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PubMed2003

Mutagenicity of bitumen and asphalt fumes.

The mutagenicity of asphalt fumes was tested with the Salmonella bioassays. The aim was to investigate if recycled additives modify the genotoxicity of emissions. Recycling of old asphalt is increasing, and we studied also the mutagenicity of emissions sampled during the re-use of asphalt. The composition of vapours and fumes were analysed by gas chromatography and by liquid chromatography. Bitumens containing coal fly ash (CFA) or waste plastics were heated to the paving temperatures in the laboratory. In the field, bitumen fumes were collected during paving of stone mastic asphalts (lime or CFA as a filler), remixing of stone mastic asphalt (lime or CFA as a filler), and of asphalt concrete. All the lab-generated vapour fractions were non-mutagenic. The particulate fractions were mutagenic with TA98 in the presence of the S9 activation. In addition, the lab-fumes from bitumen containing waste plastics were positive with both strains without S9. Only particulate fractions sampled in the field were tested. They were mutagenic with and without metabolic activation with both strains. The mutagenic potency of the field samples was higher than that of the lab-generated fumes without S9, and the remixing fumes were more mutagenic than the normal paving and lab-generated fumes with S9. The use of inorganic additive, CFA, did not change the mutagenicity of the fumes, whereas the organic additive, waste plastics, increased the mutagenicity of the laboratory emissions significantly.

Air Pollutants, Occupational↗
PubMed2001

Functional and angioarchitectural structure and classification of lingual papillae on the postero-dorsal surface of the beagle dog tongue.

A scanning electron microscopic study was done of the three-dimensional, morphological structure and classification by means of microvascular cast specimens (MVCS) of the filiform (FiP), fungiform (FuP) and circumvallate papillae (CvP) on the postero-centro-peripheral, and conical papillae (CoP) on the posteroperipheral-dorsal surface of the caudal portion of the beagle dog tongue. The characteristics and functional arrangement of each lingual papilla were as follows: the FiP densely and geometrically covered the entire postero-centro-peripheral dorsal surface. The outer structure of the FiP, consisting of both the ascending and descending branches from their tributaries, was a spoon-like capillary micro-network structure with a sharp arrowhead-like top inclined posteriorly. On the other hand, the outer structure of the FuP, appearing sporadically on the oblique lines of the FiP, was of round form consisting of a capillary microvascular network structure. The FuP, consisting of ascending and descending branches similar to the FiP, were distributed sporadically and geometrically on oblique lines in a V-form running from both peripheral sides to postero-central direction on the FiP A group of three CvPs were arranged on oblique lines in a V form from the peripheral to the postero-central region on the postero-dorsal surface. The outer shape of the microvascular network structure of the CvP was a round fence-like structure surrounding the papillary body and the papillary body consisted of an inner semi-spherical microvascular network structure. The CoP densely covered the entire postero-peripheral-dorsal surface. The exterior figure of the conical micro-network structure, consisting of both the ascending and descending branches of the CoP, was a cone-like capillary network structure, and the sharp tops were inclined posteriorly. They were classified into three types: large (L-CoP), medium (M-CoP) and small (S-CoP) according to the morphological characteristics in shape, size and the distributive position. It was conjectured that the FiP play a concentric functionally important role in transporting food and liquid from both sides in a postero-central direction towards the pharynx. And, on the other hand, the FuPs play an assistant role in receiving gustatory sensations from the masticated food and liquid on the central dorsal surface. The CoP play a functionally important role on the postero-peripheral-dorsal surface, in transporting food and liquid towards the pharynx and a complementary role of the CvP is to receive gustatory sensations from masticated food and liquid on the postero-peripheral-dorsal surface of the caudal portion of the beagle dog tongue.

Animals↗
PubMed2001

The expression of osteopontin with condylar remodeling in growing rats.

It is suggested that osteopontin may promote osteoclast binding to resorptive sites by interacting with the alphavbeta3 receptor on osteoclasts. However, the role of osteopontin in functional remodeling of bony structures remains unclear. The present study was conducted to examine the distribution of osteopontin on the condyle and explore the role in condylar remodeling in growing rats using an immunohistochemical method. Twenty Wistar strain male rats aged 7, 14, 28 and 56 days were used. In 7- and 14-day-old rats, no immunoreaction to osteopontin was detected in the cartilage cells. In 28-day-old rats initiating mastication, the thickness of condylar cartilage was decreased abruptly as compared to the younger rats. High immunoreaction to osteopontin was found in the cytoplasm of hypertrophic chondrocytes and on the trabecular bone surfaces of primary spongiosa adjacent to the osteoclasts or chondroclasts. The immunoreactions to osteopontin in the cytoplasm of hypertrophic chondrocytes were less in 56-day-old rats than in 28-day-old rats. It is shown that the alteration in mechanical loading on the mandibular condyle due to functional changes from weaning to mastication correlates with the localization of osteopontin in growing rats. Furthermore, it is suggested that osteopontin may stimulate osteoclastic resorption of calcified matrix by mediating the attachment of osteoclasts and/or chondroclasts during growth-related functional remodeling of the condyle.

Journal Article↗
PubMed2003

Micro X-ray computed tomography analysis for the evaluation of asymmetrical condylar growth in the rat.

OBJECTIVES: To investigate the influence of forced lateral bite on mandibular growth, micro X-ray computed tomography (CT) was used for the purpose evaluating condylar cartilage and cancellous bone formation in 10 male Wister rats (3 weeks of age). SETTINGS AND SAMPLE POPULATION: The rats were divided into two groups--experimental and control. In experimental group, an inclined crown was cemented onto the maxillary incisors to produce 2.5 mm shift toward the left side during mastication. Right-left differences in whole mandibular length, mandibular height, condylar size, trabecular structure of the condylar head and three-dimensional (3-D) finite element analysis were assessed using 3-D images reconstructed from micro X-ray CT scans when the mice had reached 21 weeks. MEASUREMENTS AND RESULTS: Asymmetrical growth was found in the experimental group, in which the left condylar head became thicker and shorter than the right condylar head during development. When comparing the left and right condyles of the experimental animals, histomorphometric analysis from micro X-ray CT showed that the bone volume (BV) of the cancellous bone, the surface area of the cancellous bone (BS), the BS/BV ratio, the BV fraction (BV/TV), and the trabecular thickness and trabecular number were less for the right condyle than for the left condyle. CONCLUSIONS: These findings suggested that artificial changes in the mastication do influence the growth of condylar head, condylar bone trabecular structure, and mineralization.

Animals↗
PubMed2000

Saliva tannin interactions.

Many plant foods contain tannins, compounds that bind proteins, such as mammalian enzymes. Although described as tasteless, tannins can be detected orally by their astringency. However, the actual mechanism of oral detection and the effect of tannins on mastication and swallowing have been little investigated. Here, we show from in vitro tests that tannic acid, a common standard in tests used to detect tannins, significantly reduces the lubricating qualities of human saliva both by decreasing its viscosity and increasing friction, both factors lending support to the notion that astringency is a tactile phenomenon. From the literature, it is clear that this effect depends on the presence of salivary proline-rich proteins (PRP). In a mammalian context, ingestion of tannin-rich foods in a species with salivary PRP will be signalled by interference with bolus formation during mastication while the increase in friction may also be detectable and lead to increased tooth wear if the signal is ignored. In a human context, cross-cultural preferences for tannin-rich beverages such as tea, coffee and red wine at the end of meals may be explained by reduction in adhesion of food particles to the oral mucosa allowing their rapid oral clearance.

Adult↗
PubMed2000

Functional outcomes of the retromaxillary-infratemporal fossa dissection for advanced head and neck/skull base lesions.

The retromaxillary-infratemporal fossa (RM-ITF) dissection, using a preauricular incision, was initially popularized for the treatment of temporomandibular joint disorders, facial fractures, and orbital tumors. This approach has been expanded for the treatment of advanced head and neck and skull base tumors extending into the infratemporal fossa. We studied prospectively eight consecutive patients requiring a RM-ITF dissection. Pre- and postoperative functional outcomes measured were mastication, speech, swallowing, cranial nerve function, pain, and cosmesis. A significant reduction in pain was noted postoperatively in all patients studied. Limited changes were identified in mastication, speech, swallowing, vision, hearing, or cosmesis postoperatively. The RM-ITF dissection should be considered when resecting advanced head and neck/skull base lesions that extend into this region. We have found minimal morbidity associated with this dissection. This procedure may have a useful place in palliation of patients with incurable pain caused by tumor invasion into the infratemporal fossa.

Journal Article↗
PubMed2001

Examination of the implant-abutment interface after fatigue testing.

PURPOSE: This study examined potential differences in detorque values of abutment screws after fatigue testing when the dimensions between external implant hexagon and internal abutment hexagon were altered or the implant external hexagonal shape was eliminated. MATERIAL AND METHODS: Three subsets (N = 10) of NobelBiocare implants were assessed: (1) standard external hexagon (R), (2) modified hexagon (M), and (3) circular (C) platform geometry. Thirty Procera machined abutments with 25-degree angulated loading platforms were manufactured. Abutments were retained with gold Unigrip abutment screws tightened to 32 N/cm with an electronic torque controller. Vertical scribes across the implant-abutment interface allowed longitudinal displacement evaluation. A carousel-type fatigue testing device delivered dynamic loading forces between 20 and 200 N for 5,000,000 cycles, or the approximate equivalent of 5 years in vivo mastication, through a piston to the abutment platform. Macroscopic and radiographic examination of the implant/abutment specimens was performed. The abutment screws were removed and the detorque values recorded. Bearing surfaces were examined microscopically. RESULTS: No abutment looseness or longitudinal displacements at the implant-abutment interface were noted. Radiographic examination demonstrated no indication of screw bending or displacement. The mean detorque values for R, M, and C were 14.40 +/- 1.84 N/cm, 14.70 +/- 1.89 N/cm, and 16.40 +/- 2.17 N/cm, respectively. The analysis of variance demonstrated significant differences between only designs R and C (P=.031). CONCLUSION: Increasing the vertical height, or degree of fit tolerance, between the implant external hexagon and the abutment internal hexagon or completely eliminating the implant external hexagon did not produce a significant effect on the detorque values of the abutment screws after 5,000,000 cycles in fatigue testing, or the equivalent of 5 years' of mastication for the implant/abutment specimens evaluated.

Analysis of Variance↗
PubMed2001

Potential risk of serious oral infections in the diabetic patient: a clinical report.

Diabetes has many manifestations, including increased vulnerability to bacterial and fungal infections, that may be of concern to the dental profession. Oral candidosis and other opportunistic fungal infections may be early, nonspecific signs of uncontrolled diabetes. Rhinocerebral involvement often extends to the paranasal sinuses, pharynx, palate, orbit, and brain, causing severe tissue destruction and necrosis. This clinical report describes a young woman with diabetes who developed mucormycosis of the maxilla. Tissue destruction resulted in loss of the entire premaxilla, the anterior half of the hard palate, and all maxillary teeth except for the right and left second molars. An interim clear acrylic resin prosthesis was fabricated to restore facial contours and speech and to allow mastication. This prosthesis subsequently was duplicated, and teeth were added for improved lip support, esthetics, and mastication.

Acrylic Resins↗
PubMed1999

Parameters of odontostomatognathic disability: guidelines for evaluation of impaired simple and complex human functions involving the odontostomatognathic functional system.

This paper explores the current status and the future of efforts to establish parameters of disability for the odontostomatognathic functional system ("the teeth, mouth, jaws and related structures as they subserve the functions of mastication, deglutition, digestion, speech, facial expression, respiration, sexual activity, appearance and posture"). Illness, disorders, disease or injuries involving this functional system include a broad spectrum of problems that affect the dental and paradental structures. The dentist is the primary healthcare provider (HP) in the diagnosis, treatment and impairment/disability/handicap status (IDH) decisions. The authors point out that the first stage of establishing parameters of odontostomatognathic disability was accomplished with recognition in the AMA Guides to Evaluation of Permanent Impairment of the temporomandibular joint and the masticatory musculature. The second stage will be the AMA Guides publishing of an objective rating system for functional impairment of the temporomandibular joint and the masticatory musculature. Prior to the third stage of actually establishing parameters of odontostomatognathic disability, the authors suggest that multiple objectives must be accomplished, including: 1. a change in current healthcare terminology; 2. an agreement on the organization of human physiological systems; 3. medical community acceptance of the integrated structures and functions of the odontostomatognathic functional system; and 4. an appreciation of both Level I (joint and muscle dysfunction) and Level II (complex odontostomatognathic dysfunction including problems with mastication, deglutition, digestion, speech, facial expression, respiration, sexual activity, appearance and posture). The authors conclude that once these objectives are met, parameters of odontostomatognathic disability can be established.

American Medical Association↗
PubMedDate not supplied

Occupational exposure to bitumen during road paving.

The exposure of road pavers to total particulates, bitumen fumes, semivolatile organic compounds (SVOCs), polycyclic aromatic hydrocarbons (PAHs), low-molecular-weight amines, styrene, and 1,3-butadiene was studied at 13 paving sites where 11 different asphalt mixtures were laid. Researchers analyzed 1-hydroxypyrene in the workers' pre- and postshift urine samples. The arithmetic mean concentrations of total particulates, bitumen fumes, SVOCs, and PAHs in the breathing zone of road pavers were 0.6 mg/m3, 0.29 mg/m3, 5.6 mg/m3, and 5.03 microg/m3, respectively. The highest bitumen fume concentrations (2.65 mg/m3) were measured in manual mastic laying, that is, when the paving temperature was highest. More than 90% of air impurities measured were in the vapor phase. Workers laying surface dressing were exposed to the highest SVOC concentrations (27.8 mg/m3). The paving temperature and the concentrations of bitumen fume correlated positively, but the weather conditions significantly affected the workers' exposure; for example, increased wind velocity resulted in lower concentrations of SVOCs and PAHs. Job title was not found to be a significant determinant of exposure, but exposure to bitumen fume and greater than or equal to four-ring PAHs among manual mastic pavers, and that to SVOCs and total PAHs among surface dressing workers, were significantly higher than among other pavers. Exposure during road paving operations was, on average, more than 10-fold higher to PAHs than was the exposure of a traffic controller (0.34 microg/m3) caused by automobile exhausts from background traffic. The PAHs were comprised mainly of two- and three-ring compounds. The concentrations of amines, and impurities from polymer modified bitumens, styrene, and 1,3-butadiene were below detection limits. Urinary 1-hydroxypyrene concentrations were higher among road pavers than among office workers serving as referents.

Air Pollutants↗
PubMed1982

Effect of a liquid diet on the protein composition of rat parotid saliva.

The object of the present study was to determine of the secretory proteins of rats parotid saliva were altered following parotid gland atrophy induced by feeding rats a liquid stock diet which eliminated mastication. Compared to rats fed the pelleted stock diet, the parotid glands of rats fed liquid stock diet showed 40% to 55% reductions in gland weight and content of RNA, amylase, and protein. Gland DNA content was reduced by 26%. The concentration of protein and the activities of three secretory enzymes in parotid saliva were reduced by 40% to 70%. The secretory enzymes were affected in a nonparallel manner so that per milligram of secretory protein DNase was increased, while RNase and amylase were reduced. Examination of the protein composition by acrylamide gel electrophoresis showed that several secretory proteins were no longer present. This study showed that feeding rats a standard stock diet, but in liquid form to eliminate mastication, results in a reduction in the protein concentration of parotid saliva, a loss of several secretory proteins and nonparallel changes in some of the proteins which remain.

Amylases↗
PubMed1989

The periodontal enigma: eruption versus tooth support.

The response of the periodontal ligament is reviewed when single or repeated loads are applied to the tooth, as in mastication. A more nearly elastic recovery is produced with simulated chewing than is indicated by single semi-static applications of force. The resting position of the tooth between loadings changes with the time of day and recent loading history. An unstressed tooth extrudes at a variable rate. Soon after entry into the mouth, extrusion is a progressive feature, which manifests as eruption with consequent structural rearrangement of the periodontium. Rates of extrustion are substantially higher than eruption. Experimental evidence is presented that newly erupted teeth of monkey erupt in a similar manner to rodent incisors. Thus reduction in masticatory loads allows teeth to erupt faster than control teeth. It is concluded that the ligament is well constructed to withstand the large but short-acting forces which occur in mastication and which cause relatively small, long term effects, on the position of the tooth in the alveolus. When unstressed, mechanisms in the ligament of a tooth with a developing or fully formed root, generate a continuous net force in the order of a gram tending to cause extrusion. The position a tooth adopts is determined by the interplay of these opposing sets of greatly differing forces.

Animals↗
PubMed1985

The disc of the human temporomandibular joint: design, function and failure.

The directions and limits of mandibular movements are controlled by muscles and nerves, and by biomechanical constraints in the dentition and the temporomandibular joints with their associated ligaments. This paper analyses biomechanical constraints in relation to shape, function, stability and dysfunction of the disc in the joint. It is argued that the dense part of the disc is modelled in response to condylar forces which compress it into the articular eminence thereby thinning its centre and squeezing out a thickened anulus around its rim. Because of a lack of congruence between the two articulating surfaces of the joint and a very low coefficient of friction, the disc is potentially squeezed off the condyle by compression forces during opening, closing and mastication. It is stabilized mainly by its anulus whose thick rim is unable to prolapse between the condyle and articular eminence. An important function of the elastic tissue behind the thick part of the disc may be, by contracting, to prevent the soft tissues behind the joint being nipped between the condyle/disc/temporal bone when the jaw is closing. The author suggests that during mastication the function of the disc is not only to spread the joint forces but also to limit the depth to which the condyle is compressed into the soft tissues covering the temporal bone and thereby allow the condyle (and disc) sufficient freedom to spin and slide over the temporal bone without distorting and damaging the surfaces. In other words, the function of the disc is to destabilize the condyle. In terms of biomechanical constraints the disc seems more liable to prolapse anteriorly than posteriorly. It prolapses when the compression forces which tend to wedge it off the condyle cannot be resisted by its thickened anulus. If the energy of compression is stored within the distorted disc and suddenly released there is an audible click.

Biomechanical Phenomena↗
PubMed2004

Edentulousness, denture wear and denture needs of Indian elderly--a community-based study.

India has a large geriatric population (60+ years) of 77 millions, comprising 7.7% of its total population. One of the major handicaps in the elderly is loss of teeth, affecting their mastication, dietary intake and nutritional status. The present study was planned to assess the level of edentulousness, denture wearing and denture needs of the elderly in the community and to study the correlation between oral health parameters and socio-demographic variables, diet and body mass index (BMI). A total of 1240 (716 urban and 524 rural) elderly people were studied. It was found that 60% were dissatisfied with their function of mastication because of loss of teeth and lack of dentures. The level of edentulousness was found to be high, more so in rural than in urban people and more so in advancing age, with no significant difference between male and females. The striking finding of this study was the very low level of denture wearing. Only <50% of those needing complete dentures and <13% of those needing partial dentures were wearing dentures. The denture needs of the rural elderly were higher than those of the urban elderly. Vegetarians had a higher level of edentulousness compared with non-vegetarians. The BMI was not correlated with level of edentulousness.

Age Distribution↗
PubMed2005

Physiological characterization, localization and synaptic inputs of bursting and nonbursting neurons in the trigeminal principal sensory nucleus of the rat.

A population of neurons in the trigeminal principal sensory nucleus (NVsnpr) fire rhythmically during fictive mastication induced in the in vivo rabbit. To elucidate whether these neurons form part of the central pattern generator (CPG) for mastication, we performed intracellular recordings in brainstem slices taken from young rats. Two cell types were defined, nonbursting (63%) and bursting (37%). In response to membrane depolarization, bursting cells, which dominated in the dorsal part of the NVsnpr, fired an initial burst followed by single spikes or recurring bursts. Non-bursting neurons, scattered throughout the nucleus, fired single action potentials. Microstimulation applied to the trigeminal motor nucleus (NVmt), the reticular border zone surrounding the NVmt, the parvocellular reticular formation or the nucleus reticularis pontis caudalis (NPontc) elicited a postsynaptic potential in 81% of the neurons tested for synaptic inputs. Responses obtained were predominately excitatory and sensitive to glutamatergic antagonists DNQX and/or APV. Some inhibitory and biphasic responses were also evoked. Bicuculline methiodide or strychnine blocked the IPSPs indicating that they were mediated by GABA(A) or glycinergic receptors. About one-third of the stimulations activated both types of neurons antidromically, mostly from the masseteric motoneuron pool of NVmt and dorsal part of NPontc. In conclusion, our new findings show that some neurons in the dorsal NVsnpr display both firing properties and axonal connections which support the hypothesis that they may participate in masticatory pattern generation. Thus, the present data provide an extended basis for further studies on the organization of the masticatory CPG network.

Action Potentials↗
PubMed2005

Patients' satisfaction following implant therapy. A 10-year prospective cohort study.

AIM: To analyse the patients' perception of implant therapy, 10 years following installation of titanium oral implants. MATERIAL AND METHODS: As a part of a prospective cohort study of patients with ITI(R) dental implants, 104 patients were recruited to answer a questionnaire with 13 statements on the subjective perception of implant treatment, 5-15 years after implant installation (mean: 10.2 years). In addition, the patients were asked to mark a visual analogue scale (VAS) in which 0 indicated "total discontent" and 100 "total satisfaction" with the statements mentioned in the questionnaire. Results from the qualified questions answered were then compared with those obtained from VAS analysis. RESULTS: One hundred and four patients, with 214 installed oral implants participated. Forty-eight percent of the implants were reconstructed with single crowns and 52% with fixed partial dentures (FPD). The cumulative survival rate of the implants at 10 years was 93%. Two of the statements addressing function and chewing comfort yielded very high patient satisfaction (97% highly satisfied or satisfied, mean VAS: 94+/-13). Comparing chewing comfort for teeth or implants, respectively, 72.1% perceived no difference between the two, 17.3% felt more secure when masticating on teeth and 7.7% when masticating on implants (mean VAS: 54+/-24). The vast majority (96%, mean VAS: 96+/-10) was highly satisfied or satisfied with phonetic function and with aesthetics (97%, mean VAS: 93+/-13). A great majority of the patients (93%, mean VAS: 89+/-19) had no problems with cleansing the implant reconstruction. Indeed, one-third (37%, mean VAS: 55+/-27) indicated more ease to clean implants than to clean teeth. About half of the patients (47%) had noticed bleeding of the mucosa or the gingiva following brushing. In addition, half (47%) of those noticing bleeding felt that bleeding was less marked around implants than around teeth. Again, the vast majority of patients (92%, mean VAS: 92+/-14) indicated complete fulfilment of the treatment, i.e. the outcome satisfied their expectations. The same majority (94%, mean VAS: 93+/-17) would be willing to undergo the same treatment again, and (89%, mean VAS: 93+/-16) would even recommend such treatment to friends and relatives, if indicated. The cost for implant therapy was deemed to be reasonable to a large extent (87%, mean VAS: 85+/-20). CONCLUSION: Using oral implants, more than 90% of the patients were completely satisfied with implant therapy, both from a functional and aesthetic point of view. The costs associated with implant therapy were considered to be justified. This was determined by both qualified questions and the use of VAS after 10 years of function.

Adult↗
PubMed1998

Developmental changes in enzyme activities and in structural features of rat masticatory muscle mitochondria.

The functional ability of a muscle is closely related to the activities of the mitochondria, which are energy-producing organelles in muscle cells. The development of the mammalian masticatory muscle progresses dramatically when feeding behavior changes from suckling to mastication, but it is unclear how the energy-producing systems of the mitochondria change. In this paper, the development of rat masticatory muscle mitochondria was investigated in terms of enzyme activities of the mitochondrial respiratory chain and the structural and numerical development of mitochondria, especially regarding the change in feeding behavior from suckling to mastication. Using isolated mitochondria from the masticatory muscle, we measured succinate dehydrogenase, NADH dehydrogenase, succinate-O2 oxidoreductase, and NADH-O2 oxidoreductase. These were found to be increased in the 15-day postnatal rat compared with the 0- to 10-day postnatal rat. The structural development of mitochondria was gradual in the 0- to 15-day postnatal rat. However, a notable increase was found in the cross-sectional area of mitochondria between 10 and 15 days postnatally. The number of mitochondria per muscle fiber was apparently constant during the same period. We demonstrated that the change in feeding behavior was well-correlated with an increase in mitochondrial enzyme activity, also supported by the early structural development of mitochondria.

Aging↗
PubMed1992

Interactions between dental amalgams and the oral environment.

Dental amalgam fillings interact in a complex way with the environment in the oral cavity as they are subjected to chemical, biological, mechanical, and thermal forces. These forces change the restoration's appearance and properties, while metal ions, amalgam debris, non-metallic corrosion products, and mercury vapor are released into the oral cavity. The phenomena and conditions that affect the amalgam/environment interaction include the chemistry and biochemistry of the environment, formation of biofilms on the amalgam surfaces, existence of localized corrosion cells, galvanic contacts with other metallic restorations, abrasion during mastication, and synergistic effects of the different forces. Corrosion processes result in a degradation of the functional amalgam properties, while tarnishing reactions cause discoloration. Corrosion degradation of amalgam fillings is due mainly to localized corrosion cells in pores and crevices. Corrosion on occlusal surfaces is accelerated by abrasion during mastication, which removes the protective surface films. The average total amounts of metal species, including mercury, released per day in vivo from a restoration have not been determined. Much of the reported indirect evidence for high mercury release rates is either unreliable or controversial. A more detailed investigation is needed and will require the development of more sophisticated techniques of sampling in vivo, as well as both experimental and theoretical modeling in vitro.

Copper↗