dos artigos identificados pela primeira estratégia. Ambos os estudos foram delineados com critérios rigorosos de inclusão e exclusão. Resultados: Não se constataram diferenças estatisticamente significativas e clinicamente relevantes na longevidade entre pinos metálicos e de fibra de vidro. Conclusão: O êxito clínico e a durabilidade do procedimento restaurador empregando pinos intrarradiculares dependem primordialmente da quantidade de remanescente ao redor do pino (férula), do tipo e posição do dente na arcada (o que impacta nas forças mastigatórias exercidas sobre o dente restaurado) e da aplicação correta da técnica de cimentação.Destaca-se que o pino de fibra de vidro oferece vantagens substanciais ao apresentar módulo de elasticidade similar à estrutura dentária, assegurando uma distribuição mais homogênea das forças mastigatórias e reduzindo o risco de fraturas (AU)

Dental Fiber-Post Systems: An In-Depth Review of Their Evolution, Current Practice and Future Directions.

The field of dental medicine is constantly evolving and advancing toward minimally invasive techniques. Several studies have demonstrated that bonding to the tooth structure, particularly enamel, yields the most predictable results. In some instances, however, significant tooth loss, pulpal necrosis, or irreversible pulpitis may limit the options available to the restorative dentist. In these cases, placement of a post and core followed by a crown is the preferred treatment option, provided all requirements are met. This literature review provides an overview of the historical development of dental FRC post systems as well as a comprehensive examination of the currently available posts and their bonding requirements. In addition, it offers valuable insights for dental professionals seeking to understand the current state of the field and the prospects of dental FRC post systems.

Comparative Evaluation of Artifacts Originated by Four Different Post Materials Using Different CBCT Settings.

The aim of this study was to evaluate whether cone beam computed tomography (CBCT) images in the presence of four different post materials, obtained from different kVps with varying resolutions and varying metal artifact reduction (MAR) algorithms, differed in artifact estimation, and to compare tooth regions in terms of artifact value. MATERIALS AND METHODS: Forty premolar teeth were used in this study. Root canals were treated, and teeth were randomly distributed into four subgroups (n = 10) for the preparation of post materials: titanium, gold (Nordin), quartz fiber (Bisco DT Light), and glass fiber (Rely X). The CBCT images were taken with two different kVps, three different metal artifact reduction (MAR) algorithm options, and two different resolutions. For each protocol, the effective dose was calculated according to the dose area production (DAP) value. The standard analysis of variance technique and the Tukey multiple comparison adjustment method were used to assess interactions among material types, kVp, MAR, and voxel settings. RESULTS: More artifacts were found in the middle third than in the cervical third (p < 0.05). The mean value of artifacts was highest for gold (Nordin), 90 kVp, no MAR, and 100 voxel size. Glass or quartz fiber posts at low resolution, with high MAR and 96 kVp, originated fewer artifacts. Moreover, the use of 90 and 96 kVp with 200 voxel size and high MAR provided the least amount of radiation. CONCLUSION: The best setting for radiographic follow-up of post materials on the Planmeca ProMax is 96 kVp with low resolution and high MAR; this setting produced one of the lowest effective doses. CLINICAL SIGNIFICANCE: This study estimated the best scanning protocol by lowering the effective dose to a minimum level according to the "as low as reasonably achievable" principle, as well as assessing the tooth region and the post material generating the fewest artifacts, in order to prevent image interpretation challenges such as false-positive and false-negative results stemming from the deterioration of the visibility of the root canal due to perforation, fractures, and voids in the root canal region.

Molar Incisor Hypomineralization: Awareness among Postdoctoral Dental Residents: A Cross-Sectional Study.

BACKGROUND: Molar incisor hypomineralization (MIH) is the presentation of an enamel defect, where incisors and one (or more) molars are affected. Identifying MIH is significant in restoring its visual defect and avoiding pain or other consequences of this condition. The present cross-sectional study aimed to evaluate the awareness, ability, and confidence in identifying MIH among postgraduate residents in the state of Nevada. METHODS: This cross-sectional study was conducted among postdoctoral dental residents at the School of Dental Medicine, University of Nevada, Las Vegas. This cross-sectional study used images of cases of MIH and a survey to collect the data. The survey included demographics, educational background, and basic knowledge of MIH. RESULTS: The response rate to the invitation to participate was 91%. The confidence in identifying MIH was 100%, 50%, and 33.3% for pediatric, orthodontic, and general practice residency (GPR). A total of 70% were aware of this anomaly from their predoctoral dental education and indicated the need for further related education. There was 33% confusion with fluorosis and 16.6% with amelogenesis imperfecta. A total of 66.6% of the participants indicated that they require further education relating to MIH. CONCLUSION: Within the limitations of the present investigation, MIH awareness among the investigated groups varied but was highest amongst the pediatric residents.

Evaluation of the Efficacy of Two Fibre-Reinforced Post Removal Techniques.

OBJECTIVE: The aim of this in-vitro study was to compare the amount of material (post and luting agent) and root dentine removed using two methods for removal of endodontic posts. METHODS: Human premolar teeth (n=20) were sectioned at the CEJ and fibre reinforced posts were cemented at a length of 10mm following root canal therapy. Teeth were randomly assigned to two study groups. The methods of removal compared were: the use of RTD re-access kit (Composipost, RTD, France, St Egreve) in a conventional hand-piece driven by an electric motor (Group A); or a long tapered diamond bur (FG Diamond grit bur, Dentsply Ltd, UK) in an air-driven high speed turbine (Group B). Using micro- CT the volume of material and root dentine removed for each sample was calculated. RESULTS: Both the volume of material removed and the volume of root dentine removed were significantly greater when using diamond burs. (p⟨0.001). The volume of dentine removed using the diamond bur method (mean 22.64mm³) was greater than the volume removed using the reaccess kit (mean 11.71mm³). SIGNIFICANCE: Use of a diamond bur to remove fibre reinforced endodontic post removal poses higher risk for root perforation compared to the reaccess kit.

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.

Awareness, Knowledge, Attitude and Empathy Levels of Dental Postgraduates Towards Their Patients During Practice and Research-A Questionnaire Based Survey.

Empathy is vital in ensuring the quality of the patient-clinician relationship. Empathy in the health care setting is the ability to understand a patient's experiences and feelings and communicate this understanding for better clinical outcomes in dental treatments. The study aimed to compare levels of empathy in post-graduate dental students across the different years of the master's degree course. Questionnaire forms distributed among post graduate students and awareness, knowledge, attitude, and empathy levels towards their patients were assessed. Responses of all the post-graduate students of all specialties in a dental institute were subjected to statistical analysis to know and compare their empathy towards the patients during their clinical practice and research throughout their three-year master's degree. The mean empathy score was 52.01 (maximum of 100), with a standard deviation of 6.69. The empathy scores decreased slightly from the first to the third year of the master's degree. The participant's age, marital status, place of residence, and specialties of dental post-graduation showed much significant difference in empathy levels. The study found slight significant gender differences in empathy among the participants. The empathy scores declined gradually very slightly as they were promoted to the next level in the course. The increase in empathy levels found in this study is more significant than those reported in similar studies due to the inclusion of educational and orientation programs at the time of admission into post-graduate studies.

Scattering and phase-contrast X-ray methods reveal damage to glass fibers in endodontic posts following dental bur trimming.

OBJECTIVES: There is concern that the integrity of fiberglass dental posts may be affected by chairside trimming during treatment. We hypothesize that hard X-ray methods of phase contrast-enhanced micro-CT (PCE-CT) and synchrotron based X-ray refraction (SXRR) can reliably identify and help characterize the extent of damage. METHODS: Fiberglass posts were imaged both as manufactured and following trimming with a diamond bur. Each of the posts was imaged by SXRR and by PCE-CT. Datasets from PCE-CT were used to visualize and quantify 2D and 3D morphological characteristics of intact and of damage-affected regions caused by trimming. RESULTS: The SXRR images revealed fiber inhomogeneities from manufacturing with a significant increase in internal surfaces in sample regions corresponding to damage from trimming. PCE-CT volumes unveiled the micromorphology of single fibers in the posts and some damage in the trimmed area (e.g. fractures, splinters and cracks). Area, perimeter, circularity, roundness, volume and thickness of the glass fibers in the trimmed area were statistically different from the control (p < 0.01). SIGNIFICANCE: The integrity of single fibers in the post is critical for bending resistance and for long-term adhesion to the cement in the root canals. Damage to the fibers causes substantial structural weakening across the post diameter. Glass fragments produced due to contact with the dental bur may separate from the post and may significantly reduce bond capacity. The above mentioned synchrotron-based imaging techniques can further facilitate assessment of the structural integrity and the appearance of defects in posts (e.g. after mechanical load).

Laser Treatment of Fiber Post and Final Push-Out Bond Strength: A Systematic Review and Meta-Analysis.

Purpose: This review article tries to answer this question: "What are the effects of laser surface treatment of fiber posts (FPs), compared with other surface roughening methods, on bond strength of cemented FPs?" Methods: Search was carried out in six electronic databases by focusing on defined key words. Related titles and abstracts, up to March 2019, were collected, read, and selected for quality assessments. A total of 2408 articles were included in the study at the initial stage of the searching phase. Results: Finally, seven studies were recognized to be reliable to be reviewed and meta data analysis in the study. All the studies were in vitro with a total of 340 samples. None of the Er:YAG (-0.27, 95% CI: -2.29 to 1.76; p = 0.79) and Er,Cr:YSGG (-0.04, 95% CI: -1.43 to 1.35; p = 0.95) treated samples showed any significant overall mean differences in final push-out bond strength (PBS) compared with the control groups. Conclusions: Laser pretreatment of FP surfaces might not be effective in providing high PBS. FP surface are susceptible to damage of high-level laser irradiation and might show decreased bond strength.

Surface characterization and bonding properties of milled polyetheretherketone dental posts.

PEEK has been used in many dental applications except intra-radicular post. The aim of this study is to test polyetheretherketone (PEEK) as a dental post material through tensile bond strength (TBS) and surface roughness (SR), and to compare it with glass-fiber and cast-metal posts. Thus, 60 human maxillary central incisors with a single root were endodontically treated and divided into three groups (n = 20) according to the type of post (Group P: PEEK, Group F: Glass-fiber, Group M: Cast-metal). Appropriate surface treatment was employed for each group and SR was determined by a three-dimensional non-contact profilometer before cementation. All posts were luted to the canal dentin using self-etch resin cement (Panavia F2.0). Pull-out test was performed on a universal testing machine at a speed of 0.5 mm/min crosshead speed until failure, and TBS were calculated. One-way ANOVA, Tukey's HSD, and Pearson chi-squared tests were performed for statistical analyses (α = 0.05). According to the results, group F demonstrated the highest SR (2.93 ± 0.18 µm) and lowest TBS values (10.05 ± 0.53 MPa), while group P exhibited lowest SR (1.37 ± 0.11 µm) and highest TBS values (14.33 ± 0.58 MPa) (p < 0.001). No significant differences in failure modes were identified among groups, mostly adhesive (p = 0.243). As conclusion, PEEK may be a reliable and contemporary option for dental post systems when used with appropriate surface treatment and luting agent. This high-performance polymer may be a novel candidate as a contemporary dental post system due to its superior mechanical, chemical, thermal, and esthetical properties with low risk of fracture.

Simplified ethanol wet-bonding technique: an alternative strategy for resin-dentin bonding in root canals.

The objective of this study was to evaluate the effect of the simplified ethanol wet-bonding technique on luting of posts to intraradicular dentin. The effect was assessed by push-out bond strength testing and confocal laser scanning microscopic analysis. Thirty endodontically treated roots were distributed into 3 groups (n = 10): water wet-bonding; stepwise ethanol wet-bonding; and simplified ethanol wet-bonding. After cementation of the posts, the roots were sectioned. Specimens were stored for 24 hours or 1 year before they were stressed to failure. Specimens from each group were processed for microscopic analysis. Data were analyzed using a 2-way analysis of variance and the Tukey test (α = 0.05). Statistically significant differences in push-out bond strength values were observed between the technique groups (P < 0.001) and between the storage periods (P = 0.009). The bond strength results in the group bonded using the simplified ethanol wet-dehydration approach did not differ from those in the group bonded using the stepwise ethanol technique at either storage time interval (P > 0.05). From 24 hours to 1 year, there was a similar decrease in bond strength for specimens prepared with the simplified and stepwise techniques. The microscopic results confirmed that ethanol wet-bonding technique improved the quality of the interface. The simplified ethanol wet-dehydration protocol achieved bond strengths and stability over time that were similar to those obtained with the stepwise ethanol technique and may be considered an alternative strategy to accomplish resin cement-root dentin bonding.

Semi-interpenetrating network composites reinforced with Kevlar fibers for dental post fabrication.

This study evaluates the reinforcement of semi-interpenetrating network composites of 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropyl)phenyl] propane (Bis-GMA)/ triethyleneglycol dimethacrylate (TEGDMA)/polymethyl methacrylate (PMMA) and 25% titanium dioxide (TiO2) nanofiller with surface treated Kevlar fibers for potential application as dental posts. The post material was subjected to thermo-cycling and flexural strength determined, characterised by dynamic mechanical analysis, water sorption, radiopacity and cytotoxicity tests. The results were compared with everStick®POST. Kevlar pre-treatment with acetic acid and silane coupling agent demonstrated a clear effect on the flexural strength of the composites with a significant increase compared to composites with fibers without surface treatment. The inclusion of TiO2 into the final formulation provided the desired radiopacity and improved both aesthetics and flexural strength, which exhibits a higher resistance on thermocycling. The ratios of fatigue limit to static flexural strength were about 0.73 for Kevlar and 0.58 for everStick®POST; MTT assay confirmed the absence of any toxic eluents, indicating its feasibility as new intracanal post material.

Effect of laser irradiation on push-out bond strength of dental fiber posts to composite resin core buildups: A systematic review and meta-analysis.

BACKGROUND: The bonding of fiber posts (FPs) to composite resin core buildups is a challenge due to limited penetration of resin to the polymeric matrix of FPs. This review article tries to answer this question: "What are the effects of laser surface treatment of FPs, compared to other surface roughening methods, on push-out bond strength (PBS) of FPs bonded to composite resin core buildups?" METHODS: Searches were run in seven electronic databases with a focus on proper key words. Related titles and abstracts, up to February 2019, were screened, selected, read and subjected to quality assessments. RESULTS: After the initial search, a total of 2635 articles were included in the study. Finally, 6 studies were reliable enough in methodology to be included. All the studies were in vitro with a total of 359 samples. Er:YAG (-0.05, 95% CI: -2.96 to 2.86; P = 0.97) and Er,Cr:YSGG (0.84, 95% CI: -0.12 to 1.81; P = 0.08) treated samples showed no significant overall mean differences in final PBS compared to the control groups. Moreover, pretreatment with Er,Cr:YSGG laser and sandblasting with 50 µm alumina showed an overall mean difference of -0.42 for PBS (95% CI: -1.23 to 0.39) with no significant differences. CONCLUSIONS: Laser irradiation of FPs seems to provide no significant increase in PBS values of FPs bonded to composite resin core buildups. Effects of surface treatment of FPs with laser irradiation and sandblasting with 50 µm alumina might be similar in increasing the final PBS, either.

3D FEA of cemented glass fiber and cast posts with various dental cements in a maxillary central incisor.

This study aimed to analyse and compare the stability of two dental posts cemented with four different luting agents by examining their shear stress transfer through the FEM. Eight three-dimensional finite element models of a maxillary central incisor restored with glass fiber and Ni-Cr alloy cast dental posts. Each dental post was luted with zinc phosphate, Panavia resin, super bond C&B resin and glass ionomer materials. Finite element models were constructed and oblique loading of 100 N was applied. The distribution of shear stress was investigated at posts and cement/dentine interfaces using ABAQUS/CAE software. The peak shear stress for glass fiber post models minimized approximately three to four times of those for Ni-Cr alloy cast post models. There was negligible difference in peak of shear stress when various cements were compared, irrespective of post materials. The shear stress had same trend for all cement materials. This study found that the glass fiber dental post reduced the shear stress concentration at interfacial of post and cement/dentine compared to Ni-Cr alloy cast dental post.

New functional and aesthetic composite materials used as an alternative to traditional post materials for the restoration of endodontically treated teeth.

OBJECTIVES: To tailor composites of polyethylene-hydroxyapatite to function as a new intracanal post for the restoration of endodontically treated teeth (ETT). METHODS: Silanated hydroxyapatite (HA) and zirconium dioxide (ZrO2) filled low-density polyethylene (LDPE) composites were fabricated by a melt extrusion process and characterised using infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The flexural strength and modulus were determined in dry state and post ageing in simulated body fluid and fractured surfaces analysed by SEM. The water uptake and radiographic appearance of the experimental composites were also measured and compared with a commercially known endodontic fibre post. Data were submitted to one-way analysis of variance (ANOVA) and post hoc Tukey multiple comparison tests at a level of significance P<0.05. RESULTS: The LDPE/HA composites were structurally flexible and the HA content had a significant effect on the flexural strength and modulus. A univariate analysis of variance showed no significant differences in modulus and strength (P<0.05) post accelerated ageing in simulated body fluid with very low water uptake. The melting point of the LDPE/HA composites ranged between 135 and 136°C, which would facilitate removal in case of retreatment using conventional dental heating devices. The inclusion of HA reduced the damping thereby enhancing dimensional stability, whilst the addition of zirconia yielded a semi-translucent material that was sufficiently radiopaque, comparable to commercial posts, thus yielding aesthetic materials. CONCLUSIONS: Innovative materials for restoration of ETT were developed; offering considerable benefits over the currently available material in terms of biomechanical and thermal properties. CLINICAL SIGNIFICANCE: This study provided a new option for the development of a new intracanal post made up of functional and aesthetic composites.

Preparation and characterisation of poly p-phenylene-2,6-benzobisoxazole fibre-reinforced resin matrix composite for endodontic post material: a preliminary study.

OBJECTIVES: Currently used fibre-reinforced composite (FRC) intracanal posts possess low flexural strength which usually causes post fracture when restoring teeth with extensive loss. To improve the flexural strength of FRC, we aimed to apply a high-performance fibre, poly p-phenylene-2, 6-benzobisoxazole (PBO), to FRCs to develop a new intracanal post material. METHODS: To improve the interfacial adhesion strength, the PBO fibre was treated with coupling agent (Z-6040), argon plasma, or a combination of above two methods. The effects of the surface modifications on PBO fibre were characterised by determining the single fibre tensile strength and interfacial shear strength (IFSS). The mechanical properties of PBO FRCs were characterised by flexural strength and flexural modulus. The cytotoxicity of PBO FRC was evaluated by the MTT assay. RESULTS: Fibres treated with a combination of Z-6040 and argon plasma possessed a significantly higher IFSS than untreated fibres. Fibre treated with the combination of Z-6040-argon-plasma FRC had the best flexural strength (531.51 ± 26.43MPa) among all treated fibre FRCs and had sufficient flexural strength and appropriate flexural moduli to be used as intracanal post material. Furthermore, an in vitro cytotoxicity assay confirmed that PBO FRCs possessed an acceptable level of cytotoxicity. CONCLUSIONS: In summary, our study verified the feasibility of using PBO FRC composites as new intracanal post material. Although the mechanical property of PBO FRC still has room for improvement, our study provides a new avenue for intracanal post material development in the future. CLINICAL SIGNIFICANCE: To our knowledge, this is the first study to verify the feasibility of using PBO FRC composites as new intracanal post material. Our study provided a new option for intracanal post material development.

Cytotoxicity of post and core composites as a function of environmental conditions.

OBJECTIVES: In the revised version of ISO 7405 there are so far no detailed recommendations concerning temperature and humidity during specimen production for light curing and chemically setting dental materials. The main objective of the present study was to observe if different environmental conditions during specimen production influence cytotoxicity and degree of conversion of four post and core composite materials and to investigate if cytotoxicity of post and core materials is influenced by their corresponding bonding substances. METHODS: Specimens of four different post and core composite materials (LuxaCore - Dual, Core X-Flow, Flow White and MultiCore Flow) were produced in a climate test chamber at 23°C/50% relative humidity or 37°C/95% relative humidity and were dual-cured or self-cured, with or without their corresponding bonding substances. Specimens were added to cell cultures immediately after production or after preincubation for 7 days. Specimens were incubated with L-929 fibroblasts for 72h and cell numbers determined by a flow cytometer. FTIR spectroscopic measurements of post and core materials were performed at the same temperature conditions as for the cytotoxicity assay (23°C or 37°C). RESULTS: Dual-cured specimens of all post and core composites exhibited less cytotoxicity under both environmental conditions than self-cured specimens. All self-cured specimens manufactured at 37°C/95% showed less cytotoxicity than specimens produced at 23°C/50%. All dual-cured specimens showed similar cytotoxicity at both environmental conditions. After 7 days of preincubation most dual-cured specimens produced at 23°C/50% showed less cytotoxicity than self-cured specimens (with the exception of Flow White). Compared to fresh specimens, 7-day aged specimens of most materials showed reduced cytotoxicity. Materials already showing low cytotoxicity as fresh specimens did not further reduce their cytotoxicity after 7 days of preincubation. For dual-cured materials the degree of conversion was higher compared to self-cured materials. SIGNIFICANCE: Different temperatures during specimen production have an impact on cytotoxicity and degree of conversion of dual-curing composite materials. Detailed recommendations for standardization concerning environmental conditions during specimen production are required.

Detection of looseness degree of dental posts using natural frequency analysis.

This study examines the relationship between the retention force and natural frequency of dental posts cemented with zinc phosphate cement. Forty-two decoronated maxillary incisors were collected and embedded in resin blocks. The 7-mm post spaces were prepared for all test samples prior to cementing the 13-mm Para-Posts with zinc phosphate cement. The natural frequency values and retention forces of the zinc phosphate cement-cemented Para-Posts in various liquid/powder mixing ratios were measured. Thereafter, the natural frequency values of the zinc phosphate cement-cemented posts were continuously detected during ultrasonic vibration. Moreover, both the natural frequency values and the dislodgement forces in response to ultrasonic vibrations were measured for the pretreated post samples. Results showed that the natural frequency values of the posts significantly decreased from 8.8 ± 0.8 to 5.0 ± 0.5 kHz (P < 0.05) before and after ultrasound treatment, respectively. The natural frequency values and the dislodgement forces of tested posts had a highly linear relationship (R² = 0.99, P < 0.05). These findings suggest that natural frequency is a variable for monitoring the stability status of zinc phosphate cement-cemented dental posts.

Resistência à tração de pinos de fibra de vidro intrarradiculares: efeito de diferentes agentes cimentantes / Tensile strength of glass fiber posts in the intraradicular environment: effect of different luting cements

Avaliou-se, in vitro, a força de remoção por tração dos pinos de fibra de vidro (WP) de 1,2mm (White Post DC, FGM ), cimentados com 3 diferentes agentes de cimentação: cimento de fosfato de zinco (FZ) (S.S.WHITE); cimento resinoso dual (V) (Variolink, Ivoclar/ Vivadent) e cimento resinoso de polimerização química (M) (Multilink, Ivoclar/ Vivadent). Foram utilizados 45 dentes humanos unirradiculares e as coroas removidas 3 mm aquém da junção amelo-cementária. Os grupos foram divididos em função do agente de cimentação, a seguir: G1 (controle)- WP+FZ (n=15); G2- WP+V (n=15) e G3-WP+M(n=15). As raízes foram incluídas em resina acrílica autopolimerizável. Os espécimes foram armazenados em água destilada a 37º C, por 7 dias e submetidos ao teste de remoção por tração em uma máquina de ensaio mecânico MTS 810 (MTS System Corporation), com velocidade de 0,5 mm/min. As médias obtidas foram: FZ (95.1200 MPa); V (87.0680 MPa) e M (73.0500 MPa). Os resultados foram submetidos ao teste estatístico ANOVA e Tukey (p<0,05%). Concluiu-se que o grupo dos pinos de fibra de vidro cimentados com fosfato de zinco apresentou os maiores valores de resistência à remoção por tração, mas estatisticamente diferente somente para o grupo do Multilink.

This study evaluated, in vitro, the tensile stength of glass fiber post (WP), de 1.2mm, (White Post DC, FGM) cemented with three different luting agents: zinc phosphate cement (FZ) (S.S.WHITE); dual-polymerized resin luting agents (V) (Variolink, Ivoclar/ Vivadent) and autopolymerized resin luting agents (M) (Multilink, Ivoclar/ Vivadent). Forty-five human anterior teeth had the crowns removed 3 mm on this side at the cement-enamel junction. They were divide into 3 groups, as follows: G1- (control) WP+FZ (n=15); G2- WP+V (n=15) e G3-WP+M (n=15). The roots were mounted vertically in self-cured acrylic resin. The specimens were stored in destilled water for one week at 37ºC and fixed in a testing machine MTS 810 (MTS System Corporation) and loaded in tension at a cross-head speed of 0.5 mm/min until failure. The results were: zinc phosphate cement (95.1200 MPa); Variolink (87.0680 MPa) and Multilink (73.0500 MPa). The data was analyzed using ANOVA and Tukey tests at the 0.05 significance level. It was possible conclude that the glass fiber posts cimented with zinc phosphate cement presented the largest resistance values for the tension's removal, but significant different only for the Multilink's group.