Traumatic Bone Cyst in the Mandibular Symphysis : Case Reports

Traumatic bone cyst (TBC) is an asymptomatic lesion seen most in adolescents. TBC is found incidentally on routine panoramic examinations and appears as a relatively well-demarcated unilocular radiolucency with scalloped margins. Histological examination reveals a vacant cavity of cancellous bone usually unlined or very occasionally lined with a thin connective tissue layer. The lack of lining epithelial membrane is common histological feature. The most affected site is between the mandibular canine and third molar. The involvement of the mandibular symphysis is rare. The etiopathogenesis of the TBC is unclear. TBC is treated with surgical exploration and curettage; new bone is formed in place of the lesion within 6 - 12 months of surgery. Diagnosis of TBC prior to surgical intervention has limitations in most of the cases. Both of our patients were diagnosed through radiological examination and biopsy. Neither patient had a history of trauma. After surgery, the panoramic radiograph and CBCT were used to confirm bone healing.

Pattern of isolated mandibular symphysis fracture and trends in management at a tertiary care hospital of Karachi, Pakistan.

Objective: To find the pattern of isolated mandibular symphysis fracture and trends in management at a tertiary care hospital of Karachi, Pakistan. Study Design: Crossectional study. Setting: Department of Oral Surgery, Sir Syed Medical & Dental Hospital-Karachi, Pakistan. Period: January 2018 to December 2019. Material & Methods: Eighty one patients were selected on the basis of inclusion and exclusion criteria. They were diagnosed with isolated anterior mandibular fracture on basis of detailed history, thorough clinical examination and a radiologic investigation (OPG). Etiology of fracture and gender distribution was observed, fracture pattern was observed on basis of helmet wearing. Results: There was a male predilection with a male to female ratio of 4.3:1. Road traffic accident was the commonest cause. 82.7 % of patients were not wearing helmet at time of incidence and 69% from all patients had displaced mandibular fracture which resulted in derranged occlusion. Conclusion: Isolated anterior mandibular fractures is common in younger age group, with a male predilection. Most common etiologic factor is road traffic accident. Displaced fracture pattern is prevalent among patients who were not wearing helmet at time of incidence.

Determination of Mandibular Symphysis Width in Skeletal Class I Patients with Different Vertical Patterns

Symphysis is an anatomical part of mandible that includes lower incisors and anterior chin. Mandibular symphysis is a contributing factor of facial harmony for esthetics and is a determinant for lower incisor position in orthodontic treatment planning for border line cases. This cross-sectional study was carried out in Orthodontics department, Fatima Memorial Hospital College of Medicine and Dentistry Lahore on a sample size of 90 cases using 95% confidence level. Non probability consecutive sampling technique was used. Symphyseal dimensions were measured on lateral cephalogram. Data collected was entered and analyzed in computer program SPSS version 20. Quantitative outcomes like symphysis dimensions, symphysis width, vertical pattern, and ANB were subjected to ANOVA of significance. Independent T-test was used to make the comparison between males and females on the basis of variables. Results of this study suggested thatC-C’ varies significantly between males and females, whereas the differences in symphysis width LA, and LP between males & females are statistically insignificant (P>0.05). Bone anterior to lower incisor apex varies significantly among various facial profiles with hypo divergent males exhibiting wider chin than normo divergent and hyper divergent subjects. Sexual dimorphism in symphysis width was seen among genders. Keywords: Facial harmony, lower incisor position

Is Perpendicular Double Two-Hole Plates Fixation Superior to Single Four-Hole Plate Fixation to Treat Mandibular Symphysis Fracture?—A Finite Element Study

The effectiveness of a single four-hole plate (S4HP), perpendicularly oriented four-hole and two-hole plate (Per4H2HP), and perpendicularly oriented double two-hole plate (PerD2HP) for the fixation of a mandibular fracture was studied. A finite element analysis of the mandibular symphysis fractures treated with S4HP, Per4H2HP, and PerD2HP was performed. All surface nodes were fixed in the mandibular condyle region and occlusal muscle forces were applied. The maximal von Mises stress (MaxVMS) values of the plates, screws and screw holes were investigated. The displacement of the fracture site on the lower border of the mandibular symphysis was recorded. The displacement on the lower border of the fracture sites in the S4HP group was greater than that in the Per4H2HP group and the PerD2HP group. There was no eversion at the fracture site among all groups. Both the S4HP and Per4H2HP groups showed stress concentrations on the screws close to the fracture site. The MaxVMS increased when the number of screw holes on the mandibular anterior lower border decreased. The displacement of the fracture site and eversion with Per4H2HP and PerD2HP were far lower than those with S4HP. PerD2HP is a stable and green fixation technique for mandibular symphysis fractures.

A new protocetid whale offers clues to biogeography and feeding ecology in early cetacean evolution

Over about 10 million years, the ancestors of whales transformed from herbivorous, deer-like, terrestrial mammals into carnivorous and fully aquatic cetaceans. Protocetids are Eocene whales that represent a unique semiaquatic stage in that dramatic evolutionary transformation. Here, we report on a new medium-sized protocetid, Phiomicetus anubis gen. et sp. nov., consisting of a partial skeleton from the middle Eocene (Lutetian) of the Fayum Depression in Egypt. The new species differs from other protocetids in having large, elongated temporal fossae, anteriorly placed pterygoids, elongated parietals, an unfused mandibular symphysis that terminates at the level of P 3 , and a relatively enlarged I 3 . Unique features of the skull and mandible suggest a capacity for more efficient oral mechanical processing than the typical protocetid condition, thereby allowing for a strong raptorial feeding style. Phylogenetic analysis nests Phiomicetus within the paraphyletic Protocetidae, as the most basal protocetid known from Africa. Recovery of Phiomicetus from the same bed that yielded the remingtonocetid Rayanistes afer provides the first clear evidence for the co-occurrence of the basal cetacean families Remingtonocetidae and Protocetidae in Africa. The discovery of Phiomicetus further augments our understanding of the biogeography and feeding ecology of early whales.

A new alligatoroid (Eusuchia, Crocodylia) from the Eocene of China and its implications for the relationships of Orientalosuchina

A new crocodylian, Dongnanosuchus hsui n. gen. n. sp., is described mainly based on four well-preserved skulls from the Eocene Youganwo Formation of the Maoming Basin, southeastern China. It is an alligatoroid and phylogenetically nested within the Orientalosuchina. Dongnanosuchus hsui n. gen. n. sp. differs from all other orientalosuchines primarily in certain features of the skull: (1) a preorbital ridge connects posteriorly with the dorsal orbital rim and a ridge around the anteroventral margin of the orbit, (2) the palatine is short and does not reach the posterior border of the suborbital fenestra, (3) the external mandibular fenestra is closed, and (4) the splenial joins the formation of the mandibular symphysis. The discovery of Dongnanosuchus hsui n. gen. n. sp. confirms the monophyly and North American origin of the Orientalosuchina but suggests that the clade dispersed to Asia via Beringia after diverging from the mainline rather than a sub-lineage of the Alligatoroidea in the Late Cretaceous. UUID: http://zoobank.org/f8ca22f1-6323-462e-bf32-03c6a164c82e.

Evaluation of Optimal Sites for the Insertion of Orthodontic Mini-implants at Mandibular Symphysis Region Through Cone-beam Computed Tomography

Background: This study evaluates the overall bone thickness (OBT) and cortical bone thickness (CBT) of mandibular symphysis and to determine the optimal sites for the insertion of orthodontic mini-implants.Methods: Cone-beam computed tomography (CBCT) images of 32 patients (18 males, 14 females), including 16 adults and 16 adolescents were included in this study. The sample was further categorized into three facial types: low angle, average angle, and high angle. OBT and CBT were measured at the mandibular symphysis region. All measurements were performed at six different heights (2 mm, 4 mm, 6 mm, 8 mm, 10 mm, and 12 mm from cementoenamel junction [CEJ]) and at seven different angles (0, 10, 20, 30, 40, 50, 60 degrees to the occlusal plane). Results: Neither OBT nor CBT was influenced by age or sex, except for that CBT was significantly thicker in adults than in adolescents. OBT and CBT were significantly thicker in low-angle cases than in average- and high-angle cases. Both OBT and CBT were significantly influenced by insertion locations, insertion heights, insertion angles, and their interactions. CBT and OBT gained the greatest value at the location between two lower central incisors, and became greater with the increase of insertion height and insertion angle. Both recommended and optimal insertion sites were mapped. Conclusions: Mandibular symphysis region was suitable for the placement of orthodontic mini-implants. The optimal insertion site was 6-10 mm apical to CEJ between two lower central incisors with an insertion angle being 0-60 degrees to the occlusal plane.