Facial Development,Continuous Tooth Eruption, and Mesial ...Facial Development,Continuous Tooth Eruption, and Mesial Drift as Compromising Factors for Implant Placement ... The placement

The International Journal of Oral & Maxillofacial Implants 867

Facial Development, Continuous Tooth Eruption,and Mesial Drift as Compromising Factors for

Implant PlacementDanny G. Op Heij, DDS1/Heidi Opdebeeck, MD, DDS1/Daniel van Steenberghe, MD, DDS, PhD2/

Vincent G. Kokich, DDS, MSD3/Urs Belser, DMD4/Marc Quirynen, DDS, PhD5

The replacement of teeth lost by children because of trauma can be an important indication for earlyimplant therapy. Osseointegrated dental implants, like ankylosed teeth, alter position as growth-relatedchanges occur within the jawbones (displacement, remodeling, mesial drift). Facial growth of the childand even of the adolescent, as well as the continuous eruption of the adjacent anterior teeth, createsignificant risk of a less favorable esthetic and/or functional outcome. For patients with a normalfacial profile, the placement of an implant should be postponed until growth is complete. For patientswith a short or long face type, further growth, especially the continuous eruption of adjacent teeth, cre-ates a serious risk even after the age of 20 years, as illustrated by some recent clinical studies. Thisreview aims to explain these phenomena and provides some recommendations for implant placement.INT J ORAL MAXILLOFAC IMPLANTS 2006;21:867–878

Key words: alveolar process, dental esthetics, dental implants, facial growth, jawbone, orthodontics, puberty

Arecent systematic review underlined the successand long-term predictability of dental implants

in partially edentulous patients.1 Young children whodo not have permanent teeth in the anterior maxillabecause of trauma or aplasia pose a specific thera-peutic problem. Osseointegrated implants behavelike ankylosed teeth; artificial abutments pose aproblem during continuous tooth eruption (definedas further eruption of teeth after the establishment

of occlusal contact and drift of the natural dentition).The restored implant’s lack of eruptive potentialcauses a discrepancy in the occlusal plane in youngindividuals (eg, relative infraocclusion of theimplant), with esthetic complications in the longterm. For the growing child, early implant placementposes even greater risk, because it may disturb nor-mal development of the jawbones.

Studies in young pigs have confirmed thatosseointegrating implants do not follow changes inthe alveolar processes caused by the continuouseruption of adjacent teeth.2–4 At some distance fromthe implants the tissues developed normally; how-ever, in their immediate vicinity, further developmentwas slowed. This resulted in a loss of occlusal contactfor the implant and angular bony defects around theadjacent teeth.

Similar phenomena have been observed withankylosed teeth. Malmgren and Malmgren followed42 children with reimplanted, ankylosed incisors forup to 10 years to estimate the degree of infraposi-tion.5 In children less than 10 years old, an infraocclu-sion of more than 3 mm (± 1.5 mm) could beobserved; for those between 10 and 12 years old,infraocclusion of the ankylosed teeth reached about2.5 mm; for those 12 to 16 years old, infraocclusionreached about 1.5 mm.5 A clear relationship between

1Orthodontist, Association for Orthodontics, Leuven, Belgium.2Holder of the P-I Brånemark Chair in Osseointegration, Professorand Chairman, Department of Periodontology, Oral Pathologyand Maxillofacial Surgery, School of Dentistry, Catholic Univer-sity of Leuven, Leuven, Belgium.

3Affiliate Professor, Department of Orthodontics, School of Den-tistry, University of Washington, Seattle, Washington.

4Professor and Chairman, Department of Prosthodontics, Schoolof Dental Medicine, University of Geneva, Geneva, Switzerland.

5Professor, Department of Periodontology, Oral Pathology andMaxillofacial Surgery, School of Dentistry, Catholic University ofLeuven, Leuven, Belgium.

Correspondence to: Prof Marc Quirynen, Department of Peri-odontology, Catholic University Leuven, Kapucijnenvoer 33, B-3000 Leuven, Belgium. Fax: +32 16 33 24 84. E-mail:Marc.Quirynen@ med.kuleuven.ac.be

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the degree of infraocclusion and growth intensity(before, during, and after growth spurt) was not obvi-ous; intersubject variation was very large.5 Kawanamiand coworkers followed 52 patients (age range, 6 to48 years at time of injury) with reimplanted and sub-sequently ankylosed permanent incisors for a periodof 1 to 21 years (mean, 4.2 years).6 In this study,marked infraposition was observed if the tooth wastraumatized before the age of 16 years in boys andbefore the age of 14 years in girls (0.19 to 0.62 mm/yfor boys, 0.08 to 1.00 mm/y for girls). Surprisingly,enough infraposition for ankylosis was also observedafter puberty. In patients aged 20 to 30 years old inwhom tooth reimplantation had been performed, ayearly mean infraposition rate of 0.07 mm/y (range,0.0 to 0.21 mm/y for men and 0.0 to 0.12 mm/y forwomen) was recorded. Bjerklin and Bennett reportedon the long-term survival of primary mandibular sec-ond molars (n = 59) in subjects (n = 41) with agenesisof the premolars (Fig 1).7 The mean age at the lastexamination was 20.5 years. This study demonstratedan atypical pattern for the development of infraoc-clusion, with a mean value of 0.47 ± 1.13 mm at 11 to12 years, which increased to 1.43 ± 1.1 mm at 17 to18 years (not all teeth were ankylosed). At 20 years,55% of the teeth showed an infraocclusion of 0.5 to4.5 mm.This phenomenon was explained by the con-tinuous eruption of the normally functioning teeth.

Ongoing growth of the teeth in an occlusal directionafter puberty has also been observed by Ainamo andcoworkers.8 This group followed the increase in gin-gival width over time. In a cross-sectional study com-paring volunteers at ages 23, 43, and 65 years, amean increase in width of 4 mm in the anterior max-illa was measured.

Several longitudinal studies on young adults whoreceived implant-supported restorations to replacemissing teeth have found disharmony between teethand implants (Fig 2).

Thilander and coworkers reported on a group of15 adolescents (8 boys, 7 girls) with 27 implants (19 inthe maxilla and 8 in the mandible).9–11 The implantswere placed when the subjects were between 13 to19 years old. After 3 years of loading, a clear correla-tion was established between body length growthand the extent of implant infraocclusion. Although nofurther length growth could be measured from thefourth year on, and no further craniofacial alterationsarose, the relative infraocclusion of the implantsincreased. This ongoing infraocclusion reached amean of 0.5 (± 0.6 mm) mm over the last 7 years ofthe study (the postgrowth phase). For the entire 10-year study period, mean infraocclusion was 1.0 mm(range, 0.1 to 2.2 mm). Buccal/lingual disharmony wasobserved frequently. The authors also hypothesizedthat this infraocclusion of the implants caused mar-ginal bone loss around the adjacent teeth.9

Fig 1 (a) Radiologic and (b to d) clinicalphotographs of ankylosed primary molarswhich came into infraocclusion because ofthe normal eruption of the adjacent ele-ments (18-year-old woman). The crowns ofthe primary teeth have almost completelydisappeared under the gingiva, and the adja-cent teeth are angulated. The radio-graphshows how the bone followed the eruption ofthe permanent teeth, but around the primaryteeth the process remained underdeveloped.Such anomalies can also appear after earlyimplant placement.

a b

c d

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Bernard and coworkers followed the verticalchanges of maxillary incisors adjacent to implants in agroup of adolescents (mean age, 18.4 years; range, 15to 20 years) and adults (mean age, 43.6 years; range,40 to 55 years) for a mean period of 4 years.12 Allpatients in the “young adult” group showed infraoc-clusion of the implant-supported crowns, with a verti-cal step between 0.1 and 1.65 mm. For the “matureadult” group, similar changes were observed, withinfraocclusion ranging from 0.12 to 1.86 mm (Fig 3).

These literature reports on both ankylosed teethand osseointegrated implants should draw the peri-odontologist or oral surgeon’s attention during theplanning phase to the changes in vertical and hori-zontal dimension between and within the jawbonesto understand and prevent disharmony betweenimplants and teeth.

Fig 2 Clinical record of a patient (30years old) where a solitary crown on animplant was placed 5 years ago (maxillaryright central incisor). Infraocclusion and rel-ative palatal positioning of the implant wasrelated to continuous eruption of adjacentteeth.

a b

Fig 3 (a to d) Clinical and (e to h) radio-graphic images illustrating the effect of con-tinuous eruption of a tooth (maxillary rightcentral incisor) adjacent to an osseointe-grated implant (maxillary left central incisor)at baseline (a and e), after 5 years (b and f),after 9 years (c and g), and after 12 years (dand h) of implant loading.

a b

c d

e f g h

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The placement of an implant should in principlebe postponed until after puberty or after the so-called growth spurt of the child. However, since pro-visional prosthetic solutions such as removable par-tial dentures or acid-etched partial dentures are notalways satisfactory, the parents or the children ofteninsist on a surgical solution, even before bodilygrowth is finalized. Patients and families should beinformed that the placement of implants before thecompletion of growth could jeopardize the long-term esthetic outcome, since the remaining changesin the growing alveolar process will not be followedby the implant. Moreover, continuous tooth eruptioncontinues to take place after puberty and can lead toocclusal disharmony in some patients (Fig 3).Another interfering factor is alveolar bone resorp-tion. Botticelli and coworkers found, via a re-entryprocedure, that within 4 months of single toothextraction, the buccolingual width of the alveolarcrest can show resorption up to 3 mm (in otherwords a horizontal resorption of more than 40% ofthe entire width).13 Similar observations were madeby Schropp and coworkers, who registered a reduc-tion of 50% of the ridge width after 12 months, ofwhich two thirds occurred during the first 3 monthsof healing.14 This horizontal resorption was accompa-nied by only minor changes in the vertical dimen-sion. In some instances, delaying the placement of anendosseous implant may after a while render thistreatment option impossible because of lack of suffi-cient bone volume related to its resorption. Itremains questionable, however, whether suchresorption can be prevented by immediate implantplacement in the extraction socket. The resorption ofalveolar bone occurs much more slowly in a spacecreated orthodontically (at a rate of about 1% over 4years) than in an extraction socket (about 34% over 5years).15

The present review proposes guidelines for timelyoral implant placement, taking into account thegrowth of the jawbones via displacement andremodeling. The displacement of the entire jaw bonycomplex via sutural growth will of course be fol-lowed by oral implants, so such growth does not cre-ate a major risk unless the prosthetic rehabilitationcrosses the midline suture. Conversely, bone remod-eling—the reshaping of bone by selective resorptionin some areas of its surface and apposition/deposi-tion in other areas—is not followed by implants andthus can jeopardize the long-term occlusal andesthetic outcome. Finally, continuous tooth eruptionis not limited, as is often assumed, to puberty, but cancontinue even after the age of 18 years, especially inthe case of a deviant facial type (long or short).

GROWTH OF THE JAWBONES

The growth of jawbones will be discussed accordingto direction of manifestation: transverse, sagittal, andvertical. Both the mandible and the maxilla follow adistinct chronology: growth is first completed in thetransversal plane, then in the sagittal plane, andfinally, only at a later stage, in the coronal plane. Thegrowth of the mandible is closely associated withgrowth in stature, whereas growth of the maxilla ismore associated with growth of the cranial struc-tures. These associations have been made on thebasis of longitudinal studies in which small experi-mental implants were placed in the jawbones andused as fixed reference points.16,17 These studieswere designed before the era of the use of oralosseointegrated implants.

Maxillary GrowthAfter the age of 7 years, the majority of the changesthat occur in the maxilla are the result of remodeling.

Transverse Growth. The width of the anterior por-tion of the arch is completed prior to the adolescentgrowth spurt, but for the posterior portion increasein width is closely related to increasing jaw length.The width in the anterior portion increases mainly bygrowth at the midpalatal suture (sutura palatinamediana). Changes in the intercanine distance areminimal after the age of 10 (mean increase, 0.9mm).16 The increase of the intermolar distance issmaller than the sutural widening in this area (thelatter is 3 times more in the posterior than in theanterior), which suggests an adaptation of the dentalarch. In the more posterior areas, changes can occuruntil complete tooth eruption.

Implications. The placement of an implant in acentral incisal position in a young patient (eg, 7years) can lead to a diastema with the adjacentnatural central incisor and a subsequent shift-ing of the midline to the implant side. Replace-ment of both central incisors prior to the endof transverse anterior growth could result in adiastema in between them. Case reports ofimplants placed in the anterior maxilla inpatients as young as 9 years of age do notinclude mention of problems with growth inthe transversal direction.18,19 The midpalatalsuture usually closes after puberty, around theage of 15 (but with large variation from 15 to27 years). Thus, placement of a midpalatalimplant as anchorage for orthodontic appli-ances can be planned for patients who are atleast 15 years old.

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Sagittal Growth. The maxilla increases in lengthbecause of both sutural growth and bone appositionat the maxillary tuberosity. The anterior part of themaxilla is relatively stable. However, when the maxillafollows the mandibular growth, up to 25% of thissutural growth is lost via jawbone resorption at theanterior site. The sagittal growth of the maxilla isclosely associated with the growth in skeletal bodyheight but stops earlier.

Implications. Resorption in the anterior part ofthe maxilla could result in the gradual loss ofbone on the labial side of an implant. In a casereport that described the treatment of a 13-year-old boy and an 11.5-year-old girl, prob-lems with labial fenestrations were noted asearly as 11 months after placement in the girland 19 months in the boy.20 The problemsincreased in severity with growth.

Vertical Growth. Growth of the maxilla in a verticaldirection occurs via displacement (sutural growth),remodeling, and continued eruption. The maxilla isdisplaced downward, away from the cranium, bygrowth in the orbits and by increases in the size ofthe nasal cavity and maxillary sinuses. This is the con-sequence of resorption of the nasal bone wall sur-faces and of bone apposition on the palatal and alve-olar surfaces. Vertical growth of the maxilla continuesbeyond the age at which transverse and sagittalgrowth cease. Usually adult levels of vertical growthare reached at 17 or 18 years for girls and somewhatlater for boys.

Implications. To prevent complications in thevertical plane (especially related to remodel-ing), it may be advisable to delay implantplacement until the age of 18 years.

Mandibular GrowthThe timing of mandibular growth is similar but notidentical to that of the maxilla. The mandible growsmore in a sagittal plane than the maxilla during ado-lescence. This “differential jaw growth” converts themore convex child profile to the straighter adult pro-file. In girls, mandibular growth is nearly completed 2to 3 years after menarche (usually at age 14 or 15),while for boys, growth can continue into the early20s but usually reaches adult levels by age 18.

Transverse Growth. In the anterior region growthceases very early. Almost no changes occur after erup-tion of the permanent canines because of early closureof the mandibular symphysis (in the first year of life)and the limited remodeling afterwards. In the premo-lar and molar regions, growth extends over a longer

period through bone remodeling (bone apposition atthe buccal site and resorption at the lingual site). Erup-tion of the permanent molars is accompanied by sometransversal changes in the jaw dimensions, althoughthese are restricted to a few millimeters.

Implications. The width of the anterior portionof the arch is completed prior to the adoles-cent growth spurt. Since the posterior portionincreases in width via remodeling (relative lat-eral movement), a molar or premolar implantplaced in a young patient could be shifted intoa lingual position.

Sagittal Growth. The sagittal growth of this jawresults from both endochondral growth at thecondyle and remodeling of the mandibular ramus.The growth at the condyle increases the length ofthe mandible but has no direct impact on themandibular corpus shape and thus on eventualimplants. The corpus of the mandible itself lengthensin an anteroposterior direction, mainly throughresorption at the ventral side of the ramus and boneapposition at the ramus’s dorsal surface. The result-ing increase of mandibular corpus length accommo-dates the eruption of the molars.

Implications. The sagittal growth of the mandiblehas no impact on implant placement in children.The rotation of the mandible in the sagittalplane during growth must be considered.

Vertical Growth. The mandibular height increasesby condylar growth and by bone apposition at thedentoalveolar complex (the latter especially duringtooth eruption). When sequential cephalometricradiographs are superimposed for different stages ofgrowth, it appears as though the mandible is grow-ing downward and forward from the cranium. How-ever, when small endosseous implants were placedas reference points in the mandible, the condylarprocess rather appeared to grow upward and back-ward, with little if any change at the chin.21 A normalfacial type shows only minor rotation of themandible in a sagittal plane, but the 2 other facialtypes (short and long) show a remarkable rota-tion.22,23 The relative change in position betweenmaxillary and mandibular teeth caused by this rota-tion is corrected during tooth eruption via the so-called “dentoalveolar compensation mechanism”(defined as a system trying to maintain the normalintra-arch relationship).24 As such, the rotationalgrowth of the mandible significantly affects theanteroposterior and vertical eruption patterns, whichare intimately connected.

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Implications. The mandibular rotation in thesagittal plane during facial growth is importantfor implant placement because the variation inthe compensatory amount and direction ofincisor eruption could dramatically affect therelationship between an implant and an adja-cent tooth, especially in the short and long facetypes. An implant will not make these compen-satory position changes either vertically or labi-olingually. An orthodontic colleague can helpone define the facial type (long, normal, orshort) involved.

MESIAL DRIFT OF TEETH IN THE MAXILLAAND MANDIBLE

Spontaneous mesial drift of teeth is well docu-mented.25 The lateral segment in the maxilla andmandible (canine to first molar) moves on average 5mm mesially between 10 to 21 years of age. Theincisors move only 2.5 mm buccally, causing a netloss in space, which could lead to crowding.

An implant does not take part in this “sponta-neous mesial drift of teeth.” Thus, an implant in thelateral region could stop the mesial drift, resulting inan asymmetric arch, while an implant in the anteriorregion cannot follow the teeth and will become rela-tively more lingually oriented with time.

Depending on the facial growth type and becauseof the further eruption of the teeth, vertical changescan still occur after puberty, though at a slower pacethan during the active growth phase.

CONTINUOUS ERUPTION OF TEETH IN GENERAL

The continuous eruption of teeth, ie, after occlusalcontact has been established, was evaluated on con-secutive cephalometric radiographs properly super-imposed via small endosseous implants as referencemarkers.17 The average eruption reached 1.2 to 1.5mm/y during the active growth phase, and wasreduced to an annual 0.1 to 0.2 mm afterwards, evenafter the age of 18 years. Eruption between 9 and 25years of the maxillary central incisors thus reached 6.0mm, while a movement of 2.5 mm buccally could beobserved. For the maxillary first molars, these valuesreached 8.0 and 3.0 mm, respectively. If one focuseson the timespan between 17 and 25 years of age, thismovement is reduced to an average 1 and 0.5 mm forthe incisors and 1.5 and 0.8 mm for the maxillarymolars, respectively. Large interindividual variationswere recorded, especially in short and long faces.

Ranly calculated that an implant placed in theanterior part of the maxilla at the age of 7 yearswould be located 10 mm more apically than theadjacent teeth 9 years later.26 This assumption wasconfirmed by clinical observations after the place-ment of solitary implants at the average age of 12years, which should a “relative” infraocclusion of 5 to7 mm 4 years later, sometimes combined with alabial fenestration.18,19,27 Similar changes were mea-sured in the molar region.28

Changes in the dentoalveolar complex duringadulthood were studied by Tallgren and Solow in across-sectional study calculating the average den-toalveolar height in women 20 to 29, 30 to 49, and 50to 81 years of age.29 From this study the followingobservations were made:

• The average dentoalveolar height in the 2 lattergroups was similar.

• The average dentoalveolar height in the 2 lattergroups was significantly higher both in maxillaand mandible (1.5 to 2 mm) than in the 20-to-29group.

• Lower facial height in women increased 3 to 3.5mm with age. This was associated with an “open-ing” of the mandible (ie, an increase in mandibularinclination).

A longitudinal cephalometric study confirmedthis increase in anterior face height. Patientsbetween 25 and 45 years showed a 1.6 mm increasewherefrom about 1 mm was related to continuouseruption of the maxillary incisors.30 Aging womentend to get a longer face, with more probability forinfraocclusion of an implant in the anterior, whilemen tend to grow more in the posterior regions.31,32

In 2006, Fudalej and coworkers evaluated the tim-ing of growth cessation in a sample of 300 postortho-dontic patients (unpublished data). The sample had amale:female ratio of about 50:50. The dental recordsof these patients were reviewed for an extendedperiod of time following orthodontic applianceremoval. The sample was stratified, so completion oforthodontic treatment occurred when the patientswere in their mid-teens to mid-twenties. Then, foreach patient, lateral cephalometric radiographs wereevaluated and superimposed at least 10 years afterthe completion of orthodontic treatment. By evaluat-ing this stratified cross-sectional sample using longi-tudinal statistics, the authors were able to determinethe point at which vertical growth ceased on averagein males and females. Vertical growth was assessed asthe distance from nasion to menton. When this dis-tance did not increase, it was assumed that verticalskeletal growth had ceased and therefore that space


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for tooth eruption would not be available. In females,the age at which growth of the facial skeleton ceasesvertical development is shortly after 17 years of ageon average. The vertical change from nasion to men-ton ceases at slightly more than 20 years of age onaverage in males. However, these are averages, andlarge deviations were observed. The clinician mustuse superimposed cephalometric radiographs toaccurately assess the cessation of vertical growth foreach specific patient.

Implications. Placing implants in a growing childwill mostly lead to occlusal disharmony of severalmillimeters after a few years. Thus, this should belimited to specific indications such as multipleanodontias, often associated with congenitalgrowth deviations. Then provisional prostheticsuperstructures should be used, since multiplereplacements must be considered. Even in adultsthe ongoing tooth eruption can lead to differen-tial occlusal heights, but more limited, whichoften can be dealt with by prosthetic adaptations.

DEVIATING FACIAL TYPES: SHORT ANDLONG FACE SYNDROMES

The population can be divided into normal, short, orlong facial types. These can best be observed by look-ing at the lateral profile of a person. Each of thesefacial types has its own “program” for development ofthe jawbones. Even when adulthood is reached, thesedistinct facial types keep developing in different ways.The short facial type is also described as a horizontalgrower, a forward rotator (refering to rotation of themandible), and/or a skeletal deep bite. Synonyms forthe long type are: vertical grower, backward rotator,and/or skeletal open bite. The facial types are charac-terized by a cluster of morphologic features and cantherefore be referred to as short face syndrome (SFS)and long face syndrome (LFS).

Essential Characteristics of SFS and LFSThe main differences between long and short facialtypes are schematically visualized in Fig 4.22,23 Thefacial proportion index (FPI) helps to differentiatebetween a normal face and the SFS and LFS cases.This index is calculated by subtracting AUFH fromALFH, where AUFH is the distance from anterior nasalspine (ANS) to nasion (N) and ALFH is the distancefrom the same spine to the menton (Me). Both valuesare expressed as a percentage of the anterior totalfacial height (ATFH), distance from N to Me.

This value is around 10 for a normal face, with anALFH of 55% and an AUFH of 45%. SFS is character-

ized by a small FPI (< 10), whereas this value exceeds10 for patients with LFS. Other important differencescan be obtained on a cephalometric radiograph. SFSis characterized by a smaller angle between thesella-nasion line (SN line) and the mandibular plane(this angle is 32 degrees for a normal face). The SNline represents the anterior cranial base (this is a linethrough the center of the sella tursica [s] and nasion),while the mandibular plane (MP) is the line throughthe menton and gonion. For LFS, the angle is > 32degrees). The gonial angle (formed by the intersec-tion of a line tangent to the posterior border of theramus and the mandibular plane) is relatively smallfor patients with SFS (about 110 degrees) comparedto the normal situation (125 degrees), and certainlycompared to patients with LFS, where values ofabout 129 degrees are found.

Furthermore, an SFS patient shows an enlargednasiolabial angle, a well-developed chin point, a con-cave profile with retro-position of the lips, thin curlylips, a deep plica labiomentalis, and usually a broadnose and “a toothless look” when smiling. An LFSpatient is characterized by a heightened lower facialhalf; a lump on the nose; a less obvious chin point; achin positioned down- and backward; a convex pro-file; an enlarged interlabial distance, often withtooth-exposition; a small nose and small nostrils; andfinally, a “gingival smile” (Fig 4).

Important Growth Variations in Relation to theNormal Facial TypeThe Maxilla. Maxillary growth is more pronouncedfor those with SFS in the transverse direction (1.5mm, versus 0.3 mm for the LFS), since the midpalatalfissure closes later. In the case of a narrow maxilla(which occurs often with LFS), the alveolar processgrows more in height (21 mm), while in the case of awide jaw (which occurs often with SFS), there is lessincrease in height (9.5 mm).17 The direction ofgrowth of the maxilla will also differ in the 2 facialtypes (Fig 5). The dentoalveolar complex will com-pensate and thus follow the mandibular rotation inrelation to the cranial base (SN line). This rotationproceeds forward in SFS adolescents and backwardin LFS ones.

Implication. Implants placed in the maxillary ante-rior region will eventually become more palatalcompared to the natural dentition, especially in theSFS face type. Indeed, in the maxilla the tooth move-ment in the horizontal plane is large. With the LFStype, the increased vertical movement of the nat-ural dentition could result in disharmony for oralimplants.


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The Mandible. In the mandible, facial type mainlyplays a role in growth in the sagittal and verticalplanes. The growth of the mandible for an SFS faceand an LFS face between the ages of 4 and 19 years isgraphically illustrated in Fig 6. For the SFS type, themandibular teeth move upward in a buccal direction.For the LFS type, the teeth move up but more lingually.

Implication. In SFS types, implants in the anteriorarea will end more lingual in comparison to the nat-ural dentition because of the great mesial drift. InLFS types, implants in the mandibular anterior willbecome too labial because teeth gradually rise lin-gually. Implants in SFS children and adolescents areat risk for infraocclusion in the premolar regionbecause of the above-average vertical growth in thisarea. In LFS children and adolescents, there is consid-erable risk of infraocclusion in the frontal area.

Continuous Tooth Eruption. With an SFS child (for-ward rotator), the vertical eruption of the centralincisors is not very obvious and ceases quickly (atabout 13 years), but these teeth show forward tipping(especially from 13 to 25 years) to compensate for thecontinuing forward growth of the mandible, while thesagittal growth of the maxilla is already slowing downand even seems to get shorter vertically (Figs 5 and 6).An LFS child (backward rotator), on the other hand,shows a large and prolonged vertical eruption (evenuntil 25 years), combined with a backward movementmost obvious at the age of 15 years to compensatefor the cessation of growth in the maxilla. Betweenthe ages of 15 and 25 years, the vertical tooth move-ment in an LFS face can amount to 5 mm, a distancedifficult to overcome with implants (Figs 5 and 6).


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Fig 4 Schematic image of a “nor-mal face” (NL), drawings of childrenexemplifying SFS and LFS, andcephalometric analyses of childrenexemplifying 2 subtypes of SFS and 2of LFS. The cephalometric analyseswere limited to the following charac-teristics: ATFH = anterior total facialheight (the distance between thenasion [n] and the menton [Me; low-est point on the symphysis]); ALFH =anterior lower facial height (the dis-tance between the anterior nasalspine [ANS] and Me); AUFH = anteriorupper facial height (the distancebetween the nasion and ANS); SN =the line through the center of thesella tursica (s) and N; MP = the linethrough Me and the gonion (Go),which represents the plane passingthrough the mandibular borders;SN:MP = the mandibular plane angleformed by the intersection of SN anda line between Go and gnathion(GoGn); RH = the length of the ramus(the distance from the head of thecondyle to Go); OP-PP: the distancebetween the mesiobuccal cusp of thefirst molar and the lower border ofthe palatal plane along the long axisof the first molar. SFS I is character-ized by a long ramus, a sl ightlyreduced SN:MP ratio, and normalposterior maxillary height. SFS II ischaracterized by a short ramus, aslightly reduced SN:MP ratio, andreduced posterior maxillary height(ver t ical maxil lary deficiency).Patients with LFS I have a rather longramus, increased OP-PP distance(vertical maxillary excess), and amoderately increased SN:MP angle.Those with LFS II have a short, some-times extremely short, ramus, a nor-mal OP-PP distance, and anincreased SN:MP angle.22,23 Mea-surements given in millimeters.

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RECOMMENDATIONS BY ANATOMICLOCATION

Anterior MaxillaVertical growth in this area exceeds growth in otherdimensions and continues to a later age. Implantplacement during childhood and young adulthoodmay necessitate repeated lengthening of the trans-gingival part of the implant or its prosthetic super-structure. This renders the endosseous-supraosseousratio less favorable from a biomechanical viewpoint.Since the midpalatal suture only closes at puberty oreven later in cases of SFS, maxillary transverse skele-tal growth can also have an adverse effect onimplants placed before its closure. Implant placementshould thus be delayed until skeletal growth is com-pleted. Modulation of these principles according tofacial type should also be taken into consideration.

Posterior MaxillaLarge variations exist in the amount and direction ofboth sagittal and vertical growth, and the unpre-dictability of the growth pattern adds to the diffi-culty of deciding when it is safe to place implants inthis area. Since the vertical growth occurs by apposi-tion on the alveolar aspect and resorption on thenasal or maxillary sinus area, an implant placed earlycould become submerged occlusally and penetratethe sinusal or nasal cavity. Prosthetic connections

that cross the midline will interfere with the trans-verse growth. In partial edentulism, implant infraoc-clusion may lead to long-term esthetic problems forthe implant and periodontal damage around theadjacent teeth. Implant placement can only be rec-ommended after cessation of growth. However,implant placement in the anodontic child could beconsidered under well-planned conditions, despitethe risk of problems because of the appositional andresorptive pattern of the posterior maxillary growth.


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Fig 5 Direction of growth of the maxilla andcontinuous eruption of the maxillary centralincisor and first molar (partially to follow the rota-tion of the mandible) for SFS and LFS types,respectively. In an SFS face, the rotation pro-ceeds anteriorly, while in an LFS face, themandible is rotated posteriorly. Cephalometricviews at the ages of 12 and 20 years were super-posed on the SN line. The shift in position of thecentral incisor and the first molar is shown indetail in the lower half of the figure (observationswith intermission > 1 year and < 2 years). Forthese observations, a reference line was createdin the corpus maxillae and in the zygoma for thesuperpositioning of consecutive encephalo-grams, guaranteeing that the changes illustratethe remodeling of the alveolar process. Sourcesfor this figure: Björk35 and Iseri and Solow.17

Fig 6 Graphic illustration of mandibular growth (through boneresorption and apposition, at the lower border of the mandible,the dentoalveolar complex, and the condyle) for an SFS individualand an LFS individual between the ages of 4 and 19 years. Tomonitor this growth, small implants (markers) were placed in themandible for superimposition. Based on drawings of Björk andSkieller.36

filled dots = incisor changesopen dots = molar changes

12 years of age

20 years of age

- to the posterior, + to the anterior

years of age

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Anterior MandibleThe symphyseal area causes the least problems withimplant placement, since the mandibular symphysisis closed in early childhood, and sagittal growth pri-marily occurs in the posterior part of the mandible. Inpartially edentulous patients, however, the early useof implants in this area can be contraindicatedbecause of significant compensatory changes in thedentoalveolar complex during growth.

Posterior MandibleIn the posterior mandible, large amounts of trans-verse, sagittal, and vertical growth occur. As themandible undergoes rotational growth, significantchanges occur in both the alveolus and the lower bor-der of the mandible. Such changes are largely influ-enced by the facial growth type. A conservativeapproach in the posterior mandible dictates thatimplants should not be placed until skeletal growth iscompleted. Progressive infraocclusion of the implant

precludes the early placement of implants in theseareas. A lack of reports of early implant use in theedentulous posterior mandible renders the formula-tion of recommendations impossible.

PROPER AGE FOR IMPLANT PLACEMENT

During a consensus meeting in 1995 it was decidedthat it is preferable to postpone implant placementuntil craniofacial/skeletal growth is complete, espe-cially in partially edentulous cases.33 It should benoted that the age at which growth is completevaries widely.33 It is commonly observed that thegrowth spurt is expected to occur at 12 years for girlsand at 14 years for boys; however, the age at which itoccurs can vary by as much as 6 years. Thus, when aclinician plans the use of oral implants in a child, theproblematic age period extends from 9 to 15 yearsfor girls and 11 to 17 for boys.34 If one adds to this


Op Heij et al

b c d e

Fig 7 (a) Schematic representation of growth velocity (Gr) overtime (T). (b) When the growth disk has the same width as theproximal phalanx of the second finger (PP2), the child is in theearly stage of the growth spurt. (c) The sesamoid bone (S) of thethumb usually begins to calcify during the accelerating phase ofthe pubertal growth spurt (Pre). Since a substantial amount ofgrowth is ahead, this is an inappropriate time to place animplant. (d) Capping of the middle phalanx of the third finger(MP3cap) usually occurs after the maximum growth velocity haspassed (beyond the peak of the growth curve) and indicates adeceleration of the pubertal growth spurt (Post). This correlateswith the approximate onset of menstruation in girls and deepen-ing of the voice in boys. Since most pubertal growth has beencompleted, consideration of implant placement can begin. How-ever, since the exact length and rate of growth are still unknown,some risks still exist. (e) When the epiphysis of the radius fusesand forms a bony union with the diaphysis (Ru), adult levels ofskeletal growth have been attained, and no further increase instatural height can be expected (end of growth, E). The best andsafest time to place a solitary implant adjacent to teeth is whenthe final indicator, radial epiphyseal closure, has occurred.

a

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the variability observed among face types (SFS andLFS show significant changes up to the age of 25years), even longer periods should be taken into con-sideration. The chronologic age is thus certainly notsufficient to estimate growth cessation. A clinicianshould rely on a reliable evaluation of growth by:

• Superimposing tracings of cephalometric radio-graphs taken at least 6 months apart.

• Waiting until no growth changes take place for 1year. However, the time required and the radiationinvolved are drawbacks.

• Evaluating bodily growth in length annually for 2years to make sure that annual growth is less than0.5 cm/y. Again, a time-consuming assessment.

• Observing changes of dental positions within thearch, such as the eruption of the second molar.

Another method is evaluation of the skeletal ageon the basis of a radiograph of the wrist of the leastused hand to observe to what degree the growthplates are closed (Fig 7).37 This parameter is accuratebut needs regularly repeated radiographs until theproper age is reached. Hand-wrist radiograph indica-tors can be used to place a patient in a general areaof the growth curve shown in Fig 7a. In patients withsevere anodontia or oligodontia in the anteriormandible it is possible to place implants even beforethe pubertal growth spurt. Only limited changesrelated to growth occur in this area after the age of 5to 6 years, especially when teeth are not present.

SUMMARY

It is evident that jaw growth may compromise theoutcome of oral rehabilitation using implant-sup-ported prostheses even if the implants are success-fully integrated. Lack of proper occlusion and unes-thetic situations can occur, especially in the anteriorregion. The timeframe for the development of thealveolar process can vary widely, especially in thecase of long or short facial types. The risks posed bycontinuous tooth eruption in adulthood should alsobe considered. Too often, only the growing child andadolescent are considered challenges.

ACKNOWLEDGMENT

The case shown in Fig 3 was kindly donated by U. Belser. Figs 2,4, 5, 6, and 7a were originally printed in a previous article by OpHeij and associates38 and are reprinted here by permission fromBlackwell Publishing.

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