Inclination Of Teeth Research Articles

Maxillary alveolar bone evaluation following dentoalveolar expansion with clear aligners in adults: A cone-beam computed tomography study.

To investigate the effects of maxillary orthodontic expansion on the alveolar bone tissue in adult patients treated with aligners by using cone-beam computed tomography. Thirty patients (22 females and 8 males; mean age: 36.3 years) were treated with Invisalign® aligners. Cone-beam computed tomography and digital models were obtained before (T0) and after (T1) upper arch expansion. The bone thicknesses in the cervical, middle, and apical areas of the incisors, canines, premolar, and first molars were buccally and palatally measured, totaling 96 areas and 2,880 measurements. The buccolingual inclinations and transverse measurements of the teeth were obtained from digital models to correlate them with the bone changes. The statistical tests used were Student's t-test, analysis of variance, and Pearson's correlation tests (p < 0.05). From the 96 areas evaluated, 84 revealed an increase or stability in the alveolar bone thickness and twelve displayed significant bone loss. Bone changes did not correlate with the tooth inclination and transverse measurements. Within the limitation of the present study, mild levels of upper arch expansion obtained with Invisalign® aligners in adult patients did not result in any clinically significant loss of alveolar bone thickness.

RELATIONSHIP BETWEEN THE ANGLE OF INCLINATION OF THE MAXIMUM INCLINATION TO THE SOFT TISSUE OF THE FACIAL IN BALINESE WOMEN USING THE HOLDAWAY METHOD

Introduction: Disharmony between tooth position, jaw relation and facial soft tissue has a significant effect on facial appearance. Anatomical facial appearance is determined by the lower third of the face, especially the position of the lips and related parts which are affected by the inclination of the anterior teeth. The purpose of this study was to determine whether there was a correlation between the angle of inclination of the maxillary incisors and the convexity of facial soft tissue in Balinese women using the Holdaway method. Materials and Method: This type of research was analytic observational with a cross sectional approach. This study used a sample of 31 lateral cephalometric photographs of Balinese females for tracing. Samples were taken by means of purposive sampling, based on specified criteria. Results and discussion: Pearson correlation analysis showed that the relationship between the angle of inclination of the upper incisors was significant. Conclusion: Based on this study, it can be concluded that there was a correlation between maxillary incisor inclination angle on the facial soft tissue convexity in Balinese females using the Holdaway method.

Effects of different designs of orthodontic clear aligners on the maxillary central incisors in the tooth extraction cases: a biomechanical study

BackgroundControlling the 3D movement of central incisors during tooth extraction cases with clear aligners is important but challenging in invisible orthodontic treatment. This study aimed to explore the biomechanical effects of central incisors in tooth extraction cases with clear aligners under different power ridge design schemes and propose appropriate advice for orthodontic clinic.MethodsA series of Finite Element models was constructed to simulate anterior teeth retraction or no retraction with different power ridge designs. These models all consisted of maxillary dentition with extracted first premolars, alveolar bone, periodontal ligaments and clear aligner. And the biomechanical effects were analysed and compared in each model.ResultsFor the model of anterior teeth retraction without power ridge and for the model of anterior teeth no retraction with a single power ridge, the central incisors exhibited crown lingual inclination and relative extrusion. For the model of anterior teeth no retraction with double power ridges, the central incisors tended to have crown labial inclination and relative intrusion. For the model of anterior tooth retraction with double power ridges, the central incisors exhibited a similar trend to the first kind of model, but as the depth of the power ridge increased, there was a gradual decrease in crown retraction value and an increase in crown extrusion value. The simulated results showed that von-Mises stress concentration was observed in the cervical and apical regions of the periodontal ligaments of the central incisors. The clear aligner connection areas of adjacent teeth and power ridge areas also exhibited von-Mises stress concentration and the addition of power ridge caused the clear aligner to spread out on the labial and lingual sides.ConclusionsThe central incisors are prone to losing torque and extruding in tooth extraction cases. Double power ridges have a certain root torque effect when there are no auxiliary designs, but they still cannot rescue tooth inclination during tooth retraction period. For tooth translation, it may be a better clinical procedure to change the one-step aligner design to two-step process: tilting retraction and root control.

Mandibular advancement with clear aligners and functional appliances in the treatment of skeletal ClassⅡmalocclusion: a systematic review and meta-analysis.

This study aimed to conduct a meta-analysis of the efficacy of mandibular advance clear alig-ners with traditional functional appliances as the control group. PubMed, Web of Science, Embase, Cochrane Library, China Biomedical Abstracts Database, China Knowledge Network Database, Wanfang Database, and Weipu Database were used in this study. The two groups of researchers screened the literature and extracted data based on the inclusion and exclusion criteria established by PICOS entries, and used the ROBINS-I scale for quality evaluation. Revman 5.4 and Stata 17.0 software were used for meta-analysis. Nine clinical controlled trials were included in this study with a total sample size of 283 cases. No significant difference was found in SNA, SNB, ANB, Go-Pog, U1-SN, Overjet, and other aspects between the invisible group and the traditional group in the treatment of skeletal class Ⅱ ma-locclusion patients; there was a 0.90° difference in mandibular plane angle between the two groups; the growth of the mandibular ramus (Co-Go) in the traditional group was 1.10 mm more than that in the invisible group; the lip inclination of the lower teeth in the invisible group was better controlled, 1.94° less than that in the control group. The invisible group can better control the lip inclination of the mandibular anterior teeth when guiding the mandible. Furthermore, the mandibular plane angle (MP-SN) can remain unchanged, but the growth of the mandibular ramus is not as good as the traditional group, and auxiliary measures should be taken to improve it in clinical practice.

Three-dimensional relationship between the degree of bilateral impacted mandibular third molars angulation and the mandibular dental arch parameters: a cross-sectional comparative study.

The purpose of this study was to three-dimensionally evaluate the relationship between the degree of bilateral impacted mandibular third molar (IM3M) angulation and the mandibular dental arch parameters in normal skeletal and dental malocclusion patients. In this retrospective cross-sectional comparative study, 120 adult subjects' cone-beam computed tomography (CBCT) images were three-dimensionally analyzed. The sample included 120 adults aged 20-30years, with a gender distribution of 51 male and 69 female participants. The sample was divided into 100 adults with bilateral IM3M (study group) and 20 adults with normal bilateral erupted M3M (control group). The study group was sub-divided into three groups according to the degree of IM3M buccolingual angulation (BL°): group A, < 12° on the center of the ridge (N = 30), group B, 12-24° off-center of the ridge (N = 40), group C, > 24° off-center of the ridge (N = 30). The study group was also sub-divided into two groups according to IM3M mesiodistal angulation (MD°): group 1 from 10 to 45° (N = 36), group 2 > 45° (N = 64). Comparison within and between groups was performed using one-way ANOVA followed by Tukey's post hoc test. The correlation between IM3M, BL, and MD angulation and the mandibular arch parameter was calculated using Pearson's correlation coefficient. Statistically significant differences (P < 0.001) were found between the IM3M BL° and anterior teeth inclination, arch length (AL), and inter-second molar width (inter 2nd MW) as well as between the IM3M MD° with anterior crowding and the arch length (P < 0.001). A significant positive correlation was found between IM3M BL° and anterior teeth inclination and between IM3M MD° and anterior teeth crowding and inter 2nd MW. A significant negative correlation was observed between IM3M BL° and inter 1st MW and 2nd MW. The degree of buccolingual and mesiodistal angulation of the impacted mandibular third molars was related with mandibular dentoalveolar changes. Increased buccolingual angulation is generally associated with increased anterior teeth inclination and decreased 1st and 2nd inter-molar width. The increase in mesiodistal angulations was generally related with increased anterior teeth crowding and 2nd inter-molar width. Assessment of the relationship between the impacted mandibular third molars and the degree of arch discrepancy, and the position of mandibular incisors in the three planes of space might help in the decision-making process for the extraction of the impacted third molars in adult patients.

Correlation of alveolar bone thickness and central incisor inclination in skeletal Class I and II malocclusions with different vertical skeletal patterns: A CBCT study

This study aimed to assess the alveolar bone thickness (ABT) and labiolingual inclination of maxillary and mandibular central incisors in patients with Class I and II skeletal patterns with normal-angle, high-angle, and low-angle vertical patterns. The study sample consisted of 200 cone-beam computed tomography scans of patients with skeletal Class I and II malocclusions. Each group was further divided into low-angle, normal-angle, and high-angle subgroups. Labiolingual inclinations of maxillary and mandibular central incisors and ABT were measured at 4 levels from the cementoenamel junction in the labial and lingual surfaces. The Kolmogorov-Smirnov test, independent t test, 2-way analysis of variance, and Spearman's correlation test were applied for statistical analyses. The only significant difference between Class I and II groups regarding the ABT was found at the labial side of the maxillary central incisor, 9 mm apical to the crest. At this level, the mean ABT was 0.87 mm in patients with a skeletal Class I malocclusion, which was significantly greater than that in patients with a skeletal Class II malocclusion with a mean ABT of 0.66 mm (P= 0.02). Comparisons among the vertical subgroups revealed that on the labial and lingual sides of the mandible, as well as the palatal side of the maxilla, significantly thinner alveolar bone was found in patients with high-angle growth patterns than those with normal-angle and low-angle patterns in both sagittal groups (P<0.05). Significant weak to moderate correlations were found between ABT and tooth inclination (P<0.05). Significant differences in ABT covering central incisors between patients with skeletal Class I and II malocclusion are merely observed at the labial surface of the maxilla, 9 mm apical to the cementoenamel junction. Compared with patients with normal-angle and low-angle, those with a high-angle growth pattern and Class I and II sagittal relationships have thinner alveolar bone support around maxillary and mandibular incisors.

Prediction of Mandibular Third Molar Impaction Using Linear and Angular Measurements in Young Adult Orthopantomograms

This retrospective study aimed to evaluate a possible correlation between the characteristics of the mandibular ramus and lower third molar impaction by comparing a group of subjects with an impacted lower third molar and a second group with normal eruption for an early prediction of this pathology. This comparison was made using linear and angular measurements, which were taken on digital panoramic radiographs. Materials and methods: A total of 726 orthopantomographs (OPT) were examined, and 81 were considered suitable for the present study. The results were divided into two groups: a control group and an experimental group. The control group comprised 38 cases in which patients had at least one lower third molar that had erupted, and the experimental group comprised 43 cases in which patients had at least one lower third molar that was impacted or partially impacted. In total, 16 variables (11 linear, 4 angular, and 1 ratio) were determined and measured by an experienced observer. Results: The control group had a larger retromolar space, a larger impaction angle and a higher ratio of retromolar area to the third molar, compared to the experimental group. In contrast, the experimental group showed a deeper sigmoid notch depth than the control group did. In the control group, moderate positive correlations were found between both the length of the coronoid and the width of the third molar, and the retromolar space. Furthermore, in the experimental group, moderate positive correlations were found between both the angular condyle–coronoid process and the inclination of the lower posterior teeth, and the retromolar space. Conclusion: this study showed that the angle of a lower third molar, in relation to mandibular pain, can be an index for predicting tooth inclusion.

Three-dimensional relationships between condylar volume and dentoskeletal characteristics in Class II hyperdivergent female adults

BackgroundThis study aimed to determine the differences among various volumes of condylar osseous patterns and the corresponding dentoskeletal characteristics based on the risk of temporomandibular disorder.MethodsCraniofacial spiral computed tomography data of 60 Class II hyperdivergent female adults were divided into normal, resorptive, flattened, and osteophyte groups based on condylar osseous forms. The condylar volumes of each group were compared, and their correlations with the dentoskeletal characteristics were assessed in three dimensions. Pairwise least significant difference tests were used to examine individual pairwise differences between groups, and one-way analysis of variance was used to measure differences among multiple groups. Pearson correlation and Spearman rank correlation analyses were used to determine the correlation between condylar volume and dentofacial characteristics. Statistical significance was established at p < 0.05.ResultsThe condylar volume in the normal group was significantly greater than that in the changed groups, with no significant differences between the subgroups. The decrease in condylar volume was associated with a retruded and clockwise-rotated mandible with shorter rami. Condylar volume was negatively correlated with overjet, the alveolar height of the lower anterior and posterior teeth, sagittal inclinations of the lower teeth, intermolar width of the mandibular first molars, and width between the corresponding alveolar crests.ConclusionMultiple three-dimensional dentoskeletal characteristics of Class II hyperdivergent female adults are correlated with condylar bony changes, regardless of the form. These results could be helpful in indicating potential pathological changes in the temporomandibular joint and in making proper treatment plans for these patients.

Evaluation of the predicted vs. achieved occlusal outcomes with the Invisalign® appliance: A retrospective investigation of adult patients

The aim of this study was to investigate the relationship between occlusal contacts, overbite, transverse expansion, and the buccolingual inclination of the teeth with reference to the predicted treatment outcomes and achieved outcomes related to the use of the Invisalign® appliance in mild-to-moderate Class I malocclusions. The occlusal contacts, overbite, the buccolingual inclination and transverse expansion of the maxillary arch of adult patients satisfying inclusion and exclusion criteria were measured at the initial (pre-treatment), predicted, and achieved treatment stages using metrology software. Pearson correlation coefficients and regression equations were calculated to determine the association between the initial, predicted and achieved changes in occlusal contact against the other variables. Thirty-three patients, who commenced treatment between 2013 and 2018 and satisfied inclusion/exclusion criteria were evaluated. An overall loss of posterior contact was recorded and highlighted by a significantly greater loss of contact from the maxillary buccal occlusal surfaces compared to the palatal occlusal surfaces. The mean [SD] achieved overbite outcome (2.94mm [1.17]) was greater than the predicted (1.74mm [0.87), P<0.001). The buccolingual inclination was significantly increased for the lateral incisors and first and second molars despite a predicted decrease (P≤0.007). Achieved transverse expansion showed significant variation from the predicted. The loss of posterior occlusal contact was correlated with the buccolingual inclination (r=0.70) and transverse expansion (r=0.74) of the posterior teeth. In mild-to-moderate Class I malocclusions, treatment using the Invisalign® appliance resulted in an overall loss of posterior contact. The loss of occlusal contact was correlated with deficiencies in achieved buccolingual inclination and transverse expansion of the posterior teeth. Planned bodily expansion was ineffective as most expansion occurred due to unplanned buccal tipping.

Study on damaged micro-mechanism of pipe wall during braking and anchoring process of pipeline intelligent plugging robot

Pipeline intelligent plugging robot (PIPR) realizes braking and anchoring through hard contact of slip and pipeline. This process will cause bite marks on the inner wall of the pipeline, which will aggravate corrosion and shorten the service life of the pipeline. Therefore, it is necessary to comprehensively consider slip anchoring performance and degree of pipeline damage, and optimize slip structure parameters of PIPR, to reduce the damage caused by hard contact between slip and pipeline. Based on force analysis and the hard contact mechanism of PIPR in the course of the anchoring process, the damage factors of pipe walls are analyzed, and a finite element analysis model of slip and pipeline is established. The plastic strain of the inner surface of the pipeline, the plastic strain of slip, and the von Mises stress under three parameters of slip tooth top angle, tooth inclination angle, and tooth number are comprehensively evaluated. In addition, visible indoor tests are established to verify the simulation model. The results show that the optimal tooth structure of slip is tooth top angle [Formula: see text], tooth inclination angle [Formula: see text], and tooth number [Formula: see text]. This study will provide a reference for the optimal design of the slip of PIPR. It has important engineering significance for the successful implementation of its anchoring operations.

Finite element analysis of the biomechanical effect of clear aligners in extraction space closure under different anchorage controls

Clear aligners (CAs) have attracted increasing attention from patients and orthodontists because of their excellent esthetics and comfort. However, treating tooth extraction patients with CAs is difficult because their biomechanical effects are more complicated than those of traditional appliances. This study aimed to analyze the biomechanical effect of CAs in extraction space closure under different anchorage controls, including moderate, direct strong, and indirect strong anchorage. It could provide several new cognitions for anchorage control with CAs through finite element analysis, further directing clinical practice. A 3-dimensional maxillary model was generated by combining cone-beam computed tomography and intraoral scan data. Three-dimensional modeling software was used to construct a standard first premolar extraction model, temporary anchorage devices, and CAs. Subsequently, finite element analysis was performed to simulate space closure under different anchorage controls. Direct strong anchorage was beneficial for reducing the clockwise occlusal plane rotation, whereas indirect anchorage was conducive for anterior teeth inclination control. In the direct strong anchorage group, an increase in the retraction force would require more specific anterior teeth overcorrection to resist the tipping movement, mainly including lingual root control of the central incisor, followed by distal root control of the canine, lingual root control of the lateral incisor, distal root control of the lateral incisor, and distal root control of the central incisor. However, the retraction force could not eliminate the mesial movement of the posterior teeth, possibly causing a reciprocating motion during treatment. In indirect strong groups, when the button was close to the center of the crown, the second premolar presented less mesial and buccal tipping but more intrusion. The 3 anchorage groups showed significantly different biomechanical effects in both the anterior and posterior teeth. Specific overcorrection or compensation forces should be considered when using different anchorage types. The moderate and indirect strong anchorages have a more stable and single-force system and could be reliable models in investigating the precise control of future tooth extraction patients.

Management of an impacted maxillary central incisor with surgical exposure and a 2x4 orthodontic appliance: A case Report

Dental impaction or transposition are disorders related to ectopic eruption or failure in tooth eruption, which can affect child physical, mental, and social development. This condition compromises face aesthetics, phonation, and masticatory function. The cause of impaction may vary from physical obstruction in the path of eruption, tooth material arch length discrepancy to malformation of the tooth, but supernumerary teeth are the leading cause. Failure of eruption of maxillary incisors requires early diagnosis and proper treatment planning. General principles of management of the condition include removal of physical obstruction, creation of space, and surgical exposure with or without traction. The rationale of the 2x4 orthodontic treatment of an unerupted tooth depends upon its age, position, etiology, and amount of space in the dental arch. It under the category of interceptive orthodontic procedure to prevent malocclusion near future. The present case report elaborates on case of incisor impaction with different aetiologies and varying ranges of complexity. However, it's far frequently important to continue with a surgical–orthodontic treatment. The inclination of teeth in relation to the midline and the root maturation degree determine prognosis and therapeutic timing. Thus, we are describing a case of 10 yrs. old child with, class 1 molar relationship bilaterally with missing maxillary right central incisor.

Correlation of age and skeletal effects after miniscrew assisted rapid palatal expansion.

To evaluate the skeletal and dentoalveolar effects after miniscrew assisted rapid palatal expansion (MARPE) and their correlation with the age of the patients. Settings and sample population: Sample comprised 19 patients with maxillary atresia and posterior crossbite, treated with MARPE. Cone-beam computed tomographs (CBCT) were evaluated before and after expansion. Three patients were excluded since the midpalatal suture was not opened. Thus, 16 patients (11 female; 5 male) were evaluated, with a mean age of 24.92 years (s.d.=7.60). The time between the installation of MARPE and the second CBCT was, on average, 1.64 months (s.d.=1.12). Linear and angular measurements were performed: bone thickness and level, tooth inclination, transverse dental widths, and nasal base and jugula widths. Comparison was performed with dependent t-test and correlations with Pearson coefficient. MARPE was 84.2% successful. There was significant reduction in the buccal bone thickness of the first molars and an increase in the palatal bone thickness of all teeth. First molars showed significant buccal inclination. All transverse dimensions showed a significant increase. Older patients tended to show a less maxillary transverse skeletal increase. A greater maxillary transverse increase was accompanied by a greater intermolar width increase and also a greater buccal bone loss in the mesiobuccal roots of the maxillary first molars. MARPE corrected the maxillary atresia in adult patients, with significant transverse increases, a slight decrease in buccal bone thickness and buccal inclination of the first molars, combining skeletal and dental effects. Older patients presented less transverse skeletal increases. Key words:Palatal expansion technique, skeletal anchorage, cone-beam computed tomography.

Comparative Evaluation of Skeletal and Dental Effects of Mini-Implant Assisted and Corticopuncture-Facilitated Rapid Palatal Expansion in Adults: A Randomized Clinical Study

Abstract Introduction: Conventional rapid maxillary expansion (RME) in adults is difficult due to increased skeletal maturity of the midpalatal suture. Surgically assisted rapid palatal expansion (SARPE) treatment is recommended for adults with strongly consolidated sutures but has lesser acceptance due to its invasive nature. Mini-implant-assisted rapid palatal expansion (MARPE) produced dentoalveolar side effects along with some skeletal effects in adults while being highly successful in adolescents and young adults. A lesser invasive technique combined with a purely bone-borne-rapid-maxillary-expansion appliance (BBRME) is suggested in this study to achieve maximum skeletal effects and minimize the dentoalveolar side effects of expansion in adults with completely fused midpalatal sutures as an alternative to SARPE. Aim: This study aims to evaluate and compare skeletal and dental effects of mini-implant assisted, and corticopuncture-facilitated rapid palatal expansion in adults. Material and Methods: A randomized clinical study was performed on 18 patients (mean age 20.77 years) who were randomly divided into two groups: Group A (Corticopuncture-facilitated BBRME) and Group B (conventional MARPE). Pretreatment (T0) and postexpansion (T1) skeletal and dental effects of both the groups were analyzed using cone-beam computed tomography imaging. Results: A student’s paired t-test was used to evaluate the difference in expansion achieved between the two groups (T1-T0). Group A (BBRME with corticopunctures) showed increased transverse widths at the basal bone, nasal base, and jugal processes. Group B (conventional MARPE) showed increased inclination of the posterior teeth indicating dental tipping. Both groups were successfully treated with their respective protocols but dentoalveolar side effects were significantly less in group A (BBRME) suggesting a better prognosis in BBRME group. Conclusions: Greater skeletal changes were seen in group A (BBRME) (P &lt; 0.05*) than in group B. Group B (MARPE) showed more dental side effects like dental tipping and lesser skeletal expansion. Corticopuncture-facilitated bone-borne RME (BBRME) is a viable and efficient method of maximizing skeletal expansion in adults with fully obliterated midpalatal sutures.

A new torquing method for anterior tooth inclination control: a clinical report with a 7-year follow-up

Abstract Appropriate orthodontic mechanotherapy, particularly in relation to incisor inclination control is a key consideration for successful treatment and the delivery of optimal aesthetics. A novel, easy, safe and effective torquing technique, termed Park’s cervical torque tie, has been devised. A female patient sought orthodontic treatment and presented with a Class II division 2 malocclusion with crowding but a favourable facial profile. The treatment plan involved the distal movement of the maxillary posterior teeth, decrowding and incisor inclination correction. Palatal root movement was applied to the retroclined upper incisors by a novel cervical torque tie. The treatment was successfully completed after the distalisation of the dentition and palatal root movement of the upper incisors. However, following post-treatment cone-beam computed tomography, less bone coverage was evident on the palatal surface of the upper incisors. After a seven year follow-up, the treatment results were well maintained, and cortical bone regeneration was confirmed.

Transverse differences between cleft lip and palate and non-cleft palate with skeletal Class III malocclusion using buccolingual inclination: a cone-beam computed tomography retrospective study

BackgroundThe purpose of this study was to evaluate the differences between buccolingual inclination (BI) of maxillary posterior teeth in patients with cleft lip and palate (CLP) and non-cleft palate with skeletal Class III malocclusion. We propose a method of maxillary expansion which is more suitable for patients with CLP.MethodsFor this retrospective study, 40 patients with CLP and 21 patients with skeletal Class III malocclusion were selected. The CLP group was divided into the unilateral cleft lip and palate (UCLP) and bilateral cleft lip and palate (BCLP) groups. The BI of the maxillary first premolar (BI4), maxillary second premolar (BI5) and first molar (BI6) were measured using cone-beam computed tomography, and the differences between them were compared and analyzed by Student’s t-test.ResultsThere were significant differences between cleft side BI4 and non-cleft side BI4 in the UCLP group, BI5 in the BCLP group, BI4 and BI5 in all CLP groups and the skeletal Class III malocclusion group. BI6 was similar across all three groups.ConclusionsThe premolars of patients with CLP do not exhibit the same regularity as those with Class III malocclusion; this may be related to surgical scarring of the cleft palate. Greater attention should be paid to the correction of BI in the maxillary expansion of patients with CLP.

Genetics of three-dimensional tooth inclination and angulation in orthodontic patients with Class I Occlusion: A cross-sectional study

This cross-sectional study aimed to utilize quantitative polymerase chain reaction (qPCR) to investigate the influence of genetic variance over teeth inclination and angulation in orthodontic patients with Class I occlusion. DNA was extracted from adolescent patients seeking orthodontic treatment in a single institution (from July 2018 to April 2020), who had CBCTs taken as part of initial standardized records. Patients had permanent dentition, Class I skeletal and dental classifications, with normal vertical and transverse skeletal dimensions, normal incisors inclination, no to mild crowding or spacing. qPCR was performed using genetic markers for candidate genes EPB41, TGFβ3, GHR and PAX9. Three-dimensional teeth inclinations (TI) and angulations (TA) were evaluated using Invivo6 software and correlated with genotypes. Reliability of TI and TA was assessed using intraclass correlation coefficients (ICC). Mixed models and multiple linear regression analyses were used to assess the association between each single nucleotide polymorphisms (SNP) with tooth inclination (TI) and with tooth angulation (TA). The results were evaluated at the significance level of P<0.05. Twenty four adolescent patients with mean age of 13.4±2.4 years were included in the study. ICC showed adequate intra-examiner reliability for TI and TA (0.806<r<0.988, P<0.001). Multiple linear regression analysis showed a significant association between TI and homozygous-T polymorphism for PAX9 (P=0.028) and homozygous-G polymorphism for GHR (P=0.028). Also, a significant association between TA and homozygous-A polymorphism for EPB41 (P=0.019) and homozygous-G polymorphism for GHR (P=0.001) was evident. Autosomal recessive patterns of inheritance for PAX9 and GHR with TI and for EPB41 and GHR with TA were shown. This study offers insight toward the hierarchical nature of epigenetic interactions between heredity and the environment in determining the three-dimensional positions of teeth in orthodontic patients with Class I occlusion.

Parameter Optimization and Experiment of a Seed Furrow Cleaning Device for No-Till Maize Seeding

To avoid the issues of seeds lying atop straw, where the seeds cannot germinate, during no-till maize seeding, a seed furrow cleaning device is proposed. The device uses rotating spring teeth and a curved sliding shovel to clear the straw from the seed furrow to the outside. The critical components of the side throwing mechanism, rotary disc and spring teeth design are analyzed, and the value range of the installation inclination angle, rotating speed and bending angle of spring teeth are determined. The force on the straw at the moment of starting to touch and throw it is analyzed theoretically in the three installation directions of forward inclination, radial and backward inclination on the rotary disc, and the backward inclination of the spring teeth is determined. A simulation model of the seed furrow cleaning device is established by using the discrete element method simulation software; the forwarding speed, rotating speed, installation inclination angle, and bending angle of spring teeth are used as influencing factors to carry out single-factor experiments. The influence characteristics of different parameters on seed ditch cleaning effect are analyzed from the aspects of straw cleaning quantity and soil disturbance. A field validation experiment is carried out, and the results show that when rotating speed is 180 r/min, installation inclination angle of spring teeth is 40°, and bending angle is 30°, the straw cleaning rate is 82.26%. The research could provide references to develop the no-till seeder for maize seeding.

Palatal Anterior Teeth Retraction Assisted by Temporary Anchorage Devices - A Review

Successful orthodontic resolution of bimaxillary dentoalveolar protrusion depends on successful retraction of anterior dentition, which also involves acquiring proper buccolingual inclination and vertical position of anterior teeth. To fulfill these requirements, clinicians have devised numerous biomechanical and surgical orthodontic options. A palatal retractor for retraction of maxillary anterior dentition is the result of clinician’s long-time creative endeavors and an evolution of the biomechanical design. A palatal retractor splints the maxillary anterior dentition on the lingual side with bonded mesh plates connected by a supporting wire. Two long palatally extended arms are soldered to the supporting wire where adequate retraction force can be applied. Palatal retractors have several advantages over conventional bracket/wire systems. The two most prominent ones are biomechanical superiority and esthetic invisibility. As the palatal retractor is positioned on the lingual surface of the maxillary anterior dentition, it is not visible from the frontal view and since the anterior dentition retraction constitutes a significant portion of the total treatment time in extraction orthodontic treatment, it is a distinct esthetic advantage. Biomechanical disadvantage of the conventional bracket/wire system lies in its innate ineffectiveness of the torque and vertical control because of the long distance between the point of force application and the center of resistance of the anterior dentition. A combination of TADs and palatal retractors provides the possibility of maximizing control of both the torque and vertical position. This article aims to describe clinical considerations, applications, and results of palatal retractor use in clinical cases. Keywords: extraction treatment, anterior teeth retraction, palatal retractors, temporary anchorage devices.

The effect of tooth cusp morphology and grinding direction on TMJ loading during bruxism

Increased mechanical loading of the temporomandibular joint (TMJ) is often connected with the onset and progression of temporomandibular joint disorders (TMD). The potential role of occlusal factors and sleep bruxism in the onset of TMD are a highly debated topic in literature, but ethical considerations limit in vivo examinations of this problem. The study aims to use an innovative in silico modeling approach to thoroughly investigate the connection between morphological parameters, bruxing direction and TMJ stress. A forward-dynamics tracking approach was used to simulate laterotrusive and mediotrusive tooth grinding for 3 tooth positions, 5 lateral inclination angles, 5 sagittal tilt angles and 3 force levels, giving a total of 450 simulations. Muscle activation patterns, TMJ disc von Mises stress as well as correlations between mean muscle activations and TMJ disc stress are reported. Computed muscle activation patterns agree well with previous literature. The results suggest that tooth inclination and grinding position, to a smaller degree, have an effect on TMJ loading. Mediotrusive bruxing computed higher loads compared to laterotrusive simulations. The strongest correlation was found for TMJ stress and mean activation of the superficial masseter. Overall, our results provide in silico evidence that TMJ disc stress is related to tooth morphology.