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PubMed2001

Differential expression of decorin and biglycan genes during mouse tooth development.

Small leucine-rich proteoglycans (SLRPs) have a number of biological functions and some of them are thought to regulate collagen mineralizaton in bone and tooth. We have previously identified and immunolocalized two members of the SLRPs family, decorin and biglycan, in bovine tooth/periodontium. To investigate their potential roles in tooth development, we examined the mRNA expression patterns of decorin, biglycan and type I collagen in newborn (day 19) mice tooth germs by in situ hybridization. At this developmental stage, the first maxillary and mandibular molars include stages before and after secretion of the predentin matrix, respectively. The expression of decorin mRNA coincided with that of type I collagen mRNA and was mostly observed in secretory odontoblasts, while the biglycan mRNA was expressed throughout the tooth germ, including pre-secretory odontoblasts/ameloblasts, dental papilla and stellate reticulum. However, its signal in secretory odontoblasts was not as evident as that of decorin. In mandibular incisors, where a significant amount of predentin matrix and a small amount of enamel matrix were already secreted, a similar differential expression pattern was observed. In secretory ameloblasts the biglycan mRNA expression was apparent, while that of decorin was not. These differential expression patterns suggest the distinct roles of biglycan and decorin in the process of tooth development.

Animals↗

PubMed1993

Radiological evaluation of marginal bone loss at tooth surfaces facing single Brånemark implants.

A radiologic evaluation of marginal bone loss around single implants ad modum Brånemark and their adjacent teeth was performed: 58 adults with 71 fixtures were followed up to 3 years after crown installation. The following factors were considered: age, cause of tooth loss, vertical relation between fixture and teeth, distance between adjacent teeth, distance between fixture and natural tooth, jaw region. Specified distance were measured as well as marginal bone levels around fixtures and tooth surfaces in magnified standardized intraoral radiographs. The results show a loss of marginal bone support at tooth surfaces adjacent to inserted implants during the interval between preoperative examination and crown installation that exceeds the loss during subsequent years. The largest bone loss was observed when implants were placed next to lateral upper incisors. A strong correlation was found between bone loss at adjacent teeth and the horizontal distance fixture-tooth. With decreasing distance the bone loss increased, especially in the upper incisor region. At present it seems difficult to predict which individual or individual condition may have a higher risk for bone loss, due to large intra- and interindividual variation.

Adult↗

PubMed2001

Video instruction to establish a panel of experts to compare tooth cleaning by 4 electric toothbrushes.

BACKGROUND AND AIMS: Laboratory robots can reveal differences in the cleaning of artificial tooth surfaces by different electric toothbrushes. The primary aim of this study was to establish, through video instruction, a panel of experts in tooth cleaning with an oscillating rotating electric toothbrush in an attempt to mimic the highly reproducible laboratory robot. A secondary aim was to use the "expert" panel, in an attempt to distinguish between tooth cleaning efficacy of 4 head/model combinations of the oscillating rotating electric brush. METHOD: A 24-subject panel, after video training and home habituation for up to 12 weeks with the basic model of electric brush, participated in a single examiner blind, 4-cell, randomised, cross-over study balanced for residual effects. In each period, subjects suspended tooth cleaning for 4 days. Plaque was then scored by area before and after tooth brushing for 2 min in tandem with the instructional video with the allocated brush head/model combination. RESULTS: Differences between subjects was significant, but overall plaque removal with all brushes was of the order of 85% with one subject achieving >97% plaque removal. There were significant differences between the brushes with the oscillating rotating brush with the faster head movement, in most analyses, significantly more effective than the slower oscillating rotating brush with 2 head combinations. The faster oscillating rotating brush was also significantly more effective than the most recently introduced oscillating rotating reciprocating model. CONCLUSIONS: Previous studies have shown that single uses of watch-and-follow video instruction significantly improve toothcleaning with electric toothbrushes. The present study shows that extended training using these videos results in almost complete plaque removal even when prebrushing plaque levels have been enhanced by a 4-day period of no oral hygiene. Furthermore, the establishment of an "expert" panel can distinguish between brushes of different cleaning efficiencies. However, given the level of achievement of all panel members with all brushes, the absolute differences observed are of doubtful clinical significance for gingival health. Finally, the slightly-reduced plaque removal by the 3 directional head action brush can be explained by the inability within the present protocol to habituate the subjects in its use.

Adolescent↗

PubMed1999

The relationship between water fluoridation and socioeconomic deprivation on tooth decay in 5-year-old children.

AIM: To examine the relationship between water fluoridation, socioeconomic deprivation and tooth decay in 5-year-olds. SETTING: 10,004 children: 1,051 in naturally fluoridated Hartlepool in 1991/92, 3,816 in fluoridated Newcastle & North Tyneside and 5,137 in non-fluoridated Salford & Trafford in 1993/94. OUTCOME MEASURES: Correlations between mean electoral ward dmft and ward Townsend Scores from the 1991 census. RESULTS: Regardless of the level of water fluoridation significant correlations were found between deprivation and tooth decay. Multiple linear regression models for dmft showed a statistically significant interaction between ward Townsend score, and both types of water fluoridation, confirming the more deprived the area the greater the reduction in tooth decay. At a Townsend score of zero (the English average) there was a predicted 43% reduction in decay in 5-year-olds in fluoridated areas. CONCLUSIONS: Tooth decay is strongly associated with social deprivation. The findings confirm that the implementation of water fluoridation has halved tooth decay in 5-year-old children and that the dental caries divide between rich and poor is reduced.

Child, Preschool↗

PubMed1999

Analysis of a restored maxillary second premolar tooth by using three-dimensional finite element method.

In the first part of this study some physical properties of restorative materials, amalgam, glass-ionomer and composite resin were measured experimentally. In the second part a numerical study was carried out, for which the maxillary second premolar tooth was used. The tooth model was restored with composite resin and amalgam on glass-ionomer, which was used as the base material. The stress distribution investigated was the resultant of the stresses which come from the mastication force and those resulting from the contraction and expansion of restorative materials. All calculations were carried out using the finite element method and programs were written using FORTRAN 77. A load of 450 N, at an angle of 45 degrees to the longitudinal axis was applied on the occlusal margin of the tooth. The tooth was assumed isotropic, homogenous, elastic and unsymmetrical. The distribution of compressive, tensile and shear stresses were plotted for the whole tooth structure.

Bicuspid↗

PubMed2003

Tooth contacts at the mandibular retruded position, influence of operator's skill on bite registration.

Occlusal conditions at the retruded contact position (RCP) have been thought to be among the aetiological factors for temporomandibular disorders. However, the role of these occlusal factors still remain unclear. The purpose of a series of studies was to investigate the locations of RCP contacts and to discuss their implication by the authors. In the study reported here, the influence of the operator's skill on bite registration was surveyed. Eighty-six dental students were selected as subjects. One specialist in prosthetic dentistry moved the subject's mandible up and down while guiding it gently backward until it rotated on its retruded axis. Once the initial tooth contacts were established, the operator checked them by using a thin articulating paper (direct method). On the other hand, six younger operators following precise instruction from the specialist about the technique of jaw guidance examined each of the subjects for location of RCP contacts using the indirect method. Silicone-based impression material was used for bite registration while the subject kept the jaw at this contact position (indirect method). Wilcoxon signed rank test was applied to evaluate differences between the expert operator and six younger operators regarding locations of RCP contacts. Results from the expert operator (direct method) showed that tooth contact at the first premolar was most frequently observed and the number of subjects who possessed unilateral tooth contacts was more than that with bilateral tooth contacts. On the other hand, in the case of the indirect method performed by younger operators, tooth contact patterns significantly differed from those of the direct method.

Adult↗

PubMed2002

Tooth agenesis and craniofacial morphology in an orthodontic population.

Previous reports have produced conflicting conclusions regarding the relationship among tooth agenesis, the congenital absence of teeth, and variations in craniofacial morphology. Traditional cephalometric assessment and computer-assisted morphometric analysis of jaw size were used to reexamine this relationship in a white orthodontic population. A positive diagnosis of tooth agenesis (including third molar determination) was made in 89 subjects of mixed age and sex who previously had orthodontic treatment but who were not determined to have a recognized syndrome or a craniofacial anomaly. Cephalograms for these subjects were compared with control data from subjects reported in Bolton Standards of Dentofacial Developmental Growth. Missing teeth and their locations were correlated with changes in selected linear and angular measurements of the Bolton cephalometric analysis. Area measurements of the jaw size of the subjects grouped by age were compared with Bolton cephalometric templates. Relatively little correlation was found between missing teeth and changes in cephalometric measurements. Where identified, a decreased maxillary jaw size and maxillary tooth agenesis were generally associated. Two-dimensional area measurements showed that most age groups had significant decreases in maxillary jaw size associated with tooth agenesis. Relatively few groups had significant changes in mandibular size associated with tooth agenesis.

Adolescent↗

PubMed2000

Sweet Tooth, a novel receptor protein-tyrosine kinase with C-type lectin-like extracellular domains.

A gene encoding a novel type of receptor protein-tyrosine kinase was identified in Hydra vulgaris. The extracellular portion of this receptor (which we have named Sweet Tooth) contains four C-type lectin-like domains (CTLDs). Comparison of the sequences of these domains with the sequences of the carbohydrate recognition domains of various vertebrate C-type lectins shows that Sweet Tooth CTLD1 and CTLD4 have amino acids in common with those shown to be involved in carbohydrate binding by the lectins. Comparison of sequences encoding CTLD1 from the Sweet Tooth genes from different species of Hydra shows variation in some of the conserved residues that participate in carbohydrate binding in C-type lectins. The Sweet Tooth gene is expressed widely in the Hydra polyp, and expression is particularly high in the endoderm of the tentacles. Treatment of polyps with peptides corresponding to sequences in the Sweet Tooth CTLDs results in the disintegration of the animal. These same peptides do not block adhesion or morphogenesis of Hydra cell aggregates.

Amino Acid Sequence↗

PubMed2000

Genetic basis of tooth development and dental defects.

Tooth development is under strict genetic control, and during recent years an increasing number of genes have been identified that are involved in the regulation of tooth morphogenesis. One of the organs in which development is now beginning to be understood at the gene level, the tooth is an example of a typical vertebrate organ starting as an epithelial bud and undergoing complex morphogenesis, regulated by interactions between epithelial and mesenchymal tissue layers. It has become evident that developmental regulatory genes have been conserved to a high degree during evolution and that similar gene networks regulate the development of teeth as of other vertebrate organs. So far, all genes that have been linked with early tooth morphogenesis have developmental regulatory functions in other organs, too. The majority of these genes are associated with the signaling pathways transmitting interactions between cells and tissues. They include genes encoding the actual signals as well as their receptors, mediators of signaling in the cytoplasm and transcription factors regulating gene expression in the nucleus. Deletion of the function of many of these genes in transgenic mice results in arrested tooth development, but all these mutants also show defects in many other tissues. Mutations in several of these genes in humans have been identified as causes of dental defects, mainly hypodontia.

Animals↗

PubMed2004

Mutations in AXIN2 cause familial tooth agenesis and predispose to colorectal cancer.

Wnt signaling regulates embryonic pattern formation and morphogenesis of most organs. Aberrations of regulation of Wnt signaling may lead to cancer. Here, we have used positional cloning to identify the causative mutation in a Finnish family in which severe permanent tooth agenesis (oligodontia) and colorectal neoplasia segregate with dominant inheritance. Eleven members of the family lacked at least eight permanent teeth, two of whom developed only three permanent teeth. Colorectal cancer or precancerous lesions of variable types were found in eight of the patients with oligodontia. We show that oligodontia and predisposition to cancer are caused by a nonsense mutation, Arg656Stop, in the Wnt-signaling regulator AXIN2. In addition, we identified a de novo frameshift mutation 1994-1995insG in AXIN2 in an unrelated young patient with severe tooth agenesis. Both mutations are expected to activate Wnt signaling. The results provide the first evidence of the importance of Wnt signaling for the development of dentition in humans and suggest that an intricate control of Wnt-signal activity is necessary for normal tooth development, since both inhibition and stimulation of Wnt signaling may lead to tooth agenesis. Our findings introduce a new gene for hereditary colorectal cancer and suggest that tooth agenesis may be an indicator of cancer susceptibility.

Anodontia↗

PubMed2003

Orthodontic treatment outcome: the relationship between anterior dental relations and anterior inter-arch tooth size discrepancy.

OBJECTIVE: This study investigated the pre- (T1) and post-treatment (T2) relationship between anterior (canine to canine inclusive) inter-arch tooth size ratio and various dental and skeletal variables. DESIGN: Retrospective longitudinal clinical study. SETTING: Swedish Health Board Clinic 2000. SUBJECTS: Random selection of T1 and T2 orthodontic records of 137 Swedish patients (56 male and 81 female). The sample included non-extraction (77), and four premolar extraction (60) cases across a range of dental and skeletal malrelationships. MAIN OUTCOME MEASURES: Dental cast and lateral cephalogram measurements were recorded. Exploratory modelling investigated whether a significant relationship existed between the anterior inter-arch tooth size ratio and these measurements. RESULTS: Data was normally distributed with no statistically significant differences between males and females (P = 0.88) and extraction and non-extraction (P = 0.52) treatment modalities with respect to the anterior ratio. T1 bivariate regression analysis failed to show a relationship (p < 0.05) between variables. T2 bivariate analysis showed a statistically significant relation between three variables and anterior tooth size ratio. Multiple regression analysis led to a final model where maxillary inter-canine width (P = 0.002) and upper arch crowding (0.001) were statistically significantly related to the anterior inter-arch ratio. The coefficient of determination was however uniformly low (R(2) < 0.2) for all variables. CONCLUSION: The anterior inter-arch tooth size ratio was not associated with any common pre- or post-treatment variables in the population studied, therefore measurement of an anterior tooth size ratio pre-treatment was not clinically beneficial for determining anterior dental relations post-treatment.

Adolescent↗

PubMed1999

Tooth pulp- and facial hair mechanoreceptor-evoked responses of trigeminal sensory neurons are attenuated during ketamine anesthesia.

BACKGROUND: Evidence exists that ketamine, administered systemically using a dose required for inducing a state of anesthesia, may antagonize nociceptive but not innocuous input to lumbar dorsal horn neurons. However, it is unclear whether ketamine exerts this selective action on sensory inputs to trigeminal sensory neurons. The current study was undertaken to compare the responses evoked in trigeminal sensory neurons by electrical stimuli applied to the tooth pulp versus air-puff stimuli applied to facial hair mechanoreceptors (FHMs) during quiet wakefulness versus ketamine anesthesia. METHODS: Accordingly, responses of rostral trigeminal sensory nuclear complex (TSNC) and trigeminothalamic tract neurons evoked by tooth pulp (a source of small-diameter fiber input) and FHMs (a source of larger-diameter fiber input) were recorded extracellularly from chronically instrumented cats before, during, and after recovery from the anesthetic state induced by a single (2.2 mg/kg) intravenous injection of ketamine. RESULTS: Overall, tooth pulp-evoked responses of TSNC neurons were maximally suppressed by 50% within 5 min after the intravenous administration of ketamine. Ketamine also suppressed the FHM-evoked responses of TSNC and trigeminothalamic neurons by 45%. The time course of ketamine's suppressive action was equivalent for tooth pulp- and FHM-evoked responses. However, the recovery of tooth pulp-evoked TSNC neuronal responses at suprathreshold intensities was markedly prolonged compared with neuronal responses driven by threshold stimuli or FHM. CONCLUSIONS: These electrophysiologic results in the chronically instrumented cat preparation indicate that a nonselective suppression of orofacial somatosensory information occurs during ketamine anesthesia. The prolonged recovery of suprathreshold responses of TSNC neurons mediated by small-diameter afferent fiber input may partly underlie the analgesic action of ketamine that is clinically relevant at subanesthetic doses.

Anesthetics, Dissociative↗

PubMed1999

Combining single- and double-tooth osteotomies with traditional orthognathic surgery.

Combining large-segment orthognathic surgery and unitooth or small-segment surgery is an effective approach to deal with a wide range of dentofacial deformities that have minor to severe occlusal problems. The indications for combining single- or double-tooth osteotomies with traditional orthognathic surgery were patients with dentofacial deformities and malocclusion requiring stable correction within a short overall treatment period. From 1991 to 1998, a total of 36 patients underwent combination single- or double-tooth-segment osteotomy with traditional orthognathic procedures performed at Chang Gung Memorial Hospital. The indications for surgery were maxillary protrusion (N = 5), bimaxillary protrusion (N = 19), mandibular prognathism with maxillary protrusion (N = 11), and noncleft maxillary retrusion (N = 1). The types of osteotomies performed were the Le Fort I, the anterior segmental osteotomies of the maxilla or the mandible, the palatal split, and the posterior segment in combination with single-tooth or double-tooth segments. Follow-up ranged from 12 months to 6 years and showed stability in the movements with no complications. There was no loss of any "osteotomized" segment. The average overall treatment time was approximately 18 months--5 months preoperative and 13 months postoperative orthodontic treatment. This was at least 6 months shorter in duration compared with traditional orthognathic surgery. Combining traditional orthognathic surgery with single- or double-tooth segments allows us to treat complex dentofacial deformities in the vertical, transverse, and sagittal dimensions with differential repositioning of all segments, either major or minor, simultaneously. The authors' experience with 36 consecutive patients evidence good results and demonstrate the procedure to be safe with minimal complications.

Adolescent↗

PubMed2005

Reproducibility of lateral excursive tooth contact in a semi-adjustable articulator depending on the type of lateral guidance.

The purposes of this study were (i) to compare the reproducibility of lateral tooth contacts of casts mounted in a semi-adjustable articulator when condylar guidance was set by different methods and (ii) to assess the margin of error of the variations of condylar guidance without changing lateral tooth contacts, depending on the type of lateral guidance. In subjects with different types of lateral guidance, intraoral lateral tooth contacts identified with occlusal registration strips were compared with those identified by use of a semi-adjustable articulator, setting the condylar guidance in four different ways: using protrusive wax wafers, by axiography and by adding and subtracting 5 degrees from the value of condylar guidance obtained by protrusive wax wafers. Tolerance to variations of condylar guidance without changing lateral tooth contacts was determined by increasing and decreasing the value of condylar guidance until lateral tooth contacts changed. Different ways of setting condylar guidance on a semi-adjustable articulator give rise to different values of condylar guidance in the same subject. The occlusal repercussions of these variations of condylar guidance values depend on the type of lateral guidance. Canine protection had the greatest tolerance to variations in the setting of condylar guidance without changing lateral occlusal contacts.

Adolescent↗

PubMed2004

Inability to relate tooth forms to face shape and gender.

This study aimed to examine whether there exists a gender-dependent correlation between the inverted face shape and that of the upper central incisor as the literature often suggests. Standardized portraits and anterior tooth photographs of 204 dental students were made. Standardized enlargements of facial outlines and of the upper right incisor outlines were traced. They were classified into three different shapes: tapered, ovoid and square-shaped. Ten dentists determined twice - with an intervening interval of 3 wk - the gender of the students on the basis of the anterior tooth photographs. Tooth and face shapes could be classified as tapered (25% and 27%, respectively), ovoid (39% and 41%, respectively) or square-shaped (36% and 32%, respectively). A significant correlation could be shown between face shape and gender, but not between tooth shape and gender. The dentists were correct about the gender of the subjects in 47 to 59% of all cases. The reproducibility of their judgments varied between 54% and 77%. The theory that the tooth shape should correspond to the inverted facial shape could therefore not be confirmed. In addition it could be shown that the participants were not capable of determining a subject's gender from intraoral photographs alone.

Adult↗

PubMed2006

A numeric code for identifying patterns of human tooth agenesis: a new approach.

Human tooth agenesis involves the absence of one or more teeth and often refers to a genetic or a developmental disorder. Identifying whether certain patterns of tooth agenesis are more prevalent than others may prove valuable for treatment planning, as well as for genetic research into its etiology and development. In the present article a method is described where unique values are assigned to patterns of tooth agenesis. Using the idea of binary arithmetic, the absence or presence of teeth are represented by 1 and 0, and translated into corresponding unique values, the Tooth Agenesis Code (TAC). This procedure has an advantage over existing methods in that it allows for easier data analysis. The method described in this article can advance genetic research towards the etiology of tooth agenesis, allows researchers to communicate unequivocally the phenotypes of their studied cases and it can be used in other areas of oral pathology that also require pattern recognition.

Algorithms↗

PubMed2005

Cytoskeleton and surface structures of cells directly attached to the tooth in the rat junctional epithelium.

OBJECTIVE: It is still an open question whether cells directly attached to the tooth (DAT) cells are migratory or non-migratory cells. The purpose of this study was to examine cytoskeletal and surface structures of DAT cells that might be involved in migration. METHODS: We investigated the distribution of stress fibers composed of actin filaments in DAT cells using phallacidin fluorescent dye methods in a confocal laser scanning microscope. To observe the three-dimensional structure of the DAT cell surface, the osmium maceration scanning electron microscope (SEM) method, which removes various soluble materials between DAT cells and the enamel, was employed. RESULTS: Stress fibers were found in the most apically located DAT cells, and were arranged in parallel to the presumable cervical-line, whereas some of the fibers ran parallel to the tooth axis in the more coronally located DAT cells. The parallel arrangement to the tooth axis of the fibers may be involved with migration for turnover, and the parallel accumulation to the presumable cervical-line may be concerned with the cervical contraction of DAT cells. Osmium maceration SEM images at high magnification revealed the existence of microvilli-like structures on the enamel surfaces (facing to the tooth surface) of DAT cells after removal of the soluble matrices. The thicknesses of the microvilli-like structures on the enamel surfaces and cell processes of intercellular bridges were significantly different. CONCLUSION: DAT cells possess stress fibers arranged in parallel to the tooth axis and to the presumable cervical-line in the cytoplasm, and microvilli-like structures on their enamel surfaces. These results suggest that these structures contribute to DAT cell migration.

Animals↗

PubMed1987

Development of the nervus terminalis in mammals including toothed whales and humans.

The early ontogenesis and topography of the mammalian terminalis system was investigated in 43 microslide series of toothed whale and human embryos and fetuses. In early embryonal stages the development of the nasal pit, the olfacto-terminalis placode, and the olfactory bulb anlage is rather similar in toothed whales and humans. However, toothed whales do not show any trace of the vomeronasalis complex. In early fetal stages the olfactory bulb anlage in toothed whales is reduced and leaves the isolated future terminalis ganglion (ganglia) which contains the greatest number of cells within Mammalia. The ganglion is connected with the nasal mucosa via peripheral fiber bundles and with the telencephalon via central terminalis rootlets. The functional implications of the terminalis system in mammals and its evolution in toothed whales are discussed. Obviously, the autonomic component has been enlarged in the course of perfect adaptation to an aquatic environment.

Animals↗