Effect of sintering temperature on translucency parameter of zirconia blocks.

Background: The main drawbacks of zirconia are its high refractive index and opacity. This study aimed to assess the effect of sintering temperature on the translucency of Ivoclar e. max ZirCAD (IEZ), and White Peaks Symphony (WPS) zirconia blocks. Materials and Methods: In this in vitro experimental study, 30 IEZ and 30 WPS zirconia blocks measuring 10 mm × 10 mm × 1 mm were prepared and underwent sintering in three subgroups at 1440°C, 1500°C, and 1530°C. The specimens were then photographed against a black and a white background with a standard digital camera. The L*, a*, and b* color parameters were measured using Adobe Photoshop software, and translucency was calculated. Data were analyzed using one-way ANOVA and Tukey's test (P < 0.05). Results: In both the IEZ and WPS groups, the maximum and minimum translucency parameters were recorded in 1530°C and 1440°C subgroups, respectively. The difference in the mean translucency was significant among the three subgroups of each zirconia group (P < 0.001). The mean translucency of WPS zirconia was significantly higher than that of IEZ zirconia (P < 0.01), and maximum difference was noted at 1500°C sintering temperature. Conclusion: Increasing the sintering temperature from 1440°C to 1530°C can significantly increase the translucency of IEZ and WPS zirconia blocks, and can be considered to improve the quality of zirconia restorations.

Effect of Sintering Temperature on Flexural Strength of Two Types of Zirconia.

Objectives: Any change in the sintering process can directly affect the micro-structure and properties of zirconia. This study sought to assess the effect of sintering temperature on flexural strength of IPS e.max ZirCAD MO Ivoclar (EZI) and CopraSmile White Peaks Symphony (WPS) zirconia blocks. Materials and Methods: In this in vitro, experimental study, 30 EZI and 30 WPS zirconia blocks measuring 10 x 10 x 1 mm were milled and sintered at 1440, 1500 and 1530°C in three subgroups. The flexural strength of the specimens was measured by a testing machine with piston-on-3-ball method according to ISO2015. Data were analyzed using one-way ANOVA. Results: The mean flexural strength was 1.31±0.49, 1.09±0.24 and 1.29±0.48 MPa in 1440, 1500, and 1530°C subgroups of EZI, and 1.44±0.61, 1.18±0.35, and 1.33±0.54 MPa in 1440, 1500, and 1530°C subgroups of WPS zirconia, respectively. Two-way ANOVA revealed that the effects of zirconia type (P=0.484), temperature (P=0.258) and their interaction (P=0.957) on flexural strength were not significant. Conclusion: Increasing the sintering temperature from 1440°C to 1530°C did not increase the flexural strength of EZI or WPS zirconia.

Comparative Effects of Kemphor and Chlorhexidine Mouthwashes on Tooth Staining and Gingivitis: A Randomized Controlled Crossover Clinical Trial.

Objectives: Considering the side effects of chlorhexidine (CHX), which is currently the gold-standard antimicrobial mouthwash, this study aimed to compare the effects of Green Kemphor and CHX mouthwashes on tooth staining and gingivitis. Materials and Methods: This randomized controlled crossover clinical trial evaluated 38 patients requiring CHX mouthwash following oral surgery and periodontal therapy. The patients were randomly assigned to CHX and Kemphor groups (n=19). In CHX group, patients used CHX mouthwash in the first 2 weeks, and after a 4-day washout period, they used Kemphor mouthwash for 2 weeks. This order was reverse in the Kemphor group. Gingivitis was evaluated using the Silness and Loe gingival index (GI), and tooth staining was evaluated by the Lobene index at 0 (baseline), 2 and 4 weeks. Data were analyzed by paired t-test. Results: CHX mouthwash significantly decreased the GI and increased tooth staining (gingival stains, body stains, and stain extent) at 2 weeks (P<0.05). Kemphor mouthwash significantly decreased the GI and increased tooth staining after 2 weeks (P<0.05). The GI in Kemphor group was significantly lower than that in CHX group at 4 weeks (P<0.05). Also, the tooth staining parameters in the Kemphor group were significantly lower than the corresponding values in the CHX group at 2 and 4 weeks (P<0.05). Conclusion: Kemphor had higher efficacy for reduction of GI and caused less tooth staining than CHX; thus, it may be recommended for use as an alternative to CHX.

Effect of photo core, LuxaCore, and core max II core building materials on fracture resistance of endodontically-treated teeth restored with fiber-reinforced composite posts and ParaPosts.

BACKGROUND: Post and core treatment is commonly performed for endodontically treated teeth to replace the lost tooth structure and reinforce and protect the remaining dental tissue. This study aimed to compare the effect of three-core building materials on fracture resistance of endodontically-treated teeth restored with fiber-reinforced composite (FRC) posts and ParaPosts. MATERIALS AND METHODS: This in vitro, experimental study evaluated 108 sound, single-rooted mandibular first premolars extracted for orthodontic purposes. The teeth were randomly divided into nine groups (n = 12) of control (no endodontic or restorative treatment), FRC + Photo Core (Group 2), FRC + LuxaCore (Group 3), FRC + Core Max II with bonding agent (Group 4), FRC + Core Max II without bonding agent (Group 5), ParaPost + Photo Core (Group 6), ParaPost + LuxaCore (Group 7), ParaPost + Core Max II with bonding agent (Group 8), and ParaPost + Core Max II without bonding agent (Group 9). The fracture resistance was measured by applying the load at 45° angle relative to the longitudinal axis of the tooth with a crosshead speed of 1 mm/min using a universal testing machine. Data were through descriptive statistics, Tukey's test, and one-way analysis of variance (α = 0.05). RESULTS: The mean fracture resistance was 454.0 ± 62.7, 410.8 ± 48.3, 365.1 ± 42.1, 423.7 ± 111.7, 392.4 ± 90.0, 292.3 ± 83.9, 242.3 ± 73.4, 278.2 ± 67.9, and 247.3 ± 49.6 N in Groups 1-9, respectively. Group 4 showed the highest fracture resistance, which was significantly higher than this study the value in all ParaPost and control groups (P < 0.05) but had no significant difference with the fracture resistance of other groups (P > 0.05). CONCLUSION: Fracture resistance is independent of the type of core building material used, and the tested products had no superiority over each other. The mean fracture resistance of FRC post groups were significantly higher than that of ParaPost groups. Furthermore, Core Max II + bonding agent yielded insignificantly higher fracture resistance than Core Max II without bonding agent.

The comparison of two professional prophylaxis systems in plaque removal and debonding of orthodontic brackets.

INTRODUCTION: During orthodontic treatment, patients are expected to undergo consistent periodic prophylaxis as a result of complexities in oral hygiene. The aim of this study was to investigate, analyze, and compare the effectiveness of two professional prophylaxis systems of rubber cup polishing (RCP) and air-powder polishing (APP) in patients undergoing orthodontic treatment based on different levels of plaque and pigment on teeth and the extent of attachment of brackets after prophylaxis. MATERIALS AND METHODS: A total of 50 patients were selected for this clinical trial study. A couple of months after the orthodontic treatment, the patients were placed on professional prophylaxis in terms of the plaque index. Randomized cross-arch prophylaxis (right maxilla with left mandible), RCP (left maxilla with right mandible), and APP were carried out on the patients. The main indexes in the study (number of plaque removal and debonding), the work time duration per second, and convenience of patients using visual analog scale in each of the methods were evaluated as minor factors. Data were recorded in a special checklist. RESULTS: The mean of the plaque index and the time spent on RCP were observed to be higher than APP. The average satisfaction rate of patients with RCP was higher than APP. The debonding of the bracket and the tooth was not observed in any of the methods. CONCLUSION: APP is more efficient than RCP for performing professional prophylaxis of orthodontic patients.

Effect of Resin Cement Color on the Final Color of Lithium Disilicate All-Ceramic Restorations.

OBJECTIVES: Obtaining an adequate ceramic thickness to mask the substructure color is not always feasible, and appropriate use of a cement may be the only solution. This study aimed to evaluate the effect of the color of Variolink II resin cement on the final color of lithium disilicate glass ceramic restorations. MATERIALS AND METHODS: In this in-vitro study, 90 discs of IPS e.max Press ceramic were evaluated. The ceramic discs were cemented to composite and amalgam blocks. The effect of the cement color and substructure on the final color of ceramic was analyzed by calculating the color change (ΔE) value using a spectrophotometer. Data were analyzed via three-way analysis of variance (ANOVA) and Tukey's test. RESULTS: The cement color had a statistically significant effect on the final color of ceramic (P≤0.001). The white, yellow, and translucent cements caused the highest color change (ΔE=4.558, 3.308, and 2.649, respectively). The effect of composite substructure and the yellow cement on the final color was less prominent compared to other combinations of cement and substructure (ΔE=2.043). The white cement over amalgam substructure showed the greatest effect on the final color (ΔE=4.890). The ΔE in HO group was less than that of other combinations (P<0.05), and the greatest ΔE was reported in MO group with the white cement (ΔE=6.255). CONCLUSIONS: The final color of the restoration is influenced by the cement color. Therefore, when IPS e.max Press is used over a metal core, it is recommended to use a cement with an HO ceramic.

Effect of Oral Bromelain on Wound Healing, Pain, and Bleeding at Donor Site Following Free Gingival Grafting: A Clinical Trial.

OBJECTIVES: Considering the optimal efficacy of bromelain for pain relief and wound healing, this study aimed to assess the effect of bromelain on wound healing, pain, and bleeding at the donor site following free gingival grafting (FGG). MATERIALS AND METHODS: This randomized, controlled double-blind clinical trial was performed on 26 patients with gingival recession. The patients were randomly divided into two groups of bromelain and placebo (n=13). Treatment was started on the day of surgery and was continued for 10 days. Pain, bleeding, and epithelialization at the donor site were the variables evaluated in this study using a questionnaire. The level of pain was determined using a visual analog scale (VAS) considering the number of analgesic tablets taken within 7 days postoperatively. Bleeding was determined according to the patient's report, and epithelization was assessed by applying 3% hydrogen peroxide (H2O2) to the donor site. The donor site epithelialization was assessed at 7 and 10 days after surgery. RESULTS: Bromelain caused a significant reduction in pain at the donor site (2.605±0.509) compared to the placebo (4.885±0.519; P<0.05). The number of donor sites with complete epithelialization was higher in the bromelain group compared to the placebo, but this difference was not statistically significant (P>0.05). The two groups were the same regarding postoperative bleeding (P>0.05). CONCLUSIONS: The results showed that oral bromelain (500 mg/day) can be effective in the reduction of pain at the donor site after FGG and may also enhance wound healing. Oral bromelain does not increase the risk of postoperative bleeding.

Fatigue Fracture Strength of Implant-Supported Full Contour Zirconia and Metal Ceramic Fixed Partial Dentures.

OBJECTIVES: Zirconia restorations have been suggested as a more durable and more appealing alternative to metal restorations. However, their mechanical properties may be negatively affected by fatigue due to superficial stresses or low temperature degradation. This study aimed to assess the fatigue fracture strength of three-unit implant-supported full contour zirconia and pre-sintered cobalt-chromium (Co-Cr) alloy posterior fixed partial dentures (FPDs). MATERIALS AND METHODS: In this in-vitro experimental study, 28 posterior three-unit implant-supported FPDs were fabricated of full contour zirconia and pre-sintered Co-Cr alloy, and were cemented on implant abutments. To simulate the oral environment, FPDs were subjected to 10,000 thermal cycles between 5-55°C for 30 seconds, and were then transferred to a chewing simulator (100,000 cycles, 50 N, 0.5 Hz). Afterwards, fatigue fracture strength was measured using a universal testing machine. Data were analyzed by Mann-Whitney U test. RESULTS: The mean and standard deviation of fracture strength were 2108.6±440.1 N in full contour zirconia, and 3499.9±1106.5 N in pre-sintered Co-Cr alloy. According to Mann-Whitney U test, the difference in this respect was statistically significant between the two groups (P=0.007). CONCLUSIONS: Since the fracture strength values obtained in the two groups were significantly higher than the maximum mean masticatory load in the oral environment, both materials can be used for fabrication of posterior three-unit FPDs, depending on the esthetic demands of patients.