Initial stability and bone strain evaluation of the immediately loaded dental implant: an in vitro model study

Objectives: The aim of this study was to evaluate the effects of cortical bone thickness and trabecular bone elastic modulus on the strain in the bone surrounding an immediately loaded implant. We also examined the correlations between bone structure and the following indices of primary implant stability: insertion torque value (ITV), Periotest value (PTV), and implant stability quotient (ISQ). Material and methods: The ITV, PTV, and ISQ were measured in 24 artificial jaw bone models representing cortical bone with four thicknesses (0, 1, 2, and 3 mm) and trabecular bone with four elastic moduli (137, 47.5, 23, and 12.4 MPa). Two loading conditions were applied (force of 130 N applied vertically and at 45° laterally), and the strains in the crestal region were measured by rosette strain gauges with a data acquisition system. Results: When the cortical bone thickness and the elastic modulus of trabecular bone decreased, the bone strains increased by 10.3–52.1% and 39–73.1%, respectively, for vertical loading and by 35–62% and 42.4–56.2% for lateral loading. The cortical bone thickness has a stronger correlation (R²=0.95–0.71) with ITV, PTV, and ISQ than the elastic modulus of trabecular bone (R²=0.89–0.59). Conclusions: The initial stability at the time of implant placement is influenced by both the cortical bone thickness and the elastic modulus of trabecular bone; however, these parameters are not totally linearly correlated with ITV, PTV, and ISQ. The placement of an immediately loaded implant in cases with thin cortical bone and/or weak trabecular bone can induce extreme bone strains and may increase the risk of implant failure. To cite this article:
Huang H‐L, Chang Y‐Y, Lin D‐J, Li Y‐F, Chen K‐T, Hsu J‐T. Initial stability and bone strain evaluation of the immediately loaded dental implant: an in vitro model study.
Clin. Oral Impl. Res. 22 , 2011; 691–698
doi: 10.1111/j.1600‐0501.2010.01983.x     

The Effects of Superficial Roughness and Design on the Primary Stability of Dental Implants

Background: Primary implant stability has been used as an indicator for future osseointegration and whether an immediate/early loading protocol should be applied. Implant stability is the key to clinical success. Purpose: The aim of this work was to analyze the influence of the design and surface morphology on the primary stability of dental implants. The insertion torque and resonance frequency analysis (RFA) were the parameters used to measure the primary stability of the implants. Materials and Methods: Thirty implants, divided in six groups of five samples were placed in cylinder of high molecular weight polyethylene. The groups were different upon two designs (cylindrical and conic) and three implant surfaces finishing (machined, acid etched, and anodized). The insertion torque was quantified by a digital torque driver (Lutron Electronic Enterprise Co., Taipei, Taiwan) and the resonance frequency was measured by Osstell mentor? (Integration Diagnostics AB, Göteborg, Sweden). The implant surface morphology was characterized by scanning electron microscopy, roughness measurement, and friction coefficient. Results: The machined implants showed smaller insertion torques than treated implant surfaces. There were no differences between the RFA measurements in all tested surfaces. Statistical analyses demonstrated no correlation between the dental implant insertion torque and primary stability measured by the RFA. The implants with treated surfaces showed greater roughness, a higher friction coefficient, and demanded a larger insertion torque than machined implants. The results of the surface roughness and friction coefficients are in accordance with the results of the insertion torque. The difference, across the insertion torque values, between conical and cylindrical implants, can be explained by the different contact surface area among the thread geometry of these implants. Conclusion: The maximum implant insertion torque depends on the implant geometry, thread form, and implant surface morphology. The placement of conical implants with treated surfaces required the highest insertion torque. There was no correlation between RFA and insertion torque implant.     

应用共振频率评估种植体稳定性的临床研究

目的：应用共振频率分析评估牙种植体初期稳定性和预测牙种植俸骨结合．为上颌窭提升植骨同期植入种植体和种植体早期暴露的临床应用提供客观依据方法：36个病人共植入87颗牙种植体，分为3组，A组种植体早期暴露组；B组上颌宴提升植骨同期种植组；C组常规种植组即对照组在种植体植入即刻、二期暴露或修复负重前测定种植体稳定性，每一颗种植体前后测定2次测定使用的仪器是共振频率分析仪Osstell，其数值单位是ISQ.结果：三组种植体初期稳定性数值范围是5492—80．20ISQ A组初期稳定性值最高，和其他两组之间的差异存在显著性.R组和C组之间差异没有统计学意义骨结合形成后稳定性范围在57．94—79．38ISq三组种植体的后期稳定性之间差异没有统计学意义.A组和B组初期稳定性和骨结合形成后的稳定性数值前后没有差异，C组前后稳定性差异有统计学意义.结论：共振频率分析牙种植体初期稳定性和预测骨结合是一种可靠而有效的方法，同时也提示种植体早期丞露和上颌宴提升植骨同期种植术对具有适应症的病例是可行的.     

Primary Stability of a Hybrid Self‐Tapping Implant Compared to a Cylindrical Non‐Self‐Tapping Implant with Respect to Drilling Protocols in an Ex Vivo Model

Background: Modifications of implant design have been intending to improve primary stability. However, little is known about investigation of a hybrid self‐tapping implant on primary stability. Purposes: The aims of this study were to evaluate the primary stability of two hybrid self‐tapping implants compared to one cylindrical non‐self‐tapping implant, and to elucidate the relevance of drilling protocols on primary stability in an ex vivo model. Materials and Methods: Two types of hybrid self‐tapping implants (Straumann® Bone Level implant [BL], Straumann® Tapered Effect implant [TE]) and one type of cylindrical non‐self‐tapping implant (Straumann® Standard Plus implant [SP]) were investigated in the study. In porcine iliac cancellous bones, 10 implants each were inserted either using standard drilling or under‐dimensioned drilling protocol. The evaluation of implant‐bone interface stability was carried out by records of maximum insertion torque, the Periotest® (Siemens, Bensheim, Germany), the resonance frequency analysis (RFA), and the push‐out test. Results: In each drilling group, the maximum insertion torque values of BL and TE were significantly higher than SP (p = .014 and p = .047, respectively). In each group, the Periotest values of TE were significantly lower than SP (p = .036 and p = .033, respectively). The Periotest values of BL and TE were significantly lower in the group of under‐dimensioned drilling than standard drilling (p = .002 and p = .02, respectively). In the RFA, no statistical significances were found in implants between two groups and between implants in each group. In each group, the push‐out values of BL and TE were significantly higher than SP (p = .006 and p = .049, respectively). Conclusion: Hybrid self‐tapping implants could achieve a high primary stability which predicts them for use in low‐density bone. However, there is still a debate to clarify the influence of under‐dimensioned drilling on primary stability.     

Effects of Implant Design and Surface on Bone Regeneration and Implant Stability: An Experimental Study in the Dog Mandible

Background: Previous experimental studies have shown a higher degree of bone‐implant contact for surface‐enlarged implants compared with machined implants. Yet, there is insufficient evidence that such implants show higher stability and an increased survival rate. Purpose: The purpose of this investigation was to study the integration and stability of grit‐blasted implants with retention elements on the implant neck, with and without marginal bone defects, compared with machined implants without retention elements. Materials and Methods: After tooth extraction of the mandibular premolars in six dogs, two grit‐blasted, partly microthreaded Astra Tech implants and one standard Branemark implant were bilaterally placed in each dog. On one side, 3 ± 3 mm large buccal defects were created, to expose three to four implant threads. The contralateral side served as control, and no defects were made. The animals were sacrificed after 4 months of healing. Implant stability was measured using resonance frequency analysis at implant installation and after 4 months of healing. Histologic and histomorpho‐metric evaluation was made after 4 months of healing. Results: Resonance frequency analysis indicated that all implants in the test and control groups were osseointegrated after 4 months, with a tendency toward higher implant stability for the Astra Tech implants. There was a statistically significant higher increase in resonance frequency for the Astra test implants compared with their corresponding controls. Histology and histomorphometry showed well‐integrated implants with varying degrees of bone repair at the defect sites. The greater bone‐implant contact for the Astra implants was statistically significant. No significant difference between the implants in amount of bone filling the threads was recorded. Conclusions: The Astra Tech implants tested showed a higher degree of bone—implant contact and higher level of bone regenerated at defect sites compared with the Brånemark implants. Resonance frequency analysis demonstrated a significantly higher increase in the Astra test implants compared with their control groups than did the Brånemark test implants versus their controls.     

Primary Stability Determination by Means of Insertion Torque and RFA in a Sample of 4,135 Implants

Objectives: The aims of the present study are to evaluate the primary stability of a sample of 4,135 implants and to investigate the correlations between primary stability and mechanical characteristic of the implant and bone density at insertion time. Material and Methods: The study was conducted from March 2002 to January 2009 at a private practice in Bologna (Italy). Patients were eligible for the study if they needed the insertion of single or multiple implants. Bone density, length, and diameter of each implant were recorded. During surgery for each implant, peak insertion torque (IT) was recorded; the resonance frequency analysis (RFA) values were also collected. Finally, it was recorded whether an implant was lost or removed at an early stage (within 6 months from insertion surgery). Results: A total of 1,045 consecutive patients were included in the study. A total of 4,135 of implants were inserted. The sample presented 1,184 implants inserted in a postextractive site. The mean peak IT was 34.82 ± 19.36. The mean RFA was 71.57 ± 10.63 implant stability quotient. Spearman correlation analysis shows the presence of a weak positive correlation between IT and RFA. The statistical analysis shows a relevant dependency between IT and bone quality and a very weak dependency between RFA and bone quality. Again, the statistical analysis shows a quite weak correlation between length or diameter and IT, but it shows a relevant correlation between length and RFA. Postextractive implants presented a higher mean IT and a lower RFA compared with implants inserted in healed sites. Twenty‐eight (0.7%) implants were considered to have failed and removed within 6 months. Conclusions: The results show that the implants studied obtain a good primary stability with a standard protocol. The IT and RFA appear as two independent features of primary stability. Data show that only IT is influenced by bone density as well as only RFA is correlated to the length of implants used. Finally, it is possible to obtain a good primary stability also in postextractive sites.     

Influence of bony defects on implant stability

Introduction: The purpose of this study was to analyze the evolution of implant mechanical stability in different types/sizes of bony defects using both Periotest and Osstell devices as “objective tools.” Materials and methods: Thirty‐two implants were randomly allocated to one of the four types of bone defects: marginal bone loss, peri‐apical bone defect, constant width dehiscence and constant length dehiscences. Periotest/Osstell measurements were completed before and during staged bone removal (to enlarge defect size). Results: Significant differences (P<0.05) with initial values were found after a 2 mm marginal bone removal (Osstell/Periotest); for a peri‐apical bone lesion, after removal of 5 mm (Osstell) or 8 mm (Periotest); for a 6‐mm‐long dehiscence, after removal up to 180° of the implant perimeter (Osstell/Periotest); for a 3‐mm‐wide dehiscence, after removal of 10 mm (Osstell) or 6 mm (Periotest). Conclusion: Periotest and Osstell are in general not very sensitive in the identification of peri‐implant bone destruction, except for marginal bone loss. To cite this article:
Merheb J, Coucke W, Jacobs R, Naert I, Quirynen M. Influence of bony defects on implant stability.
Clin. Oral Impl. Res. 21 , 2010; 919–923.
doi: 10.1111/j.1600‐0501.2010.01932.x     

Influence of surgical technique,implant shape and diameter on the primary stability in cancellous bone

Summary Achievement of primary stability during surgical placement of dental implants is one of the most important factors for successful osseointegration depending on various anatomical, surgical and implant‐related factors. Resonance frequency analysis (RFA) has been shown as a non‐invasive and objective technique for measuring the stability of implants. The aim of this study was to evaluate the effect of some surgical and implant‐related factors in enhancing primary stability and to estimate a correlation between RFA and insertion torque (IT) in proximal regions of cow ribs representing cancellous bone. Fifteen implant beds were prepared in the most proximal region of six fresh cow ribs. Ninety implants with three different shapes and two different diameters were placed with two different surgical techniques, and the primary stability was compared using RFA and IT. Significantly higher RFA and IT values were achieved when under‐dimensioned drilling was used as the surgical method (P < 0·01); significantly higher IT values were obtained with the use of wider implants (P < 0·01) and partially conical Astra Tech implants showed the highest IT values (P < 0·01). When all the implants were considered, significant correlations between the IT and RFA values were noted (%40·6, P < 0·05). Partially conical implants with a wide diameter to be placed with the modified surgical technique proposed appear to be useful in enhancing the primary stability in cancellous bone.     

Evaluation of primary stability in modified implants: Analysis by resonance frequency and insertion torque

Background

Changes in the macrogeometry of dental implants are known to influence primary stability and the osseointegration process.

Purpose

The purpose of the present in vitro study was to evaluate the mechanical behavior of geometric changes in the apex region of dental implants.

Methods

Thirty‐five cylindrical dental implants (Titamax Ti; Neodent) were machined at the apical third to reproduce the experimental groups: without apical cut (Wc), apical bi‐split cut, apical tri‐split cut, apical quadri‐split cut (Qs). One (control group) (Titamax Ti Ex) (n = 7) without any modifications was added. The implants had the same final dimensions (4.1 x 11 mm²). All implants were inserted into artificial bone blocks and were evaluated by insertion torque and resonance frequency by ISQ values (Osstell). Two‐tailed analysis of variance (One‐way ANOVA) and Tukey's post‐test (P < .05).

Results

Control and Qs implants showed a significant increase of the insertion torque (P < .001). For the resonance frequency, Wc and (control) implants had the greatest ISQ values. However, there's no significant difference between (control) and Qs for the ISQ values (P < .001).

Conclusion

Within the limitations of the present study, the proposed geometries at the apical third of dental implants greatly influenced its insertion torque and primary stability in vitro.     

Osstell ISQTM监测种植体稳定性的临床研究

目的：分析种植体初期稳定系数（ISQi）与植入扭矩值（ITv）在评估初期稳定性中的关系;分析不同初期稳定性种植体在骨愈合期种植体稳定系数（ISQ）的变化趋势。方法：选择牙缺失患者34例,共55枚种植体。应用Osstell ISQTM共振频率分析仪于种植体植入时测量ISQ和记录ITv,并于植入后4周、8周、12周监测ISQ变化。结果： ISQi与ITv存在强正相关性。低初期稳定性组种植体植入后ISQ呈持续上升过程,高初期稳定性组ISQ则呈先降后升趋势,4周降至最低点。结论： Osstell ISQTM能良好评价和监测种植体稳定性, ISQi与ITv均为评价种植体初期稳定性的客观指标,种植体稳定性的变化趋势与初期稳定性范围相关。