PubMed · 8300673
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J Noble. 1994. Bone surface preparation.. https://pubmed.ncbi.nlm.nih.gov/8300673/
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Post designs may have a direct effect on fracture resistance of endodontically treated teeth. This in vitro study compared the resistance of three prefabricated threaded post systems with lateral shearing forces. After endodontics were completed, prefabricated posts were inserted according to the manufacturer's instructions. A silver amalgam core was placed, and extracted human teeth were prepared to a standard size with a 1 mm gingival chamfer finished on sound dentino A cast was fabricated and cemented, and the specimens were thermocycled. The test samples were secured to an Instron testing machine and loaded until failure. Fracture patterns were recorded, fractured surface areas were measured, and compressive stresses were calculated. However, there were no statistically significant differences among threaded posts in each test group.
Preparation of an endodontic access cavity through a full crown may affect its retention. This study was undertaken to investigate the effects on molar crown retention of endodontic access cavities and their subsequent restoration. Thirty human molars were mounted in resin, crown preparations were cut and their surface areas were determined. Vented metal copings were cemented with zinc phosphate and the forces required to displace each coping were measured using a tensile-testing machine. The copings were recemented, access cavities were cut and their surface areas determined prior to the displacement forces being re-measured. The copings were recemented, assigned to two groups, and the access cavities were restored--Group 1 with amalgam; Group 2 with glass ionomer (GIC). Displacement forces were re-measured and the copings were recemented. The occlusal margins of the access cavities were bevelled and restored again prior to displacement forces being remeasured. Mean displacement forces were - Group 1: Original (kg force), 37.86 +/- 3.97; After access cavity, 29.28 +/- 3.22; Amalgam, 50.21 +/- 4.71; Amalgam + bevel, 46.45 +/- 6.21. Group 2: Original, 42.77 +/- 4.49; After access cavity, 39.25 +/- 5.91; GIC, 48.11 +/- 3.55; GIC + bevel, 39.63 +/- 5.31. Statistical analyses with paired t tests showed that retentive values with access cavities were significantly lower than with intact crowns. Amalgam or GIC restorations increased retention beyond original values, significantly with amalgam. Bevelled occlusal margins decreased retention of crowns with restored access cavities but this was not significantly different from the original values. A significant relationship existed between total surface areas of the crown preparations, areas of the occlusal tables, and retentive values for crowns without access cavities. The access cavity area, as a proportion of the total area of the preparation, was related to the decrease in retention.
UNLABELLED: Radiographic arthrography and bone scintigraphy are common diagnostic procedures used for evaluating total hip prostheses. In this study, both techniques are combined, and nuclear contrast imaging (nuclear arthrography) is added. The efficacy of the procedures is evaluated. METHODS: After intravenous injection of 99mTc-methylene diphosphonate (MDP), standard radiographic arthrography was performed in 105 patients (107 prostheses). The radiographic contrast medium was mixed with insoluble 111In-colloid (5 MBq/20 ml). After completion of the radiographic arthrography, nuclear arthrography was performed, and multiple-view dualisotope images (111In, 247-keV peak only) were recorded. Images were interpreted by superposition of the 111In image and the corresponding 99mTc-MDP image, the latter serving as a landmark for the position of the prosthesis and osseous structures. Findings at surgery were used as the gold standard. RESULTS: In both cemented and uncemented acetabular and femoral components, nuclear arthrography performed better than or equal to radiographic arthrography (70%-90% and 60%-75%, respectively). Nuclear arthrography had higher diagnostic accuracy than 99mTc-MDP images alone. CONCLUSION: Nuclear arthrography is a sensitive technique for detection of loosening of prostheses, offering added value over radiographic arthrography and bone scanning alone, especially for evaluation of the femoral component. Radiographic arthrography remains necessary not only for adequate deposition of contrast agents but also for detailed evaluation of osseous structures.