Postoperative cognitive function (POCD) has been subject to extensive research. In the literature, large differences are apparent in methodology such as the test batteries, the interval between sessions, the endpoints to be analysed, statistical methods, and how neuropsychological deficits are defined. Traditionally, intelligence tests or tests developed for clinical neuropsychology have been used. The tests for detecting POCD should be based on well-described sensitivity and suitability in relation to surgical patients. In tests using scores, floor/ceiling effects may compromise the evaluation if the tests are either too easy or to difficult. Uncontrolled testing facilities and change of test personnel may affect the test performance. Practice effects are pronounced in neuropsychological tests but have generally been ignored. The use of a suitable normative population is essential to allow correction for practice effects and variability between sessions. Missing follow-up may severely compromise valid conclusions since subjects unable or unwilling to be examined are particularly prone to suffer from POCD. In the statistical analysis of the test results, the evaluation should be based on differences between pre- and postoperative performance. Parametric statistical tests are not relevant unless the appropriate Gaussian distributions are present, perhaps after transformation of data. The definition of cognitive dysfunction should be restrictive and the criteria should be fulfilled in only a small proportion of volunteers. In the literature, these requirements often have not been fulfilled. This precludes a reasonable estimation of the incidence of POCD and the conclusions of comparative studies should be interpreted with great caution. In this review article, we present a number of recommendations for the design and execution of studies within this area. In addition, the critical reader may use these recommendations in the evaluation of the literature.

We assessed validity and reliability of data on four serious pregnancy complications and gestational age in two national registers, the Medical Birth Register (MBR) and the National Register of Hospital Discharges (NRHD). From a cohort of all women in Denmark who gave birth to their first and second singleton infant in 1982-1987, a review was made of a selected sample of 1662 medical records. Regarding registration of pregnancy complications, there was good agreement (kappa above 0.6) between medical records and the registers, and between the registers. However, there was a tendency toward understatement evidenced by low sensitivity of three of four pregnancy complications. The level of agreement (43%) for length of gestation was disappointing. The number of systematic and nonsystematic errors indicate that there was about 52% more singleton preterm deliveries in Denmark in 1982 than previously reported (6.9% instead of 4.5%). It is concluded that the validity of the Danish birth registers should be improved by explicit definitions, increased use of raw data, and data collection by motivated professionals at birth.

The aim of the present investigation was to assess the effect of four implant surface preparation methods used in the surgical treatment of experimental peri-implantitis with autogenous bone graft and expanded polytetrafluoroethylene (ePTFE) membrane. The methods were air-powder abrasive unit+citric acid, air-powder abrasive unit, gauze soaked in saline+citric acid, and gauze soaked alternately in chlorhexidine and saline. A total of 64 implants with a titanium plasma-sprayed (TPS) surface was placed in eight cynomolgus monkeys (Macaca fascicularis). After a 3-month period with plaque control, experimental peri-implantitis was induced. A bone loss of 4-6 mm was established after 9-17 months and plaque control was re-implemented. The peri-implantitis defects were surgically exposed, granulation tissue was removed, and each implant surface was prepared by one of the above-mentioned procedures. The defects were then filled with autogenous bone graft particles and covered by an ePTFE membrane. The animals were sacrificed after 6 months. Evaluation by clinical parameters, radiography including quantitative digital subtraction radiography, histology, and stereology did not reveal significant differences between the methods. Almost total bone regeneration and considerable re-osseointegration were obtained irrespective of the method applied. A mean bone-to-implant contact of 39-46% was observed within the defects. Therefore, the present study of implants with a TPS surface in cynomolgus monkeys indicates that the simplest method involving gauze soaked alternately in chlorhexidine and saline should be the preferred implant surface preparation method in the surgical treatment of peri-implantitis involving autogenous bone graft and ePTFE membrane.

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