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Distal surface caries in the mandibular second molar is a common outcome of impaction of the adjacent third molar. To determine the prevalence of this type of caries in the Netherlands, 250 radiographs were evaluated. The prevalence among the research population was 26%. Risk factors for developing distal surface caries in the mandibular second molar were partially erupted/impacted third molars with a mesioangular or horizontal angulation, an LD loss of ≥ 2mm and an increased modified DMFT score. The relation between the point of contact of the third molar and the adjacent mandibular second molar, on the one hand, and, on the other, the cemento-enamel junction of the mandibular second molar and the prevalence of distal surface caries almost reached statistical significance (p = 0.052). The relatively low prevalence of distal surface caries in the Netherlands is probably related to the current clinical guidelines recommending early extraction of partially erupted/impacted third molars, particularly in cases of third molars with a mesioangular or horizontal angulation.

Crohn's disease and ulcerative colitis are chronic inflammatory diseases of the gastrointestinal tract. In addition to bowel symptoms, patients may also have oral manifestations. This thesis investigated potential associations between disease activity in the gut, oral health, salivary gland function, and saliva composition. Patients with Crohn's disease had a significantly higher DMFT index, but showed no difference in periodontal diseases compared to a healthy control group. The saliva composition in patients with active bowel disease differed from that in patients with inactive bowel disease, suggesting that saliva analysis could potentially be used in the future to determine the degree and severity of bowel disease. The knowledge of gastroenterologists and dentists regarding oral manifestations of bowel diseases was found to be limited. Gastroenterologists and dentists valued interdisciplinary patient consultation as very useful, but the frequency of consultation was considered insufficient.

Salivary stones are hardened, stony calcifications that primarily develop in the drainage duct of a salivary gland. They can lead to obstruction of the saliva flow, resulting in swelling and pain. Since the aetiology of salivary stones remains largely unclear, this was further investigated in this PhD study. A case-control review of patient records showed that systemic diseases and lifestyle factors most likely do not play a role in their occurrence. The biochemical composition of salivary stones removed by oral-maxillofacial surgeons was examined, revealing that large salivary stones have a different inorganic composition than small salivary stones. Several salivary proteins were detected in submandibular salivary stones, including lysozyme, s-IgA, and -amylase. Clumping together of these proteins may play a role in the initial formation of salivary stones.

To analyze the portrayal of dentists in films, 259 films from the period 1907 - 2018 featuring one or more dentists, were systematically analyzed. A total of 333 dentists were identified, mostly of Caucasian origin (85%) and male (86%). 228 dentists depicted dental procedures, sometimes using gloves (41%), (splash) glasses (35%), and mouth masks (24%). The depicted dental procedures mainly consist of the use of pocket probes and mirrors (46%), drilling/filling (31%), and extractions (25%). Furthermore, dentists in films are relatively often involved in negative activities such as physical violence (29%) and sexual offences (18%). In 16 films (6%), dentists murdered people. Although there is no single stereotypical portrayal of dentists in films, the overall picture seems to need improvement as it is not contributing to the reputation of the dental profession.

In recent years, the five-year survival rate for childhood cancer has increased to about 80%. However, childhood cancer therapy can have serious long-term adverse effects on general health later in life. Of survivors, 75% experience 1 or more late effects. This PhD research aimed to gain more insight into the long-term effects on oral health of childhood cancer therapy, 15 years or more after diagnosis. This study, which is part of the Dutch Childhood Cancer Survivor Study Late Effects 2 (DCCSS LATER 2 Study), showed that oral complications such as dental developmental disorders and hyposalivation occur frequently. Most important risk factors were head and neck radiotherapy of the salivary glands, (alkylating) cytostatic agents, and age at the time of the cancer diagnosis. Dentists should be aware of childhood cancer in the medical history of their patient and of the type of therapy received. Regular dental visits are an essential part of long-term follow-up care of childhood cancer survivors.

Dental caries is a major public health problem and untreated caries has serious consequences for children. Psychosocial factors have multiple consequences, among others on the composition of saliva. Therefore, this study investigated whether stress and various salivary protein levels are associated with dental caries experience in children. The activity of the Matrix Metalloproteinases MMP-8 and MMP-9 and the total proteolytic activity in saliva turned out to be indicators for the caries experience. Salivary Alpha-Amylase seems to be a protector and was a strong indicator for caries experience. In cases where children were exposed to two different dental treatments, the level of salivary cortisol- and alpha-amylase increased, in which a distinction could be made between non-invasive and invasive treatment. The results of the study emphasise the need for further research into the way stress and salivary protein concentrations can affect the caries experience and how different dental treatments can influence the behaviour and stress levels in children.

Matrix metalloproteinases (MMPs) are enzymes involved in the remodelling and degradation of the extracellular matrix, which is essential for maintaining healthy oral tissues. It is therefore important for dental students to know the role of MMPs in biological processes and diseases. Using a questionnaire, a cross-sectional study was conducted among master's dental students from 3 universities in the Netherlands and Belgium. The general level of knowledge about MMPs of the 80 respondents was predominantly low (91.3%). Significant differences were observed among students from the various dental schools, with students from the University of Groningen and Ghent University scoring significantly higher than those from the Academic Centre for Dentistry in Amsterdam (ACTA). Gender was associated with a few questions on the relationship between MMPs and dentistry, with female students achieving higher scores. Improving dental curricula regarding MMPs and their role in dental processes seems warranted.

After a fall from his wheelchair, a 23-year-old wheelchair-dependent patient with spinal muscular atrophy type 1 was initially seen by an emergency dentist, who repositioned and splinted the luxated teeth number 31 and 32. For stabilization, the patient was subsequently referred to a centre for special dental care. In the past, few treatments had been carried out on the patient. A jaw defect and very limited mouth opening compromised dental treatment. In addition, due to the muscle disease, the patient had respiratory and breathing problems, for which he used respiratory equipment. This case describes the importance of a multidisciplinary team in the treatment of patients with spinal muscular atrophy, and the options for performing minimally invasive dental treatment, where the priority is a painless dentition.

Dry mouth has a complex aetiology which makes proper diagnosis complicated. Until now, dry mouth diagnosis has mainly focused on the overall oral dryness, without taking into account regional differences within the mouth. This research showed, among other things, that there are unique patterns of oral dryness, each with its own cause. For example, patients suffering from Sjogren's syndrome mainly experienced dryness of the posterior of the palate. Patients with dry mouth due to the side effects of medication, in contrast, experienced the front part of the tongue as the driest. These findings suggest that mapping of intraoral dryness may be a useful diagnostic tool to differentiate between possible causes of dry mouth.

To gain insight into the current knowledge of oral care providers in the Netherlands on facial skin lesions, a survey was distributed to 7,670 oral care providers. Their knowledge was tested by means of 4 multiple-choice questions and on the basis of 5 cases. The survey was completed in full by 90 respondents. The median age was 50.3 years and 62.2% were female. During dental check-ups, 55.6% always examined the face and 41.1% sometimes did so. Compared to the group 41 years old and older, the group 21-40 years of age alerted their patients more often to skin lesions (p = 0.017), was more afraid a specialist would find the referral useless (p < 0.001) and was more in need of a guideline (p = 0.049). The respondents scored 1.90 out of 4 correct answers to the knowledge questions. On the case studies, they scored 1.46 out of 5 for the correct diagnosis, 3.48 out of 5 for the correct choice of policy and 1.01 out of 5 for the combination correct diagnosis and correct policy. The total score was 2.91 out of 9. The results indicate that knowledge on aspects of skin lesions is limited and additional training and the availability of a guideline are necessary.

In a cross-sectional study, dental records of 149 individuals visiting an Academic Dental Clinic in Amsterdam who reported recreational ecstasy use, defined as no more than twice a week, were systematically analyzed and compared to a group of age- and sex-matched non-drug-users. The parameters retrieved from the dental records were decayed, missing, and filled permanent teeth-index (DMFT-index), number of endodontically treated teeth, presence of active caries lesions, periodontitis, tooth wear, xerostomia, and self-reported use of oral hygiene devices. Periodontitis, active caries lesions, and xerostomia were statistically significantly more present in ecstasy-users. Ecstasy-users brush their teeth significantly less frequent per day than non-recreational-drug-users. There were no significant differences in DMFT-index and in the devices used for brushing and interdental cleaning, and frequency of use of these interdental devices between both groups. We conclude that periodontitis, active caries lesions, and xerostomia, are more frequently present in recreational ecstasy-users compared to age- and sex-matched non-users.

Recently, the Dutch National Immunization Programme has started to offer the human papillomavirus (HPV) vaccination to boys as well as girls from the age of 10. The vaccine protects against long-term HPV infection, which can lead to cervical, anogenital and oropharyngeal cancer. Besides malignant disorders, a HPV infection can also lead to certain disorders of the skin and oral cavity. Since the national HPV vaccination campaign has probably resulted in more awareness among patients about the relation between HPV and oropharyngeal cancer, patients may consult oral healthcare professionals with questions about HPV infection. Oral healthcare professionals are thus able to play a role in preventing HPV related disorders by counseling their patients on HPV. They can also contribute to early diagnosis of HPV related oral and oropharyngeal disorder, although the possibility of detecting oropharyngeal cancer during routine dental examination  is limited.

An implantable cardioverter defibrillator (ICD) is often placed in patients at high risk of ventricular tachycardia and ventricular fibrillation. An ICD is potentially sensitive to electromagnetic interference (EMI) from dental equipment. Between 2000 to 2020, this was investigated in 7 in vitro studies and 4 in vivo studies. Most dental equipment appears to be safe for routine use in patients with an ICD. However, caution seems appropriate with regard to the use of piezoelectic and magnetostrictive scalers as some can cause EMI up to a distance of 20 to 45 centimeter. Use of an electrotome appears to be contraindicated in ICD wearers.

Artificial intelligence provides many possibilities for gaining new insights into the functioning of the oral ecosystem. The success of artificial intelligence is based on a combination of an abundance of available data, greatly increased computing powers and the development of complex machine learning algorithms. These algorithms map biological patterns on the basis of data, without being explicitly programmed, i.e. the computer recognises interactions using data only. Artificial intelligence and machine learning can be used very effectively to make predictions about specific biomarkers or groups of biomarkers that can be associated with specific clinical conditions. Such insights into the complex biological processes cannot be achieved with classical p-value-based statistics.

Tartar is formed by the precipitation of calcium phosphate on dental plaque, particularly in an alkaline environment. Fruit is acidic and contains a lot of carbohydrates besides, leading to acidification in dental plaque. In a large-scale population study, fruit consumption was therefore associated with a reduced risk of tartar build-up. Protein degradation does create an alkaline environment. However, consumption of dairy products, which are rich in protein and calcium ions, does not lead to increased formation of tartar. Oral care products containing the amino acid arginine or urea, both generating an alkaline environment, do not lead to increased tartar formation either. These studies suggest that the effect of diet on the metabolism in dental plaque is insufficient to cause an increase in tartar formation.

Worldwide and also in the Netherlands there is an increasing human papillomavirus (HPV)-attributable oropharyngeal cancer incidence. This type of cancer is more common at a younger age than the classical oropharyngeal cancer, which is usually caused by smoking and excessive drinking. Most often, the tumor occurs in the tonsils and at the base of the tongue. This study explored the level of knowledge of dentists about oropharyngeal cancer, its association with the human papillomavirus and their willingness to play a role in prevention. 7.364 digital questionnaires were sent to oral health-care providers and data from 607 dentists was analyzed. 48% of knowledge questions were answered correctly by more than half of the respondents. Significantly more female caregivers were aware of the relationship between HPV and oropharyngeal cancer and the availability of an HPV vaccine. Respondents considered it important that the relationship between HPV and oropharyngeal cancer is discussed with patients and that a protocol is developed that is useful in screening for mouth and throat cancer.

To alleviate acute dental pain, dentists and dental specialists frequently prescribe analgesics to patients, either on prescription or not. In order to effectively manage dental pain, it is advisable to follow a step-by-step plan based on the WHO analgesic ladder: step 1, start with acetaminophen step 2, add an NSAID (e.g. ibuprofen, diclofenac, naproxen); step 3, add a weak opioid (e.g. tramadol) in combination with acetaminophen or an NSAID; step 4, replace a weak opioid with a strong opioid (e.g. morphine or oxycodone). A dentist in general practice or a dental specialist needs to know, the mechanism of action and the most important interactions, contraindications and adverse effects of each of these groups of medications. Attention is needed when prescribing analgesics to risk groups such as frail elderly, pregnant and lactating women, and children.

Oral care providers frequently prescribe analgesics for the management of dental pain. To get an overview of the analgesics prescribed in the Netherlands from 2016 through 2020, we collected data from the Stichting Farmaceutische Kengetallen (foundation [for] pharmaceutical indicators). Annually, more than 300,000 analgesics are prescribed by dentists in general practice and dental specialists. The largest group concerns NSAIDs (88%), followed by weak opioids (9%), acetaminophen (2%) and strong opioids (1%). Of the NSAIDs, ibuprofen is the most prescribed by all groups of oral care providers (84-91%). Of the weak opioids, dentists and oral and maxillofacial surgeons mainly prescribe codeine and codeine/ acetaminophen (64% and 78%, respectively), while orthodontists mainly prescribe tramadol (53%). Of the strong opioids, oxycodone is the most frequently prescribed by all groups of oral care providers (77-87%). Analgesics are a large part of the prescription medications in Dutch oral care and mainly concern NSAIDs (ibuprofen) and weak opioids (codeine/ acetaminophen). There are no major differences in prescription behaviour among different oral care providers.

The coronavirus pandemic is caused by the SARS-CoV-2. Vaccination appears to offer the way out of this pandemic. Vaccines against this virus make use of the SARS-CoV-2's spike protein, an essential protein on the surface of the virus that it uses to attach itself to the host cells. In viral vector vaccines (AstraZeneca, Sputnik, Johnson & Johnson) the gene for the spike protein is introduced into an adenovirus. Following vaccination, the modified adenovirus will infect cells of the host, which will subsequently start to produce the spike protein, causing an immune response. RNA vaccines (Pfizer, Moderna) only introduce messenger RNA for the spike protein into host cells, which the messenger RNA uses to produce spike protein. Viral vector vaccines and RNA vaccines are not only faster to develop and safer to produce than traditional vaccines, they are also easier to modify to new viruses and virus variants. The latter may be of great importance for future pandemics.

Diet and nutrition play a fundamental role in general health and oral health in children and adults. Dietary guidelines have been developed to provide evidence-based recommendations for populations promoting a diet that meets the best nutritional requirements and prevents diet-related diseases such as overweight, obesity, diabetes and dental caries. Lifestyle and dietary habits are strongly influenced by the (social) media and the products on offer in the supermarkets. Knowledge of the field of the development of foodstuffs and lifestyle trends contributes to effective, appropriate and individualised advice for a healthy mouth in children. Sugar-free flavoured waters with aroma are a good alternative to fizzy drinks, they are tooth friendly and promote a healthy weight.

Current therapies for dry mouth have several drawbacks and limitations. Therefore, some patients turn to alternative medicine, such as acupuncture. Three systematic reviews of the literature found that acupuncture may have a positive effect on reducing complaints. However, in these studies, no effect on the salivary secretion rate was observed. Considering the limited number of studies and the low quality of evidence, caution is advised when recommending acupuncture as an alternative therapy for dry mouth.

A heart transplant procedure is performed on patients who have an end-stage heart disease (severe failure) for whom no other treatment is left. Patients need to take immunosuppressive drugs for the rest of their lives to prevent the rejection of a transplanted heart. A recent overview of scientific literature shows a higher risk of gingival hyperplasia, periodontal conditions, the presence of Candida species and oral malignancies compared to healthy individuals. The association between a heart transplant and dental caries is unclear. A frequent periodical dental check and professional dental cleaning is recommended for heart transplant patients.

Cardiovascular diseases are among the most common disorders in the Netherlands. Dental hygienists will often be confronted with patients who suffer from these diseases. The aim of this research was to explore the current knowledge of dental hygienists in the Netherlands about cardiovascular diseases. 979 dental hygienists in the Netherlands received a written questionnaire by post. The results were tested with the Mann-Whitney tests, the chi-square tests and the Kruskal-Wallis-H tests. A total of 150 dental hygienists participated in the study. Of the 12 case-oriented statements, the dental hygienists answered just over half of the questions correctly (on average 6.59 of 12). Dental hygienists who rated their knowledge about cardiovascular diseases high gave significantly more correct answers (average 7.04 of 12) than dental hygienists who rated themselves lower (average 6.16 of 12). This suggests that dental hygienists' knowledge of cardiovascular diseases, particularly concerning blood clotting, could be improved.

By means of an online questionnaire, the opinions of dental health practitioners on 'orthodontics' were assessed on the basis of 10 statements. There were 523 responses, 51% of which were from general practitioners, a relatively large number from orthodontists (31%) and 18% from other dental health practitioners. Concerning indication of treatment, dental health prior to treatment and the value of straightened teeth, opinions were clearly positive, somewhat more among orthodontist than among general practitioners. Patients knowledge concerning orthodontics and the negative side of orthodontics and their trust in the durability of orthodontic retention are all considered to be more positively present in patients by orthodontists than general practitioners. 1 in 3 non-orthodontists considered carrying out orthodontic procedures in the general practice to be fine. More than 90% of orthodontists disagreed. Female dental practitioners more often consider orthodontic treatment to belong with an orthodontist. The number of women was equally divided across the different groups.

A sensation of dry mouth can be determined with a general questionnaire, the Xerostomia Inventory (XI). This questionnaire, however, does not distinguish among regional differences of oral dryness. In this study, therefore, a new questionnaire was evaluated, the Regional Oral Dryness Inventory (RODI), quantifying the severity of dryness in various intraoral locations. 337 patients participated in this study with an average age of 54 ± 17 years. It appeared there is a significant difference in the sensation of dry mouth between different intraoral locations; the perceived dryness scored highest for the posterior palate and lowest for the floor of the mouth. Introduction of the RODI might help to discriminate among different potential causes of oral dryness in patients. The RODI is highly accessible and easy to carry out in dental practices during routine clinical assessment.

Saliva is a very multifaceted fluid with many different functions and it plays an essential role in oral health. With an aging population, dental professionals will increasingly be confronted with patients with reduced saliva secretion (hyposalivation) or dry mouth (xerostomia). Clinical symptoms as a result of dry mouth vary from mild to severe damage to the hard and soft tissues. Therefore it is important to establish whether a patient is suffering from hyposalivation and if so, whether the patient is able to activate the saliva secretion. Based on saliva testing, hyposalivation and dry mouth can be diagnosed in the general dental practice and be taken into account in prevention and treatment plans.

The relationship between xerostomia and reduced saliva secretion is known to occur in patients suffering from dry mouth. These are mainly (frail) older people experiencing reduced saliva secretion as a result of the use of medication. In the current research, we investigated whether the severity of xerostomia could be used as predictor for saliva secretion in young adults. 369 dentistry students participated in this study, of whom 33.4% were male and 66.6% were female, with an average age of 20.2 ± 2.4 years. It was found that the severity of xerostomia in the young adult students had a weak correlation with the unstimulated saliva secretion rate. This indicates that dry mouth complaints in this age group are not a good predictor for saliva secretion. In addition, it is concluded that hyposalivation is not restricted to older people or to specific patient groups, but that even among a trial population of young adults, individuals can suffer from dry mouth and/or reduced saliva secretion.

A 52-year-old man with a history of krokodil (desomorphine) use was admitted to the department of oral and maxillofacial surgery with drug intoxication and severe pain in his jaw. During clinical and radiological examination, several sites of exposed necrotic bone with purulent discharge were seen. In krokodil-using patients osteonecrosis of the jaw is a frequently occurring manifestation. Other oral aspects associated with the use of krokodil include mucosal changes, a high risk of caries and periodontitis. Systemic effects can interfere with dental and oral and maxillofacial treatment. Treatment consists of sequestrectomy of the necrotic bone under general anaesthesia. The clinical picture of osteonecrosis in krokodil users is similar to cases of 'phossy jaw' and Medication Related Osteonecrosis of the Jaw (MRONJ).

The image of the professions of family doctor and dentist in the Netherlands was investigated by means of a questionnaire distributed online and in four cities. In total, 270 questionnaires were analysed. The dentist was seen more as a businessman, a solo performer for whom the interests of the patient were less highly prioritised, who,was less communicative, more associated with pain, more distant, less open to dialogue and could be trusted less than the general practitioner. Respondents also felt less safe at the dentist's office than at the general practitioner's. On average, respondents rated the general practitioner significantly higher than the dentist. Dentists scored significantly lower than general practitioners on eleven of the twelve statements. The score of the profession dentist was not significantly different from that of general practitioner in only one category, professionalism. These results indicate that the image of the dental profession is worse than that of the general practitioner.

In the present study, the extent to which dental students in Amsterdam, Groningen and Nijmegen consult scientific journals and professional periodicals was explored by means of a digital questionnaire. 333 dental students (20% response rate) participated in this study, 69% of whom had experience in conducting scientific research. 65% of the students had a subscription to a dental journal. Of the Dutch-language dental journals, the 'Nederlands Tijdschrift voor Tandheelkunde' [Netherlands Journal for Dentistry] and the 'Nederlands Tandartsenblad' [Dutch Dentists' Journal] are frequently consulted journals. International publications are consulted especially by masters students, although less frequently than Dutch dental journals. The study revealed that 77% of the students consider it important that attention is paid to the development of scientific skills early in the dental curriculum in order to adequately prepare students to select and interpret publications.

Gastrointestinal symptoms are predominant in Crohn's disease. Oral manifestations may also occur. The prevalence of oral manifestations varies between 0.5% and 37%. The manifestations may coincide with or precede gastrointestinal symptoms, and can be subdivided into specific and non-specific lesions. In most patients, lesions are asymptomatic but some patients experience serious discomfort. Oral manifestations can be classified as specific lesions, such as diffuse lip and buccal swelling and cobblestones, and non-specific lesions, such as aphthous ulcers, pyostomatitis vegetans, caries, gingivitis and periodontitis. In many patients, these oral symptoms do not cause pain or discomfort and do not require treatment. For patients who do experience discomfort, pain caused by aphthous ulcers, for example, can be relieved with a lidocaine solution or a 0.1% dexamethasone gel, and corticosteroids can be used to treat pain caused by ulceration or cobblestoning. It is advisable in complex cases to consult the patient's gastroenterologist.

In this study, the prevalence of musculoskeletal symptoms among dentists and dental students in the Netherlands was inventoried by means of 2 corresponding web surveys. 196 (25% response) dentists and 359 (40% response) dental students participated. 80% of the dentists and 95% of the dental students reported to have suffered from pain in muscles and joints in the last 12 months. In particular, they mentioned complaints of the neck, the shoulders and the lower back. Dental students also frequently reported complaints of the upper back. Many physical complaints were more common among females than male students. In contrast, no gender difference was observed for dentists, but regarding this group stress proved to be an important risk factor for developing musculoskeletal complaints. Given the negative impact on the profession, further research into the prevention of musculoskeletal disorders is urgently needed, in particular about the efficiency of (postgraduate) education and occupational briefing in that domain.

Ulcerative colitis is an inflammatory bowel disease occurring relatively frequently in industrialised regions of the world. Pyostomatitis vegetans is the most characteristic pathognomonic oral manifestation but other oral abnormalities like aphthous lesions, caries and periodontitis are more prevalent in patients with ulcerative colitis. Oral care providers must be aware of these problems if they are to provide adequate oral care.

A 67-year-old woman suffered from a burning mouth feeling for 1.5 years and was referred by her dentist to a saliva clinic. At the clinic persistent xerostomia was diagnosed, and Sjögren's syndrome was suspected. After 1 year, a new measurement of the saliva secretion was carried out, which revealed a further decline in saliva secretion rate. The patient was consequently treated with an intra-oral electrostimulating device in order to stimulate the saliva secretion rate and reduce the feeling of a dry mouth. After 2 weeks, the patient experienced a considerable improvement of the subjective oral dryness.

Salivary stones or sialoliths, are calcified concrements which are most frequently located in the submandibular glands and their ducts. Their size and weight show considerable variation. The aetiology is unknown. It has been suggested that salivary stones could be related to an altered saliva composition, the anatomy of the ducts of the salivary gland and/or the fusion of microsialoliths. Salivary stones consist mainly of anorganic material such as hydroxyapatite, whitlockite and calciumphosphate, but they also contain organic components such as proteins and lipids. Treatment can consist of salivary gland massage combined with an acid diet, ultrasonic pulverisation, and surgical or sialendoscopical removal.

In 2013, a dental practice without a website is almost unthinkable. Using a sample of309 dentists drawn from the list of members of the Dutch Dental Association in 2012, a study was carried out to find out whether the dental practice of the general dental practitioner had a website. The content of each website was subsequently inventoried using a questionnaire. Eighty-nine percent of the dental practices had a website. The content of the websites, however, varied enormously. An element such as the professional registration number with a reference to the professional register were absent in 73% of the websites and the date of the most recent update of the website was mentioned only once. The name of the dentist, his or her professional qualification and an email address were missing on respectively 9%, 20% and 9% of the websites. Contracts of the practice with insurance companies were rarely clearly indicated. The websites of many practices would benefit considerably from a significant improvement.

At the request of the editorial board, H.S. Brand offers a reaction from the perspective of dental care professionals to G.H.I.M. Walenkamp's article about the present regulations for antibiotic prophylaxis for patients with prosthetic joints.

Systemic sclerosis is a relatively rare connective tissue disorder, in which a severe and progressive fibrosis of the skin and sometimes also of internal organs often develops as a result of an increased deposition of collagen. Fibrosis of the salivary glands may cause hyposalivation and xerostomia. Fibrosis of the perioral skin reduces the maximum opening of the mouth, thereby hampering dental treatment and the maintenance of oral hygiene. Periodontitis and bone resorption ofthe jaws are more frequently observed in systemic sclerosis patients.

Head and neck tumours possess several mechanisms to hinder an appropriate immune response against the tumour cell. In the first place, the tumour cells attempt to suppress the presentation of tumour-associated antigens to the cells of the immune system. Tumours also have a negative effect on the surface structures of the efferent blood vessel epithelium, thereby inhibiting the recruitment of immune cells. In addition, proteins are secreted capable of inactivating immune cells. These immunosuppressive activities of the tumour result in a deterioration of life expectancy. Several experimental methods to improve the immune response of the patient against tumour cells are currently being explored.

Education in fabricating single-tooth fixed prostheses and multi-teeth fixed prostheses is an important component of the dental curriculum. To explore the opinion of dental students on this component of the curriculum, a web-based survey was carried out among the students of the 3 dental schools in the Netherlands. The 389 completed questionnaires revealed that the education in fabricating single-tooth fixed prostheses and multi-teeth fixed prostheses started in different years of study at the 3 dental schools. Another striking difference is that the methods of preparation and the choice of materials for single-tooth fixed prostheses and multi-teeth fixed prostheses in the pre-clinical practicum in the programmes was not the same. The students of the 3 dental schools seemed to have a reasonably positive opinion of their preclinical training preparation for treating patients. The opinions of the Nijmegen Dental School students were significantly more positive than the opinions of the students at the 2 other dental schools.

Erosive tooth wear was diagnosed in the dentition of a 15-year-old girl with a Moroccan background. After an anamnesis, extensive analysis of possible risk factors and a study of the pattern of erosion, it was concluded that the erosive tooth wear was induced by daily consumption of a glass of apple cider vinegar Further investigation revealed that in North-African culture, women have used apple cider vinegar to achieve weight loss for generations. Bodybuilders are also known to make use of this method of weight reduction.