Self-curing Resin Research Articles

Biological Effects of PMMA and Composite Resins on Human Gingival Fibroblasts: An In Vitro Comparative Study.

The use of temporary resin for provisional restorations is a fundamental step to maintain the position of prepared teeth, to protect the pulpal vitality and the periodontal health as well as the occlusion. The present study aimed at evaluating the biological effects of two resins used in dentistry for temporary restorations, Coldpac (Yates Motloid) and ProTemp 4™ (3M ESPE ™), and their eluates, in an in vitro model of human gingival fibroblasts (hGFs). The activation of the inflammatory pathway NFκB p65/NLRP3/IL-1β induced by the self-curing resin disks was evaluated by real-time PCR, Western blotting and immunofluorescence analysis. The hGFs adhesion on resin disks was investigated by means of inverted light microscopy and scanning electron microscopy (SEM). Our results suggest that hGF cells cultured in adhesion and with eluate derived from ProTemp 4™ (3M ESPE ™) resin evidenced a downregulation in the expression of the inflammatory mediators such as NFκB p65, NLRP3 and IL-1β compared to the cells cultured with Coldpac (Yates Motloid) after 24 h and 1 week of culture. Furthermore, the cells cultured with ProTemp 4™ (3M ESPE ™) after 24 h and 1 week of culture reported a higher cell viability compared to the cells cultured with Coldpac (Yates Motloid), established by MTS cell analysis. Similar results were obtained when hGFs were placed in culture with the eluate derived from ProTemp 4™ (3M ESPE ™) resin which showed a higher cell viability compared to the cells cultured with eluate derived from Coldpac (Yates Motloid). These results highlighted the lower pro-inflammatory action and improved cell biocompatibility of ProTemp 4™ (3M ESPE ™), suggesting a better performance in terms of cells-material interaction.

Secondary Healing of Palatal Fistula by Simple Palatal Plate Obturator after Excision of Pleomorphic AdenomaA Case Report

Pleomorphic adenomas are the most common benign mixed tumours of the salivary glands. They typically occur at the junction between the hard and soft palate, but can also be found in the upper lip, buccal mucosa, floor of the mouth, tonsils, pharynx, and retromolartrigone. The present case of a 55-year-old woman focuses on the use of a palatal plate obturator to treat a soft palatal fistula that developed after the removal of a pleomorphic adenoma from the palate. By applying a self-cure resin to the posterior border of the palatal plate obturator, the postoperative issue of a palatal fistula was successfully managed. To aid in the healing of the palatal tissue and provide a scaffold for the regeneration of the surrounding palatal tissue, relief was applied to the intaglio surface of the palatal plate.

In vitro shear bond strength over zirconia and titanium alloy and degree of conversion of extraoral compared to intraoral self-adhesive resin cements

ObjectiveEvaluation of the Shear bond strength over zirconia and titanium alloy and degree of conversion of extraoral compared to intraoral self-adhesive resin cements.Materials and methodsNine bonding protocols were carried out on zirconia 4Y-TZP and titanium alloy (Ti-6Al-4V). Seven resin cement (one extraoral and six intraoral) were tested in the shear bond strength test and the degree of conversion measurements.ResultsThe significantly highest value was obtained for Monobond Plus + Multilink Hybrid Abutment, the extraoral resin cement for both titanium alloy (35.1 MPa) and zirconia (32.9 MPa). For each resin, significantly higher DC values were obtained for the dual-cure mode compared with the self-cure mode. Regardless of the cure mode, Nexus Universal reached the highest DC (78.4%).Discussion/ConclusionsIn this study, the extraoral self-curing resin cement showed the higher bond strength values on zirconia and titanium alloy when associated with a universal primer. Some intraoral dual-cure resin cements showed closed performances when used with universal primers. There is no direct correlation between the degree of conversion of the resin cement and the shear bond strength obtained on the prosthetic materials tested.

Nanocurcumin Release from Self-Cured Acrylic Resins; Effects on Antimicrobial Action and Flexural Strength.

The placement of orthodontic appliances into the oral area can lead to infection, inflammatory and gingival collapse. Using an antimicrobial and anti-inflammatory material in the matrix of orthodontic appliance may help to reduce these issues. This study aimed to assess the release pattern, the antimicrobial action and the flexural strength of self-cured acrylic resins after adding different weight percentages of curcumin nanoparticles (nanocurcumin). In this in-vitro study, 60 acrylic resin samples were divided into five groups (n = 12) based on the weight percentage of curcumin nanoparticles added to the acrylic powder (0 for control, 0.5, 1, 2.5, and 5%). Then, the dissolution apparatus was used for the release assessment of nanocurcumin form the resins. For antimicrobial action assessment, the disk diffusion method was used and a three-point bending test was performed with a speed of 5 mm/min to determine the flexural strength. Data were analyzed using one-way analysis of variance (ANOVA) and Post-Hoc Tukey tests (with p < 0.05 as significant level). The microscopic images showed the homogeny distribution of nanocuricumin in self-cured acrylic resins in varied concentrations. The release pattern showed a two-step release pattern for all concentrations of nanocurcumin. The one-way ANOVA outcomes indicated that adding curcumin nanoparticles to self-cured resin increased the diameter of the inhibition zones for the groups against Streptococcus mutans (S. mutans) significantly (p < 0.0001). Additionally, as the weight percentage of curcumin nanoparticles increased, the flexural strength decreased (p < 0.0001). However, all strength values were higher than the standard value (50 MPa). No significant difference was detected between the control group and the group with 0.5 percent (p = 0.57). Considering the proper release pattern and the potent antimicrobial activity of curcumin nanoparticles, then the preparing self-cured resins containing curcumin nanoparticles can be beneficial for antimicrobial aims without damaging the flexural strength to use in orthodontic removable applications.

Cytotoxicity of dental self-curing resin for a temporary crown: an in vitro study.

Residual monomer tests using high-performance liquid chromatography and cytotoxicity tests were performed to analyze the effect on the oral mucosa of a self-curing resin for provisional crown production. A cytotoxicity test was performed to confirm whether leaked residual monomers directly affected oral mucosal cells. The cytotoxicity of the liquid and solid resin polymers was measured using a water-soluble tetrazolium (WST) test and microplate reader. In the WST assay using a microplate reader, 73.4% of the cells survived at a concentration of 0.2% liquid resin polymer. The cytotoxicity of the liquid resin polymer was low at ≤0.2%. For the solid resins, when 100% of the eluate was used from each specimen, the average cell viability was 91.3% for the solid resin polymer and 100% for the hand-mixed self-curing resin, which is higher than the cell viability standard of 70%. The cytotoxicity of the solid resin polymer was low. Because the polymerization process of the self-curing resin may have harmful effects on the oral mucosa during the second and third stages, the solid resin should be manufactured indirectly using a dental model.

Glass ceramics behave like selectively etched enamel on interfaces produced with self-adhesive/ self-curing resin cement

This work aimed at analyzing the bond strength of different ceramic compositions and dental substrates to a self-adhesive/curing resin cement to determine the reliability of the bonded interfaces. The study groups were Lithium Disilicate (LD), Zirconia reinforced Lithium Silicate (ZLS), Conventional Yttria-stabilized Polycrystalline Tetragonal Zirconia (Y-TZP C), Translucent Yttria-stabilized Polycrystalline (Y-TZP T), Selective Etched Enamel (E + E); unetched Enamel (E); and Dentin (D). Twenty 2 mm thick slice specimens of each group were obtained from a cutting machine, under high speed and refrigeration, followed by polishing and inclusion in PVC tubes with acrylic resin, with their flat surfaces exposed. The self-adhesive/curing resin cement was inserted in a plastic matrix on the surface of each specimen, resulting in cylinders with an internal 1.40 mm diameter x 1 mm height. The specimens were subjected to microshear bond strength test. Qualitative failure analysis was performed by stereomicroscope and scanning electron microscope (SEM). Weibull statistical analysis was performed to obtain the following metrics: probability of failure, Weibull modulus (m) (reliability) and characteristic strength (σ0). The E + E group achieved the highest median value (24.88 MPa), lower probability of failure, greater reliability, and greater characteristic strength among all the study groups. ZLS presented the highest bond strength values (20.07 MPa) and characteristic strength but also the highest data variability. LD group presented greater reliability among ceramic materials. Dentin presented the lowest median (4.51 MPa) among all substrates evaluated. The adhesive failure mode was predominant among the failure types. Adhesive interfaces of glass ceramics presented higher characteristic strength, lower probability of failure and greater reliability, being similar to selectively etched enamel.

Effects of polishing press-on force on surface roughness and gloss of CAD-CAM composites

The aim of this study was to determine the effect of polishing press-on force on surface roughness and gloss of computer-aided design-computer-aided manufacturing (CAD-CAM) composites. The materials evaluated included a CAD-CAM ceramic, a polymer-infiltrated ceramic, and three filler-based CAD-CAM composites. The CAD-CAM blocks were sectioned, embedded in self-cured resin, finished with abrasive papers and ultrasonically cleaned. Specimens were subsequently polished using the Sof-Lex disk system with 0.5, 1.0, 1.5, and 2.0 N press-on force by means of a custom-made apparatus. Contour arithmetic mean deviation (Ra) and gloss value (GU) data were acquired with a profilometer and glossmeter, respectively, and analyzed using ANOVA/Bonferroni post hoc test and Pearson's correlation (α = 0.05). Representative samples of the various materials at baseline and after each polishing step were examined under scanning electron microscope. Mean Ra and GU values ranged from 0.096 ± 0.004 μm to 0.295 ± 0.045 μm and 13.4 ± 1.9 to 67.6 ± 11.3 correspondingly for the various material-force combinations. Surface roughness and gloss were found to be press-on force and material dependent. A moderately strong and negative correlation (rs = -0.69) existed between Ra and GU values. For optimal smoothness and gloss, ceramic and polymer-infiltrated ceramic CAD-CAM materials must be polished with a 2.0 N force, while filler-based CAD-CAM composites should, in general, be polished using a 1.0 to 1.5 N force.

Shear bond strength between denture teeth and denture base using different bonding resins and tooth surface treatments

Aim of studyThe aim of the present study was to evaluate the influence of surface treatments of the ridge lap area of PMMA acrylic denture teeth on their shear bond strength with different bonding resins to denture base milled from prefabricated PMMA block, in a two-way factorial experiment. The traditional heat-curing method was included as a reference method to compare to the proposed new method that employs digital technology. Materials and methodsFifty-four cylindrical rods were prepared from two different types of PMMA based denture resin; one specially designed for the computer-aided design and computer-aided manufacturing (CAD/CAM) milling method (groups A, n = 18 and B, n = 18) and a conventional heat-curing resin (group C, n = 18). A central maxillary incisor was selected as the experimental tooth. The specimens of each group A, B, and C were divided equally into three subgroups (a, b, c; n = 6 for every subgroup) according to three surface conditionings (no treatment, sandblasting, sandblasting plus methyl-methacrylate application, respectively). A specially designed bonding resin for digital dentures was used in group A, and a common self-curing resin for repairs in group B, while in group C the specimens were prepared by the conventional heat-curing method. Shear bond strength was determined using an electro-mechanic loading frame (MTS Insight) with a cross-head speed to 1 mm/min. ResultsThere was a statistically significant interaction between the construction method (A, B, C) and tooth surface treatment (a, b, c) (p = 0.026). After eliminating one subgroup, the effect of tooth surface treatment was not significant (p = 0.42). ConclusionsSurface treatment seems not to affect the teeth-base bond. Denture teeth bonded to a CAD/CAM denture base using PMMA self-curing resin for repairs (group B) showed the highest bond strength compared to groups A and C. Clinical significanceIn terms of bond strength, the digital denture construction method can be successfully used in everyday clinical and laboratory practice and replace effectively the conventional heat curing method.

Removal of lithium disilicate veneers with Er,Cr:YSGGL laser: now? Or after ageing?

This study was purposed to assess the impact of ageing and resin cements polymerized with different modes on the removal time of lithium disilicate (LiSi) ceramics using Er,Cr:YSGG laser. Ninety LiSi slabs (6 × 6 × 1mm) were cemented to freshly extracted bovine teeth using cements polymerized with different modes (light-curing (LC), dual-curing (DC), self-curing (SC)). The specimens were divided into subgroups according to ageing conditions (no thermal cycling, 5000 or 30,000 thermal cycling). After that, Er,Cr:YSGG laser was applied until LiSi slabs were debonded; the removal time was recorded. Vickers microhardness test, SEM and EDS analyses were performed for specimens with the longest exposure time to laser application in the groups. One uncemented sample was also used as a control. Data were analyzed with two-way ANOVA and Tukey post hoc test. Ageing and cement polymerization mode significantly affected the removal time of LiSi specimens. The removal time for the self-curing resin cement group (22.67 ± 12.68s) was significantly longer than for cements polymerized with other methods (LC = 10.833 ± 7.28s, DC = 12.0 ± 7.96s). Removal time was significantly reduced after ageing in all polymerization modes; however, there were no significant differences between 5000 (11.83 ± 7.52s) and 30,000 (11.83 ± 7.26s) thermal cycling groups. Self-curing resin cements had prolonged the laser-aided removal time for LiSi ceramics. It can be concluded that Er,Cr:YSGG laser-aided removal of LiSi veneers after clinical use can be done more faster than its immediate removal.

Clinical bracket failure rates between different bonding techniques: a systematic review and meta-analysis.

Bracket failure increases the treatment time of orthodontic therapy and burdens patients with unnecessary costs, increased chair time, and possible new appointments. To compare the bond failures of different orthodontic materials based on the results of available clinical studies. A systematic search of clinical trials was performed in the Cochrane, Embase, and Pubmed databases with no limitations. The list of investigated techniques contained conventional acid-etch primer (CM-AEP), self-etch primer (SEP), self-cure resin (SCR), and simple or resin-modified glass ionomer (RM-GIC) materials and procedures. Clinical studies reporting the failure rate of bonded brackets after using direct adhesive techniques on buccal sites of healthy teeth were included. Bracket failure rates from eligible studies were extracted by two authors independently. Risk ratios (RRs) were pooled using the random-effects model with DerSimonian-Laird estimation. Thirty-four publications, involving 1221 patients, were included. Our meta-analysis revealed no significant difference in the risk of bracket failures between SEP and CM-AEP. After 6, 12, and 18 months of bonding, the values of RR were 1.04 [95% confidence interval (CI), 0.67-1.61], 1.37 (95% CI, 0.98-1.92), and 0.93 (95% CI, 0.72-1.20), respectively. At 18 months, bracket failure was 4.9 and 5.2% for SEP and CM-AEP, respectively. Heterogeneity was good or moderate (I2 < 42.2%). The results of RM-GIC at 12 months indicated a 57% lower risk of bracket failure using SCR as compared with RM-GIC (RR: 0.38; 95% CI, 0.24-0.61). At 18 months, bracket failures for SCR and RM-GIC were 15.8 and 36.6%, respectively (RR: 0.44; 95% CI, 0.37-0.52, I2 = 78.9%), demonstrating three to six times higher failure rate than in the case of etching primer applications. A major limitation of the present work is that the included clinical trials, with no exceptions, showed variable levels of risk of bias. Another possible problem affecting the outcome is the difference between the clustering effects of the split mouth and the parallel group bracket allocation methods. The results revealed no significant difference between SEP and CM-AEP up to 18 months after application. RM-GIC had much worse failure rates than acid-etching methods; additionally, the superiority of SCR over RM-GIC was evident, indicating strong clinical relevance. Prospero with CRD42020163362.

The Influence of Metal Coping Design on Fracture Resistance of Porcelain-Fused-to-Metal Crown

The porcelain-fused-to-metal crown is the most popular indirect restoration in dentistry due to its high fracture resistance and low cost. However, unaesthetic labial margin is unacceptable to patients. Metal collar causes dark discoloration, which is worsened by gingival recession. Modification in metal collar coping has been developed to combine high fracture resistance of metal and high aesthetic of porcelain. Modification in crown fabrication including structure and composition of both nickel chromium alloy and feldspathic porcelain; application of self-cured resin cement and digital method; is meant to improve aesthetics without compromising fracture resistance. This study was an experimental laboratory research to evaluate fracture resistance of porcelain-fused-to-metal crowns with different metal coping designs. A total of 20 samples were used and divided into 4 groups according to different coping designs: (1). full metal collar; (2). full metal collarless; (3). modified metal collarless with 1.5 mm reduction; (4). modified metal collarless with 2 mm reduction. Universal Testing Machine (LRXPlus, Lloyd) was used to measure fracture resistance of all crowns. Average fracture resistance value for group 1 was 988.42 N; Group 2 was 1180.15 N; Group 3 was 1089.47 N; Group 4 was 1202.61 N. The results of statistical analysis showed that there was a difference in fracture resistance among porcelain-fused-to-metal crowns with different coping designs, although the value was not statistically significant. The higher coping reduction at labial margin, the higher the fracture resistance and standard deviation.

Investigation on the Potential Use of Polypropylene Mesh for the Reinforcement of Heat-Polymerized PMMA Denture Base Resin.

The aim of this study was to investigate the potential use of polypropylene (PP) hernia mesh as a reinforcement of PMMA denture base resin in comparison with metal and glass fiber meshes, with the expectation of enhancing the mechanical stability of the PMMA dentures in oral conditions. The control group with no mesh, the aluminum metal mesh (Al) group, the PP1 (PP mesh used on top) group, the PP2 (PP mesh used on both the top and bottom) group, the orthopedic casting tape with self-curing resin (DP0) group, and the flushed form (DPA) group were fabricated in a chromium mold. A total of 144 specimens were divided into three equal portions and subjected to: first, no treatment; second, thermal cycling only; and third, thermal cycling and chewing simulation. The flexural strength, maximum deformation, and flexural modulus were determined by a three-point bending test to compare mechanical properties. Fracture surfaces were evaluated by scanning electron microscopy. The obtained data were statistically analyzed by a two-way ANOVA test with Bonferroni corrections. The non-treated Al mesh reinforcement group exhibited the highest (82.66 ± 6.65 MPa) flexural strength, and the PP2 group treated with chewing simulation displayed the lowest (56.64 ± 4.59 MPa) flexural strength. The Al group showed the highest (7.25 ± 1.05 mm) maximum deformation and the PP2 group showed lowest (3.64 ± 0.28 mm) maximum deformation when both groups were not subjected to any treatment. The control group with no treatment exhibited the lowest (1556.98 ± 270.62 MPa) flexural modulus values, and the Al group with no treatment exhibited the highest (3106.07 ± 588.68 MPa) flexural modulus values. All the mesh groups displayed intact fractures. Any type of mesh used for reinforcement exhibited a significant change in all flexural properties (p < 0.001). The PP1 reinforcement group did not exhibit a significant change in mechanical properties when the effect of treatment was compared. Using PP hernia mesh on top enhanced the mechanical properties despite the weakening when it was used on both the top and bottom. The mechanical stability provided by the PP hernia mesh indicated it to be a promising candidate to be used for reinforcement.

Development of Orthodontic Resin with Antibacterial Property against Biofilm of Respiratory Pathogens

Orthodontic appliance made of resin is one of the main factors involving the shift of oral microbial community towards the source of pathogens by providing an extra site for adhesion and attachment of microorganisms to form biofilm associated with infections of multiple organs including respiratory tract. As a result, there is a demand for seeking of oral appliances with antimicrobial properties to reduce the risk of these infections. Here, vanillin (a principal flavoring agent with its antimicrobial property) has been incorporated to orthodontic resin and investigated the effect on biofilm formation of respiratory pathogens. The self-curing PMMA orthodontic resin samples (Siam Cement Group, Thailand) were fabricated depending on the percentage of vanillin adding (0.1% and 0.5% w/w vanillin). Resin without vanillin was used as a control. All samples were coated with sterile saliva collected from healthy volunteers. The bacterial biofilm formation assay was done by adding suspension (107 colony forming unit/mL) of Staphylococcus aureus ATCC 5638, Staphylococcus epidermidis ATCC 14990, Streptococcus pneumoniae ATCC 49619, and Pseudomonas aeruginosa ATCC 27853 to the samples and incubated in shaking incubator (120 r/min) for 120 min at 37 °C to allow the adhesion of the bacteria. Afterwards, non-adherent bacterial cells were washed out and Brain Heart Infusion broth was added and further incubated for 24 h to enable the biofilm formation. The amount of vital biofilm was quantified by Cell Counting Kit WST-8 (Dojindo Molecular Technologies, USA). It was found that the inclusion of vanillin to resin decreased the biofilm formation of S. aureus, S. epidermidis, and P. aeruginosa whereas no effect was observed on S. pneumoniae. Both the 0.1% and 0.5% vanillin concentrations could significantly inhibit the biofilm of S. aureus and P. aeruginosa whereas only 0.5% vanillin showed the inhibitory effect on S. epidermidis. Up to 40% biofilm reduction was noticed with S. epidermidis and P. aeruginosa while that of S. aureus was about 30%. In conclusion, the present data demonstrate that the development of orthodontic PMMA resin incorporated with vanillin may be a possible candidate for fabricating of oral appliance with antimicrobial property against respiratory pathogens. This suggests that it could be useful for the prevention or management of respiratory infection related to bacterial biofilm formed on oral appliances.

Assessing the effect of chemical surface treatment and joint surface preparations on transverse strength of repaired denture base resin

The present study was conducted to assess the effect of chemical surface treatment and joint surface preparations on transverse strength of repaired denture base resin. The study included 120 specimens divided into 8 groups of 15 samples each based on the combination of chemical surface treatment with either methyl methacrylate, ethyl acetate, or methylene chloride and chemical surface treatment of rounded joint, 45° bevel, and butt joint. Following surface treatment, dentures were repaired with self-cure resin. After treatment, to assess the transverse strength, they were subjected to a 3‑point bending test. Surfaces that were fractured were assessed under the microscope and were analyzed to AutoCAD for assessing cohesive or adhesive failure type and the area was measured. The study results showed that a statistically significant difference was seen in most of the comparisons done. Specimens with rounded joints and methylene chloride used for 60 seconds showed the gain of strength of 60%-70&amp; in the present study. The present study concludes that to attain better bond strength in a specimen repaired, the fractured segments of the specimens should be etched with methylene chloride for 60 s and should be given the rounded joints.

Microbiological Comparison of Different Sealing Materials for the Access Holes of Implant Restorations.

To evaluate the performance of sealing materials used in the screw-access holes of screw-retained implant final superstructures in vivo and in vitro. Twenty-one screw-access holes in the final superstructures were randomly divided into three groups (each group, n = 7). Following disinfection and isolation, all access holes were initially filled with sterilised cotton pellets of the same weight. Depending on the group, the access holes were finally sealed with either provisional composite restorations (group A), self-curing resin for provisional sealing (group B), or acrylic resin (group C). After one month of the functional period, the inner cotton pellets were collected as bacterial reservoirs. Total aerobic bacteria and total gram-negative anaerobic bacteria were measured after bacterial culture for 48 h and 72 h, respectively. In vitro evaluation of porosity using scanning electron microscopy (SEM) was also performed. Samples from superstructures sealed with provisional composite restorations showed fewer bacteria and less porosity than samples from superstructures sealed with self-curing resin for provisional sealing and acrylic resin. In this study, provisional composite restorations showed the best sealing properties. Provisional composite restorations may prevent bacterial invasion of the access holes of the final superstructures. In this study, provisional composite restorations showed the best sealing properties. Provisional composite restorations may prevent bacterial invasion of the access holes of the final superstructures.

Comparative evaluation of dimensional stability and flexural strength of different light cured tray materials with self-cured tray material: an in-vitro study

Objectives: To carry out a comparative evaluation of dimensional stability and flexural strength of different light cured tray materials with self-cured tray material as control.Materials and methods: The study was carried out in four groups based on the different available tray materials. Group A (n=30) – light cured resin (Individo Lux-VOCO™ GmbH Germany); Group B (n=30)- light cured resin (Profibase-VOCO™ GmbH Germany); Group C (n=30)- light cured resin (Plaque Photo-Willmann and Pein™ GmbH Germany); Group D (n=30)- control group-self cured resin (Asian special instant tray material Asian Acrylates™, Mumbai, India). A digital micro-meter was used to measure the length of each specimen first at 1 hour, 24 hour and 48 hour and three readings were taken up to 0.001 decimal. The values for flexural strength of each specimen were measured using the 3-point bending technique with the help of a universal testing machine. The mean values of dimensional stability and flexural strength were calculated by the one-way ANOVA and Tukey’s post-hoc test for multiple group`s comparison.Results The mean change in length (in mm) of light cured resins samples were significantly lower than self-cured resin samples at all three time intervals. The flexural strength values of light cured resin samples-Group A (84.46±13.32 N/mm2), B (83.43±14.52 N/mm2) and C (86.80±14.73 N/mm2) was significantly higher than the self-cured resin samples group D (41.29±7.93 N/mm2)Conclusions: Light cured tray materials are more dimensionally stable and have a higher flexural strength compared to self-cured tray materials.

Interfacial Biomaterial-Dentin Bacterial Biofilm Proliferation and Viability Is Affected by the Material, Aging Media and Period.

Biomaterial–dentin interfaces undergo degradation over time, allowing salivary, tissue fluid, and bacterial movement between the root filling or restoration and dentin. This study aims to investigate the effect of aging in simulated human salivary/bacterial/blood esterases (SHSE) on proliferation and viability of Enterococcus faecalis biofilm within the dentin interface with four materials used to fill/restore the endodontic space. Root canals of human anterior teeth were prepared and filled with gutta-percha and one of the following: self-cured resin composite (BisfilTM 2B, Bisco, Schaumburg, IL, USA) with either self-etch (SE) (EasyBond) or total-etch (TE) (ScotchbondTM, 3M, Saint Paul, MN, USA) methacrylate-based adhesives, epoxy-resin sealer (AH Plus®, Dentsply Sirona, York, PA, USA), or bioceramic sealer (EndoSequence® BC Sealer™, Brasseler USA, Savannah, GA, USA). Specimens were aged in SHSE or phosphate-buffered saline (PBS) for up to 360 days, followed by cultivation of steady-state E. faecalis biofilm. Depth and viability of interfacial bacterial biofilm proliferation were assessed by confocal laser scanning microscopy and live/dead staining. Data were analyzed using three-way ANOVA and Scheffe’s post hoc analyses. Initial depths of biofilm proliferation were similar among material groups (p > 0.05). All groups showed significantly deeper biofilm proliferation with increased aging period (p < 0.05). SHSE aging increased interfacial biofilm depth for TE, SE and BC (p < 0.05) but not AH. For unaged interfaces, BC exhibited the lowest ratio of live bacteria, followed by AH, TE, and SE (p < 0.05). Interfacial bacterial biofilm proliferation and viability were dependent on the biomaterial, aging media, and period.

COMPARATIVE EVALUATION OF THE SHEAR BOND STRENGTH OF TWO RESIN CEMENTS WITH THAT OF ZIRCON-BASED CROWNS – AN IN-VITRO STUDY

Introduction: Because of ceramics' exceptional esthetical qualities, the range of materials for implicitly rebuilding missing tooth structures has already grown substantially in recent years. One of the earliest ceramics, silica-based ceramics, needs an adhesive attachment to the tooth structures to keep them from breaking. Previous studies looked at the relationship between the properties of human dentine and the shear bond strength of adhesive on a polished, flat tooth structure surface. For the cementation of inlays, Onlays, crowns, posts, and veneers, resin-based adhesive luting substances are often utilized. the self-adhesive qualities are based on phosphoric-acid methacrylates, which demineralize and penetrate the tooth substrate to provide micromechanical retention.&#x0D; Methodology: This study was undertaken to investigate the shear bond strength between zirconia and two resin-luting types of cement. One is a conventionally used dual-cure resin cement and the other is a new universal self-adhesive self-cure resin cement. Methods: The two self-adhesive self-cured resin cement utilized in the current study, Panavia-F 2.0 and Rely X U 100 were two of these relatively novel products.&#x0D; Result: The number of adhesive and cohesive fractures was calculated for both groups .chi-square test was applied to compare the two parameters in both groups. it was found that 60% of Group RelyX–U100 showed cohesive fractures and 13.33% of group Panavia–F2.0 showed cohesive fractures. There was a highly significant difference found in the type of fractures shown by each group.&#x0D; Conclusion: It is thus concluded from the above study that to bond the zirconia restorations to dentin a better shear bond strength can be observed with respect to self-adhesive self-cure cement rather than the conventional dual resin cement where the application of primer &amp; etchants is required for the bonding process.

Development of Dental Poly(methyl methacrylate)-Based Resin for Stereolithography Additive Manufacturing.

Poly(methyl methacrylate) (PMMA) is widely used in dental applications. However, PMMA specialized for stereolithography (SLA) additive manufacturing (3D-printing) has not been developed yet. This study aims to develop a novel PMMA-based resin for SLA 3D-printing by mixing methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDMA), and PMMA powder in various mixing ratios. The printability and the viscosity of the PMMA-based resins were examined to determine their suitability for 3D-printing. The mechanical properties (flexural strength and Vickers hardness), shear bond strength, degree of conversion, physicochemical properties (water sorption and solubility), and cytotoxicity for L929 cells of the resulting resins were compared with those of three commercial resins: one self-cured resin and two 3D-print resins. EGDMA and PMMA were found to be essential components for SLA 3D-printing. The viscosity increased with PMMA content, while the mechanical properties improved as EGDMA content increased. The shear bond strength tended to decrease as EGDMA increased. Based on these characteristics, the optimal composition was determined to be 30% PMMA, 56% EGDMA, 14% MMA with flexural strength (84.6 ± 7.1 MPa), Vickers hardness (21.6 ± 1.9), and shear bond strength (10.5 ± 1.8 MPa) which were comparable to or higher than those of commercial resins. The resin’s degree of conversion (71.5 ± 0.7%), water sorption (19.7 ± 0.6 μg/mm3), solubility (below detection limit), and cell viability (80.7 ± 6.2% at day 10) were all acceptable for use in an oral environment. The printable PMMA-based resin is a potential candidate material for dental applications.

Retention of cemented zirconia copings on TiBase abutments.

This study evaluated the influence of resin cements and glass ionomers on tensile strength and types of failure of zirconia copings cemented on titanium base abutments. Forty-two samples were prepared, which were formed by a Cone Morse implant, a titanium abutment with the fixing screw, and a zirconia structure made using a CAD/CAM system. The samples (n = 42) were randomly distributed according to the cementing agent: resin-modified glass ionomer cement (RelyX Luting 2), self-adhesive resin cement (RelyX U200), and self-curing resin cement (Multilink N). After cementation of the copings, half of the samples from each group (n = 7) were randomly selected and subjected to thermocycling (5000 cycles). A tensile load test was performed on a universal testing machine until failure occurred (1 mm). In addition, the type of failure was analyzed using the two-way analysis of variance test and Tukey's post-hoc test (α = 0.05). Lower tensile load was observed for the glass ionomer cement (p < 0.001) regardless of the evaluation period. After thermocycling, a significant reduction in tensile load values was verified for both evaluated cements (p = 0.047). For the resin cements, failures were predominantly of the screw fracture type (82.1%) already with the use of glass ionomer cement, and 28.5% of the failures were of an adhesive type between the zirconia coping and the cement. Resin cements have better stability under tensile load compared to resin glass ionomers when cementing zirconia copings on titanium base abutments.