ObjectiveTo investigate the perceived educational and health risks associated with the COVID‐19 p... more ObjectiveTo investigate the perceived educational and health risks associated with the COVID‐19 pandemic amongst dental students and educators.MethodsA 17‐item electronic survey was sent to 496 undergraduate dental students and 53 clinical faculty members who attended clinical sessions during the outbreak period. The survey explored various aspects related to primary sources and prevention of disease exposure, dental management of suspected cases, impact of COVID‐19 on students’ clinical performance and effects of suspension of educational activities on academic performance and clinical competence.ResultsThe response rate of the students’ was 60.7% (n = 301). The majority of students reported that performing clinical work during the outbreak posed significant health concerns, resulted in a significant stress and negatively affected their clinical performance. The majority of students believed that aerosols generated during dental procedures are the major source for disease exposure ...
The aim of this pilot study was to evaluate the feasibility of a new tooth preparation assessment... more The aim of this pilot study was to evaluate the feasibility of a new tooth preparation assessment software, Preppr, as an educational tool for dental students in achieving optimal parameters for a crown preparation. In February 2015, 30 dental students in their fourth year in a five‐year undergraduate dental curriculum in New Zealand were randomly selected from a pool of volunteers (N=40) out of the total class of 85. The participants were placed into one of three groups of ten students each: Group A, the control group, received only written and pictorial instructions; Group B received tutor evaluation and feedback; and Group C performed self‐directed learning with the aid of Preppr. Each student was asked to prepare an all‐ceramic crown on the lower first molar typodont within three hours and to repeat the exercise three times over the next four weeks. The exercise stipulated a 1 mm finish line dimension and total convergence angles (TOC) between 10 and 20 degrees. Fulfillment of t...
The invention relates to an assembly of surfactant molecules and silver nanoparticles. In particu... more The invention relates to an assembly of surfactant molecules and silver nanoparticles. In particular, the inven tion relates to an assembly of aggregated micelles of an anionic Surfactant and nano-sized metallic silver particles. The invention also relates to a method for preparing the assemblies of the invention. The invention further relates to the use of an aqueous dispersion of such assemblies for treat ing or preventing bacterial infections, particularly bacterial infections of human teeth. 0002 The expanding capabilities of researchers to shape materials on the nanoscale have enabled significant and rapid growth in the development of new nanomaterials-based applications and technologies. The controlled synthesis of metal and metal oxide nanoparticles in the quantum size domain is at the forefront of nanomaterials researchdue to the fact that the properties of nanoscale materials (e.g. electronic, optical, mechanical, chemical and magnetic properties) not only differ significantly from those of bulk materials, but they become critically dependent on particle size, shape, Surface chemistry and inter-particle interactions (Grassian, V. H. J.,
With the Internet facilitating access to vast amounts of free information, dental practitioners f... more With the Internet facilitating access to vast amounts of free information, dental practitioners face providing treatment for an increasingly informed public. However, the available content is not filtered, and it can be difficult for patients to discriminate between research-informed evidence and "glamorised" material of dubious origen. Patients reasonably expect a return for their investment and want to know how long their treatment will last. Clinicians have an obligation to inform their patients so that they can make reasoned decisions about treatment options. Longevity data are also informative for health agencies setting service schedules for publicly funded treatment, and for determining settlements by insurers such as ACC. Historically, much of the prosthodontic treatment performed in practice has relied heavily on dogma, low-level anecdotal evidence, and clinical case reports. This paper considers the literature on fixed and removable prosthodontic restorations and...
Quintessence international (Berlin, Germany : 1985), 2012
To use finite element analysis to investigate the influence of insertion torque on the stress dis... more To use finite element analysis to investigate the influence of insertion torque on the stress distribution around an immediately placed oral implant. Finite element software was used to model a mandibular molar extraction socket. The properties of surrounding cancellous bone and thickness of cortical bone were modified to give four 3D finite element models (I, II, III, and IV). A wide-diameter tapered oral implant was modeled and inserted into the socket. Final insertion torques of 32, 50, and 70 Ncm were applied, and the stress profile in each model was evaluated. The maximum von Mises stresses along the buccal cortical bone adjacent to the implant neck were statistically analyzed to compare the three torque values and four bone models. At the level of the cortical bone, the greatest von Mises stress levels were generated in model IV and diminished as the bone quality increased. Significant increase in stress values at the crestal bone level was observed in all models after using 7...
The potential for cross infection through dental amalgam carriers was investigated in 37 Dunedin ... more The potential for cross infection through dental amalgam carriers was investigated in 37 Dunedin dental practices and in the University of Otago School of Dentistry. Eighteen practitioners had autoclavable carriers, but only 2 autoclaved them at least daily. The School of Dentistry disinfected plastic carriers and autoclaved metal carriers. Microbiological examination, by culturing from the most commonly contaminated carrier site, showed that the School of Dentistry method for disinfection of plastic carriers was unreliable. Autoclaving was confirmed as the preferred method of sterilisation, but many existing carriers are not suited to this technique.
Teeth are important elements in studies of modern and fossil Cetacea (whales, dolphins), providin... more Teeth are important elements in studies of modern and fossil Cetacea (whales, dolphins), providing information on feeding habits, estimations of age and phylogenetic relationships. The growth layer groups (GLGs) recorded in dentine have demonstrated application for aging studies, but also have the potential to elucidate life history phenomena such as metabolic or physiologic events. Micro-Computed Tomography (Micro-CT) is a non-invasive and non-destructive technique that allows 3-dimensional study of mineralized tissues, such as human teeth, and their physical properties. Teeth from extant dolphins (Cetacea: Odontoceti) and some fossil odontocetes were scanned in a Skyscan 1172 Micro-CT desktop system. X-rays were generated at 100 kV and 100 µA for extant samples, and at 80kV and 124 µA for fossils. 0.5 mm thick aluminum and copper filters were used in the beam. Reconstructed images were informative for most extant species, showing a good resolution of the enamel layer, dentine and ...
Dental erosion is the loss of dental hard tissue through a chemical process without action of bac... more Dental erosion is the loss of dental hard tissue through a chemical process without action of bacteria, with both enamel and dentine demineralized because of acidification in the oral cavity (Nunn 1996, Addy and Shellis 2006). It is uncertain whether the acids involved in chemical demineralization are of extrinsic or intrinsic origen. Intrinsic acids might relate to disorders of the gastroesophageal tract leading to regurgitation of gastric acid. Extrinsic acids are linked to diets rich in acidic substances or acids related to environmental factors ...
The Journal of the American Dental Association, 2008
The authors reviewed and compared gingival retraction techniques used for implants and teeth. The... more The authors reviewed and compared gingival retraction techniques used for implants and teeth. The authors searched the literature using article databases Ovid MEDLINE up to May 2008, PubMED and Google Scholar (advanced search) and the following search terms: gingival retraction, implant abutment, impressions, cement-retained implant restoration, impression coping, peri-implant tissue, emergence profile and tissue conditioning. The authors found insufficient evidence relating to gingival displacement techniques for impression making for implant dentistry. Gingival retraction techniques and materials are designed primarily for peridental applications; the authors considered their relevance to peri-implant applications and determined that further research and new product development are needed. The use of injectable materials that form an expanding matrix to provide gingival retraction offers effective exposure of preparation finish lines and is suitable for conventional impression-making methods or computer-aided design/computer-aided manufacturing digital impressions in many situations. There are, however, limitations with any retraction technique, including injectable matrices, for situations in which clinicians place deep implants.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
• A cmc boundary for sodium dodecyl sulfate with silver nitrate is reported. • The implications o... more • A cmc boundary for sodium dodecyl sulfate with silver nitrate is reported. • The implications of this boundary for silver nanoparticle synthesis are discussed. • Stable assemblies of micelle aggre- gates with Ag nanoparticles have been prepared. • Optimized synthetic conditions for the formation of the assemblies are presented. • Mechanism of assembly formation: at, above and below the cmc boundary is discussed.
Background: In the replacement of missing teeth, a paradigm shift is currently observed with imme... more Background: In the replacement of missing teeth, a paradigm shift is currently observed with immediate implant placement and/or restoration, particularly in the aesthetic zone. In molar sites, however, anatomical, occlusal and biomechanical considerations remain deterrent factors influencing the outcome of this treatment paradigm. The aim of this report was to evaluate immediate placement and immediate restoration of strongly tapered wide-diameter implant in fresh mandibular molar extraction sockets. Methods: Twenty-four 8-or 9-mm diameter implants were placed in either a fresh molar extraction socket or a healed site. All the implants received provisional crowns within 48 h. The provisional crowns were replaced with full ceramic crowns after 8 weeks of implant placement. The overall implant success rate after 1 year of service for the 24 implants in two treatment groups was 75%. Success rates were 83.3% and 66.7% for the delayed and immediate placement groups respectively, with no significant difference observed between the two groups (P = 0.35). Implant stability measurements identified the immediately placed implants to be more stable immediately after surgery than delayed placed implants. In contrast, the delayed placed implants were more stable after 8 week healing time. The rehabilitation of single missing mandibular molars by immediately placed and restored wide-diameter implants was associated with a relatively high failure rate.
Objectives: It is of imperative clinical significance to define a safe threshold for planned imme... more Objectives: It is of imperative clinical significance to define a safe threshold for planned immediate implant restoration. The aim of this report was to evaluate the prognostic accuracy of resonance frequency analysis (RFA) measurements recorded at two different times (implant placement and 8-week post-implant placement) and to determine the optimal threshold value for predicting failure risk of immediately restored/loaded implants. Material and methods: Twenty-eight 8-or 9-mm-diameter implants were placed in either a fresh molar extraction socket or a healed site. An electronic RFA device was used to record the implant stability quotients (ISQs) at implant placement surgery, 8 weeks and 1 year. Receiver operating characteristic (ROC) analysis was used to identify the optimal cut-off level. Sensitivity and specificity were also determined at the selected cut-off value. The area under the ROC curve for RFA at 8 weeks was 0.93 with a significant P-value (P = 0.001). The optimum cut-off value for detecting implant stability was 60.5 ISQ measured at 8 weeks, with sensitivity and specificity of 95.2% and 71.4%, respectively. The implant stability measurements after 8 weeks showed a better accuracy in predicting implants that were at risk of failure than those taken at the time of implant placement.
Desktop microcomputed tomography (micro-CT) offers a non-invasive 3-dimensional analysis of struc... more Desktop microcomputed tomography (micro-CT) offers a non-invasive 3-dimensional analysis of structures and their physical properties. To date, the use of micro-CT has mostly involved qualitative observations, with the extent of quantitative analysis relying on automated internal calibration by the micro-CT control software. However, the value of such calibration is limited by machine drift. For an accurate quantitative use of micro-CT, it is recognized that external means of calibration are needed. A novel system of calibration standards, also known as ‘phantoms’, is presented. A range of low mineral concentration phantoms involving triethylene glycol dimethacrylate/glycerolate dimethacrylate resin mixed with commercial pure hydroxyapatite (HAP), from 0.07 to 1.05 g/cm3, was fabricated. Sintered HAP was impregnated with the same resin, producing phantoms with medium-level mineral concentrations up to 1.90 g/cm3. These phantoms were easy to create, proved accurate and stable with rep...
ObjectiveTo investigate the perceived educational and health risks associated with the COVID‐19 p... more ObjectiveTo investigate the perceived educational and health risks associated with the COVID‐19 pandemic amongst dental students and educators.MethodsA 17‐item electronic survey was sent to 496 undergraduate dental students and 53 clinical faculty members who attended clinical sessions during the outbreak period. The survey explored various aspects related to primary sources and prevention of disease exposure, dental management of suspected cases, impact of COVID‐19 on students’ clinical performance and effects of suspension of educational activities on academic performance and clinical competence.ResultsThe response rate of the students’ was 60.7% (n = 301). The majority of students reported that performing clinical work during the outbreak posed significant health concerns, resulted in a significant stress and negatively affected their clinical performance. The majority of students believed that aerosols generated during dental procedures are the major source for disease exposure ...
The aim of this pilot study was to evaluate the feasibility of a new tooth preparation assessment... more The aim of this pilot study was to evaluate the feasibility of a new tooth preparation assessment software, Preppr, as an educational tool for dental students in achieving optimal parameters for a crown preparation. In February 2015, 30 dental students in their fourth year in a five‐year undergraduate dental curriculum in New Zealand were randomly selected from a pool of volunteers (N=40) out of the total class of 85. The participants were placed into one of three groups of ten students each: Group A, the control group, received only written and pictorial instructions; Group B received tutor evaluation and feedback; and Group C performed self‐directed learning with the aid of Preppr. Each student was asked to prepare an all‐ceramic crown on the lower first molar typodont within three hours and to repeat the exercise three times over the next four weeks. The exercise stipulated a 1 mm finish line dimension and total convergence angles (TOC) between 10 and 20 degrees. Fulfillment of t...
The invention relates to an assembly of surfactant molecules and silver nanoparticles. In particu... more The invention relates to an assembly of surfactant molecules and silver nanoparticles. In particular, the inven tion relates to an assembly of aggregated micelles of an anionic Surfactant and nano-sized metallic silver particles. The invention also relates to a method for preparing the assemblies of the invention. The invention further relates to the use of an aqueous dispersion of such assemblies for treat ing or preventing bacterial infections, particularly bacterial infections of human teeth. 0002 The expanding capabilities of researchers to shape materials on the nanoscale have enabled significant and rapid growth in the development of new nanomaterials-based applications and technologies. The controlled synthesis of metal and metal oxide nanoparticles in the quantum size domain is at the forefront of nanomaterials researchdue to the fact that the properties of nanoscale materials (e.g. electronic, optical, mechanical, chemical and magnetic properties) not only differ significantly from those of bulk materials, but they become critically dependent on particle size, shape, Surface chemistry and inter-particle interactions (Grassian, V. H. J.,
With the Internet facilitating access to vast amounts of free information, dental practitioners f... more With the Internet facilitating access to vast amounts of free information, dental practitioners face providing treatment for an increasingly informed public. However, the available content is not filtered, and it can be difficult for patients to discriminate between research-informed evidence and "glamorised" material of dubious origen. Patients reasonably expect a return for their investment and want to know how long their treatment will last. Clinicians have an obligation to inform their patients so that they can make reasoned decisions about treatment options. Longevity data are also informative for health agencies setting service schedules for publicly funded treatment, and for determining settlements by insurers such as ACC. Historically, much of the prosthodontic treatment performed in practice has relied heavily on dogma, low-level anecdotal evidence, and clinical case reports. This paper considers the literature on fixed and removable prosthodontic restorations and...
Quintessence international (Berlin, Germany : 1985), 2012
To use finite element analysis to investigate the influence of insertion torque on the stress dis... more To use finite element analysis to investigate the influence of insertion torque on the stress distribution around an immediately placed oral implant. Finite element software was used to model a mandibular molar extraction socket. The properties of surrounding cancellous bone and thickness of cortical bone were modified to give four 3D finite element models (I, II, III, and IV). A wide-diameter tapered oral implant was modeled and inserted into the socket. Final insertion torques of 32, 50, and 70 Ncm were applied, and the stress profile in each model was evaluated. The maximum von Mises stresses along the buccal cortical bone adjacent to the implant neck were statistically analyzed to compare the three torque values and four bone models. At the level of the cortical bone, the greatest von Mises stress levels were generated in model IV and diminished as the bone quality increased. Significant increase in stress values at the crestal bone level was observed in all models after using 7...
The potential for cross infection through dental amalgam carriers was investigated in 37 Dunedin ... more The potential for cross infection through dental amalgam carriers was investigated in 37 Dunedin dental practices and in the University of Otago School of Dentistry. Eighteen practitioners had autoclavable carriers, but only 2 autoclaved them at least daily. The School of Dentistry disinfected plastic carriers and autoclaved metal carriers. Microbiological examination, by culturing from the most commonly contaminated carrier site, showed that the School of Dentistry method for disinfection of plastic carriers was unreliable. Autoclaving was confirmed as the preferred method of sterilisation, but many existing carriers are not suited to this technique.
Teeth are important elements in studies of modern and fossil Cetacea (whales, dolphins), providin... more Teeth are important elements in studies of modern and fossil Cetacea (whales, dolphins), providing information on feeding habits, estimations of age and phylogenetic relationships. The growth layer groups (GLGs) recorded in dentine have demonstrated application for aging studies, but also have the potential to elucidate life history phenomena such as metabolic or physiologic events. Micro-Computed Tomography (Micro-CT) is a non-invasive and non-destructive technique that allows 3-dimensional study of mineralized tissues, such as human teeth, and their physical properties. Teeth from extant dolphins (Cetacea: Odontoceti) and some fossil odontocetes were scanned in a Skyscan 1172 Micro-CT desktop system. X-rays were generated at 100 kV and 100 µA for extant samples, and at 80kV and 124 µA for fossils. 0.5 mm thick aluminum and copper filters were used in the beam. Reconstructed images were informative for most extant species, showing a good resolution of the enamel layer, dentine and ...
Dental erosion is the loss of dental hard tissue through a chemical process without action of bac... more Dental erosion is the loss of dental hard tissue through a chemical process without action of bacteria, with both enamel and dentine demineralized because of acidification in the oral cavity (Nunn 1996, Addy and Shellis 2006). It is uncertain whether the acids involved in chemical demineralization are of extrinsic or intrinsic origen. Intrinsic acids might relate to disorders of the gastroesophageal tract leading to regurgitation of gastric acid. Extrinsic acids are linked to diets rich in acidic substances or acids related to environmental factors ...
The Journal of the American Dental Association, 2008
The authors reviewed and compared gingival retraction techniques used for implants and teeth. The... more The authors reviewed and compared gingival retraction techniques used for implants and teeth. The authors searched the literature using article databases Ovid MEDLINE up to May 2008, PubMED and Google Scholar (advanced search) and the following search terms: gingival retraction, implant abutment, impressions, cement-retained implant restoration, impression coping, peri-implant tissue, emergence profile and tissue conditioning. The authors found insufficient evidence relating to gingival displacement techniques for impression making for implant dentistry. Gingival retraction techniques and materials are designed primarily for peridental applications; the authors considered their relevance to peri-implant applications and determined that further research and new product development are needed. The use of injectable materials that form an expanding matrix to provide gingival retraction offers effective exposure of preparation finish lines and is suitable for conventional impression-making methods or computer-aided design/computer-aided manufacturing digital impressions in many situations. There are, however, limitations with any retraction technique, including injectable matrices, for situations in which clinicians place deep implants.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
• A cmc boundary for sodium dodecyl sulfate with silver nitrate is reported. • The implications o... more • A cmc boundary for sodium dodecyl sulfate with silver nitrate is reported. • The implications of this boundary for silver nanoparticle synthesis are discussed. • Stable assemblies of micelle aggre- gates with Ag nanoparticles have been prepared. • Optimized synthetic conditions for the formation of the assemblies are presented. • Mechanism of assembly formation: at, above and below the cmc boundary is discussed.
Background: In the replacement of missing teeth, a paradigm shift is currently observed with imme... more Background: In the replacement of missing teeth, a paradigm shift is currently observed with immediate implant placement and/or restoration, particularly in the aesthetic zone. In molar sites, however, anatomical, occlusal and biomechanical considerations remain deterrent factors influencing the outcome of this treatment paradigm. The aim of this report was to evaluate immediate placement and immediate restoration of strongly tapered wide-diameter implant in fresh mandibular molar extraction sockets. Methods: Twenty-four 8-or 9-mm diameter implants were placed in either a fresh molar extraction socket or a healed site. All the implants received provisional crowns within 48 h. The provisional crowns were replaced with full ceramic crowns after 8 weeks of implant placement. The overall implant success rate after 1 year of service for the 24 implants in two treatment groups was 75%. Success rates were 83.3% and 66.7% for the delayed and immediate placement groups respectively, with no significant difference observed between the two groups (P = 0.35). Implant stability measurements identified the immediately placed implants to be more stable immediately after surgery than delayed placed implants. In contrast, the delayed placed implants were more stable after 8 week healing time. The rehabilitation of single missing mandibular molars by immediately placed and restored wide-diameter implants was associated with a relatively high failure rate.
Objectives: It is of imperative clinical significance to define a safe threshold for planned imme... more Objectives: It is of imperative clinical significance to define a safe threshold for planned immediate implant restoration. The aim of this report was to evaluate the prognostic accuracy of resonance frequency analysis (RFA) measurements recorded at two different times (implant placement and 8-week post-implant placement) and to determine the optimal threshold value for predicting failure risk of immediately restored/loaded implants. Material and methods: Twenty-eight 8-or 9-mm-diameter implants were placed in either a fresh molar extraction socket or a healed site. An electronic RFA device was used to record the implant stability quotients (ISQs) at implant placement surgery, 8 weeks and 1 year. Receiver operating characteristic (ROC) analysis was used to identify the optimal cut-off level. Sensitivity and specificity were also determined at the selected cut-off value. The area under the ROC curve for RFA at 8 weeks was 0.93 with a significant P-value (P = 0.001). The optimum cut-off value for detecting implant stability was 60.5 ISQ measured at 8 weeks, with sensitivity and specificity of 95.2% and 71.4%, respectively. The implant stability measurements after 8 weeks showed a better accuracy in predicting implants that were at risk of failure than those taken at the time of implant placement.
Desktop microcomputed tomography (micro-CT) offers a non-invasive 3-dimensional analysis of struc... more Desktop microcomputed tomography (micro-CT) offers a non-invasive 3-dimensional analysis of structures and their physical properties. To date, the use of micro-CT has mostly involved qualitative observations, with the extent of quantitative analysis relying on automated internal calibration by the micro-CT control software. However, the value of such calibration is limited by machine drift. For an accurate quantitative use of micro-CT, it is recognized that external means of calibration are needed. A novel system of calibration standards, also known as ‘phantoms’, is presented. A range of low mineral concentration phantoms involving triethylene glycol dimethacrylate/glycerolate dimethacrylate resin mixed with commercial pure hydroxyapatite (HAP), from 0.07 to 1.05 g/cm3, was fabricated. Sintered HAP was impregnated with the same resin, producing phantoms with medium-level mineral concentrations up to 1.90 g/cm3. These phantoms were easy to create, proved accurate and stable with rep...
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