Luigi CanulloRoberto CocchettoFabio MarinottiDavid Pe~narrocha OltraMar�ıa Pe~narrocha DiagoIgnazio Loi

Clinical evaluation of an improvedcementation technique for implant-supported restorations: a randomizedcontrolled trial

Authors’ affiliations:Luigi Canullo, Private Practice and IndependentResearcher, Rome, ItalyLuigi Canullo, Department of Oral Surgery andImplantology, Valencia University Medical andDental School, Valencia, SpainRoberto Cocchetto, Private Practice, Verona, ItalyFabio Marinotti, Laboratory Technician, Rome,ItalyDavid Pe~narrocha Oltra, Mar�ıa Pe~narrocha Diago,Department of Oral Surgery, Valencia UniversityMedical and Dental School, Valencia, SpainIgnazio Loi, Private Practice, Cagliari, Italy

Corresponding author:Luigi CanulloVia Nizza, 46, 00198 Rome, ItalyTel.: +39 06 8411980Fax: +39 06 8411980e-mail: lugicanullo@yahoo.com

Key words: abutment design, cement remnants, chamfer, feather-edge abutment, peri-

implantitis, shoulderless abutment

Abstract

Background: Cement remnants were frequently associated with peri-implantitis. Recently, a

shoulderless abutment was proposed, raising some concern about cement excess removal.

Aim: To compare different cementation techniques for implant-supported restorations assessing

the amount of cement remnants in the peri-implant sulcus. Additional aim was to compare the

effect of these cementation techniques using two different abutment designs.

Material & methods: Forty-six patients requiring double implant-supported restoration in the

posterior maxilla were randomly divided in two groups according to the cementation modality:

intraoral and extraoral. According to the abutment finishing line, implants in each patient were

randomly assigned to shoulderless or chamfer subgroup. In the intraoral group, crowns were

directly seated onto the titanium abutment. In the extraoral group, crowns were firstly seated onto

a resin abutment replica and immediately removed, then cleansed of the cement excess and finally

seated on the titanium abutment. After cement setting, in both groups, cement excess was

carefully tried to remove. Three months later, framework/abutment complexes were disconnected

and prepared for microscopic analysis: surface occupied by exposed cement remnants and marginal

gaps were measured. Additionally, crown/abutment complexes were grinded, and voids of cement

were measured at abutment/crown interface. Related-samples Friedman’s two-way analysis of

variance by ranks was used to detect differences between groups and subgroups (P ≤ 0.5).

Results: At the end of the study, a mean value of 0.45 mm2 (�0.80), 0.38 mm2 (�0.84), and

0.065 mm2 (�0.13) and 0.07 mm2 (�0.15) described surface occupied by cement remnants in

shoulderless and chamfer abutment with intraoral cementation and shoulderless and chamfer

abutment with extraoral cementation, respectively. A mean value of 0.40 mm2 (�0.377), 0.41 mm2

(�0.39) and 0.485 mm2 (�0.47) and 0.477 mm2 (�0.43) described cement voids at the abutment/

crown interface; a mean value of 0.062 mm (�0.03), 0.064 mm (�0.35), 0.055 mm (�0.016) and

0.054 mm (�0.024) described marginal gaps. Statistics showed tendency of intraoral cementation to

have significantly higher cement remnants compared with abutments with extraoral cementation

groups. At the same time, the presence of voids was significantly higher in case of extraoral

cementation. No significant differences between groups for the variable “gap”.

Conclusions: Despite the presence of more voids, extraoral cementation reduces cement excess.

However, using low adhesivity cement and careful cement removal, a very limited quantity of

cement remnants was observed also in the intraoral cementation.

Implant-supported prostheses can be subdi-

vided into screw-retained or cement-retained.

In literature, there is actually no consensus

on which of these techniques provide better

mechanical or biological performances

though advantages and disadvantages have

been identified (Wittneben et al. 2014).

Screw-retained prostheses are more easily

retrievable (for instance, in case of loosening

of the retaining screw or chipping of the

veneering material) and, due to the reduced

vertical amount of space needed, they are

more indicated in cases with limited interoc-

clusal distance (Torrado et al. 2004).

Cement-retained reconstructions provide

easier passivation on multiple implants

Date:Accepted 4 March 2015

To cite this article:Canullo L, Cocchetto R, Marinotti F, Oltra DP, Diago MP,Loi I. Clinical evaluation of an improved cementationtechnique for implant-supported restorations: a randomizedcontrolled trial.Clin. Oral Impl. Res. 00, 2015; 1–8.doi: 10.1111/clr.12589

© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd 1

splinted frameworks, better esthetics (due to

the lack of occlusal openings) and lower costs

(Michalakis et al. 2003).

On the other hand, literature suggests that,

even after a careful removal procedure, some

residual cement may remain in the peri-

implant sulcus (Chaar et al. 2011; Sailer

et al. 2012). The risk of such event increases

as the restorations’ margins are located dee-

per subgingivally (Linkevicius et al. 2011,

2013a,b). Cement remnants have been fre-

quently associated with peri-implant disease

(Wilson 2009; Linkevicius et al. 2013a,

Korsch et al. 2014), and for this reason,

screw-retained restorations have been sug-

gested as a first choice in daily practice by

some authors (Br€agger et al. 2005).

An original cementation technique for

implant-supported restorations has been pro-

posed (Wadhwani et al. 2009) as a mean to

reduce cement remnants in peri-implant sul-

cus: a silicon abutment replica is used as an

initial “extraoral “cementation with the pur-

pose to extrude excess cement from the

crown, clean it and then place it onto the

abutment intraorally to complete setting. An

in vitro study (Chee et al. 2013) seemed to

confirm the efficacy of the method compared

with three other cementation methods.

The abutment and crown design may play

a role in increasing the risk of cement rem-

nants in the peri-implant sulcus. In fact, to

minimize cement remnants, undercuts

should be reduced to a minimum (Vindasiute

et al. 2013). Recently, a new prosthetic proto-

col aiming to improve esthetic outcomes of

prosthetic restorations on natural teeth was

presented (Loi & Di Felice 2013). This

approach is based on a feather-edge prepara-

tion of abutment teeth and the gingival adap-

tation to crowns contours. The same

principles and concepts are suggested by the

authors for cemented implant restorations

through the use of a shoulderless abutment

design. However, such geometry presents

increased undercuts, raising some concern

about the difficulty to completely remove the

excess cement.

The aim of the present study was to com-

pare in vivo two different cementation tech-

niques for implant-supported restorations in

relation to the amount of cement remnants

in the peri-implant sulcus. Additional aim

was to compare the effect of these cementa-

tion techniques using two different abutment

design, chamfer and shoulderless.

The article was written following the

CONSORT statement for improving the

quality of RCTs.

Material and methods

The present randomized controlled prospec-

tive study was performed following the prin-

ciples outlined in the Declaration of Helsinki

on experimentation involving human sub-

jects. All procedures and materials in the

present prospective study were approved by

the Ethical Committee of the University of

Valencia (# H1406287295470).

Patients were required to sign a consent

form after being informed about the study.

Between Sept 2013 and Sept 2014, accord-

ing to the power analysis, 46 consecutive

patients needing two adjacent implant-sup-

ported restorations in the posterior maxilla

were selected. Ninety implants (Premium SP;

Sweden & Martina, Padua, Italy) were

inserted in a two-stage modality.

In all patients, Premium SP implants (Swe-

den & Martina) were used (Fig. 1).

For every case, after implant osseointegra-

tion was achieved (2 months), healing abut-

ments were connected (Fig. 2). After soft

tissue healing, a silicon impression was taken

at implant level. The working cast was

scanned in laboratory (Echo, Sweden & Marti-

na), and prosthetic components were designed

and constructed with CAD CAM technology

(Echo, Sweden &Martina) (Fig. 3).

Abutment randomization

Every implant in each case was randomly

assigned to receive either an abutment with a

chamfer finish line or an abutment with a

shoulderless (feather edge) design: if the first

implant received one kind of abutment design,

the second would receive the other design.

Random assignment was performed using a

free dedicated software (www.examplerand

omxxx.com).

(a)

(f) (g) (h) (i)

(b) (c) (d) (e)

Fig. 1. Surgical phases: pre-operative buccal and occlusal overview (a, b); flap elevation, surgical guide and pre-operative CBT analysis (c, d, e); implant insertion with buccal

and occlusal overview (f, g); control X-ray (h); sutures (i).

2 | Clin. Oral Impl. Res. 0, 2015 / 1–8 © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Canullo et al �Cement technique and abutment design

For each implant, two identical titanium

abutments and Cr/Co metal frameworks

were fabricated: one for the study, the sec-

ond for the definitive restoration by CAD

CAM technology (Echo, Sweden & Martina).

The crowns for both the chamfer and the

feather-edge abutments were designed to

have a subgingival margin of maximum

1.5 mm.

An occlusal opening was made in the first

metal framework in order to have access to

the abutment screw after cementation. This

was necessary to ensure the retrievability of

the abutment–restoration complex for the

study. However, to prevent venting of luting

agent during cementation, the crown was

veneered with composite material.

Cementation technique randomization

Eugenol-free zinc oxide cement (Temp Bond,

Kerr, US) was selected as a luting agent for

this study. Before cementation, the screw

access of each abutment was filled with poly-

tetrafluoroethylene tape and sealed with pro-

visional restorative material – Cavit (3 M

UNITEK, Monrovia, CA, USA).

A thin layer of Vaseline was applied over

the external marginal contour of every crown

to reduce cement adhesion over the external

surface of the crowns and facilitate removal

excess cement. The cement was mixed

according to the manufacturer’s instructions;

a thin layer was applied to all internal sur-

faces of the crowns using microbrush (Micro-

brush International, Waterford, Ireland).

In the subgroup “intraoral cementation”,

crown was directly seated without any addi-

tional procedures (Fig. 4).

In the subgroup “extraoral cementation”, a

custom-made polyurethane resin replica of

the abutment had been previously prepared

according to ADT technique (Cocchetto et al.

2010). Every crown, after cement application,

was fully seated onto the abutment replica,

then rapidly removed, cleansed of the

extruded excess cement and finally seated on

the titanium abutment until cement setting

was complete (Fig. 5).

Random assignment was performed using a

free dedicated software (www.examplerando

mxxx.com).

After final cement setting, in all sub-

groups, a stainless steel explorer (Dentsply

International Inc., Milford, DE, USA), and

ultrasound plastic tip were used until the

researcher was confident to have removed

any eventual excess cement. Thereafter,

super floss (Curaprox, Kriens, Switzerland)

imbibed of Bio Orange Solvent (Ogna Lab-

oratori Farmaceutici, Milano, Italia) was

used to polish the abutment/crown com-

plex (Fig. 6). The cement removal proce-

dure was performed using magnifying

loupes.

Three months later, clinical measurements

were performed, and implant stability and

(a) (b) (c) (d)

Fig. 2. Second surgical phase: tissues after healing (a); healing abutments connection, occlusal and buccal overview (b, c); control X-ray (d).

(a)

(b)

(c)

(d) (e) (f)

Fig. 3. CAD design of prosthetic components (a, b, c) with different abutment design: chamfer (d) and feather edge (e). For each implant, two identical abutments and frame-

work were fabricated (f).

(a) (b)

Fig. 4. “Traditional cementation approach” subgroup: a thin layer of vaseline was softly applied over the external

marginal contour (a), while the cement was applied to all internal surfaces using a microbrush (b): crown was

directly seated without any additional procedures.

© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd 3 | Clin. Oral Impl. Res. 0, 2015 / 1–8

Canullo et al �Cement technique and abutment design

the presence of complications were recorded.

Then, the connection screw was accessed,

the abutment screw unscrewed and the

suprastructure disconnected for assessment.

Occlusal photographs of the implants’ plat-

forms and the surrounding soft tissues were

taken. The peri-implant sulcus was probed to

evaluate depth and BOP.

Immediately after, the second metal cera-

mic crown/abutment complex was defini-

tively placed (Fig. 7). Before ceramic

veneering, the two metallic frameworks had

been laser soldered.

Outcome measures

The trial tested two hypotheses. The first

one was that no difference in cement

remnants between the use of a tradi-

tional “intraoral” and an improved “extra-

oral” cementation technique would be

observed. The second one was that no dif-

ference in cement remnants between the

use of a traditional “chamfer“ and an

improved “shoulderless” abutment would

be observed.

Outcome measures were as follows:

1. cement remnants at the abutment/crown

margin

2. void of cement at the implant/abutment

interface

3. gap at the abutment/crown level

Microscopic analysis

Optical light microscope (Stemi DV 4, Carl

Zeiss, Oberkochen, Germany) was used to

measure the presence of eventual cement

remnants or gaps.

For every abutment/crown complex, the

following pictures were taken:

1. one picture (109) of the complex from

apical to coronal

2. four pictures (329) of the abutment/

crown finishing line with the abutment

laying on the interproximal aspect

3. four pictures (329) of the abutment/

crown finishing line with the abutment

inclined at 45° on the occlusal aspect

(Figs 8 and 9)

To measure eventual voids of cement at

the abutment/crown interface, removed

abutment/crown complex, after photo-

graphic analysis, was grinded and under-

went a microscopic analysis. Two pictures

for each sample were taken at 109 and 209

(Fig. 10).

Using a dedicated software (Solidworks

Premium 2012; DASSAULT SYST�EMES,

VelizVillacoublay, France), the surface

(squared microns) occupied by exposed

cement remnants was measured.

Measurements were performed by other

two blinded calibrated examiners (M.C,

C.M). The mean value of the two measure-

ments was used for the analysis.

Prosthetic failures (exposed margins and

crown decementation) were recorded.

Statistical analysis

Descriptive statistics, including mean values

and standard deviations, were calculated.

Statistical analysis of the data was con-

ducted using related-samples Friedman’s two-

way analysis of variance by ranks. The level

of statistical significance was set at P ≤ 0.05.

Results

Between Sept 2013 and Sept 2014, 62 patients

were screened for inclusion and 46 (29 male

and 17 females) participated in the study

(mean age 60.58 years, SD: 10.91). Reasons

for exclusion were as follows: not meeting

the inclusion criteria (n.12) and refused to

participate (n.4).

All surgical interventions and post-opera-

tive healing period were without any serious

complication or side effect for all patients.

At the end of the study, four patients

dropped out.

After microscopic analysis, the following

data were found:

Cement remnants: a mean value of

0.45 mm2 (SD: 0.80) was recorded with shoul-

derless abutment and intraoral cementation;

(a) (b)

(e) (f) (g)

(c) (d)

Fig. 5. “Extraoral cementation approach” subgroup: crown, after cement lying, was seated onto the abutment resin copy (a) with a gentle finger pressure (b, c, d). Once detached

the crown, all cement remnants on the external surface were removed and crown was finally seated on the titanium abutment (e, f).

(a) (b) (c)

Fig. 6. Cement excess removal after final seating: for all subgroups, stainless steel explorer (a), ultrasound tip (b)

and super floss (c) were used.

4 | Clin. Oral Impl. Res. 0, 2015 / 1–8 © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Canullo et al �Cement technique and abutment design

0.38 mm2 (SD: 0.84) with shoulderless

abutment and extraoral cementation;

0.065 mm2 (SD: 0.13), 0.07 mm2 (SD: 0.15)

with chamfer abutment and intraoral cemen-

tation, 0.072 mm2 (SD:0.14) with chamfer

abutment and extraoral cementation. Rem-

nants were mostly located below the IAJ.

Voids: a mean value of 0.40 mm2 (SD: 0.38)

was recorded with Shoulderless abutment and

intraoral cementation; 0.41 mm2 (SD: 0.40)

with shoulderless abutment and extraoral

cementation, 0.48 mm2 (SD: 0.48) with cham-

fer abutment and intraoral cementation;

(a) (b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

Fig. 8. Optical light microscope analysis on “chamfer” group: apical (a) and marginal [90°(b, c, d, e) and 45° (f, g, h, i)] overview of the implant/abutment complex.

(a) (b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

Fig. 9. Optical light microscope analysis on “feather-edge” group: apical 109 (a) and marginal 329 [90°(b, c, d, e) and 45° (f, g, h, i)] overview of the implant/abutment complex.

(a) (b) (c) (d)

Fig. 10. Optical light microscope analysis: voids of cement at the abutment/crown interface were evaluated after

crown/abutment complex grinding both in the chamfer (a, b) and shoulderless (c, d) group.

(a) (c) (d) (e) (f) (h)

(g)(b)

Fig. 7. Crown removal: after 3 months of loading (a, b, c), access to connection screw was obtained (d) and crown/abutment complexes removed (e). Immediately after, defini-

tive restoration was seated (f, g, h).

© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd 5 | Clin. Oral Impl. Res. 0, 2015 / 1–8

Canullo et al �Cement technique and abutment design

0.47 mm2 (SD: 0.43) with chamfer abutment

and extraoral cementation. Voids were mostly

located at the coronal portion of the abut-

ment/crown interface.

Gap: a mean value of 0.062 mm (SD: 0.033)

with Shourlderless abutment and intraoral

cementation; 0.064 mm (SD: 0.034) with

chamfer abutment and intraoral cementation;

0.055 mm (SD: 0.016) with shoulderless abut-

ment and extraoral cementation; 0.054 mm

(SD: 0.024) with chamfer abutment and extra-

oral cementation groups respectively.

Subgroup data were summarized in

Tables 1 and 2.

Related-samples Friedman’s two-way

analysis of variance by ranks showed signifi-

cant differences for only remnants and voids

measure (Table 3).

Pairwise comparisons (post hoc tests)

showed that “chamfer abutment with intra-

oral cementation” presented significantly

more “remnants” versus “shoulderless abut-

ment with extraoral cementation” (0.047). At

the same time, “chamfer abutment with ex-

traoral cementation” presented significantly

wider “voids” compared with “shoulderless

abutment with intraoral cementation”

(0.032).

Prosthetic complications: in the subgroup,

“extraoral cementation” 2 crowns decement-

ed after 1 week. The crowns were cemented

again with the same technique. No further

decementation was recorded.

Discussion

The principal aim of the study was to test

the efficacy of an “extraoral” cementation

technique in reducing the amount of cement

remnants in the peri-implant soft tissues. In

respect to the original technique proposed by

Wadhwani et al. (2009), in the present study,

the quality of the abutment replica was

improved using a polyurethane resin accord-

ing to the specifications of the “Abutment

duplication technique” (Cocchetto et al.

2010). The precision of the replica allowed to

further reduce the film of cement effectively

left inside the crown immediately before

cementation.

Analyzing the results, a surprisingly low

amount of cement remnants was found in all

subgroups (overall mean value of 0.25 mm2),

compared with what was expected, consider-

ing the data available in literature on the

topic so far. On the other hand, data col-

lected in the present study were in agreement

with a recently published study by Behr et al.

(2014), which demonstrated almost complete

removal of ZOE cement.

It must be highlighted that the cement rem-

nants were located only on the abutment/

crown complex and no cement was found in

the surrounding soft tissues at visual inspec-

tion at time of abutment–crown unscrewing.

This fact has been interpreted by the authors

as the consequence of two main factors: the

use of a eugenol-free zinc oxide cement and

the particularly accurate removal technique.

In fact, Zinc oxide cement is considered a

“temporary cement” for both implant- and

tooth-supported prosthesis, but in this study,

it has been chosen in alternative to “defini-

tive cements” like glass-ionomers and resin

cements used in most studies (Linkevicius

et al. 2013a,b; Vindasiute et al. 2013; Korsch

et al. 2014).

It must be pointed out that, while poly-

meric chains of resin cements were supposed

to be toxic for soft and hard tissues (Korsch

et al. 2014), the ability to reduce biofilm

growth by eugenol-free zinc oxide cement

was demonstrated by Raval et al. (2014).

Remnants of this luting cements, however,

seem to represent retentive factor impacting

on the composition of the submucosal micro-

bial biofilm, which could represent the

first step for a mucositis or even a peri-

implantitis.

Eugenol-free zinc oxide cement, in fact,

presents some advantages like radiological

detectability even in thickness of 1 mm

(Wadhwani et al. 2010) and solubility in the

oral fluids . This last feature is mostly con-

sidered a disadvantage from the biomechani-

cal standpoint (Vindasiute et al. 2013) and

has limited its use as a primary choice for

cemented implant prostheses for its supposed

unpredictable retaining capacity. However,

this negative evaluation should be reconsid-

ered. In fact, the retention of an implant-sup-

ported crown is depending on several factors:

(i) the length and surface of the abutment, (ii)

the convergence angle of axial walls, (iii) the

roughness of the abutment surface and (iv)

the cement characteristics. As demonstrated

by Schiessl et al. (2013) which pointed out

significant interactions between abutment

geometry and luting agents, the modulation

of the first three factors can be easily

obtained during the laboratory abutment cus-

tomization procedures (adding retention cou-

lisses, reducing the convergence angle,

increasing surface roughness through partial

Table 1. Mean values and SD

Cement remnants (mm2) Voids (mm2) Gap (mm)

Shoulderless abutmentIntraoral Cementation

0.455 (SD:0.80) 0.404 (SD:0.377) 0.062 (SD:0.033)

Chamfer abutmentIntraoral Cementation

0.380 (SD:0.84) 0.413 (SD:0.39) 0.064 (SD:0.035)

Shoulderless abutmentExtraoral Cementation

0.065 (SD:0.13) 0.485 (SD:0.48) 0.055 (SD:0.016)

Chamfer abutmentExtraoral Cementation

0.072 (SD:0.14) 0.477 (SD:0.43) 0.054 (SD:0.024)

Table 2. (a) Descriptive measures of shoulder-less abutment with intraoral cementation; (b)Descriptive measures of shoulderless abutmentwith extraoral cementation; (c) Descriptivemeasures of chamfer abutment with intraoralcementation; (d) Descriptive measures of cham-fer abutment with extraoral cementation

Group Remnants Voids Gap

(a)Shoulderless abutment Intraoral Cementation

Mean 0.455 0.404 0.062N 21 21 21SD 0.800 0.377 0.033Median 0 0.200 0.060Minimum 0 0 0.04Maximum 2.98 0.90 0.18

(b)Shoulderless abutment Extraoral Cementation

Mean 0.065 0.485 0.055N 21 21 21SD 0.130 0.480 0.016Median 0.020 0.900 0.050Minimum 0 0 0.04Maximum 0.59 0.90 0.20

(c)Chamfer abutment Intraoral Cementation

Mean 0.380 0.413 0.064N 20 20 20SD 0.840 0.390 0.035Median 0 0.500 0.050Minimum 0 0 0.040Maximum 2.860 1.000 0.130

(d)Chamfer abutment Extraoral Cementation

Mean 0.072 0.477 0.054N 21 21 21SD 0.140 0.430 0.024Median 0.020 0.900 0.040Minimum 0 0.02 0.03Maximum 0.59 1.10 0.18

Table 3. Related-samples Friedman’s two-wayanalysis of variance by ranks

Remnants Voids Gap

Test statistic 13.446 11.180 5.607Degrees ofFreedom

3 3 3

AsymptoticSig.(2 sided test)

0.004** 0.11** 0.132

**Statistically significant.

6 | Clin. Oral Impl. Res. 0, 2015 / 1–8 © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Canullo et al �Cement technique and abutment design

sandblasting). This could compensate the

lack of intrinsic retention capacity of zinc

oxide cement, although difference between

eugenol-free zinc oxide cement and resin

cement still remain controversial (Garg et al.

2014; R€odiger et al. 2014). Following these

principles, abutments used in the present

study have been designed with a convergency

angle of axial walls ranging from 8° to 12°

and only two crowns decemented after

1 week which were recemented with no fur-

ther complication.

The second factor, which may explain the

study results, is the cement removal tech-

nique. This was obtained firstly applying,

using a small brush, a layer of liquid vase-

line on the outer margin of the crowns, lim-

iting therefore the adherence of the cement.

Then after careful removal of excess cement

with explorer and ultrasonic plastic tips, a

dental floss with a spongy section impreg-

nated with zinc oxide solvent was used to

polish the crown/abutment interface. The

entire procedure was done with the aid of a

49 magnification optic system. The combi-

nation of these two factors (type of cement

and accurate cement cleaning) seemed suffi-

cient to remove almost all the remnants

and prevent any peri-implant soft tissue

complication.

In the present study, the margin location

for both abutment’s design was chosen at 1–

1.5 mm below the soft tissue margin. Despite

the fact that in literature, there is a consen-

sus indicating ideal margin position to be

placed at or even above the gingival margin

(Linkevicius et al. 2013a,b) to avoid the

excess peri-implant cement, it was deliber-

ately decided to select the 1.5 mm subgingi-

val position to actually create an “average”

environment reflecting more or less a real

“everyday” clinical setting in which to test

the study hypotheses.

For the same reason, it was considered that

the crown profiles should reproduce the natu-

ral anatomic contours of the teeth to be

replaced. Thus, the amount of undercuts,

which also has been correlated with an

increased difficulty of excess cement removal

(Vindasiute et al. 2013), was deliberately not

modified.

Focusing on the role of abutment morphol-

ogy, in the present study, two different

designs were analyzed:

1. a “traditional” chamfer abutment pro-

duced through CAD CAM technology by

the laboratory technician with a 1.5 mm

finishing line below the gingival margin,

therefore following the gingival architec-

ture. This was considered more in accor-

dance with clinical practice compared

with the use of standard abutments with

predetermined chamfer finish line used

in several studies.

2. a feather-edge abutment (shoulderless

and marginless are two other possible

definitions). This design is not new and

has been proposed by authors as Carl

Misch already in 1993. Recently, the idea

was mentioned by Loi & Di Felice (2013),

which presented a prosthetic protocol for

tooth-supported restorations including a

feather-edge preparation and a manage-

ment of gingival architecture through the

crown’s contour and profile. The authors

claim that improved esthetic results can

be obtained in a predictable manner, both

in tooth-supported and implant-supported

restorations. The key factors would be

the better marginal adaptation after

crown’s cementation with a minimal mi-

crogap and the thickening of soft tissue

due to increased space available for the

connective tissue when a conical geome-

try of the abutment is implemented. The

concept has gained popularity but has

raised controversies. In particular, the

possibility of an increased risk of cement

remnants in the peri-implant sulcus due

to an obvious grater undercut.

Results from the present study have not

confirmed this risk: the shoulderless design,

together with a careful cement application

and removal protocol, presents the same

amount of intrasulcular cement remnants

compared with traditional design. Addition-

ally, it must be observed that the present

study was conducted in posterior quadrants

where the undercuts are greater due to the

increased difference between the implant

platform diameter and the crown’s diame-

ter, particularly in the molar area (Vindasi-

ute et al. 2013). Moreover, there is an

increased difficulty for cement removal due

to limited access, compared with the

esthetic zone.

In these clinical cases, the extraoral

cementation technique was demonstrated to

significatively minimize the already limited

cement remnants amount found after tradi-

tional cementation technique.

Due to this limitation, the same study

design should be tested in the anterior areas,

where crown overcuts are more limited.

Regarding voids, significant differences

between extraoral and intraoral subgroups

could explain the two decementations hap-

pened in extraoral groups.

Regarding gap parameters, no statistically

significant difference was found within

the groups and subgroups, confirming the

absence of clinical differences between the

presented abutment designs and cementation

techniques.

Clinical limitations of the present study

were represented by the small follow-up

time. A longer follow-up (5 years at least)

could have prospectively demonstrated the

soft tissue reaction to eugenol-free zinc oxide

cement remnants.

Conclusions

Within the limitation of the present study,

the following conclusions can be summa-

rized:

1. Extraoral cementation could minimize

the presence of cement remnants. How-

ever, from the very limited amount of

cement remnants observed also in the in-

traoral group, a very low possibility of a

cement-induced peri-implant pathology

may be inferred. These results could

probably be associated with the use of a

eugenol-free zinc oxide cement and a par-

ticularly accurate cement removal proto-

col.

2. Compared with the abutment design,

chamfer cemented with an intraoral tech-

nique presented significant higher

amount of cement remnants if compared

to a shoulderless abutment when extra-

oral cementation technique is adopted.

3. The presence of significantly wider

“voids” was noted in the extraoral group.

4. There is no difference in regard to the

“gap” parameters between the two

abutment designs and the cementation

technique

Acknowledgements: The authors

highly appreciated the skills and commitment

of Dr Audrenn Gautier in the supervision of

the study, Dr Giuliano Iannello (Rome, Italy)

and Sandro Radovanovic (Belgrade, Serbia) for

their statistical support. Additionally authors

deeply thank Eng. Marco Cesarotto and

Carmine Magna for the professional support

in microremnants analysis.

Conflict of interest and sources offunding

The authors declare that they have no con-

flict of interests. The study was self-funded.

© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd 7 | Clin. Oral Impl. Res. 0, 2015 / 1–8

Canullo et al �Cement technique and abutment design

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Supporting Information

Additional Supporting Information may be

found in the online version of this article:

Table S1. CONSORT Checklist of Items to

Include When Reporting a Randomized Trial.

8 | Clin. Oral Impl. Res. 0, 2015 / 1–8 © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Canullo et al �Cement technique and abutment design