Reverse Torque Values of Abutment Screws After Dynamic Loading: Effects of Sealant Agents and the Taper of Conical Connections.

The purpose of this in vitro study was to evaluate the influence of taper angle in internal conical connections of implant systems and the application of chlorhexidine gel as an antibacterial agent or polyvinyl siloxane sealant on reverse torque values of abutment screws after dynamic loading. Four implant systems having different taper angles (5.4°, 12°, 45°, 60°) were tested in this study. Test specimens were divided into 3 groups: control (neither chlorhexidine gel filled nor silicone sealed), 2% chlorhexidine gel filled, and silicone sealed. The samples were subjected to a dynamic load of 50 N at 1 Hz for 500 000 cycles before reverse torque measurements. The taper angle of conical connections presented a quantitative positive correlation between the degree of the taper angle and the percentage of tightening torque loss. However, it was significant only between 60° angled connection and others except for the sealant applied groups (P = .013 for control groups and P = .007 for chlorhexidine groups). The percentages of decrease in torque values of silicon sealant-applied specimens were significantly higher than both the control and chlorhexidine groups (P values are .001, .002, .001, and .002, respectively, according to increasing taper angles), but the percentage of decrease in torque values due to chlorhexidine application was not statistically significant when compared with control groups. Gel form chlorhexidine application as an antibacterial agent does not significantly affect the implant-abutment connection stability under dynamic loads. Polyvinyl siloxane sealant may cause screw loosening under functional loads.

Effects of Denture Base Thicknesses and Reinforcement on Fracture Strength in Mandibular Implant Overdenture with Bar Attachment: Under Various Acrylic Resin Types.

OBJECTIVE: This study aimed to assess the effect of reinforcement, denture base thickness, and acrylic resin types on dynamic and static fracture strength in mandibular implant overdentures with bar attachment. MATERIALS AND METHODS: One hundred and eight experimental mandibular implant overdentures with bar attachments were fabricated in three main groups, namely unreinforced (control: C), reinforced with unidirectional glass fibers (FR), and Co-Cr cast metal (MR). Each group included denture bases of 2-, 3-, and 4-mm thicknesses and produced with conventional (CA) and high-impact acrylic (HIA) resins. Specimens were thermocycled (5,000 times, 5-55°C) then subjected to a 400,000 cyclic load regime. Unbroken specimens were then loaded until fracture by a universal testing machine. Differences in mean fracture resistance among the groups were compared using the one-way analysis of variance (with post hoc Tukey's honestly significant difference test) and Student's t-tests (α = 0.05). RESULTS: Fracture strength increased significantly when the denture base thickness was increased (p = 0.001). The 2-mm denture base thickness was not enough for reinforcement. The fracture strength of the FR groups was significantly higher than other groups for 3- and 4-mm thicknesses (p = 0.001). The fracture strength of the HIA resin was significantly higher than CA resin in FR groups (p = 0.029 and p = 0.001). MR groups showed the weakest fracture strength. CONCLUSIONS: The 2-mm denture base thickness had sufficient fracture strength without reinforcement and a positive relationship between acrylic resin thickness and fracture resistance was found.

Effects of Taper Angle and Sealant Agents on Bacterial Leakage Along the Implant-Abutment Interface: An In Vitro Study Under Loaded Conditions.

PURPOSE: The aim of this study was to compare the bacterial leakage of conical internal connection implants with different taper angles (5.4, 12, 45, and 60 degrees) and examine the efficiency of a disinfectant agent and a silicone sealant agent in the prevention of bacterial leakage under loaded conditions. MATERIALS AND METHODS: Twenty-one implant-abutment connections were studied from each implant system (Ankylos Implants, Dentsply; Bego Semados S Implants, Bego; Trias Implants, Servo-Dental; DTI Implants, DTI), for a total of 84 implants. Each system's implants were divided into three groups as follows: unsealed (control), 2% chlorhexidine gel-sealed, or silicone-sealed (n = 7 for each group). The insertion torque was applied to each abutment screw according to the manufacturers' recommendation. The specimens were partially immersed in an 8-mm E faecalis suspension. A cyclic load of 50 N was applied for a total of 500,000 cycles at 1 Hz to the specimens. Following disconnection of dental implants and abutments, microbial samples were taken from the inner threaded surface of the implants, plated, and counted under appropriate conditions. RESULTS: There were no statistically significant differences in frequency of bacterial leakage and leaked bacterial counts among the four types of connections in all groups (P > .05). The statistically significant differences were found between sealant agents and control groups in four different connection types in terms of the amount of leaked bacteria (P < .05). There was no significant difference between the amount of leaked bacteria for four connection types when comparing the chlorhexidine and silicone sealant agents (P > .05). CONCLUSION: Differences in taper angles in the internal conical connections had no significant effect on leaked bacterial counts or the frequency of bacterial contamination under dynamic loading. The application of 2% chlorhexidine gel or a silicone sealant can reduce the leaked bacterial counts and reduce the frequency of bacterial leakage.

The influence of interimplant distance in mandibular overdentures supported by two implants on patient satisfaction and quality of life.

This study evaluates the influence of interimplant distance (ID) on patient satisfaction and quality of life (QOL) of 55 patients who received mandibular overdentures supported by two implants. IDs were measured over the residual ridge crest and linearly on all of the patients' mandibular casts. The crestal detours of all patients were determined by subtracting these two values from each other. Higher IDs were associated with better QOL scores (P < .05), whereas higher crestal detour values were associated with better general comfort, chewing, ease of hygiene maintenance, esthetics, pain, and QOL scores (P < .05).

The influence of momentary retention forces on patient satisfaction and quality of life of two-implant-retained mandibular overdenture wearers.

PURPOSE: The purpose of this study was to assess the influence of momentary retention forces on patient satisfaction and quality of life of two-implant-retained mandibular overdenture wearers. MATERIALS AND METHODS: Edentulous patients who had been rehabilitated with two-implant-supported mandibular overdentures with single attachments and maxillary complete dentures at a university clinic were included in this study. The overdenture attachments were either ball or locator attachments. All the patients completed the Turkish version of the Oral Health Impact Profile-14 (OHIP-14) and the visual analog scale (VAS) satisfaction questionnaires. Momentary retention forces of the overdentures were measured using a custom-made dynamic testing machine. RESULTS: Fifty-five patients were included in this study. No statistically significant association was detected between momentary retention forces and VAS scores (P > .05), but higher retention forces presented significantly better quality of life scores in the social disability and handicap domains of OHIP-14 (P < .05). CONCLUSION: Within the limitations of this clinical study, it may be presumed that although higher instant retention force of an implant-retained overdenture provides better quality of life, it does not affect patient satisfaction.