Weakened anterior roots--intraradicular rehabilitation

Clinical application of calcium silicate-based bioceramics in endodontics

Pulp treatment is extremely common in endodontics, with the main purpose of eliminating clinical symptoms and preserving tooth physiological function. However, the effect of dental pulp treatment is closely related to the methods and materials used in the process of treatment. Plenty of studies about calcium silicate-based bioceramics which are widely applied in various endodontic operations have been reported because of their significant biocompatibility and bioactivity. Although most of these materials have superior physical and chemical properties, the differences between them can also have an impact on the success rate of different clinical practices. Therefore, this review is focused on the applications of several common calcium silicate-based bioceramics, including Mineral trioxide aggregate (MTA), Biodentine, Bioaggregate, iRoot BP Plus in usual endodontic treatment, such as dental pulp capping, root perforation repair, regenerative endodontic procedures (REPs), apexification, root-end filling and root canal treatment (RCT). Besides, the efficacy of these bioceramics mentioned above in human trials is also compared, which aims to provide clinical guidance for their clinical application in endodontics.

Reverse Cast Metallic Core Based on the Original Prosthetic Crown

The dental crown can be restored using the root in clinical situations where the dental remnant allows adequate anchorage by the use of an intraradicular retainer. After endodontic treatment, reconstruction of the dental anatomy depends on correct planning and the type of restoration to be used. This requires reestablishment of form and function with creation of anchoring features, avoiding detachment and favoring the distribution of forces, thus preventing fracture of the remnant due to functional and parafunctional forces applied on the tooth. This paper reports the clinical case of a patient who sought dental care for a full metal-ceramic crown with a cast metallic core with reduced length that had been detached from tooth 24. After clinical and radiographic examination, root integrity was verified. The patient was offered reconstruction with a cast metallic core of satisfactory length, providing adequate retention and support, with reutilization of the original prosthetic crown, serving as a reverse template of the coronal portion of this new core, providing reduction in costs and operational time.

The use of a fiber sleeve to improve fracture strength of pulpless teeth with flared root canals

OBJECTIVES

This study aimed to investigate how use of a fiber sleeve may reduce interfacial debonding and improve fracture strength of pulpless teeth with flared root canals.

METHODS

Pulpless premolars with flared root canals were restored either with a fiber-reinforced post (FRP) alone or with an FRP wrapped in a hollow tubular fiber sleeve. A normal root restored with an FRP alone served as a control. The integrity of resin-dentin and resin-fiber interfaces in the restored roots was evaluated by a stereoscopic system after penetrating a dye. Four roots were tested for each experimental group. Fracture resistance in pulpless premolars with flared root canals restored with an FRP alone or with an FRP/sleeve combination were investigated under bonded and non-bonded conditions with static fracture testing (n=8), and stress distribution in these restored premolars were tested by finite element analysis (FEA).

RESULTS

Flared root canals restored with an FRP/sleeve combination demonstrated superior integrity at the cervical resin-dentin interface to root canals with an FRP alone. Premolars with a flared root canal restored with an FRP/sleeve combination showed significantly greater fracture resistance compared with premolars restored with an FRP alone. FEA showed that once interfacial de-bonding extended to the cervical region of the root, stress concentration in the root dentin dramatically increased.

SIGNIFICANCE

The FRP/sleeve combination was effective in reducing debonding and, hence, improving the fracture strength of pulpless premolars with flared root canals.

Comparison of apical microleakage of dual-curing resin cements with fluid-filtration and dye extraction techniques

BACKGROUND

Endodontically treated teeth with excessive loss of tooth structure are frequently restored using fiber posts. In this in vitro study, the apical leakage of self- and dual-activated curing modes for dual-curing resins cementing a translucent fiber post was evaluated using computerized fluid filtration meter and dye extraction method.

MATERIAL AND METHODS

One hundred and four extracted human maxillary incisors with single root and canal were used. Experimental samples embedded in a closed system were divided into 4 groups (n=20) according to 2 dual-curing luting systems, with 2 different curing modes (either with self- or light-activation): (1) Panavia F 2.0 with self-cure, (2) Panavia F 2.0 with light-activation, (3) Clearfill SA with self-cure, and (4) Clearfill SA with light activation. Twenty-four teeth served as negative and positive controls. Translucent fiber posts were luted in the roots except in the control groups.

RESULTS

Statistical analysis indicated no significant difference in leakage among groups (p>0.05) with 4.12 × 10(-4) (Panavia self-cure), 4.55 × 10(-4) (Clearfill SA self-cure), 5.17 × 10(-4) (Panavia dual-cure), and 5.59 × 10(-4) (Clearfill SA dual-cure) in fluid-filtration method. Absorbance values for dye-extraction method were 266 nanometer (nm) (Panavia self-cure), 268 nm (Clearfill SA self-cure), 270 nm (Panavia dual-cure), and 271 nm (Clearfill SA dual-cure), in which difference among the groups were not statistically significant (p>0.05). When comparing the leakage, assessment methods results showed no statistically significant difference between the tested evaluation techniques (p>0.05).

CONCLUSIONS

Light- and self-activation curing modes of Panavia F 2.0 and Clearfill SA perform similar to each other in a closed system.

Stress distribution on dentin-cement-post interface varying root canal and glass fiber post diameters. A three-dimensional finite element analysis based on micro-CT data

Objective

The aim of the present study was to analyze the influence of root canal and glass fiber post diameters on the biomechanical behavior of the dentin/cement/post interface of a root-filled tooth using 3D finite element analysis.

Material and Methods

Six models were built using micro-CT imaging data and SolidWorks 2007 software, varying the root canal (C) and the glass fiber post (P) diameters: C1P1-C=1 mm and P=1 mm; C2P1-C=2 mm and P=1 mm; C2P2-C=2 mm and P=2 mm; C3P1-C=3 mm and P=1 mm; C3P2-C=3 mm and P=2 mm; and C3P3-C=3 mm and P=3 mm. The numerical analysis was conducted with ANSYS Workbench 10.0. An oblique force (180 N at 45º) was applied to the palatal surface of the central incisor. The periodontal ligament surface was constrained on the three axes (x=y=z=0). Maximum principal stress (σ_max) values were evaluated for the root dentin, cement layer, and glass fiber post.

Results:

The most evident stress was observed in the glass fiber post at C3P1 (323 MPa), and the maximum stress in the cement layer occurred at C1P1 (43.2 MPa). The stress on the root dentin was almost constant in all models with a peak in tension at C2P1 (64.5 MPa).

Conclusion

The greatest discrepancy between root canal and post diameters is favorable for stress concentration at the post surface. The dentin remaining after the various root canal preparations did not increase the stress levels on the root.

Mineral trioxide aggregate apical plug method for the treatment of nonvital immature permanent maxillary incisors: Three case reports

Treatment of nonvital immature permanent teeth with calcium-hydroxide is associated with some difficulties such as weakened tooth fracture, root canal reinfection and long treatment time. Mineral trioxide aggregate (MTA) apical plug method is an alternative treatment option for open apices, and has gained popularity in the recent times. In this case report, we have attempted to present successful treatment of three maxillary incisors with open apices and periapical lesions with MTA. After preparing the access cavity, the working length was determined. The root canals were irrigated with 2.5% Sodium hypochlorite (NaOCl) and disinfected with calcium-hydroxide for two weeks. MTA was then placed in the apical 3 millimeters of the root canal. The remaining part of the root canal was filled with gutta-percha and the coronal restoration was finished with composite resin. After six months the radiographic examination showed a decrease of periapical lesions. At a 1-year and 18-months follow up, radiological and clinical successful healing of the incisor teeth was seen. MTA seems as an effective material for the apical plug method for the treatment of nonvital immature permanent teeth with open apices.

An in vitro evaluation of fracture strength of endodontically treated teeth with simulated flared root canals restored with different post and core systems

PURPOSE

The objective of this study is to evaluate the fracture strength and mode of failure of endodontically treated teeth with flared canals restored with two fiber reinforced systems (glass fiber and quartz fiber) and one base metal cast post and core system.

MATERIALS AND METHODS

Forty five anterior teeth were decoronated at cemento-enamel junction and were endodontically treated. Post space was prepared and randomly divided into three groups according to post system. Specimens were loaded at 45° in a universal testing machine at a cross head speed of 0.5 mm/min until failure. The mode of failure was classified as repairable or non-repairable.

RESULTS

Teeth restored with cast posts have fracture strength twice that of teeth restored with fiber posts. Fiber-reinforced posts failed at a certain compressive force but they were repairable unlike the non-repairable fracture seen with cast posts.

CONCLUSION

The results of this study showed that, fracture strength and mode of failure in anterior teeth with flared canals varied according to the type of post used to support a crown.

A conservative single visit reattachment of fractured crown fragment

Injury of anterior teeth is a relatively common event that mainly affects children and adolescents. Dentists are confronted with managing dental trauma and restoring fractured teeth on a regular basis. Hence the techniques that speed and simplify the treatment, restore esthetics and improve long term success rate are considered of potential value. If an intact tooth fragment is present after trauma, immediate attachment of the incisal edge is a conservative yet, simple and aesthetic alternative. Fracture reattachment possesses challenging conservative and economically viable procedure within a single visit. The authors wuld report a case of fractured maxillary central incisor using fragment reattachment.

Influence of different restorative techniques on the strength of endodontically treated weakened roots

Objective. Comparing effect of different restoration techniques on fracture resistance of compromised roots. Methods. Crowns of 100 single-rooted teeth were sectioned and 10 roots were kept as negative control group (Group 1). Remaining roots were instrumented and divided into one and positive control group of 10 samples (Group 2) and 4 experimental groups of 20 samples each. Group 3: roots were obturated with gutta-percha; Group 4: roots were restored with gutta-percha, composite, and glass fiber post; Group 5: roots were obturated with Resilon; Group 6: Roots were restored with Resilon, composite, and glass fiber post. Roots were weakened before obturation in groups 2, 3, and 5 and after obturation in groups 4 and 6. Fracture strengths were measured using Dartec testing machine and fracture load was recorded in kilo-Newton. Statistical analysis was done using ANOVA and Tukeys test. Results. The fractures resistance of restored roots was significantly higher in groups 4, 5, and 6 than in Groups 2 and 3. There were no significant differences between groups 1, 4, 5, and 6. Conclusions. Restoration of weakened roots with Resilon or bonding an intermediate composite resin to coronal radicular dentin and to glass fiber post increased their fracture resistance.

Influence of crown ferrule heights and dowel material selection on the mechanical behavior of root-filled teeth: a finite element analysis

PURPOSE

This study used the 3D finite element (FE) method to evaluate the mechanical behavior of a maxillary central incisor with three types of dowels with variable heights of the remaining crown structure, namely 0, 1, and 2 mm.

MATERIALS AND METHODS

Based on computed microtomography, nine models of a maxillary central incisor restored with complete ceramic crowns were obtained, with three ferrule heights (0, 1, and 2 mm) and three types of dowels (glass fiber = GFD; nickel-chromium = NiCr; gold alloy = Au), as follows: GFD0--restored with GFD with absence (0 mm) of ferrule; GFD1--similar, with 1 mm ferrule; GFD2--glass fiber with 2 mm ferrule; NiCr0--restored with NiCr alloy dowel with absence (0 mm) of ferrule; NiCr1--similar, with 1 mm ferrule; NiCr2--similar, with 2 mm ferrule; Au0--restored with Au alloy dowel with absence (0 mm) of ferrule; Au1--similar, with 1 mm ferrule; Au2--similar, with 2 mm ferrule. A 180 N distributed load was applied to the lingual aspect of the tooth, at 45° to the tooth long axis. The surface of the periodontal ligament was fixed in the three axes (x = y = z = 0). The maximum principal stress (σ(max)), minimum principal stress (σ(min)), equivalent von Mises (σ(vM)) stress, and shear stress (σ(shear)) were calculated for the remaining crown dentin, root dentin, and dowels using the FE software.

RESULTS

The σ(max) (MPa) in the crown dentin were: GFD0 = 117; NiCr0 = 30; Au0 = 64; GFD1 = 113; NiCr1 = 102; Au1 = 84; GFD2 = 102; NiCr2 = 260; Au2 = 266. The σ(max) (MPa) in the root dentin were: GFD0 = 159; NiCr0 = 151; Au0 = 158; GFD1 = 92; NiCr1 = 60; Au1 = 67; GFD2 = 97; NiCr2 = 87; Au2 = 109.

CONCLUSION

The maximum stress was found for the NiCr dowel, followed by the Au dowel and GFD; teeth without ferrule are more susceptible to the occurrence of fractures in the apical root third.

Influence of customized composite resin fibreglass posts on the mechanics of restored treated teeth

AIM

To evaluate the mechanical behaviour of the dentine/cement/post interface of a maxillary central incisor using the finite element method and to compare the stresses exerted using conventional or customized post cementation techniques.

METHODOLOGY

Four models of a maxillary central incisor were created using fibreglass posts cemented with several techniques: FGP1, a 1-mm-diameter conventionally cemented post; CFGP1, a 1-mm-diameter customized composite resin post; FGP2, a 2-mm-diameter conventionally cemented post; CFGP2, a 2-mm-diameter customized composite resin post. A distributed load of 1N was applied to the lingual aspect of the tooth at 45° to its long axis. Additionally, polymerization shrinkage of 1% was simulated for the resin cement. The surface of the periodontal ligament was fixed in the three axes (X =Y = Z = 0). The maximum principal stress (σ(max) ), minimum principal stress (σ(min)), equivalent von Mises stress (σ(vM) ) and shear stress (σ(shear)) were calculated for the dentine/cement/post interface using finite element software.

RESULTS

The peak of σ(max) for the cement layer occurred first in CFGP1 (1.77 MPa), followed by CFGP2 (0.99), FGP2 (0.44) and FGP1 (0.2). The shrinkage stress (σ(vM) ) of the cement layer occurred as follows: FGP1 (35 MPa), FGP2 (34), CFGP1 (30.7) and CFGP2 (30.1).

CONCLUSIONS

Under incisal loading, the cement layer of customized posts had higher stress concentrations. The conventional posts showed higher stress because of polymerization shrinkage.

Calcium Hydroxide Apexification of a Large Apical Lesion

Apexification is the standard procedure for the management of immature non-vital teeth. This report presents a case of a traumatic injury to a maxillary central incisor that lead to total pulp necrosis and a large periapical lesion. Calcium hydroxide apexification was used successfully in the treatment of this case.

Bond strength of fiber posts to weakened roots after resin restoration with different light-curing times

INTRODUCTION

This study evaluated the bond strength of translucent fiber posts to experimentally weakened radicular dentin restored with composite resin and polymerized with different light-exposure time.

METHODS

Roots of 60 maxillary incisors were used. Twenty-four hours after obturation, the filling materials of root canals were removed to a depth of 12 mm, and 4 groups were randomly formed. In 3 groups, root dentin was flared to produce a space between fiber post and canal walls. In the control group, the roots were not experimentally weakened. The flared roots were bulk restored with composite resin, which was light-activated through the translucent post for 40, 80, or 120 seconds. Posts were cemented, and after 24 hours, all roots were sectioned transversely in the coronal, middle, and apical regions, producing 1-mm-thick slices. Push-out test was performed, and failure modes were observed.

RESULTS

The quantitative analysis showed significant statistical difference only among groups (P < .001). Comparing the weakened/restored groups, composite light-exposure time did not influence the results. Overall, adhesive failures occurred more frequently than other types of failures. Cohesive failures occurred only in the weakened/restored roots.

CONCLUSIONS

Intracanal root restoration with composite resin and translucent fiber posts provided similar or higher bond strength to dentin than the control group, regardless of the light-exposure time used for polymerization.

Effects of light exposure time on composite resin hardness after root reinforcement using translucent fibre post

OBJECTIVES

The purpose of this in vitro study was to evaluate the Vickers hardness (VHN) of a Light Core (Bisco) composite resin after root reinforcement, according to the light exposure time, region of intracanal reinforcement and lateral distance from the light-transmitting fibre post.

METHODS

Forty-five 17-mm long roots were used. Twenty-four hours after obturation, the root canals were emptied to a depth of 12 mm and the root dentine was artificially flared to produce a 1mm space between the fibre post and the canal walls. The roots were bulk restored with the composite resin, which was photoactivated through the post for 40s (G1, control), 80 s (G2) or 120 s (G3). Twenty-four hours after post-cementation, the specimens were sectioned transversely into three slices at depths of 2, 6 and 10mm, corresponding to the coronal, middle and apical regions of the reinforced root. Composite VHN was measured as the average of three indentations (100g/15 s) in each region at lateral distances of 50, 200 and 350 microm from the cement/post-interface.

RESULTS

Three-way analysis of variance (alpha=0.05) indicated that the factors time, region and distance influenced the hardness and that the interaction timexregion was statistically significant (p=0.0193). Tukey's test showed that the mean VHN values for G1 (76.37+/-8.58) and G2 (74.89+/-6.28) differed significantly from that for G3 (79.55+/-5.18).

CONCLUSIONS

Composite resin hardness was significantly lower in deeper regions of root reinforcement and in lateral areas distant from the post. Overall, a light exposure time of 120 s provided higher composite hardness than the shorter times (40 and 80s).

Fracture Strength of Endodontically Treated Teeth with Flared Root Canals and Restored with Different Post Systems

BACKGROUND

Many post systems are available to clinicians, yet no consensus exists about which one is better in restoring endodontically treated teeth.

PURPOSE

This study evaluated the fracture strength of teeth with flared canals and restored with two fiber-reinforced resin systems (glass fiber: FRC Postec [Ivoclar Vivadent, Schaan, Liechtenstein]; quartz fiber: D.T. Light-Post [Bisco Dental Products, Schaumburg, IL, USA]), and one custom cast base metal (Ni-Cr) post and core system.

METHODS

Thirty anterior teeth had their crowns removed below the cemento-enamel junction and were endodontically treated. The canals were prepared for post fixation, and the canal walls were flared using a taper diamond bur. The prepared roots were randomly divided into three groups according to the post system. All posts were cemented with an adhesive resin cement. For the fiber-reinforced resin posts, cores were built up using microhybrid composite. Metallic crowns were luted using zinc phosphate cement. Specimens were loaded at 45 degrees in a universal testing machine at a crosshead speed of 0.5 mm/min until failure. The mode of failure was classified as repairable or nonrepairable.

RESULTS

Teeth restored with cast posts had fracture strength twice that of teeth restored with resin posts. Fiber-reinforced resin posts failed at a compressive force comparable to clinical conditions, but all failures were repairable.

CONCLUSION

Fracture strength and mode of failure in anterior teeth with flared canals varied according to the type of post used to support a crown.

CLINICAL SIGNIFICANCE

Under the conditions of this study, cast posts are preferable to restore endodontically treated teeth with flared canals and no ferrule.