Humans ; Post and Core Technique

PURPOSE: Debonding of a composite resin core of the fiber post often occurs at the interface between these two materials. The aim of this study was to evaluate the effects of different surface treatment methods on bond strength between fiber posts and composite core. MATERIALS AND METHODS: Sixty-four fiber posts were picked in two groups (Hetco and Exacto). Each group was further divided into four subgroups using different surface treatments: 1) silanization; 2) sandblasting; 3) Treatment with 24% H2O2, and 4) no treatment (control group). A cylindrical plexiglass matrix was placed around the post and filled with the core resin composite. Specimens were stored in 5000 thermal cycles between 5degrees C and 55degrees C. Tensile bond strength (TBS) test and evaluation using stereomicroscope were performed on the specimen and the data were analyzed using two-way ANOVA, Post Hoc Scheffe tests and Fisher's Exact Test (alpha=.05). RESULTS: There was a significant difference between the effect of different surface treatments on TBS (P<.001) but different brands of post (P=.743) and interaction between the brand of post and surface treatment (P=.922) had no significant effect on TBS. Both silanization and sandblasting improved the bonding strength of fiber posts to composite resin core, but there were not any significant differences between these groups and control group. CONCLUSION: There was not any significant difference between two brands of fiber posts that had been used in this study. Although silanization and sandblasting can improve the TBS, there was not any significant differences between surface treatments used.
Androsterone ; Polymethyl Methacrylate ; Post and Core Technique

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.

Dental Porcelain ; Humans ; Post and Core Technique

BACKGROUNDFor esthetic consideration, dentin color post core materials were normally used for all-ceramic crown restorations. However, in some cases, clinicians have to consider combining a full ceramic crown with a metal post core. Therefore, this experiment was conducted to test the esthetical possibility of applying cast metal post core in a full ceramic crown restoration.

METHODSThe color of full ceramic crowns on gold and Nickel-Chrome post cores was compared with the color of the same crowns on tooth colored post cores. Different try-in pastes were used to imitate the influence of a composite cementation on the color of different restorative combinations. The majority of patients could not detect any color difference less than DeltaE 1.8 between the two ceramic samples. So, DeltaE 1.8 was taken as the objective evaluative criterion for the evaluation of color matching and patients' satisfaction.

RESULTSWhen the Empress 2 crown was combined with the gold alloy post core, the color of the resulting material was similar to that of a glass fiber reinforced resin post core (DeltaE = 0.3). The gold alloy post core and the try-in paste did not show a perceptible color change in the full ceramic crowns, which indicated that the color of the crowns might not be susceptible to change between lab and clinic as well as during the process of composite cementation. Without an opaque covering the Ni-Cr post core would cause an unacceptable color effect on the crown (DeltaE = 2.0), but with opaque covering, the color effect became more clinically satisfactory (DeltaE = 1.8).

CONCLUSIONSIt may be possible to apply a gold alloy post core in the Empress 2 full ceramic crown restoration when necessary. If a non-extractible Ni-Cr post core exists in the root canal, it might be possible to restore the tooth with an Empress 2 crown after covering the labial surface of the core with one layer of opaque resin cement.

OBJECTIVETo test the effects of different surface treatments on the adhesive strength between POPO fiber post and resin cement.

METHODS50 fiber posts were divided into 5 groups at random according to different surface treatments. Group A: Control group, no treatment. Group B: Silanization for 60 s. Group C: Etching for 30 s. Group D: Etching for 60 s. Group E: Etching for 120 s. Crowns of 45 fresh premolars were removed and assigned randomly to 5 test groups. After bonding and embedding the retentive force of the samples were tested by an universal testing machine. The morphology of the post surface was observed by a scanning electron microscope (SEM).

RESULTSThere were significant differences among the effects of different surface treatments on the adhesive strength between POPO fiber post and resin cement (P < 0.05). Group D showed the highest adhesivestrength (207.33 +/- 7.58) N. There was significant different between group D and E (P = 0.027), but there was not significant difference between group D and C (P = 0.112). Significant changes of post surface after different treatments were discovered by SEM. Surface roughness and area of fiber exposure increased.

CONCLUSIONThe adhesive strengths have been enhanced after conducting different surface treatments on the fiber posts.

OBJECTIVETo evaluate the clinical effect of indirect cast post core by two different impression methods between silicone rubber impression and agar/alginate combination impression.

METHODS389 massive destruction teeth after root canal therapy were randomly divided into two groups (group A and group B). The teeth of group A was treated by silicone rubber impression material for making indirect post core impression. The teeth of group B was treated by agar/alginate combination impression for making indirect post core impression. The effect of two different impression methods was evaluated.

RESULTSThe success rate of making indirect post core impression by silicone rubber impression method was higher than that of making impression by agar/alginate combination impression method. Significant difference was found in making indirect post core impression between premolars and molars by two different impression methods (P<0.05), while there was no significant difference in making indirect post core impression of anterior teeth by two different impression methods (P>0.05).

CONCLUSIONThe clinical effect of making indirect post core impression by silicone rubber impression method is better than that of making impression by agar/alginate combination impression method.

OBJECTIVEThis study aims to observe and compare the influences of the casting alloy post and cores on magnetic resonance imaging (MRI).

METHODSSix casting alloy post and sores were fabricated for the experimental groups, and zirconia post and core served as the control. The seven types of post and cores were of the same size and shape. Each post and core was orally fastened to a volunteer and then imaged with sequences of T1-weighted spin echo imaging (SE-T1WI), T2-weighted turbo spin-echo imaging (TSE-T2WI), and diffusion weighted imaging (DWI).

RESULTSCobalt chromium alloy post and core generated severe artifacts, whereas gold palladium alloy post and core generated no obvious artifacts, and no difference was observed between the zirconia and the gold palladium alloy post and cores (P > 0.05). The pure titanium alloy post and core produced mild artifacts. The post and cores of the titanium, nickel-cadmium, and gold platinum alloys generated moderate artifacts with no significant differences (P > 0.05).

CONCLUSIONDifferent metal post and cores have different influences on MRI. With the exception of that generated by cobalt chromium alloy, the artifact generated by the single-alloy post and core does not influence the image of the normal head and neck.

OBJECTIVETo access the effects of post's diameter on the retention of post-core restorations.

METHODSThirty-three simulant roots with same length,taper and different diameter (1.305 mm, 1.830 mm, 2.175 mm and 2.700 mm respectively) were made of polymethylmethacrylate and were divided into 4 groups. The wax patterns of post-cores were manufactured and cast. The post-cores were cemented. After that, the adhesion, frictional force and restriction of the post-core restorations were measured.

RESULTSWhen the proportion of length and diameter was smaller than 4.372, the linear regression between the post's diameter and the retention of post-core crown system was F = 107.98 + 72.08D. The linear regression between the post's diameter and the adhesion was P = 9.60 + 2.22D. The linear regression between the post's diameter and the frictional force and restriction was Q = 98.37 + 69.87D. The statistical analysis of the results indicated significant difference (P < 0.05). When the proportion of length and diameter was lager than 4.372, the retention of post-core crown system increased although the post's diameter decreased.

CONCLUSIONWhen the proportion of length and diameter was smaller than 4.372, the retention of post-core crown system increased with the decrease of the post's diameter. While the proportion was lager than a certain value, this rule did not exist.

Many patients with large-area tooth defect need cast post-core crown restoration. However, the color defect of the cast post-core will affect the final restorative result, especially that of the anterior teeth. A new technology of color masking by applying CERAMAGE polymeric porcelain to the cast metal post-core surface improves the color of a full-ceramic restoration of anterior teeth and may provide a new alternative for the aesthetic repair of anterior teeth with a large area of defective tooth.
Ceramics ; Crowns ; Dental Porcelain ; Esthetics, Dental ; Humans ; Post and Core Technique