Oral Health Impacts on Flavor and Significance in Dental Treatment.

The mouth is pivotal in the generation of flavor, the pleasure of eating, and the selection of food. Flavor-representing the integration of olfaction (smell) with gustation (physiologic taste) and as influenced by oral somatosenses-is rarely afforded attention in oral research and dental practice. This article considers the interrelationship between oral health and flavor and highlights gaps in current knowledge. Altered oral function associated with operative and restorative treatment can feasibly alter the perception of flavor through diverse ways. Oral diseases and the generation of biofilms on restorative materials have potential to influence the oral microbiota and the perception of flavor. Alterations in masticatory function (through tooth loss, restorative materials, and prostheses with nonbiological surfaces and shapes) compounded by associated influences in the composition and quantity of saliva can affect the release of odorants and tastants from foods and beverages. Furthermore, changes occur in the perception of flavor throughout life and are significant in the aging and medically compromised population with the potential to affect nutrition and pleasure. Dental research and clinical practice should be at the forefront of biomedical science in understanding and promoting the importance and relevance of flavor in the well-being of patients. However, more research is required to guide clinical practice in consideration of olfactory and gustatory function as a component of total patient care.Knowledge Transfer Statement: This commentary highlights the research gaps in knowledge pertaining to the association between oral health and flavor and the significance of flavor to dental practice.

Growth and bone remodelling in a scorbutic rat model.

This study used the scorbutic Osteogenic Disorder Shionogi rat model and a specific diet to reliably induce a state of sub-scurvy scorbutus. Under these conditions overall somatic growth was assessed, as well as that of the caudal vertebrae, as an example of scorbutic bone growth. Tail loops were then used to mechanically stress mature caudal vertebrae under scorbutic conditions, and the vertebrae's adaptation to these applied forces was assessed, using measurements of bend deformation and histologic analysis of osteogenesis. Scorbutic animals exhibited significant somatic growth retardation (p < 0.05), and abnormal reductions in osteogenesis and periosteal responsiveness to growth. Scorbutic vertebrae also showed greater bend angles of deformation (p < 0.05), and a marked reduction in cortical osseous remodelling and periosteal differentiation. It appeared that the sub-scurvy scorbutic bones were smaller, weaker and less able to adapt to physical stresses: this pattern was reflected at the histologic level.

Cytotoxicity of gallium and indium ions compared with mercuric ion.

The use of mercury in dental amalgam restorations has become the subject of political controversy despite its long history of safe clinical use, and alternative materials based on gallium and indium rather than mercury have been developed. The biological safety of these metals must be evaluated, as part of their assessment as mercury substitutes. The cytotoxicities of mercury (II) nitrate, gallium (III) nitrate, and indium (III) nitrate were assessed at concentrations between 0.001 mmol/L and 1.0 mmol/L, using L929 mouse fibroblasts and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric assay and scanning electron microscopy. The mitochondrial dehydrogenase activity at each metal ion concentration as a percentage of the control was calculated from the absorbance values. The 50% inhibition concentration of mercury (II) nitrate was 0.35 mmol/L for cells in the rapid-growth phase and at confluence; gallium (III) nitrate and indium (III) nitrate did not significantly inhibit dehydrogenase activity in either the growing or confluent phase. Gallium and indium ions were not significantly toxic under the conditions of this assay.

Sealing ability of three materials used to repair lateral root perforations.

Thirty-five extracted single-rooted human teeth were decoronalized, root filled with AH-26 and gutta-percha, and perforated at the apical one third level. Repairs of the lateral perforations were carried out with three materials: amalgam plus cavity varnish, EBA cement, and silver glass-ionomer cement. Negative controls were not perforated and positive controls had unrepaired perforations. The roots were then implanted subcutaneously in rats for 5 days to place the materials in a surgical environment. Following retrieval, the roots were placed in a solution containing 20 microCi/ml of calcium-45 for 7 days to measure microleakage. They were rinsed, sectioned, and autoradiographs of the repaired perforations were made. The autoradiographs were projected onto a screen and the extent of penetration of the radioisotope measured. Statistical analysis showed that the EBA cement group exhibited significantly less leakage than the silver glass-ionomer cement group (p < 0.05). No differences were found between the other groups. It was concluded that EBA cement provides a superior seal in lateral root perforations to silver glass-ionomer cement while amalgam was intermediate between the two.

Osteogenic capacity of collagen in repair of established periodontal defects.

Periodontal bone defects were established in four dogs, with one proximal lesion and one furcation lesion in each quadrant. These defects were treated with the implantation of collagen membranes, collagen sponge or a combination of membrane and sponge, inserted between the mucoperiosteal flaps and the bone defects. Control sites were treated in a similar surgical manner to the experimental sites, but no collagen was inserted. Substantial amounts of new bone formed in those cases treated with the collagen products, especially those treated with the membrane either with or without the sponge. The membranes limited the infiltration of small round cells, whereas in the control sites, inflammatory cells infiltrated to the bone surface. New connective tissue attachment was established in experimental situations, especially with the use of the membranes alone or in conjunction with sponge.

The biocompatibility testing of some dental amalgams in vivo.

The biological responses to some dental amalgams were determined in vivo and compared with those of dental porcelain. The technique of implantation employed in the study addressed some of the vagaries of the Recommended Standard Practices for Biological Evaluation of Dental Materials (RSP) and considered both cellular responses (inflammation, infiltration and fibrogenic cell activity) and the organizational status of the resultant encapsulation. The implantation sites for both the experimental and control were biogeometrically similar, unlike those currently recommended in RSP. At the end of the test period, all the dental amalgams tested caused minor responses reflected by the formation of thin capsules with an acceptable matrix organization. The Australian manufactured dental amalgams--Permite C, Lojic, F400, New Ultrafine and GS80 all produced even capsules with quiescent cells. By one hundred days, the capsule around Dispersalloy, although generally well formed, showed some areas of cellular activity and matrix variability. The biological responses to all the dental amalgams examined were mild and considered to be acceptable for clinical usage. The matrix organization of enveloping capsules must be considered in the determination of the biocompatibility of a dental restorative material.

Periosteal response in translation-induced bone remodelling.

Translation of transplanted bones induces strain in the periosteum and subsequent bone remodelling. This study examines the periosteal response on the leading and trailing sides of translated bones using an in vivo model where internal bone strain is virtually eliminated. Caudal vertebrae from 4 days old rats were threaded onto the arms of pre-stressed helical torsion springs and transplanted subcutaneously. In the experimental rats, the appliances were activated seven days later causing the bones to translate. Tissues were examined both optically and by transmission electron microscopy. A connective tissue sheath or capsule forms around the bones and, as the arms of the appliance move apart, traction on the enveloping soft tissues produces compression of the periosteum on the leading side and tension on the trailing side with remodelling occurring in a direction opposite to translation. The control periosteum has an ordered structure with well-delineated osteogenic, mid- and fibrous zones. During translation the periosteum on the leading side is consistently narrower than on the trailing side and shows a gradual reduction in formative activity followed by resorption in select areas. Cells and fibres are aligned predominantly parallel to the bone surface. Accelerated formation characterises the trailing side during the translation phase with increased activity and widening of all three periosteal layers. The fibrous layer merges with the connective tissue sheath which frequently is oriented approximately perpendicular to the bone surface. The direction of remodelling is reversed when translation ceases with corresponding changes visible in the periosteum, the osteoblastic layer being the last to show changes. A normal periosteal structure and remodelling pattern is regained when equilibrium of the bones within the soft tissues is attained. This study shows that the enveloping soft tissues profoundly influence the nature and rate of bone remodelling. The changes are reflected in the periosteum which functions as an integrated unit modulating the signal transmitted to the osteoblasts which play a key role in events occurring at the bone surface. Changes are not attributable to internal bone strain.

Sections from double mesas obtained at the same tissue plane.

A method for obtaining sections from two areas in the face plane of a tissue block is described. It facilitates ultrathin sectioning where virtually identical planes of section are essential but where areas of interest are too far apart to be included in a single section. Two horizontally separated mesas are prepared; sections are cut from the first with the knife rotated around its vertical axis by 2-3 degrees to provide clearance for the other. The second mesa is then sectioned with the knife rotated 4-6 degrees in the opposite direction. Similarly, by changing the vertical inclination of the block, two additional vertically separated mesas can be cut. This procedure is of great value for comparative morphometric studies of material from opposite sides of individual specimens.

Characterisation of a monoclonal antibody against native human type I collagen.

A monoclonal antibody against a pepsin-soluble mammalian type I collagen has been produced. This antibody, subclass IgG1, kappa, was specific for type I collagen and did not cross-react with a range of other collagen types or connective tissue proteins. The epitope recognized by the antibody was dependent upon an intact triple-helical structure for the collagen, and was shown by rotary shadowing and by immunoblotting of collagenase-derived fragments to be near the C-terminal of the pepsin-soluble collagen. Although the antibody had a low affinity, with Kd = 4 x 10(-7) M, it could be used for immunohistology of tissue sections and for studies of collagen produced by cells in culture. The antibody, which was raised against human collagen, also recognized type I collagens from certain other species, including calf, pig, sheep, goat and dog.

Periosteal changes in mechanically stressed rat caudal vertebrae.

When a caudal vertebra is stressed by looping the tail, remodelling results with increased formation of bone on the inner (concave) side of the loop and decreased formation on the corresponding outer (convex) side. The initial morphological changes in periosteum under stress are examined by histology, autoradiography and transmission electron microscopy. Vessel damage appears minimal and thus seems unlikely to be a trigger for the remodelling process. On stress application the connective tissue relationships in the fibrous component of the periosteum are altered immediately but changes in the osteogenic layer are delayed. On the inner side, the midzone between the cellular periosteum and the fibrous periosteum becomes drawn out and enlarged, with reorientation of the cells perpendicular to the bone. This reflects the tension exerted on the bone surface through the elastic recoil of the fibrous periosteum. On the outer side, the midzone becomes narrowed as the taut fibrous periosteum exerts a compressive force on it. The midzone, which shows a delayed response and the greatest structural change with altered stress, may buffer the osteogenic layer and so play an important role in bone remodelling. The results have considerable bearing on the establishment of bone form during normal growth and development.

Connective tissue responses to some heavy metals. III. Silver and dietary supplements of ascorbic acid. Histology and ultrastructure.

Silver-loaded ion exchange resin beads implanted into loose connective tissue of the rat pinna produced a local reaction. Initially the lesion comprised local necrosis and tissue disruption with predominantly small round cell infiltration. The subsequent organization was delayed and disordered. Fibroblasts developed grossly dilated cisternae of the rough endoplasmic reticulum. The matrix contained poorly orientated collagen fibrils of varying size and ground substance appeared condensed and granular. Distorted collagen fibrils were identified within membrane-bound vacuoles in the cytoplasm of both fibroblasts and macrophages. Abnormalities of the silver lesion were indicative of disordered collagen biosynthesis. Silver interfered with the biosynthesis and assembly of matrix components of the connective tissue. The reaction to silver beads in rats maintained on a diet heavily supplemented with ascorbic acid approached that of the control (sodium-loaded bead) with respect to the time scale, tissue reaction and tissue organization. The collagen matrix which formed was more organized and of greater density than that in the rat maintained on a normal diet. However, the repair tissue retained some of the morphological features of the legacy of silver toxicity, in particular delayed repair and dense intracellular fibrils within fibroblasts and macrophages. The excess of ascorbic acid partially ameliorated the effect of silver, possibly by compensating catabolysis of ascorbic acid caused by the presence of the released silver.

Silver wire implant of 40 years' duration: influence on local tissues.

The retention of an implanted silver wire in human tissue 40 years after surgical fixation of the frontal bone was studied post mortem by histology, transmission electron microscopy, and energy-dispersive x-ray analysis. Corrosion products of the wire were associated with a chronic inflammatory response and were bound to certain connective tissue elements; they were deposited as discrete particles, comprising silver in association with sulphur, on collagen fibrils and vascular basement membranes. Bone structure appeared normal except close to the wire, where it was replaced by a loose connective tissue in which collagen bundles were disorganized.

Periosteal structure and development in a rat caudal vertebra.

Female Sprague-Dawley rats from birth to 300 days were used to study the bone/soft tissue interrelationships of the 14th caudal vertebra with particular emphasis on the periosteum throughout growth, development and maturation. The growth of the rats follows a sigmoid curve with three phases, a developmental, a rapid growth and a maturation phase. The width/length ratio of the bone and the thickness of the periosteum are closely concurrent, with a rapid decrease during the developmental phase and a levelling off during the rapid growth phase. SEM studies established that the caudal vertebra has symmetrical lateral sides and a pronounced concavity on the ventral surface where the main vascular plexus is located. Morphological changes in the periosteum cna be described as occurring in three layers and reflect the stages seen in general somatic growth. The inner cambial layer initially contains elongated but functional osteoblasts; these become cuboidal during the rapid growth phase and ultimately are flattened and quiescent. The mid-zone with its vessels, undifferentiated and mononuclear phagocytic cells also attains its maximum development in the rapid growth period and then gradually involutes. The fibrous periosteum consists of a syncytial arrangement of fibroblasts in a collagenous matrix which becomes increasingly dense although reduced in width. Sharpey fibre bundles connect the bone with the fibrous periosteum and these become thicker with age. The mid-zone of the periosteum has not been described previously. Besides having a nutritive role and providing progenitor cells it is thought to act as a buffer modulating the interaction between bone and the covering soft tissues. With age and the deletion of the mid-zone a less sensitive periosteal response to stress can be expected.

Cationic radioisotope delivery to loose connective tissue in vivo using ion-exchange resin beads.

Ion-exchange resin beads, implanted into connective tissue, were used as the vehicle for the delivery of radiolabelled cations to determine the local distribution of lead, silver and cadmium in loose connective tissue. The system was devoid of systemic toxicity, permitted a predictable release, enabled location of released cations in respect to the site of bead implantation, afforded safety and could be used with several other cations. The radiolabels released into the tissue formed an immediate relationship with inflammatory cells and a more protracted relationship with the matrix elements of the local connective tissue. The lesion induced by the presence of the bead was complicated by the particular cation.

Stress induced periosteal changes.

The tails of Sprague-Dawley rats of approximately 50 g body mass were either left straight or bent to form a loop containing three or five vertebrae (CV). Subsequent treatment was as follows: (a) in situ: segments were removed at 0, 8, 16, 24 h, 3, 5 and 7 days and examined histologically: (b) transplants: skinned segments were transplanted autologously and examined at the same time intervals; (c) normal saline: skinned segments were placed in a 0.9% solution maintained at (i) 4 degrees C and (ii) 37 degrees C and examined 8, 16 and 24 h later. The results show that on bending a bone in situ the remodelling which occurs reflects the displacement of the soft tissues, and more specifically the periosteum, towards or away from the bone surface. Functionally the developing periosteum consists of three zones and when stressed its fibroelastic component moves away from or towards the osteogenic layer either applying tension to it stimulating bone formation, or pressure eventually inducing bone resorption. These changes are mediated via the mid-zone. The effects on the fibroelastic component alone are best seen in transplants or in normal saline at 37 degrees C where the osteogenic layer dies. The periosteum in growing bones is ideally structured to respond rapidly and sensitively to altered strain by initiating adaptive surface remodelling of bone.

Connective tissue responses to some heavy metals. I. Sodium loaded ion exchange beads as a control: histology and ultrastructure.

Ion exchange resin beads (Amberlite IR-120) were implanted into loose connective tissue as the vehicle for cations in both control and experimental studies. Beads were loaded with sodium for control purposes or with the metal of interest for subsequent experimental studies. When single control beads were implanted in the loose connective tissue of the rat pinna, they were well accepted by tissue and permitted rapid healing. The bead implantation initially produced minimal inflammatory disruption and subsequent repair at the bead-tissue interface which rapidly matured leaving no fibro-collagenous capsule. Some minor geometric rearrangement occurred in the alignment of the connective tissue to compensate for the physical presence of the bead. This system provides a valid control for studies of the effects of metal cations on tissue inflammation and repair--free from anionic complications, surface phenomena or systemic interference.

Connective tissue responses to some heavy metals. II. Lead: histology and ultrastructure.

Lead loaded ion exchange resin beads implanted into the loose connective tissue of the rat pinna induced local lesions which differed widely from those of the control (sodium loaded) beads (Ellender & Ham 1987). These lesions were characterized by changes in the granulation tissue and the approximating connective tissue. Granulation tissue contained mononuclear phagocytes in various guises, and some cells with intranuclear inclusion bodies. The matrix of the granulation tissue contained collagen fibrils having a wide range of diameters suggestive of altered collagen biosynthesis. Foci of collagen mineralization occurred in zones of combined trauma and lead impregnation. Once mineralized they became enveloped by giant cells and epithelioid cells. Lead in damaged tissues is thought to modify the protective mechanism of calcification inhibition and the biosynthesis of the matrix.

The ultrastructural localization of the corrosion products of dental amalgam.

The ultrastructural localization of corrosion products released from dental amalgam implants in rat subcutaneous tissue was studied by means of a sulphide-silver technique. Implants stimulated a prolonged inflammatory response with delayed granulation tissue formation and slow and faulty collagen formation. The metallic corrosion products were found both in cells and in association with matrix components. Intracellular metal deposits were predominantly in the cytoplasmic matrix and in vacuoles in the early (19 day) lesions, but at 60 days there was metal in many nuclei, both viable and dead. Collagen fibrils had metal on the surface and vascular basement membranes had granules of bound metals.