Statement of problem: Utilizing set screws allows easy retrieval of the prostheses with minimum cost and satisfies esthetic requirements. Set screws use is mostly governed by retrospective, anecdotal and clinical reports. The purpose was to investigate the difference in reverse torque values of fatigued one set screw or two set screws used to retain straight or curved implant prostheses in vitro. Materials and methods: Milled substructures (straight and curved) and cast superstructures retained by one or two set screws were used. There were four groups (n=8). Set screws were tested for changes in reverse torque values after simulated chewing of six months. Data (Ncm) was analyzed using 2-way ANOVA (p≤0.05). Results: No statistically significant difference in the reverse torque values between prostheses retained by one set screw and two set screws (F = 0.18, p = 0.67) or between prosthesis retained on curved bars and straight bars (F = 0.42, p = 0.52). No significant interaction was found in the reverse torque values between the number of set screws and substructure design (F = 0.32, p = 0.58). Conclusions: Under functional loading the reverse torque values are not affected by the design of the prosthesis or the number of set screws used to retain the prosthesis.

Migraine is a recurring moderate to severe, unilateral, disabling headache that can result in a progressive, chronic disease state. Migraine attacks can be triggered by factors or events, which precede the attack. Multiple trigger factors have been reported including alcohol intake. In this research project, we developed an animal model of chronic migraine, in which signs of migraine can be triggered by alcohol administration. In this animal model, repeated administration of potassium chloride to the dura, sensitizes dural afferents and renders animals susceptible to alcohol-induced ongoing pain, and hyperalgesia. Unlike most of the animal models of migraine headaches that relied exclusively on reflexive measures of evoked pain, we tested for the presence of ongoing pain after repeated potassium chloride administration to the dura. We used the conditioned place preference paradigm and the rat grimace scale tests to test the ongoing pain. Our results show that repeated potassium chloride administration to the dura caused aversion of rats to potassium chloride paired chamber. Following Alcohol IV administration, the rats present with a significant, time dependent increase in orbital tightening score, which suggest that the animals develop pain, a sign of migraine headache. Our results suggest a probable association between alcohol and development of ongoing pain in animals receiving repeated administration of potassium chloride. This model can be used to investigate the pathophysiology of alcohol-induced migraines and how it is initiated.

Dentinal hypersensitivity (DH) is characterized by temporary, sharp-shooting pain arising from exposed dentin in response to different types of stimuli, such as thermal, mechanical, osmotic or chemical elements This study looked the treatment of dentinal hypersensitivity (DH) by utilizing magnetic nanoparticles (MNPs). DH was simulated by creating a class V preparation on an extracted human tooth. 72 samples were divided into two groups. Three different MNPs (100nm, 300nm, 500nm) were applied to the class V preparation. A magnet was placed on the opposing side of the class V preparation for the experimental group. No magnet was used for the control group. All samples were decalcified, sectioned and mounted for visualization of MNPs through light and fluorescent microscopes. The percentage of dentinal tubule penetration of the three different MNP groups was calculated by measuring the total depth of the dentinal tubule from the inner surface of the preparation to the pulp. The second measurement was from the inner surface of the preparation to the depth that the MNPs travelled. Data were analyzed using ANOVA and Tukey's Honestly Significant Difference test. Overall, Smaller magnetic nanoparticles have a significantly higher percentage of dentinal tubule penetration than the larger magnetic nanoparticles with or without an external magnetic field (p≤.0005). There was no significant difference between the percentage of dentinal tubule penetration of 300nm and 500nm in control group. A significantly higher percentage of dentinal tubule penetration was found with application of the external magnetic field (p≤.0005). In conclusion, MNPs could potentially be utilized for DH treatment.

Purpose of this study was to evaluate the effect of different Locator abutment heights on the retention of overdentures. This study was conducted using four sets of edentulous mandible analogs with implants positioned at different depths relative to each other (N=40). Two implant-retained overdenture set-ups with Locator attachments at different vertical levels of 0, 2, 4, 6 mm to each other were tested for changes in peak load-to-dislodgement after simulated chewing of six months. Varying heights of Locator abutments had a significant effect on the retentive values of the pink Locator attachments. The results of ANOVA and Tukey HSD showed that the retention of Groups 0 mm and 2 mm was significantly lower than Group 6 mm. In conclusion, a difference in Locator abutment heights between the two implants did not adversely affect retention, therefore clinicians should choose Locator abutments according to the tissue thickness for implants at different levels.

Dental implants provide a major course of treatment for patients who are partially or completely edentulous. These implants are biocompatible metal anchors that are surgically positioned in the jawbone to support the prostheses where natural teeth are missing. However, the use of dental implants has some disadvantages, which can result in complications. Once the clean implant surface is exposed in the oral cavity, it is immediately coated with salivary pellicle and subsequently colonized by oral microbial species. In fact, microbial adhesion and accumulation on implants are considered to play major roles in the pathogenesis of peri-implant mucositis and peri-implantitis. The physico- chemical characteristics of specific material surface are known to significantly influence the bacterial adhesion process. Therefore, the surface characteristics of dental implants have been refined and restructured over a period of time to improve the interaction of implants with host cells and tissues. Hence, investigating the microbiological aspects related to implant surfaces will provide important insights relevant to expectations of treatment outcome. To that end, in this study, we aimed to comparatively evaluate microbial adherence and accumulation on five different types of implants. Specimens were provided by Dental Implant Systems, Biodenta Group and implant surfaces included: .3- .5 μm anodized surface, 1 μm BST surface, .8- 1.0 μm anodized surface, 1.6μm SLA surface and .3- .4 μm machined surface. To assess microbial adherence, the cariogenic bacterial species Streptococcus mutans and the bacterial pathogen Staphylococcus aureus were studied. Results from these studies were analyzed using analysis of variance (ANOVA) and significant differences were further analyzed by Tukey’s Honestly Significant Difference (HSD) test. Pearson’s r was also used to evaluate the association between surface roughness and bacterial accumulation. The present study has demonstrated that not only surface roughness but other physicochemical properties such as surface charge, energy, wettability and biological factors such as host immune response and oral hygiene influence bacterial adhesion and accumulation around implant surfaces.

Statement of problem: Dental shade guides are used to evaluate tooth color prior to restorative and prosthodontic procedures and are subjected to disinfection after use. The effect of disinfection on shade guides has not been thoroughly investigated. Purpose: The purpose of this project was to study the effect of disinfectants on changes in color of shade tabs. Materials and Methods: Changes in color (Delta E) of Vita Classic Shade Guide tabs were measured with a Vita Easyshade spectrophotometer and calculated after being subjected to Cavicide, Asepticare TB, Sporicidin, and distilled water (control) over a simulated two-years period. Statistical analysis was accomplished by a two-way analysis of variance followed by Tukey's HSD test (p<0.05) Results: There was a significant difference in the degree of shade tab color change depending on the type of disinfectant used (F=153.2, p=0.0005). There was no significant difference in the amount of shade tab color change that occurred after disinfection between the different shade tabs used (F=0.611, p=0.87) nor a significant interaction between the type of disinfectant and the different shade tabs used (F=0.7, p=0.92). Aspecticare TB showed the least significant amount of change (Delta E=0.401), Sporicidin (Delta E=0.889) and the control (Delta E=0.969) showed significantly more color change than Asepticare TB but less color change than Cavicide (Delta E=1.198). Conclusion: It has been reported that human observers can be expected to detect color differences of 1 Delta E unit under standardized laboratory conditions (Kuehni 1979). In the oral cavity, however, an average change of 3.7 Delta E units could still allow teeth to be matched as having the same color (Johnson 1989). Therefore, while the results are significant, they may not be clinically important.

The Caries Management By Risk Assessment (CAMBRA) protocol outlines an approach in which certain agents can be used to serve as protective factors toward the management of dental caries. In this study, the effects of particular CAMBRA agents on the fracture strength of lithium disilicate ceramics (commonly used in dentistry) are studied. While Chlorhexidine exhibited no effects on the fracture strength of these ceramics, Prevident showed a decrease in the fracture strength of all the ceramics studied. These results indicate that clinicians should proceed with caution when using these CAMBRA agents in patients restored with lithium disilicate ceramics. Further studies on the particular mechanisms whereby this reduction in fracture strength occurs are indicated.

Streptococcus mutans as it pertains to dental and oral health is significant for its role as the primary etiologic factor of caries. While primary caries results from initiation of lesions in virgin tooth structure, secondary caries is a significant contributing factor to the replacement of dental restorations. Caries formation is directly related to plaque accumulation, which is mediated by bacteria adhesion to intraoral surfaces. In the case of the restored tooth, bacteria must adhere to the restorative material, particularly along margins in order to cause recurrent pathology. A material that has recently come into much favor is lithium disilicate, a glass based system with fillers in a homogenous glass. Lithium disilicate restorations can be either (1) pressed or (2) milled to fabricate inlays, onlays, veneers or single unit crowns. These restorations can be full-contour, or may be cut back and subsequently modified with (3) veneering fluorapatite, or (4) glazed. With respect to bacterial adhesion to restorative surfaces, the overwhelming factor is surface roughness. The threshold for this effect has previously been found to be 0.2 µm Ra value, above which there was a positive correlation between surface roughness and plaque retention. Specimens were fabricated for each of the four preparation types per manufacturer's recommendations and incubated with S. mutans UA159 wild-type. Biofilms adherent to specimens were then sonicated, redispersed, and plated for quantification. Results were tested with an analysis of variance (ANOVA). Significant differences that were found were further analyzed by Tukey's Honestly Significant Difference (HSD) test. Pearson's r was also be used to evaluate the relationship between surface roughness and biofilm accumulation. A p-value of ≤ 0.05 was considered significant. Surface roughness, as quantified by Ra values, indicated that Press and CAD groups were not significantly different from one another, but were significantly lower than that of ZirPress/Ceram, which was lower than surface roughness of the Ceram Glaze group (F = 513.898, p ≤ 0.0005). Similarly, CFUs/ml for the CAD and Press groups were significantly lower than the ZirPress/Ceram group, which were also significantly lower than those of the Ceram Glaze group (F = 201.721, p ≤ 0.0005). A strong positive association was also seen between surface roughness and biofilm accumulation (r = .95). Many factors, such as caries risk, presence of other restorations, and individual patient hygiene, influence whether these differences in surface roughness and biofilm accumulation become clinically relevant to the formation of caries. The present study has demonstrated that different preparations vary in their surface roughness and biofilm accumulation measurements, and that these differences in surface quality are associated with bacterial adherence.

Mouth guard material is used for athletic mouth guards, temporary dental splints, whitening trays, medicinal depositories and catheter tubing. This study evaluated biofilm formation on mouth guard materials after simulated use to ascertain the propensity of mouth guards to harbor bacteria. Three different mouth guards were evaluated (n=18/group): two boil-and-bite guards, Shock Doctor® (SD) Nano 3D and The Wrightguard™ (TWG) and one custom 100% EVA Buffalo guard (EVA). In vitro wear of the fabricated guards were simulated via a chewing simulator for 120,000 cycles per guard. The most visibly worn 8x10mm section of each guard was determined and cut to standardize specimen size. All guard specimens were incubated with equal cell densities of both S. aureus (SA) and Candida albicans (CA) strains and colony-forming units (cells/ml) were measured as a quantification of biofilm growth. A one-way ANOVA with Tukey's-HSD test was used to analyze biofilm retention (CFU/ml) on non-simulated and simulated EVA, SD, and TWG guards. Neither EVA (2.89±1.09 - 3.28±0.74; p=.486) nor TWG (10.22±3.31 - 11.17±5.46; p=.725) groups exhibited a significant increase in CFUs after 6 months of simulated use. In contrast, SD guards (3.33±1.55 - 9.72±5.37; p=.019) exhibited a significant increase in mean CFUs of CA when non-simulated guards were compared to simulated guards. Like with CA, neither EVA (3.11±1.90 - 3.50±1.63; p=.712) nor TWG (9.83±4.09 - 12.56±5.58; p=.358) groups exhibited significant increases in adherent SA following 6 months of simulated use. However, Shock Doctor (5.11±2.20 - 9.67±4.77; p=.06) guards had a significant increase in adherent SA CFUs when non-simulated guards were compared to simulated guards. With chewing simulation parameters remaining constant for all guard types, significantly greater adherence could indicate a greater change in surface topography/roughness from simulated use. While EVA guards exhibited the lowest measured adherence of CA and SA, and TWG exhibited the highest CA and SA levels of adherence, neither of their respective material compositions undergo surface changes as readily as SD guards.The increased propensity of both fungal and bacterial species to adhere to mouth guards after continuous use indicates a potential concern for regular mouth guard users.

Purpose: to evaluate the effect of the number and distribution of dental implants on the occlusal pressure transmitted to the palate. Material and Methods: eight implant analogs were placed in a replica of maxilla in the areas of teeth number 3, 4, 5, 6, 11, 12, 13 and 14. Locator attachments were attached to the implant analogs. The distances between the centers of implant analogs on each side were 8 mm. Fifteen denture bases with occlusal rims were fabricated to fit on the maxillary replica. Under a load of 245 N, pressure on the palate was measured under each denture base in six different designs of Locator insertions: No Locators, 2 Locators, 4 Locators with distances of 8, 16, and 24 mm and 8 Locators. Data was analyzed using One-Way ANOVA and Tukey's HSD test. A p value of ≤0.05 was considered significant. Results: Pressure transmitted to the palate ranged from 20.67 +/- 16.06 N (mean +/- SD) for overdentures supported by 8 Locators to 85.61 +/- 27.94 N for a conventional denture (control). The amount of pressure transmitted to the palate when the overdentures were supported by 4 Locator attachments, was significantly lower than when no, or when two Locator attachments were used. However, they were not significantly different from each other. When the overdentures were supported by 8 locator attachments, the pressure transmitted to the palate was significantly lower than that of conventional dentures, overdentures supported by 2 Locator attachments and overdentures supported by 4 Locator attachments when the distance between the anterior and posterior implants was 8 mm. Conclusion: Using 4 Locator attachments produced significantly less pressure on the palate, compared to when zero or two Locators were used. When the distance between the 4 Locators was 16 or more mm, the pressure was not significantly lower than 8 Locator design, suggesting that the palate of a 4 implant-retained overdenture with a distance of 16 mm or more, does not contribute significantly to the pressure distribution under the overdenture. Considering the static nature of the load, the results of this study should be interpreted clinically with caution.