Comparison of Extra-short (4 mm) Implants Used as Distal Support of a Maxillary Full-arch Fixed Dental Prosthesis vs. 10 mm Implants Installed After Sinus Floor Elevation. A Randomized Clinical Trial
Phase: NA
Conditions: Alveolar Bone Loss
Sponsor: ARDEC Academy

Comparison of extra-short (4 mm) implants used as distal 
support of a maxillary full-arch FDPs vs. 10 mm implants 
installed after sinus floor elevation.  
A randomized clinical trial. 
 
Brief title 
Comparison of extra-short (4 mm) implants used as distal support of a maxillary full-arch 
FDPs vs. 10 mm implants installed after sinus floor elevation. 
 
Authors 
Fabio Rossi, Emanuele Ricci, Lorenzo Ferraioli, Lorenzo Tuci, Daniele Botticelli, Luca 
Cordaro, Claudio Marchetti 
 
Authors’ affiliations 
Fabio Rossi, Emanuele Ricci, Lorenzo Ferraioli, Lorenzo Tuci, Claudio Marchetti, Unit 
Scholar, Department of Biomedical and Neuromotorial Science, University of Bologna, 
Bologna, Italy 
Daniele Botticelli, BMBD, Dentist, PhD, ARDEC Academy, Rimini, Italy 
Luca Cordaro, Head of the Department of Periodontology and Prosthodontics, Eastman 
Dental Hospital, Rome, Italy 
   
Institution at which the work was carried out: 
Department of Biomedical and Neuromotor Science, University of Bologna, Bologna, Italy 
Corresponding author:  
Dott. Fabio Rossi, DDS, Unit Scholar, Department of Biomedical and Neuromotor Science, 
University of Bologna, Bologna, Italy 
Tel. +39 347 2549059 Fax: +39 051 6390234  
E-mail: farossi@libero.it 
Bologna, January 18th, 2017 

Conflict of Interest Statement 
Fabio Rossi and Luca Cordaro declare to be ITI fellows and to be involved in 
activities in favor of the Institute Straumann. 
Daniele Botticelli declares that Ariminum Odontologica, of which is co-owner, is 
receiving contributions to perform research from different implant and biomaterial 
companies. 
All the other authors declare no conflicts of interest. 
 
Acknowledgements 
Grant from ITI number 1049_2014 
 
 
 
 
 
 
 

Abstract 
Aim: to compare the survival and success rates of 4 mm implants used as distal 
support of a maxillary full-arch FDPs with standard (10 mm) implants placed in 
association with a bilateral sinus floor augmentation procedure. 
Material and Methods: Two groups will be randomly prepared, the Short group 
and the Standard group. In the Short group, one 4 mm long and 4.1 mm in 
diameter implant (extra-short implant) will be installed in each side of the posterior 
region of the maxilla. In the Standard group, bilateral sinus floor elevations will be 
performed. After 4 months of healing, one 10 mm long and 4.1 mm in diameter 
implant (standard implant) will be installed into each augmented sinus. In the 
frontal region, four 10 mm long implants will be installed in both groups. Clinical 
assessments and x-rays will be taken at prosthesis delivering (6-8 weeks after 
implant installation), and after 6, 12, 18 and 24 months. 
 
 

Introduction 
Anatomical limitations to implant insertion in fully edentulous arches are 
frequently encountered in the posterior regions of the jaws, due to the 
presence of the mandibular canal and of the maxillary sinus. In such 
situations, the installation of standard implants (≥10 mm) could be 
impossible.  
An alternative might be the use of the so-called “tilted implants” that might 
allow the use of standard implants.1 Vertical augmentation2 procedures or 
sinus floor elevation3 might allow the installation of standard implants as well. 
Another alternative is the use of short implants, as recommended in a 
consensus conference4 for the lower occurrence of complications of this 
treatment compared the use of longer dental implants installed in augmented 
sinus. Another consensus report concluded that the use of ≤6 mm long 
implants are a valid option to be used as alternative to augmentation 
procedures to reduce morbidity incidence. 
A recent article reported a high survival rate (91.7%) after 10 years of loading 
of 6 mm long implants supporting single FDPs in the posterior regions of 
both jaws.5 Recently, 4 mm long implants with a standard diameter have 
been used for the restauration of the posterior edentulous mandible with 
favorable results.6,7 However, RCTs reporting the results from full-arch FDPs 
that included 4 mm long implants placed in the posterior regions of the 
maxilla have not been published yet. 

Hence, the aim of the present study will be to compare the survival and 
success rates of 4 mm implants used as distal support of a maxillary full-arch 
FDPs with standard (10 mm) implants placed in association with a bilateral 
sinus floor augmentation procedure. 
 
Material and methods  
The Declaration of Helsinki was followed, and the protocol was approved by the 
Ethical Committee Interaziendale Bologna-Imola (protocol #15052; 9 September 
2015). 
All procedures, timing, and complications will be systematically explicated to the 
included patients and signed informed consents will be collected. The Consort 
checklist will be followed for this report (http://www.consort-statement.org/). The 
study will be registered in the ClinicalTrials.gov with the following identifier: 
xxxxxxx. 
 
Study population 
This study will be designed as an RCT study. Twenty patients have been planned 
to be included in the present RCT. Two parallel groups will be randomly arranged, 
the Short group that will include the 4 mm long implants, and Standard group that 
will include only 10 mm long implants installed 4 months after bilateral sinus floor 
elevation. Participants recruitment and all clinical procedures will be performed at 
the Department of Biomedical and Neuromotor Sciences, Dental Clinic, University 
of Bologna, RN, Italy.  

The following inclusion criteria will be adopted: 
• Edentulous maxilla  
 
• Willing to receive a full arch fixed restoration in the maxilla. 
• Latest extraction at least 8 weeks before implant insertion 
• Sinus floor height included between 4 to 6 mm 
• Bone width in the distal segments sufficient to allow the insertion of a 4 mm long 
implant of standard diameter. 
• In the anterior maxilla (from first premolar to first premolar) bone width sufficient 
to allow the insertion of 10 mm long implants of standard diameter.  
Minor horizontal augmentations with GBR procedures was allowed in the anterior 
maxilla. 
  
Moreover, the opposing arch have to present one of the following conditions: 
- natural dentition (at least 10 elements from 3.5 to 4.5) 
- FPDs of at least 10 elements (from 3.5 to 4.5) supported by teeth or implants 
- Implant supported or teeth supported overdentures 
- Adequate partial removable prostheses. 
 
Exclusion criteria: 
Systemic exclusion criteria 
• Presence of conditions requiring prophylactic use of antibiotics (e.g., history of 
rheumatic heart disease, bacterial endocarditis, cardiac valvular anomalies, 
prosthetic joint replacements). 

• Major systemic diseases, or medical conditions requiring prolonged use of 
steroids, or alcoholism or chronically drug abuse. 
• Current pregnancy or breastfeeding women 
• Smokers > 10 cigarettes per day 
• Physical handicaps that would interfere with the ability to perform adequate oral 
hygiene 
• Immunocompromised patients including patients infected with HIV 
• Conditions or circumstances, in the opinion of the investigator, which would 
prevent completion of study participation or interfere with analysis of study results, 
such as history of non-compliance, or unreliability. 
• Patients with an ongoing or previous treatment with bisphosphonates (for at least 
2 months for oral therapy or 6 months for IV injection) 
 
Local exclusion criteria  
• Local inflammation, including untreated periodontitis 
• Pre-cancerous oral lesions 
• History of local irradiation therapy 
• Severe bruxism or clenching habits 
• Patients with inadequate oral hygiene or unmotivated for adequate oral home 
care 
• Previous GBR or GTR treatment at the implant site 
• Total removable prosthesis in the lower arch 
 
Randomization and assignment concealment 

A statistician not involved in the study performed the randomization in blocks of 
four and the assignments will be sealed in coded and opaque envelopes. 
 
Masking Procedure: The surgeon will be blinded about the assignment until the 
time of the surgery. The outcome assessor will be blinded about the protocol. 
 
Implants and biomaterial used 
The implants will be offered by Institute Straumann AG, Basel, Switzerland) 
A natural bovine bone grafting material (Cerabone granules 1-2 mm, Botiss 
biomaterial GmbH, Zossen, Germany) will be used for sinus floor elevation. 
A porcine dermis collagen membrane (Collprotect membrane, Botiss biomaterial 
GmbH, Zossen, Germany) will be used to cover the antrostomy. 
Bone fillers and collagen membranes are distributed by Institute Straumann AG, 
Basel, Switzerland. 
 
Surgical procedures in the Standard implant group 
Bilateral sinus floor elevations using a lateral access will be performed using 
Cerabone as filler material and Collprotect to cover the antrostomy. After 4 months 
of healing, one bone level implant, 10 mm long and 4.1 mm in diameter, will be 
installed into each augmented sinus. In the frontal region (included between the 
second premolars), four bone level implants, 10 mm long and 4.1 mm or 3.3 mm in 
diameter will be installed. A non-submerged healing will be allowed. 
 
Surgical procedures in the Short group 

In each side of the posterior region of the maxilla, one tissue level implant, 4 mm 
long and 4.1 mm in diameter, will be installed. In the frontal region, four bone level 
implants, 10 mm long and 4.1 mm or 3.3 mm in diameter will be installed 
 
Maintenance care of the patients 
Amoxicillin and clavulanic acid will be administrated per os before and for the 
following 6 days. As painkiller, Ibuprofen 600 mg per os will be suggested if 
needed. 
 
Prosthetic procedures 
During the healing, a temporary removable prosthesis will be provided to the 
patients. 
Six weeks after implant installation, impressions will be taken and a fixed metal 
ceramic full-arch screw-retained prosthesis will be fabricated and delivered within a 
week. 
 
Clinical evaluation 
Bone quality according to Lekholm and Zarb (1985) will be subjectively evaluated 
and the insertion torque will be assessed using a ratchet device (Institute 
Straumann AG, Basel, Switzerland), and categorized as follows: 0≤15, 15<x<35, 
and ≥35 Ncm. Plaque Control record (O’Leary et al., 1972), Bleeding on Probing 
(Lang et al., 1986), and probing depths will be assessed around Short and 
Standard implants at prosthesis delivering and after 6, 12, 18, 24 months. The 

highest probing depth will be recorded and categorized as follows: 1-3 mm, 4-5 
mm, ≥6 mm. 
PROMs were compiled by each patient regarding esthetics, function, and comfort 
satisfaction using a VAS scale. 
 
Radiographic measurements 
X-rays applying a parallel technique will be taken at implant installation, at 
prosthesis delivering (baseline) and after 6, 12, 18, 24 months. The measurements 
the digital x-rays will be carried twice by the same operator (LT) using the software 
Planmeca ROMEXIS® (Helsinki, Finland). The calibration of the measurements on 
the software will be obtained using the full length of the implant.  
The distance between the implant margin and the first bone to implant contact will 
be measured at the mesial and distal aspects of the Short and Standard implants. 
 
Data analysis 
Mean values will be obtained from the double measurements made at the mesial 
and distal aspects of each implant. Mean values will be calculated between the 
distal and mesial measurements for each implant. 
At the tissue level implants, the height of the polished neck (1.8 mm) will be 
subtracted to obtain the level of the coronal margin of the rough surface. The 
marginal bone levels reported in the present article will be related to the position of 
the coronal marginal rough surface. Marginal bone changes over time will be 
calculated and differences between groups will be evaluated at implant level using 

the Mann-Whitney test included in the Statistics software SPSS (IBM Inc., Chicago, 
IL, USA) The level of significance will be set at α=0.05. 
The primary variable will be the change of marginal bone level between the 
baseline and 1 and 2 years of follow-up. 
 
Outcomes 
PRIMARY OUTCOMES  
TITLE: Survival rate of 4 mm implants 
DESCRIPTION:  
-To compare the survival rate of 4 mm implants used as distal support of a 
maxillary full-arch FDPs with standard (10 mm) implants placed in association with 
a bilateral sinus floor augmentation procedure. 
TIME FRAME: 24 months  
 
TITLE: Changes of crestal bone level 
DESCRIPTION: Change of crestal bone level measured on intraoral x-ray applying 
a parallel technique from baseline (definitive prosthesis delivering) and 2-year 
follow-up. The distance between the implant margin and the first bone to implant 
contact will be measured in millimeters at the mesial and distal aspects of the Short 
and Standard implants. 
TIME FRAME: 24 months 
 
SECONDARY OUTCOMES  
TITLE: Technical complications 

DESCRIPTION:  
Technical complications: any technical complications related to implants, 
abutments, screw loosening, prosthetic fracture or chipping of the veneer material 
expressed in number of occurrence. 
TIME FRAME: 24 months 
 
 

References 
1. Apaza Alccayhuaman KA, Soto-Peñaloza D, Nakajima Y, Papageorgiou SN, 
Botticelli D, Lang NP. Biological and technical complications of tilted 
implants in comparison with straight implants supporting fixed dental prostheses. 
A systematic review and meta-analysis. Clin Oral Implants Res. 2018 Oct;29 
Suppl 18:295-308. 
2. Cucchi A, Ghensi P. Vertical Guided Bone Regeneration using Titanium-reinforced 
d-PTFE Membrane and Prehydrated Corticocancellous Bone Graft. Open Dent J. 
2014 Nov 14;8:194-200. 
3. Raghoebar GM, Onclin P, Boven GC, Vissink A, Meijer HJA. Long-term 
effectiveness of maxillary sinus floor augmentation A systematic review and meta-
analysis. J Clin Periodontol. 2019 Jan 9. doi: 10.1111/jcpe.13055. [Epub ahead of 
print] 
4. Thoma DS, Zeltner M, Hüsler J, Hämmerle CH, Jung RE. EAO Supplement 
Working Group 4 - EAO CC 2015 Short implants versus sinus lifting with 
longer implants to restore the posterior maxilla: a systematic review. Clin 
Oral Implants Res. 2015 Sep;26 Suppl 11:154-69. 
5. Rossi F, Lang NP, Ricci E, Ferraioli L, Baldi N, Botticelli D. Long-term follow-up of 
single crowns supported by short, moderately rough implants-A prospective 10-
year cohort study. Clin Oral Implants Res. 2018 Dec;29(12):1212-1219 
6. Slotte C, Grønningsaeter A, Halmøy AM, Öhrnell LO, Mordenfeld A, Isaksson S, 
Johansson 
LÅ. 
Four-Millimeter-Long 
Posterior-Mandible 
Implants: 
5-Year 
Outcomes of a Prospective Multicenter Study. Clin Implant Dent Relat Res. 2015 
Oct;17 Suppl 2:e385-95. 

7. Esposito M, Zucchelli G, Barausse C, Pistilli R, Trullenque-Eriksson A, 
Felice P. Four mm-long versus longer implants in augmented bone in 
atrophic posterior jaws: 4-month post-loading results from a multicentre 
randomised controlled trial. Eur J Oral Implantol. 2016;9(4):393-409. 
PubMed PMID: 27990507. 
 
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