Tooth Space Research Articles

Abstract #1395486: Uncontrolled Acromegaly Resulting in the Need for LVAD as Bridge to Heart Transplant

Acromegaly is an uncommon pituitary disorder with an incidence of six per million persons. While hypertension is often encountered in these patients, heart failure rarely is seen with an incidence rate under 10%. We describe a case of an individual who was diagnosed with acromegaly after an acute exacerbation of heart failure with subsequent management requiring an LVAD to perform Transsphenoidal Surgery (TSS). 37-year-old male otherwise healthy initially presented to an emergency room and was found to be in acute heart failure exacerbation. Concerning acromegaly features included macrognathia, enlarged hands and feet, swollen phalanges, widened spacing of teeth, and frontal bossing. IGF-1 level was found 455 ng/mL. MRI showed a 10mm macroadenoma. A right heart catheterization showed elevated filling pressures. Cardiac MRI showed no defects or enhancement. Endomyocardial biopsy showed no inflammatory infiltrates or evidence of infiltrative diseases. Patient had an ejection fraction of 15% corroborated by cardiac MRI along with the presence of aortic root dilatation and mitral regurgitation. The patient started on 0.5mg of Cabergoline twice weekly and 120mg weekly Lanreotide injections. Patient stabilized with plans for further close monitoring and outpatient neurosurgical evaluation. The COVID-19 pandemic and insurance gaps led the patient to spend two years off his medicines and he was unable to be seen by his medical team. Patient was seen by our system after recurrent hospitalizations for heart failure at our sister hospital, AICD was unable to be placed due to the patient’s anatomy, he was placed on wearable cardiac defibrillator and required milrinone infusion for progression to end-stage heart failure with cardiac cachexia. At our institution, the patient was evaluated for Orthotopic Heart Transplant (OHT) but due to active GH secreting macroadenoma there was concern for OHT failure without TSS. Decision was made to utilize LVAD as Bridge-to-Transplant for OHT so the patient could be stabilized and safely undergo TSS. The patient tolerated surgeries well and is currently on the active transplant list. Heart failure is an uncommon presentation of severe acromegaly requiring multidisciplinary management. We describe a case of a patient who initially presented with heart failure too unstable for surgery. Due to the COVID-19 pandemic the patient’s disease progressed resulting in end-stage heart failure requiring LVAD placement for further treatment. We would like to draw attention to the use of LVAD placement in acromegalic patients who develop severe cardiovascular disease who are not candidates for OHT.

Abstract #1401779: Rare Case of Functional Gonadotroph Adenoma

Of all pituitary adenomas, approximately 25-35% are clinically nonfunctioning or "silent" and of those approximately 70-90% are gonadotropin adenomas making them the most common nonfunctional pituitary macroadenoma. However, it is important to know that gonadotropin adenomas can be functional and that gonadotropin excess can result in clinical symptoms and lab abnormalities. This case demonstrates an example of a functional gonadotropin pituitary adenoma overproducing FSH resulting in high-normal testosterone level in addition to compressive symptoms of the optic chiasm. 57-year-old African-American male with pre-diabetes mellitus and gout (only home meds are allopurinoL 300 MG once daily and indomethacin 50 MG three times daily) presented for evaluation of vision loss and large sellar mass on MRI. Vision loss first noted January 2022 along with occasional headaches for 3-4 months (no headaches prior). Patient eventually saw a neuro-ophthalmologist for visual field testing demonstrating left field deficits concerning for optic nerve compression. He then underwent orbital MRI which demonstrated a large sellar mass extending into bilateral cavernous sinus and effacing and displacing the optic chiasm. During visit, patient admitted to fatigue, constipation, polyuria, and nocturia. He denied‌ breast tenderness, nipple discharge, weight change, temp intolerance, skin/hair change, palpitations, tremors, increase hand/foot size, teeth spacing change, worse glycemic control, hypertension, joint pain, acne, hirsutism, striae, clotting disorders, fractures, decreased libido, or erectile dysfunction. He had no known allergies. Blood pressure109/83 | Pulse 101 | Ht 5' 10" (1.778 m) | Wt 88.2 kg (194 lb 7.1 oz) | SpO2 97% | BMI 27.90 kg/m2. Physical exam: Visual fields intact to confrontation but with some patchy deficits in the left eye only. No other notable findings. Subsequent labs demonstrated appropriate cortisol 11.8 ng/dL with normal ACTH of 17 pg/mL, normal IGF-1 of 95 ng/mL, normal TSH of 1.6 uIU/mL with normal free T4 of 0.8 ng/dL. However, prolactin was mildly elevated at 36.5 ng/mL (presumably from stalk effect given size of tumor) and FSH was impressively elevated at 70.3 mIU/mL with a normal LH of 6.5 mIU/mL and a high-normal total testosterone level of 890 ng/dL which was highly suggestive an FSH-producing functional gonadotropin adenoma. It is important to realize the efficacy of surgical resection of functional non-prolactinoma pituitary tumors, especially when the optic chiasm is involved. Patient underwent transsphenoidal resection of pituitary adenoma and indeed pathology revealed a gonadotroph adenoma with SF1 and alpha subunit. He reported slightly improved vision in left eye and had some residual occasional headaches. Awaiting post-operative labs but anticipate normalization of prolactin and FSH and a likely decrease in testosterone level. Awaiting post-operative visual field testing to demonstrate objective improvement. These should be available by the time of the conference.

Application of grey relational analysis and Taguchi method in cutter working parameters for tea-leaf mechanical harvester

The tea tree is a type of horticultural crop and agricultural crop, its leaves are used to be an important ingredient in many beverages. However, the tea-leaf harvest is mainly accomplished by hands, which has an enormous impact on the yield of tea leaves. The wide application of tea-leaf mechanical harvester could improve the harvest efficiency of the tea-leaf, and then increase the harvest yield of the tea-leaf. To improve the harvest yield of the tea-leaf, the working parameters (structural and kinematic parameter) of the cutter on tea-leaf mechanical harvester need to be considered. And the cutting diagram of the cutter was used to optimize the working parameters. In this paper, the tooth top width, tooth root width, tooth depth, teeth space and cutting speed ratio were selected as working parameters of cutter that were considered to enhance the harvest efficiency. Taguchi method coupled with grey relational analysis (GRA) was used to determine the optimal combination of working parameters. Besides, the variance analysis method was performed to statistical analyse the influence of multiple parameters. The results showed that the key parameters of the variation of cutting, re-cutting and blank ratio was the teeth space. The optimal parameter combination was 4.5 mm tooth top width, 12.5 mm tooth root width, 26.0 mm tooth depth, 45.0 mm teeth space and 0.8 cutting speed ratio. Grey relational grade of the optimal parameter combination increased 0.367 compared to the grade with initial parameter combination. Based on the optimal parameter combination, the tea-leaf harvest flatness, efficiency and quality were completely in conformity with the requirements of the tea-leaf mechanical harvester. So that, the Taguchi method coupled with GRA is a practical one to optimize the working parameters of the cutter on the tea-leaf mechanical harvester.

LncRNA XIST regulates osteoclast formation and promotes orthodontically induced inflammatory root resorption through miR-130b-3p/PTEN axis

ABSTRACT The long non-coding RNA (LncRNA) X-inactive specific transcript (XIST) regulates the biological process of osteoclasts and the process of related diseases. This study was attempted to investigate the mechanism of LncRNA XIST acting in osteoclast formation and orthodontic induced inflammatory root resorption (OIIRR). The compression force (CF) -induced cell model and the orthodontic tooth movement (OTM) rat model were designed and established in this study. The expression of LncRNA XIST, miR-130b-3p, phosphatase and tensin homolog deleted on chromosome 10 (PTEN) as well as osteoclast related marker genes and inflammatory factors level were measured in this study. The interaction among LncRNA XIST, microRNA-130b-3p (miR-130b-3p) and PTEN were researched through luciferase activity and western blot assay. Pathological sections were used to analyze root resorption and osteoclast formation. The OTM rat model was successfully constructed, which was characterized by increased tooth spacing and increased root resorption pits. PTEN and LncRNA XIST was overexpressed in OTM group. Mechanism analysis showed that the overexpression of LncRNA XIST enhanced the PTEN level by sponging miR-130b-3p. The overexpression of LncRNA XIST increased the secretion of inflammatory factors and positive osteoclasts number, but inhibited the differentiation of osteoclasts by sponging miR-130b-3p and promoting the level of PTEN. This finding demonstrates that LncRNA XIST regulates osteoclast formation and aggravated OIIRR through miR-130b-3p/PTEN axis, suggesting that LncRNA XIST may be used as potential targets for OIIRR therapy.

Casing failure mechanism and slip anchoring optimization of the compression packer in the oil and gas well

The packer is a key tool to isolate downhole pressure during well testing and completion operations. The compression packer in the oil and gas wellbore needs to be anchored by hard contact between the slips and the casing when setting, which will cause the casing to suffer from occlusal damage and shorten the working life. It is necessary to combine casing damage and anchoring performance of the slip, select suitable packer slip material, and optimize its structural parameters to reduce casing hard contact damage and increase the working life of the slips and casing. Based on mechanical analysis and hard contact mechanism of the slip during the packer setting process, and selecting the slip material lower than the mechanical properties of the casing material, a finite element analysis model of interaction between the slips and the casing was established. The changes of slip equivalent plastic strain, maximum Mises stress, and CPRESS stress under three parameters of slip tooth number, tooth space, and tooth top angle were comprehensively evaluated. The results of analysis show that with the increase in the tooth number of slips, the tooth space or the top angle, the bending moment of slips increased, and the anchoring performance decreased. As the tooth number of slips, the tooth space or the top angle decreased, the damage of slip teeth increased. The combination optimization analysis of the above parameters was carried out using the orthogonal experiment method, and the optimal top angle of the slip structure of the compression packer is 90°, the tooth space is 4 mm, and the tooth number is 20. Compared with the anchoring performance of soluble metal slips, the optimized slips significantly reduce the damage to the casing. The study will provide a theoretical basis and date support for further analysis of the anchoring performance of the slip, the reduction of casing damage, and the design of new slips.

Efficacy of a four-curvature auxiliary arch at preventing maxillary central incisor linguoclination during orthodontic treatment: a finite element analysis

BackgroundCorrect torque of the incisors is beneficial in the assessment of the effects of orthodontic treatment. However, evaluating this process effectively remains a challenge. Improper anterior teeth torque angle can cause bone fenestrations and exposure of the root surface.MethodsA three-dimensional finite element model of the maxillary incisor torque controlled by a homemade four-curvature auxiliary arch was established. The four-curvature auxiliary arch placed on the maxillary incisors was divided into four different state groups, among which 2 groups had tooth extraction space retracted traction force set to 1.15 N. Initial displacements and pressure stresses of the periodontal tissue in the maxillary incisors and molars were calculated after torque forces (0.5, 1, 1.5, and 2 N) were applied to the teeth at different stable states.ResultsThe effect of using the four-curvature auxiliary arch on the incisors was significant but did not affect the position of the molars. Given the absence of tooth extraction space, when the four-curvature auxiliary arch was used in conjunction with absolute anchorage, the recommended force value was < 1.5 N. In the other 3 groups (i.e., molar ligation, molar retraction, and microimplant retraction groups), the recommended force value was < 1 N. The application of a four-curvature auxiliary arch did not influence the molar periodontal and displacement.ConclusionA four-curvature auxiliary arch may treat severely upright anterior teeth and correct cortical fenestrations of the bone and root surface exposure.

Effect of filament types and loops number on the force degradation of elastomeric chains used for orthodontic treatment: an in-vitro study

BackgroundIn orthodontic treatment, closing spaces, specifically the extraction and scattered spaces of the anterior teeth, requires some auxiliary bias, such as an elastomeric chain. Many factors affect the mechanical properties of elastic chains. In this study, we investigated the relationship of the filament type, the number of loops, and the force degradation of elastomeric chains under thermal cycling conditions.MethodsThe orthogonal design included three filament types (i.e., close, medium, and long). Four, five, and six loops of each elastomeric chain were stretched to have an initial force of 250 g in an artificial saliva environment at 37 °C and thermocycling between 5 and 55 °C three times a day. The remaining force of the elastomeric chains was recorded at different time points (4 h, 24 h, 7 days, 14 days, 21 days, and 28 days), and the percentage of the remaining force was calculated.ResultsThe force decreased significantly in the initial 4 h and degraded mostly within the first 24 h. In addition, the percentage of force degradation increased slightly between 1 and 28 days.ConclusionsUnder the same initial force, the longer the connecting body is, the fewer the number of loops and the greater the force degradation of the elastomeric chain are.

Replacement of Missing Anterior with Maryland Bridge using Ribbond: A Case Report

Replacement of missing mandibular central incisor is difficult challenge in esthetic dentistry. Resin bonded bridges or maryland bridges can be considered as a treatment of choice in such conditions, which restore the oral function and esthetic of the patient. Maryland bridge preparation requires minimal preparation of the tooth and the bridge can be attached to the periodontally sound adjacent teeth.The combined use of polyethylene fibre and resin composite help achieve durable and functional result.This case report describes the case of esthetic restoration of a young women with midline spacing of mandibular anterior teeth.

Photon echoes using atomic frequency combs in Pr:YSO - experiment and semiclassical theory.

Photon echoes in rare-earth-doped crystals are studied to understand the challenges of making broadband quantum memories using the atomic frequency comb (AFC) protocol in systems with hyperfine structure. The hyperfine structure of Pr3+ poses an obstacle to this goal because frequencies associated with the hyperfine transitions change the simple picture of modulation at an externally imposed frequency. The current work focuses on the intermediate case where the hyperfine spacing is comparable to the comb spacing, a challenging regime that has recently been considered. Operating in this regime may facilitate storing quantum information over a larger spectral range in such systems. In this work, we prepare broadband AFCs using optical combs with tooth spacings ranging from 1 MHz to 16 MHz in fine steps, and measure transmission spectra and photon echoes for each. We predict the spectra and echoes theoretically using the optical combs as input to either a rate equation code or a density matrix code, which calculates the redistribution of populations. We then use the redistributed populations as input to a semiclassical theory using the frequency-dependent dielectric function. The two sets of predictions each give a good, but different account of the photon echoes.

Particle tracking velocimetry as a method for chip ejection studies during groove milling of particleboard

Studies on chip ejection from tools provide important information for the design of tools and effective chip collection elements used in woodworking machines. Among the chip properties, chip motion and its distribution are of particular interest for the design process. Until now, chip velocities have only been measured by manual tracking over a high-speed image sequence, which allows only a small scope of inspection. Here, we present the use of high-speed imaging in combination with particle tracking velocimetry as a new method for the semi-automatic evaluation of the magnitudes and directions of chip velocities. The methodology was tested in groove milling of particleboard. It was found that state-of-the-art particle tracking algorithms are suitable for quantitative analysis of chip motion in high-speed images. Therefore, spatial and temporal analysis of the chip velocity along the tool circumference are feasible and are presented here. In addition to chip velocity, chip collisions with the tool or other chips can be observed. This research also shows that image evaluation of chip sizes and shapes is potentially possible. In summary, the presented work provides methods that can quantitatively describe chip motion after chip formation. The experiments indicate that with each tooth engagement, new chips are formed, which initially move into the chip space at a median velocity higher than the cutting speed. After collisions with the tool and interparticle collisions, the particles leave the chip space of the tool at lower speeds. The machining tests performed with different process settings showed differences in the analysis results of chip movement. In the future, the presented methodology offers the possibility of investigating the relationships between tooth and chip space geometries, as well as different materials and the chip ejection of tools. Thus, the presented methodology provides a basis for creating a more general understanding of chip motion from machining operations, which can lead to innovations and improvements in chip collection.

Generation and Evolution of Phononic Frequency Combs via Coherent Energy Transfer between Mechanical Modes

Phononic frequency combs represent the mechanical analog of optical frequency combs. Several independent experimental studies have demonstrated the onset and evolution frequency comb response in a variety of micro- and nanoelectromechanical devices in recent years. A theoretical basis for exploring and understanding the conditions for comb generation and evolution with varying driving parameters is essential to enable future practical applications. Here, we present the comparison between modeling and experimental results on the generation and evolution mechanism of phononic frequency combs in a nonlinear micromechanical resonator from the perspective of coherent energy transfer between two mechanical modes. Phononic frequency combs emerge in a strong coupling regime involving nonlinear resonances when the amplitudes and phases of two coupled mechanical modes are modulated via coherent energy transfer. The spacing and number of comb teeth can be analytically estimated based on modeling the nature of the interaction of the coupled modes under the specified driving conditions. As the driving conditions are varied, the phononic frequency comb evolves into different forms and a phenomenological model for the system is established to accurately predict the evolution of phononic frequency combs. The alignment between experiment and model provides a basis for the engineering of this phenomenon in future device applications.

Influence of the Impact Angle on Machining in Powder Jet Processing

Powder jet machining is a blast machining process in which micrometer-order particles are projected onto a workpiece at near-supersonic speeds, to remove the workpiece (abrasive jet machining (AJM)) or to deposit the particles (powder jet deposition (PJD)). We report a novel dental treatment method for powder jet machining using hydroxyapatite, which is the main component of teeth, as deposited particles. The surfaces and interdental spaces of human teeth are not only flat, but also have complex groove structures. However, PJD and AJM exhibit impact-angle-dependent machining phases. Therefore, it is necessary to investigate the effect of the particle impact angle on machining, before dental treatment. Furthermore, because machining interacts not only with the particle impact angle but also with the particle impact velocity, a comprehensive investigation of the effects of the machining parameters is required, for delineating the phase-transition conditions. Accordingly, in this study, we conducted machining experiments using hydroxyapatite particles (particle diameter, 2.16 μm) and four different blasting angles of 30°, 45°, 60°, and 90°, to infer the machining amount. Machining efficiency was evaluated based on the amount of machining. The impact angles and velocities of the particles were calculated using computational fluid dynamics (CFD). Three-dimensional process mapping was performed using the machining amount, particle impact angle, and particle impact velocity, obtained from the experiments and CFD calculations. The results showed that PJD crossed to AJM at the impact angle of approximately 60°. Moreover, PJD exhibited high processing efficiency for impact angles above 60° and impact velocities in the 280–310 m/s range. In contrast, AJM exhibited high processing efficiency for impact angles below approximately 35° and impact velocities above 310 m/s.

Simulation-based evaluation of the 3D fluid dynamics of a coolant lubricant in the narrow-closed cutting gap during circular sawing

A method for simulation-based analysis of the 3D fluid dynamics of a coolant lubricant in the saw tooth space is presented. The examination serves on the one hand to characterize the flow around the bounding surfaces of the narrow-closed cutting gap regarding the local flow conditions. On the other hand, the outflow behaviour of the coolant lubricant out of the narrow-closed cutting gap is analysed to get a deeper understanding of the cooling mechanism. Therefore, the model design is described considering the computational domain and the boundary conditions. Finally, an evaluation method for the local flow behaviour at different surfaces and the coolant lubricant outflow of the tooth space in the narrow-closed cutting gap is illustrated.

Influence of the restoration after pulpotomy on the strength of electrical stimulus reaching the pulp space: An in vitro investigation.

The study evaluated the influence of coronal restoration after pulpotomy on the strength of electrical stimulus reaching the radicular pulp using an electric pulp test (EPT). The pulp tissue from ten freshly extracted mandibular premolar teeth was removed and replaced with an electroconductive gel. The cathode probe of Powerlab was inserted into the pulp space and the anode probe was attached to the EPT handpiece. The EPT probe coated with electro-conducting material was positioned in the middle third of the buccal crown surface. The EPT stimulus reaching the pulp space of an intact tooth at 40 numerical readings was recorded. The tooth was removed from model and endodontic access was made. The 2-mm thick mineral trioxide aggregate was placed at the cementoenamel junction followed by composite resin restoration. The experimental setup was re-established and postpulpotomy EPT stimulus data were recorded. The data collected were compared using the Wilcoxon signed-rank test. There was a statistically significant difference (P = 0.038) between observed between the strength of EPT stimulus reaching the pulp space in prepulpotomy (mean 91.18 ± 101.02 V and median 25.79 V) and postpulpotomy (mean 58.49 ± 77.13 V and median 13.75 V) tooth samples. The placement of the restoration and pulp capping agent after pulpotomy dampens the strength of EPT stimulus reaching the pulp canal space.

Justification of the width of the tooth spacing and the distance between the rows of teeth of the ripper for the harrower

The article substantiates the degree of immersion of working bodies in the soil and soil deformation on the basis of scientific and experimental studies of the harrowing unit used. The parameters of the harrow teeth, the qualitative performance of the technological process of the accepted parameters are also theoretically justified.

Management of gingival enlargement with orthodontic treatment- A case report

Gingival inflammation, fibrous outgrowth, or a combination of the two can result in gingival enlargement (GE), which has negative effects such as difficulties controlling plaque, difficulty chewing and speaking, as well as esthetic and psychological issues. Orthodontic treatment is one of the causes of gingival hypertrophy. A 20-year-old woman reported to the department of periodontics and oral implantology with a complaint of GE in relation to the front teeth. She was undergoing orthodontic treatment for treating tooth spacing in the anterior teeth. This article describes the treatment of this patient by gingivectomy to remove all extra gingival tissue. The fixed orthodontic treatment was continued with monthly periodontal checkups that were scheduled to control the gingival inflammation. The most crucial factor in successfully treating hyperplasia in patients receiving orthodontic treatment is teamwork between the periodontist and orthodontist.

Research on Vibroactivity of Toothed Gears with Highly Flexible Metal Clutch under Variable Load Conditions

The article provides a discussion on a methodology intended for testing of power transmission systems featuring an innovative highly torsionally flexible metal clutch patented by the co-authors of this paper. What this methodology takes into account is the amplitude and frequency analyses discussed in the article, as well as a sensing system based on diverse piezoelectric and magnetic phenomena, the Doppler effect, etc. Both contact and non-contact (laser measurement) methods were used during the tests. The purpose of the tests conducted at the stand, originally designed by the authors in accordance with the methodology proposed, was to evidence that using the innovative and patented, highly torsionally flexible metal clutch makes it possible to reduce the vibrations of multi-stage toothed gears, consequently reducing the forces affecting the gear bearings and those acting at the tooth space, which is to enable the service life of individual components of the power transmission systems intended for mining scraper conveyors to be significantly extended. Based on the studies and analyses performed by the authors, one can observe and conclude that the methodology proposed in the paper makes it possible to use an example of a relatively complex power transmission system in order to examine the relationships between the processes at work, i.e., the decline of the linear vibrations of the gear housing (which is undoubtedly positive in power transmission systems) at the expense of increasing torsional vibrations of the innovative clutch, the latter not to be considered unfavourable to users in the case analysed.

Structural optimization and hydraulic performance analysis of bionic pit flow channels based on a genetic algorithm

Orthogonal experiments have mostly been used in the structural optimization of drip irrigation emitter flow channels. To further improve the efficiency of the optimal design, this study used a genetic algorithm to optimize the structure of the bionic pit flow channel. Based on the structural similarity and performance optimization of the torus-margo bordered pit structure, the constitutive equation of the flow channel unit was constructed. The selection, crossover and mutation operators were set by the genetic algorithm, and the objective function value was calculated. The design variables and known variables that met the requirements were put into the computational domain model, and the pit flow channel structure was simulated and optimized. The results showed that there were large low-velocity regions at the junctions and corners of the pit flow channel units at a working pressure of 50 kPa, and no complete low-velocity vortices were observed, indicating that the flow channels had good anti-clogging performance. The distribution of flow velocity on the same cross-section was quite different, which made the flow layers collide and mix, which intensified the loss of energy, indicating that it had a good energy dissipation effect. The multivariate linear regression analysis showed that the four variables of tooth stagger value (j), flow channel angle (θ), tooth spacing (l) and inner and outer boundary spacing (h) had a decreasing degree of influence on the flow index (x). The flow index (x) was negatively correlated with the tooth stagger value (j), flow channel angle (θ) and tooth spacing (l), and positively correlated with the inner and outer boundary spacing (h). The test results of physical samples showed that the average error between the simulation results and the real values was 3.4%, indicating that the accuracy was high, which can provide a basis for the structural optimization design of related pit drip irrigation emitters.

Mother’s Knowledge regarding the Functions of Children's Primary Teeth in Salapian District, Langkat-North Sumatera

Primary teeth play a role in mastication, speech function, appearance, and as a provider of space for children's permanent teeth. Mothers need to know the functions of their children's primary teeth so they are willing to take care of their children's teeth. This study aims to see the relationship of a mother’s knowledge regarding the functions of children’s primary teeth to the number of children and the level of education in Salapian District, Langkat. This study is an analytical study with a cross-sectional design. The research subjects were 100 people; 30 prospective mothers, 30 mothers with one child, and 40 mothers with more than one child. Data were collected using the interview technique and the analytical test used was the Kruskal Wallis test with a significance value of p&lt;0.05. The results showed that 15 respondents (15%) had a good level of mother’s knowledge regarding the functions of children’s primary teeth, 36 respondents (36%) were in an insufficient category, and 49 respondents (49%) were in less category. Statistical analysis showed a significant relationship between the mother’s knowledge regarding children’s primary teeth functions the number of children and education level (p=0.001 and p=0.001). This study concluded that mothers who have many children have a better knowledge about functions of primary teeth than mothers with few children. Mothers with higher education levels have a better level of knowledge than mothers with primarysecondary education.&#x0D; &#x0D; Keywords: mother’s knowledge, functions of primary teeth, education level, number of children

Spiral Bevel Gears: nonlinear dynamic model based on accurate static stiffness evaluation

In the present paper non-linear dynamics of a spiral bevel gear pair with backlash are investigated in order to clarify the internal excitations of major importance from the vibration point of view: manufacturing errors in the teeth profile, teeth spacing errors, and elastic deformation of the teeth. In some conditions, like in the case of backside contact, the destructive effect of internal excitations can be intensified leading to complex dynamics; for such reasons here backside contacts and reverse rotation are investigated in detail using a nonlinear time-varying model. The effect of damping is investigated as well. A one-DOF model is developed in order to study the dynamic behavior; the resulting a nonlinear differential equation with time-varying mesh stiffness is solved via numerical integration based on an adaptive step-size implicit Runge-Kutta scheme. The dynamic response of the system is analyzed through time histories, phase portraits, bifurcation diagrams, and Poincaré maps. Results show that for small backlash values, the possibility of backside contact increases. Meanwhile, by increasing the backlash value, the amplitude vibration of the gear rotation rises as well. By comparing the dynamic response of the system with different damping ratios, the results show that higher damping effectively reduces gear vibration resonance, although the probability of unsteady response still exists.