A comparison of preload values in gold and titanium dental implant retaining screws.

This in vitro investigation compared the effect of using either gold or titanium retaining screws on preload in the dental implant- abutment complex. Inadequate preload can result in screw loosening, whilst fracture may occur if preload is excessive. These are the most commonly reported complications in implant-retained prostheses, and result in unscheduled, costly and time-consuming visits for the patient and the clinician. This study investigated changes in preload generation after repeated torque applications to gold and titanium screws. The test set-up consisted of an implant body, a cylindrical transmucosa abutment, and the test samples of gold and of titanium retaining screws. The implant bodies were anchored using a load cell, and the transmucosal abutments were attached using either gold or titanium retaining screws. A torque gauge was used to apply torque of 20Ncm, 32Ncm, and 40Ncm to the retaining screws. The preloads generated in each screw type were compared at each torque setting, and after repeated tightening episodes. In addition, the effect of applying torque beyond the manufacturers' recommendations was also examined. Gold retaining screws were found to achieve consistently higher preload values than titanium retaining screws. Preload values were not significantly different from the first to the tenth torque cycle. Titanium screws showed more consistent preload values, albeit lower than those of the gold screws. However due to possible galling of the internal thread of the implant body by titanium screws, gold screws remain the retaining screw of choice. Based on the findings of this study, gold retaining screws generate better preload than titanium. Torque beyond the manufacturers' recommendations resulted in a more stable implant complex. However, further investigations, with torque applications repeated until screw breakage, are needed to advise on ideal maintenance protocols.

Students' vulnerability in educational research.

Dental teaching institutions in South Africa recently implemented "learner-centred" curricula and expected educators to alter their teaching styles accordingly, but perhaps without providing adequate training in this paedagogical philosophy. At the same time, the lecturers were required to conduct evidence-based research to evaluate the outcomes. Thus, clinicians/lecturers also became researchers, using their own students or student material for assessment purposes. Previously, this form of educational research, which was carried out in normal academic settings, was not subject to review by Institutional Review Boards (IRB). However, concerns have risen that learners may be a vulnerable population due to their position in the academic institution, and the power and knowledge differentials that exist between them and the lecturer/researcher. This raises ethical concerns regarding their autonomy and ability to provide free, voluntary, informed consent to be research participants. This paper questions whether educational research may lead to student vulnerability, and proposes some recommendations for educators and institutions involved in educational research.

The scope of maxillofacial prosthodontics.

Oral cancer may affect up to 275 000 new patients per year worldwide. Many of these will be disfigured by the destruction of tissue within the face and head area. Maxillofacial prosthodontics can play a vital role in restoring such patients to a semblance of normality in appearance and function. This article will describe the role of maxillofacial prosthodontics in the treatment of these oral cancer patients.

A simple method to ensure sufficient occlusal reduction in fixed prosthodontics.

Tooth preparations for full coverage restorations must ensure there is adequate occlusal clearance to accommodate the restorative material, in both static and functional occlusion. The shape of the prepared occlusal surface should also be contoured to ensure that the created "space to restore" is evenly distributed so that the restoration will be of a uniform thickness. Many of the methods described in the literature are difficult to use clinically, especially in posterior lingual and palatal regions. This article describes how a modification of the wax wafer technique can be used to identify the exact areas of the tooth that need reduction in order to achieve the desired clearance.

The accuracy of three impression transfer techniques for implant supported prostheses.

Cast framework for osseointegrated implant retained prostheses need to be passively fitting so as not to place undue forces and stress concentrations around the fixtures. Impression materials and techniques play a key role in the accuracy and fit of the metal framework. In this study, three impression procedures were investigated to establish which was the most accurate, reliable and predictable. This included using smooth sided tapered transfer copings and unsplinted and splinted square undercut transfer copings. A metal plated master model was fabricated and used as the standard against which models poured using the different impression techniques were compared. Readings were taken with a Reflex Microscope and used to calculate the mean, standard deviation and deviation index for each test model. The results of this study suggest that direct coping transfer techniques provide comparable or better results than indirect coping transfers in master cast fabrication. There was no significant difference in impression transfer accuracy between splinted and non-splinted square impression coping transfer techniques.

Dentine hypersensitivity: a review of its aetiology, pathogenesis and management.

Dentine hypersensitivity (DH) is defined as pain arising from exposed dentine and represents a distinct clinical entity. Reported cases are increasing particularly among the younger age groups and are thought to be due to acidogenic diets, destructive habits, poor tooth brushing techniques, and the increased use of tooth whitening products. Dentine exposure may be due to a number of processes, both physical and chemical, that lead to either loss of enamel/ cementum or loss of gingival tissue. These causative factors seldom act in isolation and include erosion, abrasion, attrition, abfraction, bruxing, bleaching, medication, ageing, genetic conditions, gingival recession, and periodontal disease or procedures. There are diverse range of treatment products available, which aim at either occluding the dentinal tubules or blocking the neural transmission from the pulp. Most reversible options make use of chemical agents such as fluorides, oxalate, strontium or potassium salts, or dentine-bonding agents. Non-reversible options should only be employed after one or more of the reversible options have been attempted. These usually involve placement of permanent restorations, occlusal adjustments or periodontal flap surgery. Careful diagnosis, patient counseling and management strategies are crucial to the success of any intervention.

Accuracy of the Raypex-4 and Propex apex locators in detecting horizontal and vertical root fractures: an in vitro study.

Unforeseen root fractures during endodontic therapy are often difficult to diagnose and treat. Apex locators have been shown to be accurate in measuring the working lengths of root canals, and it was postulated whether they could also be used to determine the position of root fractures. This study was undertaken to assess the accuracy of two different apex locators in determining the position of fractures. One hundred single rooted teeth were randomly divided into two groups. One group had simulated horizontal fractures cut into them and the other group had vertical fractures. All fractures were detected in both groups using both a Propex (third generation) and a Raypex-4 (fourth generation) apex locator. The actual lengths of the fractures were then measured under 2.5 times magnification, and the results subjected to statistical analysis. Both locators produced similar results and were found to be very accurate, with measurements that correlated closely to the actual lengths. Clinically, treatment options for root fractures vary depending on their location. Thus apex locators may be a valuable aid in not only determining the presence of a root fracture, but also its exact location, which will help the clinician decide on the most appropriate management.

Flexibility of technopolymer clasps compared with cobalt-chromium and titanium clasps.

Patients often cite lack of retention and poor aesthetics as reasons for not wearing their partial dentures. Traditional metal alloy clasps have been shown to exert forces on abutment teeth that exceed those capable of producing tooth movement. In addition, metal display on anterior teeth is often unacceptable. The technopolymer materials are purported to have superior flexibility and exert less force than the metals. This study compared the flexibility and forces produced by technopolymer clasps with those exerted by cobalt-chromium and titanium clasps. The results showed that the technopolymer clasps were up to ten times as flexible as the metal clasps, and they returned to their pretest dimensions after being stretched. In addition, they exerted forces on the abutment teeth that fall within the range of those considered safe for use. This coupled with their pleasing aesthetics makes them suitable for use on periodontally compromised teeth, those with deep undercuts and on anterior teeth.

Use of technopolymer clasps in prostheses for patients due to have radiation therapy.

Patients with large oral defects as a result of a maxillectomy procedure, who are due to have postoperative radiotherapy, need to have the density of the defect restored to ensure standardised radiation distribution. This is achieved with various types of boluses that often require tissue surface positioning stents to help support them. Traditional metal-clasp retained stents were discarded as the clasps caused backscatter of the radiation beams. A radiolucent material was needed to retain these prostheses. Dental D, an acetal resin was used in the fabrication of a positioning stent. It was assessed in terms of ease of manufacture, cost, fit, retention and radiolucency. The material was found to be more costly and time-consuming to manufacture than conventional metal-retained acrylic resin prostheses, but its radiolucency made it ideal for use in patients during radiotherapy treatment. Future studies will determine if the long-term strength of the material will allow the clasps to be used in a definitive prosthesis and thus help offset the initial time and costs.

Potential risk of serious oral infections in the diabetic patient: a clinical report.

Diabetes has many manifestations, including increased vulnerability to bacterial and fungal infections, that may be of concern to the dental profession. Oral candidosis and other opportunistic fungal infections may be early, nonspecific signs of uncontrolled diabetes. Rhinocerebral involvement often extends to the paranasal sinuses, pharynx, palate, orbit, and brain, causing severe tissue destruction and necrosis. This clinical report describes a young woman with diabetes who developed mucormycosis of the maxilla. Tissue destruction resulted in loss of the entire premaxilla, the anterior half of the hard palate, and all maxillary teeth except for the right and left second molars. An interim clear acrylic resin prosthesis was fabricated to restore facial contours and speech and to allow mastication. This prosthesis subsequently was duplicated, and teeth were added for improved lip support, esthetics, and mastication.

An interim extraoral prosthesis used for the rehabilitation of a patient treated for osteoradionecrosis of the mandible: a clinical report.

In patients with tumors of the head and neck, ionizing radiation delivered in dosages that will kill cancer cells induces unavoidable changes in normal tissue. Bone cells and vascularity may be irreversibly injured, leaving devitalized bone susceptible to the development of osteoradionecrosis. This clinical report describes the fabrication of an acrylic/rubber prosthesis retained by an orthodontic headgear. The prosthesis was used to improve the mastication, speech, and saliva control of a patient treated for osteoradionecrosis of the mandible.

An 8-year assessment of maxillofacial prosthetic patients treated in a Department of Prosthetic Dentistry.

The Department of Prosthetic Dentistry at the University of the Witwatersrand, Johannesburg, serves as a referral centre for maxillofacial prosthetic patients from the surrounding general hospitals and local private clinics. This places a time and financial constraint on the department. The aim of this study was to establish the number of new patients seen annually, the causative factors associated with the various types of defects, the treatment provided and the cost per patient in terms of clinical hours and prosthesis fees. The data were taken from the records of patients treated in the maxillofacial prosthetics clinic during an 8-year period, from January 1991 to December 1998. The total number of new patients was calculated and the data were collated according to the year in which treatment commenced. Results were tabulated according to the number of new cases in each group, the aetiology of the defects, prosthetic treatment provided and the costs in terms of clinical hours and prostheses. The results of this study indicate that there is a need for a specialised Maxillofacial Prosthetic Unit. Although the present fee schedule needs to be revised, there is still a need for a substantial amount of state subsidy.

Prosthetic restoration following maxillary trauma utilising a fixed removable implant-supported prosthesis: a case report.

Patients with traumatic head injuries may suffer from tooth loss, as well as involvement of associated soft tissues and bone. Conventional prostheses are often bulky and unretentive. Osseo-integrated implants have made it possible to treat these patients with more retentive, aesthetically and functionally improved prostheses. This case illustrates the use of a fixed removable implant-supported prosthesis for a patient with severe maxillary trauma. A bar connecting the implants was individually designed to have parallel sides and vertical channels prepared in it. The corresponding removable prosthesis features retentive pins which engage the prepared grooves in the bar to provide adequate frictional retention and stability for the prosthesis. This treatment modality restored the missing teeth, alveolar bone, soft tissues and oral function while at the same time facilitating good oral hygiene.