Objective . This study determined the ultimate tensile strength (UTS) of enamel (E), dentin (D) and dentin–enamel junction (DEJ) using the microtensile technique. It was hypothesized that the UTS of dental structures varies according to location and nature. Methods . Intact occlusal enamel surfaces from extracted human third molars were etched with 37% phosphoric acid and bonded with a one-bottle adhesive system. The bonded occlusal surfaces received a resin composite build-up and teeth were serially, vertically sectioned into several 0.7 mm thick slabs. Each slab was then trimmed to a dumbbell-shaped specimen with irrigated diamond burs to reduce the cross-sectional area to approximately 0.5 mm 2 at E, D or DEJ. E was tested according to its prismatic orientation (parallel, EP; and transversally, ET) and D as function of depth (superficial, DS; middle, DM and deep, DD). Specimens were tested in tension in an Instron testing machine at 0.5 mm/min. Results were analyzed by one-way ANOVA and Duncan's Multiple Range test. Results. UTS mean values ( N =20) were, MPa (SD): DEJ, 46.9 (13.7) b ; EP, 42.1 (11.9) b ; ET, 11.5 (4.7) d ; DS, 61.6 (16.2) a ; DM, 48.7 (16.6) b and DD, 33.9 (7.9) c . Enamel stressed transversally to its prismatic orientation was significantly weaker ( p p p >0.05). Significance . The UTS of dental structures varies according to its nature and location.

Ultimate tensile strength of tooth structures

https://www.cell.com/trends/biotechnology/pdf/S0167-7799(15)00191-2.pdf

Advances in Dental Materials through Nanotechnology: Facts, Perspectives and Toxicological Aspects.

Biomechanical Properties of First Maxillary Molars with Different Endodontic Cavities: A Finite Element Analysis.

Poly methyl methacrylate (PMMA) resin is the most widely used material for fabrication of dentures since 1937 as it exhibits adequate physical, mechanical and esthetic properties. But one of the major problems faced using this material is that, it is highly prone to plaque accumulation due to surface porosities and its food retentive properties. This in turn increases the bacterial activity causing denture stomatitis. In efforts to impart antimicrobial property to these resins, various nanoparticles (NP) have been incorporated viz. Silver, Zirconia oxide, Titanium dioxide (TiO2), Silica dioxide (SiO2) etc. However, as additives they can affect the mechanical properties of the final product. Therefore, the aim of the present study was to evaluate and compare the effect of different concentration of TiO2 NP on the flexural strength of PMMA resins. Specimens made from heat polymerizing resin (DPI) without NP were used as a control group (Group A). The two experimental groups, (Group B and Group C) had 0.5 and 1 % concentration of TiO2 NP respectively. The specimens were stored in 37 °C distilled water for 50 ± 2 h. A three-point bending test for flexural strength measurement was conducted following ADA specification no. 12. The maximum mean flexural strength (90.65 MPa) belonged to the control group; and acrylic resin with 1 % TiO2 NP demonstrated the minimum mean flexural strength (76.38 MPa). But, the values of all the three groups exceeded the ADA Specification level of 65 MPa. Conclusion may be drawn from the present study that addition of TiO2 NP into acrylic resin can adversely affect the flexural strength of the final product and is directly proportional to the concentration of NP.

Effect of Anatase Titanium Dioxide Nanoparticles on the Flexural Strength of Heat Cured Poly Methyl Methacrylate Resins: An In-Vitro Study

Clinical Relevance In vitro research remains of primary importance to selecting and validating the techniques and products to be used in vivo. However, the clinical predictive value of such tests n...

In Vitro Performance of Class I and II Composite Restorations: A Literature Review on Nondestructive Laboratory Trials—Part I

The aim of this work was the introduction of the basic characteristics of contemporary polymerization light sources for composite resin curing. Two basic groups of available curing technologies are introduced. First are those that produce white light (conventional halogen lamps and plasma arc polymerization units). The second group comprises "blue light" curing devices that produce blue light at the origin of the light source. Lights belonging to this group include the blue LEDs and argon laser. Information about main characteristics of light sources (irradiance, wavelength range) and their proper choice could have a significant impact on polymerization quality and on long-life of composite restoration.

/pdf/application-of-different-light-sources-for-polymerization-of-16kscvc156.pdf

Application of different light sources for polymerization of restorative resins

The purpose of this study was to evaluate the marginal microleakage in Class II with different materials in resin composite restorations cured by using "soft start" and standard polymerization techniques. Two adhesive Class II cavities were prepared in 50 human teeth with enamel in-between. Samples were divided into 5 groups and filled with composite resins, compatible flow resin composites and bonding systems. The ocluso-mesial restorations were cured with standard curing technique, and the ocluso-distal restorations were cured with "soft start" curing technique. After thermocycling, the teeth were immersed in silver nitrate solution and sectioned for leakage evaluation. The results pointed out, after "soft start" and standard curing techniques, that the best marginal behavior in Class II restorations was obtained with Tetric Ceram / Tetric Flow composite resins, then with Filtek Z 250 / Filtek Flow, followed by Admira Admira Flow and Point / Revolution composite materials. The deepest dye penetration was found in cavities with Diamond Lite / Diamond Link composite restorations. No statistically significant difference was found in the tested composite resin restorations, whether treated with "soft start" polymerization or with standard polymerization technique, in regard to marginal micro leakage.

/pdf/influence-of-soft-start-polymerization-on-marginal-sealing-2mg3uywudt.pdf

Influence of 'soft start' polymerization on marginal sealing in resin composite restorations

The quality of interface between composite resin materials and hard dental tissues is highly dependent on the polymerization light source. Newly developed blue light- emitting diode units for light polymerization of dental restorative materials are the most innovative light source technology in dentistry nowadays. The aim of this work was to estimate the depth of cure of five different light-activating composite resins exposed to different irradiation times (5s, 10s, 20s and 40s) when the experimental LED light source was used. The tested materials were: Tetric Ceram (Vivadent), Point 4 (Kerr), Admira (VOCO), Filtek Z250 (3M) and Diamond Lite (DRM Lab., Inc). The depth of cure testing was determined using a penetrometer. Results after 40s curing time were as following: the deepest depth of cure was achieved after application of Filtek Z 250, Diamond Lite Point 4 and Tetric Ceram. For the restorative material Admira was found the lowest depth of cure for the light exposure of 40s. An experimental LED light source achieved a sufficient depth of cure (over 2 mm) for all tested materials after curing time of 10s. The polymerization light source spectral distribution should be considered in addition to irradiance as a depth of cure indicator.

/pdf/polymerization-quality-testing-of-composite-resins-cured-by-4g0ewmqfpf.pdf

Polymerization quality testing of composite resins cured by led light source

The aim of the paper was to assess influence of different types of partial dentures on dental plaque accumulation. The study was conducted in three experimental and one control group with 30 examinees each. In the first experimental group were patients with partial acrylic dentures, in the second were patients with overdentures and in the third group were the patients with metal skeletal dentures. Dental plaque on the remaining teeth was measured by Silness-Loe modified method. Dental plaque scores were obtained at a time when dentures were given to patients and after 6 and 12 months of wearing, respectively. The plaque index of all teeth after 12 months of wearing dentures was relatively low in all three examined groups which resulted from previous education and motivation of examinees for oral hygiene maintenance. However, the highest risk of oral diseases caused by dental plaque is in patients with partial acrylic dentures, then in patients with overdentures, and best preventive effect was achieved in patients with metal skeletal dentures.

/pdf/influence-of-different-types-of-partial-dentures-on-dental-2fhlys95iu.pdf

Influence of different types of partial dentures on dental plaque accumulation

Lasers and laser technology is now used in many medical and dental indications. The aim of this study was to demonstrate many excellent points that should be considered by the dentist who is contemplating the use of lasers in dental practice. The interaction of laser radiation on soft tissue enables dry and bloodless surgery, minimal postoperative swelling and scarring, and minimal postoperative pain. Lasers for hard tisues encourage efficient diagnosis of caries and improve the resistence of dental enamel to caries, laser etching of enamel, cavity preparations, photopolymerization of composite resin and sterilization of the root canal system. All staff who are involved in using lasers must be trained with regard to treatment protocols and safety measures. All personnel and the patient must wear safety-approved glasses.

Larisa Blazic

Papers

Application of different light sources for polymerization of restorative resins

Influence of 'soft start' polymerization on marginal sealing in resin composite restorations

Polymerization quality testing of composite resins cured by led light source

Influence of different types of partial dentures on dental plaque accumulation

Lasers in dentistry