Bonding and enamel prisms. Importance of cavity margin preparation for posterior composites

Preparation of the cavo-surface margin for fillings with "composites resins" is an important operative step. The good peripheral fit of the restoration and the stability of the bond between tooth and material depend on that preparation. How should the "bevel" be shaped? Scan electron microscopy of long bevels and rounded bevels show that the former seem more favorable to the fit of the filling. The section of enamel prisms is clean. The aprismatic surface area disappears. This enables to etch the cristallites in a more favorable axis as opposed to the rounded bevel.     

Correction of upper impacted canines in vestibular position with segmental osteotomy advancing the incisal block. Apropos of 5 cases

The author reports on 5 cases of segmental osteotomy advancing the upper incisal block, in the treatment of vestibular retention of an upper canine associated with an upper retro-alveolitis and/or brachypremaxillitis. This surgery is proposed as an alternative to the extraction of the 4 pre-molars, which is usually done in these cases of apparent disharmony.     

A dosimetric comparison between 3D-Conformal radiation therapy and intensity modulated radiation therapy plans in the treatment of posterior fossa boost in children with high risk medulloblastom

Objective： The work is a comparative study between two modalities of radiation therapy, the aim of which is to compare 3D conformal radiation therapy （3D-CRT） and intensity modulated radiation therapy （IMRT） in treating posterior fossa boost in children with high risk medulloblastorna; dosimetrically evaluating and comparing both techniques as regard target coverage and doses to organs at risk （OAR）. Methods： Twenty patients with high risk medulloblastoma were treated by 3D-CRT technique. A dosimetric comparison was done by performing two plans for the posterior fossa boost, 3D-CRT and IMRT plans, for the same patient using Eclipse planning system （version 8.6）. Results： IMRT had a better conformity index compared to 3D-CRT plans （P value of 0.000）. As for the dose homogeneity it was also better in the IMRT plans, yet it hasn＇t reached the statistical significant value. Also, doses received by the cochleae, brainstem and spinal cord were significantly less in the IMRT plans than those of 3D-CRT （P value 〈 0.05）. Conclusion： IMRT technique was clearly able to improve conformity and homogeneity index, spare the cochleae, reduce dose to the brainstem and spinal cord in comparison to 3D- CRT technique.