Insertion Torque Values Research Articles

Combined Immediate Loading of Zygomatic and Mandibular Implants: A Preliminary 2-Year Report of 19 Patients

A retrospective study was performed to evaluate the feasibility of simultaneous use of immediately loaded zygomatic and mandibular implants for full maxillomandibular restoration. A total of 40 zygomatic and 112 conventional implants were placed in 19 edentulous and partially edentulous patients and restored with full-arch acrylic resin prostheses within 3 hours of surgery. Implant insertion torque values were between 35 and 45 Ncm. During the 1-year follow-up period, none of the 19 patients experienced implant or prosthesis failures. The patients did not experience any sinus infections or any other surgical complications from the performed procedures. Zygomatic and conventional implants can be simultaneously placed in the maxilla and mandible and successfully loaded with an acrylic resin prosthesis using the All-on-Four concept.

Peak insertion torque values of five mini-implant systems under different insertion loads

To assess the effect of 1 and 3 kg insertion load on five makes of self-drilling mini-implants on peak insertion torque values to establish risk factors involved in the fracture of mini-implants. Two different loads were applied during insertion of 40 mini-implants from five different manufacturers (Dual Top(™) (1·6×8 mm), Infinitas(™) (1·5×9 mm), Ortho Easy(™) (1·7×8 mm), Spider Screw(™) (1·5×8 mm) and Vector TAS(™) (1·4×8 mm)) into acrylic blocks at 8 rev/min utilizing a Motorized Torque Measurement Stand. Peak insertion torque values for both loads were highest for Vector TAS followed by Ortho Easy and Dual Top and were nearly three times higher than Infinitas (original version) and Spider Screws(TM). The log-rank test showed statistically significant differences for both loads for Vector TAS, Ortho Easy and Spider Screws. Unlike other designs tested, both tapered mini-implant designs (Spider Screw and Infinitas) showed a tendency to buckle in the middle of the body but fractured at the tip. Non-tapered mini-implants fractured at significantly higher torque values compared to tapered designs under both loads. Increased pressure resulted in slightly higher maximum torque values at fracture for some of the mini-implant designs, although this is unlikely to be of clinical relevance. Tripling insertion pressure from 1 to 3 kg increased the risk of bending tapered mini-implants before fracture.

Biomechanical effects of the implant material and implant–abutment interface in immediately loaded small-diameter implants

Small-diameter implants have been available since the 1990s, but few studies have analyzed their mechanical properties. This study evaluated the effects of the implant material and the implant-abutment connection designs on the primary stability and the marginal bone strain of small-diameter implant subject to immediate loading. Insertion torque value (ITV), implant stability quotient (ISQ), and Periotest value (PTV) of three implant systems with four parameters (titanium, titanium alloy, internal and external hexagon connections) were measured after placing implants into artificial type 2 jaw-bone models. Specimens were tested under both vertical and oblique static loads at 190 N. Peak values of the principal bone strain were recorded and analyzed statistically by the Kruskal-Wallis test and multiple-comparisons Bonferroni test. PTV and ISQ were higher for the NIOSM311 (internal-hex and Ti alloy) and FOSM311 (external-hex and pure Ti) implants, respectively, than for the NOSM311 (external-hex and Ti alloy) implant. Under vertical loading the peak value of peri-implant bone strains did not differ significantly among these three implant systems. However, the peak bone strains were at least 32 % lower for the NIOSM311 and FOSM311 implants than for the NOSM311 implant under lateral loading. The implant material and the implant-abutment connection design significantly influence the peri-implant bone strain of immediately loaded small-diameter implants, but barely affect their primary stability. A commercially pure titanium implant with an internal connection has the potential to reduce the risk of implant failure of small-diameter implant related to biomechanical complications.

Reverse torque values in indexed abutments

Mechanical stability of implant-abutment set is fundamentally important for the success in implant supported rehabilitation. For this, the knowledge about torque removal values is essential. In this way, the objective of this work was to evaluate the torque reverse values in indexed abutments of Morse Taper system. Five Morse taper implants with their respective abutments were tested (n=5). Each abutment received a sequence of two consecutive torques in insertion (15Ncm) with an interval of ten minutes, and one reverse torque, all measured by digital torque wrench. The t-student test with 5% significance was used to evaluate the data. The analysis of results showed there is statistical significant difference in reverse torque values between the insertion torque value and reverse torque value intra-group, the indexed abutments presented an average percentage of torque loosing of 15% (P=0.002). It is possible to conclude that the use of indexed abutments of Morse taper system presented statistical significant reduction of reverse torque values, which in turns increase the risk of no biomechanical instability.

Effects of a newly designed apparatus on orthodontic skeletal anchorage.

Objective:An appliance was designed to increase the cortical bone surface contact area of miniscrew implants (MSIs). The purpose of this in vitro study was to evaluate the effects of this appliance on the anchorage force resistance and the stability of orthodontic MSIs.Materials and Methods:A total of 48 MSIs were placed into bone specimens prepared from the ilium of bovines. Half were placed with the newly designed apparatus and half were placed conventionally. All the specimens were subjected to tangential force loading perpendicular to the MSI with lateral displacement of 0.6 mm, using an Instron Universal Testing machine. The maximum removal torque of each tested specimen was also recorded. Both study and control groups were divided into two subgroups based on whether they had thin and thick cortical bone.Results:The test group had statistically higher force anchorage resistance and maximum insertion torque values than the control group (P < 0.001). The results were found to be more significant in cases in which the cortical bone was thin (P < 0.001).Conclusions:Within the limits of this in vitro study, the present findings suggest that the newly designed apparatus might have a favorable effect on MSI stability in patients presenting with thin cortical bone. Clinical studies are necessary to confirm the results that were observed in vitro.

Insertion torque and orthodontic mini-implants: A systematic review of the artificial bone literature

This article systematically reviewed the literature to (1) identify variables that were associated with maximum insertion torque values during the insertion of orthodontic mini-implants into artificial bone, (2) quantify such associations and (3) assess adverse effects of this procedure. Computerized and manual searches were conducted up to 24 February 2012. Selection criteria included studies that (1) recorded maximum insertion torque during the insertion of orthodontic mini-implants into artificial bone, (2) used sample sizes of five screws or more, (3) assessed maximum insertion torque with electronic torque sensors, and (4) used orthodontic mini-implants with a diameter smaller than 2.5 mm. ASTM Standards F543-07(ε1) and F1839-08(ε1) and the Cochrane Handbook for Systematic Reviews were used as guidelines for this systematic review. Quality assessments were rated according to the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach. A total of 23 studies were selected, many of which were multiple publications of the same study. Many domains in the risk of bias assessments were scored as "high" or "unclear" risk of bias. A wide variety of implant, test block, and insertion procedure-related associations with maximum insertion torque were recorded. The quality of most outcomes was classified as "moderate." Outcomes could not be combined in a meta-analysis because of high risk of bias, poor standardization, high heterogeneity, or inconsistency in direction of outcomes within or between studies. Adverse effects were only assessed in one study. Future studies should control publication bias, consult existing standards for conducting torque tests, and focus on transparent reporting.

Evaluation of relationship between preoperative bone density values derived from cone beam computed tomography and implant stability parameters: a clinical study

The aim of this study was to explore the efficacy of bone density value derived from cone beam computed tomography (CBCT) by evaluating its correlation with implant stability parameters including insertion torque value (ITV) and radiofrequency analysis in relation to different clinical variables including location, gender, age, bone quality, and implant diameter. A total of 65 implants were placed in 17 patients. The bone densities of implant recipient sites were preoperatively recorded using CBCT. Bone quality was subjectively assessed, which depends on the stiffness of the jawbone according to the Lekholm and Zarb index during drilling procedure. The maximum ITV of each implant was recorded using a digital torque meter during implant placement. Resonance frequency measurements were taken using an Osstell Mentor immediately after implant placement. Data were analyzed statistically. The mean bone density, insertion torque, and implant stability quotient values of all implants were 556 ± 80, 37.4 ± 3.3 Ncm, and 73.8 ± 7.2, respectively. Statistically significant correlations were found between bone density values from CBCT and implant stability parameters in relation to all variables. Bone density assessment using CBCT is an efficient method and significantly correlated with implant stability parameters and Lekholm and Zarb index. Thus, it is possible to predict initial implant stability and possibility of immediate or early loading using CBCT scans prior to implant placement.

Correlation Between Insertion Torque and Survival Rates in Immediately Loaded Implants in the Maxilla

To evaluate the correlation between insertion torque and the survival rate of immediately loaded implants placed in the maxilla. 390 NobelReplace (Nobel Biocare USA, Yorba Linda, CA) Select Tapered implants were placed in the maxillae of 145 patients over a 15-month period. The insertion torque was measured using a digital torque wrench. Of the 390 implants, only 9 (2.3%) failed. The 381 successful implants were placed with an average insertion torque of 72.1 N.cm. Insertion torque values of failed implants varied between 45.8 and 134 N.cm, with an average of 69.2 N.cm. Of the 9 failed implants, 8 were abutments in multiple-unit implant-supported prostheses, and 1 was a single-unit implant. Although insertion torque undoubtedly plays an important role in the primary stability and successful osseointegration of implants, there seems to be no correlation between insertion torque and implant failure above 35 N.cm threshold of insertion torque. Immediate loading of implants in the maxilla is a successful and predictable treatment option with failure rates approaching those of traditional 2-stage surgery.

Evaluation of primary and secondary stability of titanium implants using different surgical techniques

To investigate the influence of different surgical techniques on the primary and secondary implant stability using trabecular bone of goats as an implantation model. In the iliac crest of eight goats, 48 cylindrical-screw-type implants with a diameter of 4.2mm (Dyna(®) ; Bergen op Zoom, the Netherlands) were installed, using three different surgical techniques: (i) 5% undersized, using a final drill diameter of 4mm; (ii) 15% undersized, using a final drill diameter of 3.6mm; and (iii) 25% undersized, using a final drill diameter of 3.2mm. Peak insertion torque values were measured by a Digital(®) (MARK-10 Corporation, New York, NY, USA) torque gauge instrument during placement. At 3weeks after implantation, removal torque was measured. Histomorphometrically, the peri-implant bone volume was measured in three zones; the inner zone (0-500μm), the middle zone (500-1000μm) and the outer zone (1000-1500μm). Evaluation of the obtained data demonstrated no statistically significant difference between different surgical techniques regarding removal torque values. With respect to the percentage peri-implant bone volume (%BV), also no significant difference could be observed between all three applied surgical techniques for both the inner, middle and outer zone. However, irrespective of the surgical technique, it was noticed that the %BV was significantly higher for the inner zone as compared to middle and outer zone (P<0.05) around the implant. At 3weeks after implant installation, independent of the used undersized surgical technique, the %BV in the inner zone (0-500μm) peri-implant area was improved due to both condensation of the surrounding bone as also the translocation of host bone particles along the implant surface. Surprisingly, no mechanical beneficial effect of the 25% undersized surgical technique could be observed as compared to the 5% or 15% undersized surgical technique to improve primary or secondary implant stability.

Tapping insertional torque allows prediction for better pedicle screw fixation and optimal screw size selection

Background contextThere is currently no reliable technique for intraoperative assessment of pedicle screw fixation strength and optimal screw size. Several studies have evaluated pedicle screw insertional torque (IT) and its direct correlation with pullout strength. However, there is limited clinical application with pedicle screw IT as it must be measured during screw placement and rarely causes the spine surgeon to change screw size. To date, no study has evaluated tapping IT, which precedes screw insertion, and its ability to predict pedicle screw pullout strength. PurposeThe objective of this study was to investigate tapping IT and its ability to predict pedicle screw pullout strength and optimal screw size. Study designIn vitro human cadaveric biomechanical analysis. MethodsTwenty fresh-frozen human cadaveric thoracic vertebral levels were prepared and dual-energy radiographic absorptiometry scanned for bone mineral density (BMD). All specimens were osteoporotic with a mean BMD of 0.60±0.07 g/cm2. Five specimens (n=10) were used to perform a pilot study, as there were no previously established values for optimal tapping IT. Each pedicle during the pilot study was measured using a digital caliper as well as computed tomography measurements, and the optimal screw size was determined to be equal to or the first size smaller than the pedicle diameter. The optimal tap size was then selected as the tap diameter 1 mm smaller than the optimal screw size. During optimal tap size insertion, all peak tapping IT values were found to be between 2 in-lbs and 3 in-lbs. Therefore, the threshold tapping IT value for optimal pedicle screw and tap size was determined to be 2.5 in-lbs, and a comparison tapping IT value of 1.5 in-lbs was selected. Next, 15 test specimens (n=30) were measured with digital calipers, probed, tapped, and instrumented using a paired comparison between the two threshold tapping IT values (Group 1: 1.5 in-lbs; Group 2: 2.5 in-lbs), randomly assigned to the left or right pedicle on each specimen. Each pedicle was incrementally tapped to increasing size (3.75, 4.00, 4.50, and 5.50 mm) until the threshold value was reached based on the assigned group. Pedicle screw size was determined by adding 1 mm to the tap size that crossed the threshold torque value. Torque measurements were recorded with each revolution during tap and pedicle screw insertion. Each specimen was then individually potted and pedicle screws pulled out “in-line” with the screw axis at a rate of 0.25 mm/sec. Peak pullout strength (POS) was measured in Newtons (N). ResultsThe peak tapping IT was significantly increased (50%) in Group 2 (3.23±0.65 in-lbs) compared with Group 1 (2.15±0.56 in-lbs) (p=.0005). The peak screw IT was also significantly increased (19%) in Group 2 (8.99±2.27 in-lbs) compared with Group 1 (7.52±2.96 in-lbs) (p=.02). The pedicle screw pullout strength was also significantly increased (23%) in Group 2 (877.9±235.2 N) compared with Group 1 (712.3±223.1 N) (p=.017). The mean pedicle screw diameter was significantly increased in Group 2 (5.70±1.05 mm) compared with Group 1 (5.00±0.80 mm) (p=.0002). There was also an increased rate of optimal pedicle screw size selection in Group 2 with 9 of 15 (60%) pedicle screws compared with Group 1 with 4 of 15 (26.7%) pedicle screws within 1 mm of the measured pedicle width. There was a moderate correlation for tapping IT with both screw IT (r=0.54; p=.002) and pedicle screw POS (r=0.55; p=.002). ConclusionsOur findings suggest that tapping IT directly correlates with pedicle screw IT, pedicle screw pullout strength, and optimal pedicle screw size. Therefore, tapping IT may be used during thoracic pedicle screw instrumentation as an adjunct to preoperative imaging and clinical experience to maximize fixation strength and optimize pedicle “fit and fill” with the largest screw possible. However, further prospective, in vivo studies are necessary to evaluate the intraoperative use of tapping IT to predict screw loosening/complications.

Effect of Screw Insertion Torque on Push‐Out and Cantilever Bending Properties of Five Different Angle‐Stable Systems

To compare the screw push-out strength and resistance to cantilever bending of 5 different angle-stable systems using 4 different insertion torque values to tighten locking screws. In vitro mechanical testing of 5 screw-plate constructs. Screw plate constructs (n = 60) were tested; 12 of each design, 3 for each torque value. To compare push-out strength, screws were loaded in axial direction on the screw tip until loosening of the locking mechanism was recorded. For cantilever bending test, screws were loaded perpendicularly to their longitudinal axis at 2 mm of distance from the under surface of the plate. Load was applied in displacement control at 1 mm/min. There was a significant difference between the 5 different angle-stable systems regarding both push-out and cantilever bending strength. There was an influence of insertion torque value on push-out strength for 2 systems and insertion torque value influenced cantilever bending behavior only in 1 locking system. Locking mechanisms using "thread in thread" principle provided a stronger screw push-out behavior. Screws materials and core diameter of the different screws were directly related to cantilever bending strength.

Torque Removal Evaluation of Screw in One-Piece and Two-Piece Abutments Tightened with a Handheld screwdriver

Introduction: Some clinicians use a handheld screw driver instead of a torque wrench to definitively tighten abutment screws. The aim of this study was to compare the removal torque of one-piece and two-piece abutments tightened with a handheld driver and a torque control ratchet. Methods: 40 ITI implants were placed in acrylic blocks and divided into 4 groups. In groups one and two, 10 ITI one-piece abutments (Solid®) and in groups three and four, 10 ITI two-piece abutments (Synocta®) were placed on the implants. In groups one and three abutments were tightened by 5 experienced males and 5 experienced females using a handheld driver. In groups two and four abutments were tightened using a torque wrench with torque values of 10, 20 and 35 N.cm. Insertion torque and removal torque values of the abutments were measured with a digital torque meter. Results: The insertion torque values (ITVs) of males in both abutments were significantly higher than those of females. ITVs in both Solid® and Synocta® abutments tightened with a handheld screwdriver were similar to the torque of 20 N.cm in the torque wrench. Removal torque values (RTVs) of solid® abutments were higher than those of synocta® abutments. Conclusion: The one- piece abutments (solid®) showed higher RTVs than the two-piece abutments (synocta®). Hand driver does not produce sufficient preload force for the final tightening of the abutment

Biomechanical Evaluation of Undersized Drilling on Implant Biomechanical Stability at Early Implantation Times

The present study evaluated the effect of different drilling dimensions (undersized, regular, and oversized) in the insertion and removal torques of dental implants in a beagle dog model. Six beagle dogs were acquired and subjected to bilateral surgeries in the radii 1 and 3 weeks before euthanasia. During surgery, 3 implants, 4 mm in diameter by 10 mm in length, were placed in bone sites drilled to 3.2 mm, 3.5 mm, and 3.8 mm in final diameter. The insertion and removal torque was recorded for all samples. Statistical analysis was performed by paired t tests for repeated measures and by t tests assuming unequal variances (all at the 95% level of significance). Overall, the insertion torque and removal torque levels obtained were inversely proportional to the drilling dimension, with a significant difference detected between the 3.2 mm and 3.5 mm relative to the 3.8 mm groups (P < 0.03). Although insertion torque-removal torque paired observations was statistically maintained for the 3.5 mm and 3.8 mm groups, a significant decrease in removal torque values relative to insertion torque levels was observed for the 3.2 mm group. A different pattern of healing and interfacial remodeling was observed for the different groups. Different drilling dimensions resulted in variations in insertion torque values (primary stability) and stability maintenance over the first weeks of bone healing.

Design characteristics, primary stability and risk of fracture of orthodontic mini-Implants: Pilot scan electron microscope and mechanical studies

Objectives: Orthodontic mini-implants (OMIs) are increasingly used in orthodontics but can fail for various reasons. This study investigates the effects of OMI design characteristics on the mechanical properties in artificial bone. Material and Methods: Twelve self-drilling OMIs (2 small, 6 medium, 4 large) from 8 manufacturers were tested for their primary stability in simulated medium-high cancellous bone and the risk to fracture in high-density methacrylate blocks. For the assessments of the maximum insertion torque (IT) and torsional fracture (TF) 5 of each OMI were used and for the pull-out strength (POS) 10. The OMIs were inserted with a torque screwdriver (12 sec/360°) until the bottom at 8 mm depth was reached. OMI designs were analyzed with a scan electron microscope (SEM). Results: SEM images revealed a great variation in product refinement. In the whole sample, a cylindrical OMI shape was associated with higher POS (p<0.001) but lower IT (p=0.002) values. The outer and inner OMI diameters were design characteristics well correlated with POS, IT and TF values (ranging from 0.601 to 0.961). Greater thread depth was related to greater POS values (r= 0.628), although OMIs with similar POS values may have different IT values. Thread depth and pitch had some impact on POS. TF depended mainly on the OMI inner (r= 0.961) and outer diameters (r=0.892). A thread depth to outer diameter ratio close to 40% increased TF risk. Conclusions: Although at the same insertion depth the OMI outer and inner diameters are the most important factors for primary stability, other OMI design characteristics (cylindrical vs. conical, thread design) may significantly affect primary stability and torsional fracture. This needs to be considered when selecting the appropriate OMI for the desired orthodontic procedures. Key words:Orthodontic mini-implants, primary stability, insertion torque, pullout strength, torsional fracture.

Implant Biomechanical Stability Variation at Early Implantation Times in Vivo: An Experimental Study in Dogs

To demonstrate the degree of stability decrease and subsequent increase of dental implants at early implantation times in a beagle model. The mandibular premolars and first molars of eight beagle dogs were extracted and the ridges allowed to heal for 8 weeks. Thirty-two (n = 16 each group) implants were placed bilaterally, and remained in vivo for 1 and 3 weeks. The implants with comparable dimensions were divided as follows: group 1, Straumann Bone Level with SLActive surface; group 2, Nobel Speedy Replace RP with TiUnite surface. During insertion and following sacrifice, the implants were torqued to determine insertion and interface failure values. Histologic sections were prepared for microscopy. Statistical analysis was performed using Kruskal-Wallis and multiple paired and non-paired t tests considering unequal variances at a 95% level of significance. High insertion torque values were observed along with a significant decrease at 1 week in vivo (P = .003). At 3 weeks, the biomechanical fixation levels increased and were comparable to the insertion torque value. Histology showed that interfacial bone remodeling and initial woven bone formation was observed around both implant groups at 1 and 3 weeks. As time elapsed early after implantation, the biomechanical stability of dental implants initially decreased and subsequently increased.

Evaluation of the correlation between insertion torque and primary stability of dental implants using a block bone test

PurposeImplant stability at the time of surgery is crucial for the long-term success of dental implants. Primary stability is considered of paramount importance to achieve osseointegration. The purpose of the present study was to investigate the correlation between the insertion torque and primary stability of dental implants using artificial bone blocks with different bone densities and compositions to mimic different circumstances that are encountered in routine daily clinical settings.MethodsIn order to validate the objectives, various sized holes were made in bone blocks with different bone densities (#10, #20, #30, #40, and #50) using a surgical drill and insertion torque together with implant stability quotient (ISQ) values that were measured using the Osstell Mentor. The experimental groups under evaluation were subdivided into 5 subgroups according to the circumstances.ResultsIn group 1, the mean insertion torque and ISQ values increased as the density of the bone blocks increased. For group 2, the mean insertion torque values decreased as the final drill size expanded, but this was not the case for the ISQ values. The mean insertion torque values in group 3 increased with the thickness of the cortical bone, and the same was true for the ISQ values. For group 4, the mean insertion torque values increased as the cancellous bone density increased, but the correlation with the ISQ values was weak. Finally, in group 5, the mean insertion torque decreased as the final drill size increased, but the correlation with the ISQ value was weak.ConclusionsWithin the limitations of the study, it was concluded that primary stability does not simply depend on the insertion torque, but also on the bone quality.

Analysis of Primary Stability of Dental Implants Inserted in Different Substrates Using the Pullout Test and Insertion Torque

The aim of the study was to evaluate mechanical behavior of implants inserted in three substrates, by measuring the pullout strength and the relative stiffness. 32 implants (Master Porous-Conexao, cylindrical, external hexagon, and surface treatment) were divided into 4 groups (n = 8): pig rib bone, polyurethane Synbone, polyurethane Nacional 40 PCF, and pinus wood. Implants were installed with the exact distance of 5 mm of another implant. The insertion torque (N·cm) was quantified using the digital Kratos torque meter and the pullout test (N) was performed by an axial traction force toward the long axis of the implant (2 min/mm) through mount implant devices attached to a piece adapted to a load cell of 200 Kg of a universal testing machine (Emic DL10000). Data of insertion torque and maximum pullout force were submitted to one-way ANOVA and Bonferroni tests (α = 0.05). Polyurethane Nacional 40 PCF and pinus wood showed the highest values of insertion torque and pullout force, with significant statistical difference (P < 0.05) with other groups. The analysis showed stiffness materials with the highest values for primary stability.

The Influence of Cortical Width of Sheep Bone on the Primary Stability of Dental Implants: An In Vitro Study

To explore the relationship between primary implant stability and cortical bone thickness. Twenty-three implants were inserted into fresh sheep bone. The cortical width of implant recipient sites was determined using cone-beam computed tomography (CBCT). The maximum insertion torque value of each implant was recorded. Implant stability was measured using an Osstell system. Spearman's correlation coefficient was used to evaluate the correlations among variables. The cortical width and Hounsfield unit mean values were 3.3 ± 1.0 (mm) and 1468.5 ± 272.3, respectively. The correlation between cortical bone thickness and Osstell value was not statistically significant (p > 0.01). The cortical bone thickness evaluated using CBCT had no correlation with the primary stability of dental implants.

Effects of repeated sterilization cycles on primary stability of orthodontic mini-screws

To determine if repeated sterilization has deleterious effects on the clinical stability of mini-screws. Thirty each of the following mini-screws were tested: Aarhus (American Orthodontics, Sheboygan, Wisc), VectorTAS (Ormco Corporation, Orange, Calif), Dual-Top (RMO, Denver, Colo), and Ortho Anchor (KLS Martin, Jacksonville, Fla). Controls were sterilized once using a steam autoclave (Statim 5000, SciCan USA, Canonsburg, Pa). Each group of mini-screws was divided into three groups: the control (n = 10) and two test groups (n =10, each). Test groups were cycled five and 10 times respectively. All screws were inserted into custom-designed synthetic blocks that simulated mandibular bone. Maximum insertion torque and lateral displacement force data were recorded and subjected to statistical testing. Two-way analysis of variance (ANOVA) and three-way mixed ANOVA were used for statistical analyses for maximum insertion torque data and lateral displacement force data, respectively. Level of significance was established at P < .05. Insertion torque values displayed significant differences between both of the groups and sterilization cycles (P < .05). Significant differences were observed between American Aarhus mini-screws and both RMO and KLS Martin mini-screws. Ormco Vector mini-screws also differed significantly from the KLS Martin mini-screws in this comparison (P < .05). For lateral displacement, there was a significant main effect of groups, F(1,36) = 14.5 (P < .05). Significant differences were observed between American Aarhus mini-screws and all three of the other groups (P < .05). The examined groups displayed statistical differences of variable quality that may not affect their clinical stability.

Implant Primary Stability Determined by Resonance Frequency Analysis

To determine if resonance frequency analysis (RFA) correlated with insertion torque (IT), bone volume (BV), and clinical osseointegration at 6 weeks. For 18 patients, BV was evaluated histologically by retrieving bone core biopsies before placement of 40 dental implants. Peak IT was recorded at implant placement, and RFA values (implant stability quotient [ISQ]) were noted at baseline, 3 weeks, and 6 weeks. Osseointegration was evaluated at 6 weeks when torquing abutments to 30 N. ISQ values were correlated with IT, BV and abutment torquing results. Data were statistically analyzed. ISQ values significantly decreased at 3 weeks and increased at 6 weeks. There was a significant positive correlation between BV and ISQ at baseline and at 3 weeks, but not at 6 weeks, and between ISQ and jaw location, implant diameter and IT at baseline, 3 weeks, and 6 weeks. There was a significant correlation between spinning/painful implants during abutment torquing and low ISQ, low BV, and low IT values. Correlations between BV and IT values, and ISQ suggest that RFA may indicate primary implant stability. BV, IT, and ISQ values may anticipate the degree of osseointegration at 6 weeks.