Premature Contact Research Articles

A comprehensive analysis on coast side contact behaviour of thermoplastic gears against steel gear: a FEA approach

PurposeThe research paper comprehensively investigates the gear tooth deflection of standard thermoplastic gears with steel gear as the driver and driven companions. An accurate mapping of characteristic contact regions between the meshing gears was done, and the behaviour of the gear tooth in the premature and prolonged contact zones was studied.Design/methodology/approachThe study employs the finite element method to conduct a quasi-static 2D analysis of meshing gear teeth. The finite element model was created in AutoCAD and analysed using the ANSYS 19.1 simulation package.FindingsIn the polymer-polymer gear combinations, premature and prolonged contact primarily occurs along the addendum radii of meshing gears, whereas a novel contact phenomenon was observed in the coast side for polymer-metal and metal-polymer combinations, exhibiting a path perpendicular to the standard drive side contact. As well, the deflection of the tooth alters the load distribution across the interlocking gears, leading to a decrement in the root stresses.Originality/valueThe Lewis bending equation demonstrates that bending stresses depend solely on the applied load and the geometry of the tooth. It does not consider the effects of deflection. However, the computational results showed that the gear tooth deflection caused by different gear pair combinations also affects the bending stresses. The contact stresses observed in the polymer-polymer gear combination were observed to be within the material’s proportional limit. However, when a steel gear is paired with a polymer gear, the contact stresses exceed the proportional limit due to coast side contact.

Dependence of regional circulation in periodontal tissues on the condition of occlusive-articulatory disorders in patients with chronic generalized periodontitis

Abstract Introduction. The scientific substantiation of the causal relationships of traumatic occlusive forces and periodontal diseases is a difficult task and this issue is still debatable. According to available data, occlusive loads in the area of compression of periodontal ligaments lead to changes in blood circulation in lymphatic and blood vessels, which increase the inflammatory process when the adaptive capacity of the periodontal is exceeded. It is necessary to obtain additional information to choose tactics for reducing premature contacts in chronic generalized periodontitis. The aim of the study was to study the state of regional blood circulation in periodontal diseases with the elimination of occlusive obstacles by selective grinding of teeth. Results and discussion. 25 patients with occlusal interference before and after grinding were examined. In the study group, a decrease in the rheographic index by 41% and an increase in the time of rapid and slow blood filling by 1.5 and 1.6 times, respectively, before occlusive grinding were found. After the elimination of premature supracontacts, hemodynamic parameters changed in the opposite direction, the rheographic index increased, and the α1 and α2 indicators decreased. Other hemodynamic criteria studied approached the values in the comparison group. Conclusion. The results of the study confirm the expediency of minimally invasive interventions to eliminate occlusive interference in order to improve hemodynamics in periodontal tissues.

Minimal Access Retromandibular Approach to Fractures of Vertical Segment of the Mandible: A Versatile Technique

Abstract Introduction Fractures of the condylar region of the mandible, although fairly common, also generate the most debate regarding management—both closed and open treatment options have been recommended and shown to yield good results. We present our experience with a minimal access retromandibular approach to fractures of the vertical mandible. Materials and Methods This is a retrospective study of all patients who underwent open reduction and internal fixation for fractures of the vertical mandible (condyle, subcondylar region, ramus) using a retromandibular approach at a tertiary care hospital in a metropolitan city in India between January 2022 and July 2023. All fractures were approached using a standard technique through a retromandibular incision and a transparotid route. The proximal segment was mobilized, reduced, and fixed to the ramus with two 2-mm miniplates—one along the posterior border and the other along the sigmoid notch border. Postoperative guiding elastics were placed for 2 weeks without any rigid maxillomandibular fixation. Patients were followed at weekly intervals for 1 month followed by monthly visits for 6 months. At each visit, mouth opening, occlusion, and facial nerve function were assessed. Scar quality was assessed by both examiner and patient using the Patient and Observer Scar Assessment Scale (POSAS) scoring system. Results A total of 25 subcondylar fractures in 20 patients were fixed using the retromandibular approach. Nineteen were male and 1 was female. The etiology of trauma was road accident (8), fall from train (2), fall from height (5) and assault (5). Fifteen patients had unilateral fractures while 5 had bilateral fractures. All patients had concomitant fractures of the mandibular arch which were also fixed. The interval between trauma and surgery ranged from 5 to 28 days. All patients had premature molar contact on the side of fracture with anterior open bite. Mouth opening ranged from 1.5 to 2.5 cm. All the fractures could be fixed using the retromandibular approach. None of the patients developed any facial nerve dysfunction or salivary leak. The occlusion was restored to pretrauma status in all patients and was stable at 6 months' follow-up. Mouth opening ranged from 3.5 to 4 cm. The POSAS observer score ranged from 09 to 19 with a mean score of 12.7. The POSAS patient score ranged from 17 to 28 with a mean score of 20.3 revealing that all patients were extremely happy with the scar. Conclusion The minimal access retromandibular approach to the vertical mandible is a versatile technique enabling accurate reduction and fixation of fractures of the vertical segment of the mandible with good long-term functional and cosmetic results.

Barefoot pressure distribution of diabetic patients and non-diabetic volunteer subjects after sensorimotor training with an unstable shoe construction

BackgroundForty-three percent of all diabetic foot ulcers occur under the medial forefoot due to a medial deviation of elevated pressures and premature forefoot ground contact in neuropathic diabetic patients. A 6-week sensorimotor training period with an unstable shoe construction reduces in-shoe peak pressures and contact times under the medial aspect of the forefoot. MethodsThe study was designed as a Randomised Control Trial with two diabetic groups (one served as intervention group and one as control group) and one non-diabetic intervention group. Measurements for barefoot pressure distribution and contact times were taken by means of an Emed® pressure measurement platform (Novel GmbH, Munich) before and after 6 weeks. During this time the diabetic and the non-diabetic intervention groups were required to wear an unstable shoe construction (Masai Barefoot Technology, MBT®) for at least four hours per day. FindingsResults for the non-diabetic intervention group showed significantly later contact times for the medial portion of the forefoot, resulting in shorter contact times. Peak pressure was also reduced under the medial aspect of the foot while it was increased under the lateral aspect of the foot. Changes for the diabetic intervention group followed the same pattern while the values of the diabetic control group shifted away from the reference values. InterpretationA 6-week sensorimotor training period with an unstable shoe construction can change barefoot peak pressures and contact times in non-diabetic subjects and in diabetic patients in the most endangered area, i.e. the medial forefoot.

Neurophysiological assessment of the condition of the masticatory muscle group in patients with occlusion disorders and chronic generalized periodontitis

Background. Recently, the interest of dentists and physiologists has been focused on the development of a set of informative computerized techniques for an objective analysis of the functional state of the dentofacial apparatus. Achieving certain successes in conducting functional diagnostic examinations contributes to the development of algorithms for complex treatment of patients with generalized periodontitis and premature occlusal contacts.Goal. Study of the functional state of the dentofacial apparatus according to the parameters of bioelectrical activity of muscles in patients with chronic generalized periodontitis and occlusal disorders in static and dynamic conditions of the lower jaw.Materials and methods. The study involved 37 people with clinically healthy periodontium, physiological occlusion, and absence of occlusal disorders (Group 1) and 45 patients with physiological types of occlusion, generalized chronic periodontitis and premature occlusal contacts (Group 2). Functional methods included electronic registration of occlusal relationships with the T-Scan® III computer occlusion analysis system and study of the bioelectrical activity of the masticatory muscles using the Bio-EMG® III electromyography using standard functional tests.Results. In patients of group 2, in comparison with patients of group 1, neuromuscular discoordination of the functional activity of the masticatory muscles was diagnosed. This condition is confirmed by the asymmetry and lack of muscle synergy when performing the “Maximum volitional compression” test, an improvement in the symmetry of the work of the muscles of the same name on the right and left sides and the synergy of the work of the muscles of the right and left masticatory groups, as well as a statistically significant increase in the values of biopotentials m. temporalis and m. masseter during the “Maximum volitional compression on rollers” test.Conclusions. Disturbances in the coordinated work of the muscles of the craniofacial region in patients with chronic generalized periodontitis and premature occlusal contacts are realized in a statistically significant increase in the biopotentials of the masticatory muscle group at rest, a decrease in biopotentials during functional loading, as well as a reduction in the values of symmetry and synergy in relation to similar values patients of group 1.

Elastic and Elastoplastic Contact Mechanics of Concentrated Coated Contacts

Machines operate under increasingly harsher contact conditions, causing significant wear and contact fatigue. Sub-surface stresses are responsible for the premature contact fatigue of rolling element bearings, meshing gears, and cam–follower pairs. Surface protection measures include hard, wear-resistant coatings. Traditionally, contact integrity has been predicted using classical Hertzian contact mechanics. However, the theory is only applicable when the contact between a pair of ellipsoidal solids of revolution may be considered as a rigid indenter penetrating a semi-infinite elastic half-space. Many coatings act as thin bonded elastic layers that undergo considerably higher pressures than those predicted by the classical theory. Furthermore, inelastic deformation of bonded solids can cause plastic flow, work-hardening, and elastoplastic behaviour. This paper presents a comprehensive, integrated contact mechanics analysis that includes induced sub-surface stresses in concentrated counterformal finite line contacts for all the aforementioned cases. Generated pressures and deformation are predicted for hard coated surfaces, for which there is a dearth of relevant analysis. The contact characteristics, which are of particular practical significance, of many hard, wear-resistant advanced coatings are also studied. The paper clearly demonstrates the importance of using efficient semi-analytical, detailed holistic contact mechanics rather than the classical idealised methods or empirical numerical ones such as FEA. The novel approach presented for the finite line contact of thin-layered bonded solids has not hitherto been reported in the open literature.

Epidemiology of Bruxism and Temporomandibular Joint Disorders (TMD) in Iranian Adults: A Cross-Sectional Study

Objective: The prevalence of bruxism in the literature has been reported differently. The aim of this study was to assess the prevalence of bruxism in patients aged 25–40 who were referred to Kerman Dental School. Methods: This analytical descriptive cross-sectional study was performed on 320 patients referred to the Department of Oral Medicine of Kerman Dentistry Faculty in the age range of 25 to 40 years old. The prevalence of bruxism as well as TMJ disorders were evaluated. Data were collected in a questionnaire and entered into SPSS version 24. Analyzing was done by a chi-square test at a significant level of 0.05. Results: The prevalence of bruxism was 23.8%, with superiority in women. Although clenching was observed in 95.5% of the patients, 84.4% showed premature contacts on teeth, most of them related to the non-working side, and 82.9% presented premature contacts on restorations, especially on the non-working side. Regarding TMD symptoms, pain was the most common (83.4%), and clicking and crepitus were seen in 42% and 6% of the patients, respectively. Also, in 63.7% of the subjects with bruxism, jaw deviation was observed, and 18.7% showed restricted jaw movement. Conclusion: The prevalence of bruxism in the studied population is in the range of similar studies. Regarding TMD, troublesome symptoms such as pain, jaw deviation, and limited mouth opening were the only ones significantly related to bruxism.

MORPHOLOGICAL CHANGES OF RAT PERIODONTIUM IN SUPRAOCCLUSAL RELATIONS OF INDIVIDUAL TEETH IN THE AGE ASPECT

Although the issue of the occlusal load influence on the occurrence of pathological phenomena in the body has been discussed for decades, it is still a subject of debate. Pathogenic occlusion is defined as excessive occlusal forces (premature contacts and interference) that can cause injuries to the dentition, including teeth and periodontal tissues. Changes in occlusal dimensions, if not properly performed or treated, can lead to dysfunctions of the dentition, such as joint clicking, difficulty in chewing, occlusal discomfort, muscle fatigue, and pain.
 Aim: to determine the morphological changes of periodontium in rats of different age groups in the supraocclusal relationship of individual teeth in the age aspect.
 Materials and methods of the study. The study was conducted on 60 white laboratory rats aged 4 to 22 months and weighing 90 to 330 g. The rats were divided into control (30 animals) and experimental (30 animals) groups. Each group was divided into 3 subgroups (10 animals each) depending on the age of the rats: young, mature and senile. Young animals included rats aged 3 4 months with a weight of 90 100 g; mature animals aged 6-8 months with a weight of 150 170 g; senile rats 20 22 months and weighing 200 220 g. In the experimental group, the state of supraocclusion was modeled by increasing the height of the lower right second molars by placing 1 mm high filling. For the placement of the filling, 37% orthophosphorus etching gel for enamel and dentin (Latus, Ukraine), microapplicators (Latus, Ukraine), the fifth generation Prime&Bond NT adhesive system (Dentsply Sirona, Germany), the universal microhybrid light-curing composite material Latelux (Latus, Ukraine) and the photopolymerizer LED.D (WOODPECKER, China) were used according to the manufacturer's instructions. The experimental animals were withdrawn from the experiment on the 15th day by decapitation under general anesthesia with sodium thiopental. The lower jaws were skeletonized, and dental blocks were cut out in the area of the molars. For histological examination, the dental blocks were fixed in a 10% solution of neutral formalin for two days, dehydrated in alcohols of increasing concentration and embedded in paraffin. Then, sections were made from the obtained preparations on a Shandon Finesse 325 rotary microtome with a section thickness of 4-6 μm. The histological sections were fixed on degreased slides and dried. Van Gieson staining was performed. The width of the periodontal gap was determined using the ZEISS ZEN 3.7 program by Carl Zeiss Microscopy.
 Results of the study. Histometric analysis has showed significant morphological changes in the experimental group of all age categories. In young rats, the fibrinoid edema phenomena of the periodontal ligament collagen fibers were observed. In mature rats, there was a picture of mucoid edema of collagen fibers of the periodontal ligament. In senile rats, fibrinoid necrosis of collagen fibers of the periodontal ligament were discovered, an inflammatory infiltrate, macrophages and neutrophils, with a predominance of neutrophilic inflammatory microenvironment, and initial hyaline tissue changes were found. In all age groups, there was cement resorption on the lateral surfaces of the tooth root, lacunar resorption of alveolar bone tissue and the presence of a large number of osteoclasts. In senile rats, hypercementosis was determined in the apical part of the root. In the control group of all age categories, neither resorption nor disorganization of connective tissue, nor hypercementosis was detected.
 Conclusions. The study shows that traumatic occlusion leads to resorption of root and alveolar cementum in all age groups. In young rats, traumatic occlusion causes fibrinoid edema of collagen fibers of the periodontal ligament. In mature rats, traumatic occlusion causes mucoid edema of collagen fibers of the periodontal ligament. In senile rats, traumatic occlusion causes fibrinoid necrosis of collagen fibers of the periodontal ligament, initial hyaline tissue changes and hypercementosis.

The state of microcirculation in patients with periodontal diseases and disorders of the occlusal relationships of the dentition

Background. The study of microcirculation disorders, as one of the key factors in the pathogenesis of periodontal diseases, is relevant in clinical dentistry. Premature contacts, acting as provoking factors for occlusal disorders, cause overload of individual teeth and aggravate the severity of inflammatory periodontal pathology. Objective registration of capillary blood flow and associated changes in the microvessels of the arteriolar and venular units in patients with periodontopathies and occlusal dis-orders will allow us to assess the degree and nature of tissue blood flow disorders in the gum tissue.Goal. Increasing the efficiency of diagnosing microcirculatory disorders in periodontal tissues in patients with chronic generalized mild periodontitis and disorders of the occlusal relationships of the dentition.Materials and methods. Using laser Doppler flowmetry (LDF), the state of mi-crocirculation in the periodontium was studied in 78 people aged 21–35 years with intact dentition and physiological occlusion, of which 33 people (group 1) had clinically healthy periodontium and the absence of occlusal disorders (group 1), with generalized chronic pulmonary periodontitis degree and premature occlusal contacts – 45 people (group 2). The microcirculation index (M), standard deviation (σ), and coefficient of variation (КV) were assessed. To obtain objective diagnostic data, amplitude-frequency analysis of the harmonic rhythms of LDF-grams was used with spectral decomposition into harmonic components of physiological oscillations of tissue blood flow (wavelet analysis).Results. In patients of group 2, in comparison with patients of group 1, a decrease in the level of periodontal blood perfusion, a reduction in the fluctuation of erythro-cyte flow and vasomotor activity of microvessels is determined, while a decrease in “active” and an increase in «passive» modulation of tissue blood flow contributes to an increase in the volume of circulating blood at arteriovenular anastomoses when the intensity of blood flow through the vessels of the capillary bed decreases.Conclusions. Patients of group 1 were diagnosed with a normoemic type of LDF-gram, which provides a relatively high degree of intensity of tissue blood flow, balance of regulatory mechanisms, and optimal trophism of periodontal tissues. In patients of group 2 with a spastic type of LDF-gram, characterized by a reduced level of perfusion, flux, vasomotor activity of microvessels, indicators of tissue blood flow and trophic function are significantly reduced.

Analysis of the Influence of Breastfeeding and Bottle-Feeding upon the Origin of Posterior Crossbites.

(1) Introduction. An analysis was made of posterior crossbites in deciduous dentition and their relation to the type of feeding received by the child, with the objective of determining the influence of the way in which the child is fed in the early stages of life on the development of posterior crossbites. (2) Material and methods. A total of 1401 preschool children between 3 and 6 years of age from Seville (Spain) were included in the study. An intraoral exploration was carried out to assess the presence of crossbites (uni- or bilateral, and functional or not). The study was completed with a parent or legal guardian questionnaire exploring the type of feeding received by the child in the first stages of life, as well as the presence of bad oral habits and their duration. (3) Results. A total of 276 children (19.7%) presented posterior crossbite in occlusion. Uponn centering the midlines, 197 were maintained, indicating that 79 were due to premature contacts (functional crossbites). There were no significant differences in crossbites among the children who had received breastfeeding, though bottle-feeding was seen to favor crossbite. (4) Conclusions. No statistically significant relationship was found between posterior crossbites and breastfeeding, though an association between posterior crossbites and bottle-feeding was observed, with the number of crossbites increasing with the duration of bottle-feeding.

АНАЛОГОВЫЙ И ЦИФРОВОЙ ПРОТОКОЛЫ ОЦЕНКИ ИЗБИРАТЕЛЬНОГО ПРИШЛИФОВЫВАНИЯ ЗУБНЫХ РЯДОВ С ОККЛЮЗИОННЫМИ НАРУШЕНИЯМИ ПЕРЕД ДЕНТАЛЬНОЙ ИМПЛАНТАЦИЕЙ

For successful orthopedic treatment using dental implants, an objective diagnosis of pathological changes in teeth and periodontal tissues is necessary. The identification and optimization of occlusive disorders at various stages of preparation for dental surgery contributes to the normalization of osseointegration processes, expands indications for periodontal diseases. The aim of the study was to assess the normalization of occlusive disorders before dental implantation using analog and digital protocols. The study included 57 patients aged 30 to 65 years and divided into 3 groups: the first group –23 patients with chronic generalized periodontitis of mild severity; the second group–20 patients with nonphysiological location of individual teeth due to partial defects of the dentition; the control group–14 patients. Results. The assessment of occlusive disorders was carried out using occlusography methods and in the articulator "Stratos -300". In the first group–62.6% of supracontacts, in the second group – 49.3%. Occlusive correction of premature contacts was performed. The control was carried out by electronic axiography. Occlusal harmony of occlusal-articulatory relations has been achieved after selective polishing. A comfortable closing of the teeth and smooth movement of the lower jaw have been achieved. The qualitative and quantitative indicators of the axiogram have improved.

Application of 3D digital smile design based on virtual articulation analysis in esthetic dentistry: A technique

A technique for the application of a virtual articulation system in 3-dimensional digital smile design (DSD) during esthetic restoration is described. To acquire stable occlusion and a smooth jaw movement pattern without premature contacts or interference, a digital facebow and a virtual articulator were used to collect and analyze a patient’s occlusal data and jaw movement information. The original pattern of occlusal contacts and jaw movements were diagnosed as stable and copied to the digital design of the new prostheses. Preparation of the abutments, crown lengthening surgery, and definitive crown fabrication and cementation were performed according to the design. After 9 months, the occlusion remained stable, and the patient was satisfied with the outcome.

Correlating assessment between clinical features and morphologies on CT scan of mandibular condyle fracture

Background: Among mandibular fractures, condyle fractures are common injuries which directly affect the occlusal function and aesthetics of the patients. Accurate diagnosis based on clinical and radiographic features helps to choose the appropriate treatment. This study aims to evaluate clinical features, morphologies on CT Scan of mandibular condyle fractures and analyze the relationship between these characteristics. Materials and methods: A cross-sectional study on 30 patients with mandibular condyle fractures were conducted at Department of ENT - Ophthalmology - Odonto Stomatology in the Hospital of Hue University of Medicine and Pharmacy, from December 2021 to June 2023. Results: The male:female ratio was about 2:1, the main cause of fractures was traffic accidents (73.4%). The common clinical symptoms were malocclusion (96.7%) with occlusal interferences on posterior teeth and limited mouth opening (83.3%). On CT Scan, condylar neck fractures were the most common position (58.8%). There was a relationship between the side of deviated mouth opening and the affected sides (p < 0.05). In cases of unilateral condyle fractures, there was a relation between the side of premature contact on posterior teeth and the affected sides (p < 0.05). Conclusions: Fractures of condylar neck was the most common fractures in the mandibular condyle, which resulted in malocclusion, interferences on posterior teeth, limited and deviated mouth opening. There was a relationship between deviated mouth opening and premature contacts on posterior teeth with the fractured side. Key words: Mandibular condyle fracture, clinical features, CT Scan.

Influence of bad oral habits upon the development of posterior crossbite in a preschool population

BackgroundA study is made of posterior crossbite in deciduous dentition and its possible association to extrinsic factors (bad oral habits).MethodsA total of 1168 Spanish children between 3 and 6 years of age were included in the study. Exploration of the oral cavity was performed to assess the presence of crossbite (uni- or bilateral and/or functional), and a questionnaire was administered to the parents or caregivers to determine the presence of bad oral habits and their duration.ResultsIn occlusion, 19.7% of the cases (n = 230) presented uni- or bilateral posterior crossbite. On adopting centric relation confronting the midlines, crossbite persisted in 165 children, indicating that 65 cases were due to premature contacts (functional crossbite). The identified favoring factors were pacifier use, thumb sucking, oral breathing and tongue thrusting or immature swallowing.DiscussionMost studies in the literature report a relationship between posterior crossbite and bad oral habits. The proportion of posterior crossbites identified in our study (16.6%) is consistent with the data published by authors such as Kobayashi, Limeira or Paolantonio, among others, but differs from the results of Zhifei Zhou, Peres or Germa. In coincidence with most studies, we recorded a statistically significant association between posterior crossbite and bad oral habits.ConclusionsBad oral habits favor the appearance of posterior crossbite, and the duration of the habit, its intensity (in the case of thumb sucking) and type (in the case of pacifier use) act as influencing factors. Functional study characterized the types of posterior crossbites and identified those attributable to premature contacts. This aspect has not been addressed by previous studies, and we consider the findings to be very interesting for analyzing and identifying the features of true crossbites.

Intracellular fraction of zona pellucida protein 3 is required for the oocyte-to-embryo transition in mice.

In oocyte biology, the zona pellucida has long been known to operate three extracellular functions downstream of the secretory pathway, namely, encasing the oocytes in ovarian follicles, mediating sperm-oocyte interaction, and preventing premature embryo contact with oviductal epithelium. The present study uncovers a fourth function that is fundamentally distinct from the other three, being critical for embryonic cell survival in mice. Intriguingly, the three proteins of the mouse zona pellucida (ZP1, ZP2, ZP3) were found abundantly present also inside the embryo 4 days after fertilization, as shown by mass spectrometry, immunoblotting, and immunofluorescence. Contrary to current understanding of the roles of ZP proteins, ZP3 was associated more with the cytoskeleton than with secretory vesicles in the subcortical region of metaphase II oocytes and zygotes, and was excluded from regions of cell-cell contact in cleavage-stage embryos. Trim-away-mediated knockdown of ZP3 in fertilized oocytes hampered the first zygotic cleavage, while ZP3 overexpression supported blastocyst formation. Transcriptome analysis of ZP3-knockdown embryos pointed at defects of cytoplasmic translation in the context of embryonic genome activation. This conclusion was supported by reduced protein synthesis in the ZP3-knockdown and by the lack of cleavage arrest when Trim-away was postponed from the one-cell to the late two-cell stage. These data place constraints on the notion that zona proteins only operate in the extracellular space, revealing also a role during the oocyte-to-embryo transition. Ultimately, these data recruit ZP3 into the family of maternal factors that contribute to developmental competence of mouse oocytes.

The Role of Supraerupted and Distoverted Maxillary Third Molars in the Treatment of Temporomandibular Disorder: A Randomised Controlled Trial.

Objective Temporomandibular disorder (TMD) is a multifactorial disease that is classified into muscular and joint disorders. The etiology of TMD is unknown but it is related to various factors such as bruxism, uncorrected high dental restorations, and occlusal prematurities. This study aims to provide treatment modalities for TMD patients with supraerupted and/or distoverted maxillary third molars that have premature contact with the opposing arch. Methods A total of 430 subjects diagnosed with TMD were included in the study and randomized into study and control groups based on their treatment needs. A detailed case history was taken, and findings of intra and extra oral examination were recorded along with other investigations such as study model analysis, orthopantomogram (OPG), cone-beam computed tomography (CBCT), and MRI. The multiphase treatment included counseling in phase I, extraction in phase II (only for the study group), and oral appliance in the third phase. The final phase involved the restoration of edentulous areas or reduced vertical dimension. Results Extraction of supraerupted and/or distoverted maxillary third molars in the study group during phase II showed a 96% reduction in TMD when compared to the control group who did not undergo extraction. Conclusion TMD is a repetitive motion disorder, and the success of treatment relies on the elimination of causative factors, the type of appliance used, and the establishment of ideal occlusion. This study suggests that the extraction of supraerupted and/or distoverted maxillary third molars is a prerequisite for treating TMD patients.

Femoral and acetabular features explain acetabular contact pressure sensitivity to hip internal rotation in persons with cam morphology: A finite element analysis

BackgroundFemoroacetabular impingement is characterized by premature contact between the proximal femur and acetabulum. The loss of femoral head-neck concavity associated with cam morphology leads to mechanical impingement during hip flexion and internal rotation. Other femoral and acetabular features have been linked with mechanical impingement but have not been comprehensively investigated. This study sought to determine which bony features are most influential in contributing to mechanical impingement in persons with a cam morphology. MethodsTwenty individuals (10 female, 10 male) with a cam morphology participated. Finite element analyses incorporating subject-specific bony geometry derived from computed tomography scans were used to determine which femoral (alpha angle and femoral neck-shaft angle) and acetabular (anteversion angle, inclination angle, depth, and lateral center-edge angle) features accentuate acetabular contact pressure with increasing degrees of hip internal rotation with the hip flexed to 90°. To determine the best predictors of acetabular contact pressure sensitivity to internal rotation, all morphological variables were included in a stepwise regression with the final model subjected to a bootstrapping procedure. FindingsThe stepwise regression revealed that femoral neck-shaft angle, acetabular anteversion angle, acetabular inclination angle, and acetabular depth were the best combination of variables to predict contact pressure sensitivity to internal rotation, explaining 55% of the variance. Results of the bootstrap analysis revealed that a median value of 65% [37%, 89%] variance in sensitivity could be explained by these morphological variables. InterpretationMechanical impingement and the concomitant acetabular contact pressure are modulated by multiple femoral and acetabular features in persons with a cam morphology.

Numerical investigation on the premature and extended contact behaviour of engineering thermoplastic gears and its effect in gear kinematics

PurposeThis research work aims to determine the maximum load a thermoplastic gear can withstand without the occurrence of extended contact. The extended contact of polymer gears is usually overlooked in basic design calculations, although it considerably affects the gear's load-carrying ability. Although various researchers highlighted the phenomenon, an extensive investigation of the extended contact behaviour is limited. Hence the work aims to investigate the premature and extended contact behaviour of thermoplastic gears and its effect in the gear kinematics, bending stiffness, stresses induced and the roll angle subtended by the gear pair.Design/methodology/approachThe work uses finite element method to perform quasi-static two-dimensional analysis of the meshing gear teeth. The FE model was developed in AutoCAD and analysed using ANSYS 19.1 simulation package. A three-dimensional gear model with all the teeth is computationally intensive for solving a static analysis problem. Hence, planar analysis with a reduced number of teeth is considered to reduce the computational time and difficulty.FindingsThe roll angle subtended at the centre by the path of approach is higher than the path of recess because of the increased load sharing. The contact stress profile followed a unique R-F-R-F pattern in the premature and extended contact regions due to the driven tip-driver flank surface contact. A non-dimensional parameter was formulated correlating the young's modulus, the load applied and deflection induced that can be utilised to predict the occurrence of premature and extended contact in thermoplastic gears.Originality/valueThe gear rating standards for polymer gears are formulated from the conventional metal gears which does not include the effect of gear tooth deflection. The work attempts to explain the gear tooth deflection for various standard thermoplastics and its effect in kinematics. Likewise, a new dimensionless number was introduced to predict the extended contact that will help in appropriate selection of load reducing the possibility of wear.

Dental occlusion characteristics in subjects with bruxism.

Bruxism is associated with a variety of factors, some of which are oral (occlusion, joint, face shape) while others are of a systemic nature (respiratory, cardiac, neurotransmitters, stress). The relationship between bruxism and occlusion has received great attention, but it still has a lot of ambiguity. This study aimed at investigating the parameters that may affect bruxism: dental interferences or premature contacts, vicious habits, temporomandibular joint (TMJ) pain, TMJ noises, TMJ morning fatigue, snoring, obstructive sleep apnea, which may occur before bruxism, or because of chronic parafunction. We conducted an observational, analytical case-control study to determine the association between bruxism and oral cavity factors as well as general factors. Participants were chosen from a group of middle-aged Romanian population. An online questionnaire was used for data collection. A total of one hundred subjects were included in the sample. Fifty cases with bruxism were chosen as a study group, and another fifty persons of similar ages were chosen as a control group. Statistical analysis was performed using the MedCalc version 20.110 software. The study comprised subjects between 18 and 42 years old. The most prevalent age range was between 20-25 years. The female-male ratio was almost similar; 62% of the participants had sleep bruxism, 10% had awake bruxism and 28% had a combined form. The arithmetic means of the daily stress levels for both research groups' scores were 3.0 for the bruxism group and 3.24 for the control group, while the work stress was 3.04 for the bruxism group and 3.41 for the control group. Dental interferences or premature contacts, vicious habits, TMJ pain, TMJ noises, TMJ morning fatigue, snoring, and obstructive sleep apnea were evaluated. The majority of subjects received an oral splint (n=26). Bruxism was associated with stress, occlusal parameters (premature contacts and occlusion interferences), and joint pathologies. Bruxism was not found to be positively correlated with obstructive sleep apnea syndrome. There was a moderately significant association between bruxism and snoring. There was no evidence of an association between bruxism and vicious habits, dental aesthetics, or obstructive sleep apnea. Treatment significantly improved the quality of life, the masticatory and joint functions.

Need for restoration of non-carious cervical lesions – A literature review

In present scenario, restoring non-carious cervical lesions (NCCLs) is clinically common. Major reasons for this are increased elderly population, the decreasing levels of tooth loss, and possible increase in the etiologies. These factors are poor brushing technique due to which gums recede, consumption of corrosive foods and beverages, and occlusal stress concentrators (occlusal disorders, premature contact, clenching, and bruxism habits. Unfortunately, Class V restorations are known to be less durable type and they have high index of retention loss, marginal residues and secondary caries. Other problems include isolation, insertion, cutting, finishing, and polishing. The present work aims to help the dentist choose best treatment strategy, which mainly involves the stages of problem identification, diagnosis, elimination or etiological treatment and if require restoration. Finally, appropriate recovery methods are suggested for each situation.