Novel antimicrobial and bioactive resin-based clear aligner attachment orthodontic materials.

Introduction: Clear aligner orthodontic treatment provides a hygienic and esthetic alternative to fixed appliances; however, the required resin attachments can promote plaque accumulation and increase the risk of white-spot lesions in enamel. This study aimed to develop a novel resin-based antibacterial and bioactive orthodontic clear aligner attachment and evaluate its mechanical and antibacterial properties.

Methods: A resin matrix composed of urethane dimethacrylate (UDMA) and triethylene glycol divinylbenzyl ether (TEG-DVBE) was modified with 3% dimethylaminododecyl methacrylate (DMADDM) for antibacterial effects and nano-amorphous calcium phosphate (NACP) to support remineralization.

Stratification of fluoride uptake among enamel crystals with age elucidated by atom probe tomography.

Dental enamel is subjected to a lifetime of de- and re-mineralization cycles in the oral environment, the cumulative effects of which cause embrittlement with age. However, the understanding of atomic scale mechanisms of dental enamel aging is still at its infancy, particularly regarding where compositional differences occur in the hydroxyapatite nanocrystals and what underlying mechanisms might be responsible. Here, we use atom probe tomography to compare enamel from a young (22 years old) and a senior (56 years old) adult donor tooth.

Importance of Build Design Parameters to the Fatigue Strength of Ti6Al4V in Electron Beam Melting Additive Manufacturing.

The fatigue properties of metals resulting from Powder Bed Fusion (PBF) is critically important for safety-critical applications. Here, the fatigue life of Grade 5 Ti6Al4V from Electron Beam PBF was investigated with respect to several build and component design parameters using a design of experiments (DOE). Part size (i.

Contributions to enamel durability with aging: An application of data science tools.

Understanding aging of tooth tissues is the first step to developing robust treatments that support lifelong oral health. In this study selected nanomechanical, compositional and structural parameters of human enamel were characterized to assess the effects of aging on its durability in terms of the apparent fracture toughness (K) and brittleness (B). The interdependencies between aging and the enamel properties were assessed using a combination of traditional Pearson's correlation coefficient matrices and self-organizing maps (SOMs) via unsupervised machine learning.

Odontoblast apoptosis and intratubular mineralization of sclerotic dentin with aging.

Objectives: The aims of the study were to evaluate the roles of odontoblast apoptosis in the progression of tubular sclerosis of teeth from donors at different ages and assess its correlation to chemical composition and mechanical properties.

Design: Healthy human teeth were obtained and divided into young (age ≤ 25, n = 12) and old (age ≥ 60, n = 12) groups. Odontoblasts were counted with standard hematoxylin and eosin staining.

A machine learning approach to investigate the materials science of enamel aging.

Unlabelled: Understanding aging of tooth tissues is critical to the development of patient-centric oral healthcare. Yet, the traditional methods for analyzing the composition-structure-property relationships of hard tissues have limitations when considering aging and other factors.

Objective: To apply unsupervised machine learning tools to pursue an understanding of relationships between the composition and mechanical behavior of aging enamel.

Long-term antibacterial activity and cytocompatibility of novel low-shrinkage-stress, remineralizing composites.

A low-shrinkage-stress (LSS), antibacterial and remineralizing nanocomposite was recently developed; however, validation of its long-term antibacterial potency in modulating human salivary-derived biofilm is an unmet need. This study aimed to evaluate the antibacterial effect of the bioactive LSS composite before and after aging in acidic solution for 90 days using a multi-species biofilm model, and to evaluate its cytotoxicity. The LSS composite consisted of urethane dimethacrylate (UDMA) and triethylene glycol divinylbenzyl ether (TEG-DVBE), 3% dimethylaminohexadecyl methacrylate (DMAHDM) and 20% nanoparticles of amorphous calcium phosphate (NACP).

Bioactive low-shrinkage-stress nanocomposite suppresses S. mutans biofilm and preserves tooth dentin hardness.

Recurrent dental caries is one of the main reasons for resin composite restoration failures. This study aimed to: (1) develop a bioactive, low-shrinkage-stress, antibacterial and remineralizing composite and evaluate the sustainability of its antibacterial effect against Streptococcus mutans (S. mutans) biofilms; and (2) evaluate the remineralization and cariostatic potential of the composite containing nanoparticles of amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM), using dentin hardness measurement and a biofilm-induced recurrent caries model.

Novel bioactive root canal sealer with antibiofilm and remineralization properties.

Objectives: (1) To develop a novel bioactive root canal sealer with antibiofilm and remineralization properties using dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP); (2) investigate the effects on E. faecalis biofilm inhibition, sealer flow and sealing ability, compared with an epoxy-resin-based sealer AH Plus; and (3) investigate the calcium (Ca) and phosphate (P) ion release from the sealers.

Methods: A series of dual-cure endodontic sealers were formulated with DMAHDM and NACP at 5% and 20% by mass, respectively.

Contribution of Root Canal Treatment to the Fracture Resistance of Dentin.

Introduction: Although the strength and toughness of dentin decrease with age, no study has explored if restorative treatments are a contributing factor.

Methods: Multiple extracted teeth were obtained from randomly selected donors and categorized according to donor age and prior root canal treatment. The microstructure and chemical composition of radicular dentin were evaluated using scanning electron microscopy and Raman spectroscopy, respectively, and the strength was evaluated in 4-point flexure to failure.

Bonding durability, antibacterial activity and biofilm pH of novel adhesive containing antibacterial monomer and nanoparticles of amorphous calcium phosphate.

Objectives: The dentin bonding often fails over time, leading to secondary caries and restoration failure. The objectives of this study were to develop an adhesive with dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP), and investigate the effects of storage in artificial saliva for six months on the bonding durability, antibacterial activity, ion release and biofilm pH properties for the first time.

Methods: DMAHDM was added at 5% (by mass) to Scotchbond Primer and Adhesive (SBMP).

A comparative study on the wear behavior of a polymer infiltrated ceramic network (PICN) material and tooth enamel.

Objective: To investigate the wear mechanisms of a polymer infiltrated ceramic network (PICN) material, to compare its wear behavior with that of tooth enamel, and to provide evidence relevant to its clinical use.

Methods: The Vickers hardness (HV) and elastic modulus (E) of a commercial PICN material (ENAMIC) and enamel were measured. Reciprocating wear tests were performed under a ball-on-flat configuration.

The Tooth: Its Structure and Properties.

This article provides a brief review of recent investigations concerning the structure and properties of the tooth. The last decade has brought a greater emphasis on the durability of the tooth, an improved understanding of the fatigue and fracture behavior of the principal tissues, and their importance to tooth failures. The primary contributions to tooth durability are discussed, including the process of placing a restoration, the impact of aging, and challenges posed by the oral environment.

Effect of acidic agents on the wear behavior of a polymer infiltrated ceramic network (PICN) material.

Polymer infiltrated ceramic network (PICN) materials exhibit desirable properties for replacement of tooth structure. However, their durability and their integrity in various oral environments, remain relatively unknown. The primary objective of this study is to investigate the effect of acidic agents on the wear behavior of PICNs.

Extrafibrillar collagen demineralization-based chelate-and-rinse technique bridges the gap between wet and dry dentin bonding.

Unlabelled: Limitations associated with wet-bonding led to the recent development of a selective demineralization strategy in which dentin was etched with a reduced concentration of phosphoric acid to create exclusive extrafibrillar demineralization of the collagen matrix. However, the use of acidic conditioners removes calcium via diffusion of very small hydronium ions into the intrafibrillar collagen water compartments. This defeats the purpose of limiting the conditioner to the extrafibrillar space to create a collagen matrix containing only intrafibrillar minerals to prevent collapse of the collagen matrix.

Assessing the feasibility of yttria-stabilized zirconia in novel designs as mandibular anterior fixed lingual retention after orthodontic treatment.

Introduction: The purpose of this study is to explore the feasibility of yttria-stabilized zirconia (Y-TZP) in fixed lingual retention as an alternative to stainless steel.

Methods: Exploratory Y-TZP specimens were milled to establish design parameters. Next, the specimens were milled according to ASTM standard C1161-13 and subjected to 4-point flexural tests to determine material properties.

Fatigue of human dentin by cyclic loading and during oral biofilm challenge.

Fatigue caused by the cyclic loads of mastication and acid attack caused by the excretion of oral biofilms are two of the most critical challenges to the success of dental restorations and their clinical service life. The objective of this investigation was to evaluate the fatigue strength of human dentin when exposed to a simultaneous challenge of cyclic loading and acidic attack from oral bacteria. Rectangular beams of coronal dentin were obtained from third molars and subjected to cyclic flexural loading while exposed to an in-vitro microcosm biofilm model.

Protein-repellent and antibacterial functions of a calcium phosphate rechargeable nanocomposite.

Objectives: We recently developed a new rechargeable composite with nanoparticles of amorphous calcium phosphate (NACP) having long-term calcium (Ca) and phosphate (P) ion release; however, this composite was not antibacterial. The objectives of this study were to: (1) incorporate dimethylaminohexadecyl methacrylate (DMAHDM) and 2-methacryloyloxyethyl phosphorylcholine (MPC) into rechargeable NACP composite, and (2) investigate mechanical properties, protein adsorption and biofilm response of composite, and the pH of biofilm medium.

Methods: MPC, DMAHDM and NACP were mixed into a resin of ethoxylated bisphenol A dimethacrylate (EBPADMA) and pyromellitic glycerol dimethacrylate (PMGDM).

Designing Multiagent Dental Materials for Enhanced Resistance to Biofilm Damage at the Bonded Interface.

The oral environment is considered to be an asperous environment for restored tooth structure. Recurrent dental caries is a common cause of failure of tooth-colored restorations. Bacterial acids, microleakage, and cyclic stresses can lead to deterioration of the polymeric resin-tooth bonded interface.

Inhibition of matrix metalloproteinase activity in human dentin via novel antibacterial monomer.

Objective: Dentin-composite bond failure is caused by factors including hybrid layer degradation, which in turn can be caused by hydrolysis and enzymatic degradation of the exposed collagen in the dentin. The objectives of this study were to investigate a new antibacterial monomer (dimethylaminododecyl methacrylate, DMADDM) as an inhibitor for matrix metalloproteinases (MMPs), and to determine the effects of DMADDM on both soluble recombinant human MMPs (rhMMPs) and dentin matrix-bound endogenous MMPs.

Methods: Inhibitory effects of DMADDM at six mass% (0.

Adopting the principles of collagen biomineralization for intrafibrillar infiltration of yttria-stabilized zirconia into three-dimensional collagen scaffolds.

In this paper, we report a process for generating collagen-yttria-stabilized amorphous zirconia hybrid scaffolds by introducing acetylacetone-inhibited zirconia precursor nanodroplets into a poly(allylamine)-coated collagen matrix. This polyelectrolyte coating triggers intrafibrillar condensation of the precursors into amorphous zirconia, which is subsequently transformed into tetragonal yttria-stabilized zirconia after calcination. Our findings represent a new paradigm in the synthesis of non-naturally occurring collagen-based hybrid scaffolds under alcoholic mineralizing conditions.

Biomimetic silicification of demineralized hierarchical collagenous tissues.

Unlike man-made composite materials, natural biominerals containing composites usually demonstrate different levels of sophisticated hierarchical structures which are responsible for their mechanical properties and other metabolic functions. However, the complex spatial organizations of the organic-inorganic phases are far beyond what they achieved by contemporary engineering techniques. Here, we demonstrate that carbonated apatite present in collagen matrices derived from fish scale and bovine bone may be replaced by amorphous silica, using an approach that simulates what is utilized by phylogenetically ancient glass sponges.

Dual antibacterial agents of nano-silver and 12-methacryloyloxydodecylpyridinium bromide in dental adhesive to inhibit caries.

Dental resins containing 12-methacryloyloxydodecylpyridinium bromide (MDPB) showed potent antibacterial functions. Recent studies developed antibacterial resins containing nanoparticles of silver (NAg). The objectives of this study were to develop an adhesive containing dual agents of MDPB and NAg for the first time and to investigate the combined effects of antibacterial adhesive and primer on biofilm viability, metabolic activity, lactic acid, dentin bond strength, and fibroblast cytotoxicity.