Biofilm formation on stainless steel and gold wires for bonded retainers in vitro and in vivo and their susceptibility to oral antimicrobials

Poly-Ether-Ether-Ketone versus dead-soft coaxial bonded retainers: a randomized clinical trial. Part 2: periodontal health and microbial biofilm assessment

BACKGROUND

Retainers have the potential to detrimentally impact periodontal health and contribute to tooth decay.

OBJECTIVES

To investigate periodontal health and bacterial biofilm related to Poly-Ether-Ether-Ketone (PEEK) fixed retainers as compared to Dead-soft coaxial fixed retainer (DSC).

TRIAL DESIGN

A two-arm parallel groups single-centre randomized clinical trial.

METHODS

The trial included patients whose orthodontic treatment was completed and required retainers. Participants were randomly assigned into two retainer groups: PEEK retainers, prepared by computer-aided design and manufacturing into 0.8 mm wire form, and DSC retainers. The objectives included assessing periodontal health through plaque accumulation index (PI), bleeding on probing (BOP), periodontal pocket depth (PPD), gingival index (GI), calculus index (CI), and alveolar bone height (ABH) assessment. Biofilm assessment involved bacteriological screening of aerobic, facultative anaerobic, mutans streptococci, and lactobacilli. The periodontal indices and microbiological screening as well as were assessed at the debonding stage (T0), 1-month (T1), 3-month (T3), and 6-month (T6) after the commencement of the trial, except for the ABH, which was recorded using periapical radiograph at T0 and T6.

BLINDING

Single blinding of participants in addition to the bacteriological specialist.

RESULTS

Initially, the trial enrolled 46 participants, aged between 12 and 28 years, and were randomly assigned to two groups, with 23 participants in each group. Subsequently, one participant withdrew from the trial, resulting in a total of 45 participants whose data were analysed. Assessment of the periodontal indices, excluding the CI (P = .480), revealed statistically but not clinically significant differences between groups after 6-month of retention (P = .016 of PI, P = .020 of BOP, P = .05 of PPD, and P = .01 of GI). There was slight plaque accumulation, normal PPD (approximately 1 mm), healthy to mild gingivitis with a GI of less than 1 and BOP was around 10%. Concerning the ABH, there was a noticeable reduction in its score after 6 months, particularly in the PEEK group, although the difference was not statistically significant (P = .102). Furthermore, the bacteriological viable count did not show any significant difference between the groups during the recall visits.

HARMS

There have been no reported negative consequences.

LIMITATIONS

Blinding the assessor of periodontal indices was not feasible due to the nature of the intervention. The trial follow-up duration was limited.

CONCLUSIONS

Both the PEEK and DSC retainers have comparable impacts on periodontal health and bacterial accumulation and composition during the retention period.

TRIAL REGISTRATION

NCT05557136.

Biofilm formation of Streptococcus mutans, Streptococcus sanguinis, Staphylococcus epidermidis, Staphylococcus aureus, Lactobacillus casei, and Candida Albicans on 5 thermoform and 3D printed orthodontic clear aligner and retainer materials at 3 time points: an in vitro study

INTRODUCTION

Orthodontic clear aligners and retainers have numerous advantages that is making them ever increasingly popular. However, they might, similar to any other oral appliance, contribute to biofilm formation and finally dental caries or white spot lesions or gingival inflammations. The literature on biofilm formation on orthodontic clear appliances is very scarce and limited to a few microorganisms and materials. Therefore, this experimental study evaluated the biofilm formation on 5 thermoformed and 3D printed CAD/CAM orthodontic retainers in 3 intervals.

METHODS

In this in vitro study, 345 specimens (270 test discs and 45 negative controls) were created from fabricated retainers. Retainers included a 3D printed CAD/CAM material (Detax) and four thermoformed retainers [Erkodent (polyethylene terephthalate glycol [PETG]); EasyVac (polyethylene); DB (polyester based on terephthalic acid); and Clear Tech]. They were all 1 mm thick, and all completely fabricated, i.e., heated or printed. The discs were placed in 96-well plates. Microorganisms were cultured on 270 discs for 24 h (90 discs), 72 h (90 other discs), and 5 days or 120 h (90 other discs). Biofilm formation of the strains and negative controls was measured using the microtiter plate assay by ELISA reading. The microbes' ability to produce biofilm was categorized based on the comparison of average optical density (OD) of tests versus a cut-off point OD (ODc) calculated as the average of the OD of corresponding negative controls plus 3× its standard deviation: non-biofilm former [OD ≤ ODc], weak biofilm former [ODc < OD ≤ (2 × ODc)], moderate biofilm former [(2 × ODc) < OD ≤ (4 × ODc)], and strong biofilm former [(4 × ODc) < OD]. These were also converted to ranked scores between zero (no biofilm) and 3. The difference between ODs with control ODs were calculated. These were analyzed using 3-way ANOVA, 2-way ANOVA, and Tukey tests (α = 0.05, α = 0.008).

RESULTS

The 3-way ANOVA showed that the overall difference among the ΔODs of 5 retainers (all microorganisms and all intervals combined, n = 270) was not significant (F = 1.860, P = 0.119). Nevertheless, the difference among 3 intervals (F = 31.607, P = 0.0000) and the difference among the 6 microorganisms (F = 24.044, P = 0.0000) were significant. According to the Tukey test, the differences between the 1st interval with either of the other two intervals was significant (both P values = 0.000). There were significant differences between Candida albicans with all other organisms (all 5 P values = 0.0000). All other pairwise comparisons were insignificant (all 10 P values ≥ 0.1). After taking the averages of the 3 intervals, the order of the biofilm generation for different materials were as follows: Detax (average score: 1.56), Easyvac (1.67), Erkodent (1.78), Clear Tech (1.83), BD (2.28).

CONCLUSIONS

As far as these 6 microorganisms are of concern, there might not be a significant overall difference among the clear retainer materials tested in this study. A significant overall increase was observed between the first and third days, which later did not significantly increase more until day 5. The Candida albicans biofilm was more intense than the tested 5 bacteria, which themselves showed rather similar growth patterns to each other.

The oral microbiota and periodontal health in orthodontic patients

The oral microbiota develops within the first 2 years of childhood and becomes distinct from the parents by 4 years-of-age. The oral microbiota plays an important role in the overall health/symbiosis of the individual. Deviations from the state of symbiosis leads to dysbiosis and an increased risk of pathogenicity. Deviations can occur not only from daily life activities but also from orthodontic interventions. Orthodontic appliances are formed from a variety of biomaterials. Once inserted, they serve as a breeding ground for microbial attachment, not only from new surface areas and crevices but also from material physicochemical interactions different than in the symbiotic state. Individuals undergoing orthodontic treatment show, compared with untreated people, qualitative and quantitative differences in activity within the oral microbiota, induced by increased retention of supra- and subgingival microbial plaque throughout the treatment period. These changes are at the root of the main undesirable effects, such as gingivitis, white spot lesions (WSL), and more severe caries lesions. Notably, the oral microbiota profile in the first weeks of orthodontic intervention might be a valuable indicator to predict and identify higher-risk individuals with respect to periodontal health and caries risk within an otherwise healthy population. Antimicrobial coatings have been used to dissuade microbes from adhering to the biomaterial; however, they disrupt the host microbiota, and several bacterial strains have become resistant. Smart biomaterials that can reduce the antimicrobial load preventing microbial adhesion to orthodontic appliances have shown promising results, but their complexity has kept many solutions from reaching the clinic. 3D printing technology provides opportunities for complex chemical syntheses to be performed uniformly, reducing the cost of producing smart biomaterials giving hope that they may reach the clinic in the near future. The purpose of this review is to emphasize the importance of the oral microbiota during orthodontic therapy and to use innovative technologies to better maintain its healthy balance during surgical procedures.

Comparison of efficacy of thermoplastic retainer with round and rectangular bonded lingual wire retainer in the mandible two years after orthodontic treatment: a randomised controlled trial

OBJECTIVE

To analyse three protocols in maintaining the stability of orthodontic therapy results and their effect on gingival health.

MATERIALS AND METHODS

Sixty-six subjects (pre-therapeutic age 11-18 years; 68% female) randomly allocated into three retention groups of equal size were analysed. The first group had a 0.673 × 0.268 mm (0.027 × 0.011 inches) rectangular braided steel retention wire bonded to the lingual surfaces of all mandibular teeth from canine to canine, and the second group had a 0.406 mm (0.016 inches) round twisted steel wire. The third group was the control, without wires, and only with vacuum-formed retainers. All three groups had vacuum-formed removable retainers in the maxilla. The frequency of wire detachment/breakage/loss of retainer, the occurrence of crowding of mandibular incisors, and changes in intercanine width and gingival health were monitored.

RESULTS

Incidence and severity of relapse differed between groups (p = 0.001 and 0.049) being most common in the removable retainer group (incidence 68.2%; severity 0.7 ± 1.0 mm), followed by the round wire group (36.4%; 0.5 ± 1.2 mm) and rectangular wire group (13.6%; 0.1 ± 0.1 mm). The intercanine width decreased more without a bonded retainer (incidence 68.2%; severity 0.5 ± 0.7 mm) and with the round wire more (45.5%; 0.5 ± 0.7 mm) than with the rectangular (27.3%; 0.1 ± 0.3 mm). The difference was significant for incidence (p = 0.025), but not severity. Detaching of the wires/breakage/loss of retainer was similar. There were no significant differences in the accumulation of biofilm, calculus and gingivitis between appliances.

CONCLUSION

A rectangular wire is the most effective in retention, and the impact of retention appliances on gingival health is similar.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT05121220. Registered 02 October 2021 - Retrospectively registered.

CLINICAL RELEVANCE

Studying guidelines for reducing relapse, proper use of materials and appliances, the behavior of retention wires according to their profile in the retention phase, and possibilities of maintaining oral health will contribute to improving the stability of orthodontic therapy results.

Evaluation of biofilm formation on different clear orthodontic retainer materials

Aim:

To assess the chemical composition and oral biofilm formation on different types of commercially available clear orthodontic retainer materials (CORM).

Materials and Methods:

Four types of CORM commercially available were used (Clear advantage series I (CAS1), Clear advantage series II (CAS2), Endure (ES), and CENTRI FORM-clear rigid material (CFCRM)). Circular samples (12 mm diameter) of each CORM were prepared for (n = 40). Unstimulated saliva from twenty volunteers was collected. Fourier Transformation Infrared Spectroscopy (FTIR) was used for the evaluation of the chemical composition of CORM. For the quantitative assessment of oral biofilm formation, samples of each CORM were incubated for twenty-four hours, and crystal violet assay (CVA) was utilized. The degree of absorbance was measured using a spectrophotometer at 570 nm. For qualitative evaluation of oral formation, the samples of each CORM were incubated for 24 hours, and viable biofilm cells stained by acridine orange were examined under a fluorescent microscope.

Results:

FTIR findings showed that CAS2 was made of polypropylene and ES is made of polyvinyl chloride, while others were made of co-polyester. CVA results confirmed that CAS2 showed the lowest biofilm formation, which differs significantly compared to CAS1, CFCRM, and ES. No significant difference in biofilm formation was detected between CAS1, CFCRM, and ES. Viable biofilm cells staining by acridine orange showed that CAS2 demonstrated smaller microcolonies of viable biofilm cells compared with CAS1, CFCRM, and ES, which confirmed the result obtained by CVA.

Conclusions:

CAS2 showed anti-microbial activities with a decrease the in vitro biofilm formation, which may be related to its chemical composition.

Streptococcus mutans adherence to conventional and self-ligating brackets: an in vitro study

INTRODUCTION

Although self-ligating brackets presumably provide better hygiene conditions, no consensus has been reached so far.

OBJECTIVE

Therefore, the objective of this study was to evaluate, in an in vitro experimental design, the adherence of Streptococcus mutans (SM) in self-ligating and conventional brackets of different manufacturers and ligature types.

METHODS

Four commercial brands of maxillary premolar metal brackets were tested (Abzil®; Morelli®; 3M Unitek®; and GAC®). Each one was subdivided into three groups, which varied according to the type of ligature and bracket model (metallic, elastic, and self-ligating), totalizing twelve groups, composed of six brackets each. Previously sterilized brackets were initially immersed in saliva for one hour, and subsequently washed and added in a bacterial suspension, maintained in aerobiosis for 72 hours. The adhered bacteria were then separated and quantified by colony forming units (CFU/mL) counting after 48 hours of growth. The groups were compared by Kruskal-Wallis and Dunn post-hoc tests (p< 0.05).

RESULTS

Regardless of the commercial brand, self-ligating brackets had significantly less CFU/mL. However, according to comparisons performed within each commercial brand, only Abzil® self-ligating brackets had significantly lower biofilm adhesion. Among all of the self-ligating models, GAC® brackets presented the highest bacterial adhesion rate.

CONCLUSIONS

Self-ligating brackets are likely to present lower rates of biofilm adhesion. Particularly, Abzil® and GAC® self-ligating brackets are less likely to accumulate biofilm. Although such results are derived from an in vitro study, practitioners might acknowledge findings concerning bacterial adhesion as one of the relevant features to be considered during bracket selection.

Biofilm composition and composite degradation during intra-oral wear

OBJECTIVES

The oral environment limits the longevity of composite-restorations due to degradation caused by chewing, salivary and biofilm-produced enzymes and acids. This study investigates degradation of two resin-composites in relation with biofilm composition in vitro and in vivo.

METHODS

Surface-chemical-composition of two Bis-GMA/TEGDMA composites was compared using X-ray-Photoelectron-Spectroscopy from which the number ester-linkages was derived. Composite-degradation was assessed through water contact angles, yielding surface-exposure of filler-particles. Degradation in vitro was achieved by composite immersion in a lipase solution. In order to evaluate in vivo degradation, composite samples were worn in palatal devices by 15 volunteers for 30-days periods in absence and presence of manually-brushing with water. PCR-DGGE analysis was applied to determine biofilm composition on the samples, while in addition to water contact angles, degradation of worn composites was assessed through surface-roughness and micro-hardness measurements.

RESULTS

In vitro degradation by lipase exposure was highest for the high ester-linkage composite and virtually absent for the low ester-linkage composite. Filler-particle surface-exposure, surface-roughness and micro-hardness of both resin-composites increased during intra-oral wear, but filler-particle surface-exposure was affected most. However, based on increased filler-particle surface-exposure, the high ester-linkage composite degraded most in volunteers harvesting composite biofilms comprising Streptococcus mutans, a known esterase and lactic acid producer. This occurred especially in absence of brushing.

SIGNIFICANCE

Degradation during intra-oral wear of a low ester-linkage composite was smaller than of a high ester-linkage composite, amongst possible other differences between both composites. S. mutans herewith is not only a cariogenic, but also a composite-degradative member of the oral microbiome.

Comparison of oral microbiota in orthodontic patients and healthy individuals

Orthodontic treatments often include dental displacement using a fixed retainer such as braces, which may result in the accumulation of plaque that provides a suitable environment for microorganisms to cause oral infection. So, this study was designed to investigate the microbial diversity among orthodontic patients and healthy individuals.

METHODS

Fifty individuals i.e. 30 orthodontic patients and 20 normal individuals were included in this study. Samples were collected during the midterm of orthodontic treatment (10-12 months). Saliva samples were collected and total DNA was isolated. Polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) with universal primers targeting the V3 region of 16s rRNA was used to study the bacterial diversity among different orthodontic and control groups. After DGGE profile analysis, the predominant product bands from the gel were excised, cloned, and sequenced to confirm the taxonomic identity followed by its quantification by using real-time PCR with gene-specific primers.

RESULTS

Both orthodontic treatment and control groups formed two distinct clustering profiles, but the Shannon-Weaver index (H') indicated greater microbial diversity in the orthodontic group (P = 0.08). Sequence analysis and real-time PCR revealed a greater number of Pseudomonas spp. in the orthodontic group, while there was no significant difference in Streptococcal spp.

CONCLUSION

This study suggested alterations in the oral microbiota following orthodontic treatment would provide diagnostic tools to identify prevalent microbes associated with oral infections that may prove useful for developing future therapies.

In vitro methods for the evaluation of antimicrobial surface designs

Bacterial adhesion and subsequent biofilm formation on biomedical implants and devices are a major cause of their failure. As systemic antibiotic treatment is often ineffective, there is an urgent need for antimicrobial biomaterials and coatings. The term "antimicrobial" can encompass different mechanisms of action (here termed "antimicrobial surface designs"), such as antimicrobial-releasing, contact-killing or non-adhesivity. Biomaterials equipped with antimicrobial surface designs based on different mechanisms of action require different in vitro evaluation methods. Available industrial standard evaluation tests do not address the specific mechanisms of different antimicrobial surface designs and have therefore been modified over the past years, adding to the myriad of methods available in the literature to evaluate antimicrobial surface designs. The aim of this review is to categorize fourteen presently available methods including industrial standard tests for the in vitro evaluation of antimicrobial surface designs according to their suitability with respect to their antimicrobial mechanism of action. There is no single method or industrial test that allows to distinguish antimicrobial designs according to all three mechanisms identified here. However, critical consideration of each method clearly relates the different methods to a specific mechanism of antimicrobial action. It is anticipated that use of the provided table with the fourteen methods will avoid the use of wrong methods for evaluating new antimicrobial designs and therewith facilitate translation of novel antimicrobial biomaterials and coatings to clinical use. The need for more and better updated industrial standard tests is emphasized.

STATEMENT OF SIGNIFICANCE

European COST-action TD1305, IPROMEDAI aims to provide better understanding of mechanisms of antimicrobial surface designs of biomaterial implants and devices. Current industrial evaluation standard tests do not sufficiently account for different, advanced antimicrobial surface designs, yet are urgently needed to obtain convincing in vitro data for approval of animal experiments and clinical trials. This review aims to provide an innovative and clear guide to choose appropriate evaluation methods for three distinctly different mechanisms of antimicrobial design: (1) antimicrobial-releasing, (2) contact-killing and (3) non-adhesivity. Use of antimicrobial evaluation methods and definition of industrial standard tests, tailored toward the antimicrobial mechanism of the design, as identified here, fulfill a missing link in the translation of novel antimicrobial surface designs to clinical use.

Oral Biofilm Sampling for Microbiome Analysis in Healthy Children

Oral biofilm and its molecular analysis provide a basis for investigating various dental research and clinical questions. Knowledge of biofilm composition leads to a better understanding of cariogenic and periopathogenic mechanisms. Microbial changes taking place in the oral cavity during childhood are of interest for several reasons. The evolution of the child oral microbiota and shifts in its composition need to be analyzed further to understand and possibly prevent the onset of disease. At the same time, advanced knowledge of the natural composition of oral biofilm is needed. Early stages of caries-free permanent dentition with healthy gums provide a widely unaffected subgingival habitat that can serve as an in situ baseline for studying features of oral health and disease. Analysis of children's oral biofilm during different stages in life is thus an important theme in the field. Modern molecular analysis methods can provide comprehensive information about the bacterial diversity of such biofilms. To enable microbiota data comparison, it is important to standardize each step in the procedure for molecular data generation. This procedure spans from clinical sampling, Next Generation Sequencing (NGS), bioinformatic data processing, to taxonomic interpretation. One of the most critical factors here is biofilm sampling. Sampling in children is even more challenging in particular due to limited space in subgingival areas. We thus focus on the use of paper points for subgingival sampling. This article provides a detailed protocol for oral biofilm sampling of the subgingival sulcus, the mucosa, and saliva in children.

Impact of Orthodontic Treatment on Periodontal Tissues: A Narrative Review of Multidisciplinary Literature

The aim of this review is to describe the most commonly observed changes in periodontium caused by orthodontic treatment in order to facilitate specialists' collaboration and communication. An electronic database search was carried out using PubMed abstract and citation database and bibliographic material was then used in order to find other appropriate sources. Soft and hard periodontal tissues changes during orthodontic treatment and maintenance of the patients are discussed in order to provide an exhaustive picture of the possible interactions between these two interwoven disciplines.

In vivo biofilm formation on stainless steel bonded retainers during different oral health-care regimens

Retention wires permanently bonded to the anterior teeth are used after orthodontic treatment to prevent the teeth from relapsing to pre-treatment positions. A disadvantage of bonded retainers is biofilm accumulation on the wires, which produces a higher incidence of gingival recession, increased pocket depth and bleeding on probing. This study compares in vivo biofilm formation on single-strand and multi-strand retention wires with different oral health-care regimens. Two-centimetre wires were placed in brackets that were bonded to the buccal side of the first molars and second premolars in the upper arches of 22 volunteers. Volunteers used a selected toothpaste with or without the additional use of a mouthrinse containing essential oils. Brushing was performed manually. Regimens were maintained for 1 week, after which the wires were removed and the oral biofilm was collected to quantify the number of organisms and their viability, determine the microbial composition and visualize the bacteria by electron microscopy. A 6-week washout period was employed between regimens. Biofilm formation was reduced on single-strand wires compared with multi-strand wires; bacteria were observed to adhere between the strands. The use of antibacterial toothpastes marginally reduced the amount of biofilm on both wire types, but significantly reduced the viability of the biofilm organisms. Additional use of the mouthrinse did not result in significant changes in biofilm amount or viability. However, major shifts in biofilm composition were induced by combining a stannous fluoride- or triclosan-containing toothpaste with the mouthrinse. These shifts can be tentatively attributed to small changes in bacterial cell surface hydrophobicity after the adsorption of the toothpaste components, which stimulate bacterial adhesion to the hydrophobic oil, as illustrated for a Streptococcus mutans strain.