Systematic Review

Alterations of the bonedimension following immediateimplant placement into extractionsocket: systematic review andmeta-analysisLee C-T, Chiu T-S, Chuang S-K, Tarnow D, Stoupel J. Alterations of the bonedimension following immediate implant placement into extraction socket: systematicreview and meta-analysis. J Clin Periodontol 2014; 41: 914–926. doi: 10.1111/jcpe.12276.

AbstractAim: This systematic review was aimed at analysing bone dimensional alterationswithin the first year following immediate implant placement.Materials and Methods: The electronic search was conducted using MEDLINE(PubMed), Cochrane Central Register of Controlled Trials (CENTRAL) andEMBASE from January 1980 to October 2013. Quality assessment of selected arti-cles was performed using Cochrane Collaboration’s tool or Newcastle-Ottawa scaleaccording to the design of each study. A meta-analysis was performed to estimatebone dimensional reduction. Weighted mean differences in bone dimension betweenbaseline and follow-up measurement were calculated. Subgroup analysis and mete-regression were conducted to evaluate the effects of different variables.Results: A total of 1348 articles were identified following the search process. Sixstudies were included in the present review. The weighted mean buccal horizontalbone dimensional reduction (BHDr) was 1.07 mm and buccal vertical bone dimen-sional reduction (BVDr) was 0.78 mm. The weighted mean palatal bone dimen-sional reduction was 0.62 mm horizontally (PHDr) and 0.50 mm vertically (PVDr).The initial thickness of the buccal alveolar plate (TB) of the socket was the onlyvariable significantly correlated with BHDr and BVDr in meta-regression analysis.Conclusions: The bone dimensions of immediate implant sites demonstratedapproximately 0.5–1.0 mm reduction in vertical and horizontal aspects4–12 months following surgery. The results should be interpreted with carebecause of the data heterogeneity. The correlation of the socket buccal wallthickness, and other variables, with dimensional changes of the bony ridge shouldbe investigated further in controlled clinical trials.

Chun-Teh Lee1, Tzu-Shan Chiu2,Sung-Kiang Chuang3, Dennis

Tarnow2 and Janet Stoupel2

1Division of Periodontology, Department of

Oral Medicine, Infection and Immunity,

Harvard School of Dental Medicine, Boston,

MA, USA; 2Division of Periodontics, Section

of Oral and Diagnostic Sciences, College of

Dental Medicine, Columbia University, New

York, NY, USA; 3Department of Oral and

Maxillofacial Surgery, Massachusetts General

Hospital and Harvard School of Dental

Medicine, Boston, MA, USA

Key words: bone dimension; immediate

implant; meta-analysis; systematic review

Accepted for publication 28 May 2014

Immediate dental implant placementwas proposed about 40 years ago(Schulte & Heimke 1976). Severalclinical trials have demonstrated suc-cessful clinical outcomes (Lazzara

1989, Becker et al. 1998, Chen et al.2007, Sanz et al. 2013) with highsurvival rate and stable crestal bonelevels, similar to delayed implantplacement. With the improvement of

Conflict of interest and source offunding statement

The authors declare that they have noconflict of interests.

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd914

J Clin Periodontol 2014; 41: 914–926 doi: 10.1111/jcpe.12276

implant design and surface technol-ogy, immediate implantation hasbecome a common choice in toothreplacement therapy.

Immediate implantation, com-pared with delayed implant place-ment, may reduce the number ofclinical visits and surgical proce-dures, by this diminishing patientmorbidity, and in some cases, enableimmediate restoration (Lang et al.2012). It has been suggested thatimmediate implant placement pre-serves alveolar bone dimensions(Lazzara 1989, Denissen et al. 1993,Watzek et al. 1995, Paolantonioet al. 2001). However, recent experi-mental studies and clinical trials donot support this concept, demon-strating significant changes in bonyridge dimensions in the immediateimplant surgical site (Botticelli et al.2004, 2006). The buccal dimensionalchange is usually greater than thatof the lingual/palatal dimension(Botticelli et al. 2004, Brownfield &Weltman 2012). Extensive bone lossfollowing immediate implantationmay challenge osseointegration orcause aesthetic concerns, especiallyin the maxillary aesthetic zone,which is often characterized by athin buccal plate. (Januario et al.2011). It is interesting to note, thatimmediate implant sites had morepronounced bone resorption com-pared to post-extraction sites in arecent animal study (Vignoletti et al.2012a).

Additional variables to considerin evaluating changes in the bonedimensions following immediateimplantation are: use of regenerativematerials (Chen et al. 2007), implantposition relative to the wall of thesocket (Chen et al. 2009, Tomasiet al. 2010), residual bony defect inthe socket (Ferrus et al. 2010), thick-ness of the buccal wall of the socket(Tomasi et al. 2010), and the effectof different surgical techniques(Barone et al. 2013). The postextraction change of bony ridge andthe challenges it forecasts to clini-cians and patients alike, have beenobserved and described in a numberof studies (Pietrokovski & Massler1967, Johnson 1969, Schropp & Isi-dor 2008) and quantified in fewrecent reviews (Van der Weijdenet al. 2009, Tan et al. 2012), includ-ing the effect of socket preservationon bone modelling and remodelling

(Vignoletti et al. 2012b). However,no review has systematically dis-cussed bone dimensional alterationafter immediate implant placementand the effects of multiple variableson bony ridge reduction. The aim ofthis systematic review was to analysehorizontal and vertical bone dimen-sional changes in single-tooth sitefollowing immediate implant place-ment. The correlation betweendimensional changes and differentvariables was also evaluated.

Materials and Methods

This systematic review was performedby following previously outlined rec-ommendations (Needleman 2002)and PRISMA (Preferred ReportingItems for Systematic Reviews andMeta-Analyses) principles (Liberatiet al. 2009).

Focused question

The focused question was proposedby following PICO principle. “Whatare the bone dimensional changes ofpost-extraction sites, including hori-zontal width and vertical height,buccally and palatally/lingually fol-lowing immediate implant placementin humans?”

Inclusion and exclusion criteria

Inclusion criteria

• Human subject studies, whichhad at least one group defined byplacement of a immediateimplant in the site of oneextracted tooth.

• The selected studies were definedas randomized clinical trials(RCTs), controlled clinical trials,cohort studies or case series withfollow-up measurements.

• Studies that included bonedimensional changes in implantplacement sites from the baselineto the end point of bone dimen-sion measurement.

Exclusion criteria

• Bone dimension measurementsmade less than 3 months or morethan 12 months followingimplant placement.

• The study did not have detailedinformation of measurement

method, measurement referencepoint, measurement timeline,implant position, surgical proce-dure or subject numbers.

• The studies, which did not havethe measurement of buccal hori-zontal bone dimensional changeat the implantation site.

Search strategy

The electronic search was conductedin MEDLINE (PubMed), CochraneCentral Register of Controlled Trials(CENTRAL), and EMBASE fromJanuary 1980 to October 2013. Thefollowing search terms were used inPubMed database:

Intervention:immediate implant*[TW] OR ((implantplacement*[TW] OR implant installa-tion*[TW]) AND immedia*[TW])OR fresh socket*[TW] OR extrac-tion socket*[TW] OR (implant*[TW]AND (placed immediately[TW] ORimmediately placed[TW] OR immedi-ate placement*[TW] OR installedimmediately[TW] OR immediatelyinstall*[TW]))

ANDOutcome:

“Bone Resorption”[MH] OR “Alveo-lar Bone Loss”[MH] OR ((bone[TW]OR alveol*[TW] OR ridge[TW]) AND(loss*[TW] OR resorption*[TW] ORreduction*[TW] OR dimension*[TW]OR preservation[TW] OR thickness[TW] OR change*[TW] OR alter-ation*[TW] OR width*[TW] ORheight*[TW]))

TW = Text Words; it includes allwords and numbers in the title,abstract, other abstract, MeSH terms,MeSH subheadings, publication types,substance names, personal name assubject, corporate author, secondarysource, comment/correction notes,and other terms. MH =MeSH terms

A further manual search was per-formed in several journals (Appendix1). In addition, the reference lists ofselected articles were screened to findthose which might qualify for thisreview.

Quality assessment

The studies included in this reviewwere assessed by two quality assess-ment methods given they haddifferent study designs. The random-ized controlled trials were assessedby Cochrane Collaboration’s tool

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Bone changes in immediate implant site 915

(Higgins et al. 2011). “High risk ofbias”, “Low risk of bias”, or“Unclear risk of bias” was assignedto each assessment item. Newcastle-Ottawa scale (NOS) was utilizedto assess the methodological qualityof the prospective or retrospectivecohort studies (Wells et al. 2001). Thescores ranged from 0 to 9. Further-more, the evidence level of the studywas provided following Oxford Cen-tre for Evidence-Based Medicinerecommendation (March, 2009). Theassessment was performed by twoexaminers (CL, TC) independently,and the inter-examiner agreementwas analysed by kappa coefficient.Any discrepancy between the twoexaminers in quality assessment wasresolved via discussion.

Data extraction and data synthesis

Two authors (CL, TC) screened thetitles and abstracts of articles inde-pendently. The full texts of qualifiedarticles were then read and selected.The disagreement was solved by dis-cussion. When selected articles hadthe same patient cohort, only theoriginal article was included.

Data were extracted indepen-dently by the two authors (CL, TC)with a specially designed data extrac-tion form. The accuracy of extracteddata was confirmed by anotherauthor (SC). If the reviewers haddata-related questions, the authorsof the selected articles would be con-tacted. The authors reached theagreement by discussion.

Some data were not provideddirectly in the literature and was cal-culated indirectly by authors. Forexample, the data of buccal platethickness in three included studies(Chen et al. 2007, Degidi et al. 2012,Rossi et al. 2013) were calculated bysubtracting horizontal defect dimen-sion (HDD) from the distancebetween implant surface and theouter surface of the buccal alveolarplate at the same reference point.

Data analysis

The primary outcome of the studywas buccal horizontal bone dimen-sional reduction (BHDr). Buccal ver-tical bone dimensional reduction(BVDr), palatal horizontal bonedimensional reduction (PHDr), andpalatal vertical bone dimensional

reduction (PVDr) were considered asthe secondary outcomes. A positivevalue stood for the reduction ofbone dimension, and vice versa.Bone dimension was defined as thewidth and height of the bony ridgearound the implant in the presentreview. The difference between base-line and final bone dimension wasanalysed.

If the study had multiple groupsthat qualified for data analysis, thedata of each group would beextracted and treated as an indepen-dent dataset. The primary outcome orsecondary outcome of each study waspooled and analysed as a weightedmean with 95% confidence interval(CI) in random effect model (Dersi-monian–Laird test) because of theheterogeneity (v2 = 50.97, p-value < 0.01) of each dataset in pri-mary outcome (Higgins & Green2011). Heterogeneity between studieswas assessed using I-squared (I2) sta-tistics describing the variation of eachstudy. The Forest plot was utilized toillustrate the weighted mean of theoutcome in each study and the finalestimation. In order to evaluate thepossible variables causing heterogene-ity, subgroup analysis was conducted.Meta-regression was performed toevaluate the correlation between theoutcome of interest and different vari-ables. Publication bias was evaluatedby Egger’s test and funnel plot. Allstatistical analysis was performedusing STATA� (Version 11.2, 2009,Stata Corp, College Station, TX,USA). Statistical significance wasdefined as p-value < 0.05.

Results

A total of 1348 articles were identi-fied in the search process. Twentyarticles fulfilled the criteria afterreviewing the titles and abstracts.Four articles were part of the sameseries (Ferrus et al. 2010, Sanz et al.2010, 2013, Tomasi et al. 2010), andonly the original article (Sanz et al.2010), with detailed information ofprimary outcome, was selected. Arti-cles lacking clear reference points(Yukna et al. 2003, Capelli et al.2013), or with incomplete informa-tion of the bone dimensional change(Covani et al. 2003, 2004, Chenet al. 2005, Matarasso et al. 2009,van Kesteren et al. 2010, Grunder2011, Vera et al. 2012a, Assaf et al.

2013), or utilizing different definitionof the dimensional change(Koh et al.2011) were excluded. Finally, sixstudies were selected and nine groupsof datasets were extracted for dataanalysis. Figure 1 describes the pro-cess of article search and selection.Table 1 summarizes the characteris-tics of each study.

Quality assessment and heterogeneity

evaluation

The summary of quality assessmentwas described in Table 2a and b;more details were outlined in Appen-dix 2. In the randomized controlledtrials, Chen et al. 2007 generally hadhigher risk bias than Sanz et al.2010,. The mean NOS score was 6 �1.41 (range: 4–7) for the four cohortstudies. The kappa coefficient betweenthe two authors (CL, TC) in qualityassessment of RCTs and cohort stud-ies were 1.00 and 0.87 respectively.The outcomes of BHDr, BVDr, andPHDr in each study had considerableor moderate heterogeneity (Higgins &Green 2011) (Appendix 3) respec-tively (I2 = 84.3%, p-value < 0.01;I2 = 57.38%, p-value = 0.015; I2 =67.2%, p-value = 0.027) except PVDr(I2 = 0%, p-value = 0.587). The evi-dence level of each study followingOxford Centre for Evidence-BasedMedicine recommendation was sum-marized in Table 2c.

Implant survival rate, follow-up period and

subject dropout rate

Five of the six included studies dem-onstrated a 100% survival rate, whileone study reported survival rate of98.9%, 92/93 implants (Sanz et al.2010: 98.9%, 92/93), without any sig-nificant complications. The follow-upperiod of implant status, which is dif-ferent from the time of bone dimen-sion measurement, varied in eachstudy from 4 months to 3 years. Twostudies (Sanz et al. 2010, Rossi et al.2013) had dropouts, but only onestudy had a dropout rate higher than20% (Rossi et al. 2013: 25%, 3/12).

The implant characteristics, position of

implant, site of implant placement, and

time-point of measurement.

All implants in the included studieswere rough surfaced, though manu-factured by different companies.Either bone level or tissue level

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

916 Lee et al.

implants was used in these studies.The position of implant platform/shoulder was stated, but varied fromstudy to study (Table 1).

The sites of implant placementwere limited to incisors only (Roeet al. 2012), bicuspids only (Rossiet al. 2013) or both. Majority of thestudies included only maxillary sites,but two studies included mandibularsites as well (Botticelli et al. 2004,Rossi et al. 2013). The time-point offinal bone dimension measurementvaried from 4 to 12 months (Table 1).

Use of regenerative adjunctive therapy

Osseous xenografts were used insome of the studies. Two studiesused grafts to fill the remainingdefect following immediate implanta-tion (Degidi et al. 2012, Roe et al.2012). One study had three groups:grafted, grafted and resorbable bar-rier, or non-grafted immediateimplant sites (Chen et al. 2007).Three studies did not utilize osseousgrafts in conjunction with immediateimplantation (Botticelli et al. 2004,

Sanz et al. 2010, Rossi et al. 2013)(Table 1).

Surgical technique (Flap elevation or

flapless immediate implant placement)

Different surgical techniques wereemployed in the selected studies. Fourstudies utilized flap approach forimmediate implantation, while onlytwo studies (Degidi et al. 2012, Roeet al. 2012) used flapless approach.

The method of measurement

Two modes of bone dimension mea-surements were utilized: clinical,using either probe or caliper (Botticel-li et al. 2004, Chen et al. 2007, Sanzet al. 2010), or radiographic, measur-ing bone on cone beam computedtomographs (Degidi et al. 2012, Roeet al. 2012, Rossi et al. 2013).

Horizontal and vertical dimensional

change

Reference points of the dimensionalmeasurements were described inTable 1. Most studies utilized spe-cific sites that were close to the bonecrest as reference points (mid-buccal/mid-palatal implant-abutment inter-face, crest, or 1 mm subcrestally).Studies, which offered multiple refer-ence points of horizontal bonedimension measurements, close tocrestal (Roe et al. 2012), or 1 mmsubcrestal (Rossi et al. 2013) mid-facial measurements were chosen fordata analysis. Thickness of buccalalveolar plate was measured fromthe same reference point as horizon-tal bone dimension in each study.

Vertical dimension measurementswere performed from various refer-ence points, but the difference in thevertical dimension consistently repre-sented the mid-buccal or mid-palatalaspects of the crestal height change.Implant platform/shoulder was thereference point of vertical dimensionin five studies. Rossi et al. (2013) uti-lized the apex of the implant as thereference point.

In six selected studies, theweighted mean BHDr was 1.07 mm(CI: [0.84,1.31]) (Fig. 2a) and theweighted mean BVDr was 0.78 mm(CI: [0.55,1.02]) (Fig. 2b). Theresults demonstrated that buccalbone dimensional reduction wasexpected after immediate implantplacement.

Articles identified after search in databases and journals N = 1348

Articles identified after reviewing titles and abstracts by the authors N = 20

Articles eligible for data analysis N = 9

Articles included in the final data analysis N = 6

Exclude articles with unrelated topics or primary outcomes

Evaluate the eligibility: 1. Immediate implant placement in human subject

2. Randomized clinical trials (RCT), controlled clinical trials, cohort studies and case series

3. The selected studies had to include measurements of buccal horizontal ridge dimensional change and other detailed information

4. The date of final measurement should be at least 3 months and within 1 year following surgery

Articles excluded because of being the same clinical trial N = 3

Fig. 1. Search strategy and screening process.

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Bone changes in immediate implant site 917

Table

1.

Overview

oftheselected

studies

Author

Studydesign

Studygroup(s)

(Immediate

implant

placementwithor

withoutbonegraft

and/ormem

brane)

Number

ofsubjects

(implants),gender,

andmeanagein

years

(SD)

Dropout

subjects

(implant)

Implant

surface

anddesign

Implantsite

Implantposition

Flapdesign

Adjacent

tooth

presentation

Botticelli

etal.(2004)

Prospective

cohort

Bonegraft(�

)/Mem

brane(�

)N

=18(21)

0(0)

RS,TL

(2.8

mm

shoulder)

Max.&

Mand.

premolarto

premolar

SLA

part

below

crest

Fullthickness

flap

NA

Chen

etal.

(2007)

RCT

1.Xenograft(+)/

Mem

brane(�

)N

=10(10)

M/F

=4/6,

age50.4

(10.1)

0(0)

RS,TL

(1.8

or

2.8

mm

shoulder)

Max.premolar

topremolar

SLA

part

aroundcrest

Fullthickness

flap

Y:28/N

:2

2.Xenograft(+)/

Resorbable

mem

brane(+)

N=10(10)

M/F

=3/7,

age43.2

(10.8)

0(0)

3.Bonegraft(�

)/Mem

brane(�

)N

=10(10)

M/F

=3/7,

age42.1

(11.0)

0(0)

Degidiet

al.

(2012)

Prospective

cohort

Xenograft(+)/

Mem

brane(�

)N

=69(69)

M/F

=29/40,

age23–79

0(0)

RS,BL

Max.premolar

topremolar

Atleast

1mm

apicalto

palatalcrest

Flapless

Y

Roeet

al.

(2012)

Retrospective

cohort

Xenograft(+)/

Mem

brane(�

)N

=21(21)

M/F

=7/14,

age48.8

0(0)

RS,BL

Max.incisors

1mm

apicalto

buccalcrest

Flapless

NA

Rossiet

al.

(2013)

Prospective

cohort

Bonegraft(�

)/Mem

brane(�

)N

=12(12)initial

N=9(9)final

M/F

=7/5,

age49.6

(10.6)

3(3*)

RS,BL

Max.&

Mand.

premolarzones

Even

orapical

tobuccalcrest

Fullthickness

flap

Mesial-Y:9

Distal-Y:5/

N:4

Sanzet

al.

(2010)

RCT

N=95(101)initial

intotal

2(8

†)

RS,BL

Max.premolar

topremolar

Even

crest

Fullthickness

flap

NA

1.Cylindricalim

plant

Bonegraft(�

)/Mem

brane(�

)

N=45(45)final

M/F

=28/17,

age50.4

(13.1)

2.Tapered

implant

Bonegraft(�

)/Mem

brane(�

)

N=48(48)final

M/F

=20/28,

age51.8

(13.5)

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

918 Lee et al.

Author

Socket

status

Prosthetic

component

duringhealingphase

Measurement

method

Tim

eof

measurement

(month)

Horizontal

reference

point

Vertical

reference

point

Buccal

horizontal

bone

dim

ensional

reduction§

(SD)(m

m)

Buccal

vertical

bone

dim

ensional

reduction¶

(SD)(m

m)

Palatal

horizontal

bone

dim

ensional

reduction**

(SD)(m

m)

Palatal

vertical

bone

dim

ensional

reduction††

(SD)(m

m)

Buccal

plate

thickness‡

‡

(SD)(m

m)

Botticelli

etal.(2004)

NA

Cover

screw

Caliper/Bone

4OuterandInner

surface

ofthe

bonecrest

Implant

shoulder

1.9

(0.9)

0.3

(0.6)

0.9

(0.6)

0.6

(1.0)

1.4

(0.4)

Chen

etal.

(2007)

Intact

but

minor

defect

was

allowed

Healing

abutm

ent

Probe/Bone

6OuterandInner

surface

ofthe

bonecrest

Implant

shoulder

1.0.4

(0.5)

0.1

(3.4)

NA

NA

0.5

2.0.6

(0.7)

�0.5

(3.7)

0.4

3.1.1

(0.3)

1.3

(0.9)

0.4

Degidiet

al.

(2012)

Dehiscence

≤2mm

was

allowed

Immediate

provisionalization

CTscan/

Bone

12

Outerandinner

border

ofthe

bonecrestat

implantbevel

level

Implant

platform

0.88(0.51)

0.76(0.96)

NA

NA

0.76

Roeet

al.

(2012)

Intact

Immediate

provisionalization

CTscan/

Bone

12

Outerandinner

surface

at0‡,1,

2,4,6,9,

12mm

apical

totheim

plant

platform

Implant

platform

1.23(0.75)

0.82(0.64)

NA

NA

NA

Rossiet

al.

(2013)

NA

Cover

screw

CTscan/

Bone

4Outerandinner

surface

at1‡,3,

5mm

apicalto

thebonecrest

(absolute

‡/

relativevalue)

Apex

of

implant

1.9

(1.5)

0.9

(0.8)

0.6

(0.7)

0.6

(0.7)

0.8

Sanzet

al.

(2010)

Intact

but

minor

defect

was

allowed

Healingabutm

ent

Probe/Bone

4Outerandinner

surface

at

1mm

apicalto

thebonecrest

Implant

platform

1.1.2

(0.9)

1.0

(1.7)

0.6

(0.9)

0.5

(1.6)

1.0

(0.5)

2.1.0

(1.1)

1.0

(2.2)

0.4

(0.7)

0.5

(1.4)

0.9

(0.5)

BL,bonelevel,RS,roughsurface;TL,tissuelevel.

*Twopatients

refusedto

perform

thefollow-upcomputedtomographyexamination,andonepatientbecamepregnant.

†Twopatients,each

withoneim

plantplaced,dropped

outofthestudy.Six

subjects,each

withtw

oim

plants

placed,hadoneim

plantexcluded

bytossingacoin.

‡Thereference

pointwaschosenfordata

analysis.

§Buccalhorizontalbonedim

ensionwasmeasuredfrom

theoutersurface

ofbuccalhorizontalreference

pointto

implantsurface.

¶ Buccalverticalbonedim

ensionwasmeasuredfrom

thebuccalverticalreference

pointto

buccalbonecrest.

**Palatalhorizontalbonedim

ensionwasmeasuredfrom

theoutersurface

ofpalatalhorizontalreference

pointto

implantsurface.

††Palatalverticalbonedim

ensionwasmeasuredfrom

thepalatalverticalreference

pointto

palatalbonecrest.

‡‡Buccalplate

wasmeasuredfrom

theoutersurface

totheinner

surface

ofbuccalboneathorizontalreference

point.

Table

1.(continued)

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Bone changes in immediate implant site 919

Three studies (Botticelli et al.2004, Sanz et al. 2010, Rossi et al.2013) provided the data of palatalbone dimensional change. Theweighted mean PHDr was 0.62 mm(CI: [0.38, 0.86]) (Fig. 3a) and PVDrwas 0.50 mm (CI: [0.36,0.64])(Fig. 3b). The change in palatalbone dimension was less significantthan in buccal bone dimension.

Subgroup analysis & sensitivity analysis

In order to explain the heterogeneityof estimated buccal horizontal bonedimensional reduction (BHDr) of theselected studies, further analyses wereconducted in two different subgroups:graft/no graft, and RCTs/cohortstudies. The weighted mean BHDrin the no graft group was 1.32 mm(CI: [1.01,1.62]; I2 = 76.9%; 52.52%weight) and 0.79 mm (CI: [0.48,1.10];I2 = 80.0%; 47.48% weight) in thegraft group (Fig. 4a). The weightedmean BHDr in the RCTs group was0.88 mm (CI: [0.60,1.17]; I2 = 80.6%;59.41% weight), and 1.40 mm (CI:[0.87,1.93]; I2 = 90.0%; 40.59%weight) in the cohort studies group(Fig. 4b).

The subgroup analysis was alsoperformed for BVDr. The weightedmean BVDr in the no graft group was

0.86 mm (CI: [0.44,1.28]; I2 = 75.6%;60.10% weight) and 0.77 mm (CI:[0.60,0.95]; I2 = 0%; 39.90% weight)in the graft group. The weightedmean BVDr in the RCTs group was1.05 mm (CI: [0.73,1.36]; I2 = 0%;32.69% weight), and 0.67 mm (CI:[0.40,0.95]; I2 = 71.2%; 67.31%weight) in the cohort studies group.These results demonstrated the differ-ences in weighted mean BHDr andBVDr between the subgroups, thoughthe data were still significantly hetero-geneous in most subgroups.

Sensitivity analysis was per-formed to assess the robustness ofthe results from the meta-analysis.According to the results of sensitiv-ity analysis, the results of themeta-analysis were not significantlydetermined by any specific dataset orstudy (Appendix 4.).

Meta-regression analysis

Meta-regression analysis was per-formed to assess correlation of dif-ferent variables with two outcomes(BHDr & BVDr). It could not beperformed for palatal bone dimen-sional change due to insufficient dataavailability. Several variables, includ-ing buccal horizontal defect dimen-sion (bHDD), buccal vertical defect

dimension (bVDD), buccal horizon-tal bone dimension at baseline(bHDB), thickness of buccal alveolarplate (TB), use of graft material(GT), use of barrier (BR), flap eleva-tion (FLP),and measurement method(MM) were analysed. The definitionsof variables and summary of resultsare described in Table 3. TB was theonly variable demonstrating signifi-cant correlation with BHDr posi-tively (p-value = 0.035) and BVDrnegatively (p-value = 0.018). bHDBwas marginally correlated withBHDr (p-value = 0.138) and BVDr(p-value = 0.056), and significantlycorrelated with TB (p-value = 0.001).GT was not significantly correlatedwith BHDr though small p-value(p-value = 0.073). In multivariatemeta-regression model, TB was stillmarginally or significantly correlatedwith BHDr or BVDr. Combinationof other variables with TB did notincrease the coefficient of determina-tion significantly (Appendix 5).

Publication bias

No statistically significant publicationbias was detected in weighted meanbuccal horizontal bone reduction(BHDr) (Egger’s test, p-value =0.372) or weighted mean buccal verti-cal bone reduction (BVDr) (Egger’stest, p-value = 0.677). The funnel plotanalysing BHDr data demonstrates agenerally symmetric distribution(Appendix 6).

Discussion

Bone dimensional change in meta-

analysis

Bone modelling following toothextraction without implant placementhas been previously demonstrated innumerous studies and systematicreviews. One systematic reviewreported mean reduction of 3.79 �0.23 mm in the bucco-palatal/lingualwidth of the residual bony ridge and1.24 � 0.11 mm in the buccal heightof the bony ridge up to 7 months fol-lowing tooth extraction (Tan et al.2012). The value was very close toanother systematic review, whichdemonstrated horizontal mid-buccalreduction of 1.67 mm, and horizontalmid-lingual reduction of 2.03 mm(Van der Weijden et al. 2009). Thepresent analysis focused on the

Table 2. (a) Quality assessment of the randomized controlled trials included in this review.(b) Quality assessment of the cohort studies included in this review. (c) The evidence levelbased on CEBM (Center for Evidence-Based Medicine)

Bias Chen et al. 2007 Sanz et al. 2010

(a)Random sequence generation Unclear Low riskAllocation concealment Unclear Low riskBlinding of patients and surgeons High risk High riskBlinding of outcome assessment Unclear Low riskIncomplete outcome data Low risk Low riskSelective reporting Low risk Low riskOther sources of bias

Group imbalance Low risk Low riskSample size High risk High riskClinician bias High risk High risk

Botticelli et al. 2004 Degidi et al. 2012 Roe et al. 2012 Rossi et al. 2013

(b)Selection *** *** *** **Comparability * * * *Outcome ** *** *** *Total scores 6 7 7 4

Botticelli et al.2004

Chen et al.2007

Degidi et al.2012

Roe et al.2012

Rossi et al.2013

Sanz et al.2010

(c)Evidencelevel

2b 2b 2b 2b 3b 1b

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920 Lee et al.

changes of post-extraction socketwith concomitant, immediate implantplacement. Bone dimensional alterations(weighted mean BHDr: 1.07 mm,BVDr: 0.78 mm; PHDr: 0.62 mm,PVDr: 0.50 mm) under these circum-stances, though following the similarpattern of more pronounced horizon-tal reduction than the vertical dimen-sional reduction, were more modest,compared to post-extraction withoutimplant placement.

The difference between ourresults and the studies included inthe review by Tan et al. in 2012 maybe explained by several factors:inclusion criteria, lack of reportingon the integrity of the buccal wall,drilling of the buccal wall for demar-cation of the measurement site

(Lekovic et al. 1997, 1998, Camargoet al. 2000, Pelegrine et al. 2010),and the possible recruitment of siteswith compromised bone level ordefects, which will inadvertentlyaffect the results, by challenginghealing from inception. Due to ethi-cal concerns, immediate implantationsite selection is usually limited tosites with incipient buccal bone loss,at most, or in conjunction withregenerative procedures (Chen et al.2007). Another concern is the main-tenance of reference point in longitu-dinal measurements of the ridge. Inpost-extraction site studies withoutimplantation, clinical ridge widthmeasurements are often performedbetween coronal border of the buccalbony wall and the lingual wall. Most

studies do not control for thereproducible plane of measurement.Moreover, the distribution of surgicalsites in the arch is usually notreported. All these render directcomparison of studies of bonyridge response to extraction alone orwith immediate implantation chal-lenging.

The selected studies in this reviewreported dimensional changes within1 year following implantation. Inlong-term immediate implant studies,the bucco-vertical bone dimensionalreduction was more significant thanthe present results. A retrospectivestudy (Miyamoto & Obama 2011)reported bucco-vertical crest reduc-tion of 3.25 � 4.68 mm after mean47-month follow-up. Another study(Benic et al. 2012) demonstratedmean bucco-vertical change of3.1 � 4.6 mm after 7 year follow-up.These studies had small sample sizeand missing buccal plate in somecases. These variables might causethe significant mean reduction ofbuccal vertical crest. Moreover, clini-cal factors, such as compromisedimplant position, peri-implantitis,could contribute to the vertical boneloss in long-term studies. Therefore,short- term results of bone dimen-sional changes may represent earlyphysiological bone modelling moreadequately, than long-term studies,reducing the effect of extraneous,restorative, and compliance factors.

Thickness of buccal alveolar plate

Definition of thick versus thin socketwall has been suggested in literature,with 1 mm or more width used as athreshold (Braut et al. 2011). A num-ber of studies have demonstrated anassociation between a thin buccalsocket wall and a greater loss of buc-cal bone dimension during healingthan that of a thick buccal socket wall(Qahash et al. 2008, Tomasi et al.2010, Koh et al. 2011). In the presentstudy, the TB was positively corre-lated with BHDr (coefficient = 1.043;p-value = 0.035) and negatively cor-related with BVDr (coefficient =�0.79; p-value = 0.018), as is evidentfrom the meta-regression analysis. Inother words, thicker buccal socketwall was related to greater reductionin the buccal horizontal bone dimen-sion, and less reduction in the buccalvertical bone dimension, compared

(a)

(b)

Fig. 2. (a) The buccal horizontal bone dimensional reduction (BHDr) in meta-analysis.(b) The buccal vertical bone dimensional reduction (BVDr) in meta-analysis.

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Bone changes in immediate implant site 921

with the thinner socket wall. How-ever, the interpretation of the resultsis confined by the fact that the meanrange of TB in this review was from0.4 to 1.4 mm. Extremely thin buccalplate in immediate implant site mightstill be related to significant buccalhorizontal bone reduction.

Since TB was significantly corre-lated with bHDB (p-value = 0.001),and bHDB rendered marginally sig-nificant correlation with BHDr andBVDr, bHDB might be indicative ofthe future pattern of bony ridgemodelling. Wider initial buccal bonyridge had more buccal horizontalbone reduction, but less buccal verti-cal bone reduction than narrowerinitial buccal bony ridge.

It has been demonstrated thatbuccal alveolar plate thickness isgreater in premolar sites, where ridgeis wider, than in the anterior sites(Vera et al. 2012b). The correlation

between TB (bHDB) and BHDr/BVDr might be biased by the distri-bution of surgical sites. However, itwas impossible to analyse the resultsbased on the site position in dentalarch, due to insufficient informationin the original studies.

The results of present review donot contradict common clinicalobservation, that thin buccal plate isaccompanied by buccal soft andhard tissue collapse. Thinner buccalplate of immediate implantation siteundergoes more vertical bone resorp-tion than thicker buccal plate. Theloss of crestal height may lead tosoft tissue collapse both verticallyand horizontally in the most coronalarea. The reduction of crestal boneheight in a site with a thin buccalplate poses a significant clinicalproblem, even if the horizontal bonedimensional change may be less thanin a site with thick buccal plate.

Horizontal defect dimension and vertical

defect dimension

Following immediate implant stabil-ization in the extraction socket, it iscommon to observe the horizontaland vertical residual spaces or gaps,that have been referred in literatureas horizontal defect dimension(HDD) and vertical defect dimension(VDD) around the implant (Wilsonet al. 1998). In the past, variousthresholds have been suggested forHDD in decision making as to thenecessity to graft the defect for suc-cessful histologic outcome of theimmediate implant placement (Wil-son et al. 1998, Paolantonio et al.2001, Botticelli et al. 2004, Covaniet al. 2004, Tarnow & Chu 2011).

The effect of HDD and VDD onbone modelling has modest evidenceso far. One study (Ferrus et al. 2010)demonstrated the immediate implantsites with HDD ≤ 1 mm had higherpercentage of horizontal bone dimen-sional reduction (43 � 44 versus32 � 32%), and more vertical boneresorption (1.4 � 2.5 mm versus0.7 � 1.4 mm) than the sites withHDD > 2 mm, though differenceswere not statistically significant.According to the present review,bHDD and bVDD were not signifi-cantly correlated with BHDr orBVDr (Table 3). Therefore, bHDDand bVDD may not be reliablepredictors of bone dimensionalchange following immediate implan-tation.

Use of regenerative adjunctive therapy

It has been demonstrated that socketpreservation, employing principles ofbone regeneration, reduces the extentof bone reduction following extrac-tion compared to the socket healingwithout use of regenerative materials(Lekovic et al. 1997, 1998, Iasellaet al. 2003, Cardaropoli & Cardaro-poli 2008, Vignoletti et al. 2012b).However, it was demonstrated thatthe histological bone remodelling,with the net loss of the bone dimen-sions, does occur in post-extractionsites, in spite of bone grafting, withor without a barrier in the animalstudy (Araujo et al. 2011). In addi-tion, use of regenerative materials,especially barriers, may be associatedwith post-operative complications,for instance, membrane exposure,and possible infection that may lead

(b)

(a)

Fig. 3. (a) The palatal horizontal bone dimensional reduction (PHDr) in meta-analy-sis. (b) The palatal vertical bone dimensional reduction (PVDr) in meta-analysis.

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

922 Lee et al.

to compromised clinical outcomes(Nowzari & Slots 1995, Machtei2001). Use of regenerative materialsin conjunction with immediateimplantation has been supported bysome studies (Chen et al. 2007, DeAngelis et al. 2011), while othersdemonstrated only limited benefit oftheir use for ridge preservation(Covani et al. 2010, van Kesterenet al. 2010, Spinato et al. 2012).

In the present review, the use ofgraft or barrier did not show statisti-cally significant correlation with buc-cal bone dimensional reduction.However, in the subgroup (graft orno graft) analysis, the weighted meanBHDr difference between the groupswas 0.53 mm, (0.79 mm versus1.32 mm, respectively) which shouldnot be neglected. The heterogeneityof study design, only one study utiliz-

ing barriers, variety of grafting mate-rials used, preclude clear conclusionson the topic, and further randomizedclinical trials designed to assess thepossible benefits to hard and soft tis-sue by utilizing regenerative materialsin conjunction with immediateimplantation are required.

Flap elevation and flapless techniques

The benefit of flapless implant place-ment was not conclusive (Lin et al.2013). Proposed advantages of flap-less surgical technique have beendescribed as reduced morbidity forthe patient (Cannizzaro et al. 2011),preservation of the blood supply(Kim et al. 2009), maintenance of theoriginal mucogingival position, pres-ervation of the position of the gingi-val margin (Raes et al. 2011), reducedpapillary loss and inter-proximalbone resorption (Gomez-Roman2001). In conjunction with immediateimplant placement, flapless approachcould reduce gingival recession(Cosyn et al. 2012), though limitedevidence is available to confirmadvantages of bony ridge preserva-tion, except animal studies (Blancoet al. 2008). In the present review,flap technique was not significantlycorrelated with BHDr or BVDr.Flapless technique may not offer sig-nificant clinical advantage in ridgepreservation following immediateimplant placement compared to theflap approach. However, only twodatasets utilized flapless approach inthe present review. More randomizedclinical trials comparing the twoapproaches directly are required tovalidate these observations.

Measurement methods

The studies in the present review uti-lized periodontal probes or calipersto measure ridge dimensions intra-orally, or performed the measure-ments of computed tomographicimages of the ridge. The accuracy ofmeasurement by computed tomogra-phy is comparable to the accuracy ofperforming measurement intra-orallyor on casts (Chen et al. 2008, Kam-buroglu et al. 2011). Reduction ofbuccal bone dimension was not sta-tistically correlated with the methodof measurement in the presentreview. Different measurement meth-

(a)

(b)

Fig. 4. (a) The buccal horizontal bone dimensional reduction (BHDr) in subgroupanalysis (Group 0 = no graft, 1 = graft). (b) The buccal horizontal bone dimensionalreduction (BHDr) in subgroup analysis (Group 0 = randomized clinical trials,1 = cohort studies).

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Bone changes in immediate implant site 923

ods did not cause significant bias inBHDr and BVDr results.

Limitations

The results should be interpretedcarefully due to the considerableheterogeneity of the datasets, poten-tial risk of bias, small number of theselected studies, and potential vari-ance existing in these outcomes.Moreover, most included studieslacked the information of soft tissueparameters, like gingival level orthickness. It was impossible to ana-lyse the correlations among bonedimension, gingiva level, and gingi-val biotype.

Conclusion

The buccal bone dimensional reduc-tion was expected after immediateimplant placement within 1-year fol-low-up. Buccal plate thickness ofthe post-extraction socket may fore-cast a pattern of the buccal bonedimensional change. These resultscould be utilized to forecast the aes-thetic outcome, possible complica-tions, choice of biological material,and timing of implant placement.However, more randomized con-trolled trials need to be performedto directly evaluate the effects of

different variables on bone dimen-sional change.

Acknowledgements

We would like to express our sincereappreciation to Dr. Panos N. Papapa-nou, Professor of Dental Medicine,Chair, Section of Oral Sciences, Divi-sion of Periodontics, College of Den-tal Medicine, Columbia University,for his valuable suggestions in thisreview.

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Table 3. Meta-regression analysis

Dependentvariable

Buccal horizontal bonedimensional reduction (BHDr)

Buccal vertical bone dimensionalreduction (BVDr)

Independentvariable

Coefficient 95% CI* p-value Coefficient 95% CI* p-value

bHDD �0.164 �2.98,2.65 0.891 0.031 �2.13,2.19 0.973bVDD �0.063 �0.32,0.19 0.556 �0.033 �0.32,0.25 0.773bHDB 0.59 �0.24,1.42 0.138 �0.528 �1.07,0.02 0.056TB 1.044 0.10,1.99 0.035 �0.793 �1.39,�0.19 0.018GT �0.544 �1.15,0.07 0.073 �0.114 �0.77,0.54 0.693BR �0.540 �1.75,0.67 0.327 �1.298 �4.14,1.54 0.316FLP 0.056 �0.88,0.99 0.892 0.022 �0.65,0.65 0.995MM 0.178 �0.68,1.04 0.640 0.050 �0.57,0.67 0.854*95% CI: 95% confidence interval of the coefficient.Roe et al. 2012 did not report the data of bHDD, bVDD, and TB. It was excluded fromthe meta-regression analysis while independent variable was bHDD, bVDD, or TB.Buccal horizontal defect dimension (bHDD): the distance between inner surface of buccalplate and implant surface; Buccal vertical defect dimension (bVDD): the distance betweenvertical reference point (implant platform/shoulder) and the most apical point of bonydefect at buccal side; Buccal horizontal bone dimension at baseline (bHDB): the distancebetween outer surface of buccal plate and implant surface; Thickness of alveolar buccalplate (TB): the thickness of buccal plate at reference point of measurement; Usage of graftmaterial (GT): usage of graft material or not; Usage of barrier (BR): usage of barrier ornot; Flap elevation (FLP): elevate the flap or keep the flap intact (flapless) during implantsurgery; Measurement method (MM): use probe/caliper or computed tomography image tomeasure dimensional change.

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Address:Janet StoupelDivision of Periodontics, Section of Oral andDiagnostic SciencesCollege of Dental Medicine, ColumbiaUniversity630 West 168th Street, New York NY 10032USAE-mail: js108@columbia.edu

Clinical Relevance

Scientific rationale for the study:Scarcity of data regarding changesin bone dimensions following imme-diate implantation was the mainreason to undertake this study. Thepresent review systematically analy-sed the bone dimensional altera-tions of the immediate implant sites.

Principal findings: Dimensionalchange of bony ridge in immediateimplant site was calculated. Buccalalveolar bone thickness of the socketwas statistically significantly relatedto reduction of the buccal alveolardimension.Practical implications: The resultscould be utilized to predict bone

dimensional change followingimmediate implant placement andtherefore facilitate in the choice ofconcomitant or sequential therapyoptions, as guided bone regenera-tion (GBR), or timing of implantplacement.

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

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