Seung-Ryong Ha

Effect of sandblasting and various metal primers on the shear bond strength of resin cement to Y-TZP ceramic

OBJECTIVES This study was designed to evaluate the effect of sandblasting and metal primers on the shear bond strength of three commercial resin cements to Yttria-Tetragonl Zirconia Polycrystal (Y-TZP) ceramics. METHODS One hundred and twenty Y-TZP ceramic cylinders (Ø7 mm x 12 mm) were embedded in polytetrafluoroethylene (PTFE) molds using PMMA. The specimens were divided randomly into 12 groups (n=10), according to the surface treatments (control; sandblast-only; metal primer-only; sandblast+metal primer) and metal primer-resin cements (Alloy primer - Panavia F 2.0, V-primer - Superbond C&B, Metaltite - M bond) rendered. The mixed resin cements were placed onto the treated zirconia surfaces in cylindrical shape (Ø3 mm x 3 mm) using PTFE molds. All specimens were thermocycled (5 and 55 degrees C, 5000 cycles) and subjected to shear bond strength test by a universal testing machine with a crosshead speed of 0.5 mm/min. All data were statistically analyzed using two-way ANOVA and multiple comparison Scheffé test (alpha=0.05), and SEM images of the fractured areas were used to evaluate the fracture mode. RESULTS In Panavia F 2.0, the bond strength of the specimens treated with sandblasting and metal primer (Alloy primer) was significantly higher than those of the other subgroups. In Superbond C&B and M bond, sandblasting significantly increased the shear bond strength, but the effect of metal primers (V-primer and Metaltite) was not significant and there was disordinal interaction. SIGNIFICANCE Metal primers are not always effective for bonding between Y-TZP ceramics and resin cements. Even though a metal primer is not enough to be used alone, combined application with sandblasting seems to be an appropriate pretreatment for improving the bond strength of resin cement to Y-TZP ceramics, especially in Panavia F 2.0.

The effect of preparation order on the crystal structure of yttria-stabilized tetragonal zirconia polycrystal and the shear bond strength of dental resin cements

OBJECTIVES The purpose of this study was to evaluate the effect of preparation order on the crystal structure of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) and the shear bond strength of dental resin cements. METHODS One-hundred fifty pre-sintered Y-TZP cylinders (Ø 9mm×13.5mm) were prepared and divided into three groups (control group, SBS group and SAS group). Specimens in control group were not treated. Specimens in SBS group were sandblasted and then densely sintered, and specimens in SAS group were sintered in advance, and then sandblasted. The specimens were analyzed by X-ray diffractometry, confocal laser scanning microscopy and Energy dispersive X-ray spectroscopy before and after sandblasting. All specimens were embedded in polytetrafluoroethylene (PTFE) molds using PMMA and each group was divided into five subgroups. The mixed resin cements (Clearfil SA luting cement, Zirconite, Superbond C&B, Rely-X Unicem, and Multilink) were placed onto the Y-TZP surfaces using PTFE molds with Ø 3mm×3mm, followed by storage in distilled water at 37°C for 24h, and thermocycling (5000 cycles at 5°C and 55°C with a 30s dwelling time). All specimens were tested for the shear bond strengths with a universal testing machine, and fractured surfaces were evaluated by SEM. Statistical analysis was performed using one-way ANOVA and Scheffé comparison with α=.05. RESULTS Sandblasting of the zirconia significantly increased shear bond strength of resin cements, but the preparation order had no significant influence on the shear bond strength in both test groups. In SEM observation, the natures of the surface faceting of the zirconia grains were totally different between SBS and SAS groups. SBS group exhibited less monoclinic structures than SAS group. SIGNIFICANCE Sandblasting of pre-sintered Y-TZP and then sintering may induce favorable proportion of tetragonal structures. This might have positive effect on the clinical performance of zirconia restorations.

Effect of the amount of thickness reduction on color and translucency of dental monolithic zirconia ceramics

PURPOSE This study investigated the effect of amount of thickness reduction on color and translucency of dental monolithic zirconia ceramics. MATERIALS AND METHODS One-hundred sixty-five monolithic zirconia specimens (16.3 mm × 16.3 mm × 2.0 mm) were divided into 5 groups (Group I to V) according to the number of A2-coloring liquid applications. Each group was then divided into 11 subgroups by reducing the thickness up to 1.0 mm in 0.1-mm increments (Subgroup 0 to 10, n=3). Colors and spectral distributions were measured according to CIELAB on a reflection spectrophotometer. All measurements were performed on five different areas of each specimen. Color difference (ΔE*ab) and translucency parameter (TP) were calculated. Data were analyzed using one-way ANOVA and multiple comparison Scheffé test (α=.05). RESULTS There were significant differences in CIE L* between Subgroup 0 and other subgroups in all groups. CIE a* increased (0.523.7) were obtained between Subgroup 0 and other subgroups. TP values generally increased as the thickness reduction increased in all groups (R2>0.89, P<.001). CONCLUSION Increasing thickness reduction reduces lightness and increases a reddish, bluish appearance, and translucency of monolithic zirconia ceramics.

Implant-supported overdenture with prefabricated bar attachment system in mandibular edentulous patient

Implant-supported overdenture is a reliable treatment option for the patients with edentulous mandible when they have difficulty in using complete dentures. Several options have been used for implant-supported overdenture attachments. Among these, bar attachment system has greater retention and better maintainability than others. SFI-Bar® is prefabricated and can be adjustable at chairside. Therefore, laboratory procedures such as soldering and welding are unnecessary, which leads to fewer errors and lower costs. A 67-year-old female patient presented, complaining of mobility of lower anterior teeth with old denture. She had been wearing complete denture in the maxilla and removable partial denture in the mandible with severe bone loss. After extracting the teeth, two implants were placed in front of mental foramen, and SFI-Bar® was connected. A tube bar was seated to two adapters through large ball joints and fixation screws, connecting each implant. The length of the tube bar was adjusted according to inter-implant distance. Then, a female part was attached to the bar beneath the new denture. This clinical report describes two-implant-supported overdenture using the SFI-Bar® system in a mandibular edentulous patient.

Biomechanical three-dimensional finite element analysis of monolithic zirconia crown with different cement type

PURPOSE The objective of this study was to evaluate the influence of various cement types on the stress distribution in monolithic zirconia crowns under maximum bite force using the finite element analysis. MATERIALS AND METHODS The models of the prepared #46 crown (deep chamfer margin) were scanned and solid models composed of the monolithic zirconia crown, cement layer, and prepared tooth were produced using the computer-aided design technology and were subsequently translated into 3-dimensional finite element models. Four models were prepared according to different cement types (zinc phosphate, polycarboxylate, glass ionomer, and resin). A load of 700 N was applied vertically on the crowns (8 loading points). Maximum principal stress was determined. RESULTS Zinc phosphate cement had a greater stress concentration in the cement layer, while polycarboxylate cement had a greater stress concentration on the distal surface of the monolithic zirconia crown and abutment tooth. Resin cement and glass ionomer cement showed similar patterns, but resin cement showed a lower stress distribution on the lingual and mesial surface of the cement layer. CONCLUSION The test results indicate that the use of different luting agents that have various elastic moduli has an impact on the stress distribution of the monolithic zirconia crowns, cement layers, and abutment tooth. Resin cement is recommended for the luting agent of the monolithic zirconia crowns.

Prosthetic reconstruction with an obturator using swing-lock attachment for a patient underwent maxillectomy: A clinical report

Patients who underwent resection of maxilla due to benign or malignant tumor, or accident will have defect in palatal area. They get retention, support and stability from remaining tissues which are hardly optimal. The advantage of swing-lock attachment design is having multiple contacts on labial and lingual side of the abutment teeth by retentive strut and palatal bracing component. Because the force is distributed equally to abutment teeth, abutment teeth of poor prognosis can be benefited from it. It is also more advantageous to cover soft tissue defects which are hard to reach with conventional prosthesis. A 56-year-old female patient who had undergone a maxillectomy due to malignant melanoma complaining of loose and unstable surgical obturator. Surveyed crowns were placed on #12, 26, and 27. Teeth #11, 21, 22, and 23 had lingual rest seat and #24 had mesial rest seat to improve stability and support of the obturator. This clinical report presents the prosthetic management of a patient treated with obturator on the maxilla using swing-lock attachment to the remaining teeth.

Implant-retained removable overdenture using prefabricated sfi®-bar

Soussan Irani1, Alireza Monsef Esfahani2, Shahram Sabeti3 and Farahnaz Bidari Zerehpoush3 1Assistant Professor, Department of Oral Pathology, Dental Faculty, Hamadan University, Hamadan, Iran 2Professor, Department of Pathology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran. 3Assistant Professor ,Pathology Department, Loghman Hospital, Shahid Beheshti University, Tehran, IranIntroduction: Camphorquinone (CQ) is popularly-used as photosensitizer in resin composites and dentin bonding agents (DBA). The purpose of this study is to investigate the influences of CQ on cytotoxicity to human dental pulp cells. Then, its effects on the expression of cell cycle and apoptosis related genes and proteins are evaluated. Besides, the relationship between ROS formation and its toxicity is also observed.Lingual thyroid (LT) is a developmental disorder due to the failure of the thyroid gland to migrate from its anlage, foramen caecum to its prelaryngeal site. Lingual position represents the most frequent ectopic location accounting up to 90% of ectopic cases. It is found at the junction of the anterior two thirds and the posterior third, between the epiglottis and the circumvallate papillae, often asymptomatic but growing may cause local symptoms as upper airway obstruction, disphagia and hemorrhage at any time from infancy to adulthood. Thyroid scintigraphy plays the most important role in diagnosing ectopic thyroid gland but neck ultrasound, neck CTscan, neck MRI contribute as well. Treatment of this anomaly includes exogenous Lthyroxine hormone administration, radioiodine ablation therapy and surgery.BACKGROUND Dental crowding is the one of the most frequently encountered problem for an orthodontist. The relationship between crowding and various skeletal, dental and soft tissue parameters is important to establish and consider during the overall orthodontic treatment planning. This study aimed to determine the correlation of maxillary and mandibular base lengths with dental arch crowding in different malocclusions and to evaluate the gender dimorphism for these variables. METHODS A sample of 120 subjects divided into three skeletal malocclusions was further subdivided based on amount of mandibular arch crowding. Maxillary and mandibular base lengths and dental arch crowding were measured on pre-treatment lateral cephalograms and initial casts using vernier calliper respectively. Inter-group comparisons were assessed by univariate analysis of variance. Correlation between base lengths and dental crowding was assessed by Pearsons correlation (p≤0.05). RESULTS Statistically significant differences were found for maxillary (p=0.008) and mandibular base lengths (p=0.000) between different skeletal malocclusions. Mandibular base length was significantly larger in males (p=0.000). Mandibular crowding was highest in class-II and lowest in class-I (p=0.01). A significant but weak negative correlation was found between dental crowding and maxillary (r=-0.28, p=0.02) and mandibular (r=-0.20, p=0.02) base lengths, significant but moderate positive correlation between maxillary and mandibular base lengths (r=0L566, -0.000) and between maxillary and mandibular crowding (r=-0.408, p-0.000). CONCLUSIONS Maxillary and mandibular base lengths are largest in skeletal class-II and class-III malocclusions respectively. Mandibular base length is larger in males as compared to females. An increase in amount of dental crowding is weakly associated with smaller skeletal base lengths.Background: The limitations and morbidity associated with autogenous bone grafting have driven the search for predictable bone substitutes and bioimplants. Stem cells offer an interesting tool for tissue engineering, thus the purpose of this study was to observe and compare the regenerative capacity of artificial alveolar bone defect after autogenous bone grafting versus seeding of Adipose TissueDerived Stem cells (ADSCs) either alone or in combination with demineralized bone matrix (DBM). Methodology: Standardized bilateral buccal dehiscence defects (4 × 3 × 3 mm) were surgically created in 24 healthy dogs and divided into 6 groups , Control group, Autogenous bone graft group, ADSCs group, ADSCs together with autogenous bone grafting, DBM group and finally ADSCs and DBM group. All animals were subjected to histological and histomorphometric analysis. Results: Histolgic and histomorphometric analysis within the same group revealed that the coronal mean values were higher in control, ADSCs with DBM and DBM groups and the apical values were higher in the three other groups. Conclusion: This study demonstrated that the adipose derived stem cells with DBM have potential as a suitable alternative to autogenous bone in the treatment of alveolar bone defect. 3rd FUE Dental Conference Cairo 2016, April Abstract.......................................................................................................................... iiiAlthough various treatment modalities are available, which aim at the correction of a Class III malocclusion during the growth period, these have proved unsuccessful in maintaining the results for a long time. Retention appliances are required to be worn until growth is complete. And relying on the patient to cooperate over long and extent treatment protocols is a potential problem in achieving successful,stable treatment results. Surgical intervention may be still needed in a few cases.

Comparison of polymer-based temporary crown and fixed partial denture materials by diametral tensile strength.

PURPOSE The purpose of this study was to investigate the diametral tensile strength of polymer-based temporary crown and fixed partial denture (FPD) materials, and the change of the diametral tensile strength with time. MATERIAL AND METHODS One monomethacrylate-based temporary crown and FPD material (Trim) and three dimethacrylate-based ones (Protemp 3 Garant, Temphase, Luxtemp) were investigated. 20 specimens (ø 4 mm × 6 mm) were fabricated and randomly divided into two groups (Group I: Immediately, Group II: 1 hour) according to the measurement time after completion of mixing. Universal Testing Machine was used to load the specimens at a cross-head speed of 0.5 mm/min. The data were analyzed using one-way ANOVA, the multiple comparison Scheffe test and independent sample t test (α = 0.05). RESULTS Trim showed severe permanent deformation without an obvious fracture during loading at both times. There were statistically significant differences among the dimethacrylate-based materials. The dimethacrylate-based materials presented an increase in strength from 5 minutes to 1 hour and were as follows: Protemp 3 Garant (23.16 - 37.6 MPa), Temphase (22.27 - 28.08 MPa), Luxatemp (14.46 - 20.59 MPa). Protemp 3 Garant showed the highest value. CONCLUSION The dimethacrylate-based temporary materials tested were stronger in diametral tensile strength than the monomethacrylate-based one. The diametral tensile strength of the materials investigated increased with time.