Dent. J., Volume 5, Issue 2 (June 2017) – 9 articles

This study investigated the effect of sulfur-containing primers for noble metals on the shear bond strength of self-cured acrylic resin after thermal cycling (TC). Four pure metals (Au, Ag, Cu, and Pd) and type IV Au alloy were either untreated, or treated with one of the five sulfur-containing metal primers (V-Primer, Metaltite, Alloy Primer, Metal Link Primer, and Metal Primer Z). Afterwards, a brass ring was placed on the metal surface and filled with self-cured acrylic resin (n = 10). The bond strengths were measured after 24 h (TC0) and after 2000 thermal cycles at 4–60 °C (TC2000). Three-way ANOVA and Tukey compromise post hoc tests were used to analyze the data (α = 0.05). All of the sulfur-containing primers significantly improved the resin bond strength as compared to that of the non-primed group at TC0 regardless of the metal type (p < 0.05). However, at TC2000, the bond strengths between the resin and the five metals significantly decreased with respect to the values obtained at TC0 regardless of the primer (p < 0.05). The sulfur-containing metal primers, except for Metal Link Primer, were found to be more effective for improving the bond strength between the self-cured acrylic resin and Ag as compared to the other three pure metals (p < 0.05). The bond strengths between the resin and Au and type IV Au alloy at TC2000 were the highest ones when Metal Primer Z was used. Full article

Dental caries form through a complex interaction over time among dental plaque, fermentable carbohydrate, and host factors (including teeth and saliva). As a key factor, dental plaque or biofilm substantially influence the characteristic of the carious lesions. Laboratory microbial culture models are often used because they provide a controllable and constant environment for cariology research. Moreover, they do not have ethical problems associated with clinical studies. The design of the microbial culture model varies from simple to sophisticated according to the purpose of the investigation. Each model is a compromise between the reality of the oral cavity and the simplification of the model. Researchers, however, can still obtain meaningful and useful results from the models they select. Laboratory microbial culture models can be categorized into a closed system and an open system. Models in the closed system have a finite supply of nutrients, and are also simple and cost-effective. Models in the open system enabled the supply of a fresh culture medium and the removal of metabolites and spent culture liquid simultaneously. They provide better regulation of the biofilm growth rate than the models in the closed system. This review paper gives an overview of the dental plaque biofilm and laboratory microbial culture models used for cariology research. Full article

Mechanistic studies on demineralization-remineralization play a critical role in investigating caries pathogenicity, testing effects of new caries prevention methods, and developing new caries-preventing products. Simulating the cariogenic challenges in the mouth, various demineralization-remineralization models have been used for cariology research. This review aimed to provide an overview of the common mechanistic studies on demineralization-remineralization for cariology research in recent literature. Most mechanistic studies were in vitro studies (n = 294, 84%) among the 350 cariology studies indexed in the Web of Science from 2014 to 2016. Among these in vitro studies, most studies (257/294, 87%) used chemical models that could be classified as simple mineralization models (159/257, 62%) or pH-cycling models (98/257, 38%). In vitro studies consumed less expense and time than in vivo studies. Furthermore, in vitro conditions were easier to control. However, they could hardly imitate the complex structures of oral cavities, the microbiological effect of oral biofilm, and the hydrodynamic instability of saliva. The advantages of chemical models included simplicity of the study, low cost, efficiency (time saving), reproducibility, and stability of experiments. However, the “caries” generated were not biological. Moreover, the chemical models were generally basic and could not mimic a carious lesion in the complex oral environment. Full article

This paper reviews the surface ablation of early hominin teeth by attrition, abrasion, and erosive dental wear. The occurrence of these lesions is explored in a sample of South African fossil australopithecine dentitions revealing excessive wear. Interpretation of the nature of the dietary components causing such wear in the absence of carious erosion provides insight into the ecology of the Plio-pleistocene epoch (1–2 million years ago). Fossil teeth inform much of the living past by their retained evidence after death. Tooth wear is the ultimate forensic dental evidence of lives lived. Full article

The color of dental restorative material should be maintained throughout its functional lifetime in an oral environment. However, the frequent use of mouthwash may affect the color stability of these composite restorations. The aim of this study is to assess the effects of using various mouthwashes on the color stability of various dental restorative composite materials. For this purpose, four mouthwashes/gels (Flocare gel (0.4% stannous fluoride), Pascal gel (topical APF fluoride), Pro-Relief mouthwash (sodium fluoride), and Plax Soin mouthwash (sodium fluoride)), and distilled water as a control, were selected. These were divided into five groups: Group 1: Flocare gel; Group 2: Pascal gel; Group 3: Pro-Relief mouthwash; Group 4: Plax Soin mouthwash; and Group 5: distilled water (control). Prepared restorative materials samples were immersed in the groups of mouthwashes/gels and the distilled water (control) for 24, 48, and 72 h. The discoloration that all materials exhibited with all immersion groups was significantly different at each of the three time periods for all groups (p < 0.05). Results from immersion in Flocare gel, Pascal gel, Pro-Relief mouthwash, and Plax Soin mouthwash were statistically significant (p < 0.05). The color change chroma was not significant for Pro-Relief and Plax Soin mouthwash (p > 0.05). Mouthwashes/gels affect color shifting for all composite resin materials, and changes are exaggerated over time. However, discoloration effects are not perceptible to the human eye. Full article

This study investigated the softening and erosive effects of various paediatric over-the-counter (OTC) oral liquids on deciduous teeth. Twenty sectioned and polished deciduous enamel blocks were ground on the buccal surface (2 × 2 mm²) and randomly divided into five groups, immersed into four commercially-available paediatric OTC oral liquids (two for paracetamol, both sugared; and two for chlorpheniramine, one sugared and one sugar-free), with deionized water as control. The pH of the oral liquids ranged from 2.50 to 5.77. Each block was immersed into the test or control groups for 15 s, rinsed with deionized water, and Vickers micro-hardness (n = 5) was measured. After twenty cycles of immersion and hardness measurements, Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectrometry (EDS) were used to evaluate the surface morphology and chemistry of the tooth blocks, respectively. The pH values of the liquids were also recorded. Rapidly descending trends in the micro-hardness ratios of the four test groups were observed that were statistically different from the control group (p < 0.001). EDS showed an increase of Ca/C ratio after drug immersion, whereas SEM showed an enamel loss in all the test groups. Paediatric OTC oral liquids could significantly soften the enamel and render them more susceptible to caries, such that the formulation of the oral liquids is the major factor. Full article

This study aimed to explore the relationship between participating in a learning experience and the ensuing changes in confidence. A self-selected group of General Dental Practitioners (GDPs) entered a five-year, part-time postgraduate master’s training programme in restorative dentistry. Confidence in communication with patients and technical skills were measured at the start of the programme by questionnaire and at the conclusion of the programme by questionnaire and personal interview. A total of 72 clinicians started the programme; 27% (n = 20) completed the master’s degree. Assessment of confidence revealed a spread from 4/10 to 10/10 for communication with patients and clinical skills in restorative dentistry before the programme started. A total of 15% (n = 11) volunteered for interview. Analysis of qualitative data revealed (i) a perceived increase in confidence from all clinicians; (ii) a perceived greater ability to treat patients; (iii) an increase in treatment options being offered to patients; (iv) a perceived increase in treatment uptake by patients; and (v) greater job opportunities. The study showed a positive relationship between the learning experience and the perceived increase in confidence of clinicians. The increase in confidence manifested itself in better communication and clinical skills. Full article

Formal lectures have been a traditional part of medical and dental education, but there is debate as to their compulsory status. This study was designed to explore dental and medical students’ views on compulsory lectures and the use of Video-Recorded Lectures (VRL). A cross-sectional study of University of Bristol students in Years 2 to 4 was conducted using an online questionnaire. The majority of both dental (76%) and medical (66%) students felt lectures should be non-compulsory. The most common learning resources used by both dental and medical students were live lectures, lecture handouts and VRL. The majority of both dental (84%) and medical (88%) students used VRL. Most students attended lectures all of the time both before and after the introduction of VRL, even though most dental and medical students believe lectures should be non-compulsory. VRL is a popular learning resource. These findings tie-in with General Dental Council and General Medical Council recommendations that encourage self-directed learning. Dental and Medical schools should offer a range of learning resources and make use of current technology, including the use of VRL. Full article

Objectives: The purpose of this study was to develop a new technique for analyzing velopharyngeal movement and to investigate its utility. Materials and Methods: Velopharyngeal motion of 20 normal individuals was analyzed. A three-dimensional (3D) endoscope was inserted into the oral cavity, and the movement of the soft palate was measured using an exclusive fixation device. Range images of the soft palate were produced during phonation of the Japanese vowel /a/, and virtual grids were then overlaid on these images. Principal component analyses were applied to the 3D coordinates of the intersections of the virtual grids. The centers of gravity of the virtual grids were calculated, and the magnitude of the shift of the grid intersections during phonation was calculated. Results: The first and the second principal component scores were responsible for the upper posterior direction and the upper direction, respectively. The average magnitude of the shift of the center of gravity was 4.75 mm in males and 4.33 mm in females. Conclusions: Quantitative analysis of velopharyngeal movement was achieved by a method of applying principal component analysis (PCA) to the range images obtained from a 3D endoscope. There was no sex difference in velopharyngeal movement. Full article