Barker Ml

Partial least squares for discrimination

Partial least squares (PLS) was not originally designed as a tool for statistical discrimination. In spite of this, applied scientists routinely use PLS for classification and there is substantial empirical evidence to suggest that it performs well in that role. The interesting question is: why can a procedure that is principally designed for overdetermined regression problems locate and emphasize group structure? Using PLS in this manner has heurestic support owing to the relationship between PLS and canonical correlation analysis (CCA) and the relationship, in turn, between CCA and linear discriminant analysis (LDA). This paper replaces the heuristics with a formal statistical explanation. As a consequence, it will become clear that PLS is to be preferred over PCA when discrimination is the goal and dimension reduction is needed. Copyright

Clinical Trial Assessing Light Enhancement of In-office Tooth Whitening

OBJECTIVE Evaluate a light-enhanced in-office tooth whitening system in order to assess tooth color and safety. METHODS Thirty-three adults were randomly assigned to one of three treatment groups. Professional treatment involved application of a 25% H(2)O(2) gel (Discus Dental ZOOM!) with light enhancement, H(2)O(2) gel alone, or the light alone with no peroxide. The 12 anterior teeth were treated three times for 20 minutes each. Efficacy was measured objectively as L*a*b* color change using digital images, tooth shade was measured, and safety was evaluated immediately after treatment and at posttreatment days 7 and 30. RESULTS After adjusting for baseline and age, immediate (end-of-treatment) means (SE) for Deltab* (yellowness) were -3.1 (0.25) for the gel + light, -2.0 (0.25) for the gel-only group, and -2.4 (0.25) for the light-only group. Significant (p < 0.05) color rebound was evident at posttreatment day 7. By day 30, adjusted means (SE)for Deltab* were -1.7 (0.20) for the gel + light group, -1.1 (0.20) for the gel-only group, and -0.5 (0.20) for the light-only group. Both peroxide groups differed significantly (p < 0.05) from light alone on Deltab* and DeltaL*. In the gel + light group, 91% of subjects experienced tooth sensitivity, the majority of which was moderate or severe. Adverse events were low in the light-only group. CONCLUSION Use of light enhancement for in-office whitening leads to immediate color change, after which there was significant color and shade rebound within 7 days as well as moderate-to-severe tooth sensitivity during and after treatment. CLINICAL SIGNIFICANCE Increased tooth sensitivity during treatment and appreciable short-term color rebound after treatment may impact the utility of in-office tooth whitening with peroxide and light as a stand-alone esthetic procedure. (J Esthet Restor Dent 21:336-347, 2009).

Single site meta-analysis of 6% hydrogen peroxide whitening strip effectiveness and safety over 2 weeks

OBJECTIVES This research evaluated efficacy and safety of 6% hydrogen peroxide whitening strips from a clinical trials database accumulated over a multi-year period at a single site. METHODS The inclusive meta-analysis involved seven different randomized clinical trials at one dental school. Each study used 6% hydrogen peroxide whitening strips twice daily for 30min over a 2-week period. Common efficacy (digital images) and safety (examination and interview) methods were used across studies. Pooled subject-level data were analyzed using a general linear mixed model to determine overall response and effects of treatment duration on whitening. RESULTS The 148 treated subjects were 18-71 years old, with b* (yellowness) ranging from 12 to 22, and L* (lightness) ranging from 69 to 80. After 1-week strip use, the adjusted mean (S.E.) for Deltab* was -1.6 (0.08), differing significantly from baseline (p<0.0001). After 2 weeks, the adjusted mean (S.E.) for Deltab* was -2.3 (0.07), differing significantly from Week 1 (p<0.0001). The estimated correlation between Weeks 1 and 2 for Deltab* was 0.74. Study-to-study variation contributed less than 2% of Deltab* variability. Results were similar for DeltaL*, with Weeks 1 and 2 estimated means (S.E.) of 1.5 (0.13) and 2.0 (0.12). Occurrence of oral irritation (22%) and tooth sensitivity (20%) did not adversely affect whitening. Other side effects were unremarkable, and only 1 subject (0.7%) discontinued treatment early due to an adverse event. CONCLUSIONS The meta-analysis of multiple studies conducted at a single clinical site over several years establishes consistent, effective and safe vital bleaching with 6% hydrogen peroxide whitening strips.

Measuring enamel erosion: a comparative study of contact profilometry, non-contact profilometry and confocal laser scanning microscopy.

OBJECTIVES To compare three instruments for their ability to quantify enamel loss after acid erosion. METHODS 6 randomized parallel groups of bovine enamel samples were subjected to citric acid (higher acidity) or orange juice (lower acidity) erosion and remineralisation in a cycling model. Two protected shoulders were created on each of the samples using tape, to serve as reference for analysis. The time of exposure to each acid was varied, along with presence or absence of agitation. After treatment, samples were measured on 3 instruments capable of measuring step height: a contact profilometer (CP); a non-contact profilometer (NCP); and a confocal laser scanning microscope (CLSM) by three different examiners. Additionally, 3D (volume) step height was also measured using the CLSM. RESULTS Increasing acid concentration and exposure time resulted in greater erosion, as did agitation of samples while in acid solution. All instruments/methods identified the same statistically significant (p<0.05) pair-wise differences between the treatments groups. Further, all four methods exhibited strong agreement (Intra-class correlation ≥ 0.96) in erosion level and were highly correlated, with correlations of 0.99 or higher in all cases. SIGNIFICANCE All instruments/methods used in this study produced very similar conclusions with regard to ranking of enamel loss, with data showing very high agreement between instruments. All instruments were found to be equally suited to the measurement of enamel erosion.

Clinical comparison of two self‐directed bleaching systems

PURPOSE This randomized clinical trial compared the clinical efficacy and tolerability of 2 marketed self-directed vital tooth-whitening systems. MATERIALS AND METHODS Balancing for baseline tooth color, self-reported coffee/tea use, and age, 57 adult volunteers were randomized to either a whitening strip containing 6% hydrogen peroxide or a tray-based 10% carbamide peroxide/dentifrice/mouth rinse combination system. Following the manufacturers directions, the strip group bleached twice daily for 30 minutes, whereas the tray group bleached twice daily for 20-30 minutes, preceded by tooth brushing with a whitening dentifrice and followed by mouth rinsing with a whitening solution. Treatment extended for 14 days, with evaluation at day 7 and again at day 14. Whitening response was measured objectively as L*a*b* from standardized digital images of maxillary anterior teeth. Tolerability was assessed by oral examination and subject interview. Efficacy comparisons were made using analysis of covariance, whereas tolerability was compared using the nonparametric Wilcoxon rank-sum test. RESULTS Both treatments resulted in statistically significant (P < 0.01) improvements from baseline for all color parameters. For between-group comparisons, the 6% hydrogen peroxide strips yielded a nearly 3-fold reduction in yellowness (deltab*), a nearly 2-fold improvement in lightness (deltaL*), 2.6 times greater redness reduction (deltaa*), and a more than 2-fold change in overall color (deltaE*) compared to the tray-based combination system. Between-group comparisons were statistically significant for the all color parameters at both the day 7 and day 14 evaluations (P < 0.001). In general, 7-day use of the whitening strips provided significantly greater color improvement relative to the combination dentifrice/gel/rinse system at day 14. In addition, the groups differed significantly (P < 0.05) in bleaching tolerability severity-days, with the strip system demonstrating better overall tolerability compared to the combination system. CONCLUSIONS The single-step 6% hydrogen peroxide strips demonstrated better overall clinical response, in terms of both tooth-whitening efficacy and tolerability, than the multiple-step tray-based combination system.

Effects of duration of whitening strip treatment on tooth color: A randomized, placebo-controlled clinical trial

OBJECTIVES A randomized, double-blind, placebo-controlled clinical trial was conducted to evaluate efficacy and safety of 6% hydrogen peroxide whitening strip used twice daily over an extended, 6-week period. METHODS After informed consent, 40 eligible adults were randomly assigned to 6% hydrogen peroxide whitening strips (Crest Whitestrips, The Procter & Gamble Company, USA) or placebo strips without peroxide. Treatment was twice daily for 30min, and response was evaluated biweekly after initial (Week 2) and extended (Weeks 4 and 6) use. Tooth color was measured under standardized lighting conditions using digital image analysis, and safety was assessed from clinical examination and interview. Whitening was measured using data derived from digital images taken at baseline compared to post-treatment, with outcomes reported using the CIELAB color notation system. Analysis of variance and covariance were used to assess initial response, and repeated measures regression analysis was used to model color change during sustained use. RESULTS Forty subjects (25-58 years old) started the study. At baseline, L* ranged from 68.0 to 76.8, a* ranged from 8.0 to 11.8, and b* ranged from 16.4 to 23.1. Groups differed significantly (p<0.001) on all color parameters at Week 2 and thereafter, favoring the 6% hydrogen peroxide strips. Week 2 adjusted means+/-SE were -2.1+/-0.2 for Deltab* and 1.9+/-0.2 for DeltaL* for the peroxide group compared to -0.3+/-0.2 for Deltab* and 0.4+/-0.2 for the placebo group. With sustained use (Weeks 2-6), the slope for the peroxide strip was estimated as -0.3 for Deltab* and +0.2 for DeltaL* per week, with both slopes differing significantly from zero (p<0.0001), while slopes for the placebo strip were not significant (p=0.22) and nearly zero. Treatment was generally well tolerated, with adverse events confined to symptoms only. CONCLUSIONS Twice-daily use of 6% hydrogen peroxide whitening strips resulted in teeth becoming lighter and less yellow versus baseline and placebo during initial 2-week use, with no evidence of placebo response during sustained (Weeks 2-6) use.

A randomised in situ trial, measuring the anti-erosive properties of a stannous-containing sodium fluoride dentifrice compared with a sodium fluoride/potassium nitrate dentifrice

OBJECTIVES To determine if a stabilised, stannous-containing sodium fluoride dentifrice provides greater enamel protection in situ against intraoral dietary erosive challenges compared with a sodium fluoride/potassium nitrate dentifrice. METHODS A single-centre, investigator blind, randomised, supervised, two-treatment, non-brushing, four-period crossover in situ study was undertaken, with each test period being 15 days. Thirty-five healthy adult subjects were recruited to participate in the study, which included four erosive acid challenges per day. Subjects were randomised to product treatment, which included either: (1) a stannous-containing sodium fluoride dentifrice (Oral-B(®) Pro-Expert Sensitive) or (2) a sodium fluoride/potassium nitrate dentifrice (Sensodyne(®) Pronamel(®) ). Each study subject wore an intraoral appliance retaining two sterilised, polished human enamel samples for 6 hours/day. Subjects swished with an allocated dentifrice slurry twice a day and with 250 ml of orange juice for 10 minutes (25 ml/minute over a 10-minute period) four times per day. The primary and secondary outcomes for this study were enamel loss measured using contact profilometry at days 15 and 5, respectively, using parametric analysis methods. RESULTS At day 15, a 38% lower enamel loss (P < 0.0001) was observed, with estimated medians of 2.03 μm (SE 0.247) and 3.30 μm (SE 0.379), in favour of the stannous-containing dentifrice. At day 5, specimens treated with the stannous-containing sodium fluoride dentifrice demonstrated 25% less enamel loss than those treated with the sodium fluoride/potassium nitrate dentifrice. Treatment differences at day 5 were also statistically significant (P < 0.05), with estimated medians of 1.37 μm (SE 0.177) and 1.83 μm (SE 0.223), respectively. CONCLUSIONS Results of this in situ study suggest the stabilised, stannous-containing sodium fluoride dentifrice could be used to provide significantly greater protection to enamel from erosive acid challenge compared with that provided by conventional fluoride-containing products.

In situ clinical evaluation of a stabilised, stannous fluoride dentifrice

OBJECTIVES To compare the erosion protection efficacy of a stabilised, stannous fluoride (SnF2 ) dentifrice versus a sodium fluoride (NaF) dentifrice using a modified in situ clinical model. METHODS This study, a randomised parallel group in situ design with in vivo product use and ex vivo acid challenge, compared: A, a dentifrice containing 1,450 ppm F as NaF; B, a dentifrice containing 1,450 ppm F (1,100 ppm F as SnF2 + 350 ppm F as NaF); and T, tap water. Sample size was n = 4 per group (total of 12 subjects) and within each subject appliances were placed on each side of the mouth (left and right). Enamel specimens were placed in different positions of the mouth (front, mid-front, mid-rear, rear) in each appliance (total = 8 specimens per subject). Product treatment was twice per day (lingual brushing for 30 seconds followed by swishing for 90 seconds with the resultant product/saliva slurry) in vivo for 15 days, and ex vivo acid treatment (0.02 m citric acid 5 minutes four times per day; total exposure time = 300 minutes). Data were analysed using a general linear repeated measures model with treatment, side and position as fixed effects. Within subjects, correlations were modelled assuming a different correlation and variance for treatment B relative to the other groups. Pairwise treatment differences were performed using a 5% two-sided significance level. RESULTS Enamel loss (in μm) was significantly lower (P < 0.005) for treatment B versus treatments A and T. Treatment B reduced enamel surface loss by 86.9% relative to treatment A. There was no statistical difference in mean enamel loss (P = 0.51) between treatments A and T. Enamel loss was not statistically different for side (left vs. right; P = 0.44) or position (front, mid-front, mid-rear, rear; P = 0.36). CONCLUSION This modified in situ erosion model confirmed the enhanced erosion protection benefits of a stabilised SnF2 dentifrice versus a conventional NaF dentifrice, validating the ability of the model to safely and effectively demonstrate differences in the erosion protection potential of oral care products.

Placebo-controlled trial evaluating safety with 12-months continuous use of 6% hydrogen peroxide whitening strips

OBJECTIVE To assess the safety and tolerability of 6% hydrogen peroxide whitening strips over 12 months. METHODS 80 adults were randomly assigned equally to one of two treatments: 6% hydrogen peroxide strips or placebo strips. Strips were worn 5 min daily for 12 months. Safety and tolerability were assessed via oral status interviews and oral examinations at baseline and after 1, 2, 3, 6, 9, and 12 months of use. RESULTS Tooth sensitivity and oral irritation were the two most common adverse events. After 12 months use, tooth sensitivity was reported by 10% of subjects in the 6% strip group with a 95% confidence interval (CI) of (2.8%, 23.7%) and 5% of subjects in the placebo group with a 95% CI of (0.6%, 16.9%). The occurrence of reported oral irritation was 0% in the 6% strip group with a 95% CI of (0%, 8.8%) and 2.5% in the placebo strip group with a 95% CI of (0.1%, 13.2%). The occurrence of observed oral irritation was also similar between groups. The groups did not differ significantly (p>0.67) for the percent of subjects with each type of adverse event. In the 6% strip group, two subjects discontinued product use due to an adverse event (tooth sensitivity) compared to no subjects in the placebo group. Groups did not differ significantly (p>0.49) with respect to this outcome. CONCLUSION Use of 6% hydrogen peroxide whitening strips over 12 months resulted in a safety profile similar to that seen with placebo strips.

Placebo-Controlled Clinical Trial of Use of 10% Hydrogen Peroxide Whitening Strips for Medication-Induced Xerostomia

Objective: A randomized, double-blind, placebo-controlled clinical trial was conducted to evaluate the effectiveness and safety of peroxide-containing strip-based tooth whitening among subjects with medication-induced hyposalivation. Methods: Eligibility for this tooth whitening study was limited to dentate adults taking xerogenic medications with an unstimulated salivary flow ≤0.2 ml/min. After giving informed consent, 42 subjects were randomized using a 2:1 ratio to 10% hydrogen peroxide whitening strips (Crest® Whitestrips® Premium) or placebo strips without peroxide. Strips were used for 30 min twice daily for a 14-day period. Usage was unsupervised, and only the maxillary arch was treated. On days 8 and 15, efficacy was assessed from standard digital images of the anterior dentition and quantified using the Cielab color system, while safety was assessed from interviews and clinical examinations. Results: At day 8, the peroxide group experienced significant (p < 0.001) color improvement relative to baseline and placebo. Adjusted means ± standard errors for yellowness reduction were –1.65 ± 0.115 units for the peroxide group and –0.32 ± 0.170 units for the placebo group. For the increase in lightness, adjusted means ± standard errors on day 8 were 1.53 ± 0.130 units for the peroxide group and 0.37 ± 0.191 units for the controls. Continued strip use through day 15 yielded incremental color improvement for the peroxide group. Mild and transient tooth sensitivity represented the most common adverse events. No subject discontinued treatment due to a product-related adverse event. Conclusion: Twice daily use of 10% hydrogen peroxide whitening strips by adults with medication-induced xerostomia was well tolerated, with significant tooth color improvement evident within 7 days.