Tooth Surface Research Articles

Advanced Adhesive Approach to Support a Minimally Invasive Full Mouth Rehabilitation

ABSTRACTObjectivePatients who exhibit severe loss of tooth structure are challenging to rehabilitate. Conventional treatment of these patients may require adjunctive procedures of surgical crown lengthening, elective endodontic therapy and placement of posts and cores to retain full coverage crowns as part of a full mouth rehabilitation. Minimally invasive approaches to treatment of these patients provides opportunity to conserve tooth structure and to reduce adjunctive procedures by using an advanced adhesive approach to retain all ceramic partial coverage restorations as part of a full mouth rehabilitation.Clinical ConsiderationsThe use of an advanced adhesive approach to perform a full mouth reconstruction restoring occlusal vertical dimension (OVD) is described. This approach emphasizes preserving healthy tooth structure, maximizing restoration adhesion to enamel and dentin, maintaining pulpal vitality and minimizing adjunctive dental procedures. The preparation design focuses on being defect‐oriented to remove only diseased or undermined tooth structure. The all ceramic restorations are additive, where indicated, to further aid in preserving tooth structure. An advanced adhesive approach using an immediate dentin seal and resin coating over exposed dentin and composite resin cement under rubber dam isolation is used to lute the restorations. The restorations are fabricated using micro‐layered lithium disilicate ceramic to maximize the esthetic appearance of the rehabilitation where needed.ConclusionAn advanced adhesive approach to full mouth rehabilitation should be considered as a treatment option for patients exhibiting tooth surface loss as an alternative to conventional full coverage restorations when clinical parameters allow.

Allelic Variation in gtfB–gtfC Region of Natural Variant of Streptococcus mutans Without Biofilm Formation

Streptococcus mutans is primarily found in biofilms on tooth surfaces and is associated with the development of dental caries. S. mutans synthesizes water-insoluble glucan (WIG) using sucrose as a substrate, inducing the formation of three-dimensional biofilms. WIG is produced by glucosyltransferases (GTFs) encoded by the tandem and highly homologous gtfB and gtfC genes. Conversely, the homologous recombination of gtfB and gtfC readily happens, producing natural variants without WIG. These WIG− variants are thought to have ecologically pleiotropic functions; however, the molecular basis for their appearance is unclear. This study aimed to determine the sequence of the gtfB–gtfC regions of WIG− variants. We sequenced the gtfB–gtfC regions of 23 WIG− variants derived from S. mutans UA159 and revealed the presence of five alleles and four types of single homologous recombination patterns. Regardless of the allele type, the WIG− variants showed low biofilm formation and GTF activity. To the best of our knowledge, this is the first study to report the presence of alleles in WIG− variants. These findings provide important information for explaining the appearance of mechanisms in WIG− variants.

Stress Distribution in Traumatized Teeth Splinted With Fiber Localizing on Incisal/Cervical Positions: A Three-Dimensional Finite Element Analysis.

The fiber splint represents an advanced treatment for traumatized dental injuries. The complete understanding of the localization of a splint on traumatized teeth remains elusive. The aim of this study was to assess the impact of the incisal/cervical positions of the fiber splint on the stress distribution of traumatized dental roots in various occlusal relationships. Three-dimensional finite element models were generated based on a cone beam computer tomogram of a patient. The incisal and cervical splints were simulated by strips that were bonded close to the incisal/cervical labial surface of traumatic teeth. Force was loaded on the incisal ridge, incisal and cervical positions on the palatal surface of each tooth to simulate the conditions of traumatized teeth during mastication. The equivalent stress (von Mises) on the traumatic teeth and abutment teeth was calculated by Ansys software (version 2021, R1). The incisal splint effectively transferred the stress from the traumatized tooth roots to the abutment teeth when force was loaded on the incisal ridge and incisal and cervical positions on the palatal surface. Nevertheless, the reduction effect was notably diminished when the cervical splint was used. Notably, in cases of cervical splints, with a loading force on the incisal ridge, there is an increase in stress on the roots of traumatized teeth, which poses a disadvantage in the management of traumatic dental injuries. The incisal splint demonstrated a more effective transfer of stress from the roots of the traumatic teeth to the abutment teeth than the cervical splint and the raw.

Gelatin-Modified Bioactive Glass for Treatment of Dentin Hypersensitivity

When dentin is directly exposed to the oral cavity for various reasons, such as a lack of enamel on the tooth surface, external stimuli to the dentin often cause transient discomfort known as dentin hypersensitivity. In order to block the incoming stimulus signal, an ideal treatment is to induce the production of minerals to block the dentinal tubules. In this work, a dentin-desensitizing plugging material was prepared by modifying mesoporous bioactive glass with gelatin, the mineralization and desensitization effects of which were compared with Gluma in in vitro experiments. These experiments confirmed that gelatin-modified bioactive glass (MBG@PDA@Gel) is more effective than traditional desensitizing agents at blocking dentin tubules. Following the successful synthesis of MBG@PDA@Gel, as confirmed by scanning electron microscopy, transmission electron microscopy, and other tests, the treatment of demineralized dentin with MBG@PDA@Gel demonstrated that the dentinal tubules were tightly blocked under scanning electron microscopy. MBG@PDA@Gel induces minerals in deeper layers of dentinal tubules, promoting remineralization and forming a unified structure with the tubule blockage. Animal studies showed that MBG@PDA@Gel can remineralize demineralized dentin, and it is stable in the oral cavity and does not fall out. MBG@PDA@Gel not only enhances the biocompatibility of the nanoparticle but also results in an overall uniform and rapid remineralization of the demineralized dentin.

High-Speed and Low-Noise Gear Finishing by Gear Grinding and Honing: A Review

AbstractGears are important mechanical parts for transmitting power and play an increasingly important role in the machinery industry. The electric vehicle industry developed rapidly and became a vital development field of the automotive industry over the past few years. The conversion of energy increases the requirements for electric vehicle transmissions, which promotes the development of high-speed and low-noise transmission gear. This paper elaborates on the research progress of high-speed and low-noise gear finishing methods. Firstly, this review analyses the machining requirements, finishing, and specific machining technologies of high-speed and low-noise gears. The importance of gear grinding and honing in high-speed and low-noise gear machining is highlighted. Secondly, the applications of gear grinding and honing in gear modification, error compensation, and texture control are analyzed. Furthermore, the role of precision machining technology in improving gear performance is clarified. Finally, the design and processing methods of the modified tooth flank for gear modification are summarized. In addition, the influence of tooth surface texture on noise is described, and the texture change methods are explored. The well-known open problems of gear finishing are finally identified, and some new research interests are also pointed out. This review will provide valuable references for further research on gear finishing.

Exploring Dentists’ Preferences in Selecting Adhesive Systems: A Survey Analysis

Dental adhesives play a crucial role in modern dentistry by enabling the bonding of diverse restorative materials to tooth surfaces. These systems have evolved through seven generations, each characterized by unique chemical compositions and application techniques. The advancements in dental adhesives have significantly impacted restorative dentistry by preserving tooth structure, enhancing aesthetics, and ultimately improving patient outcomes and treatment options. The choice of adhesive system depends on various factors, including the clinical scenario, material compatibility, and dentist preference. Ongoing advancements in adhesive technology continue to enhance treatment outcomes and streamline procedures for dental practitioners. The development of universal adhesives capable of functioning in both etch-and-rinse and self-etch modes has further simplified clinical protocols. This study is an observational cross-sectional study conducted among Romanian dentists. A questionnaire was distributed via email to Romanian dentists, encompassing seven questions that explored the predominant use of etch-and-rinse or self-etch adhesive systems, preferred adhesive types, and commonly encountered challenges in direct restorations. Statistical analyses were conducted using DATAtab version (2024). The study highlighted the varying preferences among Romanian dentists in selecting suitable adhesive agents. Etch-and-rinse (ER) techniques predominated in direct restorations, with universal adhesives being the most frequently used. Further investigation is warranted to delve into the preferences of Romanian dentists regarding the utilization of self-etch (SE), etch-and-rinse (ER), and universal adhesives (UAs).

Impact of strontium added fluorophosphate glass on the physico-chemical properties of mineral trioxide aggregate

Mineral trioxide aggregate (MTA) is widely employed in the field of endodontics, extensively for root canal therapy. Despite being successful, MTA has certain limitations regarding its physico-chemical properties. The present investigation aims to enhance the physicochemical and mechanical behavior of MTA by formulating a cement paste by addition of strontium containing fluorophosphate glass (SrFP). The addition of strontium on to the fluorophosphate glass improves the mechanical strength of the glass network and also accelerates the mineralization process during implantation. In this regard, fluorophosphate glasses with 6 mol% of strontium content were synthesized by standard melt quenching technique and the glasses were ball milled to obtain fine powder. Cement paste was prepared by adding optimized 5 wt% of 6 mol% SrFP glass powder on to 95 wt% of MTA cement. Comparative analysis of conventional MTA with SrFP added MTA were evaluated for various properties such as pH variation, contact angle, radiopacity, compressive strength, push-out bond strength, setting expansion, sealing ability, tooth color change, surface morphology and ALP activity. The obtained results from the investigation exposed that the addition of strontium added fluorophosphate on to MTA impacts the physical properties which includes wettability, sealing ability, push out bond strength and ALP. These findings suggest that SrFP to be a promising additive to MTA with wide scope of applications in dentistry.

Applications Of Photodynamic Therapy In Periodontal Diseases

Background: According to A. Marcacci et al (1888), when many reports emerged on light absorbing properties and of fluorescence of various dyes, it became clear that dye excitation by light exerts destructive action in biological systems. This so-called photodynamic action was described as a process in which light, after being absorbed by dyes sensitizes organisms for visible light inducing cell damage. The supra- and subgingival plaque biofilm on tooth surfaces should easily be accessible for flushing with the dye and for activating them by light. Thus, periodontal diseases are promising applications of Photodynamic Therapy. Introduction: Chronic periodontitis is the most common periodontal disease which is related to the chronic accumulation of bacterial plaque. Since mechanical methods are not sufficient in the treatment of this disease, administration of local/systemic antibiotic is recommended following mechanical debridement. However, side effects of antibiotics such as microbial resistance and patient allergy led to development of alternative methods. One of these suggested methods is the antimicrobial photodynamic therapy (aPDT). PDT is a local noninvasive treatment modality without the side effects caused by antibiotics. Objectives: In this review, the mechanism of action of PDT and its application in the treatment of various periodontal conditions along with its future trends are discussed. Conclusion: Even though PDT is still in experimental stages of development and testing, the method may be an adjunct to conventional antibacterial measures in periodontology and Implant related perspectives.

Tensor based approach for tooth contact analysis of planar and spatial gearing contact

This paper presents a new method for analyzing gear tooth contact, leveraging tensor notation and discrete differential geometry. Existing analytical and numerical methods often face challenges in convergence and computational efficiency. Our proposed approach involves defining a novel tensor notation and applying it to the gear tooth contact kinematics problem. By discretizing the tooth surfaces and using tensor operations, we can accurately determine the kinematics, path of contact, and transmission error of the gear pair. To validate our approach, we compared its results with those obtained from commercial software, KISSsoft and KiMOS. The results demonstrated high accuracy, with mean absolute errors below 0.08 for specific sliding, 0.003 for sliding factor, and 0.1μm for transmission error. Furthermore, we applied our method to analyze non-involute gear types, such as S-gears, pin gearing and cosine gears. Our findings revealed the kinematic performance and contact characteristics of these gear types, providing valuable insights for gear design and optimization. In conclusion, the proposed tensor-based approach offers a promising alternative for gear tooth contact analysis, providing accurate and efficient results for a wide range of gear types.

The Hidden Danger - Understanding Periodontal Pocket

The conversion of junctional epithelium to pocket epithelium is regarded as a hallmark in the development of periodontitis. Knowledge of factors contributing to the initiation and progression of pocket formation is important. It may result in the development of better preventive measures and improved healing outcomes after therapeutic interventions. destruction of the structural integrity of the junctional epithelium, which includes disruption of cell-to-cell contacts and detachment from the tooth surface, consequently leading to pocket formation, disequilibrates this delicate defense system. One of the main variables used to evaluate the clinical success of periodontal therapy is periodontal pocket depth reduction. Therefore, reflecting on how the periodontal pocket process's role has helped guide how we perform and interpret periodontal research is important. A full understanding of periodontal pocket etiology is required to design a more precise treatment strategy and avoid the advancement of periodontal disorders.

Study on oil film spreading characteristics on the jet lubricating tooth surface of aviation herringbone gear

Purpose During the oil lubrication process of aviation herringbone gears, lubricating oil is injected into and spreads around the tooth surface. Its spreading characteristics directly affect the lubrication state and transmission efficiency of gears. This study aims to investigate the effect of changing the injection parameters and gear operating conditions on the oil film deposition during injection lubrication. Design/methodology/approach The computational fluid dynamics method was used to establish the computational domain for the simulation and optimization using an orthogonal test. The oil film spreading and thickness of the tooth surface were calculated with the change in gear speed, fuel injection distance and fuel injection speed. Optimized oil injection lubrication parameters were obtained, and design ideas were provided for the oil injection lubrication analysis of aviation herringbone gears. Findings Under different operating conditions, such as varying the injection speed, gear rotational speed and injection distance, there were differences in the distribution of the lubricating oil film formed on the tooth surface. The thickness of the oil film decreases as the distance from the injection port increases. The thickness of the oil film deposition can be increased by increasing the injection velocity and reducing the gear rotation speed. The injection distance had a relatively small effect on the spreading thickness of the deposited oil film, affecting only the dynamic spreading process of oil film deposition. Furthermore, the simulation results are compared with the analytical calculation results, and finally the experimental verification is carried out. Originality/value Oil spray lubrication characteristics are important for achieving precise gear lubrication designs in the aerospace field. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2023-0250/

DA-Net: A classification-guided network for dental anomaly detection from dental and maxillofacial images

Dental abnormalities (DA) are frequent signs of disorders of the mouth that cause discomfort, infection, and loss of teeth. Early and reasonably priced treatment may be possible if defective teeth in the oral cavity are automatically detected. Several research works have endeavored to create a potent deep learning model capable of identifying DA from pictures. However, because of the following problems, aberrant teeth from the oral cavity are difficult to detect: 1) Normal teeth and crowded dentition frequently overlap; 2) The lesion area on the tooth surface is tiny. This paper proposes a professional dental anomaly detection network (DA-Net) to address such issues. First, a multi-scale dense connection module (MSDC) is designed to distinguish crowded teeth from normal teeth by learning multi-scale spatial information of dentition. Then, a pixel differential convolution (PDC) module is designed to perform pathological tooth recognition by extracting small lesion features. Finally, a multi-stage convolutional attention module (MSCA) is developed to integrate spatial information and channel information to obtain abnormal teeth in small areas. Experiments on benchmarks show that DA-Net performs well in dental anomaly detection and can further assist doctors in making treatment plans. Specifically, the DA-Net method performs best on multiple detection evaluation metrics: IoU, PRE, REC, and mAP. In terms of REC and mAP indicators, the proposed DA-Net method is 1.1% and 1.3% higher than the second-ranked YOLOv7 method.

Cariogenic potential of the Streptococcus mutans Cid/Lrg system: an in vivo animal case study.

In our prior study using a dual-species (Streptococcus mutans/Streptococcus gordonii) competitive mouse caries model to investigate the contribution of S. mutans LrgAB to in vivo fitness, S. mutans wild-type and ΔlrgAB mutants consistently outnumbered S. gordonii and had high caries scores, even though the ΔlrgAB mutant is highly sensitive to oxidative stress. To determine whether the highly cariogenic sucrose diet used in the previous study masked the contribution of LrgAB to competitive fitness of S. mutans against S. gordonii, we recapitulated our previous mouse caries experiment with a modification in which 4% sucrose drinking water was replaced with sterile water, hypothesized to decrease the frequency of exposure of mice to sucrose, a determinant in the cariogenicity of S. mutans. Given that both S. mutans ΔlrgAB and ΔcidB mutants are sensitive to oxidative stress and share similar transcriptional profiles, these strains, as well as wild-type UA159, were tested in this modified dual-species mouse caries model. When comparing between groups the colonization within molar dental biofilms of S. mutans strains, ΔlrgAB mutant was at a level similar to the wild type, whereas S. mutans ΔcidB was modestly lower than both wild-type and S. mutans ΔlrgAB. The severity of total sulcal caries in both the ∆cidB and ∆lrgAB mutant infections was significantly lower than that of wild type. These results demonstrate that the Cid/Lrg system aids in S. mutans fitness against S. gordonii and caries potential in vivo, a phenotype likely masked in our previous study by more frequent exposure to sucrose.IMPORTANCEThe development of a mature biofilm on the tooth surface is the central event in the pathogenesis of dental caries, which primarily requires that cariogenic organisms withstand the limited resources or environmental fluctuations experienced in the oral cavity. The sensitive and heterogeneous response of the cid and lrg operons to complex external signals has been hypothesized to trigger differentiation of the Streptococcus mutans biofilm community into distinct functional subpopulations to promote survival and persistence of the S. mutans community when challenged by an unfavorable environment. The study described herein enlightens our understanding of how Cid/Lrg contributes to S. mutans pathogenic potential in vivo (caries development), warranting further research regarding the adaptive role of Cid/Lrg system in human oral biofilms toward the development of anti-caries strategies directed at the Cid/Lrg system.

Effect of a novel irrigation regimen and root canal filling material versus conventional endodontic protocols on dentin wettability.

The purpose of this study was to compare the effect of different irrigation regimens on the dentin wettability of root canal sealers. The occlusal surfaces of human molar teeth (N = 90) were removed, polished, and divided into three groups (n = 30) based on the irrigation regimen: control group (SAL), standard irrigation group (NES), and test group (ODC). Each group was randomly divided into three subgroups according to the root canal sealer: AH Plus (AHP), Total Fill BC Sealer HiFlow (TOT), and OdneFill (ODF). The contact angle was determined using the sessile drop technique. The pendant droplet method assessed the work of adhesion. Surface roughness was measured using atomic force microscopy. Data were analyzed using non-parametric tests (p < .05). ODC-ODF showed significantly lower contact angle (34.80°) than ODC-AHP (66.53°, p < .001) and ODC-TOT (85.72°, p < .001). In NES, no significant difference was found between ODF and AHP (p > .05) while both groups presented significantly lower results than TOT (p < .001, p < .001, respectively). In SAL, the difference between TOT (92.84°) and AHP (83.24°) was insignificant (p > .05), whereas ODF presented significantly lower results compared to both (p < .001, p < .001, respectively). Surface roughness was lowest in ODC (31.54nm), followed by SAL (62.30nm) and NES (72.02 nms) which was significantly (p = 0.006) higher than ODC, whereas the difference between SAL and NES was insignificant (p > .05). This study highlights the wettability of a new root canal sealer and the effect of a new irrigation activation system on the wettability of different root canal sealers. OdneFill showed superior wettability compared to other sealers while exhibiting a synergistic effect with OdneClean.

Effectiveness of Chewing Gum After Water Rinsing in Removing Remnants of Sticky Cookies From Posterior Teeth-A Prospective Interventional Study.

To evaluate the effectiveness of chewing sugarless gum (SG) after water-rinsing in removing retained Oreo chocolate cookies (CC) from occlusal surfaces of teeth with and without fissure-sealant (FS). A prospective study was performed on healthy children receiving prophylaxis at the paediatric-dentistry department. Immediately afterward, they chewed two CC. The occlusal surfaces of their posterior teeth were photographed 3 times: after 10 min, after 1 min of water-rinsing and after 4 min of chewing SG. An independent dentist screened all photos for the presence (partial or complete) or the absence of retained CC. Participants included 28 children 7-14-year-old, with 100 primary and 214 permanent molars, of which, 150 teeth had FS. After chewing two CC, 290 (92.4%) teeth had retained CC. Water-swishing removed all, partial or none of the CC in 23%, 72.4% and 4.6% of the teeth, respectively. The effectiveness of chewing SG in completely removing retained CC was significantly higher than water-rinsing (p < 0.001), OR = 43.83, Cramer's V value = 0.871, suggesting a very strong correlation. The presence of FS raised the probability of completely removing retained CC after SG or water-rinsing (p < 0.001, OR = 107.7 and 25.9), with Cramer's V = 0.66 and 0.57, respectively, means a very strong association, as compared to teeth without (For both p < 0.001). Chewing gum for 4 min was significantly more effective than water-rinsing for 1 min in removing retained CC. Moreover, FS considerably decreased the probability of retained CC on occlusal surfaces and increased the effectiveness of SG in removing it.

Dietary carbohydrates modulate Streptococcus mutans adherence and bacterial proteome.

Streptococcus mutans adherence to the tooth surface and subsequent biofilm development is modulated by the carbohydrate source, but the corresponding effect on bacterial proteome has not been previously studied. This study aimed to assess the effect of different carbohydrates on S. mutans viability and bacterial proteome at two-time points, early attachment (8 h) and biofilm maturation (24 h). Hydroxyapatite (HAp) discs coated with parotid saliva proteins were inoculated with S. mutans UA159 in Tryptone Soy Broth without dextrose supplemented with one of the following carbohydrates (n=12/treatment/time point): 1% Sucrose (S); 0.525% Glucose + 0.525% Fructose (G+F); 10% Xylitol (X); 10% Xylitol + 1% Sucrose (X+S); or culture medium without supplementation as negative control (C). Once inoculated, HAp discs were incubated for 8 h or 24 h at 37 °C and 10% CO2. After each incubation period, adhered bacteria were quantified using the plate-counting method for 6 HAp discs/group, and the remaining 6 HAp discs/group were used to extract bacterial cell wall proteins. Extracted proteins were analyzed using liquid chromatography coupled with mass spectrometry and then classified by their biological process. The study was conducted in three independent assays and the number of bacteria adhered to the HAp discs was determined at each time point and analyzed by two-way ANOVA followed by Bonferroni test (=5%). The results suggest that xylitol significantly repressed bacterial adherence and metabolism at 8 h and 24 h; however, bacterial adherence and metabolism were significantly enhanced when xylitol was combined with sucrose, showing no negative effect on S. mutans at both time points. Bacterial proteome was modulated by the carbohydrate source. The cariogenicity of S. mutans biofilms may be reduced by the alternative sweetener xylitol; however, the combination with fermentable sugars may inhibit such a beneficial effect.

Study on meshing and dynamic characteristics of herringbone gear pair considering tooth surface wear and modification

Due to errors and tooth surface wear of herringbone gear is inevitable. And tooth surface modification is the key technology to improve gear performance. Therefore, this paper studies the influence of tooth surface uneven wear and modification on herringbone gear pair's meshing and dynamic characteristics with errors. Firstly, herringbone gear pair meshing characteristic analysis model based on discrete tooth surface is established. Secondly, herringbone gear pair bending-torsion coupling dynamic characteristic analysis model considering friction is established, and the dynamic frictional force analysis process is given. Thirdly, combined with Archard's wear theory, the tooth surface uneven wear amount is obtained. The tooth surface uneven wear amount is substituted into meshing matrix as a tooth surface deviation. Finally, the meshing and dynamic characteristics of herringbone gear pair considering tooth surface wear and modification are studied by using the established analysis model of meshing characteristics and dynamic characteristics. The calculation results show that without tooth surface modification, tooth surface wear will deteriorate the meshing and dynamic characteristics rapidly. However, reasonable tooth surface modification can effectively improve meshing and dynamic characteristics of gear pair, so that the gear pair can still maintain stable transmission under wear condition.

Wearable Multifunctional Hydrogel for Oral Microenvironment Visualized Sensing Coupled with Sonodynamic Bacterial Elimination and Tooth Whitening.

Bacterial-driven dental caries and tooth discoloration are growing concerns as the most common oral health problems. Current diagnostic methods and treatment strategies hardly allow simultaneous early detection and non-invasive treatment of these oral diseases. Herein, a wearable multifunctional double network hydrogel combined with polyaniline and barium titanate (PANI@BTO) nanoparticles is developed for oral microenvironment visualized sensing and sonodynamic therapy. Due to the colorimetric properties of polyaniline, the hydrogel displays a highly sensitive and selective response for visualized sensing of oral acidic microenvironment. Meanwhile, the barium titanate in the hydrogel efficiently generates reactive oxygen species (ROS) under ultrasound irradiation, realizing non-invasive treatment in the oral cavity. Through bacterial elimination experiments and tooth whitening studies, the hydrogel can achieve the dual effect of effectively inhibiting the growth of cariogenic bacteria and degrading tooth surface pigments. Owing to the visualized sensing of the oral acidic microenvironment and efficient sonodynamic therapy function, the proposed hydrogel system offers a solution for the prevention of caries and tooth whitening, which is promising in developing the biomedical system targeting the simultaneous sensing and therapy for oral diseases.

Investigation on meshing characteristics of spiral bevel gear under wear fault evolution with assembly errors

Spiral bevel gears have the advantage of transmitting high torque and power comparing to helical gear and straight bevel gear. However, they are susceptible to wear due to factors such as high loads, poor lubrication, and surface imperfections resulting from machining. In this study, we propose an autonomous model for predicting tooth wear and analyze the meshing characteristics of spiral bevel gear (SBG) pairs under different assembly errors. Concurrently, we establish a finite element model to validate the accuracy of our meshing characteristic analyses. We also compare the distribution patterns of wear depth on the tooth surface with existing literature. Our investigation delves into meshing characteristics, encompassing transmission errors and Time-varying mesh stiffness (TVMS), considering wear evolution under assembly errors. The results demonstrate that the fluctuations in TVMS remain consistent across all four types of assembly errors examined. Gear tooth wear leads to an increase in gear backlash and fluctuations in unloaded transmission error. The meshing stiffness fluctuation of the SBG pair enlarges under wear evolution. Assembly errors result in shifts in the initial contact line and contact pattern, subsequently altering the distribution of wear depth. Different forms of assembly errors may cause a similar effect on the distribution of wear depth and meshing characteristics.

Comparing Military and Civilian Dentists' Treatment Planning Decisions: A Pilot Study.

Clinical decision-making varies among dentists. However, the literature is limited and narrow in scope regarding the variation between public and private sector dentists. Because both types of dentists' decisions can directly influence military dental readiness, it is important to understand the potential differences in diagnosis, treatment planning, and the delivery of care. The purpose of this pilot study was to compare treatment planning recommendations between civilian and military providers. Patient-level data from the 2018 Recruit Surveillance, a stratified, cross-sectional study of 1,208 randomly selected U.S. Air Force recruits, were used to evaluate treatment planning outcomes for the 2 provider groups (2 civilians; seven military providers). Treatment planning outcomes included type of noninvasive, operative, and oral surgery treatment recommended, temporomandibular disorder referrals, and orthodontic referrals. Patient demographic variables included age, gender, education, race/ethnicity, and military component ("status"). Data were examined both at the tooth level and patient level for statistical significance. Multivariate analyses were performed with statistically significant variables included in each final model for patient-level data. Data were analyzed with logistic regression and Poisson regression (alpha = 0.05). Bivariate logistic regression analyses were performed for tooth-level data. Significant differences were found between military and civilian dentists' treatment planning decisions (P < .05) for both patient-level and tooth-level data. Adjusted for significant bivariate predictors of patient demographics at the patient level, civilian dentists were more likely to refer patients for orthodontic treatment, prescribe remineralization for sound tooth surfaces, incipient caries, and carious teeth, and prescribe direct restorations for teeth with 3 to 5 carious surfaces instead of single crowns compared to military dentists. Additionally, civilian dentists were less likely to prescribe sealants for sound tooth surfaces or carious teeth. No statistically significant difference in treatment planning outcomes was observed between civilian and military dentists for sealants for incipient caries, single crowns, or extraction of third molars. At the tooth level, civilian dentists were more likely to prescribe remineralization for sound tooth surfaces, remineralization instead of sealants for carious surfaces, and extraction of third molars. No statistically significant differences were noted between civilian and military providers for recommending sealant or remineralization for teeth with incipient caries or prescribing a single crown versus placing a direct restoration on posterior teeth with 3 to 5 carious surfaces. Significant differences in treatment planning outcomes between civilian and military providers exist. Civilian providers are more likely to refer patients for orthodontic treatment and prescribe remineralization, direct restorations instead of single crowns, and third molar extractions, while military providers are more likely to prescribe sealants for sound tooth surfaces or carious teeth. Therefore, comparisons of treatment planning outcomes between civilian and military providers warrant further research.