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Context The World Health Organization set the recommended daily vitamin C intake, henceforth referred to as ascorbic acid (AA), on the basis of scurvy prevention. Double-blind AA depletion-repletion studies suggest that this recommended AA dose may be too low to prevent microvascular fragility. Objectives (1) To conduct a systematic review and meta-analysis of controlled clinical trials on whether AA supplementation leads to a reduced gingival bleeding tendency, a manifestation of microvascular fragility; and (2) to relate AA plasma levels to retinal hemorrhaging, another manifestation of microvascular fragility. Data sources Data were reviewed from 15 trials conducted in 6 countries with 1140 predominantly healthy participants with measures of gingival bleeding tendency, and from the National Health and Nutrition Examination Survey (NHANES) III of 8210 US residents with measures of retinal hemorrhaging. Results In clinical trials, AA supplementation reduced gingival bleeding tendency when estimated baseline AA plasma levels were < 28 μmol/L (standardized mean difference [SMD], −0.83; 95%CI, −1.16 to −0.49; P  < 0.002). Supplementation with AA did not unequivocally reduce gingival bleeding tendency when baseline estimated AA plasma levels were >48  μmol/L or unknown (respective standardized mean differences: −0.23, 95%CI, −0.45 to −0.01, P  < 0.05; and −0.56; 95%CI: −1.19 to 0.06, P  < 0.08). In NHANES III, prevalence of both retinal hemorrhaging and gingival bleeding tendency increased when AA plasma levels were within the range that protects against scurvy (11–28 μmol/L; respective prevalence ratios adjusted for age and sex: 1.47; 95%CI: 1.22–1.77; and 1.64; 95%CI: 1.32–2.03; P < 0.001 for both). Conclusion Consistent evidence from controlled clinical trials indicates that setting human AA requirements based on scurvy prevention leads to AA plasma levels that may be too low to prevent an increased gingival bleeding tendency. Gingival bleeding tendency and retinal hemorrhaging coincide with low AA plasma levels and thus may be reflective of a systemic microvascular pathology that is reversible with an increased daily AA intake. [ABSTRACT FROM AUTHOR]

This study aims to determine whether breastfeeding duration affects the prevalence of nonrighthandedness in later life. A systematic search for studies on this topic was completed in 2018, and risk of bias was assessed by means of the Newcastle-Ottawa scale. Seven national surveys in five countries with Individual Participant Data (IPD) were identified (n = 62,129 mother-child dyads). These surveys had low risk of bias. An IPD meta-analysis showed that breastfeeding for < 1 month, 1 to 6 months, and > 6 months, when compared to bottle feeding, was associated with a 9%, 15% and 22% decreased prevalence of nonrighthandedness, respectively (Prevalence Ratio (PR) = 0.91, 95% confidence interval (ci): 0.83, 1.00; p-value = 0.05, PR = 0.85, 95% CI: 0.79, 0.92; p-value < 0.0001 and PR = 0.78; 95% CI: 0.71, 0.85; p-value < 0.0001). This dose-response relationship was significant (p < 0.001). No significant heterogeneity across surveys was detected (p-value > 0.54). Breastfeeding for longer than 9 months was not associated with further reductions in the prevalence for nonrighthandedness (p > 0.58). It is concluded that the critical age window for establishing hemispheric dominance in handedness includes the first 9 months of infancy and is in part determined by nurture. [ABSTRACT FROM AUTHOR]

Background. Conduct a systematic review and meta-analysis on nonsurgical treatment of patients with chronic periodontitis by means of scaling and root planing (SRP) with or without adjuncts. Methods. A panel of experts convened by the American Dental Association Council on Scientific Affairs conducted a search of PubMed (MEDLINE) and Embase for randomized controlled trials of SRP with or without the use of adjuncts with clinical attachment level (CAL) outcomes in trials at least 6 months in duration and published in English through July 2014. The authors assessed individual study bias by using the Cochrane Risk of Bias Tool and conducted meta-analyses to obtain the summary effect estimates and their precision and to assess heterogeneity. The authors used funnel plots and Egger tests to assess publication bias when there were more than 10 studies. The authors used a modified version of the US Preventive Services Task Force methods to assess the overall level of certainty in the evidence. Results. The panel included 72 articles on the effectiveness of SRP with or without the following: systemic antimicrobials, a systemic host modulator (subantimicrobial-dose doxycycline), locally delivered antimicrobials (chlorhexidine chips, doxycycline hyclate gel, and minocycline micro-spheres), and a variety of nonsurgical lasers (photodynamic therapy with a diode laser, a diode laser, neodymium:yttrium-aluminum-garnet lasers, and erbium lasers). Conclusions and Practical Implications. With a moderate level of certainty, the panel found approximately a 0.5-millimeter average improvement in CAL with SRP. Combinations of SRP with assorted adjuncts resulted in a range of average CAL improvements between 0.2 and 0.6 mm over SRP alone. The panel judged the following 4 adjunctive therapies as beneficial with a moderate level of certainty: systemic subantimicrobial-dose doxycycline, systemic antimicrobials, chlorhexidine chips, and photodynamic therapy with a diode laser. There was a low level of certainty in the benefits of the other included adjunctive therapies. The panel provides clinical recommendations in the associated clinical practice guideline. [ABSTRACT FROM AUTHOR]

Vitamin D has been used to prevent and treat dental caries. The objective of this study was to conduct a systematic review of controlled clinical trials ( CCTs) assessing the impact of vitamin D on dental caries prevention. Random-effects and meta-regression models were used to evaluate overall and subgroup-specific relative-rate estimates. Twenty-four CCTs encompassing 2,827 children met the inclusion criteria. Twenty-two of the 24 CCTs predated modern clinical trial design, some of which nonetheless reported characteristics such as pseudo-randomization ( n = 2), blinding ( n = 4), or use of placebos ( n = 8). The relative-rate estimates of the 24 CCTs exhibited significant heterogeneity ( P < 0.0001), and there was evidence of significant publication bias ( P < 0.001). The pooled relative-rate estimate of supplemental vitamin D was 0.53 (95% CI, 0.43-0.65). No robust differences were identified between the caries-preventive effects of vitamin D2, vitamin D3, and ultraviolet radiation ( Prob > F = 0.22). The analysis of CCT data identified vitamin D as a promising caries-preventive agent, leading to a low-certainty conclusion that vitamin D may reduce the incidence of caries. [ABSTRACT FROM AUTHOR]