Orthodontist and periodontist’s knowledge, attitudes and aspects of clinical practice, regarding fixed lower orthodontic retainers

ABSTRACT Objective: This study aimed to assess the knowledge, attitudes, and aspects of the clinical practice of orthodontists and periodontists, regarding lower fixed orthodontic retainers. Methods: The orthodontists (n=502) and periodontists (n=269) who participated in this cross-sectional observational study received, via e-mail, questions related to the type of lower fixed retainer, dental biofilm accumulation, oral hygiene, and potential periodontal changes. The data were subjected to chi-square and Fisher’s exact tests, at 5% significance level. Results: Both orthodontists (72.3%) and periodontists (58.7%) reported that hygienic retainers accumulate more dental biofilm (p< 0.05), and 64.1% of orthodontists and 58.7% of periodontists considered that modified retainers may lead to periodontal changes (p< 0.05). There was no significant difference between the dental specialties, regarding the type of lower fixed retainer considered the easiest for the patient to perform hygiene (p> 0.05), whereas 48.6% of professionals chose the modified type. Conclusion: The modified retainer accumulates a greater amount of dental biofilm and, in the perception of orthodontists and periodontists, it may cause periodontal changes.


INTRODUCTION
The use of retainers is desired at the end of orthodontic treatment, to prevent relapse of dental movements. [1][2][3][4][5] Orthodontists are more likely to indicate fixed retainers adapted to the lower arch, because of tooth instability in the region, which requires longer stabilization periods. 1,2,6-10 Fixed retainers are more aesthetic, do not depend on patient cooperation, 6,8,11,12 and may be individualized for the diagnosis and treatment performed. 2,13,14 In this context, the 3x3 fixed bar produced with straight wire bonded to the contralateral canines, 1,12,14 the twisted wire bonded to all lower anterior teeth, 1,9,12,15,16,17 and the modified fixed retainer 1,12,14,16 are the mostly used.
Although acknowledging the benefits of using retainers in orthodontics, studies affirm that dental biofilm accumulation increases with the use of all types of fixed retainers, requiring constant periodontal health assessments to prevent potential periodontal changes. 10,13,17,20 Clinical studies analyzing periodontal parameters after using different types of lower anterior fixed orthodontic retainers have highlighted the difference in biofilm retention, and the risk of developing periodontal changes in these patients. 14,[16][17][18] However, the cost-benefit ratio of the clinical use of different Costa RSM, Vedovello SAS, Furletti-Góes VF, Custodio W, Venezian GC -Orthodontist and periodontist's knowledge, attitudes and aspects of clinical practice, regarding fixed lower orthodontic retainers 5 types of orthodontic retainers has not been defined yet, and there are no studies comparing the advantages and disadvantages of each type of retainer.
Seeking to highlight the existence of cost-benefit ratio differences among the lower fixed retainers mostly used today, and to contribute to orthodontist selection of the retainer type, this study aimed to assess the knowledge, attitudes, and aspects of the clinical practice of orthodontists and periodontists, regarding lower fixed orthodontic retainers.
This was a national cross-sectional observational study performed with orthodontists and periodontists. A structured questionnaire was created to assess the knowledge, attitudes, and clinical practices of dentists. Initially, the questionnaire was sent via e-mail to 2,553 dentists specialized in orthodontics (n = 1,565) or periodontics (n = 988). The collection ended 60 days after the initial e-mail was sent, and the data were stored in the Google Forms digital platform. The instrument consisted of a drawing, a brief description of the lower fixed retainers - 3x3 bar with straight wire (Fig 1), 3x3 bar with twisted wire (Fig 2), and modified 3x3 bar (Fig 3) -, and nine questions related to knowledge, attitudes, and clinical practice on using retainers (Table 1).

RESULTS
The final sample included 771 specialists, including 502 orthodontists and 269 periodontists. Table 2 presents the association of knowledge, attitudes, and clinical practice of orthodontists and periodontists, regarding the use of lower fixed orthodontic retainers. It was verified that the mostly used retainer, for both specialties, was the straight wire type (p < 0.05). The retainer that dentists believe accumulate the greatest amount of dental biofilm is the modified one, con-  Costa RSM, Vedovello SAS, Furletti-Góes VF, Custodio W, Venezian GC -Orthodontist and periodontist's knowledge, attitudes and aspects of clinical practice, regarding fixed lower orthodontic retainers 11 practice of both type of professionals. Thus, this study chose to include all orthodontists and periodontists, aiming at a more extensive population sample.
The findings of the present study showed that most orthodontists and periodontists consider that the modified retainer accumulates a greater amount of dental biofilm.
According to the professionals, the accumulation may be related to wire curvature in the cervical third, and to the use of a greater amount of orthodontic wire, as reported in previous studies. 14,16 The professionals also considered the modified retainer as the type that causes more periodontal damages, presenting higher difficulty to perform oral hygiene, especially because it is bonded to all dental elements, corroborating clinical studies that identified greater biofilm accumulation in this type of retainer. 17,18 However, the literature has reported that, because such retainer has free interproximal areas, it is easier for the patient to perform oral hygiene, especially for using dental floss. 17,20,21 Orthodontists and periodontists reported the 3x3 fixed retainer with straight wire as the mostly used type. This choice may be related to the ease of production and for considering this retainer to cause less periodontal damage, which may influence the preference of periodontists for it. The preference of orthodontists for this type of retainer had already been reported in previous studies. 1,12 It is also worth noting that the use of orthodontic retainer, in the opinion of orthodontists (64.0%) and periodontists (82.0%), may cause periodontal damages. However, retainers are indicated because of the action of periodontal ligament fibers, which tend to move the tooth to its original position, before orthodontic treatment, and induce relapse after removing the orthodontic appliance. 22 It was also verified that most ortho- In order to prevent periodontal changes, most periodontists recommend performing prophylaxis and scaling up to three months after installing the retainer, but orthodontists believe that the time most indicated is between three and six months.
Considering the potential for bacterial colonization in the dental biofilm, each patient should be assessed individually to determine the time to perform prophylaxis and scaling.
Costa RSM, Vedovello SAS, Furletti-Góes VF, Custodio W, Venezian GC -Orthodontist and periodontist's knowledge, attitudes and aspects of clinical practice, regarding fixed lower orthodontic retainers 13 Finally, it is important to emphasize that the choice of retainer affects biofilm accumulation and the hygiene challenges of the patient, which may even lead to periodontal changes such as clinical attachment loss and increased drilling depth.
There is no ideal type of retainer. The results of this study showed that professionals, both orthodontists and periodontists, are aware of the importance of the use of retainers and its limitations. It is also highlighted that professionals are in charge of assessing individually their cost-benefit, considering oral hygiene and the time of use for each patient, as well as determining the need for professional prophylaxis and scaling, which may vary among patients.
Considering that this study has only assessed the opinion of professionals on fixed orthodontic retainers, further studies are suggested to assess means of performing oral hygiene by patients using orthodontic retainers and the level of toothbrushing of such patients.

CONCLUSION
Orthodontists and periodontists agree that the several types of retainers are different regarding biofilm accumulation, considering that the 3x3 bar with straight wire accumulates less biofilm, followed by the twisted wire retainer, which are easier for performing professional hygiene.