Intentional angulation of an implant to avoid a pneumatized maxillary sinus: a case report

This case report describes placement of an implant in the posterior maxilla so as to avoid a pneumatized sinus and also to avoid the need for a sinus lift procedure. An 81-year-old woman presented with an edentulous span in the upper right posterior maxilla. She had been missing teeth in this area for many years, and there was a combination of resorption of the alveolar ridge and pneumatization of the maxillary sinus. Eleven years previously, implants had been placed anterior to this region, but the patient was told that implants could not be placed posteriorly unless a sinus lift was done. At the time of the current presentation she was still unwilling to undergo a sinus lift procedure but wanted to know if implants could be placed in the posterior right maxilla. A tomogram obtained with a radiographic stent in place indicated that there was insufficient bone height to allow placement of implants at the usual angulation without a sinus lift. Therefore, to avoid the need for a sinus lift, 2 implants were placed with palatal angulation as guided by a tomographically determined surgical stent. The treatment planning and surgical and restorative techniques are reviewed here. A postoperative tomogram was obtained to determine the final position of the implants. The outcome has been favourable for the patient and the clinicians. In situations where there is sufficient palatal bone medial to the maxillary sinus, placing implants at an angle may prevent the need for a sinus lift procedure, assuming that proper development of an occlusal restorative scheme is possible.     

Terthiophene-promoted electropolymerization of 3-methylthiophene is heterogeneous electrocatalysis of polyterthiophene. A general electrocatalytic mechanism

The electrochemical oxidative polymerization of 3-methylthiophene (3MT) on platinum electrodes is favoured by the presence of previously deposited polyterthiophene (PTT) films. Cyclic voltammetry CV and single sweep voltammetry SSV were used to investigate the electrocatalytic process. The CV rate of polymer growth and the SSV electrocatalytic current increase linearly with the amount of predeposited PTT. The results rule out the previously invoked electrocatalytic promotion of 3MT polymerization by terthiophene radical cations in solution. SSV analysis with other thiophene-based polymer films (e.g. 3- and 3,4-alkylsubstituted polythiophenes) and with other thiophene-based monomers (e.g. 3,4-ethylenedioxythiophene) has shown that the electrocatalytic effect is of a general nature. The formation of a charge transfer complex between the thiophene-based monomer and the oxidized thiophene-based polymer is invoked to account for the catalytic action. The results account for the previous large and unexplained body of experimental evidence of electrocatalytic effects in the electro oxidative synthesis of conducting polymers.     

Radiographs in periodonties

Intraoral radiographs are widely used in periodontal diagnosis and research. However, accurate radiographic interpretation is only possible with high quality images. Some of the technical and geometric variables to consider have been presented. Early periodontal lesions are not detected in radiographs. The amount of periodontal destruction in more advanced disease is generally underestimated. The accurate topography of periodontal pockets and the buccal and lingual aspects of the teeth cannot be visualized. Clinical probing is therefore a prerequisite for a complete periodontal diagnosis. However, radiographs are a valuable adjunct for the periodontal diagnosis and the diagnosis of trauma from occlusion. With standardized systems, radiographs may furnish additional quantitative data in clinical research.     

Facial fractures--the results of a prospective four-year-study

A prospective four-year-study of 945 fractures of the facial skeleton is presented. Details of facial trauma were collected in patients referred from the Bradford and Airedale Districts of West Yorkshire, England, an area with a population slightly in excess of half a million. Statistical analysis shows variations from previously published papers, the male to female ratio being under 2.6:1, with an average of 1.15 fractures per patient. A relatively high incidence of sports fractures is reported but the number of industrial accidents is surprisingly low. The majority of patients seen were in their third decade, the mean age being just over 25 years. The analysis also reveals that a high percentage of fractures were treated conservatively.     

Effectiveness and dentin bond strengths of two materials for reinforcing thin-walled roots.

OBJECTIVES: To investigate the effectiveness of two restorative materials for reinforcing thin-walled roots and their microtensile bond strengths to root canal dentin. METHODS: Twenty-one decoronated maxillary central incisor roots were root filled and the canals enlarged to leave approximately 1.0 mm thick dentin walls. The roots were distributed randomly to three equal groups. Group 1 (control): a large tapered cast post-core was fabricated. Group 2 (BIS-CORE): a thick layer of dual-cured composite was placed in the post-hole before fabrication of a small-diameter tapered cast post-core. Group 3 (ChemFil Superior): a thick layer of glass-ionomer was placed, as before. Metal-ceramic crowns were fabricated for all teeth. Microtensile bond strength tests and optical and atomic force microscope observations were employed to examine adhesion between the two restorative materials and the root canal dentin. RESULTS: Mechanical loading (kN) demonstrated that composite 0.64 (S.D. 0.05), but not glass-ionomer 0.49 (0.05), significantly reinforced the fracture resistance of thin-walled roots, P<0.001. Microtensile bond strengths (MPa) were 21.7 (1.6) for composite and 12.9 (1.7) for glass-ionomer, P=002. SIGNIFICANCE: A thick intermediate layer of resin-bonded composite, sandwiched between the root dentin and a small-diameter cast Ni-Cr post or dowel, increased significantly the fracture resistance of the roots.     

The effect of casting conditions on the biaxial flexural strength of glass–ceramic materials

OBJECTIVE: To assess the effect of mould and glass casting temperatures on the biaxial flexural strength (BFS) of two different types of castable glass-ceramic, using existing laboratory equipment and techniques. METHODS: Two castable glass-ceramic materials were evaluated. One glass (LG3) is based on SiO2-Al2O3-P2O5-CaO-CaF2, and is similar in composition to glasses used in the manufacture of glass-ionomer cements. The other glass (SG3) is based on SiO2-K2O-Na2O-CaO-CaF2, and is a canasite-based material. Both materials were used to produce discs of 12 mm diameter and 2 mm thickness using the same lost-wax casting process as used for metal castings. Mould temperatures of between 500 degrees C and 1000 degrees C and glass casting temperatures of between 1100 degrees C and 1450 degrees C were evaluated. The cast discs were cerammed and the biaxial flexural strength determined with a Lloyd 2000 R tester. RESULTS: A significant difference was found for the BFS in the range of mould temperatures evaluated, with the optimum investment mould temperature being 590 degrees C for LG3 and 610 degrees C for SG3 (p = 0.0002 and p = 0.019, respectively). No significant differences were seen between any of the glass casting temperatures evaluated. SIGNIFICANCE: The mould temperature for castable glass-ceramic materials produced using the lost-wax casting process can have a significant effect on BFS. The optimum mould temperature may differ slightly depending on the type of material being used. The glass casting temperature of these materials does not appear to have a significant effect on BFS.