قوة ربط الدعامات الجذریة اللیفیة الملصقة لعاج الجذر باستخدام تقنیات وض ع مختلفة للمادة اللاصقة

Transcription

1 قوة ربط الدعامات الجذریة اللیفیة الملصقة لعاج الجذر باستخدام تقنیات وض ع مختلفة للمادة اللاصقة رسالة مقدمة الى كلیة طب الفم والاسنان جامعة القاھرة تمھیدا للحصول على درجة الماجستیر فى الاستعاضات السنیة المثبتة من الطبیب/ محمد أشرف حسن مختار بكالوریوس طب وجراحة الفم والا سنان جامعة ٦ أكتوبر ٢٠٠٧ كلیة طب الفم والاسنان جامعة القاھرة ٢٠١٢

2 Bond Strength of Adhesively Luted Fiber Post to Root Canal Dentin Using Different Cement Application Techniques. Thesis Submitted to the Faculty of Oral and Dental Medicine, Cairo University, in partial Fulfillment of Requirements for Master Degree in Fixed Prosthodontics. By Mohamed Ashraf Hassan Mokhtar B.D.S (2007) Faculty of Dental Medicine (6 th of October University) Fixed Prosthodontics department Faculty of Oral and Dental Medicine Cairo University 2012

3 Review of Literature The primary function of a post is to improve the retention of the final restoration and to distribute occlusal stresses along the remaining tooth structure. (6) It has been widely demonstrated that posts do not strengthen the tooth but improve the retention of the core build up material. However, the major forward step in restoring endodontically treated teeth has been the introduction of fiber posts, in addition to, the development of effective adhesive composite cements. The elastic modulus of fiber posts is similar to that of dentine. This feature is claimed to reduce the risk of vertical root fractures. (7) Fiber reinforced posts allow teeth to flex under loading yielding improved stress distribution at the post cement dentine interface and into the root itself. Moreover, adhesive composite cements with similar mechanical properties are used for fiber post bonding, which makes the whole complex behave as a homogeneous entity during function. Since the 1980s, unfilled resin cements have been preferred to conventional zinc-phosphate cements for post luting, because they have been shown to increase the retention of the post and the overall resistance against fracture. (8) Due to the low elastic modulus of the adhesive cement, it may act as a shock absorber, thus decreasing the risk of root fractures. (9) Moreover, the elastic modulus of composite - 3 -

4 cements is in the same range of both fiber post and dentine. The resultant homogeneous biomechanical unit allows a more uniform stress distribution, which better preserves the weakened tooth structure and reduces microleakage at the dentine cement interface, secondary caries and re-infection of the peri-apical area. (10) More recently, one-step self-adhesive composite cements have been proposed as a more suitable alternative for fiber post bonding, thanks to their lower technique sensitivity and user-friendliness. (11) The bond strength of dental biomaterials can be quantitatively assessed with the push-out test. The push-out test has been considered appropriate for measuring the bond strength inside the root canal, as the shear movements are created parallel to the cement/dentin and cement/post interfaces and seems to procure similar stresses to those occurring in clinical conditions. (12) A pushout design combined with dynamic stresses (i.e., thermocycling) allows for a better understanding of dental materials properties invitro. Thermal cycling is conventionally used to simulate the thermal changes occurring in the oral cavity during eating, drinking, or breathing which may concur in stressing the adhesive interfaces. (13) A previous investigation tested the effect of 5,000 thermal cycles on the bond strength of RelyX Unicem in the endodontic space. (14) - 4 -

5 Fiber post Post and core systems have been used to restore endodnotically treated tooth for more than 250 years. They are available in a variety of materials. Cast metal post and core system have along history of successful use due to their superior physical properties. (15) Post and core may secure the long-term retention of a restoration. For many years, cast post and core restoration were the primary option for root canal treated teeth. A great variety of disadvantages associated with metallic posts have led to a controversial discussion about these systems. More precisely, the high number of root fracture and lack of translucency compared to natural teeth is considered to be the main disadvantages. However, esthetic properties of these materials are limited since gray-colored post and core is apparent when used to support translucent allceramic restoration. Moreover, corrosive products and the risk of root perforation during post removal have raised doubts about their use. (16) Additionally, their high elastic modulus can cause stress concentration within the surrounding radicular dentine, resulting in root fractures. Prefabricated post systems are also popular because they can provide satisfactory results while saving time and reducing the costs. (17) In 1990, Duret et al., introduced a non-metallic material for the fabrication of posts based on carbon fiber reinforcement - 5 -

6 principle. The presence of fiber in some materials is a further advantage because fibers distribute stresses on a wider surface area, remarkably increasing the load threshold at which the material begins to show micro-fractures. Moreover, the properties of fiber reinforced materials are well known with their high impact strength, shock absorption, increased fatigue resistance. (18) Carbon fiber posts have also come into use for prosthodontic applications. Properties such as biocompatibility and corrosion resistance make the carbon fiber post a potential replacement for conventional metallic post in many clinical situations. However, the modulus of elasticity of carbon fiber is much greater than that of dentine. Further, the use of carbon posts has generally limited esthetic expectations. Their dark underlying color can adversely influence the shade of the overlying gingival tissue and prosthetic restoration. (19) In the late 1980s zirconia posts were introduced in response to the need for a post that possessed optical properties compatible with all ceramic crown. Zirconia posts, possessed high flexural strength and fracture toughness. The choice of post materials later changed from very rigid material to materials that have mechanical characteristics that more closely resemble dentin. Fiber-reinforced composite posts provided a viable alternative to traditional rigid post materials mostly because - 6 -

7 of their similar biomechanical properties to that of dentine. In this way a monoblok unite could be created, and fracture risk of roots could be reduced. (20) Posts made up of tooth colored materials such as glass fibers have become popular because they increase the transmission of light within the root and the overlying gingival tissues. Glass fiber posts are composed of glass fibers, inorganic filler and a resin matrix. The low modulus of elasticity of fiber reinforced epoxy resin post has been reported to reduce the risk of root fracture. In addition, the restoration of the endodontically treated teeth with metal free materials eliminates the potential hazards of corrosion and hypersensitivity. Fiber-reinforced posts also have the advantage of easy removal if endodontic retreatment is required. (21) Ferrari et al (22), evaluated the treatment outcome of (cast post and core) and (Composipost) systems after four years of clinical service. The teeth used in study were divided into two groups, group 1: (cast post and cores) cemented into roo t canal preparation with a traditional technique. Group 2: (Composipost) systems were luted in to the root canal following the manufacturer s instructions. They found that group 2 showed a better clinical success than group 1 with no dislodgment or fracture of posts or roots were observed. They concluded that ideal posts should impart - 7 -

8 minimal stress on the tooth, provide adequate retention to the core and allow easy removal to permit endodontic retreatment. Sen et al 2004 (23) assessed the retention of two different prefabricated posts cemented to the root canal with four different luting cements (Rely-X ARC, Panavia F, ParaPost Cement, Flexi-Flow Natural and Adhesor) and a (Zinc Phosphate) cement. Samples were divided into five subgroups to evaluate the effect of the five different cements. They found that (Flexi-Post) dowels had a higher retention than (ParaPost) dowels for the cement groups. Le Bell et al 2004 (24) compared bonding of 3 types of fiber posts and a titanium post with either cross-linked or a semiinterpenetrating polymer network polymer matrix to composite resin cement. They found that fiber posts with semi-ipn polymer matrix had a higher pull-out force values than the prefabricated fiber posts with a smooth surface and a cross-linked polymer matrix. Moreover, the highest pull-out force was gained by serrated titanium posts. Goracci et al 2004 (12) examined the push-out method and both trimming and non-trimming variants of the micro-tensile techniques in their ability to measure accurately the bond strength of fiber posts luted into the prepared root canals. They also, investigated the existence of significant differences in the condition of adhesion created at different root levels by two resin cements. Fiber posts in endodontically treated teeth were divided into two groups according - 8 -

9 to the adhesive cement used group 1: (Excite DSC in combination with Variolink II) and group 2: ( RelyX Unicem). With each group, the bond strength of the cemented fiber posts was assessed with the trimming and non-trimming micro-tensile technique as well as with the push-out test. They found that in the push-out test, the bond strength achieved by group 1 was significantly higher than that of group 2. Moreover, it appeared that with group 1 the bond strength was higher at the coronal than that of the middle and apical third. Regarding group 2, bond strength was similar at the coronal and middle third of the roots. They deduced that the push-out test appeared to be more efficient and dependable then both trimming and non-trimming version of micro-tensile techniques. Naumann et al 2005 (25) evaluated the survival of two tapered and one parallel sided glass fiber posts systems in anterior and posterior teeth with different stages of hard tissue loss. Glass fiber posts were adhesively luted and the core was built with a composite resin. They found that higher failure rates were found for restoration of anterior teeth compared with posterior teeth. They concluded that tooth type (ant/post), type of final restoration and the presence of anterior teeth were found to be significant predictors of failure rates in endodontically treated teeth restored with glass fiber post. Kalkan et al 2006 (26) tested the bond strengths of different types of glass fiber post systems (opaque Snowp ost, translucent - 9 -

10 FiberMaster, and electrical glass Everstick). According to location (cervical, middle and apical) the roots were divided into 3 experimental groups and further sub-divided into two subgroups according to testing time (24 hours or one week). They found that the (Everstick) and (Snowpost) showed higher bond strength values than the (FiberMaster). Push -out values of the cervical segments were significantly higher than the middle and apical segments in the (Everstick) and (FiberMaster) groups w hile with the (Snowpost) group there were no significant differences between cervical and middle segments. There were no significant differences in push-out test values among testing times (24 hours and one week) for all groups. Borer et al 2007 (27) compared the retentive values of stainless steel, parallel-sided posts (ParaPost) to quartz -fiber, tapered posts (D.T.Light-Post) with two different dowel lengths (5 mm and 10 mm). They concluded that the 10 mm posts of both post systems required greater loading force than the 5 mm posts, Moreover, they concluded that there was no statistical difference in retention between quartz-fiber, tapered posts and stainless steel, parallel-sided posts when they were cemented with the same resin cement. Cagidiaco et al 2008 (28) aimed to answer questions regarding the clinical out come of endodontically treated teeth restored with fiber posts. They found that fiber reinforced composite posts

11 outperformed metal posts in the restoration of endodontically treated teeth. They concluded that placement of a fiber post may play a protective role against restoration failure and that the most common type of failure when using fiber reinforced composite materials was post debonding. Kelsey lll et al 2008 (29) investigated the effect of two surface treatments on the retention of three types of dowels placed into the prepared canals with resin cement. One type of titanium dowel and two types of fiber dowels were each used to restore all teeth in three groups following the preparation of their canals to a depth of 9mm. (ParaPost) represented the titanium dowel while (FibreKleer and FibreKor) represented the fiber dowels. The specimens were submitted to a pull-out test. They found that the bond strength associated with the (ParaPost) system was less dependent then the fiber posts even when their surfaces were roughened. They concluded than surface roughening with air abrasion increases retention in dowels cemented with resin cements. Kremeier et al 2008 (30) determined the influence of post type and luting material on push-out bond strength to dentine. The glass fiber-reinforced resin posts (Luscent Anchor) were luted using three dual-cured adhesive systems (Excite DSC/Variolink II, EnaBond/EnaCem, Prime & Bond NT/Calibra). A different brand of glass fiber post (Easy Post) and quartz fiber post (DT Light Post)

12 were luted using (Calibra). Gold posts were luted using either adhesive bonding following tribo-chemical silicate coating or conventionally using glass ionomer cement. Three slices of 2 mm height were cut perpendicular to the post from each restored root. Bond strength was determined. They found that the selection of the fiber post appears to be more important for high bond strength than the choice of the luting material. There were significant differences observed among the fiber posts but not among the luting materials. Bond strength of fiber posts was equivalent but not superior to adhesively or conventionally luted gold post. D Arcangelo et al 2008 (31) evaluated the bond strength of three adhesive/resin cement/fiber post systems to coronal, middle, and apical thirds of the dentine space. Saremco post Non-stop Fiber (Saremco), FRC Postec Plus (Ivoclar Vivadent) and Anatomical Post (Dentalica) were luted in prepared root canals using adhesive system and resin cement provided by the respective manufacturer. They found that the highest bond strength values were found in the coronal third for all experimental groups. The middle and apical thirds exhibited similar bond strengths with no statistically significant differences among them. (Saremco) and (Anatomical post systems) had the highest retentive strength, while the (Ivoclar post system) had the lowest values

13 Vano et al 2008 (32) evaluated the effect of immediate versus delayed post space preparation and cementation on the retention of different types of fiber posts in canals obturated with an epoxy resin sealer. Sixty-eight single rooted teeth were decoronated and the root canals were shaped using rotary instruments and obturated with gutta-percha and an epoxy resin sealer. The teeth were divided into four groups: group 1 (immediate), group 2 (24 hours), group 3 (one week) after root canal filling, group 4 (with no root canal obturation). They found that the delayed cementation of fiber post resulted in higher retentive strengths irrespective to the post type used. Rodig et al 2010 (33) compared the bond strength between two fiber posts (FRC Postec and DT Light Post) and different composite resin following different surface treatment of the posts. After post space preparation the posts were luted with either resin cements or a core build up material. Push-out tests were performed.they found that (FRC Postec) posts achieved higher bond strength than (DT Light post) and the cementation with the core build up material showed higher bond strengths than the resin cement. They concluded that Post type, type of surface treatment and type of resin cement were significant factors for bond strength. Also, luting with a core build up material increased the bond strength

14 Castellan et al 2010 (34) evaluated the ability of bond strength tests to measure the bond strength of fiber posts luted into root canals.the test methods were (hourglass micro-tensile), (push-out), (modified push-out) and (pull-out).they found that (pull-out) test provided the highest values of bond strength followed by (modified push-out) test both of which had a greater amount of adhesive failure while the (push-out) test showed the highest frequency of cohesive failure. They concluded that the specimen design directly influences the biomechanical behavior of bond strength tests. Poskus et al 2010 (35) analyzed the influence of post design, roughness and cement system on the retention of glass fiber posts. Forty single rooted teeth were tested with two tapered and smooth posts and two parallel-sided and serrated posts which were adhesively luted with two different resin cements: a dual-cured (Rely-X ARC) and a self-cured (Cement Post). Teeth were divided into eight groups according to the type of post and the adhesive cement used. The specimens were submitted to a pull-out test. They concluded that the glass fiber posts were not affected by post design or surface roughness nor resin cement-curing mode. Farina et al 2011 (36) assessed the in-vitro bond strength of glass fiber posts and carbon fiber posts in the cervical, middle, and apical thirds of root canals cemented with self-adhesive (RelyX - Unicem) and self-cured (Cement -Post),They used forty maxillary

15 canines divided in to 4 groups according to the cement and post used group 1 :(glass fiber post) and (RelyX), group 2 : carbon fiber post and (RelyX Unicem), group 3 :glass fiber post and Cement -Post, group 4 :carbon fiber post and Cement-post. Push out test was applied in cervical, middle, apical thirds of each specimen to assess the bond strength of cement/post complex to root canal wall. They found that the glass fiber posts presented the best results when cemented with (RelyX) and Cement -post. Self-adhesive (RelyX Unicem) presented the highest bond strength values for both glass fiber and carbon fiber posts. Moreover, the bond strength in all groups was higher in cervical third, followed by the middle then the apical thirds. They concluded that the glass fiber posts cemented with (RelyX Unicem) presented the highest bond strength values in all root thirds. Adhesives for fiber post bonding The most common failure of teeth restored with fiber posts is dislodging of the posts from the root canals. As a result of this type of failure, many investigations have been directed toward improving retention of the posts including different pretreatments of the posts and dentine or use of different luting cements. (37) Among the most commonly used dental cements, zinc phosphate, zinc polycarboxylate, glass ionomer, resin-based

16 composite and the hybrid of resin and ionomer cements. Zinc phosphate has had the longest history of success. In addition to having an extended working time, it is compatible with zinc oxide and eugenol (ZOE), which is contained in most root canal sealers. The use of resin cements has increased, and studies have reported higher retention values and resistance to fatigue for these cements compared to brittle zinc phosphate cements. The modulus of elasticity of resin cement approaches that of dentine, and therefore they may have a potential to clinically reinforce thin-walled roots. (38) The luting systems suitable for fiber post bonding can be divided into two sub-groups according to the adhesive system used to prepare the tooth prior to cementation. One group utilizes etch and rinse adhesive systems, while in other group, enamel and dentine are prepared using self-etching primers. Resin cements can be classified according to their polymerization mode into self-cured, light-cured and dual cured Self-adhesive cements were introduced in 2002 as a new subgroup of resin cements. These materials were designed with the purpose of overcoming some limits of both conventional and resin cements. Self-adhesive cements do not require and pretreatment of the tooth substrate as once the cement is mixed, application is accomplished through a single clinical step

17 RelyX Unicem adhesion mechanism to root dentine is claimed to rely on the micromechanical retention and chemical interaction between monomer acidic group and hydroxyapatite. According to the manufacturer (3M ESPE; RelyX Unicem) product profile, cements adheres to the RelyX Fiber posts by three ways which are mechanical interlocking through the micro-porous surface, chemical covalent bonds and hydrogen bonds ( 39 ). Ferrari et al (40) analyzed the efficacy of an enameldentine-bonding system in combination with resin cement by observing the extent of the resin-dentin interdiffusion zone, resin tags, adhesive lateral branch and hybrid layer used in combination with the fiber post. Two curing systems were used (Dual cure) and (self cure). They found that the two types of posts (Postec fiber post) and (EndoAesthetic fiber post) showed good adaptation to resin cements with absence of voids or bubbles at the fiber post resin cement interface. They observed using a scanning electron microscope the formation and uniformity of the resin-dentin interdiffusion zone along the length of the adhesive interface and the presence or absence of gaps. They concluded that there was a direct correlation between each clinical bonding procedure and resin tags, adhesive lateral branch and resin-dentin interdiffusion zone formation. In addition, the combination of a self curing bonding resin cement systems with fiber posts showed best results

18 Pest et al (41) evaluated the bond strength between luting cement, root dentine and fiber post through push-out test. They also examined the integration of fiber post, resin cement and composite resin through scanning electron microscopy. They concluded that the clinical affinity between fiber post and luting cement was extremely important in achieving high bond strength. The push-out tests and scanning electron microscopy showed that composite resin may be used to lute the post and restore the core, it also perform better than resin cement. Bateman et al (42) tested the retention of quartz- fiber endodontic posts cemented to extracted teeth using two cement types. Fifty-four extracted central incisors were prepared for a tapered quartz-fiber post. The prepared teeth were divided in to two groups according to the type of cement used, group 1: using conventional resin cement (RelyX ARC) and group 2: using self - adhesive resin cement (RelyX Unicem). They found that easy application and greater dependability of self-adhesive cement may improve bonding of fiber-based posts in root canals. Walter et al (43) analyzed the microtensile bond strength of two dual-cured resin cements and a glass ionomer cement to coronal dentin versus root dentin. Resin cements used were (RelyX Unicem), (Panavia F)and glass ionomer cement (FujiCEM). They found that the bond strength to coronal and root dentin were similar

19 in each cement. Moreover, when comparing the materials it was found that (RelyX Unicem) presented the highest bond followed by (Panavia F) and (FujiCEM). They concluded that although there were differences in the bond strength of the materials tested but there were no significant differences in bond strengths between coronal and root dentine substrate. Bitter et al (14) investigated the effects of luting agent and thermocycling on the bond strength to root canal dentine using push-out tests. One hundred forty four maxillary canines were root canal filled and divided in to six groups of twenty four teeth each. Fiber posts were inserted using six luting agents: (Panavia F), (Multilink), (Vairolink II), (Permaflo DC), (RelyX Unicem) and (Clearfil Core). They concluded that bond strengths were affected significantly by luting agent and root position. RelyX had higher bond strengths compared with other materials. The apical region of the canals was characterized by significantly higher bond strengths. Wrbas et al (44) tested the tensile strength of two different fiber post systems in combination with five different resin cements. Artificial root canals in bovine dentine were used in which posts were inserted using (Clearfil Core), (RelyX Unicem), (Panavia 21ex), (Panavia F2.0) and (Calibra). Titanium posts luted with (Zinc Phosphate) cement served as a control group. They concluded that the adhesion of resin cement to fiber posts and root canal dentine

20 was influenced by different factors. The combination of the fiber post system with the type of resin cement has a generally influenced the tensile bond-strength. Putignano et al (45) evaluated the bond strength at the adhesive interface between a quartz fiber post, different adhesive systems and different composite cements. Fiber posts (DT Light - Post) were cemented with group1(prime & Bond NT + Self Cure Activator and Calibra as a luting cement) group 2 (Prime + Bond NT + self Cure Activator and UniFil Core) group 3 (UniFil Bond in combination with UniFil core). Specimens were processed for push out test to evaluate bond strength at the root dentin-cement post interface. They found that there was no significant difference between the three groups. It was concluded that all materials tested had satisfactory bond strength when used for luting fiber posts. Bonfante et al (46) investigated the tensile bond strength and failure mode of glass fiber posts luted with different cements. Cements used in the test were group 1: (resin modified glass ionomer RelyX luting), group 2 : (resin modified glass ionomer Fuji Plus), group 3 : (resin cement RelyX ARC) and group 4 : (resin cement Enforce). They found that the resin cements presented higher tensile bond strength values than those presented by glass ionomer cements. They concluded that the resin cements and glass