[Effect of surface treatment on the retention of an intra canal post]

Statement of Problem: Prefabricated posts have recently become more popular due to their satisfactory results while saving time and reducing costs. Glass-fiber prefabricated posts were paid more attention because of reducing the risk of root fracture as well as minimal allergic hypersensitivity and corrosion with satisfactory cosmetic results. Surface treatment is one of the various factors that might affect retention of a post

Purpose: The purpose of this study was to evaluate the effect of surface treatment on the retention of an Iranian Eglass fiber post

Materials and Method: Thirty two intact central maxillary incisors were selected. The coronal aspect of each tooth was removed and the remaining root received endodontic therapy. The specimens were then divided into 4 groups [n=8]. Post spaces were prepared to a depth of 10mm.The posts [HtCo, Iran] received one of the surface treatments including cleaning with alcohol [Alc], air borne-particle abrasion and cleaning with alcohol [Air-Alc], cleaning with alcohol and conditioning with silane treatment [Alc-Sil] or airborne- particle abrasion, cleaning with alcohol and conditioning with silane treatment [Air-Sil]. All the posts were luted with Panavia F after conditioning the canal dentin primer [ED-primer] according to the manufacturer's instructions. After cementation, the specimens were stored at 37[degree sign]C for 30 days and subjected to simulated aging conditions, consisting of 7500 thermal cycles [5[degree sign]C/55[degree sign]C]. Retention of the posts was measured with a universal testing machine with a crosshead speed of 2mm/min. The data were analyzed using one-way ANOVA and Duncan tests [alpha=0.05]

Results: The mean retentive values [N] of the test groups were as follows: Alc=157.63 +/- 39.91, Air- Alc=171.53 +/- 47.80, Alc-Sil= 167.87 +/- 42.49, Air-Sil= 166.53 +/- 40.32. There was no significant difference between the mean values of the four groups

Conclusion: Treating the surface of HtCo Iranian post produced no significant improvement in the retention of the posts

[ effects of adhesive type and different curing methods on micro leakage and marginal adaptation of composite veneers]

The adhesives type and placement application technique may be important in long term stability and function of composite veneers. This study was conducted to evaluate the influence of dentin adhesive application techniques [pre-curing vs. non-curing] on micro leakage and marginal adaptation of indirect composite veneer restorations. A total etch bonding system, Excite/Variolink II [EXV], and a self-etching primer system, Panavia F 2.0 [PF2] were used in this in-vitro investigation. Forty-eight human central incisors were prepared for composite veneer restoration. These teeth were then divided into two groups [n=24]. Pre-cure adhesive [PC] with light cure technique as well as no pre-cure [NPC] prior to resin cement insertion in half of specimens in each group. By using these methods, we worked with four experimental subgroups [PC+EXV, NPC+EXV, PC+PF2, NPC+PF2]. Composite veneers [Tetric Ceram resin] were cemented using a dual-cured resin luting agents. All specimens were then stored in distilled water at 37°C for 24 hours before checking for marginal leakage. By random sampling, two specimens were selected from each group for SEM observations and evaluation of marginal adaptation at 1050 time magnifications. Data was analyzed by ordinal regression and link function of probit type at alpha

In vitro evaluation of the effect of two types of preparations on the fracture strength of laminates fabricated from fiber reinforced composite and ceramic

One of the popular treatment options for correction of discoloration and poorly shaped anterior teeth is veneer. Two main preparation designs for full veneers have-been developed: 1. Window preparation 2, Incisal lap preparation. The aim of this study was to compare the effect of two new design preparations on the fracture strength and retention of laminate with conventional preparation. In this in vitro experimental study, 54 human extracted central and lateral maxillary and mandibular teeth were selected. Samples were divided into three main groups [n=18] with two subgroups in each [n=9]. Group 1: Incisal lap preparation of labial surface of teeth without box preparation. Group 2: Preparation of labial surface with labial box in mesial and distal surfaces. Group 3: Preparation of labial surface with proximal box in mesial and distal surfaces. In the first subgroup of all groups, indirect composite laminate and in the second subgroup, ceramic laminate was fabricated. After cementation of laminates with dual cured resin cement [Rely X ARC], we determined the fracture strength by zwick machine and type of failure by the stereomicroscope. The data were analyzed by One-Way and Two- Way ANOVA, Tukey and student-t tests. 1] There was a significant difference between fracture strength of laminates made of two different types of materials in three types of preparations [P=0.016]. 2] In composite laminates, there was a significant difference between fracture strength of group 1 and 2 and the greatest fracture strength was observed in group 1 [P=0.019]. 3] In ceramic laminates, there was no significant difference between fracture strength of the three types of preparations, although the greatest fracture strength was observed in group 2 [P=0,055], 4] There was no significant relationship between mode of failure and type of preparation in two different laminate materials. The findings of this study demonstrated that in incisal lap preparation of labial surface of tooth without box preparation, fracture strength of composite laminates was proved to be greater than ceramic laminates, while with preparation of labial surface with labial box, fracture strength of ceramic laminates was proved to be greater than composite laminates

[Effect of based-resin desensitizing agent and self-etching adhesive resin on marginal leakage of class II amalgam restorations]

The purpose of this study was to compare marginal leakage of class II amalgam restorations lined with a resin- based desensitizing agent and a self-etching adhesive system with copal varnish. Fifty six freshly extracted human premolar teeth were divided into four groups. Class II box only cavity preparation was prepared on mesial and distal surfaces of each tooth. While the cavities in two groups were lined with desensitizing agent; Viva Sens [A] and adhesive system; Clear Fil S[3] Bond [B],one group was treated with copal varnish; Copalite [C], and last group was used as control, without any lining [D]. Spherical high copper amalgam [Oralloy] was hand-condensed into each preparation, specimens were thermocycled, stained and sectioned. Microleakage was graded using a stereomicroscope. Microleakage scores were calculated and analyzed. Kruskal-Wallis and Mann-Witheny tests were used for analysis of data [alpha=0.05]. For the leakage values of groups A and B, T-test revealed less microleakage with Viva Sens [P<0.05]. Kruskal-wallis test showed significant difference in four groups [P<0.05]. Clear Fil S[3] Bond showed less microleakage than control group, but leakage in copal varnish and Clear Fil S[3] Bond was similar. Less microleakage was revealed with Viva Sens when compared with the other groups [P<0.05]. Viva Sens reduced microleakage of Class II high copper amalgam restorations significantly more than the Clear Fil S[3] Bond and copal varnish

[Comparison of different reinforcement methods of weakened buccal walls in premolar teeth]

In order to improve the aesthetics and functional quality of restorations, the combined amalgam-composite restorations have been introduced. The aim of this study was to compare different reinforcement methods, in weakened buccal walls of premolar teeth. In this in vitro study, 70 similar and intact premolar teeth were used. The specimens were divided into seven groups of ten. In six groups, the three reinforcing materials composite [A], Compoglass F [B] and glass ionomer [C] with two methods: I: buccal and distal wall reinforcement. II: buccal, distal and pulpal floor reinforcement was used. In the seventh group [D], the Scotchbond M.P.P adhesive as a control group was applied. Then specimens were restored conventionally with amalgam and submitted to 500 thermal cycles [5°C-55°C]. The specimens were loaded through Instron testing machine at a crosshead speed of 1 mm/min with angle of 45 degree. Statistical analyzes of ANOVA, Duncan and chi- square tests were used to analyse fracture strength, location and type of fracture. The highest strength was detected in group with composite reinforcement on buccal and distal walls and pulpal floor. The highest failure mode was adhesion type and observed in composite reinforcement and control group. The highest cohesive and mixed failure mode was respectively observed in Compoglass and glass ionomer groups. This study showed that composite resin was the best material for reinforcement of weakened walls with favourable aesthetic property

[Effect of different placement techniques and curing methods on composite microhardness in class I restorations]

The polymerization of light cured composite resins is initiated from surface layer and the rate of polymerization reduces from surface to depth. The difference in hardness is in correlation with different factors such as the intensity of unit and the distance between composite and light tip. The aim of this study was to compare the effect of four different methods of filling and two light direction on microhardness of class I composite resin restorations. In this parallel interventional study, 40 intact human premolar teeth were selected. Class I cavities were prepared [4x4x4 mm]. After etching and applying Excite as a dentin adhesive, the specimens were divided into four groups [n=10] based on the filling Group l] one bulk, group 2] horizontal incremental and occlusal light curing, group 3] horizontal incremental and three directional light curing, Group 4]oblique and three directional light curing. Z100 was used for restoration of cavities. Microhardness of specimens was measured by kicker's microhardness tester in 0, 1.5, 2.5 and 3.5 mm distance from surface. Data were analyzed using ANOVA and Duncan tests [a=0.05]. The mean value of microhardness in groups 1 and 2 showed significant difference from that of groups 3 and 4 [p<0.05]. Within each group, the subsurface layer showed the highest value of hardness [P<0.05] except for group 2 that all surfaces showed a similar hardness value [p>0.05]. Based on the results of this study, incremental technique [oblique or horizontal] with three dimensional light curing is the most suitable procedure for obtaining a maximum hardness in Class I composite resin restoration

Laboratory evaluation of composite wear resistance with and without occlusal index

The polishing and finishing procedures may cause topographical changes and introduce subsurface micro-cracks in dental composite restorations. The effect of Occlusal Index on the amount of wear in the posterior composite restorations was evaluated. Likewise, a comparison was made between the wear rates of Tetric Ceram and Ideal Makoo composite resin products. A total of 40 premolars were collected and randomly divided into four groups. Occlusal Indices were prepared with a transparent acrylic resin [Duralay]. Class I cavities were prepared in all specimens. In two groups, teeth were restored with Occlusal Index. However, the restorations were completed without any Occlusal Index in the other two groups. Wear on the surfaces of these restorations were made by an oral cavity simulator and a tooth-brush machine. The vertical sections of the [pre-wear]and [post-wear] replicas were compared with a Projector Profilometer and the differences between the two sections were analyzed using two way ANOVAtest at alpha = 0.5. The results showed that the mean-wear in index groups was higher. The findings did not show any significant difference between the wear rates of the two materials used in this experimental evaluation. The uses of occlusal index dose not decrease the wear of posterior composite restorations