Forty recently extracted central incisors were sectioned and mounted in acrylic using a custom-made mounting jig. Porcelainlaminates were fabricated on the teeth and were divided into four different groups as Group A: No surface pre-treatment, Group B: Etching with 1.23% APF gel for 10 minutes, Group C: Sandblasted with 50 μm Aluminium oxide at 60 psi at 0.5 Mpa for 5 seconds at a distance of 10 mm and Group D: etching with 5%, Hydrofluoric acid for 20 seconds. All the groups except Group A were subjected to silanization after surface pre-treatment. All the porcelainlaminates were bonded to the teeth with adhesive resin luting cement. Then, the samples were subjected to shearstrength by Universal Testing Machine. The fracture load was noted in Newton and accordingly Shearbondstrength was calculated in MPa. The results were tabulated and subjected to statistical analysis. One deboned test sample from each test group was randomly selected for a qualitative assessment by SEM analysis for surface topography. The results were tabulated and subjected to statistical analysis.
The porcelain veneer technique includes the bonding of porcelain laminate to the tooth surfaceusing adhesive techniques. The success of the porcelain veneer is greatly determined by the strength and durability of the formed bond between the three different components of the bonded veneer complex, as there are the tooth surface, the luting agent and the porcelain veneer (Peumans, 2000). The aim of pre-cementation surface modification of the laminate is to modify its structure, to increase the surface area available for bonding and to create undercuts that increase the micromechanical retention and strength of the bond to the resin luting cement (Nagayassu, 2006; Spohr, 2003). IPS Empress 2 a pressable mutliphasic popular glass ceramic with a high degree of crystallinity was developed in 1998 with the same laboratory procedure and equipment used for the initial version of IPS Empress. It is composed of approximately 70% leucite, which confers improved mechanical properties. This material has generated considerable interest because of its ease of fabrication based on the lost wax technique and excellent esthetic feature. So this material was used in our study and veneering material consisted of an appetite glass ceramic (Proenca et al., 2006; Addison, 2007). HF is an inorganic acid capable of etching glass surfaces (Alex, 2011). Horn in 1983 proposed etching porcelain laminate veneer restoration with either hydrofluoric acid or Stripit solution, and it is a standard protocol to bond etchable porcelains to teeth (Lee, 2003; Spohr, 2003). The HF acid attacks the glass phase of ceramics, partially dissolving it and creating microporous retention by exposing areas of crystals which make up the crystalline phase of the material (Filho, 2004). Silanes are a class
Neis et al (2015) 55 evaluated the efficacy of differentsurface conditioning methods on the microtensile bondstrength of a restorative composite repair in three types of dental ceramics: lithium disilicate-reinforced, leucite-reinforced and feldspathic. Differentsurfacetreatments like diamond bur abrasion, 10% hydrofluoric acid etching, and tribochemical silica coating were employed. After surfacetreatments all samples were cleaned with 37% phosphoric acid + silane + adhesive and restored with composite resin. They concluded that the superficial wear with diamond bur proved to be suitable for feldspathic porcelain and for leucite-reinforced glass ceramic while hydrofluoric acid-etching is indicated for repairs in lithium disilicate-reinforced ceramic, tribochemical silica coating is applicable to leucite-reinforced ceramic. So the success of the surface treatment depends on the type of ceramic to be repaired.
Also in the above studies, Co-Cr samples showed superior bondstrength as compared to both cp Ti and Ti-6Al-4V alloy for all the surfacetreatments tested. These findings are in line with those obtained from the present study. This can be attributed to the higher flexibility of Ti-6Al-4V alloy when compared to Co-Cr alloy which is inherently more rigid due to its composition. 21,45 This is of particular clinical relevance since denture deflection during use can result in framework-resin debonding. 37 Thus special emphasis is needed in designing and fabricating stiff frameworks that can minimize denture deflection. In this regard, application of adhesive primers such as Alloy Primer can greatly enhance the bondstrength and bond durability as is evident from the results obtained in the present study.
In this group VITACOLL (a mixture of methymetha acrylate and butanone) (Fig-19) , a proprietary bonding agent was applied as per manufacturer’s instructions explicitly. After the dewaxing procedure, with a contra angle micromotor hand piece, vertical grooves were made in one direction across the entire basal surfaces of the teeth using a straight fissure tungsten carbide bur (RA 701L, SS White, Lakewood, New Jersy, U.S.A). (Fig-20 and 21). After ensuring that the entire basal surfaces of the teeth were completely free of any insulating material, VITACOLL bonding agent was applied to keep tooth bases wet for 5 minutes. They were remoistened with VITACOLL without drying out for the entire reaction time of 5 minutes. It was maintained that the bonding agent was applied only on the basal surfaces of the teeth and not poured into the mould and contact was avoided with plaster surfaces. Packing was done within 10 minutes after application of the bonding agent.
Since glazed porcelainsurface are not amenable to resin penetration for orthodontic bonding, mechanical or chemical pre-treatments of the surface is essential for successful direct bonding to porcelain. Although various surface treatment methods have been suggested each one has some disadvantages and limitations. Mechanical roughening with sandblasting is reported to provoke crack initiation within the ceramic. On the other hand, hydrofluoric acid has been found to be a harmful and irritating compound for soft tissue. Organosilane coupling agents are suggested to enhance bonding brackets to porcelain surfaces, but they fail to provide clinically sufficient bond strengths when used alone. To improve bondstrength combination of methods are recommended. 8
Ti:sapphire, the latter one which is still under clinical trial investigation, was more effective in promoting a favorable surface for adhesion. This laser improved the SBS of porcelain repair as much as using HF did.  In our study, etching with HF showed the highest SBS values compared with other groups, and HF acid was more effective than laser to facilitate better mi- cromechanical retention. This finding was in con- sistent with previous reports. [9, 13-14, 16, 18] Akyil et al. concluded that HF acid etching is the most effec- tive surface treatment for increasing the shearbondstrength between a repair composite resin and a feldspathic ceramic surface. The shearbondstrength after laser irradiation can be increased by HF acid etching, but the strength of the bond is still smaller than that after HFA etching alone.  Etching with HF acid can produce a proper surface texture, rough- ness and irregularity by dissolving the crystalline and glassy phases of the porcelainsurface. [18, 20-21] However, there are studies that claim the therapeutic effects of HF are not significantly better than the other treatments. [20-21] Furthermore, intraoral use of HF acid is well recognized for having hazardous effects on soft tissues, so it is not a practical method in dentistry, particularly if used for intraoral porcelain repairs. [4, 8, 13]
Different zirconia surfacetreatments were investigated in the present study to optimize the surface for micromecha- nical and chemical interaction with the adhesive system. Since the initial μ SBS values of experimental groups were signi ﬁ cantly higher than the control, the ﬁ rst null hypoth- esis had to be rejected. The surface treatment of the samples was required to improve the mechanical interac- tion with the resin cement. 38 Ozcan et al, 39 stated that MDP monomer bonded directly to metal oxides, and that the hydroxyl group in MDP monomer reacted with the hydroxyl group on the zirconia surface. Nevertheless, Yi et al 40 reported that the amount and ﬂ ow of functional monomer alone were not suf ﬁ cient to increase the zirconia adhesion ability without any surface pretreatment. In the same manner, several authors 41 – 43 con ﬁ rmed that the dur- able bond to zirconia ceramic could not be achieved with MDP containing cement without surface treatment.
The shearbondstrength also depends on the adhesive materials. Transbond XTTM is one of the most recommended products in current orthodontics. It has been a part of various comparative adhesion studies. In this study, all data were obtained with Transbond XTTM, which strongly associated with previous studies [26-29]. Reynolds and von Fraunhofer  stated that all the retentive designs used in the brackets tested should have an acceptable bond force levels (6– 8 MPa). However, there are various factors related to an oral environment or moisture contamination that may affect the shearbondstrength. The moisture contamination of bracket- bases with water, saliva and blood has been shown to adversely affect the shearbondstrength due to deposits of an organic adhesive layer immediately after exposure that is resistant to washing and subsequently it reduces the shearbondstrength of brackets [17,31-33]. Ahmad Sheibaninia et al.  evaluated the effect of an acidic food simulating environment on shearbondstrength of self-ligating brackets and stated that the margins of bracket-bases allows an acidic food to penetrate, which gradually decreases the shearbondstrength. So care should be taken in predicting the results to those conditions. Arunima Goswami  et al. stated that moisture contamination did not affect the shearbondstrength. It has been suggested that an adverse effect of moisture contamination on orthodontic bonding can be associated with water adsorption, which produce formaldehyde
Kulkarni et al 33 (2007) studied the effect of denture base surface pre- treatments on the bondstrength of two long term resilient liners. They found out that chemical agents such as monomer application increased the bondstrength whereas sandblasting resulted in a decrease of bondstrength. The effect of roughening the surface of the denture base on the bondstrength of the soft liner is not well established. Craig et al 13 advocated a roughened surface to improve the adhesive bondstrength whereas Amin et al 6 reported that roughening the acrylic resin base by sandblasting before applying liner material had a weakening effect on the bond. Minami 41 also found that liners bonded to smooth surface had better bond when compared to those bonded to air abraded surface. He proposed that air abraded resin surfaces may have pits, cracks, crevices, discontinuities with sharp corners and projections. These surface irregularities may not allow complete flow of the soft denture liner and may result in the formation of small voids by air entrapment. Therefore, stress concentrations may be developed in the vicinity of the bonding interface and initiate failure during bondstrength testing.
Various researchers have demonstrated that 2 minutes of etching with 10% HF gel is the best method for increasing the bondstrength of resin to feldspathic ceramic [3, 23]. Yadav et al, in 2010 reported the highest micro-shearbondstrength values in feldspathic porcelainsurface etched with hydrofluoric acid and coated with silane agent. Samples treated with airborne-particle abrasion with alumina and application of silane agent ranked second in this respect. The mode of failure was cohesive in porcelain similar to the present study result . Thus, this method was selected for the control group in our study. In the present study, two-part silane was used since the atmospheric humidity is not optimal for the pre-hydrolyzed (one part) silane . In a study by Khoroushi and Motamedi the bondstrength achieved after Ceramco3 porcelainsurface treatment with HF and silane was almost similar to that in the present study although samples were subjected to 5000 thermal cycles in the present study whereas only 1000 cycles were used in theirs .
Access cavities were prepared and the working length was established by placing a size 20 K-file (Dentsply,US ) into the canal with 1mm short of apex (Fig. 27). The root canals were prepared by Crown down technique using 6% rotary protaper file system (S1, S2, F1, F2, F3). The root canals were irrigated with 3% NaOCl solution at 37ºC and finally irrigated with normal saline (0.9%). The canals were dried with multiple sterile paper points. Master cone size 30 of 6% taper was selected (Fig. 28). All teeth were obturated by Warm vertical compaction method using 6% taper gutta percha cones of size 30 with Root canal sealer (Rc-seal, Prime dental) (Fig. 29). The decoronated and filled roots were stored for 24 hours in distilled water at 37ºC. 40
7. Cecilia Goracci et al (2005) 20 measured the adhesion between two types of translucent prefabricated FRC posts (FRC Postec, Ivoclar- Vivadent, FRC; Light-Post, RTD, LP), and two types of flowable composites used as core materials (UnifilFlow, GC, UF; Tetric Flow, Ivoclar-Vivadent, TF), with or without the application of a silane (Monobond-S, Ivoclar-Vivadent, S) on the post surface. Thirty-five beam- shaped specimens per group were obtained from cylinders of core material, which had been built up around the post by progressively adding small increments of composite resin. Each specimen was loaded in tension until failure at either one of the two post–core interfaces present in each stick. Results showed that post- silanization had a significant effect on adhesion. They concluded that application of a silane onto the post surface prior to building up the core significantly increased the post core bondstrength.
Mc Craekan MS et al  29 : evaluated the effect of three 10% carbamide peroxide home bleaching agents on the enamel surface hardness and on theresin to enamel tensile bondstrength. Eighty extracted bicuspid crowns were divided into four groups (three bleaching agents and on control) and treated with the bleaching agents for 5 consecutive days for the durations specified by the manufacture each day.Specimens in control group were subjected to no treatment. A bonding site on the buccal surface of each crown was etched with phosphoric acid and orthodonticbracket bonded in place. Specimens were thermocycled and loaded to failure in a universal – testing machine. Five hardness specimens per group were measured prebleaching and after 5 days exposure. The authors found no significant differences in resin-enamel tensile bondstrength between the study and control groups. There was also no difference in pre or post bleaching Knoop’s hardness hardness values for the four groups. The authors concluded that short-term regimens of 10% carbamide peroxide did not significantly affect enamel surface hardness or bonding ability.
J.J. LINDEN et al (1991) 13 determine the effects of porcelain opacity, chemical catalyst, and exposure time on polymerization of light- activated resin-composite cements. Samples of microfill and hybrid composites, with and without catalyst (i.e., dual-cure and visible-light- activated), were polymerized by exposure to visible light through porcelain discs of different opacities. Micro hardness testing (KHN) was used to compare degree of cure for each material at various exposure times. Porcelain opacity did not significantly affect hardness. However, the results indicated that a chemical catalyst and prolonged curing times might be essential for clinical success.
The durability of the bondstrength has been questioned due to data showing that bondstrength decreases by half or one- third after a period of storage in a wet environment and / or thermocycling.  The pH is an important factor, which may affect the rate of chemical reaction in an acidic environment led to a decrease in bondstrength.  Delamination of veneering porcelain from underlying ceramic substrates has been reported for all- ceramic restoration. This phenomenon is due to a weak bond between core and the veneering porcelain or can be the result of the use of the weak veneer ceramic.  Since there is not an opaque layer between the two ceramics as in metal- ceramics, the applied loads create stresses or direct the existing stresses towards the core that in turn may lead to veneer and sometime core cracks. 
Despite the limitations of this study, BF resin presented inferior results compared to conventional nanoparticle and microhybrid resins in the bondstrength of repairs that included surface abrasion with a diamond bur followed by acid conditioning in vitro. The type of surface treatment showed greater influence on the conventional nanoparticulate resin (z350), because the abrasion with diamond tip indicated better results for the restorative repair. When repairs with composite resins are made, the kind of material used must be taken into account, as surface detrition may favor the adhesion of certain materials over others. Future studies are needed in order to confirm the results of the present report.
This study investigated the effect of sandblasting on composite resin-alloy bond strengths with the Silicoating technique. Ag-Pd and Ni-Cr alloys were prepared for casting. The specimens were sandblasted with 37 µm or 250 µm A1203 particles under the following conditions: 3 kg/cm 2 for 30 seconds; 5 kg/cm 2 for 10 seconds, 30 seconds, and 45 seconds; and 7 kg/cm 2 for 30 seconds. After sandblasting, the alloy surface was silica-coated, and light cured composite resin was bonded to the alloy. Specimens were divided, stored in dry air for 1 week, and thermocycled from 4º to 60º C for 10² cycles. Bondstrength was measured by applying compressive shear stress. It was found that sandblasting made the alloy-water contact angle smaller and wettability greater.The adhesive strength of composite resins with alloys was influenced by sandblasting.
Sheth et al 1989 16 has conducted a two-part study to evaluate the tensile bond strengths of composite resin to several glass-ionomer cements that were (a) unetched but allowed to set in air and (b) etched for 30 s with orthophosphoric acid, and to compare them with the cohesive strength of the respective cement. Using a silver nitrate staining technique, they also evaluated the microleakage of class V cavities restored with composite resin under a base of etched or unetched glass ionbomer cement. Although there were significant differences among three cements between their cohesive strength and the resin bondstrength after the two surfacetreatments, the bond to the unetched surface was generally comparable to that of the etched surface of the cement. The remaining groups showed no statistical difference. The microleakage was similar in the two groups. SEM micrographs showed a rough topography of the unetched cement that resembled that of the etched surface. This in vitrostudy suggests that acid-etching a glass-ionomer base for resin-bonding may not be necessary for specific materials.
In Group 1, the exposed dentin surfaces were conditioned with GC cavity conditioner for a duration of 10 s, washed and air dried but not desiccated. RMGIC powder mixed with 1.5% Doxycycline, samples were incorporated with mixed material using cylindrically shaped plastic tubes with an internal diameter of 3 mm and a height of 4 mm. The material was then light-cured for 40 s vertically and also cured for 10 s horizontally at 90° angles to ensure complete polymerization of the material. For each sample, the curing tip was placed as nearly as conceivable to the glass ionomer and dentin surface.