Browsing by Author "Diefenderfer, Kim"

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    Are new dentists prepared for clinical practice? A survey of the clinical abilities of new dental graduates in the U.S. military
    (2024) Chiodo, Kathleen; Cook, N. Blaine; Capin, Oriana; Diefenderfer, Kim; Adcook, Richard
    Objective: This study aimed to identify new dentists’ competence in preventive and restorative procedures, as self-assessed by the new dentists and evaluated by their clinical supervisors. Justification: Preventive and restorative dental procedures constitute the majority of treatment provided daily in a general dentistry practice. Exploring new dentist proficiency in these foundational skills within one year of dental school graduation provides crucial information regarding the knowledge and skills new dentists attain during dental school. The military dental system is structured so that all new dentists receive close clinical oversight during their first year following graduation. Hypotheses: (1) The majority of dentists who have graduated less than one year prior to this survey will self-assess their skills in basic preventive and restorative dental procedures as “competent” or higher. (2) The majority of supervisor evaluations of new dentists will also average a level of “competent” or higher. (3) New dentists will self-assess their competence levels higher than their supervisors will evaluate them. Methods: An electronic, anonymous Qualtrics survey was sent to U.S. Air Force, Army and Navy new dentists and their clinical supervisors November 2022. Using a modified-Dreyfus model of skill acquisition, new dentists completed a self-assessment of 20 preventive and restorative procedures. Their clinical supervisors also completed a survey evaluating the proficiency level of the new dentists they oversaw. Results: 60 new dentists and 25 supervisors, accounting for 151 new dentists, responded. The proportion of competence ratings at a level of “competent” or higher (“proficient,” “expert”) was estimated, along with a 95% confidence interval, and one-sample chi-square tests were used to compare the proportion against 50%. Supervisors’ ratings of the new dentists’ skill levels were significantly lower than the new dentists’ ratings for 19 of the 20 dental procedures. Supervisors’ ratings of competent or higher were significantly greater than 50% in caries diagnosis and treatment planning, caries risk assessment, Class III anterior composite resins and posterior composite resins. Overall, supervisors rated 71.3% of new dentists at Novice or Beginner skill level. Conclusion: Supervisor ratings of the new dentists’ skill levels were significantly lower than the dentists’ ratings for the majority of procedures. New dentists and supervisors significantly disagreed on new dentists’ skill levels in the treatment of class I and II amalgams, endodontically treated teeth without a post, and crown preparation and delivery. Overall, 28.7% of new dentists were evaluated as competent in preventive and restorative procedures during their first year following dental school graduation.
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    Chlorhexidine-modified nanotubes and their effects on the polymerization and bonding performance of a dental adhesive
    (Elsevier, 2020-05) Kalagi, Sara; Feitosa, Sabrina A.; Münchow, Eliseu A.; Martins, Victor M.; Karczewski, Ashley E.; Cook, N. Blaine; Diefenderfer, Kim; Eckert, George J.; Geraldeli, Saulo; Bottino, Marco C.; Cariology, Operative Dentistry and Dental Public Health, School of Dentistry
    Objectives: The purpose of this study was to synthesize chlorhexidine (CHX)-encapsulated aluminosilicate clay nanotubes (Halloysite®, HNTs) and to incorporate them into the primer/adhesive components of an etch-and-rinse adhesive system (SBMP; Scotchbond Multipurpose, 3M ESPE) and to test their effects on degree of conversion, viscosity, immediate and long-term bonding to dentin. Methods: CHX-modified HNTs were synthesized using 10% or 20% CHX solutions. The primer and the adhesive components of SBMP were incorporated with 15wt.% of the CHX-encapsulated HNTs. Degree of conversion (DC) and viscosity analyses were performed to characterize the modified primers/adhesives. For bond strength testing, acid-etched dentin was treated with one of the following: SBMP (control); 0.2%CHX solution before SBMP; CHX-modified primers+SBMP adhesive; SBMP primer+CHX-modified adhesives; and SBMP primer+CHX-free HNT-modified adhesive. The microtensile bond strength test was performed after immediate (24h) and long-term (6 months) of water storage. Data were analyzed using ANOVA and Tukey (α=5%) and the Weibull analysis. Results: DC was greater for the CHX-free HNT-modified adhesive, whereas the other experimental adhesives showed similar DC as compared with the control. Primers were less viscous than the adhesives, without significant differences within the respective materials. At 24h, all groups showed similar bonding performance and structural reliability; whereas at the 6-month period, groups treated with the 0.2%CHX solution prior bonding or with the CHX-modified primers resulted in greater bond strength than the control and superior reliability. Significance: The modification of a primer or adhesive with CHX-encapsulated HNTs was an advantageous approach that did not impair the polymerization, viscosity and bonding performance of the materials, showing a promising long-term effect on resin-dentin bonds.
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    Effect of Chlorhexidine-Encapsulated Nanotube-Modified Adhesive System on the Bond Strength to Human Dentin
    (2019) Kalagi, Sara Arfan; Cook, N. Blaine; Diefenderfer, Kim; Bottino, Marco; Feitosa, Sabrina
    Introduction: The resin-dentin interface undergoes degradation by endogenous matrix metalloproteinases (MMPs) after adhesive procedures. Application of several MMP inhibitors such as chlorhexidine (CHX) to the demineralized collagen dentin matrix after acid-etching has been suggested to be a successful approach to prevent degradation of the hybrid layer. Further, nanotubes (HNT) have been used as a reservoir for encapsulation and controlled delivery for several therapeutic drugs with sustained release. Therefore, HNT can be encapsulated with CHX and incorporated into dentin adhesives for the possibility of enhancing the longevity and durability of the hybrid layer. Objective: To evaluate the effect of a CHX-encapsulated nanotube-modified primer/PR and adhesive/ADH on the microtensile resin bond strength (µTBS) to dentin. Materials and Methods: A commercial adhesive and its respective primer were modified by adding CHX-encapsulated nanotubes at two distinct concentrations (10 and 20 wt.%). The experimental adhesives were evaluated by degree of conversion (DC) and viscosity. Meanwhile, only viscosity was determined for the experimental primers. The prepared HNT-encapsulated with CHX (10 and 20 wt.%) powders were incorporated into the primer and/or adhesive according to the groups: ADH (control); HNT (control); 0.2% CHX; PR+CHX10%; PR+CHX20%; ADH+CHX10%; ADH+CHX20%. Human molars were selected and autoclaved; mid-coronal dentin surfaces were exposed for bonding purposes. Dentin surfaces were etched, followed by primer and adhesive application, and restored with a resin composite. After 24 hours, the teeth were sliced into beams for µTBS testing; beams collected for each tooth were equally assigned into two testing condition groups: 24 hours and 6 months. Microtensile bond strength was tested using a universal testing machine, and the types of failure were classified as adhesive, mixed, and cohesive failure. Data from DC and viscosity tests were analyzed using one-way ANOVA. Bond strength data were analyzed by pair-wise comparisons using the Sidak method to control the overall significance level at 5% for each aging time separately. Weibull-distribution survival analysis was used to compare the differences in the microtensile bond strength results among the groups after 24 hours and 6 months. Results and Conclusion: DC analysis revealed no significant differences among adhesive groups. However, ADH group had a significantly lower viscosity than modified adhesive groups, and a significantly higher viscosity than modified primer groups. Test results of stress value (MPa) by each group for each aging time revealed no significant differences among groups after 24 hours. However, after 6-month storage, modified primer groups (PR+CHX10%, PR+CHX20%) and 0.2%CHX group showed a significant difference in µTBS compared to control groups (ADH, HNT) and modified adhesive groups (ADH+CHX10%, ADH+CHX20%) in the same aging time testing (p < 0.05). When comparing the µTBS after 24 hours and 6 months, there were no significant differences among the groups except for the ADH+CHX20% group, for which MPa values were higher after 24 hours than 6 months (p = 0.0487). In conclusion, this study has demonstrated the great potential of modified dental primers with CHX-encapsulated nanotubes in preservation of the resin-dentin bond strength over a 6-month time period. Additionally, modification of dental primers and adhesives was a successful approach that didn’t compromise the characteristics or the mechanical properties of the materials and has a promising long-term effect on resin-dentin bond strength.
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    In-Vitro-Simulated Occlusal Tooth Wear Monitoring by Polarization-Sensitive Optical Coherence Tomography
    (2019) Alwadai, Ghadeer; Hara, Anderson T.; Diefenderfer, Kim; Lipppert, Frank; Cook, Norman
    Background: Erosive tooth wear (ETW) is the loss of tooth substance due to chemo-mechanical action unrelated to bacteria. ETW affects approximately 46 percent of children/adolescents and 80 percent of adults in the U.S. Visual examination indices are available for the clinical assessment of ETW. Although useful, they are subjective and heavily based on the clinical experience of the examiner. Some quantitative techniques have been proposed and used for clinically assessing erosive tooth wear, including quantitative light-induced fluorescence, ultrasonic measurement, and more recently, polarization-sensitive optical coherence tomography (PS-OCT). Objective: The objective of this study was to explore the ability of PS-OCT to objectively measure erosive tooth wear on occlusal surfaces. Method: This study was conducted in two phases. In the first phase, 10 sound extracted human lower first premolars were selected and then exposed to tooth wear simulation gradually. PS-OCT and micro computed tomography (μ-CT) were used to evaluate enamel thickness of those premolars at the buccal cusp tip during the simulation. In phase 2, 40 extracted human lower first premolars with different severity levels of ETW on occlusal surfaces were selected based on the Basic Erosive Wear Examination (BEWE) index. A total of 10 teeth (n =10) were selected for each BEWE score (0/1/2/3). PS-OCT and μ-CT were used to evaluate the enamel thickness at the highest point on the occlusal surface. Results: There was good agreement between PS-OCT and μ-CT in both phases (phase 1: 0.89 and phase 2: 0.97) with no significant difference between PS-OCT and μ-CT. Conclusion: This result shows the potential of PS-OCT as reliable method for measuring enamel thickness and monitoring tooth wear progression on the occlusal surface
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    Stepwise stress testing of different CAD/CAM lithium disilicate veneer application methods to lithium disilicate substructure
    (2019) May, Jaren Thomas; Feitosa Sochacki, Sabrina; Diefenderfer, Kim; Cook, N. Blaine
    Objective: CAD/CAM technology allows fabrication of thin lithium disilicate (LD) veneers to a LD crown substructure in place of using traditional feldspathic porcelain (FP) which has inferior mechanical properties. This project investigated the effect of different LD veneer applications to LD substructure on the biaxial flexural fatigue of LD veneer/substructure restorations. Materials/Methods: Forty-five LD discs (Ø = 120.7 mm) were fabricated that, when combined with the veneering discs, achieve final dimensions of (Ø = 121.2mm). Experimental groups were (n = 15) as follows: (1) Resin Bonded LD Veneer (RBLDV), LD veneer (Ø = 120.5 mm) adhesively cemented to LD (0.7 mm); (2) Sintered LD Veneer (SLDV), LD veneer (Ø=120.5 mm) sintered to LD (0.7 mm); (3) Sintered Feldspathic Veneer (SFV), feldspathic porcelain (FP) applied to LD discs to achieve a final dimension of (Ø = 121.2 mm). A fourth group of (1.2 mm) monolithic LD served as the control. Weibull-distribution survival analysis was used to compare the differences of the resistance to fracture after fatigue between groups. Total number of cycles were analyzed using one-way Anova (p < 0.05). Hypothesis: Adhering or sintering a thin laminate layer of LD on another LD surface would result in increased fracture resistance in comparison to sintered FP on LD. Results: The SFV group had significantly lower fatigue resistance than SLDV and RBLDV groups (p < 0.05). The RBLDV group fractures resulted in significantly more fractured fragments in comparison to the other groups. No statistical difference was observed in the number of cycles. The results also showed that the LD veneered groups presented similar resistance to fatigue as monolithic discs of the same overall dimensions. Conclusion: The hypothesis was accepted suggesting that veneering a LD substructure with a LD veneer, bonded or sintered, has increased resistance to fatigue as FP veneering material on a LD substructure. In addition, it was observed to have similar resistance to fatigue in comparison to the monolithic LD group.