JICDRO is a UGC approved journal (Journal no. 63927)

   Table of Contents      
INVITED ARTICLE
Year : 2015  |  Volume : 7  |  Issue : 3  |  Page : 132-137

Short implants - When, where and how?


Department of Implantology, Rajarajeswari Dental College and Hospital, Bangalore, Karnataka, India

Date of Web Publication31-Dec-2015

Correspondence Address:
Anjan Kumar Shah
Department of Oral and Maxillofacial Surgery, Rajarajeswari Dental College and Hospital, Mysore Road, Bangalore - 560 060, Karnataka
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2231-0754.172932

Rights and Permissions
   Abstract 

The success of dental implants has led to research in techniques in minimising surgical complexity and increasing survival. Short dental implants are increasingly being seen as an alternative to more extensive bone augmentation procedures. This paper reviews aspects of short implant literature to give some guidelines in making their use more successful.

Keywords: Short, dental, implant


How to cite this article:
Shah AK. Short implants - When, where and how?. J Int Clin Dent Res Organ 2015;7, Suppl S1:132-7

How to cite this URL:
Shah AK. Short implants - When, where and how?. J Int Clin Dent Res Organ [serial online] 2015 [cited 2019 Jul 23];7, Suppl S1:132-7. Available from: http://www.jicdro.org/text.asp?2015/7/3/132/172932


   Introduction Top


Dental implantology is one of the most dynamic topics in the clinical dentistry today. The impetus is on simplifying the treatment to make it more acceptable to both the patient and clinician. Short dental implants are one of the techniques that have developed with this aim, when anatomical barriers and lack of bone availability prevent conventional dental implant treatment. There is very little good quality evidence regarding the use of short dental implants and the available evidence is sometimes confusing. The aim of this paper is to review the evidence and provide some guidelines to the practitioner on the applications and contraindication to the use of short dental implants. In a consensus paper on bone augmentation procedures in implant dentistry, Chiapasco et al.[1] recommended the consideration of short implants as an alternative to more complex and often expensive augmentation procedures.


   Definition and History Top


Initially, dental implant literature suggested the need for implants of length 12-20 mm to provide sufficient primary stability. Thomas Driskell invented the Bicon system of dental implants in 1968, with the introduction of the 8-mm implant. Until 1979, the shortest conventional endosseous implants available were 10 mm in length. In this year, Branemark introduced the 7-mm implant. The literature can therefore, be divided into implants that are termed conventional “short implants” ranging from 7 mm to 10 mm length and “ultrashort implants” of length <7 mm. Many companies have implants as short as 5 mm in their armamentarium.

For the purpose of this review, we will look at the evidence of using implants <7 mm in length. The Bicon system itself introduced a 5-mm height implant and received the Food and Drug Administration (FDA) approval in 2008.

More recently, Straumann introduced a 4-mm Roxolid implant, with 5-year data showing a survival of 94% for these implants.[34]


   Is There a Need for Short Implants? Top


The alveolar ridge undergoes reduction in height and width after tooth loss. In the posterior maxilla and mandible, this resorption results in proximity of the maxillary sinus and inferior alveolar nerve to the alveolar crest. Advanced bone grafting procedures such as sinus augmentation or guided bone regeneration (GBR) with simultaneous implant placement have shown more intra- and postoperative complications. Therefore, placing short implants might provide higher patient satisfaction in terms of surgical procedure and treatment outcomes.[2] Oikarinen et al.[3] conducted a radiographic study in a population of 431 65-year-olds; it was found that the placement of an implant of at least 6-mm length was possible in the lateral part of the maxilla only in 38% of the cases and in only 50% of the mandible cases in the lateral zone. This excludes a huge population from the benefits of dental implants.

The procedures for increasing the available bone height in these two regions are also not without its disadvantages. Maxillary sinus lifts, zygomatic implants in the maxilla, and nerve lateralization and alveolar distraction increase the complication rate of dental implants. They also increase the cost and downtime of the treatment. Graziani [4] in a systematic review of bone augmentation procedures and their success in the maxilla noted that survival of implants in the nonaugmented maxilla was 73-100% while survival in the grafted maxilla was 36-100%. His paper suggests that although bone grafting with dental implants can be highly successful, there is greater variability of outcome in the grafted sites. Chiapasco [1] in a systematic review concluded that short implants should be seen as an alternative to more complex augmentation procedures [Table 1].
Table 1: Clinical studies on short implants

Click here to view



   Are Short Dental Implants Successful? Top


The evidence of long-term success is conflicting. A large study in the University of California, Los Angeles (UCLA) suggested failure rates of as high as 30% in 2 years and 40% in 5 years for 7-mm plasma sprayed titanium implants. It must be noted that this paper was from 1994 and the surfaces on implants have changed significantly since then. More recent papers [5],[6],[7] suggest that the success rates of 5-mm dental implants range from 83.7% to 100% survival over 1-8 years from various papers.

A recent systematic review [8] reported that short implants had a cumulative survival rate of up to 99.1% after a follow-up period of 3.2 ± 1.7 years. In a recent systematic review of short implant survival, Naert [9] concluded that machined implant of less than 10 mm had a survival rate of 81.5% against a survival of 97.2% for implants that were 10 mm and longer. Whether the same extends to rough surface and surface treated implants is unclear. A study by Deporter [9] in 2000 reported 100% survival at 11 months of porous surface implants. This variation may have something to do with changing implant surface and design in recent years. Initially, short implants were considered biomechanically unsuitable and their use was seen as simply experimental.

Finite element analysis performed by Pierrisnard et al.[10] showed that maximum stress in the implant area was largely independent of the implant length. Experimental studies on animal models [11] confirmed that the increase of implant length from 7 mm to 10 mm did not significantly improve implant anchorage in the bone. Finite element analysis [12] suggests that the maximum stresses on a dental implant are at the crest and the stress levels apical to the top 5 mm was minimal. It also suggests that the stress forces on a dental implant of length 7 mm and 10 mm were the same. Data from finite element analysis certainly suggest that implants as short as 5 mm can be as successful as conventional length implants [Figure 1] and [Figure 2]. Short implants not only appear to distribute forces similarly but the use of short implants in distal areas where dental implants would be contraindicated due to lack of bone height may reduce cantilevers and reduce the overall compressive and tensile stresses on the prosthesis by 34.7% and 19%, respectively.[13]
Figure 1: failing maxillary short implant used as distal abutment for long span bridge[35]

Click here to view
Figure 2: successfully restored short dental implants in the mandible (courtesy Bicon)

Click here to view



   Factors Affecting Success of Short Dental Implants Top


Bone type

Studies demonstrate greater success of short implants in the mandible than in the maxilla.[14] This is likely to be due to the poorer density and therefore, lower bone contact in the maxillary posterior bone. It is suggested that whenever possible, bicortical fixation of the sinus floor should be done to increase the survival of short implants in the maxilla.

A prospective multicenter study [15] was conducted in 1985 with a total of 159 edentulous patients with 558 implants. They used the Applegate-Kennedy classification to classify jaws into class 1, 2, and 4. A standard surgical procedure was followed. A clear correlation was noted with implant length failure, and most failures were represented by short implants of standard diameter, whereas the implants of wider diameter seemed to achieve better results than the standard ones. Implant loss was higher in the maxilla, particularly in type 4 bone quality, and most losses occurred in the early loading periods. This study relates implant length and maxillary bone quality with survival.

Implant diameter

A prospective multicenter study [16] was carried out in which five (7-mm) implants with 3.75 mm diameter were used and were immediately placed. A total of three implants were placed in the maxilla, and all the implants were lost. Two were placed in the mandible and one was lost. The authors concluded an 80% failure rate for the 7-mm implant in this study.

Increasing implant diameter resulted in better engagement of the buccal and lingual cortical plates and more bone-to-implant contact, thus improving stress distribution within the surrounding bone.[17] In a three-dimensional (3D) finite element analysis, it was demonstrated that increasing the implant diameter resulted in a 3.5-fold reduction in crestal strain. On the contrary, increasing the implant length resulted in a 1.65-fold reduction in crestal strain.[18]

Clinical investigations in a study regarding Endopore implants that were placed in patients with an age range of 22-72 years showed that the 7-mm length implants were 32 in number with no failures.[19] The authors attributed the success to the large surface area provided by the implant design, which was three to four times that of machined threaded implants and porous surface implants, and it allows for 3D mechanical interlock with the bone for ingrowth of the bone, and this interface effectively resists interfacial shear forces and also tensile forces created by the transverse component of occlusal loading. The functional time was 32.6 months.

Many papers demonstrate the higher survival rates of wide diameter short implants such as the 5 × 5 mm Bicon implant. The wider diameter implant increases bone contact and distributes forces better. It is suggested that when wide diameter implant placement is not possible, two implants should be considered in place of one implant.[20] A retrospective study conducted on 49 patients with edentulous mandible and bone resorption was shape E and quality 1 according to Lekholm and Zarb.[21] None of the 5 × 6 mm implants were lost in the present study, which may be coincidental or because of their limited number. They recommended this treatment procedure without hesitation for a severely resorbed mandible.

Surface texture of implants

Again, the literature around short implants is confounded by the studies involving machined surfaces and various surface modifications. Roughened surface implants appear to increase implant survival, especially in compromised bone height situations and the maxilla. A systemic review by Telleman et al.[22] suggested that machined surface implants increased the failure rate of short implants by a maximum of 29%.

This is due to mechanical interlocking that provides greater stability as well as the rough surfaces that provide a more amenable surface area for attachment of osteoblasts. Kasten [23] and associates reported that gingival cells also attached to roughened titanium surfaces three times more frequently than to smoother surfaces.

Numerous other histomorphometric and biomechanical tests, animal studies, human clinical trials, and in vitro experiments have demonstrated that implants with roughened surfaces achieve greater bone-to-implant apposition and interfacial strength than implants with conventional machined surfaces.[24],[25]

Neldam in a systematic review of short implants reported a failure of 4.3% for short Straumann titanium plasma-sprayed (TPS) implants, 1% for Straumann sandblasted and acid-etched (SLA) implants, and 0% for Astra microthreaded implants.[13]

Implant thread design

Abuhussein [26] in a review of thread design noted three important variations:

  1. A decrease in thread pitch positively influences implant stability.
  2. Increase helix angle, although increasing speed of insertion may reduce implant stability.
  3. Deeper threads have an important contribution to implant stabilization, particularly in the soft bone.


In addition, the paper noted that the inclusion of microthreads at the crest may increase bone-to-implant contact and reduce crestal bone loss but the evidence for this was not conclusive.

Platform switching and short implants

A review of the literature by Atieh [27] reports a statistically significant difference in the marginal bone levels between platform matched and platform switched implants.

While this may not be significant for standard length implants, the loss of bone may be significant for short implants. For example, a 1-mm loss of the crestal bone on an 8-mm implant results in a 12.5% loss of bone support.

Linking of implants

Splinting of implants appears to be beneficial and particularly the linking a short implant to the adjacent longer implant does seem to increase its longevity.

Different success rates were found for the splinted (97.7%) and nonsplinted (93.2%) groups.[13] The success of splinted implants was associated with no other variable, whereas nonsplinted implants exhibited a higher risk of failure when placed in men and when implants shorter than 10 mm were used. The failures in men may be due to greater bite forces although this was not clear from the data.

Avoiding immediate loading

Immediate loading of short implants has a deleterious effect to its long-term survival.[27] A one-stage versus two-stage surgical approach did not have a significant effect on the success of short implants. According to a retrospective study, immediate loading of threaded implants of 10 mm or shorter with a rough surface should be performed with caution. But investigations of immediate loading of implants of length (≤7 mm) as per this review are not found.[28] It seemed prudent to follow a two-stage implant placement approach when using short implants, as this approach has been linked with higher success rates. However, according to a review, there is no significant difference in the failure rates between one-stage and two-stage implants. The use of interim implants and the restriction of denture wearing to avoid pressure on the soft tissues during the first 3 months following surgery were additional precautions to optimize conditions for implant survival. A stress-free environment may be important because movement of as little as 10-20 μm during the early stages of wound healing can be enough to direct differentiation of mesenchymal cells into fibroblasts instead of osteoblasts.[29],[30]

Smoking

The benefits of a nicotine-free period around the time of surgery have been supported by the results of several animal studies. A study in rats has shown that smoking appears to have more adverse effects on cancellous bone than it does on cortical bone. In a rabbit model of bone graft revascularization, it was shown that inhalation of nicotine decreased vascular ingrowths into autogenouscancellous bone grafts.[31] In a prospective study of implant surgery, Bain [32] described a smoking cessation protocol in which patients stopped smoking 1 week before and 8 weeks after the implant surgery. Significantly lower implant failure rates were observed in smokers who followed this protocol (11.8%) than in those who did not (38.5%). Failure rates in compromised maxillary bone are slightly higher in smokers as compared to nonsmokers (2.6% versus 1.9%, respectively).[33]


   Conclusion Top


Based on the review of the literature and personal experience, short implants if applied correctly can be an alternative to other more complex dental implant procedures.

Recommendations

  • Short implants should be considered in the treatment plan when considering dental implants.
  • Prognosis of short implants in the maxilla is guarded.
  • Splinting of short implants may be beneficial for their long-term success and is hence, recommended.
  • A staged protocol is suggested when planning the use of short implants.
  • Short implants are an advanced surgical technique and should be utilized once the clinician is familiar with a conventional implant protocol as the margin of error in surgical technique is very small.
  • Smoking may have deleterious effect on the success of short implants and therefore, following a protocol of cessation by smokers before and after implant surgery is recommended.
  • There is insufficient literature at present to comment on the long-term success of short implants versus conventional length implants, therefore implants longer than 10mm are still recommended where height of bone is available.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.[35]

 
   References Top

1.
Chiapasco M, Casentini P, Zaniboni M. Bone augmentation procedures in implant dentistry. Int J Oral Maxillofac Implants 2009;24(Suppl):237-59.  Back to cited text no. 1
    
2.
Esposito M, Cannizzaro G, Soardi E, Pistilli R, Piattelli M, Corvino V, et al. Posterior atrophic jaws rehabilitated with prostheses supported by 6 mm-long, 4 mm-wide implants or by longer implants in augmented bone. Preliminary results from a pilot randomised controlled trial. Eur J Oral Implantol 2012;5:19-33.   Back to cited text no. 2
    
3.
Oikarinen K, Raustia AM, Hartikainen M. General and local contraindications for endosseal implants — an epidemiological panoramic radiograph study in 65-year-old subjects. Community Dent Oral Epidemiol 1995;23:114-8.  Back to cited text no. 3
    
4.
Graziani F, Donos N, Needleman I, Gabriele M, Tonetti M. Comparison of implant survival following sinus floor augmentation procedures with implants placed in pristine posterior maxillary bone: A systematic review. Clin Oral Implants Res 2004;15:677-82.   Back to cited text no. 4
    
5.
Deporter D, Ogiso B, Sohn DS, Ruljancich K, Pharoah M. Ultrashort sintered porous-surfaced dental implants used to replace posterior teeth. J Periodontol 2008;79:1280-6.   Back to cited text no. 5
    
6.
Sánchez-Garcés A, Costa-Berenguer X, Gay-Escoda C. Short implants: A descriptive study of 273 implants. Clin Implant Dent Relat Res 2012;14:508-16.   Back to cited text no. 6
    
7.
Fugazzotto PA. Shorter implants in clinical practice: Rationale and treatment results. Int J Oral Maxillofac Implants 2008;23:487-96.  Back to cited text no. 7
    
8.
Annibali S, Cristalli MP, Dell'Aquila D, Bignozzi I, La Monaca G, Pilloni A. Short dental implants: A systematic review. J Dent Res 2012;91:25-32.   Back to cited text no. 8
    
9.
Neldam CA, Pinholt EM. State of the art of short dental implants: A systematic review of the literature. Clin Implant Dent Relat Res 2012;14:622-32.  Back to cited text no. 9
    
10.
Pierrisnard L, Renouard F, Renault P, Barquinis M. Influence of implant lenght and bicortical anchorage on implant stress distribution. Clin Implant Dent Relat Res 2003;5:254-62.  Back to cited text no. 10
    
11.
Bernard JP, Szmukler-Moncler S, Pessotto S, Vazquez L, Belser UC. The anchorage of Brånemark and ITI implants of diffrentlenghts. I. An experimental study in the canine mandible. Clin Oral Implants Res 2003;14:593-600.  Back to cited text no. 11
    
12.
Akça K, Iplikçioğlu H. Finite element stress analysis of the effect of short implant usage in place of cantilever extensions in mandibular posterior edentulism. J Oral Rehabil 2002;29:350-6.  Back to cited text no. 12
    
13.
Yang TC, Maeda Y, Gonda T. Biomechanical rationale for short implants in splinted restorations: An in vitro study. Int J Prosthodont 2011;24:130-2.  Back to cited text no. 13
    
14.
Testori T, Del Fabbro M, Feldman S, Vincenzi G, Sullivan D, Rossi R Jr, et al. Amulticenter prospective evaluation of 2-months loaded Osseotite implants placed in the posterior jaws: 3-year follow-up results. Clin Oral Implants Res 2002;13:154-61.   Back to cited text no. 14
    
15.
ten Bruggenkate CM, Asikainen P, Foitzik C, Krekeler G, Sutter F. Short (6-mm) nonsubmerged dental implants: Results of a Multicenter clinical trial of 1 to 7 years. Int J Oral Maxillofac Implants 1998;13:791-8.  Back to cited text no. 15
    
16.
Langer B, Langer L, Herrmann I, Jorneus L. The wide fixture: A solution for special bone situations and a rescue for the compromised implant. Part 1. Int J Oral Maxillofac Implants 1993;8:400-8.   Back to cited text no. 16
    
17.
Petrie CS, Williams JL. Comparative evaluation of implant designs: Influence of diameter, length, and taper on strains in the alveolar crest. A three-dimensional finite-element analysis. Clin Oral Implants Res 2005;16:486-94.   Back to cited text no. 17
    
18.
Deporter D, Pilliar RM, Todescan R, Watson P, Pharoah M. Managing the posterior mandible of partially edentulous patients with short, porous-surfaced dental implants: Early data from a clinical trial. Int J Oral Maxillofac Implants 2001;16:653-8.  Back to cited text no. 18
    
19.
Bahat O. Brånemark system implants in the posterior maxilla: Clinical study of 660 Implants Followed for 5 to 12 Years. Int J Oral Maxillofac Implants 2000;15:646-53.  Back to cited text no. 19
[PUBMED]    
20.
Lekholm U, Gunne J, Henry P, Higuchi K, Lindén U, Bergström C, et al. Survival of the Branemark implant in partially edentulous jaws. A 10-year prospective multicenter study. Int J Oral Maxillofac Implants 1999;14:639-45.  Back to cited text no. 20
    
21.
Friberg B, Gröndahl K, Lekholm U, Brånemark PI. Long-term follow-up of severely atrophic edentulous mandibles reconstructed with short Brånemark implants. Clin Implant Dent Relat Res 2000;2:184-9.  Back to cited text no. 21
    
22.
Telleman G, Raghoebar GM, Vissink A, den Hartog L, Huddleston Slater JJ, Meijer HJ. A systematic review of the prognosis of short (<10 mm) dental implants placed in the partially edentulous patient. J Clin Periodontol 2011;38:667-76.   Back to cited text no. 22
    
23.
Kasten FH, Soileau K, Meffert RM. Quantitative evaluation of human gingival epithelial cell attachment to implant surfaces in vitro. Int J Periodontics Restorative Dent 1990;10:68-79.  Back to cited text no. 23
    
24.
Hagi D, Deporter DA, Pilliar RM, Arenovich T. A targeted review of study outcomes with short (< or = 7 mm) endosseous dental implants placed in partially edentulous patients. J Periodontol 2004;75:798-804.  Back to cited text no. 24
    
25.
Pommer B, Frantal S, Willer J, Posch M, Watzek G, Tepper G. Impact of dental implant length on early failure rates: A meta-analysis of observational studies. J Clin Periodontol 2011;38:856-63.   Back to cited text no. 25
    
26.
Abuhussein H, Pagni G, Rebaudi A, Wang HL. The effect of thread pattern upon implant osseointegration. Clin Oral Implants Res 2010;21:129-36.  Back to cited text no. 26
    
27.
Atieh MA, Ibrahim HM, Atieh AH. Platform switching for marginal bone preservation around dental implants: A systematic review and meta-analysis. J Periodontol 2010;81:1350-66.  Back to cited text no. 27
    
28.
Sun HL, Huang C, Wu YR, Shi B. Failure rates of short (≤10 mm) dental implants and factors influencing their failure: A systematic review. Int J Oral Maxillofac Implants 2011;26:816-25.  Back to cited text no. 28
    
29.
Esposito M, Grusovin MG, Chew YS, Coulthard P, Worthington HV. One-stage versus two-stage implant placement. A Cochrane systematic review of randomised controlled clinical trials. Eur J Oral Implantol 2009;2:91-9.  Back to cited text no. 29
    
30.
Degidi M, Piattelli A. Immediate functional and non-functional loading of dental implants: A 2- to 60-month follow-up study of 646 titanium implants. J Periodontol 2003;74:225-41.  Back to cited text no. 30
    
31.
Riebel GD, Boden SD, Whitesides TE, Hutton WC. The effect of nicotine on incorporation of cancellous bone graft in an animal model. Spine (Phila Pa 1976) 1995;20:2198-202.  Back to cited text no. 31
    
32.
Bain CA. Smoking and implant failure — benefits of a smoking cessation protocol. Int J Oral Maxillofac Implants 1996;11: 756-9.  Back to cited text no. 32
    
33.
Bain CA, Moy PK. The association between the failure of dental implants and cigarette smoking. Int J Oral Maxillofacial Implants 1993;8:609-15.  Back to cited text no. 33
    
34.
Slotte Christer, et al. Four-mm Implants Supporting Fixed Partial Dentures in the Posterior Mandible. 5-Year Results from a Multi Center Study. Presented at the 20th Annual Scientific Meeting of the European Association of Osseointegration, 10-13th October 2012. Copenhagen, Denmark: European Association of Osseointegration; 2012.   Back to cited text no. 34
    
35.


    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1]



 

Top
 
 
  Search
 
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

 
  In this article
    Abstract
   Introduction
    Definition and H...
    Is There a Need ...
    Are Short Dental...
    Factors Affectin...
   Conclusion
    References
    Article Figures
    Article Tables

 Article Access Statistics
    Viewed3724    
    Printed40    
    Emailed0    
    PDF Downloaded388    
    Comments [Add]    

Recommend this journal