The protective nature of pellicle towards toothpaste abrasion on enamel and dentine

OBJECTIVES: To determine the protective nature of pellicle towards toothpaste abrasion. METHODS: The enamel region of human enamel-dentine blocks was indented with a Knoop diamond and the profile across the enamel-dentine junction was measured. Blocks were either exposed to deionised water or placed onto intra-oral appliances and worn in the mouth to produce in situ pellicles. This was followed by a 10-day period of tooth brushing experiments. Each day, specimens were brushed with a slurry of either Toothpaste A (RDA=90) or Toothpaste B (RDA=204) for 25 cycles (10s) on a brushing machine. This was repeated three times per day for a total of 750 brushing cycles. Between brushing cycles specimens were returned to water or in situ. The geometry of the Knoop indents and the enamel-dentine profile were re-measured and the enamel and dentine wear calculated. Specimens were also prepared for TEM analyses. RESULTS: The mean enamel wear (microm) for Toothpastes A and B (water) was 0.23 and 0.06, and for Toothpastes A and B (in situ) was 0.03 and 0.08, respectively. The mean dentine wear (microm) for Toothpastes A and B (water) was 5.08 and 6.03, and for Toothpastes A and B (in situ) was 1.94 and 1.70, respectively. For Toothpaste A, the presence of in situ pellicle significantly (p<0.05) reduced enamel and dentine wear compared to water and for Toothpaste B, dentine wear was significantly reduced compared to water. After tooth brushing, residues of the in situ pellicle layer could be detected on enamel and dentine surfaces by TEM analysis. CONCLUSIONS: The study has demonstrated for the first time that the presence of pellicle can significantly reduce toothpaste abrasion.     

An in vitro biological and anti-bacterial study on a sol–gel derived silver-incorporated bioglass system

OBJECTIVES: The purpose of this study was to evaluate the in vitro antibacterial and biological activity of silver-incorporated bioactive glass system SiO(2)-CaO-P(2)O(5)-Ag(2)O (AgBG). The bacteriostatic and bactericidal properties of this new quaternary glass system along with the ternary sol-gel glass system SiO(2)-CaO-P(2)O(5) (BG) have been studied using Escherichia coli as a test micro-organism. The AGBG system thus appears to be a promising material for dental applications, since similar effects might be produced on a film of bacteria and mucous that grows on the teeth. METHODS: The SiO(2)-CaO-P(2)O(5)-Ag(2)O and SiO(2)-CaO-P(2)O(5) glass systems were synthesized by the sol-gel technique and characterized for their physicho-chemical properties. The antibacterial activity and biological properties were evaluated by determining the minimum inhibitory concentrations (MICs). Release of Ag(+) into the culture medium was measured by inductively coupled plasma (ICP) analysis. RESULTS: The in vitro antibacterial action of the SiO(2)-CaO-P(2)O(5)-Ag(2)O was compared with that of its ternary counterpart glass system. The concentrations of Ag-bioglass, in the range of 0.02-0.20mg of Ag-bioglass per millilitre of culture medium, were found to inhibit the growth of these bacteria. The Ag-bioglass not only acts bacteriostatically but it also elicited a rapid bactericidal action. A complete bactericidal effect was elicited in the early stages of the incubation at Ag-bioglass concentration of 20mg/ml and the ternary glass system had no effect on bacterial growth or viability. The antibacterial action of Ag-bioglass was exclusively attributed to the leaching of Ag(+) ions from the glass matrix. SIGNIFICANCE: One of the major advantages of incorporating silver ions into a gel glass system is that the porous glass matrix can allow for controlled sustained delivery of the antibacterial agent to dental material, used even under anaerobic conditions such as deep in the periodontal pocket. This glass system also provides long-term action required for systems which are constantly at risk of microbial contamination.     

Idiopathic isolated unilateral hypoglossal nerve palsy: a diagnosis of exclusion

This report describes the rare case of a 22-year-old male with persistent idiopathic isolated hypoglossal nerve palsy. Thorough history, examination, and investigation were needed to rule out the many causes of such a presentation. The clinical presentation showed unilateral atrophy and fibrillation of the affected side and mild deviation on protrusion to the affected side. The differential diagnosis included neoplasia, trauma, infection, endocrine, autoimmune, neurologic, and vascular causes. Investigations included magnetic resonance imaging, computerized tomography scan, chest x-ray, cerebrospinal fluid culture, and a range of hematologic tests. These led to a diagnosis of persistent idiopathic isolated hypoglossal nerve palsy.     

OmpA-like protein influences cell shape and adhesive activity of Tannerella forsythia

Tannerella forsythia, a gram-negative fusiform rod, is implicated in several types of oral anaerobic infections. Most gram-negative bacteria have OmpA-like proteins that are homologous to the OmpA protein in Escherichia coli. We identified an OmpA-like protein in T. forsythia encoded by the tf1331 gene as one of the major proteins by mass spectrometric analysis. Two-dimensional, diagonal electrophoresis showed that the OmpA-like protein formed a dimeric or trimeric structure via intermolecular disulfide bonds. A biotin labeling experiment revealed that a portion of the protein was exposed on the cell surface, even though T. forsythia possesses an S-layer at the outermost cell surface. Using a tf1331-deletion mutant, we showed that the OmpA-like protein affected cell morphology. The length of the mutant cell was reduced almost by half. Cell swelling was observed in more than 40% of the mutant cells. Moreover, the mutant exhibited decreased adhesion to fibronectin, retarded autoaggregation, and reduced cell surface hydrophobicity. These results suggest that the OmpA-like protein in T. forsythia plays an important role in cellular integrity and adhesive function.     

Effect of chlorhexidine incorporation into a self-etching primer on dentine bond strength of a luting cement

Objectives

This study investigated the effect of incorporating chlorhexidine in a self-etching primer on the bond strength of an adhesive resin cement to dentine and on antibacterial activity.

Methods

Experimental self-etching primers were prepared by adding chlorhexidine (CHX) diacetate to ED primer 2.0 (Kuraray Medical Inc.) to obtain chlorhexidine concentrations of 1.0 wt% and 2.0 wt%. Human occlusal dentine surfaces were conditioned for 30 s using the experimental primers or pure ED primer. Composite blocks were luted using Panavia F 2.0 (Kuraray Medical Inc.). After storage in water for 24 h, the bonded teeth were sectioned into 0.9 mm × 0.9 mm beams and stressed to failure in tension to examine microtensile bond strength (μTBS). Fractured surfaces were examined with a field-emission scanning electron microscopy (FE-SEM). The morphology of dentine surfaces that were conditioned with each primer was also observed under FE-SEM. An agar diffusion test was performed to examine the antibacterial effect of each primer against Streptococcus mutans and Enterococcus faecalis.

Results

Addition of chlorhexidine to the primer had significant effects (p < 0.001) on μTBS and antibacterial effect. No significant difference in μTBS was found between the groups that contained 0% and 1% chlorhexidine in the primer (p = 0.095). Conversely, the group that contained 2% chlorhexidine showed significantly lower μTBS and pronounced cohesive failures within the thin layer of the primer.

Conclusions

Incorporation of chlorhexidine into ED primer 2.0 showed significant antibacterial activities. Conditioning with the 1% chlorhexidine-containing primer had no adverse effect on μTBS.     

Myofascial temporomandibular disorder pain, parafunctions and psychological stress

Associations of evening and morning masticatory muscle pain and nocturnal electromyography (EMG) activity with psycho-behavioural factors and occlusal splint therapy were studied during a 20-week study-protocol. Over a period of almost 2 years, only eight of the 120 eligible patients were willing to enroll the study protocol. Further, four of the eight participants dropped out during the study, and approximately 20-30% of the nocturnal EMG recordings failed. Because of the impractical and unworkable nature of the protocol, the study was prematurely terminated and the results of the four remaining individuals are reported here as single-patient clinical trials. Univariate and multiple regression analyses revealed that in three of the four patients, changes in nocturnal EMG activity were associated with the period of splint therapy. However, no associations were found between the changes in nocturnal EMG activity and the observed changes in muscle pain. In two patients, the changes in muscle pain were associated with the period of splint therapy and with the changes in psychological stress. Within the limitations of single-patient clinical trials, it can be concluded that changes in chronic masticatory muscle pain seem to be more related to changes in psychological stress than to those in parafunctional activities.     

Four-year clinical performance of a lithia disilicate-based core ceramic for posterior fixed partial dentures

PURPOSE: The objective of this research was to test the hypothesis that 3-unit fixed partial dentures (FPDs) made from a moderately high-strength core ceramic will adequately resist fracture in posterior regions if fabricated with a minimal connector size of 4 mm. MATERIALS AND METHODS: Thirty ceramic FPD core frameworks were prepared using a hot-pressing technique and a lithia disilicate-based core ceramic. The maximum occlusal force was measured for each patient prior to tooth preparation. Connector heights and widths were measured for each FPD. Patients were recalled annually after cementation for 4 years and evaluated using 11 clinical criteria. All FPDs were examined by 2 independent clinicians, and rankings for each criterion were made from 1 to 4 (4 = excellent; 1 = unacceptable). RESULTS: The fracture rate was approximately 3% per year, and the proportion of good overall ratings in the nonfractured FPDs was reduced by more than 6% per year, where a good overall rating was defined to be a rank of 3 or 4 in all 11 criteria. There was little evidence that the use of either resin-reinforced glass-ionomer cement (Protec CEM) or dual-cure resin cement (Variolink II) made any difference in terms of fracture rate or overall rating (P= .30, .63, .97, and .71 for the 4 years, respectively). From a fracture resistance perspective, 4 of the 30 ceramic FPDs fractured within the 4-year evaluation period, representing an 86.7% success rate. Another FPD was replaced because of a caries lesion on 1 abutment tooth away from the margin. One FPD fracture was associated with the subject having the greatest occlusal force (1,031 N). The other 2 fractures were associated with FPDs that exhibited connector heights of less than 3 mm. All criteria were ranked good to excellent during the 4-year period for the remaining FPDs. CONCLUSION: Fractured FPDs were associated with a connector height of less than 4 mm; thus, the hypothesis was accepted.     

Non-surgical periodontal treatment of cyclosporin A-induced gingival overgrowth: immunohistochemical results

Aim:  The present study was planned to analyze the effects of a 12-month non-surgical periodontal treatment on histologic and immunohistochemical features of cyclosporin A (CsA)-induced gingival overgrowth (GO).
Materials and methods:  Gingival samples were collected from 21 liver transplant subjects exhibiting CsA-induced GO prior to, and 12 months after non-surgical periodontal therapy including oral hygiene instructions, scaling and 2-month recall appointments, and also from 18 healthy control subjects. Gingival biopsy specimens were stained with hematoxylin–eosin and monoclonal antibodies for vimentin, CD3 (T-lymphocytes), CD20 (B-lymphocytes), CD34 (endothelium) and Ki-67 (fibroblasts proliferation rate), using a streptavidin-biotin-peroxidase complex method.
Results:  Total inflammatory cells, gingival vessels and fibroblast proliferation rate demonstrated significant reduction after non-surgical periodontal treatment ( P  < 0.0001) in overgrown gingiva, while B- and T-lymphocytes remained nearly unchanged ( P  = 0.61 and 0.33, respectively). At the 12-month evaluation no significant differences were found when comparing the gingival biopsies from CsA-treated patients and those from healthy controls ( P  > 0.05).
Conclusions:  Control of clinical inflammation by means of non-surgical periodontal treatment results both in lowering of inflammatory infiltrate and in changes in connective tissue composition. Thus, plaque-induced inflammation would seem to modulate the drug-gingival tissue interaction.
Clinical relevance:  A strict plaque control program play a pivotal role in the management of transplant patients exhibiting cyclosporin A-GO.