Influence of luting agents on time required for cast post removal by ultrasound: an in vitro study

Influence of glass fiber post design and luting cements on ease of post removal and fracture strength of endodontically retreated teeth: An in vitro study

Aims and Objectives:

The aim of this study was to evaluate the time needed to remove two types of glass fiber posts cemented with two different cements and removed with two different techniques and to evaluate the fracture strength of teeth after post removal.

Materials and Methods:

Root canal treatment was completed in 80 extracted single-rooted premolars and the teeth were decoronated. Following canal preparation, the roots were coated with polysiloxane impression material and embedded in acrylic resin cubes. The specimens were randomly divided into eight experimental groups (n = 10) based on the type of fiber post inserted: Reforpost (R) or Contec Blanco (C); luting cement: Multilink-N/self-etch (M) or G-Cem/self-adhesive (G); technique of removal: Peeso reamer (P); or ultrasonic (U). The posts were removed with respective technique under magnification and the time (in seconds) of post removal was determined. Following post removal, the fracture strength of the specimens was determined using a universal testing machine. The mode of failure was also determined. Data were analyzed by three-way analysis of variance (ANOVA), one-way ANOVA, Tukey’s post hoc test, t test, and correlation. Chi-square analysis was performed to compare the failure mode. Statistical significance was set at P < 0.05.

Results:

The post and cement types had an influence in post removal time (P < 0.05). There was no role of post or cement types on the fracture strength of teeth after post removal with either technique (P > 0.05). A weak negative correlation was found between the post removal time and fracture resistance for both Peeso reamer (r = –0.373) and ultrasonic (r = –0.177) techniques. Both techniques of post removal produced a majority of favorable failures (P > 0.05).

Conclusion:

The type of post and luting cement plays a significant role in ease of post removal by Peeso reamer or ultrasonic technique. Post-removal technique had no effect on the fracture strength of teeth. Parallel serrated fiber post luted with self-etch resin cements was difficult to remove as compared with parallel smooth surface post luted with self-etch or self-adhesive resin cement.

Influence of post-core material and cement peculiarities on stress of post-cores under ultrasonic vibration: a three-dimensional finite element analysis

AIM

To analyse the effect of post-core, and cement materials and thickness of the cement lute on the stress in post-core systems under ultrasonic vibration at different frequencies and amplitudes using three-dimensional finite element analysis.

METHODOLOGY

Eight three-dimensional finite element models of a maxillary central incisor with post-cores were established. Two post-core materials (Au and Ni-Cr alloys), two cements (glass ionomer (GI) and zinc phosphate (ZP)) and two cement layer thicknesses (50 and 150 μm) were considered. Vibration loads were applied near the neck on the buccal side of the core at frequencies of 10-40 kHz and amplitudes of 10-50 μm. The maximum shear stress of the cement layer and maximum principal stress of the roots and their distributions were investigated.

RESULTS

The stresses on cements and roots increased with an increase in the frequency and amplitude of the vibration load and elastic modulus of the cements, and decreased with increasing thickness of the cement layer and elastic modulus of the post-core. Maximum cement stress was observed on the contralateral upper part of the loading side, whereas the maximum root stress was found on the ferrule where the load was applied.

CONCLUSIONS

In this simulated model, the frequency and amplitude of ultrasound needed to remove a post-core were positively related to the elastic modulus of the post-core and thickness of the cement layer and negatively related to the elastic modulus of the cements.

In vitro retention efficiency of temporary type zinc oxide cement for orthodontic forced eruption

OBJECTIVE

To assess the retention efficiency of three types of temporary zinc oxide cement trademarks on forced eruption using intracranal wire device.

METHODS

An in vitro evaluation included intracanal wire device displacement and detachment at 50g load force for 120 days and then the retention resistance at maximum load force.

RESULTS

All groups of temporary zinc oxide cements were efficient to support 50g load forces after 120 days. None statistical differences were found between groups. Zinc oxide cements supported a maximum retention load force, which exceeded in more than 84 times the lowest value obtained in controls (420g).

CONCLUSION

Zinc oxide cements are efficient to retain intracanal wire devices on forced eruption processes in vitro and allows removal of both when necessary (wire device and cement, respectively).

Direct or indirect post crowns to restore compromised teeth: a review of the literature

Post crowns are restorations which utilise the root canal space to improve the retention and resistance form of teeth which lack coronal tooth structure. In recent years there have been significant developments in the materials, systems and evidence-base surrounding the provision of post crowns. This review aims to refresh the general dental practitioner's (GDPs) knowledge of the different factors that must be considered when placing a post crown, and how these factors can help guide the dentist in their decision to provide either a direct or indirect post and core.

The Post-endodontic Adhesive Interface: Theoretical Perspectives and Potential Flaws

INTRODUCTION

The aim of this review was to analyze the potential of successful bonds of endodontic posts to radicular dentin as well as the limitations of the post-endodontic adhesive interface.

METHODS

The MEDLINE/PubMed and Web of Science electronic databases were searched. The search was augmented by a manual search of the pertinent bibliographies.

RESULTS

The post-endodontic adhesive interface finds application in the endodontic cohesive units. Many techniques and materials exist to improve the bond between endodontic posts and resin-based materials as well as between resin-based materials and radicular dentin. Different techniques used for the adhesion of metallic and fiber-reinforced posts are discussed and critically analyzed.

CONCLUSIONS

Although adhesive cementation of endodontic posts is popular, a long-term predictable bond may be compromised because of procedures related to the endodontic treatment and/or the adhesive cementation procedures. Microleakage and degradation phenomena may further jeopardize the post-endodontic adhesive interface.

Effect of time interval between core preparation and post cementation on pushout bond strength of glass fiber-reinforced posts

Introduction:

The aim of this study was to investigate the effect of timing of coronal preparation on the pushout bond strength of fiber postluted with resin cement in the root canal.

Materials and Methods:

In this experimental study, 48 mandibular human premolars were selected in a 3-week range. After root canal treatment and postspace preparation, a post #2(Angelus, Brazil) was cemented into the canal by a resin-based cement (Bifix SE, VOCO, Germany). Cylindrical resin composite cores were built on the posts. Then, the specimens were divided into 4 groups of 12 specimens each: one control group without core preparation and 3 experimental groups with core preparation that was done 15 min, 1 h, and 24 h after postcementation. One day after postcementation, each root was sectioned into 3 segments. Each slice was connected to universal testing machine. The load was applied at the speed of 0.5 mm/min till failure happened. The collected data were analyzed (SPSS/PC 20.0; SPSS Inc., Chicago, IL, USA) using two-way ANOVA and post hoc Tukey test at P < 0.05 level of significance.

Results:

Mean shear bond strength differences among interventional groups were not statistically significant (P > 0.05). Nevertheless, there were significant differences among root regions (P < 0.001).

Conclusion:

It was concluded that core preparation and its timing does not affect adversely retention of fiber post and bond strength is higher in the cervical segment.

Evaluation of a new protocol for removing metal retainers from multirooted teeth

INTRODUCTION

The aim of this study was to evaluate in vitro a new protocol for removing intraradicular retainers from multirooted teeth applying ultrasonic vibration.

METHODS

Forty mandibular molars were endodontically treated to receive cast intraradicular retainers, which were distributed into the following 4 groups: group 1: control without a slot and without ultrasound, group 2: control with a slot and without ultrasound, group 3: ultrasonic vibration in the core without a slot, and group 4: ultrasonic vibration in the core with a slot. After the intraradicular retainers were cemented with zinc phosphate, ultrasonic vibration was applied for 1 minute. The test specimens were then submitted to the traction test in the universal testing machine at a speed of 1 mm/min. The maximum traction force required to remove the intraradicular retainer was recorded in newtons, and the data were statistically analyzed using analysis of variance and the Tukey-Kramer test (P < .05).

RESULTS

The results showed statistically significant differences among the groups tested (group 1 = 234.34 N, group 2 = 201.67 N, group 3 = 139.57 N, and group 4 = 83.23 N). The lowest mean value of traction force recorded was when ultrasonic vibration was applied on the core with a slot.

CONCLUSIONS

Creating a slot in the core and the ultrasound application on all surfaces and inside the slot reduced the force required for removing intraradicular metal retainers from multirooted teeth cemented with zinc phosphate.

The influence of ultrasound on removal of prefabricated metal post cemented with different resin cements

BACKGROUND

Ultrasonic vibrations are used to remove a cemented post from a root canal requiring endodontic retreatment. Various results have been reported from the studies that evaluated the effect of ultrasonic instruments in removing the posts cemented with resin cements. The aim of this study was to evaluate the effect of ultrasonic energy on the retention of prefabricated metal post cemented with Panavia or Maxcem Elite cements.

MATERIALS AND METHODS

In this in vitro study, forty eight extracted single root premolars were decoronated with a diamond disc leaving a 13 mm long root and endodontically treated. The root canals were obturated by gutta-percha up to 5 mm with vertical condensation method and the 8 mm post-space was prepared to receive a no. 2 long Dentorama post. The roots were placed in an incubator for 48 h in 37°C and 100% humidity. After mounting the teeth in acrylic blocks, posts were cemented in the root canals using Panavia F2.0 in 24 specimens and Maxcem Elite in 24 others. For half of the specimens in each subgroup, an ultrasonic device was applied for 4 min. Universal testing machine was used to measure the force needed to remove the posts with a crosshead speed of 1 mm/min until the post came out of the canal. Kruskal-Wallis test was used for statistical analysis at 5% level of significance.

RESULTS

The removal force was not significantly different among the groups (P > 0.05).

CONCLUSION

Ultrasonic energy did not decrease the retention of posts cemented with Panavia or Maxcem Elite cements. Furthermore, it seems that there is no significant difference between removal force of self-etch (Panavia) and the self-etch self-adhesive (Maxcem Elite) resin cements.

Waiting time for coronal preparation and the influence of different cements on tensile strength of metal posts

This study aimed to assess the effect of post-cementation waiting time for core preparation of cemented cast posts and cores had on retention in the root canal, using two different luting materials. Sixty extracted human canines were sectioned 16 mm from the root apex. After cast nickel-chromium metal posts and cores were fabricated and luted with zinc phosphate (ZP) cement or resin cement (RC), the specimens were divided into 3 groups (n = 10) according to the waiting time for core preparation: no preparation (control), 15 minutes, or 1 week after the core cementation. At the appropriate time, the specimens were subjected to a tensile load test (0.5 mm/min) until failure. Two-way ANOVA (time versus cement) and the Tukey tests (P < 0.05) showed significantly higher (P < 0.05) tensile strength values for the ZP cement groups than for the RC groups. Core preparation and post-cementation waiting time for core recontouring did not influence the retention strength. ZP was the best material for intraradicular metal post cementation.

Comparison of different ultrasonic vibration modes for post removal

This in vitro study compared different ultrasonic vibration modes for intraradicular cast post removal. The crowns of 24 maxillary canines were removed, the roots were embedded in acrylic resin blocks, and the canals were treated endodontically. The post holes were prepared and root canal impressions were taken with self-cured resin acrylic. After casting, the posts were cemented with zinc phosphate cement. The samples were randomly distributed into 3 groups (n=8): G1: no ultrasonic vibration (control); G2: tip of the ultrasonic device positioned perpendicularly to core surface and close to the incisal edge; and G3: tip of the ultrasonic device positioned perpendicularly to core surface at cervical region, close to the line of cementation. An Enac OE-5 ultrasound unit with an ST-09 tip was used. All samples were submitted to the tensile test using an universal testing machine at a crosshead speed of 1 mm/min. Data were subjected to one-way ANOVA and Tukey's post-hoc tests (α=0.05). Mean values of the load to dislodge the posts (MPa) were: G1 = 4.6 (± 1.4) A; G2 = 2.8 (± 0.9) B, and G3= 0.9 (± 0.3) C. Therefore, the ultrasonic vibration applied with the tip of device close to the core's cervical area showed higher ability to reduce the retention of cast post to root canal.

Influence of ultrasound, with and without water spray cooling, on removal of posts cemented with resin or glass ionomer cements: An in-vitro study

Aims/objectives:

To evaluate in vitro the ultrasonic vibration efficacy with and without water spray cooling on the reduction of the amount of force necessary to dislodge the cast posts cemented with resin cement and to compare it with those cemented with GIC Type I luting cement.

Materials and Methods:

Sixty samples were divided into six groups: groups 1, 2, 3, posts cemented with GIC; groups 4, 5, 6, posts cemented with resin; groups 1 and 4 (controls), no ultrasound; groups 2 and 5, ultrasound without water spray; and groups 3 and 6, ultrasound with water spray. Instron testing machine was used to dislodge the posts from the root canals and the data was statistically analyzed.

Results:

Ultrasound with water spray (group 3) among the GIC groups reduced the traction force necessary to extract posts by 53.33% whereas ultrasound without water spray (group 5) among the resin groups reduced by 59.5% compared to control.

Conclusion:

Ultrasound with water is more effective in removing posts cemented with GIC because of the ultrasonic energy being transferred to the post. Ultasonics without water is more effective in removing posts fixed with resin cement probably by the indirect action of heat production.