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PubMed1990

Effects of nicotine on murine incisor development.

The effects of daily injections of nicotine sulfate on incisor development in CD-I mice were studied. Pregnant animals, injected with 0.1% nicotine sulfate at a dose of 1.67 mg/kg body weight from the 6th to the 15th day of gestation, were sacrificed on the 18th postcoital day. The 130 nicotine treated fetuses, as well as the 348 control fetuses were embedded in paraffin and sectioned in the frontal plane. The developing incisors of the experimental fetuses were retarded, less differentiated, and reduced in breadth and length. The developing incisors of the control fetuses were in the early appositional stage of odontogenesis, whereas those of the experimental population were either in the late cap or early bell stage, depending on the presence or absence of palatal cleft, which occurred in 9.6% of the fetuses.

Ameloblasts↗
PubMed1990

[Control of the incisor axis in the vestibulo-lingual direction using an original titanium-molybdenum alloy arch].

In order to restore the vestibulo-lingual orientation of the incisor axis while controlling the position of the crowns, the author suggests using a simple original arch, compatible with any of the multi-clip technics used by orthodontists. This arch is made of Titanium-Molybdenum Alloy and presents the distinctive feature of being specially shaped, on the ribbon side, so as to be introduced edgewise. Practical ease, efficiency in obtaining large amplitude, precisely controlled movements, as well as accurate measurement of torque make of this instrument a practical tool for controlling the incisor axis in the vestibulo-lingual orientation, and for improving the I/i angle warranteeing the stability of the results. This arch can be used both in monodisciplinary and multidisciplinary orthodontics, more particularly in surgical-orthodontic management of retrognathia combined with traumatic supraclusion of incisors or with linguoversions of central upper teeth.

Adolescent↗
PubMed1990

Effects of inflammatory periodontal disease ('broken mouth') on the mobility of the sheep incisor.

Loads directed linguolabially and between 0.01 N and 0.2 N were applied to a mandibular central incisor in each of 12 four-year-old ewes with evidence of inflammatory periodontal disease ('broken mouth'). For every incisor, tooth position was monitored continuously with an ultrasonic displacement transducer. Each load chosen was suddenly applied and then maintained for five minutes, producing a biphasic, viscoelastic-like response (a phase of rapid displacement being followed by a more gradual phase of creep). A similar biphasic recovery response was seen on suddenly removing the load. Comparing the findings with those obtained in a previous study for incisors in healthy dentitions, there was a considerable increase in mobility with inflammatory periodontal disease. Surprisingly, however, the patterns of the responses did not differ. The reason for the change in the amount of mobility may be related simply to the quantity of the tooth supporting tissues which is lost, although there is some evidence that qualitative changes occurring in these tissues may also be important.

Animals↗
PubMed1990

[Lead and cadmium content in deciduous incisors of children from Duisburg and Gummersbach--developing trend 1976-1988].

Shed deciduous teeth (incisors only) were collected from children (n = 199) living in Duisburg and Gummersbach (F.R.G.) in 1976 and 1988. The teeth were analysed for lead and cadmium. Considering all teeth, there was a significant of tooth lead and tooth cadmium from 1976 to 1988. The reduction was between -40 and -50% for tooth lead and -45% for tooth cadmium. Regarding tooth lead, the reduction was more pronounced in children from Duisburg, an area heavily polluted by lead and other heavy metals due to the presence of large iron and steel plants and a large lead-/zinc smelter. Teeth from the upper jaw were found to have higher lead and calcium concentrations than teeth from the lower jaw. Moreover, it was found that central incisors had higher lead and cadmium concentrations than lateral incisors. Even after the effects of jaw and tooth type had been allowed for, the reduction of tooth lead and tooth cadmium could be demonstrated. Children living in pre-war houses were found to have higher tooth lead and tooth cadmium levels than children living in post-war houses. The higher lead and cadmium burden of children living in old houses seems to be related to a higher degree of exposure to lead and cadmium via drinking water resulting from the release of these metals from old zinc-plated steel water pipes. In total, our results indicate that there has been a significant decrease of lead and cadmium exposure in West-German children since the mid-70s. The reduction of tooth lead levels parallels the decrease of blood and bone lead levels, which has been observed in previous studies.

Cadmium↗
PubMed1989

[Histological studies on the controlled eruption to the rabbit lower incisor].

In order to investigate the mechanism of eruption, the rabbit lower incisors under the influence of controlled eruption were examined. The first experiment was carried out by repeated resection of the incisal edges of both upper and lower incisors so that the rate of eruption was accelerated. The second experiment was to crown the incisors for the purpose of inhibiting the eruption. In the control group, the periodontal ligament was made up of three layers. Fibers of the inner layer were continuous to the Sharpey's fibers of the cementum, and those of the outer layer were to the alveolar bone. Fibers of the middle layer ran parallel to the tooth axis. In the repeated resection group, the distance between the root end and the bottom of socket was increased, indicating the extrusion of the tooth took place. The odontogenic tissue showed increased frequency of mitosis, and the formative end of the enamel as well as the cementum shifted cervically. The eruption rate measured by the movement of metal bead embedded in the dentin, demonstrated that the rate was increased about 2 times in the repeated resection group, while the rate of growth measured by the Tetracycline method remained 1.6 times of the control group. This discrepancy was supposed to be due to the extrusion of the tooth. In case of the crowing group, the opposite was observed; the rate of eruption was reduced to about a third. Whereas the rate of growth to about a half, probably due to the intrusion of the tooth. In the crowing group, the distance between the root end and the bottom of socket was reduced, resulting the resorption of the bone tissue, and the root became sinuous, particularly at the labial side. In the lingual side, mitotic figures of the odontogenic tissue were rarely observed. The middle layer of the periodontal ligament increased in breadth in the repeated resection group, while it reduced in breadth in the crowing group. Indicating the middle layer plays an important part to the mechanism of eruption.

Animals↗
PubMed1989

[Histological study on root resorption of upper permanent incisor].

In the permanent tooth, physiological root resorption does not occur, but inflammatory resorption occurs due to the orthodontic force, ectopic eruption of neighboring tooth and others. In this study, the morphological and histological investigation of the root resorption of the upper permanent incisors caused by the ectopic eruption of the canine was carried out. The left central incisor and lateral incisor from a 12-year-old female were examined. The roots were resorbed almost completely, and in part the resorption extended into the enamel. The results were as follows: 1. In the resorbed dentine, two types of resorption lacuna were observed. One was in direct contact with resorption tissue and the other was repaired with cementum-like tissue. 2. In the resorption lacuna, no odontoclast was recognized. 3. The pulp tissue was normal and the internal resorption was not seen. 4. On the wall of the root canal connected with root resorption, a large amount of hard tissue was formed, and on the external surface of the root, secondary cementum was formed on the primary cementum. 5. Under the scanning electron microscope, the clear dentine tubules in the resorption lacuna, the shallow, unclear resorption lacuna with deposition of the hard tissue and the various steps between them were observed.

Child↗
PubMedDate not supplied

[Lower incisor extraction in orthodontic treatment].

Lower incisor extraction in orthodontic treatment was rare. Precise diagnosis and treatment planning should be done to achieve good occlusion and facial esthetics. Criteria for lower incisor extraction included degree of crowding, tooth size discrepancy, pathologic condition, vertical overbite, sagittal incisal relationship, skeletal growth pattern and age of the patient. This article comprised case reports of three Thai patients, all demonstrating the criteria for lower incisor extraction in orthodontic treatment. With comprehensive analysis, diagnosis and treatment planning, treatment results were satisfactory.

Adolescent↗
PubMed1989

[Deciduous incisors with a serrated edge].

In contrast to the opinion accepted in the literature also the edge of the milk incisors can be triple indented. Among 619 milk incisors, examined on infants, 68 were indented, approximately 11%. Within the group of milk incisors most frequently the lower one is indented edge, in about 16%.

Child↗
PubMed1988

Formation of the tooth enamel rod pattern and the cytoskeletal organization in secretory ameloblasts of the rat incisor.

The localization of actin, myosin, tropomyosin, alpha-actinin, vinculin, and desmoplakin I/II was visualized by immunofluorescence microscopy. Antibodies against myosin, tropomyosin, and alpha-actinin and rhodamine-phalloidin labeled strongly the proximal and distal terminal webs which ultrastructurally consist of dense microfilament bundles. In the distal terminal web, the staining by these reagents occurred mostly perpendicular to the long axis of the incisor. Antivinculin stained the general area where the distal terminal web is located in the ameloblast. Anti-desmoplakin I/II labeled the junctional area associated with the proximal and distal terminal webs. The anti-desmoplakin staining was stronger along the cell border perpendicular to the long axis of the incisor. Comparison of the rhodamine-phalloidin staining pattern of the distal terminal web and the enamel secretion pattern by ameloblasts revealed that a change in the distal terminal web staining pattern preceded a change in the secretion pattern. These observations suggest that the cytoskeletal organization in the ameloblast is involved in the formation of the enamel matrix pattern in the rat incisor.

Actins↗
PubMedDate not supplied

The lingual (root analogue) and the labial (crown analogue) mouse incisor dentin promotes ameloblast differentiation.

Previous studies have suggested that mouse molar ameloblast differentiation was triggered by the predentin-dentin. Knowing that enamel is absent on the lingual surface of the mouse incisor, the aim of this study was to compare in heterotopic tissue recombinations the behavior of mouse molar inner dental epithelium associated with lingual or labial mouse incisor dentin. It was shown that root-analogue and crown-analogue incisor dentin promotes ameloblast differentiation of competent molar inner dental epithelium.

Ameloblasts↗
PubMedDate not supplied

Fractured permanent incisors among Nigerian school children.

An epidemiological survey was conducted on 2,979 Nigerian school children to assess the prevalence of fractured incisors. Of this 10- to 17-year-old group, 14.17 percent had one or more fractured incisors, with the maxillary central incisor the tooth most frequently involved in trauma.

Adolescent↗
PubMed1986

Response of the rat incisor dental tissues to penetration of the labial alveolar bone in preparation of a surgical window.

The orderly formation of rod and interrod enamel containing precisely-oriented hydroxyapatite crystallites requires a high degree of cellular cooperation. This work examines the susceptibility and response of the rat incisor enamel organ and enamel to mechanically-induced trauma. Such trauma is induced by drilling through the labial alveolar bone of the rat incisor in preparation of a surgical window for a micro-injection technique (McKee and Warshawsky, 1984). The drilling ruptures the enamel organ and removes the underlying enamel. Various experiments indicate that the enamel lesion is a result of aspiration by the rotating bur. The histology of the enamel lesion is described. Several morphological changes which may indicate attempted repair are noted as the lesion moves incisally with time due to the eruption of the tooth. It is concluded that the rat incisor enamel organ is an extremely sensitive cellular system, that if sufficiently disturbed is not capable of restablishing the cellular relations necessary to produce a new enamel layer.

Alveolar Process↗
PubMedDate not supplied

Traumatically injured primary incisors: a clinical and histological study.

World-wide epidemiological studies state that from 8 percent to 30 percent of children up to 7 years of age sustain injury to primary incisors, including crown fracture, root fracture, tooth avulsion, and dental displacement, which result in malformation of permanent incisors depending upon their state of development. In this study, traumatized primary incisors were evaluated clinically and radiographically, with the following data recorded: exact or approximate time-interval of traumatic episode(s) and extraction, mobility, color change, sensitivity to percussion/palpation, swelling, sinus tract, caries, crown/root fracture, periodontal/periapical lesions, external/internal root resorption, mineralization, and obturation. Based upon the local damage and developmental age, 138 teeth were extracted, fixed in 10 percent formalin, and processed for histological evaluation according to routine methodology. Histologic findings were: the presence of varying extent of necrosis, bacteria in the area of necrosis--not in all cases--neutrophilic leukocytes, chronic inflammatory cells, pulpal calcifications, resorption/apposition, and circulatory changes. The blood pigment distinguished hemorrhage due to extraction from pathologic circulatory changes. All the described reactions varied in intensity and extent with the time interval and the assumed force of the original trauma. Physical trauma to primary teeth caused pulpal damage, which could involve periapical tissue, depending on the extent of the initial damage.

Child↗
PubMed1987

A laboratory method for studying tooth mobility of the mandibular central incisor of the sheep.

Linguolabially directed loads of 0.01 to 1.0 N were applied to a mandibular central incisor in each of 12 four-year-old ewes with healthy mouths. For each incisor, tooth position was monitored continuously with an ultrasonic displacement transducer. On suddenly applying a load and maintaining it for five minutes, a biphasic pattern of displacement was recorded, a phase of rapid displacement being followed by a more gradual one. A similar biphasic recovery response was seen on suddenly removing the load. These patterns are viscoelastic-like. The group mean displacements showed that for all phases the responses were force-dependent, though not linearly graded. For a given load, the group mean displacements were considerably larger than those reported previously for the teeth of other animals, supporting the impression that the sheep incisor is extremely mobile. These data will provide a baseline for studies on the mobility of the teeth of sheep with inflammatory periodontal disease ('broken mouth').

Animals↗
PubMed1985

Effects of pulp removal and organ culture on adult rat incisor odontoblasts.

The morphological integrity of adult rat incisor odontoblasts was studied to determine the effects of pulp removal and subsequent incubation. From each pair of maxillary incisors one was left intact while the pulp from the other one was removed. Both series were incubated in BGJb medium according to the Trowell method. Morphometrical measurements of the thickness of the odontoblast layer and the size and shape of the odontoblast nuclei were performed on photomicrographs of transverse sections of the incisors. After pulp removal the odontoblasts seemed disorganized and their nuclei were darker and more rounded. During incubation the odontoblasts did not recover from the effect of this pulp removal and degenerative changes were frequently seen. In the culture of the complete tooth organ the morphological integrity of the odontoblasts was much better preserved. Therefore the organ culture of intact teeth seems more favourable.

Animals↗
PubMed1985

[Management of incisor supraclusion].

The orthopaedic treatment of incisor supraclusion is possible by ingression of the superior incisors under both following conditions: the ingression to be obtained should not be superior to 8 mm, and there is a strong assumption that restitution of normal labial and lingual functions will be simultaneously obtained and especially a good labial competence in function and at rest. Dr Burstone's technique of incisor ingression uses an appliance operating only on the superior dental arch with light and constant forces which can be precisely adjusted. F.E.O. is only exceptionally required for maintenance of the posterior fixation.

Adolescent↗
PubMed1985

Autoradiographic study of iron transport in rat incisor enamel.

An autoradiographic study using 55Fe was performed to investigate the distribution of iron in the ameloblasts and enamel of rat incisors. The study of methodological problems of 55Fe autoradiography revealed that in the undecalcified sections, the radiation by 55Fe within the ameloblasts and pigmented enamel produced grain scattering over the facing enamel surface and ameloblasts, respectively. The findings indicate that the autoradiographic observation of the enamel surface should be made using the incisors freed from the enamel organ and that the observation of the ameloblasts should be done in the region other than the zone of enamel pigmentation. After the 55Fe injection, 55Fe incorporation into the ameloblasts was observed in the maturation stage, reaching the maximum at 24 hours. The peak of 55Fe distribution in the ameloblasts moved from the early stage to the later stage of maturation between 24 hours and 7 days after the injection. At 3 and 7 days after the 55Fe injection, 55Fe was deposited markedly on the enamel surface at the end of maturation where the enamel pigmentation occurs. The present study established the utility of 55Fe autoradiography when applied on the undecalcified section of rat incisors and it was demonstrated that iron is incorporated into the maturation ameloblasts and secreted onto the enamel surface at the end of maturation.

Ameloblasts↗
PubMed1984

Regional ultrastructural and cytochemical comparisons of the epithelial-mesenchymal interface during rat incisor development.

A major theme in understanding epithelial-mesenchymal interactions during development focuses upon regional mesenchyme specification of epithelial differentiation. One particularly useful epidermal organ system for studying this issue is the rodent continuously growing and erupting incisor tooth organ. One advantage of this particular system resides in the regional features of the rodent incisor tooth organ. Along the labial surface, inner dental epithelial cells differentiate into ameloblasts that produce enamel extracellular matrix, whereas the epithelia along the lingual surface do not become ameloblasts and do not produce enamel matrix. This study has been designed to compare ultrastructural features of labial versus lingual surfaces, with particular emphasis upon mesenchymal cell shape, the orientation of extracellular matrix collagen, the basal lamina, and the distribution of sulfated glycoconjugates. Critical analyses of the data indicated that different microenvironments exist between epithelia and mesenchyme in the labial versus the lingual surfaces of the developing rodent incisor tooth organ.

Animals↗