Factors influencing the resonance frequency of dental implants

Evaluation of Implant Stability According to Implant Placement Site and Duration in Elderly Patients: A Prospective Multi-Center Cohort Study

The aim of this prospective study is to investigate implant stability and the reliability of different measuring devices according to implant placement site and duration in patients aged over 65 years. The study evaluated 60 implants (diameter: 3.5/4.0/4.5/5.0 mm and length: 8.5/10.0/11.5 mm) in 60 patients aged ≥ 65 years. The implant placement sites were divided into six evenly distributed sections (n = 10), i.e., maxillary right-posterior, A; maxillary anterior, B; maxillary left-posterior, C; mandibular right-posterior, D; mandibular anterior, E; mandibular left-posterior, F. Participants visited the hospital six times: implant surgery, 1V; stitch removal, 2V; 1-month follow-up, 3V; 2-month follow-up, 4V; before final restoration delivery, 5V; and after final restoration delivery, 6V. The implant stability was evaluated with the Osstell Mentor (ISQ), Periotest M (PTV), and Anycheck (IST). The mean values of ISQ, PTV, and IST were analyzed (α = 0.05). ISQ, PTV, and IST results of 4V and 5V were significantly higher than those of 1V (p < 0.05). The lowest ISQ results occurred in the E location at 4V and 5V (p < 0.05). In all mandibular locations, IST results of 6V were significantly higher than those of 1V, 2V, 3V, and 4V (p < 0.05). ISQ results were negatively correlated with PTV and positively correlated with IST, and PTV was negatively correlated with IST. By considering various factors affecting the stability of the implant, it is necessary to determine the appropriate implant load application time. This could help increase the implant success rate in elderly patients. And as a diagnostic device for implant stability and the evaluation of osseointegration in elderly patients, Anycheck was also able to prove its relative reliability compared to Osstell ISQ Mentor and Periotest M.

Reliability of implant stability measuring devices depending on various clinical conditions: an in vitro study

PURPOSE

The aim of this study was to evaluate the reliability of implant stability measuring devices depending on the location of the implant and the position of the patient.

MATERIALS AND METHODS

Six implants were installed in different dentate sextants of six artificial bone models. Implant stability was measured in three conditions of the bone model (without mounting on a phantom head, mounted on a phantom head in supine position, and mounted on a phantom head in upright position). A resonance frequency analysis device (Osstell) and two damping capacity analysis devices (Periotest and Anycheck) were used to measure implant stability. The values measured outside the phantom head were treated as controls, and the values inside the phantom head were compared using an independent t-test.

RESULTS

Osstell showed different results in two of the six divisions in both the supine and upright positions compared to outside of the mouth (P < .05). Periotest showed different results in all six parts in the supine position and in five parts in the upright position compared to outside of the mouth (P < .05). While Anycheck showed different results in five areas in the supine position compared to outside of the mouth, it showed different results in only one area in the upright position (P < .05).

CONCLUSION

In the difficult implant position for the operator to access, the implant stability measuring devices show less reliability. The accessibility of implant is greatly affected in the order of Osstell, Anycheck, and Periotest.

Monitoring Osseointegration Process Using Vibration Analysis

Osseointegration implant has attracted significant attention as an alternative treatment for transfemoral amputees. It has been shown to improve patients' sitting and walking comfort and control of the artificial limb, compared to the conventional socket device. However, the patients treated with osseointegration implants require a long rehabilitation period to establish sufficient femur-implant connection, allowing the full body weight on the prosthesis stem. Hence, a robust assessment method on the osseointegration process is essential to shorten the rehabilitation period and identify the degree of osseointegration prior to the connection of an artificial limb. This paper investigates the capability of a vibration-related index (E-index) on detecting the degree of simulated osseointegration process with three lengths of the residual femur (152, 190 and 228 mm). The adhesive epoxy with a setting time of 5 min was applied at the femur-implant interface to represent the stiffness change during the osseointegration process. The cross-spectrum and colormap of the normalised magnitude demonstrated significant changes during the cure time, showing that application of these plots could improve the accuracy of the currently available diagnostic techniques. Furthermore, the E-index exhibited a clear trend with a noticeable average increase of 53% against the cure time for all three residual length conditions. These findings highlight that the E-index can be employed as a quantitative justification to assess the degree of osseointegration process without selecting and tracing the resonant frequency based on the geometry of the residual femur.

Histological and histomorphometric aspects of continual intermittent parathyroid hormone administration on osseointegration in osteoporosis rabbit model

In implant treatment, primary stability and osseointegration are improved by continual intermittent administration of parathyroid hormone (PTH) in patients with osteoporosis. However, the histological and histomorphometric aspects are not clear. The aim of this study was to investigate the histological and histomorphometric effects of intermittent PTH administration on osseointegration in a glucocorticoid-induced osteoporotic rabbit model. Fifteen female New Zealand rabbits were prepared for the osteoporosis model with ovariectomy and glucocorticoid administration. After 1 week, five rabbits were intermittently administered PTH for 8 weeks until the end point (PTHa group) and five for 4 weeks until implant placement (PTHb group). The remaining rabbits were intermittently administered saline for 8 weeks until the end point (Control group). Dental implants were inserted into the femoral epiphyses 11 weeks after ovariectomy. After 4 weeks, the maximum removal torque (RT) of the placed implant and bone implant contact (BIC) ratio were evaluated. In addition micro-computed tomography and histomorphometric analyses were performed. The RT and BIC values were significantly higher in the PTHa group compared with those of the PTHb and Control groups (p< 0.05). Furthermore, the bone mineral densities and Hounsfield units were significantly higher in the PTHa group than those in the PTHb and Control groups. Histologic and histomorphometric measurements revealed that continuous administration of PTH improved bone density and bone formation around the implant placement site, as well as systemic bone formation. Therefore, favorable implant stability was achieved under osteoporosis.

Experimental Investigation of Vibration Analysis on Implant Stability for a Novel Implant Design

Osseointegrated prostheses are widely used following transfemoral amputation. However, this technique requires sufficient implant stability before and during the rehabilitation period to mitigate the risk of implant breakage and loosening. Hence, reliable assessment methods for the osseointegration process are essential to ensure initial and long–term implant stability. This paper researches the feasibility of a vibration analysis technique for the osseointegration (OI) process by investigating the change in the dynamic response of the residual femur with a novel implant design during a simulated OI process. The paper also proposes a concept of an energy index (the E–index), which is formulated based on the normalized magnitude. To illustrate the potential of the E–index, this paper reports on changes in the vibrational behaviors of a 133 mm long amputated artificial femur model and implant system, with epoxy adhesives applied at the interface to simulate the OI process. The results show a significant variation in the magnitude of the colormap against curing time. The study also shows that the E–index was sensitive to the interface stiffness change, especially during the early curing process. These findings highlight the feasibility of using the vibration analysis technique and the E–index to quantitatively monitor the osseointegration process for future improvement on the efficiency of human health monitoring and patient rehabilitation.

A Radiographic and Clinical Comparison of Immediate vs. Early Loading (4 Weeks) of Implants with a New Thermo-Chemically Treated Surface: A Randomized Clinical Trial

Background: Implant dentistry has evolved over time, resulting in better treatment outcomes for both patients and clinicians. The aim of this trial was to test whether the immediate loading of implants with a platform-switching design influences the marginal bone level, compared to four-week loading, after one year of follow-up. Moreover, a comparison of clinical data regarding implant survival, implant stability, and patient-reported outcome measures (PROMs) was conducted. Methods: Klockner^® VEGA^® implants with a ContacTi^® surface were placed in partially edentulous patients in the posterior areas. Group A received an immediately loaded prosthesis (one week) and Group B received an early-loaded prosthesis (four weeks). All abutments were placed at the time of surgery. Radiographic and clinical data were recorded. Results: Twenty-one patients were treated (35 implants). No implants were lost during the study. The final marginal bone level did not show differences between groups. The bone loss at 12 months at the implant level was 0.00 mm for both groups (median). The final implant quotient stability (ISQ) values did not differ between groups (median 73 and 70.25), nor did the other clinical parameters or PROMs. Conclusions: The results suggest that neither of the loading protocols with the implants used influenced the marginal bone level—not the osseointegration rate, clinical conditions, or PROMs.

Effect of leukocyte and platelet rich fibrin (L-PRF) on stability of dental implants. A systematic review and meta-analysis

The aim of this study was to assess the impact, if any, of L-PRF application in an implant bed prior to implant placement, focusing on stability by means of implant stability quotient (ISQ) values. The literature was searched in a systematic way by means of the main databases and hand searching of the most relevant journals. The inclusion and exclusion criteria were used to determine the eligible studies included in this review. Only randomised controlled trials (RCT) and controlled clinical trials (CCT) were included. A total of four RCTs were included for data extraction. The risk of bias was deemed moderate to unclear. Meta-analysis was performed to assess the effect of L-PRF, on implant stability, immediately post-insertion in three studies, after one week from the implant placement in three studies and after four weeks for all the included studies. The fixed effects model has shown Hedges g statistic for the one week varying from 0.380 to 1.401 with a pooled figure of 0.764 (95% CI 0.443 to 1.085) and for four weeks varying between 0.74 and 1.1 with a combined effect of 0.888 (95% CI 0.598 to 1.177). The results for both intervals were in favour of the use of L-PRF while the statistical difference immediately post-insertion was not statistically significant. The present systematic review, though acknowledging its limitations, suggests that L-PRF has a positive effect on secondary implant stability and that needs to be correlated to the clinical practice to measure the actual clinical effect by means of reducing treatment times.

Effects of continual intermittent administration of parathyroid hormone on implant stability in the presence of osteoporosis: an in vivo study using resonance frequency analysis in a rabbit model

OBJECTIVE

This study aimed to evaluate the effects of continual intermittent administration of parathyroid hormone (PTH) on implant stability in the presence of osteoporosis, using rabbit models.

MATERIAL AND METHODS

Fifteen female New Zealand white rabbits underwent ovariectomy and were administered glucocorticoids to induce osteoporosis, following which they were divided into three groups. The first group received intermittent subcutaneous PTH for 4 weeks until implant placement (PTH1), while the second and third groups received PTH (PTH2) and saline (control), respectively, for 4 weeks before and after implant placement. After intermittent administration of PTH or saline, titanium implants were inserted into the left femoral epiphyses of all animals, and the implant stability quotient (ISQ) was measured immediately after placement to assess the primary stability and at 2 and 4 weeks after implant placement to assess osseointegration. At 4 weeks after implant placement, histological and histomorphometric evaluations were conducted and the bone area around the implant socket was measured as a ratio of the total bone area to the total tissue area.

RESULTS

Regarding primary stability, the ISQ values for the PTH1 and PTH2 groups were significantly higher than those for the control group (p<0.05). Concerning osseointegration, the ISQ values at 2 and 4 weeks were significantly higher for the PTH2 group than for the PTH1 and control (p<0.05) groups. Histological assessments showed a thicker and more trabecular bone around the implant sockets in the PTH2 specimens than in the PTH1 and control specimens. The bone area around the implant socket was significantly greater in the PTH2 group than in the PTH1 and control groups (p<0.05).

CONCLUSIONS

Our results suggest that continual intermittent PTH administration before and after dental implant placement is effective for the achievement of favorable stability and osseointegration in the presence of osteoporosis.

ISQ calculation evaluation of in vitro laser scanning vibrometry-captured resonance frequency

Background

Implant stability testing at various stages of implant therapy by means of resonance frequency analysis is extensively used. The overall measurement outcome is a function of the resulting stiffness of three entities: surrounding bone, bone-implant complex, and implant-Smartpeg complex. The influence of the latter on the overall measurement results is presently unknown. It can be investigated in vitro by use of imbedded implants with mounted Smartpegs. This enables to keep the influence of the two other entities constant and controlled.

The purpose of this study is to verify if a laboratory laser Doppler vibrometry technology-based procedure results in comparable ISQ results after calculation of captured resonance frequency spectra by aid of the Osstell algorithm with direct Osstell IDX device measurements.

Methods

A laboratory procedure was engineered to record frequency spectra of resin-imbedded test implants with mounted Smartpegs, after electromagnetic excitation with the Osstell IDX device and laser Doppler vibrometry response detection. Fast Fourier transformation data processing of resonance frequency data resulted in determination of a maximum resonance frequency values allowing calculation of implant stability quotient (ISQ) values using the Osstell algorithm.

Results

Laboratory-based ISQ values were compared to Osstell IDx device-generated ISQ values for Straumann tissue level, Ankylos, and 3i Certain implant systems. For both systems, a correlation coefficient r = 0.99 was found. Furthermore, a clinically rejectable mean difference of 0.09 ISQ units was noted between both datasets.

Conclusions

The proposed laboratory method with the application of the Osstell algorithm for ISQ calculation is appropriate for future studies to in vitro research aspects of resonance frequency analysis implant stability measurements.

Intermittent administration of parathyroid hormone enhances primary stability of dental implants in a bone-reduced rabbit model

The aim of the study was to investigate the effect of parathyroid hormone (PTH) on primary stability of dental implants in a bone-reduced model. Ten female New Zealand white rabbits underwent ovariectomy and were administered glucocorticoid to induce osteoporosis. One group was administered PTH intermittently by subcutaneous injection for 4 weeks (PTH-group) and the other group was given injections of saline for 4 weeks (Osteoporosis; OP-group). After the administration period, implants were inserted into the distal femoral epiphyses of each animal. At implant placement, insertion torque (IT) and implant stability quotient (ISQ) were measured. Histological examination revealed newly formed trabecular bone around the implant socket in the PTH-group but not in the OP-group. The trabecular bone structures in the PTH-group appeared thicker than those in the OP-group. In the PTH-group, the mean IT value was significantly greater than that in the OP-group (29.8 ± 6.2 Ncm and 10.0 ± 2.1 Ncm, respectively; P < 0.05). The ISQ value in the PTH-group was significantly higher than that in the OP-group (74.7 ± 11.2 and 55.9 ± 13.5, respectively; P < 0.05). Intermittent PTH administration could be an effective treatment for achieving favorable primary stability of dental implants in patients with osteoporosis. (J Oral Sci 58, 241-246, 2016).

Structural stability of posterior retainer design for resin-bonded prostheses: a 3D finite element study

The purpose of this in vitro study was to compare the stress distribution and natural frequency of different shape and thickness retainer designs for maxillary posterior resin-bonded prostheses using finite element (FE) method. A 3D FE model of a three unit posterior resin-bonded prosthesis analysis model was generated. Three different shaped retainer designs, viz. C-shaped (three axial surface wraparounds), D-shaped (three axial surface wraparounds with central groove) and O-shaped (360° wraparounds), and three different thicknesses, viz., 0.4, 0.8, and 1.2 mm, resin-bonded prostheses were used in this study. The resin-bonded prosthesis analysis model was imported into an FE analysis software (ANSYS 10.0, ANSYS, USA) and attribution of material properties. The nodes at the bottom surface of the roots were assigned fixed zero displacement in the three spatial dimensions. A simulated angle of 45° loading of a 100 N force was applied to the node of the pontic lingual cusp surface. The stress distributions and corresponding natural frequencies were analyzed and resolved. The C-shaped retainer for 0.4 mm thickness recorded the greatest von Mises stresses of 71.4 MPa for all three groups. C-shaped, D-shaped and O-shaped retainer presented natural frequencies 3,988, 7,754, and 10,494 Hz, respectively. D-shaped retainer and O-shaped retainer increased natural frequencies and structural rigidity over the traditional C-shaped retainer. The maximum von Mises stresses values of the remaining tooth and prosthesis decreased with greater retainer thickness. D-shaped retainer and O-shaped retainer increased natural frequencies and structural rigidity over the traditional C-shaped retainer.

Histological comparison of healing following tooth extraction with ridge preservation using enamel matrix derivatives versus Bio-Oss Collagen: a pilot study

The goal of the present clinical study was to evaluate new bone formation in human extraction sockets augmented with enamel matrix derivatives (EMD) and Bio-Oss Collagen. Patients with symmetrical single-rooted teeth in the bilateral quadrants of the upper jaw condemned for extraction participated in this study. Following extraction, the sockets (20 sockets) were randomly augmented using either EMD or Bio-Oss Collagen. After 3 months of healing, bone biopsies were obtained and prepared for histological analyses. Dental implants were then placed. Implant stability quotient (ISQ) readings were obtained for each implant at the time of surgery and at 1 and 3 months postoperatively. The mean new bone formation was 34.57 ± 25.67% in the EMD sites and 28.80 ± 16.14% in the Bio-Oss Collagen sites. There was no significant difference between the groups. The ISQ values were significantly higher for the implants placed in the EMD sites at the first and third months, but no significant differences were observed in the ISQ values for the implants placed in the Bio-Oss Collagen sites. The augmentation of the extraction sockets with EMD or Bio-Oss Collagen leads to similar behaviour in bone regeneration.

The correlation between crestal bone resorption and implant stability during healing period using resonance frequency analysis

PURPOSE

To detect the correlation between crestal bone resorption and implant stability during healing period using resonance frequency analysis (RFA).

MATERIALS AND METHODS

Twenty-two International Team for Implantology Straumann implants were placed in the posterior maxilla or mandible in 9 patients. RFA reading was taken immediately after implant placement. Periapical radiographs were taken, and the distance from the shoulder of the healing cap to the first bone-implant contact was measured, and the average mesial and distal distances were taken. Patients were followed up at 6 and 12 weeks for data collection.

RESULTS

At 6 weeks, the correlation between crestal bone resorption and implant stability was significant (Spearman correlation test, P < 0.05) and negative correlation coefficient (r) was -0.522. At 12 weeks, the correlation between crestal bone resorption and implant stability was not significant (Spearman correlation test, P > 0.05) and negative correlation coefficient (r) was -0.119.

CONCLUSIONS

There was a significant negative correlation between the crestal bone resorption and implant stability at 6 weeks, whereas the negative correlations between the crestal bone resorption and implant stability at 12 weeks were nonsignificant.

The influence of fixation in formalin on the measurement of stability of implants using resonance frequency analysis and Periotest M®: a study in a dog

Resonance frequency analysis (RFA) and Periotest® have been widely used to evaluate measurements of the stability of implants in clinical studies and animal experiments. In animals, these measurements are often made after bone has been fixed in formalin. However, it is not yet clear how this fixation influences RFA and Periotest®, and our aim was to clarify this using the implant stability quotient (ISQ) and Periotest® value (PTV). Six titanium implants were placed, 3 into each femur, of one male dog (a beagle/labrador cross). After 2 months blocks of bone were harvested, each block containing 3 implants, and were fixed in 10% neutral formalin. Measurements were made before fixation (time 0) then at 4h, and 1, 7, 14, 21, and 28 days. ISQ values of 6 implants were evaluated 3 times on the short and long axes, as were PTV. ISQ ranged from 67.5 to 79.3 and tended to increase with time. ISQ at 7-28 days were significantly higher than that at time 0. PTV ranged from -7.7 to -7.8 and did not differ significantly among fixation times. These results suggest that fixation of bony tissue in formalin might affect ISQ, so it might be preferable to measure ISQ during the early stages of fixation.

The role of primary stability for successful immediate loading of dental implants. A literature review

OBJECTIVES

To assess the role of primary stability for successful immediate loading (IL) of dental implants.

DATA

Original articles studying the role of primary stability for successful immediate loading of dental implants were included. The reference lists of potentially relevant review articles were also sought.

SOURCES

The MEDLINE-PubMed databases were searched for appropriate articles addressing the objectives of the present study. Databases were searched from 1979 up to and including April 2010. The search was performed using a variety of keywords in different combinations. Articles published only in English language were included. Letters to the Editor, historical reviews and unpublished articles were not sought.

CONCLUSIONS

There is a significant biological response by the hard and soft tissues to IL of dental implants. Within the limitations of the present literature review, it is evident that the core issue to observe during IL is the establishment of a good implant primary stability. There is sufficient evidence to suggest that the degree of achieved primary stability during IL protocols is dependent on several factors including bone density and quality, implant shape, design and surface characteristics and surgical technique. Further research is required in situations, such as poor bone quality and quantity and multiple implants or augmentation procedures, which may challenge the attainment of primary stability during IL.

A comparative study of two noninvasive techniques to evaluate implant stability: Periotest and Osstell Mentor

OBJECTIVES

The purpose of this study was to examine the usefulness of Periotest and Osstell Mentor (a resonance frequency analysis) as nondestructive analytical tools for determining implant stability in clinics, to evaluate the precision of both instruments, and to determine the applicability of these measured values as clinically relevant indices.

STUDY DESIGN

Four adult mongrel dogs weighing about 12 to 15 kg were used in this study. Bilateral extractions of the first through the fourth mandibular and maxillary premolars were performed and a total of 48 commercially pure titanium screw implants (USII Plus; OSTEM Implant, Seoul, Republic of Korea) were placed at 4 weeks after extraction. All implants (10 mm length and 3.3 mm diameter) were self-tapping and surface-treated with resorbable blast media (RBM). Periotest values (PTVs) obtained from Periotest, and Implant Stability Quotient (ISQ) obtained from Osstell Mentor, were measured at the time of implantation, and 3 and 6 weeks after implantation. At 3 and 6 weeks after implantation, 4 dogs were humanely killed and histomorphometric analysis was performed. The new peri-implant bone formation rate (NBFR) was measured.

RESULTS

The PTV value was lower and ISQ value was higher at 6 weeks when compared with data collected at 3 weeks after implantation. The PTVs of the maxilla were higher than the mandible and the ISQ values of the maxilla were lower than the mandible. Based on the NBFR, the 6-week group showed higher bone formation when compared to the 3-week group, correlating to the observed PTV and ISQ values. Additionally, the NBFR was higher in the maxilla than the mandible. No significant difference between PTV and ISQ was also observed when PTV and ISQ were compared to NBFR.

CONCLUSION

The results indicated that the Periotest and Osstell Mentor, both noninvasive diagnostic devices, were useful and comparably reliable, showing a strong association with each other in assessing implant stability.

A comparison of the implant stability among various implant systems: clinical study

PURPOSE

To determine the change in stability of single-stage, three different design of implant systems in humans utilizing resonance frequency analysis for early healing period (24 weeks), without loading.

MATERIAL AND METHODS

Twenty-five patients were included into this study. A total of 45 implants, three different design of implant systems (group A,C,R) were placed in the posterior maxilla or mandible. The specific transducer for each implant system was used. ISQ (implant stability quotient) reading were obtained for each implant at the time of surgery, 3, 6, 8, 10, 12, 24 weeks postoperatively. Data were analyzed for different implant type, bone type, healing time, anatomical locations.

RESULTS

For each implant system, a two-factor mixed-model ANOVA demonstrated that a significant effect on ISQ values (group A = 0.0022, C = 0.017, R = 0.0018). For each implant system, in a two-factor mixed model ANOVA, and two-sample t-test, the main effect of jaw position (P > .005) on ISQ values were not significant.

CONCLUSIONS

All the implant groups A, C and R, the change patterns of ISQ over time differed by bone type. Implant stability increased greatly between week 0 and week six and showed slow increase between week six and six months (plateau effect).

Clinical study on the primary stability of two dental implant systems with resonance frequency analysis

Primary stability has a major impact on the long-term success of dental implants. The aim of this study was to investigate the correlation of resonance frequency analysis (RFA) and insertion torque of self-tapping and non-self-tapping implants and their respective differences in primary stability. A group of 263 patients were treated with a total of 602 conically formed dental implants: 408 non-self-tapping Ankylos and 194 self-tapping Camlog. The maximum insertion torque during implant placement was recorded. Resonance frequency, measured as the implant stability quotient (ISQ), was assessed once immediately after insertion and twice 3 months later. Torque values of the non-self-tapping implants were significantly higher than those in the self-tapping group (p = 0.023). RFA did not show differences between the 2 groups (p = 0.956), but a correlation between ISQ values after implantation and 3 months after implant placement was measured (r = 0.712). Within the implant systems, no correlation between insertion torque and resonance frequency values could be determined (r = 0.305). Our study indicates that the ISQ values obtained from different implant systems are not comparable. The RFA does not appear suitable for the evaluation of implant stability when used as a single method. Higher insertion torque of the non-self-tapping implants appeared to confirm higher clinical primary stability.

Natural Frequency Analysis of Osseointegration for Trans-femoral Implant

Osseointegration trans-femoral implants are a new orthopaedic anchoring method to attach prosthetic limbs. The clinical success of this promising technique depends on the effectiveness of osseointegration achieved after implantation. The aim of this study is to use the resonant characteristics of the implant system to determine the changes in stability as a reflection of boundary condition of the implant. With a small mechanical excitation, Vibration responses of the trans-femoral implant to a small mechanical excitation were measured using an accelerometer and the vibration signal was analyzed using Fast Fourier Transform (FFT) software to obtain the fundamental natural frequency (NF) of the implant system. In-vitro study was conducted using different silicone rubbers to simulate the interface condition. The result showed that a high NF corresponded to a high elastic modulus of the interface material between the implant and bone. A preliminary in-vivo study with one osseointegration trans-femoral implant patient showed that there was a decrease of NF after initial weight bearing rehabilitation. After continued weight bearing, the NF gradually returned to the pre-loading level at around day 24 and the general trend of the NF reached a stable state 38 days after the first weight bearing exercise.

Influence of Transducer Orientation on OsstellTMStability Measurements of Osseointegrated Implants

BACKGROUND

Resonance frequency (RF) analysis is frequently used to monitor implant stability in patients. The influence of transducer orientation on RF of implants placed in jawbone has not been evaluated.

PURPOSE

The aim of this study was to evaluate to what extent transducer orientation influences RF. The second aim was to evaluate if measurements taken with any particular orientation would best relate to marginal bone levels.

MATERIALS AND METHODS

Nine patients edentulous in the upper jaw received 55 implants 3 years before this study. They underwent clinical and radiographic evaluation. Using Osstell (Integration Diagnostics AB, Göteborg, Sweden), four RF measurements were made for each implant. Measurements were obtained with the transducer cantilever placed buccally (B), distally (D), palatally (P), and mesially (M).

RESULTS

All implants were clinically stable. Significant differences resulted between the measurements perpendicular to the bony crest (B, P) and the parallel ones (M, D). A tendency of negative correlation was found between marginal bone levels and implant stability quotient (ISQ) measurements; however, this correlation was not statistically significant.

CONCLUSIONS

In conclusion, when measuring the RF of dental implants using the Osstell, it has to be taken into account that the transducer orientation influences the measurement. It seems therefore advisable to standardize the orientation. Moreover, although there was a tendency, any statistical significant correlation between ISQ values and marginal bone levels could not be established.

Pilot Study in the Identification of Stability Values for Determining Immediate and Early Loading of Implants

This pilot study assessed the impact of implant stability criteria on implant loading time. Insertion torque (IT) and baseline implant stability quotients (ISQ) from resonance frequency analysis were recorded for 41 tapered-screw implants placed in the mandibles of 20 patients. Immediate (IL), early (EL) (6 weeks postoperative), or delayed (DL) (12 weeks postoperative) prosthetic loading was performed based on results and study criteria. Postoperative ISQ values were also recorded at 6 time intervals for the IL and EL groups and after healing for the DL group. All implants were definitively restored after 6 weeks of provisionalization. There were no failures, complications, or stability differences based on loading time. At week 12 of follow-up, ISQ values were slightly higher for IL implants compared with EL implants. IL and EL implants showed significantly higher cumulative ISQ values compared with DL implants. High IT and baseline ISQ values in all groups corresponded to high implant survival. Postoperative ISQ values in the IL and EL groups were less certain indicators of implant survival because of fluctuations relative to baseline values. Small sample size and inequitable patient distribution across groups skewed results. More research is needed before definitive results can be drawn. IL and EL were safely performed within the IT and ISQ ranges in this study, but it is unknown whether EL criteria would have also sufficed for IL.

Resonance frequency measurements of implant stability in the dog mandible: experimental comparison with histomorphometric data

The aim of the present study was to test the hypothesis that measurements of implant stability using resonance frequency analysis (RFA) correlate with histomorphometric data of bone anchorage. Ten adult female foxhounds received a total of 80 implants in their mandibles 3 months after removal of all premolar teeth. At the time of implant placement, torque required for bone tapping was registered as a measure of bone density and immediately after placement implant stability was assessed using RFA. RFA measurements were repeated at the time of implant retrieval after 1 month (5 dogs) and 3 months (5 dogs). Peri-implant bone regeneration was assessed histomorphometrically by measuring bone-implant contact (BIC) and the volume density of the newly formed peri-implant bone (BVD). RFA values at the time of implant placement did not correlate with the torque required to tap the bone for implant placement. After 1 and 3 months, RFA values were significantly increased compared with baseline values. BIC and BVD, however, had increased significantly during this interval. There was no correlation between bone-implant contact and RFA values nor between peri-implant bone density and RFA values. Thus, the hypothesis could not be verified. It is concluded that the validity of the individual measurement of implant stability using RFA should be considered with caution.

A numerical approach to resonance frequency analysis for the investigation of oral implant osseointegration

Experimental devices based on vibration testing are employed as non-destructive procedures for evaluating implants osseointegration. Their behaviour was evaluated considering the outcome of numerical analysis. The purpose was to use the finite element method for assessing the ability of frequency analysis in detecting the degree of oral implant osseointegration. A three-dimensional model of a mandible was obtained from tomographic survey. A single implant was considered in canine region. Two configurations were analysed, with and without a mass linked to the implant as a cantilever, reproducing experimental devices. Simulation consisted of analysing the response to impulse forces for different osseointegration levels, thus evaluating the biomechanical efficiency of the implant-bone compound. A good correlation between frequency response and osseointegration level was obtained. This was carried out by providing an impulse excitation of the implant that resulted in a vibration pattern. Within the limit of finite element analysis, the outcomes showed that numerical investigation provides understanding the behaviour of testing devices based on frequency measurements, confirming the potential of vibrations technique as non-invasive analysis for osseointegration process.

Resonance frequency analysis of one-stage dental implant stability during the osseointegration period

BACKGROUND

Currently, there is no available clinical tool to evaluate the amount of osseointegration and stability around dental implants. It has been recently suggested that changes in the stiffness of an implant in bone during healing may be monitored by using resonance frequency analysis (RFA). The aim of this study was to determine whether RFA can be integrated into the routine clinical evaluation of initial healing of dental implants.

METHODS

Thirty-one patients (18 female and 13 male; mean age of 51.7 years) were included into this study. A total of 122 implants and three different, but comparable, implant designs were evaluated by using RFA. The specific transducer for each implant system was used. ISQ (implant stability quotient) readings were obtained for each implant at the time of surgery, 3 and 6 weeks postoperatively, and at the time of loading (3 or 6 months following surgery). Data were analyzed for different healing times, various anatomical locations, implant length, and type. Average time in function was 12 months.

RESULTS

Two implants failed during healing. Implant stability was higher on the mandible compared to the maxilla for each implant system studied (Mann-Whitney test, P <0.01). ISQ readings decreased significantly at 3 and 6 weeks post-surgery compared to readings obtained at surgery (Wilcoxon matched pairs sign-rank tests, P <0.01). A recovery to the initial ISQ levels was noted at the time of implant loading. The possible effects of different types and lengths of implants to ISQ readings were examined.

CONCLUSIONS

Results of this study support the need for a clinical tool to evaluate dental implant stability prior to loading, especially for implants placed in the maxilla. It appears that implant stability is weakest at 3 to 6 weeks in one-stage non-loaded dental implants. ISQ readings can be used to determine different healing phases and the stability of dental implants. However, it is difficult to define a general standardized range of ISQ readings for successful implant integration for various implant systems. Thus, RFA values/ISQ levels should be calibrated for each implant system separately. Further studies are needed to compare the early changes seen in immediately loaded dental implants and to determine whether there is any time in which the total recovery in ISQ levels may occur.