Tensile bond strength of light-cured resin-reinforced glass ionomer cement with delayed light exposure

In the clinical situations, the time intervals between material mixing and light exposure during bracket bonding, using light-cured resin-reinforced glass ionomer cement (LCGIC), may vary for each individual bracket. This study determined the tensile bond strengths of LCGIC subjected to various time intervals, and evaluated the durability with thermocycling. Comparisons were made between LCGIC and light-cured composite resin (LCR). Two hundred and forty bovine teeth were chosen as specimens. Light exposure was performed 5, 10, 20, and 40 min after the commencement of powder/liquid mixing. The durability was evaluated by thermocycling for 2000 times at temperatures between 5°C and 55°C, with a 30-s dwell time. Tensile bond strengths of LCGIC and LCR after 5 min, representing the general condition in clinical use, equaled 5.7 ± 1.5 MPa and 5.1 ± 2.6 MPa, respectively. For the LCGIC groups, no significant differences were seen between bond strengths with and without thermocycling. Also, no significant differences were noted among any time intervals. For the LCR groups, there were also no significant differences with and without thermocycling. The tensile bond strength of LCR showed highly significant differences within groups across time. Compared with LCR, the failure sites for brackets bonded with LCGIC appeared to be predominantly at the bracket/adhesive interface. The standard deviations of LCR were high when compared with those of LCGIC. The bond strength of LCGIC with or without thermocycling surpassed the clinically required minimum. LCGIC may be an advantageous alternative to LCR for orthodontic bracket bonding. Received: October 3, 2000 / Accepted: June 19, 2001     

Local delivery of chlorhexidine gluconate (PerioChip) in periodontal maintenance patients

AIM: The aim of this randomised, split-mouth, single-blind study was to determine the efficacy of controlled-release delivery of chlorhexidine gluconate 2.5 mg (PerioChip) in patients with residual bleeding pockets (>5 mm) at least 3 months following oral hygiene and root debridement phase therapy. MATERIAL AND METHODS: 26 patients (non-smokers) were screened and potential study sites identified. Clinical parameters recorded at baseline and all subsequent visits were plaque index (PI), pocket probing depth (PPD), bleeding index (BI) and clinical attachment level (CAL). All study sites were debrided using ultrasonic instrumentation. PerioChips (PC) were placed in the selected sites of two quadrants (left or right) whilst identified sites in the remaining quadrants were left without adjunctive antimicrobial treatment. Clinical measurements were made at follow-up visits after 1, 3 and 6 months. Mean changes from baseline in PPD, BI and CAL were calculated with the patient as the experimental unit and comparability between the treatments was determined using t-tests. RESULTS: At baseline there were no significant differences between PC and control sites for mean PI, PD, BI or CAL. The mean (SE) reductions in PPD for PC and control treatments were: 0.47 (0.1), 0.46 (0.1); 0.76 (0.1), 0.55 (0.1); 0.78 (0.1), 0.45 (0.1) for months 1, 3 and 6 respectively. Only at month 6 did the difference between treatments approach statistical significance (p=0.06). Mean (SE) reductions in CAL over the same periods were: 0.17 (0.1), 0.04 (0.08); 0.38 (0.1), 0.21 (0.1); 0.43 (0.1), 0.15 (0.09) p=0.048. Mean (SE) reduction in BI between PC and control treatments only reached statistical significance at 6 months: 1.08 (0.1), 0.59 (0.1) p=0.05. CONCLUSION: These data suggest that PerioChip is beneficial for patients on maintenance therapy although the benefit is not apparent until 6 months after placement.     

Common variable immunodeficiency with unusual vegetative lesions of the tongue and labial mucosa: a case report

A case of common variable immunodeficiency with unusual vegetative lesions of the tongue and lower lip in a 28-year-old man is presented. The vegetative lesions developed over the preceding 10 months and clinically were suggestive of malignancy. The biopsy specimens showed no malignancy, and a bacterial culture of the tongue detected abundant Staphylococcus aureus. Combined treatment with a corticosteroid antibiotic ointment and povidone iodine rinse produced remarkable resolution of the lesions. Laboratory examination showed markedly decreased levels of serum immunoglobulins. Intravenous gamma globulin replacement therapy resulted in good control of infection and disappearance of the lesions.     

Possible participation of isolated epicardial cell clusters in the formation of chick embryonic epicardium

The embryonic epicardium is formed by the spreading of cells derived from the extracardiac proepicardial organ over the myocardial surface after transfer to the dorsal side of the myocardium via a bridge of villous projections. Using whole-heart immunostaining for keratin, we found that the chronology and pattern of epicardial formation in the chick was basically identical to that reported previously in the quail. However, discrete epicardial islands were observed on the ventrolateral surface of the atrioventricular canal as well as in two previously reported areas. Closer examination by scanning electron microscopy demonstrated the presence of isolated, sparsely distributed epicardial cell clusters on both the dorsal and ventral surfaces of the myocardium. These cells showed a surface morphology similar to that of the epicardial cells at the advancing edge of the spreading epicardial sheet and possessed numerous well-developed filopodia, suggesting active motility. These clusters are probably seeded onto the myocardium by vesicular transport from proepicardial villi, and our findings suggest that the resulting small, localised patches of epicardial cells might accelerate, supplement and tune the epicardial formation mediated by radial spreading of the epicardial sheet in the chick embryonic heart.     

Mixed infection of Porphyromonas gingivalis and Bacteroides forsythus in a murine abscess model: involvement of gingipains in a synergistic effect

Several microorganisms including Porphyromonas gingivalis and Bacteroides forsythus have been implicated to be etiologically important agents of periodontal disease. In this study, we determined the ability of combinations of periodontopathogenic microorganisms to cause tissue destruction in a murine abscess model. Although all bacterial combinations used in this study produced larger abscesses than did monoinfection of each bacterium, the combination of P. gingivalis and B.forsythus showed a synergistic effect on abscess formation. Since these two bacteria have been frequently found together in lesions of periodontitis, these results suggest the significance of their co-infection in the progression of periodontitis. P. gingivalis produces extracellular and cell-associated cysteine proteinases (gingipains) which appear to be involved in its virulence. The rgpA rgpB double and kgp mutants induced significantly smaller abscesses than the wild type. Moreover, the rgpA rgpB kgp triple (gingipain-null) mutant hardly showed lesion formation at all with the experimental conditions used in this study, indicating that these genes encoding gingipains are important for virulence of P. gingivalis. Mixed infection of these P. gingivalis mutants with B. forsythus showed an additive effect on abscess formation, indicating that the gingipains of P. gingivalis may play an important role in the pathological synergism between P. gingivalis and B. forsythus.     

Effects of a nutritional supplement on periodontal status

Among the recommendations for the maintenance of gingival and periodontal health, few have focused on the value of nutritional supplements. The purpose of this study was to compare the effect of certain nutritional and plant-derived nutraceuticals and a placebo tablet in the reduction of gingivitis, bleeding, probing depths, and attachment levels in a 60-day two-cell, randomized, parallel clinical trial for patients with Type II periodontal disease. The vitamin therapy was introduced as an adjunct to patient homecare to determine if there was a quantifiable improvement to soft-tissue health and periodontal damage. Sixty-three patients were randomly divided into two groups of 32 and 31 subjects and given either a vitamin tablet containing seven active ingredients (experimental treatment) or a placebo tablet. The clinical parameters assessed were the gingival index (GI), bleeding index (BI), periodontal pocket depth (PD), and attachment levels (AL), and were recorded at baseline and 60 days. Patients took the assigned tablet at breakfast and at dinner after brushing their teeth twice daily. After 60 days, the data showed a clinical reduction in the GI, BI, and PD for the experimental group (P < .0001). There were no significant changes for AL with either the experimental or the placebo group. When the data were further analyzed for pocket depths of > or = 4 mm in patients receiving the experimental treatment, there were clinically significant improvements in the GI and PD from baseline to 60 days (P < .0001), but no significant differences in the BI and AL. There were no statistical differences in any of the indices when the data were compared between men and women. The results of the present study suggest that a multi-vitamin nutritional supplement might be a beneficial adjunct to the required established periodontal treatment.     

A case of anterior open bite developing during adolescence

Imaging studies have reported on the relationship between temporomandibular joint (TMJ) degeneration and facial deformity. These studies have suggested that mandibular growth is affected by TMJ degeneration, resulting in altered skeletal structure as mandibular retrusion. However, there are very few longitudinal case reports on TMJ osteoarthrosis (OA). Progressive open bite occurred in an adolescent patient with TMJ OA. Cephalometric analysis showed a downward and backward rotated mandible, and a labial inclination of the upper incisor. Magnetic resonance imaging showed internal derangement without reduction and erosion in the right and the left condyles. Although the cause of open bite is unclear in this case, tongue thrusting, and internal derangements in the temporomandibular joint were suspected as causes of the open bite.     

Chemo-mechanical caries removal: a review of the techniques and latest developments

Chemo-mechanical caries removal involves the chemical softening of carious dentine followed by its removal by gentle excavation. The reagent involved is generated by mixing amino acids with sodium hypochlorite; N-monochloroamino acids are formed which selectively degrade demineralised collagen in carious dentine. The procedure requires 5-15 minutes but avoids the painful removal of sound dentine thereby reducing the need for local anaesthesia. It is well suited to the treatment of deciduous teeth, dental phobics and medically compromised patients. The dentine surface formed is highly irregular and well suited to bonding with composite resin or glass ionomer. When complete caries removal is achieved, the dentine remaining is sound and properly mineralised. The system was originally marketed in the USA in the 1980's as Caridex. Large volumes of solution and a special applicator system were required. A new system, Carisolv, has recently been launched on to the market. This comes as a gel, requires volumes of 0.2-1.0 ml and is accompanied by specially designed instruments.