Lack Of Dentition Research Articles

A New Species of Sternopygus (Gymnotiformes: Sternopygidae) from the Atlantic Coast of the Guiana Shield

Sternopygus sabaji, new species, is described from the Atlantic drainages of the Guiana Shield region of South America using traditional methods of morphometrics and meristics and microcomputed tomography (µCT) scans for osteological analysis. The new species is diagnosed from all other species of Sternopygus by the lack of dentition on the anteroventral surface of the endopterygoid and by the possession of a wider mouth. It further differs from its congeners by the following combination of characters: reduced humeral spot with low-contrast and poorly defined margins, possession of a light-colored mid-lateral stripe along posterior portion of lateral line, possession of 1–3 dark saddle-like markings along dorsum of smaller individuals, and a relatively low precaudal vertebrae count. This work provides the first description of a species of Sternopygus that is endemic to the Guiana Shield, joining S. astrabes and S. macrurus in elevating the species richness of the clade in that region to three species and the total number of valid Sternopygus to ten species.

Eggs and hatchlings of the Mexican salamander <i>Pseudoeurycea cephalica</i> (Caudata: Plethodontidae)

Se describe por primera vez huevos y recién nacidos de Pseudoeurycea cephalica cephalica procedentes del Parque Nacional Lagunas de Zempoala, Morelos, México. Los huevos se paracen a los de P. cephalica manni y P. belli en que no están unidos entre sí por ningún cordón. Se parecen en cuanto a constitución a los de P. nigromaculala y P. juarezi en tener dos capas gelatinosas. Los embriones tienen los pies y manos palmeados, produciéndose una reducción de la superficie palmeada a lo largo de la embriogénesis, lo cual confirma que el palmeado de pies y manos es un carácter pedomórfico. Los recién nacidos son de color gris negruzco, uniforme dorsalrnente y de color más claro ventralmente. Son robustos, con cabeza ancha, cola corta y carecen de dientes tanto vomerinos como maxilares. Esta falta de dentición ya fue encontrada anteriormente en juveniles de P. belli.

The Optimization Design of Dental Implant after the Mandible Tumor Resection and Reconstruction

Mandible defect and the lack of dentition may result in facial deformity and chewing organ defects. It happens after the surgery of oral and maxillofacial tumors. This study aims at this problem. In this study, Finite Element Analysis (FEA) was employed to reconstruct the implanted mandible for customized patient. The 3D FEA model has great importance for biomechanical analysis. Though the analysis of the biomechanical situation with different numbers of dental implants, we can optimize the location and quantity of the implants. In this way, we can improve the quality of the implants, reduce the pain of patients, reduce the operation cost and avoid secondary surgery.

Gap Arthroplasty for Mandibular Condyle Dislocation and Impaction Into the Middle Cranial Fossa

The anatomic basis of the mandible ensures the dissipation of forces along the mandible, allowing the weakest part at the condylar neck to fracture, thus preventing transfer of forces to the cranium. 1 This is the reason for the high incidence of condylar fractures. They account for approximately 25% to 30% of mandibular fractures. 2 In an adult mandible the distance between the lateral and medial pole tends to be larger in dimension than the fossa, preventing direct penetration of the fossa. However, a rounded condyle as seen in children would predispose to direct penetration into the middle cranial fossa. Other predisposing factors include a thin neck, 3 hyperpneumatized temporal bone, lack of dentition in the posterior region, or an open mouth position during impact. 4 Treatment of this injury should be individualized and should take into account the age of the patient, growth potential, the degree of glenoid fossa destruction, the risk of ankylosis, and the risk of further cranial injury.