Award Date


Degree Type


Degree Name

Master of Science (MS)


Dental Medicine

First Committee Member

Karl Kingsley

Second Committee Member

Katherine Howard

Third Committee Member

Brian Chrzan

Fourth Committee Member

Courtney Coughenour

Number of Pages



Background: Dental cavities or caries have been identified as among the most prevalent of preventable oral conditions. However, studies are discovering new information regarding the incidence and prevalence of several cariogenic organisms, including Streptococcus mutans (SM), the recently discovered Scardovia wiggsiae (SW), as well as Streptococcus sobrinus (SS). These studies have revealed varying prevalence among different populations, such as those undergoing orthodontic treatment. Based upon this information, the main goal of the current study was to assess the prevalence of specific cariogenic organisms (SS and SW) within saliva samples originally obtained from a dental school-based clinic.

Methods: The protocol for this retrospective study of DNA isolated from previously collected saliva samples was reviewed and approved by the Institutional Review Board (IRB) as exempt research. In brief, clinical DNA samples were screened for SS and SW using quantitative polymerase chain reaction (qPCR). Demographic and subgroup (Orthodontic, non-Orthodontic) analysis was also performed.

Results: This study found that pediatric (12-17 year old patient) samples were much more likely to harbor either SW or SS compared with adult (>18 year old patient) samples. In addition, this study found many more SW-positive samples among pediatric orthodontic patients compared with either adult or pediatric non-Orthodontic patients, which may suggest this population may be at higher risk for SW-related caries or other negative oral health outcomes. Finally, this study found these microbial populations to be strongly linked within the same patient samples.

Conclusions: This study has demonstrated that prevalence of SW and SS may be more highly associated with specific population subgroups, including SS observed in non-orthodontic patients and SW found among pediatric orthodontic patients. These results also differ from previous evidence, which found only minor and partially overlapping prevalence of these and other oral microbes. The results of this current study may suggest that SS and SW may be more strongly correlated within similar oral microbial communities and their presence may be directly or indirectly linked through one or more behavioral, microbial or other factors – although more research will be needed to determine these mechanisms.


Prevalence; Saliva; Scardovia wiggsiae (SW); Streptococcus sobrinus (SS)



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1031 KB

Degree Grantor

University of Nevada, Las Vegas




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Dentistry Commons