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The missing teeth of edentulous adults are most commonly replaced with complete upper and lower dentures. The most prevalent problem regarding complete dentures is the retention of the mandibular one. The testing of most denture retention systems has usually employed in-vivo testing with no prior in-vitro tests being carried out. In addition, in-vitro tests that have been carried out did not replicate the natural real situation of the oral cavity. The aim of this study was to design and develop an artificial edentulous mandibular jaw model, with the associated soft-tissue structure (artificial mucosa and reflected tissue) based on real patient parameters, to facilitate testing the retention of mandibular complete dentures. This would enable us to optimise the design and manufacture of novel systems prior to testing on real patients in a clinical trial. The objectives for this study were to firstly conduct a clinical evaluation of patients’ satisfaction with complete denture and to correlate the effect of loose mandibular denture with patient satisfaction. The second objective was to evaluate and identify the most appropriate synthetic materials that would replicate the soft tissue properties. Twelve elastic materials were assessed. These are representative of the following categories of materials: Addition and condensation-reaction silicone, polysulphide, polyether, alginate, maxillofacial impression material, soft lining material and non dental materials-chair side artist materials. Suitable substitute materials to the oral mucosa were used to construct the model. Testing of the model was conducted using a series of protocols to measure and compare the retention of mandibular dentures of varying designs (well-fitting, over- and under-extended) with and without denture adhesives (PoliGrip®, GlaxoSmithKline; Fixodent®, Procter & Gamble; Super Wernets®, GlaxoSmithKline). In conclusion, an in-vitro model of a mandibular ridge can be created to approximate the biophysical characteristics of the covering mucosa, and can be used to assess differences in the retention of various denture designs and different denture adhesives.

No description available.

The term denture stomatitis describes an inflammation of the oral mucosa in contact with the fitting surface (usually maxillary) of the denture. Although considered to have a multi-factorial aetiology, the incidence of denture stomatitis is strongly associated with poor denture hygiene and the presence of Candida albicans, in denture plaque. Dentures provided an ideal abiotic substratum for microbial attachment, retention and growth, providing hard, non-shedding of variable topography. Although a wide range of denture hygiene products and procedures are available for use, targeted activity towards Candida is not typically reported. In addition, denture cleansing protocols often use abrasive pastes and/or brushes which can alter denture topography and potentially increase the susceptibility to plaque accumulation and reduce cleanability. The aim of this work was to investigate interactions between denture surface topography and C.albicans, with a view to identifying factors that would enhance denture hygiene. Two sets of denture acrylic test surfaces were abraded in a linear direction; one using emery papers of increasing grit size, and the other by abrasion using toothbrush and dentifrices. All test surfaces were characterised using white light profilometry, enabling derivation of roughness parameters (Ra/Sa) and measurement of feature dimensions (width, depth). A method was developed that allowed biofilm growth from adherent blastospores or hyphae on these surfaces. Initial retention on the abraded surfaces increased with increasing roughness values, but there was no effect on topography on the resultant biofilm. Biofilms developed from hyphae had significantly higher biomass than those from blastospores, and also presented a more open network structure. After biofilm removal, surface roughness significantly affected retention of remaining cells: rougher surfaces retained more cells, and retention was increased by the presence of hyphae. The orientation of hyphae on the abraded surfaces did not seem to be effected by topographic features, nor by the proximity of other cells. This latter observation was confirmed using an optical tweezer method, which enabled the specific placement of individual cells, with subsequent monitoring of germ tube formation. The production of quorum sensing (QS) molecules was investigated as a factor influencing biofilm development. Using gas chromatography and mass spectrometry, volatile compounds were collected from planktonic and biofilms of C.albicans over time. Ethanol and the QS molecule farnesol were amongst the molecules identified, being produced at 4hour and 10hours respectively during the 24 hour incubation period. Farnesol was also shown to inhibit hyphal production by attached cells, when applied to the surfaces as a conditioning film, as well as in vapour form. A denture cleanser with improved anti-Candida activity was effective against blastospore and hyphal biofilms during extended 1 and 16 hour soak times. Using confocal scanning laser microscopy (CSLM) live-dead staining of Candida biofilm indicated that the denture cleanser inactivated cells throughout the biofilm, with increased effect and penetration over time, but no difference between hyphal and blastospore biofilms was observed. When mixed biofilms were generated with C.albicans and Streptococcus oralis, the presence of the bacteria appeared to increase the effect of the cleanser on Candida biofilm. It is proposed that the inactivation of the bacteria may have disrupted the biofilm and enhanced its susceptibility. However this requires further investigation. In order to reduce the accumulation of denture plaque and C.albicans, there is a need to limit substrate abrasion, reduce retention on the surface, prevent hyphal growth and ideally kill and remove denture plaque. Strategies towards these aims include targeted but gentle cleaning and the potential use of quorum sensing molecules.

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29 HIV seropositive patients and 27 seronegative patients were examined during the course of the study. Clinical data was collected from a total of 14,244 sites and subgingival plaque samples were collected from 1,461 sites. A total of 6,832 hybridisations were successfully completed, identifying over 16,000 colonies to a species level on nylon colony lifts. On initial analysis, HIV seropositive subjects had a marked tendency for increased mean attachment loss compared to the HIV seronegative controls in this sample. The HIV seropositive subjects were also found to harbour a higher mean percentage of P. gingivalis, and had a higher mean percentage of sites exhibiting suppuration than the HIV seronegative subjects. A subgroup of 9 HIV seropositive subjects was identified with widespread periodontal disease. In conclusion, this study confirms that there exists a subgroup of HIV seropositive patients who are at risk for an increased incidence of destructive periodontal disease. However, so many potential confounding factors associated with HIV infection and treatment exist, that identification of those patients who are at risk for periodontal disease may be difficult. Periodontal predictors of increased immunosuppression as HIV disease progresses are unlikely to be very powerful, even if they prove to be reliable, as not every patient with HIV infection in this study suffered from periodontal disease despite some patients having severe immunosuppression.

The present study investigated persistent digit sucking habits among referrals to a Hospital Orthodontic Department. In particular, the prevalence of habits and their effect on dentofacial morphology, dental occlusion and orthodontic treatment need were investigated. Over an eight month period 54 cases, or 6.1% of all new patients, were referred with persistent digit sucking habits. Two thirds were female, and the age range was 5 to 16 years. A Study Group of 44 cases over the age of 10 years was identified and compared with a Control Group of non digit sucking referred patients, matched for age and sex. The cephalometric data revealed digit sucking to be associated with a significant increase in maxillary prognathism, relative prognathism, maxillary incisor proclination and maxillary anteroposterior length, and to be associated with a significant reduction in interincisal angle and angulation of the maxillary plane to the cranial base. No significant differences were observed for mandibular incisor proclination, face height, maxillary mandibular plane angulation, mandibular length or cranial base characteristics. It was concluded that persistent digit sucking is an important aetiological factor for malocclusion in patients referred to a Hospital Orthodontic Department, exerting an influence in anteroposterior, vertical and transverse dimensions. Although some minor skeletal changes were detected, the changes were principally dentoalveolar.

No description available.