Research
Student Table Clinic Abstracts, 2003

The School of Dentistry has a long and distinguished history of encouraging student research. Competition is keen among both dental hygiene and dental students to develop a table clinic that firstly earns recognition during the annual School competition and secondly might get picked for state and national competition. But in addition to providing a few students with recognition, the table clinic program offers an unparalleled opportunity for all students to get first-hand experience about research.

Here are the table clinics that placed in the 2003 School of Dentistry competition. In total, 44 projects were entered. The abstracts have been shortened significantly due to space constraints. If anyone is interested in a more comprehensive report of any study, please contact the editor.

Pictured from left, SD'04 students: Linda Valleni, Andrea Carvalho, and Jean Chalker.

• Effectiveness of Electronic vs. Manual Toothbrushes in Plaque Control on Grade School Children

Faculty mentor: Dr. Wesley Okumura, assistant professor, pediatric dentistry

Statement of problem: The purpose of this study was to compare the efficacy of manual toothbrushing versus battery-powered toothbrushes in grade school children.

Materials and methods: Participants consisted of forty grade school students. All students were instructed in basic oral hygiene methods before testing began. Toothbrush types were randomly distributed and evaluations were conducted weekly. Evaluations consisted of recording plaque scores before and after the participants used their toothbrushes.

Results: The results indicated that post-brushing plaque scores for both the manual and electronic toothbrush was statistically lower than the pre-brushing plaque score (p<0.001). However, the electronic toothbrush was significantly more effective than the manual in the total removal of plaque.

Pictured from left, SD'04 students: Melissa Ramsey, Malia Kearbey, and Sam Alazyat.

• The Effectiveness of Three Maxillary Splints on Myofascial Pain

Faculty mentor: Dr. Michael Fitzpatrick, assistant professor, restorative dentistry

Statement of problem: A common treatment for myofascial pain is occlusal splints. The purpose of this study was to determine the effectiveness of three maxillary splints and their effect on myofascial pain.

Methods and materials: Twenty-one subjects with moderate and severe pain were randomly assigned to one of three splints. Splints were fabricated in the lab using ortho acrylic, and were relined and adjusted with articulating paper at chairside to ensure that centric stops, anterior guidance by anterior teeth, with no posterior interferences were established. A post-treatment clinical exam was performed identical to the initial exam to compare pain responses before and after splint therapy.

Results: All three splint types were statistically significant in reducing myofascial pain and the subjects reported a decrease in muscle pain, a reduced frequency of headaches, and a better quality of sleep. In addition, the post-treatment exam revealed that range of motion increased and there was improvement of muscle coordination in excursive movements.

Pictured from left, SD'04 students: David Wilcox, Misty Hendricks, and Nathan Dinsbach.

• Comparative Effects of an Essential Oil Mouthrinse and Dental Floss on Interproximal Plaque and Gingivitis

Faculty mentor: Dr. Yiming Li, professor and associate director, Center for Dental Research

Statement of problem: Dental flossing is considered the standard for the interproximal removal of plaque. However, many consider flossing a chore or have manual dexterity problems and therefore do not floss. The purpose of this study was to determine if an essential oil mouthrinse would be as effective on interproximal plaque and gingivitis as dental floss.

Methods and materials: Fifty-two subjects participated in a single-blind study, and were randomly divided into two groups. Group A used 20 ml of essential oils mouthrinse twice a day for 30 seconds after brushing. Group B used floss once a day in addition to brushing. After three weeks, each subject had a final plaque and gingival index score recorded.

Results: After a three-week period, there was no statistical difference between a group using dental floss and one using essential oil mouthrinse with respect to plaque and gingival index scores.

Pictured from left, SD'04 students: Mike Clark, Jon Miler, and Chad Ordelheide.

• Determining the Clinician's Ability to Evaluate Total Occlusal Convergence in Single Crown Preparations

Faculty mentor: Dr. Doyle Nick, assistant professor, restorative dentistry

Statement of problem: There is an ideal total occlusal convergence (TOC) for single crown preparations. The purpose of this study was to assess dental clinicians' accuracy in visually determining TOC.

Materials and methods: Thirteen maxillary first molar typodont teeth were prepared to a known degree using a milling machine. The teeth were prepared in a spectrum from -3 to 30 degrees, and 30 dental students and 30 LLUSD faculty members were asked to identify teeth with ideal preparations, maximum allowed taper, minimum allowed taper, and the TOC associated with each.

Results: Students significantly underestimated the amount of TOC in all categories. On average, the students were 6.27 degrees off their evaluation of total occlusal convergence in the ideal preparation and 7.93 degrees off in their evaluation of the maximally acceptable preparation. Faculty significantly underestimated the degree of total occlusal convergence for the maximally acceptable preparation. Only 16% of students and 33% of the faculty were within 3 degrees of the actual TOC for ideal preparation.

Pictured from left, SD'04 students: Lucelia Lima, Yarimell Perez, and Gabriel Enriquez.

• Effect of Delayed Activation of Light-Cured Resin Composites on Dentin Bonding Agents

Faculty mentor: Dr. Carlos Muñoz, director, Center for Dental Research
Statement of problem: Composite resins have become a popular esthetic restoration, but these technique-sensitive materials lack high bond strength characteristics. The purpose of this study was to evaluate the effect of delayed polymerization on bond strength when using resin composites on dentin. Both all-in-one and conventional adhesives were tested.

Materials and methods: Human molars were sectioned longitudinally through the mesial and distal surfaces. Tooth specimens were etched/conditioned, with the bonding agents per manufacturer's instructions carefully following how to condition the moisture content of the dentin prior to bonding. The UPI Bond Testing System was used per manufacturer's instruction to create the bonded specimen. A microhybrid composite resin was used. The first group was tested immediately. Following groups were tested at 5, 10, and 20 minute intervals. Ten teeth from each group were tested for bond strength immediately and ten were tested after 24 hours.

Results: For the immediate group, results showed for the conventional type bonding system at zero minutes; the bond strength is 37 Mega Pascals (MPa); at 5 min the bond strength is 25.62 MPa; and at 20 min it decreased to 6.21 MPa. For the self-etching system at zero min the bond strength was 24.73 MPa; 5 min was 14.64 MPa; and at 20 min it had decreased to 5.58 MPa. For the conventional type at 24 hrs the bond strength decreased 90% after 20 min. For the Self-etching type, also at 24 hrs, the bond strength decreased 85% after 20 min. Previous studies have indicated that bond strength of 25 MPa, is the minimum bond strength needed to achieve satisfactory results.

Conclusion: Delaying the polymerization of the composite resins decreases the bond strength for the conventional dentin bonding agents if polymerization of the composite is not made within the first 5 minutes of composite placement. For the self-etching system, the composite should be polymerized immediately to prevent a decrease in bond strength.

Pictured from left, SD'04 students: Sung Cho, Daehong Kim, and John Zhang.

• Effects of Increasing Concentrations of CHX on Two Persistent Dental Water Line Bacteria

Faculty mentor: Dr. James Kettering, professor, basic science faculty, School of Medicine

Introduction: Biofilm in dental unit water lines is a big concern in dentistry. Use of an antimicrobial agent, chlorhexidine (CHX), is standard protocol at LLUSD. However, after long term usage, Pseudomonas picketti and Methylbacterium mesophilicum have been found to be resistant to the current standard CHX concentration of 0.0125%. The purpose of this study was to determine the optimal CHX concentration necessary to eliminate P. picketti and M. mesophilicum from dental unit waterlines.

Materials and methods: A water sample was collected from a dental unit waterline to isolate Chlorhexidine (CHX)-resistant microorganisms. The concentrations of CHX tested were 0.01% (standard market concentration is 0.0125%), 0.1%, 0.5%, 1.0%, 5.0%, 10.0% and 20% (the highest available concentration on the market).

Results: As the concentration of CHX increased, the average zone of inhibition became larger. The minimum concentration of CHX to inhibit both types of the bacteria was 0.2%. As a control group, S. aureus and S. mutans were tested against CHX. Even the lowest concentration of CHX concentration was effective in eliminating these two control groups of microorganisms.

Conclusion: The research data showed that a CHX concentration of 0.5% gives the best inhibition of P. picketti and M. mesophilicum when compared to a current standard concentration 0.0125%. However, this 0.5% concentration might be too high for safe human use. By following a standard dental unit waterline disinfection protocol such as running the water for 15 seconds before one sees a patient, higher concentrations of CHX will be diluted and a dental unit waterline will be safe to use.

Pictured from left, SD'04 students: Derek Chu, Maile Kim, and Sean Lee.

• The Adventures of Homer and Henry: The Dental Visit

Faculty mentor: Dr. Maria Sheu, assistant professor, pediatric dentistry

Statement of problem: Many children in the United States have an inadequate knowledge of oral health and how to prevent dental diseases. Our goal was to create a multimedia educational dental experience for children.

Materials and methods: The story about Homer's and Henry's visit began with writing the screenplay. The characters were then sketched and backgrounds were designed using a Walcom Tablet and Macromedia Flash MX. After developing a storyboard to plan each scene, the animation process was started. The characters' voices were recorded using a Mackie CFX12 Mixer and Sony MZ-R30 MiniDisc Recorder. The musical score was created using the Korg Triton Pro-X Workstation. Individual scenes were sequenced together and the audio files were integrated using SoundJam MP Plus 2.5 and Adobe Premiere 6.0.

Results: A story was created about two puppies, Homer and Henry. Homer is scared to go the the dentist and Henry reassures him that the dental visit will be fine. Games were also incorporated into the story so children would be able to demonstrate their oral health knowledge.

Pictured from left, DH'03 students: Miriam Skala, Jennifer Moss, and Vicki Sindell.

• Commercially Available Streptococcus Mutans Strip Test Confirms Long-term Chlorhexidine Substantivity

Faculty mentors: Dr. George M. Lessard, professor, department of biochemistry; William Keeler, staff advisor, department of microbiology and molecular genetics; and Dr. James D. Kettering, professor, basic science faculty, School of Medicine

Statement of problem: Studies show 0.12% chlorhexidine (CHX) is a substantive, broad-range antimicrobial. This research evaluated the utility of commercially available strip tests, and to determine the duration of antimicrobial effects of CHX on Streptococcus mutans for six months.

Materials and methods: Twenty-seven subjects had baseline S. mutans levels established. Two weeks later, subjects were retested to confirm count stability. Subjects rinsed for two weeks with 15 ml of CHX mouthrinse for 30 seconds, morning and evening. Samples were then collected and tested to determine S. mutans levels. The antimicrobial effects were tested at ten weeks and six months. Each sample was tested using one S. mutans strip, and plated in triplicate on MSB agar plates.

Results: After CHX treatment, significant reduction of colony counts was measured. Twenty-three of 27 strips concurred with plate counts. Ten weeks after CHX treatment, strip tests revealed continued bacterial reduction. Six-month post treatment results are in progress.

Conclusions: Analysis (Sign Test) showed significant reduction of S. mutans after the two-week CHX treatment, confirming CHX effectiveness in reducing S. mutans levels.

Pictured from left, DH'03 students: Kristin Allen, Kelly Noto, and Sharisa Mellor.

• Comparison of Endoscopic and Tactile Detection of Calculus

Faculty mentors: Kris Wilkins, assistant professor and chair, dental hygiene; and Shirley Lee, assistant professor, dental hygiene

Statement of problem: Dental hygienists rely on tactile sensitivity to detect calculus. Endoscopic technology can identify calculus through visualization. This study compared tactile detection of calculus to endoscopic visualization.

Methods and materials: Fifty-two posterior tooth surfaces with moderate calculus were evaluated. Prior to root planing, the student recorded a calculus assessment. The student used tactile sensitivity with an ODU 11/12 explorer to determine treatment completion. Residual calculus was documented and classified by shape into one of six categories.

Results: Tactile and endoscopic detection of residual calculus concurred 1/3 of the time. Increased tactile sensitivity was observed while using the explorer, compared with the ability to access and adapt the endoscope. Decreased visibility due to tissue, blood, and water was observed with the endoscope.

Pictured from left, DH'03 students: Ramon Villanueva, Esther Sohn, and Adrian Lugo.

• Chlorhexifloss: Preparation and Antimicrobial Activity

Faculty mentors: Dr. E. Clifford Herrmann, associate professor, biochemistry and microbiology; and Dr. George M. Lessard, professor, department of biochemistry

Statement of problem: Minimizing plaque by physical removal and chemical inhibition of formation are independent roles of floss and chlorhexidine (CHX). This study targeted combining the two agents.

Materials and methods: Triplicate sets of three types of floss were treated as follows: immersed 42 hours in separate 0.12 % and 20% CHX solutions, then dried at room temperature for 24 hours. The capacity of floss to carry CHX was equated to the amount subsequently leached from treated floss. A 20 mm piece of each type of treated floss was placed on agar salivarus and saccharose plates
inoculated with S. mutans. Zones of inhibition were measured.

Results: The mean absorbed 0.12% CHX values were: sponge floss (0.38 mg), waxed floss (0.35 mg), and unwaxed floss (0.15mg) following 0.12% CHX treatment. Floss treated in 20% CHX gave values of 188, 98, and 93 mg, respectively. The zones of inhibition exhibited by floss were proportional to the CHX treatment concentrations.

Conclusion: CHX can be incorporated into dental floss, the sponge and unwaxed flosses having greater capacity.

Pictured from left, DH'03 students: Louree Afenir, Imelda Dixon, and Michael Tobola.

• Evaluation of Four Over-the-counter Oral Health Care Products

Faculty mentor: Dr. James D. Kettering, professor, basic science faculty, School of Medicine

Statement of problem: Recently, several toothpastes containing antimicrobial compounds have been formulated. The purpose of this study was to compare the efficacy of these toothpastes to toothpaste alone within a controlled environment.

Material and methods: Streptococcus mutans (S. mutans), Candida albicans (C. albicans) and Staphylococcus aureus (S. aureus) were spread on trypticase soy agar (TSA) plates using a spinner to produce a "lawn of bacteria." Four 6mm sterile paper discs were placed on each TSA plate to test the liquid and gel products. The regular toothpaste was tested using four 6 mm sterile plastic cylinders and placed on a separate TSA plate. A positive control of chlorhexidine gluconate mouthwash and negative control of phosphate-buffered saline solution were also tested. Plates were incubated for 24 hours at 370 C and zones of inhibition were then measured in millimeters and recorded.

Results: Combination toothpaste B was found to be the best antimicrobial agent in eliminating S. mutans while combination toothpaste A was the best antimicrobial against C. albicans. All three toothpastes were found to be equally effective antimicrobial agents for S. aureus.

Pictured from left, DH'03 students: Julie Weiss, Christine Gill, and Julie Gray.

• The Sterilization of Low Speed Hand Pieces using Chlorhexidine.

Faculty mentor: Dr. James D. Kettering, professor, basic science faculty, School of Medicine

Statement of problem: Since the pressure of the autoclave is extremely hard on low-speed hand pieces' inner workings, our study looked at finding another method as efficient as the autoclave which would not harm the instruments.

Methods and materials: Five low-speed hand pieces were autoclaved to sterilize them. A culture of Stapholococcus epidermidis was grown overnight. The hand pieces were soaked in a 90 ml suspension of S. epidermidis for 30 seconds and then transferred to a sterile pan. The hand pieces were soaked in chlorhexidine gluconate at different time intervals (10, 15, 20 minutes). Upon completion of the specific time, the hand pieces were rinsed in 75 ml of sterile water and shaken 10 times each. Then, 100 ml of the rinse was plated onto ten Trypticase Soy Agar plates and put in the warm incubator at 37 degrees C overnight. The plates were checked for growth or no growth. Colonies were counted and computed for colony forming units per ml (CFU). The controls were not soaked in chlorhexidine.

Results: After testing each group of low-speed hand pieces, it was found that groups soaked for 10 and 15 minutes in chlorhexidine gluconate had bacterial growth. Groups of hand pieces soaked for 20 minutes proved to have no bacterial growth.

Clinical significance: Dental offices currently using an autoclave to sterilize their low-speed hand pieces should consider using chlorhexidine as an alternative because it is as fast and effective as the autoclave without causing major damage to the instrument.