Short Dental Implants ( 6 mm) to Rehabilitate Severe Mandibular Atrophy: A Systematic Review
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Short Dental Implants (≤ 6 mm) to Rehabilitate
Severe Mandibular Atrophy: A Systematic Review
Paolo Carosi, DDS, MSc, PhD1/Claudia Lorenzi, DDS, PhD1/Mauro Laureti, MD, DDS2/
Nicola Ferrigno, DDS2/Claudio Arcuri, MD, DDS4
Purpose: This study aimed to assess the survival rate, marginal bone levels, and prosthetic success of short implants
when placed in posterior areas of severely reabsorbed mandibles. Materials and Methods: A systematic review was
performed of all randomized controlled trials with at least 10 patients with a control group where bone augmentations
were performed that were published between January 2015 and February 2020. From 77 pertinent studies, 14 full-text
publications were studied, and 6 studies fulfilled the inclusion criteria. Results: The implant survival rates of short dental
implants ranged from 92% to 96.9% with a follow-up from 1 to 5 years, and the prosthetic success rate ranged from
90% to 100% during the same follow-up. The mean marginal bone level values of involved short implants ranged from
–0.51 to –2.30 mm. Conclusion: The obtained data showed that short dental implants are a valid therapeutic choice
to rehabilitate severe mandibular atrophy in the medium to long term. Int J Oral Maxillofac Implants 2021;36:30–37. doi:
10.11607/jomi.8510
Keywords: guided bone regeneration, mandibular atrophy, short dental implants, short implants
T he rehabilitation of partially edentulous arches by
means of dental implants is a well-accepted treat-
ment. Currently, patients ask for an implant therapy
in this zone. To prevent any nerve injury, several alter-
native methods have been proposed, such as the lat-
eralization of the inferior alveolar nerve,4 vertical ridge
that is as minimally invasive and minimally morbid as augmentation (VRA),5 and guided bone regeneration
possible. Expectations are increasing, but neverthe- (GBR). These techniques can be dangerous for the pa-
less, many patients are reluctant to accept an implant tients because they are directly proportional to the sur-
treatment, and they are especially apprehensive if a geon’s skills. In addition, these techniques can lead to
bone augmentation procedure is required.1 The re- increased posttreatment morbidity, time, and costs for
habilitation of the posterior region of the mandible the patients. Actually, earlier studies reported that the
is always a hard-complexity case due to the course of lateralization of the inferior alveolar nerve could cause
the inferior alveolar nerve.2 In most cases, bone verti- moderate postoperative morbidity.6 In the last years,
cal height is enough to place a standard implant. Un- the use of short (≤ 6 mm) implants has been increasing
fortunately, several alterations affect bone quality and by clinicians and has been investigated more by several
quantity after tooth loss,3 and it is mandatory to avoid researchers.7–11 The definition of short implants is still
any nerve damage when performing implant surgery not completely defined, and as a result, interpretation
of the literature is complicated by several different defi-
nitions. Strietzel and Reichart reported that all implants
that have lengths less than or equal to 11 mm have to
be considered short.12 On the other hand, Group 1 of
1Department of Chemical Science and Technologies, PhD in the 6th ITI Consensus Conference considered “short
Materials for Health, Environment and Energy–Dentistry, Tor
dental implants” to be all dental implants that are
Vergata University of Rome, Rome, Italy.
2Department of Oral and Maxillo-Facial Sciences, “Sapienza,” ≤ 6 mm.13 Scientific evidence from several clinical stud-
University of Rome, Rome, Italy. ies reported no statistically significant differences in
3Department of Clinical Sciences and Translational Medicine,
survival rate and/or marginal bone loss (MBL) of short
School of Dentistry, Tor Vergata University of Rome, Rome, Italy. dental implants compared with standard-length den-
Correspondence to: Dr Paolo Carosi, Department of Chemical tal implants in augmented sites.14 In addition, the pos-
Science and Technologies, Via della Ricerca Scientifica, 1, 00133 sible combination between short implants and GBR
Rome, Italy. Email: carosipaolo29@gmail.com can result in a reduced complexity of the surgery.15
Furthermore, the use of short dental implants is often
Submitted April 14, 2020; accepted June 16, 2020.
©2021 by Quintessence Publishing Co Inc. related to a nonfavorable prosthetic crown-to-implant
30 Volume 36, Number 1, 2021Carosi et al
(C/I) ratio. Garaicoa-Pazmiño et al16 demonstrated that Search Strategy
an unfavorable C/I ratio is not connected to decreased The research involved electronic databases (MEDLINE,
implant survival ratio and/or increased biologic com- Embase, and Cochrane Library). The following combi-
plications. The aim of this study was to systematically nation of words was used: “short implant OR short im-
review the literature concerning implant survival rates, plants OR extrashort implant OR extrashort implants
marginal bone levels, and prosthetic success of short OR extra-short implant OR extra-short implants AND
dental implants used for severe posterior mandibular mandible.” In addition, bibliographies of reviews were
atrophy rehabilitation. analyzed and cross-checked.
Selection Criteria and Data Extraction
MATERIALS AND METHODS Two independent reviewers (P.C. and C.L.) performed
a three-stage screening procedure of all the selected
This study followed the Preferred Reporting Items for studies. Any possible disagreement was resolved by
Systematic Review and Meta-Analyses (PRISMA) state- means of additional review. First of all, the titles were
ment.17 The main question of the research was en- analyzed to eliminate studies that were not appropri-
closed in PICO (Population, Intervention, Comparison, ate. Then, all the abstracts were analyzed, and only the
Outcomes) format: “Do short implants (I) report the selected studies were involved in the full-text reading.
same clinical outcomes (O) in the posterior edentulous
mandible (P) as standard implants after bone augmen- Risk of Bias
tation procedures (C)?” The inclusion and exclusion cri- The quality of the studies involved in the review was
teria were defined by the authors before the start of the assessed by the reviewers (P.C. and C.L.) using the Co-
study. The inclusion criteria were all randomized con- chrane Collaboration tool for assessing risk of bias for
trolled trials (RCTs), based on human subjects, with at randomized trials. The potential risk of bias was classi-
least 10 patients and 1 year of follow-up after prosthe- fied as low, high, or unclear. Any disagreement was dis-
sis delivery and published in the English language. All cussed until it was resolved by consensus.
trials were designed to evaluate clinical effectiveness
of short implants to rehabilitate severe posterior man-
dibular atrophy. All studies analyzed were published RESULTS
between January 1, 2015, and February 29, 2020. The
exclusion criteria were as follows: studies reporting Identified Articles
the same data as following publications by the same The search resulted in 77 titles. After title and abstract
authors, systematic reviews, commentaries and letters screening, a total of 14 potentially relevant studies were
to the editor, case reports, in vitro studies, studies in identified. Four studies18–21 were excluded because
animal models, and case series. Relevant systematic re- they reported a unitary statistical analysis of maxillary
view papers, as well as the reference lists of all included and mandibular implant survival and MBL. Two stud-
articles, were searched by hand to identify further pub- ies22,23 were excluded because the same data were re-
lications. Full-text screening, study selection, and data ported in two other studies with longer follow-up. One
extraction were performed in duplicate, and disagree- study24 was excluded because completely edentulous
ments were resolved by consensus. mandibles were treated, another study25 was excluded
due to lack of statistical data, and another study was ex-
Types of Interventions cluded because standard-length implants were placed
The analyzed studies were RCTs or split-mouth RCTs. without performing bone augmentation procedures26
The test group was treated with short dental implants, (Table 1). In the end, five studies were included in the
and the control group was treated with bone augmen- qualitative analysis (Fig 1).
tation procedures and regular dental implants in severe
posterior mandibular atrophy. Included Studies
The five studies that met the inclusion criteria are re-
Outcome Measures ported in Table 2. The quality assessment is summa-
The primary outcome investigated by this systematic rized in Table 3. All selected studies are RCTs published
review was the implant survival rate of short dental between 2015 and 2020 and conducted in a university
implants. The secondary outcomes were marginal environment. Three studies had only one treatment
bone levels and prosthetic success rate. All the col- option that was accomplished on each patient in a
lected and analyzed data were measured before inter- random way,8–10 and two studies had a split-mouth
vention and at every yearly recall, for at least 1 year of design7,11 where both treatment modalities were per-
follow-up. formed on each patient. A total of 167 short implants
The International Journal of Oral & Maxillofacial Implants 31Carosi et al
Table 1 Excluded Studies and Reasons for Exclusion
Studies Cause for exclusion
Naenni et al (2018)18; Shah et al (2018)19; Statistical analysis is comprehensive and not divided by maxilla and mandible.
Zadeh et al (2018)20; Felice et al (2016)21
Gastaldi et al (2018)22; Felice et al (2018)23 Patients or data reported in other included studies with longer follow-up.
Guida et al (2019)24 Treatment on completely edentulous mandibles.
Bernardi et al (2018)25 Lack of data.
Rossi et al (2015)26 Bone augmentations were not performed to place standard-length dental implants.
Implant Survival Rates
Records identified through Additional records identified The overall short implant survival
Identification
database searching through other sources rates ranged from 92% to 96.9%,
(n = 77) (n = 0) with a follow-up from 1 to 5 years
in function. The standard-length
dental implant groups had implant
survival rates ranging from 84.8% to
Records after duplicates removed 100% with a follow-up from 1 to 5
(n = 77) years. Esposito et al9 in 2019 report-
ed an overall short implant survival
Screening
rate in atrophic mandibles of 96.9%
after 5 years in function. Otherwise,
Records screened
the standard-length implant group
(n = 77) had an overall implant survival rate
of 93.5% after the same follow-up
Records excluded period. Similar results are reported
(n = 63)
by Felice et al.10 The test short im-
Eligibility
plant group reported an overall im-
Full-text articles assessed for eligibility
(n = 14) plant survival rate of 95.1%, while
the control group reported an over-
Full-text articles excluded all implant survival rate of 93.6%
with reasons after 5 years in function. Another
(n = 9)
study by Felice et al11 reported that
Included
Studies included in qualitative synthesis the short implant survival rate after
(n = 5) 5 years in function was 94.1%, while
the standard-length dental implant
survival rate was 97.4% (Table 4).
Fig 1 Search strategy flowchart. Marginal Bone Levels
The MBL values were reported in
(≤ 6 mm) were placed in 76 patients, while 176 standard implants with each study involved in this review
> 6 mm length were placed in 76 patients. In four studies,8–11 implants for both implant groups. The mean
were placed in the maxilla and in the mandible. Only results from the MBL values of the short implant
mandibular implants were taken. Two studies7,8 had 1 year of follow-up, group between the studies ranged
while the other four studies had 5 years of follow-up. Concerning dental from –0.51 to –2.30 mm. The mean
implant length, the short implant group included implants of lengths of MBL values of the standard-length
4 to 6 mm with two studies reporting data on 4-mm implants7,8 and three implant groups between the studies
studies9–11 reporting data on 5-mm implants. The control groups had ranged from –0.77 to –2.64 mm.
a variety of implant lengths ranging from 8.5 to 15 mm. No immediate
loading was performed in any of the studies. The prosthetic design was Prosthesis Success Rates
assessed in order to splint multiple adjacent implants in five studies. Con- The studies involved in this system-
cerning the retention of restorations, four studies8–11 reported combina- atic review reported high prosthesis
tions between screw- or cement-retained restorations. The other study7 success rates. The values for the short
included only cement-retained restorations. implant groups ranged from 90.9%
32 Volume 36, Number 1, 2021Carosi et al
Table 2 Main Characteristics of the Studies
Control groups Short
1. C
ontrol group implants Prosthetic
Test groups patients total at 1. N
o. of short Regular implants design
1. T est group patients baseline (male, implants total 1. N
o. of regular implants total at 1. Short
at baseline (male, female) at baseline baseline Implant implant
female) 2. Age (mean, y) 2. No. of short 2. No. of regular implants total at last length (mm) group
2. Age (mean, y) 3. C
ontrol group implants follow-up 1. Short 2. Regular Follow-
3. T est group patients patients total at total at last 3. Type of grafting 2. Regular implant up
Study at last follow-up last follow-up follow-up 4. Healing period of grafted sites 3. Manufacturer group (mo)
Rokn et al 1. 11 (2, 9) 1. 11 (2, 9) 1. 25 1. 22 1. 4 1. Splinted 12
(2018)7 2. 50.3 2. 50.3 2. 23 2. 20 2. 8–10 2. Splinted
3. 10 3. 10 3. Allograft mixed with autogenous 3. Straumann
bone harvested from the external
oblique ridge area
4. 6 months
Bolle et al 1. 20 (7, 13) 1. 20 (12, 8) 1. 43 1. 46 1. 4 1. Splinted 12
(2018)8 2. 59.3 2. 63.25 2. 41 2. 39 2. 8
.5–10– 2. Splinted
3. 20 3. 19 3. Interposition of blocks of colla 11.5–13
genated cancellous equine bone 3. Global-D
4. 4 months
Esposito 1. 20 (3, 17) 1. 20 (7, 13) 1. 32 1. 31 1. 5 1. Splinted 60
et al 2. 58.6 2. 52.8 2. 30 2. 28 2. 10–13 2. Splinted
(2019)9 3. 17 3. 18 3.Interposition of blocks of colla 3. MegaGen
genated cancellous equine bone.
4. 4 months
Felice et al 1. 15 (4,11) 1. 15 (4,11) 1. 26 1. 30 1. 5 1. Splinted 60
(2019)10 2. 56 2. 56 2. 24 2. 29 2. 10–13 2. Splinted
3. 11 3. 11 3. Interposition of blocks of 3. MegaGen
anorganic bovine bone
4. 4 months
Felice et al 1. 10 (5, 5) 1. 10 (5,5) 1. 41 1. 47 1. 5 1. Splinted 60
(2019)11 2. 54.1 2. 54.1 2. 39 2. 44 2. 11.5–13–15 2. Splinted
3. 9 3. 9 3.Interposition of blocks of colla 3. No data
genated cancellous equine bone
4. 3 months
to 100%, while the values for standard-length implant the patients.4 In opposition, it is possible to use short
groups ranged from 90% to 100%. dental implants with reduced length (≤ 6 mm) to over-
come several surgery- and patient-centered issues.14 The
main question about short dental implants is how long
DISCUSSION they can survive once they are in function due to the re-
duced bone-to-implant surface. To achieve the highest
This study aimed to systematically review the literature level of evidence, only RCTs were included in the analysis
regarding clinical outcomes of short dental implants in order to add more relief to the findings. Several RCTs
in severe posterior mandibular atrophy rehabilitation. were conducted to better understand if short implant
Severe mandibular atrophy rehabilitations are always survival rates can be compared with standard dental
a difficult challenge for clinicians. Standard dental implants in augmented bone and if their use is justified
implants (≥ 10 mm) are still the best choice when an as an alternative treatment approach. There were no sta-
implant-supported rehabilitation needs to be planned. tistically significant differences between the test groups
Unfortunately, sometimes several anatomical condi- and the control groups at 5 years of follow-up in all the
tions such as reduced vertical bone heights at implant RCTs involved in this review. However, the main limita-
sites (6 to 8 mm above the mandibular canals) prevent tion of these studies is that the longer follow-up is only at
the chance to use standard dental implants. 5 years in function. These results are in accordance with
The possibility to perform VRA or inferior alveolar the systematic review presented by Ravidà et al that re-
nerve transposition is directly proportional to the sur- ported the survival rates of short dental implants in the
geon’s skills, and often these techniques lead to aug- mandible as 99%, 98.5%, 98.1%, 97.3%, and 96.2% from
mented posttreatment morbidity, time, and costs for years 1 to 5, respectively, validating the high survival rate
The International Journal of Oral & Maxillofacial Implants 33Carosi et al
Table 3 Quality Assessment
Blinding of
Random participants
Study sequence Allocation and
(year) generation Note concealment Note personnel Note
Rokn et al Low risk A randomization Low risk The allocation of each patient was sequentially High risk - The surgery treatment had to
(2018)7 list was numbered and closed in an envelope. be known by the surgeon.
created by an - It is in the rights of the
independent patients to know how they
investigator were treated.
before all the
surgeries.
Bolle et al Low risk Randomization Low risk The allocation of each patient was sequentially High risk - The surgery treatment had to
(2018)8 list was numbered and closed in an envelope. be known by the surgeon.
generated by - It is in the rights of the
one computer. patients to know how they
were treated.
Esposito et Low risk Randomization Low risk The allocation of each patient was sequentially High risk - The surgery treatment had to
al (2019)9 list was numbered and closed in an envelope. be known by the surgeon.
generated by - It is in the rights of the
one computer. patients to know how they
were treated.
Felice et al Low risk Randomization Low risk The surgeon recorded one site of his choice High risk - The surgery treatment had to
(2019)10 list was as site number 1 and the contralateral as site be known by the surgeon.
generated by number 2. Sites numbered 1 of eligible patients - It is in the rights of the
one computer. were randomized according to a split-mouth patients to know how they
design. The information on how to treat were treated.
site number 1 was enclosed in sequentially
numbered, identical, opaque, sealed envelopes.
Felice et al Low risk Randomization Low risk The surgeon recorded one site of his choice High risk - The surgery treatment had to
(2019)11 list was as site number 1 and the contralateral as site be known by the surgeon.
generated by number 2. Sites numbered 1 of eligible patients - It is in the rights of the
one computer. were randomized according to a split-mouth patients to know how they
design. The information on how to treat were treated.
site number 1 was enclosed in sequentially
numbered, identical, opaque, sealed envelopes.
of short implants in the mandible.27 In another system- addition, a prospective study by Slotte et al in 201429 re-
atic review, Papaspyridakos et al in 201828 showed how ported data from 1 to 5 years in function of short dental
short dental implants (≤ 6 mm) had high survival rates implants. The short implant survival rate was 100% after
when involved in posterior edentulous mandibular re- 1 year and 92.2% after 5 years in function. The survival
habilitations. The mean survival rate reported after peri- rate of the dental implants depends on the quality and
ods of 1 to 5 years in function was 96% for short implant quantity of peri-implant bone. The studies involved in
test groups and 98% for standard-length control groups. this review reported similar MBL after 5 years in function
The results from the RCTs by Esposito et al in 20199 and for test groups and for control groups. The test groups
Felice et al in 201910 reported implant survival rates of showed minor values in terms of mean MBL compared
short dental implant groups comparable to the surviv- with augmented control groups. The mean MBL values
al rates of the control groups. The survival rate trends in test groups were 1.34 mm,10 1.43 mm,9 and 1.72 mm11
of both groups found in the two RCTs by Esposito et al at 5 years of follow-up. These values were slightly high-
and Felice et al in the two systematic reviews27,28 dem- er compared with the ITI Consensus Statement that
onstrate that short dental implants can be a valid treat- reported mean values ranging from +0.06 mm (bone
ment option in severe posterior mandibular atrophy. In gain) to –1.22 mm. It is also notable that the mean MBL
34 Volume 36, Number 1, 2021Carosi et al
Free of
Blinding of Incomplete another
outcome outcome Selective source’s Overall
assessment Note data Note reporting Note bias Note risk
Low risk An independent Low risk Dropout Low risk All No The definitive prostheses were realized in order to Low risk
operator evaluated outcomes splint the implants if two or more implants were
the radiographies data were placed adjacent.
and led the prosthetic published.
follow-up.
Low risk An independent Low risk Dropout Low risk All No The sample size was not calculated before the Low risk
operator evaluated outcomes beginning of the study. The clinical examinations
the radiographies data were were performed not knowing the group allocation,
and led the prosthetic published. but the augmented sites could be identified
follow-up. by means of length of the dental implants. The
definitive prostheses were realized in order to splint
the implants if two or more implants were placed
adjacent.
Low risk The clinical Unclear risk Dropout Low risk All No The sample size was not calculated before Unclear
measurements outcomes the beginning of the study. It is not clear if the risk
were made by data were dropped-out patients that authors can no longer
three independent published. contact were involved in the statistical analysis as
clinicians while successful cases. The clinical examinations were
one independent performed not knowing the group allocation, but
clinician made the augmented sites could be identified by means
the radiographic of length of the dental implants. The definitive
evaluation. prostheses were realized in order to splint the
implants if two or more implants were placed
adjacent.
Low risk The clinical Unclear risk Dropout Low risk All No It is not clear if the dropped-out patients that Unclear
measurements outcomes authors can no longer contact were involved in the risk
were made by data were statistical analysis as successful cases. The clinical
two independent published. examinations were performed not knowing the
clinicians while one group allocation, but the augmented sites could be
independent clinician identified by means of length of the dental implants
made the statistical and the different radiolucency of bone.
evaluation.
Low risk The clinical measure Unclear risk Dropout Low risk All No It is not clear if the dropped-out patients that Unclear
ments were made outcomes authors can no longer contact were involved in risk
by six independent data were the statistical analysis as successful cases. The
clinicians while published. definitive prostheses were realized in order to splint
one independent the implants if two or more implants were placed
dental student made adjacent.
the radiographic
evaluation.
values of control groups of the studies included in this al,29 where the mean MBL was 0.44 mm after the first
review were slightly higher compared with the mean year in function, 0.55 mm after 3 years in function, and
MBL values reported in the ITI Consensus Statement.14 0.53 mm after 5 years in function. Rossi et al26 suggested
The control augmented groups showed a mean MBL that this may have been due to the more apical shift in
of 2.08 mm,9 2.10 mm,11 and 2.11 mm10 after 5 years in the biologic width during the first period of healing, and
function. The Consensus Statement reported mean MBLs it provides marginal bone adaptation. It is mandatory to
ranging from +0.02 mm (bone gain) to −1.54 mm.13 It is highlight that even if mean bone loss around short den-
important to observe that the main bone remodeling tal implants seems to be minor compared with standard
around short dental implants occurs during the first year dental implants, the loss of 2 mm of peri-implant bone
after the prosthesis delivery. Two RCTs by Esposito et al9 height represents 30% (for 6-mm short implants) or 50%
and Felice et al10 reported greater peri-implant bone re- (for 4-mm short implants) of the overall bone-to-implant
absorption after 1, 3, and 5 years in function and mean contact area, whereas the same bone loss for standard
MBLs of 0.94 mm, 1.33 mm, and 1.43 mm, and 1.05 mm, dental implants represents a maximum of 20% of the
1.25 mm, and 1.34 mm, respectively. The same state- overall bone-to-implant contact area. For this reason, it
ment was reported in a prospective study by Slotte et is very important to involve the patients in a long-term
The International Journal of Oral & Maxillofacial Implants 35Carosi et al
Table 4 Main Results from Selected Studies
Short implant Regular implant Marginal Short implant group Regular implant
survival rate survival rate bone loss complications group complications
1. Baseline 1. Baseline (mm) 1. P
eri-implant mucositis 1. Peri-implant mucositis Prosthetic
2. Survived 2. Survived 1. Short 2. Temporary paresthesia 2. Temporary paresthesia success (in %)
3. Dropouts 3. Dropouts implant 3. Crown loosened 3. Crown loosened 1. Short implant
4. Failed 4. Failed 2. Regular 4. Chipping of definitive 4. Chipping of definitive 2. Regular
Study 5. Percentage 5. Percentage implant crown crown implant
Rokn et al (2018)7 1. 25 1. 22 1. 1.55 1. 0 1. 5 1. 100
1-year split-mouth 2. 23 2. 20 2. 1.97 2. 0 2. 3 2. 100
RCT 3. 2 3. 2 3. 0 3. 0
4. 0 4. 0 4. 0 4. 0
5. 92 5. 92
Bolle et al (2018)8 1. 43 1. 46 1. 0.51 1. 0 1. 1 1. 95
1-year RCT 2. 41 2. 39 2. 0.77 2. 0 2. 3 2. 95
3. 0 3. 6 3. 1 3. 0
4. 2 4. 1 4. 1 4. 0
5. 95.3 5. 84.8
Esposito et al 1. 32 1. 31 1. 1.43 1. 1 1. 1 1. 95
(2019)9 2. 30 2. 28 2. 2.08 2. 8 2. 14 2. 90
5-year RCT 3. 1 3. 1 3. 0 3. 0
4. 1 4. 2 4. 1 4. 0
5. 96.9 5. 93.5
Felice et al (2019)10 1. 26 1. 30 1. 1.72 1. 1 1. 0 1. 90.9
5-year split-mouth 2. 24 2. 29 2. 2.10 2. 3 2. 10 2. 100
RCT 3. 0 3. 0 3. 1 3. 0
4. 2 4. 1 4. 0 4. 0
5. 94.1 5. 96.6
Felice et al (2019)11 1. 41 1. 47 1. 1.34 1. 0 1. 5 1. 95
5-year RCT 2. 39 2. 44 2. 2.11 2. 0 2. 7 2. 91.4
3. 0 3. 0 3. 0 3. 0
4. 2 4. 3 4. 0 4. 0
5. 95.1 5. 93.6
professional oral-hygiene program in order to prevent complications7–11 when short dental implants are
any peri-implant issues and to keep peri-implant tissues splinted. The ITI Consensus Report reminded that it
healthy. is recommended to splint short dental implants and
The use of short dental implants to rehabilitate the to avoid the risk of occlusal overload if the implant-
posterior areas of the mandible is expected to deliver supported restorations involve a single missing molar
prostheses with a nonfavorable C/I ratio due to the and/or the patient presents parafunctional habits. The
loss of vertical height in the reabsorbed areas. A sys- occlusion should be assessed and modified as neces-
tematic review16 and a retrospective study30 reported sary every maintenance visit.13 Even with the quality of
that a nonfavorable C/I ratio seems to not have any ef- the included studies in this review, there is a risk of bias
fect on bone-level changes. However, more studies are due to the small number of RCTs with a long follow-
recommended to increase scientific evidence regard- up period. Consequently, it is mandatory to take care
ing this topic. Moreover, it is important to focus on the when reading the results.
prosthetic design. Some studies have hypothesized
that splinting implants may lead to a better occlusal
load distribution.31–33 Finite element analyses report- CONCLUSIONS
ed that the occlusal load distribution on splinted im-
plants allows the implant bodies to not be overloaded Within the limitations of this systematic review, it seems
and distribution of less stress to the implant and the that short dental implants are a valid therapeutic choice
peri-implant bone.32,34 Clinical evidence of this state- to rehabilitate severe mandibular atrophy in the medi-
ment can be carried out from the studies involved um to long term. For further information, several RCTs
in this review, whereas most of the authors reported comparing long-term survival rates of short and longer
a high prosthetic success rate7–11 and few technical implants are required to collect new data.
36 Volume 36, Number 1, 2021Carosi et al
ACKNOWLEDGMENTS 16. Garaicoa-Pazmiño C, Suárez-López del Amo F, Monje A, et al. Influ-
ence of crown/implant ratio on marginal bone loss: A systematic
review. J Periodontol 2014;85:1214–1221.
This study was not financially supported by any organizations. The 17. Moher D, Liberati A, Tetzlaff J, Altman DG; PRISMA Group. Preferred
authors have no conflict of interest to declare. reporting items for systematic reviews and meta-analyses: The
PRISMA statement. Plos Med 2009;6:e1000097.
18. Naenni N, Sahrmann P, Schmidlin PR, et al. Five-year survival of short
single-tooth implants (6 mm): A randomized controlled clinical trial. J
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