Search PubMed⌕ Search

Biomedical subjects

A Vissink

Publications and source records attributed to A Vissink.

At least 163 records · Page 9Linked to original sources
PubMed1990

Treatment of the retained permanent molar.

The effect of five different treatments for retained permanent molars was evaluated in 59 patients to develop a rational guideline for adequate therapy. The results showed that a prosthetic buildup is the proper treatment if retention develops after the growth spurt, because in these cases the extent of infraocclusion is slight and relatively stable. If retention develops before the growth spurt, immediate removal of the retained molar followed by orthodontic treatment is the way to maximal success. When retention develops during the growth spurt, the tooth affected has to be observed at 6-month intervals. In such a case, no active treatment is indicated if the neighboring teeth show no tilting and the extent of infraocclusion is minor and stable. In all other cases, the teeth affected have to be removed, followed by orthodontic closure of the edentulous space. Finally, all patients must be screened regularly, because in this investigation, new cases of retention were observed relatively frequently.

Adolescent↗
PubMed1990

Irradiation-induced changes in secretion and composition of rat saliva.

The aim of this study was to monitor changes in the composition and the rate of secretion of rat whole, parotid and submandibular/sublingual saliva after local irradiation of the salivary gland region with a single dose of 10 Gy. Before and 1-30 days after irradiation, saliva samples were collected after stimulation with pilocarpine. Maximum changes in the latent period, the flow rate and the composition of parotid and submandibular/sublingual saliva were observed three days after a radiation dose of 10 Gy. Partial recovery was seen for the latent period, [Pi], [Ca2+] and concentration of amylase, whereas the flow rate and [Na+] remained low and [K+] remained high. The changes in whole saliva were similar to those observed for parotid and submandibular/sublingual saliva, although some variation was observed due to contamination with other contributions to oral fluid.

Amylases↗
PubMed1990

A functional and chemical study of radiation effects on rat parotid and submandibular/sublingual glands.

The aim of this study was to monitor composition and rate of secretion of rat parotid and submandibular/sublingual saliva following local single doses of X-rays ranging from 5 to 20 Gy. Pilocarpine-stimulated samples of parotid and submandibular/sublingual saliva were simultaneously collected with miniaturized Lashley cups before and 1-30 days after irradiation. The lag phase (period between injection of pilocarpine and start of the secretion) and flow rate were recorded and the concentrations of sodium, potassium, calcium, phosphate, and amylase were measured. With increasing dose and time, the salivary flow rate as well as sodium concentration decreased, while potassium concentrations increased throughout the follow-up period. The lag phase and the concentration of amylase reached their maximum at 3 and 10 days after irradiation, respectively. The changes in lag phase and flow rate were most obvious after doses of 15 or 20 Gy and showed a great similarity for parotid and submandibular/sublingual saliva. No dose-response relationship was observed for the changes in concentrations of calcium and phosphate. It is concluded that for radiation doses of 10 Gy and above, irreversible changes (lag phase, flow rate, potassium, sodium) were observed. A saturation of the irradiation effects (lag phase, flow rate) seems to exist at doses larger than 15 Gy. No significant differences were observed between the radiation-induced functional changes in parotid and submandibular/sublingual salivary gland tissue.

Amylases↗
PubMed1989

An adaptation of the Lashley cup for use in rat saliva collection.

A miniaturized Lashley cup for collecting rat parotid and submandibular/sublingual saliva is described. The small dimensions of the cup enabled its proper positioning on the orifices of both salivary ducts. The method avoids surgical intervention, causes no tissue damage, allows simultaneous collection of both types of saliva and its appropriate for long-term studies of salivary composition and secretion in the rat.

Animals↗
PubMed1989

Secondary retention of permanent molars: a histologic study.

The etiology of secondary retention is not well understood, but ankylosis is often considered to be an important factor in primary molars. Data concerning the mechanism of secondary retention in the permanent dentition are insufficient, although a possible role of ankylosis has been suggested. In order to analyze the frequency of occurrence and localization of ankylosis in secondarily retained permanent teeth, 26 secondarily retained molars and for comparison six normal molars were studied histologically. These data were compared with the clinical and radiographic findings. Areas of ankylosis were observed along the roots of all secondarily retained molars. In 81% of the cases these areas were located at the bifurcation and interradicular root surface. No signs of ankylosis were found in normal molars. When these results were compared with the clinical and radiographic data, it was obvious that the latter gave many false negative results, because the areas of ankylosis were often too small to be detected clinically or radiographically.

Adolescent↗
PubMed1989

In vivo study on the prevention of postradiation caries.

Postradiation caries is usually prevented by the application of topical fluorides (F) at high concentrations. The aim of this study was to develop an optimal preventive program for postradiation caries by evaluating the effects of F concentration and application procedures in subjects with radiation-related xerostomia. Six ground enamel slabs were mounted on each side of the lower denture of each of 7 xerostomia patients. Four procedures were used: no F exposure (control), neutral F gel applied every 2nd day or weekly, and a daily rinse with a F mouthwash for a period of 6 weeks. The enamel slabs were analyzed at weekly intervals by scanning optical monitoring, longitudinal microradiography, and scanning electron microscopy. In addition, hardness measurements were performed on the slabs. F analyses of the enamel slabs were done prior to their insertion in the appliances and after 6 weeks of intraoral exposure. In the control experiments severe demineralization of enamel occurred within 6 weeks. Application of F gel or the use of the F mouthrinse resulted in a significant inhibition of the demineralization process. Of the procedures evaluated, F gel applied every 2nd day was the most effective in preventing the onset of postradiation caries.

Aged↗
PubMed1988

The effect of X-ray irradiation on the demineralization of bovine dental enamel. A constant composition study.

In this study the effect of X-ray irradiation on demineralization of bovine dental enamel in vitro was investigated. Enamel specimens were irradiated with 72 Gy and subsequently demineralized (140 h) under reproducible constant composition conditions at pH = 5 in the presence of methylhydroxydiphosphonate (MHDP). Microhardness measurements after demineralization without MHDP showed significant differences (p less than 0.001) between irradiated and nonirradiated enamel specimens; no significant differences were found in the presence of MHDP. Quantitative microradiography showed that both mineral loss and lesion depth were significantly lower (p less than 0.001) for the irradiated enamel specimens compared with the nonirradiated ones. Surface layer formation was observed in irradiated enamel demineralized in a solution without MHDP. It was shown that X-ray irradiation decreased the enamel acid solubility in vitro.

Animals↗
PubMed1988

A model to investigate xerostomia-related dental caries.

The aim of this study was to develop an in vivo model in which onset, progression, and prevention of xerostomia-related dental caries can be studied. The progress of the caries process was investigated on ground and polished human enamel blocks placed in the lower denture of 7 edentulous subjects suffering from xerostomia. During a period of 6 weeks the samples were analyzed at weekly intervals by means of scanning optical monitoring, scanning longitudinal microradiography, scanning electron microscopy, and hardness measurements. Although the indentation length increased significantly within 2 weeks, no demineralization could be yet observed with scanning optical monitoring, longitudinal microradiography, and electron microscopy in most samples. Starting from the 3rd week a progressive demineralization could be observed by all methods. The mineral loss (hydroxyapatite) in the 3rd week was 0.0126 kg.m-2 (median) which increased to 0.0761 kg.m-2 after 6 weeks. Scanning electron microscopy showed a destruction which resembled that of natural xerostomia-related dental caries. From this study it may be concluded that the in vivo model developed is suitable for studying onset, progression, and prevention of xerostomia-related dental caries.

Aged↗
PubMed1987

Effect of the application of a mucin-based saliva substitute on the oral microflora of xerostomic patients.

A cross-sectional study among 46 xerostomic patients was carried out to determine the influence of a mucin-based artificial saliva on the microflora of standardized oral washings. Patient and non-xerostomic control groups were formed according to the use of saliva substitute (ad libitum or from an intraoral reservoir) and dentition (dentate, edentulous, full dentures). Only few differences were observed among the subgroups based on dentition within a specified salivary group. However, the total number of microorganisms and the proportions of veillonellae, actinomycetes, streptococci and S. salivarius were significantly reduced in xerostomic patients not using artificial saliva, whereas lactobacilli, Candida and S. mitior were significantly increased compared to the control groups. Ad libitum use of artificial saliva had little effect, but semi-continuous wetting of the oral cavity through an intra-oral reservoir reversed the xerostomia-induced shifts in the indigenous microflora. However, no significant effect was observed on the proportions of lactobacilli and yeasts, leaving a potentially acidogenic flora.

Aged↗
PubMed1986

A double-blind crossover trial of CMC- and mucin-containing saliva substitutes.

The aim of this investigation was to describe and to compare the effectiveness of a CMC- and a mucin-containing saliva substitute. 22 post-radiation patients, 17 Sjögren's Syndrome patients and 3 patients with xerostomia of unknown origin used a CMC- and a mucin-containing saliva substitute, each for 1 week in an arbitrary sequence. Neither the patient, the assistant, nor the physician were aware of the substitute being used. Each patient had to complete a questionnaire at 3 different intervals during the trial. One of the conclusions of this study is that mucin-containing substitutes are preferred by patients when compared to CMC-containing substitutes.

Adolescent↗
PubMed1986

Wetting properties of human saliva and saliva substitutes.

Contact angle measurements were employed so that we could study the wetting properties of human whole saliva and saliva substitutes containing mucins or carboxymethylcellulose (CMC) on human oral mucosa (in vivo) and on ground and polished human enamel (in vitro). A new approach was introduced for measuring contact angles on human oral mucosa in vivo. It was shown that the wetting properties of CMC- and mucin-containing saliva substitutes on human enamel were significantly better than those of human whole saliva. On human oral mucosa, the wetting properties of CMC-containing saliva substitutes and human whole saliva were comparable, but were surpassed by those of the mucin-containing saliva substitutes. Mucin-containing substitutes thus provide good wetting properties on ground and polished enamel as well as on oral mucosa.

Aged↗
PubMed1986

Treatment of oral symptoms in Sjögren's syndrome.

The most pronounced oral symptoms in Sjögren's syndrome are a dry sensation of the mouth and difficulties in swallowing and speech. Besides these patients do no sleep well and may complain about burning mucous membranes, rampant caries and candidosis. Rampant caries can be prevented by optimal oral hygiene and frequent applications of a neural 1% sodium fluoride gel. Prophylaxis of candidosis can be obtained by meticulous oral hygiene and removal of predisposing factors (e.g. poor dentures). For the other oral signs of Sjögren's syndrome only a symptomatic treatment is possible, because damage of salivary gland tissue is progressive and irreversible. Good results can be obtained by applying a mucin-containing saliva substitute, which has been shown to reduce the dry an burning sensation of the mouth as well as to improve chewing, swallowing, speech and sleeping. When applied by an atomizer it wets the oral cavity for about 30 min. A continuous wetting can be obtained using intra-oral artificial saliva reservoirs.

Humans↗