A Love Affair with Dental Floss: Is it Warranted?

Love affairs don’t usually last forever but dentistry has been preaching the message about dental flossing since the early 1800s and supposedly even before that. Johnson & Johnson was the first company that I know of to patent dental floss in 1898 and it was made of silk material. As the price of silk skyrocketed during World War II, silk was replaced with nylon. At that time, Dr Charles Bass who is often referred to as the “Father of Preventive Dentistry” insisted on twice a day toothbrushing and once a day dental flossing.

When I was young (during the pre-cretaceous period), and my gingival embrasures were healthy, daily flossing was probably adequate to disrupt interdental biofilm. When I enrolled in Fones School of Dental Hygiene, we were introduced to Trace disclosing solution and learned how to disrupt the brilliant “deep pink-stained” dental plaque. The Trace liquid or tablets would give us a snapshot of where we needed to focus our efforts and it was a real eye-opener for us.

In reading dental hygiene social media blogs about interdental cleaning, I’ve discovered that hygienists are still debating the usefulness of dental floss in comparing it to other forms of interdental cleaning devices. Personal opinion should not be discounted and is part of clinical decision making for patients, but (and this is a big “BUT”) clinicians have strong biases in the way they process experience. Therefore, we need to consider patient preferences based on unique circumstances, and even more importantly the whole body of available evidence.

For whatever reason, many American hygienists and dentists haven’t learned how to apply research outcomes to drive clinical decisions and care. Nurses and physicians, on the other hand, routinely learn how to retrieve, read, critique, and apply research.

In today’s Bachelor of Science (BS) Nursing programs, students are taught to refer to research in response to problems and questions. Sometimes, nursing schools collaborate with research librarians who help students become more competent at using information. For example, a research librarian might assist a nursing student in formulating a structured question, selecting and conducting searches of databases from which they acquire trustworthy and reliable evidence. Not only that, but the student must then learn how to critically appraise the research for its reliability, validity, and applicability to a clinical situation.

How to Find Best Research Evidence to Answer a Clinical Question

Here’s a common discussion hygienists have in Facebook groups: a practicing hygienist will pose a question about the efficacy of string flossing to reduce plaque-induced gingival inflammation in adults and others chime in, insisting other mechanical interdental devices are superior. Sometimes they don’t even mention outcomes but treat dental flossing like it’s a panacea. Let’s search databases and get an overview of what we know and don’t know about how dental flossing compares to other interdental devices. Using PubMed as our search engine, we’ll search for the best research evidence to answer the clinical question. Best evidence is viewed from a hierarchical perspective. This means that the most reliable evidence is at the top of the research pyramid (search for an image of a hierarchical research pyramid if you’ve never seen it before) and the least reliable information is at the bottom (e.g. expert opinion, reports). The level and quality of evidence are important to clinicians because they give them confidence to make clinical decisions for patients. Look for higher levels of evidence like systematic reviews instead of single studies because the conclusions of a review tend to be more reliable than a single study. The methods that scientists use to find and select studies reduce bias and are more likely to produce reliable and accurate conclusions.

A PubMed search using key words “interdental cleaning devices,” “gingival inflammation,” and “systematic review” produce several results. Cochrane Oral Health Group is a high quality systematic review source. A 2019 author team conducted a systematic review to evaluate the effectiveness of interdental cleaning devices used at home, in addition to toothbrushing, compared with toothbrushing alone, for preventing and controlling periodontal diseases, dental caries and plaque. A secondary objective was to compare different interdental cleaning devices to each other.¹ Authors concluded that floss or interdental brushes in addition to toothbrushing may reduce gingivitis or plaque or both more than toothbrushing alone and that interdental brushes may be more effective than floss. Available evidence for tooth cleaning sticks and oral irrigators is limited and inconsistent. Outcomes were only measured in the short term and participants had a low level of baseline gingival inflammation. Evidence from this SR was low to very low certainty.

Another 2019 systematic review by Slots DE et al summarized the available clinical evidence concerning efficacy of interdental cleaning devices in periodontal maintenance patients.² Of the interdental cleaning devices compared in this SR, the interdental brushes reduced plaque scores more effectively when compared to a manual toothbrush alone. Oral irrigation in 2 out of 3 comparisons indicated a positive effect on gingivitis scores and probing pocket depth. Due to scarcity of studies that met the author’s inclusion criteria for each oral hygiene device and the low certainty of resultant evidence, no strong evidence was found for any specific interdental cleaning device for patient self-care in periodontal maintenance.²

In a 2018 meta-analysis (Kotsakis GA et al) of interdental cleaning devices in the reduction of clinical indices or inflammation, researchers used a focused question using a gingival index (GI) and bleeding on probing as primary outcomes. Plaque reduction and probing depths were secondary outcomes.³ Interdental brushes and oral irrigators ranked high for reducing gingival bleeding, and toothpicks and floss were rated last. Meta-analysis demonstrated that unsupervised flossing does not yield substantial reduction in gingival inflammation. The authors concluded that there is an absence of strong evidence to recommend 1 interdental cleaning device over another and to customize recommendations and offering alternatives rather than insisting on the use of a universally recommended cleaning aid.

In 2021, authors Liang et al produced an evidence-based decision-making tree which helps individualized approaches to interdental cleaning based on embrasure size and patient-specific conditions.⁴ A total of 27 studies were included to support a decision tree. Traditional string dental floss continues to remain the first choice for individuals who are highly motivated with good manual dexterity with tight, type 1 embrasures. For individuals with closed embrasures but lack motivation and/or dexterity, the use of easy flossers, soft picks oral irrigation, and narrow interdental brushes are alternatives. For persons with type I and type II open embrasure spaces, an interdental brush has the highest evidence for its effectiveness to remove interdental plaque. Two studies showed that residual plaque could remain in lingual embrasures and therefore a lingual approach of the interdental brush is sometimes needed. The use of gum stimulators and/or woodsticks are supported when significant gingival inflammation is present. Authors recommend individual assessment and tailored oral hygiene home care instructions.⁴

There is no gold standard when it comes to selection of an interdental cleaning device for adults to reduce gingival inflammation. Ease of use, patient preference, consideration of interdental anatomy and periodontal status need to be taken into consideration when recommending an interdental cleaning device. As the above authors mentioned, customizing interdental cleaning devices makes perfect sense and oral healthcare professionals should pay close attention to their own personal bias when making these recommendations.Make sure you don’t fall into boxes that may trap you like not following the ongoing research on this subject or listening to a salesperson or colleague who is not familiar with the research evidence.

References:

1. Worthington HV, MacDonald L, Poklepovic Pericic T, Sambunjak D, Johnson TM, Imai P, Clarkson JE. Home use of interdental cleaning devices, in addition to toothbrushing, for preventing and controlling periodontal diseases and dental caries. Cochrane Database of Systematic Reviews 2019, Issue 4.

2. Slot DE et al. Mechanical plaque removal of periodontal maintenance patients: a systematic review and network meta-analysis.J Clin Periodontol. 2020: 47:107-120.

3. Kotsakis GA et al. A network meta-analysis of proximal oral hygiene methods in the reduction of clinical indices of inflammation. J Periodontol 2018 May: 89: 558-570.

4. Liang P. et al. Evidence-based strategies for interdental cleaning: a practical decision tree and review of the literature.Quintessence Int 2021: 52(1): 84-95.