Monomer Modifications of Denture Base Acrylic Resin: A Systematic Review and Meta-analysis

Effect of zirconia nanoparticles in heat-cured acrylic resins on bacterial adhesion in vegan beverages

This study aims to investigate the bacterial adhesion effect of heat-curing acrylic resins modified with zirconia nanoparticles when interacting with vegan beverages using SEM and FTIR analyses. The bacterial adhesion of heat-cured acrylic resins from Imicryl and Procryla was investigated. The focus was on modified versions of Procryla containing 1 wt% and 3 wt% zirconia nanoparticles. A total of 192 specimens (n = 48 per group) were soaked in four different solutions: distilled water, mineral water, almond milk, and water kefir. Repeated measures ANOVA revealed statistically significant differences (P < .05) in bacterial adhesion among resin groups, beverage types, and immersion times. Specifically, the addition of 1% by weight zirconia to the specimens reduced bacterial adhesion in groups immersed in distilled water (P < .001). Similarly, 3 wt% zirconia reduced adhesion in mineral water (P < .001). However, in groups exposed to other beverages, including mineral water, almond milk, and water kefir, the incorporation of either 1 wt% or 3 wt% zirconia increased bacterial adhesion significantly (P < .001). SEM images corroborated these findings, showing varying patterns of bacterial adhesion on the surfaces of different resin groups under different environmental conditions. The findings indicate the importance of resin composition and beverage type in dictating bacterial interactions on acrylic surfaces. Notably, the addition of zirconia nanoparticles, particularly in Procryla 1Z, demonstrated a significant reduction in bacterial adhesion, highlighting its potential to enhance the antimicrobial properties of acrylic materials. Key points• Zirconia reduces bacterial adhesion in water.• Higher zirconia increases adhesion in vegan beverages.

Structure, Surface Topography, and Glass Transition Temperature of Dental Poly (Methyl Methacrylate) Resin Conjugated with 3,9-bisethenyl-2,4,8,10-tetraoxaspiro [5,5] Undecane as Cross-linker: An In Vitro Research

AIM AND OBJECTIVES

To characterize and analyze the structural presentation of a new denture base copolymer with a spiro-acetal cross-linker at 10 and 20 wt.% concentrations by nuclear magnetic resonance (NMR) and field emission scanning electron microscopy-energy-dispersive X-ray (FESEM-EDX) spectroscopies. Also, to evaluate the glass transition temperature (TG) of the new copolymer.

MATERIALS AND METHODS

The investigational groups G10 and G20 were heat-cured with the new spiro-acetal cross-linker at the above-mentioned concentrations, respectively. The control group G0 was heat-cured without the new cross-linker. Nuclear magnetic resonance and EDX spectroscopies determined the copolymerization along with elemental composition. The surface characteristics were discerned by FESEM. Differential scanning calorimetry was employed to evaluate the TG of the resultant copolymer. Appropriate statistical operations were performed to compare the mean TG of the groups.

RESULTS

The new copolymer's structure with the spiro-acetal cross-linker was configured with protons, carbons, aluminum, zirconium, yttrium, and silicon atoms. The TG of the resultant copolymer was high when compared with the G0. The 20 wt.% spiro-acetal cross-linker in the copolymer exhibited the highest TG.

CONCLUSION

The spiro-acetal cross-linking comonomer incorporated in the heat-cure denture polymer produced a new denture base copolymer with elevated TG. The resultant configuration of the new copolymer was characterized, structurally presented, and confirmed.

CLINICAL SIGNIFICANCE

The new copolymer might exhibit augmented strength due to the copolymerized spiro-acetal cross-linker. Moreover, the smooth and regular surface of the copolymer would have minimum or negligible microbial adhesion due to the hydrophobicity of the spiro-acetal comonomer incorporated in the denture base composition. How to cite this article: Ravivarman C, Ajay R, Saatwika L, et al. Structure, Surface Topography, and Glass Transition Temperature of Dental Poly (Methyl Methacrylate) Resin Conjugated with 3,9-bisethenyl-2,4,8,10-tetraoxaspiro [5,5] Undecane as Cross-linker: An In Vitro Research. J Contemp Dent Pract 2024;25(5):486-493.

Formulation, Configuration, and Physical Properties of Dental Composite Resin Containing a Novel 2π + 2π Photodimerized Crosslinker - Cinnamyl Methacrylate: An In Vitro Research

AIM

To formulate and characterize the chemical structure of a new dental composite with photodimerized cinnamyl methacrylate (PD-CMA) photo-crosslinking comonomer and to evaluate the monomer-to-polymer conversion (MPC) and glass transition temperature (Tg) of the new composite copolymers.

MATERIALS AND METHODS

CMA was PD by ultraviolet C-type (UVC) irradiation. The research groups were a control group C0 without PD-CMA and two trial groups: E10 (10 wt. % PD-CMA substituted in the base comonomers (B) and diluent (D) mixture); E20 (20 wt.% PD-CMA completely replacing the diluent (D) monomer). Infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies were employed for ascertaining copolymerization (CP). The surface features and composition of the copolymers were explained by field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) spectroscopy, respectively. The MPC and Tg of the copolymers were assessed using FTIR and differential scanning calorimetry, respectively. Statistical tests were used to compare the groups.

RESULTS

The configuration of the new copolymers P (BD-Co-CMA) and P(B-Co-CMA) was confirmed. The MPC% and T g of the copolymers were better than the control. PD-CMA at 20 wt. % in the P (B-Co-CMA) copolymer exhibited the highest MPC% and Tg.

CONCLUSION

The incorporation of PD-CMA in the composite resin resulted in new P (BD-Co-CMA) and P (B-Co-CMA) copolymers with improved MPC% and Tg.

CLINICAL SIGNIFICANCE

The substitution with PD-CMA offset the shortcomings of the conventional BD comonomers concerning the mechanical properties and biocompatibility of the restorative composite resin. This might ameliorate the restorations in vivo longevity and serviceability.

The Effects of Cross-Linking Agents on the Mechanical Properties of Poly (Methyl Methacrylate) Resin

Cross-linking agents are incorporated into denture base materials to improve their mechanical properties. This study investigated the effects of various cross-linking agents, with different cross-linking chain lengths and flexibilities, on the flexural strength, impact strength, and surface hardness of polymethyl methacrylate (PMMA). The cross-linking agents used were ethylene glycol dimethacrylate (EGDMA), tetraethylene glycol dimethacrylate (TEGDMA), tetraethylene glycol diacrylate (TEGDA), and polyethylene glycol dimethacrylate (PEGDMA). These agents were added to the methyl methacrylate (MMA) monomer component in concentrations of 5%, 10%, 15%, and 20% by volume and 10% by molecular weight. A total of 630 specimens, comprising 21 groups, were fabricated. Flexural strength and elastic modulus were assessed using a 3-point bending test, impact strength was measured via the Charpy type test, and surface Vickers hardness was determined. Statistical analyses were performed using the Kolmogorov-Smirnov Test, Kruskal-Wallis Test, Mann-Whitney U Test, and ANOVA with post hoc Tamhane test (p ≤ 0.05). No significant increase in flexural strength, elastic modulus, or impact strength was observed in the cross-linking groups compared to conventional PMMA. However, surface hardness values notably decreased with the addition of 5% to 20% PEGDMA. The incorporation of cross-linking agents in concentrations ranging from 5% to 15% led to an improvement in the mechanical properties of PMMA.

On the Addition of Multifunctional Methacrylate Monomers to an Acrylic-Based Infusible Resin for the Weldability of Acrylic-Based Glass Fibre Composites

The melt strength of Elium^® acrylic resin is an important factor to ensure limited fluid flow during welding. To provide Elium^® with a suitable melt strength via a slight crosslink, this study examines the effect of two dimethacrylates, namely butanediol-di-methacrylate (BDDMA) and tricyclo-decane-dimethanol-di-methacrylate (TCDDMDA), on the weldability of acrylic-based glass fibre composites. The resin system impregnating a five-layer woven glass preform is a mixture of Elium^® acrylic resin, an initiator, and each of the multifunctional methacrylate monomers in the range of 0 to 2 parts per hundred resin (phr). Composite plates are manufactured by vacuum infusion (VI) at an ambient temperature and welded by using the infrared (IR) welding technique. The mechanical thermal analysis of the composites containing multifunctional methacrylate monomers higher than 0.25 phr shows a very little strain for the temperature range of 50 °C to 220 °C. The quantity of 0.25 phr of both of the multifunctional methacrylate monomers in the Elium^® matrix improves the maximum bound shear strength of the weld by 50% compared to those compositions without the multifunctional methacrylate monomers.

Efficacy of antimicrobial photodynamic therapy in disinfection of Candida biofilms on acrylic dentures: A systematic review

BACKGROUND

The aim of this systematic review was to critically analyze and summarize the currently available scientific evidence concerning antifungal efficacy of aPDT against Candida on acrylic surface.

METHODS

The focused question was: '"Is aPDT effective in minimizing the counts of Candida on acrylic dentures". A literature search was conducted interpedently on the following electronic research databases: PubMED/MEDLINE, Cochrane, Google Scholar and Embase. The MeSH terms used were: ((antimicrobial photodynamic therapy) OR (light) OR (laser) OR (photodynamic)) AND ((Candida) OR (denture stomatitis)) AND ((denture) OR (acrylic) OR (polymethylmethacrylate) OR (dental prosthesis)). Data was extracted from the studies and quality assessment was carried out using a modified version of the CONSORT checklist.

RESULTS

Eighteen in-vitro anti-microbial studies and 5 clinical studies were included. Twenty-two studies suggested that aPDT was effective in reducing the Candida count on acrylic dentures and one study did not have a significant effect. 19 out of 23 studies were graded as having 'medium' quality and 4 studies were graded as 'high'. Several photosensitizers, including methylene blue, porphyrin derivatives, toluidine blue-O and others were used. LED was the most popular light source used for photo-activation of the photosensitizers.

CONCLUSION

Within the limitations of this review, aPDT is effective in reducing Candida growth on acrylic dentures and may prove to be clinical effective in preventing or treating denture stomatitis. However, more long-term clinical research is required before its clinical efficacy can be determined.

Mechanical Properties of the Modified Denture Base Materials and Polymerization Methods: A Systematic Review

Amidst growing technological advancements, newer denture base materials and polymerization methods have been introduced. During fabrication, certain mechanical properties are vital for the clinical longevity of the denture base. This systematic review aimed to explore the effect of newer denture base materials and/or polymerization methods on the mechanical properties of the denture base. An electronic database search of English peer-reviewed published papers was conducted using related keywords from 1 January 2011, up until 31 December 2021. This systematic review was based on guidelines proposed by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The search identified 579 papers. However, the inclusion criteria recognized 22 papers for eligibility. The risk of bias was moderate in all studies except in two where it was observed as low. Heat cure polymethyl methacrylate (PMMA) and compression moulding using a water bath is still a widely used base material and polymerization technique, respectively. However, chemically modified PMMA using monomers, oligomers, copolymers and cross-linking agents may have a promising result. Although chemically modified PMMA resin might enhance the mechanical properties of denture base material, no clear inferences can be drawn about the superiority of any polymerization method other than the conventional compression moulding technique.

Effect of Novel Cycloaliphatic Comonomer Incorporation on the Color Stability of Thermo-polymerized Denture Base Resin

BACKGROUND

Denture during its in vivo service encounters myriad food pigments and numerous physico-mechanical dynamic changes. Denture discoloration is one of the unresolved problems that should be unraveled to satisfy the esthetic demands of the patients.

AIM

This study aims to evaluate the color stability of a novel denture base copolymer with 10% and 20% (vol/vol) concentration of cycloaliphatic comonomer.

MATERIALS AND METHODS

Control group (G0) comprises specimens made without cycloaliphatic comonomer. The specimens of trial groups G10 and G20 were fabricated with 10% and 20% cycloaliphatic comonomer, respectively. For each group, thirty specimens (n = 30) were made. The specimens (n = 10) were immersed in three food colorant solutions (erythrosine, tartrazine, sunset yellow) for 56 days after artificial thermal aging. Ultraviolet-visible spectrophotometer was employed to measure the tristimulus values and calculate the color change (ΔE) of the specimens prior to and following rapid thermal aging or immersion of the specimens in the food colorants.

RESULTS

G0 showed the highest ΔE and G20 exhibited the least with each colorant. G10 had an intermediate imperceptible ΔE with each colorant. Also, significant differences (P = .000) existed between the food colorants within each group. The highest ΔE value was observed with sunset yellow and the lowest ΔE with tartrazine with each group.

CONCLUSION

The addition of cycloaliphatic comonomer in denture base acrylic resins improved the color stability. The new copolymer with 20 Vol.% comonomer exhibited the highest color stability with all the food colorants.

Synthesis and Characterization of a Ring-Opening Oxaspiro Comonomer by a Novel Catalytic Method for Denture Base Resins

Background:

3,9-Dimethylene-1,5,7,11-tetraoxaspiro[5,5]undecane (DMTOSU) is a double ring-opening monomer that exhibits expansion upon polymerization and may be used as a denture base resin's comonomer to offset or minimize polymerization shrinkage. It's synthesis by transesterification reaction (TE) catalyzed by distannoxane is not reported in the literature. The synthesis became the prime concern because this monomer is hardly available commercially.

Purpose:

The purpose is to confirm the DMTOSU synthesis and compare the synthesized monomers obtained by two different catalytic processes through Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies.

Materials and Methods:

Scheme I synthesis was by TE catalyzed by dichlorotetrabutyl distannoxane (DCBS) yielding M1 monomer. Scheme II synthesis was catalyzed by dibutyltin oxide-carbon disulfide (DBTO-CS₂) yielding M2 monomer.

Results:

The appearance of a characteristic peak at 1212 cm⁻¹ in FTIR spectrum, a doublet at δ 4.95 in ¹H-NMR spectrum and a peak at δ 117.12 in ¹³C-NMR spectrum confirmed the synthesis of DMTOSU-M1catalyzed by DCBS, which is not significantly different from DMTOSU-M2 catalyzed by DBTO-CS₂.

Conclusion:

The catalytic action of DCBS is a successful alternative to the DBTO-CS₂ catalysis in DMTOSU synthesis.

Copolymerization of Ring-Opening Oxaspiro Comonomer with Denture Base Acrylic Resin by Free-Radical/Cationic Hybrid Polymerization

BACKGROUND

Polymerization shrinkage is an innate characteristic of thermo-polymerized denture base acrylic resin. Volumetric shrinkage is still a problem, although myriad material modifications. Ring-opening oxaspiro monomers have promising volumetric expansions of about 7%. These monomers have diminished the shrinkage in dental filling resins through copolymerization (CP). However, their CP with denture base resins is not reported yet.

PURPOSE

The aim is to confirm the CP of an oxaspiro monomer with methyl methacrylate (MMA) by radical-cationic hybrid polymerization and to assess the degree of conversion (DC) of the formed copolymer.

MATERIALS AND METHODS

The oxaspiro monomer was synthesized by a transesterification reaction. The study groups were based on the composition and thermo-polymerization method. The control and E1 groups were thermo-polymerized in water-bath, whereas the E2 group in a laboratory autoclave. Both E1 and E2 groups contained the oxaspiro monomer and cationic initiator. E2 group had an additional radical initiator. The CP and DC were confirmed and assessed by infrared spectroscopy.

RESULTS

Accentuation of carbonyl peak, the disappearance of the spiro-carbon peak, and the appearance of ether linkages in experimental groups confirmed the ring-opening. E2 group had the highest DC.

CONCLUSION

The oxaspiro monomer successfully copolymerized with MMA and had good DC.

Quality assessment tools used in systematic reviews of in vitro studies: A systematic review

BACKGROUND

Systematic reviews (SRs) and meta-analyses (MAs) are commonly conducted to evaluate and summarize medical literature. This is especially useful in assessing in vitro studies for consistency. Our study aims to systematically review all available quality assessment (QA) tools employed on in vitro SRs/MAs.

METHOD

A search on four databases, including PubMed, Scopus, Virtual Health Library and Web of Science, was conducted from 2006 to 2020. The available SRs/MAs of in vitro studies were evaluated. DARE tool was applied to assess the risk of bias of included articles. Our protocol was developed and uploaded to ResearchGate in June 2016.

RESULTS

Our findings reported an increasing trend in publication of in vitro SRs/MAs from 2007 to 2020. Among the 244 included SRs/MAs, 126 articles (51.6%) had conducted the QA procedure. Overall, 51 QA tools were identified; 26 of them (51%) were developed by the authors specifically, whereas 25 (49%) were pre-constructed tools. SRs/MAs in dentistry frequently had their own QA tool developed by the authors, while SRs/MAs in other topics applied various QA tools. Many pre-structured tools in these in vitro SRs/MAs were modified from QA tools of in vivo or clinical trials, therefore, they had various criteria.

CONCLUSION

Many different QA tools currently exist in the literature; however, none cover all critical aspects of in vitro SRs/MAs. There is a need for a comprehensive guideline to ensure the quality of SR/MA due to their precise nature.

Effect of novel cycloaliphatic comonomer on the flexural and impact strength of heat-cure denture base resin

This study aims to evaluate the impact of adding a novel tricyclodecane dimethanol diacrylate comonomer on the flexural strength (FS) and impact strength (IS) of heat-cure denture base resin at 10% and 20% (v/v) concentrations. To test the FS and IS, a sum total of 150 bar-shaped specimens were prepared according to standard specifications. For the FS, the specimens were subjected to the three-point bend test with a span length of 50 mm. For the IS, Charpy's test was executed with a span length of 60 mm. The FS was measured in MPa, and the IS was measured in kJ/m². There was a statistically significant difference (P < 0.001) between the control and experimental groups in that both the FS and IS were increased in the experimental groups relative to the control group.

Histocompatibility of Novel Cycloaliphatic Comonomer in Heat-cured Denture Base Acrylic Resin: Histomorphometric Analysis in Rats

Background:

Prosthodontics is impossible without denture base resins. Allergic reactions to these resins are not uncommon, albeit favorable properties. Monomeric modifications are being done to improve the properties of the material. Tricyclodecane dimethanol diacrylate (TCDDMDA) monomer has been recently identified and experimented as a comonomer with methyl methacrylate (MMA).

Aim:

This study aimed to investigate the histocompatibility of TCDDMDA comonomer in polymerized resin at 10% and 20% (vol/vol) concentrations in rats by histomorphometric analysis.

Materials and Methods:

Twenty-four male Wistar rats were randomly divided into the following four groups: NP group (control; n = 6), with no palatal appliance, Groups P0, P10, and P20 were fixed with palatal appliances fabricated of 100% MMA, 10% TCDDMDA + 90% MMA, and 20% TCDDMDA + 80% MMA, respectively. Weights of the animals were recorded just before the appliance placement and after 14 days. The animals were sacrificed, and the palatal tissues were processed for histopathological analysis. Histomorphometric parameters assessed were total epithelial (ET), connective tissue (CT), and keratin layer (KT) thicknesses.

Results:

No significant difference was observed regarding body weight. Group P0 showed increased ET, CT, and KT when compared to other groups. Bonferroni multiple comparison tests showed a statistically significant difference between all the groups except between P10 and P20 for all the three morphometric parameters.

Conclusion:

Palatal appliances with TCDDMDA comonomer showed good histocompatibility in rats up to 20% (vol/vol) concentration.

Effect of Novel Cycloaliphatic Comonomer on Surface Roughness and Surface Hardness of Heat-cure Denture Base Resin

Background:

Polymethyl methacrylate (PMMA) is a widely used resin in the field of prosthodontics for fabricating myriad orofacial prostheses. Albeit several advantages, it possesses certain lacunae concerning physicomechanical properties.

Purpose:

This in vitro research aimed to evaluate the surface roughness (SR) and hardness (SH) of heat-cured PMMA processed with a cycloaliphatic monomer, tricyclodecane dimethanol diacrylate (TCDDMDA), in methyl methacrylate at various concentrations.

Materials and Methods:

Groups have been divided into control (SRC and SHC) and experimental groups (SR10 and 20; SH10 and 20). Forty-five PMMA disc specimens were prepared. SR was assessed using a nanomechanical testing machine and the arithmetic roughness (Ra) was recorded. The same specimens were then subjected to Vicker’s microhardness testing and Vicker’s hardness number (VHN) was obtained. Data were compared using one-way analysis of variance (ANOVA) and post hoc Bonferroni tests (α=0.05).

Results:

The mean (standard deviation [SD]) of SRC, SR10, and 20 groups were 111.415 nm (0.789), 62.666 nm (0.482), and 41.004 nm (0.561), respectively. The mean (SD) VHN of SHC, SH10, and 20 groups were 21.003 (0.252), 23.975 (0.207), and 34.622 (0.079), respectively.

Conclusion:

The addition of TCDDMDA markedly decreased the SR and increased the SH of the experimental groups.