The Dahl Concept: past, present and future.

The Dahl appliance was described nearly 30 years ago. This removable metal bite platform was used to create inter-occlusal space, in a localised part of the mouth, to facilitate the placement of restorations on worn anterior teeth. The Dahl concept is traditionally associated with the management of worn teeth. However, the same principles can be successfully and safely applied to a variety of clinical situations. This has simplified the management of historically complex problems. The advantages are the preservation of tooth tissue and the long-term benefits that brings. This paper reviews the literature related to the Dahl concept and how the concept has developed. There is a discussion regarding possible future applications and research.

Severe emphysematous pyelonephritis: conservative management plus image-guided percutaneous drainage prior to successful elective nephrectomy. A case report and review of the literature.

Emphysematous pyelonephritis (EPN) is a severe necrotizing infection of the kidney, characterized by gas within the renal parenchyma. It is strongly associated with diabetes mellitus and ureteric obstruction. We describe the case of a young female with severe EPN and gas extending diffusely throughout the abdomen. We demonstrate the progression of her infection on CT images from initial admission to percutaneous drainage (PCD) of a large air-fluid collection and then to a period of non-resolution that required elective nephrectomy. Although emergency nephrectomy was historically indicated in EPN, image-guided PCD is emerging as an effective nephron-sparing intervention when combined with supportive care and antibiotic therapy. This can be followed by elective nephrectomy if indicated.

Orbital hydatid disease in Kenya.

We treated 7 cases of orbital hydatidosis presenting as cysts. These were successfully treated surgically using a technique that does not compromise the eye and its visual function. This need arose when it was learned that 7 eyes had been enucleated and another case put on massive steroid therapy due to misdiagnosis as malignancies by ophthalmologists visiting in this country (M. French, African Medical Research Foundation, personal communication). It is imperative to stress the diagnostic and therapeutic aspects of this condition which must be considered in the differential diagnosis of unilateral proptosis.

Crouzon's craniofacial dysostosis in Kenya.

A 5-year-old child with Crouzon's disease presented with luxation of the eyeballs and advanced endophthalmitis as a result of which both the eyes had to be enucleated. This case led us to study the family pedigree. The factors influencing the pattern of clinical presentation, and hence the ultimate treatment of orbital disease, are discussed. The case is presented to emphasise the different concept of ophthalmology in Africa so far as the presentation and management of orbital disease are concerned. Appropriate and timely attention could have prevented the complications in our patient.

Ocular tumors in Africa.

This paper is an analysis of 470 cases of oculo-orbital tumors in Kenya. The present series is compared with the major works conducted in other African and Western countries. We refer to age, sex and geographic characteristics and prevalence of tumors in different populations and stress the differences found. The major emphasis is on retinoblastoma, Burkitt's lymphoma and nasopharyngeal carcinoma. Orbital Hydatidosis is included as a differential diagnosis of unilateral propotosis. Considering all the reviews, retinoblastoma is reported in high numbers in African countries whereas uveal melanoma is extremely rare. Among the tumors of the lids and conjunctiva, squamous cell carcinoma occurs more frequently than in Caucasians. Besides retinoblastoma infiltracting the orbit, Burkitt's lymphoma is the most common orbital tumor, nasopharyngeal carcinoma in Kenya has the third highest incidence in the world. Proptosis is the hallmark of orbital disease and is the commonest manifestation sign at first attendance, a fact which validates the late presentation of most of our patients. The difficulties encountered in early diagnosis and hence the appropriate management are discussed and in concluding remarks some recommendation are made.

A laboratory evaluation of the construction of resin-bonded cast restorations.

OBJECTIVE: To compare the effect of two construction techniques and two pattern materials on the fit of resin-bonded cast restorations. DESIGN: In-vitro study carried out by one operator. SETTING: Postgraduate university hospital. SUBJECTS AND METHODS: 65 nickel-chrome castings were constructed using refractory die and lift-off techniques with wax and acrylic resin pattern material. They were cemented onto master silver dies, embedded in self-curing acrylic resin and sectioned along their long axes. Interfacial distance between the master silver die and casting was measured. RESULTS: A significant different between the range of figures in each group (Mann-Whitney Test, P < 0.01) was found. Construction techniques can be ranked in order of fit of castings: 1. Refractory die, wax patterns: 42.6 microns (SD 12.03). 2. Refractory die, acrylic resin patterns: 53.7 microns (SD.16.06).3. Conventional technique, acrylic resin patterns: 85.5 microns (SD 31.62). 4. Lift-off technique, wax patterns: 139 microns (SD 53.15).5. Lift-off technique, acrylic patterns: 172.8 microns (SD 74.04). CONCLUSIONS: Castings constructed using refractory die technique and subsequently cemented resulted in a more accurate and less variable fit than those produced with the lift-off technique. Wax patterns lead to more accurate castings than acrylic resin and locating indentations may interfere with the cementation of castings when lift-off techniques are used.

The evaluation of direct composite restorations for the worn mandibular anterior dentition - clinical performance and patient satisfaction.

This prospective split-mouth clinical trial evaluated the performance and patient satisfaction of 168 Herculite XRV direct composite restorations bonded to the worn anterior dentition of 18 patients with localized anterior tooth surface loss. One hundred and six of these restorations were placed on the mandibular anterior teeth. The restorations increased the anterior occlusal vertical dimension between 0.5 and 5 mm and the posterior occlusal contacts were restored after a mean duration of 6.2 months (range: 3-13 months) in 14 out of the 15 'Dahl' sub-group patients. The restorations were evaluated after 2.5 years of service by five examiners. Four patients and 23 mandibular restorations were lost to follow-up. Multiple clinical and restorative variables were assessed to determine their influence on restoration performance. Complete failure occurred in 6% of the restorations. Circumferential preparation and height of the restorative addition did not influence the performance of the restorations. A Visual Analogue Scale (VAS) was used to assess the patient's opinion regarding sensitivity, aesthetics, longevity and function of the worn mandibular anterior teeth. A statistically significant difference (95% CI) was found between the pre-operative and 1-month review VAS responses for aesthetics and longevity and this was maintained at the 2.5-year review. Direct composite restorations placed at an increased occlusal vertical dimension are a simple and time-efficient method of managing the worn mandibular anterior dentition. Patient's acceptance and adaptation to the technique is good and the results are accompanied with a high level of patient satisfaction that is maintained for the medium-term.

Role of communities in decision-making eye care programs.

The concept of primary health care involves educating people to live their lives in ways beneficial to their health. Communities as a whole must participate in the decision-making that is involved in such education, be it promotive, preventive, curative, or rehabilitative. I refer to this participation as "participatory communication." It is based on two fundamental tenets: 1) Everyone in a community has some special knowledge to contribute to the development of the health of that community; and 2) No person is superior to another. Subsequent to sociological and anthropological studies of communities in the Southern Sudan by the Norwegian Church Aid, the Norwegian Association of the Blind and Partially-Sighted conducted village workshops based on this concept.

Codon repeats in genes associated with human diseases: fewer repeats in the genes of nonhuman primates and nucleotide substitutions concentrated at the sites of reiteration.

Five human diseases are due to an excessive number of CAG repeats in the coding regions of five different genes. We have analyzed the repeat regions in four of these genes from nonhuman primates, which are not known to suffer from the diseases. These primates have CAG repeats at the same sites as in human alleles, and there is similar polymorphism of repeat number, but this number is smaller than in the human genes. In some of the genes, the segment of poly(CAG) has expanded in nonhuman primates, but the process has advanced further in the human lineage than in other primate lineages, thereby predisposing to diseases of CAG reiteration. Adjacent to stretches of homogeneous present-day codon repeats, previously existing codons of the same kind have undergone nucleotide substitutions with high frequency. Where these lead to amino acid substitutions, the effect will be to reduce the length of the original homopolymeric stretch in the protein.

With an eye to good practice: traditional healers in rural communities.

In Africa, certain traditional treatments for eye diseases can produce ocular damage and visual loss. However, many practices do not cause harm, and some may be beneficial. Traditional healers are often valuable resource persons, helping to provide an understanding of cultural beliefs and practices relating to eye disease, and delivering eye care at community level. These matters are discussed below with special reference to conditions in Zimbabwe.

Cataract surgery at district hospital level.

Cataract remains the leading cause of blindness worldwide, curable though, by a simple procedure. The backlog of cataract patients in developing countries is mounting despite sustainable and downright efforts by health ministries, international voluntary and non-governmental organisations [1]. The current situation has put many developing countries in a difficult dilemma. The authors present a review of a pilot-project in decentralised eye-care in Mutasa District, Zimbabwe. Cataract surgery is performed by a district general doctor as an alternative to clearing the cataract back-log in developing countries, as suggested in several studies [2-5]. It is important to persuade the health ministries to adopt this simple and cheap policy [6,7].

The influence of cement thickness on the tensile strength of two resin cements.

This study evaluated the influence of varying the cement thickness upon the tensile strength of nickel-chromium specimen cylinders cemented with Panavia Ex or Panavia 21 resin cements. A decrease in mean tensile strength of the resin-nickel-chromium alloy composite structure was recorded with an increasing cement thickness for both resin cements. Panavia 21 exhibited a significantly greater mean tensile strength than Panavia Ex at all cement thicknesses tested (P < .01).

Haemolytic disease of the newborn probably due to anti-ELO, an antibody to a low frequency red cell antigen.

Investigation of mild bilirubinaemia and a positive direct antiglobulin test in a 2 day old baby revealed that the mother's serum contained an antibody against the low frequency antigen ELO, which was present on the father's red cells. Family studies showed that the ELO antigen segregates from Rh, Gc, ADA and PGM1. The ELO antigen is enzyme resistant and therefore not likely to be part of the MNS or Duffy systems. No abnormalities were detected in immunoblotting studies. Although insufficient samples were available to attempt elution of the antibody from the cord cells, it is probable that this case represents the first reported haemolytic disease of the newborn due to anti-ELO.