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PubMed1999

A six-week clinical efficacy study of three commercially available dentifrices for the removal of extrinsic tooth stain.

The objective of this double-blind clinical study was to compare the extrinsic tooth stain removal efficacy of three commercially available dentifrices: Colgate Platinum Whitening Toothpaste with Fluoride, Aquafresh Advanced Whitening Toothpaste with Fluoride, and Crest Regular Fluoride Toothpaste. Following a baseline examination for extrinsic tooth stain, qualifying adult male and female subjects from the Toronto, Ontario, Canada are were randomized into three treatment groups which were balanced for age, gender, tobacco habits, and level of extrinsic tooth stain using the Lobene Stain Index. Subjects were instructed to brush their teeth twice daily (morning and evening) for one minute with their assigned dentifrice using a soft-bristled toothbrush. Examinations for extrinsic tooth stain were repeated after six weeks' use of the study dentifrices. One-hundred forty-nine (149) subjects complied with the protocol and completed the entire study. At the six-week examination, subjects assigned to the Colgate Platinum treatment group exhibited statistically significant reductions (p < 0.05) from baseline level with respect to extrinsic tooth stain area (49.4% reduction) and extrinsic tooth stain intensity (52.4% reduction). Statistically significant reductions (p < 0.05) for both extrinsic tooth stain parameters were also exhibited by the subjects assigned to the Aquafresh Whitening treatment group (14.0% reduction for area, 15.5% reduction for intensity). Both tooth whitening treatments provided statistically significantly greater reductions (p < 0.05) in extrinsic tooth stain than did the Crest Regular Fluoride dentifrice, which exhibited a small increase in the extrinsic tooth stain parameters over the course of the study. Additionally, the Colgate Platinum dentifrice provided statistically significantly (p < 0.05) greater removal of extrinsic tooth stain over the course of this six-week study than did the Aquafresh Whitening dentifrice. Thus, the results of the double-blind clinical study support the conclusion that the two tooth whitening dentifrices, Colgate Platinum and Aquafresh Whitening, provide significantly greater (p < 0.05) removal of extrinsic tooth stain than does Crest Regular Fluoride, a sodium fluoride/silica dentifrice. Further, the results of the study support the conclusion that Colgate Platinum dentifrice provides a greater (p < 0.05) level of extrinsic tooth stain removal efficacy than does Aquafresh Whitening dentifrice.

Adult↗

PubMed2003

[A study of Bolton tooth-size discrepancies of malocclusion patients].

OBJECTIVE: To analysis the sum and frequencies of Bolton tooth-size discrepancies Angle Class I, II, III malocclusion patients. METHODS: Measured each tooth crown mesial-distal size between the first molar of 439 dental plaster casts of malocclusion patients and obtained the sums of six anterior tooth-size and twelve tooth-size between the first molar of upper or lower and calculated the anterior and total tooth-size discrepancies by Bolton rate standards, then statistic analyses were done. RESULTS: Patients whose sums of anterior tooth-size discrepancy were pass 1.5 mm or less than -1.5 mm was 14.02% in Angle Class I malocclusion patients and 9.49% in Class II and 19.32% in Class III. Patients whose sums of total tooth-size discrepancy were pass 1.5 mm or less than -1.5 mm was 19.63% in Angle Class I malocclusion patients and 15.33% in Class II and 20.45% in Class III. The upper sum of anterior tooth-size of Class I malocclusion patients whose sums of anterior tooth-size discrepancies were pass 1.5 mm or less than -1.5 mm was always smaller than normal and the lower sum was always larger. The sums of anterior tooth-size discrepancy of Class I, II, III and total tooth-size discrepancy of Class I were always between 1.5 mm-2.5 mm or -2.5 mm(-)-1.5 mm. Patients whose sums of anterior tooth-size discrepancy were pass 3.5 mm or less than -3.5 mm was 2.34% in Class I malocclusion patients and 0 in class II and 0 in class III. Patients whose sums of total tooth-size discrepancy were pass 3.5 mm or less than -3.5 mm was 4.21% in Class I and 1.46% in Class II and 4.54% in Class III. CONCLUSION: Tooth-size discrepancy of malocclusion patients was not the general cause of malocclusion.

Adolescent↗

PubMed1986

Tooth pulp input to the shell region of nucleus ventralis posteromedialis of the cat thalamus.

A population of neurons in the somatosensory part of the nucleus ventralis posteromedialis (VPM proper) that responded to electrical stimulation of the tooth pulp were studied in cats under urethan-chloralose anesthesia. Two classes of units responsive to electrical stimulation of the contralateral canine tooth pulp were identified. One class was responsive only to tooth pulp stimulation and these units were designated as tooth pulp specific (TPS) units. The other class of units responded to mechanical stimulation of the contralateral trigeminal integument in addition to tooth pulp stimulation. Their receptive field characteristics identified them as wide dynamic range (WDR) units responsive to tooth pulp stimulation. Both classes of units were located in the shell region of the caudal VPM proper; TPS units were coexistent with trigeminal nociceptive specific (NS) units and were found in the dorsomedial as well as ventromedial parts of the NS zone. WDR units responsive to electrical stimulation of the tooth pulp were located in the dorsomedial as well as ventromedial parts of WDR zone, a narrow band, approximately 300 micron wide, just in front of the NS zone. Tooth pulp units in the dorsomedial shell region of the VPM proper responded to the maxillary canine tooth pulp, whereas those in the ventromedial shell region responded to the mandibular canine tooth pulp. Some tooth pulp units in these two regions were responsive to stimulation of both maxillary and mandibular canine teeth. Both TPS and WDR units were antidromically excited by electrical stimulation of the SI area of the somatosensory cortex. Cooling the dorsolateral surface of the caudal medulla oblongata reversibly blocked tooth pulp evoked responses of TPS and WDR units. Trigeminal tractotomy just above the level of the obex irreversibly abolished tooth pulp-evoked responses of TPS and WDR units. These findings suggested that TPS neurons in the marginal layer of the trigeminal subnucleus caudalis and WDR neurons in the lateral part of the subnucleus reticularis dorsalis relay afferent impulses derived from the tooth pulp to the shell region of the VPM proper.

Afferent Pathways↗

PubMed2002

Mouse rudimentary diastema tooth primordia are devoid of peripheral nerve fibers.

The tooth is a well-defined peripheral target organ for trigeminal nerve fibers. However, only limited information is available regarding pioneer axon guidance to the developing tooth target field. In rodents there is a toothless diastema region between incisors and molars that in the mouse maxilla contains three rudimentary tooth anlagen. Their development stop at the early bud stage when the primary nerve axons grow towards the developing first molar tooth germs. In order to provide background information for studies of regulatory mechanisms of pioneer axon guidance to the developing tooth germs, we investigated the distribution of nerve fibers in the mouse diastema tooth buds, and compared it to the axon growth to the maxillary and mandibular first molar tooth germs by immunohistochemical localization of peripherin and PGP9.5. Analysis of serial sections showed that trigeminal nerve fibers emerging from the trigeminal maxillary and mandibular nerve trunks started to grow towards the developing molar tooth germ at the early bud stage, and subsequently they diverged into buccal and lingual branches next to the condensed dental mesenchyme. During the cap stage, nerve fibers were observed around the tooth germ in the dental follicle region. In contrast, no nerve fibers were located in the vicinity of the diastema tooth primordia at any stage studied, nor did any nerve fibers appear to grow towards this region. Our results show that the development and subsequent disappearance of the diastema tooth primordia takes place without peripheral trigeminal innervation. The diastema tooth primordia may therefore be a useful model system for future studies on molecular regulatory mechanisms of pioneer axon guidance to the tooth germs, and possibly also for evolutionary studies of peripheral axon guidance mechanisms.

Animals↗

PubMed2004

Tooth development in a scincid lizard, Chalcides viridanus (Squamata), with particular attention to enamel formation.

Comparative analysis of tooth development in the main vertebrate lineages is needed to determine the various evolutionary routes leading to current dentition in living vertebrates. We have used light, scanning and transmission electron microscopy to study tooth morphology and the main stages of tooth development in the scincid lizard, Chalcides viridanus, viz., from late embryos to 6-year-old specimens of a laboratory-bred colony, and from early initiation stages to complete differentiation and attachment, including resorption and enamel formation. In C. viridanus, all teeth of a jaw have a similar morphology but tooth shape, size and orientation change during ontogeny, with a constant number of tooth positions. Tooth morphology changes from a simple smooth cone in the late embryo to the typical adult aspect of two cusps and several ridges via successive tooth replacement at every position. First-generation teeth are initiated by interaction between the oral epithelium and subjacent mesenchyme. The dental lamina of these teeth directly branches from the basal layer of the oral epithelium. On replacement-tooth initiation, the dental lamina spreads from the enamel organ of the previous tooth. The epithelial cell population, at the dental lamina extremity and near the bone support surface, proliferates and differentiates into the enamel organ, the inner (IDE) and outer dental epithelium being separated by stellate reticulum. IDE differentiates into ameloblasts, which produce enamel matrix components. In the region facing differentiating IDE, mesenchymal cells differentiate into dental papilla and give rise to odontoblasts, which first deposit a layer of predentin matrix. The first elements of the enamel matrix are then synthesised by ameloblasts. Matrix mineralisation starts in the upper region of the tooth (dentin then enamel). Enamel maturation begins once the enamel matrix layer is complete. Concomitantly, dental matrices are deposited towards the base of the dentin cone. Maturation of the enamel matrix progresses from top to base; dentin mineralisation proceeds centripetally from the dentin-enamel junction towards the pulp cavity. Tooth attachment is pleurodont and tooth replacement occurs from the lingual side from which the dentin cone of the functional teeth is resorbed. Resorption starts from a deeper region in adults than in juveniles. Our results lead us to conclude that tooth morphogenesis and differentiation in this lizard are similar to those described for mammalian teeth. However, Tomes' processes and enamel prisms are absent.

Animals↗

PubMed2006

A numerical simulation of tooth movement by wire bending.

INTRODUCTION: In orthodontic treatment, wires are bent and attached to teeth to move them via elastic recovery. To predict how a tooth will move, the initial force system produced from the wire is calculated. However, the initial force system changes as the tooth moves and may not be used to predict the final tooth position. The purpose of this study was to develop a comprehensive mechanical, 3-dimensional, numerical model for predicting tooth movement. METHODS: Tooth movements produced by wire bending were simulated numerically. The teeth moved as a result of bone remodeling, which occurs in proportion to stress in the periodontal ligament. RESULTS: With an off-center bend, a tooth near the bending position was subjected to a large moment and tipped more noticeably than the other teeth. Also, a tooth far from the bending position moved slightly in the mesial or the distal direction. With the center V-bend, when the second molar was added as an anchor tooth, the tipping angle and the intrusion of the canine increased, and movement of the first molar was prevented. When a wire with an inverse curve of Spee was placed in the mandibular arch, the calculated tendency of vertical tooth movements was the same as the measured result. In these tooth movements, the initial force system changed as the teeth moved. Tooth movement was influenced by the size of the root surface area. CONCLUSIONS: Tooth movements produced by wire bending could be estimated. It was difficult to predict final tooth positions from the initial force system.

Alveolar Process↗

PubMed2003

Social determinants of tooth loss.

OBJECTIVES: To quantify racial and socioeconomic status (SES) disparities in oral health, as measured by tooth loss, and to determine the role of dental care use and other factors in explaining disparities. DATA SOURCES/STUDY SETTING: The Florida Dental Care Study, comprising African Americans (AAs) and non-Hispanic whites 45 years old or older who had at least one tooth. STUDY DESIGN: We used a prospective cohort design. Relevant population characteristics were grouped by predisposing, enabling, and need variables. The key outcome was tooth loss, a leading measure of a population's oral health, looked at before and after entering the dental care system. Tooth-specific data were used to increase inferential power by relating the loss of individual teeth to the disease level on those teeth. DATA COLLECTION METHODS: In-person interviews and clinical examinations were done at baseline, 24, and 48 months, with telephone interviews every 6 months. PRINCIPAL FINDINGS: African Americans and persons of lower SES reported more new dental symptoms, but were less likely to obtain dental care. When they did receive care, they were more likely to experience tooth loss and less likely to report that dentists had discussed alternative treatments with them. At the first stage of analysis, differences in disease severity and new symptoms explained tooth loss disparities. Racial and SES differences in attitudes toward tooth loss and dental care were not contributory. Because almost all tooth loss occurs by means of dental extraction, the total effects of race and SES on tooth loss were artificially minimized unless disparities in dental care use were taken into account. CONCLUSIONS: Race and SES are strong determinants of tooth loss. African Americans and lower SES persons had fewer teeth at baseline and still lost more teeth after baseline. Tooth-specific case-mix adjustment appears, statistically, to explain social disparity variation in tooth loss. However, when social disparities in dental care use are taken into account, social disparities in tooth loss that are not directly due to clinical circumstance become evident. This is because AAs and lower SES persons are more likely to receive a dental extraction once they enter the dental care system, given the same disease extent and severity. This phenomenon underscores the importance of understanding how disparities in health care use, dental insurance coverage, and service receipt contribute to disparities in health. Absent such understanding, the total effects of race and SES on health can be underestimated.

Black or African American↗

PubMedDate not supplied

Gene deployment for tooth replacement in the rainbow trout (Oncorhynchus mykiss): a developmental model for evolution of the osteichthyan dentition.

Repeated tooth initiation occurs often in nonmammalian vertebrates (polyphyodontism), recurrently linked with tooth shedding and in a definite order of succession. Regulation of this process has not been genetically defined and it is unclear if the mechanisms for constant generation of replacement teeth (secondary dentition) are similar to those used to generate the primary dentition. We have therefore examined the expression pattern of a sub-set of genes, implicated in tooth initiation in mouse, in relation to replacement tooth production in an osteichthyan fish (Oncorhynchus mykiss). Two epithelial genes pitx2, shh and one mesenchymal bmp4 were analyzed at selected stages of development for O. mykiss. pitx2 expression is upregulated in the basal outer dental epithelium (ODE) of the predecessor tooth and before cell enlargement, on the postero-lingual side only. This coincides with the site for replacement tooth production identifying a region responsible for further tooth generation. This corresponds with the expression of pitx2 at focal spots in the basal oral epithelium during initial (first generation) tooth formation but is now sub-epithelial in position and associated with the dental epithelium of each predecessor tooth. Co-incidental expression of bmp4 and aggregation of the mesenchymal cells identifies the epithelial-mesenchymal interactions and marks initiation of the dental papilla. These together suggest a role in tooth site regulation by pitx2 together with bmp4. Conversely, the expression of shh is confined to the inner dental epithelium during the initiation of the first teeth and is lacking from the ODE in the predecessor teeth, at sites identified as those for replacement tooth initiation. Importantly, these genes expressed during replacement tooth initiation can be used as markers for the sites of "set-aside cells," the committed odontogenic cells both epithelial and mesenchymal, which together can give rise to further generations of teeth. This information may show how initial pattern formation is translated into secondary tooth replacement patterns, as a general mechanism for patterning the vertebrate dentition. Replacement of the marginal sets of teeth serves as a basis for discussion of the evolutionary significance, as these dentate bones (dentary, premaxilla, maxilla) form the restricted arcades of oral teeth in many crown-group gnathostomes, including members of the tetrapod stem group.

Animals↗

PubMed2004

Prevalence of self-assessed tooth discolouration in the United Kingdom.

AIMS: To determine the prevalence of perceived tooth discolouration in the United Kingdom and to investigate socio-demographic variations and satisfaction with own tooth colour. METHODS: A national cross-sectional questionnaire study was carried out using a multistage random probability sample. Assessment of people's perceptions of their own tooth colour was conducted by asking study participants to match colour to the closest of a set of photocards demonstrating different levels of tooth discolouration. A separate question asked how satisfied they were with their tooth colour. Information on socio-demographic characteristics of the population were gathered at the same time. ANALYSIS: Data was coded and entered into SPSS software. Descriptive statistics were used to determine the prevalence of perceived discolouration and satisfaction with own tooth colour. Bivariate and regression analyses were performed to explore the effect of socio-demographic variations. RESULTS: The self-assessment exercise was completed for 3215 subjects. Half of the study population perceived their tooth colour to be normal and 6% perceived that they had severe discolouration, the remainder reported themselves to have levels of tooth discolouration between these two extremes. Satisfaction with tooth colour decreased with increased discolouration. Sex, age, income and smoking, had statistically significant effects on the prevalence of perceived discolouration (P< 0.01). CONCLUSIONS: Half of the people in this study perceived themselves to have tooth discolouration. Results suggest that the general public is concerned about dental appearance in terms of tooth colour, indicated by public dissatisfaction with relatively mildly discoloured teeth. Findings may suggest that a further increase in the demand of tooth whitening services and cosmetic dentistry in general is likely. The changing emphasis and level of perceived dissatisfaction need to be taken into account in planning dental services. Evidence based approaches are needed for the appropriate management of patients who demand treatment of mild discolouration.

Adolescent↗

PubMed1996

Prognosis versus actual outcome. III. The effectiveness of clinical parameters in accurately predicting tooth survival.

Tooth loss for 100 treated periodontal patients (2,509 teeth) under maintenance care was evaluated to determine the effectiveness of commonly taught clinical parameters utilized in the assignment of prognosis in accurately predicting tooth survival. Previous studies in this series evaluated prognosis as a surrogate variable representing the condition of the tooth at a particular point. In this study, survival analysis was used to evaluate the relationship of these common clinical parameters to an actual end point, tooth loss. Robust log rank tests indicated that initial probing depth, initial furcation involvement, initial mobility, initial crown-to-root ratio, and initial root form were all associated with tooth loss. In addition, smoking and increased initial bone loss were both found to be associated with increased risk of tooth loss while fixed abutment status was associated with a decreased risk of tooth loss. A Cox proportional hazards regression model showed that initial probing depth, initial furcation involvement, initial mobility, initial percent bone loss, presence of a parafunctional habit without a biteguard, and smoking were all associated with an increased risk of tooth loss. This model suggests that patients are twice as likely to loose their teeth if there is increasing mobility, if they have a parafunctional habit and do not wear a biteguard, or if they smoke. From these data there does appear to be a relationship between the assigned prognosis and tooth loss. Teeth with worse prognosis have a worse survival rate, but the commonly taught clinical parameters used in the traditional method of assignment of prognosis do not adequately explain that relationship. Furthermore, initial prognosis did not adequately explain the condition of the tooth or accurately predict the tooth's survival. These results seem to indicate that the effect of these clinical parameters on tooth survival is only partially reflected in the assigned prognosis initially, suggesting that perhaps some of the clinical parameters should be weighed more heavily than others when assigning prognosis. Further studies are needed to develop a more accurate method for the assignment of prognosis.

Alveolar Bone Loss↗

PubMed2000

[Influence of occlusal contacts on tooth displacement].

During function, the tooth displacement path depends on occlusal contacts of the upper and lower teeth. Therefore, we must reconstruct occlusal relation carefully so as not to disturb physiological tooth displacement. In this investigation, tooth displacements were measured with the Displacement Transducer type M-3 in varying occlusal contact. The following conclusions were obtained. 1. The location of occlusal contacts influenced the tooth displacement of the upper first molar. Especially, an occlusal contact on the lingual inclination of the lingual cusp, buccal cusp had great influence. The tooth showed displacement toward the buccal direction, and it differed from the physiological tooth displacement path during clenching at the intercuspal position. 2. The location of occlusal contacts had little influence on the tooth displacement of the lower first molar. The tooth showed displacement toward the lingual direction. It was similar to the physiological tooth displacement. 3. On the upper first molar, the location of occlusal force influenced the Stress-Strain curve. Especially, the occlusal force on the buccal cusp had great influence on the amount of tooth displacement. 4. On the lower first molar, the location of occlusal force influenced the Stress-Strain curve. Especially, the occlusal force on the lingual cusp brought much displacement and a 2-phase displacement path, at times. Therefore, occlusal contacts have close relation to tooth displacement, and any occlusal reconstruction should harmonize with tooth displacement representing periodontal tissue distortion.

Adult↗

PubMed1989

[A case of a so-called congenital tooth appeared in maxilla].

The congenital teeth are not only classified by Massler et al. as a natal tooth that has erupted at birth and a neonatal tooth that erupts at neonatal period, but also divided into a normal deciduous tooth and a supernumerary tooth. The congenital teeth are mostly found in the mandibular anterior region, but extremely rare in other regions. The authors met a rare case, that had a so-called congenital tooth in the maxillary anterior region, which was a supernumerary and fused tooth. The case was a boy patient, 4 months of age, who visited the pedodontic clinic, of Ohu University Dental Hospital, with the complaint of ruber and swelling of the maxillary anterior gum pad, October 17th in 1986. By oral inspection of the dental radiogram and his past history, the authors found a odontoid material in the swelled gum pad and diagnosed it as a so-called congenital and supernumerary tooth. The tooth was extracted. The extracted tooth was investigated histopathologically. It had the v-shaped incisula at the middle of its edge, and seemed as if two teeth had coalesced. The serial preparations by the labio-lingual section showed no partition, such cementum as to divide the enamel, the dentin and the pulp near the incisula. Therefore it was diagnosed as fused tooth correctly. In the labial surface of the root formed about a third root length, the thickness of the cellular cementum was observed. It was considered as a physiological reaction to no support of the alveolar bone and to the excess mobility of the tooth. The prognosis after its extraction was good, and all normal deciduous incisors appeared in his mouth, 7 month later.

Fused Teeth↗

PubMed2000

Reiterative signaling and patterning during mammalian tooth morphogenesis.

Mammalian dentition consists of teeth that develop as discrete organs. From anterior to posterior, the dentition is divided into regions of incisor, canine, premolar and molar tooth types. Particularly teeth in the molar region are very diverse in shape. The development of individual teeth involves epithelial-mesenchymal interactions that are mediated by signals shared with other organs. Parts of the molecular details of signaling networks have been established, particularly in the signal families BMP, FGF, Hh and Wnt, mostly by the analysis of gene expression and signaling responses in knockout mice with arrested tooth development. Recent evidence suggests that largely the same signaling cascade is used reiteratively throughout tooth development. The successional determination of tooth region, tooth type, tooth crown base and individual cusps involves signals that regulate tissue growth and differentiation. Tooth type appears to be determined by epithelial signals and to involve differential activation of homeobox genes in the mesenchyme. This differential signaling could have allowed the evolutionary divergence of tooth shapes among the four tooth types. The advancing tooth morphogenesis is punctuated by transient signaling centers in the epithelium corresponding to the initiation of tooth buds, tooth crowns and individual cusps. The latter two signaling centers, the primary enamel knot and the secondary enamel knot, have been well characterized and are thought to direct the differential growth and subsequent folding of the dental epithelium. Several members of the FGF signal family have been implicated in the control of cell proliferation around the non-dividing enamel knots. Spatiotemporal induction of the secondary enamel knots determines the cusp patterns of individual teeth and is likely to involve repeated activation and inhibition of signaling as suggested for patterning of other epithelial organs.

Animals↗

PubMed2006

Prevalence of single-tooth gaps in a population-based study and the potential for dental implants--data from the Study of Health in Pomerania (SHIP-0).

INTRODUCTION: The aim of this study was to show the prevalence of single-tooth gaps in a population-based study. MATERIAL AND METHODS: The data of 3989 subjects (20-74 years of age) were taken from the Study of Health in Pomerania (SHIP-0) and classified by age, gender, and level of education. A single-tooth gap was defined as a gap of one tooth missing bordered by one or more natural teeth on either side. RESULTS: The tooth missing most in all age groups was the first molar. There were more single-tooth gaps in the maxilla than in the mandible. The lowest single-tooth gaps were found in the mandibular anterior region (<1.1%). There were no significant differences in gender (p > 0.05). The highest frequency of single-tooth gaps among all groups was found in subjects with a medium level of education and the lowest frequency was found in subjects with a high level of education. One single-tooth gap was found in 25%, whereas 16% of all subjects had 2 single-tooth gaps. The prevalence of having 1 single-tooth gap was between 3.8% and 13.1% whereas it was less than 0.5% for subjects with 5 and more single-tooth gaps. CONCLUSION: There was a high potential for dental implants to fill single tooth gaps.

Adult↗

PubMed1987

The relationships of Uronemus: a carboniferous dipnoan with highly modified tooth plates.

Previous accounts of the dentition of the Carboniferous dipnoan Uronemus have stressed the significance of the scattered small denticles. These, together with the marginal teeth and ridges, have been interpreted as primitive characters of the dipnoan dentition shared with three other genera: the Devonian Uranlophus and Griphognathus and the Carboniferous to Permian Conchopoma. Genera with tooth plates have been considered to be a monophyletic group in which tooth plates are a derived character; Uronemus has been excluded from this group in all previous investigations dealing with the significance of the dentition for determining relationships among dipnoans. The macromorphology of the dentition of Uronemus has been re-examined and correlated with the histology of all the dental tissues. Optical study of thin sections and scanning electron microscope study of the adjacent cut surfaces has shown that the hard, wear-resistant dentine of the teeth and ridges is petrodentine. The arrangement, growth, wear and histology of the dental tissues have been compared with those of denticulated and tooth-plated genera. The arrangement of new teeth relative to the tooth ridge, the pattern of wear along the ridge, and the type of dentine and its growth indicate that the dentition of Uronemus is best interpreted as a tooth plate with one long lingual tooth ridge and reduced lateral tooth rows. Therefore the marginal tooth ridges are not considered to be homologous with those of denticulate dipnoans such as Uranolophus. The presence of petrodentine, a tissue type only found in forms with tooth plates, is consistent with the view that the dentition is derived by modification of a radiate tooth plate. The denticles covering restricted regions of the palate and lower jaw are considered to have been a secondary acquisition. The suggestion that Conchopoma is a close relative of Uronemus is not accepted, and possible new relationships have been proposed. New data on Scaumenacia and Phaneropleuron, two other genera previously compared with Uronemus, are presented. Rhinodipterus, a form with elongate lingual ridges, is also discussed. Phaneropleuron is shown to have radiate tooth plates and not a marginal row of conical teeth as previously described. It is proposed that the tooth plate of Uronemus is derived from a dipterid type of plate. A discussion of some of the other factors involved in determining the relationships of the genus is given.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2002

Tooth structure removal associated with various preparation designs for posterior teeth.

The amount of tooth structure removed for various innovative and conventional preparation designs for fixed prosthodontics was quantified. Four Typodont resin teeth representing maxillary and mandibular premolars and molars were prepared in various abutment designs: adhesive, box (A2); adhesive, wing and groove (A3); mesioocclusal or distoocclusal inlay; mesio-occlusodistal inlay (13); mesio-occlusodistal onlay; partial crown; half crown (only molars); complete crown, 0.8-mm circumferential tapered chamfer (F1); complete crown, 1.0-mm circumferential rounded shoulder; and complete crown, 1.4-mm axial reduction facial shoulder, 0.7-mm lingual chamfer (F3). After tooth preparation (10 per group), the root was separated from the anatomic crown at the cementoenamel junction. Removal of tooth structure was measured by gravimetric analysis in a high-precision balance. Preparations A3 and F3 were assigned as abutments for metal-supported restorations, whereas all other preparations were used for all-ceramic restorations. When the mean structure removal of all teeth tested was compared, the adhesive and inlay abutments were the least invasive preparation designs, ranging from approximately 5.5% (A2) to 27.2% (13) tooth structure removal. Complete crowns required the most invasive preparations, ranging from 67.5% (F1) to 75.6% (F3) tooth structure removal. The tooth structure removal required for F3 retainers was almost 14 times greater than for an A2 preparation. Tooth structure removal was also influenced by the morphology of the tooth. The first comprehensive tooth preparation design classification system was introduced. The measurement system used in this study provides an accurate method of quantifying tooth structure removal for fixed prosthodontic preparations. The innovative preparation designs studied conserved significant amounts of tooth structure, yielding a better prognosis for the restored tooth.

Bicuspid↗

PubMed2005

Lifestyle and psychosocial factors associated with tooth loss in Mexican adolescents and young adults.

OBJECTIVE: The aim of the present study was to examine: (1) the prevalence of tooth loss in persons living in community dwellings and (2) the strength of the association identified between tooth loss experience and the psychosocial factors of lifestyle, stress, and anxiety. MATERIAL AND METHODS: A cross-sectional study was carried out in a convenience sample where data were collected by means of self-administered questionnaires of lifestyle and psychosocial factors (stress and anxiety) and a clinical examination. A total of 516 subjects aged 14-30 years of age were included in the study. Subjects had a visual dental examination. Prevalence and mean of tooth loss were calculated excluding third molars, and their related factors were adjusted in a binary logistic regression. RESULTS: Mean age of participants was 17.4+/-3.0 years; 45.5% were men. The prevalence of tooth loss (when at least one tooth was lost) was 20.5%. Among the 516 persons, a total of 201 teeth were lost with a mean tooth loss 0.39+/-0.95 overall. Mean tooth loss in subjects with at least one missing tooth was 1.90+/-1.26 teeth. Results adjusted by anxiety in the multivariate logistic regression model showed tooth loss was associated with lifestyle (OR=1.95, 95% CI=1.17 - 3.24), age (OR=2.65, 95% CI=1.64 - 4.26), and Angle's malocclusion II and III (OR=2.86; 95% CI=1.67 - 4.90). A slight association toward tooth loss was observed (p<0.10) in the sex and stress variables. CONCLUSIONS: Lifestyle and tooth loss have a substantial association. According to age group, these results suggest tooth loss is an oral health problem in the study population.

Adolescent↗

PubMed1990

[Influence on the movement of a complete denture caused by differences in artificial tooth materials].

An experiment using modal analysis was used to ascertain the activity of complete dentures and artificial teeth. Three types of artificial teeth were used: a porcelain tooth, a resin tooth and a hard resin tooth. Animation and displacement values were used as criteria in determining the influence that differences in tooth materials had on the activity of the complete denture. The experiment was conducted to act as an aid in denture design and the following results were obtained: 1. The resonance frequency for the different test materials ranged from mode 4 to mode 7. 2. Regarding displacement value, a value of 1 micron or more was obtained in the 1 octave bandwidth for the 250 Hz band, 500 Hz band and the 1 kHz band. Among these, maximum displacement for the upper complete denture was as follows: When a porcelain tooth was used and a vibration of 1 for mode 1 (197 Hz) was applied, the value for the 3 cusp tip was 39.48 microns and that for the labial denture border side was 43.35 microns. As for the lower complete denture, when a porcelain tooth was used and 5 oscillation was applied for mode 1 (309 Hz), the value for the 3 cusp tip was 68.38 microns and that for the rear part of the denture border was 139.2 microns. 3. Regarding the activity of the complete denture in the 250 Hz and 1 kHz bands, when a porcelain tooth was used, a curve mode was observed for the upper complete denture in the labiolingual direction with the cervical line as the border. When the resin tooth and hard resin tooth were used, it was difficult to recognize any change with the cervical line as the border. It was also difficult to recognize a change at the cervical section for the lower complete denture. 4. As for the 500 Hz band, when a porcelain tooth and a resin tooth were used, there were frequencies (300 Hz-400 Hz) at which twisting in a labiolingual direction at the cervical section was recognized for the upper complete denture as well as frequencies (400 Hz-600 Hz) where this was not recognized. A rigid body mode was recognized when the hard resin tooth was used. In addition, differences in the location for applying for vibration had an influence on the activity of the lower complete denture.

Acrylic Resins↗