Static and dynamic failure load of fiber-reinforced composite and particulate filler composite cantilever resin-bonded fixed dental prostheses

Purpose: The aim of this study was to evaluate in vitro the influence of fiber reinforcement and luting cement on the static failure load (SFL) and dynamic failure load (DFL) of simulated two-unit cantilever resin-bonded fixed dental prostheses (RBFDPs). Materials and Methods: Forty-six particulate filler composite (PFC) beams and 76 fiber-reinforced composite (FRC) beams were prefabricated and subsequently luted (RelyX ARC or Panavia F2.0) onto flat ground bovine enamel. The SFL of the different specimen types was determined with a peel test and the DEL was determined with a rotating cantilever beam fatigue testing device. Results: The PFC specimens showed a significantly lower SFL than the FRC specimens. The luting cement showed a significant effect on the SFL of the PFC specimens, but not with FRC. The DEL of PFC specimens was significantly lower than for FRC specimens. The luting cement showed a significant effect on the DFL of the PFC specimens, but not so with FRC. With both the SFL and the DEL tests all PFC beams fractured, leaving the bonded part on the tooth surface, but FRC beams partially debonded from the tooth surface, leaving fibers connected to the enamel surface to a varying extent. Coincidentally, the uncured fibers turned out to be prone to aging, an effect which has been investigated. Conclusion: Within the limitations of this study, it can be concluded that PFC without fiber reinforcement is not suitable for the fabrication of two-unit cantilever RBFDPs, despite the significant effect of the luting cement, but FRC is suitable

Three-dimensional finite element analysis of anterior two-unit cantilever resin-bonded fixed dental prostheses

The aim of this study was to evaluate the influence of different framework materials on biomechanical behaviour of anterior two-unit cantilever resin-bonded fixed dental prostheses (RBFDPs). A three-dimensional finite element model of a two-unit cantilever RBFDP replacing amaxillary lateral incisorwas created. Five frameworkmaterialswere evaluated: direct fibre-reinforced composite (FRC-Z250), indirect fibre-reinforced composite (FRC-ES), gold alloy (M), glass ceramic (GC), and zirconia (ZI). Finite element analysis was performed and stress distribution was evaluated. A similar stress pattern, with stress concentrations in the connector area, was observed in RBFDPs for all materials.Maximal principal stress showed a decreasing order: ZI >M>GC> FRC-ES > FRCZ250. The maximum displacement of RBFDPs was higher for FRC-Z250 and FRC-ES than for M, GC, and ZI. FE analysis depicted differences in location of the maximum stress at the luting cement interface between materials. For FRC-Z250 and FRC-ES, the maximum stress was located in the upper part of the proximal area of the retainer, whereas, for M, GC, and ZI, the maximum stress was located at the cervical outline of the retainer. The present study revealed differences in biomechanical behaviour between all RBFDPs.The general observation was that a RBFDP made of FRC provided a more favourable stress distribution

Effect of hydrothermal aging on the microhardness of high- and low-viscosity conventional and additively manufactured polymers.

STATEMENT OF PROBLEM Studies on the microhardness of novel additively manufactured polymers compared with well-established low- and high-viscosity composite resins with regard to chemical composition are lacking. PURPOSE The purpose of this in vitro study was to evaluate the effect of hydrothermal aging on the microhardness of various conventional and additively manufactured polymers. MATERIAL AND METHODS Cylindrically shaped specimens (N=240, n=10 per group) (Ø10×2 mm) were either additively manufactured (6 groups) or conventionally (6 groups) manufactured by using 3D (Optiprint Temp [OP; Dentona]; C&B MFH [ND; NextDent]; Saremco print CROWNTEC [SA; Saremco Dental AG]; Temp Print [TP; GC]; 3DELTA ETEMP [DM; Deltamed]; MED690 [ST; Stratasys, Ltd]) or conventional low (Gradia Direct [GR; GC]; Clearfil Majesty [CM; Kuraray Noritake]; Tetric EvoCeram [TE; Ivoclar Vivadent AG]) and high (Gradia Direct Flo [GR-F; GC]; Clearfil Majesty Flow [CM-F; Kuraray Noritake]; Tetric EvoFlow [TE-F; Ivoclar Vivadent AG]) viscous materials. All specimens were randomly allotted to 2 different aging methods (no-aging [dry] or aging by thermocycling [TC], ×6000, 5 °C-55 °C) and Vickers hardness (VH) tested (ZHV30; Zwick). Three indentations were made on each specimen (0.98-N load, duration 15 seconds). The calculated average microhardness value of each specimen was statistically analyzed by using 2-way ANOVA and Tukey post hoc tests (α=.05). Two-parameter Weibull distribution was calculated to predict the reliability of material type and aging method on VH. RESULTS The mean ±standard deviation VH ranged between 17 ±0.5 VHN and 68 ±0.5 VHN in the following ascending order: group STa.05). The mean ±standard deviation of HV for aged (37 ±1 VHN) and nonaged (35 ±1 VHN) specimens were statistically similar (P>.05). The Weibull distribution values presented the highest shape for the aged group SA (37.81). CONCLUSIONS The choice of the material had a significant effect and resulted in lower hardness for the 3-dimensionally printed materials than for the conventional composite resins. Under fatigue conditions, the choice of the material showed no significant difference when the Vickers microhardness was evaluated

Combining economic and social goals in the design of production systems by using ergonomics standards

In designing of production systems, economic and social goals can be combined, if ergonomics is integrated into the design process. More than 50 years of ergonomics research and practice have resulted in a large number of ergonomics standards for designing physical and organizational work environments. This paper gives an overview of the 174 international ISO and European CEN standards in this field, and discusses their applicability in design proces

Side effects of sodium lauryl sulfate applied in toothpastes: A scoping review

PURPOSE: To perform a scoping review on the available literature regarding the side effects of sodium lauryl sulfate (SLS) used in toothpastes. METHODS: A scoping review was performed according to the PRISMA extension using PubMed. The electronic search was supplemented with a manual search for a complete overview. A customized data collection form was used to map data which was developed to register the extracted relevant data. The results of the selected articles were classified according to effects in the mouth, on the mucous membrane or elsewhere in the body and the healing effects of SLS-free toothpaste on aphthous ulcers. The outcomes from each category were reported in separate data forms and the studies with incomplete information were excluded from the assessment. RESULTS: Possible harmful effects of SLS were reported as mucosal desquamation, irritation or inflammation of oral mucosa or the dorsal part of the tongue, ulcerations, and toxic reactions in the oral cavity. CLINICAL SIGNIFICANCE: There is limited evidence that patients with recurrent aphthous ulcers can benefit from the use of SLS-free toothpastes in terms of decrease in the number of ulcerations, duration of the ulcerations and the intensity of the pain caused by the ulcerations. It is essential to create awareness for the side effects of SLS in toothpastes but further research is needed on its effect on oral and gastrointestinal systems when used in toothpastes

Influence of retainer design on two-unit cantilever resin-bonded glass fiber reinforced composite fixed dental prostheses : an in vitro and finite element analysis study

Purpose: The aim of this study was to evaluate in vitro the influence of retainer design on the strength of two-unit cantilever resin-bonded glass fiber-reinforced composite (FRC) fixed dental prostheses (FDP). Materials and Methods: Four retainer designs were tested: a proximal box, a step-box, a dual wing, and a step-box-wing. Of each design on 8 human mandibular molars, FRC-FDPs of a premolar size were produced. The FRC framework was made of resin impregnated unidirectional glass fibers (Estenia C&B EG Fiber, Kuraray) and veneered with hybrid resin composite (Estenia C&B, Kuraray). Panavia F 2.0 (Kuraray) was used as resin luting cement. FRC-FDPs were loaded to failure in a universal testing machine. One-way ANOVA and Tukey's post-hoc test were used to evaluate the data. The four designs were analyzed with finite element analysis (FEA) to reveal the stress distribution within the tooth/restoration complex. Results: Significantly lower fracture strengths were observed with inlay-retained FDPs (proximal box: 300 +/- 65 N; stepbox: 309 +/- 37 N) compared to wing-retained FDPs (p < 0.05) (step-box-wing: 662 +/- 99 N; dual wing: 697 +/- 67 N). Proximal-box-, step-box-, and step-box-wing-retained FDPs mainly failed with catastrophic cusp fracture (proximal box 100%, step-box 100%, and step-box-wing 75%), while dual-wing-retained FDPs mainly failed at the adhesive interface and/or due to pontic failure (75%). FEA showed more favorable stress distributions within the tooth/restoration complex for dual wing retainers. Conclusion: A dual-wing retainer is the optimal design for replacement of a single premolar by means of a two-unit cantilever FRC-FDPs

Quantitative clinical evaluation of esthetic properties of incisors

OBJECTIVE: To match perfectly the optical properties of natural teeth, a scientific approach is needed by using digital technology that excludes bias to quantitatively characterize the optical properties of populations' teeth. The aim of this article is to present a method for a detailed clinical quantification of optical properties of front teeth. METHODS: A novel spectrophotometric approach was developed and applied on a preliminary group of subjects quantifying L* (luminosity) a* (quantity of green-red) and b* (quantity of blue-yellow) of enamel and enamel-dentin complex against black and white background. Based on these in vivo data, CR (opacity) and opalescence (the ability to reflect blue wavelength when white light stroke the object perpendicularly) were also calculated. RESULTS: The mean values of L* of the enamel-dentin complex against black and white background were 79.6 and 75.4, respectively. The mean values of a* were 2.5 against black and 0.8 against white background, respectively. The mean values of b* were 17.4 against black and 13.0 against white background, respectively. The mean contrast ratio was 86.7%. Opalescence value was 4.8. The mean values of L* of enamel against black and white background were 79.0 and 64.2, respectively. The mean values of a* were 2.1 against black and -0.3 against white background, respectively. The mean values of b* were 15.2 against black and 8.7 against white background, respectively. The mean contrast ratio was 60.5%. Opalescence value was 7.4. SIGNIFICANCE: The described methodology, applied on a larger group of subjects, may serve as a database for a more exact characterization of optical properties of natural enamel and dentin