Cytotoxicity of dental self-curing resin for a temporary crown: an in vitro study

BACKGROUND

Residual monomer tests using high-performance liquid chromatography and cytotoxicity tests were performed to analyze the effect on the oral mucosa of a self-curing resin for provisional crown production.

METHODS

A cytotoxicity test was performed to confirm whether leaked residual monomers directly affected oral mucosal cells. The cytotoxicity of the liquid and solid resin polymers was measured using a water-soluble tetrazolium (WST) test and microplate reader.

RESULTS

In the WST assay using a microplate reader, 73.4% of the cells survived at a concentration of 0.2% liquid resin polymer. The cytotoxicity of the liquid resin polymer was low at ≤0.2%. For the solid resins, when 100% of the eluate was used from each specimen, the average cell viability was 91.3% for the solid resin polymer and 100% for the hand-mixed self-curing resin, which is higher than the cell viability standard of 70%. The cytotoxicity of the solid resin polymer was low.

CONCLUSION

Because the polymerization process of the self-curing resin may have harmful effects on the oral mucosa during the second and third stages, the solid resin should be manufactured indirectly using a dental model.

Management of peri-prosthetic joint infection and severe bone loss after total hip arthroplasty using a long-stemmed cemented custom-made articulating spacer (CUMARS)

Background

There is little evidence on techniques for management of peri-prosthetic infection (PJI) in the context of severe proximal femoral bone loss. Custom-made articulating spacers (CUMARS) utilising cemented femoral stems as spacers was described providing better bone support and longer survival compared to conventional articulating spacers. We retrospectively report our experience managing PJI by adaptation of this technique using long cemented femoral stems where bone loss precludes use of standard stems.

Methods

Patients undergoing 1st stage revision for infected primary and revision THA using a cemented long stem (> 205 mm) and standard all-polyethylene acetabulum between 2011 and 2018 were identified. After excluding other causes of revision (fractures or aseptic loosening), Twenty-one patients remained out of total 721 revisions. Medical records were assessed for demographics, initial microbiological and operative treatment, complications, eradication of infection and subsequent operations. 2nd stage revision was undertaken in the presence of pain or subsidence.

Results

Twenty-one patients underwent 1st stage revision with a cemented long femoral stem. Mean follow up was 3.9 years (range 1.7–7.2). Infection was eradicated in 15 (71.4%) patients. Two patients (9.5%) required repeat 1st stage and subsequently cleared their infection. Three patients (14.3%) had chronic infection and are on long term suppressive antibiotics. One patient (4.8%) was lost to follow up before 2 years. Complications occurred in seven patients (33%) during or after 1st stage revision. Where infection was cleared, 2nd stage revision was undertaken in 12 patients (76.5%) at average of 9 months post 1st stage. Five (23.8%) CUMARS constructs remained in-situ at an average of 3.8 years post-op (range 2.6–5.1).

Conclusions

Our technique can be used in the most taxing of reconstructive scenarios allowing mobility, local antibiotic delivery, maintenance of leg length and preserves bone and soft tissue, factors not afforded by alternative spacer options.

Influence of Preparation and Exposure Periods of Eluates from Ocular Prosthesis Acrylic Resin in Human Conjunctival Cell Line

BACKGROUND

This study was undertaken to analyze if different preparation and exposure periods of eluates from ocular prosthesis acrylic resin influence the cytotoxicity for conjunctival cells.

METHODS

Twenty-four acrylic resin specimens were divided, according to the period of eluate exposure to Chang conjunctival cells (24 and 72 hours). Eluates were prepared in four different ways: 24, 48, and 72 hours of resin specimen immersion in medium and 24 hours of immersion in water, followed by 24 hours of immersion in medium. MTT assay was used to evaluate the cytotoxic effect. The production of IL-1β, IL-6, TNF-α, and chemokine macrophage inflammatory protein 1α was evaluated by ELISA, while the mRNA expression of type IV collagen (COL IV), transforming growth factor β (TGF-β), and matrix metalloproteinase 9 (MMP9) were evaluated by real-time RT-PCR technique. The statistical analysis was carried out using ANOVA with Bonferroni post-hoc test and the student’s t-test (p < 0.05).

RESULTS

Significant quantities of IL-6 (4.594 pg/mL) and mRNA expression of COL IV (1.58) were verified at 72 hours of eluate exposure to cells, as compared to 24 hours. After the 72-hour exposure of eluates to cells, lower cell proliferation (88.4%) and higher IL-6 quantities (12.374 pg/mL), as well as mRNA expression of COL IV (2.21), TGF-β (2.02), and MMP9 (5.75) were observed, which corresponded to 72 hours of a specimen immersed in medium.

CONCLUSION

Longer periods of eluate preparation and exposure from the acrylic resin to cells are related to higher production of proinflammatory cytokines and extracellular matrix proteins.

Bond Strength of Repaired Acrylic Denture Teeth Using Visible Light Cure Composite Resin

Background:

Although bonding to denture teeth after surface treatment with chemical agents is desirable, there is little information on the use of Visible Light Cure composite resin (VLC) as bonding denture materials.

Objectives:

To determine the effect of various surface treatments on shear bond strength between Visible Light Cure composite resin and the acrylic denture teeth interface.

Methods:

Forty cylindrical sticks of acrylic resin with denture teeth mounted atop were prepared. Various treatments were implemented upon the acrylic resin teeth surfaces. The samples were divided into four groups (n = 10). Light-cured composite resin (LC) was applied over all treated and untreated surfaces of tested groups. The shear bond was tested using a universal tensile testing apparatus with the knife-edge of a 0.8mm shear tester. Data were statistically analyzed using one-way ANOVA performed at a confidence level of 95% and significant P-value of (P ≤ 0.05).

Results:

Analysis of variance (ANOVA) showed statistically significant difference (P < 0.05) between treated and untreated teeth surfaces. The treated surfaces exhibited various levels of bond strength depending on the type of treatment.

Conclusion:

Application of VLC bonding agent with prior treatment of methylmethacrylate (MMA) on the acrylic resin denture teeth resulted in maximum bond strength with composite resin.

Design and Comparative Evaluation of In-vitro Drug Release, Pharmacokinetics and Gamma Scintigraphic Analysis of Controlled Release Tablets Using Novel pH Sensitive Starch and Modified Starch- acrylate Graft Copolymer Matrices

The present investigation deals with the development of controlled release tablets of salbutamol sulphate using graft copolymers (St-g-PMMA and Ast-g-PMMA) of starch and acetylated starch. Drug excipient compatibility was spectroscopically analyzed via FT-IR, which confirmed no interaction between drug and other excipients. Formulations were evaluated for physical characteristics like hardness, friability, weight variations, drug release and drug content analysis which satisfies all the pharmacopoeial requirement of tablet dosage form. Release rate of a model drug from formulated matrix tablets were studied at two different pH namely 1.2 and 6.8, spectrophotometrically. Drug release from the tablets of graft copolymer matrices is profoundly pH-dependent and showed a reduced release rate under acidic conditions as compared to the alkaline conditions. Study of release mechanism by Korsmeyer's model with n values between 0.61-0.67, proved that release was governed by both diffusion and erosion. In comparison to starch and acetylated starch matrix formulations, pharmacokinetic parameters of graft copolymers matrix formulations showed a significant decrease in Cmax with an increase in tmax, indicating the effect of dosage form would last for longer duration. The gastro intestinal transit behavior of the formulation was determined by gamma scintigraphy, using (99m)Tc as a marker in healthy rabbits. The amount of radioactive tracer released from the labelled tablets was minimal when the tablets were in the stomach, whereas it increased as tablets reached to intestine. Thus, in-vitro and in-vivo drug release studies of starch-acrylate graft copolymers proved their controlled release behavior with preferential delivery into alkaline pH environment.

Assessment of occupational symptoms and chemical exposures for nail salon technicians in Daegu City, Korea

OBJECTIVES

This study aimed to evaluate occupational symptoms and chemical exposures of nail salon technicians.

METHODS

Work-related symptoms of nail salon technicians in Daegu City were surveyed using a researcher-administered questionnaire, and responses were compared to those of non-exposed office workers as controls. Personal exposure level of airborne volatile organic compounds was also monitored using passive samplers.

RESULTS

A total of 159 subjects in 120 salons were interviewed. Average work-shift concentrations of 13 chemicals were measured for 50 workers from 30 salons using personal passive samplers. The most frequently reported respiratory or neurologic symptoms by nail shop technicians compared to controls were nose irritation (odds ratio [OR], 54.0; confidence interval [CI], 21.6 to 134.8), followed by headache (OR, 9.3; CI, 4.7 to 18), and throat irritation (OR, 4.3; CI, 2.2 to 8.5). For eyes and skin, 92% of respondents complained eye irritation (OR, 13.1; CI, 5.7 to 30.1). In musculoskeletal symptoms, workers reported pain or discomfort in shoulders (OR, 20.3; CI, 7.7 to 54) and neck (OR, 19.7; CI, 8.9 to 43.6). From personal measurements, the proportion of exceeding the Korean Occupational Exposure Limit was the highest for acetone with 64%, followed by toluene (50%), butyl acetate (46%), and methyl methacrylate (12%). However, the service was being provided without a proper ventilation system in most surveyed shops.

CONCLUSIONS

Based on these findings, it is warranted to have appropriate local exhaust ventilation place to ensure adequate health protection of nail shop technicians as well as customers. At the same time, greater policy interests are warranted in nail care business to protect health of both workers and customers.

Canalization and maintaining the patency of external auditory canal in a congenital aural atresia patient: a multidisciplinary approach

This clinical report describes the role of a prosthodontist in rehabilitating a patient with congenital aural atresia. The external auditory canal and structure in the middle ear fail to develop completely in cases of congenital aural atresia. Canalization procedure to establish the communication between the external ear and middle ear, and maintaining the patency of the created canal plays an important role in the success of treatment in selected patients. Post Operative external auditory canal restenosis is the most common complication after congenital aural atresia surgery. The prosthodontist has an important role in assisting ENT surgeons in canalization procedure and also maintaining the patency of the canal during healing phase.

Forehead augmentation with a methyl methacrylate onlay implant using an injection-molding technique

Background

The forehead, which occupies about one third of the face, is one of the major determinants of a feminine or masculine look. Various methods have been used for the augmentation of the forehead using autologous fat grafts or alloplastic materials. Methylmethacrylate (MMA) is the most appropriate material for augmentation of the forehead, and we have used an injection-molding technique with MMA to achieve satisfactory results.

Methods

Under local anesthesia with intravenous (IV) sedation, an incision was made on the scalp and a meticulous and delicate subperiosteal dissection was then performed. MMA monomers and polymers were mixed, the dough was injected into the space created, and manual molding was performed along with direct inspection. This surgery was indicated for patients who wanted to correct an unattractive appearance by forehead augmentation. Every patient in this study visited our clinics 3 months after surgery to evaluate the results. We judged the postoperative results in terms of re-operation rates caused by the dissatisfaction of the patients and complications.

Results

During a 13-year period, 516 patients underwent forehead augmentation with MMA. With the injection-molding technique, the inner surface of the MMA implant is positioned close to the underlying frontal bone, which minimizes the gap between the implant and bone. The borders of the implant should be tapered sufficiently until no longer palpable or visible. Only 28 patients (5.4%) underwent a re-operation due to an undesirable postoperative appearance.

Conclusions

The injection-molding technique using MMA is a simple, safe, and ideal method for the augmentation of the forehead.

Local and systemic effects of unpolymerised monomers

Methyl methacrylate (MMA), a widely used monomer in dentistry and medicine has been reported to cause abnormalities or lesions in several organs. Experimental and clinical studies have documented that monomers may cause a wide range of adverse health effects such as irritation to skin, eyes, and mucous membranes, allergic dermatitis, stomatitis, asthma, neuropathy, disturbances of the central nervous system, liver toxicity, and fertility disturbances.