Melbourne Dental School - Research Publications
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ItemNo Preview AvailableSelf-Rated Oral Health as a Valid Measure of Oral Health Status in Adults Living in Rural Australia(MDPI, 2023-06)It is unclear how well self-rated oral health (SROH) reflects actual oral health status in the rural Australian population. Therefore, this study aimed to compare the clinically assessed oral health status and SROH of adults living in rural Australia. The data were from 574 participants who took part in the Crossroads II cross-sectional study. Three trained and calibrated dentists evaluated the oral health status of participants based on WHO criteria. SROH was assessed with the question 'Overall, how would you rate the health of your teeth and gums?', with a score ranging from excellent = 5 to poor = 1. A logistic regression analysis (LRA) was performed, allowing us to assess factors associated with SROH. The mean age of participants was 59.2 years (SD 16.3), and 55.3% were female. The key results from the LRA show poorer SROH in those with more missing teeth (OR = 1.05; 95% CI; 1.01-1.08), more decayed teeth (OR = 1.28; 95% CI: 1.11-1.46), and more significant clinical attachment loss of periodontal tissue (6mm or more) (OR = 2.63; 95% CI: 1.29-5.38). This study found an association between negative SROH and clinical indicators used to measure poor oral health status, suggesting that self-rated oral health is an indicator of oral health status. When planning dental healthcare programs, self-reported oral health should be considered a proxy measure for oral health status.
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ItemNo Preview AvailableProduction and properties of adhesin-free gingipain proteinase RgpA(NATURE PORTFOLIO, 2023-07-04)The Arg-specific gingipains of Porphyromonas gingivalis RgpA and RgpB have 97% identical sequences in their catalytic domains yet their propeptides are only 76% identical. RgpA isolates as a proteinase-adhesin complex (HRgpA) which hinders direct kinetic comparison of RgpAcat as a monomer with monomeric RgpB. We tested modifications of rgpA identifying a variant that enabled us to isolate histidine-tagged monomeric RgpA (rRgpAH). Kinetic comparisons between rRgpAH and RgpB used benzoyl-L-Arg-4-nitroanilide with and without cysteine and glycylglycine acceptor molecules. With no glycylglycine, values of Km, Vmax, kcat and kcat/Km for each enzyme were similar, but with glycylglycine Km decreased, Vmax increased and kcat increased ~ twofold for RgpB but ~ sixfold for rRgpAH. The kcat/Km for rRgpAH was unchanged whereas that of RgpB more than halved. Recombinant RgpA propeptide inhibited rRgpAH and RgpB with Ki 13 nM and 15 nM Ki respectively slightly more effectively than RgpB propeptide which inhibited rRgpAH and RgpB with Ki 22 nM and 29 nM respectively (p < 0.0001); a result that may be attributable to the divergent propeptide sequences. Overall, the data for rRgpAH reflected observations previously made by others using HRgpA, indicating rRgpAH fidelity and confirming the first production and isolation of functional affinity tagged RgpA.
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ItemNo Preview AvailableMicrobiome-targeted interventions for the control of oral-gut dysbiosis and chronic systemic inflammation.(Elsevier BV, 2023-11)Recent research has confirmed the strong connection between imbalances in the oral and gut microbiome (oral-gut dysbiosis), periodontitis, and inflammatory conditions such as diabetes, Alzheimer's disease, and cardiovascular diseases. Microbiome modulation is crucial for preventing and treating several autoimmune and inflammatory diseases, including periodontitis. However, the causal relationships between the microbiome and its derived metabolites that mediate periodontitis and chronic inflammation constitute a notable knowledge gap. Here we review the mechanisms involved in the microbiome-host crosstalk, and describe novel precision medicine for the control of systemic inflammation. As microbiome-targeted therapies begin to enter clinical trials, the success of these approaches relies upon understanding these reciprocal microbiome-host interactions, and it may provide new therapeutic avenues to reduce the risk of periodontitis-associated diseases.
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ItemNo Preview AvailableComplications and treatment errors in implant positioning in the aesthetic zone: Diagnosis and possible solutions(WILEY, 2023-06)Incorrect implant positioning can lead to functional and aesthetic compromise. Implant positioning errors can occur in three dimensions: mesiodistal, corono-apical, and orofacial. Treatment solutions to manage adverse outcomes through positioning errors require an understanding of the underlying conditions and of those factors that may have led to the error being committed in the first place. These types of complications usually occur because of human factors. If errors do occur with adverse aesthetic outcomes, they are difficult and sometimes impossible to correct. Connective tissue grafts to reverse recession defects are only feasible in defined situations. The option to remove and replace the implant may be the only recourse, provided the removal process does not further compromise the site. Error in judgment by the clinician.
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ItemNo Preview AvailablePhenolic composition and antioxidant capacity of betel inflorescence extract in a simulated oral environment.(Elsevier BV, 2024-02-15)The addition of betel inflorescence (BI) and slaked lime (calcium hydroxide) to betel quid (BQ) formulation may be detrimental to human health. Here, we assessed BI extracts prepared using artificial saliva or aqueous solution with or without adding slaked lime to mimic the release of phytochemicals from BI in the oral cavity. The extracts were also profiled by HPLC-DAD-ESI-QTOF-MS/MS to understand the quality and quantity of phytochemicals released. The results indicate that slaked lime facilitates the extraction of phenolics, likely due to a high pH. In a simulated oral environment with artificial saliva, the addition of slaked lime promotes the release of safrole, a well-known carcinogen. Dominant phytochemicals detected also include eugenol, acetyl eugenol and methyl eugenol, and only a fraction of these compounds is released in the simulated oral environment. This study reveals that environmental conditions can considerably affect the extraction of phytochemicals and triggers further investigation on how chewing practices may influence the release and activity of carcinogens.
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ItemNo Preview AvailableKinematics of the jaw following total temporomandibular joint replacement surgery.(Elsevier, 2023-10-01)Total temporomandibular joint (TMJ) replacement surgery aims to improve mandibular function, reduce pain and enhance quality of life in patients suffering from end-stage TMJ disorders. Traditional post-operative jaw evaluation is carried out using measurement of maximum interincisal opening distance; however, this can correlate poorly to joint function. The present study aimed to evaluate three-dimensional (3D) jaw motion during border movements and chewing in unilateral total TMJ replacement patients and healthy controls. Motion analysis experiments were performed on six unilateral total TMJ replacement patients and ten age-matched healthy controls. Subject-specific motion tracking plates worn by each participant were registered to CT scans of each participant's skull and mandible to enable anatomical mandibular kinematics measurement using an optoelectronic system. Participants performed 15 repetitions of maximal opening, protrusion, lateral excursions, and chewing cycles. Total TMJ replacement patients had significantly smaller incisal displacements at maximum mouth opening relative to the controls (median difference: 7.1 mm, p = 0.002) and decreased anterior translation of the prosthetic condyle (median difference: 10.5 mm, p = 0.002). When TMJ replacement subjects chewed using their contralateral molars, there was a significant increase in inferior condylar translation of the non-working condyle (median difference: 9.7 mm, p = 0.016). This study found that unilateral total TMJ replacement surgery was associated with mouth opening capacity within the range of healthy individuals, but reduced anterior movement of the prosthetic condyle and restricted protrusion and lateral excursions. The results provide future direction for prosthetic TMJ design to enhance postsurgical implant functionality and improve long-term clinical outcomes for prosthesis recipients.
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ItemComplementation in trans of Porphyromonas gingivalis Lipopolysaccharide Biosynthetic Mutants Demonstrates Lipopolysaccharide Exchange(American Society for Microbiology, 2021-04-21)Porphyromonas gingivalis, a bacterial pathogen contributing to human periodontitis, exports and anchors cargo proteins to its surface, enabling the production of black pigmentation using a type IX secretion system (T9SS) and conjugation to anionic lipopolysaccharide (A-LPS). To determine whether T9SS components need to be assembled in situ for correct secretion and A-LPS modification of cargo proteins, combinations of nonpigmented mutants lacking A-LPS or a T9SS component were mixed to investigate in trans complementation. Reacquisition of pigmentation occurred only between an A-LPS mutant and a T9SS mutant, which coincided with A-LPS modification of cargo proteins detected by Western blotting and coimmunoprecipitation/quantitative mass spectrometry. Complementation also occurred using an A-LPS mutant mixed with outer membrane vesicles (OMVs) or purified A-LPS. Fluorescence experiments demonstrated that OMVs can fuse with and transfer lipid to P. gingivalis, leading to the conclusion that complementation of T9SS function occurred through A-LPS transfer between cells. None of the two-strain crosses involving only the five T9SS OM component mutants produced black pigmentation, implying that the OM proteins cannot be transferred in a manner that restores function and surface pigmentation, and hence, a more ordered temporal in situ assembly of T9SS components may be required. Our results show that LPS can be transferred between cells or between cells and OMVs to complement deficiencies in LPS biosynthesis and hemin-related pigmentation to reveal a potentially new mechanism by which the oral microbial community is modulated to produce clinical consequences in the human host. IMPORTANCE: Porphyromonas gingivalis is a keystone pathogen contributing to periodontitis in humans, leading to tooth loss. The oral microbiota is essential in this pathogenic process and changes from predominantly Gram-positive (health) to predominantly Gram-negative (disease) species. P. gingivalis uses its type IX secretion system (T9SS) to secrete and conjugate virulence proteins to anionic lipopolysaccharide (A-LPS). This study investigated whether components of this secretion system could be complemented and found that it was possible for A-LPS biosynthetic mutants to be complemented in trans both by strains that had the A-LPS on the cell surface and by exogenous sources of A-LPS. This is the first known example of LPS exchange in a human bacterial pathogen which causes disease through complex microbiota-host interactions.
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ItemNo Preview AvailableTo prescribe or not to prescribe? A review of the Prescribing Competencies Framework for dentistry(ELSEVIER SCI LTD, 2023-10)OBJECTIVES: Dentists in Australia are the second largest prescriber group, and are generally not formally taught how to prescribe. The objective of this review is to describe the Prescribing Competencies Framework and its relevance to dentistry. DATA: The four-model stage of prescribing by Coombes and colleagues, and the seven competencies within the Prescribing Competencies Framework devised by the Australian National Prescribing Service MedicineWise, are discussed and applied to dentistry. SOURCES AND STUDY SELECTION: Each of the seven competencies are analysed and detailed in the context of clinical dental practice. Competencies 1-5 describe the skillset and tasks required by dentists to safely prescribe, whereas Competencies 6 and 7 describe the clinical environment and recommended resources to support dentists to prescribe safely and effectively. CONCLUSIONS: The Prescribing Competencies Framework provides an overview of safe and effective prescribing. Prescribing is a process, and a separate skillset to clinical dentistry. The process involves information gathering, clinical assessment, effective communication and review of the patient. Access to timely and appropriate resources and relevant electronic sources of health information for clinicians are important to provide the support required for better informed prescribing decisions. The framework describes a patient-centered prescribing process, and ultimately prescribing should be a shared decision between the dentist and the patient. CLINICAL SIGNIFICANCE: Safe and effective prescribing is an integral part of dentistry and dentists are the second largest prescriber group. However, dentists display high rates of inappropriate and unnecessary prescribing, and to minimise errors, the Prescribing Competencies Framework has been established. This article details how the Framework applies to clinical practice dentistry.