An investigation into the effects of two bioceramics on rat mandibular bone

The aim of this study was to evaluate the effects of both dense hydroxyapatite and ß tricalcium phosphate on mandibular bone, in an attempt to offer guidelines for their use. The importance of these guidelines is that although both of these bioceramics have been used in clinical studies there are no established guidelines to indicate which clinical situation is best served by either dense hydroxyapatite or ß tricalcium phosphate. This is evidenced by the fact that many materials have been used as dental implants and that many shapes and forms of implants have been used in an attempt either to stabilise dentures or to restore facial form.In vitro and in vivo investigations are included in this study. The in vivo investigation, on 231 male Sprague-Dawley rats contained controlled studies on weakened and unweakened mandibular bone; cryosurgery was used to weaken bone in this investigation as previous studies demonstrated significant reduction in bone strength after cryosurgery. The in vivo studies were assessed in two ways; first, mechanical assessments of fracture strengh were determined by three-point bending tests. Second, histological examination of mandibular bone was performed in parallel to the mechanical evaluation, in an attempt to interpret fracture test results from histological findings.The investigations in this thesis indicated, for the first time, that both materials result in significant increased fracture strength of mandibular bone. The histological findings indicated that these increases in fracture strength were biologically significant.The results presented in this thesis suggest that both materials are biocompatible and that g tricalcium phosphate is more ideally used in unweakened bone whereas dense hydroxyapatite, gives its optimal effect on weakened bone, although it gives more rapid early increases in strength than does g tricalcium phosphate. It is suggested that those biomaterials may be of benefit in those clinical situations where surgery on mandibular bone may render it prone to fractur

A survey of dentists? practice in the restoration of the shortened dental arch

Objectives: The aim of this survey was to determine how a sample of dentists working in general dental practice in the UK sought to restore the mouths of patients who had shortened dental arches (SDAs). Study design: A survey was conducted over a period of six months on four commercial dental laboratories. Cases of SDAs comprising the anterior teeth and 2 to 4 premolars were examined; dental prescriptions were scrutinized and a special data collection form was completed accordingly. Results: A total of 140 SDA cases were examined. Most of these cases were for mandibular SDAs (88.6%). Of the recorded SDA cases, 67.2% were restored by cobalt-chromium based removable partial dentures (RPD); 25.7% were extended by acrylic-resin based RPDs; implants were provided to restore 8 SDA cases (5.7%); and only two SDA cases (1.4%) were extended by cantilevered fixed bridges. Neither the gender of the patient ([Chi (2)= 4.19, p>0.05) nor the length of the SDA ([Chi (2) = 6.51, p>0.05) influenced the choice of prosthesis to be implemented. Conclusions: It would appear from the results of this survey that among the different restorative treatment options for SDA, the RPD was the most popular treatment option for dentists surveyed in this UK study. Extending the SDA by either an implant-supported prosthesis or cantilevered fixed bridges did not appear to be a popular choice of treatment

A contemporary update on 'soft' linings.

This article presents a contemporary overview of soft or compliant denture lining materials. It does not focus on denture bases, which are intrinsically flexible, and suggests some clinical options which readers might wish to consider. Clinical Relevance: The aim of this article is to update clinicians on the types of compliant linings currently available and to advise on how some might be used. </jats:p

The Early Medieval Antonine wall

Archaeological fieldwork in the Forth-Clyde isthmus has been dominated by the World Heritage Monument of the Antonine Wall, the Roman frontier built in the second century a.d. Considerably less attention has been given to the evidence for post-Roman experience of the Wall and how it was remembered (and forgotten) in the subsequent centuries. This paper will briefly summarise historical notices of the Antonine Wall, then consider the archaeological and toponymic evidence for early medieval occupation. The role of the Forth-Clyde isthmus as a political frontier is shown to be less significant to our understanding of this period than the evidence for mobility, memory and the contested legacy of Rome in early medieval Scotland

Mercury's surface and composition to be studied by BepiColombo

We describe the contributions that we expect the BepiColombo mission to make towards increased knowledge and understanding of Mercury's surface and composition. BepiColombo will have a larger and more capable suite of instruments relevant for determination of the topographic, physical, chemical and mineralogical properties of the surface than carried by NASA's MESSENGER mission. We anticipate that the insights gained into the planet's geological history and its current space weathering environment will enable us to understand the relationships between surface composition and the composition of different types of crust. This will enable estimation of the composition of the mantle from which the crust was derived, and lead to better constraints on models for Mercury's origin and the nature of the material from which it formed