How does dental implant macrogeometry affect primary implant stability? A narrative review.

PURPOSE: The macrogeometry of a dental implant plays a decisive role in its primary stability. A larger diameter, a conical shape, and a roughened surface increase the contact area of the implant with the surrounding bone and thus improve primary stability. This is considered the basis for successful implant osseointegration that different factors, such as implant design, can influence. This narrative review aims to critically review macro-geometric features affecting the primary stability of dental implants. METHODS: For this review, a comprehensive literature search and review of relevant studies was conducted based on formulating a research question, searching the literature using keywords and electronic databases such as PubMed, Embase, and Cochrane Library to search for relevant studies. These studies were screened and selected, the study quality was assessed, data were extracted, the results were summarized, and conclusions were drawn. RESULTS: The macrogeometry of a dental implant includes its surface characteristics, size, and shape, all of which play a critical role in its primary stability. At the time of placement, the initial stability of an implant is determined by its contact area with the surrounding bone. Larger diameter and a conical shape of an implant result in a larger contact area and better primary stability. But the linear relationship between implant length and primary stability ends at 12 mm. CONCLUSIONS: Several factors must be considered when choosing the ideal implant geometry, including local factors such as the condition of the bone and soft tissues at the implant site and systemic and patient-specific factors such as osteoporosis, diabetes, or autoimmune diseases. These factors can affect the success of the implant procedure and the long-term stability of an implant. By considering these factors, the surgeon can ensure the greatest possible therapeutic success and minimize the risk of implant failure.

Comparison of insertion torque, implant stability quotient and removal torque, in two different implant designs with and without osseodensification. - An ex vivo bench top study.

Background: Primary stability is an important factor in influencing the outcome of dental implants. Osteotomy modification techniques mentioned, include osteotomes for bone condensation, under-preparation of osteotomy and Osseodensification (OD). The objective of our twin arm study was to assess how two different implant designs respond to conventional osteotomy drilling and how these values obtained compare with OD. Materials and methods: The study comprised a total of 80 implants inserted in pig tibia bone. Group 1a (n = 20) consisted of tapered internal implants and group 1b (n = 20) consisted of tapered pro implants, both inserted with conventional drilling. Group 2a (n = 20) consisted of tapered internal implants and group 2b (n = 20) consisted of tapered pro implants, both inserted with OD. Each implant inserted was measured for implant stability quotient (ISQ), insertion torque and removal torque. Results: Group 1a showed a significantly lower ISQ, mean insertion and removal torque and as compared to Group 1b. Group 2a and 2b had comparable mean values for all the three parameters. Inter-group comparison showed a higher ISQ and insertion torque value for group 2 than group 1. Intra-group assessment showed a significantly lower value for all parameters for sub-group a than b. Conclusions: OD enhances primary stability of implants in bone; but when no OD is used, the tapered pro implant design offers a better primary stability. This may be attributed to the active thread design.

Nonsurgical cleaning potential of deep-threaded implants and titanium particle release: A novel in vitro tissue model.

OBJECTIVES: To measure the efficiency of three cleaning modalities on two implant designs with similar diameters but different thread depths as well as the presence of titanium particles. METHODS: Sixty dyed implants (30 × 4.8 apically tapered (ATAP) and 30 × 5.0 fully tapered (FTAP)) were fixed in plastic models. The horizontal bone defects were surrounded with porcine soft tissue. Three instrumentation modalities were used to clean for 150 s: Curette (CUR), ultrasonic scaler (US), and air powder waterjet device (APWJ) with erythritol powder. Afterward, implants were photographed and scanning electron microscopic (SEM) images were taken. Titanium in the soft tissues was quantified in dissolved samples and histologically confirmed. RESULTS: For ATAP and FTAP implants, the percentage of the cleaned surface was 26.4 ± 3.0 and 17.1 ± 2.4% for CUR, 33.7 ± 3.8% and 28.1 ± 2.3% for US, and 45.5 ± 4.1% and 24.7 ± 3.8% for APWJ, respectively. SEM images showed significant implant surface changes, especially after instrumentation with CUR and US, whereas APWJ had little to no effect. Most titanium residues were found after cleaning ATAP implants with CUR (152.0 ± 75.5), followed by US (89.5 ± 73.8) and APWJ (0.3 ± 0.8). For the FTAP implants, respective values accounted for 129.5 ± 58.6 µg and 67.0 ± 14.4 µg for CUR and US, respectively. No titanium residues were detected on ATAP with APWJ. CONCLUSION: Based on in vitro data, erythritol-powered APWJ still appears to be the most efficient and gentle cleaning method. All three instruments, however, were found to have unprocessed areas depending on different implant designs, hence, clinical relevance for non-surgical approaches remains challenging and warrants further improvement.

Impact of implant thread design on insertion torque and osseointegration: a preclinical model

Background: Successful osseointegration of endosteal dental implants has been attributed to implant design, including the macro-, micro- and nano- geometric properties. Based on current literature pertaining to implant design, the resultant cellular and bone healing response is unknown when the thread thickness of the implants is increased, resulting in an increased contact area in implants designed with healing chambers. The aim of this study was to evaluate the effect of two implant designs with different thread profiles on the osseointegration parameters and implant stability at 3- and 6-weeks in vivo using a well-established preclinical dog model.Material and methods: A total of 48 type V Ti alloy implants were divided in two groups according to their thread design (D1= +0.1x/mm and D2= +0.15x/mm) and placed in an interpolated fashion into the radii of six beagles. Insertion torque was measured at time of placement, radii were extracted for histological processing following 3- and 6-week healing intervals. Histologic and histomorphometric analyses were performed in terms of bone to implant contact (%BIC) and bone area fraction occupancy within implant threads (%BAFO). Statistical analyses were performed through a linear mixed model with fixed factors of time and implant thread design.Results: Surface roughness analysis demonstrated no significant differences in Sa and Sq between D1 and D2 implant designs, which confirmed that both implant designs were homogenous except for their respective thread profiles. For insertion torque, statistically significant lower values were recorded for D1 in comparison to D2 (59.6 ± 11.1 and 78.9 ± 10.1 N⋅cm, respectively). Furthermore, there were no significant differences with respect to histological analysis and histomorphometric parameters, between D1 and D2 at both time points.(AU)

Probing the Influence of Hybrid Thread Design on Biomechanical Response of Dental Implants: Finite Element Study and Experimental Validation.

This study aimed to perform quantitative biomechanical analysis for probing the effect of varying thread shapes in an implant for improved primary stability in prosthodontics surgery. Dental implants were designed with square (SQR), buttress (BUT), and triangular (TRI) thread shapes or their combinations. Cone-beam computed tomography images of mandible molar zones in human subjects belonging to three age groups were used for virtual implantation of the designed implants, to quantify patient-specific peri-implant bone microstrain, using finite element analyses. The in silico analyses were carried out considering frictional contact to simulate immediate loading with a static masticatory force of 200 N. To validate computational biomechanics results, compression tests were performed on three-dimensional printed implants having the investigated thread architectures. Bone/implant contact areas were also quantitatively assessed. It was observed that, bone/implant contact was maximum for SQR implants followed by BUT and TRI implants. For all the cases, peak microstrain was recorded in the cervical cortical bone. The combination of different thread shapes in the middle or in the apical part (or both) was demonstrated to improve peri-implant microstrain, particularly for BUT and TRI. Considering 1500-2000 microstrain generates in the peri-implant bone during regular physiological functioning, BUT-SQR, BUT-TRI-SQR, TRI-SQR-BUT, SQR, and SQR-BUT-TRI design concepts were suitable for younger; BUT-TRI-SQR, BUT-SQR-TRI, TRI-SQR-BUT, SQR-BUT, SQR-TRI for middle-aged, and BUT-TRI-SQR, BUT-SQR-TRI, TRI-BUT-SQR, SQR, and SQR-TRI for the older group of human patients.

How do implant threads and diameters affect the all-on-four success? A 3D finite element analysis study.

BACKGROUND: The effect of different thread designs and diameters on the all-on-four concept is unclear. OBJECTIVE: The aim of the study was to clarify the differences in stress distribution of dental implants with various thread designs and diameters based on the all-on-four concept with three dimensional (3D) finite element analysis (FEA). METHODS: A 3D model of a totally edentulous mandible was used to perform the FEA. Four different models (M1, M2, M3, and M4) including 3.5 and 4.3 mm diameter dental implants with active and passive threaded designs were generated. The dental implants were positioned according to the all-on-four concept. The Von Mises stresses on dental implants and maximum and minimum principal stresses (Pmax and Pmin) on bony structures were calculated under vertical, oblique and horizontal loads. RESULTS: For Von Mises stresses, the highest stress values were detected on the distal implants for all models. Distal implants had also the highest stress values for vertical loading. The Von Mises stresses were found to be concentrated around the implant's neck. In all models the highest Pmax and Pmin stresses occurred in the bone surrounding the distal implant. It was noted that the active threaded implants showed the highest Pmax and Pmin stress values. CONCLUSION: The implant thread design and diameter might have a strong influence on the stress values in the all-on-four concept.

Finite Element Analysis of the Stress Distribution Associated With Different Implant Designs for Different Bone Densities.

PURPOSE: The main objective of this study was to investigate the influence of implant design, bone type, and abutment angulation on stress distribution around dental implants. MATERIALS AND METHODS: Two implant designs with different thread designs, but with the same length and brand were used. The three-dimensional geometry of the bone was simulated with four different bone types, for two different abutment angulations. A 30° oblique load of 200 N was applied to the implant abutments. Maximum principal stress and minimum principal stresses were obtained for bone and Von misses stresses were obtained for dental implants. RESULTS: The distribution of the load was concentrated at the coronal portion of the bone and implants. The stress distributions to the D4 type bone were higher for implant models. Increased bone density and increased cortical bone thickness cause less stress on bone and implants. All implants showed a good distribution of forces for non-axial loads, with higher stresses concentrated at the crestal region of the bone-implant interface. In implant types using straight abutments there was a decrease in stress as the bone density decreased. The change in the abutment angle also caused an increase in stress. CONCLUSIONS: The use of different implant threads and angled abutments affects the stress on the surrounding bone and implant. In addition, it was observed that a decrease in density in trabecular bone and a decrease in cortical bone thickness increased stress.

An In Vitro Evaluation of Primary Stability Values for Two Differently Designed Implants to Suit Immediate Loading in Very Soft Bone.

The achievement of sufficient implant stability in poor quality bone seems to be a challenge. Most manufacturers develop special dental implants, which are claimed to show higher stability even in very soft bone. The aim of this experimental study was to compare two recently introduced dental implants with differing thread designs. A total of 11 implants of each group were inserted in the part of the fresh bovine ribs, corresponding to very soft bone. The primary stability was measured with resonance frequency analysis (RFA) and Periotest; the average of two measurements for each method and for each implant was taken and statistical analysis was applied. The highest stability values were obtained with the ICX Active Master implants, followed by the Conelog® Progressive-Line implants placed with the very soft bone protocol. The primary stability values of the Conelog® Progressive-Line implants inserted by the very soft bone protocol and the ICX Active Master implants placed with the standard protocol showed sufficient stability for immediate loading in low-density bone. Within the limitations of this study, the thread design of the implants and underdimensioned implant bed preparation seem to be effective for better primary stability in cancellous bone.

Significance of implant design on the efficacy of different peri-implantitis decontamination protocols.

OBJECTIVE: To assess the efficacy of three mechanical decontamination methods in four types of commercially available implants. MATERIAL AND METHODS: Ninety-six implants of four commercial brands with different designs (regarding thread depth and thread pitch) were soaked in a surrogate biofilm (ink) and air-dried. Circumferential standardized peri-implant defects with 6 mm in depth and 1.55 mm in width were custom-made with a 3D printer. Stained implants were inserted in the defects and instrumented with three different methods: a titanium brush (TNB), a metallic ultrasonic tip (IST) and an air abrasive (PF). Standardized photographs were taken vertically to the implant axis (flat view), and with angulations of 60° (upper view) and 120° (lower view) to the implant long axis. The percentage of residual stain (PRS) was calculated with the image analysis software. Scanning electron microscope evaluations were performed on the buccal aspect of the implants at the central level of the defect. RESULTS: The efficacy of PF was significantly inferior to the TNB and IST in all implant designs, while there were no significant differences between TNB and IST. IST showed significantly higher PRS in the implant with the highest thread pitch, while the TNB had the highest PRS in the implant with a marked reverse buttress-thread design. The micro-thread design had the lowest values of PRS for all decontamination methods. The apically facing threads represented the areas with highest PRS for all implant designs and decontamination methods. CONCLUSION: Thread geometry influenced the access of the decontamination devices and in turn its efficacy. Implants with lower thread pitch and thread depth values appeared to have less residual staining. CLINICAL RELEVANCE: Clinicians must be aware of the importance of thread geometry in the decontamination efficacy.

Effect of the dimensions of implant body and thread on bone resorption and stability in trapezoidal threaded dental implants: a sensitivity analysis and optimization.

Implant body and threads direct the functional loads from implant to bones. Appropriate design of implant helps implant stability. Therefore, implant length, diameter, and thread depth, width, pitch, and inner angle are assessed to recognize their effects on von-Mises stress and micromotion of implant and bones. The FE model of mandible with a threaded dental implant is modeled then the central composite design is used to assess the effects of parameters. The optimization is conducted to find the optimum design; however, it reduced the Max von-Mises stress in implant-abutment, cancellous, and cortical bones by 10%, 35%, and 27%, respectively.

Bone strain measurements and implant micro-surface analysis of drill-less self-threading dental implants - preliminary in-vitro results.

Innovative implant thread design enables timesaving one-stage insertion, with no need for prior osteotomy. This technique may impair bone and implant surface. The aim of this study was to investigate the strain levels produced in surrounding bone by this new treatment approach during and after implant placement and the effect of high insertion torque on the surface microstructure of the implants. Fresh bovine bone was collected and prepared to receive 2 types of drill-less self-threading dental implants differing in their thread design. Prior to implant insertion, two strain-gauges were cemented onto the bovine bone at each of the implant's neck recipient sites, one horizontally and one vertically. 5 Type 1 and 5 Type 2 implants were inserted into the bone with insertion torque of 80 Ncm. Strain was measured during implant insertion, and residual strain was recorded for 1 hour after implant placement. Implants micro-structure were analyzed by SEM. These results were compared to osteotomy and implant insertion strain data of conventional dental implants. A clear pattern of higher vertical compared to horizontal strain levels can be seen in the drill-less implants, compared to the opposite in drilling and insertion of conventional implants. Type 2 drill-less implant showed the lowest strain levels of all groups. Highest horizontal strain levels were measured for insertion of standard implants. Strain recovery was least prominent in the insertion stage of standard implants. Significant more cervical compression zones were detected in type 1 implant. However, SA and Rx. Surface roughness measurements didn't show any differences. Favorable horizontal stress distribution was noted in the 2 types of the novel drill-less implants, and comparable or lower vertical strains compared to regular protocol was also noted. Residual strain was low within all dimensions of bone. Conventional implant insertion protocol delivers strain to the frequently vulnerable bone around the implant neck. Horizontal residual strain, both in drilling and inserting conventional implants, was higher than the insertion strain of the drill-less implants. Implant surface roughness was not impaired by high insertion torque. High torque implant insertion may induce positive strain distribution within coronal part of the supporting bone. Implant surface were not impaired by high torque insertion methods.

Impact of Different Titanium Implant Thread Designs on Bone Healing: A Biomechanical and Histometric Study with an Animal Model.

Threads of dental implants with healing chamber configurations have become a target to improve osseointegration. This biomechanical and histometric study aimed to evaluate the influence of implant healing chamber configurations on the torque removal value (RTv), percentage of bone-to-implant contact (BIC%), bone fraction occupancy inside the thread area (BAFO%), and bone and osteocyte density (Ost) in the rabbit tibia after two months of healing. Titanium implants with three different thread configurations were evaluated: Group 1 (G1), with a conventional "v" thread-shaped implant design; Group 2 (G2), with square threads; and Group 3 (G3), the experimental group with longer threads (healing chamber). Ten rabbits (4.5 ± 0.5 kg) received three implants in each tibia (one per group), distributed in a randomized manner. After a period of two months, the tibia blocks (implants and the surrounding tissue) were removed and processed for ground sectioning to evaluate BIC%, BAFO%, and osteocyte density. The ANOVA one-way statistical test was used followed by the Bonferoni's multiple comparison test to determine individual difference among groups, considering a statistical difference when p < 0.05. Histometric evaluation showed a higher BAFO% values and Ost density for G3 in comparison with the other two groups (G1 and G2), with p < 0.05. However, the RTv and BIC% parameters were not significantly different between groups (p > 0.05). The histological data suggest that the healing chambers in the implant macrogeometry can improve the bone reaction in comparison with the conventional thread design.

Three-dimensional optimization and sensitivity analysis of dental implant thread parameters using finite element analysis.

OBJECTIVES: This study aimed to optimize the thread depth and pitch of a recently designed dental implant to provide uniform stress distribution by means of a response surface optimization method available in finite element (FE) software. The sensitivity of simulation to different mechanical parameters was also evaluated. MATERIALS AND METHODS: A three-dimensional model of a tapered dental implant with micro-threads in the upper area and V-shaped threads in the rest of the body was modeled and analyzed using finite element analysis (FEA). An axial load of 100 N was applied to the top of the implants. The model was optimized for thread depth and pitch to determine the optimal stress distribution. In this analysis, micro-threads had 0.25 to 0.3 mm depth and 0.27 to 0.33 mm pitch, and V-shaped threads had 0.405 to 0.495 mm depth and 0.66 to 0.8 mm pitch. RESULTS: The optimized depth and pitch were 0.307 and 0.286 mm for micro-threads and 0.405 and 0.808 mm for V-shaped threads, respectively. In this design, the most effective parameters on stress distribution were the depth and pitch of the micro-threads based on sensitivity analysis results. CONCLUSION: Based on the results of this study, the optimal implant design has micro-threads with 0.307 and 0.286 mm depth and pitch, respectively, in the upper area and V-shaped threads with 0.405 and 0.808 mm depth and pitch in the rest of the body. These results indicate that micro-thread parameters have a greater effect on stress and strain values.

Three-dimensional optimization and sensitivity analysis of dental implant thread parameters using finite element analysis

OBJECTIVES: This study aimed to optimize the thread depth and pitch of a recently designed dental implant to provide uniform stress distribution by means of a response surface optimization method available in finite element (FE) software. The sensitivity of simulation to different mechanical parameters was also evaluated. MATERIALS AND METHODS: A three-dimensional model of a tapered dental implant with micro-threads in the upper area and V-shaped threads in the rest of the body was modeled and analyzed using finite element analysis (FEA). An axial load of 100 N was applied to the top of the implants. The model was optimized for thread depth and pitch to determine the optimal stress distribution. In this analysis, micro-threads had 0.25 to 0.3 mm depth and 0.27 to 0.33 mm pitch, and V-shaped threads had 0.405 to 0.495 mm depth and 0.66 to 0.8 mm pitch. RESULTS: The optimized depth and pitch were 0.307 and 0.286 mm for micro-threads and 0.405 and 0.808 mm for V-shaped threads, respectively. In this design, the most effective parameters on stress distribution were the depth and pitch of the micro-threads based on sensitivity analysis results. CONCLUSION: Based on the results of this study, the optimal implant design has micro-threads with 0.307 and 0.286 mm depth and pitch, respectively, in the upper area and V-shaped threads with 0.405 and 0.808 mm depth and pitch in the rest of the body. These results indicate that micro-thread parameters have a greater effect on stress and strain values.

Stress dissipation characteristics of four implant thread designs evaluated by 3D finite element modeling / 대한치과보철학회지

PURPOSE: The aim was to investigate the effect of implant thread designs on the stress dissipation of the implant. MATERIALS AND METHODS: The threads evaluated in this study included the V-shaped, buttress, reverse buttress, and square-shaped threads, which were of the same size (depth). Building four different implant/bone complexes each consisting of an implant with one of the 4 different threads on its cylindrical body (4.1 mm x 10 mm), a force of 100 N was applied onto the top of implant abutment at 30degrees with the implant axis. In order to simulate different osseointegration stages at the implant/bone interfaces, a nonlinear contact condition was used to simulate immature osseointegration and a bonding condition for mature osseointegration states. RESULTS: Stress distribution pattern around the implant differed depending on the osseointegration states. Stress levels as well as the differences in the stress between the analysis models (with different threads) were higher in the case of the immature osseointegration state. Both the stress levels and the differences between analysis models became lower at the completely osseointegrated state. Stress dissipation characteristics of the V-shape thread was in the middle of the four threads in both the immature and mature states of osseointegration. These results indicated that implant thread design may have biomechanical impact on the implant bed bone until the osseointegration process has been finished. CONCLUSION: The stress dissipation characteristics of V-shape thread was in the middle of the four threads in both the immature and mature states of osseointegration.

The influence of thread geometry on biomechanical load transfer to bone: A finite element analysis comparing two implant thread designs.

BACKGROUND: The success of dental implants depends on the manner in which stresses are transferred to the surrounding bone. An important consideration is to design an implant with a geometry that will minimize the peak bone stresses caused by standard loading. The aim of this study was to assess the influence of implant thread geometry on biomechanical load transfer and to compare the difference between two different thread designs. MATERIALS AND METHODS: A three-dimensional finite element model of D2 bone representing mandibular premolar region was constructed. Two implants of differing thread geometries, 13-mm length, and 4-mm diameter along with superstructures were simulated. One design featured fourfold microthread of 0.4-mm pitch, 0.25-mm depth in the crestal one-third; 0.8-mm pitch, 0.5-mm depth in the apical two-third. The other design had a single-pitch microthread of 0.8-mm pitch, 0.25-mm depth in the crestal one-third; 0.8-mm pitch, 0.5-mm depth in the apical two-third. A static axial load of 100-N was applied to the occlusal surface of the prosthesis. ANSYS CLASSIC 9.0 (PA,USA)software was used for stress analysis as von Mises stresses. RESULTS: A comparison of von Mises stresses between two thread designs revealed that fourfold microthread allows better stress distribution within the implant body by 43.85%, abutment by 15.68%, its superstructure by 39.70% and 36.30% within cancellous bone as compared to single-pitch microthread. The effective stress transfer to the cortical bone is lowered by 60.47% with single-pitch microthread. CONCLUSION: Single-pitch microthread dissipates lesser stresses to cortical bone while the implant body, abutment, and superstructure absorb more stress. This will have a positive influence on the bone-implant contact and contribute to preservation of crestal bone. Implant with single pitch microthread will thus be preferable to be used in areas where the amount of cortical bone available is less.

The impact of a modified cutting flute implant design on osseointegration.

Information concerning the effects of the implant cutting flute design on initial stability and its influence on osseointegration in vivo is limited. This study evaluated the early effects of implants with a specific cutting flute design placed in the sheep mandible. Forty-eight dental implants with two different macro-geometries (24 with a specific cutting flute design - Blossom group; 24 with a self-tapping design - DT group) were inserted into the mandibular bodies of six sheep; the maximum insertion torque was recorded. Samples were retrieved and processed for histomorphometric analysis after 3 and 6 weeks. The mean insertion torque was lower for Blossom implants (P<0.001). No differences in histomorphometric results were observed between the groups. At 3 weeks, P=0.58 for bone-to-implant contact (BIC) and P=0.52 for bone area fraction occupied (BAFO); at 6 weeks, P=0.55 for BIC and P=0.45 for BAFO. While no histomorphometric differences were observed, ground sections showed different healing patterns between the implants, with better peri-implant bone organization around those with the specific cutting flute design (Blossom group). Implants with the modified cutting flute design had a significantly reduced insertion torque compared to the DT implants with a traditional cutting thread, and resulted in a different healing pattern.

The effect of various thread designs on the initial stability of taper implants.

STATEMENT OF PROBLEM: Primary stability at the time of implant placement is related to the level of primary bone contact. The level of bone contact with implant is affected by thread design, surgical procedure and bone quality, etc. PURPOSE: The aim of this study was to compare the initial stability of the various taper implants according to the thread designs, half of which were engaged to inferior cortical wall of type IV bone (Group 1) and the rest of which were not engaged to inferior cortical wall (Group 2) by measuring the implant stability quotient (ISQ) and the removal torque value (RTV). MATERIAL AND METHODS: In this study, 6 different implant fixtures with 10 mm length were installed. In order to simulate the sinus inferior wall of type IV bone, one side cortical bone of swine rib was removed. 6 different implants were installed in the same bone block following manufacturer's recommended procedures. Total 10 bone blocks were made for each group. The height of Group 1 bone block was 10 mm for engagement and that of group 2 was 13 mm. The initial stability was measured with ISQ value using Osstell mentor® and with removal torque using MGT50 torque gauge. RESULTS: In this study, we found the following results. 1. In Group 1 with fixtures engaged to the inferior cortical wall, there was no significant difference in RTV and ISQ value among the 6 types of implants. 2. In Group 2 with fixtures not engaged to the inferior cortical wall, there was significant difference in RTV and ISQ value among the 6 types of implants (P < .05). 3. There was significant difference in RTV and ISQ value according to whether fixtures were engaged to the inferior cortical wall or not (P < .05). 4. Under-drilling made RTV and ISQ value increase significantly in the NT implants which had lower RTV and ISQ value in Group 2 (P < .05). CONCLUSIONS: Without being engaged to the inferior cortical wall fixtures had initial stability affected by implant types. Also in poor quality bone, under-drilling improved initial stability.

The effect of various thread designs on the initial stability of taper implants

STATEMENT OF PROBLEM: Primary stability at the time of implant placement is related to the level of primary bone contact. The level of bone contact with implant is affected by thread design, surgical procedure and bone quality, etc. PURPOSE: The aim of this study was to compare the initial stability of the various taper implants according to the thread designs, half of which were engaged to inferior cortical wall of type IV bone (Group 1) and the rest of which were not engaged to inferior cortical wall (Group 2) by measuring the implant stability quotient (ISQ) and the removal torque value (RTV). MATERIAL AND METHODS: In this study, 6 different implant fixtures with 10 mm length were installed. In order to simulate the sinus inferior wall of type IV bone, one side cortical bone of swine rib was removed. 6 different implants were installed in the same bone block following manufacturer's recommended procedures. Total 10 bone blocks were made for each group. The height of Group 1 bone block was 10 mm for engagement and that of group 2 was 13 mm. The initial stability was measured with ISQ value using Osstell mentor(R) and with removal torque using MGT50 torque gauge. RESULTS: In this study, we found the following results. 1. In Group 1 with fixtures engaged to the inferior cortical wall, there was no significant difference in RTV and ISQ value among the 6 types of implants. 2. In Group 2 with fixtures not engaged to the inferior cortical wall, there was significant difference in RTV and ISQ value among the 6 types of implants (P < .05). 3. There was significant difference in RTV and ISQ value according to whether fixtures were engaged to the inferior cortical wall or not (P < .05). 4. Under-drilling made RTV and ISQ value increase significantly in the NT implants which had lower RTV and ISQ value in Group 2 (P < .05). CONCLUSIONS: Without being engaged to the inferior cortical wall fixtures had initial stability affected by implant types. Also in poor quality bone, under-drilling improved initial stability.