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 Table of Contents  
Year : 2021  |  Volume : 13  |  Issue : 2  |  Page : 141-145

Axis of success: Primary and secondary stability of implant

1 Department of Oral Health Sciences, Zonal Hospital, Mandi, Himachal Pradesh, India
2 Department of Prosthodontics, Himachal Dental College, Sundernagar, Mandi, Himachal Pradesh, India
3 918-A Surya Enclave, Jalandhar, Punjab, India
4 Department of Himachal Dental College, Sundernagar, Mandi, Himachal Pradesh, India
5 Department of Dentistry, Universida Catolica San Antonio, (UCAM), Murcia, Spain

Date of Submission28-Jul-2020
Date of Decision21-Sep-2020
Date of Acceptance10-Oct-2020
Date of Web Publication22-Mar-2021

Correspondence Address:
Nitin Sharma
House No. 198/11, Tarna Road, Mandi, Himachal Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/IJDS.IJDS_118_20

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Primary and secondary stability mainly proceed along with mechanical phenomenon of implant engagement within the surrounding bone. Primary stability is an important element in attainment of secondary implant stability. Measuring stability of an implant helps dentist/operator about decision and timing of loading an implant. Primary and secondary implant stability is defined and discussed thoroughly. The factors affecting implant stability are classified and detailed in the simple manner in this review article. Till present time, no particular method has been established to evaluate the implant stability. Although resonance frequency analysis method evaluates stability of implants with the results outcome dependent on the sound theory, it surely cannot assure the success and failure or even long-term results of the dental implants.

Keywords: Bone, dental implant, implant stability, primary stability, resonance frequency analysis, secondary-stability

How to cite this article:
Sharma N, Nagpal A, Kundal A, Singla A, Jindal V. Axis of success: Primary and secondary stability of implant. Indian J Dent Sci 2021;13:141-5

How to cite this URL:
Sharma N, Nagpal A, Kundal A, Singla A, Jindal V. Axis of success: Primary and secondary stability of implant. Indian J Dent Sci [serial online] 2021 [cited 2021 Apr 20];13:141-5. Available from: http://www.ijds.in/text.asp?2021/13/2/141/311675

  Introduction Top

Osseointegration originated as a concept from the innovation of Per-Ingvar Branemark (1969) professor at Applied Biotechnonology, University of Gothenburg.[1]

Osseointegration is a term coined first by Branemark (1985) “immediately effective and organized communication within the vital bone and its outer surface – enveloping implant.”[1],[2],[3]

There is a marked conception that the inceptive stability of an implant and its osseointegration process include histological analysis and microscopically evaluating samples examined from bone and implant junction and removal torque test.[4],[5]

Osseointegration can also be evaluated from the stability of an implant, which eventuates at two variant stages: “Implant Primary and Secondary stability mainly proceed along with mechanical phenomenon of implant engagement within the surrounding bone. The biological implant stability results from secondary implant stability by virtue of bone remodeling phenomenon. Primary stability is an important element in achievement of secondary implant stability. The secondary stability indicates the time at which the functional loading can be successfully performed.”[3],[6],[7]

The implants' stability is affected by various elements, as follows:

Primary stability – It is influenced due to parameters like the presence of residual bone quality and bone quantity, surgical modalities, implant specifications, for example, implant geometry, length, radius, and outer surface features.[3],[8],[9]

Secondary implant stability is affected with these factors – implants primary stability, remodeling of bone, and condition of the dental implant surface.[6],[9]

The measurement of stability of implant helps dentist/operator about decision and timing of loading, permits to choose favorable protocol based on patient to patient, reveals the condition which is best for unloading, and maintains good dentist–patient communication and better case substantiation.[10]

The different modalities used for assessing dental implant stability are:

  1. The clinician's perception
  2. Percussion method
  3. Cutting resistance analysis (CRA)
  4. Reverse torque method
  5. Resonance frequency analysis (RFA)
  6. Periotest modality.[6],[7],[11]

The researches published by different authors were searched using Google Scholar and the Science Direct.com for relevant existing studies addressing determined questions. The databases subsequently were explored chronologically from 2003 till June 2020 utilizing the subsequent phrases along with various compositions: “bone,” “dental,” “immediate-loading,” “implant diameter,” “implant-length,” “quotient of implant stability,” “osseointegration,” “primary stability,” “secondary-stability,” and “RFA.”

The eligibility benchmarks were established on the human and exploratory reviews, utilization of control group articles issued only in English with citation index comprised probably linked authentic studies along with review articles of different authors.

The other step performed by us included handsearch the citation list including all the previous associated studies those were established to be applicable in the previous step. After concluding, selection of articles which satisfy selection criteria were sorted out for consideration and processed for extraction specifications. The present review article was structured to customize the summary of the relevant information regarding the concerned topic.

  Discussion Top


It is termed as biometrically achieved stability subsequently after dental implant insertion and is directly related to the outcome of mechanically associated dental implant with the surrounding bone.[6] It hampers the emergence of connective tissue coating intermediating implant and surrounding bone, accordingly certifying the bone healing.[3],[12]

Secondary stability

It is defined as that implant stability which provides biological stability of implant through the phenomenon of residual bone regeneration and bone remodeling following completion of healing period which further results in the achievement of implant stability due to newer bone generation around the dental implant, constituting biological fixation of the implant.[12],[13] The secondary stability was found to rise at 4 weeks after dental implant insertion.[12]

Factors effecting primary stability of the dental implants

Atsumi et al.[6] suggested subsequent elements affecting implant primary stability:

  1. Quantity and quality of residual bone
  2. Surgeons approach, comprising expertise and capability of operator
  3. Dental implant features, i.e., geometry of dental implant, dimensions including diameter and length, and outer surface quality.[3],[6],[14]

Factors influencing secondary stability of the dental implants

  1. Primary implant stability
  2. Modeling and remodeling of residual bone
  3. Surface features of implant.[6]

Density and quality of residual bone

Implant primary stability recognized to be positively correlated to the cortical thickness of artificial bone.[3] The residual bone quality depends on the quantity of cancellous and cortical residual bone where osteotomy is performed.[14] The poor quality as well as quantity of residual bone included as a major risk factor for a dental implant to fail due to massive bone resorption and delaying of the bone healing.[8] All the implants that were failed to satisfy the implant success benchmarks were included into the category of implant failure.[13]

Surgical technique

The drilling process followed at the implant placement site, implant macrogeometry, and condition of residual bone at the implant insertion position determines the accomplishment of primary implant stability.[3] The damage due to thermal and mechanical changes of the tissue surrounding dental implant during insertion results in damaging effects on commencing situation of the cavity holding the dental implant.[8]

Implant surface characteristics

The dental implant stability is effected by interplay within the implant design and insertion torque during dental implant placement.[15] Bone-to-implant contact is a major element primary implant stability; therefore, elements such as implant shape and implant dimensions including implant length and radius that result in a rise of contact area intermediating implant surface along with surrounding residual bone result in rise of primary stability of dental implant fixture.[8] Threaded designed implant surface, tapered wide, and long implants have more favorable influence on primary stability than custom made, nontapered, and short implants. The acid-etched implants and nonself-tapping implants have more favorable impact on primary stability than the machined surfaced implants and self-tapping implants.[3] The previous studies revealed that topography of implant outer surface and roughness of the outer surface of implant have markedly influenced the healing procedure by enhancing favorable cellular reactions and also cellular surface interactions.[9],[11] The outer surface-modified implants show higher roughness, a greater friction coefficient, and need higher insertion torque in comparison to machined dental implants. The variation within insertion-torque measurements of conical shaped implants and cylindrical shaped dental implants can be proved due to variations in intermediating surface areas within the threaded geometry of the dental implants.[8]

Various methods of evaluating implant stability

The surgeon's clinical perceptiveness

The clinical knowledge and perception of implant primary stability is mainly depend on implant mobility assessed with a blunt end shaped instrument by the surgeon.[10] The felling of good stability of an implant can be easily acknowledged by the operator with the feel of sense of sudden stop when a dental implant is placed.[7],[10] However,this method of evaluating primary implant stability is very unreliable and nonobjective method as on insertion of root form tapered implants operator encounters a firm stop resulting in pseudo-perception of greater implant stability.[10]

Radiographic analysis

The radiological analysis is noninvasive process to evaluate the primary implant stability which can be applied during various levels of healing process. The crestal bone level is evaluated with the help of bitewing imaging, as this is the main radiographic indicator for the implant success.[6] The facial bone level cannot be assessed by the periapical or panoramic views and also, the bone density and quality can be quantified by this radiographic analysis method, so this process is not useful in routine clinical practice.[7]

Cutting torque resistance analysis

Johansson and Strid[16] invented CRA and later on, Friberg et al.[17],[18] modified this procedure. It is the measure of a unit of quantity of residual bone lost due to an electrically driven machine and is evaluated by manually regulating pressure during drilling at a minimum speed to lower interoperator variation.[7],[10] A torque applying gauge associated with drilling component (e.g., osseocare) combined as an instrument for evaluation of insertion torque readings shown by Ncm to incidentally constitute J/mm3. This value is certainly utilized for bone quality evaluation during insertion of an implant.[19] Advantages of cutting torque resistance analysis include that this method can detect bone density and can also assess bone quality, as there is a interdependence within cutting resistance and quality of bone. CRA can also be used in daily practice. The major limitation of CRA is that this method can monitor implant stability only during implant placement phase.[6]

Reverse torque test method

This method was introduced by Roberts et al.[20] first time and later modified by Johansson and Albrektsson,[21],[22],[23] which indicates the value of critical torque initiating loss of implant and bone contact. Reverse torque test is utilized for evaluating implant secondary stability; however, range of osseointegration is difficult to determine, as threshold limits fluctuates according to various individuals, quantity and quality of bone, and material of implant.[7]

Modal analysis method

The modal analysis commonly known as vibration analysis is mostly used for structural analysis in engineering and health-care fields.[6] This analysis is used to measure original frequency or translation of signal in resonance that resulted from imitation of superficially balanced waves or transitory impulses. The two models used to perform this analysis are theory based and practically analyzed models. The theory-based modal analysis incorporates finite element investigations which detects the vibrational features of entities. The exploratory modal analysis includes dynamic investigations as it evaluates the mean values, specific frequency, and depletion-via vibration modality of examination.[24]


This test is used to measure the implant movement by monitoring reflection of surrounding tissues of an implant to a particular impact of weight.[7],[10] This test was first introduced and performed by Schulte and Lukas for evaluating damping effect periodontal attachment which was helpful in assessment natural tooth mobility.[25],[26] In periotest, an electromagnetically derived and electronically monitored hitting rod in a handpiece is used for blowing on the implant abutment, the barking response of which is evaluated with an accelerometer indulged into its head. The communication period within the implant and hitting element is evaluated and transformed into specific reading known as periotest value (PTV). These values were influenced by damping features of tissues enclosing implants and natural teeth.[6] The measurements of PTV range from − 8–+50 readings. Reading values (−8–0) indicate greater osseointegration, easy loading of an implant, +1–+9 indicates the requirement of investigation by clinician and assessment, mostly implants cannot be loaded, and +10–+ 50 indicates that osseointegration is inadequate for implant loading.[10]

The limitations of periotest measurements occurred due to inclination of agitating source or the striking end. The effect of striking end of the instrument on PTV is higher than that resulted from use of greater implant height due to peripheral bone loss or factors such as angulations of handpiece and repeated percussion of hitting element which are difficult to be controlled by the operator resulted in the achievement of resolution and low susceptibility to surgeons variables.[6],[27],[28]

Resonance frequency analysis

From previous times, this method had been utilized as one of the noninterceptive, dependable, easily monitored, and intentional modalities for evaluating implant stability.[29] In this method, dental implant stability and density of corresponding bone are measured at various points of time utilizing structural and vibrational principle analysis process.[10] The components of RFA machine include a small L-designed transducer which is closely adapted to abutment and implant fixture with a screw attachment. The transducer comprises two piezoceramic units, first of which vibrates at the sinusoidal signal (5–15 KHz). The second unit serves the purpose of receptor for signal and the resonance spurts from received signal showed the bending, i.e., RFA value of the measured object.[6] The RFA method has been mainly utilized to monitor the results of early loading or immediate loading of implants to determine variations over the period of time.[29] At present, two (RFA) equipments frequently utilized for practical purposes are Osstell by Integration Diagnostics [Figure 1] and Implomates by Bio Tech One. Osstell equipment is a combination of transducer, computer-assisted analyzing component, and the agitating source which earlier recorded resonance frequency in Hz while Osstell produced the implant stability quotient (ISQ) as an evaluating unit against Hz.[6],[18],[30] The implant stability can be measured along mesiodistal direction and buccolingual direction of implant, average reading of all measurements is considered as implant primary stability. The resonance frequency ranges from 3500 Hz to 8500 Hz are converted into ISQ values of 0–100 limits. The greater reading means higher implant stability, although the lower reading indicates lower implant instability. As per the indications from the manufacturer of equipment the stable implants possesses ISQ readings greater than 65 while ISQ reading lower than 50 indicates implant failure or higher probability of implant-failure.[31]
Figure 1: Osstell equipment showing primary stability measurement of dental implant

Click here to view

  Conclusion Top

In the present review of literature, the significance of achieving greater primary implant stability and its relevance for osseointegration of dental implant is highlighted. Various elements such as bone quality, quantity, implant surface features, and surgical techniques were followed for placements of dental implant and were discussed thoroughly with their marked importance for the success of the dental implants. Till present time, no particular method has been established to evaluate the implant stability definitely. Although RFA method evaluates the stability of implants with results outcome dependent on the sound theory, surely, it cannot assure the success and failure or even long-term results of the dental implants. Hence, the present indication from this review of literature is the more and more knowledge and information should be gathered from the different diagnostic methods and aids for achieving long-term implant stability. Certainly, many more researches should be initiated in the field of implant stability.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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