Single-tooth Model Research Articles

An investigation of the validity of the Bedek models and Cameriere-European formula used in dental age prediction in Turkish children.

Dental age estimation is one of the most reliable methods for determining age, commonly used for forensic, criminal, and anthropological purposes. The purpose of this study was to assess and compare the precision of the Bedek models and the Cameriere-European Formula (CF) in determinating dental age in a sample of Turkish individuals. Retrospective panoramic radiographs of 1018 subjects (497 boys and 521 girls) aged 5-14 years were evaluated using the Bedek models and the CF. The differences between calculated dental age (DA) and chronological age (CA) for each sex and age group were analyzed using the paired sample t-test and the Wilcoxon signed-rank test. The accuracy of the methods used to estimate dental age was determined by calculating the mean absolute error (MAE) based on the proximity of the dental age to the chronological age. The CF method overestimated CA by 0.1 year in the entire sample. Conversely, the Bedek models tended to overestimate CA, with the three-, four-, and seven-tooth models exhibiting the most significant difference. There was a statistically significant difference between boys and girls in the DA-CA calculation using the CF method in the entire sample. Among the Bedek models, the three- and four-tooth models had the lowest MAE in the entire sample, while the single-tooth model had the highest MAE. The CF method showed higher accuracy in predicting the age of children living in eastern Turkey compared to the Bedek Models.

Thermal Analysis of Herringbone Gears Based on Thermal Elastohydrodynamic Lubrication Considering Surface Roughness

To predict the temperature distribution of the tooth surface of a herringbone gear pair, a numerical method for the determination of frictional heat generation was proposed by establishing a thermal elastohydrodynamic lubrication (TEHL) model in the meshing zone taking surface roughness into account. According to the real micro topography of the tooth surface measured by a non-contact optical system and loaded tooth contact analysis, the friction coefficient was obtained by a TEHL analysis and then the heat generation in the contact zone was determined. With the combination of heat generation and heat dissipation analysis, the single tooth model of the herringbone gear pair due to the finite element method (FEM) was proposed and the steady-state temperature distribution of the tooth surfaces was predicted by FEM simulations. The simulation and the experimental results demonstrated good agreement, which verified the feasibility of the present numerical method.

Real-time co-site optical microscopy study on the morphological changes of the dentine’s surface after citric acid and sodium hypochlorite: a single-tooth model

BackgroundTo this day, the effects of sodium hypochlorite and chelating agents on the smear layer and on the dentine’s surface, remain not fully examined. The study is aimed to analyze the dentine's surface treated with 40% citric acid and 5.25% sodium hypochlorite according to two irrigation protocols.Materials and methodsThe study employed a computer-controlled Nikon Eclipse LV100 optical microscope. Ten roots split longitudinally with canals prepared mechanically using the MTwo system to a size of 40/04 were observed. The root halves were divided into two study groups, one half in each of the groups. According to two irrigation protocols, the dentine's surface was irrigated with 40% citric acid and 5.25% sodium hypochlorite, separated with water. Dentine surface was observed in a fixed place and photographed in 500 × magnification after each irrigation stage. The obtained images were then analyzed using computer software (NIS-Elements AR, GIMP-2.6, ImageJ 1.45s).ResultsVarious speed of removal of the smear layer and varied morphological changes of the dentine's surface were observed in both examined groups. Double irrigation of the dentine with citric acid for 30 s resulted in complete removal of the smear layer, and double irrigation for 60 s resulted in increased mean diameter of the dentine tubules (degradation of the dentine's surface).ConclusionsDouble alternating irrigation with citric acid and sodium hypochlorite for 30 s yielded satisfactory results, while double irrigation for 60 s resulted in increased mean diameter of the dentine tubules. A real time assessment of the dentine’s surface changes after both tested solutions can improve understanding of the phenomena that occur during the irrigation and as a result it might help to improve clinical outcomes in root canal treatment.

Validity assessment of a single tooth model in clenching and chewing simulations

Single tooth finite element model is widely used to investigate tooth behaviors with reducing modeling process and computational time. This study aims to examine the validity of a single tooth model in clenching and chewing actions. The single tooth model consisting of tooth #16, the periodontal ligament (PDL), and bone was subjected to coronal-apical movements. The predicted strains from the analyses were validated with the in-vitro experimental results on tooth-PDL-bone specimen. The stress distributions of tooth root and PDL were compared to those from the full skull model to evaluate reasonability of the single tooth model. The results of this study indicate that the single tooth model is able to predict valid structural and mechanical behaviors in clenching and chewing activities.

Design of a Single-Tooth Model and Its Application in Oral Scan System Assessment

Intraoral scanners have been widely used in the application of dentistry. Accuracy includes trueness and precision; they have an important position in the assessment of intraoral scanners. The existing standard models are divided into the inlay and the crown, but the operation is relatively complicated. In this study, in order to simplify the current standard model, we designed a new integration model to compare the accuracy of two intraoral scanners (CEREC and TRIOS) and an extraoral scanner (SHINING). The coordinate measuring machine measured value is the gold standard. Values of the length and angle were analyzed by converting the scanned digital impressions into an STL (standard triangulation language) format to evaluate the accuracy of the intraoral scanner and to verify the feasibility of the designed model. The result shows that the integration model can be successfully scanned and imaged. In the case of the powder-free integration model, intraoral scanner precision, trueness, 3D fitting, and imaging are better than the extraoral scanner. It can be seen straightly from the measurement result and the 3D fitting result that the intraoral scanner can acquire the shape of the standard model integrally with good repeatability. Therefore, it can be concluded that TRIOS is superior to CEREC and SHINING in accuracy, and the integration model is feasible as a reference in the examination of intraoral scanners. The performance of the newly designed integration model that can be scanned is clinically significant, suggesting that this model can be used as a standard reference model.

Influence of Bulk-Fill Composites, Polimerization Modes, and Remaining Dentin Thickness on Intrapulpal Temperature Rise

Objectives The aim of this study was to compare the effects of different bulk-fill resin composites, polimerization modes, and the thickness of remaining dentin on the increase of intrapulpal temperature. Methods Human-extracted upper premolar teeth (n = 10) were used to design a single-tooth model with remaining dentin thicknesses of 1 mm and 0.5 mm. Estelite Bulk-fill Flow (Tokuyama, Japan), Surefil SDR™ Flow (Dentsply Caulk, Brazil), Filtek Bulk-Fill Posterior (3M, USA), and SonicFill™ 2 Bulk-fill (Kerr, USA) composites were applied according to the manufacturer's instructions. The standard and high modes of a light emitted diode (LED) light curing unit (LCU) (VALO™ Utradent, USA), were used for polymerization. In order to mimic the in vivo conditions of pulpal circulation, digital flowmetry (SK-600II, SK Medical, China) was used. Intrapulpal temperature rise was measured using K type thermocoupling (CEM DT 610B, Robosem Engineering, China). Data were analyzed using three-way variance analysis (ANOVA) and the independent t-test. Results No significant statistical differences in intrapulpal temperature rise between low viscosity bulk-fill composites (SDR and Estelite) were found. The lowest intrapulpal temperature rise was found in groups which used the Filtek Bulk-fill composite. Decreases in the remaining dentin thickness increased the intrapulpal temperature rise. Significance This study demonstrated that remaining dentin thickness, filler ratio of bulk-fill composites, and power and application time of the LED-LCU may affect intrapulpal temperature rise.

In silico study of cuspid' periodontal ligament damage under parafunctional and traumatic conditions of whole-mouth occlusions. A patient-specific evaluation

Background and objectiveAlthough traumatic loading has been associated with periodontal ligament (PDL) damage and therefore with several oral disorders, the damage phenomena and the traumatic loads involved are still unclear. The complex composition and extremely thin size of the PDL make experimentation difficult, requiring computational studies that consider the macroscopic loading conditions, the microscopic composition and fine detailed geometry of the tissue. In this study, a new methodology to analyse the damage phenomena in the collagen network and the extracellular matrix of the PDL caused by parafunctional and traumatic occlusal forces was proposed. MethodsThe entire human mandible and a portion thereof containing a full cuspid tooth were separately modelled using finite element analysis based on computed tomography and micro-computed tomography images, respectively. The first model was experimentally validated by occlusion analysis and subjected to the muscle loads produced during hard and soft chewing, traumatic cuspid occlusion, grinding, clenching, and simultaneous grinding and clenching. The occlusal forces computed by the first model were subsequently applied to the single tooth model to evaluate damage to the collagen network and the extracellular matrix of the PDL. ResultsEarly occlusal contact on the left cuspid tooth guided the mandible to the more occluded side (16.5% greater in the right side) and absorbed most of the lateral load. The intrusive occlusal loads on the posterior teeth were 0.77–13.3% greater than those on the cuspid. According to our findings, damage to the collagen network and the extracellular matrix of the PDL could occur in traumatic and grinding conditions, mainly due to fibre overstretching (>60%) and interstitial fluid overpressure (>4.7 kPa), respectively. ConclusionsOur findings provide important biomechanical insights into the determination of damage mechanisms which are caused by mechanical loading and the key role of the porous-fibrous behaviour of the PDL in parafunctional and traumatic loading scenarios. Besides, the 3D loading conditions computed from occlusal contacts will help future studies in the design of new orthodontics appliances and encourage the application of computing methods in medical practice.

Modeling and analysis of cutting force in vibration-assisted broaching (VAB)

This paper aims to present a predicted force model of vibration-assisted broaching (VAB). Based on the geometric features and kinetic characteristics of broach, the model focuses on three important points: (i) the cutting force of single tooth, (ii) the number of teeth in contact with the workpiece, and (iii) the influence of simple harmonic motion (SHM). Firstly, according to the empirical approach (EA) and the shear angle (SA) theory, two kinds of single-tooth model of broaching are built. Secondly, considering the length of cutting edge and the number of cutting tooth, two multi-tooth models based on the single-tooth models are presented. Then, with the influence of broach motion, the models of VAB force are finally established. Verification experiments are conducted for the developed force model and show that the calculated results of SA model are more agreeing well with the experimental values when vibration frequency increased. In addition, the VAB model is helpful in the application of vibration broaching.

Optimization of an Induction Hardening Process for a Steel Gear Component

Computer simulation of heat treatment processes has improved significantly over the past two decades, relating to both the material models and the database accuracy. Simulations are being used more aggressively in part and process design rather than just as a trouble shooting agent, meaning heat treat simulation is maturing as an accepted technology. In this paper, an induction heating and spray quenching process of a steel gear is optimized using the commercial heat treatment software DANTE. As a hardening process, induction hardening of steel parts is gaining popularity due to: (1) the process is consistent on a part-to-part basis, making it easier for quality control; (2) the process is more environmentally friendly than oil or polymer immersion quenching because a water spray is the typical cooling agent; and (3) fatigue life can be improved due to higher and deeper residual compression in the hardened surface. Two steel grades, AISI 5120 and AISI 5130, may be used in a thin-walled spur gear. The simplified heat treatment process includes vacuum carburization, controlled cooling to ambient, induction heating, and spray quenching. During induction heating, the internal heat generated by eddy currents is used as direct input to drive the thermal model. A sensitivity based optimization method is combined with heat treatment simulation to optimize the delay and spray quenching practice after induction heating. The objective function is defined to minimize the distortion of the gear tooth while satisfying the residual stress, gear surface temperature, and final microstructure requirements. The results of a two-dimensional (2D) plane strain single tooth model are evaluated during the optimization process, the quenching practice variables are adjusted, and the quenching model is re-run until the optimization function is satisfied. The residual stresses predicted after induction hardening are then mapped to a three-dimensional (3D) whole gear model as the initial stress state of a tooth loading model for predicting gear stresses. The significant effect on fatigue behavior due to residual stresses from heat treatment is addressed.

Mechanical responses to orthodontic loading: A 3-dimensional finite element multi-tooth model

The initial mechanical response to orthodontic loading comprises biologic reactions that remain unclear, despite their clinical significance. We used a 3-dimensional finite element analysis to investigate the stress-strain responses of teeth to orthodontic loading. The model was derived from computed tomography data, with adequate boundary conditions and tissue characterization, with orthodontic hardware to provide a more accurate reflection of events during orthodontic therapy. This study also incorporated the adjacent dentition. Two cases were analyzed: a single-tooth system with a mandibular canine, and a multi-tooth system consisting of the mandibular incisor, the canine, and the first premolar, subjected to orthodontic tipping forces. The systems experienced elevated distortion strain energies in the alveolar crest, whereas the tensile and compressive stresses coincided with the apical sites clinically associated with root resorption. Stress levels were considerably greater in the multi-tooth system than in the single-tooth system. The results for the single-tooth model agree with those previously reported. The numeric studies show how orthodontic tooth movement develops different stress fields and how root resorption might occur as a result of hydrostatic compressive stress-induced tissue necrosis.

Longitudinal Co-site Optical Microscopy Study on the Chelating Ability of Etidronate and EDTA Using a Comparative Single-tooth Model

In the present study the smear layer dissolution kinetics of 18% etidronate (HEBP), 9% HEBP, and 17% ethylenediaminetetraacetic acid (EDTA) on human dentin were quantitatively and longitudinally analyzed by using a single-tooth comparative model. Coronal dentin disks were prepared from 3 maxillary human molars. A standardized smear layer was produced on the pulpal side of each disk. The smear layer–covered surface was divided into 3 similar areas. Each of these was then exposed to 1 of the 3 irrigants under investigation, whereas the others were covered with adhesive tape. Co-site image sequences of the areas under investigation were obtained after several cumulative demineralization times. Sixteen images were obtained from each dentin area of each tooth for each experimental time at 1000× magnification. An image processing and analysis sequence measured sets of images, providing data of area fraction for thousands of tubules over time and allowing us to quantitatively follow the effect of the chelating substances. The Kruskal-Wallis H test and Dunn multiple comparison test were used to analyze the data. Overall, it can be concluded that the demineralization kinetics promoted by both 9% HEBP and 18% HEBP were significantly slower than those of 17% EDTA ( P < .05). In addition, the single-tooth model is advantageous over the first co-site optical microscopy dentin assessments when different chelator solutions are compared.

Innovative 3D Dental Measurement for Tooth Model Restoration

This research develops an innovative free-form surface scanning system using laser triangulation for 3D dental data required for crown reconstruction. This novel design employs double laser diodes to produce two 45° structured-light lines projecting onto the plaster tooth models and three CCD cameras to capture deformed fringes to achieve fast and accurate 3D surface measurement of plaster tooth models. Effective strategies were implemented to overcome problems such as potential measurement occlusion and data registration inaccuracy, commonly encountered by other data scanning methods. The developed system has distinctive features such as laser projecting angles for complete surface measurement coverage, digitizing accuracy, and compact scanner volume for potential applications on 3D surface digitization of tiny industrial components. Experimental results verified that the proposed system achieves a 20µm digitizing accuracy and possesses fast scanning capability. Maximum one minute is used for a single-tooth model and 30 minutes are used for scanning the whole jaw.