An in vitro study of coronal microleakage in root-canal-treated teeth restored by the post and core technique

Comparative effectiveness of fiber and metal posts in the restoration of endodontically treated teeth: A systematic review with network meta-analysis

STATEMENT OF PROBLEM

Different varieties of fiber and metal intraradicular posts have been used for the restoration of endodontically treated teeth with insufficient sound tooth structure. Evidence on the comparative efficacy of posts in a clinical setting is insufficient to provide clear clinical guidelines and recommendations.

PURPOSE

The purpose of this systematic review with network meta-analysis was to assess the comparative efficacy of fiber and metal posts used for the restoration of endodontically treated teeth.

MATERIAL AND METHODS

A search was conducted for trials published in Medline, Scopus, PubMed, and Cochrane Central Register of Controlled Trials from inception until November 2022. The study was registered with the International Prospective Register of Systematic Reviews (PROSPERO) (CRD42022384340). A network meta-analysis was performed on data from randomized controlled trials that assessed the comparative efficacy of fiber posts and metal posts for the restoration of endodontically treated teeth. Subgroup analyses were performed to compare all the varieties of fiber and metal posts. The types of posts were ranked according to their efficacy using the Surface Under the Cumulative Ranking (SUCRA) system. The Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) approach was used to assess the level of certainty of evidence.

RESULTS

Twenty-five articles were included in the quantitative analysis. Fiber posts (RR=0.15 [95% CI: 0.06, 0.33]) significantly prevented tooth fracture as compared with no posts. Prefabricated carbon fiber posts (RR=0.06 [95% CI: 0, 0.54]) ranked highest followed by custom glass fiber posts (RR=0.15 [95% CI: 0.04, 0.52]) and prefabricated glass fiber posts (RR=0.22 [95% CI: 0.07, 0.62]) in the outcome of tooth fracture. Metal posts (RR=0.24 [95% CI: 0.12, 0.46]) ranked higher than fiber posts (RR=0.39 [95% CI: 0.27, 0.56]) in the outcome of debonding. Custom gold alloy posts (RR=0.12 [95% CI: 0.03, 0.48]), prefabricated gold alloy posts (RR=0.04 [95% CI: 0.00, 0.87]), and prefabricated titanium posts (RR=0.21 [95% CI: 0.10, 0.45]) had higher rankings in the outcome of debonding or loss of retention of a post followed by custom glass fiber posts (RR=0.37 [95% CI: 0.21, 0.63]) and prefabricated glass fiber posts (RR=0.38 [95%CI: 0.25, 0.58]). Prefabricated glass fiber posts (RR=0.40 [95% CI: 0.20, 0.81]) had statistically significant differences in the outcome of secondary caries. The GRADE approach determined a moderate level of certainty of evidence.

CONCLUSIONS

The use of a fiber post when indicated results in reduced risk of tooth fracture as compared with no post. Prefabricated carbon fiber posts, prefabricated glass fiber posts, and custom glass fiber posts reveal a lower risk of tooth fracture. Overall, the use of prefabricated glass fiber posts had a lower risk of tooth fracture, debonding, and secondary caries. However, more trials with longer follow-up periods are recommended to enhance the certainty of evidence.

Radiographic Evaluation of the Gap between Cemented Post and Remaining Gutta-Percha in Endodontically Treated Teeth Performed by Undergraduate Students: A Retrospective Cross-Sectional Study

The coronal seal in root canal-treated teeth may be compromised depending on the accuracy of post space preparation and post cementation along with remaining gutta-percha. Root canal treatment can be compromised by endotoxins released by the coronal bacteria as a result of microleakage. The study was conducted by undergraduate students to measure the gap between the cemented post and residual gutta-percha. In total, 217 endodontically treated teeth were evaluated with intraoral peri-apical radiographs. Based on the intraoral periapical radiographic examination in the CS-R4 program, Group I had no gap, Group II had a gap of >0 to 2 mm, and Group III had a gap of more than 2 mm between the end of the cemented post and the remaining gutta-percha. In total, 40% (n = 87) of the teeth had no gap, 59% (127) had a gap of >0 to 2 mm, and 1% (n = 3) had a gap of more than 2 mm between the cemented post end and remaining gutta. Chi square test revealed a significant difference in the gap between the post and remaining gutta-percha between males and females students (p < 0.001). In terms of the gap between the cemented post end and the residual gutta-percha, the root canal treated teeth with post and core by undergraduates were clinically acceptable.

Assessment of bacterial and dye penetration through post/crown interim restorations while under simulated masticatory load

The aim was to compare two temporary cements to determine which resisted bacterial and dye penetration under temporary posts/cores/crowns subjected to simulated masticatory function. Forty-six single canal human tooth roots were prepared for posts/crowns. A cotton pellet and Cavit were placed in each post space. Temporary posts/cores/crowns were cemented with Intermediate Restorative Material (IRM) (n = 23) or Tempocem (n = 23). Specimens were sterilised, then immersed in a mixture of Streptococcus gordonii and India ink, and subjected to 4 weeks simulated mastication. Dye penetration was assessed by visually inspecting the cotton pellets. Bacterial penetration was determined by placing the pellets into sterile broth and by plating them onto agar plates to confirm S. gordonii growth. There was no statistically significant difference between the cements and the dependent variables of bacterial and dye penetration. Hence, both cements are good options to cement temporary posts/cores/crowns during endodontic treatment of anterior teeth.

Restoration of Root Filled Teeth; Current Opinions and Techniques

Purpose:

To examine current decision-making preferences of Jordanian dentists when Restoring Root Filled Teeth (RFT).

Materials and Methods:

834 Jordanian general dentists, prosthodontists and endodontists were invited to participate in a validated online survey with a 62% participation rate. Respondents were invited to answer 24 questions about their preferences for techniques and materials they use to restore RFT. The questions aimed at exploring restorative strategies commonly employed by Jordanian dentists when managing root filled teeth with extensive loss of tooth structure.

Results:

A minority of dentists consider direct resin restoration as the sole restoration for RFT with extensive loss of tooth structure. Full coverage metal-ceramic and all-ceramic crowns are more popular than endocrowns when restoring RFT with indirect restoration. Fiber posts are the most popular type of posts, followed by prefabricated metal posts. Glass ionomer is the most preferred cement for luting metal posts, while conventional dual resin cement with separate etch and rinse bonding strategy is the most employed when bonding fiber posts. The majority of dentists tend not to pretreat fiber posts. Loss of post/core retention or fracture of coronal tooth structure are the two most common reasons observed by dentists when RFT fail.

Conclusion:

Use of post and core is still preferred over more conservative approaches when restoring RFT with extensive loss of coronal tooth structure. Longevity of restorations can be enhanced by training practicing dentists on evidence-based adhesive strategies.

Dental practice in the UK in 2015/2016. Part 3: aspects of indirect restorations and fixed prosthodontics

Objective

This paper reports data which helps identify changes and trends in the provision of indirect fixed prostheses in general dental practice in the UK. To determine by means of an anonymous, self-report questionnaire, the current trend in the provision of fixed prosthodontic treatments, with a special emphasis on the choice of treatment modalities, techniques and materials.

Methods

The data presented were extracted from the data obtained from a validated,121-question questionnaire distributed at random to general dental practitioners in the UK attending postgraduate meetings in 2015/2016, with a wide distribution of locations.

Results

A response rate exceeding 66% was achieved. Amalgam and light-cured composite were the preferred material for core build-up of vital teeth for around 62% of the respondents. Dentine pins were still being used by 66% of the respondents. The vast majority of respondents (92%) used a post and core to restore root-treated teeth. Fibre posts were the most commonly used (63%) type of preformed post among the respondents. Using the opposing and adjacent teeth as a reference to control tooth structure reduction during vital tooth preparation was the most common method, used by 42% of the respondents. Addition-cured silicone impression materials were the most frequently used impression material (78%). The surveyed practitioners were equally split between precious and non-precious metals as the substructure for indirect restorations. Glass-ionomer luting cements (47%) and resin-based cements (52%) were the most commonly used to cement porcelain fused to metal and zirconia indirect restorations, respectively. Laboratory made aesthetic veneers were prescribed by half of the respondents, while a third of them preferred direct resin composite as a veneer material.

Conclusion

Within the limitations of the study, it was concluded that there has been an increase in the use of adhesive bonding and metal-free restorations. Amalgam and dentine pinscontinued to be used, contrary to international trends. Studies of the type reported are considered important in investigating trends and developments in dentistry.

Restoration of the root canal treated tooth

When considering endodontically treated teeth, the quality of the restoration is important from the outset. It sheds light into possible causes of pulp necrosis or failure of endodontic treatment and influences the outcome of future endodontic treatment. A tooth undergoing endodontic treatment requires an effective coronal seal during and following completion of endodontic treatment. This paper discusses, using the available literature, the maintenance of optimal coronal seal and coronal integrity during and after root canal treatment.

Composite Resin Core Buildups With and Without Post for the Restoration of Endodontically Treated Molars Without Ferrule

OBJECTIVE

The aim of this study was to investigate the restoration of highly damaged, broken-down endodontically treated molars without the ferrule effect using glass ceramic crowns on different dual-cure composite resin core buildups.

METHODS AND MATERIALS

Thirty (N=30, n=15) decoronated, endodontically treated teeth (no ferrule) were restored without a ferrule with a direct buildup using the dual-curing composite Multicore HB (group MHB) or the dual-curing composite core buildup Multicore Flow in combination with glass-fiber-reinforced composite post (FRC post; group MFP). All teeth were prepared to receive bonded glass ceramic crowns (Empress CAD luted with Variolink II) and were subjected to accelerated fatigue testing. Cyclic isometric loading was applied to the palatal cusp at an angle of 30 degrees and a frequency of 5 Hz, beginning with a load of 200 N (×5000 cycles), followed by stages of 400, 600, 800, 1000, 1200, and 1400 N at a maximum of 30,000 cycles each. Specimens were loaded until failure or to a maximum of 185,000 cycles. Groups were compared using the life table survival analysis (log rank test at p=0.05). Average fracture loads and number of survived cycles were compared with one-way analysis of variance (Scheffé post hoc at p=0.05). Previously published data from the same authors about core buildups made of high-performance polymers (group HPP, n=15) and light-curing composite resin without FRC posts (group TEC, n=15) and with FRC posts (group TECP, n=15) using the same experimental setup were included for comparison.

RESULTS

None of the tested specimen withstood all 185,000 load cycles. There was no significant difference in mean fracture load (p=0.376), survived cycles (p=0.422), and survival (p=0.613) between MHB (facture load 859.4 N±194.92) and MFP (796.13 N±156.34). Group HPP from a previous study appeared to have significantly higher performance than all other groups except MHB. All groups with posts were affected by an initial failure phenomenon (wide gap at the margin between the buildup/crown assembly and the root).

CONCLUSIONS

HPP and MHB enhanced the performance of all-ceramic leucite-reinforced glass ceramic crowns, and insertion of a fiber-reinforced composite post was not influential when using other materials.

Modern Endodontic Planning Part 2: Access and Strategy

Poor access and iatrogenic damage can result in failed root canal treatment. Understanding tooth anatomy improves access and ensures that the clinician is cleaning and shaping the whole root canal system. If a canal is missed treatment usually fails. This paper revisits tooth anatomy and discusses how to ensure that access is optimized, but not at the expense of precious tooth structure. The concept of multi-visit root canal treatment is also addressed with emphasis on the, often overlooked, aspect of temporization. CPD/Clinical Relevance: Good anatomical knowledge of teeth is the cornerstone of endodontics. Once root treatment has begun the clinician must be logical about how many visits to take and how to temporize teeth between such visits.

CAD/CAM Polymer vs Direct Composite Resin Core Buildups for Endodontically Treated Molars Without Ferrule

OBJECTIVES

The aim of this study was to investigate the restoration of broken-down endodontically treated molars without ferrule effect using glass ceramic crowns on different composite resin core buildups.

METHODS AND MATERIALS

Forty-five decoronated endodontically treated teeth (no ferrule) were restored with a semidirect buildup using an experimental computer-aided design/computer-aided manufacturing (CAD/CAM) high-performance polymer (HPP group) or with light-curing composite core buildups of Tetric EvoCeram with (TECP group) or without (TEC group) a glass-fiber-reinforced post. All teeth were prepared to receive bonded glass ceramic crowns (Empress CAD luted with Variolink II) and were subjected to accelerated fatigue testing. Cyclic isometric loading was applied to the palatal cusp at an angle of 30° and a frequency of 5 Hz, beginning with a load of 200 N (×5000 cycles) and followed by stages of 400, 600, 800, 1000, 1200, and 1400 N at a maximum of 30,000 cycles each. Specimens were loaded until failure or to a maximum of 185,000 cycles. Groups were compared using the life-table survival analysis (log rank test at p=0.05). Average fracture loads and number of survived cycles were compared with one-way analysis of variance (Scheffé post hoc at p=0.05).

RESULTS

None of the tested specimen withstood all 185,000 load cycles. There was a significant difference in mean fracture load, survived cycles, and survival; the HPP group (fracture load 975.27N±182.74) was significantly higher than the TEC (716.87N±133.43; p=0.001) and TECP (745.67±156.34; p=0.001) groups, and the TEC and TECP groups showed no difference (p=0.884). Specimens in the TECP group were affected by an initial failure phenomenon (wide gap at the margin between the buildup/crown assembly and the root).

CONCLUSIONS

Semidirect core buildup made from high-performance polymer enhanced the performance of all-ceramic leucite-reinforced glass ceramic crowns compared with direct light-curing composite resin buildups. The use of a fiber-reinforced post system did not influence the fatigue strength of all-ceramic crowns.

'The last post?': assessment of the failing post-retained crown

Failure of a post-retained restoration can provide a challenge to the general dental practitioner (GDP) in terms of diagnosis, treatment planning and communication with the patient. The cause of failure must be identified, and a thorough assessment of the restoration, remaining tooth and its functional and aesthetic demands carried out in order to plan treatment to provide the most reliable result. Clinical Relevance: This article discusses the assessment of failing post-retained crowns, with discussion of reasons for failure, thereby assisting the GDP in decision-making and treatment planning for such teeth.

Posts--when it all goes wrong! Part 1: case assessment and management options

Posts have been used for many years to retain restorations or cores for extra-coronal restorations in endodontically treated teeth.This article discusses the variety of post systems that are available and the incidence and reasons for failure of teeth that have been restored with posts. The treatment options available for the management of such failures are considered, in addition to the indications for both non-surgical and surgical management of endodontic failures. The attitudes of dentists and the perceived complications of attempting post removal are reviewed, along with the evidence to support the prevalence of complications.

CLINICAL RELEVANCE

Failure of post-retained restorations is a relatively frequent finding due to failure of the restoration itself or the endodontic treatment. It is therefore important to understand and be aware of the various treatment options available, their indications and associated risks.

Effect of post length and diameter on remaining dentine thickness in maxillary central and lateral incisors

AIM

To investigate the effect of root canal and post-space preparation on the remaining dentine thickness in the apical region of maxillary central and lateral incisors.

METHODOLOGY

Fifty extracted maxillary incisors (25 centrals and 25 laterals) were mounted and then sectioned at two levels: 5 and 7 mm from the apex. Computerized images were obtained and a digital image analysis system was used to measure dentine thickness for each section at eight sites: labial, mesial, distal, palatal, mesio-labial, disto-labial, mesio-palatal and disto-palatal. Measurements were repeated at baseline and after both root canal and post-space preparation. Central and lateral incisors were divided into five groups each (n = 5) according to the drill used for post-space preparation: Groups 1 through 4 were prepared using Parapost drills sizes 4.5, 5, 5.5 and 6 respectively. For group 5, size 4 Gates Glidden was used.

RESULTS

For both teeth, and at the two levels there was a significant difference (P < 0.001) between the baseline dentine thickness and that remaining after post-space preparation at all sites. There was a statistically significant difference (P = 0.007) between the remaining dentine thickness at 5 and 7 mm at all sites. The average amount of dentine removed ranged from 0.20 to 0.52 mm. In all groups, and for both teeth, some specimens had <1 mm of remaining dentine thickness.

CONCLUSIONS

Posts should be used carefully when restoring root filled maxillary incisors.

Seal capability of interim post and core crown with temporary cements

The purpose of the present study was to evaluate the in vitro seal capability of interim post and core crown restorations. Eighty teeth were selected and divided into 8 groups. Four experimental groups received interim posts and core crowns. Half of each group was decoronated at the cementum-enamel junction, groups PCCH and PCZO. The other half was sectioned 2 mm coronal to the cementum-enamel junction, groups PCrZO and PCrCH. The interim post and core crowns were luted with Rely X Temp NE, groups PCrZO and PCZO; Hydro C was used for Groups PCrCH and PCCH. The control groups, PC and PCr, received uncoated post and core crowns; groups OTg and OT were left without interim post and core crowns and were totally open. Infiltration was accessed by dye exposure followed by demineralization of the teeth. The length of the infiltration was measured using digital images taken from the specimens. The images were inserted into the Image Tool 3.0 software. Kruskal-Wallis analysis of variance and Dunn's multiple comparison method were used to test for significant differences among test groups (P < .05). Groups PCrZO and PCrCH showed the least dye penetration, followed by groups PCZO and PCCH. Teeth restored with interim post and core crowns will be subject to leakage. Ethics Committee: 095/2008.

The endo-restorative interface: current concepts

Successful endodontic treatment depends on the restorative treatment that follows. The connection between endodontic treatment and restorative dentistry is well accepted, but the best restorative approaches for endodontically treated teeth have always been somewhat controversial. A plethora of information from various sources contributes to the controversy and much of it is contradictory. With the emergence of implants in mainstream dentistry, there has been more emphasis on long-term outcomes and on evaluating the "restorability" of teeth prior to endodontic treatment. The long-term viability of endodontically treated teeth is no longer a "given" in the implant era. In consequence, some teeth that might have received endodontic treatment in the past are now extracted and replaced with implant-supported prostheses if they are marginally restorable or it makes more sense in the overall treatment plan. As it is not possible to review here all the literature on the restoration of endodontically treated teeth, this article focuses primarily on current concepts based on the literature from the past 10 years or so, and provides treatment guidelines based on that research.

Restoration of endodontically treated teeth review and treatment recommendations

Coronal restorations and posts can positively influence the long-term prognosis of teeth following root canal therapy. Final sealing the canal by placing an appropriate post and core will minimize leakage of oral fluids and bacteria into the periradicular area and is recommended as soon as possible after completion of root canal filling. Glass ionomer or MTA placed over the residual root canal filling after post space preparation may be effective to prevent bacterial leakage. A ferrule of 1-2 mm of tooth tissue coronal to the finish line of the crown significantly improves the fracture resistance of the tooth and is more important than the type of the material the core and post are made of.

Influence of endodontic post type (glass fiber, quartz fiber or gold) and luting material on push-out bond strength to dentin in vitro

OBJECTIVES

To determine the influence of post type and luting material on bond strength to dentin.

METHODS

The root canals of extracted human upper central incisors were instrumented and post space was prepared using the respective drills for each post system. Glass fiber posts (Luscent Anchor, Dentatus [LA]) were luted using three dual-curing adhesive systems (Excite DSC/Variolink II, Vivadent [VL2]; EnaBond/EnaCem, Micerium [ENA]; Prime & Bond NT/Calibra, DentSply DeTrey [CAL]). A different brand of glass fiber post (EasyPost, DentSply Maillefer [EP]) and quartz fiber post (DT Light Post, VDW [DT]) were luted using CAL. Gold posts (Perma-dor, VDW) were luted either adhesively following tribo-chemical silicate coating (Rocatec, ESPE-Sil, 3M ESPE; CAL) or conventionally using glass ionomer cement (Ketac Cem, 3M ESPE). Three slices of 2mm height were cut perpendicular to the post from each restored root. Bond strength was determined by pushing out the post using a universal testing machine (/1449, Zwick).

RESULTS

For all experimental groups combined, bond strength increased from the coronal to the apical section (Friedman test: P<0.001). Significant differences were observed among the fiber posts (DT/CAL>LA/CAL; Mann-Whitney U-test with Bonferroni-Holm adjustment: P<0.05; EP/CAL ranging in between) but not among luting materials (LA/VL2, LA/ENA, LA/CAL: n.s.). The gold posts were equivalent to DT/CAL with both luting procedures.

SIGNIFICANCE

Selection of post type may be more important for bond strength than luting material. Bond strength of fiber posts was equivalent but not superior to adhesively or conventionally luted gold posts.

Association between intra-radicular posts and periapical lesions in endodontically treated teeth

Introduction:

A significant number of endodontically treated teeth restored with posts have associated periapical lesions, and several authors have discussed the probable causes of the development of these. Attention has been focused on restorative procedures performed after endodontic treatment and their association with the prognosis of endodontic therapy because a number of root-filled teeth will require post- and core-retained restorations.

Purpose:

The purpose of this study was to evaluate, by examination of periapical radiographs, whether the placement of intra-radicular posts in endodontically treated teeth may act as a risk factor for development of periapical lesions.

Material and Methods:

This case-control study analyzed periapical radiographs of 72 endodontically treated teeth with coronal restorations. All radiographs were obtained from a single private practice. Specimens were assigned to 2 groups: Group 1 (control) was composed of teeth without periapical lesions and Group 2 (case) was composed of teeth with periapical lesions. The number of teeth with and without posts in each group was recorded. Three calibrated examiners analyzed the radiographs visually under X4 magnification.

Results:

In Group 1, 28 (65.1%) out of 43 teeth were restored with posts. In Group 2, 24 (82.8%) out of 29 teeth had intra-radicular posts. The interpretation of chi-square test showed that these percentages were not significantly different (x²=2.687; p=0.101). Odds ratio was 2.571 (0.8158.118), which indicates that there was no statistically significant association between periapical lesions and posts.

Conclusion:

Intra-radicular posts placed in endodontically treated teeth were not a significant risk factor for development of periapical lesions in the practice where the cohort of patients was treated.

Tooth preparation for post-retained restorations

Failure of root canal treatment and/or post crowns can be avoided in many cases if appropriate tooth preparation is carried out. This paper discusses the rationale for the timing of post placement following root canal treatment and appropriate methods for removal of gutta-percha prior to post space preparation. The basic principles of post space preparation are described, which should reduce the risk of weakening the root unnecessarily, causing damage to the periodontium and post perforation.

Posts and the root-filled tooth

It is clear that teeth often require significant reconstruction following root canal treatment. It is also evident that there is an enormous variety of ways that can be used to achieve this. Although there is some debate about the relative contributions of the root filling and coronal restoration to endodontic success, it is agreed that the best results are gained with a good root filling and a well-sealed coronal restoration. Posts, pins and/or bonding are all possible solutions to retain the coronal restoration but it is often difficult to decide, on the basis of evidence rather than fashion or anecdote, which is preferable.

The Effect of the Distance Between Post and Residual Gutta-Percha on the Clinical Outcome of Endodontic Treatment

To determine whether the distance between the post and the residual gutta-percha influences the clinical outcome of endodontic treatment, 94 endodontically treated teeth following post and core restoration were evaluated radiographically. The teeth were divided into three groups: (I) no gap between the gutta-percha and the post; (II) a gap of >0 to 2 mm; (III) a gap of >2 mm. Treatment outcome was evaluated in follow-up radiographs, taken 1 yr after treatment and up to 5 yr posttreatment. In group I, 83.3% of the teeth were evaluated normal, 53.6% of group II, and only 29.4% of group III. A gap between the gutta-percha and the post was related to an increased rate of emerged disease in endodontically treated teeth restored with a post and core.

Adhesive Dentistry and Endodontics: Materials, Clinical Strategies and Procedures for Restoration of Access Cavities: A Review

The complexity of restorative dentistry has increased greatly in recent years, with the myriad of products used in "adhesive dentistry." So too has the "simple" matter of restoring access cavities after completion of endodontic treatment. This review discusses current methods of "bonding" to tooth structure, ceramic materials, and metals, with emphasis on those aspects that are important to endodontics. Specific materials, procedures and major decision making elements are discussed, as well as how to avoid problems in compatibility between endodontic and restorative materials.

Crowns and extra-coronal restorations: endodontic considerations: the pulp, the root-treated tooth and the crown

Endodontic considerations is the fourth in the series on crowns and other extra-coronal restorations. This article focuses strongly on contemporary biological principles, and is not intended to provide a comprehensive review of commercially available materials and techniques. Principles are illustrated in a variety of clinical case scenarios.

Endodontics: Part 2 Diagnosis and treatment planning

As with all dental treatment, a detailed treatment plan can only be drawn up when a correct and accurate diagnosis has been made. It is essential that a full medical, dental and demographic history be obtained, together with a thorough extra-oral and intra-oral examination. This part considers the classification of diseases of the dental pulp, together with various diagnostic aids to help in determining which condition is present, and the appropriate therapy.

Post placement and restoration of endodontically treated teeth: a literature review

The restoration of endodontically treated teeth is a topic that is extensively studied and yet remains controversial from many perspectives. This article reviews the major pertinent literature on this topic, with an emphasis on major decision-making elements in post placement and restoration of endodontically treated teeth. Recommendations are made for treatment planning, materials, and clinical practices from restorative and endodontic perspectives.

Collagen degradation in endodontically treated teeth after clinical function

Endodontically treated teeth restored with posts are susceptible to coronal leakage after long-term function. We hypothesize that demineralized collagen matrices (DCMs) created in dentin by acidic zinc phosphate cement within the dowel spaces degrade with time. Forty-two post-restored teeth were extracted after three periods of clinical service and were examined, by means of scanning and transmission electron microscopy, for the status of the DCMs. SEM revealed a progressive degradation of the DCMs, becoming less dense after 3 to 5 years, losing structural integrity after 6 to 9 years, and partially disappearing after 10 to 12 years. TEM revealed evidence of collagenolytic activity within the DCMs, with loss of cross-banding and unraveling into microfibrils, and gelatinolytic activity that resulted in disintegration of the microfibrils. Bacterial colonization and the release of bacterial enzymes and of host-derived matrix metalloproteinases may contribute to the degradation of collagen fibrils in root dentin after clinical function.

Restoration of endodontically treated teeth

Endodontically treated teeth have lost substantial tooth structure as a result of previous restorations, dental caries, and the access preparation for the endodontic therapy. The topic of restoring these teeth is complex and controversial, and their long-term prognosis is directly connected to the quality of the final restoration. This article describes contemporary knowledge of the biomechanical principles related to the restoration of pulpless teeth and provides a critical review of currently available materials and methods.

Interim restorations

Interim restorations are a critical component of fixed prosthodontic treatment, biologically and biomechanically. Interim restoration serves an important diagnostic role as a functional and esthetic try-in and as a blueprint for the design of the definitive prosthesis. When selecting materials for any interim restoration, clinicians must consider physical properties, handling properties, patient acceptance, and material cost. Although no single material meets all the requirements and material classification alone of a given product is not a predictor of clinical performance, bis-acryl materials are typically best suited to single-unit restorations, and poly(methylmethacrylate) interim materials are generally ideal for multi-unit, complex, long-term, interim fixed prostheses. As with most dental procedures, the technique used for fabrication has a greater effect on the final result than the specific material chosen.

An in vitro study of coronal microleakage in endodontically-treated teeth restored with posts

Coronal microleakage has received considerable attention as a factor related to failure of endodontic treatment and much emphasis is placed on the quality of the final restoration. Posts are frequently used for the retention of coronal restorations. These can be custom-made or prefabricated. Many authors have examined coronal microleakage with respect to gutta-percha root fillings and plastic coronal restorations, but few have investigated the coronal seal afforded by various post systems. The seal provided by a cemented post depends on the seal of the cement used. The purpose of this study was to compare coronal microleakage around cast and prefabricated posts using a dye-penetration method. Sixty extracted single-rooted human teeth were chemomechanically prepared. The root canals were filled with gutta-percha and sealer and they were then prepared for standard posts. Six groups, each of 10 teeth, were restored with either cast post or prefrabricated post. The posts were cemented with either glass ionomer cement (GIC), Variolink II or Durelon. The teeth were thermocycled and placed in Indian ink for one week. They were then demineralised and rendered transparent. Linear coronal dye penetration around the post was measured and compared. The least dye-penetration was observed in roots restored with a cast post and Variolink II. Dentatus posts demonstrated the most microleakage. It appears that the dentine-bonding cements have less microleakage than the traditional, non-dentine-bonding cements and adaptation of the post with the canal may be more important than the cement used.

Contemporary Perspectives On Post-Core Systems

The challenge of restoring endodontically-treated teeth has spawned a considerable diversity in foundation restorations and a plethora of publications in the dental literature. Moreover, it seems that an inverse relationship has developed between the escalating complexity in selecting a post-core system and the volume of reliable scientific data upon which clinicians base their treatment decisions. In the quest to restore aesthetics, function, and reduce the risk of treatment failure there is now a much greater emphasis on the preservation of sound tooth structure, tooth isolation for intracanal procedures, sealing the root canal and adapting the advantages and limitations of dental materials to the presenting clinical situation. The relatively recent introduction of metal-free posts into mainstream prosthodontics has added an aesthetic dimension to treatment planning. New adhesive systems and resin-based luting agents have the potential to create a genuine adhesive continuum between the tooth and post-core complex. While these developments may have significant ramifications with respect to treatment prognosis, the long-term clinical performance of contemporary post-core systems is unclear.

Temporization for endodontics

Teeth undergoing root-canal therapy are susceptible to microbial contamination from oral fluids both during and after treatment. With the exception of single-visit treatment, the use of a temporary restoration is mandatory. This review aims to provide an overview of the materials and techniques used for short- and long-term restorations during and immediately after endodontic treatment, and to make clinical recommendations. Further research is necessary to determine the effectiveness of temporary restorations in the conditions of the oral environment, especially with respect to leakage and functional demands.

Endodontic failure caused by inadequate restorative procedures: review and treatment recommendations

A review of the literature was performed to determine whether prompt placement of coronal restorations, including sealing and placement of posts and cores, can positively influence the long-term prognosis of teeth after root canal therapy. Both hand and MEDLINE searches were employed to identify peer-reviewed articles on radicular apical integrity after coronal restorations, especially where root canal space was used for post and core fabrication. A total of 41 articles published between 1969 and 1999 (the majority from the 1990s) were reviewed. The literature suggests that the prognosis of root canal-treated teeth can be improved by sealing the canal and minimizing the leakage of oral fluids and bacteria into the periradicular areas as soon as possible after the completion of root canal therapy.

Leakage of interim post and cores used during laboratory fabrication of custom posts

The aim of this study was to compare coronal microleakage in two conditions. Twenty-eight extracted upper molars were endodontically treated and divided into two groups and controls: group A: prefabricated post and core permanently cemented; and group B: prepared for a post and restored with a temporary post crown cemented with a temporary cement. The teeth were thermocycled, immersed in black India ink for 1 week, and made transparent. Results indicated that the permanently cemented, prefabricated post and core produced the best seal (p < 0.01); leakage was significantly greater with the temporary post crown and was similar to that of a positive control group.

Restoration of the endodontically treated tooth

It has been the purpose of this article to provide a rationale for the restoration of endodontically treated teeth. Treatment recommendations have been made in the areas of post design, placement technique, cements, core materials, and definitive restorations, based on a review of the clinical and laboratory data.

Setting times for endodontic sealers under clinical usage and in vitro conditions

The object of this study was to determine the set of sealers under simulated clinical versus bench-top conditions. One hundred twenty extracted teeth were divided into four groups (Roth's, Tubuliseal, Sealapex, AH26). Canal preparation and lateral condensation were performed with the four sealers (30 teeth each). Teeth were placed into 100% humidity at 37 degrees C. The same mix of sealer on a glass slab was stored within the same environment. After 1 to 8 wk the teeth were fractured longitudinally to expose the gutta-percha-sealer interface. Evaluation, both clinical and in vitro, was qualitative under a microscope with a needle tip. The degree of set was categorized as: (a) unset (smearable), (b) partially set (indented easily, but not smearable), or (3) set (not easily indentable). There were inconsistencies in setting times within and between groups. In canals most of three (AH26, Sealapex, and Tubuliseal) were partially set after 1 wk; set was complete after 4 wk. Roth's was very slow; most were unset after 8 wk. Sealers on the glass slab set much more rapidly. In conclusion, under clinical conditions, sealers set slowly (particularly Roth's) and were more delayed than when tested in vitro.

Microleakage of endodontically treated teeth restored with fiber posts and composite cores after cyclic loading: a confocal microscopic study

STATEMENT OF PROBLEM

The effectiveness of the seal obtained with carbon fiber posts and composite cores is still unclear. Both 3-step dental adhesives and self-etching adhesive primers have been suggested as adhesive systems.

PURPOSE

This confocal microscopic study evaluated the microleakage of teeth endodontically treated and restored with fiber posts and composites with 3 adhesive systems.

MATERIAL AND METHODS

A total of 72 human mandibular premolars were endodontically treated and divided into 6 groups of 12 teeth each. The first 3 groups were treated with an endodontic sealer containing zinc oxide-eugenol (ZOE) and restored with temporary filling materials containing ZOE. The last 3 groups were treated with ZOE-free materials. Post spaces were prepared in the root canals. The first group treated with ZOE-based materials was restored with fiber posts cemented with zinc phosphate cement and composite cores without adhesive. The other 2 groups of ZOE-treated teeth were restored with fiber posts cemented with All Bond 2 and Panavia 21 dental adhesives, respectively. The last 3 groups were restored with fiber posts cemented with All Bond 2, Panavia 21, and Panavia Fluoro cement, respectively. The teeth were loaded intermittently at 2 cycles per second in a moist environment and, after 300,000 cycles, immersed in a solution of Rhodamine B dye for 48 hours. A confocal microscope was used to observe the teeth. The ratio between the length of the interfaces observed and the length of the dye penetration was evaluated. Two teeth from each group acted as controls and were not subjected to dynamic loads.

RESULTS

All resin cement groups leaked significantly less than the group cemented with zinc phosphate cement. No statistically significant difference was found between the microleakage of teeth treated with ZOE-based and non-ZOE-based materials. Teeth restored with All Bond 2 dental adhesive leaked significantly less than those restored with Panavia cement.

CONCLUSION

The 3-step dental adhesive (All Bond 2) resulted in a better marginal seal than that obtained with the self-etching primers (Panavia 21 and Panavia F). The use of endodontic sealers and temporary filling materials containing ZOE had no detrimental effect on the marginal seal of carbon fiber post/composite resin core restorations.

An in vitro study into the effect of the ferrule preparation on the fracture resistance of crowned teeth incorporating prefabricated post and composite core restorations

AIM

This in vitro study investigated the effect of a ferrule preparation on the fracture resistance of crowned central incisors incorporating a prefabricated post (Parapost) cemented with Panavia-Ex and with a composite core.

METHODOLOGY

The test group consisted of 10 post crowned natural central incisor teeth with a 2-mm wide ferrule preparation, whilst the control group of 10 teeth had no ferrule. The specimens were mounted on a Lloyd universal testing machine and a compressive load was applied at an angle of 135 degrees to the palatal surface of the crown until failure occurred.

RESULTS

In both groups, failure occurred at higher loads compared with previous studies. The mean failure load was 1218 N for the unferruled group and 1407 N for the ferruled group. Statistical analysis showed no significant difference between the groups.

CONCLUSIONS

Under the conditions of this study, when composite cement and core materials are utilized with a Parapost prefabricated system in vitro the additional use of a ferrule preparation has no benefit in terms of resistance to fracture.

Corrosion by galvanic coupling between carbon fiber posts and different alloys

OBJECTIVES

The corrosion of metal type (NiCr, copper, etc.) posts in post and core restorations has been a well known fact over the last few years. A new generation of carbon fiber posts is now playing an extensive role in dental prosthetics, but these posts may, in some cases come in contact with alloys used for restoration purposes. The objective of this paper is to study the electrochemical behaviour of these posts in an artificial SAGF medium (Artificial Saliva Gal Fovet) for comparison with that observed for different alloys (gold, NiCr and amalgams) in the same medium, and to assess the coupling that might occur between these posts and alloys.

METHODS

Posts of different diameters (1-2.1 mm) were molded in resin, thus forming 10 x 3 mm pads that were mounted on a rotating electrode. Pads of identical dimensions were also made for each alloy. Voltammograms (current-tension curves) were plotted for every material in the SAGF medium at 25 degrees C with normal aeration and low aeration (bubbling purified argon) using a potentiometer with three electrodes to determine the position of the zero current potentials. Evans graphs were then plotted once the anode part of the alloy curves and the cathode part of the post curves had been processed with computer software. The potentials and the maximum coupling current densities were estimated.

RESULTS

Posts may be involved in galvanic coupling in the presence of oxygen. Galvanic activity in an aerated solution is highly probable upon contact with amalgams, but may also occur if the material in contact is NiCr alloy. Coupling between precious alloys and posts is improbable and can only induce very low currents in the presence of oxygen.

SIGNIFICANCE

This study devoted to coupling of carbon fiber posts and metals in the mouth, attracts attention to the fact that a corrosion reaction can be set-up in the infiltration conditions relevant to the prosthetic restoration.

Dental materials: 1997 literature review

This review of the published literature on dental materials for the year 1997 has been compiled by the Dental Materials Panel of UK. It continues a series of annual reviews started in 1973. Emphasis has been placed upon publications, which report upon the materials science or clinical performance of the materials. The review has been divided by accepted materials classifications (fissure sealants, glass polyalkenoate cements, dentine bonding, dental amalgam, endodontic materials, casting alloys, ceramometallic restorations and resin-bonded bridges, ceramics, denture base resins and soft lining materials, impression materials, dental implant materials, orthodontic materials, biomechanics and image processing, resin composites, and casting investment materials and waxes). Three hundred and thirty three articles have been reviewed.