Nuran Yanikoglu

Changes in the mandibular angle in the dentulous and edentulous states

STATEMENT OF PROBLEM Reliable measurement of individual gonial angles is difficult because of the superimposed images appearing on the lateral cephalograms. However, this disadvantage is not encountered in orthopantomography. PURPOSE This study determined whether the mean measurements of the mandibular angles of a group of totally edentulous patients were greater than those of unilaterally and posteriorly partially edentulous patients. Changes in the gonial angle between denture wearers and nondenture wearers in each group were also compared. MATERIAL AND METHODS A total of 134 panelipse radiographs were used for measurements of mandibular angles. All radiographs used in this study were taken with the same panelipse machine by the same person. Of the 134 radiographs, 49 were of unilaterally and posteriorly partially edentulous adults and 85 were of totally edentulous adults. RESULTS No significant differences were found between the mandibular angles when comparing partially edentulous and totally edentulous subjects. CONCLUSION Within the limits of this study, there was no significant difference between the dentulous and edentulous states.

The effect of staining solutions on the color stability of provisional prosthodontic materials

OBJECTIVES The aim of this study was to evaluate the effects of staining solutions on the color stability of self-cure provisional resin materials. METHODS The specimens were prepared for each of three auto-polymerized bis-acryl resin and auto-polymerized methyl methacrylate provisional resin material. The baseline color values were measured with a colorimeter according to the CIE L(*)a(*)b(*) color scale. After the first measurement (T(0)), specimens were placed in staining solutions (coffee, coca-cola, burn and distilled water for control group) and the other measurements were taken after 24h (T(1)), 1 week (T(2)) and 4 weeks (T(3)). RESULTS Data were analyze statistically by (a) repeated measures (ANOVA), (b) one and two way ANOVA, and (c) Tukey HSD multiple comparison tests. At the 24h immersion period, the post hoc analysis indicated that AccessCrown-coffee revealed the highest ΔE(*) values (4.4). At the second immersion period (1 week), Structur2 SC-coffee had the highest ΔE(*) values compared with other materials (5.4). CONCLUSIONS The degrees of discoloration were increased with immersion time. The methylmethacrylate resin was more resistant to discoloration than bis-acryl resins. After immersion for 30 days, the coffee solution resulted in unacceptable discoloration for all the tested materials.

Radiological evaluation of changes in the gonial angle after teeth extraction and wearing of dentures: a 3-year longitudinal study

OBJECTIVE The aim of this study was to evaluate the gonial angle measurements of 20 adult patients made from panoramic radiographs and to assess differences from dentate state to edentate state-with dentures. STUDY DESIGN A total of 100 panoramic radiographs of 20 patients were evaluated, and gonial angle sizes were measured. Panoramic radiographs were made while the patients were dentulous and in the first month, sixth month, first year, and third year after tooth extraction and wearing dentures after a 2-3-month healing period. All radiographs used in this study were made with the same panoramic machine by the same person. Gonial angles were measured by tracing a line on panoramic radiographs tangential to the most inferior points at the gonial angle and the lower border of the mandibular body and another line tangential to the posterior borders of the ramus and the condyle. RESULTS Difference in size of the gonial angle was found for both sides between continuous measurements. The gonial angle values tend to increase in both sides after tooth extractions. After the third measurement for both sides, the values start to decrease. CONCLUSION After wearing denture for 3 years, a statistically significant decrease was found in the gonial angle values according to the edentulous state (P < .05).

The Effect of Sandblasting, Er:YAG Laser, and Heat Treatment on the Mechanical Properties of Different Zirconia Cores

OBJECTIVE The purpose of this study was to evaluate the effect of surface and heat treatments on the mechanical properties and phase transformation of yttria-stabilized tetragonal zirconia (Y-TZP) materials. BACKGROUND DATA Zirconia is exposed to several treatments during dental application process. Knowing the effect of applied treatments on zirconia is essential for clinical success. MATERIAL AND METHODS Forty disk specimens of Zirkonzahn (Z) and DC-Zirkon (DC) materials were fabricated. The specimens were randomly divided into four groups according to surface [control, sandblasting, Erbium: Yttrium Aluminum Garnet (Er:YAG) laser irradiation] and heat (firing) treatments. The surface roughness (Ra, μm) was measured using a surface profilometer. The relative amount of the transformed monoclinic (m) phase was analyzed by X-ray diffractometry (XRD). Biaxial flexural strength was tested using piston-on-three-ball technique. The data were analyzed with the Kruskal-Wallis H test with Bonferroni correction, and the Mann-Whitney U test was used for pairwise comparisons. RESULTS There were no significant differences in surface roughness among the treated groups (p > 0.05), whereas sandblasting showed higher surface roughness than other treatments for both materials. Scanning electron microscopic (SEM) analyses revealed changes in surface morphology after surface treatments, especially in laser groups with the formation of cracks, and in sandblasting groups with the formation of microretentive grooves. The greatest amount of the monoclinic phase was measured after sandblasting (8.13%) for Z and (19.8%) for DC. The monoclinic phase reverted to the tetragonal phase after heat treatment. Heat treatment groups showed significantly lower flexural strength than other treatments (p < 0.05). CONCLUSIONS Heat and surface treatments influenced the mechanical properties of zirconia ceramic. The biaxial flexural strength and crystalline phase of materials decreased after heat treatments.

Evaluation of the flexural strength of dual-cure composite resin cements.

The aim of this study was to evaluate of flexural strength of some adhesive resin cements. Three dual-cure composite resin cements (Nexus 3; Variolink II, Panavia F) were prepared. The manufacturers mixing directions for the cements were followed. Adhesive resin cement was mixed, placed in the rectangular portion of the mold. Fifteen specimens were prepared for each cements. The cements were light-activated with light lamp for 40 s on both and top and bottom surfaces. The each cement specimens were divided into three groups according to time of storage and stored in distilled water for 24 h, 15, and 30 days. Total 45 specimens were stored at 37°C (98.6 0F) in distilled water for 24 h, 15, and 30 days prior to tests. The flexural strength was tested wıth a universal testing machine at a crosshead speed of 0.5 mm/min (0.02 in.) The maximum load was recorded as MPa. The results were analyzed by Analysis of Variance and Duncan test. The Panavia F resin cements content Bisphenol A was showed the highest flexural strength (80.80 MPa) (11.71 ksi) for 24 h. The lowest flexural strength was observed in Nexus 3 (51.00 MPa) (7.39 ksi). It was found significant interaction of material and time (p < 0.05). The types of cement and time of storage was statistically significant on the flexural strengths (p < 0.001).

Effect of sealer coating and storage methods on the surface roughness of soft liners

STATEMENT OF PROBLEM A soft lining is applied under a removable prosthesis for various reasons. The porosity of the lining material may increase colonization by microorganisms and cause tissue inflammation. PURPOSE The purpose of this in vitro study was to evaluate the effect of sealer coating on the surface roughness of soft lining materials under 4 different conditions. MATERIAL AND METHODS A total of 125 specimens were prepared. One high-temperature silicone-based soft lining material and 2 room-temperature-polymerized soft lining materials (1 silicone-based and 1 methacrylate-based) were used. Twenty-five specimens of each room-temperature soft lining material were coated with 2 layers of surface sealer. Additionally, 5 specimens of each material were stored in either distilled water, Coca-Cola, denture cleanser, saliva, or air. The surface roughness was measured at baseline and after 1, 7, 14, and 28 days. Surface roughness values were analyzed with repeated measures analysis of variance, and the Bonferroni multiple comparison test was performed using time-dependent groups and storage methods. RESULTS In the time-dependent groups, methacrylate-based sealer-coated soft liners exhibited a significant increase in roughness (1.74-2.09 μm, P<.001), and silicone-based sealer-coated soft liners exhibited a decrease in roughness, but it was not significant (2.16-2.02 μm, P>.05). Therefore, the sealer coating was not effective in reducing surface roughness. Among the time-dependent storage methods, the denture cleanser exhibited an almost significant increase in roughness (1.83-1.99 μm, P=.054). Coca-Cola and artificial saliva did not show a significant difference (P>.05). However, a significant decrease in roughness was found with distilled water (P=.02) and air (P<.001). CONCLUSIONS Statistically significant differences in surface roughness were found among the different types of soft liners. The sealer coating had no significant effect, and denture cleanser slightly increased the surface roughness. Contrary to expectations, the roughness did not increase in all groups over time.

The Evaluation of Flexural Strength of Composite Resin Materials with and without Fiber

The aim of the present study was to evaluate the effect of solutions, times of storage and reinforcement with fiber on the flexural strength of different composite materials. Nanofill and nanohybrid composite materials with and without fiber, a glass fiber and polyethylene fiber, were tested in the present study. 72 specimens (25×2×2 mm³) were prepared as following six groups; Group ECME: everStick Fibre / Clearfil Majesty Esthetics, Group EFU: ever Stick Fibre / Filtek Ultimate, Group RCME: Ribbond Fibre / Clearfil Majesty Esthetics, Group RFU: Ribbond Fibre / Filtek Ultimate, Group CME: Clearfil Majesty Esthetics, Group FU: Filtek Ultimate. The specimens were stored in distilled water and mouthwash and tested after 24 hours and 7 days. Data were analyzed using analysis of variance and Schefee test. It was found that the EFU group in distilled water for 24 hours had the highest flexural strength and the CME group in mouthwash for 7 days had the lowest flexural strength. The storage times and the solutions were not statistically significant factors affecting on the flexural strength. The mean flexural strength values of the RCME and the RFU groups were similar to the FU group.

SEM evaluation of surface morphologic analysis of restorative materials with three laser treatment

Objective: The aim of this study is to analyze the effect of laser treatment on surface morphology of restorative materials. Materials and Methods: The samples included 19 porcelain ceramics (Group P), 10 half yttrium stabilized zirconia (Y-TZP) and half porcelain (Group ZP), and 13 Y-TZP ceramic (Group Z). Pilot study was applied on the prepared samples to determine the effectiveness of hydroxyapatite or graphite powder before surface treatment. Following the pilot study, three laser systems were treated over all ceramic surfaces and scanning electron microscope (SEM) images were taken to do topographic analysis of the samples. Results: According to the results of pilot study; surfaces of zirconia, porcelain, and zirconia-porcelain samples were covered with graphite powder and then treated by CO 2 laser, erbium:Yttrium-aluminum-garnet (Er:YAG) and neodymium:YAG (Nd:YAG) laser. SEM observations were reported for all laser types and all laser parameters that were chosen. Conclusion: The three types of laser products; CO 2 , Er:YAG, and Nd:YAG are also effective on different output powers on different types of restorative materials.

Evaluation of the fracture resistance of computer-aided design/computer-aided manufacturing monolithic crowns prepared in different cement thicknesses

Introduction: The purpose of this study was to evaluate the fracture resistance of monolithic computer-aided design/computer-aided manufacturing (CAD/CAM) crowns that are prepared with different cement thickness. Materials and Methods: For this investigation, a human maxillary premolar tooth was selected. Master model preparation was performed with a demand bur under water spray. Master die was taken to fabricate 105 epoxy resin replicas. The crowns were milled using a CEREC 4 CAD/CAM system (Software Version, 4.2.0.57192). CAD/CAM crowns were made using resin nanoceramic, feldspathic glass ceramic, lithium disilicate, and leucite-reinforced ceramics. Each group was subdivided into three groups in accordance with three different cement thicknesses (30, 90, and 150 μm). Crowns milled out. Then RelyX™ U200 was used as a luting agent to bond the crowns to the prepared samples. After one hour cementations, the specimens were stored in water bath at 37°C for 1 week before testing. Seven unprepared and unrestored teeth were kept and tested as a control group. A universal test machine was used to assume the fracture resistance of all specimens. The compressive load (N) that caused fracture was recorded for each specimen. Fracture resistance data were statistically analyzed by one-way ANOVA and two-factor interaction modeling test (α = 0.001). Results: There are statistically significant differences between fracture resistances of CAD/CAM monolithic crown materials (P < 0.001). It is seen that cement thickness is not statistically significant for fracture resistance of CAD/CAM monolithic crowns (P > 0.001). Conclusions: CAD/CAM monolithic crown materials affected fracture resistance. Cement thickness (30, 90, and 150 μm) was not effective on fracture resistance of CAD/CAM monolithic crowns.

Effect of ceramic surface treatments on the bond strength of different composite resins

Abstract This study was aimed to observe the relationship between the different surface treatments and the bond strength of both composite based adhesive cement and zirconia ceramic. Thirty-two zirconia ceramic discs were fabricated by following the instructions of manufacturer (5 × 5 × 1.5 mm). Four subgroups were obtained from the specimens according to the specified surface treatments respectively: (a) C: control groups: no treatment; (b) SB: sandblasting with 125 μm aluminum oxide particles for 10 s; (c) SC: silica coating for 10 s; (d) Nd :YAG laser . The composite resin specimens Panavia F and Clearfil SA were introduced and polymerized to the treated bonding areas. Afterwards the specimens were stored in distilled water at 37 °C during 24 h, and the shear test was applied. The data were statistically analyzed by ANOVA and Duncan tests. The bond strength was stated significantly higher in silica coating/Panavia F group (23.35 MPa). The lowest bond strength was stated in control groups cemented with Clearfil SA (12.25 MPa). As a result it was determined that the bond strength has affected the both surface treatments and cement types (p < 0.001). The silica coating –treated zirconia ceramic recorded a significant increase in mean bond strength values.