37Dental AnomaliesDENTAL NEWS, Volume IX, Number I, 2002

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Dental Anomalies

Dr. M. Kuftinec

I - I N T R O D U C T I O N

Mladen Kuftinec, D.M.D., Sc.D.Department of OrthodonticsNew York University College of Dentistry

Some form of a dental anomaly, or atleast dental irregularity is found in near-ly every individual, including men,women and children. Some of these arerelatively mild and simple, as in rotationsof teeth, small interdental spacing andunusually shaped teeth. Others aremore complex and cause more func-tional and esthetic concerns. Among thelatter, one should include congenitallymissing, impacted and severely crowd-ed teeth and also craniofacial anom-alies, such as various forms of clefts. Anorthodontist, who is primarily concernedwith the function and esthetic of thehuman dentition, sees these anomaliesas a challenge in his efforts to change amalocclusion to a more normal and cos-metic occlusion.

It is well accepted that among all thetraits of malocclusions of the modernman, dental crowding is the most preva-lent, possibly second only to the rotationof an individual tooth. For that reason, itis not surprising that dental crowdingoccupies a central place in this special-ty’s discussions about etiology andpathogenesis of malocclusions. It couldbe well speculated that if practitionersunderstood the mechanisms of crowd-ing, they could be able, at some point, tointercept or even prevent it and thussubstantially reduce the incidence ofmalocclusion in the modern population.However, the way things stand right nowit is not very likely that this importantpublic health issue will be affected anytime soon.

T r a i t s o f M a l o c c l u s i o nSecond to dental crowding, anomaliesin the number of teeth represent a largegroup of primary factors causing maloc-clusions. This is closely followed by ananomalous position of teeth, chiefly rep-resented by impactions and ectopiceruption, but also including transposi-tions and transmigrations. Therefore,these etiologic factors should also belooked at in an effort to understand andreduce or even eliminate them in thefuture. Consequently, it is necessary torevisit some of the salient features ofthese anomalies. Particularly challeng-ing will be to summarize the recentinvestigative reports in this area, as wellas to speculate where future researchshould be directed. Once we are able tosubstantially reduce these underlyingdental anomalies, we will be wellequipped and ready to tackle evenmore complex cranio-facial problems.

Correspondence address:New York University - College of Dentistry David B. Kriser Dental CenterNew York, NY 10010-4086. Tel: 212 998 9898 - Fax: 212 995 4080

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Etiology and pathogenesis ofdental crowdingThere are two basic mechanisms in cre-ating the condition that we refer to asdental crowding. By definition, crowdingis a discrepancy between the cumula-tive widths of the dental units or teeth,and the available space to accommo-date these teeth within the alveolarbone. Thus, one can represent a ratiobetween the tooth size and the support-ing bone size. When this ratio exceedsunity, we define such a condition asdental crowding. If the ratio is one orless than unity, we don’t speak aboutdental crowding, but may, in fact, identi-fy the condition as dental spacing.Arguably, crowding exceeds spacing bya large margin, perhaps as large as 100or more to one. The ratio of exact unityor one is so rare in real life that it can,for all practical purposes, be ignored.

Calculating this ratio is not an exact sci-ence. The numerator part of the ratio isrelatively easy to measure, whether it isdone directly in the patient’s mouth oron a dental study cast. Numerous stud-ies have demonstrated that the error ofmeasurement for human dentition istypically within the calibration character-istics of the measuring device.Consequently this error is assumed tobe so insignificant that it can be ignored.Calculating the denominator of the ratio,the size of the available arch perimeter,is substantially more prone to error andinconsistency. Because various investi-gators hardly agree on definition of thedental arch characteristics and, there-fore, are not in agreement about whatshould be measured, substantial intra-and inter-investigator errors are oftenreported. Interestingly, the stated errorsdo not change the ratio’s outcome in asense of its direction [i.e. positive to indi-cate crowding and negative to indicatespacing], but tend to add to the severityof the discrepancy or the ratio’s depar-ture from unity.

The real question then is to analyzewhich of the two components of thelarger than one ratio is more likely to be

deviant from the average: the tooth sizeor the arch perimeter. While reviewingthe literature on the subject, seeminglyconvincing arguments for either compo-nent can be found. However, one mustnot ignore the most logical possibility;the one suggesting that both compo-nents contribute to some degree, albeitnot coequally. In order to illustrate thetwo separate possibilities, a study pub-lished by this writer and his coworkers inthe American Journal of Orthodontics(AJO)1 demonstrated that both individ-ual and cumulative sizes of crowdeddentitions were larger than in the non-crowded arches. This could be inter-preted as favoring the numerator to beat fault. On the other side, McNamaraand coworkers have also reported in theAJO that the arch perimeters of crowd-ed dentitions were significantly smallerthan their non-crowded counterparts.2

Their conclusions would suggest that itis the denominator that makes the basicdifference. A classic example of allow-ing the two factors to contributecoequally is the Moyer’s MixedDentition Space Analysis, where the cal-culated space is needed because ofeither overly large teeth or too littlespace within the dental arch.3

Because in most of the nature’s systemsthere is no bias toward any one factor,this writer currently believes that dentalcrowding can be equally caused by toolarge teeth and by inadequate bony sup-port within the dental arch. This, howev-er, does not preclude the use of certain“rules of thumb” in assessing the sever-ity of dental crowding. For instance, arelatively simple summation of the 20permanent teeth mesio-distal widthsshould, in average, add up to 140 mm[or a mean width of 7 mm per perma-nent tooth, not including the molars]. Ifthat sum exceeds 140 mm, one cansafely state that the dentition is largerthan normal and some degree of dentalcrowding is almost certain to ensue.1

Conversely, if one can measure theintermolar width of less than 36 mm onecould safely deduce that the bone is notsufficiently developed and, thus, it is pri-marily responsible for the encountereddental crowding. Finally, it should benoted that the presence of one of these

rules does not exclude the other frombeing present.

It is interesting to explore the secularchanges in both components of theratio. When one studies these long-termchanges, which are probably a result ofadaptive modifications to our diets andcertain environmental influences, onecan observe only modest variations.Individually these variations are insignifi-cant and probably would not be able toexplain the increased prevalence ofdental crowding. However, becausethey had been occurring in the oppositedirection, namely the size of dentitionhad increased while the available boneand thus the size of the dental arch haddecreased, the ratio has steadilychanged in favor of dental crowding.

This last statement brings yet anotherintriguing question: how does naturereact to this? Should the selective adap-tation mechanism not respond andmake a provision to resolve this appar-ent inconsistency? The responsivemechanism appears to exist and it is thecover of yet another dental develop-ment theory, the so-called ‘Field theoryof missing teeth.’ The theory, in its sim-plest form, states that as dental crowd-ing increases over the time, the last unitof the most numerous morphologicgroup will be gradually eliminated.Because we have three permanentmolars, the theory speculates that thelast in that group, or the third molar [“thewisdom tooth”] is the one that will bemissing. Because there are two premo-lars and two incisors the picture is notthat clear in terms of which tooth will bemissing. It appears that in the maxillarydental arch it is the distal [or second]incisor that is likely to be the next mostfrequently missing tooth. In themandible that distinction belongs to thesecond or distal premolar. A slightinconsistency of the Field’s theorychoice is observed with the mandibularcentral incisors, which are congenitallymissing more often than the mandibularlateral incisors.

It is interesting to explore the ways thatclinicians approach and attempt toresolve the dental crowding. If one

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accepts the premise that either theteeth are relatively large or the alveolarbone is relatively small, it will follow thatin the former case one would considerreducing the tooth substance. This isaccomplished by either extracting teethor by reducing their natural size.Reapproximating or “stripping” enamelfrom the interproximal surfaces ofselected teeth achieves a reduction inthe natural size. Clinically, one identifiesthese approaches as extraction or toothsubstance reduction methods. On theother hand, one can attempt to increaseor “grow” the available alveolar boneand develop the needed arch periphery.This approach is clinically identified asthe functionalist approach. This impliesthat some form of the functional appli-ance or method is utilized. It should benoted, however, that a great deal of con-troversy still exists in terms of whetheror not the functional appliances can pro-duce a real, net gain of the jaws or thealveolar bone. The alert reader readilyrecognizes that one method [e.g. extrac-tion approach] is not exclusive of theother [e.g. lateral arch expansion].Indeed, in many severe cases of dentalcrowding, both methods are neededand are thus employed.

This entire discussion would be serious-ly flawed were it not for at least a briefmention of the concept promoted byAngle, stating that only the entire,uncompromised complement of teethcan function properly. Such views fur-ther state that if the integrity of humandentition is compromised by extracting,for instance, premolars, then the entirestomatognathic system malfunctions.Modern dentistry largely abandonedthese views. In the 1950s and 1960s, itwas quite common and almost fashion-able to treat malocclusions with the helpof extraction of the four first premolars.Among the notable proponents of suchan approach were the most popularnames of the time, including Drs. Tweedand Begg. However, in the 1980s and1990s, the pendulum of the popularapproach swung to the opposite direc-tion and it became rather unpopular toextract teeth. In the opinion of thiswriter, clinicians have gone too far inadopting either philosophy. The ubiqui-

tous extractions of one generation ago,along with the hesitation and almost afear of extractions during the morerecent decades are both too extreme.The most rational approach to resolvingthe problems of dental crowding couldand often should consider bothapproaches and decide on the one, oreven the combination of the two, thatoffer the most desirable correction ofthis common problem.

While there are numerous anomalies inthis broad category, this paper will elab-orate on the most common ones, name-ly impactions, congenitally missingteeth, the so-called ‘peg shaped’ maxil-lary lateral incisors and transposition ofteeth. Conspicuously absent from thisdiscussion will be various forms ofdevelopmental anomalies of the faceand the mouth. This is because thereare numerous comprehensive articlesand dissertations on the topics through-out the dental literature. Similarly,because this author has publishednumerous papers on the subject ofimpactions, transposition and relatedanomalies, instead of repeating himself,he will summarize and then speculateon the future approaches and solutionsin resolving many of these anomalies.

Anomal ies of the number,shape and posit ion of atooth or teeth

A n o m a l i e s o f n u m b e r o rp o s i t i o n o f t e e t hIt is generally recognized that the mostcommon positional anomaly of a tooth isrotation. Rotations are so prevalent thatit is difficult to find a modern man orwoman with an occlusion that does notexhibit some degree of this commonanomaly. Because this anomaly is soubiquitous, many clinicians do not evenlist them as a trait of malocclusion,except when rotations are severe, e.g. a

tooth rotated more than 45 degrees.From the clinical aspect, rotations arenot overly difficult to correct, particular-ly with the use of fixed orthodonticappliances. It is important to keep inmind, however, that corrected rotationsalso represent the condition most likelyto relapse. Various strategies have beendeveloped to guard against, or to mini-mize, rotational relapse. One of the mosteffective ones is the procedure knownas supra-crestal fiberotomy [SCF], aminor surgical procedure in which thesupra-crestal gingival fibers are sev-ered.4

Ectopic position constitutes the secondmost common positional anomaly of thedentition. Within this category, the onethat concerns clinicians the most isimpaction. Even though any one toothfrom either dental arch can be impact-ed, impaction of the maxillary perma-nent canine receives most attention.This is the case for numerous reasons,including the central role that the canineplays in the function of articulation andocclusion. A second, nearly equallyimportant reason, is its role in facialesthetics.

There is an abundance of clinicalreports on the management ofimpactions. The long list of related pub-lications includes many contributions bythis writer.5-9 Many years of managingtreatments of the maxillary canineimpaction, supplemented with informa-tion from the published work have yield-ed some interesting observations:• Impactions affect approximately one

out of ten individuals [based on thevarious reports, from 3 to 18% of pop-ulation is affected];

• Excluding third molars, the maxillarycanine is the most frequently impactedtooth in humans;

• There appears to be interesting gen-der and side differences. Femalesexhibit nearly twice as many maxillarycanine impactions as males.Reportedly, the left side is significantlymore often affected than the right side[based on the various reports, fromabout 2:1 up to 6:1];

• No racial predilection could be detect-ed. Similarly, the global distribution of

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impactions seems to be quite similar.Practically no significant secularchanges can be detected, eventhough some authors predict anincrease in prevalence of impactions.This prediction is based on somewhatpreliminary conclusions, stating thathuman teeth are increasing in size atthe same time that the available boneappears to be shrinking. Note that thereader can relate this last statement todiscussion on the etiology of the den-tal crowding.

One other positional tooth anomaly, alsoaffecting the canines and particularlythe maxillary canine, is transposition. Inthis anomaly, the position in which theteeth erupt within the arch is altered.The maxillary canine can change itsplace within the arch, properly locatedbetween the lateral incisor and the firstpremolar [the so called L-C-P or 2-3-4sequence] to being transposed witheither the lateral incisor and into the xC-L, or with the first premolar, into the L-P-xC sequence. The former one has moreesthetic, while the latter one is ofgreater functional significance. 10-14

A brief mention will be made of yetanother positional anomaly of thecanines: transmigration. Transmigrationis exclusive of the mandibular perma-nent canine. In this anomaly, the caninefrom one side of the arch migratesthrough the bone and erupts on theopposite side of the arch. For instance,

the right mandibular canine migratesthrough the sympheseal area and eruptsinto the arch in the place where the leftcanine usually erupts. This anomalycould present a complex clinical prob-lem, because the clinician will be facinga situation where the canine from oneside appears to be missing, while theopposite side may appear to have asupernumerary canine.15 Like so manydental problems, this last anomaly isbest detected by radiographic examina-tion. If detected early enough, its treat-ment may not be too difficult. This willreinforce the urging of a mature teacherto obtain and examine our patients’records with care and attention to detail.

A clinician faces a large variety of dentalanomalies in his or her everyday work.This review dealt with only the mostcommon ones that particularly affect anorthodontist. A better understanding ofthese will make the work of a clinicianmore efficient and perhaps a bit moreenjoyable.

References1. Doris JM. Bernard BW. Kuftinec MM. Stom D. A

biometric study of tooth size and dental crowd-ing. American Journal of Orthodontics.79(3):326-36, 1981 Mar.

2. Howe RP. McNamara JA Jr. O'Connor KA. Anexamination of dental crowding and its relation-ship to tooth size and arch dimension. [JournalArticle] American Journal of Orthodontics.83(5):363-73, 1983 May.

3. Moyers R E. Handbook of orthodontics, Fourth Ed.,Chicago: Year Book Medical Publishers, 1988.

4. Ahrens DG. Shapira Y. Kuftinec MM. An approachto rotational relapse. American Journal ofOrthodontics. 80(1):83-91, 1981 Jul.

5. Shapira Y. Kuftinec MM. Early diagnosis and inter-ception of potential maxillary canine impaction.Journal of the American Dental Association.129(10):1450-4, 1998 Oct

6. Shapira Y. Borell G. Kuftinec MM. Stom D. NahlieliO. Bringing impacted mandibular second premo-lars into occlusion. Journal of the AmericanDental Association. 127(7):1075-8, 1996 Jul.

7. Kuftinec MM. Shapira Y. The impacted maxillarycanine: I. Review of concepts. ASDC Journal ofDentistry for Children. 62(5):317-24, 1995 Sep-Oct.

8. Kuftinec MM. Shapira Y. The impacted maxillarycanine (II). Orthodontic considerations and man-agement. Quintessence International. 15(9):921-6, 1984 Sep.

9. Shapira Y. Kuftinec MM. The impacted maxillarycanine (I). Surgical considerations and manage-ment. Quintessence International. 15(9):895-7,1984 Sep.

10. Shapira Y. Kuftinec MM. Maxillary tooth trans-positions: characteristic features and accompa-nying dental anomalies. American Journal ofOrthodontics & Dentofacial Orthopedics.119(2):127-34, 2001 Feb.

11. Shapira Y. Kuftinec MM. A unique treatmentapproach for maxillary canine-lateral incisortransposition. American Journal of Orthodontics& Dentofacial Orthopedics. 119(5):540-5, 2001May.

12. Shapira Y. Kuftinec MM. Tooth transpositions--areview of the literature and treatment consider-ations. Angle Orthodontist. 59(4):271-6, 1989Winter.

13. Shapira Y. Kuftinec MM. Stom D. Maxillarycanine-lateral incisor transposition--orthodonticmanagement. American Journal of Orthodontics& Dentofacial Orthopedics. 95(5):439-44, 1989May.

14. Shapira Y. Kuftinec MM. Orthodontic manage-ment of mandibular canine-incisor transposition.American Journal of Orthodontics. 83(4):271-6,1983 Apr.

15. Kuftinec MM. Shapira Y. Nahlieli O. A casereport. Bilateral transmigration of impactedmandibular canines. Journal of the AmericanDental Association. 126(7):1022-4, 1995 Jul.

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