Antibiotic prophylaxis for dentoalveolar surgery: is it indicated?

Usually dentists in Australia give patients oral antibiotics after dentoalveolar surgery as a prophylaxis against wound infection. When this practice is compared to the principle of antibiotic prophylaxis in major surgery it is found to be at variance in a number of ways. In major surgery, the risk of infection should be high, and the consequences of infection severe or catastrophic, before antibiotic prophylaxis is ordered. If it is provided then a high dose of an appropriate spectrum antibiotic must be present in the blood prior to the first incision. Other factors which need to be considered are the degree of tissue trauma, the extent of host compromise, other medical comorbidities and length of hospitalization. Standardized protocols of administration have been determined and evaluated for most major surgical procedures. Dentoalveolar surgery is undoubtedly a skilled and technically challenging procedure. However, in contrast to major surgical procedures, it has a less than five per cent infection rate and rarely has severe adverse consequences. Dentoalveolar surgery should be of short duration with minimal tissue damage and performed in the dental chair under local anaesthesia. Controlled studies for both mandibular third molar surgery and placement of dental implants show little or no evidence of benefit from antibiotic prophylaxis and there is an adverse risk from the antibiotic. This review concludes that there is no case for antibiotic prophylaxis for most dentoalveolar surgery in fit patients. In the few cases where it can be considered, a single high pre-operative dose should be given.     

Microbiological culture analysis of the tongue anaerobic microflora in subjects with and without halitosis

Objective:  Determination of the microflora present on the tongue dorsum of subjects with and without halitosis using conventional microbiological culture methods.
Methods:  Twenty-one halitosis and 20 control patients were recruited using a strict clinical protocol. Samples were collected from the posterior dorsum of the tongue using a sterile brush. Each sample was vortex mixed for 30 s and serial 10-fold dilutions to 10⁻⁷ were carried out. Samples were plated onto fastidious anaerobe agar (FAA) and FAA enriched with vancomycin. These were incubated under anaerobic conditions for 10 days at 37°C. Strict anaerobes were identified by metronidazole sensitivity and bacteria were identified to genus level by a combination of colony morphology, Gram staining and biochemical and enzymatic tests (rapid ID 32 A).
Results:  The predominant species in test and control groups were Veillonella sp. and Prevotella sp. Greater species diversity was found in the halitosis samples compared with controls. The halitosis samples contained an increased incidence of unidentifiable Gram-negative rods, Gram-positive rods and Gram-negative coccobacilli.
Conclusions:  There was no obvious association between halitosis and any specific bacterial genus. The increased species diversity found in halitosis samples suggests that halitosis may be the result of complex interactions between several bacterial species. The role of uncultivable bacteria may also be important in contributing to this process.     

Is There a Limit to the Superiority of Individuals with ASD in Visual Search?

Superiority in visual search for individuals diagnosed with autism spectrum disorder (ASD) is a well-reported finding. We administered two visual search tasks to individuals with ASD and matched controls. One showed no difference between the groups, and one did show the expected superior performance for individuals with ASD. These results offer an explanation, formulated in terms of load theory. We suggest that there is a limit to the superiority in visual search for individuals with ASD, related to the perceptual load of the stimuli. When perceptual load becomes so high that no additional task-(ir)relevant information can be processed, performance will be based on single stimulus identification, in which no differences between individuals with ASD and controls have been demonstrated.     

Reduced StartReact effect and freezing of gait in Parkinson’s disease: two of a kind?

Freezing of gait (FOG) is a disabling feature of Parkinson’s disease. Emerging evidence suggests that dysfunction of the pedunculopontine nucleus (PPN) and pontomedullary reticular formation (pmRF) plays a role in the causation of FOG. These brainstem structures can be examined by the StartReact paradigm, which utilizes a startling stimulus to accelerate reaction times (StartReact). Here, we examined gait initiation in PD patients with and without FOG using this paradigm. Twenty-six patients with Parkinson’s disease (12 freezers and 14 non-freezers) and 15 controls performed two tasks: rapid gait initiation in response to an imperative ‘go’ signal; and a control condition, involving a simple reaction-time task involving ankle dorsiflexion. During both tasks, a startling acoustic stimulus was combined with the imperative signal in 25 % of trials. In controls, the startle accelerated gait initiation and shortened the onset latency of tibialis anterior responses during ankle dorsiflexion. This acceleration was intact in non-freezers, but was significantly attenuated in the freezers. Independent of the occurrence of a startle, freezers showed a reduced length of the first step compared to non-freezers and controls. The diminished StartReact effect in freezers probably reflects deficient representation or release of motor programs at the brainstem reticular level due to dysfunction of the PPN, the pmRF, or both. These brainstem structures are presumably involved in integrating anticipatory postural adjustments with subsequent stepping movements. We suggest that with time-varying demands, these structures may no longer be able to coordinate the integration of anticipatory postural adjustments with steps, leading to FOG episodes.     

Higher order aberrations,refractive error development and myopia control: a review

Evidence from animal and human studies suggests that ocular growth is influenced by visual experience. Reduced retinal image quality and imposed optical defocus result in predictable changes in axial eye growth. Higher order aberrations are optical imperfections of the eye that alter retinal image quality despite optimal correction of spherical defocus and astigmatism. Since higher order aberrations reduce retinal image quality and produce variations in optical vergence across the entrance pupil of the eye, they may provide optical signals that contribute to the regulation and modulation of eye growth and refractive error development. The magnitude and type of higher order aberrations vary with age, refractive error, and during near work and accommodation. Furthermore, distinctive changes in higher order aberrations occur with various myopia control treatments, including atropine, near addition spectacle lenses, orthokeratology and soft multifocal and dual-focus contact lenses. Several plausible mechanisms have been proposed by which higher order aberrations may influence axial eye growth, the development of refractive error, and the treatment effect of myopia control interventions. Future studies of higher order aberrations, particularly during childhood, accommodation, and treatment with myopia control interventions are required to further our understanding of their potential role in refractive error development and eye growth.