Auto Polymerizing Research Articles

Comparative evaluation of effectiveness of different concentration of sodium hypochlorite with conventional irrigation method versus ultrasonic irrigation in the elimination of Enterococcus faecalis from root canals: an in-vitro study

Aim: The aim of this study is to compare the decrease in bacterial population in the root canals with 3 different concentrations of NaOCl and with two different irrigation systems Methods and Material: The study was conducted on 70 single rooted extracted teeth. Teeth were decoronated and the apices were sealed with auto polymerizing resin. The teeth were inoculated with a suspension comprising Enterococcus faecalis (E. faecalis). The canals were prepared were divided into three groups based on irrigation technique: Group 1; irrigation with 1% sodium hypochlorite, Group 2; irrigation with 3% sodium hypochlorite & Group 3; irrigation with 5% sodium hypochlorite. All three groups were divided into 2 subgroups. In subgroup A irrigation was done by conventional side vented needle and in subgroup B with passive ultrasonic agitation. A fourth control group was also added in which conventional needle irrigation was done with normal saline. The samples were inoculated on the growth media and the mean colonies units were calculated. Statistical analysis used: The statistical analysis used was Student’s unpaired t-test for intergroup comparison and one-way ANOVA and Tukey’s post hoc test for intragroup comparison. Results: In our study, groups with passive ultrasonic irrigation showed better antimicrobial effect compared to groups which use conventional needle irrigation. Conclusions: Ultrasonic irrigation showed better antimicrobial activity compared to conventional needle irrigation

Effect of Graphene Oxide Incorporation on the Strength of Denture Repair Resin

To evaluate the effect of incorporating graphene oxide nanoparticles (GO NPs) and graphene sheets on the flexural strength of an auto-polymerized (AP) acrylic resin-repaired denture. 60 heat-activated (HA) resin specimens were fabricated and randomly divided into 6 groups (n = 10). The specimens in Group I were kept intact. 50 specimens were cut into two parts with a 45-degree bevel. Group II specimens were repaired with AP resin and Group III specimens were repaired with HA resin. In the repair of Group IV, Group V, and Group VI specimens, 1%, 2% GO NPs, and graphene sheets were added to AP resin, respectively. A 3-point bending test with a universal test device measured the flexural strength. Statistical analyses of the results were performed with the Kruskal Wallis H-test. (α = 0.05) The flexural strength of Group I (130.05 ± 20.20 MPa) was the highest among all groups. The flexural strength of Group IV (67.49 ± 12.70 MPa) was significantly higher than Group V (50.87 ± 15.02 MPa) and Group VI (44.77 ± 10.70 MPa). The lowest strength value was obtained in Group VI. Adding 1% GO NPs to AP acrylic resins increases flexural strength. However, the increase in nanoparticle concentration and the addition of graphene sheets negatively affect strength.

Comparison of fracture strength, surface hardness, and color stain of conventionally fabricated, 3D printed, and CAD-CAM milled interim prosthodontic materials after thermocycling.

The purpose of this in vitro study was to investigate the fracture resistance, surface hardness, and color stain of 3D printed, CAD-CAM milled, and conventional interim materials. A total of 80 specimens were fabricated from auto polymerizing polymethyl methacrylate (PMMA), bis-acryl composite resin, CAD-CAM polymethyl methacrylate resin (milled), and 3D printed composite resin (printed) (n = 20). Forty of them were crown-shaped, on which fracture strength test was performed (n = 10). The others were disc-shaped specimens (10 mm × 2 mm) and divided into two groups for surface hardness and color stainability tests before and after thermal cycling in coffee solution (n = 10). Color parameters were measured with a spectrophotometer before and after each storage period, and color differences (CIEDE2000 [DE00]) were calculated. The distribution of variables was measured with the Kolmogorov Smirnov test, and one-way analysis of variance (ANOVA), Tukey HSD, Kruskal-Wallis, Mann-Whitney U tests were used in the analysis of quantitative independent data. Paired sample t-test was used in the analysis of dependent quantitative data (P < .05). The highest crown fracture resistance values were determined for the 3D printed composite resin (P < .05), and the lowest were observed in the bis-acryl composite resin (P < .05). Before and after thermal cycling, increase in mean hardness values were observed only in 3D printed composite resin (P < .05) and the highest ΔE00 value were observed in PMMA resin for all materials (P < .05). 3D printing and CAD-CAM milled interim materials showed better fracture strength. After the coffee thermal cycle, the highest surface hardness value was again found in 3D printing and CAD-CAM milled interim samples and the color change of the bis-acryl resin-based samples and the additive production technique was higher than the PMMA resin and CAD-CAM milled resin samples.

Impact of effervescent denture cleaning tablets on color and surface characteristics of additively manufactured and hand-cast splint materials.

This study is to evaluate the color stability, surface roughness, and hardness of additively manufactured and hand-cast splint materials after a 6-month commercially available denture cleaning tablet immersion simulation. Disc-shaped additively manufactured and hand-cast auto polymerizing acrylic resin specimens were prepared (N = 40 each). All specimens were exposed to coffee solution totally 2days. Thereafter, all specimens were immersed into three different effervescent solutions that simulated 6months of clinical use. The total color change (ΔE*ab), surface roughness (Ra), and Vickers hardness (Vh) were measured at baseline and after immersion protocols. A two-way ANOVA and Bonferroni's post hoc test were used for color change. The dependent t-test and ANOVA were used for roughness and hardness evaluation. Additively manufactured splint materials were more affected by coffee immersion. It was observed that all denture cleaning tablets induced a noticeable alteration in color of the specimens (p < 0.05). Roughness and hardness measurement changes after solution immersions were statistically significant for both splint groups (p < 0.05). On the other hand, distilled water and denture cleaning tablets created similar roughness and hardness measurements at baseline and after immersion. After 6months use of tested cleaning tables, the color stability, surface roughness, and hardness of both groups were affected. The evaluation of the surface properties of splint materials could be recommended to the dentists in periodic controls during splint treatments. The use effervescent denture cleaning tablets altered the surface characteristics of tested splint materials over time with nonsignificant difference between each other. After 6months, awareness should be raised about surface characteristics of splint materials.

Evaluation and Comparison of Impact Strength and Transverse Strength of Heat Polymerized Polymethylmethacrylate (PMMA) Denture Base Resin Repaired Using Heat Polymerizied PMMA Denture Base Resin, Auto-Polymerized PMMA Resin and A New Light Polymerizied Denture Resin: An In Vitro Study.

Repaired denture prosthesisdemands adequate transverse and impact strength. A new repairdenture base resin- "Lukafix" require to fulfil these criteria. This study evaluates and compares the transverse and impact strength of heat polymerizing, auto polymerizing and LUKAfix denture resin. 20 specimens were control(without repair), and other were test specimens which were fractured and repaired with heat polymerized PMMA resin, chemically polymerized PMMA resin and LUKAfix light polymerizing denture resin. Each group wasdivided in two subgroups. Subgroup A was subjected to transverse strength test and subgroup B to impact strength test. One way ANOVA was used to identify the mean difference among the four groups. Post-Hoc-Bonferroni was done to observe the difference between the groups. Maximum transverse strength was observed in specimens repaired with heat polymerized (48.33 ± 9.19) and least in LUKAfix denture resin (6.56 ± 1.15). Also, impact strength was maximum for heat polymerized (3.64 ± 0.41) followed by LUKAfix denture resin (2.34 ± 0.44). Repair with LUKAfix denture resin resulted inferior transverse and impact strength as compared to heat polymerized PMMA resin.

Comparative evaluation of shear bond strength of three different glass ionomer cement (conventional, zirconium-reinforced and advanced glass hybrid) in primary molars: an in vitro study.

The success of restorative materials is largely dependent on their capacity to adhere to the tooth structure and withstand the various forces present in the oral cavity. So, the aim of present study was to evaluate and compare the shear bond strength (SBS) of Type IX Glass Ionomer Cement (GIC), Zirconomer, and Gold Label Hybrid GIC in primary molars. Thirty primary molars were selected based on inclusion and exclusion criteria. The molars were polished to provide a flat dentin surface after being inserted in auto polymerizing acrylic resin. The samples were randomly divided into three groups, equally and were bonded to GIC. On the dentin surface, restoration cylinders were made using a plastic mould that had an internal diameter and height of 5mm and 3mm, respectively. The cement was manipulated according to the manufacturer's directions through the plastic mould. Then, the samples were stored at room temperature for 10days to mimic oral conditions. The Universal Testing Machine was used to test SBS. One-way ANOVA and the post hoc Tukey test were used to statistically assess the collected data. A statistically significant difference was found in all three groups (p < 0.01), with Zirconomer demonstrating highest SBS, followed by Type IX GIC and Gold Label Hybrid GIC. The SBS value of Zirconomer was better when compared to Type IX GIC and Gold Label Hybrid GIC.

AN IN VITRO COMPARISON OF OVERALL FIT OF COBALT-CHROMIUM COPINGS CASTED CONVENTIONALLY FROM INLAY CASTING WAX, PATTERN RESIN &amp; 3D PRINTED RESIN EVALUATED BEFORE &amp; AFTER CERAMIC FIRING CYCLES

Aim: To compare the overall fit of cobalt-chromium copings casted conventionally from inlay casting wax, auto polymerizing pattern resin &amp; 3D printed resin evaluated before &amp; after ceramic firing cycles. Method: A stainless-steel master die assembly was fabricated which was used to fabricate the working models. 60 working dies (Group A Inlay Casting Wax n=20, Group B Pattern Resin n=20, Group C 3D Printed Resin n=20) simulating full crown preparations werestudied. The stainless-steel master die was duplicated using polyvinyl siloxane (PVS) elastomeric impression and poured in gypsum type IV die stone. Dieswere scanned using a digital scanner. 60 cobalt-chromium (Co-Cr) metal copings were fabricated using three different techniques: inlay casting wax, autopolymerising pattern resin&amp; 3D printed resin. Each die was fired with conventional PFM ceramic. A standardized weightwas used to exert uniform pressure on the elastomeric impression material while recording the intaglio surface of the crowns (copings) fabricated before and after ceramic firings. It was thenscanned aiding in STL File. The STL files were later overlapped and evaluated on their respective working die STL file using the software. The overall fit was measured by colour surface mapping software viz before &amp; after ceramic firing cycles. Results: The copings obtained by 3D printed resin technique revealed the best overall fit before and after ceramic firing cycles amongst the three fabrication techniques. Conclusion: 3D printed resin technique had the best overall fit before and after ceramic firing cycles followed by inlay casting wax technique and pattern resin technique.

Clinical and immunological evaluation of peri-implant tissues around ultra-polished and conventional smoothness zirconia abutments. A 1-year follow-up randomized clinical trial.

This is a randomized clinical trial to compare the clinical and immunological performance of ultrasmooth versus regular-smooth zirconia abutments placed subgingivally after a period of 1 year. Sixty-two bone level platform-switched implants (NobelParallel CC) were placed epicrestally in the mandibular molar or premolar region in 62 patients. After osseointegration, implants were restored with auto polymerizing acrylic resin crowns and subsequently randomly allocated to 2 groups according to the type of screw-retained zirconia crown prescribed. The control group received custom zirconia restoration with the subgingival zirconia part conventionally polished, while the test group implants were restored with ultra-polished zirconia abutments. Periodontal parameters (PD, PI, BOP) and marginal bone level changes (MBLC) were recorded for each implant 2 months after insertion (T0), 1 month after final delivery of the crown (T2) and at the 1-year follow-up (T3). Immunological mediators from GCF (IL-1α, IL-1ra and TNF-α) were inspected at 1 month after provisional (T1) and accordingly at T2 and T3. Data was analyzed statistically, and significance level was set to α = 0.05. After 1-year, there were no significant changes in PD control - 2.18 ±0.89 mm and test - 2.5 ±0.72 mm (p = 0.073). PD between T2 and T3 dropped significantly in the test group (p = 0.037), and remained stable in the control group. PI was not different in both groups at T0 (p = 0.518) and T2 (p = 0.817). At T3, the test group (0.9 ±1.01) had a significantly lower PI than the control group (1.55 ±1.23) (p = 0.035). There was no difference in BOP positive cases between groups after 1 year (control - 61.3%, test - 51.7%, p = 0.455). The amount of IL-1ra decreased significantly in the test group (41.75 ±57.58) (p = 0.001) but not in the control group (59.59 ± 70.43) (p = 0.177). MBLC for the control and test groups after 1 year were 0.68 ±0.7 mm and 0.94 ±0.65 mm (p = 0.061). PD dynamics, PI, BOP and IL-1ra revealed better outcomes around ultra-polished zirconia abutments than around conventionally polished zirconia abutments. This article is protected by copyright. All rights reserved.

Evaluation of the effectiveness of bioactive glass fillers against Candida albicans adhesion to PMMA denture base materials: An in vitro study

BackgroundDentures with antimicrobial properties are desirable for preventing Candida albicans adhesion. This study was to assess the effectiveness of bioactive glass (BAG) on C. albicans adhesion, surface roughness, and hardness of denture base materials. MethodsHeat-polymerized (HP) and autopolymerized (AP) acrylic resins were used to fabricate 240 disk specimens (120/material, 60/C. albicans, 60/surface roughness and hardness). Specimens were divided into five groups (n = 10) based on the BAG concentration: 0.5, 1.5, 3, 5, and 7.5 wt% of the acrylic powder, with a control group comprised of unmodified specimens. Direct culture method was used to assess C. albicans adhesion. A profilometer and Vickers hardness test were used to measure surface roughness and hardness respectively. Analysis of variance (ANOVA) and post hoc Tukey’s test were used for data analysis (α = 0.05). ResultsBAG addition significantly decreased the C. albicans count when compared with the control group (P < 0.001) for both HP and AP. Regarding surface roughness, there was no change in the HP acrylic resins (P> 0.05), while the AP acrylic resins exhibited significantly higher surface roughness with BAG addition (P < 0.001). The hardness of the HP and AP acrylic resins were significantly higher with the addition of BAG (P < 0.001). ConclusionsThe addition of BAG to HP and AP acrylic resins effectively decreases C. albicans adhesion. The roughness of AP acrylic resins increases with the addition of BAG, while the hardness of both HP and AP acrylic resins increase with the addition of BAG.

Comparison of Microleakage in Nanocomposite and Amalgam as a Crown Foundation Material Luted with Different Luting Cements under CAD-CAM Milled Metal Crowns: An In Vitro Microscopic Study.

Microleakage is a persistent problem despite advancement in materials and techniques in fixed prosthodontics. This leads to the importance of sound crown foundation material and luting agents used to maintain the marginal seal. The literature is deficient with studies, comparing microleakage under various crown foundation materials and luting agents, especially with CAD-CAM (computer-aided design and computer-aided manufacturing) metal crowns. This study was aimed to compare microleakage in a nanocomposite/dentinal bonding agent and amalgam/cavity varnish as crown foundation materials luted with two different luting cements: resin-reinforced glass ionomer cement and self-adhesive resin cement, under both dry and contaminated conditions. A hundred intact, caries-free human molars were prepared to receive crown foundation material and extra coronal restorations. Amalgams with cavity varnish and nanocomposites with dentinal bonding agent in both ideal and contaminated conditions were used as crown foundation materials. After restoration, each sample was cemented with a CAD-CAM milled metal crown using two different luting agents—resin-reinforced glass ionomer cement and self-adhesive resin cements both in ideal and contaminated conditions. Cementation was followed by thermocycling of samples, immersion in erythrosine B dye, embedding in clear auto polymerizing acrylic resin and sectioning to evaluate microleakage using stereomicroscope. The mean microleakage between different luting cements on the experimental side of the facial surface was 137.64 μm and 211.01 μm for resin-reinforced GIC and for self-adhesive resin cement was 119.78 μm and 150.42 μm, under ideal and contaminated condition, respectively. There was a significant difference in mean micro-leakage between different crown foundation material and cement groups used in the study. The composites and amalgam, both when used as crown foundation material and luted with use of technically advanced CAD-CAM metal crown with self-adhesive resin cement (in both ideal or contaminated condition), showed less microleakage than in resin-reinforced glass ionomer cement. Overall, the self-adhesive resin cement showed comparatively reduced microleakage in all combinations with different crown foundations. Thus, this combination can be used in daily clinical practice to provide better protection from further decay.

Evaluation of flexural strength of denture base repaired by various materials and techniques

Traditionally complete and partial dentures are desired form of replacement for missing teeth. A variety of polymers are used for different clinical procedures in dentistry, among these polymethyl methacrylate (PMMA) is most commonly used in dental settings. But in clinical practice, cracking and fracturing of the PMMA is the frequent cause of failure of complete or partial removable dentures. Thus a good material for repair must be chosen to overcome this problem. To evaluate the flexural strength of acrylic resin repair processed by different methods. An in-vitro study was conducted with Thirty-six maxillary denture bases prepared in the Laboratory at the Department of Prosthodontics and Crown &amp; Bridge, at AB Shetty Memorial Institute of Dental Sciences, Deralakatte, Mangalore. Ethical clearance was obtained from the institutional ethical committee, to conduct this study. This study was conducted on maxillary denture bases reinforced with various materials to assess the change in midline flexural strength of the denture base. For the study 36 maxillary denture bases were fabricated and divided into three groups depending on the material were made. Group 1 Auto polymerizing resin (DPI-RR), Group 2 High impact resin (Trevalon-Dentsply), Group 3 Glass fiber reinforced resin (Acralyn-H).

Microstrain Analysis of Selective Pressure Techniques for Mandibular Complete Denture Impression: An In Vivo Study.

AimThe present in vivo study was undertaken for microstrain analysis of the selective pressure impression technique using strain gauges in mandibular complete denture impression.MethodologyTen completely edentulous patients undergoing complete denture treatment were selected for the study. For each patient, mandibular casts were made, and two custom trays were fabricated on the mandibular cast. These mandibular trays were divided into two groups: those with mandibular impressions made in the custom tray with the use of a spacer (MST) and those without a spacer (MWS). For each patient, a primary impression was made by using an impression compound. After that, the primary cast was obtained, and the custom tray was fabricated by using auto polymerizing resin. Then strain gauges were attached to the particular areas of the tray. The customized tray with zinc oxide eugenol impression material was seated in the patient's mouth for the final impression. The strain produced during impression making at different areas was recorded by a multi-channel (six) strain amplifier and data logger (8-channel digital strain indicator NIC, Jaipur, India). The data obtained were subjected to statistical analysis using an independent t-test (for quantitative data within two groups). The level of significance was set at p=0.05 (p<0.05-significant, p<0.01-highly significant, p<0.0001-very highly significant).ResultsThe comparison of the percentage of microstrain produced at the relief area with and without spacer tray design showed a statistically significant (p=0.001) result with a greater number of percentages of microstrain among those without spacers (94.19) than with spacer (72.09) tray design.ConclusionThe use of a tray with relief for selective pressure impression of an edentulous mandible resulted in a desirable pressure distribution at the alveolar crests and buccal shelves.

Comparative Evaluation of Shear Bond Strength of Bioactive Restorative Material, Zirconia Reinforced Glass Ionomer Cement and Conventional Glass Ionomer Cement to the Dentinal Surface of Primary Molars: an in vitro Study.

Statement of the Problem: The success of dental restorations depends mainly on its ability to bond to dental structures and resist the multitude of forces acting on it within the oral cavity.Purpose: Therefore, the aim of this study was to evaluate the shear bond strength (SBS) of three different glass ionomer based restorative materials.Materials and Method: In this in vitro analytical study, 30 intact primary molars were sectioned buccolingually to obtain 60 sections. These sections were embedded in auto polymerizing acrylic resin and polished to obtain a flat dentin surface. Restoration cylinders were built on the dentin surface with the help of a Teflon template called bonding jig. Each group (n= 20) was restored as group A with conventional glass ionomer cement (GIC) (GC Fuji Gold Label Type 9), group B with Bioactive restorative material (ACTIVATM KIDS BioACTIVE Restorative material), and group C with Zirconia reinforced glass ionomer cement (Zirconomer). Following restoration, SBS testing was performed using Universal Testing Machine. The data obtained were statistically analyzed using One way ANOVA test and post hoc Tukey test (p= 0.05).Results: The SBS values were significantly greater in the ACTIVA KIDS group as compared to the other two groups (p< 0.05). There was no significant difference in the SBS values between group B and group C (p> 0.05).Conclusion: The SBS of the ACTIVA KIDS to primary teeth dentin was the highest as compared to Zirconomer and conventional GIC. Therefore ACTIVA KIDS may protect primary teeth against recurrent caries and failure of the restoration.

Effects of conventional and herbal irrigants on microhardness and flexural strength of root canal dentin: An in vitro study.

Aim:The aim of this in vitro study was to compare the effects of herbal irrigants with conventional irrigants on microhardness and flexural strength of root dentin.Materials and Methods:Sixty extracted permanent maxillary canines were selected. Decoronated roots were sectioned longitudinally into buccal and lingual segments to get 120 specimens. These were embedded in auto polymerizing acrylic resin and further grounded with fine emery papers under distilled water. Of these, 100 root segments without any defects were selected, further divided into four test groups and a control group according to the irrigants used (n = 20). Group 1: 2.5% Sodium hypochlorite, Group 2: Miswak stick extract, Group 3: Cashew leaves extract. Group 4: Mango leaves extract and Group 5: Normal saline (control). All specimens were treated with 5 ml of each irrigant for 10 minutes and rinsed immediately. Dentin microhardness was measured with a Vickers indenter, and the flexural strength test was done using a universal testing machine. The data were analyzed using one-way ANOVA and the intergroup comparison by student t-test.Results:The experimental groups showed a significant reduction in microhardness values when compared with the control group. Intragroup comparison among experimental groups, herbal irrigants showed the least reduction in microhardness values at cervical, middle, and apical thirds. When compared to the control group, the flexural strength values decreased significantly with experimental groups.Conclusion:Within the limitation of this study, it was concluded that herbal irrigants were least detrimental to root dentin microhardness when compared with conventional irrigant. But the flexural strength was equally reduced by both conventional and herbal irrigants.

The Effect of Different Beverage Solutions on the Hardness of Different Acrylic Denture Teeth

Aims: To determine the effect of different beverage solutions on the hardness of different acrylic denture teeth which are commercially available. Materials and Methods: Sixty samples were prepared from three brands of artificial teeth in this study. The posterior teeth of each brand were placed in auto polymerizing acrylic resin and the occlusal surfaces were ground flat, then immersed in distilled water (control), Pepsi, coffee and tea solutions for 30 days and then the hardness were tested using Vickers microhardness tester. Results: The RMH denture teeth materials showed the highest hardness than other denture teeth materials. Pepsi was more effective than tea and coffee in reducing the hardness of different acrylic teeth materials. Conclusions: Pepsi reduced the hardness of different acrylic teeth materials during the 30 days immersion. The hardness of RMH denture teeth materials was less affective by the different beverage solutions.

OBTURATOR FABRICATION WITH MAGNET ATTACHMENT

Background: Development of science and technology led to people having birth defects (congenital), trauma or because of there sected tumor can be made of a prosthesis. Purpose: To learn the technique of making obturator with magnet attachment. Review: Assembly of magnet in obturator can improve the stability and retention of the prosthesis. Conclusion: The techniques of making obturator with magnetic attachment begins with making the double impression. The part defect is waxed on a master cast, and the contoured wax lid was fabricated on the master cast to close the hollow obturator. The lid along with the magnetic assembly was attached to the obturator with auto polymerizing resin. Obturator is inserted in the patient and created a master cast for the fabrication of denture. Wax of master cast of denture is assembled magnet for attachment to the obturator, then flasking, wax boil-out of master cast, acrylic processing, deflasking, finishing, and polishing.

Evaluation of Fluoride release from orthodontic acrylic resin by using two different polymerizations techniques: An InVitro Study

Background and objectives: Oral hygiene is mandatory for patients with orthodontic appliances and prevention of microbial biofilms in the oral environment. One method for inhibiting the growth of micro-organisms is commonly by use fluoridated dental material. The aim of this study was to evaluate releasing fluoride after addition into the orthodontic acrylic resin with 40% hydroxyethyl methacrylate, and amount of fluoride release from the orthodontic acrylic resin that was polymerized by Auto polymerization and IVOMAT polymerization. Materials and methods: Sixty disc-shaped samples measured 10 mm diameter and 1mm thickness of orthocryle were divided into two groups according to polymerization technics, thirty samples for Auto polymerization and thirty samples for polymerization by IVOMAT. Each of these groups was subdivided into three groups according to the concentration of NaF. Group A 0% NaF, Group B 10%NaF, and Group C 20%NaF. For testing fluoride release, samples stored for 28 days in deionized distilled water for testing measurements for days 1,4,7,14,21, and day 28. Precision ion meter was used to measure fluoride release. Repeated measure ANOVA was undertaken to compare fluoride release in each group. Paired sample t-test was utilized to differentiate between groups. Results: Significant difference was observed in the fluoride-releasing of both groups and within the subgroups (P≤0.05). The highest amount of fluoride release is present in 20% NaF followed by 10% NaF for Auto polymerized acrylic resin in the first day. The lowest fluoride release is presented in 10% on day 28 for IVOMAT polymerization. In general, the Auto polymerized acrylic resin had higher fluoride release than IVOMAT from all groups for 0%,10% and 20% NaF. Conclusion: Orthodontic acrylic resin has the ability to release fluoride more than 28 days for both types of polymerization technics in different concentrations.

Comparative Evaluation of Different Tooth Taper and Its Influence on Retention of Metal Crowns Luted with Resin Cements-An In Vitro Study

Background: Taper of the prepared tooth is one of the most important factor for retention while luting cements are weak but a critical link for retention Aims: Compare the influence of different tapers of prepared teeth on retention of metal crowns when luted with two commercially available adhesive resin cements Materials and Method: 48 extracted human premolars were used in this study. Each tooth was mounted in a PVC ring with auto polymerizing acrylic resin. A customized device was used to standardize the tooth preparation. Teeth were divided into 3 equal groups representing taper 6o, 12o, and 30 o. Metal crowns were fabricated for each tooth. Prepared teeth were luted with either RelyX Ultimate Clicker or Multilink Automix .Specimens were subjected to ‘Crown Pull Off’ test using Universal Testing Machine Statistical analysis used: One way ANOVA with Tukey post-hoc and Independent ‘t’ test Results: Statistically significant difference was found in the mean failure stress at 6o degree taper angle compared to 30o with p value ≥ 0.003 for both the adhesive resin cements. There was no significant difference of mean of failure stress for metal crowns luted with RelyX Ultimate Clicker and Multilink Automix Conclusions: Mean failure stress was highest at taper at 6o with a steady decrease at 12o and significant decrease at 30o taper It is utmost important for clinician to prepare the tooth within the range of 12o taper. While adhesive resin cements RelyX Ultimate and Multilink Automix are equally effective in terms of retention of the crowns.

Effect of Final Irrigation Protocol on Dentin Microhardness

Endodontic therapy is essentially a debridement procedure that requires the removal of the irritants of the canal and periapical tissue if success is to be gained. The debridement may include instrumentation of the canal, placement of medicament and irrigants. Complete cleaning of the root-canal system requires the use of irrigants that dissolve organic and inorganic material. The study aimed to evaluate changes in dentin microhardness after canal irrigation with different solutions. Twenty four freshly extracted human mandibular molars (distal roots with single canals) were used. 10mm root length was taken as standard length. The roots were embedded into auto polymerizing acrylic resin using plastic molds before the canals preparation and micro hardness test. The distal roots were prepared with one shape rotary file. Before the preparation each root was irrigated with 1ml distilled water. Then the roots were divided into four groups according to the final irrigation protocol: Group A: NaOCl 2.5%, Group B: EDTA 17%, Group C: Citric Acid 40%, Group D: Distilled Water. For (Vicker microhardness test) the same load and time 500 g test load for 20 seconds, will be conducted three times at distance 0.5mm from canal lumen ; thus there will be 9 indentations on each specimen surface. An average of the three readings for each test condition will be recorded as the VHN value of a specimen. Comparing all four groups statistically there was no significant difference among them. The mean values were found more reduced in EDTA group followed by NaOCL group, and then Control and Citric Acid groups. All the groups showed reduction in dentin microhardness. EDTA group showed the maximum reduction followed by NaOCL group, and least with Citric Acid group.

Shear Bond Strength of Acrylic Denture Teeth to PMMA and Polyamide Denture Base Materials

Introduction: Detachment of denture teeth from denture base is one of the most common reasons for costly denture repairs .This study aimed at evaluating the bond strength of an acrylic denture tooth to polyamide injection-molded thermoplastic denture base material compared with three conventional polymethylmethacrylate (PMMA) denture base resins. Materials and Method: A total of 40 acrylic denture molar teeth were randomly allocated into four groups (n=10) of heat-polymerized (HP), Auto-polymerized (AP), Injection molded (IM) and Polyamide thermoplastic (PT). All denture base/acrylic teeth combinations underwent 5000 thermal cycles (5-55◦C).Samples were subjected to shear bond strength test by a universal testing machine with a 1 mm/min crosshead speed .Data were analyzed using ANOVA and Tukey’s tests(α=0.05). Results: Mean ±SD of shear bond strength values were (MPa) 4.82±1.21, 4.52±1.67, 3.7±0.84 and 4.13±2.21 for groups HP, AP, IM and PT respectively. No significant difference was found among the experimental groups (P=0.429). Conclusion: Polyamide thermoplastic denture base resin was similar to conventional PMMA denture base materials in terms of bond strength to artificial denture teeth.