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PubMed2002

The influx of serum albumin to enamel matrix in rat incisors after trauma.

The most frequent results of trauma to tooth germs are enamel hypoplasia and enamel hypocalcification. These differing results may be due to the stage of amelogenesis at which trauma occurs. The cellular and biomolecullar events involved in the genesis of these defects are poorly understood. We hypothesized that one factor involved is the possibility that relatively high levels of serum albumin enter the enamel matrix through the damaged enamel organ, and impair mineralization of the matrix. The present study was undertaken to immunohistochemically and autoradiographically localize serum albumin in the enamel organs of rat incisors after trauma was inflicted to the mandibular incisor region of 4-day-old rats. Hemorrhage was seen surrounding the enamel organ and between the detached secretory-stage ameloblasts. One day after trauma, the most intense immunohistochemical (IHC) staining for albumin was localized in the outer layer of the enamel matrix adjacent to the detached secretory-stage ameloblasts. Albumin was also detected autoradiographically in the secretory-stage ameloblasts layer and enamel matrix. These findings indicate that serum albumin can leak between the detached ameloblasts and penetrate the enamel matrix after trauma. Leaked albumin was still present in the matrix during the maturation stage. Leaked albumin in the developing enamel could inhibit crystal growth and result in hypocalcification.

Ameloblasts↗
PubMed1998

Parathyroid hormone (1-34) receptor-binding and second-messenger response in rat incisor odontoblasts.

Even though indirect evidence indicates that PTH exerts an anabolic effect on dentinogenesis, the existence of PTH receptors and any second-messenger response in odontoblasts have not been demonstrated. The aim of this study was to investigate whether rat incisor odontoblasts express PTH receptors, and to identify which second messenger pathway the hormone may activate. Odontoblasts were dissected from rat incisors. Amino-terminal (1-34) fragment rat PTH [rPTH(1-34)] conjugated to fluorescein isothiocyanate visualized receptor sites on the cell surface. Upon incubation of odontoblasts with rPTH(1-34), cAMP formation was increased. However, no fluctuations in intracellular calcium activity were observed upon rPTH(1-34) stimulation when using Fura-2 as a Ca2+ probe. In long-time incubations, stimulation with PTH(1-34) upregulated APase activity. The results demonstrate that rPTH(1-34) evokes an anabolic response in dentinogenically active odontoblasts, and that this may be mediated through the protein kinase A/cAMP pathway, whereas no indications for Ca2+ as a second messenger were evident.

Alkaline Phosphatase↗
PubMed1998

Solitary maxillary central incisor and congenital nasal pyriform aperture stenosis.

UNLABELLED: Solitary maxillary central incisor (SMCI) and congenital nasal pyriform aperture stenosis (CNPAS) have been reported as an isolated morphogenic defect or associated with pituitary deficiency, holoprosencephaly, ocular coloboma, or chromosomal abnormalities. We report two cases and analyse 40 cases of SMCI and 24 cases of CNPAS, including 15 cases of combined SMCI and CNPAS, obtained from the literature. Of the patients with SMCI, 69% had short stature, 48% growth hormone deficiency or hypopituitarism, 23% pituitary absence or hypoplasia, and 17% had del (18p-) or r(18). Of the patients with CNPAS, 63% had SMCI, 75% were short, 43% had hypopituitarism or growth hormone deficiency, 36% had pituitary or CNS anomaly, and 33% had del (18p), r(18), or del (13q). CONCLUSIONS: Solitary maxillary central incisor and congenital nasal pyriform aperture stenosis can be a diagnostic clue to pituitary hypofunction, CNS, ophthalmological and cytogenic anomalies.

Abnormalities, Multiple↗
PubMed1996

Morphological study of amelogenesis in the rat lower incisor after thyro-parathyroidectomy, parathyroidectomy and thyroidectomy.

The effects of thyro-parathyroidectomy, parathyroidectomy or thyroidectomy upon enamel formation in the rat incisor were studied. One control group and four groups of surgically treated rats were used: parathyroid autotransplanted, thyroidectomized, parathyroidectomized, and thyro-parathyroidectomized. One month after surgery, the incisors were processed for light and electron microscopy. The present study revealed perturbations of the Tomes process morphology, of the rod pattern in the inner enamel formation, of the enamel surface, and of the mineralization after thyro-parathyroidectomy. After parathyroidectomy, only mineralization defects could be visualised. No effects were observed in enamel after thyroidectomy. A severe hypocalcemic state as seen in thyro-parathyroidectomized rats affects the enamel shape, and mineralization, and the morphology and function of secretory ameloblasts. Knowledge of the way in which the alteration of the enamel surface is produced should contribute to a better understanding of the development of tooth enamel.

Ameloblasts↗
PubMed1996

Immunohistochemical localization of carbonic anhydrase isozyme II in rat incisor epithelial cells at various stages of amelogenesis.

Carbonic anhydrase II (CAII) was purified from erythrocytes of male Sprague-Dawley rats, and its localization in rat maxillary incisor epithelial cells at various stages of amelogenesis was studied by means of immunoperoxidase staining using a rat CAII-specific monoclonal antibody. In the most apical portion of the incisor, some CAII immunoreactivity was localized in the outer or inner dental epithelium near the apical loop (i.e., the multiple layer of the outer dental epithelium and the posterior portion of ameloblasts facing the pulp). Immunoreactivity disappeared largely during the presecretory and secretory stages. CAII immunoreactivity appeared suddenly in ameloblasts during the transitional stage between enamel secretion and maturation. Immunoreactivity became intense in both ameloblasts and papillary cells during enamel maturation; the intracellular distribution of CAII was in the cytosol. The CAII signal in these cells was constant until the end of the maturation stage. These findings support the notion that the ameloblasts and papillary cells change into ion transport epithelial cells from the secretory to the maturation stage and that CAII in these cells plays an important role in the regulation of pH.

Amelogenesis↗
PubMed1998

Expression and localization of laminin-5 subunits in the mouse incisor.

Laminin-5 is associated with several epithelial tissues and forms part of the anchoring filaments of hemidesmosomes. Recent data have shown that the expression of laminin-5 subunits is impaired in junctional epidermolysis bullosa (JEB), and, in these patients, enamel hypoplasia is commonly observed. Rodent incisors are continuously growing teeth with an asymmetry between their labial and lingual sides. Enamel matrix formation is restricted to the labial side. We have analyzed the changes in the expression and localization of laminin-5 subunits (alpha3, beta3, and gamma2) in lower incisors of the mouse. The apical loop located at the end of the labial side contained stem cells and showed expression for all laminin-5 subunits. In the anterior direction, the inner dental epithelial cells (IDE) transiently lost the immunoreactivity for all subunits, whereas the transcripts for the beta3 subunit remained in the IDE. All subunit mRNAs and proteins were expressed in ameloblasts facing predentine and also in secretory and maturation stage ameloblasts. Enamel matrix contained laminin-5. On the lingual side, the expression of laminin-5 subunits was continuous from the epithelial root sheath to the epithelial rests of Malassez in the periodontal ligament. These results suggest that spatial and temporal regulation of laminin-5 subunits correlates with the histogenesis of the dental organ, ameloblast differentiation, and enamel formation and also that laminin-5 plays a role in the adhesion between dental epithelial cells and the extracellular matrix (enamel or dentine) in areas where the dental basement membrane is absent.

Amelogenesis↗
PubMed2006

The MMP activity in developing rat molar roots and incisors demonstrated by in situ zymography.

Matrix metalloproteinases (MMPs) have been expressed during root development and periodontal tissue formation, whereas it is not known if these MMP molecules are enzymatically active to degrade the extracellular matrices (ECMs). The present study was designed to investigate the gelatinolytic and collagenolytic activity in rat molar root and incisor development. Three-week old rat mandibles were frozen and cut without fixation or decalcification and processed for in situ zymography using substrates gelatin and collagen. The enzymatic activity was assessed according to the intensity of fluorescence due to the lysis of the substrates. Odontoblasts, predentin, cementum, bone and the enamel matrix showed the high activity. The present study demonstrated MMP activity in calcified tissues using in situ zymography for the first time and the possible involvement of the MMP activity in molar root and incisor development and periodontal tissue formation.

Animals↗
PubMed1977

Lower incisor extraction in orthodontic treatment.

The extraction of a single mandibular incisor can be employed as a compromise treatment of certain malocclusions, if the end result fulfills the requirements for a healthier dentition which is functionally and esthetically harmonized in relation to the surrounding structures. Indications, contraindications, and the procedure of treatment have been presented. Class I malocclusions with normal maxillary dentition and good buccal interdigitation in which there is severe lower anterior crowding are the best cases for this procedure, provided that the lower anterior arch length deficiency is greater than 4 to 5 mm. and the anterior tooth ratio is more than 83 mm. In conditions exhibiting a deep overbite pattern, reduction of the mandibular anterior unit should be avoided. Furthermore, I do not regard mandibular incisor extraction as a routine orthodontic procedure but, instead, consider it to be an almost last resort measure since it involves the most important stabilizing area of occlusion.

Adolescent↗
PubMed1977

Management of cases with upper incisors missing.

A problem often confronting the orthodontist is that of missing upper incisors. In evaluation of the individual case, the dicision as to space closure or space regaining and eventual prosthetic reconstruction can be perplexing. Various diagnostic criteria, such as skeletal relation, arch-length analysis, inclination of teeth, and dental esthetics, must be evaluated. On the basis of this diagnostic information, treatment alternative is chosen to correct the malocclusion. The solution may be found in maintaining space, necessitating postorthodontic prosthetic replacement, or closing space and thus avoiding the need for artificial teeth. Four cases are shown to illustrate different approaches to the treatment of patients with upper incisors missing. Other solutions are possible anc correct. Each case must be weighed on its own merits.

Adolescent↗
PubMed1980

A comparative analysis of intrusion of incisor teeth achieved in adults and children according to facial type.

A comparison was made of incisor intrusion achieved in adults and children with deep bite. Facial type was also examined for effect upon intrusion achieved. Fifty-five cases treated with bioprogressive mechanics were studied cephalometrically; subjects included twenty-four adults and thirty-one children. Neither age nor facial type was found to be statistically related to the amount of incisor intrusion achieved in this sample. A method of measuring intrusion at the root apices was devised and was thought to give a more accurate indication of actual bodily intrusion. More external root changes during treatment were observed for adults than for growing children. There was a wide latitude in the amount of intrusion observed in both groups and in all three facial types. Considerable overbite reduction was noted for the sample, and intrusion was found to be but one factor in this.

Adult↗
PubMed1981

Experimental intrusion of rat incisors with continuous loads of varying magnitude.

The present investigation deals with the relationship between continuous intrusive loads and the rate of intrusion of rat incisors. A method for the application of constant, defined loads by means of a closed coil spring is described. In seventeen rats the left mandibular incisor was shortened to prevent occlusion. The animals were exposed to direct light, medium, and heavy intrusive loads for a period of 12 days. Light loads (1.5 to 8.0 Gm./cm.2) did not cause active intrusion of the teeth. Medium loads (12.0 to 18.5 Gm./cm.2) initially elicited marked intrusion, followed by a short rest period after which the intrusive movement progressed steadily at a daily rate of about 25 micrometers. Heavy loads (30.5 to 32.0 Gm./cm.2) brought about active intrusion, which commenced only after 8 days of force application. The medium loads, having a magnitude in the range of rat systolic blood pressure, proved to be optimal for the intrusive movement.

Animals↗
PubMed1982

The ectopically erupted mandibular lateral incisor.

Seven cases of ectopically erupting permanent mandibular lateral incisors are reported and their orthodontic management is described. In severely crowded cases the ectopic lateral incisor was extracted. When complete transposition occurred, the teeth were aligned in their transposed positions. If malposition is detected early, orthodontic correction may prevent development of a transposition. Panoramic survey of the developing dentition at the age of 6 to 8 years is a very useful tool in the early detection of this as well as many other dental developmental anomalies.

Adolescent↗
PubMed1982

The influence of lip thickness and strain on upper lip response to incisor retraction.

Placement of teeth according to accepted cephalometric criteria does not necessarily ensure that overlying soft tissue will drape in a harmonious manner. The purpose of this research was to investigate the influence of maxillary lip thickness and lip strain on the relationship between dental and integumental tissue changes in orthodontically treated patients. Data were derived from pretreatment and retention lateral cephalometric head films of forty Caucasian subjects with Class II, Division 1 malocclusions. All patients were treated with edgewise appliances. Percentile groups were created for males and females according to the magnitude of maxillary lip thickness and lip strain. It was found that there was significant correlation between osseous changes and soft-tissue changes in both males (r= 0.83, p less than 0.01) and females (r = 0.85, p less than 0.01). Strong correlations were found between osseous changes and soft-tissue changes in subjects with thin lips (males, r equal to 0.92, p less than 0.01; females, r = 0.98, p less than 0.01), whereas no significant correlations were found in subjects with thick lips. Significant correlations were found between incisor changes and vermillion border changes in males (r = 0.61, p less than 0.01) and females (r = 0.51, p less than 0.05). Correlations were strong between incisor changes and vermilion border changes in subjects with high lip strain (males, r equal 0.92, p less than 0.01; females, r = 0.82, p less than 0.05) but were significant in subjects with low lip strain.

Adolescent↗
PubMed1982

Effects of incisor repositioning on monkey periodontium after expansion through the cortical plate.

The anterior teeth of five adult pigtail monkeys were moved lingually to correct a previously induced extreme labial displacement. (Roots had been moved through the labial bone to create bone dehiscence, loss of attachment, and gingival recession.) Eight months later, repositioning was performed with fixed appliances (Fig. 3). The teeth were retained in their more normal arch position for 5 months, after which clinical and histologic measurements were made of several periodontal parameters. The canines were not moved and served as reference teeth. Measurements were made to record changes in the levels of the gingival margin, the mucogingival junction, and the marginal bone relative to a fixed point on the tooth crowns, and the width of keratinized gingiva. Oxytetracycline was administered three times to label areas of osteogenesis in the periodontium. The incisors were retracted lingually a mean of 1.8 mm. The marginal bone level increased (moved coronally) a mean of 2.5 mm. and 3.1 mm. for maxillary and mandibular incisors, respectively (Table II). The tetracycline labels showed that osteogenesis occurred in the periodontium to a significant degree. The anchor canines had a loss of 1.1 mm. marginal bone (moved apically). Effects on gingival clefts and keratinized gingiva were slight. These observations demonstrate that in monkeys reapposition of labial bone can occur in a coronal direction, once teeth in extreme labial position with bone dehiscence and gingival recession are moved to a more normal environment. The effects on the periodontal soft tissues (width of keratinized gingiva, recession, attachment level) were, on the other hand, negligible in this study.

Alveolar Process↗
PubMed1983

The effects of continuous axially-directed intrusive loads on the erupting rabbit mandibular incisor.

A cantilever beam strain-gauge transducer was used to apply continuous light intrusive loads (0.2-0.4 and 2.5 g) to unimpeded mandibular incisors. Tooth position was continuously monitored using a variable capacitance displacement transducer. After 4 days of unimpeded eruption, the animals were divided into three experimental groups: no axial loading (6 rabbits); 0.2-0.4 g of axial loading (3 rabbits); 2.5 g of axial loading (3 rabbits). During a 4-h period, light forces (0.2-0.4 g) slowed eruption to a stop, whereas a heavier force (2.5 g) intruded the teeth. The data support Burn-Murdoch's (1981) (Archs oral Biol. 26, 939-943) contention that the eruptive force of unimpeded continuously-erupting incisors is significantly less than previously thought.

Animals↗
PubMed1986

The macroscopic appearance and associated histological changes in the enamel organ of hypoplastic lesions of sheep incisor teeth resulting from induced parasitism.

Twenty-one penned female sheep were infected with a high dose of nematodes (200,000 Trichostrongylus vitrinus and 25,000 Ostertagia circumcincta) during first incisor development when aged 7-8 months. Three sheep were infected with 200,000 T. vitrinus only; 10 sheep were untreated. Anorexia, lassitude and severe diarrhoea were seen in 14 of the infected sheep after 21-26 days. Anthelmintic was given to sheep showing undue distress to end the infection and to all remaining sheep on day 33. Animals were killed at 3 stages: during the infection, at intervals during later tooth development, and at the time of eruption of the incisor teeth, 7-8 months after the parasites were given. Hypoplasia of the labial enamel of 15 out of 19 teeth from sheep killed after recovery from the infection was classified according to the extent and depth as pits, grooves or larger areas of missing enamel with ledge-formation cervically. The amount of missing enamel related to the severity of the systemic disturbance which affected the secretory ameloblasts. During the period of active infection, some secretory ameloblasts showed vacuolization or were shorter than in controls; some cells were no longer adjacent to the organic matrix; some continued to function but abnormally and later became separated from the retained organic matrix by connective tissue. Cervically-placed ledges resulted either from the recovery and resumption of activity of some ameloblasts or from differentiation of new secretory cells after the infection ended.

Ameloblasts↗
PubMed1987

Long-term effect of loading on the fibroblast population of the periodontal ligament in the rat lower incisor.

The number and density of the cells in the tooth-related periodontal ligament (t-PDL) were related to the recovery of eruptive potential 2.5 months after load removal. Four left incisors in which eruption returned to normal (group A) and six in which eruption remained grossly impaired after a two-week application of latero-intrusive loads of 18.5 +/- 0.69 (group B) were compared to four control rats with unimpeded eruption. The incisors were demineralized, embedded in paraplast and cut into 6 micron transverse serial sections from which a three-dimensional reconstruction of the PDL was made by computerized histomorphometry, and the fibroblast population counted. The t-PDL volumes in controls and in groups A and B reached 1.15, 1.05 and 1.53 mm3, respectively; the estimated number of cells in the same PDL volumes were 2244 X 10(3), 1.659 X 10(3) and 2094 X 10(3) cells, respectively. The mean cell count/segment of PDL and the calculated number of cells/unit of periodontal tissue were significantly lower (p less than 0.001) in the formerly stressed, lateral periodontium of both experimental groups. In group B, these values were also decreased in the mesial periodontium.

Animals↗
PubMed1988

The effect of corticosteroids and cyclophosphamide on the eruption of resected incisor teeth in the rat.

It has been observed that there may be two mechanisms making resected rat incisors erupt during their phase of normal eruption rates, only one of which works during their slow phase of eruption. The effects of cyclophosphamide and corticosteroids on the eruption of non-resected teeth may also be consistent with the presence of two eruptive mechanisms, one responsive to cyclophosphamide and corticosteroids, the other not, or less, responsive to them. To see whether this previous work has, in different experiments, revealed the same pair of mechanisms, the effects of cyclophosphamide and corticosteroids on resected incisors were investigated. Cortisone accelerated their eruption and cyclophosphamide slowed it when they were erupting at normal rates, but neither compound had any effect during the initial slow phase.

Animals↗