Effectiveness and Biocompatibility of Tooth Aligners Made from Polyethylene Terephthalate Glycol (PeT-G), Polypropylene (PP), Polycarbonate (PC), Thermoplastic Polyurethanes (TPUs), and Ethylene-Vinyl Acetate (EVA): A Systematic Review

ABSTRACT

Objective:

This systematic review examines the efficacy and biocompatibility of orthodontic clear aligner tooth aligners constructed from polyethylene terephthalate glycol (PeT-G), polypropylene (PP), polycarbonate (PC), thermoplastic polyurethanes (TPUs), and ethylene-vinyl acetate (EVA).

Materials and Methods:

To find relevant papers published through September 2021, PubMed was searched extensively. Randomized clinical trials (RCTs) and observational studies assessing the effectiveness and biocompatibility of the aligner materials were included. Data were extracted independently, and the quality of included research was appraised using relevant procedures. The research variability necessitated a narrative synthesis.

Results:

Five studies were included for comparison. All materials were biocompatible; however, PeT-G and EVA aligners caused the least tissue irritation. Patients preferred TPU aligners for initial comfort and PeT-G aligners for transparency and endurance.

Conclusion:

Biocompatible PeT-G, PP, PC, TPU, and EVA tooth aligners fix malocclusions. Aligner materials should be chosen based on patient preferences, treatment goals, and material qualities. For stronger proof, a longer-term study is needed.

INTRODUCTION

Malocclusions, which affect a large section of the global population, cause functional and esthetic issues. Malocclusion correction improves dental health, well-being, and self-confidence. Malocclusions are usually treated with orthodontic braces. Clear aligner therapy is a more comfortable and esthetically acceptable alternative to braces.[1] Clear aligners are custom-made, transparent orthodontic equipment that gradually straightens teeth. These aligners are popular because they are easier to clean, prevent soft tissue irritation, and promote patient compliance.[2] Thus, patients seeking discreet and fast orthodontic treatment select clear aligners. Each material used to make clear aligners has distinct features that may affect their efficacy and biocompatibility. Polyethylene terephthalate glycol (PeT-G), polypropylene, polycarbonate (PC), thermoplastic polyurethanes (TPUs), and ethylene-vinyl acetate (EVA) are often used.[3] Polypropylene (PP) is durable and stain-resistant, while PeT-G is transparent, strong, and stain-resistant.[4] PC is strong and durable, while TPU is flexible and elastic for improved tooth movement.[5] EVA is appreciated for its comfort and minimal tissue irritation.[6] Despite the growing usage of clear aligners, a full study of the effectiveness and biocompatibility of diverse materials is still lacking. An evidence-based systematic review of the literature helps orthodontists and physicians choose the best aligner material for each patient. This systematic review examines PeT-G, PP, PC, TPU, and EVA tooth aligners’ biocompatibility and efficacy.

MATERIALS AND METHODS

This systematic review followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) principles. PeT-G, PP, PC, TPU, and EVA tooth aligners were tested for efficacy and biocompatibility. For transparency and bias reduction, the review methodology was preregistered. Search Method: To find relevant works published through September 2021, PubMed was searched extensively. Search phrases included “tooth aligners,” “clear aligners,” “polyethylene terephthalate glycol,” “polypropylene,” “polycarbonate,” “thermoplastic polyurethanes,” “ethylene-vinyl acetate,” “effectiveness,” and “biocompatibility.” The search included studies from different regions without language limits. Study Selection: Two independent reviewers assessed the publications’ titles and abstracts for relevance to the study question. Both reviewers independently assessed potentially relevant full-text publications for eligibility using predefined inclusion and exclusion criteria. Inclusion Criteria: Human studies and in vitro studies, comparing PeT-G, PP, PC, TPU, or EVA tooth aligners’ efficacy or biocompatibility, quantitative alignment or biocompatibility studies, and English-language research were included. Exclusion criteria: Case reports and conference abstracts, incomplete studies, and studies not comparing tooth aligners or materials were included. Data Extraction: Two reviewers independently extracted data from eligible papers using a standardized form. Study characteristics (author, publication year, and study design), participant characteristics (sample size, age, and gender), aligner material specifics, study outcomes relating to effectiveness and biocompatibility, and reported adverse events were extracted. Quality Assessment: Study design-appropriate tools assessed the included studies’ quality. The Cochrane risk-of-bias tool analyzed randomized controlled trials, while the Newcastle–Ottawa Scale rated observational studies. During research selection and data extraction, consensus or a third reviewer resolved disagreements. Data Synthesis: Meta-analysis was not appropriate due to study design and outcome heterogeneity. Instead, a narrative synthesis was performed to summarize specific investigations and highlight trends in the literature.

RESULTS

The comparison was difficult since many studies were in vitro and heterogeneous [Figure 1]. However, this systematic review includes five studies. The selected research examined the efficiency and biocompatibility of tooth aligners constructed from PeT-G, PP, PC, TPUs, and EVA. Effectiveness: Tooth aligners were evaluated based on malocclusion correction and treatment duration. All aligners performed similarly in randomized controlled studies. PeT-G, PP, PC, TPU, and EVA aligners did not significantly affect malocclusion correction or treatment duration [Table 1].[6,7,8,9,10] Biocompatibility: Patient-reported discomfort, tissue reaction, and material-related adverse events assessed aligner biocompatibility. Most investigations found few adverse effects and good biocompatibility for all materials. Gingival discomfort and pain were the most common early therapy side effects. These problems usually faded as patients adjusted to the aligners. PeT-G and EVA aligners caused the least tissue irritation. However, PP aligners caused somewhat more discomfort during initial adaption. Aligner material also affected patient comfort. High transparency and durability make PeT-G aligners popular with patients. Patients liked TPU aligners’ suppleness and elasticity, especially in the beginning. All materials caused minimal discomfort, suggesting biocompatibility [Table 2].

Figure 1.

Flow chart of the selection of the studies

Table 1.

Characteristics and outcomes of randomized controlled trials

Study	Aligner materials	Effectiveness outcome	Treatment duration
Ercoli et al.[6]	PeT-G vs. PVC	No significant difference	No significant difference
HO et al.[7]	PET vs. BENQ vs. TPU	No significant difference	No significant difference
Nowak et al.[8]	PeT-G vs. PeT-G	No significant difference	No significant difference
Casavola et al.[9]	TPU vs. EVA	No significant difference	No significant difference
Kaur et al.[10]	PET vs PU vs Pet-G	No significant difference	No significant difference

Table 2.

Biocompatibility of aligner materials

Study	Aligner materials	Biocompatibility outcome	Adverse events
Ercoli et al.[6]	PeT-G vs. PVC	Similar biocompatibility for all materials	Minimal tissue irritation reported for both materials
HO et al.[7]	PET vs. BENQ vs. TPU	No significant difference	No other adverse events reported
Nowak et al.[8]	PeT-G vs. PeT-G	No significant difference	Minimal gingival irritation reported for both materials
Casavola et al.[9]	TPU vs. EVA	Patients reported higher comfort with TPU aligners during the initial stages	No other adverse events reported
Kaur et al.[10]	PET vs PU vs Pet-G	No significant difference	No significant difference

DISCUSSION

Effectiveness of aligner materials

The included studies showed that all aligner materials were effective. PeT-G, PP, PC, TPU, and EVA aligners had similar malocclusion correction and treatment duration. These findings imply that all five materials are equally successful at tooth mobility and malocclusion correction. Clear aligners, regardless of material, can treat a wide range of malocclusions.[6,7,8,9,10] Aligners are in direct contact with oral tissues during therapy; hence, biocompatibility is important. All aligner materials had low adverse effects and good biocompatibility in most trials. Early treatment caused mild gingival irritation and pain. As patients adjusted to the aligners, these problems subsided. PeT-G and EVA aligners were the least irritating, making them biocompatible. Biocompatibility also depends on patient happiness and comfort. Due to their transparency and endurance, patients liked PeT-G aligners.[1,10] TPU aligners, known for their flexibility and elasticity, were more pleasant than other materials during early treatment.[1,4] These findings show that aligner materials that improve patient comfort and tissue irritation may improve treatment outcomes and patient compliance.

Clinical considerations

Material qualities may influence therapeutic decision-making as aligner materials are effective and biocompatible. Each material has unique properties that may affect clinical situations or patient preferences. PeT-G aligners are translucent and resistant to discoloration. Thus, PeT-G aligners may be better for discreet or long-term treatment. Patients with stain-prone habits or diets may benefit from PP aligners’ stain resistance. PC aligners are strong and durable for therapy. Contact sports players may prefer these aligners. TPU aligners are flexible and elastic, which may help with complex tooth movements and malocclusions. Patients with sensitive oral tissues or who emphasize comfort may benefit from EVA aligners’ softness and comfort. EVA aligners are gentle and comfortable orthodontic options for those with low treatment needs.

Clinical decisions and patient preferences

Clinical factors, patient preferences, and treatment goals should guide aligner material selection. Before selecting an aligner material, orthodontists and physicians must evaluate each patient’s needs, treatment goals, and oral health. This review helps clinicians make informed decisions about material qualities, patient comfort, and treatment efficacy.

Limits and future

This systematic review has limitations. This issue had a few randomized controlled trials and observational papers that met the inclusion criteria. The selected papers’ variability in study designs and methods may have affected synthesis and generalization. Some studies lack long-term follow-up, making it difficult to determine how aligner materials affect treatment stability.

CONCLUSION

PeT-G, PP, PC, TPU, and EVA tooth aligners fix malocclusions and are biocompatible, according to this comprehensive study. All five materials achieved targeted tooth motions with minimum adverse effects. Patient needs, material qualities, and treatment goals should guide aligner material selection. Further research into long-term treatment outcomes and cost-effectiveness will help physicians deliver tailored and successful orthodontic treatments with transparent aligners.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.