Mandibular Arch Research Articles

Comparative Study of Microbial Adhesion on Different Orthodontic Brackets - An In Vivo Study.

To study the microbial adhesion on different orthodontic brackets (conventional, ceramic, and self-ligating brackets). Three types of bracket systems i.e. self-ligating, conventional, and ceramic brackets were used consisting of 10 patients for each bracket system. Out of 30 patients 20 patients will be treated with conventional and ceramic brackets, in which, in one-half of the mouth steel ligature ties are placed and in the other half elastomeric rings would be placed. We collected swabs from the central incisors and first premolars of the both the right and left sides of both the maxillary and mandibular arches. The samples were collected three times from the above-mentioned teeth once prior to the placement of the brackets, the second and third samples after one and three months respectively. Significant variations were between the pretreatment and after one and three months of bracket placement in all three groups. Significant increase in the microbial adhesion of aerobic and anaerobic bacteria in conventional bracket form pretreatment to one and three months after bracket placement is seen. Although the colony formed by anaerobic bacteria is more in number in comparison to the aerobic bacteria. Our study reveals that the most hygienic bracket is a self-ligating bracket that should be used in patients who have poor oral hygiene. We also found that using steel ligature is more suitable as compared to elastomeric ligature in both conventional and ceramic brackets.

Retention using braided bonded wires: a 2-year follow-up of the dentition and oral hygiene with predictors of relapse

Abstract Objective To assess gingival health and predictors of relapse related to braided-wire bonded retainers after the active phase of comprehensive orthodontic treatment. Materials and methods Fifty-one subjects were recruited in a prospective study of whom 42 were available for analysis after 2 years of retention (pre-therapeutic ages 11–18 years; 66% female). A rectangular wire retainer (0.027 × 0.011″) was bonded to the mandibular incisors. Little’s index of incisor irregularity; intercanine width; the accumulation of biofilm, calculus and gingivitis; and the incidence of retainer detachment, were recorded. Subjects were examined before orthodontic therapy, upon therapy completion, and after 2 years of retention. Results The incidence of retainer detachment over the 2 years was 27%. The post-treatment incidence of irregularity was 17%, and intercanine width reduction was 24%. Calculus accumulation increased significantly during retention (p < 0.001) but not the extent of gingivitis. A multiple logistic regression demonstrated that an increase of mandibular intercanine width by ≥3 mm correspondingly increased the odds of relapse 14.3 times (95% confidence interval [CI], 1.1–196.1; p = 0.046). Patients presenting with retainer failure were 10 times (95% CI 1.6–62.8; p = 0.014) more likely to experience relapse. Subjects who experienced relapse had retainer failure earlier than those without relapse (19 vs. 23 months; p = 0.003). The occurence of relapse was not related to a treatment change in incisor irregularity, the duration of treatment, the age of the patient, gender nor to a change of intercanine width during retention. Conclusion Post-treatment changes in the mandibular arch incorporating bonded retainers were not large, but were common. An increase in mandibular incisor irregularity during retention is mostly related to treatment-induced intercanine width expansion. The bonded retainer often detached and increased calculus accumulation.

The Tumor Suppressor Adenomatous Polyposis Coli (apc) Is Required for Neural Crest-Dependent Craniofacial Development in Zebrafish.

Neural crest (NC) is a unique vertebrate cell type arising from the border of the neural plate and epidermis that gives rise to diverse tissues along the entire body axis. Roberto Mayor and colleagues have made major contributions to our understanding of NC induction, delamination, and migration. We report that a truncating mutation of the classical tumor suppressor Adenomatous Polyposis Coli (apc) disrupts craniofacial development in zebrafish larvae, with a marked reduction in the cranial neural crest (CNC) cells that contribute to mandibular and hyoid pharyngeal arches. While the mechanism is not yet clear, the altered expression of signaling molecules that guide CNC migration could underlie this phenotype. For example, apcmcr/mcr larvae express substantially higher levels of complement c3, which Mayor and colleagues showed impairs CNC cell migration when overexpressed. However, we also observe reduction in stroma-derived factor 1 (sdf1/cxcl12), which is required for CNC migration into the head. Consistent with our previous work showing that APC directly enhances the activity of glycogen synthase kinase 3 (GSK-3) and, independently, that GSK-3 phosphorylates multiple core mRNA splicing factors, we identify 340 mRNA splicing variations in apc mutant zebrafish, including a splice variant that deletes a conserved domain in semaphorin 3f (sema3f), an axonal guidance molecule and a known regulator of CNC migration. Here, we discuss potential roles for apc in CNC development in the context of some of the seminal findings of Mayor and colleagues.

Influence of occlusal collision corrections completed by two intraoral scanners or a dental design program on the accuracy of the maxillomandibular relationship

Statement of problemOcclusal collisions of articulated intraoral digital scans can be corrected by intraoral scanners (IOSs) or dental design software programs. However, the influence of these corrections on the accuracy of maxillomandibular relationship is unclear. PurposeThe purpose of this clinical investigation was to measure the effect of occlusal collision corrections completed by the IOSs or dental design software programs on the trueness and precision of maxillomandibular relationship. Material and methodsCasts of a participant mounted on an articulator were digitized (T710). The experimental scans were obtained by using 2 IOSs: TRIOS 4 and i700. The intraoral digital scans of the maxillary and mandibular arches were obtained and duplicated 15 times. For each duplicated pair of scans, a bilateral virtual occlusal record was acquired. Articulated specimens were duplicated and assigned into 2 groups: IOS-not corrected and IOS corrected (n=15). In the IOS-not corrected groups, the IOS software program postprocessed the scans maintaining the occlusal collisions, while in the IOS-corrected groups, the IOS software program eliminated the occlusal collisions. All articulated specimens were imported into a computer-aided design (CAD) program (DentalCAD). Three subgroups were developed based on the CAD correction: CAD-no change, trimming, or opening the vertical dimension. Thirty-six interlandmark distances were measured on the reference and each experimental scan to compute discrepancies by using a software program (Geomagic Wrap). Root mean square (RMS) was selected to compute the cast modifications performed in the trimming subgroups. Trueness was examined using 2-way ANOVA and pairwise comparison Tukey tests (α=.05). Precision was evaluated with the Levene test (α=.05). ResultsThe IOS (P<.001), the program (P<.001), and their interaction (P<.001) impacted the trueness of the maxillomandibular relationship. The i700 obtained higher trueness than the TRIOS 4 (P<.001). The IOS-not corrected-CAD-no-changes and IOS-not-corrected-trimming subgroups obtained the lowest trueness (P<.001), while the IOS-corrected-CAD-no-changes, IOS-corrected-trimming, and IOS-corrected-opening subgroups showed the highest trueness (P<.001). No significant differences in precision were found (P<.001). Furthermore, significant RMS differences were found (P<.001), with a significant interaction between Group×Subgroup (P<.001). The IOS-not corrected-trimmed subgroups obtained a significantly higher RMS error discrepancy than IOS-corrected-trimmed subgroups (P<.001). The Levene test showed a significant discrepancy in the RMS precision among IOSs across subgroups (P<.001). ConclusionsThe trueness of the maxillomandibular relationship was influenced by the scanner and program used to correct occlusal collisions. Better trueness was obtained when the occlusal collisions were adjusted by the IOS program compared with the CAD program. Precision was not significantly influenced by the occlusal collision correction method. CAD corrections did not improve the results of the IOS software. Additionally, the trimming option caused volumetric changes on the occlusal surfaces of intraoral scans.

Dysphagia in the Elderly with COVID-19: Implications and Comorbidities in the pandemic era

Dysphagia is frequent in the elderly population, especially in individuals with COVID-19. The aim of this integrative review was to elucidate the connection between dysphagia and COVID-19 in the elderly, focusing on the implications arising from it and associated comorbidities. Methods: A comprehensive search using the PICO strategy was conducted in six databases: PubMed/Medline, Embase, LILACS, Scopus, Web of Science, and SpeechBITE. Articles published between 2019 and 2022, without language restrictions, involving participants aged 60 years or older diagnosed with COVID-19 and exhibiting signs/symptoms of dysphagia were included. Results: The analysis included 42 articles, with the majority being case reports. The sample involved 298 older adults, with a mean age of 70.5 years and a predominance of males. The implications of dysphagia included the need for alternative feeding, laryngotracheal penetration/aspiration, adjustment in diet consistency, aspiration pneumonia and dysfunction in the orofacial and pharyngeal muscles. Pre-existing comorbidities associated with COVID-19 were identified, such as Guillain-Barré Syndrome, Myasthenia Gravis, Hypertension and Diabetes Mellitus. Conclusion: This integrative review highlights several implications of dysphagia in the elderly with COVID-19, with alternative feeding being the most mentioned. However, less than half of the studies described the implications observed among patients. The findings highlight the need for future investigations and development of appropriate therapeutic strategies aimed at improving quality of life and preventing complications in this population. Identification of the implications and comorbidities associated with dysphagia may assist in the development of more effective and safer clinical management approaches.

In-vivo evaluation of Artificial Intelligence Driven Remote Monitoring technology for tracking tooth movement and reconstruction of 3-dimensional digital models during orthodontic treatment

An in-vivo evaluation of the Dental Monitoring (DM; Paris, France) Artificial Intelligence Driven Remote Monitoring technology was conducted in an active clinical setting. Our objectives were to compare the accuracy and validity of the 3-dimensional (3D) digital models remotely generated from the DM application to 3D Digital Models generated from the iTero Element 5D intraoral scanner (Align Technologies, San Jose, Calif) of patients' dentition during in-vivo fixed orthodontic treatment. The orthodontic treatment of 24 patients (aged 14-55 years) was tracked across an average of 13.4 months. Scans of the maxillary and mandibular arches of each patient were taken by an iTero intraoral scanner and with the DM application before treatment initiation without (T0) and with (T1) the fixed orthodontic appliances and at every in-person adjustment appointment (T2-T10). The global deviation between the reconstructed digital models from the DM and iTero scans was compared at each time point using Geomagic Control-X 2020 (3D Systems, Rock Hill, SC). Descriptive analysis was conducted to determine the mean deviation at each time point for the maxillary and mandibular arches, to compare the maxilla and mandible mean deviations at each time point to the null hypothesis mean of 0 mm and the paired mean of the average at each time point between the maxilla and mandible. The findings revealed no clinically significant difference between the reconstructed digital models generated by the iTero IOS and the remotely reconstructed digital dental models generated by the DM application. DM artificial intelligence tracking algorithm can track tooth movement and reconstruct 3D digital models to a clinically acceptable degree for orthodontic application.

Evaluation of Swallowing Coordination in Infants with a History of Mechanical Ventilation Longer Than 7 Days in the Neonatal Period and Assessment of Response to Oral Stimulation Maneuver

Background: Dysphagia is a frequent complication defined as difficulty in any stage of swallowing. Infants with a history of mechanical ventilation might show difficulty in coordinating pharyngeal muscles resulting in dysphagia. Objectives: The present study aimed to show the prevalence of swallowing disorders and associated symptoms among high-risk infants with a history of prolonged mechanical ventilation. Methods: A quasi-experimental study was conducted at the Breastfeeding Research Center, Tehran, Iran. All the neonates with a history of prolonged mechanical ventilation entered the study. Parents were asked to respond to a provided questionnaire regarding their infants’ swallowing disorders. Accordingly, the infants with any symptoms were considered candidates for intervention. The parents also received simple training to perform oral sensorimotor stimulation protocol for their children. Through a follow-up visit, the questionnaire was filled up for every infant. Finally, all the data related to the responses before and after interventions were compared to show the possible effects of the interventions. Results: A total of 25 infants entered the study. The mean mechanical ventilation period was 15.95 ± 6.644 days. Concerning the frequency of swallowing complications, 24 infants (96%) had different degrees of dysphagia. After 3 - 6 months of interventions, the number of cases with symptoms of coughing (P = 0.016), spitting food out by mouth (P = 0.0001), choking (P = 0.016), humid breath (P = 0.031), poor weight gain (P = 0.002), and the need to cut food into small pieces (P = 0.004) was significantly lower than the number of cases suffering from such complications before the intervention. The results also showed that after 3 - 6 months of interventions, dysphagia symptoms in 10 out of 24 infants (41.66%) entirely and in others (38.44%) partially improved. Conclusions: The results of the present study delineated that infants with a history of prolonged mechanical ventilation were at greater risk of swallowing complications. The early diagnosis and implementation of oral sensorimotor interventions could improve different symptoms of dysphagia.

Dysphagia at 1 Year is Associated With Mean Dose to the Inferior Section of the Brain Stem

Dysphagia is a common toxicity after head and neck (HN) radiation therapy that negatively affects quality of life. We explored the relationship between radiation therapy dose to normal HN structures and dysphagia 1 year after treatment using image-based datamining (IBDM), a voxel-based analysis technique. We used data from 104 patients with oropharyngeal cancer treated with definitive (chemo)radiation therapy. Swallow function was assessed pretreatment and 1 year posttreatment using 3 validated measures: MD Anderson Dysphagia Inventory (MDADI), performance status scale for normalcy of diet (PSS-HN), and water swallowing test (WST). For IBDM, we spatially normalized all patients' planning dose matrices to 3 reference anatomies. Regions where the dose was associated with dysphagia measures at 1 year were found by performing voxel-wise statistics and permutation testing. Clinical factors, treatment variables, and pretreatment measures were used in multivariable analysis to predict each dysphagia measure at 1 year. Clinical baseline models were found using backward stepwise selection. Improvement in model discrimination after adding the mean dose to the identified region was quantified using the Akaike information criterion. We also compared the prediction performance of the identified region with a well-established association: mean doses to the pharyngeal constrictor muscles. IBDM revealed highly significant associations between dose to distinct regions and the 3 outcomes. These regions overlapped around the inferior section of the brain stem. All clinical models were significantly improved by including mean dose to the overlap region (P ≤ .006). Including pharyngeal dosimetry significantly improved WST (P=.04) but not PSS-HN or MDADI (P ≥ .06). In this hypothesis-generating study, we found that mean dose to the inferior section of the brain stem is strongly associated with dysphagia 1 year posttreatment. The identified region includes the swallowing centers in the medulla oblongata, providing a possible mechanistic explanation. Further work including validation in an independent cohort is required.

Goldenhar syndrome complicated with subglottic airway stenosis: a case report

BackgroundGoldenhar syndrome is a congenital disease that involves an absence or underdevelopment of structures that arise from the first and second pharyngeal arches and more or less severe extracranial anomalies. A variety of supraglottic malformations may be observed, including mandibular hypoplasia, mandibular asymmetry and micrognathia. Subglottic airway stenosis (SGS), which can cause difficulties in airway management during the perioperative period, is seldom emphasized in literature descriptions of Goldenhar syndrome, but can be clinically significant.Case presentationAn 18-year-old female with a history of Goldenhar syndrome presented for placement of a right mandibular distractor, right retroauricular dilator, and stage I transfer of a prefabricated expanded flap under general anesthesia. During tracheal intubation, the endotracheal tube (ETT) met resistance unexpectantly when attempting to pass through the glottis. Subsequently, we attempted the procedure with a smaller size ETT but again met resistance. With fiberoptic bronchoscope, we found that the whole segment of the trachea and bilateral bronchi were obvious narrow. Given the finding of unexpected severe airway stenosis and the associated risks with proceeding with the surgery, the operation was cancelled. We removed the ETT once the patient was fully awake.ConclusionsAnesthesiologists should be aware of this clinical finding when evaluating the airway of a patient with Goldenhar syndrome. Coronal and sagittal measurements on computerized tomography (CT) and three-dimensional image reconstruction can be used to evaluate the degree of subglottic airway stenosis and measure the diameter of the trachea.

Prosthetic rehabilitation with implant-supported fixed prosthesis in a completely edentulous patient: A clinical report

To present clinical strategies for prosthetic rehabilitation of completely edentulous patients using immediate-loading basal implants.A 58-year-old female patient was referred to the Department of Prosthodontics for restoration of her completely edentulous maxilla and mandible with a fixed full-arch implant-prosthetic rehabilitation. Since the patient lacks adequate bone in the posterior maxilla and is not willing to undergo a removable interim prosthesis, an immediate loading protocol along with 8 single-piece basal implants, including 2 pterygoid implants in the maxillary arch and 6 single-piece basal implants in the mandibular arch, was selected as the treatment option, followed by an acrylic provisional restoration. Four months later, a definitive fixed implant-supported prosthesis was delivered.This treatment strategy may be considered for rehabilitating patients with atrophic ridges demanding fixed provisional prostheses throughout the healing period and can be employed even in immediate implant placement after extraction.

Management of Class III malocclusion by orthodontic clockwise rotation of maxillo-mandibular complex – A case report

Severe Skeletal Class III malocclusions in adult patients are managed by surgical orthodontic correction and orthodontic camouflage especially in borderline cases. An orthodontic camouflage is best opted in situations where the patient is either reluctant to have an invasive procedure or mitigate other ways to obtain an ideal interincisal relation, best esthetic outcome and function. There are many ways suggested to treat Class III malocclusions non-surgically like fixed appliance with class III intermaxillary elastics, extraction of mandibular first bicuspids, extraction of mandibular first and maxillary second bicuspids and enmasse distalization of mandibular arch using temporary anchorage devices. Clockwise rotation of maxillo-mandibular occlusal complex gives promising treatment outcome in selected cases with extrusion of upper arch and possible clockwise rotation of the mandible for improving mandibular prognathism. This case report aims to illustrate a Class III non-growing patient treated by clockwise rotation of maxillo-mandibular occlusal complex for achieving optimum facial esthetics and function.

Evaluation of intercanine arch width, intermolar arch width and the canine fossa width in the determination of gender of an individual between 18 and 35 years – An in vitro analytical retrospective study

Objective s: The aim of this study is to verify and assess the usefulness of intercanine arch width, intermolar arch width, and canine fossa width in maxilla and intercanine and intermolar width in mandible for gender determination in the adult population. In medicolegal cases, estimation of gender using the skeletal remains of victims is imperative. The identity of an individual can be verified by examination of teeth and surrounding tissues from skeletal remains. Measurements from teeth and skull can help a Forensic Odontologist to identify deceased victims by age, gender, or race. The association of skeletal remains with gender gains utmost importance in cases of mass fatality such as earthquakes, tsunami, accidents, cyclones, and floods. If an individual is not in a condition to be identified, then they can be identified from the dentition or remains of dentition during any natural or manmade calamities. The benefit of determining gender in mass calamities is that accurately determined gender confines the number of missing individuals to one-half of the population in the majority cases. Many studies pertaining to maxillary arch widths have been performed yet the literature regarding mandibular arch widths remains scarce. Furthermore, in the literature, very few studies have been carried out to correlate canine fossa width and gender of an individual. Material and Methods: The study was carried out on a sample size of 120 study models, between 18 to and 35 years in department of orthodontics and dentofacial orthopedics and the samples had equal male and female distribution. A digital vernier caliper measured the intercanine arch width, intermolar arch width and canine fossa width and the parameters were measured by a single observer and statistical analysis was performed. Results: Intercanine arch width in maxillary arch was 36.38 ± 3.08 mm and 33.44 ± 2.72 mm for males and females correspondingly with P &lt; 0.001 which is statistically highly significant. Intermolar arch width in maxillary arch was 47.81 ± 3.02 mm and 45.2 ± 2.64 mm for males and females correspondingly with P &lt; 0.001 which is statistically highly significant. Canine fossa width in maxillary arch was 43.42 ± 2.58 mm and 40.36 ± 2.32 mm for males and females correspondingly with P &lt; 0.001 which is statistically highly significant. Intercanine arch width in mandibular arch was 27.43 ± 2.96 mm and 26.2 ± 1.97 mm for males and females correspondingly with P &lt; 0.05 which is statistically significant. Intermolar arch width in mandibular arch was 41.88 ± 3.47 mm and 39.89 ± 2.48 mm for males and females correspondingly with P &lt; 0.001 which is statistically highly significant. After employing the receiver operating curve, to figure out specificity and sensitivity of the parameters, high specificity of 97%, with the best sensitivity of 78% was recorded for the maxillary canine fossa width. Conclusion: The results show that in cases of mass calamities, maxillary canine fossa width will prove to be useful tool in gender determination accurately after analyzing the dental remains of young missing adults with multiple missing teeth. This will further aid the forensic odontologist to determine identity of the missing individual.

Catastrophic implant failure after immediate loading of full arch implant prosthesis and its association with CPAP therapy: A case report.

Full arch implant-supported restorations are a common treatment modality for patients with a terminal dentition or an edentulous mouth. Several mechanical and biological factors that contribute to complications or failure are already extensively documented. Some patients receiving complex implant-based treatment plans also suffer from obstructive sleep apnea (OSA). The use of a continuous positive airway pressure (CPAP) mask in some of these patients is a lesser-known factor that could contribute to implant complications or failures. This article describes how the use of a CPAP machine may be a risk factor in implant dentistry and describes a patient whose use of a CPAP machine and mask led to a catastrophic failure of mandibular full arch dental implants.

A multiple super-enhancer region establishes inter-TAD interactions and controls Hoxa function in cranial neural crest

Enhancer-promoter interactions preferentially occur within boundary-insulated topologically associating domains (TADs), limiting inter-TAD interactions. Enhancer clusters in linear proximity, termed super-enhancers (SEs), ensure high target gene expression levels. Little is known about SE topological regulatory impact during craniofacial development. Here, we identify 2232 genome-wide putative SEs in mouse cranial neural crest cells (CNCCs), 147 of which target genes establishing CNCC positional identity during face formation. In second pharyngeal arch (PA2) CNCCs, a multiple SE-containing region, partitioned into Hoxa Inter-TAD Regulatory Element 1 and 2 (HIRE1 and HIRE2), establishes long-range inter-TAD interactions selectively with Hoxa2, that is required for external and middle ear structures. HIRE2 deletion in a Hoxa2 haploinsufficient background results in microtia. HIRE1 deletion phenocopies the full homeotic Hoxa2 knockout phenotype and induces PA3 and PA4 CNCC abnormalities correlating with Hoxa2 and Hoxa3 transcriptional downregulation. Thus, SEs can overcome TAD insulation and regulate anterior Hoxa gene collinear expression in a CNCC subpopulation-specific manner during craniofacial development.

The Occlusal Characteristics of Kosovar Adolescents

Background: This study aimed to evaluate the occlusal characteristics of the maxillary and mandibular dental arches in Kosovar adolescents in relation to gender. Methods and Results: In a cross-sectional study, dental casts of 400 Kosovar schoolchildren (184 males and 216 females, mean age of 15.17 years) were evaluated. Little’s index of incisor irregularity (LII), overjet, and overbite were measured with a digital caliper, and then analyzed and compared by gender. In both the maxilla and mandible, LII for males and females was significantly different, with male values being higher than female values. In contrast, no significant differences were observed in overbite and overjet. Conclusion: In Kosovar adolescents, our findings show significant gender differences in Little's irregularity index. The overjet and overbite were higher in males than in females, but there were no statistical differences between genders in Kosovar adolescents for these parameters.

Pharyngeal Arches, Chapter 1: Normal Development and Derivatives.

The pharyngeal arches form the cornerstone of the complex anatomy of the face and neck. These embryologic structures are the foundation of face and neck development, and anomalous growth can result in craniofacial abnormalities. Surgeons who manage head and neck pathology and pathoanatomy will invariably encounter conditions associated with aberrant pharyngeal arch anatomy, and a thorough understanding of the normal and pathological development of these important structures is paramount to accurate diagnosis and treatment. This manuscript is the first of a three-part educational series that addressed the pharyngeal/branchial arch embryology, development, nomenclature, and normal anatomy (Part I), pathologic anomalies of ear and neck derived from abnormal development of the arches (Part II), and different types of orofacial clefts, including Tessier clefts (Part III).

A comparative study based on the mandibular movement track and the movement parameters of the virtual articulator in simulating occlusal adjustment.

This study aimed to compare the effects of virtual adjustment on occlusal interferences in mandibular posterior single crown and three-unit bridge restorations by using the mandibular movement track and the movement parameters of a virtual articulator. Twenty-two participants were recruited. Digital casts of the maxillary and mandibular arches were obtained using an intraoral scanner, and the jaw registration system was used to record the data of the mandibular movement track and the movement parameters of the articulator. Four kinds of restorations with 0.3 mm occlusal interferences were designed with dental design software. In particular, single crowns were designed for teeth 44 and 46, whereas three-unit bridges were designed for teeth 44-46 and 45-47, and the corresponding natural teeth were virtually extracted. Virtual adjustment of the restorations was performed using two dynamic occlusal recordings, namely, the mandibular movement track and the movement parameters of the virtual articulator. A reverse-engineering software was used to measure the root-mean-square of the three-dimensional deviation of the occlusal surfaces between natural teeth and the adjusted restorations. The differences between the two methods of virtual-occlusion adjustment were compared and analyzed. For the same group of restorations, the three-dimensional deviation of the mandibular movement track group were lower than those of the virtual articulator group, and the differences were statistically significant (P<0.05). For the four groups of restorations adjusted by the same method, the three-dimensional deviation of the 46-tooth single crown was the largest and the smallest three-dimensional deviation was that of the 44-tooth single crown. Statistical differences existed between the 44-tooth single crown and the other groups (P<0.05). For the occlusal design of posterior single crown and three-unit bridge, the mandibular movement track could be a more effective approach to virtual occlusal adjustment than the movement parameters of the virtual articulator.

Toxicity of o-phenylphenol on craniofacial cartilage development through ROS-induced oxidative stress in zebrafish embryos

O-phenylphenol (OPP), a commonly used antiseptic and bactericide, has some threat to human health and the environment. Environmental exposure to OPP may cause potential health hazards in animals and humans, and the developmental toxicity of OPP needs to be assessed. Therefore, the zebrafish model was used to evaluate the ecological impact of OPP, and the zebrafish craniofacial skeleton is mainly derived from the cranial neural crest stem cells (NCCs). In this study, zebrafish were exposed to 1,2,4 mg/L OPP from10 to 80 h post-fertilization (hpf). Our study observed that OPP could cause the early disorder of craniofacial pharyngeal arch development and lead to behavioural abnormalities. In addition, qPCR and enzyme activity revealed that OPP exposure would induce the production of reactive oxygen species (ROS) and oxidative stress. And proliferation cell nuclear antigen (PCNA) indicated that the proliferation of NCCs was reduced. The mRNA expression of genes related to migration, proliferation, and differentiation of NCCs has changed significantly under OPP exposure. Astaxanthin (AST), a widely used antioxidant, could partially rescue the craniofacial cartilage development exposed to OPP. The results showed improvements in oxidative stress, gene transcription, NCCs proliferation, and protein expression in zebrafish, suggesting that OPP may reduce antioxidant capacity and subsequently inhibit migration, proliferation, and differentiation of the NCCs. In conclusion, our study found that OPP may produce reactive oxygen species, leading to developmental toxicity in zebrafish craniofacial cartilage.

Dental changes induced by a modified Herbst appliance followed by fixed appliances: A digital dental model analysis.

Herbst therapy is an effective treatment for Class II malocclusions. However, the maintenance of the effects after fixed appliances treatment remains questionable. This retrospective study aimed to assess, using digital dental models, the sagittal and transverse dental arch changes in young patients during two Class II Division 1 treatment phases, first with modified Herbst appliance (HA) and then with fixed appliances. The treated group (TG) comprised 32 patients (17 boys, 15 girls; mean age, 12.85 ± 1.16 years) treated with HA and fixed appliances. The control group comprised 28 patients (13 boys, 15 girls; mean age, 12.21 ± 1.35 years) with untreated Class II malocclusions. Digital models were obtained immediately before and after HA therapy and after fixed appliances. Data were statistically analyzed. Compared with the control group, the TG showed an increase in maxillary and mandibular arch perimeters and in intercanine and intermolar arch widths, a decrease in overjet and overbite, and an improvement in canine and molar relationships. In the time after HA therapy until the end of fixed appliances treatment, the TG showed a decrease in maxillary and mandibular arch perimeters, overjet, upper and lower intermolar widths; an increase in molar Class II relationship; and no changes in canine relationship, overbite, and upper and lower intercanine widths. In this sample of patients treated with HA, on average, there was an improvement in the Class II relationship, which seemed to remain after fixed appliances. The transverse dental changes achieved in HA phase relapsed after treatment with fixed appliances.

Knowledge about Ergonomics and Musculoskeletal Disorders among Dental Practitioners - An Institutional-based Study

Background and Purpose: Dental students and practitioners are frequently prone to work-related musculoskeletal disorders (MSDs) due to the unawareness of ergonomic principles when practicing dentistry. The aim of the study was to assess the knowledge about MSDs in dental practitioners. Materials and Methods: A self-administered 28-item online questionnaire study was conducted among 100 dental practitioners. The study questionnaire captured demographic details of the participants as well as knowledge of ergonomic practices and MSDs and the nature of treatment. Descriptive analysis was done wherein the qualitative variables were expressed as percentages and proportions, whereas quantitative data were expressed as mean and standard deviation. The Chi-square test was used to check statistical associations and P &lt; 0.05 was considered statistically significant. Results: All the participants practiced four-handed dentistry. Only 12% of the responders stated that the ideal position for treating the maxillary arch in patient as supine, whereas 86% responded as semi-supine and 2% as sitting position. Similarly, 97% of the responders rightly answered that the ideal position for treating mandibular arch in patient as semi-supine. Forty percentage of them answered correctly that the word ergonomics means work and law. Seventy-two percentage of the responders think that knowing ergonomics is useful in routine dental practice. Fifty-eight percentage of the dentists believe that stretching exercise during work will reduce muscle tension and stress. Conclusion: The present study provides an insight into ergonomics for dental students during routine dental procedures. Hence, emphasis on providing ergonomic principles both theoretically and practically to dental health-care professionals must be placed in all educational institutions and at continuing dental health programs, and it should be included in the curriculum.