Three-dimensional accuracy of a digitally coded healing abutment implant impression system.

PURPOSE: This study examined the three-dimensional (3D) accuracy of the Encode Impression System (EN) in transferring the locations of two implants from master models to test models and compared this to the direct impression (DI) technique. The effect of interimplant angulation on the 3D accuracy of both impression techniques was also evaluated. MATERIALS AND METHODS: Seven sectional polymethyl methacrylate mandibular arch master models were fabricated with implants in the first premolar and first molar positions. The implants were placed parallel to each other or angulated mesiodistally or buccolingually with total divergent angles of 10, 20, or 30 degrees. Each master model was secured onto an aluminum block containing a gauge block, which defined the local coordinate references. Encode healing abutments were attached to the implants before impressions were made for the EN test models; pickup impression copings were attached for the DI test models. For the seven test groups of each impression technique, a total of 70 test models were fabricated (n = 5). The EN test models were sent to Biomet 3i for implant analog placement. The centroid of each implant or implant analog and the angular orientation of the long axis relative to the x- and y-axes were measured with a coordinate measuring machine. Statistical analyses were performed. RESULTS: Impression technique had a significant effect on y distortion, global linear distortion, and absolute xz and yz angular distortions. Interimplant angulation had significant effects on x and y distortions. However, neither impression technique nor interimplant angulation had a significant effect on z distortion. CONCLUSIONS: Distortions were observed with both impression techniques. However, the results suggest that EN was less accurate than DI.

Three-dimensional accuracy of plastic transfer impression copings for three implant systems.

PURPOSE: The purpose of this study was to compare the three-dimensional accuracy of indirect plastic impression copings and direct implant-level impression copings from three implant systems (Nobel Biocare [NB], Biomet 3i [3i], and Straumann [STR]) at three interimplant buccolingual angulations (0, 8, and 15 degrees). MATERIALS AND METHODS: Two-implant master models were used to simulate a three-unit implant fixed partial denture. Test models were made from Impregum impressions using direct implant-level impression copings (DR). Abutments were then connected to the master models for impressions using the plastic impression copings (INDR) at three different angulations for a total of 18 test groups (n = 5 in each group). A coordinate measuring machine was used to measure linear distortions, three-dimensional (3D) distortions, angular distortions, and absolute angular distortions between the master and test models. RESULTS: Three-way analysis of variance showed that the implant system had a significant effect on 3D distortions and absolute angular distortions in the x- and y-axes. Interimplant angulation had a significant effect on 3D distortions and absolute angular distortions in the y-axis. Impression technique had a significant effect on absolute angular distortions in the y-axis. With DR, the NB and 3i systems were not significantly different. With INDR, 3i appeared to have less distortion than the other systems. Interimplant angulations did not significantly affect the accuracy of NBDR, 3iINDR, and STRINDR. The accuracy of INDR and DR was comparable at all interimplant angulations for 3i and STR. For NB, INDR was comparable to DR at 0 and 8 degrees but was less accurate at 15 degrees. CONCLUSIONS: Three-dimensional accuracy of implant impressions varied with implant system, interimplant angulation, and impression technique.

Load fatigue performance of conical implant-abutment connections.

PURPOSE: Conical implant-abutment connections for platform switching have been recently introduced in implant systems. This study investigated the load fatigue performance of three conical abutment systems and their corresponding titanium and zirconia abutments. MATERIALS AND METHODS: Regular-diameter implants of the Ankylos (AK), PrimaConnex (PC), and Straumann (ST) systems were tested with their corresponding titanium (Ti) and zirconia (Zr) abutments tightened to the recommended torque (n = 5 implant-abutment assemblies per group). A rotational load fatigue machine applied a sinusoidally varying tensile-compressive 21 N load to specimens at a 45-degree angle, producing an effective bending moment of 35 Ncm at a frequency of 10 Hz. The number of cycles to failure was recorded, with the upper limit set at 5 million cycles. Results were evaluated through analyses of variance. RESULTS: Except for the ST Zr group, which showed no failures in four samples and one failure just below the screw head, and the AK Ti group, in which one sample was preserved without fracture, all groups experienced failure of at least one of the components, whether the abutment screw only, the abutment, and/or the implant neck. There were significant differences between systems. There was no difference between systems for the Ti abutments, and the ST group was significantly different from the AK and PC groups for the Zr abutments. CONCLUSIONS: Ti conical abutments appear to have poorer load fatigue performance compared with earlier studies of external-hexagon connections. The load fatigue performance of Zr conical abutments varied and seemed to be highly system dependent. Many of the fractures in both the Ti and Zr abutment groups occurred within the implant, and retrieval would pose a significant clinical challenge. The clinician should weigh the mechanical, biologic, and esthetic considerations before selection of any implant system, connection type, or abutment material.

Evaluation of the marginal fit of a zirconia ceramic computer-aided machined (CAM) crown system.

STATEMENT OF PROBLEM: The marginal fit of crowns is a concern for clinicians, and there is no conclusive evidence of any one margin configuration yielding better results than others in terms of marginal fit. PURPOSE: The purpose of this study was to evaluate the marginal fit with respect to gap and overhang of Y-TZP (yttria-stabilized tetragonal zirconia polycrystals) ceramic crowns and compare them with lithium disilicate pressable and complete metal crowns. The influence of margin configuration on the marginal fit was also evaluated. MATERIAL AND METHODS: Impressions were made of premolar dies prepared with shoulders or chamfers with a 20-degree total occlusal convergence (n=30). Type IV stone dies were then distributed into test groups (n=10) for the fabrication of Cercon Y-TZP, IPS Empress II, and complete metal (noble type IV alloy) crowns. The crowns were then subjected to marginal gap and overhang evaluation at 6 designated margin locations using a computerized digital image analysis system. The data were calculated and statistically analyzed using 2-way ANOVA and Bonferroni post hoc tests (α=.05). RESULTS: The overall mean (SD) marginal gap at the marginal opening for the crowns was 66.4 (42.2) µm for Cercon, 36.6 (32.1) µm for IPS Empress II, and 37.1 (22.3) µm for complete metal (control). Overall mean (SD) overhang was -15.2 (47.5) µm for Cercon, -22.1 (34.7) µm for IPS Empress II, and 30.9 (31.3) µm for complete metal (control). The ANOVA revealed significant effects by material and no significant effects by marginal configuration for marginal gap. There were significant differences in the marginal overhang values between the 2 margins, but no significant differences were found between the material groups for overhang. CONCLUSIONS: The Cercon system showed significantly larger (P<.05) marginal gaps than both the IPS Empress II and complete metal (control) crowns, but no significant differences were found in marginal overhang among the 3 material groups. There was no significant difference in marginal gap between the 2 margin configurations, namely, chamfer and shoulder, for all test groups; however, there were significant differences (P<.05) in marginal overhang values between chamfer and shoulder margins.

Critical bending moment of four implant-abutment interface designs.

PURPOSE: Critical bending moment (CBM), defined as the bending moment at which the external nonaxial load applied overcomes screw joint preload and causes loss of contact between the mating surfaces of the implant screw joint components, was measured for four different implants and their single-tooth replacement abutments. MATERIALS AND METHODS: CBM at the implant-abutment screw joint for four implant-abutment test groups was measured in vitro at 80%, 100%, and 120% of the manufacturers' recommended torque levels. Regular-platform implants with their corresponding single-tooth abutments were used. Microstrain was measured while known loads were applied to the abutment at known distances from the implant-abutment interface. Strain instrumentation was used to record the strain data dynamically to determine the point of gap opening. All torque applications and strain measurements were repeated five times for the five samples in each group. RESULTS: For the Branemark/CeraOne assemblies, the mean CBMs were 72.14 Ncm, 102.21 Ncm, and 119.13 Ncm, respectively, at 80%, 100%, and 120% of the manufacturer's recommended torque. For the Replace/Easy assemblies, mean CBMs were 86.20 Ncm, 109.92 Ncm, and 120.93 Ncm; for the Biomet 3i/STA assemblies, they were 67.97 Ncm, 83.14 Ncm, and 91.81 Ncm; and for the Lifecore/COC assemblies, they were 58.32 Ncm, 76.79 Ncm, and 78.93 Ncm. Two-way analysis of variance revealed significant effects for the test groups and torque levels. Subsequent tests confirmed that significant differences existed between test groups and torque levels. CONCLUSION: The results appear to confirm the primary role of the compressive preload imparted by the abutment screw in maintaining screw joint integrity. CBM was found to differ among implant systems and torque levels. Torque levels recommended by the manufacturer should be followed to ensure screw joint integrity.

Load fatigue performance of implant-ceramic abutment combinations.

PURPOSE: The mechanical properties and functional load performance of implant restorations coupled with metal abutments have been studied widely. However, the fatigue performance of the newly introduced ceramic implant abutments has not been reported. This study investigated the load fatigue performance of four implant systems and their corresponding zirconia ceramic abutments at the manufacturers' recommended torque levels. MATERIALS AND METHODS: Three different diameters (narrow, regular, and wide) of the Replace Select and Branemark systems and two different diameters (4.1 mm and 5.0 mm) of the Osseotite NT and Osseotite NT Certain systems provided 10 implant-abutment test groups. The abutments tested were Procera zirconia, Zireal posts, and Certain ZiReal posts. Each group had a sample size of five. A rotational load fatigue machine applied a 21-N load to the specimens at an angle of 45 degrees to produce an effective bending moment of 35 Ncm at a test frequency of 10 Hz. The number of cycles to failure was recorded. RESULTS: Twenty-nine of the 50 implant-abutment combinations tested failed. Eighteen abutments fractured. Seven implant fractures and 16 abutment screw fractures were seen, along with some damage to the implant platform in some specimens. No significant difference was seen between the implant systems, but significant differences were observed between the implant diameters. A subsequent one-way analysis of variance revealed statistically significant differences between the 10 implant-abutment test groups. CONCLUSIONS: Rotational load fatigue testing performance of zirconia abutments is dependent on the abutment diameter. Failure modes varied according to system design characteristics.

Load fatigue of teeth with different ferrule lengths, restored with fiber posts, composite resin cores, and all-ceramic crowns.

STATEMENT OF PROBLEM: There is no evidence to suggest that the ferrule length needed for an all-ceramic crown is different from that needed for a cast metal or metal ceramic crown. PURPOSE: The purpose of this study was to relate different ferrule lengths with the number of fatigue cycles needed for failure of the crown cement for an all-ceramic crown cemented with a resin cement. MATERIAL AND METHODS: Fifteen maxillary central incisors were divided into 3 groups (n=5), with ferrules of 0.0 mm (no-ferrule group), 0.5 mm (0.5-mm ferrule group), and 1.0 mm (1.0-mm ferrule group), respectively. Each tooth was restored with a 0.050-inch glass-filled composite post (ParaPost FiberWhite) and a composite resin core (ParaCore). The posts were cemented with resin cement (ParaPost Cement), and the composite resin cores were bonded to dentin using a dentin bonding agent (ParaPost Cement, Conditioner A & B). Each specimen was prepared with a 7-mm total preparation height, a 1.5-mm lingual axial wall, and a 1.0-mm shoulder around the tooth. The crowns for all specimens were pressed with a pressable ceramic material (IPS Empress 2) and cemented with resin cement (Variolink II). A 6-kg cyclic test load was applied to each specimen at 135 degrees to the long axis of the tooth. The independent variable measured was the number of load fatigue cycles required for failure of the crown cement. The data were subjected to the Kruskal-Wallis test to detect overall significance and the Mann-Whitney U test for pairwise comparisons with Bonferroni correction (alpha=.017). RESULTS: The mean (SD) number of cycles to failure for each group was: no-ferrule group, 213 (317); 0.5-mm ferrule group, 155,137 (68,991); and 1.0-mm ferrule group, 262,872 (21,432). None of the specimens in the 1.0-mm ferrule group failed. Significant differences were found between the no-ferrule group and the 0.5-mm ferrule group, and the no-ferrule group and the 1.0-mm ferrule group (P<.017), but not between the 0.5-mm ferrule group and the 1.0-mm ferrule group (P>.017). CONCLUSIONS: Specimens with a 0.0-mm ferrule survived few fatigue cycles despite the fact that both the post and crown were bonded with resin cement. Teeth with a 0.5-mm ferrule showed a significant increase in the number of fatigue cycles over the 0.0-mm group, whereas teeth with the 1.0-mm ferrule exhibited a significantly higher fatigue cycle count over the 0.0-mm but not the 0.5-mm group.

Load fatigue performance of four implant-abutment interface designs: effect of torque level and implant system.

PURPOSE: Biomechanical load-fatigue performance data on single-tooth implant systems with different implant-abutment interface designs is lacking in the literature. This study evaluated the load fatigue performance of 4 implant-abutment interface designs (Brånemark-CeraOne; 3i Osseotite-STA abutment; Replace Select-Easy abutment; and Lifecore Stage-1-COC abutment system). The number of load cycles to fatigue failure of 4 implant-abutment designs was tested with a custom rotational load fatigue machine. The effect of increasing and decreasing the tightening torque by 20% respectively on the load fatigue performance was also investigated. MATERIALS AND METHODS: Three different tightening torque levels (recommended torque, -20% recommended torque, +20% recommended torque) were applied to the 4 implant systems. There were 12 test groups with 5 samples in each group. The rotational load fatigue machine subjected specimens to a sinusoidally applied 35 Ncm bending moment at a test frequency of 14 Hz. The number of cycles to failure was recorded. A cutoff of 5 x 10(6) cycles was applied as an upper limit. RESULTS: There were 2 implant failures and 1 abutment screw failure in the Brånemark group. Five abutment screw failures and 4 implant failures was recorded for the 3i system. The Replace Select system had 1 implant failure. Five cone screw failures were noted for the Lifecore system. Analysis of variance revealed no statistically significant difference in load cycles to failure for the 4 different implant-abutment systems torqued at recommended torque level. A statistically significant difference was found between the -20% torque group and the +20% torque group (P < .05) for the 3i system. CONCLUSIONS: Load fatigue performance and failure location is system specific and related to the design characteristics of the implant-abutment combination. It appeared that if the implant-abutment interface was maintained, load fatigue failure would occur at the weakest point of the implant. It is important to use the torque level recommended by the manufacturer.

Load fatigue performance of a single-tooth implant abutment system: effect of diameter.

PURPOSE: This study investigated the load fatigue performance of narrow-, regular-, and wide-diameter CeraOne (Nobel Biocare) single-tooth implants and abutments. MATERIALS AND METHODS: Five samples of each implant-abutment combination in 3 different widths were tested at 3 applied screw torque levels (recommended torque, recommended torque +20%, and recommended torque -20%). A rotational load fatigue machine was used to apply a 21-N load, at an angle of 45 degrees to the long axis of the specimens. This loading produced an effective bending moment of 35 Ncm at the abutment-implant interface. An upper cyclic limit was set at 5 x 10(6) load cycles for all specimens. RESULTS: Two-way analysis of variance revealed a significant difference between narrow-diameter and wide-diameter implant test groups but no significant difference between the 3 torque levels for each implant diameter. In the narrow-diameter group, 6 of the 15 specimens failed (5 abutment screw failures and 1 implant failure). In the regular-diameter group, 3 of the 15 specimens failed (2 implant failures and 1 abutment screw failure). There were no failures in the wide-diameter group. DISCUSSION: The results of this study indicate that the abutment screw is not the only potential failure location. The possibility of implant fracture clinically has been previously reported for prostheses supported by both single- and multiple-implant prostheses. CONCLUSION: The wide-diameter CeraOne single-tooth implant system demonstrated superior load fatigue performance. For clinical situations with significant functional loading, the narrow-diameter implants would be at a greater risk of fatigue failure.

Displacement of implant components from impressions to definitive casts.

PURPOSE: Four possible displacements of implant components from a patient model to a definitive cast were assessed to suggest a standard method of comparing the accuracies of implant impression techniques. MATERIALS AND METHODS: Two techniques for impression making were assessed: a nonsplinted open-tray technique and a light-curing resin splinted open-tray technique. A mandibular model with 5 parallel implants was fabricated. Five definitive casts were fabricated per technique. Using a computerized coordinate measuring machine, 5 part coordinate systems were established, and 7 sets of data were obtained for each sample. From the data, the amount of displacement while connecting components and the linear and angular displacement of components during impression making and cast fabrication were calculated. The Mann-Whitney test was used to determine significant differences between the impression techniques (P < .05). RESULTS: The average displacements while connecting impression copings and abutment replicas were 31.3 and 30.4 microm, respectively. Less displacement occurred in the nonsplinted group compared to the splinted group during impression making (P = .001) but greater displacement occurred in that group during definitive cast fabrication (P = .015). DISCUSSION: In contrast to previous studies, the current study excluded displacement resulting from component connection, because displacement from that source has no relation to impression technique and cannot be controlled. CONCLUSIONS: Connecting a component produced as great a displacement as that resulting solely from a impression or cast fabrication. The nonsplinted group was more accurate during impression making but less accurate during cast fabrication.

Fatigue resistance of endodontically treated teeth restored with three dowel-and-core systems.

STATEMENT OF PROBLEM: The successful restoration of endodontically treated teeth is enhanced by a crown design employing the ferrule effect. However, it is unclear which dowel-and-core system most effectively supports successful treatment. PURPOSE: The purpose of this study was to compare the load fatigue resistance of 3 dowel-and-core systems. MATERIAL AND METHODS: Fifteen endodontically treated maxillary central incisors were sectioned perpendicular to the long axis at a point 1.5 mm incisal to the cemento-enamel junction (CEJ). At the level of the CEJ, specimens were then prepared for crowns with 1-mm complete shoulder finish lines and 1.5 mm of axial wall height. The prepared teeth were divided into 3 groups (n=5) and restored with 1 of the following dowel-and-core combinations: Group CG, cast gold dowels and cores; Group TA, titanium alloy dowels (ParaPost XH) with composite cores; or Group FR, fiber-reinforced resin dowels (ParaPost FiberWhite) with composite cores. A dentin bonding agent (OptiBond Solo) was placed prior to the composite cores. Dowel-and-core castings and titanium alloy dowels were cemented with zinc phosphate cement. The fiber-reinforced dowels were cemented with a resin cement (ParaPost Cement). The crowns for all specimens were cast with an incisal notch for applying the fatigue load. The independent variable measured was the number of load fatigue cycles required to cause luting cement failure. The data were subjected to 1-way analysis of variance and the Student-Newman-Keuls test for 3 subsets (alpha=.05). RESULTS: The mean value+/-standard deviation for the cycles to failure for each group was: Group CG: 11,897+/-4080 load cycles, Group TA: 24,384+/-8231 load cycles, and Group FR: 50,696+/-7063 load cycles. Significant differences were found between all groups ( P<.05). CONCLUSIONS: Fiber-reinforced resin dowels and bonded composite cores under fatigue loading provided significantly stronger crown retention than cast gold dowels and cores and titanium alloy dowels with composite cores under fatigue loading.

Critical bending moment of implant-abutment screw joint interfaces: effect of torque levels and implant diameter.

PURPOSE: Critical bending moment (CBM), the moment at which the external nonaxial load applied overcomes screw joint preload and causes loss of contact between the mating surfaces of the implant screw joint components, was measured with 2 types of implants and 2 types of abutments. MATERIALS AND METHODS: Using 4 test groups of 5 implant-abutment pairs, CBM at the implant-abutment screw joint was measured at 25%, 50%, 75%, and 100% of the manufacturer's recommended torque levels. Regular Platform (RP) Nobel Biocare implants (3.75 mm diameter), Wide Platform (WP) Nobel Biocare implants (5.0 mm diameter), CeraOne abutments, and Multiunit abutments were used. Microstrain was measured as loads were applied to the abutment at various distances from the implant-abutment interface. Strain instrumentation logged the strain data dynamically to determine the point of gap opening. All torque applications and strain measurements were repeated 5 times. RESULTS: For the CeraOne-RP group, the mean CBMs were 17.09 Ncm, 35.35 Ncm, 45.63 Ncm, and 62.64 Ncm at 25%, 50%, 75%, and 100% of the recommended torque level, respectively. For the CeraOne-WP group, mean CBMs were 28.29 Ncm, 62.97 Ncm, 92.20 Ncm, and 127.41 Ncm; for the Multiunit-RP group, 16.08 Ncm, 21.55 Ncm, 34.12 Ncm, and 39.46 Ncm; and for the Multiunit-WP group, 15.90 Ncm, 32.86 Ncm, 43.29 Ncm, and 61.55 Ncm at the 4 different torque levels. Two-way analysis of variance (ANOVA) (P < .001) revealed significant effects for the test groups (F = 2738.2) and torque levels (F = 2969.0). DISCUSSION: The methodology developed in this study allows confirmation of the gap opening of the screw joint for the test groups and determination of CBM at different torque levels. CONCLUSION: CBM was found to differ among abutment systems, implant diameters, and torque levels. The torque levels recommended by the manufacturer should followed to ensure screw joint integrity.

Fatigue load of teeth restored with bonded direct composite and indirect ceramic inlays in MOD class II cavity preparations.

PURPOSE: This study compared the fatigue life of human maxillary premolars restored with direct composites and indirect ceramic inlays in mesio-occlusodistal (MOD) cavities. MATERIALS AND METHODS: Ten human maxillary premolars were divided into two groups of five and restored with (1) direct composite restorations, or (2) pressed ceramic restorations. Standardized MOD cavities were prepared for both groups. Teeth in the direct composite group were restored with Z250 composite and Single Bond adhesive, and those in the ceramic group were restored with IPS Empress ceramic inlays. The ceramic inlays were luted with Single Bond and RelyX ARC cement. Under the applied test load of 11.17 kg, strain measurements were recorded from an electric resistance stain gauge bonded to the buccal surface. These strains were recorded for the (1) intact tooth, (2) cavity preparation, and (3) restored tooth. These strain measurements were used to calculate the relative tooth compliance values for each tooth. The fatigue loading was applied until reinforcement loss was registered by the strain gauge. RESULTS: A one-way ANOVA showed no significant compliance difference between the intact and restored tooth conditions, and no significant difference in fatigue cycles to failure between the two groups. CONCLUSION: There were both adhesive and cohesive failures in both restoration groups, indicating that the adhesive joint is not the only weak link in these restorations.

The effect of 3 torque delivery systems on gold screw preload at the gold cylinder-abutment screw joint.

PURPOSE: This study measured the gold screw preload at the gold cylinder-abutment screw joint interface obtained by 3 torque delivery systems. MATERIALS AND METHODS: Using a precalibrated, strain-gauged standard abutment as the load cell, 3 torque delivery systems tested were shown to have significant differences in gold screw preload when a gold cylinder was attached. RESULTS: Mean preloads measured were 291.2 N for hand torque drivers set at 10 Ncm, 340.3 N for electronic torque controllers at low setting/10 Ncm, 384.4 N for electronic torque controllers at high setting/10 Ncm; and 140.8 N for hand-tightening with a prosthetic slot screwdriver. Significant differences in screw preload were also found between operators using a hand torque driver. DISCUSSION: Hand-tightening delivered insufficient preload and cannot be recommended for final gold screw tightening. Different electronic torque controller units set at 10 Ncm induced mean gold screw preloads that ranged from 264.1 N to as high as 501.2 N. CONCLUSION: Electronic torque controllers should be regularly recalibrated to ensure optimal output.

Effect of core bonding on fatigue failure of compromised teeth.

PURPOSE: This study determined the effect of bonding a composite core on the number of load cycles to cement failure for teeth restored with complete crowns. MATERIALS AND METHODS: Ten extracted human maxillary central incisors were divided into two groups of five each. The tooth roots were at least 11 mm long, allowing an 8-mm post. Under copious irrigation, each tooth was cut to a flat plane 1 mm coronal to the buccal cementoenamel junction, perpendicular to the long axis of the tooth. The canal space was prepared to a final diameter of 1.25 mm, 8 mm deep. Each tooth was rebuilt with a 050 Parapost and Corestore. Final preparation height was 7 mm, including a 1-mm ferrule. For group 1, the core was bonded to the dentin using autocured Scotchbond Multipurpose Plus. For group 2, the core was not bonded. Following crown cementation, all teeth were subjected to a fatigue load of 4 kg at a rate of 280 cycles per minute. RESULTS: One tooth with a bonded core failed at 19,880 cycles, and the other four in this group did not fail after 100,000 cycles. All of the teeth without a bonded core failed at a cycle count of less than 100. The Mann-Whitney nonparametric test showed a significant difference between the two groups (P < .01). CONCLUSION: Bonding of a composite core to dentin prior to crown cementation provided a significantly stronger crown retention under fatigue loading.

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.