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Biomedical subjects

P Magne

Publications and source records attributed to P Magne.

41 records · Page 3Linked to original sources
PubMedDate not supplied

Interdental design of porcelain veneers in the presence of composite fillings: finite element analysis of composite shrinkage and thermal stresses.

PURPOSE: This study was conducted to optimize the interdental design (wraparound) of porcelain laminates bonded to teeth in the presence of preexisting composite fillings. MATERIALS AND METHODS: A finite element model (2-dimensional mesh generated from a horizontal cross section of a maxillary incisor) was used to evaluate the effects of luting composite shrinkage and thermal changes on the stress distribution within the ceramic. The mesh included 3 restorative designs (3 degrees of interdental wrapping) and a Class III composite filling. Curing contraction of the luting composite was simulated at baseline temperature (37 degrees C). Thermal loads from 37 to 60 degrees C and from 37 to 5 degrees C were assessed with and without preexisting composite shrinkage. Surface tangential stresses were calculated at the ceramic surface and interface. RESULTS: Curing contraction alone generated mostly compressive stresses (peaks at 15 MPa) at both the ceramic surface and interface. Stresses remained compressive (peaks at 20 MPa) when thermal changes were added, except for the conservative veneer with minimum wraparound, the margins of which showed potentially harmful tensile stress peaks (approximately 7 MPa). Deformation of the tooth-restoration complex tended to be more uniform for veneers with maximum wraparound. In the presence of thermal loads alone, opposite effects were observed on the restoration surface and the interface, with compressive stresses on one side (up to 13 MPa) and tensile stresses on the other (up to 9 MPa). This effect of proximal bending (explained by the nearby expansion/contraction of the composite filling) was attenuated by the significant reduction of the bulk of the preexisting interdental composite by the overlapping veneer. CONCLUSION: In the finite element environment, the negative effect of the nearby expanding/contracting composite fillings can be minimized by extending the veneer over the preexisting interdental restoration. Because of the precompressed state resulting from composite shrinkage, ceramics showed lower temperature-induced tensile stresses.

Composite Resins↗
PubMedDate not supplied

[The soleus syndrome. Apropos of 3 cases of intermittent claudication of venous origin].

UNLABELLED: The typical case present with a unilateral, atypical claudication with discrete oedema, occurring after repeated exercise. These paradoxical features of venous pain, aggravation with attacks, resolution after prolonged rest and the absence of arterial signs are suggestive of the disease. The syndrome may present as repeated calf thromboses or recurrent varicose veins suggesting some deep obstruction. An inflammatory and oedematous process linked to exercise is associated with a congenital predisposition: a constriction of the venous arcade at the insertion of the soleus. Phlebography confirms the absence of thrombophlebitis and shows underlying stasis and poor opacification of the deep popliteal and, most importantly, anterior hooking and actual kinking of the vein on the lateral film which persists on mild flexion. A simple surgical procedure to free the vein turns this incapacitating and potentially thrombogenic pathology into a benign condition. TITLE: Therapeutic modalities for ischaemic atrophy in its acutely painful phase or the exceptional use of corticotherapy in phlebology.

Adolescent↗
PubMedDate not supplied

Stratification of composite restorations: systematic and durable replication of natural aesthetics.

A thorough knowledge of the internal structure of natural dentition provides invaluable information for increasing the aesthetic potential in dental restorations. To achieve the optimal aesthetic results, this knowledge must be integrated in a systematic therapeutic procedure. The learning objective of this article is to guide the practitioner in clinical case analysis, evaluation, and the application of a personalized technique of stratification for each individual case in direct composite restorations. The article evaluates treatment demarcations, differences in composite stratification between anterior and posterior teeth, color selection, and the "sandwich technique." The treatment protocol section discusses the element of reference, which can be either an adjacent natural tooth or provisional restorations, permitting the diagnostic study of a more extensive case. The structure of the element of reference is analyzed as to the enamel, dentin, and incisal edge, and replicated. Since light penetration is different in the anterior and posterior dentition, the color stratification must differ accordingly. The "worn" tooth must be distinguished from the "unworn" tooth. In color selection, the luminosity and saturation of the teeth are evaluated first; tint is selected from the element of reference.

Composite Resins↗
PubMedDate not supplied

Esthetic improvements and in vitro testing of In-Ceram Alumina and Spinell ceramic.

The original In-Ceram material (In-Ceram Alumina), composed of sintered aluminum oxide subsequently infused with a glass, features interesting mechanical properties. In-Ceram Spinell was marketed more recently to improve the esthetic potential. This study compared the flexural strength of various combinations of sintered alumina and spinel infiltrated with the associated glasses. In addition, the influence of vacuum during the infusion process was investigated using density measurements. The characteristic strength (load at which 63% of the specimens had failed) was 530 MPa for the original material, 523.7 MPa when the same material was infiltrated under vacuum, 481.4 MPa when sintered alumina was infused under vacuum with the glass originally marketed for the spinel, and 283.1 MPa for the sintered spinel infiltrated under vacuum with the associated glass. A significant increase in density was observed when the infiltration firing of sintered alumina was performed under vacuum. Furthermore, the in vivo evaluation of specific esthetic parameters inherent to different types of cores was made and revealed the relative opacity of alumina; spinel was found to have the ability to blend in with the underlying substrate. Both materials demonstrated a general lack of fluorescence.

Aluminum Oxide↗