Evangelia Morou-Bermudez

Urease activity in dental plaque and saliva of children during a three-year study period and its relationship with other caries risk factors.

UNLABELLED Bacterial urease activity in dental plaque and in saliva generates ammonia, which can increase the plaque pH and can protect acid-sensitive oral bacteria. Recent cross-sectional studies suggest that reduced ability to generate ammonia from urea in dental plaque can be an important caries risk factor. In spite of this proposed important clinical role, there is currently no information available regarding important clinical aspects of oral ureolysis in children. OBJECTIVE The objective of this study was to evaluate the distribution and pattern of urease activity in the dental plaque and in the saliva of children during a three-year period, and to examine the relationship of urease with some important caries risk factors. METHODS A longitudinal study was conducted with repeated measures over a three-year period on a panel of 80 children, aged 3-6 years at recruitment. The dynamics of change in urease activity were described and associated with clinical, biological, and behavioural caries risk factors. RESULTS Urease activity in plaque showed a trend to remain stable during the study period and was negatively associated with sugar consumption (P<0.05). Urease activity in unstimulated saliva increased with age, and it was positively associated with the levels of mutans streptococci in saliva and with the educational level of the parents (P<0.05). CONCLUSIONS The results of this study reveal interesting and complex interactions between oral urease activity and some important caries risk factors. Urease activity in saliva could be an indicator of mutans infection in children.

The effect of sucrose on plaque and saliva urease levels in vivo

OBJECTIVE Dietary sugar exposures induce an immediate drop of the plaque pH. Based on in vitro observations, it was hypothesized that oral bacteria may rapidly respond to this environmental change by increasing the activity or expression of alkali-generating pathways, such as the urease pathway. The objective of this exploratory in vivo study was to determine the short-term effect of a brief sucrose exposure on plaque and saliva urease activity and expression, and to relate this effect to caries experience. METHODS Urease activity levels were measured in plaque and saliva samples collected from 20 children during fasting conditions and 30 min after rinsing with a sucrose solution. Streptococcus salivarius ureC-specific mRNA in saliva was quantified using real-time RT-PCR. The impact of host-related factors, such as age, gender, sugar consumption, salivary mutans streptococci levels and caries status on urease activity was evaluated. RESULTS Plaque urease activity under fasting conditions was higher in subjects with low caries and mutans streptococci levels. This difference was not observed after the sucrose exposure. The response of urease to sucrose in vivo did not depend on caries experience or salivary mutans levels. Significant increase in urease activity of plaque and saliva after exposure to sucrose was observed only in the subjects who had low urease levels at baseline. CONCLUSIONS The findings of this exploratory study suggest that plaque urease activity may have an important long-term influence in caries development but not during a cariogenic challenge.

Analysis of Urease Expression in Actinomyces naeslundii WVU45

ABSTRACT The hydrolysis of urea by ureases of oral bacteria in dental plaque can cause a considerable increase in plaque pH, which can inhibit the development of dental caries. There is also indirect evidence that urea metabolism may promote the formation of calculus and that ammonia release from urea could exacerbate periodontal diseases.Actinomyces naeslundii, an early colonizer of the oral cavity and a numerically significant plaque constituent, demonstrates comparatively low levels of urease activity on isolation, so this organism has not been considered a major contributor to total oral urease activity. In this study it was observed that urease activity and urease-specific mRNA levels in A. naeslundii WVU45 can increase up to 50-fold during growth under nitrogen-limiting conditions. Using primer extension analysis, a putative, proximal, nitrogen-regulated promoter of the A. naeslundii urease gene cluster was identified. The functionality and nitrogen responsiveness of this promoter were confirmed using reporter gene fusions and 5′ deletion analysis. The data indicated that regulation of urease expression by nitrogen availability in A. naeslundiimay require a positive transcriptional activator. Plaque bacteria may experience nitrogen limitation when carbohydrates are present in excess. Therefore, based on the results of this study and in contrast to previous beliefs, strains of A. naeslundii may have the potential to be significant contributors to total plaque ureolysis, particularly during periods when there is an increased risk for caries development.

Urease activity as a risk factor for caries development in children during a three-year study period: a survival analysis approach

UNLABELLED Recent cross-sectional studies suggest that reduced ability to generate alkali via the urease pathway in dental plaque may be an important caries risk factor, but it has not been assessed prospectively. OBJECTIVE To evaluate the effect of plaque and saliva urease activity on the risk for developing new caries over a three-year period in children. METHODS A panel of 80 children, three to six years of age at recruitment, was followed prospectively for three years. Plaque urease activity, saliva urease activity and dental caries were measured every six months. Survival analysis methodology was used to evaluate the effect of urease on caries development during the study period adjusted for gender, age, baseline caries levels, sugar consumption, amount of plaque, and mutans streptococci levels. RESULTS The risk for developing new caries increased in a dose-responsive manner with increasing levels of urease activity in saliva (adjusted HR(Q4 vs. Q1): 4.98; 95% CI: 1.33, 18.69) and with decreasing urease activity in plaque (adjusted HR(Q4 vs. Q1): 0.29; 95% CI: 0.11, 0.76). Multiple measurements of urease activity were conducted to overcome the variability of urease activity in this study. Baseline caries and mutans streptococci in saliva were also important predictors of caries risk. CONCLUSIONS Increased urease activity in saliva can be an indicator of increased caries risk in children, whilst increased urease activity in plaque may be associated with reduced caries risk. The reproducibility of urease measurements must be improved before these findings can be further tested and clinically applied.

Success and complications of implant-retained prostheses provided by the Post-Doctoral Prosthodontics Program, University of Puerto Rico: A cross-sectional study

STATEMENT OF PROBLEM The success rate of implant-retained prostheses in a postdoctoral prosthodontics program was unknown and could not be related to any set of potential clinical issues or patient characteristics. PURPOSE The purpose of this study was to determine the success rate of implant-retained prostheses placed by prosthodontic residents between 1997 and 2012 and to evaluate the associations between patient classifications and specific restoration characteristics as related to prosthesis success or failure. MATERIAL AND METHODS A total of 272 prostheses in 119 patients were clinically evaluated. Success was defined as the absence of prosthetic complications or any implant-related complication that affected prosthesis survival. Logistic regression was used to evaluate associations between prosthesis success/failure and a wide array of study variables, adjusting for patient age, sex, and prosthesis longevity. RESULTS The overall success rate was 71%, with a mean prosthesis age of 4.5 years (range: 4 months to 16.8 years). Implant single crowns were the most successful prosthesis type (81% success). The most common complications observed were porcelain fractures in fixed dental prostheses (15%) and lack of stability (31%) and retention (29%) in removable dental prostheses. Having a removable prosthesis (versus natural dentition) in the opposing occlusion significantly decreased the odds of success (OR=0.26, 95% CI: 0.11-0.64). Definitively cemented fixed prostheses were more successful than those cemented with an interim cement (OR=4.56, 95% CI: 1.37-15.22). CONCLUSIONS The overall success rate of the implant-retained prostheses placed in the program was low compared with previously published studies. This study revealed the need for an efficient, comprehensive recall system for patients receiving implant-retained prostheses, either fixed or removable.

Association between Type, Amount, and Pattern of Carbohydrate Consumption with Dental Caries in 12-Year-Olds in Puerto Rico

Objective: To identify the types, food sources, and pattern of carbohydrates that significantly contribute to dental caries in Puerto Rican children. Methods: As part of an island-wide cross-sectional oral health study in 1,587 twelve-year-olds, diet intake was assessed in a representative subset (n = 801) with a 24-hour dietary recall. Carbohydrate intake was quantified using a computer-based diet analysis program. Caries was assessed using the National Institute of Dental and Craniofacial Research diagnostic criteria. Odds ratios were used to associate carbohydrate intake quartiles with caries, after controlling for important confounders. Results: A total of 723 subjects had complete data. Most were females (54%) and attended public schools (77%). The caries prevalence was 33%. The highest quartile intake for the following sugars significantly increased the odds of caries compared to the lowest quartile: total carbohydrates (OR = 1.93, 95% CI = 1.08-3.46), total sugars (OR = 1.88, 95% CI = 1.01-351), sucrose (OR = 2.05, 95% CI = 1.13-3.70), fructose (OR = 1.95, 95% CI = 1.05-3.62), and inositol (OR = 2.52, 95% CI = 1.38-4.63). The main food sources of these sugars were juices, including natural juices with no added sugars, and sweetened beverages. The odds of caries also increased significantly in children whose 10% of total energy intake was from total sugars (OR = 3.76, 95% CI = 1.03-13.7). Conclusion: After adjusting for important caries risk factors, total carbohydrates, total sugars, ≥10% kilocaloric energy from total sugars, and sucrose, fructose, and inositol intake significantly increased caries risk. Our findings can help raise awareness about the potential caries risk from the main sources of these sugars, natural fruit juices and sweetened beverages, which are consumed in great quantities in many societies.