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Implications of the Xylitol for Adult Caries Trial (X-ACT) for Prevention Programs and Individuals. JP Brown 1 , BT Amaechi 1 , JD Bader 2 , GH Gilbert 3 , DA Shugars 2 , and WM Vollmer 4. 1 UTHSC San Antonio TX 2 UNC Chapel Hill NC 3 UA Birmingham AL

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slide1

Implications of the Xylitol for Adult Caries Trial (X-ACT) for Prevention Programs and Individuals

JP Brown1, BT Amaechi1, JD Bader2, GH Gilbert3, DA Shugars2, and WM Vollmer4

  • 1UTHSC San Antonio TX
  • 2UNC Chapel Hill NC
  • 3UA Birmingham AL
  • 4Kaiser Permanente CHR Portland OR

NIDCR U01DE018038, U01DE018047, U01DE018048, U01DE018049, U01DE018050

presenter disclosures
Presenter Disclosures

John P Brown

No relationships to disclose

and the X-ACT trial tested xylitol itself versus sucralose,

not commercial products containing these.

The following personal financial relationships with commercial interests relevant to this presentation existed during the past 12 months:

slide3

Trial Registration ClinicalTrials.Gov NCT00393055

Public Web Site www.kpchr.org/xact/public/index.aspx?pageid=1

Bader JD et al Design of the xylitol for adult caries trial (X-ACT) BMC Oral Health 2010 Sept 29;10:22.

Banting DW etal Examiner training and reliability in two randomized clinical trials of adult dental caries

J Pub Health Dent 2011;71:335-44.

slide4

X-ACT

Xylitol Reviews:

Hayes C, J Dent Educ, 2001 SR +

Lingström P, ActaOdont Scand, 2003 SR ?

Maguire A, Brit Dent J, 2003 TR +

van Loveren C, Caries Res, 2004 TR ?

Deshpande A, J Am Dent Assoc, 2008 SR +

Antonio, A, J Pub Health Dent, 2011 SR ?

Rethman M, J Am Dent Assoc, 2011 SR ?

SR = Systematic Review

TR = Traditional Review

slide5

Rethman, et al. Nonfluoride caries-preventive agents : Executive summary of evidence-based clinical recommendations. JADA 2011.

slide6

X-ACT

Recruitment/Enrollment

28-Day run-in period

Baseline Exam & Randomization

PLACEBO

TEST

3, 6, 9 month telephone contact and resupply

12-Month Exam

12-Month Exam

3, 6, 9 month telephone contact and resupply

24-Month Exam

24-Month Exam

3, 6 month telephone contact and resupply

33-Month Exam

33-Month Exam

slide7

X-ACT

Trial Overview

  • Randomized controlled trial
  • Double blind
  • Placebo controlled
  • Multi-site (UNC-CH, UA-B, UTHSC-SA)
  • 33 months
  • Caries-active adults 18-80
  • Xylitol lozenges (5 per day x 1mg = 5 grams/day)
slide8

X-ACT

  • Caries Examinations
  • D1 Non-cavitated Lesions; D2Cavitated Lesions
  • (ICDAS criteria with categories consolidated)
  • 9 surfaces/tooth (root and crown combined)
  • 4-day training and calibration
  • 5% reliability sample at each exam
  • Principal examiners completed >96% exams
  • Inter-examiner reliability at training: 0.67, 0.74, 0.76Kappa
  • Mean inter-examiner reliability at exams: 0.58, 0.88, 0.67, 0.71 Kappa
slide9

X-ACT

  • Analyses
  • Principal outcome: D2crude annualized increment
  • Imputed missing data
  • Negative binomial regression models
  • Controlled for age, oral hygiene, baseline
  • D2FS, fluoride exposure, dental cleaning history
  • Subgroup analyses by baseline D2FS, D2S, adherence, sex, race/ethnicity
slide10

X-ACT

Began run-in

n=945

Withdrew during run-in n=81

Declined to continue n= 173

Randomized

Baseline n=691

Placebo

n=347

Xylitol

n=344

Final Visit

n= 282 (82%)

Final Visit

n=291 (84%)

In analyses

n=331

In analyses

n=338

Telephone contact/resupply at 3, 6, 9 months each year.

Clinical exams and questionnaires at Baseline, 12, 24, and 33 months.

slide11

Sample Characteristics

1data expressed as mean (Standard deviation)

slide12

X-ACT

  • Adherence and Safety
  • Adherence assessed quarterly, by self-report and resupply quantity
  • All adherence measures highly correlated
  • Oral and GI side effects assessed quarterly
  • Severe adverse events probed for annually
slide13

X-ACT

Results

Principal Outcome Analysis

(3 sites, n=669)

Rate ratio = 0.90 95% CI 0.79-1.01 p=0.077

Prevented fraction = 0.11

slide14

X-ACT

Results

Principal Outcome: Subgroup Analyses

slide15

X-ACT

Discussion of Principal Outcome

  • First large-scale, placebo-controlled, multi-site, randomized, double-blind study of xylitol
  • Lozenges, not gum: possible mechanical plaque removal, chewing stimulates saliva
  • Adults, not children
  • Fluoride exposure from CWF
  • Regular dental attenders
slide16

X-ACT

  • Discussion of Principal Outcome – cont’d
  • Surfaces saved ~ 0.30/year
  • (crude increment), NS
  • Greater but NS effect in those with higher baseline D2FS, but not in those with higher D2S at baseline
  • No indication of dose-response
slide17

X-ACT

Conclusion re Principal Outcome

Xylitol lozenges (≤ 5gm/day),

used as a supplement,

in caries active adults (av. ~ 3 D2FS/year),

with adequate fluoride exposure,

did not substantially reduce their caries experience.

slide18

Subjects in a Secondary Analysis seeking trial efficiency through assessing non-cavitated plus cavitatedlesions (D12FS) were those who completed all four examinations –

baseline, 12, 24, and 33 months.

slide19

Regression results for treatment effect of xylitol vs placebo on increment scores of cavitated lesions (D2FS) and non-cavitated lesions (D12FS) over three cumulative time periods, increments being annualised for each period.

*Cumulative Periods, Months

Regression models fit using negative binomial regression (for D2FS increments) and standard linear regression (for D12FS increments) adjusting for clinical center, age, age-squared, dental cleaning history, self-fluoride use, and oral hygiene practices. The negative binomial gives rise to coefficients having the interpretation of ln (rate ratios, RR) while standard linear regression results in absolute differences in increment (diff). These differing expressions are in accordance with the differing statistical distributions of the two outcomes.

slide20

Regression results for treatment effect of xylitol vs placebo on increment scores of cavitated lesions (D2FS) and non-cavitated plus cavitated lesions (D12FS) over three cumulative time periods, increments being annualised for each period, for a subset of selected participants with a baseline D2FS of more than 20.

*Cumulative Periods, Months

Regression models fit using negative binomial regression (for D2FS increments) and standard linear regression (for D12FS increments) adjusting for clinical center, age, age-squared, dental cleaning history, self-fluoride use, and oral hygiene practices. The negative binomial gives rise to coefficients having the interpretation of ln (rate ratios, RR) while standard linear regression results in absolute differences in increment (diff). These differing expressions are in accordance with the differing statistical distributions of the two outcomes.

slide21

Conclusions for this Secondary Analysis, assessing non-cavitated and cavitated lesions, over 12, 24, and 33 months

The xylitol effect for cavitated lesion (D2FS) declined over time, was significant only at 12 months, and was not of a clinically relevant size.

The xylitol effect for non-cavitated plus cavitated lesions (D12FS) declined over time, was not significant and was not of a clinically relevant size.

These results mirrored the principal trial outcome.

slide22

The Secondary Analysis of selected subjects with higher lifetime caries experience at baseline showed:

4. for cavitated lesions (D2FS) a somewhat greater xylitol effect, declining over time, but significant only at 12 and 24 months

for non-cavitated plus cavitated lesions (D12FS) a decline in xylitol effect over time, significant only at 12 and 33 months.

These effects (4 and 5) were of larger magnitude, but then more total lesions were under consideration.

If non-cavitated lesions retardation (remin or stasis) was occurring, even in periods shorter than one year, this could be expected to reveal differences over a longer time as fewer lesions progressed. This was not observed.

slide23

The X-ACT trial failed to reveal a substantive and consistent effect of xylitol,

even with the inclusion of early caries lesions,

and even in those subjects with higher lifetime caries experience at baseline.

slide24

Implications of the X-ACT Xylitol Trial

  • Xylitol caries preventive effect in caries active adults with adequate fluoride exposure is small and not clinically relevant.
  • Even in subjects with higher baseline lifetime caries experience and presumably of even higher caries activity, the effect was marginal.
  • Using xylitol as a caries preventive agent in caries active adult patients is not well supported.
  • (other reviews in children have been equivocal)
  • Using xylitol in organized public programs for caries prevention is not well supported.
  • Recommending xylitol as a caries preventive agent for populations has even less grounding.
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