Short-term and long-term effects of chewing training on occlusal perception of thickness

Abstract – The aim of this study was to investigate the short-term and long-term effects of functional stimuli, induced by intense chewing and by prolonged systematic chewing training, on the response of occlusal perception of thickness. The material comprised 25 young adults divided into an experimental group (17) and a control group (8). The occlusal perception of thickness was tested by successively placing different thicknesses of aluminum foil between five pairs of occluding teeth, i.e. right and left second premolars and canines and one pair of the central incisors. The experimental group was tested 2 wk before the start of the experiment and at the start and the end of the experiment, i.e., after 4 wk systematic chewing training, and before and after 30 min intense chewing. The control group was tested on the same occasions but without performing any special chewing activity. The discrimination threshold increased in most of the subjects after 30 min of chewing, both before and after the 28-day training period. This threshold increase was found in all groups of teeth tested. No changes were found in the discrimination threshold of the teeth tested after 28 days of chewing training. In the controls no differences were found between the recording occasions. Since no statistically significant differences were observed between the groups of teeth tested, the changes in the threshold of occlusal perception after intense chewing may reflect the influence of receptors other than periodontal, for example those in TMJ and muscles, which are involved in the control of other neuromuscular mechanisms such as those that control the postural position of the mandible.     

Ontogeny of class II antigen expressing cells in rat incisor pulp

Abstract— Class II antigen expressing cells are generally associated with the early phase of the immune response. Dendritic cells and macrophages expressing these cell surface antigens have recently been demonstrated and characterized in the dental pulp. The present study was undertaken to determine when the pulp receives its immunologic defense potential by examining the temporal appearance of class II antigen expressing cells in the rat incisor pulp. Pulp tissue specimens obtained at various time periods from a gestational age of 16 days to 14 wk after birth were examined by immunohistochemistry using O x 6 as a primary antibody and the ABC-technique. Comparisons were made with tissue samples from the spleen, intestine, skin and oral mucosa. At birth, all tissues, except for the pulp, presented cells expressing class II antigen with a dendritic appearance in a number and orientation resembling the mature tissue. A complete distribution of these cells was not seen in the dental pulp until 7 weeks following birth. Data show that the dental pulp acquires its ultimate structural arrangement of immune cells later than other tissues.     

SEM and microradiographic investigation of initial enamel caries

Abstract – In this paper a combined microradiography and SEM study is presented on human enamel after a caries attack in vivo for a 4-wk period. The initial enamel caries is induced under a specially designed orthodontic band; plaque accumulation takes place under a niche in the band. The microradiography and SEM were done on the same sections. A special manipulation and breaking technique of the thin sections makes it possible to observe with the SEM, demineralized enamel areas with a mineral content known from microradiography. The results show that with a mineral content of about 50 vol. %, the observable porosity is noticeable at the prism level (interprismatically) but barely noticeable at the crystallite level. The surface morphology of the demineralized enamel is at low magnifications not very different from sound enamel. At high magnifications, however, the surface porosity becomes visible. The results indicate that the mineral in vivo losses in enamel after an initial caries attack can be explained mainly by mineral losses from interprismatic areas and from the prism peripheries.     

Aspects of mastication with bridges on osseointegrated implants

Sixteen edentulous patients were examined before and 2 months after rehabilitation with fixed bridges supported by fixtures in the mandible. Data were collected regarding bite force, chewing efficiency, chewing movements and self-estimated chewing ability. The results after rehabilitation indicated that patients with an obvious improvement of chewing efficiency showed a greater increase of the mean bite force parameters than patients with unchanged chewing efficiency. However, it was not possible to find any definite pattern of differences between the groups of patients, based on the chewing efficiency index after rehabilitation. Furthermore, after rehabilitation the test group revealed a positive correlation between the duration of the occlusion phase and bite force values, negative correlations between bite force “as when chewing” and closing velocity and between duration of the occlusion phase and opening mandibular velocity and displacement, respectively.     

Effect of fluoride addition on ionized calcium in salivary sediment and in saliva containing various amounts of solid calcium fluoride

Abstract – The aim of the present study was to estimate the fluoride concentrations necessary for the precipitation of calcium fluoride or calcium fluoride-like substances in saliva and salivary sediment, in the presence of various amounts of chemically pure calcium fluoride. Fluoride was added in increments to whole saliva to which solid calcium fluoride had been added. The ionized calcium concentration was determined immediately after centrifugation. In salivary sediments and saliva with no calcium fluoride added the ionized calcium concentration was nearly independent of the fluoride concentration added below 10 and 20 mmol/l, respectively, and at fluoride concentration above 15 and 25 mmol/l, respectively, nearly no ionic calcium was detected. In the presence of calcium fluoride the ionized calcium concentration decreased rapidly with increasing concentrations of fluoride. The more calcium fluoride added, the lower the ionized calcium concentration at a certain fluoride level. The results suggested that in the in vivosituation, caries preventive measures based on frequent oral exposure to low concentrations of fluoride may provide calcium fluoride or calcium fluoride-like substances, which will serve as a reservoir for fluoride.     

Effect of antibody preparations on glucose uptake by a cariogenic streptococcus

The effect of antisera to whole cells or cell wall components on glucose uptake by S. mutans 6715 was examined. Early stationary phase 6715 cells were treated with test scrum and incubated at 37°C in the presence of ¹⁴C-glucose. Samples were removed at timed intervals and measured in a liquid scintillation counter for radioactive uptake. Antisera to both whole cells and components known to be present on the surface of the cells reduced glucose uptake relative to normal serum. It is suggested that inhibition of glucose uptake may be one mechanism by which a caries vaccine may operate.     

SCREENING FOR MULTIPLE ENDOCRINE NEOPLASIA SYNDROME (TYPE 1) IN PATIENTS WITH PRIMARY HYPERPARATHYROIDISM

In 63 consecutive patients with primary hyperparathyroidism (HPT) a prospective screening study was undertaken for coexistent multiple endocrine neoplasma-(MEN)-syndrome type 1. The screening consisted of a clinical examination, a radiological examination of the sella turcica with skeletal tomography (and in equivocal cases computed tomography), visual field examination by perimetry and a hormonal evaluation including measurements of the serum levels of prolactin, gastrin, pancreatic polypeptide (PP) and subunits of human chorionic gonadotrophin (HCG-alpha and -beta). Clinical examination did not reveal any signs of endocrine disease suggestive of a MEN-1 syndrome. In only one case there was a radiological abnormality of the sella turcica; this patient had an empty sella syndrome and a raised serum prolactin value. All other prolactin values were within the normal range. In 41% of the patients raised serum gastrin levels were found; these tended to normalize after parathyroidectomy. As a group, patients with raised gastrin values were older than the others and generally they had hypo- or achlorhydria. The serum PP levels were raised in 28% of the patients but there was no clinical evidence of a pancreatic tumour in any of these cases, and the serum HCG-alpha and -beta levels were within the normal range in all patients but two. We conclude that the incidence of MEN-1 syndrome in unselected patients with primary HPT must be low, and that investigations for this syndrome are justified only in HPT patients with specific symptoms or with a positive family history.