OBJECTIVETo investigate the effect of coronal microleakage of cemented cast posts and cores after different interval time preparation.

METHODSCast posts and cores were fabricated for 60 of 66 extracted single-root mandibular premolars which randomly divided into 6 groups and cemented with zinc phosphate cement. The other 6 specimens acted as negative control group and positive control group. After 2, 10, 30 minutes interval time, preparation would do for preparation groups and three control groups without preparation. After dying and making transparent, the assessment of the coronal microleakage was done.

RESULTSThe results showed significant differences between each prepared group and unprepared group. No differences were defected in 3 unprepared groups. But significant differences were recorded between after 2, 10 minutes preparation groups and 30 minutes group.

CONCLUSIONHigh-speed preparation had a significant negative effect on the coronal microleakage of posts. The interval time of preparation after cemented cast posts and cores was at least between 10 and 30 minutes.

OBJECTIVETo study the influence of hand-mixed methods on the compressive strength of the zinc phosphate dental cement.

METHODSThree skilled nurses used three kinds of common clinical hand-mixed methods (included the unidirectional rotation method, the alternate pro and con bidirectional rotation method and the pulling and pushing with folding method) to mix the zinc phosphate dental cement on the same condition (i.e. same indoor temperature and humidity, the same mixing ratio, mixing time, mixing frequency and the same mixing instruments and so on). The mixed zinc phosphate cement was packed into the plastic cylinders with 10 mm-high and 5 mm-bore. After the mixed zinc phosphate cement coagulated, compressive strength was tested separately.

RESULTSThe compressive strength of the zinc phosphate dental cement mixed with the alternate pro and con bidirectional rotation method was the best, and the value was (106.11+/- 4.82) MPa. The compressive strength of the zinc phosphate dental cement mixed with the pulling and pushing with folding method was lower, and the value was (77.57 +/- 6.26) MPa. The compressive strength of the zinc phosphate dental cement mixed with the unidirectional rotation method was the lowest, and the value was (54.41 +/- 5.08) MPa. The compressive strength of the zinc phosphate dental cement mixed with the unidirectional rotation method and the pulling and pushing with folding method could not achieve the clinical required compressive strength (about 100 MPa), while the compressive strength mixed with the alternate pro and con bidirectional rotation method was above 100 MPa.

CONCLUSIONThe alternate pro and con bidirectional rotation method to mix the zinc phosphate dental cement is recommended in clinic.

Ultrasonic instruments transfer electrical energy to mechanical energy resulting in vibration used for various dental treatments. If we could know the effect of ultrasonic instruments on the dental cements within the cast crown, we could take care when conducting periodontal surgery and when using the ultrasonic instruments to remove cast crown, it would be much more convenient. The purpose of this study was to compare the bond strength of several dental cements according to ultrasonic instrumentation time In this study 4 types of cements were used to cement the specimens. They were treated with ultrasonic instrumentation for 0-5 minutes and the change in bond strength were statistically compared The results were as follows : 1. The tensile bond strength of zinc phosphate cement decreased according to the increase in time of ultrasonic instrument and showed significant differance between 0 minutes and the others and between 1 minute and 2,3,4,5 minutes (P<0.05) 2. The tensile bond strength of polycarboxylate cement decreased according to the increase in time of ultrasonic instrument and showed significant differance between 5 minutes and the others and between 4 minute and 0 minutes (P<0.05) 3. The tensile bond strength of zinc phosphate cement decreased according to the increase in time of ultrasonic instrument and showed significant differance between 5 minutes and the others (P<0.05) 4. The tensile bond strength of resin cement showed no statistically differences according to the ultrasonic instrumentation time In conclusion, it this considered that zinc phosphate cement is most affected by ultrasonic instrumentations and resin cement is the least affected. When using ultrasonic instruments the result above should be used as an index.
Crowns ; Dental Cements* ; Polycarboxylate Cement ; Resin Cements ; Ultrasonics* ; Vibration ; Zinc Phosphate Cement

The purpose of this study was to confirm the formation of hybrid layer and resin tags in dentin tissue and the possibility of bonding between luting cements used for the prosthesis and the resinous surface coated with resin bonding agents to prevent the dentin hypersensitivity after abutment preparation. Some resin bonding agents, which may have the possibility of bonding with polyacrylic acid as a liquid ingredient of polycarboxylate and glass ionmer coments, were selected. All-Bond desenstizer containing NTG-GMA and BPDM, Scotch-Bond Multipurpose plus containing HEMA, and XR-bond cotaining organophosphate were selected as a coating agent. Dental cements were zinc phosphate, polycarboxylate, and glass ionomer cement. After the exposed dentin surface of premolars was ethced with 10% phosphoric acic and coated with resin bonding agents, the monophology of treated surfaces and the resin tags and hybrid layers on sectioned surfaces were observed by SEM. Shear bond strength between the resin bonding agents and 3 kinds of cements was measured 24 hours after bonding. On the debonded surfaces of the shear bond strength tested specimens, the cement tags and the bonding sites between the resin materials and cements were examined by SEM. Following conclusions were drawn : 1. Coating of dentin with resin bonding agents had no effect on the shear bond strength of zinc phosphate cement. 2. Both of polycarboxylate and glass ionomer cements showed the increased shear bond strength by the dentinal coating with Scotch-Bond Multipurpose plus containing HEMA. However, in the case of dentinal coating with some agents containing NTG-GMA and BPDM or organophosphate, polycarboxylate cement exhibited the lowered shear bond strength, and glass ionomer cement showed the unchanged shear bond strength. 3. Complete obstructions of dentinal tubules were observed on the dentin coasted with All-Bond desensitizer or XR-bond, but distinct shape of the orifices of dentinal tubules was observed consistently on the dentin coated with Scotch-Bond Multipurpose plus 4. The hybrid layer was thickest on the dentin coated with All-Bond desensitizer, and the length of resin tags was longest one the dentin coated with Scotch-Bond Multipurpose plus. 5. On the debonded specimens which had been bonded with polycarboxylate cement or glass ionomer cement after coating with Scotch-Bond Multipurpose plus, the cement tags and the bonding sites between the resinous surface and the cements could be examined.
Acyclovir ; Bicuspid ; Dental Cements ; Dentin Sensitivity ; Dentin* ; Glass ; Glass Ionomer Cements ; Polycarboxylate Cement ; Prostheses and Implants ; Zinc ; Zinc Phosphate Cement

PURPOSE: This study was performed to investigate the retrievability of the cemented crown from the cementation type implant abutment. MATERIAL AND METHOD: The cementation type implant abutments (NEOBIOTECH implant abutment regular, 3 degree taper, 10mm length, 4mm diameter, Ti grade III, machined surface, Hwasung, Kyunggi-do) and cemented crowns were divided into 3 groups, depending on their hole angles formed in the crowns for their retrievability. The abutments and crowns were luted with 4 kinds of cements and separation test using metal wedge was executed with Instron 4465 Universal Testing Machine and the maximum impact force of the modified crown ejector was measured. RESULTS AND CONCLUSION: 1. All of the cementation type implant abutments and cemented crowns were separated with relatively small force by metal wedge. 2. The retrieving force was minimum when the metal wedge was applied perpendicular to the axis of abutment. 3. The force for retrieving crowns from abutments was maximum in resin cement group, and reduced in orders of zinc phosphate cement, glass ionomer cement and zinc oxide eugenol cement. 4. The maximum force obtained by the crown ejector was higher than the retrieval force in ZOE and GI cement and lower than that in ZPC and resin cement. 5. If it has similar conditions clinically, the cemented crowns luted with 2 types of cements (ZOE, GI cement) can be safely retrieved from the cementation type implant abutments by the modified crown ejector.
Axis, Cervical Vertebra ; Cementation* ; Crowns ; Glass Ionomer Cements ; Resin Cements ; Zinc Oxide-Eugenol Cement ; Zinc Phosphate Cement

Dislodgement of a crown or extension bridge and the loosening of a retainer of a bridge is a serious clinical problem in fixed restoration. Generally these problems are considered to be associated with deformation of the restoration. During biting, the restoration is subjected to complex forces and deforms considerably within the limit of its elasticity. Deformation of the restoration under the occlusal force induces excessive stress in the cement film, which then leads to the cement fracture. Such a fracture may eventually cause loss of the restoration. Because most of the past retention tests for full veneer crown were done without fatigue loading, they were not exactly simulating intraoral environment. And the purpose of this study was to evaluate the effect of cyclic cantilever loading on the retentive strength of full veneer crowns depending on different type of cements and taper of prepared abutment. Steel dies with 8degrees or 16degrees convergence angle were fabricated through milling and crowns with the same method. These dies and crowns were divided into 8 groups. Group 1: 16degrees taper die, cementation with zinc phosphate cement, without loading Group 2: 16'taper die, cementation with zinc phosphate cement, with loading Group 3: 8degrees taper die, cementation with zinc phosphate cement, without loading Group 4: 8degrees taper die, cementation with zinc phosphate cement, with loading Group 5: 16degrees taper die, cementation with Panavia 21, without loading Group 6: 16degrees taper die, cementation with Panavia 21, with loading Group 7: 8degrees taper die, cementation with Panavia 21, without loading Group 8: 8degrees taper die, cementation with Panavia 21, with loading After checking the fit of die and crown, the luting surface of dies and inner surface of crowns were air-abraded for 10 seconds. The crowns were cemented to the dies, with cements mixed ac cording to the manufacturer' s recommendations. A static load of 5 kg was then applied for 10 min utes with static loading device. Twenty-four hours later, group 1,3,5,7 were only thermocycled, group 2,4,6,8 were subjected to cyclic loading after thermocycling. Retentive tests were performed on the Instron machine. From, the finding of this study, the following conclusions were obtained. 1. Panavia 21 showed significantly higher retentive strength than zinc phosphate cement for all groups(p<0.05). 2. There was a significant difference in the retentive strength between 8degrees and 16degrees taper for zinc phosphate cement(p<0.05), but no significant difference for Panavia 21(p>0.05). 3. Cyclic loading significantly decreased the retentive strength for all groups (p<0.05) . 4. For zinc phosphate cement, there was 35% reduction of the retentive strength after loading in the 16degrees taper die, 25% in the 8degrees taper die, and for Panavia 21, 21% in the 16degrees taper die, 18% in the 8degrees taper die.
Bite Force ; Cementation ; Crowns* ; Elasticity ; Fatigue ; Steel ; Zinc ; Zinc Phosphate Cement

The purpose of this study was to investigate the effect of sinc phosphate cement on the enamel surface of extracted teeth. The tooth was placed in a test tube, which was subjected to 5ml of 0.2M acetate buffer at pH 4 by "window technique." The calcium content of the acetate buffer was determined by the Perkin-Elmer Model 303 Atomic Absorption Spectrophotometer. The obtained results were summarized in the following. 1. The solubility of enamel is 0.92mg/cm2. ml in control group. 2. The solubility of enamel is increased by treating these with zinc phosphate cements. 3. The solubility of enamel is 0.69mg/cm2. ml by treating with Lee Smith cement. 4. The solubility of enamel is 0.30mg/cm2. ml by treating with G-C's cement.
Absorption ; Calcium ; Dental Enamel* ; Hydrogen-Ion Concentration ; Solubility* ; Tooth ; Zinc Phosphate Cement* ; Zinc*

Bond strength of luting cements to dentin is a critical consideration for success of complete cast crowns. This study was performed to evaluate the relationship between surface characteristics of teeth prepared for complete cast crowns and retention of cemented restorations. Eighty artificial crowns were cast for standardized complete crown tooth preparations accomplished with the use of a special device on recently extracted human teeth. Coarse diamond(#102R, Shofu) and superfine finishing diamond(#SF102R, Shofu) burs of similar shape were used. Crowns in each group were randomly subdivided into four subgroups of 10 for luting cements selected for this study: zinc phosphate cement (FLECK'S), polycarboxylate cement (Poly-F), reinforced glass ionomer cement (Fuji PLUS), and adhesive resin cement (Panavia 21). Retention was evaluated by measuring the tensile load required to dislodge the artificial crown from tooth preparations with an Instron testing machine, and analysed by one-way ANOVA and Student's t-test. The obtained results were as follows ; 1. When tooth preparation was done with coarse diamond bur, retentive force was diminished in order of Panavia 21, Fuji PLUS, FLECK'S, and Poly-F. Retentive forces showed the significant difference between Fuji PLUS group and FLECK'S group(p<0.001). 2. When tooth preparation was done with superfine diamond bur, retentive force was diminished in order of Fuji PLUS, Panavia 21, FLECK'S and Poly-F. Retentive forces showed the significant difference between Panavia 21 group and FLECK'S group(p<0.001). 3. Retentive force in coarse tooth surfaces was significantly higher than that in superfine tooth surface with all luting cements(p<0.001), and cement residues were almost retained with in the cast crown in all groups.
Adhesives ; Crowns* ; Dental Instruments ; Dentin ; Glass Ionomer Cements ; Humans ; Polycarboxylate Cement ; Resin Cements ; Tooth Preparation ; Tooth* ; Zinc Phosphate Cement

PURPOSE: The purpose of this study was to evaluate the adaptation of lithium disilicate crowns fabricated by CAD-CAM (computer aided design-computer aided manufacturing) and heat-press technique to compare two different measurement methods in assessing fit of the ceramic crowns: micro CT and cross-section technique. MATERIALS AND METHODS: A prepared typodont mandibular molar for ceramic crown was duplicated and ten dies were produced by milling the PMMA (polymethylmethacrylate) resin. Ten vinyl polysiloxane impressions were made and stone casts were produced. Five dies were used for IPS e.max Press crowns with heat-press technique. The other five dies were used for IPS e.max CAD crowns with CAD-CAM technique. Ten lithium disilicate crowns were cemented on the resin dies using zinc phosphate cement with finger pressure. The marginal and internal fits in central buccolingual plane were evaluated using a micro CT. Then the specimens were embedded and cross-sectioned and the marginal and internal fits were measured using scanning electronic microscope. The two measurement methods and two manufacturing methods were compared using Mann-Whitney U test (SPSS 22.0). RESULTS: The marginal and internal fit values using micro CT and cross-section technique were similar, showing no significant differences. There were no significant differences in adaptation between lithium disilicate crowns fabricated with CAD-CAM and heat-press technique. CONCLUSION: Both micro CT and cross-section technique were acceptable methods in the evaluation of marginal and internal fit of lithium disilicate crown. There was no difference in adaptation between lithium disilicate crowns fabricated with CAD-CAM and heat-press technique except occlusal fit.
Ceramics ; Computer-Aided Design ; Crowns* ; Fingers ; Lithium* ; Molar ; Polymethyl Methacrylate ; Siloxanes ; Zinc Phosphate Cement

OBJECTIVES: To evaluate the effect of different ultrasonic tip designs on intraradicular post removal. MATERIALS AND METHODS: The crowns of forty human canine teeth were removed, and after biomechanical preparation and filling, the roots were embedded in acrylic resin blocks. The post spaces were made, and root canal molding was performed with self-cured acrylic resin. After casting (Cu-Al), the posts were cemented with zinc phosphate cement. The specimens were randomly separated into 4 groups (n = 10), as follows: G1 - no ultrasonic vibration (control); G2 - ultrasonic vibration using an elongated cylindrical-shaped and active rounded tip; G3 - ultrasonic vibration with a flattened convex and linear active tip; G4 - ultrasonic vibration with active semicircular tapered tip. Ultrasonic vibration was applied for 15 seconds on each post surface and tensile test was performed in a Universal Testing Machine (Instron 4444 - 1 mm/min). RESULTS: G4 presented the highest mean values, however, with no statistically significant difference in comparison to G3 (P > 0.05). G2 presented the lowest mean values with statistically significant difference to G3 and G4 (P < 0.05). CONCLUSIONS: Ultrasonic vibration with elongated cylindrical-shaped and active rounded tip was most effective in reducing force required for intraradicular post removal.
Crowns ; Cuspid ; Dental Pulp Cavity ; Fungi ; Humans ; Ultrasonics* ; Vibration ; Zinc Phosphate Cement