Bülent Gökçe

Bond Strengths of All-Ceramics: Acid vs Laser Etching

Various applications of dental lasers on dental materials have been proposed for surface modifications. This study evaluated whether laser etching could be an alternative to hydrofluoric acid (HF) etching. One hundred and ten lithia-based all-ceramic specimens (Empress 2) (R: 4 mm, h: 4 mm) were prepared and divided into five groups (n = 22/group). The untreated specimens served as the control, while one of the experimental groups was treated with 9.5% HF for 30 seconds. Three remaining test groups were treated with different laser (Er:YAG laser wavelength:2940 nm, OpusDent) power settings: 300 mJ, 600 mJ and 900 mJ. Ten specimens in each group were luted to the other 10 specimens by a dual-curing cement (Variolink II), and shear-bond strength (SBS) tests were performed (Autograph, crosshead speed: 0.5 mm/minute). The results were statistically analyzed (Kruskal Wallis and Mann Whitney-U, alpha = .05). Mean SBS (MPa) were 31.9 +/- 4.0, 41.4 +/- 4.3, 42.8 +/- 6.2, 29.2 +/- 4.5 and 27.4 +/- 3.8 for the control and HF, 300, 600 and 900 mJ groups, respectively. SEM evaluations revealed different surface morphologies depending on the laser parameters. The differences between HF acid and 300 mJ, when compared with the control, 600 and 900 mJ groups, were significant (p < .05). The 300 mJ laser group exhibited the highest shear-bond strength values, indicating that laser etching could also be used for surface treatments.

Effect of antioxidant treatment on bond strength of a luting resin to bleached enamel

PURPOSE The aim of this study was to comparatively investigate the effect of antioxidant treatment and delayed bonding after bleaching with carbamide peroxide on the shear bond strength (SBS) of a luting resin to enamel. MATERIALS AND METHODS Forty flat enamel surfaces were prepared from freshly extracted human molars using a low speed diamond saw, then divided into three bleaching groups (n=10/group) and a control group (n=10). Group 1 consisted of specimens bonded immediately after bleaching. Group 2 specimens were treated with an antioxidant agent, 10% sodium ascorbate, while Group 3 specimens were immersed in artificial saliva for 1 week after bleaching. Specimens in Group 4 were not bleached, but immersed in artificial saliva for 1 week before bonding. Forty ceramic blocks (Empress 2, Ivoclar) were prepared and luted to teeth using a dual-curing resin cement (Variolink II, Ivoclar). The specimens were thermocycled and the SBS tests were performed using a universal testing machine (crosshead speed: 0.5mm/min). Fracture analysis of the bonded surfaces was done using a scanning electron microscope. Statistical analysis was carried out by Kruskall-Wallis and Mann-Whitney U-tests. RESULTS While the samples that were immediately bonded after bleaching (Group I) demonstrated significantly lower shear bond strengths and 10% sodium ascorbate group (Group II) demonstrated significantly higher bond strengths than control group samples (p<0.05), no significant differences were found among delayed bonded group and control group (p>0.05). CONCLUSION Using sodium ascorbate with a concentration of 10% may be reliable for reversing the compromised bond strength.

Influence of cervical finish line type on the marginal adaptation of zirconia ceramic crowns

The current study evaluated the effect of different cervical finish line designs on the marginal adaptation of a zirconia ceramic. Four different marginal finish lines (c: chamfer, mc: mini-chamfer, fe: feather-edge and s: rounded shoulder) were prepared on phantom incisors. Die models for each preparation group (N = 28, n = 7 per finish line design group) were made of epoxy resin. Y-TZP (ICE Zirkon) frameworks were manufactured by a copy-milling system (Zirconzahn) using prefabricated blanks and tried on the master models for initial adaptation of the framework; they were then sintered, followed by veneering (Zirconzahn). The finished crowns were cemented with a polycarboxylate cement (Poly F) under 300 g load and ultrasonically cleaned. The specimens were sliced and the marginal gap was measured, considering absolute marginal opening (AMO) and marginal opening (MO) for each coping under a stereomicroscope with image processing software (Lucia). The measurements were statistically analyzed using the Kruskal Wallis, Mann Whitney and Wilcoxon Signed Ranks tests at a significance level of alpha = 0.01. Means of AMO measurement (microm) for the feather-edge finish line (87 +/- 10) was significantly lower than that of the chamfer (144 +/- 14), shoulder (114 +/- 16) and mini-chamfer finish line types (114 +/- 11) (p < 0.01). Means of MO measurements was the lowest for feather-edge finish line (68 +/- 9) (p < 0.01) and then, in ascending order, shoulder (95 +/- 9), mini-chamfer (97 +/- 12) and chamfer (128 +/- 10). The cervical finish line type had an influence on the marginal adaptation of the tested zirconia ceramic. Although the feather-edge finish line resulted in lower AMO and MO values, with its proven mechanical disadvantage, it cannot be recommended in clinical applications of zirconia crowns. This type of finish line has acted solely as a control group to test the null hypothesis in the current study. For better marginal adaptation, both shoulder and mini-chamfer finish line types could be suggested for zirconia crowns.

Bond Strength Comparison of Amalgam Repair Protocols Using Resin Composite in Situations With and Without Dentin Exposure

The replacement of defective amalgam restorations leads to loss of tooth material and weakens the tooth, creating an increased risk of cusp fracture. The repair of such defects is a minimal intervention technique. The current study compared the repair bond strengths of a resin composite to amalgam and an amalgam-dentin complex after various surface conditioning methods. The specimens (N = 50) consisted of sound human canines with cylindrical preparations (diameter: 2.3 mm, depth: 3 mm) with amalgam-dentin complex (N = 30, n = 10/per group) and two groups with amalgam only (N = 20, n = 10/per group). The teeth were embedded in auto-polymerized polymethylmethacrylate (PMMA). The preparations were filled with non-Gamma 2 amalgam. The enamel was removed to expose dentin. The specimens with the amalgam-dentin complex were randomly assigned to one of the following conditioning methods: Group 1: Silicacoating amalgam, etching dentin, silane application on amalgam, primer/bonding on dentin, opaquer on amalgam, resin composite on both; Group 2: Etching dentin, silicacoating amalgam, silane application on amalgam, primer/bonding on dentin, opaquer on amalgam, resin composite on both and Group 3: Etching dentin, primer/bonding on dentin, opaquer, resin composite. The specimens with only amalgam were assigned to one of the following conditioning methods: Group 4: Silicacoating, silane application, opaquer, resin composite and Group 5: Opaquer, resin composite. For the two control groups, where no dentin was involved (Groups 4 and 5), bonding was achieved only on amalgam and Group 5 had no conditioning. The specimens were kept in water at 37 degrees C for five weeks before bond strength (MPa +/- SD) testing (Universal Testing Machine). After debonding, the failure types were analyzed. The results were significantly affected by the surface conditioning method (ANOVA). Only dentin conditioning (Group 3) showed the highest bond strength (39.9 +/- 14). The unconditioned control group (Group 5) showed the least favorable results (1.4 +/- 0.5). Multiple comparisons (Tukey-Kramer adjustment) showed that the mean values of Group 1 (34.1 +/- 11.4), 3 (39.9 +/- 14) and 4 (35.5 +/- 4) were not significantly different (p > 0.05), but between Groups 2 (22.8 +/- 6.6) and 3 (39.9 +/- 14), significant differences were observed (p = 0.0027). For reliable repair of amalgam restorations, including dentin fractures, the amalgam surface should first be silica coated, then the dentin/enamel should be etched, washed and rinsed thoroughly. Finally, the amalgam should be silanized and primer/bonding applied onto the dentin.

Prosthetic rehabilitation of segmental odontomaxillary dysplasia: seven-year follow-up.

Segmental odontomaxillary dysplasia is an uncommon maxillofacial deformity. Clinically, overgrowth and maturation of the maxillary right or left posterior alveolus and the respective gingiva, lack of premolars, delayed eruption of the adjacent teeth, and malformed primary molars are observed. The purpose of this report was to describe the clinical and radiographic findings of a 47-year-old female with segmental odontomaxillary dysplasia and summarize the prosthetic rehabilitation with fixed and removable partial dentures. A 7-year follow-up did not reveal biomechanical or functional problems except the loss of the mandibular left central incisor and wear of the artificial teeth.

Comparison of Mouth Opening Angle Between Dentate and Edentulous Subjects

Abstract Angle of mouth opening provides information concerning temporomandibular joint mobility. The aim of this study was to compare angle of mouth opening of dentate and edentuluous subjects at similar ages. Eighty (80) subjects, 24 women and 16 men (mean age 51.2 yrs.) for the dentate group and 21 women and 19 men (mean age 52.3 yrs.) for the edentuluous group participated in the study. The angle of mouth opening measurements were performed with a mandibular goniometer at four independent sessions of three measurements. The angle of mouth opening values of the dentate group were significantly higher than that of the edentulous group. The results of this study revealed that tooth loss resulted in a decrease in angle of mouth opening values independent of gender and age. The clinical implications of this finding is that oral function might well be preserved with advancing age if dentition is maintained in good condition.

The effect of different enamel surface treatments on microleakage of fissure sealants

OBJECTIVE The aim of this study was to evaluate the effects of different techniques of surface treatment on the microleakage of fissure sealants in permanent molar teeth in vitro. MATERIALS AND METHODS 96 extracted impacted human third molars were randomly divided into 8 surface treatment groups (n=12/group) as 1. Er: YAG laser ; (Fidelis II, Fotona, Ljubljana, Slovenia) (125 mj, 20Hz) ; 2. Er: YAG laser + 37% H3PO4 (15s) ; 3. ER: AG laser + 37% H3PO4+Prime&Bond NT ; 4. Er: YAG laser + G Bond ; 5. Er: YAG laser + Prime&Bond NT ; 6. 37% H3PO4 ; 7. 37% H3PO4 + Prime&Bond NT ; 8. G Bond. Sealant material (Clinpro, 3M ESPE, Seefeld, Germany), was applied into the fissures and light-cured for 20s with LED (Bluephase C5, Ivoclar-Vivadent, Schaan, Liechtenstein). Specimens were subjected to thermocycling (1000×, 5-55°C, dwell time: 15s) and immersed in 0.5% basic fuchsin solution for 24h at 37°C. The samples were sectioned and scored on a 3 point rating scale using a light microscope with a magnification of ×20. One-way analysis of variance was used to analyze data. Multiple comparisons were analyzed using Bonferroni test (p=0.05). RESULTS Er:YAG laser showed the highest microleakage scores whereas Er YAG laser + 37% H3PO4 showed the lowest. Although 37% H3PO4 group showed higher scores than Er:YAG laser + 37% H3PO4, the difference was not statistically significant. CONCLUSION Etching fissures with phosphoric acid is sufficient prior to fissure sealant application.

Laser use vs. handpiece for tooth preparation: A preliminary in vitro study

The key fields of research of dental lasers have focused on the use of different wavelengths on hard and soft tissues; however it is not clear whether they can be used for tooth preparation for full coverage restorations or not. The objective of this study was to investigate the possibility of tooth preparation for full coverage restorations using a scanner assembly added-on Er:YAG laser system and compare the tooth preparation durations performed with dental drills and the laser. The 20 freshly extracted human molar teeth were allocated to two groups (A and B) of 10. Group A was prepared with dental drills, whereas group B was prepared with a scanner assembly added-on Er:YAG laser system. The preparation duration means of the groups were calculated and analyzed by one-way analysis of variance. The difference between group A (20, 2±1, 9 min) and B (45, 2±|3, 1 min) (P<0.01) was significant. Laser preparation took more time than the conventional rotary instrumentation. The recommended amount of tooth reduc...

A study of compressive strength between zirconia framework and veneering ceramic as a function of thermal expansion coefficient using Shell–Nielsen test method

This study investigated the adhesion between zirconia framework and four veneering ceramic (VC) materials with varying coefficients of thermal expansions (CTE). Zirconia rods (N = 40) (ICE Zirkon) (diameter: 4 mm, height: 20 mm) were milled and sintered. After firing, the zirconia rods were air-abraded and cleaned. They were randomly assigned to receive four VCs (n = 10/group), namely (a) Vita VM9 (VZ; 9–9.2 × 10−6  K−1), (b) Cerabien ZR (CZ; 9.1 × 10−6 K−1), (c) Matchmaker ZR (MM; 9.4 × 10−6 K−1), and (d) Ice Zirconia Ceramic (IZ; 9.6 × 10−6 K−1). The VCs were then fired onto zirconia rods (height: 2 mm, thickness: 2 mm) circumferentially and were thermocycled for 6000 times (5/55 °C, dwell time: 30 s). Specimens were loaded from the top of the zirconia rods (0.5 mm/min) in a universal testing machine until debonding. Shell–Nielsen bond strength values were calculated (MPa). Failure types were evaluated under SEM. The data were statistically analyzed (one-way ANOVA, Tukey’s; α = 0.05). Weibull distribution values including the Weibull modulus (m) (0.05) was calculated. The highest mean bond strength (MPa) was obtained for CZ (42.08 ± 4.08), followed by VZ (41.77 ± 4.92), MM (40.7 ± 3.64), and IZ (40.05 ± 5.78). While mean bond strength for VZ, MM, and IZ were not significantly different (p > 0.05), CZ was significantly higher than that of IZ (p < 0.05). The lowest shape value was for VZ (m = 16.94) and the highest for MM (m = 20.16). Mainly, adhesive failures followed by mixed failures were observed. VCs with a greater mismatch of CTE with the zirconia framework exhibited similar Shell–Nielsen bond strength to those with fewer mismatches. CTE mismatch did not affect the results of CZ (9.1 × 10−6 K−1) and IZ (9.6 × 10−6 K−1).

Hypohidrotic ectodermal dysplasia: a multidisciplinary approach.

Hypohidrotic ectodermal dysplasia (HED; Christ-Siemens-Touraine syndrome) is a genetic disorder characterized by sparse hair, oligodontia with peg-shaped teeth, reduced sweating, and defects in a number of other ectodermal organs. A partial or complete absence of eccrine glands can lead to recurrent severe overheating that may cause seizures and neurological deficits. This clinical report presents a 14-year-old male patient with hypohidrotic ectodermal dysplasia, including the clinical and radiographic findings, and multidisciplinary treatment. The Schedule for Affective Disorders and Schizophrenia for School Aged Children-Present and Lifetime Version (K-SADS-PL) was administered to patient along with mother to assess for any psychiatric disorders. The screening and rating scales completed by mother and two teachers to evaluate the severity of attention deficit hyperactivity disorder (ADHD) symptoms, and other behavioral problems. Patients academic performance, adaptive functioning, and problem behavior was evaluated using The Teacher Report Form. Mental capacity was assessed with the Wechsler Intelligence Scale for Children (WISC-R). Illness Perception Questionnaire Revised was used to systematically assess illness representation attributes and emotional representations of illness. On the psychiatric diagnosis assessment using K-SADS-PL sub-threshold attention deficits and anxiety symptoms were determined. In this case we established a multidisciplinary approach in his treatment with pediatric, dermatological, and dental examinations, beside his psychiatric evaluation. The prosthetic rehabilitation included restoring upper teeth with copings and fabrication of upper and lower complete dentures. Metal framework was not incorporated in the partial denture design allowing modifications as the oral and maxillofacial development continued. Removable complete or partial dentures without metal framework is a treatment of choice until the completion of facial growth at which definitive treatment is considered.