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



Introduction: Selenomonas noxia (SN) is a gram-negative, anaerobic bacteria, which contributes to development and progression of periodontal disease. Some evidence now suggests Streptococcus mitis (SM), a gram-positive, facultative bacterium contributing to the etiology of dental caries and periodontal disease, may also influence the prevalence of SN within subgingival complexes. Based upon the overall lack of prevalence data, the objective of this study was to evaluate presence of SN and SM using qPCR among saliva samples taken from pediatric, adult, and orthodontic dental school clinics.

Methods: This study involved a retrospective analysis of previously collected saliva samples from an existing biologic repository. Screening for microbial presence of SN and SM was performed in duplicate using quantitative polymerase chain reaction or qPCR.

Results: From the repository containing N=1,176 samples, a total of n=196 samples were identified. Screening for SN revealed significantly higher prevalence among Pediatric Orthodontic samples (28.3%) compared with Adults (5.5%), P=0.001. No significant differences were found between Pediatric non-Orthodontic samples (16.7%) and Adult non-Orthodontic samples (12.5%), P=0.2343. Screening for SM revealed similar prevalence among Adult Orthodontic (27.8%) compared with Pediatric Orthodontic (31.7%) samples, P=0.3912. However, significant differences were observed between Pediatric non-Orthodontic (46.7%) and Adult non-Orthodontic samples (17.5%), P=0.0001.

Conclusions: This study is among the first to evaluate SN and SM co-occurrence among Pediatric and Adult Orthodontic and non Orthodontic patient samples. The increased prevalence of both SN and SM among Pediatric patients, and Orthodontic samples more specifically, may suggest further research is needed to more fully understand the oral health risks facing these specific patients. The differential results in co-occurrence only observed among the Orthodontic patients may also suggest orthodontic therapy may be sufficient to alter oral behaviors or the oral habitat thereby altering the oral microbial constituents and possibly changing oral health and the risk for developing oral disease.


Clinical patient; qPCR screening; Selenomonas noxia; Streptococcus mitis



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1166 KB

Degree Grantor

University of Nevada, Las Vegas




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Microbiology Commons