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At least 235 records · Page 13Linked to original sources
PubMed1990

Development of the dentition in Alligator mississippiensis: upper jaw dental and craniofacial development in embryos, hatchlings, and young juveniles, with a comparison to lower jaw development.

Development of the upper dentition in Alligator mississippiensis was investigated using a close series of accurately staged and aged embryos, hatchlings, and young juveniles up to 11 days posthatching, as well as some young and old adult specimens. Studies from scanning electron microscopy, light microscopy, acetate and computer reconstructions, radiography and macroscopy were combined to elucidate the details of embryonic dental development, tooth initiation pattern, dentitional growth, and erupted functional dentition. The results were compared with those from the lower jaw and related to the development of other craniofacial structures. Approximately 17 early teeth in each jaw half develop as surface teeth, of which 13 project for 1 to 12 days before sinking into the mesenchyme. The first three teeth initiate directly from the oral epithelium at Ferguson stages 14-15 (days 15-19 after egg laying), before there is any local trace of dental lamina formation. All other teeth develop from a dental prolamina or lamina; and with progressive lamina development, submerged teeth initiate from the aboral end leading to the formation of replacement teeth. All teeth form dentin matrix, but 12 early teeth do not form enamel. Approximately 20 embryonic teeth are resorbed, 6 are transitional, and 42 function for longer periods after hatching. The embryonic tooth initiation pattern (illustrated by defining a tooth position formula) does not support the previous models of Odontostichi, Zahnreihen, and Tooth Families, each of which postulates perfect regularity. Up to three interstitial tooth positions develop between sites of primary tooth initiation, and families with up to five generations at hatching are at first arbitrarily defined.

Alligators and Crocodiles↗
PubMed2006

Developmental and evolutionary origins of the vertebrate dentition: molecular controls for spatio-temporal organisation of tooth sites in osteichthyans.

The rainbow trout (Oncorhynchus mykiss) as a developmental model surpasses both zebrafish and mouse for a more widespread distribution of teeth in the oro-pharynx as the basis for general vertebrate odontogenesis, one in which replacement is an essential requirement. Studies on the rainbow trout have led to the identification of the initial sequential appearance of teeth, through differential gene expression as a changing spatio-temporal pattern, to set in place the primary teeth of the first generation, and also to regulate the continuous production of replacement tooth families. Here we reveal gene expression data that address both the field and clone theories for patterning a polyphyodont osteichthyan dentition. These data inform how the initial pattern may be established through up-regulation at tooth loci from a broad odontogenic band. It appears that control and regulation of replacement pattern resides in the already primed dental epithelium at the sides of the predecessor tooth. A case is presented for the developmental changes that might have occurred during vertebrate evolution, for the origin of a separate successional dental lamina, by comparison with an osteichthyan tetrapod dentition (Ambystoma mexicanum). The evolutionary origins of such a permanent dental lamina are proposed to have occurred from the transient one demonstrated here in the trout. This has implications for phylogenies based on the homology of teeth as only those developed from a dental lamina. Utilising the data generated from the rainbow trout model, we propose this as a standard for comparative development and evolutionary theories of the vertebrate dentition.

Ambystoma↗
PubMed1989

[The surgical-orthodontic classification of retained and dystopic teeth of the second dentition in dysostosis cleidocranialis].

Dysostosis cleidocranialis concerns both teeth and jaw and is characterized by supernumerary teeth, dentitio tarda, tooth impaction and eventually follicular cysts. The concept of treatment can be divided in two stages: 1. At the beginning of the delayed secondary dentition (dentitio tarda) the operative removal of the supernumerary tooth germs and 2. corresponding to the belated morphological development (dentitio tarda) the operative exposure of the impacted teeth of the secondary dentition. The first operation facilitates a morphological development and especially a vertical drift without any obstacles. The second becomes necessary when only the morphological development, but not the vertical drift of the teeth of the secondary dentition takes place. The operative exposure is done using a self-developed technique [13, 18]. At the same time as the exposed teeth undergo a spontaneous vertical drift, orthopedic treatment for anomaly is started.

Adolescent↗
PubMed2003

Maxillary canine displacement and genetically determined predisposition to disturbed development of the dentition.

BACKGROUND: The relationship between maxillary canine displacement and the simultaneous occurrence of "genetically determined predisposition to disturbed development of the dentition" as defined by Hoffmeister was investigated in 675 patients. PATIENTS AND METHODS: Panoramic radiographs taken of each patient during the first and the second mixed dentition periods were evaluated. Canine inclination and the distance between the tip of the canine and a line connecting the cusps of the molars were computed in five different age groups according to Dausch-Neumann. RESULTS: Statistical analysis revealed 34 patients with "potential canine displacement", who exhibited further symptoms of "genetically determined predisposition to disturbed development of the dentition" significantly more frequently than the total group. The symptoms concerned were agenesia, displaced tooth buds, rotated or tilted incisors, aplasia and microdontia of lateral incisors. CONCLUSION: Careful follow-ups in patients with a predisposition to disturbed dental development enables risks to be anticipated and canine displacement to be detected at an early stage.

Child↗
PubMed1975

Early or late cervical traction therapy of Class II malocclusion in the mixed dentition.

It was the purpose of this investigation to evaluate the effect of cervical traction in Class II malocclusions in which treatment was started either early or late in the mixed dentition. Evaluation of the data indicated that the amount and direction of growth were of the greatest importance for effective treatment. Vertical growth appeared to be of particular importance and correlated to the anteroposterior improvement of the relationship between the maxilla and the mandible. Cervical traction, as advocated in this study, was more favorable in the early mixed dentition. A greater amount of growth and a subsequent increased reduction in the ANB angle was recorded during this period. The effect of treatment upon the maxilla, as revealed in posterior movement of the maxillary molar and the pterygomaxillary fissure, was more evident in early treatment. Great individual variability was observed, but in cases in which there was a severe discrepancy in the relationship between the maxilla and the mandible treatment in the early mixed dentition may be essential.

Cephalometry↗
PubMed1981

The effects of maxillary expansion using a quad-helix appliance during the deciduous and mixed dentitions.

Ten subjects, five in the deciduous dentition and five in the mixed dentition (mean age = 6 years 9 months), had functional posterior cross-bites successfully corrected with fixed lingual arch wire expansion appliances of the quad-helix design. The appliance, in the context of "early" treatment, produced midpalatal suture separation on each subject as evidenced on occlusal radiographs. While the relative orthopedic and orthodontic changes were not determined, the maxillary intermolar and intercanine transverse measurements showed significant increases in all subjects, with mean values of +5.3 mm. and +4.1 mm., respectively. The active phase of treatment averaged 30 days and 1.1 adjustments for the desired expansion to be achieved. Incorporating a standard 6-week retention period, the total appliance wear time had a mean value of 75 days. Following a 3-month postretention adjustment period, relapse of the intermolar and intercanine transverse dimensions presented mean decreases of -1.5 mm. and -1.9 mm., respectively. The relapse potential was successfully compensated for by overexpansion of 2 to 3 mm. during the active phase of treatment. No significant differences were demonstrated between the deciduous- and mixed-dentition groups during the course of maxillary expansion with the quad-helix appliance.

Child↗
PubMed1984

Intensive treatment of severe Class II malocclusions with a headgear-Herbst appliance in the early mixed dentition.

In the correction of large sagittal discrepancies in the relationship between the maxilla and the mandible, the orthopedic effect of treatment is often of small magnitude when compared with the dentoalveolar changes. A group of patients with severe Class II malocclusions were treated to assess the effects of a therapeutic approach which specifically took into consideration important factors such as type of anchorage, amount of force, age at start of treatment, and intensity of treatment to obtain the maximal orthopedic improvement. A special headgear-Herbst appliance was designed and short intensive treatment, lasting 5 months, was performed in the very early mixed dentition. Comparison with an untreated control group revealed the dramatic effects of treatment. The overall average change in the sagittal relationship between the maxillary and mandibular teeth was 7.5 mm after active treatment. The posteriorly directed effect on the maxilla of 3.1 mm was due to a combination of distal movement of the dentoalveolar arch and of posterior translation of the basal portion of the maxilla. The anteriorly directed effect upon the mandible of 4.4 mm was due mostly to anterior movement of the basal part of that bone, with a small part resulting from labial movement of the lower incisors. This appeared to be the result of a stimulation of growth of the mandibular condyles, a change in mandibular morphology, and an anteroinferior change in position of the condyles with a possible anterior translation of the glenoid fossa. After a 10-month posttreatment period during which an activator was used during the initial 6 months, a new comparison between the treated group and the control group was made. Growth continued to the same extent in the treated group as in the control group. However, a tendency toward relapse in overjet of 2.3 mm was observed, leading to some modifications in the treatment approach in recently started cases. A short period of interceptive orthopedic treatment in the very early mixed dentition may be indicated to correct skeletal deviations and establish a normal relationship between the maxilla and the mandible. Treatment could then be followed by a period without appliance wear until final dentoalveolar adjustments, if necessary, are made in the permanent dentition.

Activator Appliances↗
PubMed2005

Sucking habits and facial hyperdivergency as risk factors for anterior open bite in the mixed dentition.

INTRODUCTION: The aim of this study was to evaluate sucking habits and hyperdivergency as risk factors for anterior open bite in mixed-dentition subjects. METHODS: Anamnestic and pretreatment cephalometric records of 1710 mixed-dentition subjects were assessed for sucking habits, dental open bite, and facial hyperdivergency. RESULTS: The rate of anterior open bite was 17.7%. Multiple logistic regression showed that both prolonged sucking habits and hyperdivergent vertical relationships significantly increased the probability of an anterior dentoalveolar open bite, with a prevalence rate of 36.3%. This was 4 times the prevalence of sucking habits and facial hyperdivergency in subjects without anterior open bite (9.1%). CONCLUSIONS: Prolonged sucking habits and hyperdivergent facial characteristics are significant risk factors for anterior open bite in the mixed dentition.

Age Factors↗
PubMed2006

Sexual differences in Turkish dentition.

Sexual variation in the human skeleton and dentition is of great concern for both anthropologists and odontologists. Assessment of variation in dental size gives a clue about the behavior of a population, and also differences between the sexes. This study deals with sexual differences in a Turkish sample of individuals ranging in age from 20 to 29 years. The sample is composed of 28 buccolingual (BL) and mesiodistal (MD) dimensions of upper and lower dentition (I1 through M2). Dental casts of 50 males and 50 females were analyzed using discriminant function statistics. The results indicated that 8 of the upper and 7 of the lower dimensions were significantly greater in males. Many of the differences were located in the anterior teeth of both jaws. In a stepwise function applied to both arches, the lower and upper canine BL, lower canine and P1 MD, and lower I2 BL were used as the most discriminating variables. When the front teeth (i.e., I1, I2, and C) are used in separate functions, only the canine BL of the lower jaw and I2 and C BL of the upper jaw were found to have the discriminating variables. Classification accuracy was 81% for the total sample, 76% for upper front and 81% for lower front teeth. In conclusion, dentition in Turkish people seems to be less sexually dimorphic than the populations with which they were compared (Jordanians, Swedish and South Africans) as was determined by the percent of accuracy obtained. In comparison with other populations, as anticipated, Turkish dental size is closest to the Jordanian sample and farthest from the South African whites.

Adult↗
PubMed1996

Role of posterior transverse interarch discrepancy in Class II, Division 1 malocclusion during the mixed dentition phase.

Posterior transverse interarch discrepancy (PTID), measured as the difference between the maxillary and mandibular intermolar widths, was investigated in a sample of 60 Class II, Division 1 subjects during the mixed dentition phase. Two main groups were detected: Class II group 1 (30 subjects) with PTID and Class II group 2 (30 subjects) without PTID. A sample of 30 Class I subjects in the mixed dentition phase was used as a control group. In Class II group 1, PTID was found to be due to a significantly narrower maxillary arch. The craniofacial skeletal features of both Class II groups and of the Class I group were assessed. The Class II group with PTID showed mandibular retrusion associated with a posteriorly displaced mandible of normal size (functional mandibular retrusion). The Class II group without PTID had mandibular retrusion due to a micrognathic mandible (anatomic mandibular retrusion). The relevance of these findings for treatment planning in Class II, Division 1 malocclusion in the mixed dentition was stressed.

Adolescent↗
PubMed1995

Early mixed dentition treatment: postretention evaluation of stability and relapse.

Twenty-five patients who underwent early mixed dentition treatment were evaluated during the following stages: pretreatment (early mixed dentition), phase 2 (early permanent dentition), and postretention (average of 9.5 years). All patients were treated with a removable passive lingual arch. The mandibular incisors were judged to have satisfactory alignment at phase 2 evaluation and had no further orthodontic treatment. Nineteen of 25 cases (76%) demonstrated clinically satisfactory mandibular alignment postretention. Intercanine width decreased in 72% of the cases postretention and arch length decreased in 100% postretention. Intermolar width increased in 18 of 25 (72%) of the cases during treatment and remained stable in 17 of 25 (68%) of the cases. No predictors or associations could be found to help clinicians in determining the long-term prognosis of dental stability.

Adolescent↗
PubMed2000

Effect of serial extraction alone on crowding: spontaneous changes in dentition after serial extraction.

We examined changes in dentition after serial extraction in subjects who wore no appliances to determine the relationships between changes in dentition and improvement in dental crowding. Mandibular dental casts and lateral cephalograms from 31 subjects who had undergone serial extraction without orthodontic treatment were analyzed at 3 stages: before extraction of the deciduous canines (T1), after extraction of first premolars (T2), and at the end of the observation period (T3). Although movements of the first molar cusp and apex from T2 to T3 were significantly greater than from T1 to T2, movements of the incisor cusp and apex from T1 to T2 were significantly greater than from T2 to T3. The first molar tipped mesially from T1 to T2 but tipped distally from T2 to T3. The distal tipping of the incisor from T1 to T2 was significantly greater than from T2 to T3. These results suggest that the main changes in dentition from T1 to T2 are different from those from T2 to T3. The correlations between the annual change in the canine movement or tipping from T2 to T3 and the annual change in the irregularity index at the same time were significant. These results suggest that the canine movement or tipping contributed to the correction of the anterior crowding from T2 to T3.

Analysis of Variance↗
PubMed2003

Quantitative effects of a nickel-titanium palatal expander on skeletal and dental structures in the primary and mixed dentition: a preliminary study.

The present study analysed the six-month effects of a nickel-titanium (NiTi) palatal expander on the dental and palatal structures of four primary (mean age 5.8 years) and nine mixed dentition children (mean age 8.7 years), with a posterior unilateral crossbite. Standardized dental and palatal landmarks were digitized using a three-dimensional (3D) electromagnetic instrument. Collected data were analysed with geometric-mathematical models. During a six-month interval, the natural growth and development of the dental arches and hard tissue palate was negligible, as assessed in seven control children (two in the primary dentition, mean age 4.4 years; five in the mixed dentition, mean age 7.7 years). In all children the crossbite was completely corrected. Indeed, dental expansion was always more than or corresponded to the palatal expansion. A smoothing of the size-independent (shape) palatal curvature in the transverse plane was observed. No differences in maximum palatal height were noted. Symmetrical derotation of the anchorage teeth in a distal direction occurred in almost all children. The inclination of the facial axis of the clinical crown (FACC) in the anatomical transverse plane of those teeth with differences between dental and palatal expansion always showed significant modifications (vestibular inclination up to 16.7 degrees). The clinical crown height of anchorage teeth remained nearly the same in all patients. No significant modifications in mandibular arch size were observed. The increase in maxillary arch width, especially in younger children, was probably due to a combination of different effects: opening of the midpalatal suture, tipping of the alveolar process, and molar tipping.

Alveolar Process↗
PubMed1984

Occlusal forces in prosthetically restored dentitions: a methodological study.

The present paper describes a method developed to study occlusal forces in prosthetically restored dentitions. Using this method the magnitude, duration and frequency of the forces can be measured in various parts of the dentition simultaneously. The measurements are based on the use of strain gauge transducers of such dimensions that they can be mounted into artificial crowns, bridge-pontics or removable dentures, without interfering with the occlusion. The output signal of each transducer is linear for forces up to 300 N which corresponds to an amplitude (elastic deformation) of 20 microns. At least four transducers are used distributed over the tooth-arch to create bilateral and simultaneous contacts. They are mounted in a supraoccluding position of 20 microns in relation to non-transducer areas. This means that on jaw closure each transducer registers all the force transmitted to that part of the prosthetic construction represented by the transducer, provided there is no force leakage to non-transducer areas. The sum of these local forces constitutes the total force acting on the entire dentition at any given moment.

Bite Force↗
PubMed1991

Five-year follow-up study of adolescents with intact and restored dentitions: personality traits.

The personality traits of 66 of a sample of 70 adolescents aged 19-21 years were re-examined after 5 years by means of a personality inventory (KSP). A total of 15 subjects had intact dentitions (group I), while 13 subjects had had some fillings in their teeth since the first examination (group FI), and 38 subjects had restored dentitions at both examinations (group F). The findings of this study are in agreement with those of the earlier study of Kampe, Edman and Molin (1986). On both occasions the subjects with restored dentitions had higher scores on the Somatic Anxiety and Muscular Tension scales. The differences were more pronounced for the female subjects. With regard to muscular tension, there was a significant interactive effect, with higher values for the female subjects in group F. Individuals with high scores for the Clinical Dysfunction Index (DiII and DiIII) also had the highest scores on the Somatic Anxiety and Muscular Tension scales, thus confirming the validity of the muscle palpation. The hypothesis of a correlation between personality factors and dental-filling therapy was neither accepted nor rejected. The subjects in group F had the highest scores on both occasions on the Somatic Anxiety and Muscular Tension scales, although the subjects in group FI had the lowest scores. Further studies are required, and another 5-year follow-up study of this material could be conclusive.

Adolescent↗
PubMedDate not supplied

Developmental plasticity and disparity in early dipnoan (lungfish) dentitions.

Although the lungfish (Dipnoi) belong within the Osteichthyes, their dentitions are radically different from other osteichthyans. Lungfish dentitions also show a uniquely high structural disparity during the early evolution of the group, partly owing to the independent variation of odontogenic and odontoclastic processes that are tightly and stereotypically coordinated in other osteichthyans. We present a phylogenetic analysis of early lungfishes incorporating a novel approach to coding these process characters in preference to the resultant adult dental morphology. The results only partially resolve the interrelationships of Devonian dipnoans, but show that the widely discussed hypothesis of separate tooth-plated, dentine-plated, and denticulated lineages is unlikely to be true. The dipnoan status of Diabolepis is corroborated. Lungfish dentitions seem to have undergone extensive and nonparsimonious evolution during the early history of the group, but much of the resulting disparity can be explained by a modest number of evolutionary steps in the underlying developmental processes, those for dental formation (odontogenic) and those for the remodeling of dentine tissue (odontoclastic). Later in lungfish evolution, this disparity was lost as the group settled to a pattern of dental development that is just as stereotypic as, but completely different from, that of other osteichthyans.

Animals↗
PubMed1980

Aging and mastication: changes in performance and in the swallowing threshold with natural dentition.

Few comprehensive studies of oral function have been conducted on adult populations. A "Longitudinal and Cross-Sectional Study of Oral Health in Healthy Veterans" was activated at the VA Outpatient Clinic in Boston in 1969; it included general oral and dental examinations as well as tests of masticatory performance and the swallowing threshold. The current investigation involved 863 subjects from the "Dental Study" who had either their natural teeth or a fixed replacement for missing teeth. Masticatory performance as measured by the subject's ability to reduce a test portion of cut carrot by a mandatory number of chewing stroked remained constant for persons with complete or partially compromised natural dentition. Swallowing threshold performance as measured by the particle size acceptable for swallowing remained constant for persons with complete dentition. Tooth loss significantly decreased the swallowing threshold performance and increased the particle size which the subject was willing to swallow. Older subjects increased the number of chewing strokes and the time required for this test, an observation not related to performance as measured by final particle size. Only with compromised dentition, however, did this increased effort result in increased performance.

Adult↗
PubMed1994

A meta-analysis of normal ranges for root surface areas of the permanent dentition.

The typical values and normal ranges of the permanent dentition root surface areas were estimated based on a meta-analysis of 4730 root surface area measurements collected from 22 published studies between 1950 and 1992. A typical dentition root surface area, excluding 3rd molars, was 75 cm2, and 95% of the dentitions had a total root surface area somewhere between 65 cm2 and 86 cm2. The prognostic significance of particular values of root surface areas for dental treatment outcomes requires further investigation.

Analysis of Variance↗