Effects of Implanting Torques on Implant Osseointegration in an Animal Model

Objective: To investigate the effect of insertion torque on implant osseointegration in an animal model. Methods: First, the first to fourth premolars of nine healthy adult beagles’ mandibular were extracted to form an edentulous area, and then the beagles were equally divided into three groups with different torques (low torque: 10–30 Ncm; medium torque: 30–50 Ncm; high torque: > 70 Ncm). Three implants were placed on each side of the edentulous area of the beagles (54 total), and the dogs were observed for 8 weeks. Implant performance and removal torque values (RTV) were determined at 1, 4, and 8 weeks after surgery. In addition, the expression ratios of OPG and RANKL mRNAs in the surrounding bone tissue were determined. Results: None of the 54 implants showed loosening or loss, and no significant bone resorption was observed. The removing torques and the expression ratios of OPG and RANKL mRNAs showed differences at 1 and 4 weeks after surgery, while they converged at 8 weeks after the surgery (p > 0.05). Conclusion: The osteointegration process lasted approximately 8 weeks depending on the difference in parameters, and all parameters showed the same values even though the insertion torques at the beginning were different.

Effect of Hafnium Coating on Osseointegration of Titanium Implants: A Split Mouth Animal Study

The behaviour of hafnium as surface coating in biological environments has not been studied. Little is known about osseointegration of hafnium-coated titanium implants. Thus, further studies of hafnium coating under biological conditions are required in order to determine the suitability of this material, as a surface coating for biomedical application. The aim of the study is to analyse the difference between hafnium-coated titanium and uncoated titanium by evaluating the osseointegration ability of hafnium metal and mechanism of which promotes better bone integration. The study was conducted with a split mouth design on 16 Wistar Albino rats of both sexes, at the age of 6-7 months, weighing 2526.5 ± 74.4 g . Self-tapping titanium osteosynthesis screws ( 4 mm × 2 mm ) (LeForte System Bone Screw®) were implanted in the mandible of rats: Group A (pure titanium screws, n = 12 ) and Group B (hafnium-coated screws, n = 12 ). The implanted screws’ stability was checked and noted with a specially customised torque apparatus during insertion and removal of implant. The tissue sections were then processed for hematoxylin and eosin and Masson’s trichrome for bone and connective tissue examination, after 4 and 8 weeks of placement. Hafnium coating appears to have offered similar biocompatibility (aspartate transaminase (AST), alanine aminotransferase (ALT), and creatine kinase (CK) enzyme assay), statistically significant improvement (independent Student’s t -test, p < 0.05 ) in insertion torque ( 25.42 ± 3.965 ) and removal torque ( 29.17 ± 2.887 ) than commercially pure titanium with insertion torque ( 22.08 ± .575 ) and removal torque ( 25.42 ± 2.575 ). Hafnium coating in the rat mandible showed promising osseointegration with good tissue biocompatibility. Further human trials of hafnium-coated implants are needed to understand the biological behaviour better to enhance clinical performance.

Long-term evaluation of factors affecting removal torque of microimplants

Background The current study aimed to evaluate factors affecting the long-term stability of microimplants using removal torque and the correlation between removal torque and clinical variables. Materials and methods This research evaluated 703 microimplants placed in 354 patients (mean age: 30.4 ± 12.1 years). The removal torque was evaluated according to various clinical variables including sex, age, placement site, microimplant size, and placement method (self-drilling versus pre-drilling). Pearson correlation and stepwise multiple linear regression analyses were performed to investigate different variables and their association with removal torque. Results The mean removal torque was significantly higher in the mandible (4.46 N cm) than in the maxilla (3.73 N cm). The values in the posterior teeth/retromolar areas were significantly higher than those in the anterior teeth area. There were no significant difference in terms of sex. Teenagers had a lower removal torque than older adults in the mandible, but not in the maxilla. Microimplants with a greater length and diameter, except for those with a greater diameter in the maxilla, was associated with a higher removal torque. Regardless of placement torque, the removal torque convergently reached approximately 4 N cm in both placement methods. The removal torque was significantly correlated with screw length in the self-drilling group and with diameter in the pre-drilling group. Conclusions Removal torque was related with placement site, age, placement method, and length and diameter of microimplants.

Effect of Application of a Bio-Adhesive on the Removal Torque Value and Rotational Misfit at the Implant–Abutment Junction: An In Vitro Study

The aim of this study was to assess the effect of application of a recently developed bio-adhesive (Impladhesive) to abutment screw threads on the removal torque value and rotational misfit at the implant–abutment junction. This in vitro study evaluated 20 implant fixtures and 20 straight abutments. Specimens were randomly divided into two groups (n = 10) with/without adhesive application. In the adhesive group, the abutment was dipped in Impladhesive before torquing. In the control group, the abutment was torqued conventionally without adhesive application. The removal torque value was recorded after completion of the cyclic loading of 500,000 cycles with 2 Hz frequency and 75 N load. Rotational misfit was recorded using a video measuring machine. After applying the torque, the change in the bisector angle on the abutment hex was recorded for each implant. The biocompatibility of Impladhesive was evaluated using a MTT cell vitality assay. Normal distribution of data was assessed using the Kolmogorov–Smirnov test. Data were analyzed using a t-test and Pearson’s correlation coefficient The application of Impladhesive at the implant–abutment interface resulted in significantly greater mean removal torque value compared to the control group (p = 0.008). In addition, the mean rotational misfit at the implant–abutment interface was significantly lower in the use of Impladhesive compared to the control group (p = 0.001). In addition, the cell vitality was found to be greater than 80% at all evaluated time points. It can be concluded that the application of Impladhesive on the abutment screw significantly decreased rotational misfit and increased the removal torque value. Future studies are needed to evaluate the efficacy of this bio-adhesive an in vivo setting.

Screw removal torque evaluation in implants with cone morse and external hexagon platforms in anterior cantilever

This study aims to evaluate the screw removal torque on prosthetic platforms of Cone Morse (CM) and External Hexagon (EH) implants in crowns with anterior cantilever. Materials and Methods: in vitro study with a sample consisting of 20 test specimens of 2 elements (21 and 22), with n = 40; load is simulated on element 21 or on cantilever of 22. Samples were divided into 4 groups consisting of 10 test specimens on CM implants (groups 1 and 2), and 10 test specimens on EH implants (groups 3 and 4). The test specimens were manufactured using cylindrical PVC pipes measuring 22 x 19.05 mm filled with acrylic resin. The implants were fixed with a centralization device. Components used were EUCLAs and UCLAs with a chrome-cobalt alloy molten base. The metal bases were scanned, the crowns were digitally waxed, made on CAD/CAM system, and cemented on the metal bases with Panavia cement. Torque was applied using 20N for CM and 32N for EH, according to the manufacturers’ instructions. The test specimens were then subjected to a cycling process consisting of 1,000,000 cycles at a frequency of 2 Hz. The cyclic process applied axial forces to the surface (palate face of 21 and 22). Two cycling processes were carried on, the first on the palate face of 21 and the second on the palate face of 22. Between the two, screws were removed and replaced by new ones. The screw removal torque was measured using a digital torque meter. Results were analyzed with Student’s t test and variance analysis. Statistical calculations were conducted in SPSS 23 using 5% of significance. Results: Student’s t test showed significantly lower removal torque values in comparison with initial torque for both CM and EH connection implants and force applied to elements 21 and 22 (p < 0.001) or 22 (p < 0.001). Considering torque loss, there was no significant effect of the interaction between type of implant connection and site of force application (p = 0.094). Removal torque was significantly lower than initial torque for both implants (CM and EH). Conclusion: Torque loss occurred both in CM and EH. There was no significant effect of the interaction between connections and site of force application.

Effect of Abutment Type and Tightening Sequence on Torque Maintenance Capacity after Mechanical Cycling in Splinted Implant-Supported Restorations

The aim of this study was to compare the screw removal torque of mini-conical prosthetic components and straight trunnion of indexed morse taper implants after mechanical cycling. The sample consisted of 40 implants and 20 mini-conical prosthetic components (MC group) and 20 straight trunnion components (ST group). Each group consisted of 10 specimens, with 2 implants in each, and cobalt–chromium metallic crowns were screwed into each sample. The components of the MC group received a torque of 20 N-cm with a digital torque wrench, and after 10 min were retightened with the same value as the initial torque. The components of the ST group received a torque of 30 N-cm, with a digital torque wrench, and after 10 min, they were retightened with the same value. The screws of the respective crowns of the two groups received a torque of 10 N-cm and after 10 min were retightened with the same value. Each group was subjected to the fatigue test in a mechanical cycler at 2,000,000 cycles, with a load of 250 N and frequency of 4 Hz. At the end of the fatigue test, the loosening torque of each screw of the specimens was measured through a digital torque wrench. The data were analyzed by two-way ANOVA and a Tukey test. In both groups, there were loss of torque. The results showed no statistic difference between MC and ST groups (p > 0.05).

Implant-abutment screw removal torque values between customized titanium abutment, straight titanium abutment, and hybrid zirconia abutment after a million cyclic loading: an in vitro comparative study

Purpose The aim of this study was to compare removal torque values after mechanical cyclic loading and bending moment after the static compression testing of customized titanium abutment compared with prefabricated and hybrid abutments. Materials and methods The study was developed according to ISO 14801:2016. Sixty implants were divided into three groups equally: Straight titanium abutment group, Customized titanium abutment group, and Hybrid zirconia abutment group. Abutments were fabricated with zirconia restoration. Forty five implants underwent for cyclic loading. The removal torque values were measured after a fatigue test was conducted at 0 cycles (control), 50,000 cycles and 1,000,000 cycles. In the second experiment, 15 implants were divided into the same groups. Then, bending moments were investigated. Results The mean initial removal torque value was significantly higher than 50,000 cycles and 1,000,000 cycles (P < 0.001). The comparison of mean removal torque value between types of abutments was not significantly different (P > 0.05), and the bending moments of all abutments were not significantly different (P > 0.05). Conclusions From the boundary of this in-vitro study, it could be concluded that customized titanium abutment and hybrid abutment were not significantly different in terms of removal torque values after the fatigue test. The bending moment between types of abutment were not significantly different. Thus, it could be concluded that abutment type does not significantly influence abutment stability or fracture strength.

An In Vitro Analysis on Polyurethane Foam Blocks of the Insertion Torque (IT) Values, Removal Torque Values (RTVs), and Resonance Frequency Analysis (RFA) Values in Tapered and Cylindrical Implants

Background: Several different dental implant microgeometries have been investigated in the literature for use in low-density bone sites. The polyurethane solid rigid blocks represent an optimal in vitro study model for dental implants, because their composition is characterized by symmetrical linear chains of monomers of hexa-methylene sequences producing a self-polymerization process. The aim of the present investigation was to evaluate the primary stability of cylindrical and tapered implants positioned into low-density polyurethane solid rigid blocks. Materials and Methods: Two different macrogeometries, cylindrical (4 mm diameter and 10 mm length) and tapered dental implants (4.20 mm diameter and 10 mm length), were investigated in the present study. The implants were inserted into 10 PCF and 20 PCF polyurethane blocks, with and without an additional cortical layer. The insertion torque (IT) values, the removal torque values (RTVs), and the resonance frequency analysis (RFA) values were measured and recorded. Results: A total of 80 sites were tested, and a significant increased primary stability (PS) was detected in favour of tapered dental implants when compared to cylindrical implants in all experimental conditions (p < 0.05). Higher IT, RT, and RFA values were measured in tapered implants in 10 and 20 PCF polyurethane blocks, both with and without the additional cortical layer. Conclusions: Both implants showed sufficient primary stability in poor density substrates, while, on the other hand, the tapered microgeometry showed characteristics that could also lead to clinical application in low-density posterior maxillary sites, even with a drastically decreased bone cortical component.

Effect of Abutment Type and Tightening Sequence on Torque Maintenance Capacity after Mechanical Cycling in Splinted Implant-Supported Restorations

The aim of this study was to compare the screw removal torque of mini conical prosthetic components and straight trunnion of indexed morse taper implants, after mechanical cycling. The sample consisted of 40 implants and 20 mini-conical prosthetic components (MC group) and 20 straight trunnion components (ST group). Each group consisted of 10 specimens, with 2 implants in each, and cobalt-chromium metallic crowns were screwed into each sample. The components of the MC group received a torque of 20 N.cm with a digital torque wrench and after 10 minutes were retightened with the same value as the initial torque. The components of the ST group received a torque of 30 N.cm, with a digital torque wrench and after 10 minutes, they were retightened with the same value. The screws of the respective crowns of the two groups received a torque of 10 N.cm and after 10 minutes were retightened with the same value. Each group was subjected to the fatigue test in a mechanical cycler at 2.000.000 cycles, with a load of 250 N and frequency of 4 Hz. At the end of the fatigue test, the loosening torque of each screw of the specimens was measured through a digital torque wrench. The data were analyzed by two-way ANOVA and Tukey test. In both groups, there were loss of torque. The results showed no statistic difference between MC and ST groups.

Functional and Antioxidant Properties of Plastic Bottle Caps Incorporated with BHA or BHT

In this study, we prepared new antioxidant active plastic bottle caps by incorporating butylated hydroxyanisole (BHA) or butylated hydroxytoluene (BHT) and 2% (w/w) white masterbatch in high-density polyethylene (HDPE). Fourier-transform infrared (FT-IR) spectrometry revealed that the antioxidants and HDPE were uniformly mixed with noncovalent bonding. In addition, the differential scanning calorimetry (DSC) test revealed that the change in melting point and initial extrapolation temperature of the antioxidant active caps was not significant. Sensory evaluation and removal torque tests validated the suitability of the antioxidant active plastic bottle caps in industrial application. The antioxidant activity increased with a greater concentration of BHA and BHT incorporated in both antioxidant active caps (p < 0.05) and with more impact on the BHA cap compared to BHT cap in terms of antioxidant activity. Migration experiments for 10 days at 40 °C and 2 h at 70 °C showed that active antioxidants in the plastic bottle cap were more easily released into fatty foods and milk products that are highly sensitive to oxidation, and the migration of BHA and BHT did not exceed the maximum amount specified in (EC) No 1333/2008 (<200 mg/kg). As such, the antioxidant active plastic bottle caps inhibited oxidation, thereby ensuring higher food quality.