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.     

Analysis of heat generation using ultrasonic vibration for post removal

This study measured the temperature of the root surface and post during the application of ultrasonic vibration to cemented posts to simulate post removal procedure. Root canal therapy was performed on ten extracted maxillary incisors. A stainless steel Parapost was cemented into each prepared post space. Ultrasonic vibration was applied to the post and temperatures were recorded at the coronal post and the cervical root surface. Data were analyzed with ANOVA using the independent variables of (a) time of ultrasonic application (15, 30, 45 and 60 s) and 2) location (post and root surface). Greater temperature increase was observed at the post (52.6 degrees C, SD 11.1; 82.6 degrees C, SD 20.1; 111.0 degrees C, SD 29.1; 125.3 degrees C, SD 33.2) compared to the root surface (9.5 degrees C, SD 4.6; 17.5 degrees C, SD 4.8; 25.4 degrees C, SD 7.3; 32.2 degrees C, SD 8.1) for each time period, P < 0.001. Ultrasonic application to the post for longer than 15 s generates high temperature on the root surface.     

The removal of fractured post fragments in general dental practice using ultrasonic vibration

This paper describes an evidence-based clinical procedure that is suitable for the removal of fractured metal post fragments using ultrasonic vibration in general dental practice, particularly when non-resin-based cements have been used. Fragments of posts cemented with resin-based cements are likely to be extremely difficult to remove. The use of non-resin-based cements is recommended for luting posts, as fragment or total post removal is much easier with these materials.     

Influence of endodontic sealer cement on fibreglass post bond strength to root dentine

Aim To test the hypothesis that the composition of endodontic sealer cements and the time elapsed between root filling and fibreglass post fixation interferes with adhesion to root canal dentine. Methodology Sixty bovine incisor roots were divided into five groups (n = 12): CI, unfilled; SI, filled with a calcium hydroxide‐based cement‐Sealer 26, and immediate post fixation; S7, Sealer 26 and post fixation after 7 days; EI, filled with a zinc oxide and eugenol‐based cement‐Endofill and immediate fixation; and E7 Endofill and post fixation after 7 days. The posts were cemented with adhesive system and dual resin cement. Ten roots were cross‐sectioned to obtain two 1‐mm‐thick discs for each cervical (TC), middle (TM) and apical (TA) third of the prepared root portion. The posts were submitted to a micropush‐out test. The other two teeth were evaluated using scanning electron microscopy to analyse the bond interface. Data were analysed using anova , Tukey and Dunnett tests (P < 0.05). Results Group EI was associated with a significant reduction in bond strength values irrespective of the root region; TC = 3.50 MPa (P = 0.0001); TM = 2.22 MPa (P = 0.0043) and TA = 1.45 MPa (P = 0.003). Region of canal had an influence on the values for the cement used in group E7, in which only the TA presented differences from the CI. Conclusions Endofill interfered negatively with the bond to root dentine along its full length and in the TA when post fixation was delayed for 7 days. Bond strength decreased from crown to apex in all groups.     

Temperature rise of the post and on the root surface during ultrasonic post removal

AIM: To determine the temperature rise on the root surface caused by ultrasonic post removal using different devices and techniques in a laboratory setting. METHODOLOGY: Two ultrasonic devices, one piezoelectrical (Pi) and one magnetostrictive (Ma), were investigated. A serrated titanium post was placed into the distal root canal of a human mandibular first molar. Four coolant parameters were utilized: no air, no water, no evacuation (NN), air only with high-speed evacuation (A), 15 mL min(-1) water coolant with high-speed evacuation (W15) and 30 mL min(-1) water coolant with high-speed evacuation (W30). Five simulated post removals were measured at two locations, the post (P) and the root (R), for each coolant parameter. Temperature rise was measured at 30, 60, 90 and 120 s intervals using calibrated infrared thermography (n = 80). Temperatures were recorded at 45 ms intervals. Data were analysed using repeated measures anova with the Scheffe post hoc test (P < or = 0.05). RESULTS: The overall mean pooled effect showed that temperature rise for P = 20.1 +/- 27.9 degrees C and R = 10.9 +/- 7.9 degrees C were significantly different. Significant differences in temperature rise were: Pi > Ma, P > R, NN > A = W15 = W30 however, A > W30. CONCLUSIONS: There were significant differences in temperature rise as a function of ultrasonic device, location on the tooth and cooling method utilized for post removal.     

Comparison of two ultrasonic instruments for post removal

The relative performance of two different ultrasonic units commonly used clinically for post removal was evaluated using tips designed specifically for post vibration. Twenty-four extracted maxillary and mandibular cuspids with crowns removed at the labial cementoenamel junction were treated endodontically. Post spaces were made 10 mm into the roots before cementing a 16 mm #5 (0.050-inch) Para-Post with zinc phosphate cement. The teeth were divided into three similar groups of eight. Post retention was assessed in group 1. Ultrasonic vibration was applied to groups 2 and 3 until post removal. The average force required to dislodge the posts from the teeth in group 1 (control group, no ultrasound) was 40.5 kg (SD = 12.3 kg). The average time for post removal in group 2 (Spartan) was 4:52 min (SD = 2:26). The average time for post removal in group 3 (Enac) was 1:31 min (SD = 0:34). The difference between groups 2 and 3 was statistically significant (p < 0.005). Use of ultrasonic tips designed for post vibration and maximization of audible sound level during ultrasonic treatment of posts seem to play an important role in the effectiveness and efficiency of post removal. The results obtained indicate that both the Enac ultrasonic unit with the ST-09 vibration tip and the Spartan ultrasonic unit with the Analytic VT-S tip were effective. Nevertheless, the Enac ultrasonic unit with the ST-09 vibration tip was clearly more efficient under these study conditions, resulting in typical post removal times of <2 min.     

Effect of obturation technique on sealer cement thickness and dentinal tubule penetration

AIM: To compare the average sealer cement film thickness and the extent and pattern of sealer penetration into dentinal tubules in association with four obturation techniques in curved root canals. METHODOLOGY: Mesial canals of 44 extracted mandibular molars were randomly divided among the SimpliFill, continuous wave, Thermafil and 0.04 matched taper (master cones) lateral compaction obturation groups (22 canals per group). AH26 sealer cement was coloured blue-black using Sudan Black B dye. Roots were sectioned 1, 3 and 5 mm from the working length. Specimens were photographed under 25x magnification, mounted as 35 mm slides and projected. Average sealer cement thickness (measured at 10 points around the canal wall), depth of dentinal tubule penetration and frequency of voids were determined at the 1, 3 and 5 mm levels. Data were analysed statistically for effect of obturation technique and level of section on sealer thickness and on the depth and distribution of tubule penetration. RESULTS: Thermafil demonstrated superior GP adaptation at all levels with a mean overall sealer cement thickness of 2.2 microm, followed by lateral compaction (11.1 microm), continuous wave (12.2 microm) and SimpliFill (47.6 microm). SimpliFill also demonstrated the highest frequency of voids (P < 0.05). Sealer cement penetrated dentinal tubules as far as the outer one-third of dentine, with greater penetration observed buccally or lingually (P < 0.001). Penetration was not significantly affected by obturation technique, but on average was deeper and more frequent at the 3 and 5 mm levels than at the 1 mm level (P < 0.001). CONCLUSIONS: Sealer thickness was strongly dependent on obturation technique. Assuming that minimal sealer thickness and fewer voids are good measures of long-term sealing ability, Thermafil resulted in the best outcome. Consistent, extensive sealer penetration into dentinal tubules was seen and was unrelated to the obturation technique.     

The effect of working parameters on root substance removal using a piezoelectric ultrasonic sealer in vitro

Abstract. This study assessed defect depth and volume resulting from root instrumentation using a piezoelectric ultrasonic sealer with a slim scaling tip in vitro. Combinations of the following working parameters were analyzed: lateral forces of 0.5 N, 1 N, and 2 N; tip angulations of O°. 45°. and 90°; power settings of low. medium and high: and instrumentation time of 10 s. 20 s. 40 s. and 80 s. Defects were quantified using a 3D optical laser scanner. Overall, lateral force had the greatest influence on defect volume compared to instrument power setting and tip angulation (β-weights 0.49±0.04, 0.25±0.D4, and 0.14±0.04, respectively). The effects on defect depth were highest for tip angulation followed by lateral force and instrument power setting (β-weights 0.48±0.04. 0.34±0.04, and 0.25±0.04, respectively). Interestingly, al all power settings, the highest defect volume and depth by far were found after combining 45° tip angulation with 2 N of lateral force. The efficacy of the assessed piezoelectric ultrasonic sealer may be adapted to the various clinical needs by adjusting the lateral force. tip angulation, and power setting. To prevent severe root damage it is crucial to use the assessed sealer at a tip angulation of close to 0°.     

An investigation of the heat induced during ultrasonic post removal

The purpose of this study was to investigate the potential for temperature increase along the external root surface during ultrasonic post removal in a simulated clinical environment. Thirty-seven extracted teeth were decoronated, instrumented, and then obturated with gutta-percha and sealer. Post spaces were prepared, followed by cementation of stainless steel posts. A simulated clinical environment was created by using a polymethylmethacrylate sheet with holes custom fitted for the extracted teeth and then suspended over a heated water bath. Two thermocouples were attached at 6 and 12 mm from the top of the post along the external root surface. Teeth were divided into 3 test groups, no coolant, air-cooled, and water-cooled. Temperature changes were recorded by using a Vishay 5000 Strain Smart system. Results demonstrated that a significant difference existed in the average heat rates between the upper and lower thermocouples for no coolant and water-cooled groups at the medium setting and the air-cooled group at the high setting. The average heat rates were significantly different between the 2 thermocouples for all 3 groups when comparing the 2 ultrasonic power settings. Results indicated that the average heat rate was less for the water-cooled group when using a medium power setting.     

Effect of plastic-covered ultrasonic scalers on titanium implant surfaces

Objectives: Maintaining oral health around titanium implants is essential. The formation of a biofilm on the titanium surface will influence the continuing success of the implant. These concerns have led to modified ultrasonic scaler instruments that look to reduce implant damage while maximising the cleaning effect. This study aimed to assess the effect of instrumentation, with traditional and modified ultrasonic scalers, on titanium implant surfaces and to correlate this with the oscillations of the instruments. Materials and methods: Two ultrasonic insert designs (metallic TFI‐10 and a plastic‐tipped implant insert) were selected. Each scaler probe was scanned using a scanning laser vibrometer, under loaded and unloaded conditions, to determine their oscillation characteristics. Loads were applied against a titanium implant (100g and 200 g) for 10 s. The resulting implant surfaces were then scanned using laser profilometry and scanning electron microscopy (SEM). Results: Insert probes oscillated with an elliptical motion with the maximum amplitude at the probe tip. Laser profilometry detected defects in the titanium surface only for the metallic scaler insert. Defect widths at 200 g high power were significantly larger than all other load/power conditions (P<0.02). Using SEM, it was observed that modifications to the implant surface had occurred following instrumentation with the plastic‐tipped insert. Debris was also visible around the defects. Conclusions: Metal scalers produce defects in titanium implant surfaces and load and power are important factors in the damage caused. Plastic‐coated scaler probes cause minimal damage to implant surfaces and have a polishing action but can leave plastic deposits behind on the implant surface. To cite this article:
Mann M, Parmar D, Walmsley AD and Lea SC. Effect of plastic covered ultrasonic scalers on titanium implant surfaces.
Clin. Oral Impl. Res. 23 , 2012; 76–82
doi: 10.1111/j.1600‐0501.2011.02186.x     

The effect of ultrasonic removal of various root-end filling materials

Aim  To compare residual root-end filling material in apical root-end cavities following their removal with ultrasonic retrotips.
Methodology  Thirty single-rooted teeth were filled with Thermafil and AH Plus sealer. Root-ends were resected at 90°, 3 mm from the apex. Root-end cavities were prepared with diamond burs and ultrasonic retrotips and filled with one of three filling materials: group I: Retro-TC (calcium silicate-based cement), group II: IRM (Dentsply, Germany), group III: Vitrebond (3M ESPE, USA). After 30 days of storage, ultrasonic retrotips were used to remove materials from the root-end cavities. The ultrasonic application time was fixed at 60 s. Polyether impressions and replicas of the root-ends were made. Root apices and replicas were examined by one operator under a scanning electron microscope. Remnants of residual materials were evaluated using a four-level scoring system; fractures, smear layer and exposed dentinal tubules were also examined.
Results  Forty per cent of the specimens filled with Retro-TC revealed complete removal of the material with exposure of dentinal tubules, whilst 60% contained residual cement. Twenty per cent of specimens filled with IRM were completely devoid of material, whereas 80% had retained material. Ten per cent of specimens filled with Vitrebond retained a moderate amount of material whilst 90% had substantial retention of the material. Statistically significant differences were found ( P  < 0.05) amongst the three groups of materials.
Conclusions  Retro-TC was successfully removed in 40% of cases using ultrasonics retrotips for 60 s, whereas IRM and Vitrebond specimens had evidence of retained material in 80% and 90% of all specimens respectively.     

Simplified cementation of lithium disilicate crowns: Retention with various adhesive resin cement combinations

Statement of problem

A composite resin cement and matching self-etch adhesive was developed to simplify the dependable retention of lithium disilicate crowns. The efficacy of this new system is unknown.

Effect of eugenol-containing endodontic sealer on retention of prefabricated posts luted with adhesive composite resin cement.

Reported studies have implicated eugenol in the reduction in retention of restorations luted with chemically cured composite resin cement. This study investigated the effect of residual eugenol in the root canal on the retention of ParaPost dowels cemented with Panavia EX composite resin. An attempt was also made to identify and to determine the most effective cleansing procedure. Findings of this study demonstrated a substantial decrease in retention of posts luted with Panavia composite resin cement in the presence of eugenol. Irrigation with ethyl alcohol (ethanol) or etching with 37% phosphoric acid gel was found to be effective in restoring the resistance to dislodgment of the posts, but alcohol produced the most consistent and reliable results.     

Effect of two fiber post types and two luting cement systems on regional post retention using the push-out test.

OBJECTIVE: To investigate regional root canal push-out bond strengths for two fiber-reinforced post types using two adhesive systems. METHODS: The crowns of 24 recently extracted sound maxillary central incisors were sectioned transversely 2 mm coronal to the labial cemento-enamel junction, and the roots treated endodontically. Following standardized post space preparations, fiber-reinforced posts (C-POST; AESTHETI-PLUS) were placed using two adhesive systems (acid-etch ONE-STEP PLUS/C&B CEMENT; self-adhesive RelyX Unicem), in four equal groups. Push-out bond strength tests were performed at four sites in each root. Results were analyzed using split-plot ANOVA, with a=0.05 for statistical significance. RESULTS: AESTHETI-PLUS quartz fiber-reinforced posts showed significantly higher push-out strengths than C-POST carbon fiber-reinforced posts (P<0.0001). The separate acid-etch adhesive system resulted in significantly higher bond strengths than the self-etch self-adhesive system (P<0.0001). Bond strengths decreased significantly from coronal to apical root canal regions (P<0.0001). SIGNIFICANCE: The quartz fiber-reinforced post placed using the separate acid-etch adhesive system provided significantly better post retention than the carbon fiber-reinforced post placed using the self-etch self-adhesive system.