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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 7  |  Issue : 2  |  Page : 122-129

Assessment of primary stability of immediate implants placed in the maxillary and mandibular anterior region using resonance frequency analysis


1 Division of Prosthodontics, ADC R and R, New Delhi, India
2 Division of Prosthodontics, Military Dental Centre, Pune, Maharashtra, India

Date of Submission12-Aug-2018
Date of Decision27-Sep-2019
Date of Acceptance10-Oct-2019
Date of Web Publication8-Oct-2020

Correspondence Address:
Kamal Verma
Division of Prosthodontics, Military Dental Centre (East), Kirkee, Pune, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/cjhr.cjhr_87_19

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  Abstract 


Background: A matter of controversy in implant dentistry concerns the most appropriate method to determine implant stability. Many methods have been reported in the literature including periotest and resonance frequency analysis (RFA). However, there is no consensus regarding the ideal method to determine implant stability. Materials and Methods: A total of 50 patients male and female in the age group of 18–38 years, each having at least one tooth indicated for extraction (either maxillary or mandibular anterior teeth) were selected. Fifty Xive implants (Friadent, Dentsply, Germany) were placed into fresh extraction sockets and immediately loaded. Implants were evaluated by clinical and radiographic methods. Implant stability was measured using periotest and RFA at the time of implant placement, 3 months, 6 months, 9 months, and 12 months postoperatively. Results: The mean mobility values for periotest decreased over a period of observation, and all implants consistently produced readings between −8 and + 7. The RFA values during the period of observation increased, and it was in the range of 49–100. Statistical analysis using regression analysis showed that percentage improvements in stability during each period were statistically highly significant in respect of periotest and RFA (P = 0.0001). Conclusions: A clinical trend of an implant stability quotient (ISQ) of more than 49 with a range of 49–98, is probably descriptive of osseointegrated implants. However, according to our experience, implants with a primary stability above 50 ISQ may be sufficient for successful immediate loading while implants below 40 could be dealt with caution and conventional loading can be considered in such cases.

Keywords: Immediate loading, periotest, resonance frequency analyzer


How to cite this article:
Viswambaran M, Verma K. Assessment of primary stability of immediate implants placed in the maxillary and mandibular anterior region using resonance frequency analysis. CHRISMED J Health Res 2020;7:122-9

How to cite this URL:
Viswambaran M, Verma K. Assessment of primary stability of immediate implants placed in the maxillary and mandibular anterior region using resonance frequency analysis. CHRISMED J Health Res [serial online] 2020 [cited 2020 Oct 24];7:122-9. Available from: https://www.cjhr.org/text.asp?2020/7/2/122/297584




  Introduction Top


Dental implants are the most preferred treatment option nowadays for the management of partially and completely edentulous arches. The success of dental implants depends on a number of factors: proper case selection, precise clinical and laboratory protocols, occlusal factors, and postoperative oral hygiene maintenance. Among all these factors prosthetic loading and the kind of occlusal scheme plays a crucial role in a long-term prognosis of implants. Prosthetic loading is done based on the initial implant stability. The different prosthetic loading protocols suggested by the scientific community include immediate, early, and delayed protocols. Immediate loading is possible in patients with high bone density and adequate primary stability. Long-term prognosis of the implant is also dependent on the implant stability. It is a proven fact that extreme micromotion during the initial reparative period following surgical insertion of implants will result in loss of osseointegration.[1],[2] If the implant is not stable during surgical placement, it is better to go ahead with conventional loading. Otherwise, excessive micromotion due to lack of primary stability can result in fibrous integration between implant and adjoining bone. Therefore, success of immediate loading to a larger extent depends on primary stability and the clinicians worldwide acknowledge the significance of stability for osseointegration.[3]

The evaluation of implant stability remained a challenge for clinicians since there was no definitive predictable method with adequate scientific evidence for a long time. There are different methods explained by different authors with conflicting results creating confusion in the minds of operator. Histologic analysis, electron microscopic evaluation, radiographic methods, tapping the implant with a metallic instrument and evaluating the resultant sound, pull and push through tests, periotest instrument, rotational stiffness formed on impact, and reverse torque application.[4],[5],[6] None of these techniques are false proof, and there are a number of issues to be addressed. Among the different methods described, Periotest (Medizintechnik Gulden, Germany) and Osstell Mentor (Osstell, Integration Diagnostics, Savadaled, Sweden) are highly popular. Periotest values (PTVs) and implant stability quotient (ISQ) values give us an indication of primary and secondary stability. However, these two equipment differ in design and working principles. Therefore, there is a need to study the association between PTVs and ISQ values and also to determine what values are considered safe in terms of stability for taking a decision on immediate loading. Earlier studies using resonance frequency analysis (RFA) have described resonance frequency in Hertz as a factor to define implant stability.[6],[7] Nevertheless, there is a lacuna in the available scientific information regarding ISQ values that reflects adequate primary stability, especially for immediate loading. Therefore, the study was carried out to assess the roles of periotest and RFA in determining the stability of dental implants and the value of these methods in predicting implants that are at risk to fail.


  Materials and Methods Top


A total of 50 patients both male and female in the age group of 18–38 years, each having at least single tooth designated for extraction (either maxillary or mandibular anterior teeth) were carefully chosen based on a strict inclusion criteria. The selection was based on the following criteria – the American Society of Anesthesiologists classification P1 (normal and healthy) patients, presence of a single failing tooth with intact adjacent dentition, sufficient bone availability apical to the extraction site for stabilization, and sufficient bone in terms of quantity and quality on all sides to accommodate an implant of appropriate dimension. Standard surgical protocols and prosthodontic protocols were followed by a single operator after obtaining written informed consent from the patient and completing preoperative investigations. Routine investigations, including cone-beam computed tomography, were done for treatment planning. The surgical procedures were carried out under local anesthesia (lignocaine 20 mg/ml with adrenaline 1:80,000) with proper asepsis. Fifty root form implants (Xive Implant System, Friadent Dentsply, Mannheim, Germany) were surgically placed after atraumatic extraction and immediately loaded with acrylic provisionals. Ten patients were excluded from the study due to the lack of primary stability, and they were rehabilitated in the conventional manner. After placement, all implants were evaluated at baseline, 1 month, 3 months, 6 months, 9 months, and 12 months. The soft-tissue response was assessed with modified plaque index, gingival index (GI), and probing depth analysis. Radiographic evaluation was carried out using intraoral periapical radiographs. Radiographs were standardized by means of the long cone paralleling technique. The digital analysis was done with Corel DRAW™-11 software (Corel corporation, Canada) [Figure 1]. After enlarging the image to actual implant dimensions, the bone level was measured from the crestal bone level to the implant crest module at proximal surfaces.
Figure 1: Radiographic analysis of crestal bone level

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The periotest (Periotest S 3218, Medizintechnik Gulden) was used for the measurement of implant stability and degree of osseointegration [Figure 2]. In addition to periotest, implant stability measurements were also performed by use of RFA. The analysis of RFA was made using an Osstell Mentor apparatus (Osstell, Integration Diagnostics, Savadaled, Sweden) [Figure 2]. After the attachment of smart peg, the measurement was started in the mesiodistal direction (along the jaw-line) followed by buccolingual direction (perpendicular to the jaw-line). Each measurement was repeated four times, and the average value was taken. After each measurement, the ISQ values were recorded and used as the baseline for the next measurement performed. Following standard surgical procedure, immediate loading was done with acrylic provisional [Figure 3] after ensuring primary stability. It was ensured that minimum insertion torque was 15 N-cm and ISQ value was not <50. Definitive Porcelain fused to metal (PFM) restorations were cemented after 6 months.
Figure 2: Periotest and resonance frequency analyzer

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Figure 3: Immediate implant placement and loading

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  Results Top


The evaluation of the following parameters was carried out at baseline, 1 month, 3 months, 6 months, 9 months, and 12 months. The evaluation of the following parameters was carried out at baseline, 1 month, 3 months, 6 months, 9 months, and 12 months: plaque index, GI, probing depth, crestal bone level, and assessment of implant stability using RFA and periotest. The probing depth was evaluated only at 6, 9, and 12 months. For analysis, we have used the Statistical Software MINITAB1513 (IBM software, Armonk, New York). We have used regression analysis, single sample t-test, paired t-test, and two-way analysis of variance test with generalized linear model wherever applicable.

Regression analysis of plaque index with respect to full mouth as well as the implant site has shown that rate of decrease in the plaque index in both cases were statistically significant (b = −0.0001528, F = 7.4703, P = 0.007 and b = −0.0003291, F = 39.1667, P = 0.0001, respectively). However, the rate of decrease is much higher in case of the implant site. The analysis of GI has been carried using the same statistical tests as in the case of the plaque index. Results of regression analysis have shown that rate of change in GI in respect of full mouth is not significant (b = 0.0000813, F = 1.26616, P = 0.262) whereas rate of change with respect to implant site is statistically significant (b = 0.0001666, F = 8.37709, P = 0.004). The evaluation of mean probing depth over different periods has shown that the changes were the same for lingual and distal surfaces. Differences of mean pocket depth between all remaining pairs of sites were statistically significant, distal = lingual <Buccal <Mesial.

During the analysis of crestal bone level, we have documented the significance of % decrease in crestal bone levels at mesial and distal sites during different periods as well as the total change after 12 months [Table 1]. The decrease is statistically highly significant for both sites for all periods (P = 0.0001 in all cases). Periotest evaluation has shown that the data generally remained negative indicating good stability [Table 2]. Results of RFA evaluation is shown in [Table 3]. The ISQ values ranged between 49.6 and 104 reflecting acceptable stability for immediate loading.
Table 1: Analysis of crestal bone level: Different periods and overall (mesial, distal)

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Table 2: Periotest values

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Table 3: Resonance frequency analysis values

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The results of testing the significance of percent changes in perio and RFA values (using one-sample t-test) during different periods as well as total change is reflected in [Table 4]. Percentage improvements during each period are statistically highly significant in respect of periotest and RFA (P = 0.0001 in each case). For these characters also, we have fitted regression of perio as well as RFA values with time (month) to see the significance of the rate of improvement in stability. The regression between RFA and perio values has also been studied to test the predictive capability of one on the other along with Pearson's coefficient of correlation between perio and RFA values [Figure 4]. Regression plot signified improvement in stability over time (P = 0.0001) with respect to both periotest and RFA. The regression plot also showed that each can be used as a predictor for the other (P = 0.0001). The correlation (−0.601) between these two was also statistically significant (P = 0.0001) as expected.
Table 4: Percentage changes: Different periods and overall (Periotest and resonance frequency analysis)

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Figure 4: Regression plot resonance frequency analysis versus periotest values

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  Discussion Top


The introduction of osseointegrated implants signifies a defining moment in the history of dental sciences. Immediate implant placement and loading have been a widely accepted treatment protocol among dental surgeons due to the quick results and better patient acceptance. The decision regarding extraction and immediate placement of the implant should be made only after there is absolute assurance of primary stability. Bone loss does occur after tooth extraction, and the remaining amount of bone is crucial for subsequent rehabilitation with dental implants. Bone resorption happens both buccolingually and apicocoronally. The highest rate of resorption occurs in the first 6 months' postextraction. The placement of implants immediately after extraction may reduce the amount of bone loss.[8],[9],[10]

Standard textbooks and available literature describe three types of protocols for implant loading. These are delayed, early and immediate loading. The delayed occlusal loading protocol means loading of implant with prosthesis 3–6 months after surgical placement depending on the site, i.e., mandible or maxilla. In early occlusal loading, the implant is subjected to prosthetic loading/occlusion between 2 weeks' and 3 months' postsurgery. In immediate occlusal loading, the implant is placed under occlusal loading within 72 h after surgical placement.[11],[12] There is wide acceptance for immediate loading nowadays due to various advantages compared to conventional or delayed loading. From a patient perspective, there is reduction in treatment time which enhances the psychological comfort, immediate esthetic rehabilitation, and function.[13],[14] Implant stability is an vital element to be considered before prosthetic loading for long-term success. This includes both primary and secondary stabilities. During initial implant placement, sufficient primary stability is mandatory to permit undisturbed bone healing. Secondary stability achieved through osseointegration allows optimal distribution of functional loads through the bone-implant interface. A poor primary stability can lead to implant failure.[15] It is an established fact that a micromovement between 50 and 150 μm during the initial healing period post insertion of implants will lead to fibrous integration and subsequent bone resorption.[16],[17] Immediate loading is an established and highly successful protocol, as evidenced by various authors, and they explained high primary stability as one of the prime requisites for immediate loading.[18],[19],[20],[21],[22]

The different methods used to evaluate implant stability are tapping method,[23] radiography, cutting torque resistance analysis, percussion test, and impact hammer method.[23] However, none of these methods were false proof. Therefore, a more reliable measure of implant stability was required, and this was resolved by an innovative technique called RFA. Nondestructive vibration analysis has been widely used in manufacturing and engineering technologies to detect the presence of internal flaws in composite materials.[24] In 1994, Meredith introduced in the field of implant dentistry a vibratory nondestructive testing method: Resonance frequency.[25] Since 1999, this method of analysis has been commercially available as the Osstell™ equipment (Integration Diagnostics, Goteborg, Sweden). This method has no adverse effect on the implant since there is actual contact required. The smart-peg measures the resonance frequency values as ISQ from 1 to 100. If the displayed value is <45 that indicate the implant is failing during the subsequent phase or there is no primary stability during immediate placement. ISQ assessment of around 60–70 indicates that there is enough stability during primary phase and satisfactory osseointegration during subsequent period.

Although RFA is being extensively used for evaluation of implant stability, information is lacking in the following areas: (i) available evidence did not reflect the what is the ideal ISQ value at the time of implant placement and subsequent periods in case of immediate loading to predict implant success, (ii) most of the conclusions and recommendations are based onin vitro studies that are difficult to apply inin vivo clinical settings, (iii) it is also imprudent to describe average range of ISQ readings for osseointegrated implants of different manufacturers, and (iv) from the available scientific information, it is clear that many of the studies related to RF focused on the Branemark or ITI systems. Hence, it is difficult to apply the same standards to other popular systems such as Xive. There is also confusion regarding the most appropriate method to determine implant stability. Many methods have been reported in the literature, including periotest and RFA.[7],[25],[26],[27] Since the existing literature is sparse in this field, and there is no clear cut guidelines to give any insight as to whether such gadgets can accurately determine stable functioning dental implants, the present study was carried out to assess the success of immediate implants in fresh extraction sites and to compare two methods of evaluation of implant stability, i.e., RFA and periotest.

The results of soft-tissue evaluation, the mean plaque index for full mouth and implant decreased from baseline to 1 month, 3 months, 6 months, 9 months, and 12 months. The rate of decrease in the plaque index in both cases was statistically significant (b = −0.0001528, F = 7.4703, P = 0.007 and b = −0.0003291, F = 39.1667, P = 0.0001, respectively). The reductions in plaque indices were similar for both implant and full mouth in both groups. This is in resemblance to earlier studies where there have been reductions in the plaque indices.[19],[28] with reference to GI, the mean gingival indices have shown increase with intermittent fluctuations. This could be due to change in the pattern of oral hygiene maintenance over a period of time. The same was observed in other studies.[29]

Mean values for probing depth for 3 months differed significantly from 9 months to 12 months (t = 2.582, P = 0.0266 and t = 4.700, P = 0.00001, respectively). On an average probing depth values were increasing. However, this does not indicate an inflammatory phase, and similar findings were reported in other studies too.[28]

In the present study, since the implant is placed into extraction socket, there will be bone gain during the initial phase. Crestal resorption does occur concurrently with the remodeling of the socket. Therefore, crestal bone level changes are described rather than resorption. There are time-dependent marginal bone level changes around implants after immediate loading. There was significant percentage decrease in crestal bone levels at mesial and distal sites during different periods [Table 1]. Decrease is statistically highly significant for both sites for all periods (P = 0.0001 in all cases). These changes are due to the bone remodeling that occurs after extraction and is concomitant with other studies.[30],[31]

The mean mobility values for periotest decreased over a period of observation. In the present study, all implants consistently produced readings between −8 and +7 (average − 2.25) from baseline to 9 months [Table 2]. Similar findings were reported by other researchers.[4],[6]

The ISQ values varied with different studies and are quite confusing. Al-Nawas et al. were of the opinion that an ISQ threshold value of 65.5 at implant placement, the chances of implant failure is more.[32] Others have shown ISQ value falling within the wide range of 57 and 74 are acceptable.[9],[12],[18] However, there is no consensus regarding what is normal and acceptable, especially in cases of immediate loading. The decision to immediately load in this study was based on the initial stability values over 50, and this is acceptable, as evidenced by our success rates. As shown in [Table 3], it is evident that for all the 40 implants the baseline RFA values were above 50 except case no 28 where it is 49. The values during the period of observation increased (mean value of 78), and it was in the range of 49–100. In our study also, we found that RFA values were more or less stable during repeated measurements indicating implant stability and RFA proved to be a very effective tool for evaluation of implant stability. The increase in stability values during the period of observation is attributed the bone healing process and successful osseointegration. The stability values were higher for mandible compared to maxilla because of differences in bone density. The same was observed by other researchers.[33] We were not able to find any correlation between ISQ values and bone levels. The crestal bone changes seen were within normal limits and were part of the bone remodeling process. According to some of the previous studies, a negative correlation existed between ISQ and bone levels.[34]

Periotest and Osstell Mentor are the classic methods to assess the stability of implant. These tools gauge implant stability during surgical placement, the status of osseointegration during a subsequent phase, and the survival of the implant prosthesis after prosthetic loading. The design and manufacturers recommendations for both the tools are different; and therefore, the interpretation of the observed results is also different. Therefore, one of the primes of the objective of this study was to find out any association between periotest and ISQ values. During the analysis of data, it was found that the mandible displayed higher ISQ and a lower PTV in comparison to the maxilla. The quality and quantity of bone do affect the readings. The mandible is dense and more compact compared to maxilla. Statistical analysis using regression analysis showed that percentage improvements in stability during each period were statistically highly significant in respect of periotest as well as RFA (P = 0.0001 in each case) [Figure 4]. For these characters also, we have fitted regression of perio and RFA values with time (month) to see the significance of the rate of improvement in stability. Regression between RFA and PTVs has also been studied to test the predictive capability of one on the other along with the Pearson's coefficient of correlation between periotest and RFA values. There was definitive improvement in stability values over a period of time for both the tools and a visible association between them. Many studies have indicated the presence of an association between PTVs and ISQ.[35],[36] From clinical and research data, it is quite evident that both periotest and RFA can be successfully employed to predict stability.[35],[36] As independent tests are not reliable, a combination of different methods should be employed. Among the various methods described, periotest and RFA seem to be the ideal choice and can be effectively combined to evaluate the stability. From our results, it is evident that there is a strong relationship between PTVs and ISQ values of Osstell Mentor. Moreover, both methods provide an association with the degree of osseointegration. However, some of the limitations of this study include the small sample size and brief evaluation period. More multicenter studies with larger sample size need to be taken to substantiate the results.

The technique is highly beneficial during implant placement to verify the degree of primary stability existing and then take a call accordingly to load implants immediately or not. If there is questionable primary stability, it is better to load the implants in a conventional manner. The evaluation of stability is equally important in the postsurgical phase. A decrease in resonance frequency during function is indicative of failure of osseointegration. This is a warning signal to the clinician that the implants are failing and there is a need to do some rescue procedure. In conclusion, both periotest and RFA technologies are reliable in terms of the measurement of implant stability. The timing of loading is entirely dependent on the clinician based on a number of factors. A combination of methods should be used for the evaluation of primary implant stability rather than depending on a single tool.


  Conclusions Top


A fundamental prerequisite for implant success is substantial primary stability at the time of insertion and following loading of the implant. Clinical and basic research indicates that dental implant stability at the time of surgery is important for therapeutic success. Within the limits of the current study, the following conclusions were drawn:

  1. A single test may not fully reflect the nature of the bone-implant anchorage. In fact, periotest and RFA may play different roles and provide information at different levels. Osstell and PeriotestR systems proved to be sensitive in measuring dental implant stability
  2. Immediate provisional restorations can be done using even minimal quantitative criteria with implants placed at relatively low torque (minimum 15 N-cm insertion torque) and ISQ values (minimum 50 ISQ)
  3. ISQs, PTVs, periapical radiographs, and clinical recordings suggested peri-implant bone formation, satisfactory esthetics and functional efficiency with the survival rate of 100% for all implants
  4. Implants exhibited a range of 49–98 ISQ with a mean value of 64.50 ISQ at baseline and 88 ISQ after 1 year of loading. All the implants were asymptomatic and functionally stable during the 1 year follow-up without significant changes in resonance frequency. These findings represent the range of stability for integrated Xive implants
  5. A clinical trend of an ISQ of more than 49 with a range of 49–98, is probably descriptive of osseointegrated implants. However, according to our experience, implants with a primary stability above 50 ISQ may be sufficient for successful immediate loading while implants below 40 could be dealt with caution and conventional loading can be considered in such cases.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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Lachmann S, Laval JY, Jäger B, Axmann D, Gomez-Roman G, Groten M. Resonance frequency analysis and damping capacity assessment. Part 2: Peri-implant bone loss follow-up. Anin vitro study with the periotest and osstell instruments. Clin Oral Implants Res 2006;17:80-4.  Back to cited text no. 36
    


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