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Preoperative assessment of labial boneperforation for virtual immediate implantsurgery in the maxillary esthetic zoneA computer simulation study

Cheng-En Sung, DDS; David L. Cochran, DDS, MS,PhD; Wan-Chien Cheng, DDS, PhD; Lian-Ping Mau,DDS, MS; Po-Hsien Huang, DDS, MS; Wen-Hui Fan,MD; Yi-Shing Shieh, DDS, PhD; Ren-Yeong Huang,DDS, PhD

F or the past several decades, the suc-cessful use of osseointegrated implantshas evolved into an integral treatmentoption for patients who are partially and

completely edentulous.1 Traditionally, the pres-ence of sufficient bone volume is the mostimportant prerequisite for dental implant pla-cement; therefore, to provide state-of-the-artdental implant treatment, clinicians shouldsuggest that patients wait for months after toothextraction to ensure adequate alveolar bonehealing and remodeling.2,3 On the other hand,to meet the increased demands for maximizingesthetic results and minimizing treatment pro-cedures, some investigators have reported thatplacing a 1-stage implant into a fresh socketimmediately after tooth extraction may bepossible for various indications.2,4

In recent years, investigators have reportedthe results of studies addressing the healingdynamics between soft and hard tissues arounddental implants, the rapid advancement ofgrafting materials, and the refinement of surgicaland restorative techniques to allow for improvedpredictability and prognosis for immediate

Copyright ª 2015 American Dental Association. All rightsreserved.

ABSTRACT

Background. In this computer simulation study, the authorsinvestigated the frequency distribution of labial bone perforation(LBP) between various sagittal root position (SRP) classes withrespect to the anterior maxillary osseous housing and evaluated theassociated factors correlated with a higher risk of LBP when per-forming a virtual immediate implant surgery in the esthetic zone.Methods. The authors analyzed cone-beam computed tomogra-phy (CBCT) images from 285 qualified study participants (1,449teeth) to determine the probability of LBP when associated withselected variables, such as tooth type, SRP class, and morphologicparameters. The authors examined associated factors and analyzedthe adjusted odds ratios by means of multiple logistic regressionanalysis.Results. The overall probability of LBP was 81.7%, which pre-sented statistically significant differences between each specifictooth type and SRP class (all P < .001). After adjusting for otherfactors, the authors found that the maxillary central incisor was 2.37times more likely to have LBP than the canine. SRP class I was 4.9times more likely to be associated with LBP when compared withSRP class IV.Conclusions. When a clinician performs an immediate implant inthe anterior esthetic zone, he or she should be aware that the specifictooth type, SRP class, and morphologic features of fossa concavitiesare associated with a risk of experiencing LBP.Practical Implications. Presurgical cross-sectional images canbe analyzed to identify anatomic features relative to LBP in themaxillary esthetic region, and this can avoid unpleasant complica-tions, specifically when performing immediate implant procedures.Key Words. Cone-beam computed tomography; dental implants;maxilla; dental esthetics; risk assessment; dental implantation.JADA 2015:146(11):808-819

http://dx.doi.org/10.1016/j.adaj.2015.04.007

ORIGINAL CONTRIBUTIONS

808 JADA 146(11) http://jada.ada.org November 2015


implants placed into fresh extraction sockets.2,4

However, it should be emphasized that imme-diate implant placement and restoration in themaxillary esthetic zone is still critical and chal-lenging.1,3 This is mainly because of the limitedvolume of hard tissue in this zone, the unfa-vorable biotypes of soft tissue, inadequateimplant position, poor primary stability, andgaps between implant and socket, among otherissues, that may lead to difficulty in achieving theprimary stability of the implant, an unsatisfac-tory esthetic outcome, and ahigh rate of implantfailure.2,5

An insufficient or thinwall of labial bone in themaxillary anterior teeth isprone to perforation, dehis-cence, or both, after a clini-cian places an immediateimplant in the estheticzone.6,7 In a clinical scenario,the clinician usually positionsimmediate implants alongthe palatal slope of theextraction socket. However,unintentional slipping ofdental implants positionedtoward thin labial bone fre-quently leads to the perfora-tion or fracture of the labialplate.7 Consequently, theclinician should consideraugmenting the hard or softtissue in the site of theimplant. Stringent case se-lection, comprehensiveassessment, and propertreatment planning before surgery are suitable ways toreduce surgical accidents and complications such as labialbone perforation (LBP) in the esthetic zone.6 However,there is a paucity of information about how a clinicianshould assess the risk of labial plate perforation and othermorphologic parameters in the esthetic zone of ananticipated extraction site.

The amount of information that a clinician can gleanfrom a 2-dimensional (2-D) dental radiograph is sub-stantial.8 However, traditional radiographs cannot alwaysprovide sufficient information, and clinicians usingtraditional radiographs note that radiographs may havesome limitations associated with performing preopera-tive assessment and postsurgical evaluation, such asdetermining the localization and amount of bone vol-ume in a labiopalatal direction in an anterior estheticzone. Consequently, using an imaging modality with3-dimensional (3-D) capability—for example, cone-beam

computed tomography (CBCT)—is essential to enhancediagnosis and treatment planning while performing animmediate implant placement.9

The purpose of this computer simulation study wasto investigate the frequency distribution of LBP andfenestration between various sagittal root position (SRP)classes with respect to the anterior maxillary osseoushousing and to evaluate the associated factors that arecorrelated with having a higher risk of experiencing LBPwhen a clinician performs an immediate implant surgeryin the anterior esthetic zone.

TABLE 1

Reliability of intra- and interobservationsfor nominal variables measurement.INTRAOBSERVATION FREQUENCY k

Perforation (Yes Versus No) 1/50 0.913

SRP* Classification (Class I, II, III, IV) 1/50 0.912

INTEROBSERVATION

Perforation (Yes Versus No) 1/50 0.923

SRP Classification (Class I, II, III, IV) 1/50 0.922

* SRP: Sagittal root position.

TABLE 2

Reliability of intra- and interobservations for continuousvariables measurement.INTRAOBSERVATION FIRST

OBSERVATION,MEAN (SD*)

SECONDOBSERVATION,MEAN (SD)

MEASUREMENTERRORS,

MEAN (SD)

ICC† CRONBACH a

Concavity Angle(Degree)

147.21 (8.21) 147.32 (8.03) 1.29 (0.12) 0.982 0.991

Tooth-Ridge Angle(Degree)

13.49 (4.41) 12.93 (4.33) 0.86 (0.821) 0.98 0.99

Residual LabialBone Thickness(mm‡)

�1.38 (0.99) �1.35 (0.97) 0.134 (0.015) 0.985 0.993

INTEROBSERVATION OBSERVER 1,MEAN (SD)

OBSERVER 2,MEAN (SD)

MEASUREMENTERRORS,

MEAN (SD)

ICC CRONBACH a

Concavity Angle(Degree)

147.21 (8.21) 147.58 (8.35) 1.182 (0.18) 0.989 0.989

Tooth-Ridge Angle(Degree)

13.49 (4.14) 13.01 (4.39) 0.71 (0.82) 0.992 0.992

Residual LabialBone Thickness (mm)

�1.38 (0.99) �1.36 (0.93) 0.132 (0.144) 0.992 0.992

* SD: Standard deviation.† ICC: Intraclass correlation coefficient.‡ mm: Millimeters.

ABBREVIATION KEY. 2-D: 2-dimensional. 3-D: 3-dimensional. CA: Concavity angle. CBCT: Cone-beamcomputed tomography. LBP: Labial bone perforation. RLBT:Residual labial bone thickness. SRP: Sagittal root position.TRA: Tooth-ridge angle.


JADA 146(11) http://jada.ada.org November 2015 809


METHODSPatient recruitment,confidentiality, andimage acquisition. Allparticipants in this studywere Taiwanese patientsundergoing treatment(that is, dental implantplacement) at theDepartment of Den-tistry, Tri-Service Gen-eral Hospital, Taipei,Taiwan. In our study,board-certified radiolo-gists acquired all imagesby using a CBCT ma-chine (NewTom 5G, QRsrl) from November2009 through December2013. These radiologistsoperated the x-ray tubeat an accelerated poten-tial of 110 kilovolts peakwith a beam current of11.94 milliamperes, andthey automatically ad-justed the exposure timeaccording to the area ofscanning (about 7 sec-onds for a full arch). Wefixed the field of view at30.5 square centimeters� 20.3 cm2. The resolu-tion and separation ofeach slice was 0.15 milli-meters. We did not spe-cifically acquire theCBCT scans for thisproject. We saved thescans in a Digital Imag-ing and Communications in Medicine (that is, DICOM)format, and we saved these data in encrypted files thatwere confidentially protected, yet retrievable if needed. Theinstitutional review board of Tri-Service General Hospital,National Defense Medical Center approved the projectand protocol (TSGHIRB 2-102-05-064).

Inclusion and exclusion criteria of selected images. Theimages we selected from unidentified CBCT images hadto fulfill the following inclusion criteria (as describedpreviously)8,9: the image had to show 1 permanentmaxillary central incisor, lateral incisor, or canine thatwas erupted fully and had fully formed apexes; and eachtooth had to be positioned normally and have normalalignment, with a harmonious incisal line across themaxillary anterior teeth.

We excluded images if the patient had a history oforthodontic treatment, orthognathic surgical treatment,grafted alveolar ridge, supernumerary or impacted teeth,preexisting alveolar bone destruction, perforation,dehiscence, or a combination of these caused by peri-odontal disease or traumatic injury around the investi-gated region; if the images were unclear or incompleteowing to reasons of scattering or beam-hardening arti-facts; if the images had a pathologic lesion or evidentroot resorption; or if the images indicated a missingtooth, dental misalignment, or a dental implant.

Two calibrated, well-trained periodontists (C.-E.S.and R.-Y.H.) displayed all the images on a 19-inchliquid-crystal display monitor with a 1,920- x 1,080-pixel resolution (ChiMei, Innolux Corporation, Tainan,

Figure 1. Four types of sagittal root positions (SRP) (class I, II, III, and IV) in relation to the anterior maxillary osseoushousing (upper panels are graphic illustrations and lower panels are radiographic images).




Taiwan) and reoriented and inspected the images in adimly lit environment. They performed intraexaminerand interexaminer calibration for nominal andcontinuous variables to assess the reliability of thedata on the basis of whether the anatomic diagnosiscould be made using the CBCT images, and theyevaluated 50 randomly selected images. The examinersused the k statistic for analysis before discussing andresolving their disagreements.10 The k statistic valuesfor nominal variables (that is, perforation and SRPclassification) were 0.913 and 0.912 for intraobserveragreement and 0.923 and 0.922 for interobserveragreement, respectively (Tables 1 and 2). Tables 1 and 2summarize the measurement errors, intraclass correla-tion coefficient (ICC), and Cronbach a values. Aftercalibration, the 2 examiners separately evaluated the

images, and theydiscussed any dis-agreement in theirinterpretations of theimages until theyreached a consensus.

Assessment andclassification of theSRP. We used com-mercially available 3-Dnavigation software(ImplantMax 4.0,Saturn Imaging) tocapture and analyze thequalified CBCT imagesthat met the inclusionand exclusion criteria.We selected for viewinga sagittally sectionedimage of the region ofinterest and the centersection of each investi-gated tooth.

Figure 1 illustrates4 types of SRPs of themaxillary anteriorteeth in relationshipto the osseous housing,according to the defi-nition described pre-viously by Kan andcolleagues.11

-Class I: the root ispositioned against thelabial cortical plate;-Class II: the rootis centered in themiddle of the alveo-lar housing withoutengaging either the

labial or the palatal cortical plates at the apical third ofthe root;-Class III: the root is positioned against the palatalcortical plate;-Class IV: at least two-thirds of the root is engagingboth the labial and palatal cortical plates.

Virtual implant placement and determination ofLBP. We selected a parallel root form implant withcarrying diameters (4.2 mm, 3.0 mm, and 4.2 mm fora central incisor, a lateral incisor, and a canine, respec-tively) from an implant database available in the software(ImplantMax 4.0) to mimic the size of each investigatedtooth root. We used the selected sizes that were usedmost commonly in the anterior esthetic zone that cor-responded with the indicated tooth type, and we deter-mined these samples according to the results of studies

Figure 1. (Continued)




conducted by Misch.12 We virtually placed the selectedimplants along the palatal slope of the investigated toothroot, with 4 mm of the implant anchored in native bone,because this was considered to be the minimal amountrequired to achieve primary stability and to ensure thesurvival of the immediate implant.12,13 We judged theLBP when the virtual implant extruded the outline ofthe labial cortical bone in the sagittally sectioned images(Figure 2).

Measurements of morphologic features of maxillaryanterior esthetic zone. We measured the followingmorphologic and dimensional parameters of the teethand alveolar ridge according to the results of previousstudies6,14-16:-Residual labial bone thickness (RLBT): the labiopal-atal distance between the deepest point of the labial plate(point D) to the external surface of the virtual implant

surface perpendicularly, where Line A is the connectionof the incisal edge and the root apex bisecting the labialand palatal halves of the tooth (Figure 2).14,15

-Concavity angle (CA): the angulation line D-C (thatis, the line connecting points D and C, with pointC defined as the most external point of the labial plate)and line D-P (that is, the line connecting points D and P,with point P defined as the most external point of thelabial plate superior to point D, and relatively higherthan the apex of the tooth along the apicocoronal con-tinuum) (Figure 3A).6

-Tooth-ridge angle (TRA): the angulation betweenline A and line B, where line B represents the linerunning through the labiopalatal midpoint of the alve-olar process (Figure 3B).16

Figure 2. Radiographs of labial bone perforation and residual labialbone thickness occurring when a virtual implant is placed along thepalatal slope of an investigated tooth root, with 4 millimeters of implantanchored in native bone in the anterior esthetic zone. The labiopalataldistance is between the deepest point of the labial plate (point D) tothe external surface of virtual implant surface perpendicularly, in whichline A is the connection of the incisal edge and the root apex bisectingthe labial and palatal halves of the tooth. Measurements of RLBT include(A) nonperforation and (B) perforation sites in the anterior esthetic zone.

Figure 3. Radiographs of the morphologic parameters regarding labialbone perforation in the esthetic zone. A. The concavity angle representsthe angulation line D-C (that is, the line connecting points D and C, withpoint C defined as the most external point of the labial plate and inferiorto point D) and line D-P (the line connecting points D and P, with point Pdefined as the most external point of the labial plate superior to point D,and relatively higher than the apex of the tooth along the apicocoronalcontinuum). B. The tooth-ridge angle represents the angulation betweenline A and line B, in which line B represents the line running through thelabiopalatal midpoint of the alveolar process. Line A is the connection ofthe incisal edge and the root apex bisecting the labial and palatal halvesof the tooth.




Statistical ana-lysis. We calculated themean (standard devia-tion) values for eachmeasurement. We ex-pressed the occurrenceof LBP as the percentageof the number of siteswith perforation dividedby the total number ofcorresponding investi-gated sites. We usedthe c2 test and 1-wayanalysis of variance testto examine differenceswith categorical vari-ables, such as the fre-quency distribution of4 types of SRP classand the labial perfora-tion of the investigatedtooth in the maxillaryanterior esthetic zone. Inaddition, we performedcomparisons betweenthe mean values ofRLBT, CA, and TRAat nonperforation andperforation sites byconducting independentt tests. Using multiplelogistic regressionmodeling, we deter-mined the odds ratioof variables and adjust-ments for confoundingvariables that made animportant contributionto the probability ofLBP. We performedall statistical analysesusing statistical software(PASW statistics 18.0,SPSS). We set the levelof statistical significanceat P < .05.

RESULTSOf the 339 participants(2,034 teeth) available forthis study, 285 partici-pants (1,449 teeth) qual-ified for further analysis according to the inclusionand exclusion criteria. The frequency distribution of in-cluded teeth were central incisor (n ¼ 486; 33.5%), lateralincisor (n ¼ 491; 33.9%), and canine (n ¼ 472; 32.6%).

In addition, the reasons for observed teeth being ex-cluded from the study were pathologic lesion or changes(51.3%), missing (46%), and unclear and scattered images(2.7%) (data not shown). The SRP class I ridge was the

TABLE 3

Frequency distribution of 4 types of sagittal root positionclass of investigated teeth in the maxillary anterior estheticzone.VARIABLE SRP*

CLASS ISRP

CLASS IISRP

CLASS IIISRP

CLASS IVP

n % n % n % n %

Right 641 87.6 73 10.0 1 0.1 16 2.3.357

Left 627 87.3 79 11.0 3 0.4 9 1.3

Central Incisor 426 87.7 53 10.9 3 0.6 4 0.8

< .001Lateral Incisor 398 81.1 73 14.9 1 0.2 19 3.8

Canine 444 94.1 26 5.5 0 0.0 2 0.4

Central Incisor, Right 218 89.0 23 9.4 1 0.4 3 1.2

< .001

Central Incisor, Left 208 86.3 30 12.4 2 0.8 1 0.4

Lateral Incisor, Right 197 79.4 38 15.3 0 0.0 13 5.2

Lateral Incisor, Left 201 82.7 35 14.4 1 0.4 6 2.5

Canine, Right 227 95.0 12 5.0 0 0.0 0 0.0

Canine, Left 217 93.1 14 6.0 0 0.0 2 0.9

Total 1,268 87.5 152 10.5 4 0.3 25 1.7


TABLE 4

Frequency distribution of labial bone perforation ofinvestigated tooth in the maxillary anterior esthetic zone.VARIABLE PERFORATION NONPERFORATION P

n % n %

Tooth

Right 600 82.1 131 17.9.734

Left 584 81.3 134 18.7

Central incisor 416 85.6 70 14.4

< .001Lateral incisor 353 71.9 138 28.1

Canine 415 87.9 57 12.1

Central incisor, right 210 85.7 35 14.3

< .001

Central incisor, left 206 85.5 35 14.5

Lateral incisor, right 179 72.2 69 27.8

Lateral incisor, left 174 71.6 69 28.4

Canine, right 211 88.3 28 11.7

Canine, left 204 87.6 29 12.4

Tooth-AlveolarRidge (SRP* Class)

SRP class I 1,152 90.9 116 9.1

< .001SRP class II 11 7.2 141 92.8

SRP class III 2 50.0 2 50.0

SRP class IV 19 76.0 6 24.0

Total 1,184 81.7 265 18.3





most common, with 87.5% (n ¼ 1,268) of examined teethfalling into this category. The least common ridge wasSRP class III, which was evident only in 0.3% (n ¼ 4)of the qualified images. Table 3 summarizes the fre-quency distribution of the SRP class for each tooth type.Specifically, among SPR class I ridge morphology, canineteeth (94.1%) were the most prevalent, compared withcentral incisors (87.7%) and lateral incisors (81.1%)(Table 3). Significant differences existed between toothtype and each type of SRP ridge morphology (P < .001)(Table 3).

The overall probability of LBP was 81.7% (1,184 teeth),and the perforation was most likely to occur in canineteeth (n ¼ 415; 87.9%), compared with central incisors(n ¼ 416; 85.6%) and lateral incisors (n ¼ 353; 71.9%)(Table 4). When examined by the ridge classification,LBP was most likely to occur at the SRP class I ridge(90.9%) compared with other SRP ridge types (Table 4).The probability of LBP was significantly different be-tween each specific tooth type (P < .001) and SRP ridgetype (P < .001) (Table 4).

We summarized and described the morphologicparameters, including RLBT (Table 5), CA (Figure 4),and TRA (Figure 5), of all examined teeth as follows: Ofthe analyzed tooth type, RLBT (Table 5), CA (Figure 4),and TRA (Figure 5) all exhibited significant differencesbetween each tooth type (P < .001). In addition, RLBT(Table 5) and CA (Figure 4) in the nonperforation groupwere statistically higher than in the perforation group,whereas TRA was much lower in the nonperforationgroup than in the perforation group (Figure 5). Allof these values had a significant effect on the probabilityof LBP (all P < .001).

We further identified the association between theselected variables and the probability of LBP in eachinvestigated tooth (Table 6). After adjusting for tooth-,alveolar ridge-, and tooth-alveolar ridge–associated fac-tors, we found that our results showed that virtuallyplaced immediate implants at the maxillary centralincisor were 2.37 times (95% confidence interval [CI], 1.38-4.07; P ¼ .002) more likely to cause LBP when comparedwith virtually placed immediate implants at the canine(reference group). The probability of LBP reduced by6.7% for every 1-degree increase in the fossa concavityangle (95% CI, 0.92-0.95; P < .001) (Table 6). The resultsalso showed that when the tooth is classified as SRP class Ior class II, it is 4.91 (95% CI, 1.83-13.13; P ¼ .002) and 0.03(95% CI, 0.01-0.09; P < .001) times more likely to haveLBP when compared with the SRP class IV (referencegroup), respectively (Table 6).

DISCUSSIONImmediate placement of a dental implant into a freshextraction socket has attracted attention since the firstarticle was published about this topic more than 30 yearsago.17 This procedure can provide significant advantages,including a decreased need for additional surgical pro-cedures, shorter treatment time, improved esthetics,and enormous psychological benefits for patients.17 Asthe prevailing scientific documentation for placing im-mediate implants is driven by the restoration rather thanby the available bone, clinicians should base their deci-sion to place an immediate implant on the position ofthe implant in the esthetic zone and on having a 3-Dimage from which to plan the ideal implant position.7

Although limited data exist concerning the axis of the

TABLE 5

Comparisons of the residual labial bone thickness (in millimeters) in theperforation and nonperforation sites of investigated tooth in the maxillaryanterior esthetic zone.VARIABLE TOTAL,

MEAN (SD*)P PERFORATION, MEAN (SD) P

Yes No

Right �1.51 (1.57).095

�1.97 (1.32) 0.61 (0.60) < .001

Left �1.37 (1.53) �1.83 (1.30) 0.61 (0.63) < .001

Central Incisor �1.60 (152)

< .001

�1.96 (1.32) 0.54 (0.59) < .001

Lateral Incisor �0.91 (1.45) �1.54 (1.15) 0.71 (0.64) < .001

Canine �1.82 (1.54) �2.15 (1.35) 0.45 (0.52) < .001

Central Incisor, Right �1.74 (1.55)

< .001

�2.11 (1.24) 0.46 (0.48) < .001

Central Incisor, Left �1.45 (1.49) �1.80 (1.28) 0.63 (0.68) < .001

Lateral Incisor, Right �0.90 (1.41) �1.53 (1.07) 0.74 (0.67) < .001

Lateral Incisor, Left �0.92 (1.49) �1.56 (1.24) 0.68 (0.62) < .001

Canine, Right �1.90 (1.58) �2.21 (1.40) 0.47 (0.49) < .001

Canine, Left �1.77 (1.50) �2.08 (1.32) 0.43 (0.57) < .001

Total �1.49 (1.55) �1.90 (1.31) 0.61 (0.61) < .001

* SD: Standard deviation.




implant in the sagittalview, clinicians shouldunderstand that it isimportant to examineteeth that are scheduledfor extraction andreplacement with an im-mediate implant6,11,16,18

because the location ofthe implant in relation tothe adjacent teeth andmorphologic features ofthe ridge in 3 axes couldhave a critical impact onthe long-term stabilityand harmony of “pinkand white esthetics”around the dentalimplants.6,11,19

Investigators haveproposed several classi-fication systems toanalyze SRP with respectto the osseous housing inthe anterior maxilla.11,18

For example, Lau andcolleagues18 used CBCTto classify maxillarycentral incisors byanalyzing the positionand angulation of theteeth, and Kan andcolleagues11 further eval-uated the association ofthe position of maxillaryanterior teeth with theirosseous housing, cate-gorizing them as class Ithrough class IV. In thisstudy, we found that, ofthe 4 categorized toothpositions and sagittal-sectional maxillary ridgemorphologies proposedby Kan and colleagues,11

SRP class I ridge wasthe most common, with87.5% (n ¼ 1,268) ofexamined teeth fittinginto this category, inwhich the canine teeth(94.1%) were the mostprevalent (P < .001)(Table 3). This highprevalence of SRP classI ridges is consistent

180

160

140

120

100500

Right Left

Central Incisor

Right Left

Lateral Incisor

TOOTH TYPE

Right Left

Canine

Total Perforation Nonperforation

180

160

140

120

100500CO

NCA

VIT

Y A

NG

LE (

DEG

REE

)

Right

ARCH

LeftA

P = .377

P < .001 P < .001

180

160

140

120100500CO

NCA

VIT

Y A

NG

LE (

DEG

REE

)

Central Incisor Lateral Incisor

TOOTH TYPE

CanineB

P < .001P < .001

P < .001

P < .001

CON

CAV

ITY

AN

GLE

(D

EGR

EE)

C

P < .001P < .001

P < .001

P < .001

P < .001

P = .001 P = .001

Figure 4. The comparisons of concavity angle for teeth at the right side arch and the left side arch (A); centralincisor, lateral incisor, and canine (B); and each tooth type between total, perforation, and nonperforation sites (C).Data represent means and standard deviations. Lines under the P values indicate statistical differences betweenthe Perforation and Nonperforation categories. Statistically significant differences were expressed as P < .05.




with the results of pre-vious studies,11 in whichthe percentage of SRPclass I ridges variedfrom 81.1%11 to 84.6%18,19

of all examined teeth.Moreover, our resultsdemonstrated that thefrequency of SRP classIII ridges was the least(0.3%; range, 0-0.8%;Table 3), which is si-milar to previously re-ported results (0.7%;range, 0-1.5%),11 illus-trating the rarity of thisroot position. On thecontrary, our results ofthe frequency distribu-tion of SRP class II andclass IV were not in linewith the results report-ed by the investigatorsof a previous study.11

Knowing these results,clinicians who areplacing immediate im-plants in the maxillaryanterior estheticzone should understandthat performing a seriesof evaluations, especiallyincluding sagittal-sectional tomographicimages for SRP class Iand class IV, wouldprovide useful informa-tion for clinicians whoare proposing alternativetreatment plans to avoidthe occurrence of LBP(Table 4).

The possibility of im-mediate implant perfora-tion over the labial boneplate may lead to futureimplant failure, anesthetically compromisedcondition, or both.4-7

However, it is difficult toestablish how frequentlyLBP will happen whenan immediate implant isplaced on the long axisof the existing socketbecause concomitant

Total Perforation Nonperforation

30

20

10

0

TOO

TH-R

IDG

E A

NG

LE (

DEG

REE

)

Right Left

ARCH

A

P = .52

P < .001 P < .001

30

20

10

0TOO

TH-R

IDG

E A

NG

LE (

DEG

REE

)

Central Incisor Lateral Incisor

TOOTH TYPE

CanineB

P < .001 P < .001

P < .001

P < .001

30

20

10

0

TOO

TH-R

IDG

E A

NG

LE (

DEG

REE

)

Right Left

Central Incisor

Right Left

Lateral Incisor

TOOTH TYPE

Right Left

CanineC

P < .001P < .001P < .001P < .001

P < .001

P = .001 P = .11

Figure 5. The comparisons of tooth-ridge angle for teeth in the right-side arch and the left-side arch (A); centralincisor, lateral incisor, and canine (B); and each tooth type between total, perforation, and nonperforation sites (C).Data represent means and standard deviations. Lines under the P values indicate statistical differences betweenthe Perforation and Nonperforation categories. The statistically significant differences were expressed as P < .05.




complications vary. In our study, the overall probabilityof LBP in the maxillary esthetic zone (from central incisorto canine) was 81.7% (Table 4); however, in a similar studyby Chan and colleagues,6 the investigators demonstratedthat only 18.75% of LBP were reported in the maxillaryincisor region (central incisor and lateral incisor). Of all theinvestigated teeth (n¼ 1,449), the central incisor (n¼ 416;28.7%) and the canine teeth (n ¼ 415; 28.6%) were themost likely to cause LBP (Table 4); however, our predictedprobability of LBP in the incisor region (n ¼ 769; 53.07%)(Table 4) is still much higher than the results of a previousstudy conducted by Chan and colleagues6 (53.07% versus18.75%, respectively). We could attribute such a diver-gence to the interaction of study design, classificationsystems, regions of interest, dentate status, and racial andethnic reasons.6,7,11,16,18 To avoid the high incidence of LBPin the esthetic zone, it is necessary to achieve an accuratediagnosis and treatment planning through comprehensiveoral examination and tomographic images before pursu-ing immediate implant placement. Interestingly, our re-sults showed that when the root apex was used as a guidefor drilling an immediate implant in the anterior region,teeth classified as SRP class I were 4.9 times more likely tohave LBP when compared with teeth classified as SRPclass IV (reference group) (Table 6), but this result has notbeen reported by the investigators of previous studies.Thus, the specific tooth type and ridge type could have asignificant impact on the occurrence of LBP (all P < .001)(Table 4).

Although the investigators of numerous studies haveexamined the regional anatomic features around the

maxillary anterior alveolar ridge,6,16,20,21 there is limitedinformation concerning the associated risk factors con-tributing to the occurrence of LBP. Investigators havereported that concavity depth and implant ridge angle arerelated significantly to the occurrence of fenestration andthat these factors should be evaluated carefully beforesurgery.6 In our study, the discrepancy of regionalmorphologic parameters, such as RLBT (Table 5),CA (Figure 4), and TRA (Figure 5) were statisticallydifferent in the nonperforation sites than in the perfo-ration sites. Moreover, the results show that the proba-bility of LBP will diminish by 6.7% for every 1-degreeincrease in the angle of the fossa concavity (95% CI, 0.92-0.95; P < .001) (Table 6). Accordingly, we recommendthat clinicians conduct meticulous preoperative exami-nations (that is, using 3-D CBCT analysis) and carefullychoose among adequate treatment approaches (that is,computer-aided implant planning, bone grafting pro-cedures, and a more palatally placed implant) to allow forthe simplification of subsequent treatments and theoptimization of esthetic outcomes.2,22 Moreover, to pre-vent LBP when performing osteotomy surgery in theesthetic zone, clinicians may find it necessary to make aminor modification of implant size or inclination in high-risk situations, such as those with SRP class I ridges(Table 6).

There is limited information regarding the spatialrelationship between the regional factors and theprobability of labial plate perforation associatedwith placing immediate implants in the maxillaryesthetic zone. This study represents the first time that

TABLE 6

Multiple logistic regression analysis of variables contributing to labial boneperforation during virtual immediate implant placement.*VARIABLE UNIVARIATE MULTIVARIATE

OR† 95% CI‡ P OR 95% CI P

Tooth

Central incisor 0.801 0.559-1.147 .226 2.374 1.384-4.071 .002

Lateral incisor 0.358 0.258-0.495 < .001 0.446 0.291-0.682 < .001

Canine Referent Referent

Alveolar Ridge

Fossa cavity angle 0.954 0.941-0.966 < .001 0.933 0.915-0.950 < .001

Residual labial bone thickness 0.001 < 0.001-0.004 < .001

Tooth-Alveolar Ridge

SRP§ class I 3.512 1.455-8.473 .005 4.905 1.833-13.128 .002

SRP class II 0.026 0.009-0.075 < .001 0.029 0.009-0.092 < .001

SRP class III 0.35 0.041-2.977 .336 0.36 0.031-4.251 .418

SRP class IV Referent

Tooth-ridge angle 1.408 1.351-1.468 < .001

* Odds ratios were adjusted for all other variables.† OR: Odds ratio.‡ CI: Confidence interval.§ SRP: Sagittal root position.




investigators examined the associated factors (such asspecific tooth type, fossa concavity angle, and SRPclass) and analyzed the adjusted odds ratio by meansof multiple logistic regression analysis. Clinically, therisk of having LBP occur during immediate implantplacement increases when the clinician places theimplant deeper toward the apical bone to achieveprimary stability.4,11,16 Moreover, some investigatorshave suggested that using multislice 3-D informationobtained through a variety of techniques such as CBCTalso would be helpful in presurgical diagnosis andtreatment planning for placing an immediate implantin the maxillary esthetic zone.6,11,18 These assessmentsallow the clinician and patient to consider treatmentoptions (for example, guided bone regeneration, soft-tissue grafting, or using a delayed implant protocol) ifthe site exhibits a high risk of having a labial plateperforation as a result of immediate implant placement.

The prevailing concept for implant placement is basedon a restoration-driven treatment plan with precise 3-Dpositioning of the implant and future restoration, ratherthan on the amount of available bone.23 The presurgicalassessment of proposed immediate implant sites requiresspecific and accurate data; thus, the information obtainedfrom the diagnostic casts, radiographs, and direct ob-servation all are essential for the selection of an optimalimplant type and the length and diameter at the apical,mid-body, and coronal level customized to the originalsocket as much as possible. We should note that 2-Dradiographic examination, such as panoramic and peri-apical radiographs, still can be considered as a safe,quick, simple, low-cost, and low-dose presurgical diag-nostic tool for implant treatment planning.6,8 However,series pre-extraction sagittal-sectional computedtomography provides additional information whencompared with conventional radiography, and this typeof information is important to treatment planningfor immediate implant placement in the anterior estheticzone.6,11,16,18 According to the results of our study, par-ticipants who planned to receive immediate implantsurgery in an anterior esthetic zone had received a strongrecommendation to receive the CBCT examination as aroutine presurgical assessment, especially when the im-plant sites were associated with inadequate bone volumeor quality, undeterminable proximity to vital structures,and insufficient inter-radicular spacing.

When applying the findings of this study to clinicalscenarios, clinicians must consider certain tooth- (that is,tooth root shape, root long axis), ridge- (that is, fossaconcavity, labial bone volume), and tooth-alveolar ridge–(that is, SRP classification) associated factors beforeplacing an immediate implant. When clinicians collec-tively assess these risk factors, the results can provideuseful information so that clinicians can achieve stableesthetic outcomes for immediate implant placement inthe esthetic zone.

CONCLUSIONFrom the results of this study, we conclude that patientswho plan to receive immediate implant surgery in theanterior esthetic zone should receive strong recommen-dations from their clinicians to undergo a CBCT exam-ination as a routine presurgical assessment. In addition,we recommend that clinicians pay special attention tothe high probability that LBP will occur in maxillaryanterior teeth, and that this situation may complicate theesthetic outcome if an immediate implant is placed alongthe axis of the tooth. More specifically, we note that thereis a higher risk of experiencing LBP, because it is asso-ciated with the specific tooth type, concavity angle, andSRP class when performing an immediate implant sur-gery in the anterior esthetic zone. n

Dr. Sung is a resident, Department of Periodontology, School of Dentistry,Tri-Service General Hospital and National Defense Medical Center, Taipei,Taiwan.Dr. Cochran is a professor and chairman, Department of Periodontics,

School of Dentistry, The University of Texas Health Science Center at SanAntonio, San Antonio, TX.Dr. Cheng is an attending dentist, Department of Periodontology, School

of Dentistry, Tri-Service General Hospital and National Defense MedicalCenter, Taipei, Taiwan.Dr. Mau is an attending dentist, Department of Dentistry, Chi Mei

Medical Center, Liou Ying, and a lecturer, Department of Long Term Care,Chung Hwa University of Medical Technology, Tainan, Taiwan.Dr. Po-Hsien Huang is an attending dentist, Department of Dentistry,

Kaohsiung Armed Forces General Hospital, Kaohsiung, Taiwan.Dr. Fan is an attending physician, Department of Family and Community

Medicine, Tri-Service General Hospital and National Defense MedicalCenter, Taipei, Taiwan.Dr. Shieh is a professor and dean, School of Dentistry, Tri-Service General

Hospital and National Defense Medical Center, Taipei, Taiwan.Dr. Ren-Yeong Huang is an assistant professor, Department of

Periodontology, Tri-Service General Hospital and National Defense MedicalCenter, No.325, Sec.2, Chenggong Rd., Neihu District, Taipei City 114,Taiwan, e-mail [email protected]. Address correspondence toDr. Ren-Yeong Huang.

Disclosure. None of the authors reported any disclosures.

The study was self-funded by the authors and their institution.

The authors acknowledge Ms. Jing-Shu Huang, MS (Department ofPublic Health, National Defense Medical Center), for her help with sta-tistical analysis. The authors appreciate Dr. Cathy Tsai, DDS, for her helpwith manuscript editing, and Mr. Yu-Feng Lin (Hi-Aim BiomedicalTechnology), Ms. Yi-Shing Lin, and Ms. Li-Chin Yu (Tri-Service GeneralHospital) for their help in taking computed tomography scans and pro-cessing the images.

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Author's personal copy - Taiwan-Healthcare · implants placed into fresh extraction sockets.2,4 However, it should be emphasized that imme-diate implant placement and restoration