Search Results (157)

The present work explores the effects of dental splints from a mechanical standpoint, aiming to provide a practical tool for the surgical decision-making process regarding splint cross-section dimensions. Our investigation centers on the anatomical structure of a pentamorphic dental arch encompassing central and lateral incisors and one canine on each side. Using parametric in silico models built up by means of an ad-hoc procedure, geometry, material properties, and boundary conditions are defined on a parametric anatomical model that can be tailored using RX-derived geometrical information. Two general cases have been considered, one with the splint and the other splintless, and a sensitivity analysis has been performed by varying the splint section height and thickness. The results show the diminishing mobility at the apex and basis of the diseased incisors, demonstrating the effectiveness of the periodontal treatment. Moreover, the stress due to physiological loads moves away from diseased teeth toward the healthy ones due to the splint effects, focusing on the splint–glue–canine contact zone and highlighting the crucial role played by the canine in fixing the entire dental structure. To establish a preliminary mechanical assessment of the dental structure’s safety and to confine its actual value within a mechanically reasonable range, a synthetic “traffic-light” indicator of stress-based failure risk is proposed. It is felt that the tool proposed in this study can help surgeons assess the pre-operative patient-specific mechanical effects of the splint treatment, driving the design and choice of periodontal splints. By linking splint geometry to mechanical safety via a stress-based indicator, the method supports the optimized design and selection of splints, improving treatment reliability while preserving comfort and clinical effectiveness. Full article

Reconstructing original cusp dimensions in worn molars represents a fundamental challenge across dentistry, anthropology, and paleontology, as dental wear obscures critical morphological information. In this proof-of-concept study, we present a standardized machine learning pipeline for predicting original cusp height, specifically the horn tips of the enamel–dentine junction (EDJ), in worn lower molars using three-dimensional morphometric data from micro-computed tomography (micro-CT). We analyzed 40 permanent lower first (M1) and second (M2) molars from four hominin groups, systematically evaluated across three wear stages: original, moderately worn (worn1), and severely worn (worn2). Morphometric variables including height, area, and volume were quantified for each cusp, with Random Forest and multiple linear regression models developed individually and combined through ensemble methods. To mimic realistic reconstruction scenarios while preserving a known ground truth, models were trained on unworn specimens (original EDJ morphology) and tested on other teeth after digitally simulated wear (worn1 and worn2). Predictive performance was evaluated using root mean square error (RMSE) and coefficient of determination (R²). Our results demonstrate that under moderate wear (worn1), the ensemble models achieved normalized RMSE values between 11% and 17%. Absolute errors typically below 0.25 mm for most cusps, with R² values up to ~0.69. Performance deteriorated under severe wear (worn2), particularly for morphologically variable cusps such as the hypoconid and entoconid, but generally remained within sub-millimetric error ranges for several structures. Random Forests and linear models showed complementary strengths, and the ensemble generally offered the most stable performance across cusps and wear states. To enhance transparency and accessibility, we provide a comprehensive, user-friendly software pipeline including pre-trained models, automated prediction scripts, standardized data templates, and detailed documentation. This implementation allows researchers without advanced machine learning expertise to explore EDJ-based reconstruction from standard morphometric measurements in new datasets, while explicitly acknowledging the limitations imposed by our modest and taxonomically unbalanced sample. More broadly, the framework represents an initial step toward predicting complete crown morphology, including enamel thickness, in worn or damaged teeth. As such, it offers a validated methodological foundation for future developments in cusp and crown reconstruction in both clinical and evolutionary dental research. Full article

This work presents the design, fabrication, and characterization of a three-dimensional FeCo-based flux-modulator microwinding intended for integration into high-torque axial-flux Vernier micromotors. The proposed micromotor architecture modulates the stator magnetic flux using 12 magnetically isolated FeCo teeth interacting with an 11-pole permanent-magnet rotor. The design requires the manufacturing of complex three-dimensional micrometric parts, including three teeth and a cylindrical core. Such a complex design cannot be manufactured using conventional micromanufacturing lithography or 2D planar methods. The flux-modulator envelope dimensions are 250 μm outer diameter and 355 μm height. It is manufactured using a femtosecond laser-machining process that preserves factory-finished surfaces and minimizes heat-affected zones. In addition, this micrometric part has been wound using 20 μm diameter enamelled copper wire. A dedicated magnetic clamping fixture is developed to enable multilayer microwinding of the integrated core, producing a 17-turn inductor with a 60.6% fill factor—the highest reported for a manually wound ferromagnetic-core microcoil of this scale. Geometric and magnetic characterization validates the simulation model and demonstrates the field distribution inside the isolated core. The results establish a viable micromanufacturing workflow for complex 3D FeCo microwindings, supporting the development of next-generation high-performance MEMS micromotors. Full article

Background: Composite restorations are the standard of care for posterior teeth due to their aesthetic properties and conservative nature. However, the choice between direct and semi-direct techniques can influence clinical longevity and performance. Objectives: This study aimed to compare the clinical performance of two restorative approaches: a direct technique and the semi-direct onlay technique in terms of aesthetic quality, surface finish, wear resistance, marginal integrity, and overall clinical efficiency over a two-year period. Methods: A total of 348 composite restorations were placed in 192 patients. Each restoration was evaluated at four timepoints: baseline (T0), 6 months (T1), 1 year (T2), and 2 years (T3). Clinical performance was assessed using standardised 5-point rating scales across the five dimensions. Repeated-measures ANOVA assessed changes over time, while Wilcoxon signed-rank and Mann–Whitney U tests were used for intra- and inter-group comparisons. Results: Significant time effects were observed across all clinical parameters (p < 0.0001). The direct technique exhibited superior initial results in aesthetics and surface finish at T0 and T1 (p < 0.001), but differences diminished by T3. In contrast, the semi-direct technique demonstrated improved performance in wear resistance and marginal integrity at T2 and T3. Both techniques showed progressive deterioration, particularly in marginal adaptation. Conclusions: The direct technique offers enhanced short-term aesthetics and procedural efficiency, while the semi-direct approach provides superior long-term durability and marginal adaptation. Full article

Background: Lingual orthodontic systems have recently advanced with the introduction of fully customized CAD/CAM-based designs featuring self-ligating (SL) mechanisms. This study aimed to evaluate the three-dimensional accuracy of a customized SL lingual system in reproducing digitally planned tooth positions. Methods: A total of 280 teeth were analyzed following treatment with a fully customized self-ligating lingual system (Harmony^®, Aso International Inc., Tokyo, Japan). Digital models obtained before treatment (T0), from the setup (TS), and after treatment (T1) were superimposed using a best fit algorithm in GOM Inspect. Tooth movements were quantified across seven biomechanically relevant parameters including tip, torque, rotation, buccolingual, mesiodistal, vertical, and overall displacement. Predicted and achieved movements were compared using paired t tests and Bland–Altman analysis. Results: The fully customized SL lingual appliance achieved an overall dentition accuracy of 92.1%. Mean accuracy for linear tooth movements was 94.5% ± 2.1% in the maxilla and 93.8% ± 2.5% in the mandible. For angular movements, mean accuracy was 90.8% ± 3.4% in the maxilla and 89.3% ± 3.9% in the mandible. The highest precision was observed in anterior teeth for mesiodistal (96.2%) and buccolingual (95.8%) movements, whereas the lowest accuracy occurred in rotational movements of the posterior segments (87.1%). No statistically significant differences were found between predicted and achieved movements for most parameters (p > 0.05). Conclusions: The fully customized SL lingual orthodontic system demonstrated high accuracy in reproducing digitally planned tooth movements, particularly in the anterior segments. Although accuracy was slightly lower in the posterior regions, the overall outcomes remained mechanically and clinically acceptable across all evaluated dimensions. Full article

Objectives: The aim of this study was to investigate the relationship between the diameter of iatrogenic root perforations and the fracture resistance (FR) of endodontically treated teeth. Methods: Sixty-five single-rooted teeth were sectioned at 13 mm from the anatomic apex. Their weight and the mesiodistal (MD) and buccolingual (BL) dimensions were recorded in order to ensure their allocation into five homogeneous groups (N = 13); Group 1 (control group): teeth remained intact, Group 2: teeth were instrumented but not perforated, Group 3: teeth were instrumented and perforated with a 2.1 mm bur, Group 4: teeth were instrumented and perforated with a 1 mm bur, and Group 5: teeth were instrumented and perforated with a 0.5 mm bur. All perforations were created at the same spot in the buccal surface of the roots. To further standardize the defects, an apparatus ensured that the cutting bur was positioned with a steady angle of 105° to the external root surface. A universal testing machine was used for fracture testing by applying a compressive vertical load at a speed of 1 mm/min until root fracture. The recorded forces were statistically analyzed with one-way analysis of variance (ANOVA) and post hoc Tukey test. Results: The mean fracture load was 342.68 ± 146.45 N for Group 1, 322.96 ± 98.62 N for Group 2, 214.65 ± 71.32 N for Group 3, 212.66 ± 77.89 N for Group 4, and 307.14 ± 109.16 N for Group 5. However, only the differences between groups 1–3 and 1–4 were statistically significant (p < 0.05). Conclusions: The teeth with 2.1 mm and 1 mm perforations were found to have significantly decreased FR. Full article

Background and Objectives: Dentigerous cysts are benign odontogenic lesions associated with the crowns of impacted teeth and are the second most common odontogenic cyst after radicular cysts. Despite being described as slow-growing, their growth has not been numerically quantified. This study aims to determine the radiological growth rate of dentigerous cysts through quantitative analysis, to clarify their biological behavior, improve clinical management, and guide future research by filling a significant gap in the literature. Materials and Methods: In this retrospective study, records of 187 patients diagnosed with dentigerous cysts at Dicle University between 2020 and 2024 were reviewed. Twelve patients with cysts associated with mandibular impacted third molars and at least two high-quality panoramic radiographs taken at different time points were included. In all of these patients with adequate and suitable radiographic records, the dentigerous cysts were associated with mandibular third molars, which contributed to the standardization of imaging and measurements. All images were obtained using the same digital system and converted to DICOM format. Maximum anteroposterior (A–P) and inferosuperior (I–S) dimensions were measured twice by the same examiner, and mean values were recorded. Follow-up intervals were noted, and monthly dimensional changes were evaluated. Due to the rarity of untreated cases, a sample of only 12 patients was considered meaningful. Results: Most patients were female, with no significant gender differences in age or follow-up time. Cyst dimensions increased over time, showing marked enlargement in the anteroposterior (A–P) direction and a similar upward trend in the inferosuperior (I–S) dimension. Conclusions: In our study, growth in the anteroposterior direction was higher than that in the inferosuperior direction, and no significant differences in growth rates were observed with respect to sex or age. Full article

This paper investigates global optimization methods applied to the design of a one-stage gearbox, aiming to partially automate the design using artificial intelligence. The developed software autonomously determines the gearbox parameters (number of teeth, gear width, modulus, etc.), optimizes them, and then models the assembly in Siemens NX CAD (computer-aided design). The direct connection between optimization and CAD leads to a faster designing process. The literature review reveals that the field of machine design is quite conservative, and only a few articles with some similarities to our research have been found. The paper describes gear dimensioning and the application of the Ipopt algorithm to the optimization of gear-pair parameters. Then, it addresses shaft design and bearing selection through multi-objective optimization using the NSGA-II algorithm, balancing cost, weight, and volume while meeting strength and durability constraints. The paper also describes the transfer of the optimized parameters and the creation of a CAD model. The last part is dedicated to the problems encountered, their potential solutions, and the advantages of the new approach. The proposed approach delivers a functional, optimized CAD model in about 10 min, providing a notable speed advantage over typical manual workflows. Full article

Background and Objectives: The aim of this study was to evaluate the radiographic progression of non-surgically managed jaw lesions that remained untreated due to patient deferral or refusal of surgery. Radiographic changes were assessed using two panoramic radiographs obtained at different time points, with a focus on dimensional progression, morphological characteristics, and anatomical involvement. Materials and Methods: A total of 85 non-surgically managed intraosseous cystic and cyst-like jaw lesions were evaluated on two panoramic radiographs obtained at least one year apart. Histopathological confirmation was available for 26 of the lesions (30.6%), while the remaining cases were evaluated radiographically due to the absence of surgical intervention or accessible pathology records. Assessments included localization, size, shape, internal structure, borders, association with non-erupted teeth, root resorption, tooth displacement, involvement of anatomical structures, and cortical changes such as thinning, expansion, or destruction. Nonparametric statistical comparisons were used to assess time-dependent changes and differences between follow-up groups. Results: A total of 57 lesions occurred in the mandible and 28 in the maxilla, predominantly in the posterior regions. The mean vertical/horizontal measurements of the intraosseous lesions was found to be 10.9 ± 4.6 mm/12.2 ± 6.5 mm (Mean ± SD) on the initial panoramic radiographs (Med: 10.0–IQR: 6.50/Med: 12.0–IQR: 8.75) and 14.8 ± 5.3 mm/17.5 ± 8.3 mm (Mean ± SD) on the second panoramic radiographs (Med: 14.5–IQR: 6.75/Med: 16.0–IQR: 10.75), respectively. Both vertical and horizontal dimensions showed a statistically significant increase between the two time points (p < 0.05). Initially, 41 lesions exhibited corticated margins; at follow-up, an additional 33 non-corticated lesions developed cortication. Lesions without corticated margins on the initial images exhibited significantly greater vertical and horizontal growth than those with corticated borders (p < 0.05). Lesions followed for 3–5 years showed significantly greater dimensional changes compared with those observed for shorter or longer intervals (p < 0.05). Lesion shape, internal structure, and multilocularity remained largely stable. Conclusions: Within the limitations of this retrospective study, non-surgically managed jaw lesions showed a tendency to increase in size over time. While the development of corticated borders may be associated with reduced growth activity, panoramic radiography alone is insufficient for definitive assessment, and regular radiographic follow-up should be considered within a broader clinical context. Full article

The present study explores bone healing patterns induced by orthodontic (OE) and surgical extrusion (SE) of structurally compromised teeth, where extrusion techniques are commonly used in rehabilitation. Changes in the trabecular bone were assessed by means of fractal analysis (FA) of consecutive periapical radiographs. (2) The present study is a retrospective case–control study. Pre- and post-treatment periapical radiographs from 44 adults undergoing orthodontic (OE) or surgical extrusion (SE) were retrieved. The radiographs were taken at T0 (pre-treatment), T1 (post-treatment), T2 (3-month follow-up), and T3 (6-month follow-up). Bone density (fractal dimension, FD) was analyzed in the apical and proximal bone regions (ROIs) of the extruded teeth, and both intra-group and inter-group differences were examined. (3) In all the regions of interest (ROIs), statistically significant intra-group differences in terms of bone density (FD) for both groups were found. In the OE group, the FD value increased, respectively, at T1, T2, and T3 in the apical ROI, compared to T0. For the proximal ROI, nearly the same trend was observed, respectively, at T1, T2, and T3 versus T0. As for the SE group, a statistically significant increase in the apical ROI was noted at T1, T2, and T3 when compared to T0. The same trend was registered in the proximal ROI compared to T0. However, no statistically significant inter-group differences in FD were detected between the two groups. (4) Orthodontic extrusion and surgical extrusion both resulted in an increased bone density (FD) despite the different healing patterns. Further prospective studies with a longer follow-up in this field are required. Full article

The main role of panoramic radiography lies in its rapid screening capability and its ability to detect and identify bone lesions, pathologies, and tooth-bearing structures. Since panoramic radiographs are widely used, they provide a good view of the jaw bones, maxillary sinus, and temporomandibular area. However, their major limitation is the reduced ability to accurately assess bone conditions, particularly in evaluating cortical integrity or identifying subtle, nondisplaced, or greenstick-type fracture lines. Other limitations include the presence of artifacts, image distortion, magnification variability, and high sensitivity to patient and film positioning, all of which can compromise image quality and diagnostic confidence. This 2D imaging method is still used worldwide, especially by dentists; however, this type of radiograph can be unpredictable due to structural superimposition and reduced ability to clearly establish, measure, and verify the precise dimensions, boundaries, and areas occupied by selected lesions. Many patients undergo panoramic imaging to assess possible mandibular fractures after trauma or following the removal of cysts, tumors, or impacted teeth. In most cases, the occurrence of a fracture without displacement can be misjudged, omitted, or underestimated. In such cases, either cone-beam computed tomography is performed or a detailed clinical examination before or during surgery, followed by intraoperative assessment, helps identify a possible fracture line, bone bending, mandibular instability, or the potential need for simultaneous prophylactic plating during dental procedures or the use of maxillomandibular fixation. This paper presents the author’s own experience regarding the limitations of panoramic radiographs in estimating bone condition and detecting fracture lines. Therefore, it is essential to highlight the role of prophylactic (preventive) mandibular plating (PMP) or fixation and to clarify when it should be considered. Full article

Background: Precise localization of the mental foramen (MF) is essential to avoid mental nerve injury during implant placement, osteotomy, periapical surgery, and regional anesthesia. However, MF morphology and canal orientation show population-specific variability, and comprehensive morphometric data combining cadaveric dissection and CBCT analysis remain limited in Koreans. This study aimed to provide clinically applicable MF reference values for Korean adults. Methods: Thirty-two hemimandibles from 16 dentate Korean cadavers were examined through direct anatomical dissection. MF position relative to teeth, shape, vertical and horizontal diameters, and distances to the gingival margin, inferior border, and mandibular midline were measured. CBCT imaging of 12 hemimandibles was used to assess the internal trajectory and opening direction of the mental canal. Results: The MF was most frequently located below the second premolar (75%), followed by the P2–M1 region (15.6%). Round foramina (62.5%) were more common than oval forms. Mean distances from the MF to the gingival margin, inferior border, and midline were 16.6 mm, 15.5 mm, and 26.5 mm, respectively. The mean horizontal diameter of the MF was 3.0 mm, and the mean vertical diameter was 2.2 mm. CBCT analysis revealed two emergence patterns—posterolateral (50%) and lateral (50%). Conclusions: This study identified the positional characteristics, diameters, and canal emergence patterns of the MF in a cadaveric sample using dissection and CBCT. The findings regarding MF location, dimensions, and the opening direction of the mental canal provide practical anatomical information that may support safer implant placement, mental nerve blocks, and anterior mandibular surgery. Full article

Background/Purpose: The study aimed to analyze the dimensions and width-to-length ratios of the maxillary anterior teeth in young native Cambodian adults and to assess their relationship with the golden proportion, symmetry, and sexual dimorphism. Materials and Methods: Maxillary study casts of 193 eligible Cambodian subjects, aged 18 to 25 years, were retrospectively evaluated. The width and length of their maxillary anterior teeth were measured using a digital caliper. Descriptive statistics, independent-samples t-test at 95% confidence intervals, Kolmogorov-Smirnov, Shapiro-Wilk, and Kruskal-Wallis tests were performed to analyze the data. Results: There was a high level of similarity between first and second quadrant measurements. Females showed slightly higher standard deviations for central incisors and lateral incisors than males across most ratios, indicating more variability in the width-in-length ratios for females. Males exhibited significantly greater tooth dimensions than females. The following results showed statistical significance with p < 0.05 and 95% confidence intervals. The mean crown width of the central incisors was 8.16 mm in males (CI: 8.03–8.29) and 7.87 mm in females (CI: 7.78–7.96). For the lateral incisors, the mean crown width was 6.69 mm in males (CI: 6.53–6.85) and 7.64 mm in females (CI: 7.43–7.85). The width-to-length ratio of the central incisors was higher in females (mean = 0.88; CI: 0.86–0.91) compared with males (mean = 0.87; CI: 0.84–0.89). Overall, proportional relationships remained consistent across genders. The golden proportion guideline was not applicable, as observed ratios ranged from 0.90 to 1.67 (all below 1.618), and RED values exceeded 80%. The null hypothesis was rejected due to the significant gender differences found in tooth dimensions and width-to-length ratios. Conclusions: There was no significant difference in maxillary anterior tooth dimensions for the right and left sides among the Cambodian population. Males had statistically larger teeth than females. Width-to-length ratios were greater in females for central incisors; however, the proportional relationships between the genders remained relatively consistent. The golden proportion and RED proportions did not exist within this population. A smaller size characterizes Cambodian dentition compared to that of other ethnic groups. Finally, these results can serve as an indicator for planning customized esthetic treatment in Cambodians. Future studies with larger sample sizes are needed to ensure the representation of the whole Cambodian population. Full article

Background/Objectives: To systematically compare the clinical and patient-reported outcomes of soft tissue grafts harvested from the palate and tuberosity, in root coverage surgeries. The primary outcomes assessed were graft dimension, tissue thickness, and postoperative discomfort. Methods: A comprehensive search was conducted in PubMed, Web of Science, OVID Medline, and Scopus databases, covering studies published till December 2023. Eligible studies included clinical studies and clinical trials involving medically fit adults who underwent intraoral soft tissue grafting for mucogingival procedures around teeth. A total of 1209 records were initially identified, with 13 studies meeting the inclusion criteria. Data was extracted and assessed for bias. Results: Graft dimension in terms of thickness was generally higher for tuberosity grafts (2.9 ± 0.5 mm) compared to palatal grafts (2.3 ± 0.6 mm). Tuberosity grafts demonstrate less volume changes in buccolingual thickness. One study reported decreased postoperative pain for tuberosity compared to palate donor sites. Risk of bias assessment using ROB 2 and ROBINS-I tools showed that most included studies exhibited low risk across key domains. Among randomized trials, two studies raised some concerns due to limitations in blinding and allocation concealment. Non-randomized studies showed a moderate risk primarily in confounding and outcome measurement, consistent with inherent observational design limitations. Conclusions: The palate remains a well-established and reliable source of soft tissue grafts. Limited evidence from a single short-term comparative clinical study suggests that tuberosity may offer potential advantages, such as greater graft thickness, reduced volume changes, and less postoperative discomfort. However, the comparative evidence between tuberosity and palatal donor sites is derived from a single short-term study and conclusions must therefore be interpreted with caution. Standardized clinical trials with long-term follow-up are needed to confirm these observations. Clinical Relevance: This review provides clinicians with a preliminary evidence-based perspective into the use of tuberosity as a donor site for soft tissue grafting, an area with limited published data, and highlights its potential to enhance patient outcomes and comfort in mucogingival surgery and emphasizing the need for further research in this area. Full article

Planetary gears consisting of simple external gear wheels and an internal ring gear are widely used in industry in various fields. This type of drive is most commonly found in robots, and it is also frequently used in the automotive industry, such as in wheel hub drives, in addition to general engineering. This study investigates the design of simple planetary gears manufactured with involute gearing. In simple internal gear planetary gears, the orbiting motion of the planetary gear is transferred to the output shaft by a radial balancing clutch and converted into rotary motion through the planetary gear’s guiding holes and the output element’s pins. The guiding holes reduce the planetary gear teeth strength, and the rim thickness “h” has a fundamental influence on the resulting tooth root stress. The main objective of this research is to design external gears with relief for simple planetary gears with a rim thickness “h” that does not decrease the load-carrying capacity. The dimensioning of involute gearing is well known, but the tooth root weakening effect of the clearance holes in such planetary gears is not known. Therefore, this paper focuses on analyzing how the size and position of the guiding holes influence tooth root stress, using finite element method (FEM) calculations performed in SolidWorks 2023. This study aimed to determine the rim thickness “h” required for the design of such a gear in order not to weaken the load-carrying capacity of the gear teeth. As a result of the research, the design of the guiding holes and the wheel relief holes can be performed with an accurate knowledge of their influence on tooth stress. The research results also make it possible to design this type of planetary gear using simple analytical calculation algorithms. Our goal was to define a simple design limit that could be used specifically in the preliminary design phase. This allows designers to determine the positions and dimensions of the guiding holes in the preliminary design phase without affecting the tooth stress. Full article