Detorque Values Research Articles

Effect of implant‒abutment connections on abutment screw loosening: An in vitro study.

The widespread use of dental implants as a predictable treatment choice has drawn attention to their complications as a major challenge despite their high clinical success rates. In this context, loosening of the abutment screw in posterior single crowns is the most common problem; the use of adequate preload and proper anti-rotational features at implant‒abutment interface appear to be two main solutions to such a problem. The present study evaluated the effect of implant‒abutment connections in four different implant systems before and after cyclic loading. Intra-Lock, Dentis, Xive, and Dio implant systems were used in this study. Each system underwent one million cycles of dynamic forces eight times with a magnitude of 110 N. For each specimen after tightening the screw with a torque of 32 Ncm, the detorque values were measured and recorded by a digital torquemeter after and before cyclic loading. Data were analyzed by Kolmogorov-Smirnov, Levene's, one-way ANOVA, and post hoc Tukey tests. Initial detorque values between the study groups showed significant differences (P<0.0001). Pairwise comparisons showed significantly lower primary detorque values in the Dentis system compared to the three other systems (P<0.0001). After cyclic loading, significant differences were observed between the study groups (P<0.0001). Pairwise comparisons of the groups showed significant differences between all the systems after loading. The type of implant‒abutment connection is an essential factor influencing the amount of abutment screw loosening.

Does the index in Morse taper connection affect the abutment stability? An in vitro experimental study.

The present study compared three different implant and abutment sets of type Morse taper (MT) connection, with- and without-index, were analyzed regarding their mechanical behavior without and with cyclic load application simulating the masticatory function. Ninety implant and abutment (IA) sets were used in the present study, divided into three groups (n = 30 samples per group): Group A, Ideale solid straight abutment (one piece) without index; Group B, Ideale abutment with an angle of 30-degree (two pieces) without index; Group C, Ideale abutment with an angle of 30-degree (two pieces) with index. The abutment stability quotient (ASQ) values, detorque value and rotation angle were measured before and after the cycling load. Twenty IA sets of each group were submitted to mechanical load at 360,000 cycles. The ASQ without load were 64.7 ± 2.49 for the group A, 60.2 ± 2.64 for the group B, 54.4 ± 3.27 for the group C; With load were 66.1 ± 5.20 for the group A, 58.5 ± 6.14 for the group B, 58.9 ± 2.99 for the group C. Detorque values were lower in groups B and C compared to group A (p < 0.05). In conclusion, the presence of the index did not influence the stability values. However, solid straight abutments (group A) showed higher values of stability compared to groups of angled abutments (groups B and C).

Short implants: Influence of different diameters, torques, and transmucosal heights of straight prosthetic abutments on screw preload loss after cycling.

This study evaluated the influence of different implant diameters, insertion torques, and transmucosal heights on the loosening of abutments installed on short implants, after mechanical cycling. The Morse taper connection implants (n=96) tested were 5mm high, divided according to the platform diameter: 4 or 6mm. A universal abutment was coupled to each implant (with different transmucosal heights: 1 or 5mm). The sets were subdivided into 20- and 32-Ncm torque. After the cycle fatigue test, the detorque values were measured with a digital torque indicator. After mechanical cycling, the mean detorque values obtained for the abutment with 20-Ncm insertion torque were lower than for implants with 32-Ncm insertion torque, regardless of the platform diameter or transmucosal height. In the 20-Ncm torque group, there was no statistically significant difference in the detorque values between platform diameters or transmucosal heights. Otherwise, for 32-Ncm sets, a smaller platform diameter (4mm), and a longer transmucosal height (5mm) showed the lowest detorque values. In conclusion, implants placed with 32-Ncm insertion torque and abutments with 1mm transmucosal height and a 6mm implant diameter demonstrated the highest detorque values.

Effect of Different Applied Torque Maintenance Times on Detorque Values of Abutment Screws in Single Implant-Supported Fixed Prostheses

We evaluated the effect of maintaining the applied torque for one minute on the reverse torque value (RTV) as compared to immediate torque application and retorquing after 10 minutes. A total of 48 screws were used to torque the abutment utilizing three different protocols (A–C); immediate torque application to the recommended 35 Ncm, torque applied to the recommended 35 Ncm, followed by retorquing of the same screw after 10 minutes and abutment screws were torqued to the recommended 35 Ncm, and the torque was held for one minute. The gap size between the implant and supra-structure was measured at three fixed points for each surface. Data were analyzed using SPSS software (α = 0.05). The mean RTV for 1 minute, immediate, and 10 minutes was 32.68±2.04 Ncm, 32.5±0.93 Ncm, and 30.54±0.90 Ncm, respectively. The difference between RTV in the 1-min and 10-min protocols was significant (P &lt;0.05). Pearson’s coefficient demonstrated a negative correlation between RTV and the gap between the supra-structure and the implant interface (r =−0.43, P &lt;0.01). When tightening abutment screws of implant-supported single crowns, holding the applied torque for 1 minute has proven to be efficient. Furthermore, larger gap values between the supra-structure and the implant inversely affect RTV, forcing the clinician to take caution to have a well-fitted supra-structure with as minimal a gap as possible.

To determine the effect of plasma nitriding treatment 56 on screw loosening and surface topography of different 78 implant-abutment screw systems with and without thermocycling: An in vitro study.

The aim of this study was to evaluate and compare the effect of plasma nitride-treated abutment screws of two different implant systems on screw loosening and surface topography with and without thermocycling. This was an in-vitro experimental study. Fifty-two abutment screws (Group A: 26 Genesis and Group B: 26 Bredent) underwent plasma nitride treatment and were subdivided into two groups, one without thermocycling and one with thermocycling. Dynamic load was applied and detorque values were evaluated for determining the screw loosening using "independent t-test" with the help of IBM SPSS Statistics 20 and scanning electron microscopy was done to check for surface topography. Inter- and intragroup comparisons were done using independent t-test (SPSS: Statistical Package for the Social Sciences software version 20). Plasma nitriding treatment genesis implant system abutment screw showed more screw loosening (P < 0.05) and surface roughness as compared to bredent with and without thermocycling. From the present study, it was shown that plasma nitride-treated abutment screws decreased the occurrence of screw loosening favoring the bredent implant-abutment system more than the genesis implant-abutment system.

Evaluation of the effect of oral health care product on the reverse torque value of the titanium prosthetic screw of an implant-supported crown following cyclic loading

Purpose of the study: To comparatively evaluate in vitro the effect of oral health care product on the reverse torque value of the titanium prosthetic screw of an implant-supported crown following cyclic loading. Materials and methods: Ten titanium screw-retained implant Co-Cr crowns without application of oral health care product (Group I) and ten titanium screw-retained implant Co-Cr crowns with the application of oral health care product (GC Tooth Mousse) (Group II) were connected to their respective analogs and prosthetic screws were torqued to 30 Ncm using a digital torque meter. Reverse Torque Values were measured before cycling loading and all the twenty samples were subjected to a cyclic loading simulating six months’ duration of the function. Reverse Torque Values were subsequently measured postcyclic loading. The results were analyzed using the Paired ‘t’ test and the Independent ‘t’ test. Results: The mean precyclic loading reverse torque values were 26.12 Ncm (Group I) and 26.57 Ncm (Group II) and the mean postcyclic loading reverse torque values were 22.49 Ncm (Group I) and 24.10 Ncm (Group II). There was no significant loss of preload for Group II test samples prior to cyclic loading compared to Group I test samples. Cyclic loading resulted in reduction of reverse torque values for both Group I and Group II test samples, indicating screw loosening. After cyclic loading, Group II test samples showed significantly higher detorque value than Group I test samples. Conclusion: Cyclic loading resulted in screw loosening in both test groups. Screw loosening was found to be significantly less for Co-Cr prosthetic screw-retained implant crown with the application of GC Tooth Mousse than Co-Cr prosthetic screw-retained implant crown without application of GC Tooth Mousse.

Comparison of reverse torque values of abutment screws with the application of oil-based and water-based antibacterial agents.

Using antibacterial agents to remove the foul odor of the implant cavity and prevent peri-implantitis can affect the detorque values and lead to the loosening of the abutment screw. This study investigated the effects of tetracycline and chlorhexidine gel on detorque values. This in vitro study was carried out on three groups of five implants. Group G1 was the control group, and no material was applied to the implant cavity. In group G2, the implant cavity was first filled with artificial saliva and then with chlorhexidine gel. In group G3, the implant cavity was first filled with artificial saliva and then with tetracycline. The abutments were tightened with 25 N/cm2 and then loosened. Finally, the detorque values were calculated. The highest detorque values were recorded in group G1. Group G3 showed the lowest detorque values. ANOVA showed significant differences in mean detorque values (P<0.05) between the three groups. According to this study, applying antibacterial agents decreased the detorque values and increased the risk of screw loosening. The reduction of detorque values was more pronounced with the oil-based antibacterial agent (tetracycline).

Bacterial infiltration and detorque at the implant abutment morse taper interface after masticatory simulation

This study evaluated the bacterial infiltration and the detorque of indexed and non-indexed abutments of Morse taper implants (MTI) after mechanical cycling (MC). 40 MTI were distributed into four groups: IIA (indexed implant abutments); NIIA (non-indexed implant abutments); IIAMC (indexed implant abutments submitted to MC); NIIAMC (non-indexed implant abutments submitted to MC), which were carried out under one million 5 Hz frequency and 3 Bar pressure. After mechanical cycling, all groups were immersed in a bacterial solution in Brain Heart Infusion Agar. After detorque, the bacteria infiltration was evaluated by counting the colony-forming units. For the bacterial infiltration, analysis was applied to the Kruskal–Wallis test (p = 0.0176) followed by Dunn’s test. For the detorque analysis, the two-way repeated-measures ANOVA was applied, followed by the Tukey’s test (p < 0.0001). Bacteria infiltration was highly observed in NIIA (p = 0.0027) and were absent in IIAMC and NIIAMC. The detorque values for IIA (19.96Ncm ± 0.19Ncm), NIIA (19.90Ncm ± 0.83Ncm), and NIIAMC (19.51Ncm ± 0,69Ncm) were similar and remained close to the initial value, while IIAMC (55.2Ncm ± 2.36Ncm) showed an extremely significant torque value increase (p < 0.0001). The mechanical cycling resulted in mechanical sealing of the implant-abutment interface, preventing bacterial infiltration in the indexed and non-indexed specimens, and increasing the detorque strength in the group of indexed abutments.

Effect of Lateral Cyclic Loading on Screw Loosening in Morse Taper Implant-Straight Abutment Connection

Background: Screw loosening is a common problem that can lead to mechanical and biological failure of dental implants. This study aimed to assess the effect of lateral cyclic loading on screw loosening (detorque value) in Morse taper implant-straight abutment connection.&#x0D; Methods: This in vitro, experimental study evaluated 12 dental implants with Morse taper implant-abutment connection. Dental implant-abutment assemblies were mounted in transparent acrylic resin blocks with 45-degree angle relative to the acrylic surface. The abutment screw was torqued to 30 N/cm by a digital torque-meter and retorqued after 10 minutes. The assemblies were then randomly divided into two groups (n=6). In the test group, lateral cyclic loads with 75 N magnitude and 1 Hz frequency were applied at 45-degree angle relative to the longitudinal axis of the fixture. After 500,000 cycles, the detorque value was measured at the implant-abutment interface by a digital torque-meter. The assemblies in the control group did not undergo cyclic loading. The detorque values were compared between the two groups using the Student t-test (alpha=0.05).&#x0D; Results: The mean detorque value was 23.17±1.33 N/cm in the control and 21.3±3.38 N/cm in the test group. According to the Student t-test, this difference was not significant (P=0.4).&#x0D; Conclusion: According to the present results, application of lateral cyclic loads had no significant effect on screw loosening (detorque value) of Morse taper implant-straight abutment connection but insignificantly increased the torque loss.

Behavior of implant and abutment sets of three different connections during the non-axial load application: An in vitro experimental study using a radiographic method

During the masticatory cycle, loads of different intensities and directions are received by the dental structures and/or implants, which can cause micromovements at the junction between the abutment and implant. The objective of this in vitro study was to evaluate the behavior of three different implant connections subjected to different load values using a digital radiography system. Additionally, the torque values for removing the abutment screws were also measured and compared. Ninety sets of implant and abutment (IA) were used, divided into three groups according to the type of connection (n =30 per group): EH group, external hexagon type connection; IH group, internal hexagon connection; and, MT group, Morse taper connection. MT group showed the better vertical misfit behavior at the three intensity of load applied, in comparison with EH and IH groups. In the analysis of torque maintenance (detorque test), MT group showed higher values of detorque when compared with the measured values of EH and IH groups (p <0.001). The IA sets of EH and IH groups showed a microgap in all levels of applied loads, unlike the MT group this event was not observed. In the detorque test, MT group increase in the torque values when compared to the initial torque applied, unlike EH and IH groups showed a decrease in the initially torque applied in all conditions tested. A positive correlation was detected between the misfit and detorque values.

Comparison of the Effect of Four Different Abutment Screw Torques on Screw Loosening in Single Implant-Supported Prosthesis after the Application of Mechanical Loading

Background The complications of implant-supported prostheses can be classified into mechanical and biological ones, one part of which is associated with screw loosening. This study was aimed to compare the effect of four different abutment screw torque techniques on screw loosening in single implant-supported prostheses following the application of mechanical loading. Materials and Methods In this experimental study, a total of 40 implants in acrylic blocks (6 × 10 × 20 mm) were mounted perpendicular to the surface. They were then randomly divided into four groups: (1) torquing once with 30 Ncm, (2) torquing three times with 30 Ncm and 5-minute intervals, (3) torquing once with 30 Ncm, opening the screw, and retorquing with 30 Ncm, and (4) torquing once with 35 Ncm. The torque values were confirmed by using a digital torque meter. Then, the samples underwent a force (2 cps, 0.453–11.793 kg) for three hours before the measurement of detorque values. The screw loosening force (torque) was then measured and recorded. The obtained data were analyzed by SPSS (version 22) software using one-way ANOVA and Tukey post hoc test at a 5% error level. Results The maximum mean detorque values of the abutment screws in single implant-supported prostheses were reported for groups 4 (27.8 ± 1.3), 1 (26.8 ± 1.3), and 3 (25.1 ± 1.3), and the minimum mean detorque value was found in group 2 (24.9 ± 1.2). Moreover, no significant difference was observed between groups 2 and 3 (p > 0.05), but a significant difference was found between groups 1 and 3 and other groups (p < 0.05). Conclusion The increase in the torque value increased the torque loss. However, the detorque value in group 4 showed the least difference with the value recommended by the manufacturer (30 Ncm).

Effect of crown height on the screw joint stability of zirconia screw-retained crowns

Statement of problemMedium- to long-term data for the performance of zirconia crowns with titanium (Ti) bases are sparse, particularly when the crown height space and occlusal loads are high. PurposeThe purpose of this in vitro study was to assess the effect of the height of zirconia screw-retained implant crowns with a Ti base on the screw joint stability after cyclic loading. A secondary aim was to investigate the survival of zirconia crowns of different heights after cyclic loading. Material and methodsTwenty-one internal connection implants were secured between fiberglass-reinforced epoxy resin sleeves. Mandibular first molar monolithic zirconia crowns with 3 different heights (6 mm, 10 mm, and 14 mm) were milled and bonded to the Ti bases (n=7). The screws were tightened to 30 Ncm, and a 30-degree 120-N cyclic load was applied to the crowns at 2 Hz for 5 million cycles. After 5 million cycles, the crowns were evaluated for stability, and the same protocol was repeated for 275-N and 435-N loads for 5 million cycles each. After loading, the detorque values were recorded. Failure was characterized based on whether the crown, screw, and/or implant fracture was observed. The detorque values were analyzed by using a 1-way-ANOVA with the restricted maximum likelihood estimation. The percentage of torque loss was calculated. The LIFETEST procedure was used to analyze the survival probability of the groups (α=.05). ResultsThe effect of crown height on the detorque values of screws was not found to be statistically significant (P>.05). The mean detorque value for 6-mm crowns was 23.5 Ncm, 24.4 Ncm for 10-mm crowns, and 22.1 Ncm for 14-mm crowns. A significant effect of crown height was found on the survival (P=.006), and the time-to-failure survival of 14-mm crowns was significantly lower than the survival of 6 mm and 10 mm crowns (P=.020), where no failures were observed. Four 14-mm crowns failed between the 1 and 2 million cycles after the loads were increased to 435 N. The failure modes were the same for all the crowns, implants, and screws fractured. ConclusionsWhen the tested internal connection implant was used, the crown height did not affect the detorque values, and 14-mm crowns performed similarly to the shorter crowns in terms of torque loss after cyclic loading. However, survival of the 14-mm crown-implant complex was lower, resulting in screw and implant fractures.

Effect of Crown Height on the Screw Stability of Titanium Screw-Retained Crowns.

The aim of this in vitro study was to evaluate the effect of crown height on the screw stability of screw-retained titanium implant crowns subjected to cyclic loading conditions. Twenty-one implants with internal hex connections were placed in epoxy resin holders. Mandibular first molar screw-retained titanium implant crowns with UCLA type, crown-abutment connections were CAD/CAM fabricated. Seven crowns of 3 different heights (6 mm, 10 mm, and 14 mm) were made. The crowns were seated onto the implants and screws were tightened to 30 Ncm. The implants were clamped into holders and stepwise cyclic loads were applied to the occlusal surface at 30-degree angles to the long axes of the crowns. The detorque values were measured after each 5 million cycles. Before increasing the applied load, the crowns were secured with new screws and tightened to 30 Ncm. Failure times, survival estimates and detorque values were then analyzed. (alpha = 0.05). Crown height did not significantly affect detorque values. However, five 14-mm crowns failed with varying fractures during the 475 N loading condition. Overall, a significantly lower survival for 14 mm crowns was found compared to 6 mm and 10 mm crowns (p = 0.004). Crown heights of one-piece screw-retained titanium implant crowns did not significantly affect detorque values. Screw fracture, however, was greater for crown height of 14 mm than those of 6 mm and 10 mm.

A new design of a multifunctional abutment to morse taper implant connection: Experimental mechanical analysis

The objective of this study was to evaluate a new design of multifunctional abutment for Morse taper implant connections, relative to the retentive stability after the application of cyclic loads in cemented and screwed crowns. Multifunctional abutments with two different angulations in the seating portion of the crown were tested, forming 2 groups (n = 30 samples per group): Group Abut11, where Smart abutments with an angle of 11.42° were used; Group Abut5, where Ideale abutments with an angle of 5° were used. Fifteen samples from each group received cemented crowns (CC) and another fifteen screwed crowns (SC). All crown samples were subjected to the mechanical cycling test at 360,000 cycles at a frequency of 4 Hz and 150 N of the load. The samples with CC were subjected to the tensile test to remove the crowns, while in the samples with SC, the detorque value of the fastening crown screws was measured. The mean tensile strength value of CC in the Abut11 group was 131.9 ± 13.5 N and, in the Abut5 group was 230.9 ± 11.3 N; while the detorque mean value in samples with SC 5.8 ± 1.8 N for the Abut11 group and, 7.6 ± 1.1 N for Abut5 group. Significant statistical differences were found between the two groups in both situations tested (p < 0.05). The multifunctional abutments, presenting a lesser angulation of the crown-seating portion, showed higher values of retention of the CC and a lesser screw loosening of torque of the fixing screws in the SC after the application of cyclic loads when compared to the abutments with more angulation in the crown-seating portion.

Effect of sealing gel on the microleakage resistance and mechanical behavior during dynamic loading of 3 implant systems

Statement of problemSealing products have been produced to reduce microleakage at the implant abutment interface. However, little is known about their effectiveness and any alterations in mechanical behavior of implant systems with their application. PurposeThe purpose of this in vitro study was to evaluate the effect of a silicone sealing gel on implant abutment interface microleakage, abutment screw torque loss, and thread wear of implant systems in a simulated oral environment. Material and methodsFive specimens each of 3 implants systems (Nobel, Straumann, and WEGO) that included sealed and unsealed groups were analyzed (N=30). Before assembling the components, toluidine blue solution was injected to the implant intaglio cavity to evaluate implant abutment interface microleakage. After tightening to the recommended torque, 20 to 200 N of 30-degree off-axis dynamic force was applied at 2 Hz for 48 hours. The toluidine blue solution was extracted to test optical density values at 1, 3, 9, 24, 33, and 48 hours. Detorque values were measured before and after cycling loading, and torque loss rates were calculated. The abutment screw morphologies were observed by using scanning electron microscopy. The coefficient of friction tendency of applying sealing gel was explored with a ball-on-flat configuration. One-way ANOVA and Student t test were used for statistical analysis (α=.05). ResultsThe optical density value increased with the loading time, especially for Straumann group. The sealing gel decreased the implant abutment interface microleakage of Straumann assemblies after cyclic loading of 9 hours (P=.044), whereas no statistical difference was found for Nobel (P=.140) or WEGO groups (P=.402) at 6 time points. Torque loss occurred during tightening and further increased after dynamic cyclic load in each group. Among the 3 implant systems, Straumann implants reported the best antiloosening property (P<.001). The application of sealing gel reduced the initial (P=.048) and final (P=.032) torque loss rate in all the 3 systems. Scanning electron microscopy observations revealed the bottom thread tended to have more abrasion than the first thread. After applying sealing gel, less thread abrasion was found in Nobel and WEGO assemblies, whereas the protective effect was not evident for the Straumann group. The coefficient of friction of sealed group (0.17 ±0.026) was significantly (P=.012) lower than that of unsealed group (0.24 ±0.044). ConclusionsThe silicone sealing gel improved the immediate fastening and long-term antiloosening performances of 3 implant systems, decreased the implant abutment interface microleakage of Straumann system, and reduced abutment screw thread abrasion of the Nobel and WEGO systems.

Influence of abutment angulation on loss of prosthetic abutment torque under mechanical cycling

Statement of problemInternal conical connections provide mechanical stability for the prosthetic abutment and implant connection. However, some clinical situations require the use of angled prosthetic abutments that may increase stress on supportive implants by difference force vectors under cyclic loading. PurposeThe purpose of this in vitro study was to measure the screw loosening values of prosthetic abutments with internal conical connections (indexed and nonindexed) having different angles under mechanical cycling. Material and methodsThirty-six implants (4.0×13 mm, Titamax) with internal conical connections and their respective universal prosthetic abutments (n=36, 3.5×3.3 mm) were divided into indexed and nonindexed groups (n=18) with abutment inclinations of 0 (straight), 17, and 30 degrees. An insertion torque of 15 Ncm was applied according to the manufacturer’s specifications. The specimens underwent fatigue testing of 500 000 cycles at a frequency of 2 Hz with a dynamic compressive load of 120 N at an angle of 30 degrees. The detorque values were measured by using a digital torque meter and tabulated for statistical analyses. ResultsThe specimens with indexed abutments had mean ±standard deviation detorque values of 6.72 ±2.29 Ncm under mechanical cycling, whereas those with nonindexed abutments had values of 8.98 ±1.84 Ncm. In the indexed group, the lowest detorque value was observed for abutments at 30 degrees compared with the straight group (P<.05). As for nonindexed abutments, similar detorque values were observed after increasing the abutment inclination (P>.05). ConclusionsA decrease in detorque values in the indexed abutments related to their inclination was found under mechanical cycling, whereas the prosthetic abutments with 30 degrees of angulation had the lowest values. No decrease was found in the nonindexed abutments.

Effect of Wet Field on the DE Torque Values of Abutment Screws

Screw loosening is amongst the most prevalent mechanical problems in dental implant prosthetics. Clinicians will know if the reverse Detorque values are compromised by contamination of the implant abutment screw hole either by blood , saliva or saline. Research have shown that the drying of the implant cavity may decrease the preload value when the abutment screw is closed and thereafter increase the likelihood of abutment screw loosening. Mobility of the prosthesis, or screw fracture and increase the risk of peri-implant soft-tissue inflammation. This study aims to assess and compare the effect of wet and dry fields while torqueing the abutment screws on the DE torque values. 40 Nobel bio care implant analogues mounted in plaster models were used in this study. The samples were divided into four groups dry abutment screws, artificial saliva, blood and normal saline. All the abutment screws were tightened till 20 Ncm and left aside for 15 minutes. After 15 minutes the abutment screw were DE torqued, and the DE torque values were noted for tall the groups. When analysed using paired sample t-test there was no significant difference with artificial saliva (p=0.269). There was statistical difference with blood (p=0.00) and with saline (p=0.00). Based on this study, the presence of saliva decreases the DE torque values of the abutment screws, whereas Blood and saline increase the DE torque values of the abutment screws. The presence of blood clot might be the reason for the increase in DE torque values which might decrease once the clot disintegrates. Clinicians should prevent contamination of the screw hole by blood and saliva; if contamination arises, sanitation of the infected screw and also the screw hole until final tightening is advised.

Comparison of the Effect of Two Different Abutment Diameters on Detorque Value Using Cyclic Loading and Thermocycling

Comparison of the Effect of Two Different Abutment Diameters on Detorque Value Using Cyclic Loading and Thermocycling

Effect of different maintenance time of torque application on detorque values of abutment screws in full-arch implant-supported fixed prostheses.

The effect of different maintenance time of torque application and screw loosening in full-arch implant-supported prosthesis remains uninvestigated. To examine the effect of different maintenance time of torque application on detorque values of implant abutment screw in full-arch implant-supported fixed complete denture. Passively fitting framework supported by four implants stabilized on resin model torqued to 35 N-cm and maintained for different times; instant torque application (protocol A), 10 seconds (protocol B), and 30 seconds (protocol C) were used. Detorque values were recorded during removal of the screws. Comparison between mean torque and detorque values were made using paired sample t-test. The mean removal torque values of each protocol were compared using three-way analysis of variance (ANOVA). The mean removal torque values were lower than the applied torque for all the protocols. The highest mean removal torque value was found in the immediate protocol (A) (24.44 ± 1.7), followed by the 30 seconds protocol (C) (23.37 ± 1.75), and then by the 10 seconds protocol (B) (23.35 ± 1.6). All these differences were found to be statistically significant between torque and detorque values (P = .001). However, the differences among detorque values were not statistically significant (P > .05). The application of 35 N-cm for different maintenance time of torque application on implant abutment screw did not appear to affect the detorque value in a multiple implant-supported fixed prosthesis. Maintaining the torque for prolonged time (10 seconds or 30 seconds) was not significantly associated with higher preload than instant torque application in full-arch implant-supported prosthesis.

Influence of Transmucosal Height on Loss of Prosthetic Abutment Torque After Mechanical Cycling

The aim of this study was to measure and record the universal transmucosal abutment height, and then evaluate whether it influenced loosening of the abutment screw by analyzing the torque and detorque values after mechanical cycling. Thirty-six implants, model CM Unitite, with internal conical connections (3.5 × 10 mm) and respective universal prosthetic abutments (n = 36, 3.25 × 6 mm), were divided into three groups (n = 12 each) with respective transmucosal heights of 0.8, 3.5, and 5.5 mm. Insertion torque of 20 Ncm was used in accordance with the manufacturer's specifications. Afterward, the samples were submitted to fatigue tests consisting of 500,000 cycles at a frequency of 2Hz, a dynamic compressive load of 120N, and an angle of 30°. The detorque values were measured with a digital torque meter and tabulated to perform statistical analyses; a level of significance of 5% was adopted. The mean detorque values (SD) obtained were 22.83 (6.30), 22.5 (5.45), and 19.41 (4.69) Ncm for transmucosal abutments with heights of 0.8, 3.5, and 5.5 mm, respectively, and showed no statistically significant difference ( P = .262). The authors of this study concluded that the transmucosal height of prosthetic abutments submitted to mechanical fatigue did not influence the detorque values.