PURPOSE: The purpose of this study was to evaluate the bond strength of composite resin on the fracture surface of metal-ceramic depending on the repair systems and surface roughening methods. MATERIALS AND METHODS: A total of 30 disk specimens were fabricated, 15 of each were made from feldspathic porcelain and nickel-chromium base metal alloy. Each substrate was divided into three groups according to the repair method: a) application of repair system I (Intraoral Repair Kit) with diamond bur roughening (Group DP and DM), b) application of repair system I with airborne-particle abrasion (Group SP and SM), and c) application of repair system II (CoJet Intraoral Repair System, Group CP and CM). All specimens were thermocycled, and the shear bond strength was measured. The data were analyzed using the Kruskal-Wallis analysis and the Mann-Whitney test with a significance level of 0.05. RESULTS: For the porcelain specimens, group SP showed the highest shear bond strength (25.85 +/- 3.51 MPa) and group DP and CP were not significantly different. In metal specimens, group CM showed superior values of bond strength (13.81 +/- 3.45 MPa) compared to groups DM or SM. CONCLUSION: Airborne-particle abrasion and application of repair system I can be recommended in the case of a fracture localized to the porcelain. If the fracture extends to metal surface, the repair system II is worthy of consideration.
Alloys ; Dental Instruments ; Dental Porcelain*

The purpose of this study was to investigate the quantity of debris which was extruded apically after canal instrumentation using different types of enlarging instrument in endodontic resin models. Five groups of 9 endodontic resin models were instrumented using each different technique : hand instrumentation without early coronal flaring, hand instrumentation after early coronal flaring, and three nickel-titanium engine-driven instrumentations (Hero 642, Protaper, K3). Debris extruded from apical foramen during instrumentation was collected on preweighed CBC bottle, desiccated and weighted using electronic balance. The results were analyzed using Kruskal-wallis test and Mann-Whitney U rank sum test at a significance level of 0.05. The results were as follows: 1. All of instrumentation techniques produced apically extruded debris. 2. Group without early coronal flaring extruded significant more debris than groups with early coronal flaring. 3. There was no significant difference among early coronal flaring groups. The early coronal flaring is very important to reduce the amount of debris extruded apically.
Dental Instruments ; Tooth Apex

OBJECTIVEThis in vitro study is to evaluate the effect of ultrasonic power settings and cooling methods on fracture behavior of the separated nickel titanium instruments during ultrasonic removal.

METHODS40 discarded and 10 new nickel titanium instruments were used to establish the separated instrument removal model. The discarded instruments were divided into four groups according to two ultrasonic power settings(6 or 10) and different cooling methods (using water coolant or without using water coolant), and all the new instruments were put into the group in which ultrasonic vibration was used at a higher power setting (10) without using water coolant. The time required for fracture of the separated instruments was recorded.

RESULTSThe time was longer with statistical significance at a lower power setting compared with that at a higher power setting regardless of the use of water coolant. The time was longer with statistical significance by the use of water coolant compared with that without using coolant regardless of power settings (6 or 10). The time required for fracture of the new instruments was longer than that of the discarded instruments with statistical significance.

CONCLUSIONDuring ultrasonic removal of separated nickel titanium instruments, water coolant could decrease the occurrence of fracture. When removing separated nickel titanium instruments with ultrasonic vibration, an attempt without coolant shouldn't be made at a higher power setting.

PURPOSE: The purpose of this study was to evaluate and compare three polishing systems on the surface roughness and phase transformation of monolithic zirconia. MATERIALS AND METHODS: 100 disk shaped specimens (10 mm diameter, 3 mm thickness) were fabricated from monolithic zirconia blocks. 20 specimens were left as a control group and remaining specimens were grinded by diamond bur to simulate the occlusal adjustments. Grinded specimens were randomly divided into 4 groups: group G (no polishing), group M (Meisinger, zirconia polishing kit), group E (EVE Diacera, zirconia polishing kit), and group P (EVE Diapol, porcelain polishing kit). Surface roughness was measured with profilometer and surface topography was observed with SEM. XRD analysis was performed to investigate the phase transformation. Statistical analysis was performed with one-way ANOVA and Tukey's post hoc tests at a significance level of P=.05. RESULTS: All polishing groups showed a smoother surface than group G. Among 3 polishing systems, group M and group E exhibited a smoother surface than the group P. However, no significant differences were observed between group M and group E (P>.05). Grinding and polishing did not cause phase transformations in zirconia specimens. CONCLUSION: Zirconia polishing systems created a smoother surface on zirconia than the porcelain polishing system. Phase transformation did not occur during the polishing procedure.
Dental Instruments ; Dental Porcelain ; Occlusal Adjustment

OBJECTIVEThe purpose was to analyze the effects of three sterilization methods (dry heat sterilization, steam sterilization, and chemical sterilization) on the corrosion of dental fissure bur.

METHODS200 dental fissure burs were distributed to 10 groups. Bending strength, elastic modulus, and torsional strength were measured by bending and torsional instrument and calculated with special designed software. Among the three sterilization methods, the steam sterilization group showed the most evident.

RESULTSThe corrosion was most severe in steam sterilization group, followed by chemical sterilization, dry heat sterilization. With the sterilization time increased, bending strength, elastic modulus, and torsional strength decreased respectively. Of the three sterilization methods, the mechanical properties were decreased most evidently by steam sterilization, followed by chemical sterilization and dry heat sterilization.

CONCLUSIONIt is proved that the bending strength, elastic modulus and torsional strength have a tight relationship with the corrosion of dental fissure burs. The corrosion was most severe in steam sterilization group, followed by chemical sterilization, dry heat sterilization. In regards of the corrosive effect, the dry heat sterilization might be the best way to sterilize the dental fissure burs.

OBJECTIVETo evaluate the shaping ability of hand-used ProTaper on curved canals using Endodontic Cube.

METHODSFifty-four curved root canals in vitro were selected and divided into three groups according to the curved degree (alpha), group A: 0 degrees < or = alpha < 25 degrees , group B: 25 degrees < or = alpha < 40 degrees , group C: 40 degrees < or = alpha < 55 degrees . Endodontic Cube was assembled, and each sample was sectioned perpendicular to the axis of the tooth into four sections with Isomer-Buhler in low speed. Then the root canals were prepared with hand-used ProTaper. Before and after shaping, photograph of all the sections were taken under a stereomicroscope. Statistical analyses were performed.

RESULTSThe dentin cutting quantity of the whole canal prepared with ProTaper in group B and C was larger than that of group A. The deviation distance of the whole canal prepared by ProTaper in group C was significantly larger than that in group A, and the deviation distance in middle portion larger than that in group B. The maintaining ability in the middle portion of group C by ProTaper was worse than that of group A and B.

CONCLUSIONSThe curvature of root canal may increase the cutting quantity of the -dentin and reduce the ability of remaining original canal shape prepared by ProTaper.

OBJECTIVEComparing the dental handpiece' s cleaning effect between manual cleaning and machine cleaning.

METHODSEighty same contaminated dental handpieces were randomly divided into experimental group and control group, each group contains 40 pieces. The experimental group was treated by full automatic washing machine, and the control group was cleaned manually. The cleaning method was conducted according to the operations process standard, then ATP bioluminescence was used to test the cleaning results.

RESULTSAverage relative light units (RLU) by ATP bioluminescence detection were as follows: Experimental group was 9, control group was 41. The two groups were less than the recommended RLU value provided by the instrument manufacturer (RLU < or = 45). There was significant difference between the two groups (P < 0.05).

CONCLUSIONThe cleaning quality of the experimental group was better than that of control group. It is recommended that the central sterile supply department should clean dental handpieces by machine to ensure the cleaning effect and maintain the quality.

Dental Instruments ; Humans ; Root Canal Preparation

PURPOSE: The purpose of this in vitro study was to evaluate the effect of surface grinding and polishing procedures using high speed zirconia diamond burs with different grit sizes on the phase transformation and flexural strength of zirconia.
Dental Instruments ; Diamond ; In Vitro Techniques ; Occlusal Adjustment

ABSTRACT In the management of periodontitis patients, periodontal risk assessment (PRA) tool is currently being applied during periodontal review (PR). However, an assessment of risk profiles during examination and diagnosis (E&D) may and would effectively assess and diagnose patients’ periodontal conditions, provide personalised treatment planning, and render an enhanced patient care through periodontal management by risk assessment (PEMBRA). From a retrospective study on selected records of 81 patients treated for chronic periodontitis, the PRA profiles of the patients were evaluated during E&D and two to three months after completion of nonsurgical periodontal therapy (NSPT) during PR. The results were analysed using SPSS version 24 for descriptive statistics. On E&D, the patients presented with 25.9% localised and 74.1% generalised chronic periodontitis. Of these, 2.5% of low-risk patients on E&D increased to 21% during PR signifying an improvement after the treatment. However, the medium-risk patients have a slight increase from 32% to 35%, and patients with a high risk of 62% were reduced to 43%. The improvement of the risk profiles for both low and high-risk groups was mostly contributed by the reduction in the plaque score, percentages of bleeding on probing (BOP), and probing pocket depth (PPD) ≥ 5 mm. This evidence-based evaluation of PRA tool during E&D and PR is important for PEMBRA as it encouraged the clinicians to adopt periodontal management through basic periodontal examination, detailed periodontal charting, radiographic interpretation, tooth per tooth prognosis, diagnosis, and targeted NSPT.
Risk Assessment ; Periodontal Diseases -- diagnosis ; Dental Instruments