Tooth Depth Research Articles

Survival of nonsurgically splinted mandibular anterior teeth during supportive maintenance care in periodontitis patients

Background/purposeSplinting mobile teeth is a choice to improve the patient's oral comfort. The purpose of this study was to assess the survival and stability of mobile anterior mandibular teeth after splinting in patients with periodontitis undergoing supportive periodontal therapy (SPT). Materials and methodsPatients with splinted mobile anterior mandibular teeth were assessed retrospectively. Periodontal statuses were recorded at baseline and follow-up visits. Tooth and splint survival as well as splint repairs were recorded. Multilevel Cox regression analyses were performed to evaluate patient- and tooth-related factors that might have influenced the survival rates of splints. ResultsSixty-one patients, collectively having 161 splints, were followed for an average of 5.44 years. On average, probing depth (PD) of splinted teeth decreased from 4.31 mm to 2.93 mm and clinical attachment loss (CAL) decreased from 5.02 mm to 4.58 mm. Alveolar bone was stable in the follow-up period. None of the splinted teeth were extracted, The overall survival rate of the splints was 65.2%. Splints made of composite resin alone were associated with a higher risk of breakage when compared to splints composed of composite resin with mesh grid strips. ConclusionSplinting showed long-term survival and splinting combined with periodontal supportive treatment is a feasible option to maintain mobile mandibular anterior teeth.

Research, Modelling and Prediction of the Influence of Technological Parameters on the Selected 3D Roughness Parameters, as Well as Temperature, Shape and Geometry of Chips in Milling AZ91D Alloy.

The main purpose of the study was to define the machining conditions that ensure the best quality of the machined surface, low chip temperature in the cutting zone and favourable geometric features of chips when using monolithic two-teeth cutters made of HSS Co steel by PRECITOOL. As the subject of the research, samples with a predetermined geometry, made of AZ91D alloy, were selected. The rough milling process was performed on a DMU 65 MonoBlock vertical milling centre. The machinability of AZ91D magnesium alloy was analysed by determining machinability indices such as: 3D roughness parameters, chip temperature, chip shape and geometry. An increase in the feed per tooth fz and depth of cut ap parameters in most cases resulted in an increase in the values of the 3D surface roughness parameters. Increasing the analysed machining parameters did not significantly increase the instantaneous chip temperature. Chip ignition was not observed for the current cutting conditions. The conducted research proved that for the adopted conditions of machining, the chip temperature did not exceed the auto-ignition temperature. Modelling of cause-and-effect relationships between the variable technological parameters of machining fz and ap and the temperature in the cutting zone T, the spatial geometric structure of the 3D surface “Sa” and kurtosis “Sku” was performed with the use of artificial neural network modelling. During the simulation, MLP and RBF networks, various functions of neuron activation and various learning algorithms were used. The analysis of the obtained modelling results and the selection of the most appropriate network were performed on the basis of the quality of the learning and validation, as well as learning and validation error indices. It was shown that in the case of the analysed 3D roughness parameters (Sa and Sku), a better result was obtained for the MLP network, and in the case of maximum temperature, for the RBF network.

Quantifying the potential of morphological parameters for human dental identification: part 1-proof of concept.

In forensic identification, lack of eccentric characteristics of intact dentitions hinders correct ante-mortem/post-mortem (AM/PM) matching. It remains unclear which morphological dental parameters hold strong potential as identifiers. This study aimed to establish a method to quantify and rank the identifying potential of one (or a combination of) continuous morphological parameter(s), and to provide a proof of concept. First, a statistic was defined that quantifies the identifying potential: the mean potential set (MPS). The MPS is derived from inter-observer agreement data and it indicates the percentage of subjects in the AM reference dataset who at least need to be considered to detect the correct PM subject. This was calculated in a univariate and a multivariate setting. Second, the method was validated on maxillary first molar crowns of 82 3D-digitally scanned cast models. Standardized measurements were registered using 3D modeling software (3-Matic Medical 12.0, Materialise N.V., Leuven, Belgium): tooth depth, angles between cusps, distances between cusps, distances between the cusps, and the mesial pit. A random sample of 40 first molars was measured by a second examiner. Quantifying and ranking the parameters allowed selecting those with the strongest identifying potential. This was found for the tooth depth (1 measurement, MPS = 17.1%, ICC = 0.879) in the univariate setting, and the angles between cusps (4 measurements, MPS = 3.9%) in the multivariate setting. As expected, the multivariate approach held significantly stronger identifying potential, but more measurements were needed (i.e., more time-consuming). Our method allows quantifying and ranking the potential of dental morphological parameters as identifiers using a clear-cut statistic.

The Post-Cementation Periodontal Response to Resin Retained Bridge

Objective: To compare the mean periodontal health of resin retained abutment tooth with its baseline score.Study Design: Quasi-experimental study.
 Place and Duration of Study: Department of Prosthodontics, Armed Forces Institute of Dentistry Rawalpindi Pakistan, from Oct 2019 to Mar 2020.
 Methodology: Before starting abutment preparation, the baseline scores for gingival index, plaque index and periodontal pocket depth of the abutment teeth were calculated. The gingival index was calculated using a blunt probe, whereas the periodontal pocket depth of the teeth in both groups was calculated using a calibrated periodontal probe.
 Results: According to the results recorded there was a significant difference seen in the mean periodontal health of abutment teeth before and after the cementation of the resin-bonded bridge. Our calculated p-value (0.001) indicated definitive significance associated with both the groups i.e., before and after the score of gingival indices and before and after the score of periodontal pocket depth, after 30 days of provision of the resin-bonded bridge.
 Conclusion: There was a significant association found in the mean periodontal health of abutment teeth before and after the cementation of the resin-bonded bridge.

Efficacy and safety of piezocision in accelerating maxillary anterior teeth en-masse retraction: study protocol for a randomized controlled trial

BackgroundOrthodontic treatment is commonly more time-consuming in adults than in teenagers, especially when it comes to the maxillary en-masse retraction, which may take 9 months or even longer. As to solve this concern, orthodontists have been striving to seek new methods for shortening orthodontic treatment time. Piezocision, as a popular alternative treatment, has been widely used in different types of tooth movement. However, its effect on en-masse retraction of maxillary anterior teeth remains unclear. This randomized controlled trial intends to figure out the role piezocision plays in accelerating en-masse retraction.MethodsThis protocol is designed for a prospective, single-center, assessor-blinded and parallel-group randomized controlled trial. Twenty adult patients aged from 18 to 40 whose orthodontic treatment required bilateral maxillary first premolars extraction will be randomly assigned to the piezocision group and the control group at a ratio of 1:1. The piezocision group will undergo en-masse retraction immediately after the piezo surgery, while the control group will start en-masse retraction directly. Both groups will be followed up every 2 weeks to maintain the retraction force until the end of space closure. The space closing time is set as the primary endpoint. Meanwhile, the secondary endpoints include the change of root length, labial and palatal alveolar bone thickness, vertical bone height, probing depth of maxillary anterior teeth, cephalometric measurements, visual analogue scale, and postoperative satisfaction questionnaire.DiscussionThis study will attempt to provide more convincing evidence to verify whether piezocision will shorten the time of en-masse retraction or not. Distinguished with previous studies, our study has made some innovations in orthodontic procedure and primary outcome measurement, aiming to clarify the efficacy and safety of piezocision-assisted en-masse retraction in Chinese population.Trial registrationChinese Clinical Trial Registry ChiCTR 1900024297. Registered on 5 July 2019

Final Colour of Ultratranslucent Multilayered Zirconia Veneers, Effect of Thickness, and Resin Cement Shade

Background Aesthetic restorations should be able to mimic the natural colour depth of teeth, affected by several factors including material properties. There is a lack of information regarding the effect of cement shade and material thickness on the final colour of ultratranslucent multilayered zirconia veneers. Objectives This study evaluated the effect of ceramic thickness and resin cement shade on the final colour of different layers of ultratranslucent multilayered (UTML) zirconia veneers. Methods This in vitro study produced 90 rectangular-shaped specimens with nonsintered Katana UTML monolithic zirconia (Kuraray Noritake Dental, Tokyo, Japan), shade A1 blocks. Ceramic samples were prepared in two groups of 0.7 mm and 0.5 mm thicknesses, 45 of each (a: 8 × 11 × 0.5 mm; b: 8 × 11 × 0.7 mm). Specimens of each thickness were further divided into 5 groups: universal, clear, brown, white, and opaque (n = 9). Each adhesive resin cement (Panavia V5) was applied between the ceramic samples and composite substrate. The colour values were measured using a spectrophotometer in baseline and after resin cement application according to the CIELab system. For all samples, ΔE00 values were obtained. Data were evaluated with SPSS 25 using the three-way ANOVA test (p < 0.05). Results The factors of cement shade, ceramic thickness, and ceramic layers have statistically significant effect on ΔE00 values (p < 0.001). The results showed lower ΔE00 values with thicker ceramic veneers. Tukey test results showed that the opaque and brown shade had a significantly greater ΔE00 values comparing to universal (p = 0.004), clear, and white shades (p < 0.001). Conclusion The colour change was greater in lower ceramic thickness. Different shades of resin cement and layers of UTML zirconia differently affected the final colour.

Modelling and experiment for grinding forces of gear form grinding considering complete tooth depth engagement

Grinding is an essential gear finishing method. Grinding force analysis and prediction are critical to understand grinding mechanisms. By using a geometry model for gear form grinding and surface grinding mechanisms, a theoretical model was established to calculate the gear form grinding force. By considering the complete tooth depth engagement between tooth grooves and wheel profiles during form grinding, three segments of the involute, transition arc and tooth bottom line, which were included in complete tooth groove profiles, were analysed using the model. Contact relations among the normal grinding depth, wheel equivalent radius, wheel linear velocity and wheel profile were obtained. In addition, grinding experiments were outperformed on the basis of the single tooth, and the unknown coefficients of the form grinding force calculation model were acquired. The effects of the grinding depth, feed speed and grinding speed on grinding force were analysed using the grinding force model. The comparison of the predicted values of the form grinding force model with the experimental results, indicated that the relative errors of tangential and normal grinding forces are within ±10% and ±12%, respectively. The results confirmed the accuracy of gear form grinding force calculation model. These findings play a key role in parameter optimisation during gear form grinding.

Accuracy of three digital waxing–guided trial restoration protocols for controlling the depths of tooth preparation for ceramic veneers

Statement of problemThe accuracy of digital waxing–guided trial restoration protocols that have been implemented with ceramic veneers has not been reported. PurposeThe purpose of this in vitro study was to evaluate the accuracy of 3 digital trial restorations fabricated from digital waxing for ceramic veneers. Material and methodsA uniform 0.3-mm digital waxing added to the facial surface of 30 maxillary central typodont incisors was created in a software program. The trial restorations were fabricated on typodont teeth with autopolymerizing acrylic resin by using a silicone index based on 3-dimensionally printed casts designed from the digital waxing. The 30 maxillary central incisors were divided into 3 groups: the depth cutter (0.5 mm, Komet) (DC) group, the round bur (1.5 mm, Diatech) (RB) group, and the specially designed calibrated depth bur (laser mark of 0.5 mm, Gaofeng) (CD) group. The 3 groups were randomly prepared with a random number table by 2 experienced prosthodontists aiming to produce an even facial clearance of 0.5 mm. The dimensional differences in the standard tessellation language (STL) files between the surfaces of the original teeth, digital waxing, trial restorations, and prepared teeth in the software program were measured and analyzed at the same 9 points on the labial surface. One-way ANOVA with a post hoc test was used to identify significant discrepancies between trial restorations and waxing and differences in the reduction depth of typodont teeth (RDT) and the reduction depth (RD) among the 3 techniques (α=.05). The mean relative differences (MRDs) were calculated to determine the accuracy (%). ResultsThe thickness of the trial restorations was significantly greater than that of the digital waxings, with a discrepancy of 0.20 ±0.14 mm, especially at the cervical site. With the use of a trial restoration, the RDTs of the middle (-0.01 ±0.11 mm) and cervical locations (0.09 ±0.20 mm) showed significantly smaller preparation depths than did the other locations. Significant differences in RD were found among the 3 guided techniques (P<.05). Group DC presented the most accurate result of 0.51 ±0.08 mm with an MRD of 2%, whereas the results of 0.57 ±0.10 mm with an MRD of 14% and 0.60 ±0.11 mm with an MRD of 20% were obtained from group RB and group DC, respectively. ConclusionsThe trial restoration was significantly thicker than its corresponding waxing. The DC technique presented the most accurate reduction result among the 3 protocols examined.

A Calculation Method for Tooth Wear Depth Based on the Finite Element Method That Considers the Dynamic Mesh Force

Gear wear is a progressive material removal process that gradually changes the tooth profile shape and dynamic mesh force, where the dynamic mesh force affects the tooth surface wear. To describe this process, a spur gear dynamic model that includes the mesh stiffness and unloaded static transmission error (STE) of the worn tooth profile is proposed for calculating the dynamic mesh force. Then, based on the finite element method (FEM), a dynamic contact analysis model that considers the dynamic mesh force is proposed for calculating the time-varying contact stress and relative sliding distance of the tooth surface mesh point. Finally, combined with the Archard wear model, a tooth wear depth calculation method that considers the worn tooth profile and the dynamic mesh force is proposed. In addition, the wear depth and dynamic characteristics under different wear times are studied.

Short-term effect of thermoplastic resin removable partial dentures on periodontal health: A randomized cross-over trial.

This study aimed to compare the short-term effects of thermoplastic resin removable partial dentures (TR-RPDs), referred to as non-metal clasp dentures, with those of metal-clasp-retained RPDs (MC-RPDs) on the periodontal health of abutment teeth. A randomized cross-over trial was conducted in 28 partially dentate patients. Participants were randomized into two groups and received MC-RPDs followed by TR-RPDs, or vice versa, for 3 months. Periodontal clinical parameters, such as the plaque index, gingival index, probing pocket depth, tooth mobility, and microbiological status of the abutment teeth, were evaluated at the delivery and 3 months after using each RPD. Of the 28 patients enrolled, 24 (mean age, 67.3 years) completed the trial, and 55 abutment teeth were evaluated. The periodontal condition of the abutment teeth did not deteriorate after 3 months of using both types of RPDs. There was no statistically significant difference in the plaque index, gingival index, probing pocket depth, tooth mobility, and the red complex bacteria between TR- and MC-RPDs (p >0.05). The Periotest value for TR-RPDs was significantly lower than that for MC-RPDs (p <0.05). However, this difference was not clinically significant. These results suggest that the influence of TR-RPDs on the periodontal health of abutment teeth was limited within 3 months of use.

Enhancement of plastic flow in lateral direction by torsional oscillation in upsetting and lateral extrusion

Plastic flow of hollow cylinders under combining axial compression with torsion was examined in upsetting and in lateral extrusion. The hollow cylinders with initial height/outer diameter of 0.5–2.5 and initial inner/outer diameter of 0.3–0.9 were compressed/extruded and simultaneously twisted with respect to the axisymmetric forging axis in one-way or cyclic alternating. Due to superposition of torsional shear stress, the lateral metal flow was found to be assisted. Barreling of the workpiece was reduced by approximately 10 % in upsetting with torsion/compression speed of 6 °/mm. The enhancement of the plastic flow in upsetting was applied to fill up tooth cavity in lateral extrusion. The extruded tooth depth of the workpiece was approximately 5–7% larger in lateral extrusion with torsion/extrusion speed of 30°/mm. In addition, cyclic alternating torsion was effective to extrude evenly in the tooth thickness direction due to the periodic reversal of die rotation in peripheral direction.

Research on machining parameter optimization in finishing milling with multiple constraints

High efficiency and high precision milling, as the eternal goal of CNC machining, needs to balance many constraints for selecting the most reasonable processing parameters. This paper presents an efficient machining parameter optimization method for finishing milling operation with multiple constraints. Firstly, under the multiple constraints of parameter feasible region, milling force, milling stability, roughness, and machining contour accuracy, a multi-variable parameter optimization model with machining efficiency as the objective is established. A four level cycle optimization strategy has been detailly described for solving the optimization problem, in which the feed per tooth is optimized by using the golden section method, and with the aid of the random vector search method, the spindle speed, radial, and axial depth cuts are both numerically iterated. The optimal machining parameter combination of the tooth number, feed per tooth, spindle speed, radial, and axial depth of cuts are achieved at last. Finally, the experimental verification results show that the proposed method can greatly improve the machining efficiency under chatter free condition and achieve an efficient finishing milling with consideration of the multiple constraints.

Dimensional Accuracy and Surface Quality of AZ91D Magnesium Alloy Components after Precision Milling.

This study investigates a precision milling process conducted with the use of conventional end mills and a standard CNC (Computer Numerical Control) machine tool. Milling tests were performed on samples of AZ91D magnesium alloy using TiB2- and TiAlN-coated three-edge end mills measuring 16 mm in diameter. The following technological parameters were made variable: cutting speed, feed per tooth and axial depth of cut. The effects of precision milling were evaluated by analysing the scatter of dimension values obtained in successive tool passes. In addition to that, deviations from the assumed nominal depth as well as obtained ranges of dimension varation were analysed. The study also examined surface quality obtained in the precision milling process, based on the basic surface roughness parameters: Ra, Rz and RSm. Results have confirmed that the use of conventional cutting tools and a standard CNC machine tool makes it possible to manufacture components characterized by relatively small scatter of dimension values and high accuracy classes. Additionally, the results have shown that the type of tool coating and variations of individual technological parameters exert impact on the dimensional accuracy and surface quality obtained.

Investigation on the Depth of Slip Hanger Teeth Bite into Casing and the Mechanical Properties of Casing under Different Suspension Loads in Ultra-Deep Wells

There is great difficulty in controlling the setting load of the large-size slip casing hanger in the Northwest Oilfield in China, and a reasonable setting load is of great significance. This paper studied the relationship between slip hanger bite depth and suspension load in the Ф 273 mm WE-type slip hanger in the Northwest Oilfield in China through experiment, theoretical computation, and finite element analysis. The accuracy of the finite element model was proved by comparing the finite element simulation results with the experimental bite marks on the casing surface. The study results show that the bite mark of the slip insert in the casing is deeper in the lower part of the sitting position. When the hanging load increases from 1000 kN to 6000 kN, the maximum bite depth of the slips in the casing gradually increases with the suspension load. The residual collapse strength of the casing decreases correspondingly. When the residual collapse strength decreases to a certain value, the maximum suspension force corresponding to the bite depth of the slip insert can be obtained. Based on the finite element research results and theoretical equations, the stress distribution on the casing wall where the slips bite the deepest is obtained by derivation. The suggestions on improving the material structure of the casing under this stress were proposed. The limit of the setting load of the large-size casing wellhead for avoiding casing collapse was obtained, which is of great significance for guiding field-casing setting.

Influencing factors of effective tooth depth in the cylindrical gear rolling process with axial infeed

Influencing factors of effective tooth depth in the cylindrical gear rolling process with axial infeed

Design of double teeth metallic card clothing for the high-efficiency carding process by computational fluid dynamics

The design of metallic card clothing, which is one of the most important devices in the textile industry, has always been based on operational experience. With the development of types of fibers and the requirements for the quality of yarns, those principles concluded by engineers seem to be losing their efficiency. Recent research found that airflow played an important role in the card process, which means airflow should be carefully studied. Computational fluid dynamics (CFD) simulation greatly helps in the analysis of airflow because the gauge between carding elements is too narrow to put in any measuring device. In the present study, with the help of CFD simulation, the air around different carding clothing with varied tooth depth was analyzed. It was concluded that the carding efficiency improvement in card clothing with lower tooth depth may be related to more concentrated air velocity at the tooth tips. This resulted in more probabilities that fibers would get through the cylinder surface at the teeth tips, so that the fibers could be caught by flat-top needles more efficiently. With this assumption, a new generation of card clothing called “double teeth” containing two teeth in a single section has been invented. The new configuration design of card clothing was then applied in several spinning mills on an industrial scale for experiments. The results showed about a 30% improvement in production at the same quality level as conventional card clothing, which implied the usefulness of the newly applied principles related to airflow. Despite the difficulty in the study of the complex carding process, the new airflow analysis method has shown an optional and worthwhile way of thinking that could make a difference in future research in the textile industry.

Acoustical behavior of loss-optimized involute gears

The progressing electrification of vehicle drive systems focuses more and more on efficient high-speed concepts. Increasing the motor speed leads to a higher power density of the electrified power train and thereby to an increased range for battery electric vehicles. The high rotational speeds cause new challenges in designing gearboxes regarding the efficiency and the acoustical behavior. Most present gearings in conventional vehicles are designed with high tooth depths to ensure low noise excitation behavior combined with the best possible efficiency. By changing the gear geometry to smaller tooth depths with higher pressure angles, it is possible to further decrease gear losses. However, the loss-optimized gear geometry must not jeopardize the beneficial acoustical behavior. In theoretical studies, the acoustical behavior of loss-optimized gears are investigated and compared to gearings designed according to the state of the art. Design calculations of the excitations of all ideal gears without deviations are on similar levels. However, application of such gear geometries faces severe challenges because the sensitivity to manufacturing deviations may be high. In this paper, simulation results and test results between low-NVH gears and loss-optimized gears are documented and analyzed.

CHARACTERIZATION OF LEAF FEATURES IN SOME BLACKBERRY GENOTYPES COLLECTED FROM THE BLACK SEA REGION

In this study, morphological characterization studies regarding to leaf characteristics (leaf length, leaf width, leaf cross section shape, leaf edge waviness, swelling between leaf veins, leaf tooth depth, dominant leaflet number, leaf shape, green color intensity on the upper part of the leaf and brightness on the upper part of the leaf) were carried out in some blackberry genotypes collected from the Black Sea Region of Turkey, according to the definition lists of UPOV (International Association for the Protection of New Plant Varieties). The measurements and observations made were transformed into feature scores, and using these scores, dendrogram and principal component analysis (PCA) related to morphological features were obtained. In the dendrogram obtained according to the morphological characterization data, the similarity level between the materials was determined between 0.50-1.00 and the average similarity coefficient was found as 0.75. The dendrogram consists of 2 main clusters (A and B). According to the dendrogram, genotypes obtained from Samsun (Çarşamba 1), Samsun (Çarşamba 2) and Ordu (Gülyalı), Bartın (Center) and Rize (Küçükçayır) regions were found to be the closest genotypes with 1.00 similarity level. In addition, as a result of the principal component analysis (PCA), the similarities and differences within the blackberry genotypes were clearly revealed. It was determined that they consisted of three main groups and two outer groups in their distribution on the two-dimensional plot.As a result of the study, it was determined that there is a certain level of variation between blackberry genotypes. The data obtained from this study will help to protect the diversity and to evaluate it with different studies.

Experimental investigation of helical gear tooth crack location and depth detection using moving average method on transmission error

Gear systems are the most useful and essential power transmission systems in the high-speed industry due to their accuracy. It is necessary to make sure that these systems work without defects such as tooth cracks. Therefore, detecting the location and depth of cracks in gear systems is very important. In this research, a new approach is proposed to detect the crack location, and accordingly, some statistical indicators are used to estimate the crack depth in the helical gear tooth. To this end, after explaining the helical gear mesh stiffness and tooth-root crack modeling, the helical gear pair dynamic is modeled. Then, the vibration data of a helical gear system is obtained by an experimental test rig, and the moving average method is undertaken to precisely detect the crack location. The crack depth ratio is estimated using the crest factor, impulse factor, clearance factor, and [Formula: see text] and [Formula: see text] which are applied to the simulation results and the experimental signal. According to these results, the crest factor, impulse factor, and clearance factor calculated the crack depth ratio with a good agreement, and the indicators [Formula: see text] and [Formula: see text] estimated it with a more significant error. Also, the average of estimated values is calculated, indicating a better result than each indicator alone.

Bearing strength and failure behaviour of composite pre-tightened multi-tooth joint

The bearing strength and failure behaviour of a new composite pre-tightened multi-tooth joint was studied experimentally and numerically. Four groups of different types of specimens were fabricated by varying key design variables including the pre-tightening force, tooth depth, tooth length, and number of teeth. Axial tensile tests were performed to determine the bearing capacity, failure modes, and load distribution law of the specimens. Furthermore, a three-dimensional continuum damage mechanics (CDM) model was established based on the Pinho theory and nonlinear shear constitutive model. Finally, the corresponding numerical results were compared with the experimental results and demonstrated good agreement. The results indicated that in a certain range, the bearing capacity of the joints increased with an increase in the pre-tightening force, tooth depth, tooth length, and number of teeth. The designed multi-tooth joint has four typical failure modes: crushing failure, shear failure, longitudinal splitting failure, and fibre breakage. The load distribution ratio of each tooth of the joint is non-uniform, and it is significantly affected by the number of teeth and failure mode. The comparisons among the experimental and numerical results indicated that the CDM model is effective for predicting the bearing strength and failure behaviour of the multi-tooth joints.