Stain removal, abrasion and anticaries properties of a novel low abrasion dentifrice containing micro-fibrillated cellulose: in vitro assessments.

OBJECTIVES: This laboratory study assessed the performance of a novel fluoride dentifrice containing micro-fibrillated cellulose (MFC) and entrapped silica. METHODS: Removal of extrinsic stains was assessed using the pellicle cleaning ratio (PCR) method, and radioactive dentin abrasivity (RDA) was measured, to calculate a cleaning efficiency index (CEI). Fluoride efficacy was evaluated using widely used remineralization and fluoride uptake methods. The test product (Protegera™) was compared to common dentifrices (Crest - Cavity Protection™ and ProHealth™, Sensodyne Pronamel™, Arm & Hammer™ Advanced Whitening, Crest ProHealth™, and Colgate Optic White™). RESULTS: The PCR for the MFC dentifrice (141) was comparable to three known marketed stain-removing dentifrices (Arm & Hammer™ Advanced Whitening, Crest ProHealth™, and Colgate Optic White™) but it had a significantly lower RDA (88 ±6) than 5 other products. This gave it the highest CEI of the tested products (2.0). In a 10-day pH cycling study, the fluoride efficacy of the MFC product was comparable to Sensodyne Pronamel and Crest Cavity Protection. The MFC dentifrice was superior for promoting fluoride uptake into incipient enamel lesions compared to the USP reference dentifrice. CONCLUSION: The MFC dentifrice has low abrasion, but despite this, it is highly effective in removing stained pellicle. It also is an efficacious fluoride source when compared to relevant commercially available fluoride dentifrices with high dentin abrasivity. CLINICAL SIGNIFICANCE: The addition of micro-fibrillated cellulose to a fluoride dentifrice gives a low abrasive product that can effectively remove external stains, and serve as an effective fluoride source. This combination of benefits seems well suited to enamel protection and caries prevention.

Application of Nanomaterials in Endodontics.

Recent advancements in nanotechnology have introduced a myriad of potential applications in dentistry, with nanomaterials playing an increasing role in endodontics. These nanomaterials exhibit distinctive mechanical and chemical properties, rendering them suitable for various dental applications in endodontics, including obturating materials, sealers, retro-filling agents, and root-repair materials. Certain nanomaterials demonstrate versatile functionalities in endodontics, such as antimicrobial properties that bolster the eradication of bacteria within root canals during endodontic procedures. Moreover, they offer promise in drug delivery, facilitating targeted and controlled release of therapeutic agents to enhance tissue regeneration and repair, which can be used for endodontic tissue repair or regeneration. This review outlines the diverse applications of nanomaterials in endodontics, encompassing endodontic medicaments, irrigants, obturating materials, sealers, retro-filling agents, root-repair materials, as well as pulpal repair and regeneration. The integration of nanomaterials into endodontics stands poised to revolutionize treatment methodologies, presenting substantial potential advancements in the field. Our review aims to provide guidance for the effective translation of nanotechnologies into endodontic practice, serving as an invaluable resource for researchers, clinicians, and professionals in the fields of materials science and dentistry.

Optical penetration models for practical prediction of femtosecond laser ablation of dental hard tissue.

OBJECTIVES: To develop and practically test high-precision femtosecond laser ablation models for dental hard tissue that are useful for detailed planning of automated laser dental restorative treatment. METHODS: Analytical models are proposed, derived, and demonstrated for practical calculation of ablation rates, ablation efficiency and ablated morphology of human dental enamel and dentin using femtosecond lasers. The models assume an effective optical attenuation coefficient for the irradiated material. To achieve ablation, it is necessary for the local energy density of the attenuated pulse in the hard tissue to surpass a predefined threshold that signifies the minimum energy density required for material ionization. A 1029 nm, 40 W carbide 275 fs laser was used to ablate sliced adult human teeth and generate the data necessary for testing the models. The volume of material removed, and the shape of the ablated channel were measured using optical profilometry. RESULTS: The models fit with the measured ablation efficiency curve against laser fluence for both enamel and dentin, correctly capturing the fluence for optimum ablation and the volume of ablated material per pulse. The detailed shapes of a 400-micrometer wide channel and a single-pulse width channel are accurately predicted using the superposition of the analytical result for a single pulse. CONCLUSIONS: The findings have value for planning automated dental restorative treatment using femtosecond lasers. The measurements and analysis give estimates of the optical properties of enamel and dentin irradiated with an infrared femtosecond laser at above-threshold fluence and the proposed models give insight into the physics of femtosecond laser processing of dental hard tissue.

Laser fluorescence assessment of dental caries arrest with two silver fluoride agents in patients with special needs- a preliminary report.

PURPOSE: While silver diamine fluoride has been used extensively for caries arrest and desensitising, silver fluoride (AgF) at neutral pH may also have value as a minimally invasive dental caries treatment. This study explored the effectiveness of two AgF products (AgF/KI and AgF/SnF2) when used in adult patients with special needs (SN) who had high caries risk and salivary gland hypofunction. METHODS: This split-mouth clinical study, over two appointments 3-months apart, compared the impact of a single application of AgF/KI (Riva Star Aqua, SDI) and AgF/SnF2 (Creighton Dental CSDS, Whiteley) on matched carious lesions in the same arch, by clinical visual-tactile (cVT) assessment of caries status and laser fluorescence (LF, DIAGNOdent) evaluation of bacterial load in the lesions, using repeated measures analysis. RESULTS: Twelve participants were recruited in the study. A total of 56 teeth (28 pairs) were included. Both AgF products gave a significant decrease in caries activity as measured by cVT (P < 0.0001) and LF (P = 0.0027). There were no statistically significant differences between the two AgF treatments, with response rates for improvements in active lesions of 92% in the AgF/KI arm, and 96% in the AgF/SnF2 arm. There was no effect of tooth type, lesion type, arch type, plaque metabolism and plaque area at the site level on outcomes, nor was there a clustering effect of sites in a patient level analysis. Overall, LF was superior to cVT for detecting lesions that still progressed despite treatment (P = 0.0027). CONCLUSION: A single application of AgF/KI or AgF/SnF2 has high predictability (over 90%) for achieving arrest in active caries lesions in adult patients with SN and high caries risk. Clinical assessment should use visual-tactile examination combined with LF readings to detect lesions that are still progressing and that require additional treatments. Future studies should compare these AgF modalities with SDF and explore factors such as time between applications and the need for repeated applications. TRIAL REGISTRATION: The study was registered with the Australian Clinical Trials Registry (ACTRN12621001139864p) on 23/08/2021.

Awareness of dental complications with oral piercings.

OBJECTIVES: To investigate knowledge and awareness of dental complications with oral piercings among adults with oral piercings, a control population with no piercings and body-piercing professionals in South-East Queensland, Australia. METHODS: Participants recruited from public and private dental clinics and body-piercing professionals from piercing centres in the same region completed questionnaires to assess knowledge and attitudes. RESULTS: Respondents comprised 54 pierced individuals, 54 controls and 35 body-piercing professionals. Only 13% of the pierced group were informed about oral piercing-related complications, and 14% of body-piercing professionals did not warn their clients about long-term complications. The latter included chipped teeth (26%) and gingival recession (15%). About 76% play with their piercing, developing teeth grinding (15%), jaw clenching (15%) and sleep disturbances (4%). Interestingly, 41% of those with oral piercings advised others against getting piercings. CONCLUSIONS: There is a lack of awareness about dental-related complications among pierced individuals and body-piercing professionals. A significant proportion of pierced individuals advise others against getting piercings. Body piercers do not consistently advise clients about risks associated with oral piercings. Thus, it is recommended that programmes be developed to improve awareness of oral and dental complications associated with oral piercings.

Measuring ergonomic interventions and prevention programs for reducing musculoskeletal injury risk in the dental workforce: A systematic review.

PURPOSE: Pain from musculoskeletal disorders (MSD) is experienced by all types of dental clinicians, leading to forced reduction of work capacity and premature retirement. Prolonged static posture is a major contributor to MSD in dentistry. Currently, there is no uniform ergonomic training in dentistry to prevent MSD. This systematic review explored and summarized methods and technologies for baseline and ongoing measurements of ergonomic intervention and prevention programs for reducing postural risk and for prevention of MSDs. METHODS: The review was conducted in accordance with PRISMA guidelines. The literature search included PUBMED, Embase, CINAHL and the Cochrane Library, and identified relevant observational, experimental, quasi-experimental, research, and intervention studies. Quality was rated using a validated standardized instrument. RESULTS: A total of 20 studies were included, of which 4 were rated as being of the high quality. Methods ranged from observers to motion sensors. Ten studies focused used established measuring tools (PAI, RULA, REBA), while nine studies focused on effectiveness of alternative methods of measurement. One study identified ISO standard 11226 for baseline comparisons. Evolving technologies were found to be suitable for baseline measurements of posture, and for feedback for developing sustainable postural behaviors. No studies measured ongoing postural performance improvement. CONCLUSIONS: This systematic review adds to current evidence for the expanded and improved use of early training and testing of postural competence to reduce MSD risk among dental professionals. Further studies using technologies to assess the impacts of ergonomic training and testing among dental professionals are warranted.

Investigation of laser wavelength effect on the ablation of enamel and dentin using femtosecond laser pulses.

We investigated the effect of femtosecond (fs) laser ablation of enamel and dentin for different pulse wavelengths: infrared (1030 nm), green (515 nm), and ultra-violet (343 nm) and for different pulse separations to determine the optimal irradiation conditions for the precise removal of dental hard tissues with the absence of structural and compositional damage. The ablation rates and efficiencies were established for all three laser wavelengths for both enamel and dentin at room temperature without using any irrigation or cooling system, and the surfaces were assessed with optical and scanning electron microscopy, optical profilometry, and Raman spectroscopy. We demonstrated that 515 nm fs irradiation provides the highest rate and efficiency for ablation, followed by infrared. Finally, we explored the temperature variations inside the dental pulp during the laser procedures for all three wavelengths and showed that the maximum increase at the optimum conditions for both infrared and green irradiations was 5.5 °C, within the acceptable limit of temperature increase during conventional dental treatments. Ultra-violet irradiation significantly increased the internal temperature of the teeth, well above the acceptable limit, and caused severe damage to tooth structures. Thus, ultra-violet is not a compatible laser wavelength for femtosecond teeth ablation.

Effectiveness of Mouthwashes in Managing Oral Diseases and Conditions: Do They Have a Role?

Antimicrobial mouthwashes are considered to reduce dental plaque biofilm and thus the potential to prevent plaque-induced oral diseases, particularly periodontal diseases. The effectiveness of mouthwashes relates to this antiplaque role, as well as, their tooth-whitening potential and ability to mask/mange malodour (halitosis). There is also a growing interest in the use of mouthwashes as an adjunctive measure in post surgical and post-dental care, while the COVID-19 pandemic has given a new lease of life to mouthwashes as an oral antispetic that may be useful in reducing the oral viral load. The mode of action of mouthwashes varies, depending on their active ingredients, concentrations, and mode and frequency of use, as does their potential effectiveness. This article aims to provide a narrative overview of the evidence of the effectiveness of the most widely used mouthwashes in managing oral diseases, oral conditions, and adjunctive care roles.

The application of lasers in vital pulp therapy: a review of histological effects.

Vital pulp therapy (VPT) is primarily intended to preserve the vitality of pulp tissues, which have been exposed for any reason. Various materials and techniques have been proposed to improve treatment outcomes, including the use of lasers. This study aimed to review the histological results of different dental lasers including low-level lasers, carbon dioxide (CO2), erbium-doped yttrium aluminum garnet laser (Er:YAG), neodymium-doped yttrium aluminum garnet (Nd:YAG), erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers, and diode lasers for VPT. This focused review included a comprehensive electronic search of Scopus, MEDLINE, Web of Science, and Google Scholar databases from 2000 to 2022 by two independent investigators. Different combinations of keywords were used, and reference mining of related papers was done. The review included studies related to histologic evaluation of laser-assisted vital pulp therapy that stated the laser parameters that were used. Articles with radiographic or clinical assessments or articles lacking necessary data were excluded. Non-English articles were excluded unless their abstract was in English and encompassed the necessary data. Most studies indicated the efficacy of lasers for reduction of inflammation, acceleration of healing, and increasing the thickness of dentinal bridge. According to the evidence, lasers used in combination with pulp capping agents are beneficial to enhance the success rate of VPT.

Antimicrobial stewardship: Prescribing across the primary care health professions.

We examined the patterns of antibiotic prescribing by medical and non-medical prescribers (dentists, nurse practitioners, and midwives) in Australia. We explored trends in the dispensed use of antibiotics (scripts and defined daily dose [DDD] per 1000 population/day) by Australian prescribers over the 12-year period, 2005-2016. We obtained data on dispensed prescriptions of antibiotics from registered health professionals subsidized on the Pharmaceutical Benefits Scheme (PBS). There were 216.2 million medical and 7.1 million non-medical dispensed prescriptions for antibiotics over 12 years. The top four antibiotics for medical prescribers were doxycycline; amoxicillin, amoxicillin plus clavulanic acid, and cefalexin, constituting 80% of top 10 use in 2005 and 2016; the top three for non-medical were amoxicillin, amoxicillin plus clavulanic acid and metronidazole (84% of top 10 use in 2016). The proportional increase in antibiotic use was higher for non-medical than medical prescribers. While medical prescribers preferentially prescribed broad-spectrum and non-medical prescribers moderate-spectrum antibiotics, there was a large increase in the use of broad-spectrum antibiotics over time by all prescribers. One in four medical prescriptions were repeats. Overprescribing of broad-spectrum antibiotics conflicts with national antimicrobial stewardship initiatives and guidelines. The proportional higher increase in antibiotic use by non-medical prescribers is a concern. To reduce inappropriate use of antibiotics and antimicrobial resistance, educational strategies targeted at all medical and non-medical prescribers are needed to align prescribing with current best practice within the scope of practice of respective prescribers.

Mesoporous Core-Cone Silica Nanoparticles Can Deliver miRNA-26a to Macrophages to Exert Immunomodulatory Effects on Osteogenesis In Vitro.

Nanoparticles can play valuable roles in delivering nucleic acids, including microRNAs (miRNA), which are small, non-coding RNA segments. In this way, nanoparticles may exert post-transcriptional regulatory influences on various inflammatory conditions and bone disorders. This study used biocompatible, core-cone-structured, mesoporous silica nanoparticles (MSN-CC) to deliver miRNA-26a to macrophages in order to influence osteogenesis in vitro. The loaded nanoparticles (MSN-CC-miRNA-26) showed low-level toxicity towards macrophages (RAW 264.7 cells) and were internalized efficiently, causing the reduced expression of pro-inflammatory cytokines, as seen via real-time PCR and cytokine immunoassays. The conditioned macrophages created a favorable osteoimmune environment for MC3T3-E1 preosteoblasts, driving osteogenic differentiation with enhanced osteogenic marker expression, alkaline phosphatase (ALP) production, extracellular matrix formation, and calcium deposition. An indirect co-culture system revealed that direct osteogenic induction and immunomodulation by MSN-CC-miRNA-26a synergistically increased bone production due to the crosstalk between MSN-CC-miRNA-26a-conditioned macrophages and MSN-CC-miRNA-26a-treated preosteoblasts. These findings demonstrate the value of nanoparticle delivery of miR-NA-26a using MSN-CC for suppressing the production of pro-inflammatory cytokines with macrophages and for driving osteogenic differentiation in preosteoblasts via osteoimmune modulation.

Amelioration Strategies for Silver Diamine Fluoride: Moving from Black to White.

Topical cariostatic agents have become a reasonable alternative for managing dental caries in young children. Silver diamine fluoride (SDF) is a practical topical approach to arrest caries and avoid extensive and risky dental treatment. However, the literature demonstrates a parental hesitation towards accepting SDF because of black unaesthetic tooth discolouration following application. The rapid oxidation of ionic silver darkens demineralised tooth structure permanently. In this regard, nano-metallic antimicrobials could augment or substitute for silver, and thereby enhance SDF aesthetic performance. Recently, biomedical research has drawn attention to selenium nanoparticles (SeNPs) due to their antimicrobial, antioxidant, and antiviral potencies. Various in vitro studies have examined the effect of SeNPs on the virulence of bacteria. This narrative review explores practical issues when using SDF and suggests future directions to develop it, focusing on antimicrobial metals. Several methods are described that could be followed to reduce the discolouration concern, including the use of nanoparticles of silver, of silver fluoride, or of selenium or other metals with antimicrobial actions. There could also be value in using remineralising agents other than fluoride, such as NPs of hydroxyapatite. There could be variations made to formulations in order to lower the levels of silver and fluoride in the SDF or even to replace one or both of the silver and fluoride components completely. Moreover, since oxidation processes appear central to the chemistry of the staining, adding SeNPs which have antioxidant actions could have an anti-staining benefit; SeNPs could be used for their antimicrobial actions as well. Future research should address the topic of selenium chemistry to optimise how SeNPs would be used with or in place of ionic silver. Incorporating other antimicrobial metals as nanoparticles should also be explored, taking into account the optimal physicochemical parameters for each of these.

Influence of eight debridement techniques on three different titanium surfaces: A laboratory study.

OBJECTIVES: Debridement methods may damage implant surfaces. This in vitro study investigated eight debridement protocols across three implant surfaces to assess both biofilm removal and surface alterations. MATERIAL AND METHODS: One hundred sixty commercially pure titanium discs were treated to simulate commercially available titanium implant surfaces-smooth, abraded and abraded and etched. Following inoculation with whole human saliva to create a mixed species biofilm, the surfaces were treated with eight debridement methods currently used for clinical peri-implantitis (n = 10). This included air abrasion using powders of glycine, sodium bicarbonate and calcium carbonate; conventional mechanical methods-piezoelectric scaler, carbon and stainless steel scalers; and a chemical protocol using 40% citric acid. Following treatment, remaining biofilm was analysed using scanning electron microscopy and crystal violet assays. For statistical analysis, ANOVA was applied (p < 0.05). RESULTS: All debridement techniques resulted in greater than 80% reduction in biofilm compared with baseline, irrespective of the surface type. Glycine powder delivered through an air polishing system eliminated the most biofilm. Mechanical instruments were the least effective at eliminating biofilm across all surfaces and caused the greatest surface alterations. Citric acid was comparable with mechanical debridement instruments in terms of biofilm removal efficacy. Titanium surfaces were least affected by air abrasion protocols and most affected by mechanical methods. CONCLUSIONS: Mechanical protocols for non-surgical debridement should be approached with caution. Glycine powder in an air polisher and 40% citric acid application both gave minimal alterations across all implant surfaces, with glycine the superior method in terms of biofilm removal.

Root canal cleaning in roots with complex canals using agitated irrigation fluids.

The internal topography of the root canal is complex, especially for the mesial root of the permanent first molar. In response to such challenges, enhanced irrigation protocols have been developed, using laser pulses to agitate fluids and enhance the removal of microbial deposits. The aim of this laboratory study was to assess the effectiveness of laser agitation of sodium hypochlorite in removing multispecies biofilms grown in the mesial root of the permanent first molars. The five agitation groups (N = 12 roots for each) were: 940 nm diode laser (superpulsed mode, 50 µs/pulses at 20 Hz using 20 mJ/pulse); 1064 nm Nd: YAG laser (200 µs/pulse at 20 Hz using 20 mJ/pulse); 2940 nm Er: YAG laser (50 µs/pulse at 15 Hz using a 400/14 conical tip in the SWEEPS protocol, with 20 mJ/pulse); passive ultrasonic agitation at 28 kHz (positive control); and irrigation with a 27-gauge side vented needle for 2 min per canal (negative control). Biofilm removal was assessed by confocal microscopic imaging of root slices at 1, 4 and 7 mm from the root apex. None of the tested methods were effective in completely eradicating biofilm from the most confined regions of the root canal system. The greatest challenge was cleaning the isthmus regions. There was a positive correlation between canal cleaning and isthmus cleaning, suggesting that increased effectiveness in cleaning root canal walls is associated with more effective isthmus cleaning. Wider and narrow isthmuses were cleaned better than long and narrow isthmuses.

Antibody response to BNT162b2 mRNA vaccine in gingival crevicular fluid.

BACKGROUND: This prospective cohort study aimed to evaluate the antibody responses in non-invasive gingival crevicular fluid (GCF) and unstimulated whole saliva to the SARS-CoV-2 Spike unit 1 receptor-binding domain (S1-RBD) protein following administration of the mRNA BNT162b2 vaccine. METHODS: This longitudinal study recruited 37 participants with no prior COVID-19 exposure (eight people recruited prior to the COVID-19 pandemic - labeled pre-COVID, 16 vaccinated and 13 non-vaccinated participants). An enzyme-linked immunosorbent assay (ELISA) was used to determine antibody levels against S1-RBD in saliva (n=90) and GCF (n=80) samples obtained at 1 and 3 weeks after dose 1, and 3 days, 7 days, and 3 weeks after dose 2. To determine previous SARS-CoV-2 infection status, anti-nucleocapsid (N) Ig levels were determined in samples from the pre-COVID (saliva as reference), non-vaccinated (saliva and GCF), and vaccinated (saliva and GCF) participants at 1-week post-dose 1 using ELISA. RESULTS: Salivary levels of anti-N antibodies measured in samples from vaccinated and nonvaccinated participants were comparable to those in pre-COVID saliva samples collected between October 2018 and September 2019, thus confirming that all study participants had no prior SARS-CoV-2 infection. Overall, the levels of anti-S1-RBD antibodies peaked at 3 weeks after dose 2 in both saliva and GCF for all three immunoglobulin isotypes. Notably, the concentration of anti-S1-RBD antibodies in GCF was significantly higher than in saliva at all time points. CONCLUSION: This study establishes GCF and saliva as viable alternative non-invasive sources to monitor levels of antibodies following vaccination, with GCF demonstrating feasibility as a biofluid source for the detection of antibodies against SARS-CoV-2 S1-RBD antigen.

Positive oral health outcomes: A partnership model improves care in a rural Indigenous community.

OBJECTIVE: The purpose of this study was to explore the benefits of a partnership between a university dental school and a Community Controlled Health Service, specifically in relation to improving the oral health of an underserved rural Indigenous community. We sought community opinions on health and social outcomes arising from the service provided by the dental student clinical outplacement. SETTING: In Dalby, Queensland. PARTICIPANTS: In total, 38 participants in five focus groups were representative of local Indigenous community Elders, community health support group members and management and staff. DESIGN: A descriptive qualitative study employing semi-structured audio-recorded focus group discussions conducted with purposefully selected Indigenous community groups to explore participant views and experience of the partnership model. Qualitative data were analysed using thematic content analysis. RESULTS: The Indigenous community representatives expressed positive benefit in both their general and oral health awareness, in improved access to dental care provided in their own safe space, while they were pleased to assist with students' learning. They viewed the partnership as mutually beneficial. Suggestions for enhancement of the oral health service were also offered. CONCLUSION: This partnership between a university and a Community Controlled Health Service provides sustainable positive social and health benefits for the targeted Indigenous community and for the wider local population, while simultaneously providing enhanced educational benefits for students on clinical outplacement. Translation and uptake of this successful model of care would benefit both underserved communities and dental and other health care professional educators worldwide.

Clinical Assessment of Plaque Removal Using a Novel Dentifrice Containing Cellulose Microfibrils.

Dentifrice performance in the removal of dental plaque is influenced by the interactions of dentifrice components with tooth surfaces. This randomized controlled clinical study assessed the effectiveness and safety of a novel fluoride dentifrice formulation that included a micro-fibrillated cellulose network with entangled microcrystalline cellulose and silica particles (ProtegeraTM), and compared this to a positive control fluoride dentifrice (Crest Cavity Protection™). Whole mouth dental plaque levels in 82 healthy adults were measured after the first supervised use, and following a week of twice daily use at home. Overall, the test dentifrice was at least three times and up to four times more effective in whole-mouth plaque reductions, with a 38.6% reduction on first use, a 30.9% reduction at day 7, and a 41.6% reduction from day 1 to day 7, compared to reductions of 12.0%, 9.6% and 11.6%, respectively for the positive control, and up to seven times more effective in lingual plaque reductions, than the reference dentifrice (p < 0.001), with a 27.7% reduction on first use, a 22.3% reduction at day 7, and a 31.0% reduction from day 1 to day 7, compared to reductions of 4.4%, 2.2%, and 4.5%, respectively, for the positive control. No safety issues arose from the use of the test dentifrice. These results indicate that including micro-fibrillated cellulose enhances plaque removal effectiveness, without causing adverse changes to oral soft tissues.

The Prevalence of Middle Mesial Canals in the Second Mandibular Molars of an Iranian Subpopulation: A Cross-Sectional CBCT Study.

Background Missed additional canals are a common reason for the failure of root canal treatments. The prevalence of additional canals in molar teeth can vary because of ethnic differences. Hence, this study aimed to determine the prevalence and distribution of middle mesial canals (MMCs) in the second mandibular molars using cone beam computed tomography (CBCT), for an adult population from Kerman in southeast Iran. Methodology De-identified retrospective provided CBCT scans from three private radiology centers in Kerman were reviewed (131 patients; 58 males (44.3%), 73 females (55.7%); age range: 13 to 54 years, mean age: 33). The presence of MMCs in mandibular second molars (222 teeth; 112 left and 110 right) was recorded, along with the morphology of the distal roots in the same teeth. Frequency data were analyzed using the Chi-square test and Fisher's exact test. Results The overall prevalence of MMC in the second mandibular molars was 2.3%. MMCs were found both unilaterally and bilaterally. More MMCs were found in females than males (2.7% vs. 1.7%), and on the left side (2.7% vs. 1.8%), but these differences were not statistically significant (p=1.0). There was no association between the existence of MMC in the mesial root and a second canal in the distal root of the same tooth. Conclusion Based on CBCT scans, the overall prevalence of MMC in mandibular second molars in this population was just below one in 44. Clinicians performing endodontic treatment on second molars should check for the presence of MMC so that this possible additional canal is not missed.

Mechanical and Metallurgical Characterization of Nickel-Titanium Wire Types for Rotary Endodontic Instrument Manufacture.

This study aimed to evaluate and compare the effects of ambient temperature and post-manufacture heat-treatment on the mechanical behavior of nickel-titanium (NiTi) wires. Four types of commercial NiTi variants (Stock NiTi, heat treated "Blue", "Gold", "Superflex", all Dentsply Maillefer, Ballaigues, Switzerland) were stressed in a tensile testing machine in a temperature-controlled water bath at three different temperatures. Stress and strain values were extrapolated from the raw data, and 2-way ANOVA and Tukey's test for multiple comparisons were performed to compare the differences of the mechanical constants. Differential scanning calorimetry (DSC) tests established the martensitic transformation starting (Ms), finishing (Mf) and austenitic (reverse-martensitic) starting (As) and finishing (Af) points. Austenitic modulus of elasticity and transformation stress values increased with temperature for all NiTi groups. The martensitic modulus of elasticity, maximum transformation strain and ultimate tensile stress were not significantly affected by temperature changes. Stock NiTi and Gold wire samples presented with clearly delineated austenitic and martensitic transformations in the DSC experiments. Differences in manufacturing/heat treatment conditions and ambient temperature affect the mechanical behavior of nickel-titanium and may have clinical implications. Further improvements to the experimental setup could be considered to provide more accurate measurements of strain.

A Comparative Study of Mesoporous Silica and Mesoporous Bioactive Glass Nanoparticles as Non-Viral MicroRNA Vectors for Osteogenesis.

Micro-ribonucleic acid (miRNA)-based therapies show advantages for bone regeneration but need efficient intracellular delivery methods. Inorganic nanoparticles such as mesoporous bioactive glass nanoparticles (MBGN) and mesoporous silica nanoparticles (MSN) have received growing interest in the intracellular delivery of nucleic acids. This study explores the capacity of MBGN and MSN for delivering miRNA to bone marrow mesenchymal stem cells (BMSC) for bone regenerative purposes, with a focus on comparing the two in terms of cell viability, transfection efficiency, and osteogenic actions. Spherical MBGN and MSN with a particle size of ~200 nm and small-sized mesopores were prepared using the sol-gel method, and then the surface was modified with polyethyleneimine for miRNA loading and delivery. The results showed miRNA can be loaded into both nanoparticles within 2 h and was released sustainedly for up to 3 days. Confocal laser scanning microscopy and flow cytometry analysis indicated a high transfection efficiency (>64%) of both nanoparticles without statistical difference. Compared with MSN, MBGN showed stronger activation of alkaline phosphatase and activation of osteocalcin genes. This translated to a greater osteogenic effect of MBGN on BMSC, with Alizarin red staining showing greater mineralization compared with the MSN group. These findings show the potential for MBGN to be used in bone tissue engineering.