Effect of intraoral scanning distance on the marginal discrepancy of milled interim crowns.

PURPOSE: To compare the marginal discrepancy between milled interim crowns fabricated using intraoral digital scans acquired at different scanning distances. MATERIALS AND METHODS: Ten acrylic typodont teeth were prepared for interim crowns. Three different resin frames of 2.5-, 5-, and 7.5-mm heights were fabricated and attached to an intraoral scanner (Omnicam). Three groups were created based on the different scanning distances tested: 2.5 mm (Group A), 5 mm (Group B), and 7.5 mm (Group C). Intraoral digital scans were performed on four tooth surfaces: mesial, distal, buccal, and lingual (n = 10). Each experimental scan was used to design and fabricate a milled polymethylmethacrylate anatomically contoured crown. Vinyl polyether silicone was used three times to assess the marginal discrepancy of the specimens by measuring five marginal points on digital photographs. One-way analysis of variance test was used to analyze the data, followed by Tukey's honestly significant difference test (α = 0.05). RESULTS: The mean marginal discrepancy values in Group C were significantly higher than those in Groups A (p ≤ 0.000) and B (p = 0.001). There was no significant difference between Groups A and B (p = 0.702). There were no significant differences among the four surfaces in any of the scanning distance groups (p1  = 0.583, p2  = 0.390, and p3  = 0.135; p > 0.05). CONCLUSIONS: The interim crowns fabricated with a scanning distance of 7.5 mm showed the greatest marginal discrepancy when compared with crowns fabricated using 2.5- and 5-mm scanning distances.

Comparison of heat transfer through various fixed prosthetic materials during grinding.

PURPOSE: To measure and compare the mean temperature values due to heat generated during the grinding of different prosthetic materials with diamond burs using a high-speed instrument with and without water cooling. MATERIALS AND METHODS: In total, 120 disk-shaped specimens (10 × 2 mm), each with a smaller disk in the center (3 × 2 mm), were fabricated from yttrium-stabilized zirconia, monolithic zirconia, glass-ceramic, indirect composite, polyetheretherketone (PEEK), and cast metal (Ni-Cr alloy). The specimens were divided into six groups (n = 20) according to material type. The specimens in each group were ground continuously with a high-speed handpiece and diamond burs with (n = 10) and without (n = 10) water cooling until the smaller disks were removed. Two different methods (thermocouple and thermal camera) were used to measure the temperature during the grinding process. Results were analyzed using two-way ANOVA and paired samples t test (P < .05). RESULTS: PEEK had the lowest mean temperature values and metal had the highest values, both with and without water cooling, according to data measured with a thermocouple. Zirconia and monolithic zirconia samples without water cooling had the highest mean temperature values when measured with a thermal camera. Both with and without water cooling, composite samples had the lowest mean temperature value for thermal camera measurements. CONCLUSION: Water cooling is strongly recommended when grinding all prosthetic materials. The heat transferred to the supporting teeth may depend on the thermal conductivity of the material used.

The effect of different denture cleansing solutions on the retention of polyetheretherketone locator attachments.

PURPOSE: Prosthetic cleansing solutions have been reported to cause retention loss in implant locator attachments due to the chemical alterations of these attachments. This study aimed to investigate the effects of different denture cleansing solutions on attachments with different retention values. MATERIALS AND METHODS: In this study, 160 polyetheretherketone locator attachments were divided into 4 groups according to their attachment retention values (yellow, pink, clear, and violet). Forty attachments from each group were soaked in four different cleansing solutions (n = 10). The attachments from the four groups were immersed in water, sodium hypochlorite, Corega, and Protefix solutions for a period equivalent to 6 months, according to the manufacturer's recommendations. The locator attachments were then subjected to testing using a universal testing machine. Maximum load to dislodgement according to different solutions was evaluated by one-way ANOVA test. Statistical significance was set at p < 0.05. RESULTS: The effect of denture cleansing solutions on the retentive values of attachments was statistically significant (p < 0.001). Among all cleansing solutions, the highest retention value was found in the violet attachments, and the lowest retention value was found in the yellow attachments. The lowest retention value (0.72 ± 0.05 MPa) was observed when the yellow attachments were immersed in Protefix solution, and the highest retention value (1.96 ± 0.15 MPa) was observed when the violet attachments were immersed in the Corega solution. CONCLUSION: For different colored attachments, different cleansing solutions can be suggested to patients.

A 3D finite element analysis of stress distribution on different thicknesses of mineral trioxide aggregate applied on various sizes of pulp perforation.

OBJECTIVES: The aim of this study was to evaluate the stress distribution on different thicknesses of mineral trioxide aggregate (MTA) placed on various widths of pulp perforations during the condensation of the composite resin material. MATERIALS AND METHODS: The mandibular molar tooth was modeled by COSMOSWorks program (SolidWorks, Waltham, MA). Three finite elemental analysis models representing 3 different dimensions of pulp perforations, 1, 2, and 3 mm in diameter, were created. The perforation area was assumed as filled with MTA with different thicknesses, 1, 2, and 3 mm for each pulp perforation width, creating a total of 9 different models. Then, a composite resin material was layered on MTA for each model. A 66.7 N load was applied and an engineering simulation program (ANSYS, Canonsburg, US) was used for the analysis. Results were presented considering von Mises stress criteria. RESULTS: As MTA thickness increased, the stress values recorded within the area between pulp and MTA decreased. Strain was decreased when the thickness of MTA increased. CONCLUSIONS: Stresses at MTA-pulp interface and strain on MTA decreased with the increase in MTA thickness. CLINICAL RELEVANCE: In clinical practice, when MTA is required for pulp capping, using a thick layer of the material seems to be a better option in order to reduce the stress under forces of hand condensation of overlying restorative materials.

In Vitro Evaluation of Shear Bond Strength of Three Primer/Resin Cement Systems to Monolithic Zirconia.

PURPOSE: To investigate the shear bond strength (SBS) of various primer/resin cement systems to monolithic zirconia under different levels of storage. MATERIALS AND METHODS: Disk-shaped specimens of monolithic zirconia (10 × 3 mm, n = 72) were polished with silicon carbide paper, and the bonding surfaces were sandblasted with aluminum oxide (Al2O3). The samples were divided into three groups (n = 24) according to primer/cement system: Z-PRIME Plus/DUO-LINK (Bisco); Clearfil Ceramic Primer Plus/PANAVIA SA (Kuraray); and Single Bond Universal Adhesive/RelyX Ultimate (3M ESPE). After bonding was completed, each group was divided into two subgroups (n = 12) under different levels of 24-hour storage and thermocycling. The specimens were embedded in acrylic molds, and SBS tests were conducted. Modes of failure were also evaluated. The data were analyzed using one- and two-way analysis of variance (ANOVA) and Tukey Honest Significant Difference test. Significance was set at P < .05. RESULTS: The highest and lowest SBS values were observed in the Kuraray (12.52 ± 1.34 MPa) and Bisco (5.32 ± 0.54 MPa) systems, respectively, in the thermocycled groups (P < .05). Similarly, in short-term storage groups, Kuraray had the highest (16.47 ± 1.5 MPa) and Bisco the lowest (7.43 ± 1.06 MPa) SBS values (P < .05). Regardless of adhesive system used, thermocycling significantly decreased the SBS of all cement groups (P < .05). Of the failures, 49% were adhesive, 45% were mixed, and 6% were cohesive. CONCLUSION: A methacryloyloxydecyl dihydrogen phosphate-containing resin cement is recommended to provide a durable bond for monolithic zirconia.

Influence of Post Space Preparation on the Apical Leakage of Calamus, Single-Cone and Cold Lateral Condensation Obturation Techniques: A Computerized Fluid Filtration Study.

PURPOSE: Apical microleakage between the root canal and periapical tissues is considered a common cause of endodontic failure. The aim of this study was to evaluate the apical microleakage of various obturation techniques after immediate post space preparations with different drills. MATERIALS AND METHODS: One hundred twenty human single-rooted teeth were selected for this study. The coronal portions were removed to achieve a uniform length of 15 mm. All root canals were instrumented with ProTaper Next rotary files using crown-down technique. The 120 roots were randomly assigned to 3 experimental groups according to obturation technique (n = 40). The root canals were obturated with lateral condensation in group 1, single-cone technique in group 2, and Calamus 3D obturation system in group 3. Each group was divided into two subgroups (n = 20) according to drill types (Gates Glidden and Peeso drills) leaving 5 mm of apical gutta-percha. The apical microleakage was measured using the computerized fluid filtration meter method. The results were evaluated using Kruskal-Wallis test with Bonferroni Corrected Mann-Whitney U multiple comparison post hoc tests. RESULTS: There was no statistically significant difference between obturation techniques after post space preparation with Peeso drills (p > 0.05). In Gates Glidden drill groups, single-cone technique demonstrated higher leakage (0.0051 ± 0.0037 µl x min-1 × cmH2 O-1 ) than Calamus techniques (0.0019 ± 0.0012 µl x min-1 × cmH2 O-1 ) (p < 0.017). CONCLUSIONS: Gates Glidden drills caused the highest apical leakage in teeth obturated with single-cone technique.

Reliability of the Osstell Implant Stability Quotient and Penguin Resonance Frequency Analysis to Evaluate Implant Stability.

PURPOSE: To evaluate the reliability of the Osstell implant stability quotient (ISQ) and Penguin resonance frequency analysis (RFA) devices in measuring implant stability. MATERIALS AND METHODS: Forty implants were embedded in self-curing acrylic resin, soft-lining material, polyvinyl siloxane impression material, and polycarboxylate cement (n = 10). After the initial setting times were completed, the stability of each implant was measured with Osstell ISQ and Penguin RFA with 3 repeated measurements. The "intraclass correlation coefficient" evaluated the correspondence between the measurements (P < 0.05). RESULTS: Polyvinyl siloxane impression material had lower ISQ values than soft-lining material, self-curing acrylic resin, and polycarboxylate cement in both devices (P < 0.05). The intraclass correlation was 1.00 in self-curing acrylic resin and 0.48 in polycarboxylate cement (P < 0.05) for Osstell. This value was 0.95 in self-curing acrylic resin and 0.38 in polycarboxylate cement (P < 0.05) for Penguin. There was no correlation between the repeated measurements in soft-lining material and polyvinyl siloxane impression material for both devices (P > 0.05). The repeatability was 0.90 for Osstell and 0.60 for Penguin (P < 0.05). CONCLUSIONS: Osstell ISQ and Penguin RFA are reliable only when the implants are embedded in stiff materials. Osstell ISQ is more reliable than Penguin RFA.

Evaluation of morphology of the nasopalatine canal using cone-beam computed tomography in a subgroup of Turkish adult population.

PURPOSE: The aim of the study was to evaluate the anatomy and morphology of the nasopalatine canal (NPC) using cone-beam computed tomography (CBCT) and to determine variations of the NPC in relation to age, gender, and status of edentulism of anterior maxilla. METHODS: Patients scheduled for CBCT imaging for further radiographic evaluation of the maxilla with various reasons were consecutively enrolled in this study. Reformatted sagittal and coronal slices were analyzed with regard to dimensions and anatomic characteristics of the NPC. The correlation of age, gender, and status of edentulism of anterior maxilla with all the variables were evaluated. RESULTS: The study comprised 157 subjects with a mean age of 49.64 years. The analysis of the diameter of the incisive foramen revealed a mean of 4.48 mm whereas the diameter of the palatine foramen revealed a mean of 2.88 mm. The mean length of NPC was 10.87 mm and found significantly longer in males and patients with anterior teeth. In terms of incisive foramen and palatine foramen diameter, there was not any significant difference between males and females and between patients with and without anterior teeth (p > 0.05). CONCLUSION: There was relationship between the gender of the patients and the length of the NPC, with significantly lower mean values in females. This result suggests that careful analysis of anatomical structures by taking into consideration some variables would aid the clinician in performing a safer surgical intervention and prevent possible complications. CNCT scanning prior to implant surgery specifically in edentulous patients with severely atrophic maxillae might be a good diagnostic tool to guide the clinician for a safer and predictable procedure.

3D FEA of Hollow and Solid Design Zirconia Dental Dowels.

PURPOSE: The aim of this study was to evaluate the stress distribution of hollow and solid design zirconia dowels. MATERIALS AND METHODS: Finite element analysis (FEA) was used to investigate the influence of different dowel designs on the stress distribution of zirconia dowels. The coronal diameter of the dowel was 2.2 mm, the apical diameter was 1.8 mm, and the length was 15 mm. The diameter of the hollow space was 1.2 mm. Occlusal forces (both parallel and oblique) of 100 N were applied from the wider edge of the dowels simulating loads acting on the incisor during clenching and incising. The results were expressed in terms of von Mises criteria. RESULTS: FEA revealed differences in stress distribution. During parallel load, the maximum tensile stress of the hollow design (89.40 MPa) was greater than the solid design (43.30 MPa). During oblique load, the maximum tensile stress of the hollow design (1437.90 MPa) was greater than the solid design (917.96 MPa). The maximum deformation was observed in the coronal part of the dowel in both designs under the two load directions. CONCLUSIONS: FEA results showed that the hollow design zirconia dowels presented higher tensile stress.

Patients' knowledge and awareness of dental implants in a Turkish subpopulation.

PURPOSE: The purpose of this study was to evaluate the patients' knowledge on dental implants in a Turkish subpopulation. MATERIALS AND METHODS: Five hundred twenty seven Turkish adults referred to Yeditepe University Faculty of Dentistry, Istanbul, Turkey, were presented with a questionnaire including 20 questions regarding the level of information and awareness about the dental implants. The data were collected and statistical analyses were performed with Chi square test to compare the descriptive data. RESULTS: Among 527 subjects, 54% were female and 46% were male with a mean age of 42.2 years. The rate of patients' implant awareness was 27.7%. When the patients were questioned about the treatment options for rehabilitation of tooth missing, 60.9% of patients were informed about fixed partial denture, followed by conventional complete denture (32.5%) and removable partial denture (24.9%). Six percent reported that they were very well informed about the dental implants whereas 48.2% were poorly informed. The information sources of the implants were from the dentist (44.5%), printed media (31.6%) and friends and acquaintances (17.3%), respectively. Sixteen percent of the population believed that their implants would last forever. CONCLUSION: The dentists should give more detailed information to the patients about dental implants and tooth-supported fixed partial dentures in the future.

Prosthetic rehabilitation of maxillary dentoalveolar defects with fixed dental prostheses: two clinical reports.

Traumatic injuries or congenital malformations may cause soft and hard tissue defects resulting in the loss of alveolar bone and attached mucosa. Restoring the defective area presents a challenge for clinicians. The prosthetic rehabilitation of 2 patients with maxillary dentoalveolar defects with 2 different prosthetic designs is presented. The esthetic and functional requirements of the patients were fulfilled.

Management of a fractured implant abutment screw: a clinical report.

In an abutment screw fracture, it is generally a challenge for the clinician to remove fractured fragments. In some cases, the screw cannot be removed, and alternative solutions should be considered. This clinical report describes the replacement of a ball attachment with a fractured screw, which was impossible to retrieve, with a cast dowel with ball attachment. The patient who presented to the Department of Prosthodontics, Yeditepe University, Faculty of Dentistry was a 65-year-old woman, wearing a mandibular complete denture supported by two implants for 4 years. She complained about the loss of retention of the denture because of the fractured abutment screw, and it was found that another dentist had previously tried to retrieve the fractured screw with no success. It was decided to construct a cast dowel with ball attachment to improve retention without sacrificing the implant. The interior of the implant and the fractured screw were machined with a rotating instrument. An impression was taken with a metal strip and silicone-based materials. In the laboratory, a stone die was generated from the impression, and a custom-made cast dowel with ball attachment was constructed. It was then cemented with glass ionomer cement and connected to the denture with the direct method. The alternative procedure described in this clinical report was successful for the removal of the fractured abutment screw and use of the existing denture.