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 Table of Contents  
Year : 2018  |  Volume : 18  |  Issue : 3  |  Page : 189-195

Systematic analysis of factors that cause loss of preload in dental implants

Department of Prosthodontics, Adhiparasakthi Dental College, Melmaruvathur, Tamil Nadu, India

Date of Submission16-Oct-2017
Date of Acceptance28-Mar-2018
Date of Web Publication05-Jul-2018

Correspondence Address:
Dr. S Nithyapriya
Department of Prosthodontics, Adhiparasakthi Dental College, Melmaruvathur, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jips.jips_294_17

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Screw loosening is the most common factor associated with dental implant failure. One of the major cause for screw loosening is the “loss of preload”. Several factors including screw geometry, material properties particularly stiffness, surface texture and condition of mating surfaces, degree of lubrication, rate of tightening, integrity of joint etc.
Objective: This review analyses the factors that are responsible for the loss of preload.
Material and Methods: Screw geometry, Implant- Abutment Connection type (external hexagon platform, morse taper), Material properties viz Stiffness, Resilience, Materials viz gold, titanium, titanium alloy, Surface texture of the abutment screw, Condition of mating surfaces, Lubrication, Torque value, Rate of tightening (10, 20, 35N and retorque after 10mins) are taken into consideration in this study. The MEDLINE-PubMed database was searched from September 2016 to 10 years previously. Several journals were hand searched and from cross references. The outcome analysed are the factors that are responsible for loss of preload.
Results: The search yielded 84 articles. After excluding duplicated abstracts and applying the inclusion and exclusion criteria, 36 studies were eligible for analysis. The result shows that loss of preload can occurs depending upon the type of material used, torque method, torque sequences, abutment connection type, influence of lubrication, abutment collar length. However we detected some potential limitations in the studies selected, mainly a minimum number of samples used for the study. Hence we suggest further studies to guarantee an excellence in methodological quality.
Conclusion: Based on the available data it can be summarized that the knowledge of preload loss must be known for the clinicians to avoid such screw loosening and subsequent implant failure.

Keywords: Abutment screw, dental implant, preload

How to cite this article:
Nithyapriya S, Ramesh A S, Kirubakaran A, Mani J, Raghunathan J. Systematic analysis of factors that cause loss of preload in dental implants. J Indian Prosthodont Soc 2018;18:189-95

How to cite this URL:
Nithyapriya S, Ramesh A S, Kirubakaran A, Mani J, Raghunathan J. Systematic analysis of factors that cause loss of preload in dental implants. J Indian Prosthodont Soc [serial online] 2018 [cited 2021 Dec 8];18:189-95. Available from: https://www.j-ips.org/text.asp?2018/18/3/189/234911

  Introduction Top

The most common failure associated with dental implant is screw loosening and fracture of implant.[1] One of the major causes for screw loosening is the “loss of preload.” Preload is the axial force in the neck of the screw, which is between the first mating thread and head of the abutment screw.[2] The tensile force clamps the abutment to the implant.[3] The relationship between applied torque and preload depends on several factors including screw geometry, material properties, surface texture, degree of lubrication, rate of tightening, and integrity of joint.[2] This study aim at determining the factors which causes loss of preload in dental implants. This systematic review is focused on the factors which cause loss of preload that leads to dental implant failure.[4],[5],[6]

  Methodology Top

Search strategies

The following analysis was performed according to the guidelines and the principles of the PRISMA statement for a systematic review.

Focused question (Patients, Intervention, Comparison, and Outcomes)

The review is focused on: “what are the factors causing loss of preload which eventually leads to dental implant failure?”

The following medical subjects headings terms: “abutment screw,” “preload,” “dental implants,” and their related entry terms were used in different combinations using the Boolean Operators “AND” and “OR” for the research. In addition, manual search was made [Figure 2].
Figure 2: Pudmed search

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([dental implants] AND abutment screw]) AND preload.

Inclusion criteria

Loss of preload, screw loosening, screw fracture, screw geometry, implant-abutment connection type (external hexagon platform, Morse taper), material properties, namely, stiffness, resilience, and materials, namely, gold, titanium (Ti), Ti alloy, surface texture of the abutment screw, condition of mating surfaces, lubrication, torque value, rate of tightening (10, 20, 35N, and retorque after 10 min), and integrity of joint.

Exclusion criteria

Functional habits such as bruxism, clinical syndromes (such as epilepsy, psychological disorders, and osteoporosis) implant fracture.


Other inclusion criteria are as follows (a) articles published in English language; (b) human studies; (c) studies which have the relationship between dental implants and loss of preload; (d) animal studies; (e) systematic reviews; (f) cohort studies; and (g) randomized controlled trial (RCT).

Other exclusion criteria are as follows (a) articles published in another language other than English; (b) studies that does not have the relation between dental implants and loss of preload; (c) full text articles that were not available on the database searched; (d) duplicated articles; (e) letters to editor; and (f) commentaries. Studies other than RCT, systematic reviews and cohort studies were eliminated to reduce bias.

Data extraction

All studies which met the inclusion and exclusion criteria for review were obtained and screened independently and were analyzed using PRISMA guidelines [Figure 1]. The following data were extracted from the studies included for review reference, study design, number of implants, group specification of the study, initial torque, preload, and loss of preload. The quality of the various studies was not considered in the final analysis; therefore, no quality assessment has been done.
Figure 1: Flowchart of the search process

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  Discussion Top

Preload is the initial load when a torque is applied to the screw. The preload is a contributing factor for the stability of screw connection parts, is affected by various mechanical factors.[5] One of which is the settling effect or embedment relaxation. The settling effect occurs due to microroughness on the two contact surfaces so that when initial torquing of the screw is applied, the rough areas collapse and leads to screw loosening. Hence, preload must be maintained to prevent joints from separating.[1],[5],[6],[10]

The present review is investigated to determine the factors that are responsible for loss of preload and screw loosening.

  Type of Material Top

Six articles, which includes 102 implants the preload values of different types of materials were evaluated. In comparison between gold, Ti, Ti alloys and surface treated Ti, gold exhibits higher preload value than other elements. It is then followed by Ti alloys, surface-treated Ti, and pure Ti type of material [Table 2].[14],[16],[28],[31],[37],[38],[40],[41],[42],[44]
Table 2: Type of material

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  Torque Method Top

Two articles, compared the efficacy of manual torque with that of the digital torque meter, out of which one article is a systematic review. By the result, researchers found that calibrated torquing devices are mandatory as the abutment should not be over tightened or under tightened to avoid misfiting of the implant abutment complex [Table 4].[2],[3],[21],[25],[34],[45]
Table 4: Torque method

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  Torque Sequence Top

Seven articles evaluated the torquing sequence for the maintenance of preload values and found that retorquing after 10 min of initial torque is efficient to maintain the preload value [Table 1].[1],[6],[12],[18],[23],[27],[30],[32],[33],[37],[43]
Table 1: Torque sequence

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  Abutment Connection Type Top

Of the seven articles, two articles were concluded by doing a study in about 56 implants and found the result that design of joint was not significant in affecting the preload values. And also, other articles which includes 51 implants, showed that internal hexagon type exhibits greater preload than external hexagonal type [Table 3].[8],[11],[15],[16],[17],[19],[20],[22],[24],[26]
Table 3: Abutment connection type

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  Influence of Lubrication Top

Dry lubricant coatings such as 60–80 nm Ti nanoparticles, Vaseline, and human saliva were used as a lubricating agent in about three studies. Eighty-five implants were evaluated for this influence of lubrication on preload values. Results found that lubricants decreases the friction and thereby helps in maintenance of preload by regulating the settling effect [Table 5].[7],[9],[13],[29],[39]
Table 5: Influence of lubricant

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  Abutment Collar Length Top

One article evaluated the significance of abutment collar length in a total of 15 implants and found that increase in the height of abutment collar length has a significant influence on the torque loss of abutment-implant screw after cyclic loading [Table 6].[35],[36]
Table 6: Abutment collar size

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  Summary Top

As per the results of the studies include we can summarizes the following.

  • Gold fixation screws provides higher preload values than Ti and Ti alloy screws
  • Calibrated torquing device is mandatory to get adequate preload
  • Retorquing of abutment screws after 10 min of the initial torque should be performed during implant abutment connection
  • Abutments with more extensive contact areas with implant have been associated with a lower incidence of toque loss
  • Internal connection type has higher preload value than external hexagon type
  • Results found that lubricants decreases the friction and thereby helps in maintenance of preload by regulating the settling effect.

  Conclusion Top

Ideally, the use of lubricated gold screws with internal connection type should be placed with calibrated torquing device and retorquing it after 10 min of the initial torque gives the maximum preload. Since screw loosening is the major reason for implant failure due to embedment relaxation, one should know the reason behind it. The knowledge of preload loss must be known for the clinicians to avoid such screw loosening and subsequent implant failure.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Breeding LC, Dixon DL, Nelson EW, Tietge JD. Torque required to loosen single-tooth implant abutment screws before and after simulated function. Int J Prosthodont 1993;6:435-9.  Back to cited text no. 1
Goheen KL, Vermilyea SG, Vossoughi J, Agar JR. Torque generated by handheld screwdrivers and mechanical torquing devices for osseointegrated implants. Int J Oral Maxillofac Implants 1994;9:149-55.  Back to cited text no. 2
Burguete RL, Johns RB, King T, Patterson EA. Tightening characteristics for screwed joints in osseointegrated dental implants. J Prosthet Dent 1994;71:592-9.  Back to cited text no. 3
Sakaguchi RL, Borgersen SE. Nonlinear contact analysis of preload in dental implant screws. Int J Oral Maxillofac Implants 1995;10:295-302.  Back to cited text no. 4
Weiss EI, Kozak D, Gross MD. Effect of repeated closures on opening torque values in seven abutment-implant systems. J Prosthet Dent 2000;84:194-9.  Back to cited text no. 5
Siamos G, Winkler S, Boberick KG. Relationship between implant preload and screw loosening on implant-supported prostheses. J Oral Implantol 2002;28:67-73.  Back to cited text no. 6
Tzenakis GK, Nagy WW, Fournelle RA, Dhuru VB. The effect of repeated torque and salivary contamination on the preload of slotted gold implant prosthetic screws. J Prosthet Dent 2002;88:183-91.  Back to cited text no. 7
Khraisat A, Hashimoto A, Nomura S, Miyakawa O. Effect of lateral cyclic loading on abutment screw loosening of an external hexagon implant system. J Prosthet Dent 2004;91:326-34.  Back to cited text no. 8
Kitagawa T, Tanimoto Y, Odaki M, Nemoto K, Aida M. Influence of implant/abutment joint designs on abutment screw loosening in a dental implant system. J Biomed Mater Res B Appl Biomater 2005;75:457-63.  Back to cited text no. 9
Byrne D, Jacobs S, O'Connell B, Houston F, Claffey N. Preloads generated with repeated tightening in three types of screws used in dental implant assemblies. J Prosthodont 2006;15:164-71.  Back to cited text no. 10
Piermatti J, Yousef H, Luke A, Mahevich R, Weiner S. An in vitro analysis of implant screw torque loss with external hex and internal connection implant systems. Implant Dent 2006;15:427-35.  Back to cited text no. 11
Al Jabbari YS, Fournelle R, Ziebert G, Toth J, Iacopino AM. Mechanical behavior and failure analysis of prosthetic retaining screws after long-term use in vivo. Part 3: Preload and tensile fracture load testing. J Prosthodont 2008;17:192-200.  Back to cited text no. 12
Guda T, Ross TA, Lang LA, Millwater HR. Probabilistic analysis of preload in the abutment screw of a dental implant complex. J Prosthet Dent 2008;100:183-93.  Back to cited text no. 13
Stüker RA, Teixeira ER, Beck JC, da Costa NP. Preload and torque removal evaluation of three different abutment screws for single standing implant restorations. J Appl Oral Sci 2008;16:55-8.  Back to cited text no. 14
Tsuge T, Hagiwara Y. Influence of lateral-oblique cyclic loading on abutment screw loosening of internal and external hexagon implants. Dent Mater J 2009;28:373-81.  Back to cited text no. 15
Park JK, Choi JU, Jeon YC, Choi KS, Jeong CM. Effects of abutment screw coating on implant preload. J Prosthodont 2010;19:458-64.  Back to cited text no. 16
Kim KS, Lim YJ, Kim MJ, Kwon HB, Yang JH, Lee JB, et al. Variation in the total lengths of abutment/implant assemblies generated with a function of applied tightening torque in external and internal implant-abutment connection. Clin Oral Implants Res 2011;22:834-9.  Back to cited text no. 17
Guzaitis KL, Knoernschild KL, Viana MA. Effect of repeated screw joint closing and opening cycles on implant prosthetic screw reverse torque and implant and screw thread morphology. J Prosthet Dent 2011;106:159-69.  Back to cited text no. 18
Gracis S, Michalakis K, Vigolo P, Vult von Steyern P, Zwahlen M, Sailer I, et al. Internal vs. external connections for abutments/reconstructions: A systematic review. Clin Oral Implants Res 2012;23 Suppl 6:202-16.  Back to cited text no. 19
Ferreira MB, Delben JA, Barão VA, Faverani LP, Dos Santos PH, Assunção WG, et al. Evaluation of torque maintenance of abutment and cylinder screws with Morse taper implants. J Craniofac Surg 2012;23:e631-4.  Back to cited text no. 20
Butignon LE, Basilio Mde A, Pereira Rde P, Arioli Filho JN. Influence of three types of abutments on preload values before and after cyclic loading with structural analysis by scanning electron microscopy. Int J Oral Maxillofac Implants 2013;28:e161-70.  Back to cited text no. 21
Murmura G, Di Iorio D, Cicchetti AR, Sinjari B, Caputi S.In vitro analysis of resistance to cyclic load and preload distribution of two implant/abutment screwed connections. J Oral Implantol 2013;39:293-301.  Back to cited text no. 22
Al-Sahan MM, Al Maflehi NS, Akeel RF. The influence of tightening sequence and method on screw preload in implant superstructures. Int J Prosthodont 2014;27:76-9.  Back to cited text no. 23
Bernardes SR, da Gloria Chiarello de Mattos M, Hobkirk J, Ribeiro RF. Loss of preload in screwed implant joints as a function of time and tightening/untightening sequences. Int J Oral Maxillofac Implants 2014;29:89-96.  Back to cited text no. 24
Jörn D, Kohorst P, Besdo S, Rücker M, Stiesch M, Borchers L, et al. Influence of lubricant on screw preload and stresses in a finite element model for a dental implant. J Prosthet Dent 2014;112:340-8.  Back to cited text no. 25
Shin HM, Huh JB, Yun MJ, Jeon YC, Chang BM, Jeong CM, et al. Influence of the implant-abutment connection design and diameter on the screw joint stability. J Adv Prosthodont 2014;6:126-32.  Back to cited text no. 26
Delben JA, Barão VA, Dos Santos PH, Assunção WG. Influence of abutment type and esthetic veneering on preload maintenance of abutment screw of implant-supported crowns. J Prosthodont 2014;23:134-9.  Back to cited text no. 27
Doolabh R, Dullabh HD, Sykes LM. A comparison of preload values in gold and titanium dental implant retaining screws. SADJ 2014;69:316-20.  Back to cited text no. 28
Krishnan V, Tony Thomas C, Sabu I. Management of abutment screw loosening: Review of literature and report of a case. J Indian Prosthodont Soc 2014;14:208-14.  Back to cited text no. 29
Xia D, Lin H, Yuan S, Bai W, Zheng G. Dynamic fatigue performance of implant-abutment assemblies with different tightening torque values. Biomed Mater Eng 2014;24:2143-9.  Back to cited text no. 30
Jo JY, Yang DS, Huh JB, Heo JC, Yun MJ, Jeong CM, et al. Influence of abutment materials on the implant-abutment joint stability in internal conical connection type implant systems. J Adv Prosthodont 2014;6:491-7.  Back to cited text no. 31
Villarinho EA, Cervieri A, Shinkai RS, Grossi ML, Teixeira ER. The effect of a positioning index on the biomechanical stability of tapered implant-abutment connections. J Oral Implantol 2015;41:139-43.  Back to cited text no. 32
Bulaqi HA, Mousavi Mashhadi M, Geramipanah F, Safari H, Paknejad M. Effect of the coefficient of friction and tightening speed on the preload induced at the dental implant complex with the finite element method. J Prosthet Dent 2015;113:405-11.  Back to cited text no. 33
Bulaqi HA, Mousavi Mashhadi M, Safari H, Samandari MM, Geramipanah F. Effect of increased crown height on stress distribution in short dental implant components and their surrounding bone: A finite element analysis. J Prosthet Dent 2015;113:548-57.  Back to cited text no. 34
Sarfaraz H, Paulose A, Shenoy KK, Hussain A. A three-dimensional finite element analysis of a passive and friction fit implant abutment interface and the influence of occlusal table dimension on the stress distribution pattern on the implant and surrounding bone. J Indian Prosthodont Soc 2015;15:229-36.  Back to cited text no. 35
[PUBMED]  [Full text]  
Siadat H, Pirmoazen S, Beyabanaki E, Alikhasi M. Does abutment collar length affect abutment screw loosening after cyclic loading? J Oral Implantol 2015;41:346-51.  Back to cited text no. 36
Bacchi A, Regalin A, Bhering CL, Alessandretti R, Spazzin AO. Loosening torque of universal abutment screws after cyclic loading: Influence of tightening technique and screw coating. J Adv Prosthodont 2015;7:375-9.  Back to cited text no. 37
Yilmaz B, Gilbert AB, Seidt JD, McGlumphy EA, Clelland NL. Displacement of implant abutments following initial and repeated torqueing. Int J Oral Maxillofac Implants 2015;30:1011-8.  Back to cited text no. 38
Lee HW, Alkumru H, Ganss B, Lai JY, Ramp LC, Liu PR, et al. The effect of contamination of implant screws on reverse torque. Int J Oral Maxillofac Implants 2015;30:1054-60.  Back to cited text no. 39
Rezende CE, Griggs JA, Duan Y, Mushashe AM, Nolasco GM, Borges AF, et al. An indirect method to measure abutment screw preload: A pilot study based on micro-CT scanning. Braz Dent J 2015;26:596-601.  Back to cited text no. 40
Peixoto HE, Bordin D, Del Bel Cury AA, da Silva WJ, Faot F. The role of prosthetic abutment material on the stress distribution in a maxillary single implant-supported fixed prosthesis. Mater Sci Eng C Mater Biol Appl 2016;65:90-6.  Back to cited text no. 41
Mattheos N, Li X, Zampelis A, Ma L, Janda M. Investigating the micromorphological differences of the implant-abutment junction and their clinical implications: A pilot study. Clin Oral Implants Res 2016;27:e134-43.  Back to cited text no. 42
Al-Otaibi HN, Almutairi A, Alfarraj J, Algesadi W. The effect of torque application technique on screw preload of implant-supported prostheses. Int J Oral Maxillofac Implants 2017;32:259-63.  Back to cited text no. 43
Dincer Kose O, Karataslı B, Demircan S, Kose TE, Cene E, Aya SA, et al. In vitro evaluation of manual torque values applied to implant-abutment complex by different clinicians and abutment screw loosening. Biomed Res Int 2017;2017:7376261.  Back to cited text no. 44
Basílio MA, Abi-Rached FO, Butignon LE, Arioli Filho JN. Influence of liquid lubrication on the screw-joint stability of Y-TZP implant abutment systems. J Prosthodont 2017;26:656-8.  Back to cited text no. 45


  [Figure 1], [Figure 2]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]

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