The Effectiveness of a Magnetized Water Oral Irrigator (Hydro Floss)
on Plaque, Calculus & Gingival Health.

Johnson, KE et a, J Clin Periodontol 1998; 25: 316-321

The abstractís conclusions are not supported by the data. The study was designed as a 3-month crossover (control and experimental groups switching at 3 months) to eliminate criticism that the study design did not rule out randomly higher plaque and calculus formation between the two groups, a real possibility given the small sample size. However, despite repeated patient instruction, the differences between control and experimental groups were not statistically significant (i.e. no differences), so the authors just ignored it as a presumed anomaly. They also discarded all data relevant to lingual calculus. This is highly suspicious since the data tables show that both the lingual PI and interproximal GI were statistically and significantly higher than facial and non-proximal surfaces. Despite having dismissed the undesirable data, the study was unable to find any significant differences in the overall calculus index between experimental and control groups.

Other Problems:

  1. Statistical power of the study is weak. N=29 (only 16 control & 13 experimental subjects).
    USC biostatisticians calculate that 200 patients would be required to achieve adequate statistical power to make confident conclusions regarding changes in Gingival(GI) and Periodontal (PI) Indices.
  2. The rationale for Hydro Floss efficacy (inhibiting electrovalent bonding of plaque to the tooth) is based on dated concepts with supporting citations at least 24-38 years old. We now know that bacteria attach through a variety of mechanisms, including electrovalent but also ionic, hydrostatic and Van Der Waals forces. The authors further mislead readers by implying that the Hydro Floss uses the same the hydromagnetic technique used to reduce lime and scale in pipes. It doesnít. The ionization of water in treated pipes is continuous, not episodic as in oral irrigation. Further, crevicular fluid are replaced every 5-15 minutes, rapidly normalizing the sulcular environment post irrigation.
  3. Contradiction: The Gingival Index
  4. (GI) and the Standard Loe & Silness Index data for facial, lingual, mesial and distal sites is listed as highly significant (p=0.0091), but 3 month data for the same scores is reported as a 27.5% reduction and not significant.
  5. Contradiction: Plaque Index
  6. (PI) Standard Turesky index: (F, L) reported as weakly significant (p=0.0343), but 3 month data for same scores reported as 2.2% and not significant.
  7. Accretion Data: Study uses a new, n
  8. on-standard index. (Watt index: F, MF, ML, L, DL)
    A modified Watt index was re-measured after prophy, but comparative data is absent.
    The study reports a strong positive association between the Watt accretion (calculus) index and the Turesky plaque index, but the Watt accretion index is actually a combined calculus and plaque index. Since plaque is incorporated into the Watt index, itís hardly surprising to see it correlate with Turesky.

    The Watt Index data are non-significant (p=0.593) To claim, as the authors do that it "Approaches significance" is not the same as being significant.

    Oddly, and unlike the GI and PI indices, only the facial data were considered for measuring accretion. This is highly suspicious, since despite instructing patients to specifically irrigate the mandibular anterior teeth, the study concluded: "Regardless of treatment or period, lingual surfaces had statistically significantly higher plaque indices than facial surfaces. Difference in plaque index was affected more by period than treatment." "Ö the overall reduction in the indices occurring over the 2 trial periods was not necessarily due to the treatment (magnetized) but possibly to the fact that water oral irrigation was used or a placebo effect."
  9. The study claims a 64% reduction in calculus (3-month), but the underlying calculations are based on statistically non-significant data. Such claims are meaningless and deceptive.
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