Search Results (331)

Barrel tools are increasingly used in high-precision machining of free-form surfaces. However, limited studies evaluate their performance specifically on spherical geometries, where tool–surface contact characteristics differ significantly. Understanding how tool geometry and process parameters influence surface quality and cutting forces in such cases remains underexplored. This study evaluates how barrel cutter radius and varying machining parameters affect cutting forces and surface roughness when milling internal and external spherical surfaces. Machining tests were conducted on structural steel 1.1191 using two barrel cutters with different curvature radii (85 mm and 250 mm) on a 5-axis CNC machine. Feed per tooth and radial depth of cut were systematically varied. Cutting forces were measured using a dynamometer, and surface roughness was assessed using the Rz parameter, which is more sensitive to peak deviations than Ra. Novelty lies in isolating spherical surface shapes (internal vs. external) under identical path trajectories and systematically correlating tool geometry to force and surface metrics. The larger curvature tool (250 mm) consistently generated up to twice the cutting force of the smaller radius tool under equivalent conditions. External surfaces showed higher Rz values than internal ones due to less favorable contact geometry. Radial depth of the cut had a linear influence on force magnitude, while feed rate had a limited effect except at higher depths. Smaller-radius barrel tools and internal geometries are preferable for minimizing cutting forces and achieving better surface quality when machining spherical components. The aim of this paper is to determine the actual force load and surface quality when using specific cutting conditions for internal and external spherical machined surfaces. Full article

Primary teeth play a crucial role in a child’s development, particularly in maintaining space for permanent teeth. The premature loss of a primary tooth can lead to orthodontic issues, making the use of space maintainers essential to ensure proper growth and development of permanent teeth. To preserve space, the fabrication of a space maintainer is necessary. Since conventional space maintainers do not restore masticatory function, this study presents an innovative solution for space preservation following the extraction of the first primary molar through the design of the functional space maintainer KOS&MET (Key Orthodontic System and Materials Enhanced Therapy). The space maintainer was designed using the 3Shape Dental Designer 2023 version software tool and manufactured via additive 3D printing, utilizing a metal alloy with high resistance to masticatory forces. The crown is supported by the primary canine, while an intraoral window is created to monitor the eruption of the successor tooth. This design does not interfere with occlusion and enables bilateral chewing. Masticatory performance was assessed using two-color chewing gum, and the results showed improvement after cementing the space maintainer. This innovative approach not only preserves space for permanent teeth but also enhances masticatory function, contributing to the proper growth and development of the jaws and teeth. Full article

Study design: Trends in the utilization of Mandibulo-Maxillary Fixation (MMF) are shifting nowadays from tooth-borne devices over specialized screws to hybrid MMF devices. Hybrid MMF devices come in self-made Erich arch bar modifications and commercial hybrid MMF systems (CHMMFSs). Objective: We survey the available technical/clinical data. Hypothetically, the risk of tooth root damage by transalveolar screws is diminished by a targeting function of the screw holes/slots. Methods: We utilize a literature review and graphic displays to disclose parallels and dissimilarities in design and functionality with an in-depth look at the targeting properties. Results: Self-made hybrid arch bars have limitations to meet low-risk interradicular screw insertion sites. Technical/clinical information on CHMMFSs is unevenly distributed in favor of the SMARTLock System: positive outcome variables are increased speed of application/removal, the possibility to eliminate wiring and stick injuries and screw fixation with standoff of the embodiment along the attached gingiva. Inferred from the SMARTLock System, all four CHMMFs possess potential to effectively prevent tooth root injuries but are subject to their design features and targeting with the screw-receiving holes. The height profile and geometry shape of a CHMMFS may restrict three-dimensional spatial orientation and reach during placement. To bridge between interradicular spaces and tooth equators, where hooks or tie-up-cleats for intermaxillary cerclages should be ideally positioned under biomechanical aspects, can be problematic. The movability of their screw-receiving holes according to all six degrees of freedom differs. Conclusion: CHMMFSs allow simple immobilization of facial fractures involving dental occlusion. The performance in avoiding tooth root damage is a matter of design subtleties. Full article

Gear whine noise is governed not only by intentional microgeometry modifications but also by unavoidable pitch (indexing) deviation. This study presents a workflow that couples a tooth-resolved surface scan with a calibrated pitch-deviation table, both imported into a multibody dynamics (MBD) model built in MSC Adams View. Three operating scenarios were evaluated—ideal geometry, measured microgeometry without pitch error, and measured microgeometry with pitch error—at a nominal speed of 1000 r min⁻¹. Time domain analysis shows that integrating the pitch table increases the mean transmission error (TE) by almost an order of magnitude and introduces a distinct 16.66 Hz shaft order tone. When the measured tooth topologies are added, peak-to-peak TE nearly doubles, revealing a non-linear interaction between spacing deviation and local flank shape. Frequency domain results reproduce the expected mesh-frequency side bands, validating the mapping of the pitch table into the solver. The combined method therefore provides a more faithful digital twin for predicting tonal noise and demonstrates why indexing tolerances must be considered alongside profile relief during gear design optimization. Full article

Background: Artificial intelligence (AI) is increasingly integrated into orthodontic workflows, including digital model analysis modules embedded in orthodontic software. While these systems offer efficiency and automation, the accuracy and clinical reliability of AI-generated measurements and diagnostic assessments remain unclear. Therefore, to use AI systems safely and effectively in clinical orthodontics, it is important to check their results by comparing them with those of experienced orthodontists. Methods: Digital models of 48 patients were analyzed by the Orthodontist group and two AI platforms: Titan (full) and SoftSmile (Bolton only). Three orthodontists independently measured all variables using 3Shape OrthoAnalyzer, and group means were used for comparison. A subset of models was reanalyzed after two weeks to assess consistency. Data distribution was evaluated, and appropriate statistical tests were applied. Reliability was assessed using intraclass correlation coefficients (ICC) and Cohen’s kappa. Results: Almost perfect agreement was observed between the orthodontists and Titan AI in molar classification (κ = 0.955 right, κ = 0.900 left; p < 0.001), with perfect agreement reported across all groups—including between the orthodontists themselves—for Angle classification (κ = 1.00). In anterior and overall Bolton analyses, no meaningful agreement was found between the orthodontists and AI platforms. However, in a subset of patients where all three methods identified the tooth size discrepancy in the same arch (either maxilla or mandible), no significant differences were found in anterior (p = 0.226) or overall Bolton values (p = 0.795). Overjet, overbite, and space analysis values showed significant differences between the orthodontist and Titan groups (p < 0.001). ICC analysis indicated good to excellent intra- and inter-rater reliability within the orthodontist group (≥0.77), while both AI systems demonstrated excellent internal consistency, with ICC values exceeding 0.95. Conclusions: AI-based platforms showed high agreement with orthodontists only in Angle classification. While their performance in Bolton analysis was limited, significant differences were observed in other linear measurements, indicating the need for further refinement before clinical use. Full article

Background: The behavior of soft tissues following recession type 1 (RT1) and/or non-carious cervical lesions (NCCLs) treated with class V restorations is not well understood. These conditions cause both functional and esthetic issues. Recent studies show that increased cervical thickness can influence gingival tissue response. This suggests that restoration design has a key impact. This study aims to evaluate the effect of tooth shape modification on gingival tissue response and periodontal health with 3D analysis. Methods: Seven patients with buccal gingival recession and NCCL were selected, resulting in 50 treated teeth. Patients underwent class V buccal restorations using the BOVR technique. Three-dimensional evaluation through scanned dental impressions was performed at baseline and at T1 to monitor tissue profile changes in the buccal zenith sagittal plane. The average observation period was 4 months. Following the assessment, linear measurements were calculated according to standard planes. These measurements aimed to monitor transverse and axial tissue modifications. Probing depth, plaque index, and bleeding index were also recorded. Results: Increased tooth thickness led to tissue alteration. Greater composite thickness was significantly associated with an increase in tissue thickness (p ≤ 0.001) and gingival creeping (p ≤ 0.001) at the free gingival margin. Periodontal health remained unaffected, and 50% of the teeth required no additional surgical treatment due to satisfactory outcomes. Conclusions: Class V restorations that increase cervical thickness may promote soft tissue volume gain over a 4-month period without compromising periodontal health. A 4-month observation period is recommended before considering the surgical correction. Full article

Background/Objectives: Dental implants represent a viable solution for replacing missing teeth; however, multiple disconnections and reconnections of intermediate abutments contribute to the apical displacement of the peri-implant connective tissue barrier, resulting in additional marginal bone loss. To the best of our knowledge, no definitive customized abutments currently exist that are specifically designed according to the morphology of the tooth to be replaced and its position within the dental arch, allowing for digital planning within the prosthetic implant design and insertion during the surgical procedure without subsequent disconnection. Methods: The First Biological Respect (FR) technique, described in this case report, enables the digital planning not only of the implant but also of the patented FR customized-shaped, definitive abutment and associated FR prosthetic components. The FR technique was applied to a case involving an immediate post-extraction implant in position 12. Results: With the limitations of a case report, the application of the FR protocol demonstrated stable crestal bone levels at the 1-year follow-up. Additionally, soft tissue volume was maintained at 6 months, reflecting the accuracy of the customized prosthetic components in supporting, guiding, and protecting peri-implant soft tissues. At the 1-year follow-up, an increase in soft tissue volume was observed, likely attributable to tissue maturation and the further customization of the definitive prosthetic elements. Conclusions: The FR technique represents a viable therapeutic alternative that, through its patented, fully customized components, allows for the digital planning of the implant, as well as the customized definitive abutment, coping, provisional, and final prosthetic framework. This facilitates a single-stage surgical and prosthetic approach. By eliminating the need for repeated abutment disconnections, this method supports the long-term stability of both hard and soft peri-implant tissues while also reducing overall treatment time for both clinician and patient. Further studies involving larger patient cohorts are necessary to validate this protocol. Full article

Background: Autogenous tooth transplantation is a valuable option for dental rehabilitation, particularly in young patients. Template-guided approaches, using 3D-printed replicas of donor teeth, have recently emerged as a method to increase precision and reduce extraoral time—two critical factors in maintaining periodontal ligament (PDL) vitality, which is essential to improve long-term outcomes. Methods: This report presents the case of a 12-year-old patient who underwent autotransplantation of tooth 18 to the site of tooth 75, which exhibited ankylosis. Patients exhibiting unfavorable root anatomy and morphology, systemic conditions, or completed root development were not considered for this technique. A patient-specific donor tooth replica was digitally designed and 3D-printed via CAD/CAM manufacturing to preoperatively shape the recipient site. The transplanted tooth 18 was then inserted with an extraoral time of less than one minute and subsequently stabilized using a flexible titanium trauma splint (TTS). Results: Longitudinal clinical and radiographic follow-up over 12 months confirmed favorable healing without signs of complications. Conclusions: This case illustrates the practical advantages of a fully digital, template-guided workflow in managing anatomically complex cases. Full article

Cosmetic restorative dentistry focuses on restoring teeth affected by caries or trauma using materials that mimic natural teeth in shape, texture, and color. Composite resins, particularly nanofilled composites, are widely used due to their superior mechanical and aesthetic properties. Accurate tooth color selection is crucial, and methods include visual (shade guides) and instrumental (spectrophotometers, colorimeters, and intraoral scanners). Newer biomimetic composites, such as Admira Fusion 5 and Clearfil Majesty ES-2 Universal, simplify shade selection through advanced optical technologies. A randomized clinical study involving 30 patients compared the color-matching accuracy of two biomimetic composite resins: Admira Fusion 5 (Voco) and Clearfil Majesty ES-2 Universal (Kuraray). The study utilized the Vita Easyshade spectrophotometer and the Primescan intraoral scanner. Patients were treated following standardized protocols, and shade accuracy was evaluated pre- and post-restoration using Cohen’s Kappa index. Admira Fusion 5 showed higher shade-matching accuracy, with good agreement between pre- and post-restoration measurements using both instruments. Clearfil Majesty ES-2 Universal demonstrated lower reproducibility in shade matching, particularly in posterior teeth, with lower agreement in pre- and post-tests. Instrumentation Comparison: Primescan showed slightly better performance than Easyshade, but both provided comparable results. In conclusions, universal composites may not always achieve optimal shade matching in posterior teeth. Layered composites provide better color adaptability. While digital instruments enhance shade accuracy, combining them with visual methods yields the best clinical outcomes. Further research with larger sample sizes is needed to improve shade-matching techniques in aesthetic restorative dentistry. Full article

Background and Clinical Significance: To describe the effectiveness of alveolar ridge preservation under the radiological and histological analysis of a customized resorbable scaffold three-dimensionally printed with polycaprolactone (PCL) reinforced with a coating of a copolymer of polycaprolactone-block-polyethylene glycol (PCL–PEG) by electrospray. Case Presentation: A 62-year-old male with vertical root fractures of teeth #14 and #15. From the cone beam CT (CBCT) image, the scaffold root replicas were designed with the shape of the roots and printed with PCL coated with PCL–PEG by electrospray. The scaffold was inserted into the alveolar bone and maintained with a tension-free flap closure. After six months, a CBCT of the surgical site and histological analysis of a bone sample at the dental implant installation site were performed. After 6 months, the wound in tooth #14 was closed, clinically proving no adverse reaction or complications. The histological analysis of the bone sample showed new bone formation with lamellar structure, Haversian canal structure, and osteocyte spaces. However, the scaffold in tooth #15 was exposed and not osseointegrated, and it was covered with membranous tissue. Histologically, the sample showed tissue compatible with lax connective tissue with mixed inflammatory infiltrate. In tooth #14, the dental implant presented an insertion torque >35 Ncm and was rehabilitated three months after its installation. Conclusions: Three-dimensional printed PCL scaffolds showed the ability to regenerate vital and functional bone with osseointegration capability for maxillary bone regeneration and oral rehabilitation based on dental implants. A case of inadequate scaffold osseointegration accompanied by lax connective tissue formation is shown. Full article

It is well understood that burr size and shape, as well as surface quality attributes like surface roughness in milling parts, vary according to several factors. These include cutting tool orientation, cutting profile, cutting parameters, tool shape and size, coating, and the interaction between the workpiece and the cutting tool. Therefore, burr size cannot be formulated simply as a function of direct parameters. This study proposes an ensemble learning regression model to accurately predict burr size and surface roughness during the slot milling of aluminum alloy (AA) 6061. The model was trained using cutting parameters as inputs and evaluated with performance metrics such as mean absolute error (MAE), mean squared error (MSE), and the coefficient of determination (R²). The model demonstrated strong generalization capability when tested on unseen data. Specifically, it achieved an R² of 0.97 for surface roughness (Ra) and R² values of 0.93 (B5, B8), 0.92 (B2), 0.86 (B1), and 0.65 (B4) for various burr types. These results validate the model’s effectiveness despite the nonlinear and complex nature of burr formation. Additionally, feature importance analysis via the F-test indicated that feed per tooth and depth of cut were the most influential parameters across several burr types and surface roughness outcomes. This work represents a novel and accurate approach for predicting key surface quality indicators, with significant implications for process optimization and cost reduction in precision machining. Full article

Interdisciplinary decision-making significantly influences both the therapeutic potential and clinical outcomes, shaping clinical attitudes and management strategies. As the integration between endodontic and restorative-prosthetic considerations becomes increasingly prevalent, it is essential to understand how different dental specialists, particularly general dental practitioners, prosthodontists and endodontists, approach clinical decision-making and collaborate to optimize patient care. Objectives: This study aims to identify practice disparities in post-endodontic crown placement to inform national policy reforms, including standardised timing protocols and interdisciplinary referral criteria. Methods: A structured questionnaire was distributed to dentists practicing in Romania, yielding 238 collected responses. Results: Substantial variability was found in clinical approaches: diagnostic imaging preferences indicated frequent use of periapical radiography (83.49%) and CBCT (53.67%). Over 70% expressed high confidence in CBCT’s diagnostic precision, significantly higher than periapical radiography (Wilcoxon Signed-Rank test, p < 0.00001). A statistically significant majority (69.3%, binomial test, p < 0.001) preferred delaying definitive crown placement until radiographic healing of periapical lesions. Logistic regression analysis showed endodontists were significantly less likely to choose invasive treatments compared to other specialists (p = 0.027). Although clinicians widely recognize the significance of prosthetic planning, its early integration into the overall treatment strategy has been inconsistent. Conclusions: This study points out the necessity for standardised guidelines that clearly integrate prosthetic planning into endodontic decision-making, enhancing predictability and tooth preservation. Full article

This study proposes an asymmetric pitch control technique for electric oil pumps with symmetric gear-type pumps in order to reduce noise and vibration. For vane pump noise reduction, mechanical asymmetric pitch arrangements of each vane are widely used. However, the mechanical asymmetric pitch arrangement approach is not applicable in gear-type pumps due to structural limitations. The proposed asymmetric pitch control method provides similar effects to the mechanical asymmetric pitch arrangement by employing instantaneous motor torque controls for an electric oil pump with a gear-type pump. The magnitude of motor torque for each pump tooth is determined with an asymmetric pitch formula, which has been widely used for mechanical vane pumps in previous studies and patents. A formula for the shape of instantaneous motor torque is proposed for the analysis of pressure fluctuations of pumps, which is a combination of trigonometric and exponential functions. The calibration factors for the magnitude and shape can be adjusted according to the characteristics of a given pump. The experimental results for a 400 W electric pump show that the proposed method reduced and dispersed the noise peak by approximately 4 dB(A) in comparison with the normal control, and affected hydraulic performance with a less than 1% decrease in flow rate in not only pump-level but also gearbox-level test environments. Full article

The influence of machining parameters on the generation of dust particles during the machining of carbon fiber-reinforced polymer (CFRP) composites remains insufficiently understood. These particles, which stay suspended in the air, pose a serious health risk to operators. This study examined the effects of cutting conditions—specifically cutting speed, feed per tooth, and depth of cut—and the impact of delaminations formed during CFRP drilling on the size, shape, and quantity of hazardous dust particles. Experiments were conducted using a commercially available uncoated cemented carbide cutting tool. The analysis of dust particle size and morphology, as well as the evaluation of delamination, was performed using microscopic and tomographic methods. The results demonstrate that reducing the cutting speed led to a decrease in particle size for the investigated CFRP material. Furthermore, it was observed that tool wear results in the generation of smaller particles. Simultaneous delamination during drilling was found to significantly affect the structural integrity of the composite material. Full article

This study used geometric morphometrics to investigate the carapace features of Chinese mitten crabs (Eriocheir sinensis) from non-traditional/emerging origins (Zhenlai County and Bosten Lake) and identify differences in features relative to crabs from traditional origins (Yangcheng Lake). Thirty-five landmark data points on the crab carapace were extracted based on the geometric morphometrics landmark point approach and standardized to obtain the mean shape of the crabs from the three origins. The carapace morphologies of crabs from the three different origins varied. Compared to the average morphology, the first lateral tooth of the carapace of the Zhenlai crab was shorter, and the M pattern was enlarged in males, whereas the first and second lateral teeth of the crabs from the other two origins were longer, and the M pattern was reduced. In female crabs, distinct morphological variations were observed across regions. In Zhenlai crabs, the lateral teeth were shorter, and the M pattern was enlarged. In Bosten crabs, the frontal tooth was shorter, the first and second lateral teeth were longer, and the posterior carapace margin was narrowed. In Yangcheng Lake crabs, the frontal and third lateral teeth were elongated, and the M pattern was narrowed. The discrimination accuracy of individual female and male crabs from different origins reached 100%. The results confirm that the carapace geometric morphometric method represents a convenient and non-lethal method of tracing E. sinensis origins in fine-scale production areas. Thus, this study provides guidance on developing a characteristic industrial chain for aquatic products of emerging origins, which may help to promote the sustainable development of the aquaculture industry in associated areas. Full article