Subtraction radiography has been developed in 1934 by the Dutch radiologist B. Ziedses des Plantes. The technique is based on the subtraction of two radiographic images. As a result, only the differences remain visible, and structures which have been unaltered in between both exposures, are suppressed. The technique was introduced also in dental radiology in the eighties in the last century. Since then, many studies have been performed showing the benefit of this technique in dental diagnosis. A requirement for reliable results is that the two radiographs which are used for the subtraction have equal brightness and contrast, as well as a completely identical projective geometry. Since radiographic images can be acquired digitally, methods have been developed to make density and contrast equal for both images used for the subtraction process even after the images have been taken, using dedicated software programs. The projection geometry of two images can be made identical in this way as well. Because of this, the technique can also be applied in general dental practice.

To consider the value of prognostic factors in the development of a squamous cell carcinoma from a leukoplakia of the oral mucosa, a retrospective study was performed. Clinical and histological data of 104 patients with oral leukoplakia were analyzed. Leukoplastic lesions with dysplasia in the initial biopsy (n = 38) had been treated by excision (n = 28), by laser evaporation (n = 6) or a combination of these treatments (n = 4). Non-dysplastic lesions (n = 66) had been excised (n = 48), evaporised (n = 17) or treated by excision as well as laser evaporation (n = 1). During follow-up of maximal 6 years (mean 3.6 years), 12 patients had developed an infiltrative squamous cell carcinoma at the site of the primary lesion, 2 within a period of 24 months. No relation could be found between on the one hand size (p > 0.2), clinical aspect (p > 0.2), location (p > 0.45), and primary treatment (p > 0.15) of the lesion, and on the other hand the risk of developing a squamous cell carcinoma. Only a relation could be found between (the intensity of) dysplasia and the development of a squamous cell carcinoma (p < 0.001). It was concluded that because of the high risk of developing a squamous cell carcinoma, patients with a dysplastic mucosal oral lesion should be followed during a prolonged time.

This article is a shortened and adapted translation in Dutch of an opinion paper in the British Dental Journal. The article describes the benefits and rationales of conscious sedation with restraint versus general anaesthesia, in order to assist parents and dentists in the process of decision making whether general anaesthesia or conscious sedation should be given to young children. The author stresses that the English author’s point is not fully objective. In the Netherlands, treatment of children during conscious sedation or general anaesthesia is less available, but availability wil l improve shortly. The most preferable approach is still prevention of dental problems in young children.

The aim of periodontal treatment is to make and keep the periodontal tissues healthy. A proper diagnosis including the assessment of the different risk factors is essential before successful treatment can be carried out. Oral hygiene instruction together with supra- and subgingival cleaning is a basic part of the treatment. Antibiotic treatment and smoking cessation programs also contribute to a good clinical result. Until the seventies, when almost nothing was known about riskfactors and antibiotic therapy, no study was performed to assess the long-term effect of periodontal surgery being part of the treatment. Therefore a study was performed to assess clinically, radiographically and histologically the effect of periodontal surgery and oral hygiene on artificial periodontal defects. The results were reported in the thesis ‘Surgery and oral hygiene on artificial periodontal defects in beagle dogs’. This study established that periodontal surgery can contribute to a healthy periodontium. A good oral hygiene is a prerequisite. These results have been confirmed by a longterm study in private practice. Pocketdepths of 5 mm and more after initial treatment is a good criterion in the decision making for periodontal surgery.

A 45-year-old patient had a progressive ulcer of the tongue. Routine examination, including a biopsy was not conclusive and could not entirely rule out a malignancy. The final diagnosis was made after generalised lesions eveloped, after which specific serological tests confirmed the diagnosis ‘syphilis’. The patient was treated with benzathinbenzylpenicillin and his complaints disappeared. In view of the increasing incidence of this disease remains an important consideration in case of ulcerative or other lesions in the oral cavity.