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Biomedical subjects

R M Frank

Publications and source records attributed to R M Frank.

At least 19 recordsLinked to original sources
PubMed2000

The clinical utility of the Hopkins Verbal Learning Test as a screening test for mild dementia.

OBJECTIVE: The purpose of this study was to determine whether the Hopkins Verbal Learning Test (HVLT) could be used as a valid and reliable screening test for mild dementia in older people, and to compare its performance to that of the Mini-Mental State Examination (MMSE). METHOD: Using a cross-sectional design, we studied three groups of older subjects recruited from a district geriatric psychiatry service: (1) 26 patients with DSM-IV dementia and MMSE scores of 18 or better; (2) 15 patients with psychiatric diagnoses other than dementia; and (3) 15 normal controls. The relationship of each potential cutting point on the HVLT and the MMSE was examined against the independently ascertained DSM-IV diagnoses of dementia using a Receiver Operating Characteristic (ROC) analysis. RESULTS: The subjects consisted of 21 (37.5%) males and 35 (62.5%) females with a mean age of 74.7 (SD 6.1) years and a mean of 8.5 (SD 1.8) years of formal education. ROC analysis indicated that the optimal cutting point for detecting mild dementia in this group of subjects using the HVLT was 18/19 (sensitivity=0.96, specificity=0.80) and using the MMSE was 25/26 (sensitivity=0.88, specificity=0.93). CONCLUSIONS: The HVLT can be recommended as a valid and reliable screening test for mild dementia and as an adjunct in the clinical assessment of older people. The HVLT had better sensitivity than the MMSE in detecting patients with mild dementia, whereas the MMSE had better specificity.

Aged↗
PubMed1999

Ultrastructure of human dentine 40 years ago--progress and perspectives.

In the 1959 premier issue of the Archives of Oral Biology, the first TEM observations were presented of sections of undecalcified human mature dentine produced with diamond knives. The odontoblast process was clearly shown to be a cytoplasmic extension of the odontoblast. The peritubular dentine appeared to be more calcified than the intertubular dentine and contained hydroxyapatite as demonstrated by selective area electron diffraction. In the 40 years which followed, significant progress was made in TEM methodology, including improvements in fixation and embedding, development of ultrastructural cytochemistry and immunocytochemistry, and the use of electron microscope autoradiography. Additionally, we saw the advent of SEM and HRTEM. Thus, better knowledge was gained of (1) the odontoblast and its process and the lamina limitans, (2) the dentinal nerve fibrils and (3) the HRTEM aspects of dentine. Interestingly, to the present day, diamond knives have continued to serve as the best tool for preparing thin sections of non-decalcified mature hard tissue for TEM and HRTEM, not only for dentine but also for bone, enamel and cementum.

Dentin↗
PubMed1994

Effect of fluoride varnish and solution on enamel erosion in vitro.

The effect of fluoride varnish and solution on initial enamel erosion was studied. Enamel specimens prepared from human third molars were treated for 24 h with Duraphat varnish (2.26% F) or for 48 h with NaF solution (1.2% F), washed, and immersed in cola beverage (pH 2.6) for up to 15 min. The surface microhardness was measured using a Vickers diamond in a Leitz indentation apparatus at base-line, after fluoride treatment, and after 1, 5, and 15 min exposure to acidic drink. The specimens were then prepared and studied using a JEOL JSM-35 scanning electron microscope. The results showed that both fluoride treatment caused an increase in enamel hardness values and subsequent inhibition of softening which was statistically highly significant. Scanning electron micrographs revealed the difficulty of removing Duraphat varnish from the enamel surface, and remnants of varnish were seen irrespective of vigorous sonication in acetone. However, in areas devoid of varnish, erosion was observed as mainly irregular lesions similar to those seen in the NaF solution treated and control specimens. The present study showed that treatment of enamel with topical fluoride prior to acidic challenge can inhibit initial erosion.

Adult↗
PubMed1994

Periodontal guided tissue regeneration with a new resorbable polylactic acid membrane.

The aim of the present study was to evaluate the use of 3 types of biodegradable, high molecular weight DL-lactic acid (PLA) membranes containing respectively 0%, 10%, and 30% low molecular weight oligomers for obtaining guided tissue regeneration following treatment of experimental buccal periodontal defects created surgically in 6 young adult beagle dogs. On the buccal aspects of test and control teeth, a mucoperiostal flap was raised and the buccal alveolar bone removed. The exposed root surfaces were scaled and a notch was prepared in the root surface at the level of the reduced crest. PLA membranes containing respectively 0%, 10% and 30% oligomers, drawn at random, were placed over the experimental defects, while no membrane was placed over the control roots. The animals were sacrificed 2, 4, and 6 months after surgery. For comparison between control sites (without membrane) and experimental sites (with 3 types of membrane), serial bucco-lingual sections were made of the experimental and control sites and studied histologically and histometrically. It appeared that a satisfactory regeneration of the periodontal tissues could be obtained with all 3 types of experimental PLA membranes and statistically significant differences could be observed for epithelial attachment, alveolar bone regrowth, connective tissue attachment, and new cementum formation in the experimental group when compared with the controls. All 3 types of membranes were well tolerated. The resorption of the membranes started in the coronal portions and extended progressively in an apical direction and the resorption time seemed to be related to the content of oligomers. PLA membranes could be used as interesting alternatives for GTR in advanced human periodontal lesions.

Alveolar Process↗
PubMed1993

Human amelogenesis: high resolution electron microscopy of nanometer-sized particles.

Growth of inorganic crystals of enamel is described as a two-stage process with growth of ribbon-like crystals in length and width, followed by their development in thickness. In early stages of crystal growth during human amelogenesis nanometer-sized particles with a mean diameter of 1.1 nm were described between ribbon-like crystals. These small particles had a crystalline structure but their lattice parameters did not seem to be directly related to those of calcium phosphates. The nanometer-sized particles appear to correspond to initial stages of apatite crystal growth. Their localization close to ribbon-like crystals and their progressive increase in size and number may indicate that they represent a precursor phase for these crystals. Nucleation areas at both extremities, of elongated ribbon-like crystals could be involved in the two-directional growth of ribbons and/or in nanometer-sized particle nucleation.

Amelogenesis↗
PubMed1993

Biocompatibility and resorbability of a polylactic acid membrane for periodontal guided tissue regeneration.

The biocompatibility and degradation processes of biomembranes made of a mixture of a high molecular weight racemic polylactic acid (PLA50P) with 0, 10, 20 and 30% w/w racemic polylactic acid oligomers (PLA50p) were assessed for morphological changes in subcutaneous abdominal membrane implantations after 15, 21, 30 and 60 d in 45 Wistar rats. These membranes, prepared for periodontal guided tissue regeneration, showed excellent tissue tolerance without an inflammatory reaction. The higher the content in low molecular weight polylactic acid, the higher the degradation rate. At 60 d, the resorption process was almost complete. This process was initiated by outgrowths of short vascular septa, which developed into lobular networks infiltrating the membranes, which were progressively replaced by normal fibrous connective tissue.

Animals↗
PubMed1993

Observation of the loss of the hydroxyapatite sixfold symmetry in a human fetal tooth enamel crystal.

A deviation from the hydroxyapatite hexagonal symmetry of a human tooth enamel crystal observed by high-resolution electron microscopy is reported. This symmetry deviation is characterized by: (1) 'preferential' planes that can be indexed as (100) with an intensity that differs from the (300) and the other (100) hexagonal equivalent planes; and (2) streaking of higher order reflections in the optical diffractogram of the image of the crystal. Computer simulations show that similar 'preferential' planes can also be observed at specific crystal tilt angles (and/or beam tilt and/or objective aperture misalignment) and at crystal thickness/microscope defocus values in images of hydroxyapatite crystals observed along the [0001] or [2243] zone axes. The streaking of higher order reflections in the optical diffractogram is related to a deformation of the crystal itself and does indeed show a symmetry deviation of the crystal under observation.

Crystallography↗
PubMed1993

Caries prevalence in 6- to 15-year-old French children based on the 1987 and 1991 national surveys.

The caries prevalence in a multi-stage probability sample of 18,786 children representative of all French children 6-15 years of age was studied in 1991 and compared with the results of a similar survey made in 1987. A significant decline in dental caries in France became evident. This decline, observed in primary as well as in permanent teeth, was of variable magnitude among the different age groups. At the age of 6, 48.6% of the children were totally caries-free in 1991. At the age of 12, the DMFT and DMFS indices were 2.59 and 4.72, respectively, representing a corresponding decrease of 38% and 37%. In 1991, more caries-affected teeth or surfaces were filled, whereas fewer caries-affected teeth or surfaces were untreated. Females and children living in rural areas had a higher caries prevalence in both surveys. Pit-and-fissure lesions were the predominant caries types. Dental fluorosis was very uncommon; 96.1% of the 18,786 children examined in 1991 were totally free of any such lesions. Average plaque and calculus indices were similar in 1987 and in 1991, but a decrease of 25% was observed in the average gingival indices. Although the relative contributions of various preventive factors leading to this caries reduction are not clear, it should be noted that use of fluoridated salt (250 mg/kg KF) started in January, 1987. The sale of fluoridated dentifrices and the use of fluoride tablets and sugar substitutes increased during the period from 1987 to 1991.

Adolescent↗
PubMed1993

Short-term effect of cyclosporin injections on experimental gingival inflammation in the rat.

Experimental gingivitis was induced in 2 groups of 10 adult Wistar rats by feeding them a high sucrose diet for 30 days. Since cyclosporin has an immunosuppressive effect on the stimulation of T lymphocytes, the test group received 5 intraperitoneal injections of cyclosporin A from day 20 to 30 while the control group received no additional treatment. The gingival regions of the molars were studied in light and transmission electron microscopy. In both groups, a well-differentiated wall of polymorphonuclear neutrophils (PMNs) was present between the dental plaque and the papillary epithelium and no bacterial invasion occurred despite the local absence of T lymphocytes in the test group. It can be concluded that T lymphocytes are not involved in the mechanism of bacterial invasion.

Animals↗
PubMed1992

Human amelogenesis. I: High resolution electron microscopy study of ribbon-like crystals.

Ribbon-like crystals, from developing enamel of human fetuses, were studied by high resolution electron microscopy. These crystals were classically described as the first organized mineral formed during amelogenesis. They were characterized by a mean width-to-thickness ratio (W.T-1) of 9.5, and 40% were bent. On lattice images we noted the presence of the central dark line (CDL) associated with white spots. Both structures were found in crystals with a minimum thickness of 8-10 nm. CDLs were localized in the center of the crystals and seemed to be linked to the initial growth process, but their exact structure and function were not fully determined. We were able to study the structure of the ribbon-like crystals with a Scherzer resolution close to 0.2 nm. The good correspondence between experimental and computed images showed that their structure was related to hydroxyapatite (HA). In addition, the presence of ionic substitutions and deficiencies were also compatible with HA. In this study, about 50% of the crystals showed structural defects. Screw dislocations were the most often noted defects and were observed within crystals aligned along five different zone axes. Low- and high-angle boundaries were also detected. Low-angle boundaries, found in the center of the crystals, could thus be related to CDLs and be implicated in the nucleation step of crystal formation, whereas high-angle boundaries could result from the fusion of ribbon-like crystals. Such mechanisms could induce an acceleration of the growth in thickness of the crystal observed during the maturation stage of amelogenesis.

Amelogenesis↗
PubMed1992

Effects of carbon dioxide, Nd:YAG and carbon dioxide-Nd:YAG combination lasers at high energy densities on synthetic hydroxyaptite.

The aim of this study was to determine the crystalline structure and chemical alterations of synthetic hydroxyapatite after irradiation with either CO2, Nd:YAG or CO2-Nd:YAG combination lasers at high energy densities of 500-3,230 J.cm2. Further, dissolution kinetics of the lased material were analysed and compared with those of unlased apatite. Electron microscopy showed that the lased material consisted of two kinds of crystals. From the micrographs their diameters varied from 600 to 1,200 A and from 3,000 to 6,000 A, respectively. The larger crystals showed 6.9-Angström periodic lattice fringes in the transmission electron microscope. alpha-Tricalcium phosphate (TCP) was identified by X-ray diffraction. Selective-area electron diffraction identified the large crystals to consist of tricalcium phosphate while the smaller crystals were probably hydroxyapatite. Assays of dissolution kinetics showed that at these high energy densities lased material dissolved more rapidly than unlased synthetic hydroxyapatite due to the higher solubility of TCP.

Aluminum Silicates↗
PubMed1992

Urinary fluoride excretion in children using potassium fluoride containing salt or sodium fluoride supplements.

With the introduction of fluoridated domestic salt in France in 1986, questions have arisen with respect to its efficacy in caries prevention. It has been of interest to compare the urinary excretion of fluoride in children who consume fluoridated salt to that in children who take fluoride tablets. Ninety-three schoolchildren, 10-14 years of age, participated in the study and were divided into four groups: group I consumed fluoridated salt with every meal; group II ate at a school restaurant once a day and consequently consumed fluoridated salt at only their evening meal, as fluoridated salt is not authorized for use in collective restaurants; group III consisted of children taking fluoride tablets (1.0 mg F/day) exclusively, and group IV did not receive any systemic administration of fluoride for prevention and constituted a low-fluoride control group. Total 24-hour urine samples were collected from all subjects. The average daily urinary flow rates varied from 0.51 to 0.68 ml/min, but showed no statistically significant differences among the groups. The average urinary fluoride concentrations were 0.60, 0.30, 0.99, and 0.28 mg/l, respectively, for groups I-IV. The mean 24-hour urinary fluoride concentrations and excretion rates for children who consumed fluoridated salt at all meals (group I) were not statistically different from those using tables (group III). There were also no statistically significant differences between groups II and IV. The differences between urinary fluoride concentrations and excretion rates of groups I and III, as compared with group IV, were statistically significant.

Administration, Oral↗
PubMed1991

Effects of complete denture wearing on temporomandibular joints: a histomorphometric study.

At autopsy, 54 human temporomandibular joints were distributed in three groups. The first group was made up of 14 joints of dentate subjects (mean age = 51 years). The second group was composed of 12 temporomandibular joints of totally edentulous patients who had lost their teeth for at least 10 years (mean age = 82 years). The third group was composed of 28 joints of edentulous patients who had been wearing complete dentures for at least 20 years (mean age = 66 years). Sagittal serial decalcified sections were studied by light microscopy and was submitted to histomorphometry. Group 1 was characterized by a deep mandibular fossa with well-marked cortical layers of the temporal bones and the condyles. The fibrocartilages were multilayered and the articular disks had biconcave outlines. In group 2 a flattening of the mandibular fossa was observed, with a thinning of the cortical and spongy bones. The fibrocartilages were thin and not multilayered. In group 3, the structure of joints was similar to that of group 1. The mean values of the surfaces, thicknesses, and lengths of the measured parameters were systematically highest in group 1, whereas these mean values in group 3 were similar to or had a tendency to be close to the means of group 1. In contrast, the mean values of group 2 were always the lowest. It can be concluded that complete dentures had a favorable protective effect on temporomandibular joint structures.

Adult↗
PubMed1991

HREM study of irradiation damage in human dental enamel crystals.

Several phenomena have been observed during the examination of human dental enamel crystals (mainly constituted by hydroxyapatite (OHAP] by high-resolution electron microscopy (HREM) at 300 and 400 keV: orientation-dependent damage in the form of mass loss from voids or uniform destruction of crystal structure, beam-induced diffusion creating outgrowths at the crystal surfaces, recrystallization of the bulk crystal and crystallization of the inorganic components of the matrix surrounding the crystals. These beam-induced crystals have the CaO structure. The phenomena observed are most likely due to various electron-crystal interaction mechanisms (ballistic knock-on damage, electronic excitations, temperature rise, etc.). In this paper, the contribution of the ballistic process to the phenomena observed is discussed. The quantitative description of the knock-on collisions rests on the McKinley-Feshbach cross-section formula. The minimum ion displacement energies which appear in this expression have been estimated on the basis of the electrostatic ion binding energies, and the covalent bond energies if required. It is shown that hydroxyl, calcium and oxygen ions can effectively be displaced by the incident 300 and 400 keV electrons. Thus, the formation of CaO crystals by the combination of calcium and oxygen ions diffusing from their initial sites inside the OHAP lattice can tentatively be explained.

Adult↗
PubMed1991

Compositional variations in apatites with respect to preferential ionic extraction.

Detection of ionic losses from the apatitic structure (Ca10(PO4)6(OH)2) by high-resolution electron microscopy was investigated theoretically. Linear image analysis showed the need for an objective aperture of at least 3.7 nm-1 to visualize four different coordinates (CaII, OH-, P and mid-point between CaII-P bond). High-resolution image analysis and plotting of OH- column intensity against specimen thickness showed an inverse proportionality between composition and OH- image intensities for very thin specimens (less than 2 nm). Image intensity variation would be detectable experimentally, but the preparation of such thin specimens by ultramicrotomy is impossible.

Apatites↗
PubMed1991

Ultrastructural demonstration of the importance of crystal size of bioceramic powders implanted into human periodontal lesions.

Stages in bone formation were studied ultrastructurally after the implantation of the following 3 bioceramic powders into human periodontal lesions: (1) beta-tricalcium phosphate whitlockite (Synthograft) consisting of particles with a mean length of 229 +/- 87 microns in SEM and appearing in TEM as crystals with a mean diameter 488 +/- 192 nm; (2) an hydroxyapatite (Bioapatite) which consisted of particles with a mean length of 283 +/- 87 microns in SEM and of crystals with a mean diameter of 146 +/- 47 nm in TEM; and finally (3), a microsized hydroxyapatite consisting of elongated platelets with a mean length of 32 +/- 4 microns in SEM, composed of small crystals with a mean diameter of 38 +/- 16 nm in TEM. In a preliminary experiment in rats, it appeared that the microsized hydroxyapatite implanted into the alveolar region after first molar extraction exhibited biocompatibility. In 6- and 12-month biopsies, it appeared that bone formation in association with the 3 bioceramics tested in human periodontal lesions occurred through similar mechanisms at the ultrastructural level. After the appearance of peripheral fibroblast-like or osteoblast-like cells with an interposed layer reminiscent of an osteoid tissue, collagen fibrils were observed in the intercrystalline spaces. These spaces subsequently underwent mineralization, with deposition of bone apatite crystals followed by the peripheral deposition of a thin inner bone layer with a granular appearance and an outer normal bone layer of either woven bone, lamellar bone or bone with parallel calcified collagen fibrils. These bone nodules, however, formed around the bioceramic particles at highly variable time intervals. Bone formation was observed around Synthograft and Bioapatite implants only in 12-month biopsies, and thicker layers of peripheral bone were observed with the latter hydroxyapatite implant. With microsized hydroxyapatite, a significant amount of peripheral bone formation had already occurred by 6 months, strongly suggesting an important effect of crystal size on bone formation.

Adult↗