Design of Multi-Functional Bio-Safe Dental Resin Composites with Mineralization and Anti-Biofilm Properties.

This study aims to develop multi-functional bio-safe dental resin composites with capabilities for mineralization, high in vitro biocompatibility, and anti-biofilm properties. To address this issue, experimental resin composites consisting of UDMA/TEGDMA-based dental resins and low quantities (1.9, 3.8, and 7.7 vol%) of 45S5 bioactive glass (BAG) particles were developed. To evaluate cellular responses of resin composites, MC3T3-E1 cells were (1) exposed to the original composites extracts, (2) cultured directly on the freshly cured resin composites, or (3) cultured on preconditioned composites that have been soaked in deionized water (DI water), a cell culture medium (MEM), or a simple HEPES-containing artificial remineralization promotion (SHARP) solution for 14 days. Cell adhesion, cell viability, and cell differentiation were, respectively, assessed. In addition, the anti-biofilm properties of BAG-loaded resin composites regarding bacterial viability, biofilm thickness, and biofilm morphology, were assessed for the first time. In vitro biological results demonstrated that cell metabolic activity and ALP expression were significantly diminished when subjected to composite extracts or direct contact with the resin composites containing BAG fillers. However, after the preconditioning treatments in MEM and SHARP solutions, the biomimetic calcium phosphate minerals on 7.7 vol% BAG-loaded composites revealed unimpaired or even better cellular processes, including cell adhesion, cell proliferation, and early cell differentiation. Furthermore, resin composites with 1.9, 3.8, and 7.7 vol% BAG could not only reduce cell viability in S. mutans biofilm on the composite surface but also reduce the biofilm thickness and bacterial aggregations. This phenomenon was more evident in BAG7.7 due to the high ionic osmotic pressure and alkaline microenvironment caused by BAG dissolution. This study concludes that multi-functional bio-safe resin composites with mineralization and anti-biofilm properties can be achieved by adding low quantities of BAG into the resin system, which offers promising abilities to mineralize as well as prevent caries without sacrificing biological activity.

Questionnaire survey on hands-on simulation training using a dental humanoid robot (SIMROID®).

INTRODUCTION: A dental humanoid robot, SIMROID®, is able to replicate the actions characteristic of human beings and enable training for communicating with patients and coping with unexpected situations. This study assessed user experiences via a survey questionnaire following hands-on training on the SIMROID®. MATERIALS AND METHODS: A total of 112 participants, consisting of 50 high school students who visited AUSD (Asahi University School of Dentistry) to participate in open campus events, 42 fourth-year students at AUSD and 20 dental students from Mexico State Autonomy University, University of Siena and Peking University took the survey. The participants observed the movements and reactions of a SIMROID® robot placed on a dental unit for approximately 20 min after which they completed a questionnaire survey. Both Japanese and English versions of the questionnaire were prepared for local and visiting foreign dental students. The questionnaire comprised 8 items, with a further two items for those undertaking dental training and an open comment field. RESULTS: All participants who observed the SIMROID® completed the questionnaire giving a 100% response rate. Generally, simulation training with SIMROID® was highly appreciated by all participants. The comprehensive evaluation score for SIMROID® was 4.56 ± 0.50 points for high school students, 4.05 ± 0.82 points for students at AUSD and 4.70 ± 0.47 points for foreign dental students, showing all participants had a very positive experience and impression of the SIMROID®. CONCLUSIONS: Therefore, simulation training using SIMROID® seems beneficial learning tool.

Bioactivity of human dental pulp-derived stem cells with boron-controlled S-PRG filler eluate by anion exchange.

Surface pre-reacted glass-ionomer (S-PRG) filler is a bioactive glass filler capable of releasing various ions. A culture medium to which was added an S-PRG filler eluate rich in boron was reported to enhance alkaline phosphatase (ALP) activity in human dental pulp-derived stem cells (hDPSC). To clarify the role of boron eluted from S-PRG fillers, the modified S-PRG filler eluate with different boron concentrations was prepared by using an anion exchange material. Therefore, elemental mapping analysis of anion exchange material, adsorption ratio, hDPSCs proliferation and ALP activity were evaluated. For statistical analysis, Kruskal-Wallis test was used, with statistical significance determined at p<0.05. ALP activity enhancement was not observed in hDPSC cultured in the medium that contained the S-PRG filler eluate from which boron had been removed. The result suggested the possibility that an S-PRG filler eluate with controlled boron release could be useful for the development of novel dental materials.

Bacterial adhesion and antibacterial property of coating materials containing theobromine and S-PRG filler.

Theobromine (TB) has been reported to promote tooth remineralization, strengthen tooth substance, and relieve dentin hypersensitivity. This study aimed to evaluate experimental tooth coating materials containing TB and surface pre-reacted glass-ionomer (S-PRG) fillers by examining the effects on bacterial adhesion and antibacterial properties. In addition, the amount of TB eluted from the coating material was measured. There was no significant difference in bacterial adhesion depending on the presence or absence of TB in the coating material, however, a significant decrease in the amount of bacterial adhesion was observed when S-PRG fillers were added to the coating material. The amount of eluted TB did not differ depending on the type of the filler in the coating material. It was suggested that TB could be used to develop a new dental material with the potential ability to inhibit the initiation and progression of dental caries.

Color changes and shear bond strength to simulated caries lesions treated with a novel solution of 20% silver nanoclusters in polymethacrylic acid.

The aims of the study were: (1) To compare the staining effect on demineralized dentin simulating caries between silver nanoclusters (AgNCls) synthesized using polymethacrylic acid (PMAA) and silver diammine fluoride (SDF), and (2) to measure the shear bond strength (SBS) of a glass ionomer cement (GIC) to simulated caries lesions with and without the application of AgNCls/PMAA or SDF. Dentine blocks 4 mm thick from twenty-four non-carious third molars were sectioned and coated with nail varnish (Revlon, New York, USA). Simulated caries lesions on occlusal dentin surfaces were created (66 h in 0.05 M acetate buffer 2.2 mM calcium/phosphate pH 5.0). Specimens were divided into groups and treated with (n = 8): (A) 20% AgNCls/PMAA; (B) SDF 38% (Fagamin, Tedequim, Córdoba, Argentina); or (C) without treatment. AgNCls/PMAA or SDF were applied on the exposed surfaces with a microbrush for 10 s. Samples were incubated for 24 h at 37 °C at 100% relative humidity. Surface color was measured according to the CIE-L*a*b* system before and after demineralization (R0 and R1), 24 h and one week after treatment (R2 and R3), using a spectrophotometer (CM-600D Konica Minolta Sesing Inc., Japan). Groups A and B received an extra application of AgNCls/PMAA or SDF before a conventional GIC (Fuji IX-Gold Label, GC Corp, Tokyo, Japan) was bonded using a mold, 4 mm diameter × 3 mm high. For SBS, a Universal Testing Machine (Digimess RS-8000-5, China)-crosshead speed of 1 mm/min-was used. Statistical analysis was performed using ANOVA, Student-t and Scheffe-test at a significance of p < 0.05. Group A presented a stable color p = 0.24 between R1-R2 and R1-R3 in contrast to significant color changes in Group B (p = 0.02). SBS was higher (p < 0.01) in Group A (10.4 ± 2.7 MPa) compared to Groups B (3.3 ± 1.3 MPa) and C (4.0 ± 0.4 MPa), where no differences between the latter groups were observed (p = 0.77). Results of this preliminary study demonstrated that 20% AgNCls/PMAA did not stain simulated carious dentin and improved SBS of the GIC. The relevance of this study relies on the development of a therapeutic system to potentially arrest caries lesions without staining.

Nonrestorative Caries Treatment: A Systematic Review Update.

Caries is the most prevalent chronic noncommunicable disease. Strategies to prevent its onset and early interventions to arrest the progression of early lesions have been emphasised throughout recent decades to avoid or delay the restorative spiral of the tooth. More individuals are retaining their natural teeth into old age, thereby necessitating ongoing restorative dentistry intervention for their maintenance. The aim of this systematic review was to update the state of the art regarding clinical studies reporting the effectiveness of different nonrestorative caries treatment options in the 5-year period from 2017 to 2022. Relevant articles were retrieved from 2 electronic databases, including randomised clinical trials (RCTs) published from January 2017 until April 2022, assessing effectiveness and secondary effects of at least one nonrestorative caries treatment option, carried out with adults and/or children with noncavitated or cavitated carious lesions on either primary or permanent teeth and diagnosed by radiographs or visual/tactile assessment. All 35 included articles presented the results of RCTs with a follow-up period ranging from 6 to 84 months. Most of these studies were considered high-quality articles with a low risk of bias. Sealants and fluoride gels and varnishes were mentioned in 12 studies as effective strategies to prevent the onset of caries lesions and to arrest them in the early stages. Resin infiltration reported high caries arresting rates in noncavitated proximal lesions in 10 publications. Silver diammine fluoride presented high caries-arresting rates in open dentin lesions, both in primary and permanent dentitions as well as in root caries lesions that were accessible for cleansing. New evidence has been published between 2017 and 2022 as the result of numerous clinical studies providing further evidence of the effectiveness of nonrestorative caries treatment options.

A conceptual model for clinical psychomotor skill development in an era of simulated and virtual reality.

Psychomotor skill development is central to a beginner practitioner's learning pathway. Curriculum constraints around time, access to facilities and resources in health professions education have prompted the growth in alternative approaches to clinical skill development in both simulation and direct patient care. Among these is the increased incorporation of virtual reality (VR) systems with haptic feedback alongside traditional, solid simulations. Given the rapid growth in the adoption of technological affordances to support skill development, it is cogent to pause and examine whether the underpinning concepts regarding psychomotor skill development that have driven much of the approaches to teach clinical skill acquisition in dentistry remain fit-for-purpose. This conceptual paper proposes a new taxonomy for clinical simulation psychomotor skill development in the era of increasing variety of simulation modalities.

Clinical assessment of resin-coating technique applied to exposed dentin after crown preparation.

The resin-coating technique, in which exposed dentin surfaces are covered using a thin-film coating material, was approved in the Japanese public health insurance system in December 2019. The purpose of this study was to evaluate clinical cases treated using the resin-coating technique with Hybrid Coat II (HC II) after tooth preparation on vital teeth. A total of 134 cases from patients who visited nine dental clinics were examined from the clinical records. Clinical signs and symptoms of cases before, during, and after treatment and at the time of recall were evaluated. The resin-coating was applied as either a single application with HC II (86.6%) or a combined application of HC II and a flowable resin composite (13.4%). The success rate without any symptoms of sensivity to cold water was 92.5% (124 cases). The current results indicated that the resin-coating with HC II is a reliable treatment for the tooth preparation of vital teeth.

Fluoride-Releasing Self-Etch Adhesives Create Thick ABRZ at the Interface.

A fluoride-releasing adhesive system is expected to promote mineralization of demineralized dentin/enamel around a composite restoration, thereby contributing to the longevity of the restoration. Scanning electron microscopic (SEM) and transmission electron microscopic (TEM) observations revealed the formation of an "acid-base resistant zone" (ABRZ) beneath the hybrid layer when dentin was treated with a self-etch adhesive system. A thicker ABRZ was formed from the upper slope to the end of the outer lesion, indicating greater resistance against an acid-base challenge, when a fluoride-releasing self-etch adhesive system was used. The slope formation of a fluoride-releasing adhesive is believed to be due to fluoride-release from the adhesive. Quantitative assessment of the acid resistance was performed at the interface using the region of interest (ROI) mode of a digital image analysis software package. The area of the ABRZ is influenced by the concentration of fluoride release from the adhesive resin. The threshold of fluoride concentration in the adhesive may exist to influence the morphology of the ABRZ. X-ray absorption fine structure (XAFS) analysis of the dentin treated with different concentrations of NaF-mouth rinses suggested that different fluoride concentrations result in the formation of different chemical compounds, such as fluorapatite and CaF2-like structures, on the dentin surface. This may explain the differences in µTBS values and morphological appearance of the ABRZ. NaF is effective in enhancing the enamel/dentin bond durability and also helps create a high quality of ARBZ to improve the clinical success of restorations.

Evaluation of bonding performance and multi-ion release of S-PRG fillercontaining self-adhesive resin composite.

The bonding performance of a surface pre-reacted glass ionomer (S-PRG) filler-containing self-adhesive flowable resin composites to enamel and dentin were evaluated using a tensile bond test with thermal cycling. Also, the quantities of various ions released from the materials were measured using ICP atomic emission spectrometry and a fluoride ion electrode. The initial bond strengths of the materials were approximately 6 MPa, and decreased after thermal cycling. The S-PRG filler-containing self-adhesive flowable resin composites materials exhibited much higher ion release compared with the commercial self-adhesive flowable resin composite possibly due to different acidic monomers contained. It was suggested that the S-PRG filler containing self-adhesive flowable resin composites should be limited as a lining material or to restore small cavities in non-stress bearing areas.

Comprehensive characterisation of flexural mechanical properties and a new classification for porosity of 11 contemporary ion-leaching dental restorative materials.

The objectives of this study were to evaluate 4 aspects of ion-leaching restorative materials (ILMs): 4-point bending flexural strength (4 PB-FS) and relative mechanical properties; biaxial flexural strength (B-FS) in relation to 4 PB-FS; porosity; and surface morphology. Eleven ILMs were used for the 4-point bending test. Bar-shaped (n = 15) samples were fabricated, stored in distilled water for 7 days. Then 4 PB-FS and the other mechanical properties were determined. Five ILMs were selected for the B-FS test using disk specimens (n = 15). The correlation between 4 PB-FS and B-FS was addressed. After the 4 PB test, 5 randomised fragments from each material were used to make 0.5 mm-thick sections for light microscopy to investigate the degree of porosity using reflected and transmitted lights. Eight ILMs were selected for quantitative analysis of the fractional % pore volume (PV%) due to their relative pore prominence using ImageJ software. One-way ANOVA/Dunnett's T3 was used to test for significance. Resin-based ILMs (RB-ILMs) were ranked first (p < 0.05) for 4 PB-FS values (53.3-110.2 MPa) followed by resin-modified glass-ionomer cements (RMGICs; 30.9-44.3 MPa) and high-viscosity glass-ionomer cements (HVGICs; 12.9-19.6 MPa), respectively. 'Flexural modulus' (4 PB-E) and 'flexural toughness' (4 PB-T) of ILMs varied even though similar 4 PB-FS values were observed. There was a positive correlation (p < 0.001) between 4PB-FS and B-FS (R2 = 0.992) with B-FS>4 PB-FS. There was no correlation between PV% and 4 PB-FS. In summary, material type played a major role in 4 PB-FS outcomes, whereas PV% seemed to have a minor effect when evaluating each material group of ILMs. Brittleness/ductility of ILMs was observed when determining 4 PB-E and 4 PB-T relative to 4 PB-FS. When selecting materials for posterior load-bearing dental restorations in high-caries risk patients, RB-ILMs or RMGICs would be more appropriate due to their superior flexural properties compared with recently introduced HVGICs. The decision for each situation will also be dependent on further evidence of the ion-leaching capacity.

The prevalence of non-carious cervical lesions (NCCLs) with or without erosive etiological factors among adults of different ages in Tokyo.

OBJECTIVES: To evaluate the prevalence of non-carious cervical lesions (NCCLs) on teeth with or without erosive etiological factors across a broad range of ages of Japanese adults. MATERIALS AND METHODS: The study sample consisted of a total of 1108 subjects aged 15 to 89 years in Tokyo, Japan. Two examiners evaluated NCCLs and dental erosion (DE) during a full-mouth examination. Subjects were asked to complete a self-administered daily diet, habits, and health condition questionnaire. Subjects who had frequent acid consumption or gastric reflux and at least one tooth with initial enamel wear were placed in the erosion present (EP) group, and the remainder of subjects were placed in the erosion not present (EN) group. Logistic regression analyses were carried out to identify etiological factors of NCCLs associated with DE. RESULTS: Overall prevalence of NCCLs was 60.2%; the prevalence increased with age. There were no statistical differences in the prevalence of NCCLs between the EP and EN groups, except for the 60-69 years group. Multiple logistic regression analysis showed the frequency of consumption of carbonated soft drinks, citrus juice, and acidic fruits such as oranges; tooth brushing pressure; and bruxism were associated with the presence of NCCLs. CONCLUSION: There were no statistical differences in the prevalence of NCCLs with or without erosive etiological factors except for the 60-69 years group. CLINICAL RELEVANCE: NCCL distribution increased with age, and erosive risk factors caused by change in dietary habits might affect the incidence of NCCLs for elders. TRIAL REGISTRATION: UMIN000041982.

Effect of repair systems on dentin bonding performance.

The purpose of this study was to investigate the influence of phosphoric acid etching, metal primer or silane coupling agent application on dentin bonding performance of a 2-step self-etch adhesive system. Human dentin surfaces were prepared and divided into four groups depending on the pre-treatment method: no pretreatment (Clearfil SE Bond 2, CONTROL); 40% phosphoric acid (K-Etchant GEL, K); metal primer (Alloy Primer, AP); or silane coupling agent (Porcelain Bond Activator, PB). The specimens were sectioned into beams, separated into 2 subgroups (n=20): no thermocyling or thermocycled (TC), and subjected to a µTBS test and an acid-base challenge for SEM observation. Statistically lower results were observed between K and AP groups, PB and CONTROL, and PB with/without TC (p<0.05). SEM images at the dentin-adhesive interface revealed that all groups produced an acid-base resistant zone (ABRZ), with a funnel-shaped erosion under the ABRZ for the K group.

Potential use of silver diammine fluoride in detection of carious dentin.

This study aimed to examine whether discoloration of carious dentin after silver-diammine-fluoride (SDF) application might be used as a mean to detect demineralized-dentin. Fourty specimens were obtained from 20 human permanent teeth. Teeth were sectioned through the center of carious lesions to create 2-halves in which each half was assigned to a treatment group. Specimens were divided into two groups (n=20) (each half was assigned to one group) according to solution, namely Caries Check (CC), or SDF. SDF group was subdivided into 2 groups: light-cured and 2-day storage groups. The specimens were tested using light-microscope, microhardness test and SEM/EDS analysis. Repeated-measures ANOVA was used for statistical analysis. The light-microscope showed superficial discoloration in the CC-group while SDF (2-day storage) group showed deeper discoloration for the lesion area. SDF showed significant increase in the hardness compared with the CC-group. SDF showed potentiality to be used as an assisting-tool for caries detection.

Operators matter - An assessment of the expectations, perceptions, and performance of dentists, postgraduate students, and dental prosthetist students using intraoral scanning.

OBJECTIVE: to assess the expectations, perceptions and performance of different operators with varying backgrounds and training in the use of full-arch intraoral scanning (IOS). METHODS AND MATERIALS: Dentists (DENT), postgraduate dental students (DPG), and student prosthetists (PROS) were invited to join an IOS training workshop. Participants completed a satisfactory scan of a mannikin-mounted typodont with the total scanning time (TST) recorded. They also completed anonymised pre and post-training questionnaires covering their background, and IOS expectations and experience. Statistical analysis was performed using the Mann-Whitney U, Kruskal Wallis, and chi-square tests. Open-ended questions were analysed manually and using Leximancer. RESULTS: Twenty-seven participants were recruited: 10 DENT; 10 PROS; and 7 DPG. Positive expectations of IOS was reported by 93 % of participants. Combined TST was 285 ± 83 s, with the PROS TST significantly longer (p < 0.05, 337 ± 79 s). Further training need was reported by 60 % of PROS and 50 % of DENT versus 14 % of DPG. Positive IOS experience was reported by 96 % of participants, 74 % perceived it to be accurate, and 63 % found it easy to use. Eighty-five percent of all participants stated that cost would influence their decision of adopting IOS in their practice. CONCLUSION: Expectations and perceptions of IOS were overwhelmingly positive, irrespective of operator background and experience. Scanning performance and training needs depended on the operator's background. Cost of IOS remains a barrier to acquiring the technology. CLINICAL SIGNIFICANCE: IOS training must be customised to accommodate the needs of different operators. The cost of IOS needs revision to improve its accessibility.

The effect of different light curing units on Vickers microhardness and degree of conversion of flowable resin composites.

This study aimed to assess the influence of different light curing units (LCUs) on the polymerization of various flowable resin composites. Three LCUs (Optilux 501, Elipar™ DeepCure-L LED and Bluephase®20i) and eight flowable resin composites: MI FIL Flow, Estelite Flow Quick, Estelite Universal Flow (medium), Estelite Universal Flow (super low), Beautifil Flow Plus, Clearfil Majesty ES Flow, Filtek Supreme Ultra flowable and TetricEvo Flow were tested. For Vickers microhardness (VHN) test and degree of conversion (DC), specimens were prepared and polymerized for 20 s. VHN test was performed at top surfaces (3 indentations) and DC for each specimen was measured using Fourier transform infrared (FT-IR) spectroscopy after 24 h dry storage in dark at 37˚C. The data were analyzed with 2-way ANOVA and t-test with Bonferroni correction. DC and hardness values showed a relationship between materials and LCUs. The curing efficacy of LCU type may depend on the material composition.

Remineralising effects of fluoride varnishes containing calcium phosphate on artificial root caries lesions with adjunctive application of proanthocyanidin.

OBJECTIVES: To evaluate the remineralising effects of fluoride (F) varnishes containing bioavailable calcium-phosphate compound (Ca-P) based remineralisation systems and 5000 ppm F toothpaste (FTP) on root caries lesions (RCLs) and the potential effects of proanthocyanidin (PA) for the treatments of RCLs when used as an adjunct to F regimens. METHODS: Demineralised root dentine and a pH-cycling model were used to mimic RCLs and the oral environment. Remineralising effects of MI VarnishTM (MIV) containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and Clinpro™ White Varnish (CPWV) containing tri-calcium phosphate (TCP) along with FTP and PA were evaluated regarding the birefringence, elemental composition, mechanical properties and mineral density of remineralised dentine with DuraphatTM as a comparison. RESULTS: MIV, CPWV and DuraphatTM promoted the incorporation of F into RCLs and increased mineral density but did not change microhardness of root dentine significantly. Surface microhardness increased significantly when MIV or CPWV was used with 5000 ppm FTP. Application of PA with F regimens significantly increased subsurface mineral density. When PA was applied with MIV or CPWV along with FTP, the highest ion uptake and relative mineral gain (%ΔZ) was achieved, and significant increase of microhardness was up to 30 µm depth. Generally, MIV was associated with a higher mineral content gain than CPWV. SIGNIFICANCE: Treatment of carious root surfaces remains challenging due to the complex pathological processes and difficulty in restoring the highly organised structure of root dentine. Treatment strategies targeting both remineralisation and preservation of the dentinal organic matrix have the potential to improve the fluoride-mediated remineralisation approaches.

Effects of a surface prereacted glass-ionomer filler coating material on biofilm formation and inhibition of dentin demineralization.

OBJECTIVES: This study investigated the ability of a surface prereacted glass-ionomer (S-PRG) coating material to inhibit the biofilm formation and demineralization of dentin. METHODS AND MATERIALS: Dentin specimens were randomly divided into three groups: (1) no coating (control), (2) S-PRG filler-containing coat, and (3) a nonS-PRG filler-containing coat. Streptococcus mutans biofilms were grown on the dentin surfaces in a microcosm for 20 h. Then, the quantity of bacteria and water-insoluble glucan in the retained biofilm on the dentin surface were measured. Regarding demineralization inhibition test, specimens were demineralized for 5 days then sectioned into halves and observed under confocal laser scanning microscope (CLSM). One-way ANOVA and Tukey's HSD were used for statistical analysis. RESULTS: The estimated mean surface roughness for specimens in the S-PRG group was statistically significantly higher than the estimates for both the nonS-PRG and the control group specimens. The quantity of bacteria and water-insoluble glucan/mm2 revealed that the S-PRG group prevented biofilm formation and bacterial adhesion to the dentin surface compared with the control and nonS-PRG groups. The S-PRG group recorded the highest acid-resistance ability with no surface loss. CONCLUSION: Application of S-PRG barrier coat on dentin surfaces can inhibit biofilm formation as well as protecting the dentin surface against demineralization. CLINICAL SIGNIFICANCE: Coating material containing S-PRG fillers might be used for caries prevention, through inhibiting biofilm formation, enhancing mineralization, and reducing acidic attack by cariogenic bacteria.