Prof. Riaan Mulder

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https://hdl.handle.net/10566/1705

Position:	Paediatric Dentistry Clinics
Department:	Orthodontics & Paediatric Dentistry
Faculty:	Faculty of Dentistry
Qualifications:	BChD (UWC), MSc (UWC)
	My publications in this repository
ORICD iD	0000-0002-8722-7632
More about me:	here, here and here
Tel:	021 959 3159
Fax:	021 959 2287
Email:	rmulder@uwc.ac.za

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Now showing 1 - 13 of 13

Ion release of chitosan and nanodiamond modified glass ionomer restorative cements
(UWC, 2019) Mulder, R
Purpose: Ion release from glass ionomer restorative cements (GICs) plays an important role in GICs. The ion release from chitosan and nanodiamond-modified glass ionomers was assessed. Materials and methods: Three GICs (Fuji IX, Ketac Universal and Riva Self Cure) were modified in the powder phase per weight by adding 5% or 10% of a commercially available chitosan powder (CH) or nanodiamond (ND) powder to the GICs. The specimens with dimensions 4 mm diameter and 6 mm height manufactured from the 15 GIC formulations were allowed to set for 1 hr and subsequently placed in neutral de-ionised water. The released ions were assessed using inductively coupled plasma-mass spectrometer (ICP-MS) to determine the elemental release. Additionally, three different disc-shaped specimens (3 mm in diameter and 1 mm thick) were constructed from each material for scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (SEM-EDS) microanalysis to establish an ion weight percentage. Results: There were no significant differences in the ion release between the control materials for aluminium, silicon and strontium. The ion release from CH and most NDmodified GICs were significantly (p<0.00001) increased compared to the control materials. CH modifications significantly increased the ion release of aluminium, sodium, silicon and strontium for all three control materials (with the exception of the strontium release from Ketac Universal that was modified with 5% chitosan). Conclusion: Ion release can be advantageous to tooth structure due to the interaction of chitosan with the GIC chemistry and moisture during maturation. Ion release up to five times greater than the control was noted for some ions. Keywords: glass ionomer cement, chitosan, nanodiamond, ICP-MS, aluminium, strontium
Application of lasers in orthodontics
(South African Dental Association, 2017) Mulder, Riaan; Melman, Geoffrey; Karic, Vesna
Laser is the acronym for Light Amplification by Stimulated Emission of Radiation, a usage that dates back to approximately 50 years ago. In 1960, the first functioning laser was built by the American physicist Maiman at the Hughes Research Laboratories by using a synthetic ruby crystal made of aluminum oxide and chromium oxide. In general, lasers are composed of the three principal parts: an energy source, an active medium and a set of two or more mirrors that form a resonator. Properties such as wavelength are determined primarily by the active medium, which can be a gas, crystal or a solid-state conductor.
Cavity preparation using hard tissue lasers in operative dentistry
(South African Dental Association, 2017) Karic, Vesna; Mulder, Riaan; Melman, Geoffrey
A laser is a device that delivers coherent, monochromatic and collimated light as a form of energy. Most dental laser devices emit invisible light in the infrared portion of the electromagnetic spectrum. On May 7, 1997, the Food and Drug Administration (FDA) cleared for marketing in the United States the first erbium: yttrium - aluminum -garnet, or Er: YAG, laser for use in preparing cavities in the teeth of living human subjects.
A comparative study to determine the shock absorption ability of two popular mouth guards available on the South African market
(Electronic Doctor (E-Doc) Publishers & SADA, 2017) Mohamed, Nadia; Grobler, Sias Renier; Basson, N. J.; Osman, Yusuf Ismail; Mulder, Riaan
It is expected that most mouth guards will provide some level of protection to teeth. In this study a device was developed to measure the relative impact absorption of two different mouth guards (Proform, Type III vacuum-formed and Max, Type IV pressure laminate). Seven of each of the two types of mouth guards were made and each batch was exposed to between six and 10 impact trials.
Lasers in periodontics
(Electronic Doctor (E-Doc) Publishers & SADA, 2017) Melman, Geoffrey; Karic, Vesna; Mulder, Riaan
Ablation has been described as the expansive vaporisation of tissue. In periodontal procedures the ablation capacity of the laser can be used for excision and incision of pathology. The Erbium doped lasers can be used effectively for soft tissue procedures with or without water. It is essential that the air supply is turned off when soft tissue procedures or any procedure with a flap is performed, to prevent subcutaneous emphysema. Hard tissue lasers are effective in bone ablation provided that the water is present preventing collagen denaturation and necrosis of the targeted tissue.
Bio-active restorative materials as alternative pit and fissure sealants in pediatric and preventative dentistry: In vitro investigation
(MedCrave, 2017) Perchyonok, Tamara; Mulder, Riaan
BACKGROUND: It has been more than 40 years since the pit and fissure sealants were first used clinically. During this time, pit and fissure sealants have been shown to be effective in reducing the risk of occlusal caries. AIM: The aim of the investigation is to further develop and evaluate a versatile designed chitosan based bio-active materials on for use as bonding free fissure sealant/fissure protectors on permanent dentition and evaluate remineralization/demineralization capacity of the materials through pH cycling, as well as shear bond strength etch and no etch prototype as well as measurement of Vickers hardness of the newly designed materials and compare the property with the commercially available standard. RESULTS: In general there was an increase in bond strength of the enamel treated with the modified Premise containing nanodiamond: chitosan materials compared to the bond strength of the conventionally bonded teeth. It is seen that release of phosphorus into the dematerializing solution (i.e. loss of phosphorus from the samples) showed larger amplitude (from 600.2mg to 101.3 mg) than the uptake of phosphorus by the samples from the re-mineralizing solution (from 125.2 mg to 66.1 mg). Therefore, the treatment with chitosan seems to act more on the demineralization of tooth enamel with little effect on the remineralization process. Regarding the net phosphorus loss (net P loss), it can be seen that net demineralization occurs in all cases. However, the net amount of phosphorous released by the control group samples was significantly higher than those groups treated with chitosan. The net P loss for the control group was 475 mg of P, whereas the groups containing chitosan had a net P loss in the range of 30-182 mg. When a 1mm layer is assessed all the materials including the Premise control indicated a conversion of above 96%, which is the upper limit of the conventional fissure sealant material which makes the newly designed bioactive materials suitable for the application as fissure sealant materials. The important aspect of any newly designed/ developed restorative material is cytotoxicity as Grobler et. al [1] investigated the cytotoxic effect of nanodiamonds and also the effect of the incorporation in a dental material (Premise), who found a higher shear bond strength (p < 5%) after 3 months of Premise treated with nanodiamonds, chitosan, cyclodextrin (CD) and combinations thereof than for the control Premise. The sequence for the Vickers hardness was: CD (32.5) < nano (34.8) < CD Nano (38.8) < Premise (39) < Chitosan Nano (42.2). Nanodiamonds (92%) and the combination of chitosan + nanodiamonds (93%) showed little cytotoxicity. The shrinkage was lower for all the additions than for Premise alone. CONCLUSION: All modified Flowable bio-active materials can be further developed in effective fissure sealant material based on the acceptable in vitro results and cytotoxicity data.
Lasers in paediatric dentistry
(South African Dental Association, 2016) Mulder, Riaan; Karic, Vesna; Melman, Geoffrey
Many clinicians will be faced with the un-cooperative paediatric patient presenting at their practices with a “fear of the unknown”. Establishing trust with these patients is essential in order to achieve a productive interaction with the child. The hard tissue lasers (Er:YAG and Er,Cr:YSGG) have the advantage of not producing the high pitched sound and vibrations associated with turbines. The ‘tellshow- do” method can be used to illustrate the water spray with the lowest possible energy setting of the laser in the paediatric patient’s mouth, which may assist in alleviating fear associated with the restorative procedures.
Introduction to dental lasers
(South African Dental Association, 2016) Mulder, Riaan; Karic, Vesna; Melman, Geoffrey
It was Albert Einstein who in 1917 defined the theory of the Stimulated Emission of Radiation, developing and expanding on the work of Niels Bohr, who in 1913 had formulated the Spontaneous Emission theory. Einstein described the electrons of molecules being excited by a source of energy, usually heat, and directed in a specific way. The excited electron releases a spontaneously emitted photon which interacts with a molecule of the active medium, causing those electrons to move to a less stable, higher energy state and producing further photons. This process exponentially increases the number of identical photons which are focused by mirrors at either end of the laser tube and emitted into the delivery system. The acronym “LASER” represents “light amplification by stimulated emission of radiation”.
Are fissure sealants still relevant as a caries preventive measure?
(South African Dental Association, 2016) Mulder, Riaan
The groundwork for fissure sealants was completed in 1955 and lead to the introduction in 1971 of the Nuva-Seal Fissure Sealant by L.D Caulk. Since caries predominantly affects the pits and fissures of the teeth of children, these sealants have been shown to be a valuable preventive procedure. FS are cost effective and provide an ideal preventive measure for children who have restricted access to dental services. However the advent of dental lasers, caries detection systems, fluoride varnishes and novel adhesive systems may have displaced FS as a preventive measure of choice. The aim of this investigation was to establish whether FS remain a relevant preventive measure for the anatomically vulnerable fissure system.
Towards bioactive containing restorative materials: from design to testing in vitro approach
(Symbiosis, 2015) Perchyonok, Tamara; Mulder, Riaan; Grobler, Sias Renier; Zhang, Shengmiao
In any repair of a tooth with permanent restorative materials, the interface is always a sensitive region. The appearance of adhesive materials was a great step forward in dealing with the problems of this region and improving the overall performance of the restorations. However, contemporary adhesive materials do have a major disadvantage, namely that their durability is limited, a limitation which often arises due to their inadequate marginal adaptation. Restorative materials in the new era aim to be “bio-active” and long lasting. As part of our continuous interest in developing the novel bioactive containing restorative materials, we evaluated the effect of the additional bio-actives (such as chitosan, β-carotene, guar gum resin and the combination of the materials) to the commercially available flowable restorative materials such as Premise on the volumetric shrinkage, flexural strength, compressive strength, the surface hardness of the “bio-active” containing composite
The use of laser-based technologies in dentistry: Ethical issues and safety considerations
(South African Dental Association, 2015) Naidoo, Sudeshni; Mulder, Riaan
The use of laser-based technologies in general dental practice in South Africa is growing each year both in numbers and in scope of use. It has been shown to be beneficial in treating a wide range of oral and dental conditions as well as being used as a therapeutic tool in tissue management. They have been used in the practice of dentistry for over thirty years and recently there have been numerous advertisements in the dental press regarding the advantages of owning and using lasers and how it can be a good marketing tool for a dental practice. In the United States patients seek out practices utilising laser technology and nearly two thirds of patients surveyed thought that dentists should own a laser. How can practitioners ensure that they are using laser treatment for their patients in a responsible and ethical manner?
Towards bioactive dental restorative materials with chitosan and nanodiamonds: evaluation and application
(SciDoc Publishers, 2015) Mulder, Riaan; Grobler, Sias Renier; Moodley, Desi; Perchyonok, Tamara
BACKGROUND/PURPOSES: Recently various articles showed beneficial effects of the addition of different the beneficial effect (bond strength and longevity) of the addition of different bioactive compounds towards dental materials. compounds towards dental materials. Therefore, the aim of this work was to evaluate the effect of the addition of bioactive materials and combination thereof (chitosan/nanodiamond or cyclodextrin/nanodiamond) to a dental composite. MATERIALS AND METHODS: The flowable composite Premise by Kerr was used as the standard control dental material. Premisewas also modified to contain: 10% nanodiamonds/Premise, 10% chitosan/nanodiamonds/Premise, 10% cyclodextrin/ nanodiamonds/Premise and 10% cyclodextrin/Premise and tested for their dentin bond strength, volumetric shrinkage, Vickers hardness and cytotoxicity. RESULTS AND CONCLUSION: Beneficial effects of the addition of different bioactive compounds towards dental materials were proved. A higher shear bond strength (p < 5%) was found after 3 months of Premise treated with nanodiamonds, chitosan, cyclodextrin (CD) and combinations thereof than the control Premise. The sequence for the Vickers hardness was: CD (32.5) < nano (34.8) < CD Nano (38.8) < Premise (39) < Chitosan Nano (42.2). Chitosan was found to increase the mouse 3T3 fibroblast cell survival rate (113%), while nanodiamonds (92%) and the combination of chitosan + nanodiamonds (93%) showed little cytotoxicity. The shrinkage was lower for all the additions than for Premise alone. Nanodiamonds and the combination chitosan + nanodiamonds showed little cytotoxicity towards mouse 3T3 fibroblast cells.
Volumetric change of flowable composite resins due to polymerization as measured with an electronic mercury dilatometer
(Herbert Publications Ltd., 2013) Mulder, Riaan; Grobler, Sias Renier; Osman, Yusuf Ismail
BACKGROUND: To determine the total volumetric change and the relative speed of shrinkage of bulk fill flowable composites during polymerization. MATERIALS AND METHODS: A specially designed electronic mercury dilatometer was used to determine the volumetric change. The light intensity was 500mW/cm2. The mercury dilatometer measured the volumetric change every 0.5 seconds during the 35 second irradiation exposure time. The materials tested were Z250 as standard and control. Four bulk fill flowable composites were tested. RESULTS: The sequence of total volumetric change was found to be: Z250 < Filtek bulk fill < Xtra-Base bulk fill < SDR < Venus bulk fill. The speed of shrinkage of the bulk fill flowables was faster than that of Z250, while the 2 flowables with the highest shrinkage speed (SDR and Venus) also had the highest total volumetric change. Of the different materials tested the volumetric change of Z250 (1.13%) was the lowest and significantly less (p<0.05) than that of SDR (1.55%) and Venus (1.72%). The material with the highest filler content (Z250) also showed the lowest shrinkage (1.13%) but this effect could not be seen in the flowables. In general, it was found that a 35 second irradiation period (with a light intensity of 500mW/cm2) was satisfactory for complete polymerization of the resins. CONCLUSIONS: The volumetric changes and speed of shrinkage were higher for all 4 bulk fill flowable composites than for Z250. SDR and Venus flowables had the fastest and highest volumetric shrinkage. Clinical significance: The manufacturers of bulk fill flowable composites advocate filling layers of 4mm. However, because of the high shrinkage values found in this study it should be suggested that the standard 2mm layer increments still be used.

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