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Oral Maxillofac Surg9:142-153, 2011

Classification of Maxillary CentralIncisors—Implications for Immediate

Implant in the Esthetic Zone

Sze Lok Lau, BDS(HK), MDS(OMS)(HK), AdvDipOMS(HK), MOSRCS(Edin),

FHKAM(DS), FCDSHK(OMS),*

James Chow, MBBS(HK), BDS(HK), MDS(OMS)(HK), FHKAM(DS),

FCDSHK(OMS), FDSRCS(Eng), FRCD(C),†

William Li, BDS(HK), MDS(OMS)(HK), AdvDipOMS(Hk), MOSRCS(Edin),

FRACDS, FHKAM(DS), FCDSHK(OMS),‡ and

Lop Keung Chow, BDS(HK), MDS(OMS)(HK), MOSRCS(Edin), FHKAM(DS),

FCDSHK(OMS)§

Purpose: This is the first study to analyze the positions and angulations of the central maxillary incisorswith reference to the alveolus, providing data for clinicians to achieve good esthetic results for immediateimplant placement in the esthetic zone.

Materials and Methods: A total of 300 cone beam images were selected randomly. Five aspects weremeasured: the thickness of the palatal and buccal bone at their mid-root and apical level and the apicalbone height. A classification was established according to the positions and angulations of the tooth.

Results: The data from 170 cone beam images were included in the present study. The mean thicknessof the buccal bone at the mid-root level was 0.9 � 0.4 mm and at the apical level was 2.04 � 1.01 mm.The mean thickness of the palatal bone at the mid-root level was 3.76 � 1.37 mm and at the apical levelwas 8.51 � 2.54 mm. The mean apical bone height was 9.53 � 2.76 mm. The proportion of incisorspositioned more buccally (type B) was 78.8%, 19.4%, and 1.8% positioned midway (type M) and morepalatally (type P), respectively. Regarding the angulation, 49.9% were classified as type 2 (toward buccal),34.7% as type 3 (toward buccal, with the long axis anterior to the A point), and 15.4% were categorizedas type 1 (toward palatal or parallel to the alveolus).

Conclusions: We recommend that clinicians appreciate the socket in 3 dimensions to achieve a goodoutcome. According to the difficulty of achieving good results, the cases were categorized as levels I toIII and recommendations were given.© 2011 American Association of Oral and Maxillofacial Surgeons
J Oral Maxillofac Surg 69:142-153, 2011
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hroughout the past 40 years, dental implantation hasradually changed our thoughts about the line be-ween saving a tooth and extraction, as well as tootheplacement therapy. With rapid advances in graftingaterials and refinements in the surgical and pros-

hetic protocols, the restoration of a single tooth gap

eceived from Branemark Osseointegration Centre, Hong Kong,

eople’s Republic of China.

*Specialist in Oral and Maxillofacial Surgery.

†Specialist in Oral and Maxillofacial Surgery.

‡Specialist in Oral and Maxillofacial Surgery.

§Specialist in Oral and Maxillofacial Surgery.

Address correspondence and reprint requests to Dr Lau: Brane-

ark Osseointegration Centre, Hong Kong, Room 1901, The Cen-

142

y a dental implant has become the reference stan-ard. Traditional guidelines have suggested a 2- to-month healing period after dental extraction to al-

ow sufficient bone infilling and remodeling beforeental implant placement,1,2 after which, a 3- to-month healing period should be allowed before the

er, 99 Queen’s Road Central, Hong Kong, People’s Republic of

hina; e-mail: [email protected]

2011 American Association of Oral and Maxillofacial Surgeons

278-2391/11/6901-0020$36.00/0

oi:10.1016/j.joms.2010.07.074

mailto:[email protected]

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LAU ET AL 143

mplant is exposed and loaded with a fixed prosthe-is.1,2 However, the negative effect of tooth extrac-ion on the volumetric hard and soft tissue changes inhe buccolingual and vertical dimensions has beeneported extensively in published studies. Using diag-ostic casts,3-5 radiographs,6-8 and direct measure-ents9 to evaluate the magnitude of bone resorption,

t has been reported that during the first 4 monthsfter extraction, the mean bone reduction was 5 to 7m buccolingually8,9 and 2 to 4.5 mm vertically.6

ecause such bone resorption will strongly affect themplant placement and, thus, the esthetics outcome,linicians started to insert the implant directly intohe extraction socket immediately after extraction,nder the assumption that this would reduce theone resorption. The first case report of this tech-ique was published in 1976.10 Since then, numeroustudies have been published regarding the refinementf this technique.11-13 Additional clinical research hashown that the outcomes of immediate implant place-ent, delayed implant placement, and implant place-ent in healed socket sites were all comparable.14

The multiple advantages of immediate implant place-ent are well known, especially in the esthetic zone,

uch as the maxillary central incisors. These advantagesnclude a reduction in the number of surgeries, a reduc-ion of the total treatment time, the preservation oflveolar bone,15-17 the maintenance of a good soft tissuerofile,18 and the reduction of the patients’ psychologi-al trauma owing to the loss of a front tooth.19 However,uch therapy is not without drawbacks. The greatestroblem for clinicians is the unpredictability of the long-erm soft tissue stability. The problem of soft tissueecession is usually exacerbated in patients with rela-ively thin buccal bone and thin gingival biotypes.20

ecause the gingival biotype cannot be changed, theritical aspect of achieving esthetic success depends onhe ideal 3-dimensional implant position21 and the main-enance of adequate buccal bone thickness over themplant buccal surface.22 Immediate implant therapyas been reported to be very technically demanding14

nd requires an understanding of all these aspects andore. Failure to do so will result in an adverse outcome,

efeating the initial objectives of the therapy itself. Im-ediate implantation is never easy, especially when the

emand for long-term stable esthetic results is high;hus, case selection is of the utmost importance.

The criteria for implant success have been chang-ng, and interest in the esthetic outcome is becoming

major concern. Implant dentistry has graduallyvolved from a bone-driven surgical protocol to aestorative and biologically driven protocol. Theresent study is the first to analyze the positions andngulations of the central maxillary incisors with ref-rence to the alveolar bone. Our results will provide
ata for clinicians to achieve the best long-term es- a
hetic results. The thicknesses of the bone at theuccal and palatal side were evaluated, as was theone height at the apical tooth region. A new classi-cation is introduced to categorize the different toothositions and angulations, providing a reference toelp avoid compromising the buccal bone thicknessnd to prevent fenestration and perforation duringmplant placement. Different types of teeth were alsoanked according to their difficulties for achievingood long-term results, and general recommendationsor their management were given.

aterials and Methods

A series of 300 cone beam (CB) images of theaxilla taken from April 2006 to August 2006 were

andomly selected from the computer record at theental Implant and Maxillofacial Centre in Hongong. All CB images were taken with the same ma-hine (I-CAT cone beam volumetric tomography andanoramic dental imaging system; Imaging Sciencenternational, Hatfield, PA). The head positions weretandardized by aligning the patient’s head with hor-zontal and vertical reference lines, constructed using

beam of light. The patient’s head was positioneduch that the horizontal reference beam was at theevel of the patient’s eyes and the vertical referenceeam was passing through the patient’s facial midline.nce the ideal head position had been located, theatient’s head was fixed with a head frame. The CB

mages were viewed and measured by the softwarerovided. Each image was examined to identify a fully

ormed, intact, and healthy permanent central upperight incisor (tooth 11) for analysis. If the centralpper right incisor was missing, the upper left central

ncisor was selected for analysis. The CB imaging dataere excluded if any radiographically detectable

namel or dentine defect, caries, apical pathologiceatures, periodontal alveolar bone loss, restoration ofny kind, or fracture was present or when both cen-ral incisors were missing.

Landmarks were identified and marked in the com-uter before the measurements were done. The sag-

ttal section of the chosen incisor was viewed at theenter of its mesial-distal dimension. As shown inigure 1, both the palatal line (line 1) and the buccaline (line 2) were marked by a line best-fit to thealatal alveolar surface and the buccal alveolar sur-

ace, respectively. The alveolar line (line 3) wasarked by bisecting the palatal and buccal lines. This

ndicated the angulation of the alveolar process in theagittal plane. The angulation of the tooth root wasndicated by its long axis (line 4), and this axis was

arked by the midpoint of a line drawn from the buccalnamel-dentine junction to its palatal counterpart, the
pex of the root. The present study involved measure-

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144 CLASSIFICATION OF MAXILLARY CENTRAL INCISORS

ent of the residual bone thickness and angulations ofhe extraction sockets. The long axis of the tooth root,nstead of the long axis of the whole tooth, was used,ecause the range of the crown-root angle is 25.5° foraxillary central incisors.23 From these reference lines,measurements were performed, using the built-in mea-

uring function of the computer software. The measure-ents are shown in Figure 2.A line was drawn from the mid-point of the long axis

FIGURE 1. Landmarks for measurement.

au et al. Classification of Maxillary Central Incisors. J Oralaxillofac Surg 2011.

f the root perpendicularly from the palatal bone to-LM

ard the buccal bone surface. The thickness of theuccal bone at the mid-root level (measurement I) waseasured from a point at the buccal root surface to the

uccal bone surface along this line. The palatal bonehickness at the mid-root level (measurement II) waseasured from a point at the palatal root surface toward

he palatal bone along this same line. The thickness ofabial bone at the apical level (measurement III) wasefined as a line perpendicular to the long axis of theoot, from the apex of the root toward the buccal boneurface. The thickness of the palatal bone at the apicalevel (measurement IV) was defined as the distancef the line perpendicular to the long axis of the rootrom the apex of the root toward the palatal boneurface. The apical bone height (measurement V) was

IGURE 2. Measurements of bone thickness at different aspectsmeasurements I to V).


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LAU ET AL 145

easured along the long axis of the root from the rootpex toward the superior bone surface.

From the CB measurements, the positions and angu-ations of the tooth roots were classified with referenceo the alveolar process. By comparing the buccal andalatal bone thickness at the mid-root level, their posi-ions with reference to the mid-alveolar line were de-ned and classified as follows (Fig 3): type B (closer tohe buccal alveolar surface); type M (midway betweenhe buccal and palatal alveolar surface); and type Pcloser to the palatal alveolar surface). Comparing thengulations of the alveolar process with the long axis ofhe roots, the angulations were classified as follows (Fig): type 1 (root apex angulated toward the palatal sider parallel to the alveolus); type 2 (root apex angulatedoward the buccal side with the long axis passing pos-erior to point A); and type 3 (root apex angulatedoward the buccal side with the long axis passing ante-ior to point A).

FIGURE 3. Classification ac

au et al. Classification of Maxillary Central Incisors. J Oral Maxillofac

All measurements and classifications were per-ormed by 2 investigators. Reliability tests were alsoerformed to check the consistency and accuracysing the Statistical Package for Social Sciences, ver-ion 11.0, software (SPSS, Chicago, IL). Studies of thisype are exempt from approval by the local institu-ional review board.

esults

The CB imaging data from a series of 300 randomlyelected patients were accessed initially. The imagesere all examined to identify useful data according to

he defined inclusion and exclusion criteria. The CBmaging data from 170 patients were included in thenal analysis. Of the excluded 130 patients, 109 had aefective incisor (eg, caries, infections, restorations,eriodontal bone loss, or fracture) and 21 had bothentral incisors missing. The mean patient age was 47

to position and angulation.
cording
Surg 2011.

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ears (range 13 to 85). Of the 170 patients, 76 (45%)ere males and 94 were females (55%).The mean thickness of the buccal bone at theid-root level (measurement I) was 0.9 mm (range

.1 to 1.99), and the mean thickness of the palatalone at the mid-root level (measurement II) was 3.76 �.37 mm (range 0.5 to 10.1). The mean thickness ofhe buccal bone at the apical level (measurement III)as 2.04 � 1.01 mm (range 0.1 to 7.72), and theean thickness of the palatal bone at the apical level

measurement IV) was 8.51 � 2.54 mm (range 2.56 to2.41). The mean apical bone height (measurement) was 9.53 � 2.76 mm (range 2.15 to 17.2). Theseeasurements are listed in Table 1.Additional analysis of the measurements revealed

hat 57% of the patients had a buccal bone thicknesst the mid-root level of less than 1 mm (Table 2), and2.4% of patients had a palatal bone thickness at theid-root level of less than 4 mm—up to 86.5% ofatients had a thickness of less than 5 mm (Table 3).imilarly, the buccal bone at the apical level wasuch thinner than its palatal counterpart. The buccal

one thickness at the apical level was less than 5 mmn 98.8% of the patients, and more than one half of theatients (51.8%) had a thickness of less than 2 mmTable 4). In contrast, 96.5% of patients had a palatalone thickness at the apical level of 5 mm or more,nd more than one half of the patients (55.9%) had ahickness of 8 mm or more (Table 5). Regarding thepical bone height, measured from the apex of the

Table 1. MEASUREMENT RESULTS

Measurement(mm)

Thickness at Mid-RootLevel

Buccal Bone(Measurement I)

Palatal Bone(Measurement II)

ean 0.90 3.76edian 0.89 3.69

tandard deviation 0.40 1.37aximum 1.99 10.10inimum 0.10 0.50

au et al. Classification of Maxillary Central Incisors. J Oral Max

Table 2. THICKNESS OF BUCCAL BONE AT MID-ROOT LEVEL (MEASUREMENT I)

Thickness (mm) Patients (n)

�0.5 23 (13.5)�1.0 97 (57)�1.5 158 (92.9)�2.0 170 (100)

ata in parentheses are percentages.


LM

oot to the nasal floor, almost one half of the patients47.6%) had at least 10 mm of bone height; 97.6% hadmm or more of bone height and 71.2% of patients

ad 8 mm or more of bone height (Table 6).A classification of the positions and angulations of

he central incisors with reference to the alveolarone was established. Most of the central incisors78.8%) were positioned more buccally within thelveolar bone (type B), 19.4% were positioned inidway (type M), and 1.8% were positioned morealatally (type P; Table 7). Regarding the incisor an-ulations, almost one half (49.9%) of the central inci-ors were classified as type 2, 34.7% were classified asype 3, and 15.4% (26 cases) were categorized as type. An analysis that combined both the position andhe angulation type showed that most were type B238.2%). The incidence of type B3 (34.7%) was onlylightly less than that of type B2, followed by type M211.7%). No type P2, P3, or M3 was found in ouratient series. The rest of the types were few and are

isted in Table 7.A reliability test was done to determine the accu-

acy of the measurements and classifications betweenhe 2 investigators. The correlation coefficients forhe different measurements are listed in Table 8 andeflected the good consistency between the 2 inves-igators.

Thickness at Apical Level

Apical Bone Height(Measurement V)

cal Boneurement III)

Palatal Bone(Measurement IV)

2.04 8.51 9.531.96 8.40 9.571.01 2.54 2.767.72 22.41 17.200.10 2.56 2.15

Surg 2011.

Table 3. THICKNESS OF PALATAL BONE AT MID-ROOT LEVEL (MEASUREMENT II)


�2 8 (4.7)�3 40 (23.5)�4 106 (62.4)�5 147 (86.5)�6 159 (93.5)


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LAU ET AL 147

iscussion

The present study aimed to provide data to aid thereatment planning of immediate implant in the es-hetic zone using a CB imaging technique. With rapiddvances in surgical and imaging techniques, the de-and for accuracy in 3-dimensional and volumetriceasurements is ever increasing. CB imaging has be-

ome the standard for implant planning, especially inhe highly esthetically demanding areas. Numeroustudies have been published to support the routinese of CB imaging in implant dentistry, including thedvantages of convenience, accuracy, and relativelyow radiation dosage.24-27 Increasingly, more clini-ians have been incorporating this into daily practice.Only the roots of the maxillary central incisorsere evaluated in the present study, instead of thehole tooth. Neither were the crown-to-root relation-

hips measured. This was because it was reported byryant et al23 that only a mean of 1.74° is presentetween the long axis of the root and the crown oformal central maxillary incisors. With priority giveno a restorative driven concept, if implants could belaced into the extraction sockets exactly at the samengulations as the roots inside the alveolar bone, itould provide an ideal 3-dimensional position for therosthetic crown and only a simple straight stockbutment would be needed. Thus, it is important to

Table 4. THICKNESS OF BUCCAL BONE AT APICALLEVEL (MEASUREMENT III)


�1 17 (10.0)�2 88 (51.8)�3 152 (89.4)�4 164 (96.5)�5 168 (98.8)



Table 5. THICKNESS OF PALATAL BONE AT APICALLEVEL (MEASUREMENT IV)


�5 164 (96.5)�6 153 (90)�7 126 (74.1)�8 95 (55.9)�9 61 (35.9)

�10 38 (22.4)


tau et al. Classification of Maxillary Central Incisors. J Oralaxillofac Surg 2011.

valuate the root position 3 dimensionally beforelacement.Although it might be worthwhile information, we

urposely did not include the measurements of theuccal and palatal bone thickness at the crestal re-ion, because of the uncontrollable high percentagef error owing to its relative thinness. Although mag-ification is possible in the computer, the resolutionill be too low for measurement. Moreover, a beamardening effect is always present over the edge,aking measuring the bone thickness at the crestal

evel worthless.As previously mentioned, the main drawback of

mmediate implant placement into the extractionockets has been the lack of predictability of theong-term soft tissue profile, especially on the buccalspect. Thus, the position of implant placement isritical and is a limiting variable. Although it wasreviously believed that the bone remodeling and softissue recession over an extraction socket would berrested by inserting a dental implant into the socket,ecent studies have failed to support this.28-30 It haseen confirmed that, irrespective of the placement ofdental implant, bone resorption after extraction will

till occur, leading to a loss of bone volume.28-30 It haslso been reported that the buccal bone resorbs morehan the lingual or palatal bone after extraction, be-ause it is composed of bundle bone alone. In con-rast, lingual or palatal bone is composed of corticalone, at least at the outermost surface; thus, theesistance to resorption is better.31 The mid-buccalecession of an immediate implant placed into a freshxtraction socket has been reported to be 0.55 to.75 mm at 1 year of follow-up.32,33 However, long-erm data are still not available to determine whetherdditional resorption occurs. Kohal et al34 havehown that pressure of the inserted implant on theony wall can result in microfractures, leading torestal bone loss. Therefore, the ideal placement of anmmediate implant should be aimed toward obtaining

aximum bone-to-implant contact to achieve goodrimary stability and promote greater osseointegra-

Table 6. APICAL BONE HEIGHT (MEASUREMENT V)


�4 166 (97.6)�6 153 (90.0)�8 121 (71.2)

�10 81 (47.6)



ion.35,36 However, the key to long-term good esthetic

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esults is to avoid exerting pressure on the crestalony wall, particularly on the buccal aspect.With respect to the classification reported in the

resent study, both the position and the angulationypes were categorized into different ranks accordingo their difficulty for achieving ideal esthetic results inmmediate implant cases. The classification levels areevel I to level III (Fig 4).

LEVEL I

Level I (M1, P1) indicates that the implant could belaced with the same angulation as the extractionocket, without compromising the primary stabilitynd long-term esthetic outcome because of the com-on features of a relatively thicker buccal bone. Be-

ause no modification of the drilling angle would beequired, a straight stock abutment could be used.hese types are the most straightforward for bothurgery and its restoration of all the levels. However,nly 9.5% of patients had extraction sockets catego-ized as this level (Fig 4).

Type M1 should be ideal for immediate implantases. This type of tooth lies in the middle of thelveolar bone and root apex, angulated away from theuccal wall. When placing an implant into the extrac-ion socket, enough bone will be present to supporthe implant, thereby achieving good primary stabilitynd enough bone-to-implant contact for good os-eointegration. Also, the implant angulation will beerfect for the superstructure. Moreover, enoughuccal bone is present to support the overlying gin-

Table 7. CLASSIFICATION

Type B

1 5.9 (10) 72 38.2 (65) 113 34.7 (59)

Total 78.8 (134) 19

ata are presented as parentheses, with numbers in parent

au et al. Classification of Maxillary Central Incisors. J Oral Max

Table 8. INTERINVESTIGATOR RELIABILITY TEST

Investigation Correlation Coefficients

Measurement I 0.955Measurement II 0.805Measurement III 0.830Measurement IV 0.876Measurement V 0.898Classifications 0.922


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iva, thus minimizing mid-buccal recession andhrinkage of the papillae. However, only 7.7% of type1 were reported (Table 7).Although type P1 is not as perfect as type M1, these

ypes are still good, because they will have enoughuccal bone to support the overlying soft tissue. Rel-tively less bone will be present at the palatal side;owever, the palatal soft tissue is very thick and thealatal bone can resist resorption much better. Theecession of palatal tissue will be less significant, ifny occurs, and the esthetic demand is usually notigh on the palatal side. Similar to those with type M1,hose with type P1 were in the minority, with only 3atients (1.8%) classified as having type P1 (Table 7).

LEVEL II

Level II (B1, B2, M2, M3, P2, P3) is more technicallyemanding. The angulation of the implant should be

Type

P Total

) 1.8 (3) 15.4 (26)) 0 (0) 49.9 (85)

0 (0) 34.7 (59)) 1.8 (3) 100 (170)

Surg 2011.

IGURE 4. Levels according to difficulty in achieving good long-erm esthetic results for immediate implant.

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LAU ET AL 149

hanged to avoid thinning of the buccal bone toaintain a long-term stable esthetic outcome, be-

ause it has the common disadvantage of a relativelyhin buccal plate. The angle of the implant should belaced more palatally to avoid compressing or drillinghe buccal bone, minimizing the chance of perfora-ions and fenestrations. Because a discrepancy existsetween the implant angle to the original tooth, anngled abutment should be chosen to obtain goodsthetics. More than one half of the cases (55.8%)ere categorized as level II (Table 7).Regarding the positions of the maxillary central

ncisors, most were type B (78.8%); thus, most of theeeth lie more buccally. Type B1 (5.9%) is not ideal formmediate implantation, because it is close to theuccal wall, indicating relatively thinner buccal bone.owever, type B1 is not the most challenging of this

evel because it does not angulate toward the naturalepression of the buccal alveolus. The chance ofdditional thinning of the buccal wall or fenestrationill be reduced.The least favorable types of maxillary central inci-

ors for immediate implant are those positioned nearhe buccal wall with the apex pointing toward theuccal side (types B2 and B3; type B3 was categorizeds difficult [level III] and was included in the nextection). A type B2 tooth would naturally produce ahin buccal plate at both the crestal and the apicalegion. For immediate implant placement, good pri-ary stability is mandatory, especially for those

cheduled to have immediate placement of a provi-ional crown. When achieving good primary stability,ressure is almost always present on the buccal bone,ither at the apical region or at both the apical and therestal regions. Because this type has a thin buccallate, any pressure exerted on it will significantly

ncrease the risk of bone resorption, leading to theoss of soft tissue in the long term. However, a majorroportion of patients will have these types (type B2,8.2%). This explains the “physiologic” bone and softissue loss on the buccal side in some immediatemplant cases. Although it can be difficult to achieveood primary stability, clinicians will still need tovoid overcompression of the buccal plate in suchases. This explains why these cases are so technique-ensitive.

Our data suggest that the buccal bone of maxillaryncisors were, on average, thin. The mean thicknessf the buccal bone at the mid-root level (measure-ent I) was only 0.9 mm, and the buccal bone at the

pical level (measurement III) was 2.04 mm. Morehan one half of the patients (57%) have a buccal bonehickness at the mid-root level of less than 1 mmTable 2), and 51.8% of patients had a buccal bonehickness at the apical level of less than 2 mm (Table
). It is critical not to drill over the buccal area—even t
he side of the implant drill should not be cutting onhe buccal plate during osteotomy, especially for type, because it is expected to be thinner than otherypes. Otherwise, the risk of perforation or thinningown the already thin buccal plate will be high. Tableprovides a reference for the apical radius of com-only used implant brands for immediate implant in

he esthetic zone, which ranges from 1.35 to 1.75m. More than one half of the patients had a buccal

one thickness of less than 2 mm at the apical region,ndicating that placing implant drills exactly along thexis of extraction sockets will result in a high risk oferforation, especially when placing the implanteeper toward the apical bone to achieve primarytability.

The mean thickness of the palatal bone at the apicalevel (measurement IV) is much greater than its buc-al counterpart. We found an average of 8.51 mm ofalatal bone at this region, with a maximal thicknessf 22.41 mm (compared with an average of 2.04 �.01 mm). More than one half (55.9%) of the patientsad a thickness of 8 mm or more and 96.5% of pa-ients had a thickness of 5 mm or more (Table 5). Inontrast, the thickness of the palatal bone at theid-root level (measurement II) had a mean of only

.76 mm, and 76.5% of patients have a bone thicknessf less than 3 mm. This probably resulted from theontour of the palatal vault. Thus, the more apicallylaced, the thicker the palatal bone. However, this isot the same for the buccal aspect owing to theatural depression at point A and, sometimes, thextreme root angulations, such as a type 3 tooth.hus, the implant should be placed more palatally in

he extraction socket, because more bone will beresent in that area to achieve good implant stabilitynd to avoid thinning of the buccal wall. However,he implant should also be placed more palatally at

Table 9. APICAL DIMENSIONS OF COMMONLYUSED IMMEDIATE IMPLANTS IN ESTHETIC ZONE

Implant BrandApical Diameter

(mm)Radius(mm)

nkylos (A type), DensplyFriadent 3.5 1.75sseoSpeed (4.5), Astra TechDental 3.5 1.75

apered Internal (3.8 mm),BioHorizons 2.8 1.40

TI (Bone Level), Straumann 3.5 1.75eplace Tapered Groovy (RP),Nobel Biocare 2.7 1.35

apered Screw-Vent (3.7mmD), Zimmer Dental 3.1 1.55


he apical area, pivoting around the mid-root level.

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his is because the palatal bone is relatively thicker athe apical area than at the mid-root region. Cliniciansust also be careful not to angulate the apex of the

mplant too palatally, otherwise, the coronal part ofhe implant will be tilted too buccally. This can lead tovercompression, or even perforation, on the buccalrestal wall, making the coronal platform point out-ard buccally and compromising the esthetic out-

ome. A recent study confirmed that the buccal-lin-ual position of the implant shoulder is a verymportant factor determining the degree of buccal

arginal tissue recession.37 It was reported that anmplant with a shoulder positioned at, or buccally, to

line drawn between the cervical margin of thedjacent teeth resulted in 3 times more recession thann implant with a shoulder positioned lingually oralatally to this line.37 If an ideal angulation for goodpical stability without exerting excessive pressuren the buccal wall and without placing the shoulderuccal to this line cannot be achieved, clinicians canlways consider choosing an implant with a smalleroronal diameter.Regarding the apical bone height (measurement V),

t was recorded that 97.6% of patients had a boneeight of 4 mm or more, and 90% of patients had aone height of 6 mm or more (Table 6). The generalecommendation for the placement of immediate im-lant in an extraction socket in the apical dimension

s to engage the implant 3 to 5 mm beyond the apexf the socket to achieve good primary stability.38,39

he results of the present study have shown adequateone is present at the apical area. Even when therimary stability is not optimal, the implant coulde placed deeper to achieve this, because usuallyore than enough bone is present at this region

almost one half of the patients had 10 mm or more ofpical bone height). However, a suitable implantength should carefully be chosen, because the apical-oronal position of the implant shoulder is also anmportant factor in determining the long-term softissue profile and the esthetic outcome.21,40,41 Theength of the implant should be optimal, deep enougho provide good apical stability, without perforation,nd the shoulder positioned with, or slightly apical to,he buccal marginal bone crest (around 3 to 4 mmrom the buccal gingival margin38,42,43 or 3 mm apicalo the cementoenamel junctions of the periodontallyound adjacent tooth44).

Unlike type B2, types M2, M3, P2, and P3 haveimilar characteristics, including a relatively thickeruccal plate. However, the root apexes will pointoward the buccal side. If the implant were placedxactly into the extraction socket with the same an-ulation, the risk of perforation would be very high.he general recommendation for all level II cases is

hat the implants should be inserted with a modifiedLM

ngulation with reference to the extraction socket,nd in this case, more palatally.

LEVEL III

The type B3 tooth is the most challenging case withespect to achieving good long-term esthetic out-omes because it not only will have a very thin buccallate, but also the long axis of the tooth apex will bengulated very buccally, passing anterior to the natu-al contour of the maxillary alveolar bone (Fig 5A).his type is mostly seen in patients with maxillarylveolar hyperplasia and angle Class II division 2 oc-lusion. Because a large difference exists between thengulations of the alveolar bone and the tooth, themplant position will be compromised, regardless of

hether a bone-driven or restorative-driven protocols used (Figs 5A,B). Sometimes, traditional guidelinesan be followed for such cases by extracting the

IGURE 5. Examples of level III socket. A, Large difference be-ween angulations of original tooth and future implant. B, Extremengulation requiring traditional treatment or socket transformation.


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LAU ET AL 151

ooth, with or without simultaneous grafting, andnserting the implant several months later. As such,lthough the advantages of immediate implantationould not be achieved, the long-term soft tissue sta-ility will be more predictable.If enough bone is present at the palatal and apical

spects, an attempt could be made by placing themplant both palatally and apically to avoid touchinghe buccal plate. However, even if primary stabilityan be achieved, the difference will still be largeetween the angle of the implant and prostheticrown. An angled abutment will always be needed.One should be familiar with the implant system one

s using, whether an angulated temporary abutment isvailable, and, if so, the different angles available iflanning an immediate provisional crown. The finalestoration should also be considered before the im-lant is inserted. Most often, for an abutment with aelatively big angle, a step of metal will be present onhe buccal aspect. It can sometimes show through theuccal gingiva, compromising the esthetic outcome.lacing the implant further apically can be done toolve this problem. Customized abutments or a ce-amic abutment can also be used according to theosition and angulation of the implant. However, the im-lant position will most often be controlled by theone available for such cases. Thus, type B3 is veryechnically demanding for immediate implant, be-ause it is both a bone-driven and a prosthetic-drivenrocedure.If the demand for a good esthetic outcome and

mmediate provisional restoration is very high, aocket transformation procedure can be done byrafting the buccal wall in the first stage, followed byxtraction of the problematic tooth and a normalmmediate implantation protocol several monthsater. Thus, a type B3 (level III) socket could beransformed iatrogenically to an easier type, such asype B2 (level II) or, even, type M2 (level II), keepinghe advantages of immediate implant. However, morevidence is needed to justify the long-term success ofhis treatment concept.

In conclusion, the bone availability in all dimen-ions should be considered to achieve a good implantsthetic. The angulation and position of the originalooth should be well appreciated 3-dimensionally dur-ng the planning stage. This is best performed by

easurement of a CB image. A suitable implant typend the length and diameter at the apical, mid-body,nd coronal level should be customized to the originalocket as much as possible. Tapered-screw implantsre suggested, because they can fit to the extractionocket better, and primary stability can be achievedasily. After an atraumatic extraction, all granulationissue should be removed. A flapless approach is rec-
mmended to minimize the breakdown of the blood
LM

upply from the periosteum to the buccal plate duringhe flap raising. For level I cases, inserting the implantith the same angulation of the socket using a stan-ard drilling protocol will be straightforward. For

evel II cases, the implant angulation should behanged to a more palatal aspect at the apical region,ivoting around the mid-palatal area. It is recom-ended to first use a round bur to create a step at thealatal aspect of the apical area of the socket beforesing a straight drill to ensure that the hardness of theortical bone and natural contour of the socket doesot misguide the operator to drill parallel toward thepical long axis (Fig 6). The implant should be in-erted with good primary stability, without exertingressure on the buccal wall. To ensure the absence ofressure on the buccal bone, the operator can leave aap between the implant surface and the buccalone, as long as the primary stability is not compro-ised. The gap can be treated with grafting materials

nd/or a barrier membrane to achieve maximum os-eointergration and good soft tissue healing, depend-ng on the gap size.12,14,45-48 The implant shoulderhould be optimally placed in terms of the depth anduccal-palatal dimension. A provisional crown shoulde considered whenever possible for soft tissue sup-ort, favoring the long-term esthetic outcome,31 byelecting an appropriate abutment. For level III cases,xtra precautions should be given to the prostheticiece owing to its extreme angulations. One shoulde familiar with the different types of abutments avail-ble, as well as their dimensions and shapes. Themplant can be placed deeper apically to avoid buccalhowing of the metal margin of an angulated abut-

FIGURE 6. Drilling with a round bur toward palatal aspect.


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ent. A traditional protocol can sometimes be fol-owed to achieve a more predictable long-term resulty grafting or preserving the alveolar ridge before

mplant placement. However, if the esthetic require-ent is very high, a socket transformation procedure

hould be considered.It is never easy to achieve long-term stable esthetic

esults with immediate implantation. However, it isot impossible, provided that a good case selectionrotocol is in place and surgery is performed byxperienced operators.

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