MAXILLARY MIDLINE DIASTEMAS_A LOOK AT THE CAUSES

JADA, Vol. 130, January 1999 85

lowest incidence inpeople of Chinesedescent (1.7 per-cent).3

In a study of5,307 patients,Richardson andcolleagues4 foundthe incidence ofmaxillary midlinediastemas to behigher in blacksthan in whites andhigher in boys thanin girls of the samerace at age 14years. They foundthe incidence to be26 percent in blackboys, 19 percent inblack girls, 17 per-cent in white boys

and 12 percent in white girls. Keene’s study of183 white male Navy recruits found that 8 per-cent of them had diastemas greater than 0.5 mil-limeters.5

Another study of nearly 10,000 patients in SouthIndia, however, found an incidence of only 1.6 per-cent.6 It is clear that the incidence of midline di-astemas varies greatly with the population and agegroup studied, but diastemas are a significant mal-occlusion factor in some population groups.

Maxillary midline diastemas generally havebeen studied by lumping them into one largegroup, with little consideration given to the con-tributing factors. However, not all maxillary mid-

Maxillary anteri-or spacing, or di-astemas, are acommon estheticcomplaint of pa-tients. Although afew entertainmentcelebrities haveused a midlinemaxillary diastemaas a successfultrademark, manypeople find it es-thetically displeas-ing. In fact, a re-cent studyinvolving Europeanadults found thatpatients with abroad midline di-astema were per-ceived as being lesssocially successful and of lower intelligence.1 Inthat study, maxillary anterior spacing was equalto crowding and even more of an esthetic liabilitythan excessive overjet or protruding incisors.

The esthetic importance of maxillary anteriorspacing varies both culturally and racially as wellas with the incidence of diastemas within a givenpopulation. The incidence of diastemas variesgreatly with age and race. In 5-year-olds, the inci-dence has been reported to be as high as 97 per-cent,2 with the incidence decreasing with age. Astudy from Great Britain reported a higher inci-dence of maxillary midline diastemas in blacks(5.5 percent) than in whites (3.4 percent), and the

MAXILLARY MIDLINE DIASTEMAS: A LOOK AT THE CAUSESLARRY J. OESTERLE, D.D.S., M.S.; WILLIAM CRAIG SHELLHART, D.D.S., M.S.

Background. Maxillary midline diastemas are a com-mon esthetic problem that dentists must treat. Many innovativetherapies have been used, varying from restorative procedures tosurgery (frenectomies) and orthodontics. At times, these proce-dures have been performed by the dentist without full apprecia-tion of the factors contributing to the diastemas.Case Description. Before the practitioner can de-termine the optimal treatment, he or she must consider the con-tributing factors. These include normal growth and development,tooth-size discrepancies, excessive incisor vertical overlap of dif-ferent causes, mesiodistal and labiolingual incisor angulation,generalized spacing and pathological conditions. A carefully de-veloped differential diagnosis allows the practitioner to choosethe most effective orthodontic and/or restorative treatment.Clinical Implications. The differential diagnosisleads to a treatment approach that most effectively addresses thepatient’s problem. By treating the cause of the diastema, ratherthan just the space, the dentist enhances both the patient’s den-tal function and appearance.

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line diastemas are the same. Inthis article, we examine thevarious contributing factors, indescending order of frequency,to enable the practitioner tomake a differential diagnosisand to better tailor treatment tothe patient’s specific problem.

Maxillary midline diastemasare a part of normal develop-ment in children. In adults,tooth-size discrepancies and ex-cessive vertical overlap of theincisors are the most commonfactors in the development of di-astemas. Incisor mesiodistal an-gulation, generalized spacing,labiolingual incisor inclination,frenums and pathological condi-tions are less frequent, but im-portant, contributing factors.The ultimate effect of these fac-tors depends on whether the oc-clusal anteroposterior relation-ships are normal. Variationsfrom Class I create other anteri-or space problems that are asso-ciated with Class II and ClassIII malocclusions.

NORMAL GROWTH ANDDEVELOPMENT

Maxillary anterior diastemasare a normal part of dental de-

velopment. Spacing in the fullprimary dentition is normal andan indicator of space availablefor the eruption of permanentteeth. As the permanent maxil-lary incisors erupt, a diastemais frequently created and oftenpersists throughout the mixeddentition until the canine teetherupt (Figure 1). After the erup-tion of the central incisors, thelateral incisors erupt incisallyalong the central roots, tippingthe central crowns distally andoften increasing the size of thediastema between the centralincisors. Only after the cuspidserupt down along the lateral in-cisor roots and finally into fullocclusion does the maxillarymidline diastema close.

The cross-sectional studies ofRichardson and colleagues,4

Gardiner7 and Weyman8 allshow a decrease in the inci-dence of diastemas with in-creasing age through the mixeddentition phase. The even morepowerful longitudinal study byPopovich and colleagues9 founda similar relationship. ThePopovich study used the studymodels of the same 471 pa-tients at ages 9 and 16 years to

determine changes in the inci-dence of maxillary midline di-astemas. Eighty-three percentof the patients with a diastemaat 9 years of age had no di-astema at 16 years of age, with-out having undergone anytreatment. In the approximate-ly 10 percent of the samplewith persistent diastemas, gen-eralized spacing or an initialmidline diastema larger than 3mm was present.

As the above studies found,the great majority of di-astemas close after the erup-tion of the maxillary canineteeth and require no interven-tion by the dentist. Only di-astemas larger than 2 mm10

and diastemas in patients withgeneralized spacing are at riskof not closing with normal de-velopment.10 It is important fordentists to recognize this oftenabnormal-appearing maxillarydental arrangement and nottreat what is, in fact, normaldevelopment.

TOOTH-SIZE DISCREPANCIES

Tooth-size discrepancies are amajor cause of diastemas. Themost common tooth-size dis-crepancy is small or peg-shapedmaxillary lateral incisors. Thesmall maxillary lateral incisorsallow distal drifting of the max-illary central incisors and cre-ate a midline diastema. Thereare at least two methods of de-termining whether tooth-sizediscrepancies are present.

Bolton analysis. A commonmethod is the Bolton analy-sis,11,12 which mathematicallycompares the size of the maxil-lary teeth with the size of themandibular teeth. A mismatchbetween the maxillary andmandibular teeth is commonlycalled a Bolton discrepancy and,

86 JADA, Vol. 130, January 1999

CLINICAL PRACTICE

Figure 1. A diastema between the maxillary central incisors as well asmild lower incisor crowding is normal during the mixed dentition phase.


as defined by Bolton, relatesonly to the relative mesiodistaldimensions of the teeth. Eventhough the Bolton analysis ap-pears to be a relatively simpleprocedure, some variation existsamong even experienced dentalpractitioners who measure theteeth13; hence, the results mustbe viewed with caution.

Diagnostic cast setup.Another method of evaluatingtooth-size discrepancies is a di-agnostic cast setup, which re-quires mounted dental casts.The anterior teeth are removedfrom the cast and then waxed


CLINICAL PRACTICE

Figure 2. Excessive anterior vertical overlap is shown. A. Owing to the shape of the lingual surface of themaxillary incisor, excessive vertical overlap of the incisors can increase the circumference of the maxillaryarch and result in a maxillary midline diastema. B. If maxillary incisor overeruption is the cause of the exces-sive anterior vertical overlap, maxillary incisor intrusion will allow retraction of the maxillary incisor and clo-sure of a maxillary midline diastema. C. If mandibular incisor overeruption is the cause of the excessive ante-rior vertical overlap, mandibular incisor intrusion will allow retraction of the maxillary incisor and closure of amaxillary midline diastema.

A

B

C


back onto the casts in theirproper relationship; the final re-lationship and spacing of theteeth are then evaluated andcompared with the original rela-tionships. The dentist must ex-ercise caution in repositioningthe teeth so that the alignmentand angulation are realistic andachievable. The diagnosticsetup enables the dentist tosimulate intraoral positions andmeasure the amount of spaceremaining after orthodonticalignment of teeth as well asplan appropriate restorativeprocedures.

Treatment. Diastemasbased on tooth-size discrepancyare most amenable to restora-tive and prosthetic solutions.The most appropriate treatmentoften requires orthodonticallyclosing the midline diastema,then moving the small tooth orpeg-shaped lateral incisor into aposition between the central in-cisor and cuspid that optimizesthe esthetic and restorative re-sult. The best contour and es-thetics are achieved if the peg-shaped lateral incisor is moremesial in the space. Placementof the peg-shaped lateral incisormust be determined by the clin-ical requirements of the par-ticular restorative or prostheticprocedure.14

EXCESSIVE ANTERIORVERTICAL OVERLAP

Excessive anterior verticaloverlap (overbite) of the anteri-or teeth is another commoncause of excessive spacing inthe maxillary arch (Figure 2).When the size of the maxillaryteeth match that of themandibular teeth (no Boltondiscrepancy) and the anteropos-terior occlusion is normal (thatis, Class I), an increase in thevertical overlap of the anterior

teeth results in an increase inthe circumference of the maxil-lary arch (spacing) or in crowd-ing of the lower incisors. Thisphenomenon occurs as a resultof the wedge-shaped lingualsurface of the maxillary in-cisors. When there is little orno lower incisor crowding, themaxillary incisors move for-ward and the circumference ofthe maxillary arch increases asthe vertical incisor overlap in-creases. When this occurs,spacing develops between themaxillary anterior teeth, creat-ing diastemas (Figure 2A).

When a patient has excessive

anterior vertical overlap, thechallenge for the dentist is todevelop a differential diagnosisof the source of the problem.This is critical to producing thebest functional and esthetic re-sult. Possible problems are ex-cessive vertical alveolar devel-opment of the maxillary incisorsor mandibular incisors, inade-quate vertical dimension of oc-clusion, or a combination ofboth of these.

Excessive vertical alveo-lar development of the max-illary incisors. It is not un-common in patients with a lackof horizontal mandibular posi-tion (that is, mandibular retro-gnathia) or a long lower face(that is, from the base of thenose to the bottom of thechin)—with the mandible rotat-ed downward and backward—tohave the maxillary alveolus

compensate via excessive alveo-lar vertical development. Thiscan be an isolated finding orpart of a patient’s skeletal de-formity. To evaluate the maxil-lary incisor, the dentist mustcarefully examine the patient’sface clinically and cephalometri-cally. A key indicator of maxil-lary incisor vertical position isthe amount of incisor exposedbeneath the resting upper lip.In patients with an upper lip ofnormal length, 2 to 3 mm of in-cisor should be visible below thevermilion border of the upperlip. Female patients can gener-ally tolerate a greater amountof incisor exposure than males,with exposures as high as 5 mmbeing esthetically pleasing.15-17

Treatment. If a patient has amaxillary midline diastema, ex-cessive overbite, excessive ex-posure of the maxillary incisorbelow the resting lip and a nor-mal upper lip length, the appro-priate treatment is intrusion ofthe maxillary incisors. After or-thodontic intrusion of the max-illary incisors and the resultingreduction of the vertical overlapof the incisors, the maxillaryincisors can be retracted intothe horizontal space createdand the midline diastemaclosed (Figure 2B). Great caremust be taken in not overin-truding the maxillary incisor,since the lip tends to lengthenwith aging.

When severely excessive in-cisor exposure is combined withan excessively long lower face,the best esthetic solution maybe orthodontics and orthog-nathic surgery to alter the max-illa. However, care must betaken in evaluating the maxil-lary incisor relative to the lip,since it is greatly affected by liplength. A short upper lip cancreate the same effect as exces-


CLINICAL PRACTICE

Diastemas based ontooth-size discrepan-cy are most amenableto restorative andprosthetic solutions.


sive maxillary alveolar verticaldevelopment. In the typical pa-tient, the upper lip is approxi-mately one-half the distancefrom the pupil to the base ofthe nose (subnasale).

Excessive vertical alveo-lar development of themandibular incisors. This isanother possible cause of in-creased vertical overlap of theincisors (Figure 2C). Patientswith this condition have a nor-mal lower facial height, a nor-mal relationship between themaxillary incisors and thelower border of the upper lipand a pronounced lower curveof Spee. Frequently, a pro-nounced step in the occlusalplane is present in the lowercuspid or incisor area. This isnot uncommon in Class II mal-occlusions when either the max-illary teeth are labial to theirnormal position or the mandibu-lar teeth are lingual to theirnormal position. In a Class IImalocclusion, the best result isachieved when the Class II mal-occlusion and the anteroposteri-or positioning of the teeth andjaws are corrected.

Fine18 suggests that in a pa-tient with a Class II malocclu-sion, dental prematurities maycause a forward shift of themandible that can result in pro-gressive splaying or spacing ofthe anterior teeth; he suggestsocclusal equilibration to a cen-tric relationship position. Whenthe arches are in the proper re-lationship in an anteroposteriordirection, excessive verticalalveolar development of thelower incisors can cause spacingbetween the maxillary incisorsand, consequently, a midlinediastema.

Treatment. The appropriatetreatment for excessive verticaldevelopment of the mandibular

incisors is lower incisor ortho-dontic intrusion, which decreasesincisor vertical overlap. Once thisis done, the maxillary incisorscan be retracted and the midlinediastema closed (Figure 2C).

Lack of vertical dimen-sion of occlusion. Anothervertical problem that can leadto a maxillary midline diastemais a lack of vertical dimension ofocclusion (that is, an increasedanterior vertical overlap due toinsufficient posterior vertical di-mension). This can occur either developmentally or as a result of tooth loss. The denti-tion frequently appears likethat of overerupted mandibular

incisors, with an excessive vertical overlap of the incisors.The difference between over-erupted mandibular incisorsand lack of vertical dimensionof occlusion is that the lowerface is shorter than normalwhen there is a lack of verticaldimension of occlusion.

Characteristics of a shortlower face include a short loweranterior facial height, a flatmandibular plane resulting in aprominent chin, and the peri-oral lip and facial creasingtraits of inadequate vertical di-mension. Measuring the pa-tient’s lower face relative to theheight of the upper face willalso diagnostically demonstratea short lower face. In a patient

with normal facial height rela-tionships, the distance from thegreatest prominence of the fore-head (the glabella) to the lowerborder of the upper lip (thestomion) is equal to the distancefrom the upper lip to the lowestpoint on the soft-tissue chin.These measurements are an in-dication of soft-tissue heightand can be made clinically onthe patient or on the cephalo-metric radiograph.

Treatment. The treatment ofchoice for a maxillary midlinediastema with excessive verticalincisor overlap due to a defi-cient vertical dimension of oc-clusion is to increase the verti-cal dimension of occlusion. Thiscan be done orthodontically byusing an anterior bite plane andorthodontic appliances to enablethe mandible to rotate down-ward and backward and toallow vertical alveolar develop-ment of the posterior teeth,while decreasing the incisorvertical overlap. After the verti-cal relationship is corrected, themaxillary incisors can be re-tracted and the diastemaclosed.

Loss of the vertical dimen-sion of occlusion is commonlycaused by loss of posteriorteeth. Orthodontically upright-ing tipped molars and replacingthe missing teeth with fixedprostheses or implants is thepreferred way to increase andmaintain the vertical dimensionof occlusion. Again, once thevertical overlap of the incisorsis decreased, the maxillary in-cisors can be moved linguallyinto the overjet (horizontalspace) created, thus decreasingthe circumference of the maxil-lary arch and closing the maxil-lary midline diastema.

If the patient has a longlower face, the above treatment


CLINICAL PRACTICE

The mesiodistal angu-lation of the incisorsis another critical fac-tor that dentists mustevaluate when con-templating treatmentfor midline diastemas.



CLINICAL PRACTICE

Figure 3. Mesiodistal crown angu-lation is shown. A. Excessive dis-tal crown angulation, particularlyon flat-sided central incisors, cangive the appearance of a dias-tema when the central incisorcrowns are in contact, but at agingival level. B. A patient exhibit-ing excessive mesial root angula-tion of the maxillary incisors, cre-ating an apparent diastema whilethe incisors are nearly in contactin the cervical area of the teeth.C. Maxillary incisor crowns thatare mesially inclined occupy morespace in the arch than do uprightcrowns. Mesially inclining thecrowns of the maxillary incisors isone method of increasing the ef-fective tooth mass of the upper in-cisors and creating sufficient archcircumference to close a dias-tema when the maxillary teeth areslightly smaller than the mandibu-lar teeth.

of rotating the mandible down-ward and backward is not indi-cated. In these patients, all ef-forts must be made to avoidincreasing the length of an al-ready long lower face. Dentistsmust avoid using molar upright-ing, which allows molar extru-sion, or an anterior bite plane,which allows the mandible torotate downward and backward.Downward and backward rota-tion of the mandible in patientswith an already excessive lowerfacial height will have a detri-mental effect on facial esthetics,increase any tendency toward a

A

C

B


Class II malocclusion and de-crease posttreatment estheticsand stability.

MESIODISTAL ANGULATION

The mesiodistal angulation ofthe incisors is another criticalfactor that dentists must evalu-ate when contemplating treat-ment for midline diastemas.When the maxillary incisorcrowns are distally inclined, adiastema may appear to be pre-sent, although the incisors areactually in contact (Figure 3).With excessive distal crown an-gulation, the contact point ofthe central incisors moves gin-givally, leaving what appears tobe a diastema at the incisaledge of the teeth (Figure 3, Aand B). This phenomenon is en-hanced by the mesial contour ofthe incisors.

Incisors that have little con-vexity on their mesial surfaceare more affected by mesiodistalcrown angulation, while incisorswith a more convex mesial sur-face are more forgiving and tendto maintain their contact pointat a more incisal level. The moreconvex the mesial surface of themaxillary central incisor, theless likely the incisors will ap-pear to have no contact. Thus, insome patients, orthodonticallychanging the angulation of thecrowns to a more distal inclina-tion will move the contact moreocclusally and treat the appar-ent diastema.

Mesiodistal crown angulationalso influences the amount ofarch length or space betweenthe cuspids. Less maxillary archcircumference is present whenthe incisors are uprightmesiodistally. The more thecrowns are angulated mesially,the more arch length or archcircumference is increased

(Figure 3C). Therefore, themore upright the crowns, thegreater the possibility of anteri-or spacing; the more mesiallyinclined the crowns, the lesslikely that there will be spacebetween the teeth.

Treatment. For a patientwith a maxillary midline di-astema, it is important for thedentist to evaluate the crown an-gulation of the four maxillary in-cisor teeth. We believe the besttreatment is to change the incli-

nation of the maxillary incisorcrowns. Closing the midline di-astema in these patients can bedone by orthodontically increas-ing the mesial crown angulationto occupy greater arch circumfer-ence, while maintaining good an-teroposterior relationships withthe mandibular incisors and op-timum anterior guidance.

The amount of crown angula-tion that can be placed in theupper incisors is determined byboth esthetics and root position.While mesial crown angulationenhances the smile line of theupper incisors, excessive crownangulation can detract fromupper incisor esthetics. Root po-sition is an even more criticalfactor. Too much mesial crownangulation may cause the roots

of the central incisors to contactthe roots of the lateral incisors,or the roots of the overangulatedlateral incisors to contact theroots of the cuspids. Forced rootcontact during orthodontic treat-ment can result in root resorp-tion of both contacting teeth.

Another consideration is thespacing that develops below the contact point of the maxil-lary central incisors when theyare excessively mesially in-clined, thus creating an inter-dental space that the gingivalpapilla cannot fill. This darkspace, unfilled by gingival tis-sues, can create an unestheticdistraction from an otherwiseesthetic result.

GENERALIZED SPACING

Generalized spacing in the den-tal arches can result from dis-crepancies between tooth sizeand jaw size, muscle imbal-ances, thumb or finger habits,or missing or impacted teeth.Generalized spacing is seen asspaces, not only between theanterior teeth, but also betweenthe posterior teeth in both themaxillary and mandibular arch-es. The combination of largejaws and normal or small teethis usually due to inherited char-acteristics, but it can be a signof endocrine imbalances.Endocrine imbalances that re-sult in excesses of growth hor-mone, such as acromegaly, cancause abnormally large jawsrelative to the size of the teeth.Conversely, normally sized jawswith abnormally small teethcan also contribute to general-ized spacing of the dentition.

Muscles. Lip habits or mus-cle weakness can also contributeto generalized spacing. In pa-tients with flaccid lips and littlemuscle tone, the teeth maymove and stay in a labial or buc-


CLINICAL PRACTICE

Generalized spacingin the dental archescan result from dis-crepancies betweentooth size and jawsize, muscle imbal-ances, thumb orfinger habits, ormissing or impactedteeth.


cal position. These patients ex-hibit wide, ovoid arches and alack of interproximal tooth con-tact. Lip habits in which the pa-tient habitually positions thelower lip behind the upper in-cisors can also result in themovement and maintenance ofthe maxillary incisors in a labialposition, thus increasing thearch circumference and creatinga maxillary midline diastema.

Tongue position. Anotherpossible muscular cause may betongue position. Tongue thrust-ing has been discounted as aproblem because of the shortcontact times; however, tongueposition at rest can affect toothposition.19 Other habits that cancontribute to a maxillary mid-line diastema include thumb orfinger sucking or any habitsthat result in a long-term pro-truding or separating force onthe maxillary anterior teeth.

Missing or impactedteeth. Spacing in the maxillaryarch can also be caused by miss-ing or impacted teeth, creatinga midline diastema. Missing lat-eral incisors enable the centralincisors to drift distally and cre-ate a midline diastema. Im-

pacted cuspids can also allowincisors to drift distally, creat-ing a midline diastema. Evenmissing second bicuspids cancreate sufficient space in thearch to allow the incisors todrift distally, thus creating amidline diastema.

Treatment. One treatmentoption is to orthodontically re-align the teeth, create space forthe missing tooth and insert areplacement tooth to maintainproper arch dimensions and di-astema closure. Another optionis to orthodontically close thespace. This has been done suc-cessfully with missing maxil-lary lateral incisors, which arereplaced with a cuspid tooth.20,21

Esthetics can be a problembecause of the larger size anddifferent shape of the cuspid.However, careful reshaping ofthe cuspid, use of bondedrestorative materials and morelingual inclination of the cuspidroot to avoid the usual cuspidroot prominence can minimizethis problem.22,23 Maintainingclosure of the diastema requiresthat arch integrity be restoredand all arch spaces closed. If animpacted cuspid is the cause of

excessive maxillary spacing andit is not severely impacted, thedentist should uncover the cus-pid and bring it into properalignment.

LABIOLINGUAL ANGULATION

Labiolingual angulation of themaxillary incisors also has aneffect on anterior arch circum-ference and can create a maxil-lary midline diastema. If theoverjet and posterior occlusionare ideal (Class I), but the max-illary incisors are excessivelyupright, the maxillary incisorroots and contact points will bedisplaced anteriorly.24 This canresult in maxillary arch spac-ing, which, at first glance, maybe attributed to a tooth-size dis-crepancy (Figure 4). Uprightmaxillary incisors are oftencombined with excessive verti-cal development of the maxil-lary or mandibular incisors, cre-ating excessive anterior verticaloverlap of the incisors. Thisoverlap, combined with uprightmaxillary incisors, further exac-erbates the increase in maxil-lary arch circumference and in-creases the likelihood of a


CLINICAL PRACTICE

Figure 4. Labiolingual angulation is shown. Maxillary incisors that are excessively upright labiolingually havetheir contact points in a more anterior position than normally inclined incisors, resulting in an increase in archcircumference and the possibility of maxillary incisor spacing.


maxillary mid-line diastema.

Treatment.To correct a diastema createdby an overly upright incisor, thedentist must orthodonticallymove the maxillary central in-cisor roots lingually. In somepatients, particularly adults,the ability to do this may belimited by the thickness of theanterior alveolus. This type ofmovement also exerts a consid-erable mesial force on the poste-rior teeth and may move themaxillary posterior teeth for-ward if not carefully controlled.

FRENUMS

Although excessively large labi-al frenums have been cited as acause of diastemas, most or-thodontists tend to discounttheir influence. The frenummay be more a result of a di-astema being present than acause of it.9 The character of themaxillary suture between themaxillary incisors has been im-plicated in diastema mainte-nance. A larger-than-normalmaxillary midline suture hasbeen reported to create andmaintain a diastema as a resultof gingival fibers inserting intothe suture, rather than acrossthe suture.10 Rarely does afrenectomy close a diastemathat would not have otherwise

closed during normal develop-ment. According to Proffit andFields,19(p486) when removal of theexcessive frenum tissue is indi-cated, the diastema must beclosed (or nearly closed) or-thodontically before tissue is re-moved to avoid the possibility ofthe surgical scar tissue main-taining the diastema.

There are some rare circum-stances when developmentalproblems do appear to be re-sponsible for a diastema.Midline clefts have been report-ed to occur in association withfrenums, but are a result of afailure of the midline tissues tocross the midline, leaving asmall midline fissure that main-tains a diastema; this can bedemonstrated with an instru-ment or dental floss.25,26

This uncommon problem re-quires surgery to restore morenormal interproximal anatomyto the gingival tissues beforethe diastema is fully closed.Simple surgical correction of thecleft probably will not result indiastema closure. Even in theseunusual circumstances, the di-astema must be orthodonticallyclosed, with the surgical proce-dure occurring just before orafter final space closure so thatthe scar tissue does not createproblems.

PATHOLOGICAL CONDITIONS

Thorough evaluation of the areaof the midline diastema is criti-cally important. Periodontaland radiographic examinationwill disclose any abnormal find-ings in the midline area thatmight contribute to the midlinediastema. Supernumerary teethor mesiodens can physicallyprevent the maxillary centralincisors from meeting in themidline. Other pathological con-

ditions, such as cysts or fibro-mas in the maxillary midline,can also prevent normal centralincisor positioning. Anothercause can be periodontal in-flammation secondary to perio-dontal disease or foreign bodiesin the periodontal ligament.

SUMMARY

Maxillary midline diastemasare an esthetic concern formany patients. The cause of adiastema can be determined byevaluating several factors andmaking a differential diagnosis.Excessive vertical overlap of theincisors increases the circumfer-ence of the maxillary arch andby itself can be a major factor inproducing and maintaining amidline diastema. Discrep-ancies in the size of the maxil-lary teeth relative to themandibular teeth, particularlysmall or peg-shaped lateral in-cisors, as well as missing or im-pacted teeth, can be a majorcause of maxillary diastemas.

Other factors that can be con-tributory include the inclinationof teeth mesiodistally and labio-lingually. The occlusion of theteeth, not only in the verticalbut anteroposterior dimension,can be another important con-tributing factor. Other factorscontributing to maxillary di-astemas can be pathologicalconditions, muscle weaknessand supernumerary or missingteeth. To achieve the most es-thetic and functional result,dentists must carefully deter-mine the contributory factors toa maxillary midline diastema intheir patients. ■

1. Kerosuo H, Hausen H, Laine T, ShawWC. The influence of incisal malocclusion onthe social attractiveness of young adults inFinland. Eur J Orthod 1995;17:505-12.

2. Taylor JE. Clinical observations relatingto the normal and abnormal frenum labii su-perians. Am J Orthod 1939;25:646-60.

3. Lavelle CL. The distribution of diastemas


CLINICAL PRACTICE

Dr. Oesterle is an as-

sociate professor

and chair,

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Growth and

Development,

Campus Box C284,

University of

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4200 E. Ninth Ave.,

Denver, Colo. 80262.

Address reprint re-

quests to Dr.

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Dr. Shellhart is an as-

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MAXILLARY MIDLINE DIASTEMAS_A LOOK AT THE CAUSES