Insertion Torque Measurements Research Articles

Measurement of Implant Insertion Torque in Intentionally Undersized Osteotomy Site Preparation in the Posterior Maxilla: A Prospective Clinical Study.

Achieving adequate primary stability for dental implants in the posterior maxilla is challenging due to the area's low bone density and fine trabecular bone. Low primary implant stability can compromise the long-term success of the implant. This study aims to evaluate the effect of intentionally undersized osteotomy sites on the insertion torque of implants placed in type 4 bone density in the posterior maxilla, regardless of the surgeon's tactile sense of the bone density. The conventional implant placement technique was performed in the posterior maxilla by intentionally omitting the last drill of the recommended drilling sequence protocol. The insertion torque was measured using an integrated surgical motor software. The study included 72 implants in patients of both genders and different age groups. The retrieved samples were divided into four groups, with insertion torque ranging from 11 Ncm to 48 Ncm. The mean insertion torque was 26.51 ± 0.18 Ncm for all cases (P = .001). No significant difference was found in the mean insertion torque between different age groups (26.51 ± 2.845, P = .84). However, a significant difference was observed between male and female cases (P = .84). Most implant insertion torque measurements vary significantly between cases in the intentionally underprepared posterior maxillary osteotomy site. The last drill should be omitted for all preparations of the posterior maxillary implant sites. Intentionally minimizing the osteotomy site is recommended for all posterior maxillary implant cases.

Influence of diameter and length on primary stability in various implant site densities-An in vitro study in polyurethane blocks.

The influence of dental implant length and diameter on primary stability in various bone densities is not well understood. To in vitro study the effect of length and diameter on resonance frequency analysis (RFA), insertion torque (IT) and displacement (DP) measurements of dental implants in different implant site densities. Dental implants of four different diameters (Ø 3.5, 4.0, 4.5 and 5.0 mm) and three different lengths (7, 11 and 15 mm) (Neoss Ltd, Harrogate, UK) were placed in polyurethane blocks of three different densities (Sawbones Europe AB, Malmö, Sweden). The primary stability was assessed by RFA (ISQ) (Osstell, Osstell AB, Gothenburg, Sweden) and insertion torque measurements (ITmax in N cm) (iChiropo™, Bien-Air Dental SA, Bienne, Switzerland). In addition, the blocks were mounted in a rig and a lateral force of 25 N cm was applied to the implants and the DP was measured in μm with a micrometer gauge placed on the opposite side of the load transducer. Statistical analyses using linear and quadratic models were applied. Implant length, diameter and block density were found to be significant independent predictors of RFA, ITmax, and DP measurements. Implant length had a strong effect, while the effect of diameter in general was subtle, particularly in the softest block. Implant length affects primary stability more than implant diameter in polyurethane blocks of uniform density along the whole length of the tested implants.

Lag Screw Trajectory in Supination-External Rotation Fractures: Does the Direction of the Fibula Lag Screw Have an Effect?

BackgroundThe fracture obliquity of supination-external rotation injury of the fibula is often amenable to lag screw insertion. The purpose of the study was to determine whether biomechanical differences exist between lag screws inserted from an anterior to posterior direction and from a posterior to anterior direction and the thickness of the anterior and posterior fibular cortices were correlated with biomechanical testing.MethodsTen cadaver fibulae were harvested and submitted to material testing following 3.5-mm cortical screw insertion from either an anterior to posterior direction or a posterior to anterior direction. Screw torsional insertion strength and axial pullout strength were measured. Computed tomography images of 40 consecutive patients undergoing preoperative planning for fractures excluding the fibula were examined to define fibular cortical thickness and correlate anatomic findings with the biomechanical testing.ResultsThe axial pullout strength of lag screws inserted from posterior to anterior was significantly greater than that of lag screws inserted from anterior to posterior (p < 0.05). Screw insertion torque measurements demonstrated a similar trend although the data did not reach statistical significance (p = 0.056). The anterior cortex of the distal fibula exhibited a radiographically greater thickness than that of the posterior cortex at the same level (p < 0.001).ConclusionsFor oblique fractures of the distal fibula, posterior to anterior lag screw insertion exhibited improved biomechanical properties when compared with a similar screw inserted from anterior to posterior. These results correlated with the thicker cortical bone present along the anterior fibula.

Comparison of the primary stability of orthodontic miniscrews after repeated insertion cycles.

To compare the primary stability of miniscrews after repeated cycles of insertion through insertion torque (IT) measurements and resonance frequency analysis (RFA). Sixty titanium miniscrews were divided into two groups according to the insertion protocol: one with predrilled sites and the other self-drilled into porcine iliac crest bone specimens. Each group had three cycles of reinsertion. After each insertion, the IT and RFA were measured. The IT was measured by using a torque meter, and the RFA was measured using the Osstell ISQ device. A total of five miniscrews of each group were selected for sequential assessment of the morphology of their tip and threads using scanning electron microscopy after each insertion cycle. No statistically significant differences were found in the IT values of miniscrews reinserted up to three times in the group with predrilled surgical sites. The IT value increased significantly with the number of reinsertions in the self-drilled group. The RFA value decreased as the number of insertions increased in both groups. Under the conditions of this in vitro study, reinserting miniscrews deteriorates the integrity of their tip and thread. Reinsertion should be discouraged particularly when insertion sites are not predrilled.

A pilot animal study aimed at assessing the mechanical quality of regenerated alveolar bone

Purpose Bone regeneration procedures are often evaluated based on biologic aspects only. As regenerated bone also has to ensure primary implant stability, the goal of this study was to determine the mechanical quality of regenerated bone. Materials and methods Six adult minipigs were allocated for this experiment with four mandibular study sites each established following tooth removal. Two different types of bovine bone mineral as well as autogenous bone were used for augmenting three-walled defects, while native bone served as the control. Implants were placed after 12, 18, and 24 weeks of healing, and bone quality was determined using intraoperative compressive testing (BoneProbe), insertion torque measurements, and resonance frequency analysis. The mandibles were then harvested for determining bone mineral density (BMD) and bone-to-implant contact (BIC). Statistical analysis was based on two-way analysis of variance of aligned rank transformed data and Spearman's rank correlation tests (α = .05). Results The effects of the factors healing time and material on the parameters tested were too small to be significant (P ranging from .34 to .98). Weak correlations were observed for implant insertion torque with BoneProbe measurements in the cortical (0.481; P = .032) and in the trabecular area (0.639; P = .002). BoneProbe measurements in the trabecular part and in the cortical part also correlated with each other (0.477; P = .035). Conclusion While differences may exist between bone regenerated using different biomaterials with respect to biologic behavior, differences in the mechanical properties determining primary implant stability seem to be minor. Implant insertion torque measurements appear to be a reliable tool for determining bone quality if only one specific implant type is considered.

A retrospective case series report on a novel aggressively threaded and tapered implant

Background: Firm primary implant stability is considered as one determinant of success with implant therapy. A novel tapered implant with aggressive threading aiming at high primary stability, also in low bone densities, using a simplified drilling protocol has recently been developed. Aim/Hypothesis: To retrospectively evaluate the primary stability, clinical and radiographic performance of 25 tapered and aggressively threaded implants in 15 consecutive patients after one year of follow-up. Materials and Methods: The study comprised of the first 15 consecutive patients (13 female, 2 male) treated with 25 implants (Proactive Edge, Neoss AB, Gothenburg, Sweden) using a one-stage protocol and loaded for at least one year (Figures 1 and 2). Five implants had been placed in the mandible and 20 in the maxilla for seven single tooth replacements, seven partial bridges and one full bridge. Insertion torque/time curves were registered during placement with an Elcomed drilling unit (W&H Austria GmbH, Bürmoos, Austria). RFA measurements were taken after implant placement using a PenguinRFA instrument (IDSAB, Gothenburg, Sweden). The implants were either restored immediately (n = 5) or after 6 to 8 weeks of healing (n = 20). Marginal bone levels were evaluated in baseline and one-year intraoral radiographs. Results: All implants achieved firm primary stability as assessed with insertion torque (42.6 + 17.0 Ncm, range 13-80 Ncm) and RFA (76.9 + 3.7 ISQ, range 66-84 ISQ) measurements. Thirteen of the implants (all 3.5 mm in diameter) could be placed after the use of one spiral drill only. The remaining implants (4.0 mm, n = 10, 5.0 mm, n = 2) were placed after using two spiral drills. No implant was lost during the one-year of follow-up. The mean marginal bone resorption was 0.5 + 0.6 mm after one year. Conclusions and Clinical Implications: The present case series report showed that the novel implant and simplified drilling protocol resulted in firm primary implant stability. Promising clinical and radiographic outcomes were seen after one year. However, clinical studies including more patients and implants are needed. Keywords: dental implants, primary stability, clinical follow-up, case series Figure 1: The Neoss Proactive Edge implant in different diameters, Figure 2: Postoperative (left) and one-year (right) intraoral radiograph of one implant used for a maxillary molar replacement.

Rationale for a reverse tapered body shift implant for immediate placement

Immediate implant placement holds considerable value, yet primary implant stability is often a critical factor. The aim of this study was to evaluate the stability, volumetric viability, and buccal gap size of reverse tapered body shift (RTBS) implants after immediate placement. Peak insertion torque measurements of two RTBS designs (apical 40% vs. apical 50%), relative to conventionally tapered implants, were assessed in simulated extraction sockets prepared in synthetic bone blocks. Additionally, the proximity of the RTBS implants to neighbouring teeth and anatomical structures, and the buccal gap distance were evaluated in human cadavers. The mean (± standard deviation) insertion torque was 12.00±1.40N•cm for the conventionally tapered implants (n=50), 35.36±2.74N•cm (n=50) for RTBS-1, and 48.20±2.90N•cm (n=50) for RTBS-2; the difference between designs was statistically significant (P<0.01). In total, 40 RTBS implants (20 per design) were placed in six cadaveric premaxillae. Only one locus was inappropriate for both RTBS implant designs, due to the proximity of neighbouring teeth. The average buccal gap for both implant designs was 2.8mm (P=0.104). The improved primary stability and increased buccal gap size with RTBS implants may enhance the feasibility of immediate placement. The study findings should be further validated in clinical trials.

Effect of Drilling Speed on Dental Implant Insertion Torque.

The specific aim of this study was to examine whether slow drilling speeds (15 rpm) produce pilot holes that result in different implant insertion torques than pilot holes made with higher speed drilling (1500 rpm). To accomplish this, a new method is presented for transferring samples from a drilling machine onto an implant insertion torque measuring apparatus while maintaining the same center of rotation. Simulated bone blocks of polyurethane were used with 2 densities of foam to mimic trabecular and cortical bone. Pilot holes drilled using both drilling methods were morphologically characterized at macro and micro scales. Nobel Biocare Nobel Active implants were then placed. Profilometer and optical imaging were used to determine changes in the pilot hole morphology. Recorded insertion torque measurements were used to quantitatively contrast implants inserted into holes drilled using the 2 speeds. Although there were slight qualitative and quantitative differences between the low- and high-speed drilled pilot holes, the differences were insufficient to cause a statistically significant change in insertion torque.

A Pilot Animal Study Aimed at Assessing the Mechanical Quality of Regenerated Alveolar Bone.

Bone regeneration procedures are often evaluated based on biologic aspects only. As regenerated bone also has to ensure primary implant stability, the goal of this study was to determine the mechanical quality of regenerated bone. Six adult minipigs were allocated for this experiment with four mandibular study sites each established following tooth removal. Two different types of bovine bone mineral as well as autogenous bone were used for augmenting three-walled defects, while native bone served as the control. Implants were placed after 12, 18, and 24 weeks of healing, and bone quality was determined using intraoperative compressive testing (BoneProbe), insertion torque measurements, and resonance frequency analysis. The mandibles were then harvested for determining bone mineral density (BMD) and bone-to-implant contact (BIC). Statistical analysis was based on two-way analysis of variance of aligned rank transformed data and Spearman's rank correlation tests (α = .05). The effects of the factors healing time and material on the parameters tested were too small to be significant (P ranging from .34 to .98). Weak correlations were observed for implant insertion torque with BoneProbe measurements in the cortical (0.481; P = .032) and in the trabecular area (0.639; P = .002). BoneProbe measurements in the trabecular part and in the cortical part also correlated with each other (0.477; P = .035). While differences may exist between bone regenerated using different biomaterials with respect to biologic behavior, differences in the mechanical properties determining primary implant stability seem to be minor. Implant insertion torque measurements appear to be a reliable tool for determining bone quality if only one specific implant type is considered.

Reliability of clinical techniques for evaluating alveolar bone quality and primary implant stability.

A novel device for intraoperative compressive testing of alveolar bone during implant surgery has been introduced. It was the goal of this study to compare the performance of this device with traditional methods used for determining alveolar bone quality and primary implant stability. Implant surgery in human cadaver bone was performed by two implantologists differing in experience. Bone quality was rated radiographically, based on tactile sensation during drilling and using intraoperative compressive tests. Implant stability was evaluated using insertion torque measurements and resonance frequency analysis. Statistical analysis was based on two way ANOVA followed by Tukey multiple comparisons and Pearson's product moment correlation. The level of significance was set at α = .05. Human cadaver bone was ranked according to implant insertion torque. Radiographic assessment, tactile sensation during drilling, and implant stability measurements did not allow differentiating bone types in all instances. Cortical BoneProbe measurements showed a significant trend towards higher measurement values in greater bone quality types (P < .01); in trabecular bone this trend was also present but was not statistically significant. Significant correlations existed between BoneProbe measurements and most other parameters evaluated. Despite the limited number of measurements performed, intraoperative compressive testing of bone may be an option for objectively classifying alveolar bone quality.

Examination of the influence of a reverse tapered body shift on the mechanical performance of dental implants in extraction sockets

Background As a result of continuous development, changes in the macro geometry of dental implants over time have had a profound influence on their mechanical behaviour and the osseointegration process. Aim/Hypothesis The objective of the present in vitro study was to evaluate the mechanical performance of dental implants with macro geometric changes to the apical region, relative to conventional implants. Material and Methods Comparative insertion torque measurements were conducted between conventionally tapered implants and the newly designed reverse tapered body shift implants (see Figure 1). All implants were placed in simulated extraction sockets created in orthopaedically-certified synthetic bone blocks with a density of 0.32 g/cm3. The simulated extraction sockets were created by drilling a 5 mm deep osteotomy with a diameter of 5.3 mm, to ensure that the coronal section of the implants had no influence on the insertion torque performance. Thereafter, the osteotomies for the implants were prepared as per the manufacturers guidelines. For the sake of comparison, all implants had a total length of 11.5 mm and a coronal diameter of 3.0 mm, whereas the newly designed implant had a reverse tapered body shift with a diameter of 3.5 mm. Results In total, 40 insertion torque measurements were recorded (20 in the control group and 20 in the test group). The average insertion torque for the conventionally tapered implants was 8.45 Ncm (SD = 0.69), whereas the average insertion torque in the test group was 12.55 Ncm (SD = 1.61). To convert these in vitro results to a more clinically relevant situation, the percentage increase in insertion torque between the two groups was calculated. On average, the newly designed reverse taper body shift implant achieved 49% greater insertion torque, compared with a conventional implant of the same coronal diameter and length. Conclusions and Clinical Implications Reverse tapered body shift implants achieve an average of 49% greater primary stability in extraction sockets than conventionally tapered implants with the same coronal diameter and length. This may overcome issues with primary stability in cases of immediate placement. FIGURE 1

Insertion torque and resonance frequency analysis (ISQ) as predictor methods of implant osseointegration

Aim Determining appropriate primary stability at time of implant placement is a key therapeutic decision. The aim of the study was to compare insertion torque and implant stability quotient (ISQ) obtained at the time of implant placement, as predictors of osseointegration.Methods There were 31 implants evaluated in the maxilla and 29 in the mandible. A “High Torque Indicating Ratchet Wrench” was used for the measurement of insertion torque and a “Osstell Mentor®” to register the ISQ value at the end of each surgery. At 6 weeks counter-torque was performed on each implant using a “Low Torque Indicating Ratchet Wrench” applying 20 to 32 Ncm. Successful osseointegration was appropriately obtained with torque insertion of 35 or more and an ISQ of 60 or more without mobility, as well as torque insertion less than 35 and an ISQ less than 60 with mobility. The results, contrary to those described above, were considered to be failure.  The use of ROC (Receiver Operating Characteristic) curves establishes differences between the two methods. Contingency tables and Kappa statistics were used to analyze the coincidence results between methods. Insertion torque was used as the Gold Standard. The significance level used is I±â‰¤0.05.Results In the ROC curve analysis, the area of value was 0.611 (p> 0.05). The Kappa statistic value was 0.208 (p> 0.05) and there are no discrepancies between success and failure between the two methods compared.Conclusion Both methods tend to have the same results in relation to the studied variables.

Achievable accuracy of hip screw holding power estimation by insertion torque measurement

BackgroundTo ensure stability of proximal femoral fractures, the hip screw must firmly engage into the femoral head. Some studies suggested that screw holding power into trabecular bone could be evaluated, intraoperatively, through measurement of screw insertion torque. However, those studies used synthetic bone, instead of trabecular bone, as host material or they did not evaluate accuracy of predictions. We determined prediction accuracy, also assessing the impact of screw design and host material. MethodsWe measured, under highly-repeatable experimental conditions, disregarding clinical procedure complexities, insertion torque and pullout strength of four screw designs, both in 120 synthetic and 80 trabecular bone specimens of variable density. For both host materials, we calculated the root-mean-square error and the mean-absolute-percentage error of predictions based on the best fitting model of torque-pullout data, in both single-screw and merged dataset. FindingsPredictions based on screw-specific regression models were the most accurate. Host material impacts on prediction accuracy: the replacement of synthetic with trabecular bone decreased both root-mean-square errors, from 0.54 ÷ 0.76 kN to 0.21 ÷ 0.40 kN, and mean-absolute-percentage errors, from 14 ÷ 21% to 10 ÷ 12%. However, holding power predicted on low insertion torque remained inaccurate, with errors up to 40% for torques below 1 Nm. InterpretationIn poor-quality trabecular bone, tissue inhomogeneities likely affect pullout strength and insertion torque to different extents, limiting the predictive power of the latter. This bias decreases when the screw engages good-quality bone. Under this condition, predictions become more accurate although this result must be confirmed by close in-vitro simulation of the clinical procedure.

Effects of recycling on the biomechanical characteristics of retrieved orthodontic miniscrews.

ObjectiveThe aim of this study was to compare recycled and unused orthodontic miniscrews to determine the feasibility of reuse. The comparisons included both miniscrews with machined surfaces (MS), and those with etched surfaces (ES).MethodsRetrieved MS and ES were further divided into three subgroups according to the assigned recycling procedure: group A, air-water spray; group B, mechanical cleaning; and group C, mechanical and chemical cleaning. Unused screws were used as controls. Scanning electron microscopy, energy-dispersive X-ray spectrometry, insertion time and maximum insertion torque measurements in artificial bone, and biological responses in the form of periotest values (PTV), bone–implant contact ratio (BIC), and bone volume ratio (BV) were assessed.ResultsMorphological changes after recycling mainly occurred at the screw tip, and the cortical bone penetration success rate of recycled screws was lower than that of unused screws. Retrieved ES needed more thorough cleaning than retrieved MS to produce a surface composition similar to that of unused screws. There were no significant differences in PTV or BIC between recycled and unused screws, while the BV of the former was significantly lower than that of the latter (p < 0.05).ConclusionsThese results indicate that reuse of recycled orthodontic miniscrews may not be feasible from the biomechanical aspect.

A One-year Follow-up Study of a Tapered Hydrophilic Implant Design Using Various Placement Protocols in the Maxilla.

Purpose:To study the clinical/radiographic outcomes and stability of a tapered implant design with a hydrophilic surface when placed in the maxilla using various protocols and followed for one year.Methods:Ninety-seven consecutive patients treated as part of daily routine in two clinics with 163 tapered implants in healed sites, in extraction sockets and together with bone augmentation procedures in the maxilla were evaluated after one year in function. Individual healing periods varying from 0 to 6 months had been used. Insertion torque (IT) and resonance frequency analysis (RFA) measurements were made at baseline. Follow-up RFA registrations were made after 6 and 12 months of loading. The marginal bone levels were measured in intraoral radiographs from baseline and after 12 months. A reference group consisting of 163 consecutive straight maxillary implants was used for the comparison of baseline IT and RFA measurements.Results:Five implants failed before loading, giving an implant survival rate of 96.9% and a prosthesis survival rate of 99.4% after one year. The mean marginal bone loss after one year was 0.5 mm (SD 0.4). The mean IT was statistically significantly higher for tapered than for straight reference implants (41.3 ± 12.0 Ncm vs 33.6 ± 12.5 Ncm, p < 0.001). The tapered implants showed a statistically insignificantly higher mean ISQ value than the straight references implants (73.7 ± 6.4 ISQ vs 72.2 ± 8.0 ISQ, p=0.119). There was no correlation between IT and marginal bone loss. There was a correlation between IT and RFA measurements (p < 0.001).Conclusion:The tapered implant showed a high survival rate and minimal marginal bone loss after one year in function when using various protocols for placement. The tapered implant showed significantly higher insertion torque values than straight reference implants.

Relationship Between Insertion Torque and Resonance Frequency Measurements, Performed by Resonance Frequency Analysis, in Micromobility of Dental Implants: An In Vitro Study.

To evaluate the micromobility of dental implants under occlusal loading in relation to stability measurements of resonance frequency analysis and insertion torque. The sample comprised of 24 implants inserted in 12 fresh cow ribs. Insertion torque and Osstell implant stability quotient (ISQ) measurements were recorded. An "ad hoc" acrylic premolar was made on a temporary abutment and screwed to each implant, and a force of 100 N was subsequently applied at an angle of 6 degrees. Implant micromotion was measured using a Questar microscope with a resolution of 2 μm and an image analysis program. Data show a statistically significant inverse correlation between the ISQ values and implant micromotion under a load of 100 N (R = 0.86, P < 0.0001). The same relationship is found between insertion torque and implant micromotion, although the relationship is linear up to 34 N·cm and becomes exponential for higher values (R = 0.78, P < 0.0001). A direct correlation is established between insertion torque and ISQ values. There is an inverse relationship between both ISQ and insertion torque values and implant micromotion under a load of 100 N.

Relation between bone density and primary implant stability

This study aims to relate bone density in Hounsfield units (Hu) with the primary implant stability measured by insertion torque (Ncm) and resonance frequency analysis (ISQ). Ten patients were included in this study. A total of 54 implant sites were provided from 10 computerized tomography scans. The computerized tomography scan was used for the preoperative evaluation of bone density for each patient. The bone mean density around planned implants was determined with Physioplanet TM software. Bone quality according resistance to drilling, insertion torque and resonance frequency measurements were recorded. A statistically significant relationship was observed between bone quality density and location with ISQ values. This research demonstrates a strong relationship between the bone density values from computerized tomography and the location in the maxillaries. A correlation exists between bone quality, according to the Lekholm & Zarb classification, and Hu computerized tomography values. The primary implant stability measured with resonance frequency analysis depends on bone density values, bone quality and implant location.

Biomechanical Properties of Orthodontic Miniscrews. An In-vitro Study

Comparing five commercially-available miniscrew types for skeletal anchorage with regard to the biomechanical properties influencing their primary stability. Included in this study was a total of 196 self-tapping and self-drilling miniscrews having a diameter of 2 mm (or the largest possible diameter of the manufacturer in question), a thread shaft length of 10 mm, or the longest miniscrew supplied by the manufacturers. The screw types tested were the FAMI 2, Orlus mini-implant, T.I.T.A.N. Pin, tomas-pin and Vector TAS. Insertion and loosening torque measurements, and pullout tests in axial (0 degrees), 20 degrees and 40 degrees directions, as well as test series with and without pilot hole drilling were performed. Bovine femoral heads having the same bone mineral density (BMD) were used as bone-testing material. Higher insertion torques were found for the cylindrical FAMI 2 screw, the conical Orlus mini-implant and the Vector TAS screw (with mean values of 39.2 Ncm, 32.1 Ncm and 49.5 Ncm) than for the cylindrical T.I.T.A.N. pin and tomas-pin. Insertion without predrilling led the insertion torques of all five screws to rise significantly. We noted statistically significant differences among the five screws in the pullout tests. Those highly significant differences at axial (0 degrees) and 20 degrees angles were not apparent at the 40 degrees pullout angle. Compared with the pullout forces (load) in the axial direction, the cylindrical screws' load values decreased markedly according to the angle (by up to -46.6%). The reduction in pullout force in conjunction with an increasing angle was much less pronounced in the conical screws (-0.8% to -29.0%). The tomas-pin demonstrated the highest pullout force and stiffness values throughout the tests. A total of five tomas-pins, two Orlus mini-implants and one FAMI 2 screw fractured during the pullout tests. Results from our insertion torque measurements suggest that a conical screw design will provide greater primary stability than cylindrical screw types. The cylindrical screw design's superiority was evident in the pullout tests. All the miniscrews' primary stability rose after drill-free insertion. The tomas-pin screws, although biomechanically superior to the other screws, were most prone to fracture.

Biomechanical comparison of four different miniscrew types for skeletal anchorage in the mandibulo-maxillary area

This study compared four miniscrew types for skeletal anchorage (Aarhus, FAMI, Dual Top and Spider) regarding their biomechanical properties contributing to primary stability. Insertion torque measurements and pull-out tests in axial (0°) as well as in the 20° and 40° direction were performed. Stiffness of the screw–bone construct was calculated from the load–displacement curve. Conic FAMI and Dual Top screws had higher insertion torques. Insertion torques were raised by drill-free insertion of FAMI and Dual Top screws. Statistically significant differences were found between the 4 screw types in pull-out tests. The highly significant differences between the four screws for peak load in the axial (0°) and 20° direction were not apparent in 40° angular loads. For the conical screws, peak load values increased in angular compared with axial load. The Dual Top screw achieved the highest values for peak load and stiffness. 12 Dual Top and 1 Spider screw heads fractured in the pull-out tests. A conical drill-free screw design achieves higher primary stability compared with cylindrical self-tapping screws. This effect was more obvious in insertion torque estimations rather than in pull-out tests. The Dual Top screws, although biomechanically superior to other screw types, were most prone to fractures.

Bone Formation Following Implantation of Bone Biomaterials Into Extraction Sites

Adequate bone volume is imperative for the osseointegration of endosseous implants, but postextraction resorption and remodeling may challenge implant placement. The use of bone biomaterials has been advocated to fill extraction sites and to enhance primary implant stability during osseointegration. The objective of the case series was to evaluate bone formation histologically and biomechanically in extraction sites following implantation of three commercially available bone biomaterials to compare their ability to allow guided bone regeneration. Thirty-six periodontally involved teeth were extracted from eight healthy non-smoking subjects. At least two bone biomaterials, a synthetic sponge based on polylactic-polyglycolic acid technology (FIS), bovine porous bone mineral (BPBM), or a natural coral derivative physically and chemically transformed into a calcium carbonate ceramic (COR), and one non-grafted control were applied to the extraction sockets within each subject and were covered by an expanded polytetrafluoroethylene device. The devices were removed after 2 months, and trephine biopsies were obtained from each site 4 months later. At that time, endosseous implants were placed in 25 of the sites, and healing abutments were placed; measurements were taken 4 to 6 months later with an electronic mobility testing device. The percentage of residual biomaterial was 5.6% +/- 8.9% for FIS (P <0.001), 20.2% +/- 17.0% for BPBM (P <0.05), and 12.0% +/- 16.4% for COR (P <0.001). The amount of residual biomaterial after 6 months showed a significant relationship with the insertion torque measurements during the first third of implant insertion (P <0.05) and with values of the electronic mobility testing device at the abutment connection (P = 0.05). Histologically, new bone apposition was seen on BPBM particles. FIS sites showed similar ingrowth of blood vessels and osteocytes as empty controls. All sites revealed good primary stability at implant insertion and proper implant rigidity at abutment placement, indicating that early implant osseointegration was not influenced by the application of bone biomaterials used in this study.