Think before you prescribe: how dentistry contributes to antibiotic resistance.

Antibiotic resistance presents a daunting challenge to health professionals worldwide and has the potential to create major problems for modern health care, resulting in more medical expenditure, extended hospital stays and increased morbidity and mortality. Advanced genome sequencing technologies present a complex picture of resistance, extending our understanding beyond the pharmacotherapeutic interface between pathogens and antibiotics. This review discusses the global scope and scale of antibiotic resistance and contextualizes it for the dental practitioner, emphasizing the role we must play in limiting the progression of resistance through antibiotic stewardship and disease prevention.

Metagenomic Insights into Transferable Antibiotic Resistance in Oral Bacteria.

Antibiotic resistance is considered one of the greatest threats to global public health. Resistance is often conferred by the presence of antibiotic resistance genes (ARGs), which are readily found in the oral microbiome. In-depth genetic analyses of the oral microbiome through metagenomic techniques reveal a broad distribution of ARGs (including novel ARGs) in individuals not recently exposed to antibiotics, including humans in isolated indigenous populations. This has resulted in a paradigm shift from focusing on the carriage of antibiotic resistance in pathogenic bacteria to a broader concept of an oral resistome, which includes all resistance genes in the microbiome. Metagenomics is beginning to demonstrate the role of the oral resistome and horizontal gene transfer within and between commensals in the absence of selective pressure, such as an antibiotic. At the chairside, metagenomic data reinforce our need to adhere to current antibiotic guidelines to minimize the spread of resistance, as such data reveal the extent of ARGs without exposure to antimicrobials and the ecologic changes created in the oral microbiome by even a single dose of antibiotics. The aim of this review is to discuss the role of metagenomics in the investigation of the oral resistome, including the transmission of antibiotic resistance in the oral microbiome. Future perspectives, including clinical implications of the findings from metagenomic investigations of oral ARGs, are also considered.

Reducing composite restoration polymerization shrinkage stress through resin modified glass-ionomer based adhesives.

BACKGROUND: The aim of this study was to determine whether employing resin modified glass-ionomer based adhesives can reduce polymerization contraction stress generated at the interface of restorative composite adhesive systems. METHODS: Five resin based adhesives (G Bond, Optibond-All-in-One, Optibond-Solo, Optibond-XTR and Scotchbond-Universal) and two resin modified glass-ionomer based adhesives (Riva Bond-LC, Fuji Bond-LC) were analysed. Each adhesive was applied to bond restorative composite Filtek-Z250 to opposing acrylic rods secured within a universal testing machine. Stress developed at the interface of each adhesive-restorative composite system (n = 5) was calculated at 5-minute intervals over 6 hours. RESULTS: The resin based adhesive-restorative composite systems (RBA-RCS) demonstrated similar interface stress profiles over 6 hours; initial rapid contraction stress development (0-300 seconds) followed by continued contraction stress development ≤0.02MPa/s (300 seconds - 6 hours). The interface stress profile of the resin modified glass-ionomer based adhesive-restorative composite systems (RMGIBA-RCS) differed substantially to the RBA-RCS in several ways. Firstly, during 0-300 seconds the rate of contraction stress development at the interface of the RMGIBA-RCS was significantly (p < 0.05) lower than at the interface of the RBA-RCS. Secondly, at 300 seconds and 6 hours the interface contraction stress magnitude of the RMGIBA-RCS was significantly (p < 0.05) lower than the stress of all assessed RBA-RCS. Thirdly, from 300 seconds to 6 hours both the magnitude and rate of interface stress of the RMGIBA-RCS continued to decline over the 6 hours from the 300 seconds peak. CONCLUSIONS: The use of resin modified glass-ionomer based adhesives can significantly reduce the magnitude and rate of polymerization contraction stress developed at the interface of adhesive-restorative composite systems.

Influence of implant abutment angulations on the fracture resistance of overlaying CAM-milled zirconia single crowns.

BACKGROUND: An in vitro study was performed to assess the effect of three implant abutment angulations and three core thicknesses on the fracture resistance of overlaying computer-aided manufacturing (CAM) milled zirconia (Cercon(®) system) single crowns. METHODS: Three groups, coded A to C, with different implant abutment angulations (group A/0°, group B/15° and group C/30° angulation) were used to construct 15 crowns for each angulation. Forty-five overlay restorations were milled using the Cercon(®) system with zirconium core thicknesses of 0.4, 0.6 and 0.8 mm using five crowns for each angulation. The final restorations were prepared and stored in distilled water at mouth temperature (37°C) for 24 hours prior to testing. The restorations were cemented using Temp Bond(®) . The load required to break each crown and the mode of failure were recorded. All the results obtained were statistically analysed by the ANOVA test (level of significance p < 0.05). Tested crowns were examined using a stereomicroscope at 40X and selected crowns (five randomly selected from each group were further examined by scanning electron microscopy) to reveal the zirconia-ceramic interface and to determine the fracture origin. RESULTS: Implant abutment angulations significantly (p < 0.05) reduced the fracture resistance of overlaying CAM-milled zirconia single crowns. The fracture loads of Cercon(®) crowns cemented onto abutment preparations with a 30° angulation were the lowest of the groups tested. The core thickness (0.4 to 0.8 mm) did not significantly (p > 0.05) affect the fracture resistance of the CAM-milled zirconia single crowns. SEM showed that the origin of the fracture appeared to be located at the occlusal surfaces of the crowns and the crack propagation tended to radiate from the occlusal surface towards the gingival margin. CONCLUSIONS: The implant angulation of 30° significantly (p < 0.05) reduced the fracture resistance of overlaying CAM-milled zirconia single crowns. Reducing the core thickness from 0.8 mm to 0.4 mm did not affect (p > 0.05) the fracture resistance of overlaying CAM-milled zirconia single crowns.

A survey of the efficiency of visible light curing units.

OBJECTIVES: The purpose of this study was to survey the efficiency of visible light curing units in dental practices across Australia. METHODS: Survey forms were distributed to representatives of 3M Health Care to complete when visiting dentists in their working areas. The information collected included the type and age of the unit, curing times used, history of maintenance, replacement of components, and the light intensity reading. RESULTS: Of the 214 light curing units surveyed, approximately 27% recorded a light intensity of 200 mW cm-2 or less, a level regarded as inadequate to cure a 2-mm thick increment of composite resin. An additional 26% registered an output of between 201 and 399 mW m-2. This level would be considered acceptable with additional curing time; however, 44% of practitioners were curing for 20 s or less. A negative correlation was found between the age of the unit and the intensity recorded. Nearly 50% of respondents had never checked the light output of their unit. CONCLUSIONS: The results indicate that just over one-half of the light curing units surveyed were not functioning satisfactorily. An obvious reduction in intensity was noted with the older units. There is a substantial lack of awareness among dentists of the need for maintenance and regular checking of the light intensity of these units.

Marginal seal of cervical tooth-coloured restorations. A laboratory investigation of placement techniques.

Incremental placement of composite resin has been suggested as a means of overcoming the contraction that occurs during polymerization of the composite material and as a consequence should allow an improved gingival dentine seal. Numerous incremental placement techniques for composite resin restorations have been documented in the literature. This study examined four different methods of placing Silux in class V cavities, located in the region of the cemento-enamel junction, and lined with Vitrabond. None of the placement methods used completely sealed either the enamel or dentine margins. Of the four techniques employed, the one which involved incremental placement of the gingival component first showed the least amount of leakage at the dentine margin. This result, however, was only significantly different from that of the bulk placement method. In the majority of cases where leakage did occur at the dentine margin, it progressed no further than the Vitrabond lining. It appeared that the high initial adherence to dentine of the light cured glass-ionomer cement prevented deeper penetration of the dye.

Microleakage of glass ionomer/composite resin restorations: a laboratory study. Part 2. The influence of bonding systems.

Acid-etching and bonding of composite resin to bevelled enamel margins has been reported to produce a reliable seal. However, achieving a seal with dentine and cementum margins is more difficult. Four different dentine bonding systems were used in combination with Silux composite resin to restore cervical cavities in vitro. None of the bonding systems used completely sealed either the occlusal or gingival margins. Of the four systems, GLUMA provided the best seal at both the occlusal and gingival margins.

Microleakage of glass ionomer/composite resin restorations: a laboratory study. 1. The influence of glass ionomer cement.

Acid-etching of enamel margins, often combined with bevelling and use of a low viscosity resin, has resulted in improved sealing of composite restorations. When enamel is absent and margins involve dentine or cementum, microleakage is more often observed. The use of glass ionomer cement, as both a restorative material and as a base combined with a veneer of composite resin, has been advocated as a means of minimizing microleakage where margins are placed in dentine or cementum. Four restorative techniques incorporating glass ionomer cement were used, in vitro, to restore cervical cavities. After thermal cycling, dye penetration was scored along occlusal and gingival margins. In all instances the gingival margin exhibited a less reliable seal than the occlusal margin. The sandwich restorations produced a superior seal at both occlusal and gingival margins when compared with glass ionomer restorative cement.

Recognition and prevention of failures in clinical dentistry. Aesthetic dental materials--posterior.

Despite the widespread use of posterior composite resins and the availability of porcelain and composite resin inlays to restore posterior teeth, clinical researchers express caution regarding their use. Two main concerns include: the technique sensitive nature of the procedures involved and limitations in the performance of these restorations due to the physical properties of the materials. Composites are prone to wear, fracture and a lack of marginal seal; whilst porcelain is brittle, difficult to manipulate and has the ability to wear opposing enamel. Longevity of the newer systems has not yet been determined and as such they should be regarded as experimental. Patients who request these restorations need to be provided with a thorough explanation of the advantages and disadvantages of each type of restoration; following this, careful clinical judgment and conservative use of these materials is recommended for optimum results.

The relevance of a systemic model for the study and treatment of anorexia nervosa in adolescents.

A systems model describing interactions between social, familial, intrapsychic and physiological levels in anorexia nervosa is described. The role of escalating positive cycles in producing severe pathology is emphasized. The general relevance of the model for understanding different clinical pictures and for focusing treatment interventions and further research is outlined.

Acid etching of a glass ionomer cement base: SEM study.

The effects of acid-etching duration on the surface of a glass ionomer cement designed for use as an intermediary layer between composite resin and dentine were investigated. Cement topography changes occurred which could be related to etch duration. When compared with enamel etched for a similar period, undue loss of cement substance was not observed for any of the etch times used.

The treatment and outcome of anorexia nervosa in adolescents: a prospective study and five year follow-up.

This study reports the treatment and five year follow-up of 25 adolescent (mean age 14.9 yr) anorexics seen early in their illness (mean duration 8.08 months) and fulfilling Feighner's criteria. Results are reported along four parameters at treatment termination and at follow-up; weight, menstrual function, eating patterns and social life. At follow-up 76% are rated as excellent or good, 16% fair or continuing in treatment and 8% as relapsed. This represents a significant improvement over results at treatment termination. It is concluded that anorexia nervosa in adolescence can have a good outcome for the majority but it is undemonstrated which are the crucial variables regarding treatment modalities and patient selection nor did any clear prognostic factors emerge. A hypothesis regarding the therapeutic effect of the follow-up is suggested.