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Osteometry of the glenohumeral joint.

Measurements made from radiographs of the shoulder are often used for evaluation of the position of a shoulder prosthesis after surgery. The distances measured from a radiograph are subject to projection errors arising from positioning of the patient in front of the x-ray cassette and from the direction of the x-ray beam at the time of the exposure. The projection error was studied on radiographs of the glenohumeral joint in cadaver preparations. Measurements of the spatial relationship between the glenohumeral joint and the scapula changed by 10% to 50% when the specimen was rotated by 20 degrees around an axis through the glenohumeral joint. The values measured on radiographs of the proximal humerus changed by less than 10% when the humerus was rotated by 20 degrees (exorotation and endorotation). Proposals are made for specific measurements in evaluating the shoulder before and after a prosthesis is implanted.

Aged↗

The effects of glenoid component alignment variations on cement mantle stresses in total shoulder arthroplasty.

Loosening of the glenoid component has been cited as the most frequent cause of patient dissatisfaction with total shoulder arthroplasty, and it has been demonstrated in clinical studies that misalignment of the prostheses can be a causative factor. Finite element analyses of five different glenoid component alignments (central, anteverted, retroverted, inferiorly inclined, and superiorly inclined) were conducted in order to predict changes in the survivability of the cement mantle surrounding the glenoid component. The potential for mechanical failure of the mantle in the centrally aligned implant, during unloaded abduction, was seen to be lower than for any other alignment. Normal bone outperformed simulated rheumatoid models in all cases. Retroversion was worse than anteversion, and superoinferior misalignment was worse than anteroposterior. The quality of the supporting bone stock was found to be particularly significant to cement survivability, more so than the occurrence of eccentric loading of the joint. Shear forces acting on the glenoid component were found to be more detrimental than axial forces, resulting in a greater likelihood of failure toward the extremes of motion. The study suggests that significant efforts should be made to align the glenoid component correctly and also to ensure suitably consistent support of the prosthesis within the bone.

Arthroplasty, Replacement↗

A retrospective comparison of two definitive impression techniques and their associated postinsertion adjustments in complete denture prosthodontics.

PURPOSE: To compare the number of postinsertion adjustment visits required by edentulous patients whose dentures were made from border-molded definitive impressions using modeling plastic impression compound (traditional technique) with patients whose dentures were made from border-molded definitive impressions using heavy-body vinyl polysiloxane impression material. MATERIALS AND METHODS: In this retrospective clinical study, 78 patients were treated with the traditional technique (custom impression trays border molded with gray modeling plastic impression compound) and 78 were treated with the modified technique (custom impression trays border molded with heavy-body vinyl polysiloxane impression material). In both techniques, definitive wash impressions were made with light-body vinyl polysiloxane impression material. Postinsertion visits were quantified for 1 year after the dentures were inserted. RESULTS: The average number of adjustment visits for patients treated with the traditional technique was 2.68. The average number of adjustment visits for patients treated with the modified technique was 2.68. The data were compared using Student t tests. There was no significant difference in the number of adjustments required for patients whose dentures were made with either technique (t = 0.000, p = 1.00). There was no significant difference in the number of post-insertion visits required by patients from either population. CONCLUSIONS: Within the limitations of this clinical study, border-molding custom denture impression trays with vinyl polysiloxane impression material provided similar results in terms of postinsertion visits for one year as compared to dentures made from impressions border molded with modeling plastic impression compound.

Appointments and Schedules↗

Inpatient management of lower extremity amputations.

The in-hospital care of the amputee is crucial; careful preoperative, intraoperative, and postoperative regimens set the stage for a successful clinical outcome. Caring for the patient undergoing amputation is much more than choosing the correct level at which to cut. Early aggressive rehabilitation; careful attention to postoperative complications; and appropriate physical therapy, occupational therapy, and counseling all play pivotal roles. Thorough knowledge of these issues helps to increase the likelihood of a successful outcome and to keep morbidity to a minimum.

Amputation, Surgical↗

The effect of add power on distance vision with the acuvue bifocal contact lens.

PURPOSE: This study was designed to determine if subjective evaluation of quality of distance vision with the Acuvue Bifocal contact lens could be correlated with high- and low-contrast acuity scores. METHODS: LogMAR visual acuities of 20 non-presbyopic subjects were measured using high and low-contrast Bailey-Lovie charts. Each subject wore an Acuvue Bifocal contact lens with add powers +1.00, +1.50, +2.00, and +2.50, each optimized for best distance acuity. RESULTS: Subjects showed significantly decreased acuities with increasing add; a low-contrast target heightened this effect. Subjects reported a reduction in quality of distance vision, increasing fluctuation, ghosting/shadows, and halos around lights that correlated with increasing add power. CONCLUSIONS: Our findings suggest that the Acuvue Bifocal contact lens may be expected to perform best for presbyopes with low-to-moderate bifocal add requirement, and that clinicians should anticipate decreased low-contrast acuity and reduced overall quality of vision as add powers are increased.

Adult↗

[Endoprosthesis implantation in the elbow joint].

Previously used total elbow prostheses were mainly constrained hinged implants. Their early clinical results were favourable but they failed due to a high rate of loosening already a few years after implantation. The cause for the early loosening was the great forces across the elbow joint which were directly transmitted to the prosthesis-bone interface in these implants. Therefore, these implants were abandoned. Afterwards, unlinked, semiconstrained or non-constrained resurfacing devices were introduced. In these devices, the soft tissues constrain the joint and therefore absorb part of the transmitted forces. The rates of loosening were significantly improved and rarely the cause of early failure. But resurfacing implants require intact condyles and collateral ligaments. These implants can, therefore, only be used in a limited number of indications, and postoperative instabilities are known complications. The currently most frequently used device is the semiconstrained Coonrad-Morrey prosthesis. It is a floppy hinge which allows valgus-varus and rotational laxities. Therefore, a part of the forces across the elbow joint are absorbed by the soft tissues. The loosening rate is not a clinical problem any more, and is with 4% 10 years after implantation (rheumatoid arthritis) similar to that of total hip or knee replacement. Furthermore, this device is stabilised with a small anterior flange to the anterior cortex of the humeral shaft. Condyles and collateral ligaments are therefore not necessary neither for short nor for long-term stability. The Coonrad-Morrey total elbow prosthesis can therefore be used for almost every indication, such as severe destruction of the elbow joint and even in case of complete loss of the distal humerus. The long-term outcome with this prosthesis for the treatment of rheumatoid arthritis is favourable with 96% of very good and good results. Function is restored with an average flexion of 131 degrees, a mean loss of extension of 28 degrees, and an unrestricted pronation and supination. The rate of complications for patients with rheumatoid arthritis is 10%. Similarly, the results for Coonrad-Morrey total elbow replacement for posttraumatic arthrosis are favourable with 83% of satisfactory results. Most patients consider their elbow as improved compared to preoperatively, but pain relief is obtained only in three quarters of the patients. The rate of complications is high with 30%, indicating the total elbow replacement is contraindicated for strenuous labour and sports activities.

Arthritis, Rheumatoid↗

[Single intervention for treatment of Salmonella typhimurium-induced symptomatic abdominal aortic aneurysm with spondylitis].

Simultaneous treatment of Salmonella typhimurium-induced symptomatic abdominal aortic aneurysm with associated spondylitis. Bacterially infected aneurysms associated with local spondylitis, while representing a potentially fatal clinical picture, are an operative challenge for vascular surgeons and orthopaedic surgeons alike. In this context, the concurrent occurrence of an infection with Salmonella typhimurium as a causative agent is a rare observation. The case report gives an outline of the simultaneous vascular and orthopaedic surgical procedure. The subrenal mycotic aneurysm was removed in a first step. The continuity of the aorta was restored centrally through an autogenic aortic graft with caudal anastomosis to a dacron vascular prosthetic tube. Initially, the latter was chosen of excessive length so as to facilitate the orthopaedic surgeon's approach. Upon completion of stabilising surgery of the vertebral column, the dacron tube was reduced in length as necessary and the surgical area was enclosed with an omentum majus plastic mesh. No complications were noted during the 18-month follow-up period.

Aneurysm, Infected↗

Simultaneous force measurements in 3 dimensions on oral endosseous implants in vitro and in vivo. A methodological study.

A novel piezo-electric force transducer was developed that is mounted directly on ITI-implants and allows for simultaneous force measurements in 3 dimensions. The reliability of this measuring method in vitro and in vivo was evaluated. For test and calibration measurements 5 edentulous patients with 2 mandibular implants were selected and master casts obtained with original implants in situ. Preload of the abutment screw was measured with a torque controller by repeated tightening and loosening. The introduction of additional preloads when bar connectors or telescopes were mounted was examined on the casts and in the mouth. Tests were carried out to identify the influence of screw tensions on force measurements by loading the implants in vertical and transverse directions. Calibration measurements in vivo and in vitro were carried out by means of a spring balance. A regression model was calculated to analyze the influence of the applied preload on measured forces. The mean preload value was 315, ranging from 200 to 480N. A significant correlation of applied loads to measured forces was found (r = 0.99). It was independent of the preload in vertical direction but dependent in transverse direction. No additional tension of the abutment screw was ever observed when bars were mounted. Calibration measurements with the spring balance showed that bars contribute to load sharing between the implants. Comparable results were found for all measurements in vitro and in vivo. It was concluded that the new piezo-electric transducer is an adequate instrument to measure forces in 3 dimensions on ITI-implants.

Dental Abutments↗

Measurements of bone and frame-work deformations induced by misfit of implant superstructures. A pilot study in rabbits.

This in vivo study used a 3-D photogrammetric technique to measure distortion of 3 unit implant frame-works and bone surrounding osseointegrated implants after securing misfitting superstructures to the implants. Four adult loop-eared rabbits were provided with 3 implants each in the proximal part of 1 tibia each. After a healing period of 8 weeks, a titanium frame-work was connected with a misfit to the central implant. Three-dimensional photographs were taken before and after securing the central screw, which induced a calculated mean preload of 246 N. Measurements and comparisons of the topography of the frame-works and surrounding bone before and after tightening the central screw indicated a complex and inconsistent deformation pattern. Generally, it could be observed that the top edge of the central cylinder showed vertical movement towards the bone of about 150 microns, always in combination with a rotation of the entire super-structure. The head of the central implant seemed to show a corresponding displacement towards the frame-work of about 50 to 200 microns. Bone deformation was found to be basically localized between the implants, where compressions of about half a millimetre were observed. This concentration of bone deformation as a result of misfit may be one contributing factor to initial marginal bone loss, occasionally observed after insertion of implant supported prostheses.

Animals↗

Clinical and SEM evaluation of all-ceramic chair-side CAD/CAM-generated partial crowns.

The effect of hardware and software on the quality of Cerec all-ceramic partial crowns was investigated in this cross-sectional study. Partial crowns (n = 818) had been adhesively placed in 496 patients between 1993 and 1997 using Cerec 1 and Cerec 2 units (groups 1 and 2) as well as Cerec 2 with wall-spacing software (group 3). From each group, 25 randomly selected partial crowns were evaluated using modified United States Public Health Service (USPHS) criteria. Of these, 12 were randomly selected in each group, replicas taken and examined in a scanning electron microscope for marginal interfacial width and for continuous margin adaptation. Interfacial width of group 1 (308 +/- 95 micro m) was significantly larger than those of groups 2 (243 +/- 48 micro m) and 3 (207 +/- 63 micro m). Continuous margin adaptation at the tooth-luting composite and luting composite-restoration interfaces showed only minor differences in groups 1 (94.5 +/- 8% and 95.5 +/- 2%), 2 (98.1 +/- 1% and 97.5 +/- 1.4%) and 3 (96.8 +/- 3% and 96.8 +/- 2%). Pooled clinical rating was excellent or good at 97% for all groups, indicating acceptable restoration quality except for one breakage in group 1.

Adult↗

Dental implants. 7. Basic restorative techniques.

Some restorative techniques for implant supported restorations will be familiar to dentists used to providing conventional crown and bridgework. The differences and principles involved when using implants are identified.

Dental Abutments↗

Funding the GDS.

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Financing, Government↗

The use of hypnosis in the management of 'gagging' and intolerance to dentures.

Hypnosis is not a therapy, but can provide the clinician with a set of techniques which may be used to augment or facilitate a particular course of treatment. The importance of the patient's history and clinical findings in the diagnosis of intolerance to dentures and the selection of patients for hypnosis is discussed. Principles of treatment using relaxation, anxiety control, conditioning/desensitisation and confidence boosting techniques are described. Some examples of typical case histories are used to illustrate the application of a variety of techniques that have been found to be successful.

Adaptation, Psychological↗

Preparation of guide planes using a reciprocating handpiece.

A reciprocating handpiece and attachments have been found effective in preparing guide planes prior to the construction of removable partial dentures. A comparison was made of the enamel surface prepared using the reciprocating handpiece and a conventional rotary handpiece. Two-stage and three-stage techniques for each handpiece were compared. Scanning electron micrographs showed that a smoother surface was created by the reciprocating handpiece.

Bicuspid↗

Complications and maintenance requirements of implant-supported prostheses provided in a UK dental hospital.

AIM: To assess the nature, timing and frequency of complications associated with implant therapy and to assess maintenance requirements of implant-supported prostheses. DESIGN: Retrospective analysis. SETTING: The Dental Hospital in Newcastle upon Tyne. METHOD: Dental records of 60 patients provided with implant-supported prostheses were examined. Data were compiled on the number of fixtures placed per patient, the type of prosthesis provided, complications during the surgical and prosthodontic phases, and peri-implant soft tissue complications. RESULTS: 66 prostheses were placed on 236 fixtures over a 6-year period. Surgical complications included fixture loss (n = 6), dysaesthesia (n = 12), and the need for a guided tissue regeneration procedure (n = 10). Common maintenance requirements were tightening of components (n = 11), clip replacement (n = 7) and repair of conventional prostheses opposing implant supported prostheses (n = 7). Plaque control was unsatisfactory with almost half of the subjects requiring intensive oral hygiene instruction and scaling at the first post placement review. CONCLUSIONS: Prosthodontic maintenance requirements were high, particularly during the first year. Surgical complications were relatively infrequent. A case was made for a rigorous oral hygiene programme to reduce the potential for fixture loss through neglect. The financial cost associated with the maintenance of implant-supported prostheses should be incorporated in their overall funding.

Dental Clasps↗