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Biomedical subjects

J N Walton

Publications and source records attributed to J N Walton.

At least 19 recordsLinked to original sources
PubMed1998

The economics of complete dentures and implant-related services: a framework for analysis and preliminary outcomes.

It is not always clear that the implant-prosthesis offers distinct advantages over the conventional complete denture for managing the edentulous jaw. This article discusses the measurement, distribution, impact, and management of the edentulous jaw, and describes a framework for analyzing the economic costs and benefits associated with the conventional denture and the implant prosthesis. There are physiologic and psychosocial costs and benefits to both the conventional denture and the implant prosthesis, which indicates that neither method is distinctly superior. The physiologic costs are low and the psychosocial costs are similar for both treatments, whereas the direct financial costs associated with the implant prosthesis are substantially higher.

Bone Resorption↗
PubMed1997

An outcomes assessment of a hybrid-PBL course in treatment planning.

As part of an ongoing process of curriculum development, a new course was developed at the University of British Columbia (UBC) to address problems such as lack of student enjoyment of the learning process, poor student preparedness for clinical treatment planning, and underdeveloped critical thinking skills in students beginning their clinical experience. The new course utilized a hybrid problem-based learning (PBL) format that provided students with an overview in lecture format while encouraging active learning in small group tutorials and seminars. Half the second-year class was randomly selected to participate in the new course, while the other half received the standard lectures on the subject. An outcomes assessment examined whether the aforementioned problems had been addressed in the new course. Course participants completed a post-course evaluation, and all students completed a self-assessment of their preparedness and progress in treatment planning and diagnostic. Clinical instructors, who were blind to the identity of the new course participants, were asked to independently assess each student using the same criteria. Results indicate that students who participated in the hybrid-PBL course enjoyed the learning process and later rated themselves as being better prepared and improving more in the areas of treatment planning and diagnostic records than their counterparts, although the latter results were not routinely statistically significant (p < 0.1). Instructor evaluations supported these differences between the two groups.

British Columbia↗
PubMed1996

Apical root strain as a function of post extension into a composite resin core.

This study tested the hypothesis that there is no difference in the amount of strain measured in the root of an extracted tooth at the apical end of a prefabricated post, whether a composite resin core completely covers the head of the post or the post is exposed at the occlusal surface of the core. Twenty extracted teeth were measured (1) after endodontic treatment (baseline), (2) after a composite resin core was fabricated over a prefabricated post, and (3) after a cast crown was cemented. The teeth were randomly divided into two groups after baseline testing. In group 1, the post was buried within the core, and in group 2, the head of the post was exposed on the occlusal surface of the core. Analysis of results indicated a statistically significant decrease in strain from the baseline to the crown when 1 mm of composite resin covered the head of the post. However, based on the small strain values measured, the difference may not be clinically significant.

Composite Resins↗
PubMed1995

In vitro changes in clips and bars used to retain implant overdentures.

Although implant-retained overdentures are a less expensive alternative to fixed implant-supported prostheses in certain situations, problems with retentive clips fracturing and needing frequent replacement have been reported. This study compared baseline and posttest retention of metal and plastic clip-retained overdenture analogs and monitored surface changes in bars and clips throughout the testing process. A laboratory model was made with two implant analogs processed into an acrylic resin platform to which three bars were fitted. Two overdenture analogs were made and retained on the model with metal or plastic clips. Each bar-clip assembly was subjected to 5500 insertion and removal cycles to simulate 3 years of in vivo insertion and removal. Although the differences in retention between metal and plastic clips and between clips before and after testing were statistically significant, it is questionable whether they are clinically significant. Neither clip fracture nor loss occurred during this study, which suggests that it may be functional or parafunctional loading and not repeated insertion and removal of an implant overdenture that may cause the stated problems.

Acrylic Resins↗
PubMed1994

Problems with prostheses on implants: a retrospective study.

Prosthetic parameters for implant success have not been well defined but should include patient satisfaction and prosthesis maintenance, including adjustments and repairs. In addition, differences between fixed and removable implant-supported prostheses (ISPs) should be quantified. This study retrospectively evaluated both patient satisfaction and maintenance for 156 patients. Removable ISPs averaged almost three times as many adjustments per prosthesis (2.1 versus 0.8 per fixed ISP) and more than twice as many repairs (1.9 per removable ISP versus 0.9 per fixed ISP). The most common adjustments were to the contour of both types of prosthesis, and the most frequent repairs involved the retentive clips with removable ISPs and the gold screws with fixed ISPs. The incidence of repeat repairs was more than twice as high with removable prostheses compared with fixed prostheses. However, the repairs to opposing dentures most often needed were for conventional dentures opposing fixed ISPs. The vast majority of repairs were needed within the first year of service. Despite the high maintenance needed, patients were satisfied with both types of ISP, with the exception of limited satisfaction with cleansability, particularly with fixed restorations. The high incidence of early repairs, and the greater potential for a removable ISP requiring adjustment and repair, should be considered both when discussing options with the patient and when estimating treatment and maintenance costs before the commencement of implant therapy.

Adult↗
PubMed1994

Fabrication of an implant surgical guide using a denture replica technique.

The outcome of the prosthodontic phase of implant treatment is affected by the position of implant fixtures within the dental supporting tissues; therefore, surgical guides are often used to facilitate ideal fixture placement. This article describes the fabrication and modification of a wax replica of the patient's existing prosthesis, which is converted into a surgical guide. This approach permits accurate fixture placement relative to planned tooth positions in the implant-supported prosthesis, without the need to fabricate a new conventional denture prior to surgery.

Dental Implantation, Endosseous↗
PubMed1992

Esthetic alternatives for posterior teeth: porcelain and laboratory-processed composite resins.

Porcelain and laboratory-processed composite inlays and onlays are enjoying increasing popularity as a result of heightened patient concern over the esthetics and biocompatibility of restorative materials. This paper reviews current clinical concerns about porcelain and indirect composite restorations, focusing on indirect procedures, microleakage, technique sensitivity, long-term serviceability, finish and polish, abrasion, and wear resistance. The available data indicate that there are still significant limitations to the routine use of these esthetic alternatives for posterior restorations.

Bicuspid↗
PubMed1986

A survey of crown and fixed partial denture failures: length of service and reasons for replacement.

The mean length of service of all restorations observed in this study was 8.3 years. Caries was the most common cause of failure, affecting 22.0% of the units failed and leading to the necessity for replacement of 24.3% of the units observed. Mechanical problems accounted for 69.5% of the failed units as opposed to 28.5% for oral disease. Resin veneer metal crowns provided the longest service of all crown types observed (13.9 years) and failed most frequently because of worn or lost veneers. The complete veneer metal crown had a life span of 6.1 years and was most likely to fail because of caries or defective margins. Ceramic-metal crowns also showed a relatively short period of service at 6.5 years, needing replacement primarily because of porcelain failure or poor esthetics. The resin-veneer metal crown also provided the longest service as a retainer, with a mean length of service of 14.7 years. This was closely followed by the partial veneer retainer (14.3 years), while the ceramic-metal retainer had the shortest life span (6.3 years). No apparent relationship was found between the span of prosthesis and its length of service. The six-unit canine-to-canine fixed partial denture exhibited the greatest longevity of the prostheses studied (10.4 years), while the two-unit cantilever fixed partial denture provided a mean of only 3.7 years of service before replacement was required.

Crowns↗
PubMed1986

Mitochondrial myopathies. A clinico-pathological study of cases with and without extra-ocular muscle involvement.

The clinical and pathological features of 28 patients with mitochondrial myopathy were reviewed. The cases were divided into a group with involvement of the extra-ocular muscles alone or with limb muscle involvement, and a group with a facioscapulohumeral syndrome or generalised weakness without extra-ocular muscle involvement. Cardiac and central nervous system manifestations occurred particularly in the first group which included six patients with multisystemic features and two with the complete Kearns-Sayre syndrome. Diabetes mellitus occurred in the second group only. Quantitative histology on limb muscle biopsies showed a higher proportion of fibres with abnormal mitochondrial aggregates in the second group. No one type of mitochondrial inclusion or other ultrastructural change was specific for either group of cases. The findings illustrate the clinical heterogeneity of cases of mitochondrial myopathy and the lack of specificity of any of the myopathological changes for different subgroups of patients.

Adolescent↗
PubMed1984

Psychometric and cranial CT study in myotonic dystrophy.

Twenty-two adults with myotonic dystrophy were assessed for evidence of intellectual impairment and cranial CT abnormalities. Psychometric evaluation demonstrated significantly lower verbal and performance IQs in the MD subjects than in matched normal controls. The reduced performance IQ was not simply related to loss of fine motor skills. No significant differences were found in memory and personality assessments between the MD and control groups. Lateral ventricular surface area was measured on CT scans using a semiautomated image analysis technique and was found to have a positive correlation with age in a control group of 45 normal scans (r = 0.833, P less than 0.001). This correlation was lacking in the MD group of subjects (r = 0.345, P greater than 0.05), in eight of whom the ventricular surface area was above the upper limit for age found in the control group. Asymptomatic areas of focal atrophy were found in two subjects. There was no correlation between ventricular size and severity or duration of the disease or verbal or performance IQ.

Adolescent↗
PubMed1983

A multifocal extra-abdominal desmoid tumour.

The literature on multifocal aggressive fibromatosis is reviewed and the fifth case recorded is reported. It conforms with the histopathological criteria for aggressive fibromatosis. Conservative local excision and radiotherapy have controlled the disease with preservation of a functioning limb.

Axilla↗
PubMed1981

Carrier testing in families of isolated cases of duchenne muscular dystrophy. Creatine kinase activities in female relatives of mothers with normal CK activity.

A study of the serum creatine kinase (CK) activity in the female relatives of mothers of isolated cases of Duchenne muscular dystrophy (DMD) was undertaken.. It was restricted to the relatives of mothers with normal serum CK values. Ninety-eight females in 19 families were studied; none was found to have a serum CK activity more than 3 SD above the normal mean. This evidence, derived from a study in which the measurement of serum CK activity was used as the sole means of detecting carriers, suggests that very few distant female relatives in such families are carriers of the gene and provides some evidence against the hypothesis that mutation is a rare cause of isolated cases of Duchenne muscular dystrophy.

Adolescent↗
PubMed1979

Carrier detection in Duchenne muscular dystrophy: Assessment of the effect of age on detection-rate with serum-creatine-kinase-activity.

In 40 known carriers of the gene for Duchenne muscular dystrophy (mean age 38 years) the detection-rate with a standard assay of serum-creatine-kinase was 53%. In 52 daughters of known carriers (mean age 16 years) the detection-rate was 45% after correction of age. This implies a much higher detection-rate (about 90%) in young carriers and suggests that discrimination between carriers and noncarriers may best be achieved by testing in childhood.

Adolescent↗
PubMed1979

An evaluation of some carrier detection techniques in Duchenne muscular dystrophy.

Some recently described abnormalities in the serum and red cell membranes in Duchenne dystrophy have been examined as methods of carrier detection in a single-blind controlled study. Twelve carriers (4 definite, 3 probable and 5 possible carriers previously found to have raised creatine kinase levels) and 12 normal female controls of the same age, were examined on 3 separate occasions at approximately two-weekly intervals. Analysis of age-dependent red cell shape changes, serum haemopexin levels, red cell K+ efflux rate, sensitivity of red cell ghost membrane ATPase to ouabain, membrane protein phosphorylation studies and lactate dehydrogenase isoenzyme profiles on agarose gel electrohoresis all failed to distinquish carriers from controls. The carriers suffered muscle cramps more frequently than the controls and all but one carrier and two control subjects were correctly identified by manual muscle strength testing, certain proximal muscles in paricular being consistently weaker in carriers than in the control group subjects. Scalar electrocardiography revealed higher values for the R/S ratio in Leads V1 and V2 and the sum (R-S) in V2.

Adenosine Triphosphatases↗