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Influence of sodalite zeolite infiltration on the coefficient of thermal expansion and bond strength of all-ceramic dental prostheses

Naji GA, Omar RA, Yahya R

J Mech Behav Biomed Mater, 2017 03;67:135-143.
PMID: 28006713 DOI: 10.1016/j.jmbbm.2016.12.007

In all-ceramic systems, a high incidence of veneer chip-off has been reported in clinical studies. Coefficient of thermal expansion (CTE) behaviour is one of the factors that may increase residual stress in the interface and influence the veneer/core bond strength. Therefore, this study aimed to evaluate the effect of sodalite zeolite-infiltration on the CTE behaviour and bond strength of different all-ceramic prostheses. The case-study groups were synthesized sodalite zeolite-infiltrated alumina (IA-SOD) and synthesized sodalite zeolite-infiltrated zirconia-toughened alumina (ZTA) (IZ-SOD), while the control groups were glass-infiltrated alumina (IA-glass) and glass-infiltrated ZTA (IZ-glass). Forty cylindrical-shaped samples measuring 5 mm in diameter and 10 mm in height were tested for CTE using a thermo-mechanical analyser machine, and forty disc-shaped ceramic samples measuring 12 mm in diameter and 1.2 ± 0.2 mm in thickness were prepared using specially designed stainless steel split mould and veneered by cylinder-shaped (2 mm high × 2 mm diameter) low-fusing porcelain (Vita VM7). The veneer/core samples were sintered and tested for shear bond strength using a high precision universal testing machine. Scanning electron microscope, stereo microscope, atomic force microscope, and energy-dispersive X-ray spectroscopy were used to investigate the structural characteristics of samples at the fracture surface. The collected data were analyzed with a one-way ANOVA and Tukey HSD test (α=.05). IZ-SOD revealed highest CTE and shear bond strength values, while the IA-glass revealed the lowest values than the other groups. There was no significant difference in CTE and bond strength among IZ-SOD, IA-SOD and IZ-glass samples (p>0.05). The experimental SOD zeolite-infiltrated samples revealed higher CTE mismatch and bond strength along with a more favourable mode of failure than did the commercial glass-infiltrated samples. Sandblast technique is considered as effective conditioning procedure for enhancing the surface roughness of SOD zeolite-infiltrated frameworks which subsequently improving the bond strength.
Contour Analysis of Three-Dimensional Peri-Implant Mucosal Model as an Endpoint Analysis of Photofunctionalization Effects on Implant Abutment Materials

Razali M, Chai WL, Omar RA, Ngeow WC

Materials (Basel), 2023 Aug 09;16(16).
PMID: 37629819 DOI: 10.3390/ma16165529

INTRODUCTION: The objective of this study was to examine the effect of photofunctionalization on the soft-tissue contour formed at the interface of various abutment materials using end-point analyses obtained from the three-dimensional oral mucosal model (3D-OMMs).
METHODS: Commercially pure titanium (CPTi), alumina-toughened zirconia (ATZ), and yttria-stabilized zirconia (YSZ) made into discs shapes were classified into two groups: UV-treated (PTx) and non-treated (NTx). The materials in PTx groups were exposed to UV light for 12 min. Human gingival fibroblasts and TR146 epithelial cell lines co-cultured on the acellular dermal membrane were used to construct the 3D-OMM. After 4 days of culture, the discs were inserted into the holes prepared within the membrane of 3D-OMMs. The contour formed by the tissue was evaluated after 14 days of culture.
RESULTS: The UV treatment of abutment materials resulted in the formation of more non-pocket-tissue types among the PTx group (p = 0.002). Of all materials tested, soft tissue contour around YSZ showed higher scores for the non-pocket type in both non- and UV-treated groups.
CONCLUSIONS: The non-pocket type of tissue attachment was frequently found in all surfaces modified by photofunctionalization, particularly zirconia. The 3D-OMM can be used to evaluate the biological endpoints of implant surface modifications.
Incorporation of Green Capping Agents to Reduce Silver-Mediated Dentine Staining

Asghar M, Yahya R, Yap AUJ, Azzahari AD, Omar RA

Caries Res, 2022;56(3):149-160.
PMID: 35871511 DOI: 10.1159/000525505

Silver diammine fluoride (SDF) is known as a noninvasive, cost-effective, safe, and simple method of dental caries treatment. However, staining and discoloration seem inseparable with SDF and continue as a cosmetic concern. Research is ongoing to overcome these issues, for example, by using glutathione (G) or potassium iodide among others. Therefore, the study aimed to investigate the effects of incorporating different concentrations of capping agents on SDF chemistry and SDF-mediated tooth staining at different time points. Tannic acid (TA), gallic acid (GA), carboxymethyl chitosan (CM), and G at different concentrations (5, 10, and 15% w/v) were incorporated in 30% SDF. FTIR and UV-Vis spectroscopies of the prepared solutions was performed to evaluate chemical changes. Time-dependent color changes (ΔE) in bovine dentine specimens (6 × 6 × 1 ± 0.25 mm3) were measured spectrophotometrically at application/washup, 1 and 3 h, after 1, 2, 4, 7, and 14 days. Results showed suppression of FTIR peaks at 3,358 cm-1 and 1,215 cm-1 in capping agent-modified SDF indicative of a successful capping effect of the silver ions, which was corroborated by UV-Vis blueshift of ∼∆32 nm. The capping effect on SDF increased proportionally with the concentrations of TA, GA, CM, and G used. A more pronounced tooth staining reduction however was shown more in TA- and G- rather than in GA- and CM-modified SDF. At day 14, SDF showed the highest mean ΔE(50.14 ± 2.14), while 15% TA showed the lowest ΔE(30.14 ± 0.81). In conclusion, capping agent incorporation significantly reduced SDF-mediated tooth staining. This reduction in staining is more dependent on the respective capping agent functional groups than concentrations per se. The potential of capping agents to minimize tooth staining of SDF was TA>G>CM>GA.
Approaches to minimize tooth staining associated with silver diamine fluoride: A systematic review

Asghar M, Omar RA, Yahya R, Yap AU, Shaikh MS

J Esthet Restor Dent, 2023 Mar;35(2):322-332.
PMID: 36628650 DOI: 10.1111/jerd.13013

OBJECTIVE: To the effectiveness of different strategies to overcome silver diamine fluoride (SDF)-mediated tooth staining.
MATERIALS AND METHODS: Four online databases (PubMed, ScienceDirect, Scopus, and Web of Science) were searched using different MeSH terms and Boolean Operators to retrieve the articles (until June 2021), followed by a hand-search of the reference list of the included articles. All full-text, original studies in English that evaluated SDF staining and at least one SDF modification/alternative were included.
RESULTS: Among the assessed studies, nine studies explored the stain-minimization effect of potassium iodide (KI) post-application following SDF treatment. Among these, eight concluded that KI application after SDF treatment significantly reduced tooth staining, while one showed marginal staining following glass ionomer restoration of the SDF-treated dentine. Additionally, one study applied potassium fluoride (KF) and silver nitrate (AgNO3 ) concurrently to mitigate SDF-mediated staining. One study compared SDF staining with polyethylene glycol (PEG)-coated nanoparticles containing sodium fluoride (NaF), and another used nanosilver fluoride (NSF) for staining comparison with SDF.
CONCLUSIONS: Within the limitations of this study, the addition of different materials to SDF has proven to be a beneficial strategy for overcoming tooth staining associated with SDF. Future studies are warranted, particularly clinical trials, to validate these findings.
CLINICAL SIGNIFICANCE: SDF-mediated tooth staining is a serious concern that limits its clinical use. A review of various strategies to overcome this problem will help clinicians enhance its clinical use and patient acceptance.