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20 Mar 2017

By Tim Donley


Why dental professionals should rethink their allegiance to flossing



Interproximal areas have long been regarded as being the most difficult to adequately debride. For years, dental professionals have drilled their beloved, “brush and floss” mantra into anyone who would listen. 

Flossing in particular has long been the unofficial benchmark of one’s dedication to their oral health. Dental professionals often begin their assessment of patients’ ability to maintain their oral health by questioning whether the patient flosses regularly. The general public understandably has been conditioned to believe that flossing is integral to the successful management of their oral health. Scientific evidence suggests otherwise.


Systematic reviews are designed not only to identify all relevant information contained in the literature, but also to evaluate the quality of the information (Ismail & Bader 2004). However, the available evidence tells only part of the story. Evidence-based dentistry (EBD) has three important components: the best available scientific evidence, a dental professional’s clinical skill and judgment, and each individual patient's needs and preferences. Only when all three are given due consideration in individual patient care is EBD actually being practiced (Kishore et al 2014). In this age of EBD, perhaps it is time for dental professionals to rethink their allegiance to flossing.


Credit for the invention of dental floss as we know it goes to Dr. Parmly, a New Orleans dentist, who in 1815 began advising his patients to clean between their teeth (Sanoudos & Christen 1999). In his textbook, Dr. L. S. Parmly suggested that with daily use of “waxed silken thread interproximally, the teeth and gums will be preserved free from disease” (Parmly 1819). Despite the availability of other means of interproximal hygiene over the ensuing years, the legendary importance of flossing as the cornerstone to a preferred level of oral health continued to grow despite a paucity of evidence to support the use of floss as a part of an effective daily hygiene regimen. For maximum effectiveness, any recommended method of patient directed interproximal debridement must take into account patient preferences for the technique, compliance with using the cleaning aid and the evidence supporting the likely outcome. 


An ideal inter-dental cleaning device should be user friendly, have no deleterious soft-tissue or hard tissue effects and interrupt biofilm effectively over the entire intended surface (Sälzar et al. 2015). In America the percentage of people who actually use floss on a regular basis is dismal (Delta Dental Survery 2014). Undesired removal of hard and soft tooth structure in patients who adhere to a daily flossing routine can often be observed (Hallman et al. 1986).


Image_001.pngFig 1. Removal of tooth structure in patient who hasflossed twice daily for 30 years. 

Despite the fact that few people actually do it, flossing remains the most commonly recommended method for interproximal daily hygiene. Even more disconcerting is the lack of evidence supporting the use of dental floss. The conclusion from a recent systematic review suggested, “The dental professional should determine, on an individual patient basis, whether high-quality flossing is an achievable goal. In light of the results of this comprehensive literature search and critical analysis, it is subsequent reviews of the available literature concluded that a routine instruction to use floss is not supported by scientific evidence” (Berchier et al, 2008).


Subsequent reviews of the available literature examining whether flossing has a decided periodontal oranti-caries therapeutic advantage are remarkably consistent. The evidence does not demonstrate an advantage of flossing over other interproximal oral hygiene methods in terms of periodontal or tooth surface (anti-caries) health (Hujoel et al. 2006, Sambunjak 2011; Sälzer 2015). In fact, other methods of patient driven debridement may be more effective than flossing. Effective interproximal hygiene requires a device that affects as much of the exposed tooth surface as possible (Sälzer 2015).


Floss interrupts periodontal and caries pathogens via mechanical dislodgement only when the floss threads contact the tooth surface. Against flat or convex interproximal surfaces floss, used properly, may be able to effectively interrupt the pathogenic bacterial biofilm. However, recession of the gingival margin, especially posteriorly, can expose a root surface which has a morphology that does not lend them to contact with floss. Patients that are faithful with regular flossing and even use an ideal technique will have no effect on the potential biofilm on the concave portions that comprise most interproximal tooth surfaces.


Image_002.pngFig 2. Floss is ineffective in interproximal areas whichhave concave areas. 


Slot et al. (2008) showed that an interdental brush (IDB) can be a useful device to complement tooth brushing. The evidence suggests that interdental brushing is the most effective method to interdentally remove plaque (Slot et al. 2008, Poklepovic et al. 2013). When the papilla fills the interdental space, floss has the potential to reach the involved tooth surfaces. However, when any papillary recession has occurred an interdental brush size should be selected which fits snugly into the entire space to encourage maximum contact between the brush bristles and the tooth surface (Jackson et al. 2006). A variety of IDB shapes and sizes are required in clinical practice to accommodate all inter-dental spaces (Sälzer 2015). Because only scant evidence exists, no systematic reviews are available concerning differences in brush handles (straight or angled), brush shape, filament type, and durability or method of brush insertion into the interproximal site.


Nevertheless, it seems reasonable to recommend that patients use an interproximal brush at every interproximal site where one fits. Floss use should be recommended only at sites where an interproximal brush does not fit. As with any oral hygiene aid, it is critical to verify proper use of the IDB. While evidence is lacking concerning ideal technique, inserting the brush from both the buccal and lingual (as opposed to insertion only from the buccal), would maximize the amount of interproximal surface area being contacted by IDB filaments. Insertion of the IDB from only one direction can result in portions of 
the interproximal surface which would not normally be affected by tooth brushing, to also not be affected by the brush.


Image_003.pngFig 3a. Inserting an interdental brush only from thebuccal



Fig 3b. Tooth brushing alone cannot reach interproximal surfaces. (3a) will result in some interproximal toothwhich is not normally affected by tooth brushing. 


To insure maximum debridement, the chosen IDB size should be large enough to fill the entire interproximal space. 


Image_005.pngFig 4a. Brush is too small and biofilm may remain onsome interproximal surfaces. 


Fig 4b. Correct brush size for this interdental space. 


The bacterial initiation of the host inflammatory process that leads to periodontal pocket formation is well understood (Kornman et al. 1997). The overwhelming evidence confirming the adverse relationship between oral inflammation and systemic disease (Linden et al. 2013), suggests that consistently adequate daily cleaning can pay dividends to oral and systemic health.


In this age of EBD simply telling every patient to floss can no longer be justified. Despite the long entrenched allegiance to flossing by dental professionals it is time to take a different approach.




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Chaves ES, Wood RC, Jones AA, Newbold DA, Manwell MA, Kornman KS. Relationship of "bleeding on probing" and "gingival index bleeding" as clinical parameters of gingival inflammation. J Clin Periodontol. 1993 Feb;20(2):139-43.

Delta Dental 2014 Oral Health and Well-Being Survey. Accessed on July 3, 2015 at https://www.deltadental.com/DDPAOralHealthWellBeingSurveyBrochure2014.pdf

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Kornman KS, Page RC, Tonetti MS. The host response to the microbial challenge in periodontitis: Assembling the players. Periodontol 2000. 1997;14:33-53.

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Linden GJ, Lyons A, Scannapieco FA. J Clin Periodontol. Periodontal systemic associations: review of the evidence.2013;40Suppl 14:S8-19.

Parmly LS. A Practical Guide to the Management of the Teeth; Comprising a Discovery of the Origin of Caries, or Decay of the Teeth. Philadelphia, PA: Collins & Croft. 1819. p. 72

Sälzer S, Slot DE, Van der Weijden FA, Dörfer CE. Efficacy of inter-dental mechanical plaque control in managing gingivitis – a meta-review. J Clin Periodontol 2015; 42 (Suppl. 16): S92–S105.

Sambunjak D, Nickerson JW, Poklepovic T, Johnson TM, Imai P, Tugwell P, Worthington HV. Flossing for the management of periodontal diseases and dental caries in adults. Cochrane Database of Systematic Reviews 2011, Issue 12.

Sanoudos M, Christen AG. Levi Spear Parmly: the apostle of dental hygiene. Journal of the History of Dentistry 1999;47 (1): 3–6.

Schätzle M1, Löe H, Bürgin W, Anerud A, Boysen H, Lang NP. Clinical course of chronic periodontitis. I. Role of gingivitis. J Clin Periodontol. 2003;30:887–901.

Slot, D. E., Dörfer, C. E. & Van der Weijden, G. A. (2008) The efficacy of interdental brushes on plaque and parameters of periodontal inflammation: a systematic review. International Journal of Dental Hygiene 6, 253–264.

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