Dutch dentists’ involvement in orthodontic retention: monitoring, opinions, competence and communication gaps

Abstract

Background/Objectives

To assess Dutch dentists’ experience, competence and opinions on various aspects of orthodontic retention with bonded retainers and identify any gaps that may exist in practice and communication.

Materials/Methods

A web-based questionnaire was sent to 1000 randomly selected general dentists, covering their (i) experience, competence and opinion in bonded retainer monitoring and maintenance, (ii) knowledge of unintentional active bonded retainers, (iii) responsibility for bonded retainers, and (iv) orthodontic practitioners’ communication.

Results

The response rate was 23.6% (n = 236). Orthodontic treatment was performed by 24% of dentists. Dentists were familiar with follow-up (98%), repairs (95%) and placement (77%) of bonded retainers. The more hours involved in treatment, the more competent they felt in repairing BRs (P = .025). However, over a quarter felt insufficiently competent in repairing (26%) and placement (33%) of bonded retainers. When patients requested their dentist to remove their bonded retainer, 89% informed them about possible consequences, and 41% referred them to their orthodontic practitioner. Awareness of torsional movements of anterior teeth due to unintentionally active bonded retainers was high (77%). Almost two thirds (64%) believed that dentists should check bonded retainers one year after placement. Respondents felt insufficiently informed by orthodontic practitioners regarding several aspects of the retention phase. One-third (34%) would appreciate additional training.

Limitations

The main limitations of this study are the low response rate, which could result in non-response bias, and the focus on bonded retainers only.

Conclusions/Implications

Dutch dentists are well informed about the possibility of torsional movements due to unintentionally active bonded retainers. Clear communication between orthodontic practitioners and dentists is essential for effective long-term follow-up and shared responsibility. Knowledge and skills regarding monitoring and maintenance of bonded retainers should be integrated into dental curricula and postgraduate courses.

Introduction

The goal of orthodontic treatment is not just to improve aesthetics, function, and occlusion, but also to ensure that treatment results remain stable [1]. However, teeth tend to migrate back to their initial position, a phenomenon known as relapse [2]. Post-pubertal growth and ageing also contribute to post-treatment changes, even in individuals who have never had orthodontic treatment [3, 4]. Given the unpredictable nature of these changes, we must assume that every patient is at risk of post-treatment changes [5].

Retention is essential to prevent these post-treatment changes. In 1988, Little suggested lifelong retention as the only way to maintain stability [6]. Current guidelines recommend to continue retention indefinitely [7]. Since 2006, the preference for lifelong retention has increased in the Netherlands, typically involving a combination of a bonded retainer (BR) and a removable retainer (RR) in the maxillary arch (54%), and a BR alone in the mandibular arch (83%) [8, 9]. For retention with RRs, vacuum-formed retainers (VFRs) are preferred over Hawley-type retainers (HRs) [10].

A significant disadvantage of bonded retainers (BRs) is their high failure rate, which ranges from 1%–53%. This variation is partly due to differences in how failures are recorded and, more importantly, the length of the observation period [11]. The primary issue with BRs—particularly flexible round spiral wire BRs—is the unintentional movement of teeth while the retainer remains attached [12]. The reported prevalence of this phenomenon varies from 1.1%–43% and may result from factors such as deformation during bonding or mastication, untwisting of the multi-stranded wire, or parafunctional activities. These unintentional tooth movements often require retreatment [13]. In severe cases, a tooth may migrate beyond the bony envelope, necessitating its removal as the only viable solution [14].

Lifelong retention requires long-term commitment from the patient, and lifelong retainer check-ups [10, 15]. Most orthodontists typically monitor retention 12–24 months post-treatment [9]. It is impossible for orthodontists to indefinitely supervise every patient with retainers [9, 16]. Consequently, it is crucial to ask the general dental practitioner (GDP) to take over these check-ups and repairs [10, 16, 17]. This procedure is endorsed by a clinical practice guideline (CPG) for orthodontic retention [18, 19]. Effective communication between orthodontists and GDPs, as well as proper training for GDPs in monitoring and management of retainers and their side-effects, are prerequisites for taking over this task.

Previous surveys among GDPs in several European countries have revealed reluctance to monitor retainers and a lack of communication from orthodontists. Moreover, about 60%–80% of the GDPs were unaware of unintentional side-effects of BRs [20–22]. Since the introduction of the CPG for orthodontic retention in the Netherlands in 2018, GDPs have received more structured guidance in the management of orthodontic retention. Furthermore, recent research on the unintentional effects of BRs may also have enhanced their knowledge [13]. Therefore, this study aims to assess Dutch dentists’ experience, competence, and opinions on various aspects of orthodontic retention with BRs, and identify any gaps that may exist in practice or communication regarding orthodontic retention.

Subjects and methods

Research design and ethical approval

This study was designed as a cross-sectional questionnaire-based survey among Dutch GDPs. One thousand general practitioners were randomly selected from the member database of the Royal Dutch Dental Association (Koninklijke Nederlandse Maatschappij tot bevordering der Tandheelkunde, KNMT). The sample consisted of general practitioners working in the Netherland and registered in the public register for Professions in Individual Health Care (Beroepen in de Individuele Gezondheidszorg-register, BIG-register).

The Medical Ethics Review Committee of the University Medical Center Groningen (METc UMCG) reviewed the research protocol, registered under UMCG M22.305032 and METc UMCG 2022/497 and concluded that this study is clinical research not involving human subjects as meant in the Medical Research Involving Human Subjects Act (in Dutch: Wet Medisch-Wetenschappelijk Onderzoek – WMO) and, therefore, WMO approval was not required.

Questionnaire

The web-based questionnaire was carried out in collaboration with the KNMT. The questionnaire was previously used in an study of Swiss GDPs’ and adjusted to include additional aspects to be addressed. In March 2022, a pre-pilot study was conducted, by staff members not involved in the study, to determine the reliability of the additional questions, and some questions were adjusted. There was no need to repeat the pilot study. The time required to complete the questionnaire was approximately 10 minutes. It was a prerequisite that the participants actively participated in patient treatment.

The questionnaire (Supplementary Material) consisted of five parts. Part A addressed background information about the individual GDP. Part B focused on the monitoring and management of BRs. Part C examined the competence felt by the GDPs regarding the repair and placement of BRs. Part D assessed the knowledge of GDPs regarding unintentional side effects of BRs. Part E addressed the responsibility for orthodontic retention, and the communication from orthodontic practitioners (i.e. orthodontists and GDPs treating patients orthodontically) with dentists. In November 2022 the questionnaire was send out electronically. A reminder was sent twice, after 1 month and after 2 months. Data was collected by an independent research institute (KBA Nijmegen, the Netherlands).

Statistical analysis

All statistical analyses were performed using the Statistical Package for Social Sciences (SPSS) (version 28, IBM, Armonk, NY, USA). Background information on the GDPs was described using descriptive statistics, such as percentages, numbers, means, and standard deviations. The Shapiro-Wilk test was applied to test for normality of continuous variables. The Chi-square test or Fisher’s Exact test was used to determine significant differences in distribution for crosstabs. The Mann-Whitney U test was used to determine significant differences in continuous variables between two independent groups, and the Kruskal-Wallis test was used for more than two independent groups. To determine correlation between two continuous variables the Spearman’s rank correlation coefficient was used, while for correlations between a continuous and an ordinal variable the Kendall rank correlation coefficient was used. The significance level was set at P = .05.

Results

Sample

The response rate was 24.4% (244 out of 1000 GDPs). Eight GDPs did not work clinically and were excluded, making the final sample size N = 236 and response rate 23.6%. Table 1 gives an overview of the characteristics of the participants. Male GDPs spent significantly more hours per week working clinically (mean 30.5 hrs, SD 7.3), than female GDPs (mean 27.4 hrs, SD 7.1) (Mann-Whitney U test, Z = −3.425, P < .001). A significant correlation was found between GDPs’ age and clinical hours per week (Pearson correlation coefficient, ρ = −0.20, P = .002); the older the GDP, the fewer clinical hours per week. Orthodontic treatment was performed by 24.3% (n = 53) of GDPs. These GDPs were significantly older (mean 50.5 yr, SD 12.0) than GDPs who did not do so (mean 46.5 yr, SD 12.7) (Mann-Whitney U test, Z = −2.015, P = .044).

Monitoring and management of bonded retainers

Almost all GDPs (98.2%, n = 221) assessed the structural integrity of the BRs during the regular dental check-up, typically using a mirror and dental probe (Fig. 1a and b). This task was also performed by dental assistants (22.7%, n = 51) and dental hygienists (20.4%, n = 46). More than half of the respondents (58.7%, n = 132) perceived this procedure as easy or very easy. A minority rated it as difficult or very difficult (4.9%, n = 11). The more hours the respondents were involved in patient treatment per week, the more competent they felt in detecting bond failures (Kendall rank correlation coefficient, τ_b = 0.135, P = .012). GDPs often gave advice on BR cleaning, mainly with interdental brushes and toothpicks (Fig. 1c and d).

Respondents were familiar with repairing and placing BRs, since 95.2% (n = 218) reported repairing them and 77.1% (n = 175) reported placing them (Supplementary Table 1). Of GDPs who placed and repaired BRs, 95% (n = 207) repaired and 89% (n = 154) placed BRs in patients who had been treated elsewhere. In addition, 63% (n = 109) reported placing BRs to prevent further anterior misalignment in patients who never had orthodontic treatment. Overall, dentists who repaired and placed BRs were older (mean 55.0 yr, SD 11.1, and mean 52.3 yr, SD 12.2, respectively) than those who did not (mean 47.4 yr, SD 12.6 and mean 46.5 yr, SD 12.5)(Mann-Whitney U test, Z = −1.969, P = .049 and Z = −2.904, P = .004, respectively).

If failures (bond failure or broken retainer) were detected during the regular dental check-up, patients were offered various recommendations for intervention (Supplementary Table 2). Especially if tooth displacement was involved, it was often advised to contact the orthodontic practitioner (77.5%, n = 172). About one third of the respondents (35.1%, n = 78) always recommended contacting the orthodontic practitioner regardless of tooth displacement or not. Respondents who treated orthodontic patients themselves (Chi-square test, χ² = 5.58, P = .018), GDPs who placed BRs (χ² = 10.43, P = .001), and male respondents (χ² = 9.90, P = .002), were significantly less likely to always refer their patient to an orthodontic practitioner in case of any problem with a BR.

Supplementary Table 3 clarifies which practitioners generally took care of patients in the clinic presenting with or reporting a failure of their BR. Almost 40% of BR failures was handled within the clinic (36.6% + 3.1% = 39.7%, n = 89). Nearly one third (30.4%, n = 68) of the GDPs left the choice where to have the BR repaired to the patient.

Dentists were at most once a month requested by patients to remove their BR (70.9%, n = 156). Most frequent dentists’ interventions and aspects important for the dentists to grant this request were ‘Inform patient about the possible consequences of BR removal’ (88.6%, n = 195) and ‘Refer to the orthodontic practitioner’ (40.9%, n = 92) (Supplementary Table 4).

Dentists’ opinions on the BR only bonded to the lower cuspids and the BR bonded to all lower incisor is displayed in Fig. 2. Their opinion was that the latter had a better retention capacity, accumulates more plaque, and causes more problems while removing calculus and during restorative work. The older GDPs were, the less satisfied they were with retainers only bonded to the lower cuspids (Kendall rank correlation coefficient, τ_b = −0.132, P = .020).

Dentists’ competence regarding repair and placement of bonded retainers

The degree of competence felt by GDPs when repairing or placing BRs varies from more than insufficient to more than sufficient (Table 2). The more hours dentists were involved in patient treatment per week, the more competent they felt in repairing BRs (Kendall rank correlation coefficient, τ_b = 0.125, P = .025). Also, GDPs who placed BRs themselves felt more competent in placing BRs (Chi-square test, χ² = 16.49, P < .001), than dentists who did not. On the other hand, GDPs who were older felt less competent in placing BRs (Kendall rank correlation coefficient, τ_b = −0.109, P = .046).

GDPs indicated the need for additional theoretical and practical education (57.4%, n = 120 and 39.4%, n = 82 respectively). Of these, 33.5% (n = 70) indicated to need both. GDPs who studied in Utrecht or abroad (Chi-square test, χ² = 13.10, P = .022) expressed a greater need for education, compared to GDPs who studied in Amsterdam, Nijmegen or Groningen. Also, GDPs who indicated the need for additional education were younger (mean 45.4 yr, SD 11.1) than those who did not (mean 49.3, SD 12.9)(Mann-Whitney U test, Z = −2.240, P = .025).

Unintentionally active bonded retainers

The greater part of GDPs was familiar with unintentionally active BRs, had observed it in a patient, and referred or would refer their patients to the orthodontic practitioner, 76.8% (n = 166), 73.1% (n = 158) and 83.8% (n = 181) respectively (Supplementary Table 5). More than half of them also informed the patient regarding the problem (55.1%, n = 119). GDPs treating patients orthodontically (Chi-square test, χ² = 40.80, P < .001), and male dentists (χ² = 6.27, P = .012) were less likely to refer their patients to an orthodontic practitioner. Dentists who always referred patients to an orthodontic practitioner in case of bond failures or broken BRs, were also more likely to refer for unintentional side effects (Chi-square test, χ² = 4.46, P = .035). They predominantly became aware of this phenomenon during their dentistry study (45.2%, n = 75), additional courses (45.2%, n = 75), and through scientific literature (30.7%, n = 51).

Responsibility and communication

Respondents’ opinion was that orthodontic practitioners and dentists are largely responsible for the retainer after insertion, 82.0% (n = 173) and 72.5% (n = 153) respectively. More than one third (37.9%, n = 80), thought that the orthodontic practitioner, dentist, and patient are jointly responsible for this (Table 3). Respondents felt that the orthodontic practitioner should check the retainer during the first year after insertion (59.2%, n = 125). Also, almost two-thirds of respondents believed that after the first year this task should be performed by the dentist (64.0%, n = 135).

GDPs appreciated to receive information from the orthodontic practitioner regarding the start and duration of the retention phase, retainer type, and by which practitioner the retainer is preferably monitored. The frequency with which dentists were informed about these topics does not correspond to their wishes (Table 4). Approximately half of the GDPs had some agreements regarding monitoring of BRs and retention follow-up with orthodontic practitioners to whom they referred their patients (60.7%, n = 128).

Discussion

This study aimed to obtain current data on Dutch GDPs experience, competence and opinions regarding orthodontic retention with BRs. The results highlight that most Dutch dentists check, repair or (re)place BRs, however 26% and 33%, respectively, felt not sufficiently trained in performing the tasks of repairing and placing BRs, and 34% wished continued education.

Monitoring and management of bonded retainers

Almost all Dutch GDPs assessed the structural integrity of BRs during regular dental check-ups and reported to repair them in case of bond failures. This finding is consistent with Swiss GDPs but contrasts with their British and French counterparts, who are less involved in BR assessment due to factors like lack of knowledge, financial constraints, and the belief that BR maintenance is the orthodontic practitioners’ responsibility [20–22]. In the Netherlands, GDPs are reimbursed for repairing BRs in patients under 18, which might explain their greater involvement in this aspect of care.

The assessment of BRs was also performed by dental assistants (22.7%) and dental hygienists (20.4%) which is in accordance with Dutch law. Almost one-third of GDPs allow patients to decide whether to have their BRs repaired in the clinic or by an external orthodontic practitioner, reflecting a shared decision-making approach that empowers patients in their healthcare choices.

Almost 63% of GDPs reported that they place BRs to prevent further anterior misalignment in patients who never had orthodontic treatment, although there is no sound scientific evidence to support this approach.

Dentists’ competence regarding repair and placement of bonded retainers

While most GDPs reported being familiar with checking and repairing BRs, a significant proportion felt inadequately competent in performing these tasks. Almost half of the dentists expressed interest in additional training on orthodontic retention, aligning with findings from studies on GDPs in the UK and France [20, 22, 23]. The demand for training highlights a gap in the undergraduate dental curriculum, where knowledge and skills related to BRs are insufficiently covered. This study suggests integrating these topics into dental education and offering postgraduate courses to improve competency in BR management.

Unintentionally active bonded retainers

The key issue with BRs is the phenomenon of ’unintentionally active retainers’, which was first described in 2007 [24]. The presence of an orthodontic retention wire, without any apparent detachment or fracture, causes unintentionally tooth movement. Early detection is crucial to prevent the need for retreatment. Severe cases require orthodontic retreatment and even periodontal surgery [25, 26]. If unnoticed, this phenomenon can lead to devastating complications such as complete avulsion of the apex and ultimately loss of teeth [13].

Our study found that nearly three-quarters of GDPs in the Netherlands were aware of unintentionally active retainers and would refer patients back to an orthodontic practitioner after identifying this problem. Only a small percentage was not familiar with this condition and had never seen it (6.5%), whereas another 16.7% was not familiar and had possibly seen it in a patient. This awareness level is higher than in Switzerland and France, where far fewer GDPs were familiar with this complication (respectively ± 40% and 19%) [21, 22]. The findings emphasize that all dental health practitioners should be aware of the possibility of unintentionally active retainers, and be able to identify them. This can prevent the worsening of unintentional tooth movements. Greater awareness of the phenomenon can be achieved by adapting dental curricula, scientific publications and providing courses in the field of orthodontic retention.

The exact cause of unintentionally active retainers remains unclear, but it may be related to factors like deflection of the wire during bonding, wire distortion during mastication, parafunctional activities lasting at least 6–8 hours per day, the use of wire material with a low torsional and bending stiffness, or untwisting of multi-stranded round wires, and the resulting tooth displacements often require retreatment [27–30]. Dutch and New Zealand orthodontists have expressed concern about the potential for certain round wire materials to contribute to this problem, leading some to change the type of wire used in BRs [9, 10].

To limit the risk of tooth movement caused by unintentionally active retainers, some orthodontists recommend dual retention, using both a BR and a RR [26, 31]. This approach could help prevent unwanted tooth movement, and provides backup in case of bond failures.

Responsibility and communication

A significant proportion of our respondents believed that the orthodontic practitioner should check the retainer during the first year after placement, and that after the first year this task should be performed by the dentist. Two-thirds of Dutch orthodontists check BRs 3–4 times for 1.5–2 years [9]. The combination of increased mobility of the teeth and the increased failure rate of BRs during the first months after debonding underlines the importance of BR check-ups during this period [11].

Since almost 100% of our respondents indicated to monitor and repair BRs in case of bond failure, it can be concluded that they feel responsible for retention with BRs, which was also confirmed by their opinion on this topic. They are not obliged to repair or replace BRs, but if they do not, they must refer the patient back to the orthodontic practitioner, who has the task to repair or replace BRs. To overcome the lack of a clear concept on how to properly organize the long-term follow-up of BRs, a better communication from orthodontic practitioners to GDPs is mandatory. Unfortunately, not all GDPs received communication about the termination of orthodontic treatment, and many reported being insufficiently informed regarding all aspects of the retention phase.

GDPs opinions and knowledge on various aspects of orthodontic retention with BRs are important issues since lifelong retention with BRs generated an increasing number of patients requiring retainer maintenance and monitoring [8, 9]. Recent publications in European countries revealed that GDPs’ opinion and knowledge on orthodontic retention with BRs vary, and a clear concept on how to properly organize the long-term follow-up of BRs was lacking [20–23]. This might be solved by capturing this topic in the update of the CPG for orthodontic retention.

In summary, Dutch GDPs are generally more willing to monitor, repair, and place BRs than their counterparts in Great Britain and Eastern France [20, 22]. This may be related to the fact that, in the Netherlands, there are no financial restrictions in this regard. However, many GDPs feel insufficiently competent in BR management and would appreciate additional training. Most Dutch GDPs (75%) were aware of unintentionally active BRs, while this percentage for Swiss GDPs was less than 40%, and in Eastern France only 18.6% [21, 22]. This study highlights the need for better communication between orthodontic practitioners and GDPs to ensure that patients receive appropriate long-term retention follow-up.

Conducting qualitative research through focus groups with both dentists and orthodontic practitioners will provide a better insight into the strengths and weaknesses of each professional group in managing orthodontic retention. This could enhance understanding and communication between dentists and orthodontic practitioners, which will ultimately only improve patient care. In addition, expanding this study to other European countries and including patient perspectives would provide valuable insights. This will provide a broader scientific basis for the CPG for orthodontic retention.

Limitations

Our final response rate was with 23.6% low, although, the KNMT confirmed that the respondents were representative for the total invited sample, and for all KNMT members. A web-based survey was chosen since this method is cost-effective, easy to carry out, and the data are captured directly in electronic format, making analysis straightforward [32]. This method is known to yield significantly lower response rates than postal surveys, possibly resulting in non-response bias [33]. There is, e.g. a risk that mainly GDPs participated who are highly interested in the subject or GDPs who have had bad experiences with bonded retainers. This type of bias can affect the validity of the results. However, a recent publication suggests a scant relationship between non-response bias and response rates [34]. This study concerned orthodontic retention in general but was focused on bonded retainers. How dentists handle removable retainers remains unclear.

Conclusions

• - Dutch dentists are well informed about the possibility of torsional movements due to unintentionally active bonded retainers, however the goal should be that all dental professionals worldwide are familiar with this phenomenon.

• - There is a growing need for continuing education into knowledge and skills regarding monitoring and maintenance of bonded retainers. This should also be integrated in the undergraduate dental curriculum.

• - Clear communication between orthodontic practitioners and dentists about the retainer type, duration of retention, and monitoring is essential for effective long-term follow-up and shared responsibility.

Acknowledgements

We gratefully acknowledge the intellectual and financial support and assistance with the distribution of the questionnaire and data collection by the KNMT. Our special thanks go to Prof. J.J.M. Bruers and Dr B.A.F.M. van Dam from the Research & Information provision Department of the KNMT, for their assistance in the adjustment of the questionnaire. The authors also wish to thank all dentists who participated in the survey.

Author contributions

Marissa Schreuder (Conceptualization [equal], Data curation [equal], Formal analysis [equal], Methodology [equal], Writing—original draft [equal]), Jens Padmos (Conceptualization [equal], Data curation [equal], Formal analysis [equal], Methodology [equal], Visualization [equal], Writing—original draft [equal]), Anne-Marie Renkema (Conceptualization [equal], Methodology [equal], Supervision [lead], Writing—review & editing [equal]), and Anne Marie Kujpers-Jagtman (Conceptualization [supporting], Writing—review & editing [equal])

Conflict of interest

The authors do not have any conflicts of interest to declare.

Funding

The distribution of the questionnaire and data collection was funded by the KNMT.

Data Availability

The supplementary materials and survey (in Dutch) are available online. The data underlying this article will be shared on reasonable request to the corresponding author.

References