Browsing by Author "Patel, Mangala"

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An Evaluation of The Properties of a Non-Phthalate-Based Commercial Dental Tissue Conditioner Incorporated with Antifungal Agents
(Queen Mary University of London, 2024) Alharbi, Ali; Patel, Mangala; Karpukhina, Natalia; Agha, Amani
Denture stomatitis is one of the highest prevalence among denture wearers. It is characterised by an inflammation and redness of the oral mucosa under the denture. It is a multifactorial disease that is caused by denture trauma and accompanied by candida infection. The management of this condition would involve eliminating the cause of denture trauma and treating the fungal infection. Tissue conditioners are soft denture liners that are used to treat denture stomatitis by relieving the denture bearing area from denture trauma. They consist of acrylic powder, a plasticiser and ethanol. One main disadvantage of these materials is that the leaching of plasticiser, resulting in an increase in hardness of the material. The plasticiser that was commonly used in earlier formulations was phthalate-based; however, due to their questionable biocompatibility, the use of phthalate plasticisers has been banned from Europe. The plasticiser that is used nowadays is a citrate-based or benzoate plasticiser. However, the properties of citrate or benzoate-based tissue conditioners have not been evaluated. Furthermore, the addition of antifungal agents, such as Nystatin or chlorhexidine digluconate, can enhance the treatment of denture stomatitis. Therefore, the aim of this project was to evaluate the properties of commercial citrate based (Viscogel) and benzoate based (Coe Comfort) tissue conditioners with (and without) the incorporation of drugs (Nystatin via Nystan or chlorhexidine digluconate via Corsodyl, both at 33% v/v). The commercial tissue conditioners were evaluated with respect to some physico-mechanical properties and drug release behaviour. The physico-mechanical properties included hardness (using Shore A), water absorption behavior (gravimetrically), gelation time (using an oscillating rheometer) and surface roughness (using a non-contact 3D white light profilometer). The drug and plasticiser release were evaluated using UV-Vis spectrophotometry. The samples were divided into 3 groups (i.e. Control Groups, Nystatin Incorporated Groups, and Chlorhexidine Digluconate Incorporated Groups). Each group had 2 sub-groups of Citrate-Based Tissue Conditioner (Viscogel) and Benzoate-Based Tissue Conditioner (Coe Comfort). The results showed that the hardness of Viscogel was high at baseline compared to Coe Comfort. The increase in hardness following immersion in deionised water over time was rapid in Viscogel. The incorporation of drugs resulted in softer tissue conditioners. Moreover, Viscogel had a longer gelation time compared to Coe Comfort; however, both tissue conditioners gelation time had increased after the addition of either drug. Furthermore, due to the change in opacity of both tissue conditioners during water immersions in water, it was not possible to accurately record surface roughness using a non-contact profilometer. The UV data showed that both commercial tissue conditioners have the potential to act as drug delivery systems; however, drug release from Viscogel was significantly higher than from Coe Comfort. Plasticiser (triethyl citrate) almost completely (>99%) leached out of Viscogel after 12 weeks of immersion in deionised water; whereas, only 15% of benzyl benzoate leached from Coe Comfort at 12 weeks, presumably due to the fact that triethyl citrate has a higher water solubility compared to benzyl benzoate, and benzyl benzoate having a bulkier chemical structure.
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Assessment of Wear Characteristics, Longevity and Stiffness of Essix-type Retainers
(Saudi Digital Library, 2023) Alfadil, Lina; Fleming, Padhraig; Patel, Mangala; Pandis, Nikolaos; Fleming, Padhraig
Objective: To compare four commercially-available Essix-type retainers in terms of longevity, wear characteristics, stiffness, and their range of rigidity. Design and Setting: An in vitro study conducted at Queen Mary University of London. Materials and Methods: Four groups of thermoplastic materials were included: Duran (PETG), Essix C+ (Polypropylene), Vivera, and Zendura (Polyurethane). A working typodont was fabricated to evaluate surface wear characteristics using a wear machine with a customised jig. Retainers were measured for tensile test and water absorption was measured at five different time points up to 6 months after initial immersion in two different physical states and two different solutions. Hydrolytic degradation was also evaluated using FTIR spectroscopy. Results: Essix C+ was the most flexible retainer with Vivera the stiffest material. Zendura and Essix C+ had the most surface wear and highest absorption rates. Only Essix C+ displayed signs of degradation following water absorption. Conclusions: All materials displayed characteristic levels of flexibility and were susceptible to water absorption. Duran 1.5mm performed similarly to Vivera in relation to stiffness and wear properties. While Zendura and Vivera have similar chemical structures, they exhibited differences concerning wear resistance and water absorption. Further clinical research evaluating the clinical relevance of these laboratory findings is required. Clinical relevance: Characteristic patterns of wear and rigidity of four commercially-available Essix-type retainers were observed. This information should help in the tailoring of retainer material based on a case-by-case basis.
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Investigating the Formation of Apatite and The Role of Bioactive Glass and Hydroxyethyl Methacrylate in Resin-Modified Glass Ionomer Cement
(Saudi Digital Library, 2023-11-30) Alshehri, Bandar; Karpukhina, Natalia; Patel, Mangala
Background: Secondary caries is one of the most common causes of dental restoration replacement. A compromised marginal seal caused by polymerisation shrinkage might result in secondary caries. Therefore, the capacity of a restorative material to form apatite at the tooth-restoration interface could lower the incidence of secondary caries. Objective: This project aimed to evaluate the capability of resin-modified glass ionomer cements (RMGICs) to form apatite on immersion in a medium simulating the oral environment. The role of bioactive glass (BAG) incorporated in experimental RMGICs in forming apatite was evaluated. Factors that enhance apatite formation, including hydroxyethyl methacrylate (HEMA), were also explored. Methods: Novel RMGICs with varying HEMA concentrations, 30% (referred to as HEMA-RMGIC) or 15% (referred to as THFM-RMGIC), and different polyacrylic acid (PAA) concentrations, (20%, 10%, or 0%), with and without 10 wt% experimental BAG, were developed. These RMGICs were evaluated alongside an experimental glass ionomer cement (GIC) and a commercial restorative material (ACTIVA™ BioACTIVE-RESTORATIVE™). The ability of these materials to form apatite in set cement discs immersed in artificial saliva (AS) for up to 24 months was evaluated using 31P magic-angle spinning nuclear magnetic resonance (31P-MAS-NMR), 19F-MAS-NMR, X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The post-experiment AS solutions for each material were analysed using pH metre, ISE, and ICP-OES. A water absorption experiment was conducted for up to 6 months in AS, to evaluate the impact of the materials’ hydrophilicity on apatite formation. Three-point flexural strength (TFS) and modulus (TFM) were analysed after 24 hours and 1 month in AS. Results: 31P MAS-NMR, 19F MAS-NMR, XRD and FTIR of the experimental compositions demonstrated evidence of increasing apatite formation over time. No significant difference in apatite formation was found between the experimental RMGICs and the different HEMA and PAA concentrations, while the hydrophilicity of experimental compositions had a limited effect. The substitution of 10 wt% of the experimental glass with BAG accelerated apatite formation. Conversely, the commercial material showed no signs of apatite formation. High fluoride release was observed from HEMA-RMGIC and GICs. As the immersion time of experimental samples increased, substantial consumption of Ca and P ions from their immersion media was identified. THFM-RMGIC exhibited the lowest % weight changes among experimental compositions. Incorporating BAG into THFM-RMGIC increased the % weight change, however, it was comparable to HEMA-RMGIC. THFM-RMGICs displayed the highest TFS amongst the other experimental compositions. BAG incorporation did not significantly affect the TFS except for HEMA-RMGIC. Following immersion for 1 month in AS, a significant reduction in TFS was observed. TFM was also significantly reduced, only in RMGICs with BAG, after one month in AS. TFM of THFM was significantly higher than all experimental and commercial materials. Conclusions: Experimental RMGICs and GICs formed apatite, following immersion in AS, with time, however, the apatite formation within RMGICs was higher. In addition, substituting 10 wt% of ionomer glass powder with BAG significantly enhanced apatite formation by experimental RMGICs. The presence of HEMA played a role in enhancing apatite formation within RMGICs. Substituting 50% of HEMA for biocompatible monomer (THFM) in RMGIC significantly decreased % weight change, enhanced flexural strength and modulus, and did not compromise apatite formation. These materials could be beneficial in reducing microleakage at the tooth restoration interface and in preventing the development and progression of secondary caries.
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Investigation into the effect of a custom-made jig to enhance guide plane preparation and partial denture framework retention
(Queen Mary University of London, 2024-07) Alokla, Mohammad; Patel, Mangala; Friel, Tim
Tooth loss is a common disease and removable partial denture (RPD) is an option to replace ‎missing ‎teeth. One of the major issues of RPDs is reduced retention. Guide plates are RPD ‎components that ‎restrict the path of insertion and improve frictional retention. Dental practitioners ‎have to prepare ‎parallel guide planes on abutment teeth which is difficult to achieve clinically. The ‎invention of a ‎custom cutting guide using computer-aided design and computer-aided ‎manufacture (CAD-CAM) ‎technology by 3Shape TRIOS® software may enhance the accuracy of ‎preparing parallel guide planes, ‎thus improving the RPD retention. The aim of this project was to ‎create a cutting guide using a novel ‎process in CAD-CAM technology and investigate the effect ‎on guide plane preparation and RPD ‎retention. ‎ In this project, a bounded saddle master model was selected and duplicated into 40 printed resin ‎‎models. Four abutment teeth were included in the tests. The upper right second molar (UR7), the ‎‎upper right first premolar (UR4), the upper left second molar (UL7), the upper left first premolar ‎‎(UL4) ‎were utilized. The duplicated models were divided into two groups. In the first group (A), 20 ‎cobalt-‎chromium (Co-Cr) frameworks were fabricated without guide plane preparation for 20 ‎printed models, ‎and the frameworks retention were assessed. In the second group (B), 20 Co-Cr ‎frameworks were ‎designed and fabricated based on prepared guide planes on 20 models. The ‎guide plane preparations ‎of group B were performed using a custom-made jig. The model base ‎was used as a standardised ‎reference for designing the jig and assessing the accuracy of guide ‎plane preparations. The retention of ‎group B frameworks were measured and the accuracy of ‎guide plane preparations were evaluated. ‎ The results showed that the average of maximum load for testing retention of RPD frameworks ‎was ‎‎1.887 ± 2.779 N (N=Newtons) in group A unprepared models and 0.350 ± 0.575 N in group B ‎prepared ‎models. The accuracy assessment of prepared guide planes in group B showed that the ‎‎average angle ‎between the model base and UR7 guide plane was 102⁰ ± 1.21 degrees. ‎The ‎average angle between the ‎model base and UR4 was 93⁰ ± 1.86 degrees. The average angle ‎between the model base and UL4 was ‎‎92⁰ ± 2.03 degrees. The average angle between the ‎model base and UL7 was 103⁰ ± 2.39 degrees. Also, ‎the measurement of parallelism ‎between ‎opposing guide planes on the right and left bounded saddles ‎of prepared guide planes in group B ‎showed that the ‎average angle on the right side between UR7 and ‎UR4 was 15⁰ ± 2.47 degrees, ‎and the ‎average angle on the left side between UL7 and UL4 was 15⁰ ± ‎‎3.36 degrees. Lastly after ‎guide plane preparation in group B, the average of maximum depth tooth ‎reduction on UR7 ‎0.38 ‎‎± 0.09 mm, UR4 ‎0.36 ± 0.09 mm, UL4 ‎0.43 ± 0.14 mm, and UL7 ‎0.42 ‎± 0.11 mm.‎ In conclusion, the resin custom-made Jig that was designed using 3Shape software resulted in ‎non-‎parallel guide planes and divergent guide plane angle which reduced retention of Co-Cr ‎frameworks in ‎group B prepared models compared to group A non-prepared models. Therefore, ‎the chosen design of ‎the jig negatively influenced the accuracy of guide plane preparation and ‎framework retention. ‎
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