Influence of reminder therapy for controlling bacterial plaque in patients undergoing orthodontic treatment: A systematic review and meta-analysis

The harmonious alignment of teeth makes it easier to perform proper hygiene and has been claimed to decrease the incidence of caries and periodontal diseases.¹  In developing efficient strategies to correct tooth position, the specialist should not take for granted the importance of an effective oral hygiene protocol.²  When facing hygiene challenges, many orthodontic patients tend to exhibit poor oral health and plaque accumulation.² 

Plaque increase is a troubling side-effect of fixed orthodontic therapy and deserves special attention.³  A performance drop in hygiene has been reported after the start of treatment, and a slight improvement is only seen after the 20th week, which causes the patient to present worse oral health indices at the end of treatment.²  Moreover, it has been reported that during the middle part of orthodontic treatment, patient enthusiasm and motivation tend to decrease progressively, often leading to worsening oral hygiene.¹ 

Aiming to decrease the incidence of bacterial plaque during orthodontic treatment, various measures have been suggested such as reminder therapy.^4–7  Mobile phone (smartphone) technology, with its numerous resources and applications for short message service (SMS), is widely available.⁸  Many patients, especially adolescents and preadolescents, are avid users of smartphone technology and prefer receiving text messages for communication or reminders.⁵  It is known that around 75% of users in the age group between 12 and 17 years often send and receive text messages.⁹  Communication via text message has the potential to connect patients with information transmitted by health professionals, but the role of these applications is little known.¹⁰ 

Scientific evidence has shown that reminder therapy has been an effective ally for improving the results of proposed treatment in different health fields.^11–13  However, the scientific literature is controversial and there is not a consensus yet about the actual effect of this intervention regarding the oral hygiene of patients being treated orthodontically. Therefore, this systematic review aimed to assess the scientific evidence regarding the influence of reminder therapy on plaque index, gingival index, and white spot lesion development in patients undergoing orthodontic treatment.

This systematic review was performed following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) statement¹⁴  and the Cochrane guidelines.¹⁵  The systematic review protocol was registered at PROSPERO database, CRD42017077671.

Clinical trials assessing the influence of reminder therapy on the bacterial plaque index in patients undergoing orthodontic treatment were included without restrictions of year, language, or publication status. The following were excluded: studies not related to the topic and review studies, case reports, letters to the editor or editorials, congress abstracts, personal opinions, and books and/or book chapters.

Two reviewers performed the search independently (IFPL and WAV). Table 1 shows the electronic databases accessed with the gray literature included. The descriptors were searched in the databases DeCS (Health Sciences Descriptors), MeSH (Medical Subject Headings), and Emtree (Embase Subject Headings). The Boolean operators “AND” and “OR” were used to enhance the research strategy through several combinations. The bibliographic research was developed in August 2017. The results obtained were exported to the software EndNote Basic/Online (Thomson Reuters, Toronto, Canada), desktop version, and the duplicates were removed.

The selection of studies was performed in three phases. In phase 1, two reviewers (IFPL and WAV) systematically analyzed the titles independently. The articles in which titles met the objectives of the study were selected for phase 2. In the second phase, the same reviewers systematically analyzed the abstracts. At this point, the eligibility criteria were applied. The articles in which titles met the objectives of the study but did not have abstracts available were fully analyzed in phase 3.

In the third phase, full texts were obtained for the preliminarily eligible studies, and these were evaluated to verify whether they fulfilled the eligibility criteria. When the two reviewers disagreed, a third reviewer (LRP) was consulted to make a final decision. The studies that were rejected were registered separately, clarifying the reasons for exclusion.

Two authors (APBL and WAV) extracted the following data with spreadsheets especially designed for data extraction: article identification (author, publication year, country of the study), sample characteristics (number of patients in each study, mean age, gender distribution), type of intervention (type of reminder, format, periodicity of intervention, recipient of the reminder), methods for obtaining the results (form of biofilm assessment, location or teeth assessed, periodicity of assessment), and duration of the study. As a calibration exercise, the reviewers discussed the eligibility criteria and applied them to a sample of 20% of the studies retrieved to determine interexaminer agreement. After achieving a proper level of agreement (κ = 0.81–0.85), the reviewers read all of the studies independently. Disagreements were resolved by consensus and supervision of the gold standard (LRP). An e-mail was sent to the authors whose studies presented insufficient data or information that would prevent summarizing and making comparisons to data from the other eligible articles so that additional information could be provided.

The risk of bias of the studies selected was assessed by the Joanna Briggs Institute Critical Appraisal Checklist for Randomized Controlled Trials tool.¹⁶  Two authors (WAV and IFPL) independently assessed each domain regarding the potential risk of bias.

The software Review Manager, version 5.3 (RevMan; Cochrane Collaboration, London, United Kingdom) was used for the meta-analysis. Heterogeneity among the studies was assessed with the I² statistic and classified as follows: low (I² < 25%), moderate (I² = 50%), and high (I² > 75%).¹⁷  The outcomes assessed were plaque index (continuous variable), gingival index (continuous variable), and white spots (dichotomous variable).

Forest plots were constructed for each meta-analysis using random effects.^15,18  The differences in continuous outcomes were reported through the standardized mean difference, 95% confidence interval (CI), and P value. The difference in dichotomous outcomes was reported through the relative risk estimate, 95% CI, and P value. All statistical tests were two-tailed, and significance was fixed at P < .05. Funnel plots to assess the probability of bias were not produced because fewer than 10 studies were included in the models. A summary of the overall strength of evidence available was assessed using the Grades of Recommendations Assessment, Development, and Evaluation tool.¹⁹ 

Figure 1 depicts the search process, identification, inclusion, and exclusion of articles. During the first phase of study selection, 332 results were found, distributed in eight electronic databases and 9 records on gray literature. After analyzing the abstracts, only six articles were eligible for the analysis of full texts. The references of the six initially eligible articles were carefully assessed to determine if there was an article that was possibly skipped in the main search strategy. One additional study was located and added. Therefore, seven articles went on to the qualitative analysis of the results.

Table 2 shows a summary of the main characteristics of the studies. The analysis resulted in a total sample of 574 participants. The mean age of the groups ranged from 12.8 to 18.7 years. The female gender was a majority in all studies, except for one⁸  that did not clarify the gender ratio in each group.

In all studies,^{1,4–7,20,21}  all patients received hygiene instructions through videos or lectures during the first visit. The method of reminder was exclusively text messaging in three studies.^4,5,20  In one study,⁶  the groups were created in which one group received text messages and the other received phone calls. In another study,²¹  the reminders were sent via notification through an application. Two other studies^1,7  associated text messaging with videos, voice messages, and scientific articles. Two studies^4,20  sent reminders only to the parents/guardians, whereas four studies^1,5,6,21  sent reminders only to the patients. One study⁷  sent reminders only to patients aged older than 18 years or to the guardians of patients aged younger than 18 years.

Six studies^1,4–7,21  presented low risk of bias and one study²⁰  presented moderate risk of bias assessed by the JBI Critical Appraisal Checklist for Randomized Controlled Trials tool. Table 3 shows detailed information on the risk of bias of the studies included. Item 4 was considered as “yes” only for the studies in which the participants were unaware that the text messages were part of the research. Item 5 of Table 3 was considered not applicable for all studies, considering that it was impossible to blind the individual who was applying the treatment (sending the reminder). The items marked as “uncertain” with regard to the randomization of the studies signify that the method of allocation in each group was not clearly presented. The studies^1,4,6,21  that were considered as “yes” in item 6 were those affirming that the evaluators of the control and interference groups were blind to the allocation of participants.

Three studies^1,6,21  assessed the plaque index using the modified Silness and Loe Index. Two studies^5,21  used the modified Turesky plaque index, one study⁵  used computed planimetry, and one study⁷  did not indicate the assessment method. Three studies assessed the gingival health indices also by the Silness and Loe^1,21  and the modified Silness and Loe⁴  indices. One study⁷  did not indicate the method used. Three studies^1,4,20  also verified the incidence of white spots during the clinical examination. All studies performed plaque disclosure, gingival examination, and white spot inspection before the start of the study, and all of them showed similar indices for the control and experimental groups.

Only four studies^1,4,5,20  presented sufficient data to be included in the quantitative analysis. Figures 2 to 4 show the forest plots produced from the meta-analysis. There were major differences regarding oral hygiene and oral clinical condition in the control and experimental groups. Considering the overall estimates, it was found that the experimental group showed lower scores for the plaque index (standardized mean difference = −1.22; 95% CI = −2.03 to −0.42; P = .003) and the gingival index (standardized mean difference = 1.49; 95% CI = −2.61 to 0.37; P = .009). Moreover, there was a lower occurrence of white spots (relative risk = 0.53; 95% CI = 0.38 to 0.74; P < .001) in the experimental group. The overall evidence rated by the Grades of Recommendations Assessment, Development, and Evaluation approach was considered high quality (Table 4).

The hygiene challenges that the users of fixed orthodontic appliances face is a problem in dentistry, considering that poor hygiene may lead to caries or white spots, which are common when wearing orthodontic appliances.²  Hence, this systematic review sought to assess whether reminder therapy had a positive influence on the reduction of plaque index, gingival index, and white spots in patients undergoing orthodontic therapy.

Bacterial plaque accumulation occurs because of poor oral hygiene, and it is common during orthodontic treatment because the orthodontic accessories make oral hygiene more difficult to maintain.²  Scientific evidence has shown that optimal oral health maintenance during orthodontic treatment should be a gold standard in practice today.³  Attempting to work toward this achievement, studies^1,4,5,20,21  have been performed recently to determine the effects of sending reminders of oral hygiene reinforcement via text, video, or voice messages.

The use of mobile phones (smartphones), with their various resources and applications for text messaging (SMS), has revolutionized the means of interpersonal interaction and communication. Their use is increasingly present in the daily lives of people, surpassing geographical, social, and cultural barriers.⁸  A recent survey found that more than 5 billion people (67% of the world population) use some type of mobile device in the world, and 4 billion of them use smartphones specifically.²²  Because it is an instant-messaging and low-cost technology, the text message has been extensively used by smartphone users.^8,9  Sending reminders via text, video, or voice messages became a major research tool within the health environment, improving the efficiency of service provision.¹⁰ 

Concerned about the clinical outcomes of patients, recent studies^12,13  have applied text messaging to verify patient improvement in several situations. The current study verified that the type of reminder that authors mostly used were text messages, and they were used in six eligible studies^1,4–7,20  (Table 2). This may be because the text message is a more discrete tool than video or voice messages, ensuring a structured communication without emotional influence.⁶  However, studies should be conducted to verify the reach and efficiency of each type of reminder. Although the studies did not discuss the influence of periodicity for sending the reminders, it is possible to believe that the shorter the period between reminders, the more positive the results.

The plaque index is an important tool to assess not only oral hygiene but also the motivation and self-care of the patient during treatment.²³  Orthodontic patients experience barriers to controlling plaque, considering that the orthodontic appliance extends the areas of bacterial plaque retention, which complicates hygiene.²  Although the studies included in this systematic review assessed the plaque index in periods prior to and after 3 months, it was decided in this review to assess the results after 3 months. This decision was based on social psychology because, according to this field of study, an average of 66 days are required to transform a behavior into an automatic habit.²⁴  Therefore, all of the studies included that assessed the plaque index^1,4,5,20  observed an improvement when comparing the experimental group to the control group.

The gingival index is a reliable tool for identifying the periodontal health condition.²⁵  Several indices have been used for this purpose, and the Silness and Loe and modified Silness and Loe, in which the scores are ranked according to degree of gingival inflammation, were chosen by the authors of the eligible studies.^1,4  It is known that orthodontic treatment may elevate the values of the gingival index and contribute to the development of periodontopathogenic bacteria.⁴  A statistically significant reduction of the gingival index was found when the studies compared the experimental group with the control group. This finding reinforces that the motivation and education on oral hygiene are essential for the success of orthodontic treatment.²⁶ 

White spot lesions are signals of demineralization from poor oral hygiene.²⁷  These decalcifications have been commonly observed in patients subjected to orthodontic treatment,²⁸  and several studies^28,29  have been developed to assess the prevalence of these lesions in this group of patients, thus demonstrating its clinical significance. It has been reported that white spots are clinically detected after 4 weeks of orthodontic treatment.³⁰  However, this information is still controversial because some authors¹  suggest that white spots become clinically visible after the first 6 months of treatment.

The eligible studies of this systematic review showed a significant difference between the incidence of white spots in the participants exposed to the reminder therapy in comparison to those who were not exposed to it, with assessments at the third month and between 3 and 6 months (Figure 2). In the period from 3 to 6 months, this difference became even more evident. This may be explained due to the higher amount of time available for the development of lesions so they could manifest clinically. Therefore, encouraging the education of patients and reinforcing the importance of oral hygiene using reminder therapy is a valuable tool to help reduce the development of white spots.

This study is not free from limitations. Despite the comprehensive nature of this review, there was a high heterogeneity among studies. The studies varied especially regarding the sample size and time of follow-up of the participants. When only two articles are considered for meta-analysis, the results should be interpreted with caution. Further studies are recommended to determine whether the effects of reminder therapy persist over time as well as to assess whether it contributes to a better quality of life regarding oral health.

This review was original and contributed to the development of scientific knowledge from two main perspectives. First, it is the first systematic review with meta-analysis that investigated the influence of reminder therapy on oral hygiene and the clinical oral condition of patients undergoing orthodontic treatment. Second, an extensive search strategy was applied without any restriction of language or publication date and including the “gray literature,” seeking to avoid selection and publication biases.

Overall, based on the high-quality evidence found, we note the following:

• Reminder therapy is a valuable strategy for encouraging better oral hygiene in patients undergoing orthodontic treatment.

• Reminder therapy may contribute to improvements in the plaque and gingival indices as well as to a lower occurrence of development of white spot lesions.