Relating nickel-induced tissue inflammation to nickel release in vivo.

Nickel has a number of adverse biological effects that have made the use of nickel in biomedical implants controversial. Yet information about the distribution of nickel in tissues around nickel-containing implants is scarce. The purpose of the current study was to use a laser ablation technique, combined with inductively coupled mass spectroscopy, to assess the spatial distribution of nickel around nickel-containing implants in vivo. Polyethylene, pure nickel wire, or a nickel-containing alloy (Ni-Cr) were implanted subcutaneously into rats for 7 days. The tissues were analyzed for Ni content and inflammation at 1-mm intervals up to 5 mm away from the implants. The sham surgery sites and the polyethylene caused mild to moderate inflammation 1-2 mm from the implant site with no detectable nickel in the tissue. The nickel wire caused severe inflammation up to 5 mm away from the implant site with necrosis for 1 mm around the implant. Nickel concentrations reached 48 microg/g near the implants, falling exponentially to undetectable levels at 3-4 mm from the implants. The Ni-Cr wire caused inflammation equivalent to polyethylene, with less than 4 microg/g of nickel present in the tissue for 1-2 mm around the implants. The current study showed that the laser-ablation technique was well suited for the analysis of soft tissues for metal-ion content, and that the nickel distribution in tissues correlated well with overt tissue inflammation.

The effects of dietary ferric iron and iron deprivation on the bacterial composition of the mouse intestine.

The influence of dietary ferric iron on the intestinal microbiota of mice was investigated with a view to promoting benign lactic acid bacteria (which have minimal iron requirements) in order to enhance colonization-resistance potential. Three groups of eight mice received a diet differing only in iron content, for a period of 12 weeks. Dietary iron deprivation resulted in overall increased small intestinal bacterial populations, including lactic acid bacteria, but these differences were generally not significant (p > 0.05). With the exception of coliforms, all examined bacterial groups (anaerobes, micro-aerophiles, lactobacilli, and enterococci) were significantly (p < 0.05) elevated in the colons of iron-deprived mice. The relatively low numbers of total anaerobes in the colons of iron-replete and iron-overloaded mice suggested that, as well as promotion of bacteria under iron-deprived condition, provision of ferric iron suppressed bacteria, probably by oxidation of normally reduced environments.

Morphological and biochemical studies of the elastic fibres in the craniomandibular joint articular disc of the tight-skin mouse.

The tight-skin (TSK) mouse is characterized by the hyperplasia of loose connective tissues, and of excessive growth of cartilage and of bones including the mandible. Since the fibroelastic connective tissues of the craniomandibular joint (CMJ) are essential to the functions of this joint, the present histological study compared the presence and general distribution of elastic fibres in CMJ discal tissues of TSK and normal mice. The excised CMJs were processed for light microscopy. The tissues were fixed, demineralized, embedded in paraffin, sectioned and then stained with resorcin-fuchsin to demonstrate elastic fibres. There were no obvious histological differences in either the amount or the distribution of elastic fibres in the discs from the two groups. In both groups, elastic fibres were found in the disc and in many of the attachments of the disc to the mandible and squamosal bone. In addition to the morphological preparations, articular discs and samples of lung tissue were excised from other mice and subjected to a radioimmunoassay for desmosine in order to estimate the amounts of elastin in these tissues; the amount of elastin was significantly reduced in the TSK lung, but the amounts of elastin in the TSK and normal CMJ discal tissues were not significantly different statistically. These morphological and histochemical results suggest that the distribution and quantity of elastic fibres in the TSK mouse disc are not significantly different from those in the normal mouse articular disc. Moreover, these data may be interpreted to either suggest a differential effect on the elastic fibres in different TSK tissues, or to support the suggestion that abnormal degradation of elastic fibres may not be characteristic of the TSK mouse.

Cariostatic and ultraconservative sealed restorations: nine-year results among children and adults.

The objective of this clinical study was to evaluate the long-term efficacy of placing sealed posterior composite restorations for arresting active caries. The tooth preparation for this bonded and sealed restoration was limited to placing a bevel in the enamel only, without the removal of the carious lesion. The radiographic and clinical performance of these ultraconservative sealed composite restorations placed over caries (CompS/C) was compared over a period of nine years with: 1) ultraconservative, localized sealed amalgam (AGS) restorations with no extension for prevention, and 2) traditional, unsealed amalgam restorations (AGU) with the usual extension for prevention outline form. Sealant retention with > 50 percent to 100 percent of the margins occurred in 64 percent of CompS/C and 82.5 percent of AGS restorations. After nine years the cumulative failure rates were 16 percent for CompS/C, 2.5 percent for AGS, and 17.1 percent for AGU restorations. Thus, the clinical performance of CompS/C restorations was slightly superior to that of the traditional AGU restorations. The AGS restorations were definitely superior to the traditional AGU restorations and to the CompS/C restorations in both children and adults alike. Complete sealant retention over CompS/C and AGS restorations was equivalent between children and adults (P = 0.14 and 0.74, respectively). A higher percentage of open margins in CompS/C restorations was seen, however, in children (17.4 percent) than adults (1.94 percent). This study has shown that Class I caries can be arrested by the CompS/C restoration.

Morphological alterations in the elastic fibers of the rabbit craniomandibular joint following experimentally induced anterior disk displacement.

Elastic fibers are important components of the connective tissue that attaches the articular disk of the craniomandibular joint (CMJ) to the skull and mandible. Biopsies of the articular disk proper and bilaminar zone (BZ) tissues from patients with anterior disk displacement (ADD) have shown previously that there is a marked loss of elastic fibers. In the present study, the effects of inducing ADD on the elastic fibers in the rabbit CMJ disk proper, BZ and condylar cartilage were investigated. The right CMJ was exposed surgically and the discal attachments were severed except for the BZ attachments. Then, the disk was displaced anteriorly and sutured to the zygomatic arch. The CMJs were removed after 1, 2 or 6 weeks and processed for histochemical demonstration of elastic fibers. The results showed osteoarthritic changes following ADD, and a significant decrease in the number of the elastic fibers in the disk proper and BZ. The remaining elastic fibers were abnormal in their appearance and orientation. In addition, ADD led to the appearance of fine elastic fibers among the chondrocytes in the hyaline cartilage of the condyle that were not present in the cartilage of the control condyle. We conclude that induced ADD can lead to a significant loss of elastic fibers in the articular disk, and result in the appearance of elastic fibers within the cartilage of the mandibular condyle.

Cariostatic and ultraconservative sealed restorations: six-year results.

The objective of this clinical study was to determine the ability of an ultraconservative, sealed composite resin restoration, without a traditional cavity preparation and without the removal of the carious lesion, to arrest Class I caries. Tooth preparation was limited to placing a bevel in the enamel. These restorations were compared, over 6 years, with (1) ultraconservative, localized, sealed amalgam restorations with no extension for prevention and (2) traditional, unsealed amalgam restorations with the usual extension for prevention outline form. Caries was arrested by the ultraconservative, sealed composite resin restorations for 6 years. Complete sealant retention on the sealed amalgam restorations was somewhat lower than that on the sealed composite resin restorations; conversely, partial sealant retention was higher for the sealed amalgam group. The marginal integrity of the sealed amalgam restorations was significantly superior to that of the unsealed amalgam restorations. The sealant also protected Class I posterior composite resin restorations against wear.

Sealed restorations: 5-year results.

This clinical study determined the feasibility of a sealed resin composite restoration to arrest dental caries using a minimal tooth preparation: a bevel in enamel only without removal of the carious lesion. These ultra-conservative sealed composite restorations placed over caries (CompS/C) were compared with ultra-conservative sealed amalgam restorations (AGS) that had no "extension for prevention". The CompS/C restorations were also compared with the traditional (unsealed) amalgam restorations (AGU) with the "extension for prevention" outline form. Caries progress, as determined by standardized radiographs, revealed that after 5 years caries remained arrested under the CompS/C restorations; the marginal integrity was similar for the CompS/C and the AGS groups, and exhibited highly significant superiority to the AGU restorations (Chi square, P less than = 0.00004). Complete sealant retention over the amalgam restorations (AGS group) was less than over the composite restorations (CompS/C), and conversely, partial sealant retention was higher for the AGS group. Sealants also appeared to protect the posterior composite restorations against wear.

In vitro effects of elastase on rabbit craniomandibular joint articular disks.

This in vitro study correlates morphologic and radioimmunoassay (RIA) findings on the effects of elastase on the elastic fibers that are found in the rabbit craniomandibular joint (CMJ) articular disk. Articular disks were removed from rabbit CMJs at necropsy, and cut sagittally into two pieces which were incubated in 0.3 ml of phosphate-buffered saline containing either 0, 12.5, 25 or 50 units of porcine pancreatic elastase for either 1, 3 or 24 h. The quantitative RIA findings correlated well with the qualitative light-microscopic observations in that both methods showed a reduction in the amounts of elastin in the CMJ disks following enzyme treatment. However, the morphologic appearance of most of the elastase-treated disks suggested that the destruction of the elastic fibers was more extensive than was suggested by the results of the RIA which indicated that some elastin remained in the tissues of the disks even when the highest enzyme level and longest incubation period were combined. The results of this study also support the interpretation that the resorcin-fuchsin-stained fibers in the rabbit CMJ disk are elastic fibers.

The effect of tensile strength on the clinical effectiveness and patient acceptance of dental floss.

This study compared the clinical effectiveness and subjective approval of 2 waxed dental flosses that differed significantly in tensile strength and wax content. At the initial appointment, subjects (20 1st-year dental students) were instructed to stop interproximal cleaning on 2 contralateral quadrants in order to allow plaque to accumulate on these surfaces for 1 week. 1 week later, subjects were instructed to begin flossing these 2 contralateral quadrants with 1 of the 2 types of floss for the next 1-week period, while withdrawing interproximal cleaning on the opposite 2 contralateral quadrants. After flossing these 2 quadrants for 1 week, the subjects began flossing the opposite 2 contralateral quadrants with the same floss. After 2 weeks of flossing contralateral quadrants, the 1st floss was withdrawn and replaced with the alternative floss for another similar 2-week trial period. At the end of each 2-week trial period, subjects completed subjective questionnaires concerning the floss they had used during the previous 2-week period. Pre- and post-flossing plaque indices were calculated for each week for both flosses, and compared statistically by a repeated measures analysis of variance. The results showed that both flosses significantly reduced interproximal plaque deposits, and had equal subjective approval. However, neither the greater-strength nor the lower-wax content of the experimental floss was associated with an increase in clinical effectiveness or with a change in subjective approval.

Morphological study of lectin binding in the rabbit temporomandibular joint disc.

Glycoconjugates of the extracellular matrix are important for the normal mechanical functions of connective tissue structures such as the temporomandibular joint disc. Since lectins are known to bind to sugar residues with high affinity, a variety of lectins were used to study the presence and distribution of glycoconjugates in the temporomandibular joint disc. Discs were removed from 6 to 8-month-old rabbits and either sectioned in a cryostat and processed for light microscopy or fixed in 2% glutaraldehyde and processed for electron microscopy. The frozen sections were incubated with fluorescein- or peroxidase-conjugated lectin solutions. Ultrathin sections mounted on grids were incubated with lectins combined with a colloidal gold marker system for electron microscopical study. Our results indicate that Canavalia ensiformis agglutinin (ConA) showed little or no binding to the discal tissue. Triticum vulgaris agglutinin (WGA) and Maclura pomifera (MPA) were bound strongly to both the synovium and the extracellular matrix and WGA also bound to the territorial matrix of chondrocyte-like cells. Glycine max and Arachis hypogoea agglutinins (SBA and PNA), were localized in the synovium and extracellular matrix but to a lesser degree than WGA and MPA. WGA, MPA, Griffonia simplicifolia II and Ulex europaeus were bound by discal fibroblasts. WGA was also localized in lysosomes of synovial A-cells (macrophages). The electron microscopical studies with lectins and colloidal gold marker systems indicated that some areas of the disc may be fibrocartilagenous as had been suggested by earlier immunohistochemical studies using monoclonal antibodies to characteristic glycosaminoglycans (GAGs) in cartilage.

Altered lipid metabolism in parvovirus-infected cells.

A broad spectrum of cell lipid alterations are known to occur as a consequence of various viral infections. These changes include inhibition of lipid synthesis, stimulation of lipid synthesis and changes in the proportions of various lipids. The current study examined the effects of two parvoviruses on lipids of rat kidney (NRK) cells. Cells were infected with H-1 or Kilham rat virus (KRV) and the effects on 14C-acetate incorporation determined. Results showed that H-1 virus rapidly inhibited lipid formation (in 1 h) while KRV produced a similar effect beginning around 8 h. Pretreatment of the cells with cycloheximide did not alter this response. Fatty acid analysis by gas chromatography did not reveal major alterations in this component of total cell lipids although some fatty acids became undetectable by 18 h post-infection. The data suggest that these parvoviruses, especially H-1 virus, are able to rapidly alter lipid formation following infection and that this effect may be mediated by a virion component.

Morphological and biochemical evidence for elastic fibres in the Syrian hamster temporomandibular joint disc.

Elastic fibres are considered to be important for the normal biomechanical functions of the TMJ. The objective here was to correlate morphological evidence for the presence of elastic fibres in discal tissues with biochemical evidence for elastin. For light microscopy, the joints were removed en bloc, processed for paraffin embedding, sectioned and stained with resorcin-fuchsin. For biochemical study, a radioimmunoassay for desmosine was used to estimate the amount of elastin in excised articular discs. The histological preparations showed that numerous elastic fibres were present in various areas of the disc and in some of the discal attachments to surrounding bone. Radioimmunoassay also indicated that elastin was present in these tissues. Therefore, the biochemical findings support the morphological in suggesting that elastic fibres are present in the articular disc of the hamster TMJ.

Localized prepubertal periodontitis: literature review and report of case.

This case describes a young, healthy, white female who demonstrated anterior alveolar bone loss along with premature loss of her primary incisors. The alveolar bone loss remains unexplained. The root surfaces of most of the primary anterior teeth exhibited one or more eroded areas devoid of cementum with some evidence in two teeth of cellular resorptive activity. These findings suggest that premature root resorption was occurring concurrently with unexplained extensive alveolar bone loss. The child will be examined periodically to determine whether this process of bone loss with subsequent tooth loss will involve additional primary or permanent teeth.

Distribution of putative elastic fibers in rabbit temporomandibular joint tissues.

This study describes the general distribution of putative elastic fibers in the connective tissues that comprise the articular disk and some of the adnexal tissues of the rabbit temporomandibular joint. Joints were removed en bloc and processed for light-microscopic study. The fibroelastic tissues of the bilaminar zone of the articular disk and the various attachments of the disk to the mandibular condyle contained numerous elastic fibers. Since these morphologic data indicate the presence of many elastic fibers, we suggest that the rabbit temporomandibular joint may serve as a model system to study the functional consequences of selectively altering the quality or quantity of elastic fibers in these tissues.

Replication of rat virus in neonatal calvaria in culture.

Rat Virus, a parvovirus of rodents that produces a variety of developmental disturbances of the head and face in neonatal animals, was examined for its ability to replicate in neonatal calvariae in vitro. The bones were isolated and infected with RV within 1 d of birth and cultured for up to 7 d. Virus from the bones and supernatant was titered, and the cellular location of replication determined using in situ hybridization. The virus readily replicated in the isolated bony tissues, reaching titers of nearly 10(7) plaque-forming units/ml. Using viral and complementary strand-specific probes, replication sites were located in the sutures and calvarial bones, as well as in cartilages thought to be part of the neurocranium. Results suggest that the virus localizes and replicates in cells necessary for the normal growth and development of the skull.

Regeneration of submandibular gland autografts in sympathectomized rats.

This morphologic study compares the regenerative response in submandibular gland (SMG) autografts placed in the tongues of previously sympathectomized rats to autografts placed in tongues of sham-sympathectomized rats. We hypothesized that sympathectomy would alter the process of cellular proliferation and inhibit cytodifferentiation in regenerating SMG autografts. Either 1 week, or 8 to 11 weeks following the SMG autografting procedure, the rats were sacrificed and their tongues were removed and sectioned in a cryostat. Frozen tissue sections containing the SMG autografts were either reacted for cholinesterase activity, treated with a glyoxylic acid mixture to induce histofluorescence, or stained for histologic examination. In addition, 3H-thymidine labeled and unlabeled cells were counted in autoradiographs of 1-week autografts, and these counts were used to calculate labeling indices. The 1-week SMG autografts from both the sympathectomized and the sham-sympathectomized rats were similar in histologic appearance, and neither group of autografts contained cholinesterase-positive or monoaminergic nerve fibers. The 8- to 11-week autografts from sympathectomized and sham-sympathectomized rats contained cholinesterase-positive fibers, but monoaminergic fibers were present in the autografts only from the sham-operated rats. Acinar cells were observed in one-third of the 8- to 11-week autografts of both the sympathectomized and sham-sympathectomized rats. This finding suggests that sympathectomy did not prelude cytodifferentiation in the autografts. The autoradiographic data revealed no statistically significant difference between the mean labeling indices of the 1-week autografts from the sympathectomized and sham-sympathectomized rats, which suggests that sympathectomy also did not alter the level of cellular proliferation in the autografts.

Histochemical demonstration of monoaminergic and cholinesterase-positive nerve fibres in regenerating rat submandibular gland autografts.

A cholinesterase localization method and a monoamine histofluorescence technique were used to locate nerve fibres in regenerating rat submandibular gland autografts. Experimental rats had a portion of one submandibular gland excised and cut into small fragments which were autografted immediately into the middle one-third of the tongue. Control rats had a portion of one submandibular gland removed and discarded, and their tongues were sham-operated. Seven to ten weeks later, the rats were killed and the tongues were removed, frozen and sectioned in a cryostat. A light microscopical study of the tongue sections subjected to the cholinesterase technique showed that the submandibular gland autografts contained many nerve fibres that exhibited cholinesterase activity. These cholinesterase-positive nerve fibres were distributed throughout the autografts. The fibres were associated with the numerous duct-like structures and the less numerous acini. In addition, ultraviolet illumination of tongue sections after treatment with a glyoxylic acid mixture revealed histofluorescent monoaminergic nerves within the autografts. These fibres were less prominent than the cholinesterase-positive fibres and appeared to run primarily along blood vessels within the autografts. The results suggest that autonomic nerves are present within regenerating submandibular gland autografts.

Effects of prior culture or isoproterenol injections on the regeneration of rat submandibular gland autografts.

This study compares the acinar cell regenerative response in submandibular gland (SMG) autografts that were cultured before grafting to the rat tongue with the acinar cell regenerative response in direct SMG autografts to the tongue. In addition, the effects of isoproterenol on direct SMG autografts were studied. A portion of the left SMG was excised from each rat and cut into fragments which were autografted either immediately into the middle one-third of the rat's tongue; or were cultured for 1, 4, or 7 days and then autografted to the donor's tongue. After 8 weeks the rats were killed and the tongues were removed and processed for light microscopic study. The histologic preparations showed evidence of cytodifferentiation into acinar cells in four of the previously cultured SMG autografts. Some of the direct SMG autografts did not contain acinar cells, whereas other direct SMG autografts contained numerous acinar cells and even striated ducts. In the SMG autografts that were cultured for 1 day before autografting and in the direct SMG autografts, the most pronounced regenerative responses were seen in autografts that contained ductlike structures that were apparently connected to the epithelial surface of the tongue. Lastly, isoproterenol appeared to accelerate the regenerative response in some of the direct SMG autografts, and the drug caused acinar cell hypertrophy in two of the direct SMG autografts.