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European Journal of Oral Sciences Apr 2022The present study reports on the long-term drug release and mechanical properties of bioactive dental filling materials based on chlorhexidine diacetate (CHX) or...
The present study reports on the long-term drug release and mechanical properties of bioactive dental filling materials based on chlorhexidine diacetate (CHX) or octinidine (di)hydrochloride (ODH) incorporated in a composite based on dimethacrylates or an ormocer. CHX or ODH were added to a nano-hybrid ormocer (O) and a nano-hybrid composite (C) with the amount of 2 wt% to achieve four matrix-drug combinations: O-CHX, O-ODH, C-CHX, and C-ODH. Drug extraction and release were measured using high-performance liquid chromatography with diode-array detection (HPLC-DAD), while drug distribution was assessed by using energy dispersive X-ray spectroscopy (EDX). Drug release in water at 37°C was observed over 87 d. To determine the material properties, the water absorption, water solubility, flexural strength and hardness were measured and compared to the reference materials. Persistent drug release over 87 d was observed for both ODH-based systems and both ormocer-systems, with the longest duration of activity seen for the O-ODH combination. Persistent drug release was achieved via the loosening of the polymer network indicated via decreasing polymerization enthalpies, enhanced water absorption, and water solubility. As a consequence, the flexural strengths of the materials were reduced. However, surface hardness was hardly reduced. ODH seems to be more adequate than CHX for the design of bioactive dental filling materials based on nano-hybrid ormocer and composites.
Topics: Anti-Infective Agents; Composite Resins; Dental Materials; Drug Liberation; Materials Testing; Methacrylates; Organically Modified Ceramics; Surface Properties; Water
PubMed: 34935216
DOI: 10.1111/eos.12840 -
Clinical Oral Investigations Dec 2020To perform a review on the influence of preheating and/or heating of resinous and ionomeric materials on their physical and mechanical properties and to discuss the...
OBJECTIVES
To perform a review on the influence of preheating and/or heating of resinous and ionomeric materials on their physical and mechanical properties and to discuss the benefits and methods of preheating/heating that have been used.
MATERIAL AND METHODS
A search was performed in the Pubmed, Scopus, Scielo, and gray literature databases. In vitro studies published from 1980 until now were searched using the descriptors "composite resins OR glass ionomer cements OR resin cements OR adhesives AND heating OR preheating." Data extraction and quality of work evaluation were performed by two independent evaluators.
RESULTS
At the end of reading the search titles and abstracts, 74 articles were selected. Preheating of composite resins reduces viscosity, facilitates adaptation to cavity preparation walls, increases the degree of conversion, and decreases the polymerization shrinkage. Preheating of resin cements improves strength, adhesion, and degree of conversion. Dental adhesives showed good results such as higher bond strength to dentin. However, unlike resinous materials, ionomeric materials have an increase in viscosity upon heating.
CONCLUSIONS
Preheating improves the mechanical and physical properties. However, there is a lack of clinical studies to confirm the advantages of preheating technique.
CLINICAL RELEVANCE
Preheating of dental restorative materials is a simple, safe, and successful technique. In order to achieve good results, agility and training are necessary so the material would not lose heat until the restorative procedure. Also, care is necessary to avoid bubbles and formation of gaps, which compromises the best restoration performance.
Topics: Composite Resins; Dental Bonding; Dental Cements; Dental Materials; Dentin; Glass Ionomer Cements; Heating; Materials Testing; Resin Cements
PubMed: 33083851
DOI: 10.1007/s00784-020-03637-2 -
The Science of the Total Environment Mar 2022Dental materials are currently undergoing a revolution. Mercury use, including traditional amalgam (mercury-containing) material used in dental fillings, is now being...
Dental materials are currently undergoing a revolution. Mercury use, including traditional amalgam (mercury-containing) material used in dental fillings, is now being widely regulated under the Minamata convention, and dental amalgam is currently being replaced by resin formulations in dentistry. These resin-based materials can be tuned to offer varying material properties by incorporation of a range of nano- and micro-particle based 'fillers' for different dental properties and applications. However, these innovations may have a concomitant effect on the waste streams associated with common dental applications, in particular the potential for higher concentrations of novel micro- and nanomaterials within wastewater streams, and a potential route for novel nanomaterials into the wider Environment. These new materials may also mean that wastewater filtering apparatus commonly deployed at present, such as amalgam separators, may be less efficient or insufficient to capture these new filler materials in dental facility wastewater. In this work, we analyse dental wastewater streams from three dental facilities in Ireland with differing amalgam separators in place. The potential overall toxicity, particulate load and physicochemical properties are analysed. The overall risk posed by these new materials is also discussed.
Topics: Dental Amalgam; Dental Materials; Dental Waste; Ireland; Mercury; Wastewater
PubMed: 34963598
DOI: 10.1016/j.scitotenv.2021.152632 -
Journal of the Mechanical Behavior of... Oct 2021The aim of this study was to investigate whether there is a relation between impact strength and flexural strength of different composite and ceramic materials used in...
AIM
The aim of this study was to investigate whether there is a relation between impact strength and flexural strength of different composite and ceramic materials used in dental restorations.
MATERIALS AND METHODS
The three-point-bending test was used to determine the flexural strength and flexural modulus, and the Dynstat impact test was used to determine the impact strength of different composite and ceramic dental materials. The relation between the flexural strength and impact strength was mathematically investigated and a three-dimensional finite element analysis model of the impact test set-up was created to verify these results.
RESULTS
We found a relation between the impact strength, a, the flexural strength, σ, and the flexural modulus, E, which can be represented by the formula: a=λ(σ⁄E), where λ is a constant dependent on the test set-up.
CONCLUSION
The obtained impact strength of materials is specific to the test set-up and dependent on the geometric configuration of the test set-up and the specimen thickness. The clinical significance of this investigation is that roughness and fatigue have far more influence on the impact strength than the flexure strength.
Topics: Ceramics; Dental Materials; Dental Porcelain; Flexural Strength; Humans; Materials Testing; Pliability; Surface Properties
PubMed: 34214922
DOI: 10.1016/j.jmbbm.2021.104658 -
Dental Materials : Official Publication... Jan 2023This study aimed to evaluate the influence of new resin-based CAD-CAM implant-supported materials on posterior crown restoration stress and strain concentrations.
OBJECTIVE
This study aimed to evaluate the influence of new resin-based CAD-CAM implant-supported materials on posterior crown restoration stress and strain concentrations.
METHODS
A previous 3D implant model was edited to receive a cement-retained posterior crown manufactured with different CAD/CAM materials (Estelite P Block, Estelite Block II or Estelite Layered Block). Each solid model was exported to the computer-aided engineering software and submitted to the finite element analysis of stress and strain. Material properties were assigned to each solid with isotropic and homogeneous behavior according to the manufacturer information. A vertical load of 600 N was applied in the occlusal region of the crown, via a simulated food bolus, and stress was calculated in Von Misses (σVM) for the implant, abutment and screw, Maximum (σMAX) Principal Stresses for the crown and microstrain for the bone.
RESULTS
All simulated materials showed acceptable stresses levels with a similar stress pattern among the models. At the crown intaglio region and cement layer, however, differences were observed: Estelite P Block showed a lower tensile and shear stresses magnitude when compared to other resin-based materials with lower elastic modulus.
SIGNIFICANCE
The stress effect of different resin-based CAD-CAM implant-supported crowns is predominant in the crown and cement layer, with Estelite P Block showing 7.4 % versus 9.3 % and 9.2 % for Estelite Block II and Estelite Layered Block of crown failure risk.
Topics: Dental Porcelain; Dental Implants; Crowns; Dental Materials; Dental Cements; Computer-Aided Design; Dental Stress Analysis; Dental Prosthesis, Implant-Supported; Finite Element Analysis; Materials Testing; Dental Prosthesis Design
PubMed: 36566152
DOI: 10.1016/j.dental.2022.12.001 -
Journal of Esthetic and Restorative... Sep 2021To determine color and translucency stability of present-day resin-based restorative materials.
OBJECTIVE
To determine color and translucency stability of present-day resin-based restorative materials.
MATERIALS AND METHODS
Disk-shaped (1.0 × 10 mm) resin composites (Filtek Universal, 3M ESPE; Spectra ST, Dentsply Sirona; Gradia Direct X, GC America; Estilite Quick, Tokuyama; Harmonize, Kerr; ACTIVA Bioactive-Restorative, Pulpdent) were prepared and divided into four staining groups (n = 5); coffee (55°C), grape juice (5°C), deionized water (25°C) and thermocycling (20 000 cycles, 5°C to 55°C with a 30-second dwell time). Spectrophotometer measurements were taken at baseline and 14 days for each group and the color stability (CIEDE2000) and changes in the translucency parameter (RTP ) and luminous transmittance of each composite were determined. A 2-way analysis of variance (ANOVA) using maximum likelihood estimations was used for analysis for these changes, with subsequent pairwise comparisons using Bonferroni-corrected Student's t tests and an experiment-wise α = 0.05.
RESULTS
A significant interaction (P < .0001) between material and treatment was found for each change in the esthetic property tested over 14 days. Multiple significant differences between materials for each treatment and between treatments for each material were identified.
CONCLUSIONS
The severity of color change and translucency of resin-based materials are dependent on their type, mostly affected by the coffee staining medium. Nano-filled resin composite is most resistant to color change and with stable translucency after artificial aging.
CLINICAL RELEVANCE
Nano-filled resin composite may be the most esthetically durable resin- based restorative material. Micro-hybrid resin composite and resin-modified glass ionomer restorative material are susceptible to color change and losing their translucency. Hot coffee solution may shorten the esthetic lifespan of a resin-based material.
Topics: Color; Composite Resins; Dental Materials; Humans; Materials Testing; Spectrophotometry; Surface Properties
PubMed: 32797672
DOI: 10.1111/jerd.12640 -
Journal of Dentistry Aug 2020To identify antibacterial additives and screening/assessment approaches used to evaluate the antibacterial activity of resin-based restorative dental materials... (Review)
Review
OBJECTIVES
To identify antibacterial additives and screening/assessment approaches used to evaluate the antibacterial activity of resin-based restorative dental materials containing these additives.
DATA
In vitro studies that compared the antibacterial effects of resin-based restorative dental materials with and without antibacterial additives were screened. Risk bias was assessed, and the following data were extracted: antibacterial additive, parental dental material, curing mode, bacterial growth outcome assessment, samples used as a substrate for bacterial growth, inoculum complexity, and culture time as an indicator of biofilm maturity.
SOURCE
Arksey and O'Malley's five stages framework using Medline (OVID), EMBASE, and Scopus (Elsevier) databases guided this review.
STUDY SELECTION
From 6503 studies initially identified, 348 studies were considered eligible for full-text screening, and 153 were included for data extraction. Almost all studies have a high sampling bias related to both sample size and blindness. Quaternary ammonium monomers were the most investigated additive (45 %), and the most prevailing parental material was resin composite (49 %). There was extensive methodological heterogeneity among the studies for outcome assessment with the majority using resin composite disks (78 %), mono-species Streptococcus mutans as the inoculum (54 %), and a relatively short period of biofilm growth (≤24 h).
CONCLUSION
The findings herein present the urgent need for improved biological efficacy studies in this important and exciting field. There is a need for efforts to improve study designs to mimic the oral environment in vivo and to develop standardized methods to help understand and optimize these materials.
CLINICAL SIGNIFICANCE
Most studies that incorporate antibacterial additives into resin-based materials claim promising results by bacterial reduction. However, these results should be interpreted with caution due to significant variation in the methods applied for quantifying bacterial growth, the frequent lack of complexity in the biofilms, and the often-short duration of biofilm growth.
Topics: Anti-Bacterial Agents; Biofilms; Composite Resins; Dental Materials; Materials Testing; Streptococcus mutans
PubMed: 32387506
DOI: 10.1016/j.jdent.2020.103369 -
Journal of the American Dental... Jan 2021Zirconia is a relatively new dental material used for indirect dental restorations. Little is known about how dental practitioners are using this material in their...
BACKGROUND
Zirconia is a relatively new dental material used for indirect dental restorations. Little is known about how dental practitioners are using this material in their practice.
METHODS
A survey on zirconia restorations was developed and administered electronically through e-mail communications to the American Dental Association Clinical Evaluators (ACE) Panel on August 31, 2020. Reminders were sent to nonrespondents, and the survey closed 2 weeks after the launch date.
RESULTS
When using zirconia for a restoration, respondents choose it to restore natural teeth (99%) more often than implants (76%). Almost all respondents (98%) use it for posterior crowns, whereas approximately two-thirds (61%) use it for anterior crowns. Restoration removal or replacement and shade matching and translucency were the top 2 cited disadvantages of zirconia, whereas most of the respondents (57%) cited flexural strength or fracture resistance as the biggest advantage. Fine diamonds and ceramic polishers are used most often to polish and adjust zirconia restorations, whereas coarse diamond rotary instruments and those made specifically for zirconia are most frequently used for removing these restorations. Compared with metal ceramic restorations, more than 50% of respondents experience debonding more often with zirconia restorations.
CONCLUSIONS
Dentists recognize the favorable fracture resistance and flexural strength properties of zirconia, and most use similar techniques when adjusting and removing this material. Removing these restorations and shade matching are a struggle for many.
PRACTICAL IMPLICATIONS
Dentists may benefit from tips on the best methods to remove, shade match, and adhesively bond zirconia restorations.
Topics: American Dental Association; Ceramics; Crowns; Dental Materials; Dental Porcelain; Dental Prosthesis Design; Dental Restoration Failure; Dental Stress Analysis; Dentists; Humans; Professional Role; Surveys and Questionnaires; United States; Zirconium
PubMed: 33250170
DOI: 10.1016/j.adaj.2020.10.012 -
Dental Materials : Official Publication... Oct 2020To measure the degrees of conversion (DC), conversion kinetics, and the effect of post-irradiation time on rapid photo-polymerized bulk-fill resin composites under...
OBJECTIVE
To measure the degrees of conversion (DC), conversion kinetics, and the effect of post-irradiation time on rapid photo-polymerized bulk-fill resin composites under conditions equivalent to clinical depths of 1 and 4mm.
METHODS
36 specimens (n=3), based on two resin composites incorporating PowerCure rapid-polymerization technology in two consistencies (PFill; PFlow) and two comparators with matching consistencies (Eceram; EFlow), were investigated from the same manufacturer (Ivoclar AG, Liechtenstein). Specimens were prepared within 4mm diameter cylindrical molds, of either 1mm or 4mm depths respectively, to simulate near-surface and deep locations in a bulk-fill restoration. The independent variables in this study were: materials, thickness and time. Two high irradiance polymerization protocols were utilized for PowerCure materials: 2000 and 3050mW/cm for 5 and 3s, respectively. A standard (1200mW/cm) polymerization protocol was used with control materials. FTIR was utilized to measure DC in real-time for 24h post-irradiation. The data were analyzed using Welch's-ANOVA, Games-Howell post-hoc test, kinetic dual-exponential sum function and independent sample t-tests (p=0.05).
RESULTS
The DC of the materials ranged between 44.7-59.0 % after 5min, which increased after 24h reaching 55.7-71.0 % (p<0.05). Specimen thickness did not influence the overall DC. At 5min, the highest DC was shown in EFlow. But PFlow, irradiated for 3s and 5s exhibited comparable results (p>0.05). PFill composite irradiated with the 3s and 5s protocols did not differ from ECeram (p>0.05). Specimen thickness and material viscosity affected polymerization kinetics and rate of polymerization (RP). Faster polymerization occurred in 1mm specimens (except PFill-5s and ECeram). PFill and PFlow exhibited faster conversion than the controls. RP varied across the specimen groups between 4.3-8.8 %/s with corresponding DC between 22.2-45.3 %.
SIGNIFICANCE
Polymerization kinetics and RP were influenced by specimen thickness and material viscosity. PFill and PFlow materials produced an overall comparable conversion at 5min and 24h post-irradiation, despite the ultra-short irradiation times, throughout the 4mm specimen thickness.
Topics: Composite Resins; Dental Materials; Kinetics; Materials Testing; Polymerization; Surface Properties
PubMed: 32798046
DOI: 10.1016/j.dental.2020.07.008 -
Journal of Prosthodontics : Official... Apr 2023To measure the flexural strength and Weibull characteristics of aged and nonaged printed interim dental material fabricated with different layer thickness. (Comparative Study)
Comparative Study
PURPOSE
To measure the flexural strength and Weibull characteristics of aged and nonaged printed interim dental material fabricated with different layer thickness.
MATERIAL AND METHODS
Bars (25×2×2 mm) were additively fabricated by using a polymer printer (Asiga Max) and an interim resin (Nexdent C&B MFH). Specimens were fabricated with the same printing parameters and postprocessing procedures, but with 7 different layer thickness: 50 (control or 50-G group), 10 (10-G group), 25 (25-G group), 75 (75-G group), 100 (100-G group), 125 (125-G group), and 150 μm (150-G group). Two subgroups were created: nonaged and aged subgroups (n = 10). A universal testing machine was selected to measure flexural strength. Two-parameter Weibull distribution values were computed. Two-way ANOVA and Tukey tests were selected for statistical evaluation of the data (α = 0.05).
RESULTS
Artificial aging methods (p < 0.001) were a significant predictor of the flexural strength computed. Aged specimens acquired less flexural strength than nonaged specimens. The Weibull distribution obtained the highest shape for nonaged 50-G and 75-G group specimens compared with those of other nonaged groups, while the Weibull distribution showed the highest shape for aged 125-G specimens.
CONCLUSIONS
The flexural strength of the additively fabricated interim material examined was not influenced by the layer thickness at which the specimens were fabricated; however, artificial aging techniques reduced its flexural strength. Aged specimens presented lower Weibull distribution values compared with nonaged specimens, except for the 125-G specimens.
Topics: Flexural Strength; Dental Materials; Materials Testing; Surface Properties; Stress, Mechanical; Printing, Three-Dimensional; Polymerization; Polymers
PubMed: 35924435
DOI: 10.1111/jopr.13582