Laboratory Studies of Nonlinear Optical Signals for Caries Detection.

Multiphoton confocal microscopy and nonlinear spectroscopy are used to investigate the caries process in dentin. Although dentin is a major calcified tissue of the teeth, its organic phase comprises type I collagen fibers. Caries drive dentin demineralization and collagen denaturation. Multiphoton microscopy is a powerful imaging technique: the biological materials are transparent to infrared frequencies and can be excited to penetration depths inaccessible to 1-photon confocal microscopy. The laser excitation greatly reduces photodamage to the sole focal region, and the signal-to-noise ratio is improved significantly. The method has been used to follow pathologic processes involving collagen fibrosis or collagen destruction based on their 2-photon excited fluorescence (2PEF) emission and second harmonic generation (SHG). Combining multiphoton imaging with nonlinear spectroscopy, we demonstrate that both 2PEF and SHG intensity of human dentin are strongly modified during the tooth caries process, and we show that the ratio between SHG and 2PEF signals is a reliable parameter to follow dental caries. The ratio of the SHG/2PEF signals measured by nonlinear optical spectroscopy provides valuable information on the caries process, specifically on the degradation of the organic matrix of dentin. The goal is to bring these nonlinear optical signals to clinical application for caries diagnosis.

A functional natural dentition for all--and for life? The oral healthcare system needs revision.

The cost of dental care adds to the costs of the already overburdened health sector. Do we - as patients and as society -receive oral health care that is both aligned with the actual disease experience and also, critically based on up-to-date scientific knowledge about the major oral diseases? In many places, the practice of dentistry reflects a response to disease patterns that once existed and is based on diagnostic and therapeutic approaches that are no longer valid. Instead, a new cadre of dental professionals is needed, one that is capable of meeting the actual health needs of our populations. This cadre should ensure that patients maintain a functioning dentition from cradle to grave based on cost-effective disease control principles. There is an urgent need to: (i) reconsider the roles of the different oral health cadres involved in the provision of oral health care; (ii) integrate oral health into general healthcare services; and (iii) restructure the training of oral health personnel. We advocate a radical reform of the oral healthcare system involving the training of two new types of professionals integrated with the general healthcare system: The oral healthcare provider - a highly skilled professional specialised in the diagnosis and control of oral diseases and with a profound understanding of oral health as part of general health - and the oral clinical specialist - whose role is the provision of advanced oral rehabilitation, able also to treat people with complex chronic diseases and multiple medications.

Dental caries in Rome, 50-100 AD.

Scarce information exists on the clinical features of dental caries in the Imperial Roman population and no structural data on caries lesions from this period have so far been published. We report on the findings of 86 teeth (50-100 AD) found during archaeological excavations of the temple of Castor and Pollux in the Forum Romanum. We found that nearly all teeth had large carious cavities extending into the pulp. The distribution and size of the caries lesions were similar to those found in contemporary adult populations in Africa and China living without access to dental care. Most lesions had a hypermineralized zone in the dentin at the advancing front of the carious cavities as revealed by micro-computed tomography. This biological dentin reaction combined with the morphology of the cavities might indicate that some temporary topical pain relief and intervention treatment slowed down the rate of lesion progression. This is indirectly supported by examination of cavities of similar size and depth from a contemporary population without access to dental health care. In contrast to the lesions in the Roman teeth, these lesions did not exhibit a hypermineralized dentin reaction. We investigated whether the Pb isotopic composition of enamel and/or dentin of a single tooth matched that of a sample of an ancient Forum water lead pipe. The Pb isotopic composition of the tooth did not match that of the tube, suggesting that the subjects were exposed to different Pb sources during their lifetime other than the lead tubes.

A global perspective on changes in the burden of caries and periodontitis: implications for dentistry.

The structure and contents of most oral health care systems and the contents of dental curricula reflect a deep-rooted tradition for attempting to cure oral diseases by refined technological means. However, better oral health conditions for the world's populations necessitate the application of up-to-date scientific knowledge to control the major oral diseases. This review points out that not only should the structure and contents of oral health care delivery systems be based on state-of-the-art knowledge about the biology of the oral diseases; they must also take into account the trends for change in caries and periodontal diseases within and between populations, and acknowledge the impact of changes in treatment philosophies for these trends. The oral disease profiles for populations in low- and high-income countries are briefly described, and it is concluded that the rapidly changing disease profiles observed in high-income countries necessitate re-thinking of the future role and organization of dentistry in such countries. The priorities for low- and middle-income countries must be to avoid repeating the mistakes made in the high-income countries. Instead, these societies might take advantage of setting priorities based on a population-based common risk factor approach. If such an approach is adopted, the training of personnel with oral health care competence must be rethought. The authors suggest three different cadres of dental care providers to be considered for an approach that allows health care planners in different populations around the world to prioritize appropriate oral health care with due respect for the socio-economic conditions prevailing.

Prevalence of dental fluorosis in German schoolchildren in areas with different preventive programmes.

In a retrospective study in two different regions of Germany, 1,041 fifteen-year-old pupils were examined for dental fluorosis. The adolescents had taken part in different caries prevention programmes. There were 746 subjects in the study group and 295 subjects in the control group. For each participant, specific aspects of early development, diet and fluoride exposure in group prevention programmes and at home were determined by means of questionnaires. The Thylstrup-Fejerskov index was used to classify the fluorosis scores on the buccal surfaces of teeth 11, 12, 13, 14, 15 and 16 after compressed air drying of the teeth. Binary logistic stepwise regression analyses were conducted to identify associations between fluorosis and potential influence factors. A distinction was made between early and late developing tooth parts. The significance level was set at alpha = 0.05. Fluorosis prevalence in the regions studied was 7.1 and 11.3%, respectively. The difference was not statistically significant (p = 0.052; chi square). Binary logistic stepwise regression analysis revealed that 'early start of toothbrushing' was a statistically significant predictor of dental fluorosis in the early-mineralizing enamel (OR = 1.99, p = 0.027). For the late-mineralizing enamel no single independent variable was identified as a significant predictor of dental fluorosis.

What constitutes dental caries? Histopathology of carious enamel and dentin related to the action of cariogenic biofilms.

Substantial pH fluctuations within the biofilm on the tooth surface are a ubiquitous and natural phenomenon, taking place at any time during the day and night. The result may be recordable in the dental tissues at only a chemical and/or ultrastructural level (subclinical level). Alternatively, a net loss of mineral leading to dissolution of dental hard tissues may result in a caries lesion that can be seen clinically. Thus, the appearance of the lesion may vary from an initial loss of mineral, seen only in the very surface layers at the ultrastructural level, to total tooth destruction. Regular removal of the biofilm, preferably with a toothpaste containing fluoride, delays or even arrests lesion progression. This can occur at any stage of lesion progression, because it is the biofilm at the tooth or cavity surface that drives the caries process. Active enamel lesions involve surface erosion and subsurface porosity. Inactive or arrested lesions have an abraded surface, but subsurface mineral loss remains, and a true subsurface remineralization is rarely achievable, because the surface zone acts as a diffusion barrier. The dentin reacts to the stimulus in the biofilm by tubular sclerosis and reactionary dentin.

Changing paradigms in concepts on dental caries: consequences for oral health care.

Kuhn proposed in his Structure of Scientific Revolutions (1962) that the theoretical framework of a science (paradigm) determines how each generation of researchers construes a causal sequence. Paradigm change is infrequent and revolutionary; thereafter previous knowledge and ideas become partially redundant. This paper discusses two paradigms central to cariology. The first concerns the most successful caries-preventive agent: fluoride. When it was thought that fluoride had to be present during tooth mineralisation to 'improve' the biological apatite and the 'caries resistance' of the teeth, systemic fluoride administration was necessary for maximum benefit. Caries reduction therefore had to be balanced against increasing dental fluorosis. The 'caries resistance' concept was shown to be erroneous 25 years ago, but the new paradigm is not yet fully adopted in public health dentistry, so we still await real breakthroughs in more effective use of fluorides for caries prevention. The second paradigm is that caries is a transmittable, infectious disease: even one caused by specific microorganisms. This paradigm would require caries prevention by vaccination, but there is evidence that caries is not a classical infectious disease. Rather it results from an ecological shift in the tooth-surface biofilm, leading to a mineral imbalance between plaque fluid and tooth and hence net loss of tooth mineral. Therefore, caries belongs to common 'complex' or 'multifactorial' diseases, such as cancer, cardiovascular diseases, diabetes, in which many genetic, environmental and behavioural risk factors interact. The paper emphasises how these paradigm changes raise new research questions which need to be addressed to make caries prevention and treatment more cost-effective.

Expression of aquaporin isoforms during human and mouse tooth development.

Previously, we described the development of hyaluronan (HA) deposition in human tooth germ tissues that are consistent with water transport in different stages of tooth development. The aquaporins (AQP) constitute a family of membrane water channels that are expressed in many organs. However, there are no data available about the expression pattern of aquaporin water channels in dental structures. In the present study we have characterised the expression of six different aquaporin isoforms (AQP1-5, AQP-9) in developing human and mouse tooth germs by immunohistochemistry using isoform specific antibodies. In the "bell stage" AQP1 was expressed in endothelial cells of small vessels whereas no other structures of the tooth primordial were labeled. AQP2, AQP3 and AQP9 immunoreactivity was not observed in tooth germs, whereas strong AQP4 and AQP5 expression was observed in dental lamina, inner enamel epithelium, stratum intermedium, stellate reticulum and the outer enamel epithelium. Oral epithelium also exhibited AQP4 and AQP5 immunolabeling. During development of the matrices of the dental hard tissues AQP4 and AQP5 immunostaining was observed in the odontoblasts and their processes, as well as in the secretory ameloblast and their apical processes. Immunolabeling controls were negative. In conclusion, AQP4 and AQP5 are expressed in tooth germ tissues in early development in cells that previously have been shown to express HA and/or CD44, indicating that AQP water channels may play a role for ECM hydration during tooth development.

Periodontal conditions among adults in Southern Thailand.

OBJECTIVE: To describe the periodontal conditions among 30-39- and 50-59-year-old rural Thais from the Province of Songkhla, Southern Thailand. METHODS: A total of 359 dentate persons were given a clinical examination comprising recordings of plaque and calculus in six teeth, and bleeding on probing, attachment level and pocket depth in six sites of all teeth present, except third molars. The same examiner carried out all examinations. Information on religious faith, smoking habits and use of betel was obtained by interview. A subset consisting of 60 persons was reexamined for attachment level 6 months later by another examiner. RESULTS: The oral hygiene conditions were poor with abundant amounts of both plaque and calculus. Gingival bleeding was essentially ubiquitous. The prevalence of attachment loss > or = 4 mm was 92% among 30-39-year-olds and 100% among 50-59-year-olds. The average percentage of sites affected in the two age groups was 23.9% and 63.9%. Pockets > or = 4 mm were seen in 84% of the 30-39-year-olds and in 93% of the 50-59-year-olds. Older age, Thai Buddhist faith and a high percentage of sites with calculus were significant positive predictors of a high percentage of sites with attachment loss > or = 4 mm, whereas older age and Thai Buddhist faith were the only statistically significant predictors of a high percentage of sites with attachment loss > or = 7 mm. CONCLUSION: The results indicate that this Thai population may have more widespread and severe periodontal destruction than other Asian populations, but failed to confirm the contention that Muslim faith is associated with more severe periodontal destruction.

Dental fluorosis: chemistry and biology.

This review aims at discussing the pathogenesis of enamel fluorosis in relation to a putative linkage among ameloblastic activities, secreted enamel matrix proteins and multiple proteases, growing enamel crystals, and fluid composition, including calcium and fluoride ions. Fluoride is the most important caries-preventive agent in dentistry. In the last two decades, increasing fluoride exposure in various forms and vehicles is most likely the explanation for an increase in the prevalence of mild-to-moderate forms of dental fluorosis in many communities, not the least in those in which controlled water fluoridation has been established. The effects of fluoride on enamel formation causing dental fluorosis in man are cumulative, rather than requiring a specific threshold dose, depending on the total fluoride intake from all sources and the duration of fluoride exposure. Enamel mineralization is highly sensitive to free fluoride ions, which uniquely promote the hydrolysis of acidic precursors such as octacalcium phosphate and precipitation of fluoridated apatite crystals. Once fluoride is incorporated into enamel crystals, the ion likely affects the subsequent mineralization process by reducing the solubility of the mineral and thereby modulating the ionic composition in the fluid surrounding the mineral. In the light of evidence obtained in human and animal studies, it is now most likely that enamel hypomineralization in fluorotic teeth is due predominantly to the aberrant effects of excess fluoride on the rates at which matrix proteins break down and/or the rates at which the by-products from this degradation are withdrawn from the maturing enamel. Any interference with enamel matrix removal could yield retarding effects on the accompanying crystal growth through the maturation stages, resulting in different magnitudes of enamel porosity at the time of tooth eruption. Currently, there is no direct proof that fluoride at micromolar levels affects proliferation and differentiation of enamel organ cells. Fluoride does not seem to affect the production and secretion of enamel matrix proteins and proteases within the dose range causing dental fluorosis in man. Most likely, the fluoride uptake interferes, indirectly, with the protease activities by decreasing free Ca(2+) concentration in the mineralizing milieu. The Ca(2+)-mediated regulation of protease activities is consistent with the in situ observations that (a) enzymatic cleavages of the amelogenins take place only at slow rates through the secretory phase with the limited calcium transport and that, (b) under normal amelogenesis, the amelogenin degradation appears to be accelerated during the transitional and early maturation stages with the increased calcium transport. Since the predominant cariostatic effect of fluoride is not due to its uptake by the enamel during tooth development, it is possible to obtain extensive caries reduction without a concomitant risk of dental fluorosis. Further efforts and research are needed to settle the currently uncertain issues, e.g., the incidence, prevalence, and causes of dental or skeletal fluorosis in relation to all sources of fluoride and the appropriate dose levels and timing of fluoride exposure for prevention and control of dental fluorosis and caries.

Actinobacillus actinomycetemcomitans in a rural adult population in southern Thailand.

The prevalence of Actinobacillus actinomycetemcomitans isolates was examined in a rural population of southern Thailand. Sixty individuals aged 30-39 and 50-59 years were randomly selected from a group of 363 persons, living in four villages, who had been clinically examined previously. A subgingival plaque sample was taken with a curette from the mesial aspect of the two upper and lower first molars. Each sample was dispersed in 3.3 ml of VMGA III transport medium and spread onto Trypticase Soy Broth with Bacitracin and Vancomycin (TSBV)-agar plates on the same day. After incubation in 10% CO2 for 5 days the plates were examined for typical A. actinomycetemcomitans colonies which were tested for catalase activity. Each strain was further tested for biochemical characteristics, serotyped against serotype-specific antisera a-e and ribotyped after DNA digestion using the restriction endonucleases HindIII and EcoRI. For 53 (88%) of the 60 individuals, A. actinomycetemcomitans was present in at least one subgingival sample, which is considerably higher than the prevalence in Western European adults. In 11 individuals, two or three different strains were found. Serotypes a and c were the most prevalent, and serotype b was found only once among 46 tested isolates. Eleven ribotypes were found among the 46 strains. While the same ribotype could be found among individuals of the same village, no ribotype of A. actinomycetemcomitans was unique for individuals of any one village. The study demonstrated a high prevalence of A. actinomycetemcomitans among adults of the rural population of southern Thailand and indicates that this species is present as part of the resident oral flora in this population.

Age-related and site-specific changes in the pulpodentinal morphology of rat molars.

The rat molars are frequently used as experimental models in endodontic research, but there is little systematic information available on the influence of age on the pulpodentinal organ in Wistar rat molars and it is often difficult to evaluate more subtle changes following experimental interventions. The aim here was to describe changes with age in first upper Wistar rat molars with specific reference to the pulpodentinal organ. Animals were perfused with glutaraldehyde at 19 days, 1, 3, 6, 8, 12, 16, or 24 months of age. First upper molars from 56 animals were demineralized in EDTA, embedded in Epon, and processed for light and transmission electron microscopy. Substantial variation in the structure of the dentine and odontoblasts was observed within the root canals and the coronal pulp chamber. In general, odontoblasts changed from a tall, columnar morphology in the coronal pulp chamber to a more cuboidal or flattened shape near the apex, particularly towards the interradicular space. Secondary dentine formation was more pronounced along the mesial aspect of the root chamber and corresponding to the bottom of fissures. Local tertiary dentine formation was layered in the upper pulp chamber, corresponding to occlusal attrition of the cusp. In several molars a local formation of irregular tertiary dentine was observed cervically in the mesial pulp chamber. After 1 year, a distinct protrusion of irregular dentine extended into the mesiocervical pulp, apparently corresponding to a denudation of cervical root dentine. Experimental pulp-capping studies frequently use first upper rat molars with perforations made through the mesial aspect of the crown; such perforations might be close to the irregular dentine in the mesiocervical region. In conclusion, this study identifies age-associated and regional changes of pulpodentinal morphology in first upper rat molars. Therefore, evaluation of morphological alterations following vital-pulp experiments should be done in specific age groups and at specific sites in the pulp.

Periodontal microbiota and clinical periodontal status in a rural sample in southern Thailand.

We sought to determine (i) the association of subgingival bacterial profiles to clinical periodontal status in a population with limited access to dental care in Thailand, and (ii) the external validity of our earlier findings from a similar study in rural China. We examined 356 subjects, 30-39 yr old and 50-59 yr old, with respect to clinical periodontal status and subgingival plaque at maximally 14 sites per subject. Checkerboard hybridizations were used to analyse a total of 4343 samples. The prevalence of the 27 species investigated ranged between 87.2% and 100%. Discriminant analysis based on microbial profiles classified correctly 67.5% of all deep (> or = 5 mm) and 64.2% of all shallow sites, and 67.4% of all subjects with and 69.3% of all subjects without > or = 3 deep pockets. High colonization by 'red complex' bacteria was four times as likely (95% Confidence Limits (CL) 2.5-6.6) in subjects with > or = 10 sites with attachment loss of > or = 5 mm, and 4.3 times as likely (95% CL 2.6-7.1) in subjects with > or = 30 such sites. The data confirmed (i) the ubiquitous prevalence of the bacteria investigated in subjects with no regular access to dental care; and (ii) the high odds for periodontal pathology conferred by increased levels of specific periodontal bacteria.

Pulp-capping with recombinant human insulin-like growth factor I (rhIGF-I) in rat molars.

The aim of this study was to explore pulp healing and reparative dentinogenesis following pulp-capping by using recombinant human insulin-like growth factor I (rhIGF-I). Exposures were made through the mesial pulp horn in first upper molars in two-month-old Wistar rats. The pulp was covered with one dose of sterile 4% methylcellulose gel containing either 400 ng rhIGF-I or saline in contralateral controls. The exposure site was closed with sterile Teflon membrane, and the cavity was filled with IRM cement. Additional molars were capped with Dycal as controls. After 3, 7, or 28 days, animals were anesthetized and fixed by intravascular glutaraldehyde perfusion. Molars were decalcified and processed for histological analysis and cut with membrane and residual methacrylate from IRM in situ. Only specimens with acceptable pulp sealing according to blinded microscopy control were included. On day 3, identical inflammatory responses in the upper pulp were observed in molars with rhIGF-I gel or control gel. On day 7, granulation tissue ingrowth had partly replaced inflammatory infiltration in both groups. After 28 days, complete dentin bridging and tubular dentin formation were observed more frequently and closer to the test substance containing rhIGF-I. The reparative dentin response to capping with rhIGF-I was similar to that after the use of Dycal. In conclusion, microscopic control of membrane sealing in situ gives valid information on the more subtle pulp effects of growth factors. The observations suggest that pulp-capping of rat molars by means of rhIGF-I enhances reparative dentinogenesis in comparison with vehicle controls.

Ten-year incidence of dental caries in adult and elderly Chinese.

Only very few longitudinal studies on dental caries are available in adults and elderly. Therefore, the aim of the present study was to describe the patterns of lesion progression in a group of adult and elderly Chinese followed over a 10-year period of time. In 1984, 587 persons aged 20-80 years were examined and by 1994, 440 of these were still available and re-examined by the same two examiners. All restorations, periodontal conditions and dental caries were recorded for all teeth and surfaces. Only caries data are reported here. Dental caries on coronal surfaces was classified as sound, non-cavitated, cavitated without or with pulp involvement or filled. On root surfaces, lesions were classified as sound, active caries or restored. Prior to analysis of the data, a series of drop-out analyses was carried out showing that most of the drop-outs were above 60 years of age at baseline, and death of participants was the major drop-out reason. A total of 2,114 teeth were lost, 36% of which had a deep dentin lesion at baseline. The distribution of persons according to number of new lesions/restorations over 10 years was highly skewed in all age groups, the prevalence increasing with age. Molars had the highest risk of becoming carious/restored over the 10-year period, and a remarkably low proportion of teeth had the same caries diagnosis after 10 years, indicative of lesion progression. When comparing the 1984 DFT/DMFT with the figures for 1994, there were no statistically significant differences indicating that the period and cohort effects cancel out each other. There was a significant increase with age of the number of new DFT. It can be concluded that dental caries is a major health problem in contemporary adult and elderly Chinese populations, and that caries incidence increases with old age.

The effects of xylitol-containing chewing gums on dental plaque and acidogenic potential.

The aim of this study was to test the hypothesis that the chewing of xylitol- or xylitol/sorbitol-containing chewing gum reduces plaque formation and the acidogenic potential of dental plaque. Thirty healthy volunteers aged from 19 to 28 yrs were randomly allocated to one of three test groups, chewing either xylitol-, xylitol/sorbitol-, or sucrose-sweetened gums. A three-day plaque accumulation period of no oral hygiene was instituted prior to and at the termination of the chewing gum program, which lasted 33 days. Plaque quantity was assessed on the basis of protein content of individual plaque samples collected by a standardized technique. Acidogenic potential of individual baseline and test plaque samples was assessed by the quantity of various organic acids formed from D-(U-14C)glucose. Identification of extracellular and intracellular metabolites was performed by HPLC. Statistical evaluation of data was performed according to paired comparisons of individual baseline and post-chewing data. Plaque formation, acidogenic potential, and glycolytic profiles were similar at baseline and after the gum-chewing periods. Also, there was no intracellular accumulation of glycolytic metabolites within the plaque bacteria to indicate the inhibition of glycolysis. The study thus leads to the conclusion that, in young adults with low caries experience, exposure of the oral cavity to acceptable doses of xylitol or xylitol and sorbitol has no effect on the microbial deposits on the teeth.