Biomedical subjects

R M Frank

Publications and source records attributed to R M Frank.

At least 37 records · Page 2Linked to original sources

PubMed1991

Experimental erosion of dentin.

Experimental erosion in human dentin was investigated with scanning electron microscopy. Erosion was caused by solutions containing either 0.030 mekV/g malic acid (pH 3.4), 0.034 mekV/g phosphoric acid (pH 2.6), or 0.038 mekV/g citric acid (pH 2.8). Test specimens prepared from the coronal parts of erupted third molars were immersed in the solutions from 30 s to 60 min. When compared with controls, exposure of dentin tubules was observed in all the specimens already after 30 s immersion, irrespective of the acid used. Mineral loss was seen to progress at the interface between peritubular and intertubular dentin in specimens immersed for 60 s in the acidic solutions. Longer times of immersion resulted in hollowing of the tubular openings by complete destruction of the peritubular dentin. Surface roughness and porosities were seen also at the intertubular areas. Although based on a simplified study model, our results may explain why so many patients with erosions suffer from painful sensitivity of their teeth: the acids causing erosion can expose inner dentin structures to outer stimuli by significant enlargement of the dentinal tubules.

Acid Etching, Dental↗

PubMed1991

Scanning electron microscopic study of the effect of salivary pellicle on enamel erosion.

A bovine tooth model system was used to study the effect of experimental salivary pellicle on enamel erosion. Test blocks with varnish-covered control surfaces in each specimen were immersed into an acidic cola beverage (pH 2.6) for 120 min, either with or without the pellicle which was grown for 7 days by using clarified human saliva. After immersion, the pellicle was removed from some specimens with 10% sodium hypochlorite (20 h at 20 degrees C) and ultrasonic bath (60 s) to study its effect on erosion. All specimens were then studied in the scanning electron microscope. The specimens without pellicle (positive controls) showed gross erosion with prism core dissolution in all study blocks. The specimens with pellicle showed occasionally a film-like integument covering the apparently intact test surfaces with adjacent enamel surfaces slightly eroded. The erosion, however, was not of the same magnitude as in the positive controls. After removing the pellicle, the enamel surfaces showed pitted appearance of the prism heads; the demineralization seemed to attack more the prism sheath areas. Thus, salivary pellicle was found to protect the underlining enamel from erosion in vitro.

Animals↗

PubMed1991

Progression and surface ultrastructure of in vitro caused erosive lesions in human and bovine enamel.

Surface prismatic and aprismatic human enamel and unpolished or diamond-polished specimens of bovine enamel, with test and control surfaces on each studied block, were immersed in phosphoric acid containing cola beverage (pH 2.6) and citric or malic acid containing sports drinks (pH 2.8 and 3.4, respectively) for 15-180 min. The specimens were then prepared and studied in a JEOL 35C scanning electron microscope. In human aprismatic surface enamel an irregular type of dissolution was observed, with severely affected areas adjacent to less affected ones. Prismatic human and bovine specimens showed a characteristic dissolution where initial erosion after 15 min immersion was seen to affect specifically the prism sheath areas. Longer immersion caused dissolution of enamel prism cores followed by interprismatic areas. In bovine enamel malic acid affected least the surface ultrastructure when compared with citric and phosphoric acids after 15-30 min of immersion, but thereafter no difference was observed between the acids in causing erosion. Diamond-polished enamel was found more liable to erosion than non-polished enamel. Thus, the structure of enamel greatly modified the progression of in vitro caused erosion, in particular in human tooth specimens.

Animals↗

PubMed1991

Bacterial invasion of periodontal tissues after experimental immunosuppression in rats.

A moderate gingivitis was produced in 3 groups of 10 adult Wistar rats with diet 2000 of Keyes and Jordan (1964) delivered for 30 days with a controlled feeding unit. The first group served as untreated control. The second group received 5 intraperitoneal injections of cyclosporine A (15 mg/kg body weight) from day 20 to 30 to interfere with the activation of T lymphocytes and interleukin synthesis. The third group received 2 intraperitoneal injections of cyclophosphamide (100 mg/kg on day 20 and 25) which induced a severe neutropenia. The gingival areas between the upper molar regions were prepared for light and transmission electron microscopy. In the untreated control group, a layer of polymorphonuclear neutrophils (PMN) was observed between the dental plaque and the junctional epithelium with a round cell infiltration in the superficial connective tissue. No bacterial invasion was observed. In the cyclosporine group, despite the action on T lymphocytes, no bacterial invasion occurred, but a differentiated PMN layer was present between the apical dental plaque and the junctional epithelium. In the cyclophosphamide group an important bacterial invasion was observed in the interdental epithelium as well as in the underlying connective tissue. In the local absence of PMNs, a mixed flora of Gram positive and negative bacteria of various shapes invaded epithelial as well as connective tissue cells and came in contact with the alveolar crestal bone. Resorption of the alveolar crestal bone scored according to the Keyes and Gold method (1955) was significantly more important in the cyclosporine and the cyclophosphamide group when compared to the controls (p less than 0.05). No statistical difference in bone resorption was noted between the cyclosporine and the cyclophosphamide groups. It can be concluded that the PMN layer constitutes the first line of defense opposed to bacterial invasion of the periodontal tissues.

Alveolar Bone Loss↗

PubMed1991

[Histological comparison of the effect of different implanted hydroxyapatites in the animal periodontium].

The effect of various types of synthetic hydroxyapatites (HA), coated or not with collagen or human plasmatic fibrin, has been studied after 3 month implantation either in freshly extracted alveoli in miniature pigs or in experimentally induced periodontal lesions in beagle dogs. The best histological results were observed in HA without organic coating. The Bioapatite consisting in crystals with a mean size of 146 nm +/- 47 nm were well integrated in the alveolar bone. Similar results were obtained with micro-sized hydroxyapatite, with a mean crystal size of 38 nm +/- 16 nm. But at 3 months, this HA type was still actively integrated in bone with osteogenesis. When these 2 types of HA were coated with collagen or plasmatic fibrin, they were less well incorporated in alveolar bone and were even able to develop localized and moderate inflammatory reactions. The main purpose of synthetic HA is to promote alveolar bone formation in periodontal lesions. For an improved tissular regeneration, it is recommended to use simultaneously in the future synthetic HA together with resorbable biocompatible synthetic membranes.

Alveolar Bone Loss↗

PubMed1990

Immunolabelling of SR protein and serotype polysaccharide in Streptococcus mutans.

Immunoelectron microscopy was used to determine the accessibility of gold-labelled monoclonal antibodies, specific for the SR protein and serotype polysaccharide, to the surface of viable cells of Streptococcus mutans. The results indicate that both antigens are simultaneously accessible to their respective antibodies.

Antibodies, Monoclonal↗

PubMed1990

High-resolution electron microscopy of human enamel crystals.

The structure of enamel crystals obtained from four human premolars has been studied by high-resolution electron microscopy (HREM) in the [0001], [2110], [1540], [0110] and [1213] crystallographic directions at various microscope defocus and crystal thickness values. The resolution obtained has not previously been reported for human enamel crystals. In all cases, it was possible to match the experimental images to images calculated using the atomic positions of mineral hydroxyapatite. However, a deviation from hexagonal symmetry characterized by marked (1010) planes of intensity different from the one of the (3030) and (1010)-type planes was observed. In this work, we present an improvement of Scherzer resolution of 0.25-0.20 nm over previous work on biological enamel crystals. This improvement of resolution has permitted the incorporation of crystallographic reflections of higher spatial frequencies into the imaging process of the microscope and has led to a more precise structure determination of the crystals studied.

Adult↗

PubMed1990

Comparison of lead levels in human permanent teeth from Strasbourg, Mexico City, and rural zones of Alsace.

A comparative study of the mean lead concentrations in enamel and dentin of human premolars and permanent molars was conducted by means of a systematic sampling procedure with energy-dispersive x-ray fluorescence analysis. In a first series of analyses, no significant statistical differences in mean lead concentrations at various levels of enamel and dentin were noted between young patients of Strasbourg and those of small villages of Alsace, nor between elderly patients living in these two locations, despite the fact that motor traffic was significantly lower in the rural zones. However, in both locations, a significantly higher concentration of lead was observed in enamel and dentin in relation to age. In a second series of analyses, the mean lead concentrations of both dental hard tissues of premolars and permanent molars of young individuals from Strasbourg, rural Alsace, and Mexico City were compared. Significantly higher mean lead concentrations were found in enamel and dentin samples from Mexico City. This was most evident for inner coronal dentin (5.7 and 6.1 times greater than in teeth of Strasbourg and rural zones of Alsace, respectively) and for pulpal root dentin (6.9 and 8.9 times greater than in teeth of Strasbourg and rural zones of Alsace). It is proposed that the higher lead concentrations are related to the higher lead content of motor gasoline and to more intense traffic conditions. The dental hard tissues appear to be of value for the study of environmental lead pollution.

Adolescent↗

PubMed1990

Structural events in the caries process in enamel, cementum, and dentin.

The structural events observed in enamel, cementum, and dentin during the caries process have been reviewed. In incipient enamel lesions, the prevailing concept of an almost intact surface layer has been seriously challenged by SEM and TEM observations demonstrating structural pathways (such as enlarged prism junctions or sheaths) from the enamel surface to the sub-surface lesion. The destruction in this latter location consisted of (1) enlarged prism junctions, (2) diffuse mineral destruction in the prism cores, and (3) destruction of the interprismatic substance. In root caries, the destruction of cementum started along junctions between calcified layers of extrinsic (Sharpey) and intrinsic collagen fibers as well as along incremental lines. Invasion of Gram-positive micro-organisms followed these enlarged junctions. Dentin caries was similar in coronal and root caries. It consisted of sclerosis of the lumens of the dentinal tubules, followed by an important gradient of demineralization of intertubular dentin and destruction of occluded tubular lumens and peritubular dentin. Bacterial penetration occurred initially in the dentinal tubules and was followed by bacterial invasion and destruction of the intertubular dentin. Various phenomena of crystalline remineralization were described in enamel and dentin. Whereas in enamel and dentin caries, an important gradient of demineralization was observed before bacterial invasion, a simultaneous destruction of the mineral and organic components seemed to occur in cementum.

Dental Caries↗

PubMed1990

[Preventive dentistry in France].

In France, oral prevention has recently progressed in various aspects of dental caries prophylaxis which is reviewed in this paper. A better knowledge of dental caries prevalence has been obtained at a national level and the French Government authorized in October 1985 salt fluoridation for a period of 5 years which in addition to other means of caries prevention such as fluoridated toothpastes and various local and topical procedures has increased the potentials of fluoride use in France. In addition a larger use of fissure sealants has been encouraged. It is hoped that the introduction of salt fluoridation in France will reduce the caries incidence to a DMFT not more than 3 for the 12 year old children thus fulfilling the WHO goals for oral health in the year 2000.

Adolescent↗

PubMed1990

High resolution electron microscopy of young apatite crystals in human fetal enamel.

Apatite crystal growth in enamel has been followed during the secretory stage in 5 month-old human fetuses. The crystals were observed in a high resolution transmission electron microscope operating at 300 kV. This microscope has a Scherzer resolution of 0.19 nm and for each micrograph, the absence of astigmatism and drift was checked with optical diffractograms. Crystals in various stages of growth from approximately 3 to 10 unit cells in thickness could be observed along [0001] and mean value of 1010 zone axes. For growing crystals, a highly ordered atomic structure with an ionic distribution consistent with hydroxyapatite was noted as demonstrated by the correspondence of computer simulated and observed images. Moreover, most of the crystals showed structural defects such as edge dislocations and periodically repeated strain fields created by screw dislocations. The observed dislocations were described by Burgers vectors running parallel to mean value of 1120 axes.

Computer Simulation↗

PubMed1989

Zinc and strontium analyses by energy dispersive X-ray fluorescence in human permanent teeth.

The zinc and strontium content of enamel and dentine from humans aged 9-64 yr was analysed, after systematic sampling, by X-ray fluorescence. Relatively high levels of zinc were found in both hard tissues but there was no significant increase with age. Zinc content decreased significantly from outer to inner enamel and increased significantly again from peripheral to pulpal coronal and root dentine. The strontium content was significantly higher in enamel than in dentine; there was a significant increase with age in enamel but not in dentine. However, outer and inner enamel showed no significant difference in strontium content. Almost similar amounts of strontium were found in coronal and root dentine.

Adolescent↗

PubMed1989

Immunolocalization of Streptococcus mutans sr gene product in recombinant Escherichia coli.

A direct post-embedding immunogold method was used to determine the subcellular localization of the expression product of Streptococcus mutans sr gene in Escherichia coli cells. Immunolabelling was principally localized in the cytoplasm and was absent in the periplasmic space and extracellular compartment. We observed no difference in the localization of the labelling between bacteria originated from solid or liquid cultures. No difference in saliva binding could be observed between recombinant E. coli or control E. coli cells. These results showed that the cloned SR protein was not accessible at the surface of the host cell.

Bacterial Proteins↗

PubMed1989

Ultrastructural study on human root caries.

Superficial root caries lesions of incisors and premolars of 24 patients aged 52-60 years were studied by scanning electron microscopy and transmission electron microscopy. In the predominantly gram-positive bacteria of the root dental plaque, a great number of corncob configurations were observed. Bacterial infiltration into cementum occurred without any gradient of demineralization and mainly followed the borders between calcified cementum bundles as well as incremental lines. The narrow channels which were filled initially by a single row of gram-positive bacteria broadened progressively with simultaneous destruction of the apatite minerals and the collagenous matrix. Root dentin invasion showed great similarities to coronal dentin with an important gradient of demineralization. In the deep layers, sclerosed tubules contained sometimes rhombohedral crystals. In more superficial layers, bacterial invasion occurred initially in still partially sclerosed tubules. Tubular lumens as well as lateral side branches which had lost their peritubular dentin were filled with gram-positive microorganisms. An important diffuse destruction of the apatite minerals was observed at this stage in the intertubular dentin which still presented typical cross-banded collagen fibrils. The confluence of enlarged dentinal tubules filled by numerous microorganisms led to large bacterial zones with complete destruction of root dentin.

Bacteria↗

PubMed1989

National survey of caries prevalence in 6-15-year-old children in France.

The prevalence of dental caries in France is not known on a nationwide basis, despite the fact that a number of epidemiological studies have been conducted in various parts of the country. The aim of the present study was to provide a national baseline examination of the dental health of children in 1987 since, beginning in November, 1986, the sale of fluoridated salt began in France. A multi-stage probability sample of 19,366 children was selected as representative of the 6-to-15-year-old population. The sample covered all the 95 departments of France. Teams of well-calibrated examiners were constituted in each of the sixteen Faculties of Dental Surgery of France. The prevalence of caries for each age group was determined by means of DMFT, DMFS, dft, and dfs indices. Periodontal conditions were assessed by means of the Plaque Index (Silness and Löe, 1964), the Calculus Index (Marthaler, 1966), and the Gingival Index (Löe and Silness, 1963). Calculation of the mean DMFT index showed, respectively, 0.5 and 1.0 new carious teeth per year under and over the age of 11. The mean values of the DMFT index at ages 6, 12, and 15 were, respectively, 0.5, 4.2, and 6.9. Under the age of 11, the mean DMFS index increased by one between each successive age group and by nearly two over the age of 11. The mean values of the DMFS index at ages 6, 12, and 15 were, respectively, 0.8, 7.6, and 13.0. The percentage of caries-free children decreased from 32.2% at age 6 to 7.9% at age 15.

Adolescent↗

PubMed1989

The effects of airborne fluorides on oral conditions in Morocco.

The purpose of this study was to determine the prevalence and severity of dental caries and dental fluorosis, as well as various other oral conditions, in 2378 subjects (ages seven to 60) living in the fluoridated area of Khouribga and the non-fluoridated area of Beni Mellal, Morocco. The community index of dental fluorosis (CFI) ranged from 1.99 to 2.80 in the high-fluoride area: Over 90% of the population was affected, and more than one-third of the subjects showed moderate dental fluorosis. However, in Beni Mellal, more than 96% of the dentate subjects examined were free of dental fluorosis, and the CFI of 0.02 was considered not significant. Significant differences were observed between the two areas with respect to caries prevalence. DMFT and DMFS indices were markedly lower in the fluorosis area of Khouribga. The oral conditions of subjects appeared to be better in Khouribga, where the gingival and calculus indices were significantly lower than in Beni Mellal. The analyses of covariance showed no significant differences in plaque accumulation (PI) between the Khouribga and Beni Mellal samples. However, a close statistical correlation was found between PI and GI in Beni Mellal and Khouribga.

Adolescent↗

PubMed1989

Crystallographic properties of a series of synthetic hydroxyapatites.

The crystallographic properties of hydroxyapatites synthesized at temperatures of 200 degrees C, 500 degrees C, 900 degrees C and 1250 degrees C, designated HAP200, HAP500, HAP900 and HAP1250, respectively, were studied using X-ray powder diffraction. Values of a-axis length for the hydroxyapatites ranged from 9.406 A to 9.416 A, which were smaller than the corresponding value for stoichimetric hydroxyapatite, a = 9.418 A. Generally, the a-axis length decreased with the synthesis temperature, except for HAP500 which showed the smallest value. Crystallinity of the hydroxyapatites, measured by X-ray diffraction peak broadening as full width at the half-maximum value (FWHM), increased with the synthesis temperature, although HAP500 showed a decrease. These results suggest that the synthetic hydroxyapatites contained some carbonate ions, probably at the A-site of the apatite structure, and that the structure was depleted of carbonate ions at about 500 degrees C.

Crystallography↗

PubMed1989

[The role of mechanical factors in the development of cervical wedge-shaped erosions].

The surface of single or multiple cervical wedge-shaped defects was studied with a scanning electron microscope. After an initial stage during which the root surface became smooth and polished, the developed lesions had an angular shape with the presence of one or several grooves of 0.2 to 0.3 mm in width at the angle vertex. The presence of these grooves forming horizontal gutters strongly suggested the existence of a horizontal brushing movement. Beside these large grooves, a more or less parallel network of fine striae was observed. The lesion surfaces consisted of dentin with obliquely oriented tubules which were not completely sclerosed. Relatively thin bacterial layers were present on these surfaces. The presence of horizontal wear gutters seemed to confirm the traumatic origin of the wedge-shaped defects connected with toothbrushing.

Adult↗