Search Results (122)

Background/Objectives: Despite advances in preventive dental care, tooth enamel erosion remains a relevant concern, and very few comparisons of surface topography have been carried out under controlled conditions in the laboratory. This study primarily aimed to conduct a qualitative morphological evaluation, supported by semi-quantitative image analysis, of the effects of commonly consumed beverages on human enamel morphology and colour, and to explore their relationship with beverage acidity in an in vitro model. Methods: Forty-two human teeth were allocated at random into seven different groups, each containing six molars. These groups were Coca-Cola, orange juice, lemon juice, coffee, chlorhexidine, regular mouthwash without chlorhexidine, and one control group. Following a 24 h exposure to a simulated saliva environment at 37 °C, the test samples were then subjected to a five-day erosion cycle. SEM analysis was used to examine the enamel alterations after evaluating the morphology of the enamel surface and by digital image analysis. Results: Scanning electron microscopy, SEM, showed how erosion of the teeth’s surface increased with the acidity of the drink. The extensive exposure of the crystal prisms, along with the severe loss of intercrystalline material and honeycomb weathering patterns, was all brought about by Coca-Cola and lemon juice. The moderate erosion brought on by orange juice in tests resulted in partially exposed prisms. Both the mouthwashes and the coffee exhibited similar impacts on the tooth enamel in a microscopic view. Minimal enamel prism rods were exposed due to either the coffee or the mouthwash. The surface characteristics were found through a digital image analysis, which indicated alterations in surface texture. Conclusions: Under these immersion conditions, highly acidic beverages produced the most pronounced enamel surface changes, whereas coffee induced mainly staining and neutral mouthwashes caused minimal modification. These results reflect qualitative morphological trends and should not be interpreted as clinical outcomes. Full article

Streptococcus sanguinis (S. sanguinis) is an oral commensal and early colonizer of the tooth surface that contributes to dental biofilm homeostasis. Zinc oxide nanoparticles (ZnO NPs) are often incorporated into dental restorative materials to enhance mechanical performance and confer antibacterial properties; however, their effects on S. sanguinis have not been thoroughly studied. Here, we investigated the antimicrobial and antibiofilm efficacy of ZnO NPs against this bacterial species. ZnO NPs exhibited a minimal inhibitory concentration (MIC) of 100 µg/mL and caused rapid, dose-dependent suppression of intracellular ATP levels and overall metabolic activity within 2–4 h of exposure. ZnO NPs induced reactive oxygen species (ROS) production in a dose-dependent manner. The free radical scavenger α-tocopherol partly prevented the antibacterial effect of ZnO NPs, suggesting that lipid peroxidation contributes to ZnO NP-mediated toxicity, although it is not the sole mechanism involved. Short-term exposure (2 h) to ZnO NPs did not significantly affect membrane integrity or cellular morphology, whereas prolonged treatment (24 h) resulted in pronounced membrane permeabilization, membrane hyperpolarization, and cellular swelling. Computational morphometric analyses of high-resolution scanning electron microscopy (HR-SEM) images of planktonic growing bacteria after a 24 h treatment confirmed a significant, dose-dependent increase in cell surface area and surface roughness. Importantly, ZnO NPs also reduced the metabolic activity and compromised the structural integrity of mature, preformed biofilms. Collectively, these findings demonstrate that ZnO NPs exert antimicrobial and antibiofilm effects against S. sanguinis through early metabolic inhibition associated with oxidative stress followed by progressive membrane dysfunction. Full article

Zirconia is a material that mimics human teeth and has been extensively studied and applied. This study investigated the surface modifications of dental zirconia induced by two UV-C wavelengths (222 and 254 nm). A total of 72 zirconia specimens were prepared and divided into groups for irradiation at varying distances (1, 6, 12 cm) and durations (40, 120, 480 and 1440 min), with three specimens retained as untreated controls. Surface changes were assessed by measuring colour difference (ΔE) and water contact angle, and by analyzing surface morphology and elemental composition using SEM and EDX, and XRD was employed to determine the crystalline structure. The results showed that both wavelengths induced clinically perceptible colour changes (ΔE > 2.0), with the most pronounced effect at 6 cm for 222 nm and 1 cm for 254 nm. WCA decreased significantly with irradiation time, showing a linear correlation with log(time), and 222 nm irradiation yielded lower WCA than 254 nm. While SEM revealed no morphological changes, both UV treatments significantly increased the Zr/O ratio compared to the control. XRD tests confirmed that UV-C irradiation does not damage the zirconium oxide crystal structure. It is concluded that both UV-C wavelengths can alter the colour and enhance the wettability of zirconia; these modifications are particularly relevant for dental restorative applications, specifically in the fabrication of anterior tooth crowns, where achieving a natural tooth-like appearance is desired. Full article

During the assembly process of the bolter miner cutting drum, the varying installation postures of the cutting picks result in unique and non-repetitive irregular gaps between the tooth seat bottom surface and the cylindrical rotating surface. Such gaps are constrained by dual-surface geometry and lack batch statistical regularity, making traditional methods such as shim filling, selective assembly, or on-site welding inadequate for achieving high-precision fitting and reliable process implementation. To address this challenge, this paper proposes an automatic design method for compensation bodies based on computer-aided design, realizing a shift from experience dependence to algorithm-driven design. This method transforms the complex dual-surface gap filling problem into a serialized geometric modeling process: first, smooth extrapolation of the tooth seat bottom surface is achieved through a point sequence prediction model based on minimum mean square error; second, surface projection is simplified to boundary curve projection, enabling precise mapping onto the cylindrical surface and generating trimming surfaces; finally, a ruled surface is constructed to integrate the extended surface with the trimming surfaces, automatically generating a compensation body fully adapted to the gap morphology. Case verification demonstrates that this method can automatically and accurately generate compensation bodies that meet dual-surface fitting requirements, significantly improving geometric adaptability and weldability. This research not only resolves a critical technical bottleneck in the assembly of bolter miner cutting drums but also provides a universal and scalable computational framework for the intelligent compensation design of non-repetitive dual-surface gaps in complex equipment. Full article

Background/Objectives: Dental caries is one of the most prevalent chronic diseases in childhood. Rotary bur handpiece excavation has been the standardised mechanical benchmark for infected dentine removal in the primary dentition, but it is associated with noise, vibration, and nociceptive triggers that influence behavioural cooperation in paediatric patients. CMCR gels have been developed for selective softening and excavation of infected primary dentine without macroscopic removal of adjacent sound tissue at the protocol-defined site. The objective of this review was to systematically synthesise the evidence on chemomechanical caries removal (CMCR) using Papacarie or Brix 3000 compared with infected dentine excavation using rotary bur handpiece instrumentation in the primary (deciduous) dentition, focusing on excavation effectiveness, paediatric procedural tolerance, anaesthetic requirement, dentine surface morphology at the excavation interface, and protocol-level operative duration per primary molar. Methods: A systematic search was performed in PubMed, Web of Science, and Scopus for English-language studies from database inception to 31 December 2023. Although no eligible paediatric dental records addressing CMCR gels for excavation of infected primary dentine were identified before 2009, the earlier literature was not intentionally excluded; rather, it did not retrieve topic-specific matches meeting the eligibility criteria. Clinical and in vitro investigations evaluating CMCR gels (Papacarie or Brix 3000) for excavation of infected primary dentine in primary molars were eligible. Outcomes were aggregated qualitatively by excavation approach and reported per primary molar at the individual study protocol level. Quantitative pooling or meta-analysis was not conducted due to heterogeneity in study designs and lack of unified denominators across the included literature. Results: Fifteen studies were included (randomised clinical trials, observational clinical investigations, clinical comparative studies, and in vitro assessments) evaluating infected dentine excavation in primary molars. CMCR gels achieved successful excavation of infected primary dentine with dentine preservation at the adjacent non-infected interface without macroscopic loss of sound tissue. Individual study protocols that reported paediatric pain outcomes during primary-molar excavation registered lower pain scores, reduced acoustic/vibratory stress, lower anaesthetic escalation cycles, and decreased local anaesthesia requirement per primary molar compared with rotary bur handpiece excavation arms. Dentine surfaces analysed under SEM protocols at the infected excavation interface described patent tubules, absence of compacted smear at the interface, preserved intertubular dentine, and no iatrogenic gouging or macrofracture of non-infected primary dentine per molar at the individual study level. Operative duration for CMCR ranged from 10 to 25 min per primary molar per tooth, while rotary bur handpiece excavation required 3–10 min per primary molar per tooth, depending on cavity extension and dentine hardness, as defined by each study protocol. Microleakage and bond-strength assays performed in vitro at the individual protocol level did not register disadvantage signals traceable to adhesive or sealing incompatibility following CMCR gel excavation per primary molar. Conclusions: CMCR with Papacarie or Brix 3000 enables protocol-level selective excavation of infected primary dentine in primary molars, reducing acoustic, vibratory, and nociceptive triggers that influence behaviour and local anaesthetic requirement per primary molar. Clinical inference should be restricted to infected dentine excavation per primary-molar denominators, avoiding extrapolation to all caries depths or all deciduous-tooth types. Standardised paediatric primary-molar infected dentine excavation trials with homogeneous denominators, bias-controlled outcome instruments, and longitudinal follow-up are required to strengthen cavity-depth indications, pulp-proximal excavation reliability, and restorative longevity guidance in the primary dentition clinical workflow. Full article

Background/Objectives: Artificial teeth in complete dentures are classified according to the materials used: porcelain (PO) or composite resin (CR). However, these materials’ effects on function, patient satisfaction, and quality of life (QOL), as well as occlusal wear, remain unclear. We compared PO and CR complete dentures in edentulous patients by assessing masticatory function, patient satisfaction, and oral health-related QOL at 3, 6, and 12 months post-insertion, as well as occlusal surface morphology owing to material differences. Methods: In this open-label, randomized, single-center, parallel-group study, participants were edentulous patients who visited our hospital and underwent treatment with new complete dentures. The outcomes were oral health-related QOL; subjective satisfaction, assessed using a visual analog scale; and masticatory performance, evaluated with gummy jelly and were assessed at baseline and 3, 6, and 12 months post-denture insertion. Occlusal surface impressions were taken twice, digitized as STL models, superimposed, and analyzed for wear. The Wilcoxon rank-sum test was used to compare between groups. Results: All evaluated items showed improvement. However, no significant differences were observed between the PO and CR groups, including between the amount of wear observed in the two groups. However, the PO group showed a tendency toward less wear. Extended observation may be required to clarify the long-term effects of artificial tooth materials. Conclusions: In the short term, the artificial tooth material did not influence masticatory function, oral health-related QOL, or patient satisfaction. Full article

Background: Intentional tooth replantation (ITR) is a promising treatment option for preserving teeth in cases where conventional endodontic therapy is challenging, or when previous endodontic treatment and apicoectomy have been unsuccessful. The procedure involves extracting the compromised tooth, preserving the alveolar socket and root surface, performing extraoral endodontic therapy, and replanting the tooth in the alveolar socket. Objective: An increase in evidence-based support for ITR has improved the viability of ITR as a treatment option for patients. This review aims to further establish and provide new areas of potential research for ITR with respect to root morphology, extraction, and surgical techniques, maintenance of the tooth socket, and methods for post-op stabilization. Materials and Methods: A literature review was performed across PubMed from 1 January 1980 to 1 July 2025, with a focus on oral surgery techniques, atraumatic extraction techniques, topographical discrepancies in root system anatomy, and ITR procedural outcomes. Conclusions: Although ITR is not a common procedure performed in contemporary clinical practice, gathering sufficient data on the variables influencing the procedure may help patient outcome and improve communication between the endodontist and oral surgeons. Full article

Sodium hydroxide (NaOH) and hydrochloric acid (HCl) are household chemicals used to disfigure victims in forensic contexts due to their high availability and apparent effects, which alter both the structural integrity and composition of skeletal elements. NaOH dissolves soft tissues and produces violent, exothermic reactions but, ostensibly, fails to alter the structure and color of bones and teeth. HCl is considered one of the most destructive chemical agents utilized, causing rapid demineralization of hard tissues. Current works focus on total dissolution times, rather than on discrete changes and the potential for personal identification. This research aims to comprehensively assess the intervallic micro- and macroscopic changes occurring in chemically altered bones and teeth. Analyses were conducted to investigate how morphological shape and surface area-to-volume ratios may affect the degree of alteration and to evaluate the feasibility of DNA isolation and profiling. The relationships between these factors were not linear, and the results show a variable pattern of alteration and DNA yields depending on the treatment and duration of exposure. Teeth were found to be better sources for obtaining higher quality and yield of DNA compared to bones, and complete STR profiles were obtained from all tooth samples. Overall, this pilot study highlights the challenges of analyzing taphonomically altered remains and underscores the need for effective identification methods. Full article

To investigate the contact performances and meshing characteristics of gears systematically, an improved comprehensive meshing stiffness model of spur gears with consideration of the tooth surface morphology, lubrication, friction, and thermal effects is presented based on the thermal elastohydrodynamic lubrication (TEHL) theory. The fractal feature of the tooth surface morphology is verified experimentally and characterized by the Weierstrass–Mandelbrot fractal function. Based on this, the rough contact stiffness, oil film stiffness, and thermal stiffness are introduced into the stiffness model. Comparisons between smooth and rough models are carried out, and the maximum temperature rise is increased by 24.7%. Subsequently, the influences of the torque, rotational speed, and fractal parameters on the oil film pressure and thickness, friction and temperature rise, and contact stiffness and comprehensive meshing stiffness are investigated. The results show that the oil film pressure and the maximum temperature rise increase by 125.18% and 69.08%, respectively, with an increasing torque from 20 N·m to 300 N·m. As the rotational speed is increased, the oil film thickness sharply increases, the rough peak contact area and friction reduce, and the stiffness fluctuation weakens. For fractal parameters, the oil film pressure and film thickness, friction, and temperature rise are nonlinear with changes in the fractal dimension D and fractal scale characteristic G. The results reveal that this work provides a more reasonable analysis for understanding the meshing characteristics and the design and processing of gears. Full article

Objective: This in vitro study quantitatively compared the time-dependent remineralization potential of three professional agents on artificially induced enamel lesions using Scanning Electron Microscopy (SEM) and energy-dispersive X-ray analysis (EDX). Methods: Sixty extracted sound molars were randomly assigned to three groups (number = 20): G_CPP-ACP, treated with casein phosphopeptide–amorphous calcium phosphate; G_Zn-HA, treated with zinc-hydroxyapatite; and G_F-ACP, treated with fluoridated amorphous calcium phosphate. The crown of each tooth was divided into three areas: one represented the control (CTRL, sound enamel), one underwent demineralization (DEMIN, demineralized enamel), and the third one was at first demineralized and then treated with a remineralizing agent, allowing intra-sample comparison. Artificial lesions were produced by immersion in 0.1 M lactic acid (72 h). Groups were subdivided according to remineralization time (7, 14, 21, and 28 days). Samples underwent daily treatment under a pH-cycling regimen. Surface morphology and Ca/P ratios were evaluated by SEM-EDX, and data were statistically analyzed (p < 0.05). Results: All agents promoted a progressive increase in Ca/P ratio over time, confirming a time-dependent remineralization effect. At day 7, G_Zn-HA showed higher Ca/P values, but from day 14 onward, G_F-ACP produced significantly greater mineral gain than the other groups (p < 0.05). By day 21, G_F-ACP reached Ca/P values approaching CTRL, while G_CPP-ACP and G_Zn-HA remained at lower levels, reaching a plateau respectively at 21 and 14 days. SEM observations supported these findings: G_CPP-ACP and G_Zn-HA showed partial surface recovery, whereas G_F-ACP exhibited a compact, homogeneous enamel-like structure at 28 days. Conclusions: All tested agents demonstrated time-dependent remineralization, enhanced with prolonged exposure, suggesting that the time of application represents a key factor for clinical success. Full article

Bamboo fiber is a prime green fiber due to its renewability, biodegradability, and high specific strength. Bamboo-fiber-reinforced epoxy (BFRE) composites have seen extensive use and shown great promise for natural biofiber-reinforced friction materials. Inspired by the decussated fiber alignment of bovine enamel, this study investigated how fiber orientation influences the tribological properties of BFRE composites. Specifically, the proportion of fibers oriented vertically to the surface was varied at seven levels: 0%, 25%, 33%, 50%, 67%, 75%, and 100%. The tribological performance was assessed through wear reciprocating testing and microscopic morphological characterization techniques. Results indicate that the bio-inspired fiber decussation can reduce the wear loss of the BFRE composites. Among all bio-inspired BFRE composites, BFRE composites with 67% vertical fibers achieve the best wear resistance. The vertical fibers in the BFRE composites can withstand pressure to provide a “compression–rebound” effect, while the parallel fibers can resist shear stress. The decussated structure inhibits crack initiation and propagation during wear and promotes transfer film formation, reducing wear loss. The findings expand understanding of the correlation between the bovine-tooth-like decussated structure and its tribological mechanisms, thereby offering essential guidance for the biomimetic design of high-performance BFRE composites for friction material application. Full article

Background/Objectives: This study aimed to investigate the association between the position of impacted mandibular third molars and the morphology of the lingual cortical bone using cone beam computed tomography (CBCT), and to determine how impaction depth and angulation influence the risk of lingual cortical perforation. Methods: CBCT scans of 120 impacted mandibular third molars from 71 adult patients were retrospectively evaluated. Teeth were classified based on Pell & Gregory’s and Winter’s classifications. Lingual cortical morphology was categorized as undercut, parallel, slanted, or round. The relationship between the root apex and the lingual plate was classified as non-contact, contact, or perforating. Linear measurements included cortical lingual bone thickness and the distance from the apex to the outer surface of the lingual cortex. Results: Lingual bone morphology showed significant associations with both impaction depth and angulation, with parallel morphology more common in deeper and more angulated impactions. Lingual cortical perforation was observed in approximately 30% of the teeth, predominantly at the apex, with horizontal and deeply impacted molars (Class II, Level C) representing the highest-risk configurations. Although cortical thickness and apex-to-cortex distance were significantly smaller in apically perforated cases, no definitive threshold could be established, and these parameters were insufficient as standalone predictors at the cementoenamel junction or mid-root levels. Conclusions: Tooth angulation and impaction depth are significant predictors of lingual bone morphology and perforation risk. CBCT imaging is therefore recommended beyond low-risk cases (Level A, Class I, vertical) to improve preoperative planning, strengthen informed consent, and guide surgical strategies aimed at minimizing complications and enhancing patient safety. Full article

While the machining of Inconel 718 has been widely studied, its cast counterpart Inconel 713LC remains underexplored, despite its relevance in high-temperature aerospace and energy components. This work presents a comprehensive investigation of dry milling behavior in Inconel 713LC, focusing on the interplay between tool wear, cutting forces, surface integrity, and chip formation across a broad range of cutting parameters. A stable process window was identified: 30–50 m/min cutting speed and 0.045–0.07 mm/tooth feed, where surface roughness remained below Ra 0.6 µm and tool life exceeded 10 min. Outside this window, rapid thermal and mechanical degradation occurred, leading to flank wear beyond the 550 µm limit and unstable chip morphology. The observed trends align with those in Inconel 718, allowing the cautious transfer of established strategies to cast alloys. By quantifying key process–performance relationships and validating predictive models for tool life and cutting forces, this study provides a foundation for optimizing the dry machining of cast superalloys. The results advance sustainable manufacturing practices by reducing reliance on cutting fluids while maintaining surface and dimensional integrity in demanding applications. Full article

This study evaluated the physicochemical and morphological properties of tooth enamel in patients with caries-predisposing SNPs (rs4694075 in AMBN and rs2337359 in TUFT1 genes), based on the DMFT index. We included 40 of 120 individuals (aged 19–43), collecting stimulated saliva and 58 healthy teeth extracted for orthodontic/surgical reasons. Saliva DNA was genotyped. Enamel properties were assessed using Vickers microhardness, deposition thickness, and calcium content. Genotype and allele frequencies aligned with the literature. The TUFT1C/C genotype subgroup showed a significantly higher DMFT index (p = 0.03) compared to the T/T genotype, while AMBN showed no such correlation. Calcium content, microhardness, and enamel thickness were similar across all polymorphic variants of both genes. A statistically significant correlation (p = 0.003) was found between reduced enamel calcium content and a higher DMFT index. Despite existing literature on the subject, the studied SNPs did not reflect any correlation with morphological or physicochemical changes in enamel. The above results suggest that genetic variability identifies patients classified by dentists as being at higher risk of caries, even though these patients follow a non-cariogenic diet and adhere to a hygiene regime. As no structural or physicochemical changes in the enamel of this group were observed, the potential cause may be disturbances in the remineralisation mechanisms or enamel surface properties that promote biofilm adhesion in polymorphic patients. Intensive tooth calcification control algorithms using LIF and RVG, as well as remineralisation cycles to increase hydroxyapatite saturation with calcium phosphates and bioadhesive fluoride delivery systems for long-term biofilm control, are used to more effectively prevent or slow down the progression of caries. Full article

Tooth bleaching is a widely used esthetic treatment; however, bleaching agents can temporarily alter the surface morphology of enamel, increasing surface roughness and porosity, which may lead to increased susceptibility to discoloration. This in vitro study investigated the effectiveness of fluoride varnish in preventing immediate discoloration of bovine incisors after bleaching. Specimens were bleached with 35% hydrogen peroxide and treated with either Clinpro White Varnish (CW) or Enamelast Fluoride Varnish (EN), whereas control specimens received no treatment after bleaching. The samples were immersed in coffee for 24 h, and the color difference (ΔE₀₀) was calculated using the CIEDE2000 formula. The surface morphology of enamel was examined using SEM. The fluoride varnish groups showed significantly lower color difference values than the control group (p < 0.05), with ΔE₀₀ reduced by approximately two-thirds in both the CW and EN groups. SEM observations showed that the enamel surfaces in the varnish-treated groups exhibited reduced surface irregularities compared to the untreated group, suggesting remineralization. These results suggest that the immediate application of fluoride varnish after bleaching can effectively reduce short-term discoloration by providing physical protection and promoting remineralization. Fluoride varnish may serve as a simple and effective strategy to maintain whitening outcomes and minimize early discoloration. Full article