Flexural strength of glass fibre‐reinforced posts bonded to dual‐cure composite resin cements

Davis P, Melo LSD, Foxton RM, Sherriff M, Pilecki P, Mannocci F, Watson TF. Flexural strength of glass fibre‐reinforced posts bonded to dual‐cure composite resin cements. Eur J Oral Sci 2010; 118: 197–201. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci The aims of this study were to evaluate the flexural strength of two different types of glass fibre‐reinforced posts bonded to dual‐cure composite resin cements. Forty glass methacrylate‐based fibre posts (GC Fiber Post) and 20 glass fibre inter‐polymerizing network posts (everStick POST) were divided into three groups. Group 1 contained 20 GC posts that were bonded to a dual‐cure composite cement (UnifilCore). Group 2 contained 20 Stick Tech posts that had adhesive applied (Scotchbond Multipurpose resin) and were bonded to a dual‐cure composite resin cement (RelyX Unicem). Group 3 contained 20 GC posts that were pretreated with a silane‐coupling agent before being treated with resin and composite, as in group 1. A 4‐point bend test was carried out to failure on all of the groups. Failure modes were determined using scanning electron microscopy. Pretreatment of the post surface with the silane‐coupling agent did not increase the flexural strength. The flexural strength of the Stick Tech post was significantly lower than the flexural strength of the GC post. The mode of failure for the GC Posts was adhesive, whereas the Stick Tech posts failed cohesively. Different flexural strengths and failure modes were observed among the two fibre post–resin systems.     

Guided Endodontics versus Conventional Access Cavity Preparation: A Comparative Study on Substance Loss Using 3-dimensional–printed Teeth

Introduction

The aim of this in vitro study was to compare endodontic access cavities in teeth with calcified root canals prepared with the conventional technique and a guided endodontics approach regarding the detection of root canals, substance loss, and treatment duration.

动静态导航技术在牙髓根尖周病治疗中的应用及展望

根管治疗及根尖手术是处理牙髓根尖周病的常规方法。相比裸眼操作,口腔手术显微镜的普及和应用有效提高了治疗精准度及预后。然而,在面临严重根管钙化、根尖周病损定位困难或毗邻重要解剖结构等复杂情况时,即使经验丰富的术者在进行显微牙髓治疗的过程中也存在风险因素。近年来,随着数字化信息技术的快速发展,动静态导航技术为应对疑难复杂牙髓根尖周病提供了行之有效的治疗新模式,即通过锥形束CT拍摄、口内扫描、结合导航软件设计手术虚拟入路,继而在三维打印导板或实时导航设备的辅助下进行精准根管治疗或根尖手术。本文对导航牙髓治疗的分类、特点以及国内外临床应用现状进行了系统阐述。     

Guided endodontics of calcified canals: The drilling path of rotary systems and intracanal dentin wear

This study evaluated the drilling path (mm) and the dentin wear (mm³) of two instruments used during guided endodontic access. Twenty mandibular incisors with calcified canals were selected using cone-beam computed tomography (CBCT) and fixed in articulated models. Preoperative CBCT scans were performed in combination with intraoral scanning, and the images were reconstructed in the Blue Sky Bio software for access planning and printing the guides. The access cavity was drilled with 1.0-mm-diameter bur (DSP) and 0.8-mm-diameter bur (Munce). Postoperative CBCT was performed, and the images obtained preoperative and postoperative were superimposed for the analyses. Data were analysed by a t-test and linear regression (α = 0.05). No difference was found in the drilling path (p = 0.422). However, the Munce bur had higher dentin wear than the DSP bur (p = 0.011). A positive linear correlation (R² = 0.859) was found between the factors.     

Mechanical properties of glass‐fibre‐reinforced composite posts after laser irradiation with different energy densities

The aim of the present study was to evaluate the effect of the surface treatments on flexural strengths and flexural modulus of glass‐fibre‐reinforced composite (GFRC) posts. Sixty‐three posts were randomly divided into 9 groups (n = 7), and various surface treatments were performed. The control group was left untreated. Other groups were treated with 9% hydrofluoric acid, sandblasting with 120 µm Al₂O₃ particles and Er,Cr:YSGG laser irradiation with different powers (1 W, 2 W, 3 W, 4 W, 5 W and 6 W). The samples were subjected to 3‐point bending test, and data were calculated. Statistical analysis was performed. The flexural strengths of fibre posts treated with sandblasting, hydrofluoric acid, 1 W and 2 W laser were statistically similar with control group (P > 0.01). However, the flexural strength of fibre posts treated with 3 W, 4 W, 5 W and 6 W laser was statistically lower than control group (P < 0.01). High laser irradiations cause melting on the post surface and breaks in fibrils.     

Frequency and distribution of teeth requiring endodontic therapy in an Argentine population attending a specialty clinic in endodontics

Objectives: To determine the frequency and distribution of 975 teeth in need of endodontic treatment in an Argentine patient pool and to compare the results with previously published surveys. Methods: Of the 975 teeth from 860 individuals (age range 7–86 years) were endodontically treated during 2007 by postgraduate students enrolled in a specialisation programme in Endodontics. All patients were examined clinically and radiographically. For each case, information was collected in a questionnaire including location of the affected tooth, age and gender and reasons for endodontic treatment. Data were analysed by the Student t‐test, the Fisher exact test, and the chi‐square test with a significance of P < 0.05. Results: Of the 975 treated teeth, 543 (55.69%) were maxillary and 432 (44.30%) mandibular teeth. 635 (65.13%) were from females and 340 (34.87%) from males. Significant differences were found between the maxillary and mandibular arch (P = 0.01). Molars and premolars required significantly more frequent endodontic treatment than canines and incisors (P < 0.001). The most frequently treated tooth was the mandibular right first molar (9.12%) followed by the mandibular left first molar (7.07%). The most frequently diagnosed pathosis was irreversible pulpitis (36.00%), pulp necrosis (30.80%), apical periodontitis or the presence of easily discernible periapical radiolucent areas (27.20%). Caries (59.18%) and failure of previous endodontic treatment (26.97%) were responsible for most of the affected teeth. Conclusions: Comparison with previous surveys revealed that more females than males received endodontic treatment and that mostly molars and premolars were in need of endodontic treatment. The high number of root filled teeth requiring retreatment is in agreement with a pattern similar to that observed in other countries and supports the need for more specialists in endodontics in the Republic of Argentina.     

Effect of EDTA conditioning upon the retention of fibre posts luted with resin cements

Aim To determine if a final rinse with EDTA improves the short‐term in‐tooth retentive strength of adhesively luted fibre‐reinforced composite posts. Methodology Six different commercial fibre post systems were tested. Post spaces in extracted human anterior teeth were irrigated with either 6% NaOCl or 6% NaOCl followed by 17% EDTA. Posts were luted using the manufacturer’s recommended bonding agent and luting cement. Two different sizes of post were tested for each post system. After 24 h of storage, the retentive strength of the post to the tooth (14 per group, 336 total) was tested using a pull‐out technique. Three‐way anova and the Student–Newman–Kuels test were used to test the effects of irrigation regimen, post size and post brand on the retentive strength of the fibre post. Results Almost every sample failed at the interface between dentine and luting cement. Irrigation method did not have any significant effect (P > 0.14) for any group other than ParaPost Fibre White (P < 0.001). The overall retention of a post appeared to be correlated to the amount of surface texture on the post; the smooth ICEPost was the least retentive brand, the textured FibreKor and the ParaPost Fibre White posts were moderately retained, and the threaded Flexi‐Post Fibre and the Flexi‐Flange Fibre posts were the most retentive brands tested. For all brands, larger diameter posts were more retentive than smaller diameter posts (P < 0.008). Conclusions A final rinse of EDTA did not improve the short‐term retention of fibre posts except for ParaPost Fibre White.     

A one step procedure for luting glass fibre posts: an SEM evaluation

AIM: To evaluate the ability of two luting procedures for bonding translucent fibre posts to form resin tags, adhesive lateral branches, and resin dentine interdiffusion zones (RDIZ). METHODOLOGY: Forty root filled teeth, extracted for periodontal reasons, were selected for the study. The teeth were randomly divided into four groups of 10 each. Group 1: One Step, light-cured (LC) 20 s + dual link resin cement (LC 20 s); group 2: One Step, not light-cured (NLC) + dual link resin cement (LC 30 s); group 3: One Step (NLC) + dual link resin cement (LC 60 s); group 4: One Step (NLC) + dual link resin cement (LC 90 sec). Forty translucent fibre posts (DT posts, RTD) were inserted. Then, root specimens were processed for scanning electron microscope (SEM) observations to assess the continuity of the RDIZ, the presence or absence of gaps and the density and morphology of resin tags using a four-step scale method. RESULTS: With all luting procedures the formation of a RDIZ occurred. However, the microscopic examination of adhesive interfaces revealed that the percentage of RDIZ was significantly higher in group 1 than in the other three groups (P < 0.05). Group 4 had a higher percentage of RDIZ than group 3, which in turn exhibited a greater percentage than group 2, but these differences were not statistically significant (P > 0.05). Resin tag formation was evident in all the groups. The characteristic reverse cone shape of resin tags was always noted in the coronal and middle third of all groups, and in the apical third of group 1. In the apical third a shorter length and a less uniform appearance of resin tags were noted in groups 2, 3 and 4. CONCLUSIONS: In this laboratory study, when bonding a translucent fibre post into a root canal, the luting procedure including light curing of the adhesive solution before the placement of the cement was more satisfactory, from a SEM standpoint, than the procedure involving the simultaneous curing of adhesive and cement (one step procedure).     

In vitro fracture resistance of premolar teeth restored with fibre‐reinforced composite posts using a single or a multi‐post technique

The purpose of this study was to evaluate the reinforcing effect of fibre‐reinforced composites (FRC) applied in premolar teeth with different techniques and minimally invasive post space preparation. Fifty extracted and endodontically treated premolar teeth were used. The teeth were divided into five groups (n = 10) depending on the restorative technique (Groups 1–5). Group 1: one single conventional post, Group 2: one main conventional and one collateral post, Group 3: one elastic post, Group 4: one main elastic and one collateral post, and Group 5: individual post formed of elastic posts. After cementation and core build‐up, the specimens were submitted to static fracture resistance test. Fracture thresholds and fracture patterns were measured and evaluated. Group 4 showed the highest average fracture resistance among the tested groups. The multi‐post techniques (group 2 and 4) exhibited statistically higher fracture resistance compared to group 1. Regarding fracture patterns, there was no statistically significant difference between the tested groups. Within the limitations of this study, the application of multiple elastic or conventional FRC posts or a single elastic post in the same root canal is beneficial in terms of fracture resistance compared to a single conventional FRC post. The elasticity or the number of posts did not influence the fracture patterns.     

A new classification system for the restoration of root filled teeth

The aim of this report is to (i) review the current literature on the status of root filled teeth, (ii) analyse the most important factors in decision‐making, (iii) discuss the current restorative concepts, and (iv) classify both the evidence and clinical practice in a way that seeks to be clear, understandable and helpful for clinicians. Restoration of root filled teeth represents a challenge for the clinician and remains a controversial subject. The guidelines describe a new classification that is drawn from evidence presented in the literature and also from clinical expertise‐based reviews. It describes five categories of teeth.     

Accuracy and Efficiency of a Dynamic Navigation System for Locating Calcified Canals

IntroductionCalcified canals present a challenge during endodontic treatments. The purpose of this study was to compare the accuracy and efficiency of a dynamic navigation system (DNS) to the freehand (FH) method for locating calcified canals in human teeth.MethodsSixty human single-rooted teeth with canal obliteration were selected and mounted in dry cadaver jaws. Based on cone-beam computed tomographic scans of the jaws, the drilling path and depth were virtually planned to use X-Guide software (X-Nav Technologies, LLC, Lansdale, PA). Access preparation was made with navigation in the DNS group and without guidance in the FH group by 2 operators with different levels of experience. Postoperative cone-beam computed tomographic scans were taken of all teeth. Linear and angular deviations and reduced dentin thickness at 2 levels were measured. The time for locating the canal, the number of mishaps, and the unsuccessful attempts were determined and analyzed.ResultsThe mean linear and angular deviations, reduced dentin thickness (at both levels), the time for access cavity preparation, and the number of mishaps in the DNS group were significantly less than the FH group (P ≤ .05). The unsuccessful attempts were not different between the 2 groups (P > .05). The time for access preparation was significantly shorter for the board-certified endodontist in the FH group (P ≤ .05).ConclusionsThe DNS was more accurate and more efficient than the FH technique in locating calcified canals in human teeth. This novel DNS can help clinicians avoid catastrophic mishaps during access preparation in calcified teeth.     

Clinical evaluation of a carbon fibre reinforced carbon endodontic post

This study reports a prospective clinical trial comparing a carbon fibre reinforced carbon (CFRC) endodontic post with a conventional prefabricated post. Twenty-seven single rooted maxillary anterior teeth in 18 patients (nine males and nine females; age range 18-60 years) were restored either with a CFRC post or a wrought precious alloy control. Cast type III gold alloy cores were used in conjunction with both post groups. The CRFC posts (n = 16) were cemented with a composite luting agent and the conventional posts (control) were cemented with zinc phosphate. Four failures were recorded in the CFRC post group at 24, 29, 56 and 87 months, compared with one failure in the control group at 84 months. These results suggest that post-retained crowns utilizing a CFRC material and a composite resin luting agent do not perform as well as conventional wrought precious alloy posts.     

Difficulty levels of extracted human teeth used for pre‐clinical training in endodontics in an Australian dental school

This study aimed to determine the difficulty level of extracted teeth treated by undergraduate students for pre‐clinical endodontic training. Two independent observers assessed a consecutive sample of 1000 periapical radiographs of extracted teeth used in endodontic pre‐clinical training. Chi‐square test was used to evaluate the adjustment of the distribution, and inter‐ and intra‐examiner agreement were calculated. Minimal, moderate and high difficulty teeth represented 23.1%, 52.1% and 24.8%, respectively. The presence of curvature was the most common grading factor, with ‘moderate curvature’ reported in 28.7%, and ‘extreme curvature’ reported in 15.6% of the sample. A difference in the distribution of frequencies was found, favouring the moderate category (P < 0.001). The inter‐ and intra‐examiner strength of agreement were 0.78 and 0.86, respectively. More than 50% of the teeth were categorised as moderate complexity. Almost one‐quarter of the total sample, in particular molars, was classified as high complexity, thus unsuitable for undergraduate pre‐clinical training.     

Effect of Er:YAG laser on removal of fibre posts from root canal

The aim of this study was to evaluate the efficiency of Er:YAG laser in translucent fibre post removal. 60 human single-rooted anterior teeth were divided into three groups (n = 20) according to post diameters (Exacto1-E1, Exacto2-E2, Exacto3-E3) and subdivided according to laser application. Fibre posts were cemented to endodontically treated teeth, and the specimens were sliced with a thickness of 1.0 ± 0.2 mm. Er:YAG laser was applied and the push out bond strength test was performed. Two-way analysis of variance was used to perform the statistical analysis. Push out bond strengths at apical area were significantly lower in all test groups (p < 0.05). Laser application caused increase in all radicular thirds, but it was significant for E1 and E3 groups. Laser application to the post-dentine interface enhances the connection between post and dentine.