Molecular and cell biology of the gingiva.
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Animals↗
Biomedical subjects
L J Walsh
Publications and source records attributed to L J Walsh.
Orthodontic tooth movement in the prednisolone-treated rat.
Adverse effects of corticosteroids on bone metabolism raise concerns as to whether steroid treatment may influence orthodontic movement. This study examined the effect of prednisolone on orthodontic movement using an established rat model. The corticosteroid treated group (N = 6) was administered prednisolone (1 mg/kg) daily, for a 12-day induction period; the control group (N = 6) received equivalent volumes of saline. On day 12, an orthodontic appliance was placed which exerted 30 g of mesial force to the maxillary first molar. Animals were sacrificed on day 24 and tooth movement was measured. Sagittal sections of the molars were stained with haematoxylin and eosin, and for tartrate-resistant acid phosphatase (TRAP) activity. While there were no significant differences in the magnitude of tooth movement between the 2 groups, steroid-treated rats displayed significantly less root resorption on the compression side and fewer TRAP-positive cells within the PDL space on the same side. This suggests steroid treatment suppressed clastic activity.
Acid Phosphatase↗
An assessment of techniques for dehydrating root canals using infrared laser radiation.
Infrared lasers have been used for debridement and sterilisation of both soft and hard tissues, but there have been few studies of such laser applications in endodontics. The present laboratory study was undertaken to examine the feasibility of using pulsed infrared laser radiation to remove moisture from root canals (with an adjunctive sterilising effect). Canals were prepared in extracted teeth and a standardised technique used to fill the apical half of the root canal with saline. Pulses of CO2 or Nd:YAG laser energy were delivered into the root canal system via miniature applicators and residual fluid determined, as well as temperature changes on the root surface. With the CO2 laser, long pulse durations were effective at dehydrating the canals, but elicited deleterious thermal changes both locally within the canal as well as on the root surface. With Nd:YAG laser treatment, large temperature increases on the root surface occurred even with low powers and low pulse frequencies, and extended times were necessary for dehydration. With higher powers and pulse frequencies, complete dehydration could be achieved in less than 60 seconds, however root surface temperatures increased approximately 25 degrees, and the radicular dentine was damaged by the production of plasma. Dehydration of root canals could not be achieved safely with these two infrared lasers, and damage to both radicular dentine and the periodontal ligament would occur if these techniques were to be applied clinically. Alternative methods which do not exert significant thermal effects should be investigated.
Aluminum Silicates↗
Preventive dentistry for the general dental practitioner.
Although the prevalence of dental caries has decreased gradually in the past three decades in the Australian population, dental caries remains the primary reason for tooth loss in Australia. At the community level, total health expenditure on the treatment of dental caries (and its consequences) is substantial. Accordingly, caries prevention is an important focus at both the individual and community levels. This paper outlines the principles upon which modern caries prevention is based and stresses the importance of manipulating the oral environment (in terms of salivary parameters, ions, pH and the oral flora) as a major strategy for effective long-term caries prevention. Practical advice is provided on the correct home use of preventive agents, including chewing gums, chlorhexidine, fluorides, bicarbonate rinses and phosphopeptides.
Alkalies↗
Safety issues relating to the use of hydrogen peroxide in dentistry.
Hydrogen peroxide is used widely in professionally and self-administered products. Hydrogen peroxide is a highly reactive substance which can damage oral soft tissues and hard tissues when present in high concentrations and with exposures of prolonged duration. This report provides an overview of health issues relating to the use of hydrogen peroxide, with an emphasis on safety with prolonged exposure to low concentrations of peroxide products. There is good evidence for the safety of hydrogen peroxide when used at low concentrations on a daily basis over extended periods of time, in self-administered oral health care products such as dentifrices and mouthrinses. These low concentrations neither damage oral hard or soft tissues, nor do they pose a significant risk of adverse long-term effects. Caution should be exercised with the increasingly higher concentration peroxide products used for 'walking' or 'power' bleaching due to the possibility of chemical irritation of oral soft tissues with injudicious use. The volumes of material and application times should be controlled carefully. Thorough education of patients is particularly important with self-applied gels because of the lack of professional supervision with such products. Such education is part of the duty of care of the dentist who supplies bleaching gels for at-home use.
Anti-Infective Agents, Local↗
Changes in the periodontal status of patients undergoing bone marrow transplantation.
BACKGROUND: Patients receiving an HLA-matched bone marrow transplant (BMT) from a relative or unrelated donor undergo a permanent alteration of their immune system, followed by a prolonged period of immunodeficiency. This study aimed to examine alterations in the periodontal status of patients over 6 months post-bone marrow transplantation. METHODS: Thirty-seven patients scheduled for bone marrow transplantation participated in this study. One calibrated examiner carried out periodontal examinations (clinical and radiographic) immediately prior to and at 3 and 6 months after transplantation. All patients followed an intense oral care program. Subgingival plaque samples were analyzed by enzyme-linked immunosorbent assay (ELISA) for the presence of Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, and Prevotella intermedia. Data were subjected to statistical analyses to determine the relationships between the frequency distribution of the radiographic and clinical variables over time. RESULTS: Gains in clinical attachment level (CAL) of > or =2 mm at 4 or more sites from baseline to 6 months post-BMT were noted in 9/16 patients (56%), while 6/16 (38%) patients experienced a loss of CAL > or =2 mm at 4 or more sites in the same period. At a site level, 4.8% of sites exhibited a gain in CAL > or =2 mm between baseline and 3 months post-BMT while 2.3% of sites showed a loss of CAL > or =2 mm in the same period. From baseline to 6 months, a gain in CAL of > or =2 mm was recorded at 3.1% of sites, and 2.4% of sites experienced a loss of > or =2 mm. A significant improvement in the gingival index occurred between all sequential time periods when assessed at a site level. At a patient level, 11/18 (61%) patients showed a significant change in gingival index between baseline and 3 months and 10/16 (63%) between baseline and 6 months. There was no significant relationship between clinical changes and the prevalence of the periodontal pathogens at the various time periods. CONCLUSIONS: An improvement in periodontal health was recorded between baseline and 6 months post-transplantation. Most of the improvement in periodontal status was noted in the first 3 months after BMT, with a slight decline in periodontal health between 3 and 6 months post-transplant. No significant alteration was noted in the prevalence of periodontal pathogens during the study period.
Adolescent↗
Periodontal implications of immunodeficient states: manifestations and management.
The importance of the immune system in modulating the host response to plaque is well recognised, and in this context the immune system is clearly a risk/modifying factor for human periodontal disease. This review examines the periodontal manifestations of subjects with immunodeficiencies and considers potential preventive protocols for the periodontal management of these patients.
Aging↗
Raman spectroscopic studies of CO2 laser-irradiated human dental enamel.
While the effects of carbon dioxide (CO2) laser radiation on the physical properties of human dental enamel are well characterized, little is known regarding laser-induced chemical changes. In this study, enamel was exposed to CO2 laser radiation to induce fusion and recrystallization, and the Raman spectra recorded using both dispersive and Fourier-transformed (FT) Raman spectroscopy. Spectra were compared to a heart-treated specimen of hydroxyapatite (HAP) and enamel. Laser irradiation induced chemical changes which differed from those induced by heat treatment. Comparing the Raman spectra of lased enamel to HAP and tricalcium phosphate (TCP), it is evident that CO2 laser irradiation of enamel causes the partial conversion of HAP to TCP. The effect of laser irradiation is not merely a simple local heating effect as previously thought, since simple heating of enamel leads to the formation of both TCP and Ca(OH)2, while laser treatment of enamel results in the formation of TCP but not Ca(OH)2.
Carbon Dioxide↗
Removal of orthodontic bonding resin residues by CO2 laser radiation: surface effects.
OBJECTIVE: The purpose of this in vitro study was to evaluate the potential use of pulsed CO2 laser radiation to remove selectivity residues of orthodontic bonding resin that remain after debonding of fixed orthodontic appliances. SUMMARY BACKGROUND DATA: Current techniques used for removal of orthodontic bonding resin after removal of fixed appliances include rotary instruments, debonding pliers, and ultrasonic scalers. These techniques, however, are time-consuming and inefficient, and may damage tooth enamel. METHODS: A standardized cylinder of orthodontic bonding resin was bonded to the buccal surfaces of 100 extracted premolar teeth, which were then divided into 10 groups of 10 specimens each. In 9 groups, the resin was ablated using 1 of 9 different laser parameters, while in the remaining control group, the resin was removed with a slow speed tungsten carbide bur. Specimens were evaluated by light microscopy and scanning electron microscopy (SEM) to assess the amount of resin remaining and the extent of the damage to the underlying enamel. RESULTS: The 2 W/100 ms combination was optimal, with a high efficiency of resin removal and the least enamel damage. Higher laser powers increased the extent of enamel damage without enhancing resin removal. CONCLUSIONS: This laser technique appears promising, however, further studies of the extent of thermal changes at the level of the dental pulp are necessary to establish more fully the risk-benefit ratio.
Analysis of Variance↗
Morbidity from asthma in relation to regular treatment: a community based study.
BACKGROUND: The extent to which asthma morbidity in the community occurs in patients who are having relatively little treatment or in those on step 3 or above of the British asthma management guidelines is uncertain. We have looked at this in a community population in southern Nottinghamshire. METHODS: A cross sectional review of treatment in all patients over the age of four with diagnosed asthma was carried out in five large general practices (population 38 865) in 1995/6 using computerised general practice records. The patients' usual treatment was obtained from prescription data and categorised by the appropriate step on the British guidelines on asthma management. Two measures of morbidity, the request for 10 or more short acting beta agonist inhalers a year or the need for a course of oral corticosteroids in the last year, were related to the regular treatment of the patients. RESULTS: Of the 3373 patients (8. 7%) given a diagnosis of asthma, the percentage on steps 1, 2, 3, 4, and 5 of treatment were 54%, 22%, 11%, 3.6%, and 1%, respectively, with a further 8% having had no treatment. During the past year 13. 6% had been prescribed 10 or more beta agonist inhalers and 12.5% had received at least one course of oral corticosteroids. Both measures occurred more frequently in patients taking more prophylactic treatment (step 3 or above). Nevertheless, because most patients were on steps 1 and 2 of the treatment guidelines, more than half the patients requiring high doses of inhaled beta agonists or a course of oral prednisolone came from those taking low dose or no regular inhaled corticosteroid. CONCLUSIONS: Evidence of morbidity from asthma was found in many patients taking little or no prophylactic medication and this should be amenable to improved education. A different approach may be needed for patients with continuing morbidity who are already taking higher doses of prophylactic medication.
Adolescent↗
The effect of orthodontic treatment on salivary flow, pH, buffer capacity, and levels of mutans streptococci and lactobacilli.
Fixed orthodontic treatment has been shown to cause an increased incidence of enamel demineralisation. The purpose of this study was to investigate the changes in stimulated salivary flow rate, pH, buffer capacity, and the levels of mutans streptococci (MS) and lactobacilli in patients undergoing therapy with fixed orthodontic appliances. Saliva samples, plaque index scores and dietary histories were taken from 21 sequential patients before the start of treatment, and one month and three months after placement of brackets and bands. There was a statistically significant increase in stimulated salivary flow rate, pH, buffer capacity, plaque index scores, and in the levels of MS and lactobacilli after three months of active treatment. It is postulated that the balance between the cariogenic challenge posed by high levels of MS and lactobacilli, and the reparative effects of concurrent increases in salivary flow rate, pH and buffer capacity, determines the likelihood of mineral loss or gain over time. A failure to follow basic preventive measures may increase the risk for some patients of enamel decalcification during orthodontic treatment with fixed appliances.
Adolescent↗
Characterization of serum antibodies to Porphyromonas gingivalis in individuals with and without periodontitis.
Although Porphyromonas gingivalis is a defined pathogen in periodontal disease, many subjects control the infection without experiencing loss of attachment. Differences in host susceptibility to the disease may be reflected in the pattern of humoral antibodies against specific P. gingivalis antigens. The aim of this study was to determine the presence of antibodies against immunodominant P. gingivalis antigens as well as the isotype and subclass of anti-P. gingivalis antibodies against outer membrane antigens in four groups of patients: P. gingivalis-positive, 1) with and 2) without periodontitis, and P. gingivalis-negative, 3) with and 4) without periodontitis. Antigens of molecular weight 92, 63, and 32 kDa and lipopolysaccharide were found to be immunodominant. Group 1 subjects showed a significantly higher response to the 92 and 63 kDa antigens compared with other groups. The response to lipopolysaccharide was significantly higher in group 1, and lower in group 4 than in groups 2, 3. Immunoglobulin G1 (IgG1), IgG2 and IgM antibodies against P. gingivalis outer membrane were present in all subjects, while only some subjects were seropositive for IgG3, IgG4 and IgA. There were no differences in concentrations for IgG1, IgG3 and IgM. The IgG2 concentration in group 4 was significantly higher than in groups 1 and 2, while the IgG4 concentration in group 4 was significantly lower than in other groups. The frequency of seropositivity for IgG4 and IgA was lowest in group 4, while IgG3 seropositivity was almost exclusively seen in healthy patients in groups 2, 4. These findings suggest that the presence of IgG3 may reflect non-susceptibility to the disease, while lack of IgG4 may be indicative of periodontal health and lack of infection.
Adult↗
Characterization of unmyelinated axons uniting epidermal and dermal immune cells in primate and murine skin.
The present study was undertaken to characterize further the structure and function of cutaneous nerves which we have previously shown to associate with skin immune cells (Hosoi et al., Nature 1993: 363:159). Ultrastructurally, axons were prominent within the superficial dermis and epidermis in neonatal murine skin, but they were inconspicuous in adult murine and primate skin. Immunohistochemical and immunoultrastuctural evaluation of normal adult human and simian skin for neural cell adhesion molecule (N-CAM), however, defined a plexus of axons surrounding superficial dermal mast cells and extending as delicate, vertical branches into the overlying epidermal layer. Antibodies to neuropeptides substance P, calcitonin gene-related peptide, and to nerve cell-specific clathrin (LCb subunit) also reacted with this neural plexus. Double labeling disclosed intimate associations of N-CAM-positive axons with dermal chymase-positive mast cells as well as with epidermal CD1a-positive Langerhans' cells by confocal scanning laser microscopy. Functionally, capsaicin applied to forearm skin revealed by 6 h discharge of mast cell chymase and induction of E-selectin in adjacent microvascular endothelium, events consistent with release of substance P from axons and subsequent stimulation of cytokine-mediated mast cell-endothelial interaction. Identical application of capsaicin to human skin xenografted to immunodeficient mice, and thus experimentally lacking in unmyelinated axons, failed to show similar findings. These results provide additional support to the concept that an elaborate network of cutaneous axons may play a functional role in regulation of skin inflammation and immunity.
Adult↗
Associations between mast cells and laminin in oral lichen planus.
Mast cell numbers are increased significantly in oral lichen planus (OLP). In other inflammatory conditions, mast cells frequently adhere to extracellular matrix proteins such as laminin. The aim of this study, therefore, was to determine whether the distribution of mast cells in OLP is related topographically to laminin in vascular and epithelial basement membranes. Monoclonal antibodies for tryptase, laminin and the alpha6beta1 CD49f laminin-binding integrin were used to identify mast cells, basement membranes (blood vessels and basal epithelium) and the "classical" laminin adhesion receptor, respectively. A double-labelling immunoperoxidase technique was employed to examine and compare mast cell-laminin relationships in OLP (n=19) and normal buccal mucosa (NBM, n=13). In both OLP and NBM, the majority of mast cells were located close to vascular basement membranes. Quantitative studies revealed that the number of mast cells associated with the laminin of vascular basement membranes (distance <1 microm) was two-fold and three-fold higher, respectively, in the superficial and deep layers in OLP compared with NBM (P<0.001). The frequency distribution of mast cells associated with basal epithelium was not statistically different in both groups (P>0.05). The association of mast cells with laminin may be an important determinant of mast cell density in OLP During OLP lesion formation and progression, the preferential distribution of mast cells in the immediate perivascular region provides an ideal situation for mast cell-derived mediators to influence the vascular endothelium.
Angiogenesis Inducing Agents↗
Differing roles of the tutor in problem-based learning: the Queensland experience.
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Education, Dental↗
Implementing problem-based learning into professional and dental education.
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Education, Dental↗
PBL as a tool for integrating anatomy into the dental curriculum.
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Anatomy↗
Immunohistological study of lesions induced by Porphyromonas gingivalis in a murine model.
A previous study used a mouse model to demonstrate protection after challenge with Porphyromonas gingivalis ATCC 33277. In the present study, this same model was used to determine the phenotype of cells recruited into the lesions during the course of the protective immune response after immunization with this periodontal pathogen. BALB/c mice were immunized with 100 micrograms of P. gingivalis outer membrane antigens per mouse weekly for 3 weeks followed by challenge with live organisms 3 weeks after the final immunization. Hematoxylin and eosin-stained sections showed inflammatory infiltrates in all lesions from control (immunized with adjuvant only) and immunized mice. The lesions developed central necrotic cores surrounded by neutrophils, phagocytic macrophages and lymphocytes. Neutrophils were the predominant cells in the lesions 1 day after challenge with significantly more in immunized than control mice. Acid phosphatase and nonspecific esterase-positive macrophages were detected at day 4 and became the predominant cells in the healing lesions. CD4- and CD8-positive T-cells were present from day 1, and while numbers increased over time, there were no significant differences in control or immunized mice. When mice were depleted of CD4 or CD8 cells prior to immunization with P. gingivalis, fewer neutrophils were found in the lesions 1 day after challenge compared with undepleted immunized mice. Acid phosphatase and nonspecific esterase-positive macrophages were not affected by T-cell depletion. The results suggest that the P. gingivalis-induced lesion in immunized BALB/c mice is consistent with a strong innate immune response involving the recruitment of neutrophils in the first instance which may be under the control of T cells. This is followed by the infiltration of phagocytic macrophages which are involved in the healing process and do not appear to be regulated by T cells.
Analysis of Variance↗