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REVIEW ARTICLE
PREDICTABILITY OF SHORT DENTAL IMPLANTS A LITERARY REVIEW
Harish Konde1
HOW TO CITE THIS ARTICLE:
Harish Konde. “Predictability of short dental implants a literary review”. Journal of Evolution of Medical and
Dental Sciences 2013; Vol2, Issue 31, August 5; Page: 5720-5727.
ABSTRACT: Implant Dentistry is a developing science which has become very predictable in various
clinical situations. One of the clinical situations is to deal with compromised bone for implant
placement where advanced surgical procedures and materials are used. But sometimes extensive
surgical procedures may not be planned for various reasons, in which case short implant is a boon to
clinical practice. So, before advising short implants, it is very important to know the evidence behind
the success, indications, and limitations. Hence this article focuses on the various aspects of short
implants which will help a clinician in making a judgement.
INTRODUCTION: The use of dental implants for treatment of partial & complete edentulism has
become effective recently. Dental implant serves as a load bearing device that not only sustains
masticatory forces, but also transfers load to per implant bone. Dental implants can however have
limitations in situations of either reduced bone height or presence of anatomical structures such as
extensive maxillary sinus pneumatization, proximity to tooth socket, inferior alveolar nerve &
mental foramen. It was assumed at the time of introduction of dental implants that longer implants
would be more beneficial in clinical use than their shorter counterpart due to improved crown to
implant ratio& greater implant surface for osseointegration. However with recent technological
advances in the design & surface characteristics of dental implant, shorter implants are equally
successful based on the evidence. An introspect into the review & success of this procedure can
bring about a viable treatment option for compromised bone length in clinical practice.
RATIONALE: The use of short implants is justified by the fact of the bone/implant interface
distributes most of the occlusal forces to the most superior portion of the implant body, close to the
alveolar crest. Studies on finite element analysis demonstrate that implant length does not have
relevant effect on the tension distribution because the most concentration is on alveolar crest
surrounding the implants. The forces acting on the implant supported prosthesis are produced by
masticatory muscles and should be analysed and transferred within the physiological limits of the
system.
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Edentulism in the posterior region of maxilla will not only lead to alveolar ridge resorption
but also results in shifting of maxillary sinus towards the alveolar crest minimizing the superior
inferior level of bone available. In clinical situations with little bone availability, short implants are a
simple & predictable alternative. An implant is considered short when presenting a length smaller
than 10mm overtime, but none of the short implants available are less than 6mm in length.
The pattern of bone losses after tooth extraction at both maxilla’s posterior area and
mandible is different. Maxilla presents a greater horizontal loss at buccal palatal direction, with a
slow vertical loss. Maxilla’s vertical bone loss occurs in two directions-the natural height
remodelling undergone by the bone and maxillary sinus pneumatization. On the other hand the
mandibular vertical bone loss occurs mainly at the vertical direction, generally resulting in a smaller
bone height. This type of bone loss and presence of important anatomical areas in the planning of
atrophic posterior arches is complex. The rehabilitation of the patient in such limited situations
involves advanced surgical techniques i.e. bone grafts, maxillary sinus lifting which there by
increases the treatment length and cost. The tensions generated on the implant, prosthetic
components and bone tissues are directly proportional to the force applied and inversely
proportional to the low distribution area. Tensions coming from the axial loads are distributed
uniformly on the prosthetic components and the bone tissue.
INDICATIONS / Factors influencing short implant placement:
1. Masticatory Forces: Forces acting on implant supported prosthesis are produced by
masticator muscles &transferred within physiological limit to the system.
2. Unfavourable crown /implant ratio
3. Quality of bone- Low quality may compromise the longevity of short implant.
In addition to the overload increase, the tensions &deformities tend to be greater on the
bone in which rigidity is decreased.
4. Systemic illnesses & smoking habits -They are capable of acting as risk factors for success of
short implants due to load distribution host responses to bacterial action leading to an
increased risk of periodontal diseases & peri implantitis.
5. Anatomic considerations- In both maxilla & mandible, the height & width of available bones
are crucial for placement of implants. In addition, bony undercuts can cause perforation of
cortical bone during osteotomy and lead to subperiosteal implant placement and apices of
teeth may be very close to osteotomy site.
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Maxillary arch: Anatomic consideration in maxilla include maxillary sinus posteriorly, nasal
floor anteriorly and nasopalatine canal. Iatrogenic perforation in maxillary sinus can occur if
implants are too long for available bone height. Implant placement in posterior region is
challenging, given the possibility of sinus problems, insufficient space between the arches &
previous bone resorption. Enlargement of maxillary sinus [pneumatization] can occur due to
bone loss from the internal aspect of sinus wall.
Mandibular arch: The inferior dental canal in the resorbed mandible is an important
anatomic consideration in the mandible. The inferior dental canal may also be positioned
more superiorly in some patients. In the inter foramen area, the amount of bone resorption
and anatomy of mental nerve must be considered to avoid injury or perforation of cortical
plate or impinging on the mental nerve. Other anatomical considerations include anterior
looping of mental nerve & the lingual foramina. In addition, many patients may include
presence of bifid mandibular canal & accessory mental foramina.
6. Less invasive - Short implants placement are less complex and less invasive than the
placement of longer implants in clinical sites where prior adjunctive ridge augmentation,
localised bone grating, inferior mandibular nerve repositioning or maxillary sinus elevation
would be required. Short implant result in limited bone removal& is less traumatic.
Quota studies; short implants simplify treatment in the post resorbed maxilla &mandible &
reduce the number of situations where adjunctive therapy is required. Even if required the
degree of invasiveness is considerably reduced. Short implants can be placed if passive bone
graft resorption has occurred at a site situated for longer implants. They remove the need for
cantilever that might otherwise be required to avoid placing implants in an area with
resorbed bone. A short implant is less invasive than longer implant with adjunctive therapy
to create sufficient bone. It results in less pain & discomfort for the patient &shorter healing
period& overall time. In addition, dental implants offer viable &successful alternative to the
treatment that had otherwise result in the destruction of healthy tooth structure, such as
placement of bridge
7. Alternative treatment option for Angulated implant- Angulated implants are increasingly
being discussed as an alternative treatment option in situations of limited vertical bone
height. The objective of placing implant ina tilted position is to utilize as much bone as
possible, bypassing adjacent structures [i.e. Mental foramen, maxillary sinus etc] and
increase the surface area for restorative support. Restorations can be inserted on these
implants via angulated abutment.
Recommendations: the case of angulated implant should remain confined to situations of
favourable bone quality. Angulated implants should only be placed after suitable 3dplanning, leading to 3d – treatment guidance. Greater inclination of implant leads to
increased force level at the implant bone &implant abutment interfaces, therefore extensive
angulations should be avoided. Inter implant angulation should be confine17d to a single 3d
plane to simplify prosthetic restorations. Single tooth restorations & cantilever bridges as
angulated implants should be avoided, and the aim should be to splint the implant. Adequate
training & clinical experience is a must.
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REVIEW: Studies have suggested that cumulative success rates for implant >10mm is in the range of
91.85% - 99.4%. However other studies, utilizing larger patient sample sizes have success rates in
the range of 83.7% - 88.95%. This discrepancy can be attributed to the different lengths of implant
alone. Placement of longer implants becomes problematic due to anatomic limitations & bone
availability.
Malo’16 et al stated that a short implant of 7 and 8.5 mm with modified surfaces and adequate
placement technique almost matches the success rate of implants. Tawil & Younan17 observed 262
machine implants of 10 or 12mm which supported 163 prosthesis with 8.5% mandible and 11.5 %
maxilla. Implants surface treatment is another primary resource capable of increasing upto 33% of
the bone implant contact percentage which is beneficial to tension contribution. Modifications in
surface morphology were developed to improve the mechanical imbrications between bone tissues
and implant surface favouring the stability and forces dissipation. Further treatment increases the
osseointegration.
A study was conducted of survival rate of short implants less than 10mm installed in
partially edentulous patients. A systematic search was conducted in the electronic database of
MEDLINE. A total of 2600 short length of 5 to 9.5mm were analysed. An increase in implant length
was associated with increase in implant survival. The findings from this systematic review give
evidence that short implants (less than 10mm) can be placed successfully with a tendency towards
increasing survival rate. Installation of shorter dental implants in the mandible has better prognosis
over installations in the maxilla. Surface topography and augmentation procedure preceding the
implant installation did not affect the failure rate of short implants. Using finite element analysis a
series of different experimentally designed short and mini implants have been analysed with regard
to the load transfer to the bone and have been compared to the respective standard implants. Short
implants were inserted in the posterior bone segmented and loaded in osseointegra1ted state with
the force of 300 newtons. Increased bone loading was observed for short and mini implants as
compared with standard implants exceeding the physiological limits of 100 mega pascals . Short
implants have following advantages biomechanically there is bone loading which is more than that
compared to the standard implants.
Success & Survival of implants: Success is defined by immobility, absence of peri implant
radiolucency vertical bone loss <0.2mm annually flowing the implant’s first year of service, absence
of persistent and/or irreversible signs or symptoms of such as pain, infections, neuropathies,
paresthesia or violation of the mandibular canal.Teixierira18et al reported on the survival of 60
hydroxylapatite implants, 8-mm long, placed in the poste1rior mandible of partially edentulous
cases. Over an observation period of 5 years, 2 implants failed, leading to a failure rate of 3.3%.
Deporter19 et al published early data on 48 implants, 7 and 9 mm long. After a mean
observation period of 32.6 months none of the implants had failed. All implants were placed in the
posterior mandible, and 83% were single-tooth restorations. Regarding implants placed in posterior
locations in the maxilla, Deporter19 et al reported on 26 implants, 5, 7 and 9mm long, placed with
simultaneous sinus elevation. After a mean follow up of 11 months, none of the implants had failed.
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Tenbruggenkate22 et al reported on short, plasma sprayed implants, 6-mm long, placed in both
jaws. When only the short implants placed in the premolar and molar locations were considered a
failure rate of 14% was observed in the maxilla.
Failure of Implants: Failure as decided by the implant length.
Distribution of failed implants by length (TABLE 1)13
Implant length(mm)
7
8.5 Total
Number of implants placed
17 294 311
Number of failed implants
2
11
13
Percentage of failed implants 11.8 3.7
4.2
SURFACE TREATMENT OF SHORT IMPLANTS: The review of literature in Table 2 shows that the
best short implants results are achieved with implants having textured surfaces. These Osseotite
implant data show short length outcomes are equivalent to standard length implants. The increase
in surface area by the textured surface exceeds the reduction in surface area as seen with decreased
implant length. Thus minimum osseous contact surface area is maintained. Compared to machined
surface, the Osseotite surface showed a higher bone to implant contact in poor quality bone. Thus
combination of higher surface area and contact osteogenesis contribute to higher survival rates of
short implants.
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(TABLE 2)13: Short implants (<10mm) in partially edentulous cases
References
Quiryen
Naert
Nevins and
Lekholm
Et al14
Et al15
langer16
Et al17
Implant type
Machined Machined
Machined
Machined
Maxilla
Number of
34
30
55
implants placed
Number of failed
4
3
8
implants
Failure rate*
11.7
10.0
14.5
Mandible
Number of
31
28
64
implants placed
Number of failed
5
1
1
implants
Failure rate*
16.1
3.6
1.5
Maxilla +
mandible
Number of
120
implants placed
Number of failed
8
implants
Failure rate*
6.6
Wyatt
andzarb18
Machined
Lekholm
Totals
Et al 19
Machined
22
141
4
19
18.2
13.5
79
202
2
9
2.5
4.4
12
132
3
11
25.0
8.3
*percentage
(Table 3 )13: Short implants (<10mm) in partially edentulous posterior cases
Implant type
Maxilla
Number of implants
placed
Number of failed
implants
Failure rate*
Jent and
leckholm20
Machined
References
Teixerira
Deporter
Et al8
Et al 21
Hydroxyapatite Porous
Deporter
Et al12
Porous
Testori
Et al22
Osseotite8
Totals
15
26
41
2
0
2
13.3
0
4.9
Mandible
Number of implants
placed
Number of failed
implants
39
60
48
147
3
2
0
5
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Failure rate
Maxilla + mandible
Number of implants
placed
Number of failed
implants
Failure rate*
*percentage
7.7
3.3
0
3.4
22
1
4.5
CONCLUSION: Certain clinical situations may not be congenial for additional augmentative
procedures & may demand short implants. As enough evidence through research & clinical scenarios
exist, the clinical judgement should be based on the evidence & availability of newer technological
advances as against involving advanced augmentative procedures. The advantages & drawbacks
should be considered before adopting a technique or material. Short implants are such a boon in
certain clinical situations, but at the same time cannot be a universal choice of treatment.
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AUTHORS:
1. Harish Konde
PARTICULARS OF CONTRIBUTORS:
1. Professor, Department of Prosthodontics,
Vydehi Dental College and Research Centre,
White field, Bangalore.
NAME ADRRESS EMAIL ID OF THE
CORRESPONDING AUTHOR:
Dr. Harish Konde,
SA2-42, Vijaya Enclave,
Bilkehalli, S.R.S. Nagar, OFF Bannerghatta Road,
Bangalore, PIN – 560076.
Email – [email protected]
Date of Submission: 28/06/2013.
Date of Peer Review: 29/06/2013.
Date of Acceptance: 29/07/2013.
Date of Publishing: 01/08/2013
Journal of Evolution of Medical and Dental Sciences/ Volume 2/ Issue 31/ August 5, 2013
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