Evaluation of sources of uncertainties in microtensile bond strength of dental adhesive system for different specimen geometries

Objective: The aim of this research is to use finite element analysis (FEA) to quantify the effect of the sample shape and the imperfections induced during the manufacturing process of samples on the bond strength and modes of failure of dental adhesive systems through microtensile test. Using the FEA prediction for individual parameters effect, estimation of expected variation and spread of the microtensile bond strength results for different sample geometries is made. Methods: The estimated stress distributions for three different sample shapes, hourglass, stick and dumbbell predicted by FEA are used to predict the strength for different fracture modes. Parameters such as the adhesive thickness, uneven interface of the adhesive and composite and dentin, misalignment of axis of loading, the existence of flaws such as induced cracks during shaping the samples or bubbles created during application of the adhesive are considered. Microtensile experiments are performed simultaneously to measure bond strength and modes of failure. These are compared with the FEA results. Results: The relative bonding strength and its standard deviation for the specimens with different geometries measured through the microtensile tests confirm the findings of the FEA. The hourglass shape samples show lower tensile bond strength and standard deviation compared to the stick and dumbbell shape samples. ANOVA analysis confirms no significant difference between dumbbell and stick geometry results, and major differences of these two geometries compared to hourglass shape measured values. Induced flaws in the adhesive and misalignment of the angle of application of load have significant effect on the microtensile bond strength. Using adhesive with higher modulus the differences between the bond strength of the three sample geometries increase. Significance: The result of the research clarifies the importance of the sample geometry chosen in measuring the bond strength. It quantifies the effect of the imperfections on the bond strength for each of the sample geometries through a systematic and all embracing study. The results explain the reasons of the large spread of the microtensile test results reported by various researchers working in different labs and the need for standardization of the test method and sample shape used in evaluation of the dentin-adhesive bonding system. © 2007 Academy of Dental Materials.

Analysis of the compressive behaviour of the three-dimensional printed porous titanium for dental implants using a modified cellular solid model

A set of cylindrical porous titanium test samples were produced using the three-dimensional printing and sintering method with samples sintered at 900 °C, 1000 °C, 1100 °C, 1200 °C or 1300 °C. Following compression testing, it was apparent that the stress-strain curves were similar in shape to the curves that represent cellular solids. This is despite a relative density twice as high as what is considered the threshold for defining a cellular solid. As final sintering temperature increased, the compressive behaviour developed from being elastic-brittle to elastic-plastic and while Young's modulus remained fairly constant in the region of 1.5 GPa, there was a corresponding increase in 0.2% proof stress of approximately 40-80 MPa. The cellular solid model consists of two equations that predict Young's modulus and yield or proof stress. By fitting to experimental data and consideration of porous morphology, appropriate changes to the geometry constants allow modification of the current models to predict with better accuracy the behaviour of porous materials with higher relative densities (lower porosity).

Assessing the needs of informal caregivers to cancer survivors: a review of the instruments

Objective: Cancer may impact negatively on an informal caregiver's health long after treatment has ended. This review identifies the self-report measures currently in use to measure caregivers need for support and determines their scientific soundness and clinical utility.

Method: A systematic electronic database search of Medline, CINAHL, PsychINFO, BNI ProQuest was conducted. The psychometric properties and clinical utility of needs assessment tools for caregivers of cancer survivors (excluding advanced disease) were extracted and summarised.

Results: Seven cancer survivor caregiver needs assessment tools were identified. Data on instrument development was well reported, although variability was noted in their structure and content. The majority demonstrated some degree of reliability and validity; only two were evaluated for test–retest reliability (CaSPUN and SPUNS) with only the SPUNS showing a high degree of reliability over time. The Health Care Needs Survey (HCNS), Needs Assessment of Family Caregivers-Cancer (NAFC-C) and Cancer Caregiving Tasks Consequences and Needs Questionnaire (CaTCoN) have been validated at various stages of the cancer continuum. Minimal data was available on responsiveness.

Conclusion: All assessment tools identified require further psychometric analysis. For research purposes, the use of the SPUNS (with its acceptable test–retest reliability) appears most appropriate; although its length may be of concern for clinical use; therefore, the shorter SCNS-P&C is likely to be more suitable for use clinically. At present, the NAFC-C demonstrates a great potential in both the research and clinical environments; however, it requires further psychometric testing before it can be fully recommended. Further analysis is necessary on ideal response formats and the meaning of a total needs score.

Sound Synthesis for Contact-Driven Musical Instruments via Discretisation of Hamilton's Equations

Physical modelling of musical instruments involves studying nonlinear interactions between parts of the instrument. These can pose several difficulties concerning the accuracy and stability of numerical algorithms. In particular, when the underlying forces are non-analytic functions of the phase-space variables, a stability proof can only be obtained in limited cases. An approach has been recently presented by the authors, leading to unconditionally stable simulations for lumped collision models. In that study, discretisation of Hamilton’s equations instead of the usual Newton’s equation of motion yields a numerical scheme that can be proven to be energy conserving. In this paper, the above approach is extended to collisions of distributed objects. Namely, the interaction of an ideal string with a flat barrier is considered. The problem is formulated within the Hamiltonian framework and subsequently discretised. The resulting nonlinearmatrix equation can be shown to possess a unique solution, that enables the update of the algorithm. Energy conservation and thus numerical stability follows in a way similar to the lumped collision model. The existence of an analytic description of this interaction allows the validation of the model’s accuracy. The proposed methodology can be used in sound synthesis applications involving musical instruments where collisions occur either in a confined (e.g. hammer-string interaction, mallet impact) or in a distributed region (e.g. string-bridge or reed-mouthpiece interaction).

Two-year survival of ART restorations placed in elderly patients: A randomised controlled clinical trial

OBJECTIVES: Older dentate adults are a high caries risk group who could potentially benefit from the use of the atraumatic restorative treatment (ART). This study aimed to compare the survival of ART and a conventional restorative technique (CT) using rotary instruments and a resin-modified glass-ionomer for restoring carious lesions as part of a preventive and restorative programme for older adults after 2 years.

METHODS: In this randomised controlled clinical trial, 99 independently living adults (65-90 years) with carious lesions were randomly allocated to receive either ART or conventional restorations. The survival of restorations was assessed by an independent and blinded examiner 6 months, 1 year and 2 years after restoration placement.

RESULTS: Ninety-six (67.6%) and 121 (76.6%) restorations were assessed in the ART and CT groups, respectively, after 2 years. The cumulative restoration survival percentages after 2 years were 85.4% in the ART and 90.9% in the CT group. No statistically significant between group differences were detected (p=0.2050, logistic regression analysis).

CONCLUSIONS: In terms of restoration survival, ART was as effective as a conventional restorative approach to treat older adults after 2 years. This technique could be a useful tool to provide dental care for older adults particularly in the non-clinical setting. (Trial Registration number: ISRCTN 76299321).

CLINICAL SIGNIFICANCE: The results of this study show that ART presented survival rates similar to conventional restorations in older adults. ART appears to be a cost-effective way to provide dental care to elderly patients, particularly in out of surgery facilities, such as nursing homes.

An analysis of the attitudes of dental patients attending general dental practice in Galway

AIM: To describe the patterns of dental attendance and attitudes towards tooth loss of general dental practice patients in Galway.

OBJECTIVES: 1. To determine the pattern of adult dental attendance in general practices in Galway; and, 2. To examine the oral health attitudes of these patients.

METHOD: Questionnaires were distributed to 311 consecutive adult patients in the waiting rooms of ten general dental practices in Galway, which were randomly selected from the telephone directory.

RESULTS: A total of 254 of the 311 questionnaires distributed were fully completed, returned and included in the results, giving a response rate of 81.7%. A total of 59% of dentate participants attended their dentist for annual or biannual examinations compared to 23% of edentate patients. Some 10.5% of medical card holders and 0.5% of non-medical card holders were edentulous.

CONCLUSIONS: The data from the survey indicated that medical card holders in Galway were more likely to be edentulous than nonmedical card holders. Edentate patients were less likely to be regular dental attenders than dentate patients.

Is the shortened dental arch an underused treatment strategy in the Republic of Ireland?

OBJECTIVES: To determine the proportion of Republic of Ireland 35-44 and 65+ year-olds currently satisfying the criteria for a classic shortened dental arch (SDA) of 20 anterior teeth.

RESEARCH DESIGN: Secondary analysis of data collected in the 2000/02 epidemiological survey of the oral health of Irish adults.

CLINICAL SETTING: Participants underwent a clinical oral examination in health board dental clinics and completed a detailed interview pertaining to dental and general health.

PARTICIPANTS: The analysis is based on a random sample of adults, aged 35 to 44 years (n = 978), and 65 years and older (n = 714).

MAIN OUTCOME MEASURES: The SDA was measured as 20 teeth in the mouth in the positions normally described as from the left second premolar to the right second premolar in each arch.

RESULTS: Only one of the 35-44 year-olds and none of the 65+ year-olds had teeth in their mouths in positions normally described as a classic SDA. However, of the 35-44 year old age group only five patients who had at least a premolar dentition of 20 contiguous teeth had been provided with a removable denture compared to one patient from the 65+ years group.

CONCLUSIONS: Very few older patients in the Republic of Ireland have a SDA based on the measure used. However, very few have been provided with removable dentures where they already possess at least a premolar dentition of 20 contiguous teeth. Suggested reasons for this may include limitations of the data recorded, patient preferences and economic factors.

Do removable dental prosthesis have an impact on tooth loss?

DESIGN: A multi-centre randomised controlled study in 14 dental schools. This report is an interim analysis at 3 years.

INTERVENTION: Patients were allocated to either the Removable dental prosthesis group (RPD)-109 patients or the no prosthesis group (SDA) -106 patients. Patients had to be older than 35 years with no molars in the study jaw. Follow-up visits were scheduled at 4 to 8 wks (baseline), at 6 months, and at 1, 2, 3, 4, and 5 yrs after treatment.

OUTCOME MEASURE: Time to loss of first tooth following intervention or no intervention.

RESULTS: 81 patients received a RDP and 69 patients received no treatment in the end. This is a reduction of 26% and 35% respectively from the time when they were randomised to the two groups. Tooth loss occurred in 13 of the RDP group (16% of those who received the RDP, 12% of those allocated to the group at the start) with 5 of these being in the study jaw and 8 in the opposing jaw. Tooth loss occurred in 9 of the SDA group (13% of those who received SDA, 9% of those who were allocated to the group at the start) with 5 in the study jaw and 4 in the opposing jaw. The respective Kaplan-Meier survival rates at 38 months were 0.83 (95% CI: 0.74-0.91) in the RDP group and 0.86 (95% CI: 0.78-0.95) in the SDA group.

CONCLUSIONS: The difference in tooth loss at three years between patients treated with RDP and those not treated with RDP was not significant.

Attitudes of Irish dental graduates to vocational training

INTRODUCTION: Vocational training (VT) is a mandatory 12 month period for UK dental graduates after graduation. Graduates of Irish Dental Schools are eligible to enter the general dental service in Ireland or obtain an NHS performers list number in the UK immediately after qualification. Reports would suggest that some graduates of Irish Dental Schools are choosing to take part in VT in the UK and find the experience beneficial. This study aimed to record the uptake of VT amongst recent graduates from University College Cork and to document their experiences. It was designed to compare the attitudes and experiences of graduates of Irish Dental Schools who undertook VT compared with those who entered the general dental service.

METHOD: A self-completion questionnaire was distributed by e-mail to dental graduates from University College Cork who had graduated 2001-2007. Responses were returned by e-mail or post.

RESULTS: The response rate was 68.9%. There has been an increase in the numbers of graduates taking part in VT each year since 2004. 92.5% of Vocational Dental Practitioners (VDPs) found their experience beneficial as they received a guaranteed source of income, had a supportive peer network and worked in a positive learning environment. However, some felt that they earned a lower income than their associate colleagues, others found the pace of practice slow and that the duration of the training period was excessive. Eighty-five per cent of VDPs would choose the same position again after graduation as compared with 61.8% of associates (P < 0.001). Ninety per cent of VDPs would advise current undergraduates to take part in VT as compared with 51% of associates (P < 0.001). A larger proportion of VDPs had taken part in postgraduate studies but there was no significant difference between the two groups.

CONCLUSIONS: Larger proportions of recent graduates are undertaking vocational training.--The majority of VDPs and associates find their initial employment position beneficial.--VDPs benefit from a guaranteed source of income, a supportive peer network and a positive learning environment.--Some associates suffered from a lack of support, feeling isolated and overwhelmed with patients.--The majority of previous VDPs and associates would recommend VT to current undergraduates.--Almost 40% of associates would now choose to take part in VT if given the opportunity.

Limitations of Dental Panoramic Tomography in the anterior mandible

Dental Panoramic Tomography (DPT) is a widely used and valuable examination in dentistry. One area prone to artefacts and therefore misinterpretation is the anterior region of the mandible. This case study discusses a periapical radiolucency related to lower anterior teeth that is discovered to be a radiographic artefact. Possible causes of the artefact include a pronounced depression in the mental region of the mandible or superimposition of intervertebral spaces. Additional limitations of the DPT image include superimposition of radio-opaque structures, reduced image detail compared to intra-oral views and uneven magnification. These problems often make the DPT inappropriate for imaging the anterior mandible.

CLINICAL RELEVANCE: Panoramic radiography is often unsuitable for radiographic examination of the anterior mandible.

A study of patient attitudes towards fasting prior to intravenous sedation for dental treatment in a dental hospital department

INTRODUCTION: Intravenous sedation is the most commonly used method of sedation for the provision of adult dental care. However, disparity exists in pre-operative fasting times in use for patients throughout the United Kingdom.

AIMS: The aims of the study were to obtain information on the effects of existing extended pre-operative fasting regimens, to canvas patient opinions on the fasting process, and to record their positive and negative experiences associated with it.

METHODS: A prospective cross-sectional descriptive study using survey methodology was conducted of adult patients attending a dental hospital for operative treatment under intravenous sedation. Sixty-four questionnaires were distributed over a four-month period, beginning 2nd October 2007.

RESULTS: The surveyed patient pool consisted of 38 females and 14 males with a mean age of 32.4 years. The response rate achieved was 81.2%. Seventy-one per cent of patients indicated that normally they consumed something for breakfast, the most common items being tea and toast. Fifty-one per cent of patients indicated that they would wish to eat the same as normal prior to their appointment and 59% wished to drink as normal. Only 19% of respondents reported that they did not wish to eat anything, with 8% preferring not to drink anything at all. Seventy-nine per cent of the patients reported that they had experienced at least one adverse symptom after fasting and 42% had experienced two or more such symptoms. In general, those patients with more experience of sedation found fasting less unpleasant than those attending for the first time (P<0.05). In addition, one-quarter of all patients indicated that the fasting process had made them feel more nervous about their sedation appointment.

CONCLUSIONS: The extended fasting regimen prior to intravenous sedation appeared to affect patients' wellbeing, as the majority reported adverse symptoms.

Pre-operative fasting for intravenous conscious sedation used in dental treatment: are conclusions based on relative risk management or evidence?

Intravenous sedation is a widely used pharmacological method of patient management commonly used in dental surgery for the treatment of anxious patients. Variety exists in fasting regimes between different centres offering dental sedation, with some advocating starvation in line with general anaesthesia protocols and others not enforcing starvation at all. The currently available guidelines on fasting protocols are ambiguous and open to interpretation partly because they are based on expert opinion rather than evidence-based research. This article reviews the available evidence on the subject of pre-operative fasting and discusses current guidelines.

Patient preferences for dental clinical attire: a cross-sectional survey in a dental hospital

AIMS AND OBJECTIVES: This cross sectional descriptive study was designed to survey patient opinion towards dental clinical attire, name badges and commonly used cross-infection control measures.

METHOD: Patients attending a dental hospital for a consultation appointment were asked to complete a questionnaire accompanied by photographs of models portraying a range of clinical attire. A representative sample of patients completed 188 questionnaires over a four week period.

RESULTS: The study found that the majority of patients felt clinical attire was important and that they preferred dental professionals to wear name badges. The majority of patients also preferred dentists to use both safety glasses and face masks. When asked to indicate which clinical attire was most appropriate for a consultant/specialist to wear, the overwhelming opinion was that of smart dress accompanied with a white coat. In addition, most respondents wished their dentist to wear a traditional white, dental tunic.

CONCLUDING REMARKS: It is hoped that this study will be informative for the dental team and that the results will be taken into consideration when considering appropriate clinical attire in accordance with patient opinions.

Accelerated rehabilitation of an edentulous patient with an implant retained dental prosthesis: a case report

This case report details the successful rehabilitation of an edentulous patient using a complete upper prosthesis and a lower implant retained overdenture. The provision of care was split between a specialist centre and a primary care setting. This approach reduced inconvenience to the patient. Modern surgical and prosthodontic techniques also reduced the total delivery time. After initial consultation a new set of complete dentures was prescribed with changes in design to the originals. The patient was also planned for placement of two mandibular implants to stabilise and retain the mandibular denture. The first line of treatment involved provision of a new set of dentures constructed by the patient's general dental practitioner. Dental implants were then placed in a specialist centre and the patient returned to the dental practice for attachment of the lower denture to the dental implants. The benefits and success of mandibular implant retained dentures are well documented. With delivery of the overdenture, the patient reported increased satisfaction with his prostheses which allowed him to eat a greater range of foods and enabled him to feel confident when speaking and socialising.