Precision of three-dimensional CT-assisted model production in the maxillofacial area

Individual skull model fabrication was introduced into preoperative diagnostics in maxillofacial surgery in the mid-1980s. The aim of the present study was to collect information on the reproducibility of a skull model milled from hardened polyurethane foam. This model was based on the CT data of a real skull. Twenty comparative studies were carried out on both the model and the original skull, the model showing an average inaccuracy of 1.6 mm. The deviations ranged between 0.0 and 3.6 mm; the general trend favouring enlargements. The total deviation of the model as compared to the original skull was 1.8%. A convincing aspect of the model, which cannot be obtained by any other method, is its plasticity and the possibility of 3 D orientation on a lifesize model. This new method is already used in preoperative planning of corrections of post-traumatic defects and craniofacial deformities as well as in tumour surgery. Correspondence to: P. Solar     

Immunohistochemical detection of 6-oxo-PGF1 alpha and PGE2 in radicular cysts

Prostaglandin synthesis in the wall of radicular cysts was determined by immunohistochemistry and radiothinlayer chromatography. PGE2 is predominantly produced by plasma cells and histiocytic elements, whereas much less is synthesized by fibroblasts and endothelial cells as estimated using immunohistochemistry. 6-oxo-PGF1 alpha, however, was primarily found to be generated by endothelial cells and fibroblasts; only small amounts seem to be derived from histiocytic elements and plasma cells. The response of the cystic epithelium to anti-PGE2 and anti-6-oxo-PGF1 alpha antibodies was negative or showed only minimal staining. It can thus be concluded that the granulation tissue and its cellular components modulating the inflammatory process are the main source of prostaglandin synthesis in the wall of radicular cysts and may therefore be responsible for the resultant osteolytic activity.     

IGF-I binding and IGF-I mRNA expression in the post-ischemic regenerating rat kidney.

The localization of IGF-I peptide and IGF-I mRNA was investigated in the post-ischemic regenerating rat kidney using immunohistochemistry and non-radioactive in situ hybridization techniques. In addition, the distribution and relative quantity of IGF-I binding sites were studied by autoradiographic ligand-binding techniques. Two and three days after the injury, morphological signs of an intense regenerative activity was evident. By this time a substantial number of the regenerating cells were stained with a monoclonal antibody against the M1 subunit of ribonucleotide reductase, a proliferative marker used. Low proliferative tubular cells, replacing those that had been injured, were seen lining the tubular basement membrane. By seven days, the morphology in the cortex was quite normalized, while cells of the S3 segments in the outer medulla remained dedifferentiated. The regenerative cells expressed IGF-I peptide and IGF-I mRNA in a transient manner and this was found to correlate better to cell differentiation than cell division. In addition, non-tubular cells, predominantly macrophages, expressed both the IGF-I peptide and the mRNA. The IGF-I binding was significantly increased in the regenerative zone at all times studied and began to decline at day seven. The binding characteristics were found to be compatible with binding to the IGF-I receptor. Altogether, these findings provide circumstantial evidence that IGF-I is of trophic importance in the regeneration of renal tubular cells. The data are compatible with a local production and action of IGF-I, suggesting an autocrine and/or paracrine mode of action during the regenerative process.     

The impact of healthcare costs in the last year of life and in all life years gained on the cost-effectiveness of cancer screening

It is under debate whether healthcare costs related to death and in life years gained (LysG) due to life saving interventions should be included in economic evaluations. We estimated the impact of including these costs on cost-effectiveness of cancer screening. We obtained health insurance, home care, nursing homes, and mortality data for 2.1 million inhabitants in the Netherlands in 1998–1999. Costs related to death were approximated by the healthcare costs in the last year of life (LastYL), by cause and age of death. Costs in LYsG were estimated by calculating the healthcare costs in any life year. We calculated the change in cost-effectiveness ratios (CERs) if unrelated healthcare costs in the LastYL or in LYsG would be included. Costs in the LastYL were on average 33% higher for persons dying from cancer than from any cause. Including costs in LysG increased the CER by €4040 in women, and by €4100 in men. Of these, €660 in women, and €890 in men, were costs in the LastYL. Including unrelated healthcare costs in the LastYL or in LYsG will change the comparative cost-effectiveness of healthcare programmes. The CERs of cancer screening programmes will clearly increase, with approximately €4000. However, because of the favourable CER''s, including unrelated healthcare costs will in general have limited policy implications.     

Characteristic features of trabecular bone in edentulous mandibles

Background: The density and architecture of the alveolar trabecular bone are crucial to the stability of an endosseous implant. A significantly higher implant failure rate can be expected when implants are placed in alveolar bone with reduced density and stability. Therefore, the present study aimed to describe the trabecular bone structure of edentulous mandibles. Method: Two hundred and seventy‐eight bone sections, including the lateral incisor, first premolar, and first molar regions, were obtained from 128 edentulous lower jaws (68 females and 60 males; mean age: 77.58 years). Ground sections were prepared for each region using the ‘sawing and grinding’ technique. The following standard structural histomorphometric parameters were determined using a semiautomatic image analysis: trabecular bone volume, trabecular thickness, trabecular number, trabecular separation, and the trabecular bone pattern factor, which describes the connectedness of cancellous bone structures. Also, the maximum height of the jaw section was determined, to detect any possible correlations between vertical height and histomorphometric parameters. Results: All the histomorphometric parameters examined showed an unexpectedly huge range of variation. The mean trabecular bone volume ranged between 20.9% and 36.9%. The mean trabecular thickness showed values between 165.9 and 224.7 μm. The mean trabecular number ranged between 1.22 and 1.77/ mm, and the mean trabecular separation ranged between 436.7 and 720.0 μm. The mean trabecular bone pattern factor showed values between ?0.05 and ?3.01/ mm. The maximum height of the jaw sections showed values between 16.05 and 23.42 mm. The trabecular bone volume, thickness, number and connectivity were significantly lower in the molar region than in the incisal and premolar regions. Significant sex‐specific differences were found in all the regions, female mandibles showing a smaller amount and lower connectivity of cancellous bone than male mandibles. No correlation could be found between the maximum height of the jaw and the histomorphometric parameters of the cancellous bone. Conclusion: A possible explanation for the difference in the density between the incisal and the molar region may be that molars are generally lost at an earlier age than anterior and premolar teeth. As a result, atrophy‐related resorptive and remodeling processes commence earlier and progress further in this region than in the anterior and premolar regions. Sex‐specific differences are probably due to an increased postmenopausal bone loss of the females.     

Dental caries at five and twelve years in a South African Indian community: a longitudinal study

In 1979, 515 of 767 available Indian children born in Lenasia in 1974 were examined and their dental caries status was described. In 1986, 515 of the original 715 were re-examined in order to determine the pattern of dental caries in the primary and permanent dentitions of the same individuals. In contrast to studies in the literature in which treatment records have been used, both investigations were formal epidemiological field studies using calibrated examiners and WHO (1971) caries diagnostic criteria. A firm association was found between caries in the primary and permanent dentitions (r = 0.34).     

Use of DI-S and CPITN as predictors in dental caries studies in the primary dentition

The DI-S (simplified oral debris index), CPITN (Community Periodontal Index of Treatment Needs) and dmfs (dental caries experience in the primary dentition were recorded in 395 5-year-old black children living in rural and urban areas of Southern Africa. The DI-S and CPITN were grouped, independently and together, to examine their use as simple field methods of predicting dental caries. For each grouping the sensitivity, specificity and positive and negative predictor values were calculated. A CPITN grouping of 0 or of two or more sextants with bleeding, provided the most convenient specificity, sensitivity and predictor values. It is recommended that this simple method should now be used in prospective studies of caries activity.