Effect of Sterilization on Bond Strength and Mechanical Properties of Fiber Posts.

PURPOSE: To determine the effects of two different sterilization methods on the pull-out bond strength, flexural strength, and elastic modulus of glass-fiber posts. MATERIALS AND METHODS: A total of 69 glass-fiber posts were used. The posts were divided into three groups according to applied sterilization method: 1) control, 2) ethylene oxide gas (EOG), and 3) autoclave. The microstructure of three posts from each group was evaluated by SEM and energy-dispersive X-ray spectroscopy (EDS). Thirty glass-fiber posts were used to evaluate pull-out bond strength. The three-point bending test was performed to analyze the flexural strength on another 30 glass-fiber posts. Failure modes were categorized microscopically after the pull-out test. After the three-point bending test, micromorphology at the bending area was examined using SEM. RESULTS: One-way ANOVA indicated no statistically significant differences among the group means in terms of bond strength (p > 0.05), flexural strength (p > 0.05), or elastic modulus (p > 0.05). EDS revealed that the weight percentage of surface oxygen atoms in the EOG- and autoclave-sterilization groups were significantly higher. SEM images were similar. CONCLUSION: The results of this study show that glass-fiber posts can be sterilized either by autoclave or EOG when necessary, without any negative effect on bond strength, flexural strength, or elastic modulus.

Production of a Piece of Custom-Made Abutment Screwdriver: Technique and Case Report.

Crown fractures, framework fractures, and abutment screw loosening or screw fracture are examples of mechanical implant failures. Abutment screw loosening is a serious problem that can result in abutment screw fractures. This clinical report describes the production method of a custom-made abutment screwdriver piece for a patient with abutment screw loosening.

Clinical Outcomes After Immediate and Late Implant Loading for a Single Missing Tooth in the Anterior Maxilla.

PURPOSE: This study compared the clinical outcomes of 1-year follow-up of immediate and late implant loading after implant restoration of a single tooth in the anterior maxilla. MATERIALS AND METHODS: Thirty-three patients with missing teeth in the anterior maxilla were included in this study (18 immediate loading and 15 late loading). Standard periapical radiographs were obtained to evaluate the vertical bone loss around the implant. For both implant groups, periimplant parameters (probing depth, gingival bleeding index, gingival index (GI), modified plaque index, width of keratinized gingiva) were evaluated. RESULTS: There were no significant differences in bone loss, the widths of keratinized gingiva, the GI, and modified plaque index between the immediate implant loading and late implant loading groups (P > 0.05). A significant difference in the probing depth was observed between these groups at the initial and 1-month evaluations (P < 0.05). Significant differences in bleeding indices between these groups were observed at months 3 and 6 (P < 0.05). CONCLUSIONS: When selecting appropriate patients (adequate primary stability, patient compliance with the surgeon's recommendations), immediate implant loading may be an alternative method to late loading protocol for replacement of a missing tooth in anterior maxilla.

Effect of fluid contamination on reverse torque values in bone-level implants.

INTRODUCTION: Screw loosening is one of the most common mechanical complications within the prosthetic components of dental implants. Clinicians must know if reverse torque values (RTVs) are affected by contamination of the implant abutment screw hole with either blood, saliva or chlorhexidine. METHODS: Forty implants were divided into 4 groups (n = 10). Implants were embedded in epoxy resin and placed in a digital torque meter. Screw holes of 30 implants were contaminated with either chlorhexidine (CG), fresh human saliva (SG), or blood (BG), and the remaining noncontaminated screws served as a control group (NC). Abutment screws were tightened using a hand-held torque meter (25 N·cm). Thermocycling (1500 cycles) was performed, and abutment detorque values were calculated using the digital torque meter. RESULTS: RTVs were lower than insertion torque values for all groups. According to Tukey HSD Test, blood contamination of abutment screws resulted in significantly lower RTVs (18.950 ± 2.641 N·cm) when compared with controls. CONCLUSIONS: Blood contamination of abutment screw holes was shown to significantly decrease RTVs. Blood contamination may result in greater loosening of implant screws in clinical practice.

In vitro fracture resistance of endodontically treated roots filled with a bonded filling material or different types of posts.

AIM: This study aimed to compare the fracture resistance of roots filled with a bonded material, fiber posts, or titanium post systems. METHODS: Canals in the first group were filled with AH Plus and gutta-percha cones, and roots in the second group were filled with Epiphany sealer and Resilon cones. The root fillings (60 roots) were removed up to 4 mm from the canal apex to obtain 10-mm-deep post spaces, and posts were cemented. The groups were as follows: AH Plus control group, Epiphany control group, AH Plus fiber post group, AH Plus titanium post group, Epiphany fiber post group, and Epiphany titanium post group. Fracture tests were performed by using an Instron testing machine. The force was applied at a 45° axial angle with a constant speed of 1 mm/min. For each sample, the force at which fracture occurred was recorded in units of newtons. Statistical analysis was carried out by using analysis of variance test. RESULTS: There was no statistically significant difference between all groups (P > .05). CONCLUSIONS: Titanium posts, fiber posts, and Epiphany root canal filling systems were found to have no reinforcing effect on endodontically treated roots.

Vertical ridge augmentation using sandwich osteotomy: 2 case reports.

The placement of dental implants in atrophic jaws is a challenging procedure due to inadequate bone quantity. This anatomic limitation can be overcome by various treatment methods such as onlay bone graft, inlay bone graft (known as sandwich osteotomy), and distraction osteogenesis. Two female patients with complaints of atrophic mandible were included in this study. Both patients were treated with a segmental mandibular sandwich osteotomy with interpositional grafts. This is called a sandwich osteotomy technique because a section of the jaw bone is separated from the main part and a bone graft is inserted between the 2 parts. The postoperative period was uneventful, and sufficient bone gain was obtained in both patients. Sandwich osteotomy is an effective technique to gain vertical bone height in atrophic jaws.

Effect of chewing on dental patients with total denture: an experimental study.

In this study, we have explored the prospect of assessing and following level of total denture adaptation by use of EMG signals recorded during gum chewing. Total of 14 edentulous patients, 6 women and 8 men, with an average age of 63±9 years, were recruited. Separate EMG recordings were obtained from left and right temporalis and masseter muscles of the patients for a period of 10 seconds, while they were chewing a sugar-free gum on their left and right sides. EMG recordings were repeated at three times: before, right after, and six months after the placement of the denture. We have tried to standardize environmental and individual factors during EMG recordings. The EMG data have been pre-processed and analyzed using Discrete Wavelet Transform (DWT) and obtained features were statistically evaluated using the paired sample t-test. Chewing activity on the right and left side is analyzed by making comparisons of muscle activity between before and right-after cases and before and six-months-after denture fixation cases. A comparison between right and left side mastication is also made at different time points. We have suggested and implemented a new test and comparison procedure in order to assess adaptation to denture fixation using EMG analysis. In this study, the results indicate that DWT based EMG analysis is instrumental in evaluating denture adaptation and as time progresses the adaptation to denture and hence chewing efficiency increases in patients with total denture replacement.

Two case reports involving implants and fractured healing caps.

The widespread use of endosseous osseointegrated implants to replace missing natural teeth increases the chances of implant complications and failures, despite the high initial success rate reported in the literature. Implant and healing cap fracture are possible rare complications that can cause significant problems for both clinicians and patients. This article reports on 2 unique cases of implant and healing cap fracture, their possible causes, and how the cases were managed.

Effect of different provisional cement remnant cleaning procedures including Er:YAG laser on shear bond strength of ceramics.

PURPOSE: The purpose of this study was to evaluate the effect of provisional cement removal by different dentin cleaning protocols (dental explorer, pumice, cleaning bur, Er:YAG laser) on the shear bond strength between ceramic and dentin. MATERIALS AND METHODS: In total, 36 caries-free unrestored human third molars were selected as tooth specimens. Provisional restorations were fabricated and cemented with eugenol-free provisional cement. Then, disc-shaped ceramic specimens were fabricated and randomly assigned to four groups of dentin cleaning protocols (n = 9). Group 1 (control): Provisional cements were mechanically removed with a dental explorer. Group 2: The dentin surfaces were treated with a cleaning brush with pumice Group 3: The dentin surfaces were treated with a cleaning bur. Group 4: The provisional cements were removed by an Er:YAG laser. Self-adhesive luting cement was used to bond ceramic discs to dentin surfaces. Shear bond strength (SBS) was measured using a universal testing machine at a 0.05 mm/min crosshead speed. The data were analyzed using a Kolmogorov Smirnov, One-way ANOVA and Tukey HSD tests to perform multiple comparisons (α=0.05). RESULTS: THE DENTIN CLEANING METHODS DID NOT SIGNIFICANTLY AFFECT THE SBS OF CERAMIC DISCS TO DENTIN AS FOLLOWS: dental explorer, pumice, cleaning bur, and Er:YAG laser. CONCLUSION: The use of different cleaning protocols did not affect the SBS between dentin and ceramic surfaces.

Effects of Finger Pressure Applied By Dentists during Cementation of All-Ceramic Crowns.

OBJECTIVES: To compare the finger pressure applied by dentists during cementation and to examine the effect of gender and time of day on finger pressure. METHODS: Fifteen dentists (9 males, 6 females) formed a study group and 10 master dies in premolar shape and Turcom Cera all-ceramic crowns were prepared to measure the maximum finger pressure applied by dentists during cementation. The dentists performed a total of 300 cementation processes. One-way analysis of variance and independent t tests were used to evaluate the results. RESULTS: A statistically significant difference was found in the amount of pressure applied during cementation (P<.005). However, there was no significant difference for time of day or gender according to one-way analysis of variance. CONCLUSIONS: Our results show that finger pressure varies by dentist. For this reason, the optimum pressure should be determined exactly. Special equipment or an apparatus could be developed to apply that pressure.

Tensile bond strength of a lithium-disilicate pressed glass ceramic to dentin of different surface treatments.

The effects of desensitizer, disinfectant, saliva, blood, and hydrogen peroxide on the tensile bond strength between adhesive and ceramic as well as between adhesive and dentin were examined. Sixty 7x3 mm pressed ceramic discs of IPS e.max were fabricated and randomly assigned to six groups of different dentin surface treatments (control, desensitizer, disinfectant, saliva, blood, and hydrogen peroxide). Representative samples of fractured specimens were observed by SEM (scanning electron microscopy). There were significant differences between the control group and saliva, blood, and hydrogen peroxide groups (p<0.05). However, there were no significant differences between any other dentin surface treatment groups (p>0.05). Results of this study suggested that only saliva, blood, and hydrogen peroxide influenced the tensile bond strength between dentin and ceramic.

Bacterial adhesion of porphyromonas gingivalis on provisional fixed prosthetic materials.

BACKGROUND: When provisional restorations are worn for long term period, the adhesion of bacteria becomes a primary factor in the development of periodontal diseases. The aims of this study were to evaluate the surface roughness and bacterial adhesion of four different provisional fixed prosthodon-tic materials. METHODS: Ten cylindrical specimens were prepared from bis-acrylic composites (PreVISION CB and Protemp 3 Garant), a light-polymerized composite (Revotek LC), and a polymethyl methacrylate-based (Dentalon) provisional fixed prosthodontic materials. Surface roughness was assessed by profilometry. The bacterial adhesion test was applied using Porphyromonas gingivalis (P. gingivalis) and spectro-fluorometric method. Statistical analysis was performed using ANOVA and Dunnett t-tests. RESULTS: All tested materials were significantly rougher than glass (P < 0.05). Revotek LC had the greatest fluorescence intensity, PreVISION and Protemp 3 Garant had moderate values and all of them had significantly more bacterial adhesion compared to glass (P < 0.05). Dentalon had the lowest fluorescence intensity among the provisional fixed prosthodontic materials. CONCLUSION: The quantity of bacterial adhesion and surface roughness differed among the assessed provisional fixed prosthodontic materials. The light-polymerized provisional material Revotek LC had rougher surface and more bacterial adhesion compared with the others.

The effect of dentin desensitizer with different layers on thermal changes on the pulp during fabrication of provisional restoration.

PURPOSE: This study investigated the effects of different desensitizers and an adhesive material application on pulpal temperature rise during direct provisional restoration polymerization. MATERIALS AND METHODS: Two dentin desensitizers (Systemp, Ivoclar; BisBlock, Bisco) and a dentin adhesive (Prime Bond, Dentsply) were applied to the dentin surfaces as single layer or double layer. One autopolymerizing methacrylate (Prevision, Heraeus Kulzer) and one light polymerizing composite (Revotek LC, GC) provisional restoration materials were used in this study. A total of 160 dentin disks were prepared from extracted molars. These dentin disks were placed on an apparatus developed to measure temperature rise. After the desensitizer or dentin adhesive application, provisional materials were polymerized according to the manufacturers' instructions. The temperature increase was measured under the dentin disk with a J-type thermocouple wire that was connected to a data logger. Differences between initial and highest temperature reading were taken, and 10 readings were averaged to determine the mean value in temperature rise. Statistical analysis was performed with three-way analysis of variance followed by Tukey HSD test (alpha = 0.05). RESULTS: Temperature rise varied according to the provisional restoration material used (composite resin, methacrylate) (p < 0.001), the agent thickness (single, double) (p < 0.001), and the agent (desensitizer, adhesive) (p < 0.001). The composite resin-based provisional material induced higher thermal changes than methacrylate based provisional material (p < 0.01). CONCLUSION: The thickness of desensitizing agents affected the thermal changes; however, the desensitizers did not affect on the intrapulpal temperature although the type of provisional material used may be effective.

Effects of current provisional restoration materials on the viability of fibroblasts.

OBJECTIVES: The aim of the present study was to evaluate the cytotoxic effects of three different provisional restoration materials on fibroblasts. Two bis-acrylic based [Tempofit Duomix (Detax), Protemp 3 Garant (3M ESPE)] and one urethan dimethacrylate [Revotek LC (GC Corporation)] based provisional restoration materials used. METHODS: Materials were prepared according to the manufacturers' instructions in standard teflon disks (2x5 mm) and four samples were extracted in 7 ml of Basal Medium Eagle with 10% new born calf serum and 100 mg/ml penicillin/streptomycin for 24 hours. The L929 fibroblast cells were plated (25.000 cells/ml) in well plates, and maintained in a CO(2) incubator at 37 degrees C for 24h. After 24 hours, the incubation medium was replaced by the immersed medium in which the samples were stored and the L929 fibroblasts were incubated in contact with eluates for 24 hours at 37 degrees C for 24h. The fibroblast cell viability was analyzed by measuring the mitochondrial activity with the methyltetrazolium test (MTT). Twelve well used for each specimen and experiment repeated for two times. The data was statistically analyzed by Mann-Whitney U tests. RESULTS: The results showed that, Revotek LC and Protemp 3 Garant were not cytotoxic for fibroblast cells when compared to control group (P>.05). However, Tempofit duomix was cytotoxic for L929 fibroblasts when compared to control group and other tested materials (P<.05). CONCLUSIONS: Taking into consideration the limitations of an in vitro study, our study indicate that provisional restoration materials might have cytotoxic effects on fibroblasts and should be selected carefully for clinical applications.

The effect of different fiber concentrations on the surface roughness of provisional crown and fixed partial denture resin.

OBJECTIVES: The aim of this study was to investigate surface roughness in provisional crown acrylics, after polishing, reinforced with different concentrations of glass fibers. METHODS: A total of 48 disk-shaped specimens were prepared using autopolymerizing acrylic resin. These specimens were divided into four groups according to the level of glass fiber added: Group A (no fiber), Group B (0.5%), Group C (1%) and Group D (2%). After polishing the specimens, an average surface roughness (Ra) value was calculated using a profilometer from four randomly selected points on the surface. RESULTS: A significant difference was determined among the surface roughness values of provisional crown resins to which different concentrations of fiber had been added (P<.001). Tukey's test was then used to perform paired comparisons of the data between the different groups, and a significant difference was found between Group A (no fiber) and the other groups, between Group B (0.5%) and Group D (2%) and between Group C (1%) and Group D. On the other hand, there was no significant difference between Group B and Group C. CONCLUSIONS: The reinforcement of provisional crown and fixed partial denture resin with glass fibers increases surface roughness.