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Biomedical subjects

A L Symons

Publications and source records attributed to A L Symons.

At least 19 recordsLinked to original sources
PubMed2000

A histological study of the effect of growth hormone on odontogenesis in the Lewis dwarf rat.

The effect of growth hormone (GH) on the dentition has been described in children with pituitary dwarfism where teeth fail to form; those that do form tend to be reduced in size and the eruption potential is diminished. The aim here was to examine the effect of GH on odontogenesis via molar development in Lewis (control), dwarf (Dw) and Dw GH-treated (Dw+GH) rats aged 3, 6, 9, 12 and 15 days. Dw+GH animals received a twice-daily dose (65 microg/kg) of GH which commenced at 2 days of age. Animals were killed, mandibles removed, processed to embedding in paraffin, sectioned and stained for histological examination of molar morphology during development. Variations in enamel mineralization and root development were observed. In 6-day-old animals, enamel mineralization was delayed in Dw and Dw+GH animals. Root initiation was evident at 6 days of age in controls but was not observed until 9 days of age in Dw and Dw+GH animals. At 12 days of age, maturation of enamel in Dw and Dw+GH animals remained delayed. By 15 days of age no variation in tooth development was evident. These data indicate that enamel mineralization is affected by the level of circulating GH in the rat. A specific deficiency of GH did not appear to delay bone resorption prior to tooth emergence.

Animals↗
PubMed1999

External apical root resorption of posterior teeth in asthmatics after orthodontic treatment.

External apical root resorption is an undesirable sequela of orthodontic treatment, resulting in loss of tooth structure from the root apex. It has been proposed that systemic factors, such as the inflammatory mediators produced in asthma, may enter the periodontal ligament and act synergistically to enhance root resorption. The aim of this study was to determine if asthmatic patients exhibited a higher incidence or severity of external apical root resorption compared with healthy (no medical conditions) patients after fixed orthodontic treatment. Records were obtained from patients treated with fixed appliances; 99 were healthy and 44 had asthma. Using OPGs (panoral films), posterior external apical root resorption was measured on all first and second premolars, mesiobuccal and distobuccal roots of the upper first molars, and mesial and distal roots of the lower first molars, giving 4 measurements per quadrant. A 4-grade ordinal scale was used to determine the degree of external apical root resorption. Combined tooth analysis (adjusted for treatment time, appliance, and extractions) showed that asthmatics had significantly more external apical root resorption of posterior teeth after treatment compared with the healthy group (P =.0194). Tooth-by-tooth analysis (adjusted for treatment time, appliance, extractions, headgear, overbite, overjet, sex, and age at start of treatment) found the upper first molars were most susceptible to external apical root resorption. Although the incidence of external apical root resorption was elevated in the asthma group, both asthmatics and healthy patients exhibited similar amounts of grade 2 (moderate) and grade 3 (severe) resorption.

Adult↗
PubMed1999

Expression of transforming growth factor-beta receptors types II and III within various cells in the rat periodontium.

This study reports the immunohistochemical localization of TGF-beta receptor type II (T beta R-II) and type III (T beta R-III) in cells of the forming periodontal ligament (PDL) in rat first molar roots. Mandibular periodontium was obtained from 3, 6 and 12-wk-old rats. This represented tissue from the initial, pre-mature and post-mature stages of root and periodontal development, respectively. Mandibular bone chips and molar roots were used to isolate osteoblasts, fibroblasts and cementoblasts. Cells were obtained using a 2-step trypsinization and explant technique, and cultured in Dulbecco's modification of Eagle's medium (DMEM) under routine cell culture conditions. Cells were cultured on coverslips for the purpose of detecting TGF-beta receptors, and compared with whole tissue sections using the same detection method. Cells which stained positively for T beta R-II and T beta R-III on both paraffin sections and cultured cell slides were counted. Both receptors were expressed in the various periodontal tissue compartments. PDL fibroblasts, cementoblasts and osteoblasts were stained positively for T beta R-II and T beta R-III. Endothelial cells were noted to be positive for T beta R-II only. T beta R-II was more widely distributed in cells than T beta R-III, but T beta R-III was extensively localized in the extracellular matrix. Both receptors were expressed on the cell membrane and also localized in the cytoplasm. The findings for paraffin sections were consistent with the immunohistochemical staining of cultured cells. The percentage of cells which stained positively for T beta R-II was greater (approximately 85%) than that for T beta R-III (approximately 60%) in all major types of the PDL cells on both paraffin sections and cultured cell slides. Extensive location of TGF-beta receptors in both cells and extracellular matrix suggests that several binding sites are available for TGF-beta s to interact with target cells during development and following maturation of the periodontium.

Animals↗
PubMed1999

Should cementoblasts express alkaline phosphatase activity? Preliminary study of rat cementoblasts in vitro.

BACKGROUND: A well-characterized cell culture model for cementoblasts is essential to understand the mechanisms of periodontal ligament (PDL) reattachment and regeneration. Whether cementoblasts express alkaline phosphatase (ALP) activity in vivo and in vitro remains to be determined. METHODS: Using a 2-step method of enzyme digestion/explant culture, osteoblasts, gingival/PDL fibroblasts, and cementoblasts were obtained from alveolar bone, gingiva, and the root surface of rat first molars and cultured. Initially, bone sialoprotein (BSP) was immunolocalized on tissue sections of periodontium and on cultured cells to distinguish mineral-forming cells from fibroblasts. Proteins were extracted from these cells to assess ALP activity by using an enzyme assay. RNA was extracted from the same cell source to detect ALP mRNA by reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: Cultured PDL/gingival fibroblasts were spindle shaped. Osteoblasts were irregularly shaped, and cell clusters/nodules were observed as they approached confluence. The cementoblasts manifested a polygonal shape and had two morphotypes: osteoblast-like and cuboidal or stratified. BSP was localized within the mineralized tissues and in osteoblasts and cementoblasts in culture and in tissue sections. The highest level of ALP activity was found in osteoblasts, a moderate level in PDL fibroblasts, and the lowest level in gingival fibroblasts. The cementoblasts lacked ALP activity, and this was reflected by a very weak signal (or no signal at all) for ALP mRNA in the cementoblasts. CONCLUSIONS: These studies indicate that cells consistent with a cementoblast-like phenotype may be successfully cultured, and that they lack ALP activity.

Alkaline Phosphatase↗
PubMed1999

Insulin-like growth factor-I (IGF-I) and IGF-I receptor (IGF-IR) immunoreactivity in normal and osteopetrotic (toothless, tl/tl) rat tibia.

Insulin-like growth factor-I (IGF-I) plays a major role in regulating cell growth. This study examined the immunohistochemical distribution of IGF-I and IGF-I receptor (IGF-IR) in tibias from normal and osteopetrotic (toothless, tl/tl) rats, following treatment with colony stimulating factor-1 (CSF-1). In normal rats, immunoreactivity for IGF-I and IGF-IR was detected in cells of the articular and epiphyseal cartilage, secondary ossification centres, zones of resting and proliferating chondrocytes and bone marrow. Bone marrow cells immunoreactive for IGF-I and IGF-IR were significantly reduced in the tl/tl rat (p < 0.001) compared with normal animals. Treatment of tl/tl rats with CSF-1 increased immunoreactivity for IGF-I and IGF-IR in bone marrow cells as well as the number of TRAP positive osteoclasts. This increase was the result of recruitment of a range of hematopoietic cell types, including eosinophils, polymorphs and a substantial number of monocyte-like cells demonstrating strong immunoreactivity to IGF-I/IGF-IR. The differences in relative immunoreactivity for IGF-I/IGF-IR by bone marrow cells in untreated and CSF-1-treated tl/tl rats indicate a CSF-1-dependent recruitment of cells bearing surface IGF-IRs which may be mediated by an increase in local or systemic IGF-I.

Acid Phosphatase↗
PubMed1998

Expression of transforming growth factor-beta 1 (TGF-beta1) in the developing periodontium of rats.

Transforming growth factor-beta 1 (TGF-beta1) has been reported to be expressed within several tissue compartments of developing molar crowns and therefore is implicated in tooth development. Additionally, TGF-beta1 may also play a crucial role in tissue repair and regeneration. The aim of this study was to determine the distribution of TGF-beta1 in the developing periodontal attachment apparatus (cementum, periodontal ligament, and alveolar bone) in Lewis rats. Animals aged 3, 6, and 12 wks were killed, their mandibles removed, fixed, demineralized, and processed in paraffin. The localization of TGF-beta1 in tissues was detected by polyclonal goat antibodies against human TGF-beta1 by means of immunoperoxidase techniques. TGF-beta1 messenger RNA was detected by in situ hybridization with a cocktail oligonucleotide probe. Cell counts were determined for analysis of the percentage of cells stained positive for TGF-beta1. Results revealed that TGF-beta1 was expressed in the developing alveolar bone, periodontal ligament, and cementum at all stages of tissue development studied. Staining was stronger at sites of cementum and alveolar bone compared with the periodontal ligament. Intensity of the positive staining, based on 3 grades, indicated a similarity between the tissues obtained from different ages, but varied between several cell types. Cementoblasts and osteoblasts stained more strongly than fibroblasts. Large numbers (approximately 90%) of the osteocytes in developing bone expressed TGF-beta1; however, in mature bone, fewer osteocytes stained for TGF-beta1. The percentages of positively stained cementoblasts, osteoblasts, and fibroblasts in the periodontal space were greater at the apical portion than at the cervical portion of the root. TGF-beta1 mRNA was expressed in osteoblasts, some bone marrow cells, cementoblasts, and fibroblasts. This study indicates that TGF-beta1 may play an important role in the modulation of tissue formation and development of the periodontium.

Aging↗
PubMed1996

The effect of fissure morphology and pretreatment of the enamel surface on penetration and adhesion of fissure sealants.

Fissure sealants have been used successfully as a means of preventing fissure caries. This effectiveness is directly related to sealant retention and retention is dependent upon a meticulous method of application. The aims of this study were to determine if sealant adhesion and penetration were affected by the variation in preparation of the enamel surface, or by pretreatment of the enamel surface with dentine adhesive systems, in fissures of varying morphology. Non-carious posterior teeth were visually examined and sorted according to fissure type, classified as shallow, deep or intermediate. Occlusal fissures were sealed using one of six methods, thermocycled for 200 cycles between 5 and 55 degrees C, in artificial saliva, then placed in a 1.5% procion orange dye for 3 min. Teeth were sectioned bucco-lingually and examined with a light microscope for (i) penetration of the sealant into the fissure pattern and (ii) adhesion of the sealant. All sealant techniques employed in this study adapted well to the enamel surface as the 1.5% procion Reactive orange dye failed to penetrate any of the sealed tooth sections. Shallow fissures were well obturated in both lateral and vertical dimensions. Sealants adapted well to the vertical walls at the orifice of deep fissures but generally failed to penetrate into the deeper aspects. Reducing the etching period with 37% phosphoric acid resulted in increased voids between the sealant and enamel surface and poorer adaptation to the vertical walls. The addition of dentine adhesive systems, Scotchbond Multi-Purpose and All-Bond 2, enhanced the vertical penetration of the sealant, particularly in deep fissures. It is proposed that the dentine adhesive systems may improve the retention rate of sealants in deep fissures particularly if the fissure is not completely dry prior to resin placement.

Acid Etching, Dental↗
PubMed1996

The effect of a vital bleaching technique on enamel surface morphology and the bonding of composite resin to enamel.

This study examined the effect of a nightguard vital bleaching procedure on enamel surface morphology and the shear bond strength of a composite resin luting cement to enamel. Extracted human teeth were bleached for 1 week using a vital bleaching product. Control teeth were brushed with a fluoride toothpaste and processed similarly to the bleached teeth, however the bleaching product was substituted with artificial saliva in the night guards. Teeth were stored in artificial saliva for 24 h, 1, 6 or 12 weeks and then examined for any surface changes using light and scanning electron microscopy. The effect of etching surfaces with 37% phosphoric acid was examined at the scanning electron microscope level. The shear bond strength of composite resin luting cement to both buccal and lingual surfaces of bleached and control teeth was determined. Light microscopy investigation suggested the bleaching process resulted in a loss of mineral from enamel which was evident 24 h after bleaching and was sustained following 12 weeks storage in artificial saliva. Scanning electron microscopy showed a definite change in the surface texture of the bleached enamel surface. Acid etching of the bleached enamel surface produced loss of prismatic form and the enamel appeared overetched. The mean shear bond strength between composite resin luting cement and etched enamel tended to be lower for bleached enamel surfaces, however no significant difference in shear bond strength was noted between control and experimental groups. The results of this study suggest that bleaching resulted in changes to the surface and subsurface layers of enamel. Although surface changes were observed in the etched enamel, the shear bond strength of composite resin luting cement to etched bleached enamel appeared to be clinically acceptable.

Acid Etching, Dental↗
PubMed1996

Decreased growth hormone receptor expression in long bones from toothless (osteopetrotic) rats and restoration by treatment with colony-stimulating factor-1.

Growth hormone (GH) is known to regulate growth and development of skeletal tissues. This study examined the distribution of growth hormone receptor (GHR) expression in tibias from normal and osteopetrotic tl/tl rats. For normal 2 week-old rats, GHR expression was detected immunocytochemically in cells of the articular and epiphyseal cartilage, primary and secondary ossification centres, zone of resting cartilage and bone marrow. Within the marrow, GHR immunopositive cells were concentrated in the central cone and largely excluded from the zone of immature progenitors at the periphery. For the marrow haemopoietic compartment, GHR expression was almost restricted to the nucleus in large mononuclear cells, adipocytes and megakaryocytes. A population of small lymphocytelike cells in the marrow periphery expressed GHR on the plasma membrane. GHR was not detected in mature erythroid cells, macrophages, granulocytes, or osteoclasts. The expression of GHR was significantly reduced in bone marrow cells of the tl/tl rat (p < 0.001) compared with normal animals. Injection of recombinant CSF-1 into tl/tl rats every 48 hours for 2 weeks from birth restored GHR-positive cells to the central core of the marrow space. The most striking change was the appearance of substantial numbers of mononuclear cells expressing abundant GHR on the cell surface. We infer that these cells are a novel subset of CSF-1 responsive cells involved in bone resorption. The differences in relative expression of GHR by bone marrow cells in untreated and CSF-1-treated tl/tl rats suggests a CSF-1-dependent recruitment of cells bearing surface GHRs.

Animals↗
PubMed1996

A family case report: disturbances in tooth form and eruption of the second premolar.

This report describes a family who demonstrated anomalies of tooth form and eruption of the lower second premolar. Observation of the second premolars remaining in the mother's and father's dentitions included ectopic eruption with impaction and substantial spacing between the first and second premolars. Four siblings were also examined--three boys aged 15, 14 and 12 years, and one girl aged 11 years. Anomalies of the second premolar recorded in the males and female include: congenital absence, ectopic eruption with impaction, delayed eruption and spacing. Associated anomalies included: congenital absence of other permanent teeth and spacing. It appears that the defect in tooth form and eruption is of a genetic origin, affecting both males and females. The condition(s) did not appear to be associated with a syndrome and the human papilloma virus lesions noted in all family members were not considered to be related to the dental defects. This family demonstrated two anomalies of the lower second premolar: congenital absence and disturbance in tooth eruption. The question raised by this case report is whether these two anomalies are inherited as separate traits or whether failure of tooth eruption is a variation in expression of the same genetic factor that results in oligodontia.

Adolescent↗
PubMed1995

Interleukin-1 (IL-1) bioactivity and inhibition of IL-1 bioactivity in supernatant fluid from cultured microphthalmic (mi) mice teeth of different ages.

A functioning dental follicle and bone resorption are necessary for tooth eruption. In the microphthalmic (mi) mouse, bone resorption is defective and teeth fail to erupt. Local bone metabolism involves the production of cytokines such as interleukin-1 alpha (IL-1 alpha) and transforming growth factor-beta (TGF-beta). The production of these cytokines by dental tissues during eruption may be fundamental to tooth movement. Molars from mi mice were cultured and supernatants tested for the presence of these cytokines using bio-dot blotting and ELISA. A thymocyte bioassay was used to test supernatants for IL-1 bioactivity and IL-1 inhibition bioactivity. IL-1 alpha and TGF-beta were detected in all supernatants. Supernatants demonstrated no IL-1 bioactivity but inhibited IL-1 bioactivity which varied with concentration of supernatant, age and animal. This study demonstrated that cultured developing teeth secrete IL-1 alpha and TGF-beta however, concentrations varied in normal and pathological states. While IL-1 alpha was present in the supernatants, all demonstrated a variable ability to inhibit IL-1 bioactivity. This ability may influence local bone metabolism and hence tooth eruption.

Aging↗
PubMed1994

In vitro development of lower first molars from the osteopetrotic microphthalmic (mi) mouse.

While the precise mechanism of tooth eruption remains unknown it has been established that for tooth eruption to occur a functioning dental follicle is essential and normal bone resorption is required. In the osteopetrotic microphthalmic (mi) mouse, teeth fail to erupt and development is affected. In the present study, an organ culture technique was established to culture successfully lower first molars from normal and affected mi mice so as to determine if developmental defects were intrinsic to the dental tissue or whether such defects were a result of local environmental factors. Tissue was cultured for up to 13 days and development assessed morphologically at varying time intervals using standard light microscopy. Teeth developed similarly in both animal groups studied. The only variation in the appearance of cultured tissue occurred in the cervical loop region with more curling evident in dental tissue from the affected animals. The results of this study therefore showed that dental tissue from both normal and affected mi mice can be cultured for up to 13 days and that there is no difference in their development. It would appear that these teeth have the same ability to develop and consequently erupt, however the local environment influences tooth development and alters the eruption potential.

Ameloblasts↗
PubMed1993

Anomalies associated with hypodontia of the permanent lateral incisor and second premolar.

Apart from the molars the most commonly congenitally absent tooth is the second premolar followed by the permanent lateral incisor. From a total of 5127 patients, congenital absence of the permanent lateral incisor occurred with a frequency of 2.2 per cent and absence of the second premolar with a frequency of 3.4 per cent. In association with hypodontia of these teeth other dental anomalies were observed. Absence of other teeth was observed as the most likely associated dental anomaly. Other anomalies recorded included disturbances in spacing of the dentition, and problems associated with tooth eruption and exfoliation.

Anodontia↗
PubMed1992

Ectopic eruption of a maxillary canine following trauma.

Traumatic events at an early age may lead to developmental dental anomalies and ectopic tooth eruption. A case is reported in which a traumatic injury at two months of age resulted in the development of supernumerary teeth in the upper right premaxillary region. The maxillary canine ectopically erupted or transposed into the space left by the missing central incisor and eliminated the need for a prosthesis in this region.

Child↗
PubMed1992

Physiological root resorption of primary molars.

Physiological root resorption of primary molars was assessed using bitewings and orthopantomograms. Thirty-six per cent of teeth examined demonstrated reduced root resorption of one or more roots. Excepting the lower first primary molar, the present study recorded a relatively high incidence of uneven root resorption during the exfoliative process, particularly evident for the upper second primary molar. Discrepancy in size between the premolar and its predecessor, as well as the position of the developing permanent tooth in relation to primary root structure influences the pattern of root resorption. Therefore, constant monitoring of teeth demonstrating uneven resorption is required to avoid the complications associated with over-retained teeth.

Child↗
PubMed1991

Dental abnormalities associated with a chromosome 2 deletion.

This case report describes the dental and physical anomalies observed in a young female patient who had a chromosome abnormality involving deletion of the q 33-q 35 region of chromosome 2. The dental dysplasia observed in this patient is proposed to be of genetic origin but the complication of anoxia at birth makes it difficult to assign the intellectual and physical impairments solely to the genetic deletion.

Child, Preschool↗
PubMed1991

The floor of the pulp chamber following pulpotomy.

The purpose of this study was to investigate the incidence of pulpal floor damage caused by operator error in a standard pulpotomy exercise, and to determine if this damage produced significant changes in dentin morphology and thickness at the base of the pulp chamber. One hundred and fourteen primary molar teeth were utilized in this study, 61 having pulpotomies and the remainder untreated. The dentin thickness in the furcation was measured on all the teeth and the pulpal floor morphology was examined using both light and scanning electron microscopy. The difference in thickness of dentin in the furcation of pulpotomized and non-pulpotomized teeth was not statistically significant. Less than fourteen per cent of pulpotomized teeth showed damage to the pulpal floor and this damage was only minimal in all cases. This study therefore suggests that damage to the pulpal floor during preparation is unlikely to be a factor contributing to failure of pulpotomies.

Dental Pulp Cavity↗