The prevalence, location, and size of enamel pearls on human molars

abstract — Of 8,854 extracted molars in Norwegians, 201 teeth contained a total of 219 macroscopically detectable enamel pearls. The uncertainty in tooth determination had a limited effect upon the prevalence figures. Maxillary molars showed a higher prevalence than mandibular molars. The highest prevalence, 4.6%, was found on maxillary third molars. With few exceptions, the pearls were located in the bifurcation area or in the furrow between incompletely separated roots. The mean pearl diameter was 0.96 mm, and the mean distance to the cemento-enamel junction 2.8 mm. The relationship between enamel pearls and cervical enamel projections is discussed. It is suggested that simple enamel pearls and cervical enamel projections are of a similar nature and origin. The enamel of composite enamel pearls is probably initiated in a different way.     

Identification of cellulose fibers in oral biopsies

Abstract – Oral biopsies comprising five periapical cysts, three cases of exuberant granulation tissue in extraction sockets and one case of a mandibular radiopaque structure, all displaying material consistent with cellulose fibers on routine histologic examination, were subjected to histochemical, polarization, fluorescence and scanning electron microscopical, energy dispersive X-ray and chemical investigations. Routine screening of periapical lesions with polarization microscopy and identification of possible cellulose fibers with Calcofluor White is advocated. Further, attention is drawn to endodontic paper point material as an etiologic factor in postendo-dontic periapical inflammatory processes.     

Circumferential continuity of perikymata in human dental enamel investigated by scanning electron microscopy

Abstract – Theoretically the perikymata may represent one of two possible configurations: closed circles or continuous spirals. In the present study one randomly selected perikyma groove in one randomly selected tooth (the mandibular first premolar of a 12-yr-old girl) was tracked around the circumference of the crown in the scanning electron microscope. It was found that the perikymata geometrically represented closed circles. The possibility of methodologic error was excluded.     

Nocturnal electromyographic evaluation of bruxism patients undergoing short term splint therapy

Eight confirmed bruxist subjects were investigated using portable electromyographic equipment. Nocturnal masseteric muscle activity, as measured by electromyography, was reduced immediately following the insertion of a full arch maxillary stabilization splint. It remained low until the splints were removed, at which time all but one subject's EMG values returned to pretreatment levels. Although the short term splint therapy did not show a permanent reduction in EMG levels, a dramatic reduction has been demonstrated during treatment.     

A scanning electron microscope study of the three-dimensional extent of Retzius lines in human dental enamel

A method involving carefully planned sectioning and grinding of human maxillary first premolars, allowing enamel structure to be studied with the SEM in more than one plane at the same time, was employed to demonstrate the extent of Retzius lines within the confines of the three-dimensional enamel cap. It was found that the Retzius lines behaved as could be predicted by the theory stating that the striae represent one-dimensional cuts of two-dimensional, curved growth planes. Retzius lines in adjoining planes were continuous across the edge where the two planes met. In a supernumerary tooth, the surface of its hypoplaslic tooth tip was continuous with distinct Retzius lines. The present observations provide for the first time direct morphologic verification of the supposed nature of Retzius lines, with reference to extent and continuity in three-dimensional space.     

Glycolate Causes the Acidosis in Ethylene Glycol Poisoning and is Effectively Removed by Hemodialysis

ABSTRACT Six male patients with severe ethylene glycol poisoning were studied with respect to the origin of the metabolic acidosis. The plasma concentrations of ethylene glycol were 4–41 mmol/l and treatment included alkali, ethanol and hemodialysis. Plasma analysis by isotachophoresis and whole blood lactate determinations showed that glycolate (17.0–29.3 mmol/l), lactate (1.4–6.2 mmol/l) and β-hydroxybutyrate (≤1.8 mmol/l) were present in elevated concentrations contributing to the acidosis. Oxalate (≤0.33 mmol/l), glyoxylate (<0.2 mmol/l) and formate (<0.4 mmol/l) concentrations were negligible and did not contribute to any significant degree to the acidosis. The elevated plasma glycolate concentration was highly correlated to the anion gap (r=0.923) and the glycolate made up for 96.1% (n=6, range 84.7–108.8) of the increased anion gap. We conclude that glycolate accumulation is the main reason for the metabolic acidosis in ethylene glycol poisoning. The mean dialysator (1.6 m²) clearances of glycolate at a blood flow of 200 ml/min in two patients were 137 ml/min (n=9, SD±8, range 125–149) and 144 ml/min (n=11, SD±8, range 133–158). By applying first order kinetics during hemodialysis a volume of distribution of glycolate of 0.55 l/kg was found, assuming that the dialysator clearance equals the total body clearance of glycolate. Thus glycolate, the probable main metabolite of ethylene glycol, is efficiently removed by hemodialysis.     

The prevalence and distribution of cervical enamel projections reaching into the bifurcation on human molars

abstract — A total of 8,854 extracted molars in Norwegians were examined for the occurrence of long cervical enamel projections. The uncertainty in tooth determination was incorporated into the prevalence figures. Mandibular molars showed a higher prevalence than maxillary molars. Within each jaw, second molars showed the highest prevalence, first molars the lowest. The great majority of the projections occurred on the buccal aspect of the tooth. Possible explanations of divergences from previous studies are discussed.     

The temporomandibular joint in young adults at autopsy: a morphologic classification and evaluation

Macroscopic features of temporomandibular joints (TMJs) were studied in young adults who comprise the largest portion of individuals seeking TMJ treatment. Deviation in form (DIF), arthrosis, size, shape and disc displacement were evaluated on ninety-five autopsied TMJs. Few TMJs (13%, 12/95) showed no intracapsular changes. Thirty-nine per cent (37/95) of the TMJs displayed mild-to-marked DIF in all three TMJ components. Smaller changes were more prevalent and tended to appear in the younger TMJs. Condylar changes were more exuberant and extensive compared to the other components. Minor arthrotic lesions were visible in 3% (3/95), and all displayed DIF. Disc displacement was found in 12% (11/95) and was more common in women (P greater than 0.05). Folding and deformation of the articular disc was associated with disc displacement (P less than 0.01), the direction of which was mostly anteromedial. Most of the unchanged condyles' components had curved, slightly rounded, convex, and elliptical shapes when viewed from different planes (P less than 0.01). Applied in diagnosis, the presence of DIF can be inferred from features which deviate from the above shapes. The concept that the above macroscopic changes might be a precursor to TMJ arthropathy in susceptible individuals is compatible with the results of this study, but the most apt characterization is that TMJ changes in this age group are adaptive phenomena occurring in order to cope with the details of articular fit and function.     

Toxicokinetics of Formate during Hemodialysis

ABSTRACT. During hemodialysis in a methanol poisoned patient, formate elimination followed first order kinetics with a plasma half-life of formate of 165 min. The mean dialysator (1.6 m²) clearance of formate was 148 ml/min (n=8, SD ± 11, range 128–161) at a blood flow of 215 ml/min. By applying first order kinetics, a volume of distribution of 0.5 l/kg was found, assuming that the dialysator clearance equals the total body clearance of formate. Formate, the main toxic agent in methanol poisoning, is thus probably more effectively removed by hemodialysis than methanol. This fact, and the very slow endogenous methanol elimination during appropriate ethanol treatment, should be considered when deciding on the treatment of a methanol poisoned patient presenting with metabolic acidosis.     

Coronary risk factors in middle aged men as influenced by fish oils and smoking

The influence of fish oil supplementation on several coronaryrisk factors in blood was studied in 165 middle-aged employedmen (69 smokers, 96 nonsmokers). In earlier studies smokinghas been shown to increase, and fish oils to reduce the coronaryrisk. This raises the question whether the effect of fish oilson coronary risk factors in blood might differ in smokers andnonsmokers. Groups were supplemented for 10 weeks with eithervarious fish oils, or with olive oil. In response to fish oilsupplementation, mean serum triglyceride concentration was reducedfrom 1.4 to 1.1 mmol/1, and - regardless of smoking habits -total cholesterol (TC) levels were reduced from 6.2 to 6.0 mmol/1,and high density lipoprotein cholesterol (HDLc) increased from1.2 to 1.4 mmol/1 at the end of the supplementation period.In the olive oil group there was no effect on serum triglycerides,but TC fell from 6.4 to 5.9 mmol/1, and HDLc rose from 1.3 to1.4 mmol/1 during the supplementation period. ApolipoproteinA levels fell significantly (by 7% to 8%) in both the pooledfish oil group and the olive oil group, whereas apolipoproteinB levels remained unchanged. A compound atherogenic index includingTC, HDLc and apolipoproteins, was significantly reduced onlyin nonsmokers given fish oil. The effect of various commerciallyavailable concentrates of fish oils seemed to differ accordingto their content of omega-3 fatty acids. The results suggestthat cessation of smoking may be of significance in increasingthe benefit from intake of fish oils.