Grabar aumenta retencion del poste

SAVE OFFLINE

Effect of dentin conditioning on retention of airborne-particle-abraded, adhesively luted glass fiber-reinforced resin posts Zakereyya S. M. Albashaireh, BDS, MSc, PhD,a Muhamad Ghazal, DDS,b and Matthias Kern, Dr Med Dent, Phdc Jordan University of Science and Technology, Irbid, Jordan; School of Dentistry, Christian-Albrechts University, Kiel, Germany Statement of problem. The smear layer covering root canal dentin as a result of post space preparation procedures may negatively affect the retention of adhesively cemented glass fiber-reinforced resin posts. Purpose. The purpose of this study was to evaluate the retention of airborne-particle-abraded glass fiber posts luted with 3 different bonding systems after conditioning the canal dentin with acidic conditioning methods. Material and methods. Post spaces were prepared in 6 groups of 8 endodontically treated single-rooted teeth. Glass fiber-reinforced resin posts were airborne-particle abraded and luted after etching the canal dentin with phosphoric acid and/or applying XP Bond, Clearfil New Bond, or ED Primer. The groups with their respective etching time, primer, and cement combinations were as follows: XP15: 15 seconds of phosphoric acid treatment, XP Bond and Calibra; XP30: 30 seconds of phosphoric acid treatment, XP Bond and Calibra; NB15: 15 seconds of phosphoric acid treatment, Clearfil New Bond and Panavia 21; NB30: 30 seconds of phosphoric acid treatment, Clearfil New Bond and Panavia 21; ED: ED Primer only and Panavia 21; ED15: 15 seconds phosphoric acid treatment, ED Primer and Panavia 21. Specimens were stored in water for 30 days and subjected to simulated aging conditions. Post retention was measured in tension at a crosshead speed of 2 mm/min. Data were analyzed using Mann-Whitney and Kruskal-Wallis tests followed by post hoc comparisons using Langley method (α=.05). The dislodged posts and canals were examined microscopically at x8 and x20 magnification to evaluate the mode of failure. Results. For each group, the mean (SD) retention in N was: XP15: 376.8 (39); XP30: 305.5 (27); NB15: 370.3 (31); NB30: 297.6 (52); ED: 301.6 (43); ED15: 373.8 (46). The retention values of ED15, NB15, and XP15 were significantly higher than those of ED, NB30, and XP30 groups, respectively. Microscopic evaluation demonstrated that the failure mode was primarily mixed. Conclusions. Luting posts with Panavia 21 or Calibra after etching the dentin with phosphoric acid for 15 seconds produced significantly higher retention values than treating dentin for 30 seconds or with ED Primer, only. (J Prosthet Dent 2008;100:367-373)

Clinical Implications To achieve the highest retention of glass fiber-reinforced posts evaluated, etching of the canal dentin with phosphoric acid for an additional 15 seconds improves the retention when using ED Primer and Panavia 21, while the recommended etching time should not be increased when using Clearfil New Bond and Panavia 21 or XP Bond and Calibra.

a

Associate Professor, Department of Restorative Dentistry, Faculty of Dentistry, Jordan University of Science and Technology. Visiting Assistant Professor, Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, ChristianAlbrechts University. c Professor and Chairman, Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, ChristianAlbrechts University. b

Albashaireh et al

368

Volume 100 Issue 5 Glass fiber-reinforced resin post systems were introduced in the last decade1 and have gained popularity because of their inherent advantages with respect to biomechanical properties, and because they increase the transmission of light within the root and overlying gingival tissues. They are easy to remove in the event of treatment failure,2 eliminate the potential hazards of corrosion and allergic hypersensitivity associated with metal posts,3 and have a low modulus of elasticity that has been reported to reduce root fracture.4 Clinical assessment of post treatment failures demonstrated that post cementation into a root canal remains a concern.5 Clinical studies reported that for restorations placed with adhesively luted fiber posts, failure most commonly occurred due to debonding of the post.4,6,7 Dislodgement of posts occurs after some years as a result of dynamic mechanical loading.8 Resin cements are commonly used for luting glass fiber-reinforced posts in root canals to increase their retention.9 It has been reported that the use of resin cements significantly increases retention of posts compared with other cements.10-12 Airborne-particle abrasion of the post surface significantly improved the retention compared to treatment of the posts with ED Primer (Kuraray, Osaka, Japan), a self-etching material.9 In another study, airborne-particle abrasion of the smooth post surface more than doubled its retentive strength.13 Low bond strength values were reported for root dentin1,14 compared to those reported for coronal dentin.15 The retention of posts luted with resin cement may be influenced by the endodontic procedure performed,16 the type of irrigation materials used in the preparation,17 and the C-factor, the ratio of bonded to unbonded surfaces in post preparations.16,18 Another factor that may influence post retention is the formation of the smear layer.19 This layer is formed on the canal dentin, with smear plugs usually extending 1 to 2 μm into den-

tinal tubules but occasionally penetrating as far as 10 μm.20 The treatment of the smear layer before post cementation may be important for achieving increased success with the post treatment.19,21 Some manufacturers recommend the application of self-etching primers before luting posts in the root canals with their resin cements. The primary objective of applying these agents to smear layercovered dentin is to incorporate the smear layer into the hybrid layer22 and facilitate the penetration of adhesives into the dentinal tubules to form an interdiffusion zone with resin tags and adhesive lateral branches between the adhesive material and etched dentin.23-25 Gaps resulting from incomplete impregnation of adhesives into demineralized dentin were demonstrated within and beneath the hybrid layer.26,27 Etching of dentin with 37% phosphoric acid for 15 seconds removes the smear layer completely and demineralizes the subsurface dentin.22 However, post space preparation might produce a thick smear layer28 that covers root canal walls and the orifices to the dentinal tubules, so that etching for a longer time might be required to achieve optimal bonding. Moreover, the use of different luting resins and dentin conditioning methods might affect long-term retention of posts significantly, as the degree of smear layer removal might be influenced by the duration of etching. Previous work9,13,29 has primarily focused attention on the effect of different post surface textures on retentive strength. Only limited data is available on methods for conditioning the root dentin before luting posts in the post space. Therefore, the purpose of this study was to evaluate the influence of different acidic conditioning methods on the retention of posts treated with airborne-particle abrasion. The null hypothesis was that the retention of glass fiber-reinforced resin posts in root canals would not be influenced by conditioning the dentin of the post space with phos-

The Journal of Prosthetic Dentistry

phoric acid for 15 seconds more than the recommended etching time.

MATERIAL AND METHODS The pulp spaces in 48 single-rooted extracted teeth were prepared, and airborne-particle-abraded glass fiber-reinforced resin posts were adhesively luted after conditioning the post space dentin with acidic methods. The posts were subjected to aging simulation and their retention was measured afterwards. Extracted caries-free and visually assessed fracture-free, human maxillary anterior and premolar teeth were selected, cleaned of calculus deposits, debrided of soft tissues, and stored in 0.1% thymol solution (Caelo, Hilden, Germany). Each tooth was sectioned with a diamond rotary cutting instrument (837KR.012; Gebr Brasseler GmbH, Lemgo, Germany) under water spray 1-2 mm coronal to the cemento-enamel junction. Roots with distinctly oval canals were excluded from the study. With this selection process, 48 root specimens were chosen. The pulpal tissues were removed with a barbed broach of an appropriate size (Dentsply Maillefer, Ballaigues, Switzerland). The canals were prepared with a ProTaper rotary system (X-smart, Ref A 1004; Dentsply Maillefer) according to the manufacturer’s guidelines, using s1 and s2 shaping files, followed by f1, f 2, and f 3 finishing files (Dentsply Maillefer). Sodium hypochlorite solution (3%) (Hedinger, Stuttgart, Germany) was used to irrigate the canals throughout instrumentation. The root canals were dried with matching color-coded paper points (ProTaper Paper Points, Ref A 022W; Dentsply Maillefer). Canals were obturated with a gutta-percha cone (ProTaper Gutta Percha Points, Ref A 022X; Dentsply Maillefer) matching the last file used to prepare the apical third of the canal to the working length and eugenol-free epoxyamine resin sealer (AH Plus sealer; Dentsply DeTrey, Konstanz, Germa-

Albashaireh et al

369

November 2008 ny). Lateral condensation using a finger spreader and fine accessory guttapercha points (Dentsply DeTrey) was performed until the canals were completely obturated. Subsequently, the access cavities and apexes were sealed with modeling wax (Henry Schein, Melville, NY). The roots were stored in 0.1% thymol solution at room temperature for at least 72 hours. Notches were prepared in the roots to prevent dislodgement from the embedding material. Gates Glidden burs (Dentsply Maillefer) were used to remove 10 mm of gutta-percha from the root canal. The roots were mounted on custom-made copper rings with autopolymerizing acrylic resin (Technovit 4000; Heraeus Kulzer, Wehrheim, Germany). A custom-made surveyor was used to ensure that the copper ring was parallel to the long access of the canal. A 10-mm-deep post space was prepared using a yellow color-coded precision drill (EasyPost Precision Drill, Ref C0601; Dentsply Maillefer) matching the diameter of a yellow color-coded EasyPost. Post space preparations were accomplished using a handpiece mounted on the surveyor. At the conclusion of the preparation, the post spaces were irrigated with a 3% sodium hypochlorite solution and dried with paper points. The 48 prepared roots were divided into 3 pri-

mary groups (n=16) according to the bonding system used for each group: Panavia 21 and ED Primer (Kuraray); Panavia 21 and Clearfil New Bond (Kuraray); and Calibra and XP Bond (Dentsply DeTrey). Each main group was subdivided into 2 subgroups (n=8) according to the etching time used (Table I). The etchant gel, Panavia Etching Agent V (Kuraray) or DeTrey Conditioner 36 gel (Dentsply DeTrey), was applied with a syringe and a needle into the canal space for the specific time, and then thoroughly removed by rinsing with distilled water applied with a syringe. Canals were dried with paper points. A single drop of XP Bond solution was dispensed into a dish (CliXdish; Dentsply DeTrey), and a drop of autopolymerizing activator, SCA (Dentplsy DeTrey), was added and mixed in. The mixture was introduced into the canals of the root specimens in the XP Bond groups using the brush provided. Excess adhesive was removed from the canal with paper points. The dentin surface of the post space was left undisturbed for 20 seconds. Air was blown gently but thoroughly into the canal from an air syringe for 5 seconds to evaporate solvents until a glassy shining surface was observed. In the New Bond groups, after acid etching and thorough water rinsing and drying, a drop from the catalyst liquid was dispensed into a well of a

dappen dish, and a drop of the universal liquid was added to the catalyst drop. The 2 liquids were mixed quickly and applied on the dentinal surface of the post space using the brush provided. Excess adhesive was removed from the canal using paper points. The solvents were evaporated with a gentle stream of air for 5 seconds. One drop of each ED Primer liquid, A and B, was dispensed into a mixing well of a dappen dish and mixed for 3-5 seconds. The mixture was applied to the canal surfaces of the roots in the ED Primer groups with the provided brush and left to dry for 60 seconds. Excess primer was removed with a paper point to prevent pooling in root canals and polymerization. Canals were dried with a gentle air stream for 5 seconds. The post was mounted on a custom-made revolving wheel, and each quadrant of the post surface was airborne-particle abraded using 50-mm alumina particles (Heraeus Kulzer) at 2.5-bar pressure (36.3 psi) for 5 seconds. Posts (yellow color-coded Radix Fiber Posts; Dentsply Maillefer) were luted either with Calibra esthetic resin cement or with Panavia 21, an adhesive phosphate monomer containing composite resin cement (Table I). The resin cements were mixed and applied according to the manufacturers’ instructions. Equal amounts of the catalyst and the universal pastes

Table I. Test groups and their codes; lot numbers and manufacturer details for materials Main Groups XP Bond

New Bond

Subgroups

Etchant

Etching Time (s)

Primer/ Adhesive

Luting Resin

XP15

phosphoric acid

15

XP Bond

Calibra

XP30

phosphoric acid

30

XP Bond

Calibra

NB15

phosphoric acid

15

Clearfil New Bond

Panavia 21

NB30

phosphoric acid

30

Clearfil New Bond

Panavia 21

ED

self-etching

0

ED Primer

Panavia 21

15

ED Primer

Panavia 21

ED Primer

ED Primer ED15

phosphoric acid and self-etching ED Primer

Albashaireh et al

Lot Number 071116

41222

41126

Manufacturer Dentsply DeTrey, Konstanz, Germany Kuraray, Osaka, Japan

Kuraray

370

Volume 100 Issue 5 were dispensed by turning the syringe of each paste one complete turn. The dispensed pastes were then mixed for 20-30 seconds using a plastic spatula. For all groups, cement was introduced in the post space with a metal file. The posts were inserted in a custom-made holder mounted on a surveyor; the apical 2-thirds of posts were coated with the resin cement and seated in the post space so that the long axis of the post space and copper ring holder were parallel to the long axis of the post. A load of 20 N was then applied for 10 minutes using a custom-made loading apparatus. Meanwhile, excess cement was removed with a sponge pellet, and the bonding margin of Panavia 21 cement was covered with oxygen-blocking gel (Oxyguard II; Kuraray). The bonding margin of the cement (Calibra; Dentsply DeTrey) was light polymerized with a continuous output of greater than 700 mW/cm2 for 20 seconds by positioning the light guide tip of a light-polymerizing unit (Optilux 500; Demetron Kerr Corp, Danbury, Conn) at a 1- to 2-mm distance from the resin. The loading apparatus and specimen were placed in an oven at 37°C during Panavia 21 polymerization. The specimens were stored in water at 37°C for 30 days and then thermal cycled (Willytec/SD Mechatronik GmbH, Feldkirchen-Westerham, Germany) for 7500 cycles (5°C/55°C) with a dwell time of 30 seconds and a transition time of 6 seconds. They were subjected to 300,000 cycles of mechanical loading parallel to the long axis of the post with a masticatory simulator (Willytec/SD Mechatronik GmbH) at 30-N force and 1.6 Hz. The mechanical loading pattern was equivalent to 1 year of clinical function.9 The cyclic loading force was within the reported range of 17 to 44 N for occlusal forces recorded during mastication and swallowing in prosthetically restored dentitions.30 For the retentive force test, a screw-driven universal testing machine (Zwick Z010; Zwick GmbH, Ulm, Germany) was used to apply a

tensile load parallel to the long axis of the posts at a crosshead speed of 2 mm/min. The portion of the post that extended from the root was grasped with a custom-made device. A chain of 4 links between the device and the upper grip of the testing machine allowed for self-alignment during testing.9 The force (N) required to dislodge each post was recorded. Nonparametric tests were preferred, as the sample size was not considered large enough for parametric analyses. Intraprimary group comparisons between the subgroups of the same bonding system (XP15 versus XP30; NB15 versus NB30; and ED versus ED15) were conducted using the Mann-Whitney test. Interprimary group comparisons between the 3 subgroups of “baseline etching time” (XP15 versus NB15 versus ED) and between the 3 subgroups of “additional 15 seconds added to baseline etching time” (XP30 versus NB30 versus ED15) were performed using the Kruskal-Wallis test; as a result, significant differences with P