Surface EMG of jaw elevator muscles: effect of electrode location and inter-electrode distance

This study addresses methodological issues on surface electromyographic (EMG) signal recording from jaw elevator muscles. The aims were (i) to investigate the sensitivity to electrode displacements of amplitude and spectral surface EMG variables, (ii) to analyse if this sensitivity is affected by the inter-electrode distance of the bipolar recording, and (iii) to investigate the effect of inter-electrode distance on the estimated amplitude and spectral EMG variables. The superficial masseter and anterior temporalis muscles of 13 subjects were investigated by means of a linear electrode array. The percentage difference in EMG variable estimates from signals detected at different locations over the muscle was larger than 100% of the estimated value. Increasing the inter-electrode distance resulted in a significant reduction of the estimation variability because of electrode displacement. A criterion for electrode placement selection is suggested, with which the sensitivity of EMG variables to small electrode displacements was of the order of 2% for spectral and 6% for amplitude variables. Finally, spectral and, in particular, amplitude EMG variables were very sensitive to inter-electrode distance, which thus should be fixed when subjects or muscles are compared in the same or different experimental conditions.     

Adaptation of salivary Lactobacillus strains to xylitol

OBJECTIVE: Acid production from sugars is one of the virulence factors of cariogenic bacteria. To eliminate this factor, many authors have suggested using sugar substitutes like xylitol, which is not fermented by most oral bacteria. The aim of this work was to investigate whether oral strains of lactobacilli unable to utilise xylitol could become able to utilise this polyol. DESIGN: Twenty-eight oral strains and six ATCC strains of lactobacilli were tested. None was initially able to produce acids from xylitol. Media containing only xylitol was used in order to see if an adaptation was possible. The acid production from xylitol was measured by recording the pH variations of the culture medium. The acids produced were identified by HPLC. RESULTS: After a 15-days culture, 10 strains produced acids. After a 40-days culture, 11 more strains produced acid. When acid production occurred, lactic, formic, acetic, propionic and butyric acids were the organic acids formed by all the strains. CONCLUSIONS: Adaptation of oral strains of lactobacilli to xylitol can occur in vitro.     

Guidelines for infection control in dental health care settings--2003

BACKGROUND: The Centers for Disease Control and Prevention, or CDC, is the lead federal agency for disease prevention in the United States. It has been 10 years since CDC infection control guidelines for dental health care settings were last published. During those 10 years, new technologies and issues have emerged, and other CDC infection control guidelines for health care settings have been updated. RESULTS: In light of these developments, CDC collaborated with experts in infection control to revise its infection control recommendations for dental health care settings. Existing guidelines and published research pertinent to dental infection control principles and practices were reviewed. This article provides background information, describes the process used to create these guidelines, and lists the new recommendations. CLINICAL IMPLICATIONS: CDC believes that dental offices that follow these new recommendations will strengthen an already admirable record of safe dental practice. Patients and providers alike can be assured that oral health care can be delivered and received in a safe manner.     

Radiation-induced impairment of osseous healing with vascularized bone transfer: experimental model using a pedicled tibia flap in rat

Aim of this study was to establish an appropriate animal model for investigating the healing of vascularized osseous transplants to irradiated recipient sites applying metabolic, vascular and immunologic experimental studies. In 20 Wistar rats (male, weight 300-500 g), a pedicled osseous tibia flap was raised and transferred to a subcutaneous pocket in the ipsilateral groin. The remaining tibia was stabilized with a monocortical titanium miniplate. To create a pre-irradiated transplant bed, the donor-area including the adjacent bone of the tibia was irradiated with a total dose of 50Gy (5 x 10 Gy) in 10 animals. The interval between irradiation and retransfer of the non-irradiated pedicled tibia flap was 4 weeks. Ten animals received no radiation. Evaluation of osseous healing and the success of the transferred flap were based on a clinical and quantitative histomorphometric assessment. Testing for significant differences was performed using the non-parametric Mann-Whitney U-test. The rate of complete osseous healing in the non-irradiated animals was 90%. In contrast there was no significant bone union observed in the group of the pedicled flaps grafted to the pre-irradiated (50Gy) recipient site (P = 0.001). Similarly bone formation in the transitional zone between bone graft and recipient bone was significantly lower in the preirradiated group (P < 0.001) (16.9 +/- 3%) in contrast to the non-irradiated transplant bed (47.9 +/- 6%).     

Polymorphous low-grade adenocarcinoma--a rare and aggressive entity in adolescence

Polymorphous low-grade adenocarcinoma (PLGA) is an uncommon tumour that usually affects the minor salivary glands, particularly in the palate. It is rare in young patients, and here we report a case in a teenage girl. She presented at the age of 16, although the lesion had been noticed 2 years previously. The tumour showed histopathological features of PLGA, but recurred locally, behaved aggressively, and ultimately metastasised to cervical lymph nodes. This was accompanied by an altered histological picture, with a papillary cystic pattern and necrosis becoming progressively more prominent. PLGA is not always a low-grade lesion and some tumours, notably those with a papillary cystic growth pattern, may require more aggressive treatment.     

Efficacy of A-dec's ICX dental unit waterline treatment solution in the prevention and treatment of microbial contamination in dental units

OBJECTIVE: Even though some chemical agents can disinfect biofilms in dental unit waterlines, there remains concern that all remnants of the biofilm matrix are not eliminated. Even with periodic treatments, the bacterial populations in dental unit waterlines recur rapidly. In addition, with some previously tested products, patient safety, as well as toxic, caustic and corrosive residual chemicals are also a concern. This study evaluated ICX, A-dec's new water treatment solution, in a series of experiments for prevention, microbial spectrum of activity, minimum inhibitory time determination, and treatment of established biofilms. METHODOLOGY: New dental unit waterline tubing was treated continuously during simulated patient care over 28 days with municipal water. It was then treated with ICX. Effluents from lines with established biofilms (averaging > 10(4) CFU/ml at day 0) were treated to assess levels of CFU counts within 21 days of exposure to ICX. RESULTS: Tubing treated with ICX did not develop a detectable biofilm using ruthenium red staining, and microbes in effluents remained undetectable. CONCLUSION: ICX is effective in maintaining the effluent within the American Dental Association's and the Centers for Disease Control's recommendation for < 500 CFU/ml. In addition, considering the preliminary finding that ICX reduces microbial contamination of effluents from established biofilm lines, it may be useful in long-term treatment alone or when coupled with a shock treatment to assist in biofilm destruction.     

Nurse-delivered brief interventions for hazardous drinkers with alcohol-related facial trauma: a prospective randomised controlled trial

AIMS: To assess the impact of two methods of brief nurse-delivered brief interventions in reducing drinking variables in hazardous drinkers with alcohol-related facial injuries. METHODS: A randomised controlled trial of two brief interventions involving hazardous drinkers with facial trauma in three Oral and Maxillofacial Surgery outpatient clinics in the West of Scotland; 194 patients were recruited and randomised to have either a nurse-led brief motivational intervention (intervention group) or a leaflet about alcohol misuse (control group). Patients were followed up at 3 and 12 months after the intervention and drinking variables reassessed. RESULTS: A brief motivational intervention for alcohol provided by a nurse was more effective than a leaflet in helping some patients with facial trauma to reduce their alcohol consumption 12 months after the intervention (p<0.05). CONCLUSIONS: Facial trauma in the West of Scotland is strongly associated with alcohol misuse and is a recurrent disease, particularly among those who drink heavily. A nurse-delivered brief motivational intervention is effective in helping patients with high scores in the Alcohol Use Disorders Identification Test to reduce their drinking, and this effect was apparent 12 months after the intervention.     

Effect of a topical antimicrobial paste on healing after extraction of molars in HIV positive patients: randomised controlled clinical trial

AIM: To assess the efficacy of a medicated dressing in the socket on the healing after dental extractions in HIV positive patients. PATIENTS AND METHODS: Forty HIV positive patients with CD4 counts below 200 cells/mm(3) who were to have molar teeth extracted were randomly allocated to have the socket dressed with a medicated paste (Rifocort) with camphorated parachlorophenol and iodoform) and sutured (treated group), or merely sutured (control group). RESULTS: The sockets in the treated group healed more quickly than in the control group.     

Temporomandibular joint internal derangement: detection with 12.5 MHz ultrasonography

The purpose of this study was to determine whether 12.5 MHz ultrasonography (US) could be used to assess the presence or absence of temporomandibular joint (TMJ) internal derangement (ID). In 48 consecutive patients with TMJ disorders 192 TMJ positions were investigated by US to analyse the functional disc-condyle relationship (DCR). In order to compare the respective findings with those of a diagnostic method offering a high accuracy, coronal and sagittal magnetic resonance imaging was carried out immediately afterwards. With US showing a sensitivity of 0.58 and 0.75, and a specificity of 0.92 and 0.84 for disc displacement with and without reduction, the data revealed US to be marginal in detecting the presence, but sensitive in detecting the absence of the respective types of a TMJ ID. In addition, with a positive predictive value of 0.83 and 0.71, and a negative predictive value of 0.81 and 0.87 for disc displacement with and without reduction, the results indicate that US may be insufficient in establishing a correct diagnosis for the presence or absence of the respective types of TMJ ID. Regarding the diagnosis of absence or presence of TMJ ID, the results demonstrate high-resolution (HR)-US to be sensitive in detecting the absence, and reliable in predicting the presence of TMJ ID. In view of the fact that the 12.5 MHz US technique proved to be a reliable diagnostic aid for the detection of normal, and the prediction of abnormal DCR, the results of this study should be of further interest and encourage research in its potential uses and diagnostic capabilities.     

Marginal adaptation and fracture resistance of adhesively luted glass fibre-composite reinforced molar crowns with different inner crown surfaces

OBJECTIVES: This study compared the influence of different inner crown surfaces on the fracture resistance and marginal adaptation of adhesively fixed glass fibre-reinforced molar crowns. MATERIALS AND METHODS: Vectris/Targis crowns were constructed with an inner framework of glass fibres (directly on the tooth) or an inner veneering composite layer between the fibre-framework and the tooth-substance. Both groups were sandblasted inside using Al(2)O(3); 50 microm grain size (200 kPa, 20 s) and silane coated. A control group had the inner fibre framework, but was neither sandblasted nor silane coated. The crowns were adhesively cemented on extracted human teeth, and thermally cycled and mechanically loaded (TCML: 6000 x 5 degrees C/55 degrees C; 1.2 x 10(6) x 50 N, 1.66 Hz). The marginal adaptation before and after TCML was evaluated and the fracture resistance was investigated using a Zwick universal testing machine. RESULTS: After TCML the proportion of 'perfect margin' of the control group decreased significantly at the interface crown/cement. For the variations with an inner fibre framework or inner composite layer the marginal adaptation or fracture resistance did not decrease significantly after ageing. The fracture resistance values were control: 1509N+/-486; inner fibre framework: 1896N+/-342; inner composite layer: 1754N+/-340. CONCLUSIONS: In the case of the investigated fibre framework and veneering composite, the inner surface of glass fibre-reinforced molar crowns can be covered with a composite layer or with a glass fibre framework. Both methods achieve comparable high fracture strengths and reliable marginal adaptation.