Atiye Nilgun Ozturk

Evaluation of the marginal fit of full ceramic crowns by the microcomputed tomography (micro-CT) technique.

Objective: To evaluate the marginal gap (MG) and absolute marginal discrepancy (MD) of full ceramic crowns with two finish line designs, shoulder and chamfer, using microcomputed tomography (micro-CT) before and after cementation. Materials and Methods: Sixty extracted human maxillary premolar teeth were divided into two groups based on the finish line design: Group I: 90° shoulder and Group II: 135° chamfer. The specimens were further grouped based on the type of full ceramic crown they received: Group A: Feldspathic Cerec inLab ceramic system, Group B: Cerec inLab aluminum oxide ceramic system and Group C: Lithium disilicate press ceramic system. Before cementation, five crowns from each group were scanned using micro-CT in two sections, sagittal and coronal, to determine the MG and MD values for four regions of the crown (sagittal buccal, sagittal lingual, coronal mesial and coronal distal). After cementation and thermal cycling, the scanning was repeated. Measurements were obtained from 10 points for each region, 80 points totally, to evaluate the MG and MD values. Files were processed using NRecon and CTAn software. Results were statistically analyzed using one- and two-way ANOVA and Tukey HSD tests (P = 0.05). Results: Full ceramic systems showed clinically acceptable marginal adaptation values. The Feldspathic Cerec inLab ceramic system generally presented the lowest variance, except in the MG values of the coronal mesial region. The MG and MD values of all ceramics increased significantly after cementation, except in the shoulder preparation design (sagittal buccal region) for MG and in the chamfer preparation design (sagittal lingual region) for MD values. Conclusions: Full-ceramic crowns showed clinically acceptable marginal adaptation values. The Feldspathic Cerec inLab ceramic system (Vitablocs Mark II) generally presented the lowest variance when compared with the other ceramics, except for the MG values on the mesial surface of the coronal section.

Temperature rises during tooth bleaching with different light-curing units

The aim of this study was to evaluate the influence of three different light-curing units on the temperature rise induced in the pulpal cavity, when bleached with 35% hydrogen peroxide (HP). Forty extracted maxillary central incisors were randomly divided into four groups according to photoactivation procedure (n = 10). Whiteness HP (WHP) bleaching agent which contains 35% HP bleach was placed on the facial tooth surface and no photoactivation device was used (control); an blue light-emitting diode (LED, 40 s), a diode laser (4 W, Continous mode, 20 s), and Nd:YAG laser (4 W, 60 Hz frequency, 20 s). Temperature rise in the pulpal chamber was measured with a J-type thermocouple wire that was connected to a data logger before and immediately after each 20–40 s application. One tooth of each group was selected for scanning electron microscope analysis. Data were analyzed using one-way ANOVA followed by the Games Howell post hoc test at a preset α of 0.05. One-way ANOVA revealed that there was a significant difference among the light-curing units (p < 0.05) and between control group and light-curing units (p < 0.05). The Nd:YAG induced significantly, which resulted in higher temperature increase than other light-curing units (10.7 °C). The LED unit produced the lowest temperature changes (3.2 °C) among the light-curing units. The presence of the bleaching gel did not cause a temperature increase in control group (0 °C). The results suggested that using light-curing units caused temperature changes in the intrapulpal cavity during tooth bleaching. The use of LED will be more safer for pulpal health when assisted with WHP bleaching gel.

The effect of surface treatments on the bonding strength of ceramic inlays to dentin

Abstract Aim: To compare and evaluate the effects of different surface treatments on surface roughness and the microtensile bonding strengths of four different ceramics to dentin. Methods: 160 human molar teeth were used. The teeth were divided into four groups (n = 40). FC (Finesse), LC (IPS Empress Esthetics), LDC (IPS Empress e-Max) and MZC (Zirkonzahn Prettau) ceramic restorations were prepared. The specimens were divided into eight groups: (1) control, (2) air abrasion (AA), (3) HF acid etching (HF), (4) experimental hot etching (EHE), (5) Nd:YAG laser irradiation, (6) Nd:YAG laser + air abrasion, (7) Nd:YAG laser + HF acid, and (8) Nd:YAG laser + experimental hot etching. The surface roughness of the ceramics was determined with atomic force microscopy. After the cementation process, the specimens were thermal cycled and subjected to a microtensile bond strength (MBS) test. Two-way ANOVA and a Tukey’s test were used to analyse the surface roughness and MBS values of variance (p = 0.05). Results: HF acid etching showed the highest surface roughness in FC (p < 0.05). HF increased MBS in LC specimens where AA and HF increased MBS in LCD specimens. For the MZC specimens, AA and Nd:YAG + AA was effective in increasing the MBS (p < 0.05). Conclusion: Different surface treatments must be applied to different ceramics to improve the mechanical retention and MBS.

A different wax sculpture technique for implant-retained auricular prosthesis

Replacement of missing ears is a challenging task in which extensive array of materials and techniques have been employed. This article describes a different and simplified procedure for fabricating auricular prostheses very similar to the intact left ear of the patient. A 65-year-old male patient was referred to the Department of Prosthodontics with the loss of the right ear. In this case, the impression was made using hydrocolloid material (alginate) from the both defected and the opposite side. After hardening of the stone casts, a custom-made transparent splint plate was designed for the left auricular side. The splint was reversed and a cast model of the right auricular side was obtained as pouring the dental stone into transparent orthodontic splint. After getting the impression from cast model, conventional wax pattern and try on process was done. Finally, silicone elastomer was polymerized and the retention of the prosthesis acquired with the magnetic attachments. The technique described is economical, conventional, and time-saving. Furthermore, the prosthesis imitates the patients intact auricular tissue.