Effects of the presence of probiotic bacteria in the aging medium on the surface roughness and chemical composition of two dental alloys

The Micromechanical Properties and Surface Roughness of Orthodontic Retainer Wires-An In Vitro Analysis

BACKGROUND

Despite the large variety of retainer wires available, no studies could be found comparing the micromechanical properties and surface roughness of different retainer wires. Such characteristics affect the survival of the fixed retainer in terms of both fracture resistance and resistance to debonding from the tooth. Therefore, the aim of the present study was to examine and compare those characteristics in popular retainer wires.

METHODS

six different popular orthodontic retainer wires were subjected to instrumental indentation based on the Oliver and Pharr method. The geometric surface structure was analysed using a non-contact profilometer.

RESULTS

stainless steel wires had a higher hardness and a higher elastic modulus compared to titanium wires and white gold chain. The titanium wire and the white gold chain showed much more roughness than other wires.

CONCLUSIONS

stainless steel wires are the most resistant, considering both the shape retention capacity and the ability to resist abrasive wear. The titanium wire showed the lowest hardness and, thus, the highest susceptibility to deformation. Bond-a-braid, Retainium and Orthoflex white gold are more resistant to fracture than other steel wires. Titanium wire and chain retainer wires have more roughness, which is a great advantage in terms of mechanical adhesion to composite materials.

Corrosion of Fixed Orthodontic Appliances: Causes, Concerns, and Mitigation Strategies

The orthodontic supply market is a prosperous billion-dollar industry, driven by an increasing demand for orthodontic appliances. The supremacy of metallic first-generation biomaterials is evident for manufacturing brackets, archwires, bands, and other components due to their well-recognized chemical inertness, spontaneous passivation, biocompatibility, and favorable mechanical properties combination. However, the oral cavity is the ultimate corrosion-promoting environment for any metallic material. In this work, the general picture of the intraoral degradation of fixed orthodontic appliances is first addressed, from the causes to the harmful effects and their oral clinical implications. Current mitigation strategies are also pointed out, including the alloys’ bulk composition adjustment combined with new and advanced manufacturing processes and/or their surface treatment or coating deposition. The versatile use of thin films and coatings stands out with different deposition technologies: Many in vivo and in vitro efforts have been devoted to oral aging, from monolithic to composite architectures and micro- to nano-scale materials, to meet the best and safest oral practice demands. Unfortunately, literature data suggest that even the existing commercially available protective coatings have drawbacks and are fallible. Further multidisciplinary research is still required to effectively mitigate the corrosion behavior of fixed orthodontic appliances.

Temporal dynamics of adhesion of oral bacteria to orthodontic appliances

Adhesion of the most common dental biofilm bacteria to alloys used in orthodontics in relation to surface characteristics was analyzed. Streptococcus mutans (S. mutans), Streptococcus oralis (S. oralis), Veillonella parvula (V. parvula), and Aggregatibacter actinomycetemcomitans (A. actynomicetemcomitans) were incubated for 4 h with nickel-titanium (NiTi) and stainless-steel (SS) wires. The surface roughness and free energy of the alloys, as well as the hydrophobicity of the alloys and bacteria, were assessed. NiTi had higher surface free energy and rougher (p<0.001) and more hydrophilic surfaces than SS (p<0.001). The hydrophobic properties of the bacteria decreased in the following order: V. parvula>S. oralis>S. mutans>A. actynomicetemcomitans. Bacterial adhesion generally increased over time, though this pattern was influenced by the type of alloy and the bacteria present (p<0.001). In a multiple linear regression, the principal predictor of adhesion was bacterial hydrophobicity (p<0.001), followed by time (p<0.001); alloy surface characteristics had a low influence.

Influence of probiotics on the periodontium, the oral microbiota and the immune response during orthodontic treatment in adolescent and adult patients (ProMB Trial): study protocol for a prospective, double-blind, controlled, randomized clinical trial

BACKGROUND

Orthodontic treatment with fixed appliances is often necessary to correct malocclusions in adolescence or adulthood. However, oral hygiene is complicated by appliances, and prior studies indicate that they may trigger oral inflammation and dysbiosis of the oral microbiota, especially during the first 3 months after insertion, and, thus, may present a risk for inflammatory oral diseases. In recent periodontal therapeutic studies, probiotics have been applied to improve clinical parameters and reduce local inflammation. However, limited knowledge exists concerning the effects of probiotics in orthodontics. Therefore, the aim of our study is to evaluate the impact of probiotics during orthodontic treatment.

METHODS

This study is a monocentric, randomized, double blind, controlled clinical study to investigate the effectiveness of daily adjuvant use of Limosilactobacillus reuteri (Prodentis®-lozenges, DSM 17938, ATCC PTA 5289) versus control lozenges during the first three months of orthodontic treatment with fixed appliances. Following power analysis, a total of 34 adolescent patients (age 12-17) and 34 adult patients (18 years and older) undergoing orthodontic treatment at the University Hospital Erlangen will be assigned into 2 parallel groups using a randomization plan for each age group. The primary outcome measure is the change of the gingival index after 4 weeks. Secondary outcomes include the probing pocket depth, the modified plaque index, the composition of the oral microbiota, the local cytokine expression and-only for adults-serum cytokine levels and the frequencies of cells of the innate and adaptive immune system in peripheral blood.

DISCUSSION

Preventive strategies in everyday orthodontic practice include oral hygiene instructions and regular dental cleaning. Innovative methods, like adjuvant use of oral probiotics, are missing. The aim of this study is to analyse, whether probiotics can improve clinical parameters, reduce inflammation and prevent dysbiosis of the oral microbiota during orthodontic treatment. If successful, this study will provide the basis for a new strategy of prophylaxis of oral dysbiosis-related diseases during treatment with fixed appliances.

TRIAL REGISTRATION

This trial is registered at ClinicalTrials.gov in two parts under the number NCT04598633 (Adolescents, registration date 10/22/2020), and NCT04606186 (Adults, registration date 10/28/2020).