The dynamics of the oral microbiome and oral health among patients receiving clear aligner orthodontic treatment

Comparative characterization of supragingival plaque microbiomes in malocclusion adult female patients undergoing orthodontic treatment with removable aligners or fixed appliances: a descriptive cross-sectional study

Objectives

This study aimed to explore the effects of removable aligners and fixed appliances on the supragingival bacterial communities in adult female patients undergoing orthodontic treatment.

Methods

Supragingival plaque samples from 48 female individuals underwent microbiome analysis (16S rRNA gene sequencing) using PacBio Sequel sequencing. The study included 13 adults without orthodontic treatment needs as the control group (Group C), and 35 patients with comparable initial orthodontic conditions who received treatment at a university clinic in Beijing, China. The treatment involved either traditional fixed brackets (Group B, n = 17) or Invisalign® aligners (Group AT, n = 18). Bioinformatics methods were used for data analysis.

Results

From the 48 plaque samples, a total of 334,961 valid reads were obtained, averaging 6,978 sequences per sample. The 16S rDNA sequences were classified into 25,727 amplicon sequence variants (ASVs). Significant variances in alpha and beta diversity among the groups were noted. Group B microbiome exhibited an increased presence of Gram-negative bacteria. At the phylum level, Actinobacteriota was significantly more prevalent in Group C samples, while Bacteroidota was enriched in Group B samples. Family-level relative abundance analysis showed a notable increase in Saccharibacteria (formerly TM7) and Prevotellaceae in Group B. Genus-level analysis revealed a significant rise in Lautropia in Group AT. Fixed orthodontic appliances were linked to oral microbiome changes, notably an enhanced relative abundance of anaerobes, including periodontal pathogens.

Conclusion

The observation points to the impact of orthodontic appliance on the oral microbial community, highlighting the difference between traditional braces (Group B) and clear aligners (Group AT)in terms of the predominance of anaerobic and gram negative bacteria. This emphasizes the importance of considering the microbiological effects when choosing orthodontic appliance and underscores the need for tailored oral hygiene practices for individuals undergoing these treatments. This research might provide insights that could assist in the development of innovative cleaning techniques and antibacterial materials.

Orthodontic Practitioners' Knowledge and Education Demand on Clear Aligner Therapy

OBJECTIVES

Clear aligner therapy (CAT) has been gaining popularity amongst the orthodontic community. No systematic course on CAT has been reported to date. The objectives of this study were to determine practitioners' knowledge and to offer insights for future tailored courses on CAT.

METHODS

An online questionnaire was distributed. The questionnaire comprised personal background information, predictability of tooth movement through CAT, and CAT knowledge that practitioners demanded to learn. Four senior expert orthodontists' answers to the predictability of tooth movement through CAT were averaged to be a standard reference. Descriptive statistics, 1-way analysis of variance (ANOVA), principal component analysis, Student t test, and multivariate logistics regression analysis were performed with significance set at P < .05.

RESULTS

In total, 190 practitioners participated in this study. As compared to the standard reference, participants overestimated the predictability of difficult-to-be-achived tooth movements (eg, molar mesialisation; P < .0001). Strategy of managing troubleshooting cases and extraction cases ranked the highest CAT knowledge that participants requested to learn. Practice type, number of completed CAT cases, number of undergoing CAT cases, years of practice, education background, and time of using CAT were the influencing factors of the questions regarding the predictability of tooth movement through CAT and CAT knowledge that were demanded to be learned.

CONCLUSIONS

The predictability of difficult-to-be-achieved tooth movement through CAT is often overestimated by practitioners with limited clinical experience. Tailored education on CAT, especially managing troubleshooting cases and extraction cases, should be designed for all practitioners.

Characteristics of oral microbiota and oral health in the patients treated with clear aligners: a prospective study

OBJECTIVES

In this prospective clinical study, the effect of clear aligners on periodontal health and oral hygiene was examined. As the same time, microbial changes of the aligner tray and subgingival microbiota community were investigated.

METHODS

The study recruited fifteen patients, and clinical parameters were recorded at three different time points: before the initiation of aligner treatment (T0), 1 month after treatment onset (T1), and 3 months after treatment onset (T3). Plaque samples were collected from the inner surface of aligners and subgingival sulcus at each of these time points. The microbial composition of the samples was analyzed using 16S rRNA gene sequencing, and changes were evaluated based on the abundance of amplicon sequence variants (ASVs).

RESULTS

Reduction in plaque index and improvement in periodontal health were observed. In aligner tray plaque samples, the relative abundance of Streptococcus increased significantly, as well as the richness and diversity of microbiota decreased substantially as the duration of treatment time. In subgingival plaque samples, alpha and beta diversity of microbiota did not change significantly.

CONCLUSIONS

During the clear aligner treatment, the patients' periodontium remained in a healthy condition, and clear aligner treatment had no significant impact on the composition of subgingival microbiota. The structure of the aligner tray microbiota altered significantly at both phylum and genus levels and attracted a unique and less diverse microbiota community.

CLABSINABSICAL RELEVANCE

Clear aligner treatment has no significant impact on periodontal health and subgingival microbiota composition of patients.

Does the composite attachment of clear aligners compromise the effectiveness of dental bleaching? An in vitro study

INTRODUCTION

This study aimed to evaluate the effectiveness of dental bleaching with hydrogen peroxide 35% on the surface below the attachments.

METHODS

Twenty-four blocks of bovine incisors were equally divided into 2 groups. The control group comprises the enamel surface free of attachments, whereas the attachment group comprises the enamel surface with attachment. Initial staining of samples was performed with black tea for 7 days; then, an attachment was made in the attachment group with Z250 resin and new staining for another 7 days in all samples. After staining, in-office bleaching was performed in both groups, and the attachments from the attachment group were removed. Color reading was performed with a spectrophotometer at all stages: initial (baseline), after 7 days of staining, after 14 days of staining, after immediate bleaching, and after 24 hours of bleaching. The color difference was calculated, and data analysis was performed using the t test for intergroup analysis.

RESULTS

The results showed effective bleaching in both groups; however, there was a statistically significant difference in color change between them 24 hours after bleaching.

CONCLUSION

It was concluded that the presence of attachment did not impair the action of the bleaching agent on the tooth surface.

Impact of Clear Aligners on Oral Health and Oral Microbiome During Orthodontic Treatment

The demand for clear aligners has risen over the past decade because they satisfy patients' desire for less noticeable and more comfortable orthodontic appliances. Because clear aligners are increasingly used in orthodontics, there is a big push to learn more about the physiologic and microbial changes that occur during treatment. The present work highlighted further links between clear aligners and changes in oral health and the oral microbiome and provided plaque control methods for clear aligner trays. Existing literature revealed that clear aligners have no significant influence on the structure of the oral microbiome during orthodontic therapy. Clear aligner treatment demonstrated promising results in terms of controlling plaque index, gingival health, and the prevalence of white spot lesions. Nevertheless, grooves, ridges, microcracks, and abrasions on the aligner surface would provide a prime environment for bacterial adherence and the development of plaque biofilms. A combination of mechanical and chemical methods seems to be a successful approach for removing plaque biofilm from aligners whilst also preventing pigment adsorption.

Preparation of Nanocomposites for Antibacterial Orthodontic Invisible Appliance Based on Piezoelectric Catalysis

Compared to fixed orthodontic appliances with brackets, thermoplastic invisible orthodontic aligners offer several advantages, such as high aesthetic performance, good comfort, and convenient oral health maintenance, and are widely used in orthodontic fields. However, prolonged use of thermoplastic invisible aligners may lead to demineralization and even caries in most patients' teeth, as they enclose the tooth surface for an extended period. To address this issue, we have created PETG composites that contain piezoelectric barium titanate nanoparticles (BaTiO₃NPs) to obtain antibacterial properties. First, we prepared piezoelectric composites by incorporating varying amounts of BaTiO₃NPs into PETG matrix material. The composites were then characterized using techniques such as SEM, XRD, and Raman spectroscopy, which confirmed the successful synthesis of the composites. We cultivated biofilms of Streptococcus mutans (S. mutans) on the surface of the nanocomposites under both polarized and unpolarized conditions. We then activated piezoelectric charges by subjecting the nanocomposites to 10 Hz cyclic mechanical vibration. The interactions between the biofilms and materials were evaluated by measuring the biofilm biomass. The addition of piezoelectric nanoparticles had a noticeable antibacterial effect on both the unpolarized and polarized conditions. Under polarized conditions, nanocomposites demonstrated a greater antibacterial effect than under unpolarized conditions. Additionally, as the concentration of BaTiO₃NPs increased, the antibacterial rate also increased, with the surface antibacterial rate reaching 67.39% (30 wt% BaTiO₃NPs). These findings have the potential for application in wearable, invisible appliances to improve clinical services and reduce the need for cleaning methods.

Microbiome and metabolome associated with white spot lesions in patients treated with clear aligners

White spot lesions (WSLs) have long been a noteworthy complication during orthodontic treatment. Recently, an increasing number of orthodontists have found that adolescents undergoing orthodontic treatment with clear aligners are at a higher risk of developing WSLs. The oral microbiota and metabolites are considered the etiologic and regulatory factors of WSLs, but the specific impact of clear aligners on the oral microbiota and metabolites is unknown. This study investigated the differences in the salivary microbiome and metabolome between adolescents with and without WSLs treated with clear aligners. Fifty-five adolescents (aged 11-18) with Invisalign appliances, 27 with and 28 without WSLs, were included. Saliva samples were analyzed using 16S rRNA gene sequencing and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS); the data were further integrated for Spearman correlation analysis. The relative abundances of 14 taxa, including Actinobacteria, Actinomycetales, Rothia, Micrococcaceae, Subdoligranulum, Capnocytophaga, Azospira, Olsenella, Lachnoanaerobaculum, and Abiotrophia, were significantly higher in the WSL group than in the control group. Metabolomic analysis identified 27 potential biomarkers, and most were amino acids, including proline and glycine. The metabolites were implicated in 6 metabolic pathways, including alanine, aspartate and glutamate metabolism; glycine, serine and threonine metabolism; and aminoacyl-tRNA biosynthesis. There was a correlation between the salivary microbial and metabolomic datasets, reflecting the impact of clear aligners on the metabolic activity of the oral flora. A concordant increase in the levels of Lachnoanaerobaculum, Rothia, Subdoligranulum and some amino acids had predictive value for WSL development. In summary, when adolescents undergo long-term clear aligner therapy with poor oral hygiene habits, clear aligners can disrupt the balance of the oral microecosystem and lead to oral microbiota dysbiosis, thereby increasing the risk of developing WSLs. Our findings might contribute to the understanding of the pathogenesis of WSLs and provide candidate biomarkers for the diagnosis and treatment of WSLs associated with clear aligners.

Isolation of Clinical Microbial Isolates during Orthodontic Aligner Therapy and Their Ability to Form Biofilm

The purpose of this study is to calculate microbiological composition of aligners after a day of wearing them. To date, the dental market for orthodontists offers many ways to correct bites. Aligners are transparent and almost invisible from the teeth. They are used for everyday wear to correct the incorrect position of the teeth, which was once considered the prerogative of braces. Scientists worldwide have repeatedly considered questions regarding the interaction between aligners and the oral cavity's microflora; however, the emphasis has mainly shifted toward species composition and antibiotic resistance. The various properties of these microorganisms, including biofilm formation, adhesion to various cells, and the ability to phagocytize, have not been studied so widely. In addition, these characteristics, as well as the microorganisms themselves, have properties that change over time, location, and in certain conditions. In this regard, the problem of biofilm formation in dental practice is always relevant. It requires constant monitoring since high contamination of orthodontic materials can reduce the effectiveness of local anti-inflammatory therapy and cause relapses in caries and inflammatory diseases of the oral cavity. Adhesive properties, one of the key factors in forming the architectonics of biofilms, provide the virulence factors of microorganisms and are characterized by an increase in optical density, determining the duration and retrospectivity of diagnostic studies. This paper focuses on the isolation of clinical microbial isolates during aligner therapy and their ability to form biofilms. In the future, we plan to use the obtained strains of microorganisms to create an effective and safe biofilm-destroying agent. We aimed to study morphometric and densitometric indicators of biofilms of microorganisms persisting on aligners.

Changing clear aligners every 10 days or 14 days ? A randomised controlled trial

Objectives:

To compare 10-day and 14-day change regimens to achieve orthodontic tooth movement (OTM) in patients wearing clear aligners and to determine their subsequent pain perception.

Material and methods:

A total of 175 clear aligner patients were assessed for eligibility. Seventy-two patients were randomly assigned to a 10-day group (N = 36) and a 14-day group (N = 36) and were instructed to change the appliances every 10 or 14 days, respectively. OTM efficacy and OTM variation between the actual and predicted OTM digital models measured by shell-to-shell deviation, as well as pain perception determined by a visual analog scale (VAS), were assessed at T0 (baseline, before the placement of the aligners), T1 (stage 8, after completion of aligners #8), and T2 (stage 16, after completion of aligners #16).

Results:

The 10-day and 14-day groups showed similar OTM efficacy at both T1 and T2 for all types of tooth movements (p > 0.09 for all) and similar OTM shell-to-shell deviation at T1 (p = 0.06) and T2 (p = 0.22). The two groups also had similar VAS scores of pain perception throughout the study (p > 0.05 for all).

Conclusion:

The 10-day and 14-day groups showed similar tooth movement and pain perception, suggesting that the clear aligners may be changed every 10 days without a significant compromise in the clinical efficacy of OTM and patient comfort.

Trial registration:

ChiCTR, ChiCTR-IOR-15007532. Registered 17 November 2015, https://www.chictr.org.cn/showproj.aspx?proj=12500

Aligner therapy in adolescents: first-year results on the impact of therapy on oral health-related quality of life and oral hygiene

OBJECTIVES

The aim of this multicenter clinical study was to examine the oral health-related quality of life and oral hygiene in adolescents before and during aligner therapy.

MATERIALS AND METHODS

Forty subjects (18 ♀, 22 ♂; mean age: 13.6 years) scheduled for aligner therapy (Invisalign® Teen) were given oral health-related quality of life questionnaires, Oral Health Impact Profile (OHIP-G14) and Psychosocial Impact of Dental Aesthetic Questionnaire (PIDAQ), to complete within their treatment (visit 1: 0 start of therapy; visit 2: 0 + 4 weeks; visit 3: 0 + 10 weeks; visit 4: 0 + 6 months; visit 5: 0 + 1 year). To assess oral hygiene, a questionnaire to take home was used, and plaque level was evaluated with the Quigley-Hein Plaque Index (TMQH) modified by Turesky et al. RESULTS: The OHIP-G14 mean score before aligner therapy was 3.3 ± 3.2, and 4.9 ± 5.4 after 1 year. The PIDAQ showed a positive psychological change in the well-being, as well as a more effective at-home oral hygiene regime. On average, the TMQH remained at a low level (grade 2 of 0-5). The initial insertion of the aligners caused the most significant changes in all parameters (except TMQH).

CONCLUSION

Oral health-related quality of life is only slightly affected during the first year of aligner therapy in adolescents. Oral hygiene at home is intensified and there is no increased dental plaque accumulation.

CLINICAL RELEVANCE

Dentofacial esthetics is a subset of the so-called Oral H-Related Quality of Life (OHRQoL) which should be considered more during orthodontic therapy.

The predictability of orthodontic tooth movements through clear aligner among first-premolar extraction patients: a multivariate analysis

BACKGROUND

The purpose was to determine the predictability of tooth movements through clear aligner among premolar extraction patients and to explore the effects of various factors on tooth movements.

METHODS

A total of 31 extraction patients (10 males and 20 females; age 14-44) receiving clear aligner treatment (Invisalign) were enrolled in this study. The actual post-treatment models and pre-treatment models were superimposed using the palatal area as a reference and registered with virtual post-treatment models. A paired t test was used to compare the differences between actual and designed tooth movements of maxillary first molars, canines, and central incisors. A multivariate linear mixed model was performed to examine the influence of variables on actual tooth movements.

RESULTS

Compared to the designed tooth movements, the following undesirable tooth movements occurred: mesial movement (2.2 mm), mesial tipping (5.4°), and intrusion (0.45 mm) of first molars; distal tipping (11.0°), lingual tipping (4.4°), and distal rotation of canines (4.9°); lingual tipping (10.6°) and extrusion (1.5 mm) of incisors. Age, crowding, mini-implant, overbite, and attachments have differential effects on actual tooth movements. Moreover, vertical rectangular attachments on canines are beneficial in achieving more predictable canine and incisor tooth movements over optimized attachments. Lingual tipping and extrusion of incisors were significantly influenced by the interaction effects between incisor power ridge and different canine attachments (p < 0.05).

CONCLUSIONS

Incisors, canines, and first molars are subject to unwanted tooth movements with clear aligners among premolar extraction patients. Age, crowding, mini-implant, overbite, and attachments influence actual tooth movements. Moreover, vertical rectangular attachments on canines are beneficial in achieving more predictable incisor tooth movements over optimized canine attachments.

Clinical efficacy of photodynamic therapy on halitosis: a systematic review and meta-analysis

Halitosis is a widespread health problem with complex factors, and therapeutic effects sometimes are unsatisfactory. Plenty of clinical trials have tried to prove the effectiveness of photodynamic therapy (PDT), but the results are indeterminate. This study aimed to evaluate the clinical efficacy of PDT on halitosis. We searched PubMed, Cochrane Library, Embase, Web of Science, and Scopus from inception to August 10, 2022, and only studies about the PDT on halitosis were included. The criteria for meta-analysis comprised randomized controlled trials (RCTs) comparing the treatment of PDT with tongue scraper (TS) immediately after the halitosis therapy and during a 7-, 14-, 30-, and 90-day follow-up. Eight eligible studies involving 345 patients were included in this study. It was shown that PDT (MD =  - 34.49, 95% CI [- 66.34, - 2.64], P = 0.03) or PDT + TS (MD =  - 67.72, 95% CI [- 101.17, - 34.28], P < 0.001) had better efficacy than TS on the H2S concentration reduction immediately after the halitosis therapy. No significant differences were observed in reducing the H2S among TS, PDT alone, and PDT + TS at the follow-up. Besides, no difference between PDT and TS was found in the reduction of CH3SCH3 and CH3SH. Based on the current evidence, PDT and PDT + TS demonstrate efficacy in the treatment of halitosis in the short term, and PDT was shown to be a beneficial and promising therapeutic method.

An In Vivo Study on the Development of Bacterial Microbiome on Clear Orthodontic Retainer

OBJECTIVES

The objective of this study was to see how the bacterial composition changes on clear orthodontic retainer over a 14-day period.

METHODS

Saliva and plaque samples collected from a clear retainer surface were obtained from five healthy volunteers receiving retainer treatment. Prior to clear retainer delivery, patients had not been wearing any other appliances. Patients were instructed to wear their clear retainer for the 14-day period, taking them off to eat and to clean them with a soft-bristle toothbrush. The bacterial composition was determined via Illumina MiSeq sequencing of the bacterial 16S rRNA. After bioinformatics processing using the QIIME pipeline, the intra- and intergroup biodiversity of the sample was analyzed.

RESULTS

The bacterial composition changed over a 14-day period in the saliva and on the clear retainer. When comparing the different phylum levels between saliva and clear retainer' microbiota, the Firmicutes were significantly increased 1.26-fold (p = 0.0194) and 1.34-fold (p = 0.0123) after 7 and 14 days of retainer treatment when compared to saliva, respectively. The Campylobacteriota were significantly decreased 1.80-fold (p = 0.05) in the clear retainer when compared to saliva at 7 days. At the genus level, several microbiota were significantly increased in relative abundance in the clear retainer after the 14-day period.

CONCLUSION

These findings reveal that the presence of a clear retainer in the mouth might lead to enamel changes or periodontal tissue destruction, especially after 14 days of use.

Microbiological Advances in Orthodontics: An Overview and Detailed Analysis of Temporary Anchorage Devices

Dental biofilm is the initiating factor of oral diseases, such as periodontitis and caries. Orthodontic treatment could alter the microbiome structure balance, and increase the risk of such diseases. Furthermore, fixed appliances can induce temporary changes in the microbiome community, and the changes that clear aligners bring are smaller by comparison. Temporary anchorage devices (TADs) are skeletal anchorages that are widely used in orthodontic treatment. Microorganisms affect the occurrence and development of inflammation surrounding TADs. At present, existing researches have verified the existence of plaque biofilm on the surface of TADs, but the formation of plaque biofilm and plaque composition under different stable conditions have not been fully understood. The development of high-throughput sequencing, molecular biology experiments, and metabonomics have provided new research ideas to solve this problem. They can become an effective means to explore the microbiome surrounding TADs.

Cleaning and Disinfection Protocols for Clear Orthodontic Aligners: A Systematic Review

(1) Background: Clear orthodontic aligners support the development of oral biofilms, which could lead to interferences with the oral microbiota already existing and the deterioration of oral health, with the development of dental caries, periodontal disease and even systemic infections. Therefore, preventive oral health care requires a cleaning and disinfection procedure for aligners. (2) Methods: A systematic review of the literature was conducted across four databases following the PRISMA guidelines up to May 2021, combining an electronic and a manual search. Prospective studies, including randomized controlled trials (RCTs), crossover studies (COSs) and controlled clinical trials (CCTs), published in the English language without time restrictions, evaluating the efficacy of cleaning and disinfection protocols for clear orthodontic aligners by comparing them with a placebo or a negative control, were included. The article selection, data extraction and risk of bias assessment were performed by two independent blinded review authors. In case of disagreement, a third author was solicited throughout the selection process. (3) Results: Among the 221 articles screened in the search process, 4 studies were included in the review, all designed as crossover studies (single arm without randomization with the same sequence of different cleaning and disinfection protocols for each participant). Different cleaning and disinfection methods were studied such as mechanical methods (brushing with toothpaste or vibration), chemical methods/pharmaceutical products (chlorhexidine antibacterial substance, anionic or cationic detergents or effervescent tablets) or combinations of both. (4) Conclusion: Although the determination of the most remarkable method of cleaning and disinfection was impossible because no direct comparison was conducted between all these methods, a multi-step protocol, including the combination of a mechanical and a chemical method, seems to be the most effective approach. Further research is needed to define the most preventive oral health care protocol. Registration: PROSPERO CRD 42021278498.

An in vitro biofilm model system to facilitate study of microbial communities of the human oral cavity

The human oral cavity is host to a diverse microbiota. Much of what is known about the behaviour of oral microbes derives from studies of individual or several cultivated species, situations which do not totally reflect the function of organisms within more complex microbiota or multispecies biofilms. The number of validated models that allow examination of the role that biofilms play during oral cavity colonization is also limited. The CDC biofilm reactor is a standard method that has been deployed to study interactions between members of human microbiotas allowing studies to be completed during an extended period under conditions where nutrient availability, and washout of waste products are controlled. The objective of this work was to develop a robust in vitro biofilm-model system from a pooled saliva inoculum to study the development, reproducibility and stability of the oral microbiota. By employing deep sequencing of the variable regions of the 16S rRNA gene, we found that the CDC biofilm reactor could be used to efficiently cultivate microbiota containing all six major phyla previously identified as the core saliva microbiota. After an acclimatisation period, communities in each reactor stabilised. Replicate reactors were predominately populated by a shared core microbiota; variation between replicate reactors was primarily driven by shifts in abundance of shared operational taxonomic units. We conclude that the CDC biofilm reactor can be used to cultivate communities that replicate key features of the human oral cavity and is a useful tool to facilitate studies of the dynamics of these communities.

Taxonomic Analysis of Oral Microbiome during Orthodontic Treatment

Background

Orthodontic appliances induce significant changes in the oral microbiome, but this shift in microbial composition has not been well established by the available evidence yet.

Objectives

To perform a systematic review of existing literature in order to assess the taxonomic microbial changes in orthodontic patients during Fixed Appliance Treatment (FAT) and Clear Aligner Treatment (CAT), using next-generation sequencing (NGS) technique of the bacterial 16S rRNA gene. Search Methods and Selection Criteria. The search for articles was carried out in PubMed, including articles published in English until May 2021. They included every human study report potentially relevant to the review. Data Collection and Analysis. After duplicate study selection and data extraction procedures according to the PICOS scheme, the methodological quality of the included papers was assessed by the Swedish Council on Technology Assessment in Health Care Criteria for Grading Assessed Studies (SBU) method.

Results

The initial search identified 393 articles, 74 of which were selected by title and abstract. After full-text reading, six articles were selected according to inclusion criteria. The evidence quality for all the studies was moderate.

Conclusions

Orthodontic treatment seems to transiently affect the composition of subgingival microbiome, although not salivary, maintaining a stable microbial diversity. Different results were found in the shift of microbiome between plaque and saliva, depending on the type of orthodontic treatment. This review should be interpreted with some caution because of the number, quality, and heterogeneity of the included studies.

Essential Attributes of Clear Aligner Therapy in terms of Appliance Configuration, Hygiene, and Pain Levels during the Pandemic: A Brief Review

Fixed orthodontic treatment has been compromised at many levels during the pandemic period, as clinics underwent a prolonged lockdown and patients could not be treated regularly. With the end of the pandemic nowhere in sight, may be it is time to put newer tools, such as clear aligner therapy, for better use. Fixed orthodontic appliances by nature are not always self-limiting, which, if left unmonitored over a long period may cause undesirable side effects, pain, and discomfort. The undesired tooth movements that may occur with arch wire-guided mechanics in addition to problems with cut wires or removed brackets may be minimized with the use of aligners. While the benefits of using aligners are for all to see, they do require extensive planning and careful evaluation of the progress. This article reviews the advantages of using aligners during the pandemic period and how it can be beneficial in helping orthodontists resume their practice.

Changes in the Microbiome of the Inner Surface of Clear Aligners After Different Usage Periods

Clear aligners are removable orthodontic appliances that cover the tooth surface. The microbial composition and pH of the inner surface of aligners directly affect the enamel health. In this study, eight subjects who used the same type of clear aligners were instructed to brush their teeth normally and to not clean their aligners until sampling. Saliva and the contents of the inner surface of the aligners (liquid and plaque) were collected at 0 h (T0), 4 h (T4), 8 h (T8), 12 h (T12), and 24 h (T24) after usage, and pH values and microbial compositions were measured. The microbial composition was analyzed with 16S rRNA gene sequencing, and changes were assessed based on operational taxonomic unit abundance. The pH, alpha diversity values, and abundance of specific microbes on the inner surface of the aligners gradually decreased from T0 to T24 (P < 0.05). An insignificant increase in microbial community beta diversity was observed from T0 to T24. Principal component analysis revealed that the microbial composition at T0 was different from at T12 and T24. The relative abundances of phylum Firmicutes (P < 0.01), orders Lactobacillales and Bacteroidales (P < 0.05), and genus Streptococcus and species Streptococcus infantis increased significantly, while those of genera Actinomyces and Rothia and species Rothia aeria decreased significantly at T24 (P < 0.05). These findings reveal that uncleaned aligners might lead to enamel damage, especially after continuous usage for 12 h. Thus, clear aligners should be cleaned after 12 h of usage or at least within 24 h of usage.

The impact of fixed orthodontic appliances on oral microbiome dynamics in Japanese patients

Fixed orthodontic appliances are common and effective tools to treat malocclusion. Adverse effects of these appliances, such as dental caries and periodontitis, may be associated with alteration of the microbiome. This study investigated the impact of these appliances on the dynamics of the oral microbiome. Seventy-one patients were selected. Supragingival plaque samples were collected before placement (T0) and six months after placement (T1). Saliva samples were collected at T0 and T1, and then when appliance removal (T2). Microbial DNA was analyzed by 16S rRNA meta-sequencing. The diversity analysis indicated dynamic changes in the structure of the oral microbiome. Taxonomic analysis at phylum level showed a significant increase in Bacteroidetes and Saccharibacteria (formally TM7) and decrease in Proteobacteria and Actinobacteria over time, in both plaque and saliva. Genus level analysis of relative abundance indicated a significant increase in anaerobic and facultative anaerobes in both plaque and saliva. Fixed orthodontic appliances induced measurable changes in the oral microbiome. This was characterized by an increase in relative abundance of obligate anaerobes, including periodontal pathogens. It can be concluded that this dysbiosis induced by fixed orthodontic appliances is likely to represent a transitional stage in the shift in microbiome from healthy to periodontitis.

Behaviour of Human Oral Epithelial Cells Grown on Invisalign® SmartTrack® Material

Invisalign aligners have been widely used to correct malocclusions, but their effect on oral cells is poorly known. Previous research evaluated the impact of aligners’ eluates on various cells, but the cell behavior in direct contact with aligners is not yet studied. In the present study, we seeded oral epithelial cells (cell line Ca9-22) directly on Invisalign SmartTrack material. This material is composed of polyurethane and co-polyester and exhibit better mechanical characteristics compared to the predecessor. Cell morphology and behavior were investigated by scanning electron microscopy and an optical cell moves analyzer. The effect of aligners on cell proliferation/viability was assessed by cell-counting kit (CCK)-8 and 3,4,5-dimethylthiazol-2-yl-2,5-diphenyl tetrazolium bromide (MTT) assay and live/dead staining. The expression of inflammatory markers and proteins involved in epithelial barrier function was measured by qPCR. Cells formed cluster-like structures on aligners. The proliferation/viability of cells growing on aligners was significantly lower (p < 0.05) compared to those growing on tissue culture plastic (TCP). Live/dead staining revealed a rare occurrence of dead cells on aligners. The gene expression level of all inflammatory markers in cells grown on aligners’ surfaces was significantly increased (p < 0.05) compared to cells grown on TCP after two days. Gene expression levels of the proteins involved in barrier function significantly increased (p < 0.05) on aligners’ surfaces after two and seven days of culture. Aligners’ material exhibits no cytotoxic effect on oral epithelial cells, but alters their behavior and the expression of proteins involved in the inflammatory response, and barrier function. The clinical relevance of these effects has still to be established.

An objective system for appraising clear aligner treatment difficulty: clear aligner treatment complexity assessment tool (CAT-CAT)

BACKGROUND

Recent years have witnessed a remarkable evolution of clear aligner technology and clear aligners are becoming more and more versatile in treating orthodontic patients. The aim of this study was to develop an objective evaluation system for assessing clear aligner treatment difficulty.

METHODS

A total of 120 eligible patients (100 patients for developing and testing the evaluation system and 20 patients for validating this system) were recruited in this retrospective cross-sectional study. Based on clinical data (dental models, radiographs and photographs), complexity levels of cases were evaluated by two experts and regarded as the gold standard. Difficulty scores were determined through an evaluation system encompassing three domains (dental model analysis, radiographic examinations and clinical examinations). The reliability of the evaluation system was examined through analyzing the agreement between complexity levels and difficulty scores. Moreover, multivariable linear regression test was used to examine the independent association of each variable (e.g. overbite and crowding) with the complexity level.

RESULTS

The results revealed that the assessment of treatment difficulty by this objective evaluation system substantially matched the gold standard (R² = 0.80). The multivariable regression test revealed that complexity level was significantly associated with difficulty score (p < 0.001), age (p = 0.015), tooth extraction (p < 0.001), treatment stage (p < 0.01) and the number of difficult tooth movement (p = 0.005). This objective evaluation system elaborated in this study was viable and reliable in appraising clear-aligner treatment difficulty in clinical practice.

CONCLUSIONS

We suggest orthodontists and general practitioners use this objective evaluation system (CAT-CAT) to appraise clear aligner treatment difficulty and to select appropriate clear aligner patients.