Effect of Er:YAG Laser Application and Sandblasting on Shear Bond Strength of Veneering Ceramic to Zirconia Core.

Objectives: Porcelain chipping and delamination are among the shortcomings of all-ceramic restorations. This study aimed to assess the effect of laser irradiation and sandblasting on shear bond strength (SBS) of zirconia to veneering porcelain. Materials and Methods: In this in vitro, experimental study, 60 zirconia blocks were randomly divided into three groups (n=20) for surface treatment with Er:YAG laser, sandblasting, and no surface treatment (control). Each group was randomly divided into two subgroups (n=10) for porcelain application by the layering or the pressing technique. The surface roughness, SBS, and failure mode were determined and analyzed using two-way ANOVA, Tukey's HSD test, Chi-square test, and Pearson's correlation test (alpha=0.05). Results: The mean SBS was 8.16±3.66 MPa, 9.32±2.7 MPa, and 11.85±3.06 MPa in the control, laser, and sandblasting groups, respectively. The SBS was significantly different among the three groups (P=0.002). The failure mode of the three groups was not significantly different (P>0.05). The sandblasted group showed significantly higher surface roughness than the control and laser groups (P<0.001). Conclusion: Sandblasting yielded higher SBS particularly when the porcelain was applied by the layering technique. Although laser irradiation increased the SBS, the difference with the control group was not statistically significant.

Enhancing oral function: A case report on mandibular overdenture utilization with custom-made subperiosteal implant.

Subperiosteal implants, previously set aside because of complications, are now emerging again as effective treatments for severe mandibular atrophy, aided by recent improvements in digital dentistry. Traditional dentures in such cases often face challenges with support and retention, necessitating complex regenerative procedures. This paper presents a case report of a 54-year-old male patient with significant mandibular atrophy who received a custom-made subperiosteal implant, showcasing promising results. The implant was precisely designed utilizing computed tomography (CT) scans, a 3D-printed model, the selective laser melting (SLM) technique, and constructed with biocompatible Ti6Al4V material. This innovative approach offered a practical solution, resulting in high patient satisfaction and no complications over a year of use.

Comparison of Stress and Strain Distribution Patterns in Canine Implant and Maxillary Bone in Three Occlusal Schemes Using Finite Element Analysis.

OBJECTIVES: This study aimed to compare the pattern of stress and strain distribution in canine implant and maxillary bone in the anterior group function (AGF), posterior group function (PGF), and canine guidance (CG) occlusal schemes by finite element analysis (FEA). MATERIAL AND METHODS: In this in vitro experimental study, a dental implant (10 × 4.1 mm) was inserted at the site of the maxillary canine in a model of the maxilla in Mimics software. The implant was scanned three-dimensionally and the data were transferred to SolidWorks software. The von Mises stress, shear stress, deformation, and strain were calculated in the AGF, PGF, and CG occlusal schemes by FEA. STATISTICAL ANALYSIS: Data were analyzed by ABAQUS software to calculate the stress transferred to the canine implant and maxillary bone in the three occlusal schemes. RESULTS: The maximum and minimum von Mises stress, elastic strain, shear stress, and deformation were noted in the AGF and PGF occlusal schemes, respectively, in all teeth. CONCLUSION: The PGF showed minimum von Mises stress, elastic strain, shear stress, and deformation in the canine implant and maxillary bone. Thus, it appears than the PGF is the best occlusal scheme for maxillary canine implant followed by the CG scheme.

Shear Bond Strength of Colored and Sandblasted Zirconia to Ceramic Veneers Fabricated by the Pressing and Layering Techniques: An In Vitro Study.

Introduction: Porcelain-veneered zirconia (PVZ) restorations are increasingly used due to their optimal esthetics and high strength. However, chipping of porcelain limits the application of PVZ restorations. The aim of this study was to assess the shear bond strength (SBS) of colored and sandblasted zirconia to ceramic veneers fabricated by the pressing and layering techniques. Materials and Methods: Sixty cubic zirconia specimens (10 × 10 × 2 mm) were assigned to three groups according to their surface treatment: (I) control, (II) sandblasting with 50 µm alumina particles (S), and (III) coloring (C). Each group was subsequently divided into two subgroups according to the porcelain-veneering technique: (I) layering (L) and (II) pressing (P). The specimens underwent 10,000 thermal cycles between 5 and 55°C, and their biaxial SBS was measured in an electromechanical universal test machine (0.5 mm/min with 2.5 kN load cell). The failure mode was also assessed under a stereomicroscope. Three samples were randomly selected from each subgroup (n = 18) for examination of zirconia-phase transformation by X-ray diffraction (XRD). Two-way and one-way ANOVA followed by the post hoc Tukey test were used to analyze statistical differences among the groups and subgroups (α = 0.05). Results: The sandblasted zirconia with press porcelain (SP) subgroup showed the highest (24.40 ± 8.16 MPa) and the colored zirconia with press porcelain (CP) subgroup showed the lowest (13.76 ±3.62 MPa) SBS. All failures were cohesive. Rate of phase transformation in layered porcelain was significantly lower than that in pressed porcelain (P < 0.01). Conclusion: The sandblasted group showed the highest and the colored group showed the lowest SBS; the layered group showed higher SBS than the pressed group.

The effect of different methods of cleansing temporary cement (with and without eugenol) on the final bond strength of implant-supported zirconia copings after final cementation: An in vitro study.

Background: The temporary cement remaining inside the dental prosthesis can act as a source of microbial colonization and contamination and decrease the final cement retention. Consequently, complete removal of temporary cement before permanent cementation is suggested. This study aimed to assess the effect of different cleaning methods for removing temporary cement on the tensile bond force (TBF) of permanently cemented implant-supported zirconia copings. Materials and Methods: In this in vitro study fifty titanium abutments were screwed onto 50 analogs with 30 Ncm torque into in acrylic resin blocks. Each abutment was scanned separately, and 50 zirconia copings were designed and milled. Permanent resin cement was used to cement copings of control group (N = 10). Copings were divided into two temporary cementation types that in each group, two cleansing methods were used: Temp-S (temporary cement with eugenol and sandblasted after debonding), Samples of the control group were placed in the universal testing machine, and the TBF values were recorded. Samples of the test groups after debonding and cleaning the abutments were subjected to cement with permanent resin cement, aging, and removing. Levene test, two-way analysis of variance (ANOVA), and Tamhane post hoc tests were applied. α = 0.05. Results: The highest and lowest TBF values were found for the TempNE-SU (554.7 ± 31.5 N) and Temp-S (492.2 ± 48 N) groups, respectively. The two groups of isopropyl alcohol baths in ultrasonics in combination with sandblasting showed statistically higher TBF values than the other two groups that used only sandblasting (P < 0.001) and had similar values compared to the control group. Conclusion: Sandblasting combined with immersion in an ultrasonic bath containing isopropyl alcohol resulted in statistically similar values to the values of cementation with resin cement from the beginning. However, cleaning the inside of the copings only by sandblasting method reduced the values of the final retention force in comparison to cement with permanent resin cement from the beginning.

Stress Distribution in 5-Unit Fixed Partial Dentures with a Pier Abutment and Rigid and Nonrigid Connectors with Two Different Occlusal Schemes: A Three-Dimensional Finite Element Analysis.

Objectives: This study aimed to assess stress distribution in 5-unit fixed partial dentures (FPDs) with a pier abutment and rigid (RC) and nonrigid connectors (NRCs) with the canine rise and group function occlusal schemes by finite element analysis (FEA). Materials and Methods: In this FEA study, a geometrical model of the maxilla with natural teeth and periodontal ligament (PDL) was three-dimensionally designed and meshed by ANSYS and Pro/Engineer software programs. A 5-unit FPD was then designed to replace the lost first premolar and first molar teeth; the second premolar served as a pier abutment, and the canine and second molar served as terminal abutments. Two FPDs were designed with RC and NRC. Each FPD was analyzed with the canine rise and group function occlusal schemes (a total of 4 models). The first and second molars (180 N), premolars (120 N), and canine (80 N) teeth were subjected to progressive vertical and oblique (12-degree) loads, and maximum von Mises stress and strain in teeth and connectors were calculated for each model. Results: The models had 73704 elements and 137732 nodes. The connector design and occlusal scheme had significant effects on stress distribution in FPDs. The highest von Mises stress (73.035 MPa) was recorded in FPD with RC and group function occlusal scheme. The lowest von Mises stress (0.004 MPa) was recorded in FPD with NRC and canine rise occlusal scheme. Conclusion: Oblique forces created greater stress, and FPD with NRC and canine rise occlusal scheme decreased stress in FPD and increased stress in the tooth crown.

Prosthetic reconstruction of a patient with an irradiated rhinectomy and upper lip resection with a maxillofacial prosthesis and removable complete dentures: A clinical report.

When surgery is performed to remove aggressive cancer, the extent of the lesion commands the amount of tissue removed. The removal of extensive tissue such as crucial landmarks complicates prosthesis design. This clinical report describes the prosthetic reconstruction of a patient who underwent tumor resection of the upper lip, anterior portion of the nasal cavity, and cartilaginous portion of the nasal septum, as well as subsequent radiation therapy. The prosthetic rehabilitation consisted of magnetic attachments, eyeglasses, and silicone adhesives. The applied technique effectively covered the site of squamous cell carcinoma removal providing natural color and form.

Investigation of the effect of bonding factors on strength of porcelain bond to soft metal alloys after application of thermal cycle.

Background: The chemical bond between the metal and the porcelain component is likely to fail in metal-porcelain restorations. This is due to the thick oxide layer that Cr-Co alloys create. This study aimed to investigate the effect of metal conditioner on controlling the oxide layer formed on the surface of the Sintron alloy and the strength of the metal-porcelain bond. Materials and Methods: In this in vitro study, 33 samples were divided into three groups based on surface treatment (n = 11). In all three groups, an oxide layer was created. In the first group, Shofu metal conditioner, in the second group, metal conditioner of Creation, and in the third group, no metal conditioner was applied. All samples were then subjected to 3000 heat cycles between 5° and 55°C with a stop time of 5 s. The specimens were then placed in a universal testing machine for shear bond testing. A force was applied between the alloy and the porcelain by a 5 kN load cell at the speed of 1 mm/min until a fraction occurred. Intergroup comparison was made by the one-way analysis of variance followed by the Tukey's multiple comparisons test (α = 0.05) . Results: The mean shear bond strength of the first group was 34.93 MPa and the mean shear bond strength of the second group was 31.37 MPa. The mean shear bond strength of the first and the second group was significantly higher than the third group (23.37 MPa) (PV < 0.001). Conclusion: The use of metal conditioners between ceramill Sintron alloy and porcelain (Vita VMK MASTER) led to increasing the bond strength.

Prevalence of Proximal Contact Loss between Implant-Supported Prostheses and Adjacent Natural Teeth: An Umbrella Review.

Contact loss between the implant prosthesis and adjacent natural teeth is a clinical complication whose overall prevalence is uncertain. Therefore, the main purpose of this umbrella study was to evaluate the extent of contact loss between implant prostheses and adjacent natural teeth. Electronic database of MEDLINE/PubMed, Cochrane, and Google Scholar was searched until August 2021 without considering language restrictions and according to Preferred Report Items for Systematic and Meta-Analysis guidelines (preferential reporting items for systematic review and meta-analysis). Inclusion criteria were systematic/meta-analysis review articles related to contact loss between implant prostheses and adjacent natural teeth. Inclusion criteria and risk of bias for the selected systematic/meta-analysis review studies were assessed by two or three qualified researchers, and the fourth researcher was used to resolve the ambiguities. From 43 eligible articles, five systematic/meta-analysis review studies were selected for this study. Important information such as the range of contact points, the prevalence, and the location of the contact loss was extracted. Three research studies had a low risk of bias and were considered clinical evidence. Analysis of low-risk studies showed that the superiority of open contact loss was excessive. Prevalence of proximal contact loss was more in mesial contact, especially in the mandibular arch. No significant differences were reported in sex or between the posterior and anterior regions.

The effect of different cleansing methods for removing temporary cement on the tensile bond force of permanently cemented implant-supported metal copings: An in vitro study.

OBJECTIVES: Complete cleaning of temporary cement before permanent cementation of cement-retained implant-supported prosthesis (CISP) when recementing the crown is critical. This study evaluated the effect of different cleaning methods for removing traces of temporary cement on the final tensile bond force (TBF) of CISP recemented with resin cement. MATERIALS AND METHODS: Seventy computer-aided design/computer-aided manufacturing metal implant-supported copings were prepared and distributed into seven groups (N = 10). Copings of six groups (60 samples) were cemented with temporary cement with eugenol and subjected to 5000 thermocycling. After debonding by a universal testing machine, the internal surfaces of the copings were cleaned using one of the six following methods: 1-an ultrasonic water bath (UW), 2-sandblasting, then washing with water (SW), 3-sandblasting and an ultrasonic water bath (SUW), 4-an ultrasonic isopropyl alcohol bath (UA), 5-sandblasting, then washing with isopropyl alcohol (SA) or 6-sandblasting and an ultrasonic isopropyl alcohol bath (SUA). Then the subjects were subsequently cemented by dual-cure self-adhesive resin cement. In the seventh group (control, N = 10), the copings were cemented by dual-cure self-adhesive resin cement without the temporization phase. The TBF was tested using a universal testing machine with a cross-head speed of 1 mm/min. Two-way analysis of variance (ANOVA) and post-hoc Tamhane tests were used for statistical analysis at a significance level of α = .05. RESULTS: The maximum mean of TBF value was observed in SUA group (845 ± 203 N), and the minimum was observed in the temporary cement group (49 ± 20 N). All groups which were cleaned with isopropyl alcohol showed significantly higher TBF values compared with those cleaned with water. CONCLUSIONS: Cleaning of the inner surface of metal copings after debonding with sandblasting and isopropyl alcohol results in the highest value of TBF by eliminating the effect of remaining eugenol and removing traces of temporary cements.

An Umbrella Review of Systematic Reviews and Meta-Analyses Evaluating the Success Rate of Prosthetic Restorations on Endodontically Treated Teeth.

MATERIALS AND METHODS: The electronic search was conducted in the MEDLINE/PubMed, Cochrane, and Google Scholar databases until November 2020, regardless of language limitations. The inclusion criterion was as follows: S/M-R regarding prosthetic restorations in endodontically treated teeth. Three qualified researchers evaluated the inclusion criteria and bias risk. The fourth investigator was referred to when facing any doubtfulness. RESULTS: From 43 achieved S/M-R, 14 studies were selected for this inquiry. Primary extracted information included success rate, survival rate, and postendodontic failure rate. Five S/M-R had a moderate risk of bias, and nine S/M-R had a low risk of bias and were considered strong clinical evidence in this examination. According to the low-risk reports, the success rate of fiber posts was higher than that of metal posts; the rate of root fracture in metallic and fiber posts was alike; the failure rate for fiber posts was comparable to fixed partial dentures or single crowns; the construction of endocrowns was likely to perform better than intracanal posts, composite resin, or inlay/onlay restorations. CONCLUSION: It appears that with practice and experience, deciding which type of restoration to choose changes. In dental restorations associated with root canal therapy, the single crowns are likely to be a proper option. Nevertheless, due to the heterogeneity of the studies, more clinical assessments are required to achieve more specific findings in this field.

Comparison of the Effect of Four Different Abutment Screw Torques on Screw Loosening in Single Implant-Supported Prosthesis after the Application of Mechanical Loading.

BACKGROUND: The complications of implant-supported prostheses can be classified into mechanical and biological ones, one part of which is associated with screw loosening. This study was aimed to compare the effect of four different abutment screw torque techniques on screw loosening in single implant-supported prostheses following the application of mechanical loading. MATERIALS AND METHODS: In this experimental study, a total of 40 implants in acrylic blocks (6 × 10 × 20 mm) were mounted perpendicular to the surface. They were then randomly divided into four groups: (1) torquing once with 30 Ncm, (2) torquing three times with 30 Ncm and 5-minute intervals, (3) torquing once with 30 Ncm, opening the screw, and retorquing with 30 Ncm, and (4) torquing once with 35 Ncm. The torque values were confirmed by using a digital torque meter. Then, the samples underwent a force (2 cps, 0.453-11.793 kg) for three hours before the measurement of detorque values. The screw loosening force (torque) was then measured and recorded. The obtained data were analyzed by SPSS (version 22) software using one-way ANOVA and Tukey post hoc test at a 5% error level. RESULTS: The maximum mean detorque values of the abutment screws in single implant-supported prostheses were reported for groups 4 (27.8 ± 1.3), 1 (26.8 ± 1.3), and 3 (25.1 ± 1.3), and the minimum mean detorque value was found in group 2 (24.9 ± 1.2). Moreover, no significant difference was observed between groups 2 and 3 (p > 0.05), but a significant difference was found between groups 1 and 3 and other groups (p < 0.05). CONCLUSION: The increase in the torque value increased the torque loss. However, the detorque value in group 4 showed the least difference with the value recommended by the manufacturer (30 Ncm).

In Vitro Evaluation of the Effect of Different Luting Cements and Tooth Preparation Angle on the Microleakage of Zirconia Crowns.

INTRODUCTION: Discrepancy between the crown border and prepared tooth margin leads to a microleakage that eases the penetration of microorganisms and causes the dissolution of luting cement consequently. Several factors should be considered to achieve optimal fitness, including tooth preparation taper and type of cementing agent. The study aimed to determine the relation of tooth preparation taper and cement type on the microleakage of zirconia crowns. MATERIALS AND METHODS: Fifty-six freshly extracted premolars without caries and restorations were selected as the study sample and divided into two groups of different tapering degrees (6 and 12 degrees). Zirconia copings were designed and fabricated by the CAD/CAM system. The samples were divided into four subgroups for cementation, and each subgroup was cemented with a different luting cement (n = 7). After 5000 thermocycles at 5°C-55°C and dye penetration, the specimens were sectioned in the mid-buccolingual direction, and a digital photograph of each section was taken under a stereomicroscope. Data were analyzed by the Kruskal-Wallis and Mann-Whitney tests (α = 0.05). RESULTS: The results showed significant differences among the four types of luting cement in marginal permeability (PV < 0.001). Regardless of the type of cement, the 12-degree tapering resulted in a lower microleakage (46.4% without microleakage) with statistically significant differences from the 6-degree tapering (PV = 0.042). CONCLUSION: Within the limitations of this study, increasing the tapering degree of the prepared tooth for CAD/CAM zirconia copings improved the marginal fit and decreased the microleakage score. In addition, total-etch resin cement indicated the least microleakage.

Laser Treatment of Fiber Post and Final Push-Out Bond Strength: A Systematic Review and Meta-Analysis.

Purpose: This review article tries to answer this question: "What are the effects of laser surface treatment of fiber posts (FPs), compared with other surface roughening methods, on bond strength of cemented FPs?" Methods: Search was carried out in six electronic databases by focusing on defined key words. Related titles and abstracts, up to March 2019, were collected, read, and selected for quality assessments. A total of 2408 articles were included in the study at the initial stage of the searching phase. Results: Finally, seven studies were recognized to be reliable to be reviewed and meta data analysis in the study. All the studies were in vitro with a total of 340 samples. None of the Er:YAG (-0.27, 95% CI: -2.29 to 1.76; p = 0.79) and Er,Cr:YSGG (-0.04, 95% CI: -1.43 to 1.35; p = 0.95) treated samples showed any significant overall mean differences in final push-out bond strength (PBS) compared with the control groups. Conclusions: Laser pretreatment of FP surfaces might not be effective in providing high PBS. FP surface are susceptible to damage of high-level laser irradiation and might show decreased bond strength.

Frequency distribution of temporomandibular disorders according to occlusal factors: A cross-sectional study.

BACKGROUND: Temporomandibular disorder (TMD) is a common condition affecting the temporomandibular joint and causes pain and discomfort. However, the role of factors contributing to this problem is still controversial. The purpose of this cross-sectional study was to determine the correlation of occlusal factors and parafunctional habits with TMD and The determination of TMD prevalence among patients referring to Isfahan Dental School in 2017. MATERIALS AND METHODS: In this cross-sectional study, A total of 200 patients between 20 and 50 years were examined and questioned based on the Research Diagnostic Criteria for Temporomandibular Disorders assessment instrument. The association of occlusal factors (dental relationship, lateral occlusal scheme, horizontal differences between centric occlusion and Maximum intercuspation (MI), difference between MI and mandibular resting position) and parafunctional habits (bruxism/clenching and habits) with TMD was analyzed using Chi-square tests and independent sample t-test (α = 0.05). Binomial logistic regression analysis was performed with respect to confounding variables. RESULTS: The prevalence of TMD in the studied sample was 58.9%. Only bruxism showed a significant difference between TMD and non-TMD groups (P < 0.05). Other parafunctional and occlusal factors did not act as influential factors for TMD. CONCLUSION: Parafunction may play an important role in the initiation of TMD, although other habits and occlusal factors are considered as noninfluential factors. However, larger sample size and multicenter sampling are recommended for the future studies.

Assessment of the relationship between maximum occlusal force and median mandibular flexure in adults: A clinical trial study.

AIM: The narrowing of the mandible during opening and protrusion movements is defined as median mandibular flexure (MMF). MMF is caused by the attachment of mandibular muscles; therefore, it can be assumed that a greater amount of maximum occlusal force (MOF) may cause more flexion and could affect the survival of dental and implant restorations. The purpose of this study was to evaluate any relationship between MOF and MMF in a sample of adults. SETTINGS AND DESIGN: In vivo - comparative study. MATERIALS AND METHODS: In this descriptive, cross-sectional, nondirectional study, a sample of 90 volunteers were recruited (45 men and 45 women). MOF was measured by applying the strain gauge receptor to the first molar region, and MMF was measured by calculating the variation in the intermolar distance by a digital caliper with an accuracy of 0.01 mm using an impression and resulted in the stone cast during the maximum opening and closed-jaw positions. The body mass index (BMI) also was calculated. STATISTICAL ANALYSIS: Data were analyzed using the SPSS software (version 23) inferential and descriptive statistics, linear regression, and Pearson correlation coefficient. P < 0.05 was considered statistically significant. RESULTS: There was no statistically significant relationship between MOF and MMF (P = 0.78), but there was a significant association between MOF and BMI (P < 0.001, r = 0.475) and gender. CONCLUSION: Although MOF and MMF are both important and effective factors in the success of prosthetic restorations, one cannot be expected by the other and both should be considered in the treatment plan separately.

The Correlation of Clinical Outcomes (Marginal Bone Loss, Probing Depth, and Patient Satisfaction) With Different Prosthetic Aspects of Implant Overdentures: A Five-Year Retrospective Cohort Study.

Implant overdentures increase retention, stability, support, and subsequently comfort and patient satisfaction with removable dentures. This study aimed to investigate the correlation of clinical outcomes (marginal bone loss, probing depth, and patient satisfaction) with different prosthetic aspects of mandibular implant overdentures. Seventy-four implant overdenture wearers who had received their overdentures between 1 to 5 years ago were selected using simple cluster sampling. The data investigated included mucosal health of the mouth, condition of peri-implant tissues, marginal bone loss (MBL), and patient satisfaction. The relationship of MBL and probing depth (PD) with independent variables was assessed by Pearson and Spearman's rho correlation coefficients. The comparisons of MBL, PD, patient satisfaction, and tissue irritation among different states of independent variables were done by analysis of covariance, Tukey and Tamhane post-tests, and chi-square tests (α = 0.05). A total of 186 implants were evaluated. The mean ages of participants and overdentures were 61.62 ± 9.28 (year) and 38.45 ± 16.64 (month), respectively. The survival rate and success rate were calculated to be 100% and 97.8%, respectively. Higher width of attached gingiva was correlated with less PD significantly (P = .006). Gingival index (P < .001) and plaque index (P = .006) were correlated with PD positively. Mean MBL for those who needed matrix/patrix adjustment was significantly higher than that of those who did not need it (P = .025). Taking into account our small sample size, the results of this study suggest that healthy peri-implant mucosa is significantly correlated with the presence of attached gingiva and appropriate oral health care. Furthermore, patients receiving implant overdentures should be informed about the importance of regular recalls.

Comparison of the accuracy of open-tray and snap-on impression techniques of implants with different angulations.

BACKGROUND: A precise transfer of the position of an implant to the working cast is particularly important to achieve an optimal fit of the final restoration. Different variables affect the accuracy of implant impression. The purpose of the present study is to compare the accuracy of open-tray and snap-on impression techniques in implants with different angulations. MATERIALS AND METHODS: In this experimental study: A reference acrylic resin model of the mandible was fabricated. Four implants were positioned with the angles of 0°, 10°, 15°, and 25° in the model. Ten impressions were prepared with open-tray technique and ten impressions were made using snap-on technique. All impressions were made from vinyl polysiloxane impression material. Linear (Δx, Δy, and Δr) and angular displacements (Δθ) of implants were evaluated using a coordinate measuring machine. Measured data were then analyzed using two-way analysis of variance and Tukey's test (α = 0.05). RESULTS: The results showed that the accuracy of open-tray impression technique is significantly different from snap-on technique in Δx (P = 0.003), Δy (P = 0.000), Δr (P = 0.000), and Δθ (P = 0.000). Implants with 25° angulation are significantly less accurate than 0°, 10°, and 15° implants in Δx, Δy, Δr, and Δθ. Fifteen-degree implants are less accurate than 0° and 10° ones in Δθ. CONCLUSION: Regarding the findings of this study, it can be concluded that snap-on technique is less accurate than open-tray technique, and the accuracy of 25° implant is less than that of 0°, 10°, and 15° implants.

Role of laser or photodynamic therapy in treatment of denture stomatitis: A systematic review.

STATEMENT OF PROBLEM: Denture stomatitis (DS) is an inflammatory oral lesion that occurs mostly in elderly denture wearers and that can negatively affect their quality of life. The conventional treatment plan for DS is topical or systemic fungicidal drug therapy, which are not without side effects. PURPOSE: The purpose of this systematic review was to evaluate the clinical outcomes of using low-level laser therapy (LLLT) or photodynamic therapy (PDT) in the treatment of DS by reviewing high-quality published articles. MATERIAL AND METHODS: The Cochrane Library, Web of Science, Google Scholar, PubMed, ProQuest, Scopus, Embase, and Ovid databases were searched using appropriate key words. Related titles and abstracts published up to May 2017 were screened and selected based on defined inclusion criteria. The full texts of all selected articles were read, and citation lists were checked for missing references. All randomized controlled trials (RCT) were subjected to quality assessments. RESULTS: A total of 760 articles were included in the study after the initial search. Six studies were selected for assessment of eligibility, and 4 of them were sufficiently reliable in methodology and randomization to be included in the study. The applied wavelength varied from 455 nm to 830 nm. Also, the highest energy patients were exposed to was 122 J/cm2, and the lowest was 1 J/cm2. Exposure times ranged from 10 seconds to 26 minutes in the reviewed studies. CONCLUSIONS: Based on the available RCTs, LLLT has a significant role in the clinical treatment of DS. However, the results of PDT were similar to those of conventional antifungal therapies.

Effect of ceramic cooling protocols and zirconia coloring on fracture load of zirconia-based restorations.

BACKGROUND: Residual thermal stresses in dental porcelains can cause clinical failure. Porcelain cooling protocols may affect the amount of residual stresses within porcelain and also porcelain-zirconia bond strength. The objective of this study was to assess the effect of cooling protocols on the fracture load of porcelain veneered zirconia restorations. MATERIALS AND METHODS: Forty zirconia bars (31 mm × 6.5 mm × 1.35 mm ± 0.1 mm) were fabricated by computer-aided design and computer-aided manufacturing technology. Half of the specimens were immersed in the coloring agent for 2 min before sintering (yellow group). Thus, the specimens were divided into two groups of white (W) and yellow (Y) samples (n = 20). Heat-pressed ceramic was applied to all bars. After pressing, half of the samples in each group were immediately removed from the oven (fast cooling) while the other specimens remained in the partially open door (30%) oven until the temperature reached to 500°C. Samples were thermocycled for 5000 cycles and subjected to modified four-point flexural strength test by a universal testing machine at a crosshead speed of 0.5 mm/min. Two-way ANOVA, One-way ANOVA followed by post hoc Tukey honest significant difference tests were used for data analysis (α = 0.05). RESULTS: Fractures were cohesive in all samples (within the porcelain adjacent to the interface). Two-way ANOVA showed that the effect of cooling protocol on the fracture load of samples was statistically significant (P < 0.001). In addition, the fracture load of W and Y groups was significantly different (P < 0.001). The white slow group showed the highest fracture load (179.88 ± 23.43 N). CONCLUSION: Slow cooling protocol should be preferably applied for zirconia restorations. Coloring agent used in this study had a significant negative effect on fracture load.