Inferring parrotfish (Teleostei : Scaridae) pharyngeal mill function from dental morphology, wear, and microstructure

Morphology, occlusal surface topography, macrowear, and microwear features of parrotfish pharyngeal teeth were investigated to relate microstructural characteristics to the function of the pharyngeal mill using scanning electron microscopy of whole and sectioned pharyngeal jaws and teeth. Pharyngeal tooth migration is anterior in the lower jaw (fifth ceratobranchial) and posterior in the upper jaw (paired third pharyngobranchials), making the interaction of occlusal surfaces and wear-generating forces complex. The extent of wear can be used to define three regions through which teeth migrate: a region containing newly erupted teeth showing little or no wear; a midregion in which the apical enameloid is swiftly worn; and a region containing teeth with only basal enameloid remaining, which shows low to moderate wear. The shape of the occlusal surface alters as the teeth progress along the pharyngeal jaw, generating conditions that appear suited to the reduction of coral particles. It is likely that the interaction between these particles and algal cells during the process of the rendering of the former is responsible for the rupture of the latter, with the consequent liberation of cell contents from which parrotfish obtain their nutrients.

Orthodontic tooth movement in the prednisolone-treated rat

Adverse effects of corticosteroids on bone metabolism raise concerns as to whether steroid treatment may influence orthodontic movement. This study examined the effect of prednisolone on orthodontic movement using an established rat model. The corticosteroid treated group (N = 6) was administered prednisolone (1 mg/kg) daily, for a 12-day induction period; the control group (N = 6) received equivalent volumes of saline. On day 12, an orthodontic appliance was placed which exerted 30 g of mesial force to the maxillary first molar. Animals were sacrificed on day 24 and tooth movement was measured. Sagittal sections of the molars were stained with haematoxylin and eosin, and for tartrate-resistant acid phosphatase (TRAP) activity. While there were no significant differences in the magnitude of tooth movement between the 2 groups, steroid-treated rats displayed significantly less root resorption on the compression side and fewer TRAP-positive cells within the PDL space on the same side. This suggests steroid treatment suppressed elastic activity.

Dietary and nutritional aspects of tooth wear

There is a general perception that the problem of tooth wear is increasing due to elements of the modern diet and due to increased retention of dentition into older age. Tooth wear encompasses erosion, abrasion and attrition of dental tissues – these often co-exist – yet in general, erosion is of more significance to the young and attrition is of more significance to the older population. Diet plays a significant role in the aetiology of tooth wear and likewise advanced tooth wear in older age may impose dietary restrictions with consequences for dietary intake and nutritional status. There is a need to increase the awareness of the disease of tooth wear and the associated nutritional problems. At present, the aetiology of tooth wear is poorly understood – especially with respect to the role of diet. Clearer information on how best to measure and monitor the incidence and prevalence is needed in order to obtain longitudinal data on trends in tooth wear and to monitor the factors that contribute to this condition. These issues will be addressed in the following presentations: 1) What is tooth wear? Aetiology, measurement and monitoring, 2) The role of diet in the aetiology of dental erosion, 3) Groups at increased risk of tooth wear: Eating disorders, ‘dieters' sportsmen and those with impairments, 4) Tooth wear in older adults: nutritional implications. In summary this symposium seeks to: 1) increase awareness of the disease of tooth wear, and its associated nutritional problems 2) increase understanding of the aetiology of tooth wear, especially the dietary role, 3) provide information on how to measure and monitor tooth wear, 4) highlight future research requirements in the area of tooth wear and diet.

ANOMALIAS DENTAIS ASSOCIADAS ÀS AGENESIAS

O objetivo deste estudo retrospectivo foi avaliar a prevalência de anomalias de posição (irrupção ectópica de canino superior para palatino, transposição dental, distoangulação de segundos pré-molares inferiores, mesioangulação de segundo molar inferior permanente e infraoclusão de molares decíduos), de número (supranumerários) e de tamanho (microdontias) em pacientes com agenesias de dentes permanentes, comparando-as com as prevalências esperadas para a população em geral, além de testar a hipótese de que pacientes com agenesia de dentes permanentes apresentem uma prevalência aumentada de hipoplasia de esmalte. Para tanto, a amostra deste estudo foi composta por 351 pacientes, com a presença de agenesia de no mínimo um dente permanente, na faixa etária entre 8 e 30 anos e com prontuários clínicos preenchidos. A amostra foi coletada a partir do exame das documentações ortodônticas pertencentes aos arquivos de uma escola de aperfeiçoamento profissional em Ortodontia, de uma clínica radiológica odontológica e de consultórios particulares de ortodontistas. O material de estudo englobou radiografias panorâmicas e periapicais, modelos de gesso, fotografias intra e extraorais e prontuários clínicos devidamente preenchidos. Inicialmente foi analisada a reprodutibilidade das avaliações pela porcentagem de concordância utilizando Kappa, com intervalo de confiança de 95%. O teste de qui-quadrado foi utilizado para comparar as prevalências de agenesias e anomalias na amostra com as prevalências esperadas segundo a literatura científica, considerando o nível de significância de 5%. Analisou-se, ainda, o grau das associações pela razão de chances ( odds ratio ) e o respectivo intervalo de confiança de 95%. A prevalência de agenesias dentais na amostra, excluindo os terceiros molares, foi de 88,6%. Dos 351 pacientes, 128 (36,4%) apresentavam agenesia no arco maxilar, 108 (30,8%) no mandibular e 115 (32,8%) nos dois arcos. Em relação ao hemiarco maxilar esquerdo, 52,4% apresentavam agenesia, no direito 55,0%, no mandibular esquerdo 48,7% e no direito 47,3%. Das anomalias associadas avaliadas, 28,5% microdontia, 28,2% hipoplasia de esmalte, 7,4% apresentavam irrupção ectópica de canino superior por palatino, 6,6% distoangulação, 3,9% transposição de canino/pré-molar superior, 4,3% infraoclusão, 3,7 supranumerário, 3,7% mesioangulação, 0,6% transposição de incisivo/canino inferior, e, quando comparadas com a população em geral, observou que 96,1 vezes mais chance de apresentar mesioangulação do segundo molar inferior; 34,6 vezes mais chance de apresentar distoangulação; 15,9 vezes mais chance de apresentar transposição canino/pré-molar superior; 14,3 vezes mais chance de apresentar transposição de incisivo/canino inferior; 9 vezes mais chance de hipoplasia; a microdontia do incisivo lateral apresentou 8,1 vezes mais chance; 5,2 vezes mais chance de apresentar irrupção ectópica do canino superior por palatino, e, em relação à infraoclusão, apresentando uma menor chance do que a população geral. A partir dos resultados obtidos, verificou-se uma forte associação entre a agenesia de dentes permanentes, correlacionando com outras anomalias dentais importantes. Foi constatado de que pacientes com agenesia de dentes permanentes apresentam uma prevalência aumentada de hipoplasia de esmalte e de que agenesias e outras anomalias associadas apresentam-se interligadas geneticamente entre si.

Immunohistochemical expression of E-cadherin and beta-catenin in ameloblastomas and tooth germs

OBJECTIVE: The aim was to analyze the expression of E-cadherin and beta-catenin in ameloblastomas and tooth germs to determine their roles in cell differentiation processes and invasiveness compared with odontogenesis. STUDY DESIGN: Twenty-one ameloblastoma cases (16 solid and 5 unicystic tumors) and 5 tooth germs were submitted to the immunohistochemical detection of E-cadherin and beta-catenin. Immunoreactivity was evaluated using descriptive and semiquantitative analysis, investigating the location and intensity of staining. The Fisher exact test was performed, and P values of <.05 were considered to indicate statistical significance. RESULTS: There was no statistically significant difference in the expression of E-cadherin and beta-catenin between solid and unicystic ameloblastomas (P = .59; P = .63; respectively). The same was found when comparing solid and unicystic ameloblastomas with the tooth germs for both E-cadherin (P = .53; P = .44; respectively) and beta-catenin (P = .12; P = .16; respectively). Nuclear staining of beta-catenin was observed in only 4 cases (3 solid and 1 unicystic tumor). CONCLUSION: The results showed no differences in the expression of E-cadherin or beta-catenin between tooth germs and solid and unicystic ameloblastomas. The expression of these molecules seems mainly to be related to the process of cell differentiation.

Immunoexpression of integrins in ameloblastoma, adenomatoid odontogenic tumor, and human tooth germs

The expression of integrins alpha2beta1, alpha3beta1, and alpha5beta1 in 30 ameloblastomas (20 solid and 10 unicystic tumors), 12 adenomatoid odontogenic tumors (AOTs), and 5 human tooth germs in different stages of odontogenesis was analyzed. The distribution, location, pattern, and intensity of immunohistochemical expression were evaluated. Intensity was analyzed using scores (0 = absence, 1 = weak staining, and 2 = strong staining). No difference in the immunoexpression of the integrins was observed between solid and unicystic ameloblastomas. When these two ameloblastoma types were pooled into a single group, the following significant differences were found: immunoexpression of integrin alpha2beta1 was stronger in ameloblastomas than in AOTs and tooth germs, and the expression of integrin alpha5beta1 was stronger in ameloblastomas than in AOTs. The lack of detection of integrin alpha3beta1 in tooth germs and its detection in the odontogenic tumors studied suggest that this integrin might be used as a marker of neoplastic transformation in odontogenic tissues.

Immunoexpression of integrins in ameloblastoma, adenomatoid odontogenic tumor, and human tooth germs

The expression of integrins alpha2beta1, alpha3beta1, and alpha5beta1 in 30 ameloblastomas (20 solid and 10 unicystic tumors), 12 adenomatoid odontogenic tumors (AOTs), and 5 human tooth germs in different stages of odontogenesis was analyzed. The distribution, location, pattern, and intensity of immunohistochemical expression were evaluated. Intensity was analyzed using scores (0 = absence, 1 = weak staining, and 2 = strong staining). No difference in the immunoexpression of the integrins was observed between solid and unicystic ameloblastomas. When these two ameloblastoma types were pooled into a single group, the following significant differences were found: immunoexpression of integrin alpha2beta1 was stronger in ameloblastomas than in AOTs and tooth germs, and the expression of integrin alpha5beta1 was stronger in ameloblastomas than in AOTs. The lack of detection of integrin alpha3beta1 in tooth germs and its detection in the odontogenic tumors studied suggest that this integrin might be used as a marker of neoplastic transformation in odontogenic tissues.

Tooth wear in Irish teenagers: a laboratory and epidemiological study

Aim: To investigate the characteristics, development and determinants of toothwear among Irish schoolchildren. Methods: A cross-sectional (examination at 16-years-old) and longitudinal (examinations at 5-,12-,14-years) study were conducted. Two indices were used to measure toothwear, children/parents completed a demographic profile and questionnaire on oral hygiene and dietary practices, health, and lifestyle in both studies. Saliva was collected from consenting 16-year-olds. The explanatory variables for the cross-sectional and longitudinal study were derived from children/parents responses. Differences in salivary profiles were determined for subsets; the protein concentration was determined with Bradford protein assay and protein carbonyl concentration (a protein oxidation marker) was determined spectrophotometrically. Gel-electrophoresis and mass spectrometry determined proteins and ion chromatography inorganic ions. Statistical significance was accepted at p<0.05. Results: At 16-years-old the prevalence of toothwear with dentine visible was 44%. No difference in salivary flow rates existed. In unstimulated saliva a higher mean, protein carbonyl (p<0.0001) and total calcium concentration (p<0.002) existed for the group with moderate toothwear. In stimulated saliva the moderate toothwear group had a lower mean protein concentration(p<0.0001). The 2-DE protein spots prepared for a sub-group differed between those with toothwear and without. Mass spectrometry, identified one of the different proteins as IgA. For 16-year-olds, the self-reported factors indicated that brushing after breakfast was associated with lower toothwear scores(p<0.03). Nail-biting, being asthmatic or reporting a dry mouth were associated with higher toothwear scores(all p<0.05). Eating an apple daily or less was associated with less toothwear(p<0.002). In the longitudinal study toothwear into dentine at age five or 12-years was associated with more toothwear at age 14(all p<0.05). Discussion: The results illustrate the multifactorial aetiology of toothwear. The biochemical and physical correlates of saliva with toothwear requires further research. Conclusion: The impact of previous toothwear, salivary, dietary and personal factors on toothwear in the early permanent dentition is demonstrated.

Tooth replacement for partially dentate elders: a willingness-to-pay analysis

Objectives: The primary aim of this study was to investigate partially dentate elders' willingness-to-pay (WTP) for two different tooth replacement strategies: Removable Partial Dentures (RPDs) and, functionally orientated treatment according to the principles of the Shortened Dental Arch (SDA). The secondary aim was to measure the same patient groups' WTP for dental implant treatment.Methods: 55 patients who had completed a previous RCT comparing two tooth replacement strategies (RPDs (n=27) and SDA (n=28)) were recruited (Trial Registration no. ISRCTN26302774). Patients were asked to indicate their WTP for treatment to replace missing teeth in a number of hypothetical scenarios using the payment card method of contingency evaluation coupled to different costs. Data were collected on patients' social class, income levels and other social circumstances. A Mann-Whitney U Test was used to compare differences in WTP between the two treatment groups. To investigate predictive factors for WTP, multiple linear regression analyses were conducted.Results: The median age for the patient sample was 72.0 years (IQR: 71-75 years). Patients who had been provided with RPDs indicated that their WTP for this treatment strategy was significantly higher (€550; IQR: 500-650) than those patients who had received SDA treatment (€500; IQR: 450-550) (p=0.003). However patients provided with RPDs indicated that their WTP for SDA treatment (€650; IQR: 600-650) was also significantly higher than those patients who had actually received functionally orientated treatment (€550; IQR: 500-600) (p<0.001). The results indicated that both current income levels and previous treatment allocation were significantly correlated to WTP for both the RPD and the SDA groups. Patients in both treatment groups exhibited little WTP for dental implant treatment with a median value recorded which was half the market value for this treatment (€1000; IQR: 500-1000).Conclusions: Amongst this patient cohort previous treatment experience had a strong influence on WTP as did current income levels. Both treatment groups indicated a very strong WTP for simpler, functionally orientated care using adhesive fixed prostheses (SDA) over conventional RPDs. Clinical significance: Partially dentate older patients expressed a strong preference for functionally orientated tooth replacement as an alternative to conventional RPDs.