Journal of Dental Medicine

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Many different methods are suggested to restore endodontically treated teeth. Prefabricated posts can not be indicated for all teeth and cast posts require extra time and cost. In addition, with the introduction of full ceramic restorations, achieving the ideal esthetic with metal post underneath them may be problematic or impossible because the darkness of the metallic posts may show through the highly translucent all ceramic restorations. In this article the review of litature and describiton of applied methods of different procedure in restoring the root canal therapied teeth and few techniques of non metallic posts fabrication such as fiber reinforced composite and zirconium oxide posts have been described.

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Posterior composite restorations, due to polymerization contraction, result in microleakage. Different methods have presented to reduce this phenomena. The aim of this study is to evaluate the effects of flowable and condensable composites to reduce microleakage. Seventy extracted human teeth were prepared with proximal class II cavities with gingival margin 1 mm below CEJ. The teeth randomly were divided into 7 groups. Groups I & II were restored with a dentin bonding (DB) agent plus a Prodigy condensable (Kerr Co.) composite, placing incremental or bulky, respectively.. In groups IK IV, V a dentin bonding agent was applied and then cavities were restored with Tetric flow composite resin as a base plus either a hybrid composite (Tetric ceram, Vivadent Co.) or a Prodigy condensable composite (Cond), placing bulky or incremental. Groups VI and VII were restored with a resin modified glass ionomer (GI) (Fuji II Lc Co.) as a base plus either Prodigy condensable or Tetric ceram. Restorations were polished, thermocycled, and immersed in 0.3% basic fushin. After that samples were sectioned and studied under a stereomicroscope to evaluate dye penetration. Results showed that all restorations showed some degree of microleakage and according to kruskall- wallis statistical analysis, there were not any significant differences between all groups (P-0.051). Then fore pair comparison, between groups. Mann-Whitney analysis was used and no statistical difference was observed. However. Gh DB- Tetric group showed the least microleakage and DB+ Cond (bulk) the most one. Due to lack of an" statistical difference among different materials methods, it is concluded that no method or restorative material have been able to eliminate microleakage in margins completely yet, and using a flowable composite resin, in place of resin modified glass ionomer or using a condensable composite, instead of conventional In brid composites, do not have any effect

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Composite resin restorative materials, that nowadays are used as tooth-colour materials, have both benefits and weaknesses. One of these weaknesses is the contraction resulted from resin polymerization which influences on the composite dentin bond strength and it has been tried to be eliminated by different bonding systems. The aim of this in-vitro study was to compare the dentin bond strength of two dentine adhesive systems: multi-step Scoth Bond Multipurpose (SBMP) and single- step Excite, by two composites of Ideal Makoo and Tetric. One hundred sixty (160) sound human molars were selected. At first they were debrided and mounted with acrylic resin in molds. The enamel of the buccal surface was eliminated by diamond burs. To provide a flat dentin surface, it was removed about lmm. Then, based on the type of dentin adhesive, they were divided into two groups of 30 teeth and were applied on the exposed dentine surface according to the manufacturer's instructions. Then, each group was divided into two subgroups of 15, based on the type of composite resin. Cylinders of the desired composite resin, attached to the dentin surface, were used for 80 seconds. The samples were stored in 100% humidity (37°c) for 24 hours. The bond strengths was measured by a cross head blade with the speed of 2mm/min. Variance analysis and Duncan test, with 95% confidence level, showed that statistically, two factors of adhesive and composite, interact on each other, in bond strength. There was no significant difference in bond strength, between two composites with similar adhesives, however, comparing two different adhesives with the same composite, showed that the bond strength of Tetric with Excite (28.39) was more than that of SBMP (17.98 Mpa). Finally, it was recognized that among four experimental groups, there was only a significant difference in bond strengths, between Tetric-Excite with Tetric- SBMP. This study shows that dentin bond strength is influenced by dentin bonding agents, composite type and dentin structure, and using a type of composite with a dentin bonding agent, manufactured by the same company, results in a higher bond strength.

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Nowadays, application of implants as a new method for replacing extracted teeth have been improved. So, many researches have been performed for improving the characteristics of implants. The aim of this study was to design and produce a desired coating in order to obtaining two goals including improvement of the corrosion behavior of metallic endodontic implant and the bone osseointegration simultaneously. Stainless steel 316L (SS), cobalt-chromium alloy (Vit) and commercial pure titanium (cpTi) were chosen as metallic substrates and hydroxyapatite coating (HAC) were performed by plasma-spraying (PS) process on three different substrates. A novel double layer Hydroxyapatite/Titanium (HA/Ti) composite coating composed of a HA top layer and a Ti under layer was prepared using PS and physical vapor deposition (PVD) process respectively on SS. Structural characterization techniques including XRD, SEM and EDX were utilized to investigate the microstructure, morpholgy and crystallinity of the coatings. Electrochemical potentiodynamic tests were performed in physiological solutions in order to determine and compare the corrosion behavior of the coated and uncoated specimens behavior as an indication of biocmpatibility. Results indicated that the cpTi possesses the highest and SS the lowest corrosion resistance (highest corrosion current density) between uncoated substrates. This trend was independent to the type of physiological environment. The HA coating decreased the corrosion current density of HA coated metallic implants but did not change that trend. HAC acted as a mechanical barrier on the metallic substrate but could not prevent the interaction between metallic substrate and environment completely. The HA/Ti composite coating improved the corrosion behavior of SS. The corrosion current density of HA/Ti coated SS decreased and was exactly similar to single HA coated cpTi in physiological solutions. The results indicated that HA/Ti composite coated SS could be used as an endodontic implant and two goals including improvement of corrosion resistance (biocompatibiiity) and bone osseointegration could be obtained simultaneously.

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Dentin bonding agents create stronger bonding between dental composites and dentin. But, none of them can prevent the microleakage. The important factors of progressing microleakage are the stress of polymerization shrinkage of resin composite and removal of smear layer in total-etch technique. The aim of this study was the evaluation of the effect of experimental method (modifying smear layer and etching of enamel margin) and comparison with the total-etch technique. In this experimental method, 60 extracted human molar teeth were disinfected. Then, class 5 cavities were prepared on the buccal surface and 1 mm above CEJ. The specimens were divided randomly to 6 groups with iO samples in each group. The specimens groups were:
1- Scotchbond Muiti- Purpose Plus Adhesive System (S.B.M.P.P) +Tetric composite
2- S.B.M.P.P + Ariston composite
3- Ariston liner + Ariston composite
4- S.B.M.P.P without enamel and dentin etching + Tetric composite + rebonding with Flowable Tetric
5- S.B.M.P.P without enamel and dentin etching + Ariston composite + rebonding with Flowable Tetric
6- S.B.M.P.P without enamel and dentin etching + Tetric composite
After finishing and polishing, the specimens were termocycled, stained with fushin, sectioned within the specimens and evaluated for dye penetration with stereomicroscope. Wilcoxon Sign and Kruskal Wallis tests were used for statistical analysis.
Results showed that group 3 had microleakage more than groups of 1, 2 and 5 (P<0.0 5) and this difference was significant. There was no significant difference among the other groups.

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Statement Problem: A few studies have been conducted about bioglass posts.
Aim: The aim of this study was to compare bioglass posts with prefabricated metallic posts in clinical performance of extensive composite restorations for anterior endodontically treated teeth.

Materials and Methods: Sixty endodontocally maxillary anterior teeth, with horizontally or vertically destruction, were selected. Teeth were divided into two groups based on the kind of post: Metallic prefabricated parapost and bioglass post. Each group was divided into three subgroups based on anterior bite: normal, deep bite and edge to edge. Gutta-percha was removed from 2/3 of canal length for parapost and 1/3 for bioglass post. After etching with phosphoric-acid (37%) and applying dentine bonding syntac, Duo cement was used for the adhesion of bioglass post and a self cured composite (Degufil) for parapost. Restoration was done with a hybrid composite (Heliomolar). Follow up studies, radio-graphically and clinically, were done every three months for a 1.5-year period. Exact Fisher and Pearson tests were used for data analysis.
Results: Apical lesion was not observed in any of the radiographs. Post seal was increased by resin cement and dentin bonding agent. Post type did not significantly affect on the clinical success rate of the restorations. The retention of restoration, for both posts, was the same. Crown destruction had no significant effect on success rate. The type of anterior bite had a significant effect on success rate, as the total 6.6% failure rate was related to the patients with anterior deep bite.
Conclusion: It is suggested to use metallic paraposts and bioglass posts, in extensive composite restorations for patients with deep-bite, more conservatively.

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Statement of Problem: Composite reins have recently become popular for posterior teeth restorations. Gap formation and subsequent microleakage are of the complications resulting from such restorations. One of the techniques to overcome polymerization shrinkage of composite resins is sandwich technique (application of glass ionomer as a base beneath the composite resin). Since polymerization patterns in two types of composite resins (light cure and self cure) differ from each other, various effects on the bond strength between glass ionomer and dentin are expected.
Purpose: The aim of this in vitro study was to evaluate the effects of self- cure and light- cure composite resins in sandwich technique on the bond strength of light cure glass ionomer and dentin.
Materials and Methods: 40 extracted human premolars were selected and divided into four groups:Group 1: Light cure glass ionomer of 1mm thickness was placed on dentin.Group 2: 1mm thickness of light cure glass ionomer plus a mass of self cure composite resin of 2mm thickness were placed.Group 3: 1mm thickness of light cure glass ionomer plus light cure composite resin as two separate 1mm layer were placed.Group 4: 1mm thickness of light cure glass ionomer with 37% phosphoric acid etching followed by two separate layers of light cure composite resin of 1 mm thickness were placed.SEM was used to determine gap size ai Gl- dentin and Gi- composite interlaces. The findings were analyzed by ANOVA and t-student tests.

Results: Groups 1 and 2 showed no gap at Gl-dentm interface and also cracks were not observed in all these specimens. In group 3, there was gap between light cure GI and light cure composite resin and cracks were seen in GI, too. Group 4 showed gap at both interfaces and more cracks were seen in GI. Groups I and 2 showed the least gap formation and group 4 showed the most. Statistically significant difference was found between groups 3, 4 and group 1 (control), 2.
Conclusion: Base on this study, the application of self-cure composite resin on light cure GI showed no gap and crack formation on Gl-dentin and Gl-composite interfaces and GI itself. However, light cure composite resins and glass ionomer etching aggregated crack and gap formation.

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Statement of Problem: Despite the improvements achieved in the field of dental composites, their strength, longevity, and service life specially in high stress areas is not confirmed. Finding better fillers can be a promising step in this task.

Purpose: The purpose of this study was to investigate the effect of the filler type on the mechanical properties of a new experimental dental composite and compare these with the properties of composite containing conventional glass filler.

Materials and Methods: Experimental composites were prepared by mixing silane-treated fillers with monomers, composed of 70% Bis-GMA and 30% TEGDMA by weight. Fillers were different among the groups. Glass, leucite ceramic and lithium disilicate were prepared as different filler types. All three groups contained 73% wt filler. Comphorquinone and amines were chosen as photo initiator system. Post curing was done for all groups. Diametral tensile strength (DTS), flexural strength and flexural modulus were measured and compared among groups. Data were analyzed with SPSS package using one-way ANOVA test with P<0.05 as the limit of significance.

Results: The results showed that the stronger ceramic fillers have positive effect on the flexural strength. Ceramic fillers increased the flexural strength significantly. No significant differences could be determined in DTS among the groups. Flexural modulus can be affected and increased by using ceramic fillers.

Conclusion: Flexural strength is one of the most significant properties of restorative dental materials. The higher flexural strength and flexural modulus can be achieved by stronger ceramic fillers. Any further investigation in this field would be beneficial in the development of restorative dental materials.

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Statement of Problem: Blood contamination is a common problem in dentistry that can decrease bond strength dramatically which may be affected by methods of decontamination as well.

Purpose: The aim of this study was to evaluate and compare the influence of blood contamination on shear bond strength of composite and compomer to dentin using Prompt L-Pop as an adhesive system. Also, to assess the effectiveness of different surface treatments on the bond strength.

Materials and Methods: In this experimental study, 120 molar teeth were sectioned to provide flat occlusal dentinal surfaces. Specimens were embedded in acrylic resin with the flat surface exposed. The dentinal expose surfaces were polished to 600 grit. The teeth were randomly divided into five groups of twelve specimens (F1–F5) for compomer material and five other groups (Z1- Z5) for composite resin. After application of Promt L-Pop to dentinal surfaces of specimens, the surfaces in all groups, except for F1 and Z1, (as controls) were contaminated with human blood and then one of the following surface treatments was applied. Groups F2 and Z2 without any treatment, groups F3 and Z3 rinsing with water, groups F4 and Z4 rinsing with water and reapplication of adhesive, groups F5 and Z5 rinsing with NaOCl and using Prompt L-Pop again. Restorative materials were applied to treated surfaces using plastic molds. After thermocycling, shear bond strengths, mode of failures and morphology of dentin-material interfaces were evaluated. The data were statistically analyzed using Factorial analysis of Variance, One-Way ANOVA, Duncan, T-student and Chi-Square tests with P<0.05 as the limit of significance.

Results: Compomer showed statistically significant higher bond strength in comparison to composite (P<0.001). Duncan test showed significant differences between all compomer groups, except between groups F4 and F5, and between all composite groups except for groups Z1 and Z4 and for groups Z2 and Z3.

Conclusion: Based on the findings of this study, shear bond strength of compomer material was significantly higher than composite. Blood contamination reduced bond strength, but rinsing contaminated dentin with water or NaOCl and reusing Prompt L-Pop increased bond strength in both materials.

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Statement of Problem: Evaluation of fracture properties is a basic principle for true assessment of brittle materials’ properties. Resin–based composite materials are being used extensively in today’s dentistry. Fracture toughness is considered an important parameter for providing useful information about material’s nature, properties and its resistance to fracture.

Purpose: The purpose of this study was to evaluate the fracture toughness of a resin composite produced in the country and to compare it with that of other standard materials.

Materials and Methods: Four types of resin composite materials were used as follow to prepare 60 specimens (n=15 for each group), A) Tetric Ceram (Ivoclar–Vivadent) B) Brilliant (Coltene-Whaledent) C) SpectrumTPH (Dentsply) and D) Ideal Macoo (Ideal Macoo, Iran). Specimens of 5 mm diameter ( 0.1 mm) and 2 mm depth (±0.1 mm) were prepared in a central notch (90 notch angle) PTFE mold. Then specimens were light cured with two applications of overlapping exposures for a total of 120 s and were stored in distilled water at 37ºC for 48 hours, A cylindrical roller of 3 mm diameter was seated inside the V sections and fracture was accomplished in a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed by one–way ANOVA and post-hoc paired Tukey HSD test with P<0.05 as the limit of significance.

Results: The mean KIC and torque to fracture (T) values for each material tested were A) 3.080.42, 16.992.34, B) 2.880.63, 16.041.98 C) 3.400.53, 18.752.93 and D) 2.870.46, 15.782.57 MN/m3/2SD and N/mmSD, respectively. Group C showed significantly the highest mean KIC and T values among groups tested which was significantly higher than that of group B and D (P<0.05). The mean KIC and T values for groups A, B, and D were not significantly different (P>0.05).

Conclusion: From evaluating the fracture properties of materials tested in this study it was concluded that the mean fracture toughness value for SpectrumTPH (Dentsply) was significantly higher than that of Ideal Macoo resin composite material (Ideal Macoo, Iran). The F.T value for Ideal Macoo was considered acceptable as it was not significantly different from that of other resin composite materials tested.

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Statement of Problem: The relatively poor wear resistance of dental composite in stress bearing posterior situations has restricted wider clinical application of this restorative material.

Purpose: The aim of this study was to evaluate the three body abrasive wear of a dental composite based on a new filler (leucite: KAl Si2O6) and to compare it with the wear resistance of a composite based on commonly used Aluminium – Barium Silicate filler.

Materials and Methods: This research was an interventional study done in Iran polymer institute. Five specimens were considered in each group. All ceramic IPS Empress® (Ivoclar- Vivadent) ingots based on leucite crystals were ball milled, passed through an 800 sieve and used as filler. Experimental composites were prepared by mixing the silane- treated fillers with monomers (BisGMA and TEGDMA). Camphorquinone and amine were used as photoinitiator system. Degree of conversion of the light-cured and post-cured composites was measured using FTIR spectroscopy. The prepared pastes were inserted into plexy-glass mold and light cured (700 mw/cm2, 40 s). Then for maximum degree of conversion specimens were post- cured (120ºC, 5 hours). Three body abrasion wear testing was performed using a wear machine with 50 rpm rotational movement. In this machine, pumice (150 meshes) was used as the third body. Weight loss of specimens in each group was measured by balance after each 50 hours. After wear testing SEM examination was made specimens in each group. The data were analyzed and compared using ANOVA and Tukey HSD tests (P<0.05). Tetric Ceram was tested as commercial composite.

Results: There were significantly differences between three body abrasive wear of composites. The ranking from lowest to highest was as follows: leucite composite (19%) < Tetric Ceram (22%) < glass composite (28%). leucite composite showed the highest wear resistance value, propably due to the crystalliniy and hardness of filler.

Conclusion: Introduction of this new filler as an alternative to glass filler, significantly increases the wear resistance of the resin composites. Further investigations on mechanical properties of new composites would be beneficial in the development of new dental materials.

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Background and Aim: The majority of commercial curing units in dentistry are of halogen lamp type. The new polymerizing units such as blue LED are introduced in recent years. One of the important side effects of light curing is the temperature rise in composite resin polymerization which can affect the vitality of tooth pulp. The purpose of this study was to evaluate the temperature rise in two different composite resins during polymerization with halogen lamps and blue LED.

Materials and Methods: This experimental study investigated the temperature rise in two different composites (Hybrid, Tetric Ceram/Nanofilled, Filteke Supreme) of A2 shade polymerized with two halogen lamps (Coltolux 50, 350 mW/cm2 and Optilux 501 in standard, 820 mW/cm2 and Ramp, 100-1030 mW/cm2 operating modes) and one blue LED with the intensity of 620 mW/cm2. Five samples for each group were prepared and temperature rise was monitored using a k-type thermocouple. Data were analyzed by one-way ANOVA, two-way ANOVA and Tukey HSD tests with P<0.05 as the limit of significance.

Results: Light curing units and composite resins had statistically significant influence on the temperature rise (p<0.05). Significantly, lower temperature rise occurred in case of illumination with Coltolux 50.There was no significant difference between Optilux 501 in standard curing mode and LED. Tetric Ceram showed higher temperature rise.

Conclusion: According to the results of this study the high power halogen lamp and LED could produce significant heat which may be harmful to the dental pulp.

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Background and Aim: With recent introduction of packable composites, it is claimed that they apply less stress on tooth structure because of reduced polymerization shrinkage, and similarity of coefficient of thermal expansion to tooth structure. However, the high viscosity may in turn cause less adaptation, so it is not clearly known whether these materials strengthen tooth structure or not. The aim of this study was to evaluate fracture resistance of maxillary premolars, receiving hybrid or packable composite restorations with different methods of application and curing.

Materials and Methods: In this experimental study, seventy five intact premolars were randomly assigned to five groups of 15 teeth each. One group was maintained intact as the control group. Similar MOD cavities were prepared in the other teeth. The teeth in group two were restored with Spectrum in incremental layers and light cured with 500 mw/cm2 intensity. The third group were filled with Surefil and cured with light intensity of 500 mw/cm2. The groups four and five were restored with Surefil in bulk technique with two different modes: 500 mw/cm2 intensity and a ramp mode (100-900 mw/cm2) respectively. After thermocycling, force to fracture was assessed and degree of conversion (DC) at the bottom of cavities was evaluated for different modes and methods. The curing and placement methods in groups tested for DC (A to D) were the same as fracture resistance groups (2 to 5). Data were analyzed using one way ANOVA and Tukey HSD tests with p<0.05 as the limit of significance.

Results: All the restored groups showed significantly less fracture resistance than the control group, but had no significant difference among themselves. DC of Spectrum was higher than Surefil. Bulk method with 500 mw/cm2 light intensity, significantly decreased DC. DC in bulk method with high light intensity was not significantly different from incremental method with 500 mw/cm2 light intensity.

Conclusion: Placement techniques, light intensity and type of composite had no influence on the fracture resistance. The use of packable composite with bulk technique and 500 mw/cm2 intensity or less is not recommended in 4 mm depth cavities due to insufficient DC.

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Background and Aim: Sufficient polymerization is a critical factor to obtain optimum physical properties and clinical efficacy of resin restorations. The aim of this study was to evaluate wear rates of composite resins polymerized by two different systems Light Emitting Diodes (LED) to and Halogen lamps.

Materials and Methods: In this laboratory study, 20 specimens of A3 Tetric Ceram composite were placed in brass molds of 2*10*10 mm dimensions and cured for 40 seconds with 1 mm distance from surface. 10 specimens were cured with LED and the other 10 were cured with Halogen unit. A device with the ability to apply force was developed in order to test the wear of composites. After storage in distilled water for 10 days, the specimens were placed in the wear testing machine. A chrome cobalt stylus with 1.12 mm diameter was applied against the specimens surfaces with a load of 2 kg. The weight of each samples before and after 5000, 10000, 20000, 40000, 80000 and 120000 cycles was measured using an electronic balance with precision of 10-4 grams. Data were analyzed using t test and paired t test. P<0.05 was considered as the limit of significance.

Results: Mean weight in both groups had statistically significant difference before and after all cycles (P<0.05). In halogen group 5000 and 10000 cycles led to significant difference with 40000, 80000 & 120000 cycles (P<0.05). In LED group 20000 cycles had significant difference with both 5000 and 120000 cycles (P>0.05).

Conclusion: Based on the results of this study, LED and halogen light curing units resulted in a similar wear rate in composite resin restorations.

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Background and Aim: Stainless steel crown (SSC) is the most durable and reliable restoration for primary teeth with extensive caries but its metalic appearance has always been a matter of concern. With advances in restorative materials and metal bonding processes, composite veneer has enhanced esthetics of these crowns in clinic. The aim of this study was to evaluate the shear bond strength of SSC to composite resin using different surface treatments and adhesives.

Materials and Methods: In this experimental study, 90 stainless steel crowns were selected. They were mounted in molds and divided into 3 groups of 30 each (S, E and F). In group S (sandblast), buccal surfaces were sandblasted for 5 seconds. In group E (etch) acidic gel was applied for 5 minutes and in group F (fissure bur) surface roughness was created by fissure diamond bur. Each group was divided into 3 subgroups (SB, AB, P) based on different adhesives: Single Bond, All Bond2 and Panavia F. Composite was then bonded to specimens. Cases were incubated in 100% humidity at 37°C for 24 hours. Shear bond strength was measured by Zwick machine with crosshead speed of 0.5 mm/min. Data were analyzed by ANOVA test with p<0.05 as the limit of significance.

Results: There was no statistical interaction between surface treatment and adhesive type (P>0.05) so the two variables were studied separately. No significant difference was observed in mean shear bond strength of composite among the three kinds of adhesives (P>0.05). Similar results were obtained regarding surface treatments (P>0.05).

Conclusion: Based on the results of this study, treating the SSC surface with bur and using single bond adhesive and composite can be used successfully to obtain esthetic results in pediatric restorative treatments.

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Background and Aim: Patients always complain about metallic color of amalgam restorations. Covering amalgam by composite can solve this problem. Since polymerization shrinkage is a serious shortcoming in composites, application of the combined amalgam and composite restoration is one of the methods to reduce leakage in the cervical margins of posterior restorations. The aim of this invitro study was to evaluate the microleakage of amalgam/composite interface when Rely-X ARC adhesive resin cement was used in the joint.

Materials and Methods: Twenty-four sound extracted premolars were chosen. Mesial and distal class II conventional cavities were prepared and the samples were divided into 4 groups of 12. In all groups, the bases of the cavities were restored with amalgam and then the remaining part was filled by composite resin. Specimens in groups 1 and 2 were restored with composite-resin, immediately after condensing amalgam without or with application of Rely-X ARC (3M, ESPE) respectively. In groups 3 and 4, composite resin were applied 24 hours after condensation of amalgam, without or with application of Rely-X ARC respectively. After polishing and thermocycling, all specimens were prepared for dye penetration and the degree of leakage was scored and analyzed using Kruskall Wallis test with p<0.05 as the level of significance.

Results: The frequency of dye penetration in different groups was obtained. The most and the least scores were observed in groups 3 and 4 respectively. No statistically significant difference was observed in different methods.

Conclusion: None of the methods in this study could seal the amalgam/composite-resin interface.

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Background and Aim: Light cured composites and other restorative materials are quite common in dentistry today. Successful restorations are dependent on efficiency of curing light unit, eg. the intensity of emitted light and its wave length. The aim of this study was to evaluate the efficiency units of curing, in private dental offices in Tehran.

Materials and Methods: In this descriptive cross sectional study, light curing devices in 240 private dental offices were evaluated randomly. Light intensity was measured by radiometer, debris on the fan and cracks and scratches on the filter were directly observed and the age of the device, frequency of changing the bulb and satisfaction of the dentist with regard to the light curing unit were recorded in a questionnaire. Data were analyzed using Spearman and t test, with p<0.05 as the level of significance.

Results: The results showed that 53.8% of the units had intensities more than 300 mW/cm². The intensity of 30.4% of curing light units were between 20 and 300 mW/cm² and 15.8% had intensities lower than 200 mW/cm². There was a negative relation between light intensity and the age of the unit, frequency of bulb changing or scratches on the filter and debris on the fan.

Conclusion: The results of this study showed that the light intensities of about 46% of light curing units used in private dental practices and clinics were inadequate. Since factors like aging of the curing light unit, frequent bulb changing, increasing the amount of debris on the fan and scratches on the filter reduce the light intensity, regular quality control of these devices is essential.

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Background and Aim: An important purpose of adhesive dentistry is restriction of cavity preparation to carious dentin removal and conservation of sound dentin. Application of caries disclosing agents and cavity disinfectants can help achieving this goal. The aim of this study was to evaluate the effect of caries disclosing agents and cavity disinfectants on microleakage of composite resin restorations.

Materials and Methods: This experimental in-vitro study was performed on class V cavities in 48 extracted human sound premolars. The teeth were randomly divided into four equal groups. In group 1 caries detector dye (Seek, Ultradent, USA) and in group 2 cavity disinfectant (Consepsis, Ultradent, USA) were applied on dentinal surfaces. In group 3 both mentioned materials were applied. Group 4 was considered as control group. PQ1 bonding agent and Amelogen composite were used to restore the cavities. Gingival microleakage was assessed by dye penetration. Data were analyzed by Kruskall Wallis and Dunn tests. P<0.05 was the level of significance.

Results: Group 2 showed the least and group 4 showed the highest microleakagehowever no statistical significant difference was found among the groups.

Conclusion: The use of caries disclosing agent (Seek) and cavity disinfectant (Consepsis Liquid) did not adversely affect the sealing ability of dentin bonding resins.

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Background and Aim: Halogen lamp is the commonly used light source for composite photo polymerization. Recently, high power halogen lamps, LED and plasma arc are introduced for improving the polymerization. The aim of this study was to investigate the effect of conventional and high power halogen lamps and LED light curing unit on degree of conversion of two different composite resins.

Materials and Methods: In this in vitro experimental study two halogen units (Coltolux 50 with the intensity of  330 mW/cm² and Optilux 501 with two different operating modes of standard with the intensity of 820 mW/cm² and Ramp with the intentsiy of 100-1030mW/cm²) and one LED light curing unit (620 mW/cm²) were used. The composites were hybrid (Tetric ceram) and nanofilled (Filteke supreme). Each materials/curing method contained three samples and degree of conversion (DC) was measured with FTIR. Data were analyzed statistically with one way and two way ANOVA, Tukey HSD. P<0.05 was considered as the limit of significance.

Results: Tetric ceram revealed higher DCthan Supreme. Tetric ceram showed a significant decrease in DC when Coltolux 50 was used in comparison to LED and Optilux 501. The latters did not show significant effect on DC of this material. DC of Supreme polymerized with various curing modes was not significantly different.

Conclusion: Based on the results of this study, degree of conversion in hybrid composites was higher than nanofilled. In comparison with conventional halogen lamp (Coltolux 50), high intensity halogen lamps and LED unit significantly lead to higher degree of conversion in hybrid composites.

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Background and Aim: Considering flexural strength of fiber-reinforced composites (FRC) and also the role of conservative cavities in protecting sound tissue of abutments, the aim of this study was to evaluate the fracture resistance of these bridges by handmade samples in vitro.

Materials and Methods: In this experimental in vitro study, 44 sound newly extracted teeth were used to make 22 fixed inlay bridges including 11 three unit anterior upper inlay bridges substituting clinical model of upper central and 11 three unit posterior lower inlay bridges substituting clinical model of lower first molar. Specimens were prepared with FRC and mounted with artificial PDL in acryl. Cases were exposed to final load by using Universal Testing Machine (Instron 1195) with the speed of 1 mm/min. Statistical analysis was performed by Kolmogorov- Smirnov, independent sample T and Kaplan-Meier tests with p<0.05 as the level of significance.

Results: Based on the statistical tests, the 95% confidence interval of mean was 450-562 N in anterior and  1473- 1761 N in posterior area. Fracture strength was high in the studied groups. Fractures in both groups occurred on composite facing, and the framework remained intact. The highest percentage of fracture in posterior teeth was in the middle of pontic towards the distal connector and in the anterior teeth in the lateral connector, between central pontic and lateral abutment. Using the independent sample T  test a significant statistical difference was observed between two groups (P<0.001). The fracture resistance of anterior samples was lower than the posterior ones.

Conclusion: Based on the results of this study regarding the high fracture resistance in both areas FRC inlay bridges could be recommended for upper anterior and lower posterior teeth in clinical dentistry certainly more studies are needed to ascertain this treatment option.