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Biomedical subjects

A H Schuurs

Publications and source records attributed to A H Schuurs.

At least 19 recordsLinked to original sources
PubMed2000

Pulp capping with adhesive resin-based composite vs. calcium hydroxide: a review.

The results of some short-term experiments suggest that direct capping of a vital pulp with the modern resin-based composite systems may be as effective as capping with calcium hydroxide. Total cavity etching with 10% phosphoric acid seems to be safe for the exposed pulp, but unless annulled by calcium hydroxide 35% phosphoric acid may be disastrous. For hemostasis and cleaning of the pulp wound both sodium hypochlorite and saline seem suitable, whereas the effectiveness of a 2% chlorhexidine solution is questionable. Although hard-setting calcium hydroxide cements may induce the formation of dentin bridges, they appear not to provide an effective long-term seal against bacterial factors. Within a few years, the majority of mechanically exposed and capped pulps show infection and necrosis due to microleakage of such capping materials and tunnel defects in the dentin bridges. It is unknown whether newer types of resin containing calcium-hydroxide-products will act as a permanent barrier. The cytotoxicity of the resin-based composites and the temperature rise during polymerisation may not be of concern, but microleakage, sensitisation and allergic reactions may pose problems. Based on available data, pulp capping with resin-based composites may be said to be promising, but more and long-term research is mandatory before the method can be recommended.

Acid Etching, Dental↗
PubMed2000

[Hormone dysregulators. Pseudo-estrogens in dental composite resins and sealanta?].

A number of polluting chemicals in the ecosystems must be characterized as hormone disruptors. Among others, male animals appear to become feminized by the action of the so-called pseudo-estrogens and under their influence mens' fertility is said to decrease. Composites and sealants based on Bis-GMA resin may contain bisphenol-A as an impurity and Bis-DMA, from which in saliva bisphenol-A will be formed by hydrolytic degradation. Therefore, in extreme circumstances a weak estrogenic effect is not impossible on the short-term. However, the amounts of these probably not very potent estrogenic compounds are small, thereby resulting in a tolerable risk on the short term. Long-term-effects and synergism with pseudo-estrogens from other sources prompt further studies in order to verify the safety of the Bis-GMA containing products.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2000

[Oral lichen planus, amalgam and other restorative materials].

Mucosal lesions in the oral cavity, identical to oral lichen planus (OLP), as a consequence of contact with in particular dental silver amalgam may be due to an allergic reaction to mercury or, possibly, a toxic effect on the oral mucosa. Substitution of amalgam preferably by gold--unless sensitisation to gold exists--often results in remission, which sustains a pathogenic role of amalgam in OLP. Substitution of amalgam should be considered if the mucosal lesions correspond topographically to the restorations and epicutaneous patch testing results in a positive reaction on mercury.

Dental Amalgam↗
PubMed1999

Reproductive toxicity of occupational mercury. A review of the literature.

OBJECTIVES: This paper aims to give the dental practitioner insight into the potential reproductive effects of handling dental silver amalgam, c.q. mercury. DATA SOURCES: Experimental studies on animals, case reports and epidemiologic studies. STUDY SELECTION: Experimental animal studies show high doses/concentrations of mercury to increase the risk of reproductive disorders, e.g. infertility, spontaneous abortion, stillbirth and congenital malformations. Some case reports suggest an association between the disorders in humans and high levels of mercury. Therefore, the present article reviews epidemiological studies on the relationship between occupational exposure to mercury, mainly as vapour in the dental practice, and females' procreative ability. Studies concerning the reproductive effects of males' occupational mercury body burden are scarce. The reproductive risk of patients' mercury uptake from silver amalgam fillings is assessed. CONCLUSIONS: It seems warranted to conclude that negative reproductive effects from exposure to mercury in the dental office are unproven, but safe levels have not been established. Seemingly problems are unlikely to occur, unless a poor hygiene causes the mercury concentration in the air to exceed females' time-weighted long-term Threshold Limit Value (TLV). Consequently, in view of the in general low amounts of mercury stemming from dental amalgam fillings, the population at large is at even less risk than dental staff. The effects of occupational elemental mercury concentrations lower than the TLV on the menstrual cycle, conception, male fertility and children's behaviour need, however, more research.

Animals↗
PubMed1999

[Cutaneous and mucosal reactions to dental materials].

The concentration of substances released by dental materials is usually too low to cause systemic-toxic effects, but there is the potential to induce dermatoses in especially dentists as well as mucositis in mainly dental patients. The cytotoxic irritative and allergic diseases are successively described categorized according to their pathogenesis. The identification of the diseases, which often have a similar appearance, depends on history-taking and patch testing. Non-dental sensitization is of diagnostic importance.

Dental Materials↗
PubMed1998

[Syndromes and sequences].

In order to introduce a series of articles on syndromes, the differences between syndromes and diseases are discussed, their causes summarized, annotations are made with regard to genotype and phenotype, and the diagnosis and frequency are described.

Disease↗
PubMed1998

[Working with mercury: cause of infertility in women?].

According to animal experiments, case reports and epidemiological studies, exposition to a high concentration of metallic mercury vapour may cause an increase in reproductive problems. A report on this matter is summarized here as far as it regards women. It seems warranted to conclude that negative reproductive effects are unlikely unless, due to a failing hygiene, the concentration of mercury vapour exceeds the MAC (maximum approved concentration) for women. However, the relationship between concentrations smaller than females' MAC value and problems with cycle and conception need more research.

Animals↗
PubMed1997

[Relation between mercury and Alzheimer's disease?].

Mercury from dental silver amalgam has been suggested to be linked with Alzheimer's disease. The percentage in the population (formerly) possessing amalgam restorations exceeds that of Alzheimer patients. Therefore, low levels of mercury in the brain are unlikely to cause the disease. However, studies indicating increased levels of mercury in Alzheimer brains compared to controls have been criticised. In contrast, it has been proven that an inherited trait accounts for a minor proportion of Alzheimer's patients. Moreover, education--or related psychosocial factors--instead of amalgam has been found to be associated with the disease. Therefore, it does not seem warranted as yet to conclude that mercury is an etiological factor in Alzheimer's disease.

Alzheimer Disease↗
PubMed1997

[Amalgam use and mercury emission in the Netherlands].

An overview is presented of the emission of mercury to the environment by restoring teeth with amalgam, extraction, replacement of amalgam, and the final phase of teeth. Important input data were the trade figures of amalgam. The emission of mercury from amalgam fillings are characterized by diffuse spreading. Many small sources are together a substantial source of the leakage of mercury to the environment. Amalgam adhering to cotton-wool and in extracted teeth deliver a relevant contribution to the mercury load in municipal waste. The total mercury emission from dental amalgam to the environment in the Netherlands is at the estimate 500 kg a year, with a worst case maximum of 935 kg.

Dental Amalgam↗
PubMed1997

[Gallium: an alternative for amalgam?].

Some of the physical properties of gallium-based dental alloys for restorative goals equal those of dental silver amalgam, but the results of the relatively few and short-term studies of their clinical behaviour differ. Corrosion, discoloration, rough surface, expansion and fractures of the margins and possibly the teeth, may pose serious problems and are assessed to make the clinical use premature. Handling characteristics are less favourable than for silver amalgam. Gallium alloys release a substantial amount of gallium. Results of toxicity studies with cell cultures differ. Compared to some brands of silver amalgams the alloys seem to be somewhat more cytotoxic during a longer period of time. However, the gallium released by the restorations would be insufficient to harm the patients. Implants of (early) alloys evoked more serious reactions than silver amalgam. Sensitization is not reported, but few restorations have been made and allergic studies are scarce.

Chemical Phenomena↗
PubMed1996

Dutch dentists' conceptions of dental silver amalgam.

A sample of 468 dentists completed a questionnaire on their conceptions of amalgam. A minority (1-3%) reported that amalgam often causes toxic, galvanic and/or allergic side-effects. A considerably larger number (10-30%) stated that such side-effects 'sometimes' occur, while less respondents (6-11%) said they did not know. 60-80% said that such side-effects do not exist, or rarely. If a patient requested the removal of amalgam, one-third of dentists would do so often for cosmetic or toxic reasons, but only one-fifth in the case of a proven allergy. A very substantial percentage would not remove amalgam except for cosmetic reason. Substantial minorities thought that amalgam should not be used for pregnant women or children, or admitted that they did not know. The use of amalgam was rejected by 5%, while 9% could not decide whether they were for or against its use. Multivariate analysis reveals the existence of two dimensions in the data. The first dimension, referred to as "acceptance-of-amalgam", makes it possible to distinguish a subsample (about 9%) consisting of "rejectors-of-amalgam". On the second dimension, referred to as "conviction", a subsample (almost 20%) of "doubters" can be discerned, alongside "convinced adversaries" (about 4%) and "convinced advocates" (some 25%). The majority of the respondents are thought to be more or less in favour of the use of amalgam.

Attitude of Health Personnel↗
PubMed1996

[Supplementary selenium , an antidote against mercury?].

The consequences of both a high and a low intake of selenium are described in this article. Mercury released by dental silver amalgam might affect the protective functions of selenium. However, the literature does not sustain the existence of such an effect. In view of the small margin between safe and toxic doses of selenium and the absence of a scientific consensus as to the possible toxic effects of mercury from amalgam (additional to dietary mercury), it does not seem to be warranted to advise suppletion of selenium.

Antidotes↗
PubMed1996

[Selenium and mercury. (Un)healthy antagonism?].

The trace element selenium is involved in the protection against damage caused by free radicals. Selenium prevents carcinogenesis and growth of neoplasms. However, the mechanism is insufficiently known. Furthermore, selenium interacts with mercury, thereby preventing toxic reactions to high doses of mercury. The intake of selenium and the desired minimum and maximum concentrations are described.

Animals↗
PubMed1996

[Damage to the dental pulp by composite bonding systems: leakage or toxicity].

The fourth generation bonding systems demonstrate an excellent adhesion to the dental hard tissues. The marginal seal along the composite-resin restoration does, however, not totally prevent microleakage and, moreover, the bonding system may deteriorate with time. Due to the attention that has been given to possible microleakage, the toxic effects of composite and its components have got less attention in recent years. The present article deals with the question whether the dental pulp is damaged by either microleakage and/or components of the bonding system.

Adhesives↗
PubMed1996

[General health damage by restorations of composite].

It seems warranted to state that the fourth generation bonding systems have diminished the probability of bacterial damage to the dental pulp. Dentin and in particular the bonding system may protect the pulp partly at least against toxic side-effects of the numerous components leaching from the composite and against the temperature rise caused by the setting reaction. Generalized toxic side-effects caused by the substances released by the restoration and its bonding system are not impossible and are suspected because of in vitro research, but they are assessed to be unlikely in vivo. Generalized and local allergic reactions may appear. The prevalence of allergy to composite may be higher than due to dental silver amalgam, lichenoid lesions excepted. Yet, allergic reactions are not often reported, supposedly because it is either not observed or possibly due to a lack in awareness of such symptoms.

Composite Resins↗
PubMed1995

Dentists' views on cervical hypersensitivity and their knowledge of its treatment.

A random sample of 400 Dutch general practitioners was asked to complete a questionnaire dealing with the prevalence, conditions and therapies of cervical hypersensitivity of their patients. According to the 259 responding dentists an average of 10% of their patients suffered from moderate cervical pain. The estimated mode for severe pain was 1%. More than two thirds of the dentists reported inadequate brushing of the teeth to cause the hypersensitivity, about one half acknowledged periodontal causes, well over one quarter mentioned the involvement of dietary acids, and about one sixth implicated psychosomatic factors. Other causal factors were mentioned less often. Of the therapies available, the home-care methods appeared to be promoted most often, i.e. brushing with therapeutic toothpastes (77%), improvement of oral hygiene (51%) and local self-application (with finger) of a therapeutic toothpaste or fluoride preparations before the night (41%). Well over 50% reported to apply occasionally bondings/varnishes and 28% said to make sometimes cervical fillings. Other therapeutic possibilities were not, or very seldom, used.

Attitude of Health Personnel↗
PubMed1995

Effects of ethinylestradiol on the course of spontaneous autoimmune disease in NZB/W and NOD mice.

Sex hormones affect (auto)immune responses in various ways. Investigations of the effects of estrogens have produced contradictory results. We studied the effects of gender, gonadectomy and of (supra)physiological doses of (the orally active) ethinylestradiol (EE) in two spontaneous autoimmune disease models: the NZB/NZW F1 and NOD mice. In both models we confirmed the female preponderance and the aggravating effects of gonadectomy in males but not in females. The accelerated mortality found in NZB/W mice treated with supraphysiological doses of EE was not associated with increased proteinuria, increased IgG-type anti-DNA levels or increased mononuclear cell infiltrations in the submandibular gland. In contrast, we found a severe reduction in body weight and in the weights of various organs (indications of toxicity), and a decrease rather than an increase in proteinuria and in mononuclear cell infiltrations (indications for autoimmunity). Physiological doses of EE did not significantly affect disease symptoms. In the NOD model a near-physiological, non-toxic dose of EE did not cause consistent changes on immunological disease symptoms either. Therefore, we conclude that the sexual dichotomy in spontaneous autoimmune models is due to protective effects of androgens and that the mortality by estrogens is due to toxic effects rather than accelerated autoimmunity.

Animals↗