Surface Microstructural Changes and Release of Ions from Dental Metal Alloy Removable Prostheses in Patients Suffering from Acid Reflux

Effects of disinfection with a vinegar-hydrogen peroxide mixture on the surface characteristics of denture acrylic resins

OBJECTIVE

This study aimed to investigate changes in the surface characteristics of two denture resins when disinfected with a vinegar-hydrogen peroxide (VHP) mixture.

MATERIALS AND METHODS

Microwave-polymerized or 3D printed acrylic resin disks were immersed for 900 min (simulating 90 daily uses) in the following solutions (N = 10): water; 0.5% sodium hypochlorite; hydrogen peroxide and water dilution (1:1 ratio); vinegar and water dilution (1:1 ratio); and VHP mixture. Surface roughness, Knoop microhardness, surface free energy, and scanning electron microscopic images were assessed before and after the immersions. Results were compared using the 2-way ANOVA for repeated measures and Tukey test, at 5% significance.

RESULTS

Surface roughness and microhardness did not differ (P > .05) among the solutions and times. Surface free energy and its dispersive component increased (P < .05) for all solutions. All solutions, except for water and VHP mixture, degraded microtopography.

CONCLUSIONS

The VHP mixture was not deleterious to conventional and 3D-printed resin surfaces.

CLINICAL RELEVANCE

Conventional and 3D printed resin dentures can be disinfected with a VHP mixture in a 1:1 ratio because this mixture does not substantially affect the surface characteristics after 90 daily immersions. On the contrary, sodium hypochlorite, hydrogen peroxide, and vinegar solutions, even in low concentrations, should be used with caution for denture disinfection because they may alter the resin microtopography over time.

Effect of Fluoride Content of Mouthwashes on the Metallic Ion Release in Different Orthodontics Archwires

Metal ion release studies were carried out on three of the most commonly used orthodontic wires in the clinic: austenitic stainless steel, Ti-Mo, and superelastic NiTi, using three mouthwashes with different fluoride concentrations: 130, 200, and 380 ppm. Immersions were carried out in these mouthwashes at 37 °C for 1, 4, 7, and 14 days, and the ions released were determined by inductively coupled plasma-mass spectrometry (ICP-MS). All wires were observed by scanning electron microscopy (SEM). The results showed a moderate ion release in the stainless steel wires, with nickel and chromium values of 500 and 1000 ppb in the worst conditions for the wires: concentrations of 380 ppm fluoride and 14 days of immersion. However, in the Ti-Mo and NiTi alloys, an abrupt change in release was observed when the samples were immersed in 380 ppm fluoride concentrations. Titanium releases in Ti-Mo wires reached 200,000 ppb, creating numerous pits on the surface. Under the same conditions, the release of Ni and Ti ions from the superelastic wires also exceeded 220,000 ppb and 180,000 ppb, respectively. This release of ions causes variations in the chemical composition of the wires, causing the appearance of martensite plates in the austenitic matrix after 4 days of immersion. This fact causes it to lose its superelastic properties at a temperature of 37 °C. In the case of immersion in 380 ppm mouthwashes for more than 7 days, rich-nickel precipitates can be seen. These embrittle the wire and lose all tooth-correcting properties. It should be noted that the release of Ni ions can cause hypersensitivity in patients, particularly women. The results indicate that the use of mouthwashes with a high content of fluoride should not be recommended with orthodontic archwires.

Effects of disinfection with a vinegar-hydrogen peroxide mixture on the surface composition and topography of a cobalt-chromium alloy

STATEMENT OF PROBLEM

Choosing the best disinfection agent for removable partial dentures may be challenging since most commercially available disinfection solutions alter the properties of the metal framework.

PURPOSE

The purpose of this in vitro study was to analyze the changes in the surface topography and elemental composition of a cobalt-chromium (Co-Cr) alloy when immersed in a vinegar-hydrogen peroxide mixture.

MATERIAL AND METHODS

Disk-shaped specimens (N=50) were fabricated with Co-Cr alloy and randomly distributed into 5 groups (N=10) according to the immersion solutions: distilled water (control) (W); 0.5% sodium hypochlorite (H); 3% hydrogen peroxide and water in a 1:1 ratio (HP); vinegar and water in a 1:1 ratio (V); and vinegar and 3% hydrogen peroxide mixture in a 1:1 ratio (VHP). The immersions simulated 90 uses of 10 minutes each. The surface topography and the elemental composition were analyzed with scanning electron microscopy and energy-dispersive spectroscopy, before (T0) and after (T1) the immersions. The 2-way ANOVA for repeated measures was used for statistical comparisons (α=.05).

RESULTS

The tested mixture (VHP) did not change the metal surface topography or increase the oxygen proportion, indicating that no corrosion occurred. Similarly, groups W, HP, and V had no topographic changes and nonsignificant statistical differences at T1 for elemental composition (P>.05). However, the specimens immersed in sodium hypochlorite (H) showed staining, surface irregularity, composition change, with an appearance of 22.56% more oxygen, 41% less chromium, and 28.77% less cobalt at T1 (P<.05).

CONCLUSIONS

The immersion of Co-Cr alloy in a vinegar-hydrogen peroxide mixture did not change the surface structure of the metal.

Minimization of Adverse Effects Associated with Dental Alloys

Metal alloys are one of the most popular materials used in current dental practice. In the oral cavity, metal structures are exposed to various mechanical and chemical factors. Consequently, metal ions are released into the oral fluid, which may negatively affect the surrounding tissues and even internal organs. Adverse effects associated with metallic oral appliances may have various local and systemic manifestations, such as mouth burning, potentially malignant oral lesions, and local or systemic hypersensitivity. However, clear diagnostic criteria and treatment guidelines for adverse effects associated with dental alloys have not been developed yet. The present comprehensive literature review aims (1) to summarize the current information related to possible side effects of metallic oral appliances; (2) to analyze the risk factors aggravating the negative effects of dental alloys; and (3) to develop recommendations for diagnosis, management, and prevention of pathological conditions associated with metallic oral appliances.

Effect of Fluoride Content of Mouthwashes on Superelastic Properties of NiTi Orthodontic Archwires

The influence of sodium fluoride (NaF) concentration in mouthwashes on the properties of superelastic NiTi orthodontic wires has been studied. In this work, 55.8%Ni and 44.2%Ti (in weight) wires were introduced in commercial mouthwashes with different NaF contents (0, 130, 200 and 380 ppm). The release of Ni²⁺ and Ti⁴⁺ ions was by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) at 1, 4, 7 and 14 days. Superelastic orthodontic wires present at oral temperature the austenitic phase which is transformed into a plastic phase (martensite) by cooling. The temperatures at which this occurs are influenced by the chemical composition. The release of ions from the wire will produce variations in the temperatures and stresses of the stress-induced martensitic transformation. M_s, M_f, A_s, A_f were determined by Differential Scanning Calorimeter (DSC). The transformation stresses (austenite to stress induce martensite) were determined with a servo-hydraulic testing machine at 37 °C. The surfaces for the different times and mouthwash were observed by Scanning Electron Microscope (SEM). The release of Ni²⁺ in mouthwashes with 380 ppm NaF concentrations reaches 230,000 ppb in 14 days and for Ti⁴⁺ 175,000 ppb. When NaF concentrations are lower than 200 ppm the release of Ni and Ti ions is around 1500 ppb after 14 days. This variation in compositions leads to variations in M_s from 27 °C to 43.5 °C in the case of higher NaF concentration. The increasing immersion time and NaF concentrations produce a decrease of Ni in the wires, increasing M_s which exceed 37 °C with the loss of superelasticity. In the same way, the stresses (tooth position corrective) decrease from 270 MPa to 0 MPa due to the martensitic phase. The degradation can produce the growth of precipitates rich in Ti (Ti₂Ni). These results are of great interest in the orthodontic clinic in order to avoid the loss of the therapeutic properties of superelastic NiTi due to long immersion in fluoride mouthwashes.

Annual review of selected scientific literature: A report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

This comprehensive review of the 2018 dental literature is provided to inform busy dentists about progress in the profession. Developed by the Committee on Scientific Investigation of the American Academy of Restorative Dentistry, each author brings discipline-specific expertise to one of the 8 sections of the report including (1) prosthodontics; (2) periodontics, alveolar bone, and peri-implant tissues; (3) implant dentistry; (4) dental materials and therapeutics; (5) occlusion and temporomandibular disorders; (6) sleep-related breathing disorders; (7) oral medicine and oral and maxillofacial surgery; and (8) dental caries and cariology. The report targets important information that will likely influence day-to-day treatment decisions. Each review is not intended to stand alone but to update interested readers so that they may visit source materials if greater detail is desired. As the profession continues its march toward evidence-based clinical decision-making, an already voluminous library of potentially valuable dental literature continues to grow. It is the intention of this review and its authors to provide assistance in navigating the extensive dental literature published in 2018. It is our hope that readers find this work useful in the clinical management of patients moving forward.

Nickel ion release from dental alloys in two different mouthwashes

Background . Mouthwashes are widely used as adjuncts to mechanical oral hygiene procedures. Nonetheless, there is little information regarding the effect of various mouthwashes on the amount of ions released from the nickel-chromium (Ni‒Cr) alloys used in the fabrication of fixed prostheses. Therefore, the present study was conducted to evaluate the effect of two types of mouthwash on the release of Ni ions from dental alloys. Methods . Forty-two disk-shaped specimens were prepared with a diameter of 10 mm and a height of 2 mm. Two mouthwashes were examined in this study: Oral B and Listerine. A control group was also considered using distilled water. Each Ni‒Cr disk was immersed in the mouthwashes and distilled water in polypropylene test tubes, and then incubated at 37°C to simulate the oral temperature. After 45 days of incubation, the samples were tested for Ni ions using inductively coupled plasma mass spectroscopy. Data were analyzed using ANOVA. Results . In the Halita group subjects exhibited 2.04±0.65 reduction in OLS. OLS reduction in the chlorhexidine group was 1.95±0.74. Statistical analysis showed no significant difference between the two groups (P>0.05). Conclusion . As the results indicated, the amount of ion release was within the safe limits in the two experimental groups. However, it is recommended that prescribe Listerine mouthwash should not be prescribed for the patients with a history of Ni allergy.