Symmetrical Teeth Research Articles

Assessment of mechanical allodynia in healthy teeth adjacent and contralateral to endodontically diseased teeth: a clinical study.

The present study investigated the prevalence of mechanical allodynia (MA) in healthy teeth adjacent and contralateral to endodontically diseased teeth. This cross-sectional study included 114 patients with symptomatic irreversible pulpitis and apical periodontitis in permanent mandibular first molars who possessed healthy teeth adjacent and contralateral to the endodontically diseased tooth. The mechanical sensitivity of the teeth was determined by percussion testing. The presence or absence of pain on percussion in the teeth adjacent and contralateral to the endodontically diseased tooth and the tooth distal to the contralateral symmetrical tooth was recorded according to coding criteria. The prevalence of MA was computed as a percentage, and binary logistic regression analysis was done. The Fisher exact test and Mann-Whitney U test were used for binary and ordinal data. Age and sex did not influence the prevalence of MA. An increased prevalence of MA was found in patients with higher levels of spontaneous pain (p < 0.001). The prevalence of allodynia was 57% in teeth adjacent to endodontically diseased teeth and 10.5% in teeth contralateral to endodontically diseased teeth. In addition, on the ipsilateral side, there were more painful sensations distal to the diseased tooth than mesially. Despite being disease-free, teeth adjacent and contralateral to endodontically diseased teeth exhibited pain on percussion. There was a direct association between the severity of the patient's pain and the presence of MA.

Symmetry of pathological processes in the oral cavity

The human dentition is characterized by bilateral symmetry, inextricably linked with the equivalent functional load falling on the right and left sides of the row. Some articles of domestic and foreign authors contain conclusions that testify to the symmetry of the carious process in the oral cavity. However, these data are collected on different populations, an incomplete set of teeth and using a limited range of diagnostic methods. The aim of this work was to determine the distribution of a symmetrical carious process in a population of Russian patients of different ages using a wide range of diagnostic tools. Materials and methods. To achieve this goal, 403 patients were examined: 167 men and 236 women. The mean age was 27.37±12.09. In addition to the examination, patients were prescribed an orthopantomogram, and, according to indications, a cone-beam computed tomography. Results. After examination and analysis of orthopantomography images, symmetrical caries was found in 386 patients. In 17 examined patients, symmetrical caries was not detected, and therefore patients were additionally prescribed cone-beam CT. Ultimately, signs of a symmetrical carious lesion were detected in all 100% of patients. Discussion. Our results confirm the data of other researchers on the presence of the symmetry phenomenon in the development of carious processes. Conclusions: 1) When a carious process occurs and develops, in 100% of cases there are signs of damage to the hard tissues of both symmetrical teeth. 2) The use of cone beam computed tomography makes it possible to finally confirm the symmetry of the carious process, and this method should be included in the mandatory standard for diagnosing caries in dental institutions. 3) Asymmetry of the carious process can occur only in cases of unilateral/asymmetrical traumatic or other lesions in the maxillofacial region in history. 4) Microorganisms should not be considered the causes of a symmetrical carious lesion, since they realize their pathogenic effects already in altered tooth tissues, in violation of the integrity of the enamel, pulp trophism, etc.

The Effect of Ground and Unground Enamel on the Clinical Performance of Direct Composite Build-up After Orthodontic Treatment: Five Years of Follow-up.

To assess the clinical performance of restorations with ground and unground enamel for diastema closure. Twenty-four patients attended and received two to ten composite build-ups for diastema closure. The restorations were performed separately by grinding and not grinding the enamel on the proximal surfaces on symmetric teeth. A nanofill direct composite (Filtek Ultimate Universal Restorative System, 3M ESPE, St Paul, MN, USA) was used with a three-step etch-and-rinse adhesive (Scotchbond Multi-Purpose, 3M ESPE) for restorations. Restorations were evaluated according to the modified United States Public Health Service (USPHS) criteria at baseline and 1-, 2-, 3-, 4-, and 5-year recalls. The cumulative success rate of direct composite build-up with ground and unground enamel was 100% and 88.7%, respectively. Six restorations with unground enamel failed due to fracture. No significant difference was found between the restorations with ground enamel and unground enamel with regard to the evaluation criteria. The 5-year success rates of restorations with ground and unground enamel were excellent. The success rate of restorations with ground enamel was higher than that of restorations with unground enamel. Fracture was the reason for failure in the restorations with unground enamel.

Evaluation of human growth hormone (somatropin) in socket healing: a split-mouth randomized controlled trial.

The study is designed as a split-mouth randomized clinical trial. The selected patients were indicated for bilateral symmetrical tooth extraction, where each patient had an indication to extract two symmetrical teeth in anatomy and number of roots. Somatropin was applied to the tooth socket of the randomly selected side after tooth extraction by gel foam, and the control side was filled with gel foam only. A clinical follow-up of the soft tissue was done 7 days after tooth extraction to evaluate clinical aspects of the healing process. Radiographic follow-up was performed using a cone-beam computed tomography scan to assess volumetric changes of alveolar bone in the extraction area prior to and 3 months after the surgical procedure. A total of 23 patients (aged 29.1±9.5 years) participated. The results showed a statistically significant association between somatropin application and better preservation of the bony dimensions of the alveolar ridge. Bone loss was -0.691±0.628mm for the buccal plate on the study side compared to -2.008±1.175mm on the control side. The level of the lingual/palatal plate bone loss was -1.052±0.855mm on the study side compared to -2.695±1.878mm on the control side. The bone loss of alveolar width was -1.626±1.061mm on the study side compared to -3.247±1.543mm on the control side. The results also showed better healing of covering soft tissues (P<0.05), as well as bone density in the socket where somatropin was applied, which has been statistically significant. The data from this study demonstrated that the application of somatropin in tooth sockets postextraction showed an effective contribution to reducing alveolar bone resorption and improving bone density following extraction, in addition to better healing of covering soft tissue.

Measurement and analysis of maxillary anterior teeth color in the chinese population.

To measure the difference in the crown color of the maxillary anterior teeth in the Chinese population, to study its potential regularity, and to provide a reference for the colorimetry of oral anterior teeth restoration. Using VITA Easyshade Advance4.0 spectrophotometer (the colorimetric system is CIE-1976-L*a*b*), adult patients who were treated in Sanming Integrated Medicine Hospital, Fujian Province, China, from January 2022 to June 2022 160 patients (88 males, 72 females, aged 20-60 years) were used as the survey subjects, and the L*a*b* of 1/3 of the crowns of 6 anterior teeth (central incisors, lateral incisors, canines) were measured Value, statistical analysis was performed with SPSS 26.0 software. The mean L* values of maxillary central incisors, lateral incisors, and canines in the Chinese population were: (73.02±4.41), (69.96±4.70), (65.14±4.21); the mean a* values were: (-0.54±4.21) 0.35), (0.22±0.63), (1.40±0.62), and the mean values of b* were: (14.50±3.23), (18.60±3.94), (23.64±3.30). 1. There was no significant difference in L*a*b* value between left and right symmetrical teeth with the same name (P>0.05). 2. There was no statistical difference in the L*a*b* value between genders (P>0.05), 3. There was a statistical difference in L*a*b* value between different tooth positions (P< 0.05). 4. There were significant differences in L*a*b* values in different age groups (P< 0.05). 1. The color of the labial crown of maxillary anterior teeth in the Chinese population is related to different age groups and tooth positions but not gender. 2. In the Chinese population, the color of the maxillary anterior teeth on the labial side gradually decreased from the central incisor to the distal end of the dental arch while the chroma gradually increased. 3. With age increase, the L* and a* values of the upper central incisors, upper lateral incisors, and upper canines gradually decrease, and the b* value gradually increases. The teeth became darker, more yellow, and redder. 4. In the clinical colorimetry of the upper anterior teeth, the contralateral tooth with the same name is preferred. Suppose the tooth with the same name is missing at the same time. In that case, when using the adjacent teeth as a reference, the different brightness and chroma between the central incisors, lateral incisors, and canine teeth should be compared. Change trend to determine. 5. A uniform tooth color should not be selected for anterior restoration, and age should be considered when choosing a color for the patient. Key words:Upper anterior teeth, Crown color, CIE-1976-L*a*b*, spectrophotometric colorimeter.

Determining The Sex of a Person by Odontometric Parameters Using Logistic Regression Equations

The development of personal identification methods based on bone remains, which are used to diagnose the population of Azerbaijan, is a priority task due to the unresolved issue. In this scenario, a new method for quickly determining sex by teeth is in demand, as it should increase the efficiency of the work of forensic experts. The purpose of this study was to develop modern methods for diagnosing human sex using odontometric studies. At the craniological collection of Azerbaijanis, the sizes of teeth were studied. On 7 teeth of the upper and 7 teeth of the lower jaw, 3 parameters were measured (in this case, symmetrical teeth were considered as a single array). Each of the 14 anatomical teeth was represented by 80 male and 80 female teeth. For odontometric procedures, a Mutitouyo digital caliper (accuracy 10 microns) was used. The results of odontometry were analyzed by statistical methods using ROC analysis. Mathematical modeling was carried out using the MATLAB statistical software package. With the help of ROC-analysis, the data obtained during odontometry were considered. 6 odontometric signs were established, which are interconnected with gender. The most correlated with gender were the bucco-lingual diameter of the upper canine, as well as the heights of the crowns – the second lower molar, lower incisors, lower canine and upper medial incisor. Using mathematical modeling, we have developed 6 logistic regression equations that can be used to determine the gender of a person by the size of his teeth. The predictive potential of the equations was also evaluated using ROC analysis procedures. As a result of the study, based on odontometric indicators and by using ROC analysis, diagnostic equations were obtained to determine the sex of a person by the size of the teeth. The equations have not yet been verified on independent samples, so they cannot yet be unconditionally recommended for practice. Nevertheless, the authors count on the high legitimacy of their own models due to the fact that they used a fairly powerful mathematical apparatus.

Determination of human sex by odontometric characteristics using equations of logistic regression

BACKGROUND: The development of methods for identifying a person based on bone remains, which are adapted for diagnosing the population of Azerbaijan, is a priority in view of the incompleteness of solving this problem. In this situation, a new way to quickly determine the sex by teeth appears to be in demand because it should increase the efficiency of the work of forensic doctors.&#x0D; AIM: To develop a modern technique for diagnosing a persons sex using odontometric signs.&#x0D; MATERIALS AND METHODS: Teeth sizes were studied at the craniological collection of Azerbaijanis. On the seven teeth of the upper and seven teeth of the lower jaw, three parameters were measured (while symmetrical teeth were considered a single array). Each of the 14 anatomical teeth was represented by 80 male and 80 female teeth. A digital caliper (Mutitouyo; accuracy 10 microns) was used for odontometric procedures. Odontometry results were analyzed by statistical methods using receiver operating characteristics curve analysis. Mathematical modeling was conducted using the MATLAB statistical software package.&#x0D; RESULTS: With the help of the receiver operating characteristic curve (ROC) analysis, the data obtained in the course of odontometry were studied. Six odontometric signs were related to sex. The most sex-related parameters were the buccolingual diameter of the upper canine, heights of the crowns of the second lower molar, lower incisors, lower canine, and upper central incisor. Using mathematical modeling, six logistic regression equations have been implemented, which help determining the sex of an individual by the size of his teeth possible. The predictive potential of the equations was also assessed using the ROC analysis.&#x0D; CONCLUSION: Based on odontometric indicators and ROC analysis, diagnostic equations for determining the sex of a person by the teeth size were obtained. The equations have not yet been verified on independent samples; therefore, they cannot yet be unconditionally recommended for practice. Nevertheless, the authors count on the high legitimacy of their models because they used a fairly powerful mathematical apparatus.

Semantic Graph Attention With Explicit Anatomical Association Modeling for Tooth Segmentation From CBCT Images.

Accurate tooth identification and delineation in dental CBCT images are essential in clinical oral diagnosis and treatment. Teeth are positioned in the alveolar bone in a particular order, featuring similar appearances across adjacent and bilaterally symmetric teeth. However, existing tooth segmentation methods ignored such specific anatomical topology, which hampers the segmentation accuracy. Here we propose a semantic graph-based method to explicitly model the spatial associations between different anatomical targets (i.e., teeth) for their precise delineation in a coarse-to-fine fashion. First, to efficiently control the bilaterally symmetric confusion in segmentation, we employ a lightweight network to roughly separate teeth as four quadrants. Then, designing a semantic graph attention mechanism to explicitly model the anatomical topology of the teeth in each quadrant, based on which voxel-wise discriminative feature embeddings are learned for the accurate delineation of teeth boundaries. Extensive experiments on a clinical dental CBCT dataset demonstrate the superior performance of the proposed method compared with other state-of-the-art approaches.

A digital workflow for pair matching of maxillary anterior teeth using a 3D segmentation technique for esthetic implant restorations

We investigated a state-of-the-art algorithm for 3D reconstruction with a pair-matching technique, which enabled the fabrication of individualized implant restorations in the esthetic zone. This method compared 3D mirror images of crowns and emergence profiles between symmetric tooth pairs in the anterior maxilla using digital slicewise DICOM segmentation and the superimposition of STL data. With the outline extraction of each segment provided by 100 patients, the Hausdorff distance (HD) between two point sets was calculated to identify the similarity of the sets. By using HD thresholds as a pair matching criterion, the true positive rates of crowns were 100, 98, and 98%, while the false negative rates were 0, 2, and 2% for central incisors, lateral incisors, and canines, respectively, indicating high pair matching accuracy (> 99%) and sensitivity (> 98%). The true positive rates of emergence profiles were 99, 100, and 98%, while the false negative rates were 1, 0, and 2% for central incisors, lateral incisors, and canines, respectively, indicating high pair matching accuracy (> 99%) and sensitivity (> 98%). Therefore, digitally flipped contours of crown and emergence profiles can be successfully transferred for implant reconstruction in the maxillary anterior region to optimize esthetics and function.

Validation and Profile Modification of a Spur Gear to Improve the Gear Tooth Strengths

The idea of using asymmetric tooth forms has gained momentum in gearing design. Similar to symmetric basic rack gears, tooth action parameters are established in the first stage. The second stage involves calculating the unified generating basic rack for a set of mated gears. In some cases, it is possible to determine the features of specific fundamental rack tooth profiles for each gear in a transmission. Gearings with asymmetrical profiles have the advantage of having a higher-pressure angle than operational profiles (as a result of a lower pressure angle than non-operating profiles) and the possibility for a considerable improvement in the face contact ratio. In this study, symmetric and asymmetric tooth profiles will be compared using the finite element analysis tool Ansys. Asymmetric (different pressure angle) and symmetric (different pressure angle) tooth profiles will be designed and built in the 3D modelling software CATIA. The designs made with different materials will go through structural examination (mild steel and EN 32 steel).

The effectiveness of logistic regression equations for solving problems of determining the sex of a person by odontometric parameters

New methods of personal identification based on bone remains are always of interest to researchers. The new method proposed by us for rapid determination of sex by teeth is also likely to be in demand, since it should increase the efficiency of the work of forensic experts.The purpose of this study was to develop modern methods for diagnosing human sex using odontometric studies.At the craniological collection of Azerbaijanis, the sizes of teeth were studied. On 7 teeth of the upper and 7 teeth of the lower jaw, 3 parameters were measured (in this case, symmetrical teeth were considered as a single array). Each of the 14 anatomical teeth was represented by 1120 male and 1120 female teeth. For odontometric procedures, a Mutitouyo digital caliper (accuracy 10 microns) was used. The results of odontometry were analyzed by statistical methods using ROC analysis. Mathematical modeling was carried out using the MATLAB statistical software package.With the help of ROC-analysis, the data obtained during odontometry were considered. 6 odontometric signs were established, which are interconnected with gender. The most correlated with gender were the bucco-lingual diameter of the upper canine, as well as the heights of the crowns – the second lower molar, lower incisors, lower canine and upper medial incisor. Using mathematical modeling, we have developed 6 logistic regression equations that can be used to determine the gender of a person by the size of his teeth. The predictive potential of the equations was also evaluated using ROC analysis procedures.As a result of the study, based on odontometric indicators and by using ROC analysis, diagnostic equations were obtained to determine the sex of a person by the size of the teeth. The authors have not yet tested the effectiveness of the equations on independent samples of skulls, so they cannot yet be unconditionally recommended for practice. However, they count on the high legitimacy of their own models, because they used a fairly powerful mathematical apparatus.

Magnetic Equivalent Circuit Modelling of Synchronous Reluctance Motors

This paper proposes a modelling technique for Synchronous Reluctance Motors (SynRMs) based on a generalized Magnetic Equivalent Circuit (MEC). The proposed model can be used in the design of any number of stator teeth, rotor poles, and rotor barrier combinations. This technique allows elimination of infeasible machine solutions during the initial machine sizing stage, resulting in a lower cohort of feasible machine solutions that can be further optimized using finite element methods. Therefore, saturation effects, however, are not considered in the modelling. This paper focuses on modelling a generic structure of the SynRM in modular form and is then extended to a full SynRM model. The proposed model can be iteratively used for any symmetrical rotor pole and stator teeth combination. The developed technique is applied to model a 4-pole, 36 slot SynRM as an example, and the implemented model is executed following a time stepping strategy. The motor characteristics such as flux distribution and torque of the developed SynRM model is compared with finite elemental analysis (FEA) simulation results.

Sprocket with asymmetric teeth for roller chain drives of vehicles

The analysis of results of experimental research of vehicle roller chain drives equipped with sprockets with symmetric teeth is presented in first part of this article. It is proved, that sprocket tooth profile influences significantly the distribution of the payload between the chain hinges and the sprocket teeth. It is suggested that sprockets with asymmetric teeth provide a more rational payload distribution between the chain and the sprocket. The second part of the article contains a description of the methodology for determining the optimal angles of sharpening of the asymmetric sprocket tooth profiles for roller chain drives. The preliminary results of experimental studies of the operability of chain drives equipped with sprockets with asymmetric teeth are also presented.

Effect of Propolis Paste and Mouthwash Formulation on Healing after Teeth Extraction in Periodontal Disease.

This study investigated the antimicrobial effects of a mouthwash containing propolis and the effect of a propolis paste formulation on dental healing after teeth extraction in patients with periodontal disease. In the mouthwash experience, the population comprised 40 patients, which were divided as follows: the control mouthwash, 0.2% chlorhexidine (v/v) mouthwash, 2% (w/v) propolis mouthwash, and propolis + chlorhexidine mouthwash. The study of the propolis paste comprised a population of 60 patients with periodontal disease, and a total of 120 symmetric tooth extractions were performed. Propolis showed antimicrobial activity by itself, and especially with the chlorhexidine association. Three days after surgery in the teeth treated with control paste, only 13.4% had completely healed; however, with propolis paste, in 90% of the periodontal sockets, healing was complete. In addition, a reduction in Streptococci mutans and Lactobacilli cfu was observed with propolis, and especially with the association of chlorhexidine + propolis. Propolis mouthwash reduced bacterial proliferation, especially in association with chlorhexidine. Propolis paste is a viable alternative for socket healing after dental extraction. The knowledge gained from these findings will provide a foundation for similar propolis therapies in order to improve the healing process after dental surgery.

Performance analysis of asymmetric toothed strain wave gear

Strain Wave Gear (SWG) or Harmonic Drive (HD) shows moderate performance under symmetrical involute teeth. Teeth interference, excessive teeth meshing, vibration due to improper teeth engagement are the major drawbacks of strain wave gear under symmetrical involute teeth. In the present paper, an attempt has been made to improve the performance of strain wave gear by replacing the symmetrical involute teeth with asymmetrical involute teeth. Present investigation finds that under ‘asymmetric toothed strain wave gear’, aspects such as teeth interference, teeth engagement and teeth contact stress of strain wave gear are improving clearly and as a consequence some other aspects such as individual teeth strength, load carrying capacity, tooth endurance are also improving inherently. In the present analysis for symmetrical teeth 20°–20° pressure angle and for asymmetrical teeth, three different combinations of pressure angles such as 25°–20°, 30°–20° and 35°–20° are taken.

Numerical analysis of magnetic grease seal pole teeth optimization based on pressure bearing capacity

The static magnetic field model of the magnetic grease seal was established by the nonlinear magnetic field finite element method. The influence of three typical pole teeth with different seal gaps, namely rectangular teeth, single-side trapezoid, and symmetrical teeth, on pressure bearing capacity was analyzed. The results show that the maximum pressure bearing capacity of the optimized structure is from large to small: symmetric trapezoid teeth, single-sided trapezoid teeth, rectangular teeth. The seal gap increased by 0.1 mm and pressure bearing capacity decreased by 12 %. If the teeth width was doubled, the pressure bearing capacity can be increased by 17.8%, with an optimum range of 1.8 mm to 2.2 mm. The interval length of the teeth doubled, the pressure bearing capacity increased by 30.65 %, and the optimum range for the interval length of the teeth was 1.8 mm to 2.0 mm. There was no significant correlation between teeth height and pressure bearing capacity. The study on the optimization of the teeth structure based on pressure bearing capacity could provide a reference for technical personnel to improve the efficiency and rationality of the design of the teeth for the sealing of the magnetic grease.

Computerized Generation of Asymmetric Straight Bevel Gear

To carry out any type of analysis and study the gear drives, the primary steps include the graphical representation of the gear drive under consideration. In this study, the mathematical formulations of the tooth surface, tooth root surface, and tooth root transition surface of symmetric straight bevel gear were formulated based on the planning principle. The proposed modification has been done on the mathematical formulation of the symmetric tooth profile to consider the effect of asymmetric tooth profiles (which are characterized by different pressure angles on the loaded and unloaded sides). As a result of this study, a computer program based on the above mathematical formulation has been built to represent the final shape of symmetric and asymmetric teeth profiles of straight bevel gear for different design parameters.

Evidence on vegetative and inflorescence morphology of Chloranthaceae (Angiospermae) from the Early Cretaceous (middle–late Albian) of Spain

The near-basal angiosperm family Chloranthaceae (with four living genera) is prominently represented in the Early Cretaceous fossil record by pollen and flowers, but its leaves, other vegetative parts and inflorescences are less well known. Here, we report impressions of leaves, stems and inflorescences from the middle–late Albian Escucha Formation of Teruel Province (NE Spain) that help redress this imbalance and bring into clearer focus the morphological and systematic diversity of this key group in the early angiosperm radiation. We used parsimony analysis of a morphological dataset of living and fossil Chloranthaceae to evaluate the position of the fossils on a molecular-based tree of extant taxa. Todziaphyllum elongatum gen. et sp. nov., with festooned semicraspedodromous venation and asymmetrical chloranthoid teeth, is most parsimoniously placed on the stem lineage of the living genus Hedyosmum. Leaves of Alcainea eklundiae gen. et sp. nov., with festooned semicraspedodromous venation and symmetric teeth, occur attached to stems in opposite pairs at swollen nodes with sheathing leaf bases and interpetiolar stipules, along with compound spikes of flowers with a monosymmetric androecium of three stamens, each flower subtended by a bract. This represents the first time that fossil leaves, stems and inflorescences of Chloranthaceae have been found in organic connection. Alcainea may be sister to Sarcandra, Chloranthus or the clade consisting of both genera, like the mesofossil Canrightiopsis. Leaf Type A, with festooned craspedodromous venation and symmetrical teeth, may be related to Ascarina. These observations provide direct evidence for the distinctive vegetative and inflorescence morphology of Chloranthaceae in the Early Cretaceous. They are consistent with the level of diversification inferred from coeval chloranthaceous pollen and floral mesofossils, including lines nested in crown group Chloranthaceae but not in any of living genera, and exhibiting character combinations not retained in living Chloranthaceae. http://zoobank.org/urn:lsid:zoobank.org:pub:08B96BA0-3B27-48A1-9E8F-CB5811AE8C07

Coordinated labio-lingual asymmetries in dental and bone development create a symmetrical acrodont dentition

Organs throughout the body develop both asymmetrically and symmetrically. Here, we assess how symmetrical teeth in reptiles can be created from asymmetrical tooth germs. Teeth of lepidosaurian reptiles are mostly anchored to the jaw bones by pleurodont ankylosis, where the tooth is held in place on the labial side only. Pleurodont teeth are characterized by significantly asymmetrical development of the labial and lingual sides of the cervical loop, which later leads to uneven deposition of hard tissue. On the other hand, acrodont teeth found in lizards of the Acrodonta clade (i.e. agamas, chameleons) are symmetrically ankylosed to the jaw bone. Here, we have focused on the formation of the symmetrical acrodont dentition of the veiled chameleon (Chamaeleo calyptratus). Intriguingly, our results revealed distinct asymmetries in morphology of the labial and lingual sides of the cervical loop during early developmental stages, both at the gross and ultrastructural level, with specific patterns of cell proliferation and stem cell marker expression. Asymmetrical expression of ST14 was also observed, with a positive domain on the lingual side of the cervical loop overlapping with the SOX2 domain. In contrast, micro-CT analysis of hard tissues revealed that deposition of dentin and enamel was largely symmetrical at the mineralization stage, highlighting the difference between cervical loop morphology during early development and differentiation of odontoblasts throughout later odontogenesis. In conclusion, the early asymmetrical development of the enamel organ seems to be a plesiomorphic character for all squamate reptiles, while symmetrical and precisely orchestrated deposition of hard tissue during tooth formation in acrodont dentitions probably represents a novelty in the Acrodonta clade.

Prediction of injection molding parameters for symmetric spur gear.

Polymer gears pose major advantages, like noiseless operation, resistive against corrosion, low weight, ability to damp vibrations, ease of manufacturability, and ability to operate without lubrication like in printers, household appliances, etc. In order to enhance mechanical properties of gear materials, various reinforcing materials are added such as glass and carbon fibers. The orientation of these fibers and distribution are critical parameters at the microstructural level for polymer reinforced with short fibers, which defines the strength and life of gears. The geometric accuracy and precision of molded gears are improved by the injection molding technique. The fiber orientation prediction is a new and novel aspect for high performance and life, as these injection-molded gears have complex patterns of fiber orientation. This also affects material properties such as elastic modulus, strength, and gear geometrical dimensional properties shrinkage and warpage. In this present work, an attempt is made to develop 3D symmetric spur gear tooth geometry using Autodesk Fusion 360. The injection molding parameters such as fiber orientation tensor, volumetric shrinkage at ejection, weld lines, deflection, and confidence in filling are studied for modeled gear having symmetric teeth profile for unreinforced and 20%, 30%, 40%, 50%, and 60% glass fiber-reinforced nylon 6/6 (PA66) by using Autodesk Moldflow Adviser 2017. The result obtained from mold simulation tool indicates that fiber orientation tensor for varying glass fiber contents was close to unity. The volumetric shrinkage considerably reduced from unreinforced PA66 to glass-reinforced PA66.Graphical abstract.