Drifting, tipping, supraeruption, and segmental alveolar bone growth

COFFEY

12.

13. 14.

15. 16. 17.

Ogle RE. David LJ, Ortman I IR. (:l~nic,ll WC;~I‘ study of a new’ acrylic resin tooth material: Part II. J PKOYI.III I I )YYI 53:807. 198.5. Greenwood ART: Wear testing equipmrnt for 5) nthetil. resin teeth. J Dent Res 34~741. 1955. Cornell JA, Jordan JS, Ellis S, Rose EE: A method of compwinl: the wear resistance of various metals used m ,wtilici.rl trrth. J Am Dent ASSOC 54:608, 1957. Myerson RL: The use of porcelain and plastic wet11 in opposing complete dentures. J PROWHET DE& I 7:025. 195’. Sweeney WT, Yost EL. Fcr JG: Physical proprr~ies of plastic teeth. J Am Dent r\ssoc X833, 1958. Norman RL: Frictional resistance and dental lxosthetws. J PR~STHET

18. 19. 20.

21.

22. 23.

DENT

14~45.

tipping, supraeruption, bone growth

Paul Kaplan,

D.D.S.,

Dover

Base,

Air

Force

280

27. 2x. 2’).

30.

31. 32.

and segmental

Del.

D

Department

20.

,Jemt ?I‘, Karlsson S, Hedegard B: hlandibular movrments in young adults recorded by intraorally placed light-emitting diodes. J Ptwsrwr DENT 42:669, 1979. Ahlgren J, Owall B: Muscular activity and chewing force: 11 polygraphic study of human mandibular movements. Arch Oral Biol 15:271, 1970. Nyquist G, Owall B: hlasticatory load regiwation during function. Odont Revy 19:45, 1968. I)eLong R, Douglas WII, Pintado h,I Real world xrurac)of r~~mputcr qxphic~s. I)cn~ hl,rlrr 1:27. 19X5 Bragq GM: Principles of Experimentation and %Irasurement. Chicago, 1974, Prentice-Hall, Inc.. p 95. Barry BA: Engineering Measurements. New York, 1964. John Wiley & Sons, p 49. Raptis Ci%, Powers JM, Fan PL: Frictional behavior and surface failure of acrylic resin denture teeth. J Dent Res 60:908. 1981. Raptis C:S, Powers Jhl, Fan PL: Wear characteristics of porcelain denture teeth. Wear 67:177, 1981. Craig RG: Restorative Denral hlaterials. St. Louis. 1980, The CV Mosby Co, p 418.

M.S.*

Dover,

rift and tip are terms used interchangably to describe a tooth that has shifted in angle and position from its original vertical or upright position. Each of these terms, however, represents a different clinical entity and neither accurately describes most shifted posterior teeth. A basic misunderstanding originated from the concept that tooth movement is independent of its supporting alveolar bone. Tooth movement and position cannot be considered separately from the movement and development of the segment of alveolar bone in which a tooth develops. It is possible for a tooth to maintain a constant position relative to the bone which supports it; the supporting alveolar bone may alter its position or angulation. Without understanding how

*Chief,

25.

1964.

Thompson JC: Attrition of acrylic teeth. Dent PI-AU Dent Ret 15:233, 1965. Monasky GE, Taylor DF: Studies on wear of porcrlain. rnamel and gold. J PROSTHET DENT 25:299, 1971. Oashi M, Nihei M, Hasegawa K. Chen TE: A pilot manufacture of biting abrasion testing machine for the full denture and its test results. J Nihon Lniv Sch Dent 15:96. 1973. Harrison A, Lewis TT: The development of an abrasion testing machine for dental materials. J Biomed RIatet- Rcs 9:341, 1975. McKinney JE: Apparatus for mexurmg wear of dental restorative materials. Wear 76:337, 1982. DeLong R. Douglas bVI.1: Development of an ,wtilic,ial oral environmen: for the resting of dental restoratives: Biaxial force and movement control. J Dent Res 62:33, 1983.

Drifting, alveolar

24.

ET AL

of Prosthodontics.

alterations in tooth and alveolar positions occur, treatment to the dentition is compromised from the initial diagnosis. This article identifies and defines the elements of tooth movement and alveolar bone growth that result in a clinically altered tooth position. INITIAL

GROWTH

The maxilla has a complex growth pattern. As Graber’ states, “It is a dynamic process in which specific local areas come to occupy new actual positions in succession as the entire bone enlarges. The growth shifts and changes involve corresponding and sequential remodeling adjustments to maintain the same shape, relative positions, and constant prop6rtions of each individual area in the maxilla as a whole.” Palatal growth follows the principle of the expanding “V.” Additive growth on the free ends increases the distance AUGUST

1985

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54

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2

NONORTHODONTIC

TOOTH

MOVEMENT

between them; the buccal segments move downward and outward, the maxilla itself moves downward and forward.‘, ’ The maxilla completes its width early in life. There are a number of observers who feel that the maxillary width more closely follows the neural growth curve, which is differentially complete quite early. This is in contrast to the downward and forward maxillary growth, which follows the general growth curve and continues to parallel pubertal changes elsewhere.’ Enlow and Bang’ reported that postnatal growth of the human maxilla parallels that of the mandible in that the forward and downward movement of the growing bone as a whole is a result of growth that takes place in a posterior direction with corresponding repositioning of the entire bone in a forward course. The generalization that the maxilla is thrust downward and forward by growth in posterior and superior parts of the bone is an oversimplification that does not consider the complex varieties of growth that takes place in other specific sites of the maxilla. Enlow and Bang2 also suggest that the various remodeling movements of the growing maxillary bone contribute to a functional basis for the drifting of teeth. Adjustments in the position of erupted and unerupted teeth appear to be acquired as a result of growth and can be considered to be remodeling movements of tooth-bearing bone. Mandibular length is determined by growth at the mandibular condyle, combined with apposition of bone on the posterior border of the ramus. Continuous growth of alveolar bone with the developing dentition increases the height of the mandibular body. The alveolar process of the mandible grows upward and outward on an expanding arc to permit the dental arc to accommodate the larger permanent teeth.’ The original location of the teeth and the alveolar process in which they are contained is the result of a complex growth mechanism in an ideal state in which each tooth acts as a feedback control to localized alveolar growth. It is reasonable to assume that the early loss of teeth leads to an interruption in arch integrity and development of growth patterns that force independent segmental alveolar growth to occur. The maxilla or mandible is capable of such dynamic change throughout life if existing equilibrium is disrupted. The rate of change may vary, but the altered maxillae and mandibles of elderly patients leave no doubt as to the ability of teeth to drift, tip, and of segmental bone to grow late in life. ALTERATION

IN TOOTH

POSITION

Historically, many orthodontists felt that when they removed the four first premolars and completed orthodontic therapy, the third molars would have a better chance to erupt normally because they would have more “room.” Through a survey, Love and Adams3 indicated that the predominant alteration in tooth position was THE

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Fig. 1. Distal drift of premolars force and stopping contact.

depicts both initiating

still perceived as a “mesial” movement and that this movement was closely related to age. What is labeled “tipping” actually consists of a mandibular third molar with a short occlusal-cervical height and a prominent segmentof alveolar bone projecting anteriorly from the inferior portion of the ascending ramus. In the maxilla, a downward growth of a distinct posterior segmentof the alveolar ridge is usually noted. The term tipped is usually applied to both these situations, although the downward growth of the maxillary posterior segmentmay sometimesbe called “supraeruption.” Clarification of the terms drift, tip, and tilt is required for a more complete understanding of nonorthodontic tooth movement. In addition to the traditional terms, an additional descriptive term, segmentalbone growth, is introduced to more accurately describeactual movement of a segmentof tooth-bearing alveolar ridge. It is only with clearly understandableterms that a clear diagnosis of an oral condition can be made and a definitive treatment plan developed. DRIFT Drift is the mesial or distal movement of a tooth through a stable alveolar ridge. It can often be observed in the premolarsof either dental arch and is occasionally noted in the canines. Distal drift of the molars is not commonly noted. Distal drift of the premolars often occurs simultaneouslywith rotation. Drift is usually not equal; the secondpremolar tendsto drift more posteriorly than the first premolar.

Interproximal

contacts are not

usually maintained although interproximal tissue is generally healthy. The distally drifted premolarsusually lack the normal cusp-fossarelationships. However, they generally exhibit no mobility. Occlusal contact often appears to be the driving force of drift, and drift occurs until occlusal contact is within physiologic toleration the supporting alveolar segment(Fig. 1).

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Fig. 2. Mesial tip and possible supraeruption of maxillary second molar; tipped forward by distal contact, held in position by mesial contact.

Fig. 3. Supraeruption. Teeth adjacent to maxillary molar hold alveolar ridge in place. Mesial rotation places holding contact on distal surface of second mandibular premolar.

TIP Tipping is the movement from a line perpendicular to the alveolar segment that supports the tooth. It rarely occurs alone; usually it occurs simultaneously with drift and is driven by eccentric occlusal contacts. The key force in tipping is the driving occlusal contact. If no tooth contact is noted or has been present previously, possible forces generated by the tongue and mastication may be considered (Fig. 2). SUPRAERUPTION Supraeruption is the eruption of a tooth from its fully erupted position without alteration in the position of its supporting alveolar bone level. The tooth erupts vertically until a point of stability occurs. This point of stability 282

Fig. 4. Supraeruption of maxillary first molar in ct,::. junction with inferiorly directed segmental alveolar growth of maxillary distal segment.

is usually an occlusal contact either in centric occlusion or eccentric position. A tissue stop is possible. For example, when a first molar that opposes a first molar is extracted or lost, the opposing first molar may supraerupt, particularly if the teeth adjacent to the missing tooth are held in place vertically and horizontally by the teeth in the opposing arch. The opposing first molar ma) then supraerupt into the vacant space until such time as an occlusal contact in either centric or eccentric movcment occurs (Fig. 3). This form of supraeruption, while often considered to have only a vertical component of movement, may have more of a horizontal component than expected. The usual pattern of the supraerupting first molar impacting on the distal marginal ridge of the mandibular second premolar, combines with the close apposition of root structure to the mesial root of the maxillary second molar, indicates that a pivot may br responsible for at least a portion of the supraeruption. True supraeruption is not observed as a rule unless teeth are present both mesially and distally to the supraerupted tooth. When opposedin the oppositearch, theseadjacent teeth stabilize the alveolar bone level and force the unopposedtooth to seeka new equilibrium by supraeruption. An unusual exception to this is the supraeruption of a single distal toot.h in an otherwise stabilized maxillary arch. Such a toath avoids occlusal stops in all forms and, if its opposing tooth is lost, is capable of true supraeruption (Fig. 4). SEGMENTAL

ALVEOLAR

BONE GROWTH

Segmentalbone growth is a tooth-bearing segmentof alveolar ridge that alters its position when either adjacent or opposing teeth, by their loss or abnormal development, have altered the normal feedback relationshipsnecessaryfor normal growth and development.It is

NONORTHODONTIC

TOOTH

MOVEMENT

Fig. 5. Alveolar bone growth of segment containing mandibular second and third molars. Molar position remains constant; segment arcs mesially into site left by resorbing alveolar segment that had supported first mandibular molar.

the long term sequela to extraction at any age, although its effects are seen most quickly in the young person. The effects, although slower in development, can be no less striking in the elderly. The segment of alveolar process involved in bone growth may be of any size but seems to be most clearly

defined when a group of posterior teeth are separatedby the lossof a secondpremolar and first molar from the second remaining anterior teeth. When a maxillary premolar and first molar are lost, the alveolar process that contains the maxillary secondand third molars will arc mesially, inferiorly, and to someextent buccally if unopposedby mandibular teeth. If opposed,it will arc in those directions until occlusal contacts provide sufficient feedback to terminate the growth. If the mandibular second premolar and first molar are lost, the alveolar segmentthat containsthe secondand third molar will arc mesially and superiorly into the resorbing alveolar processwhere the missing first molar originally developed (Fig. 5). When

it occurs simultaneously

with

the growth

Fig. 6. Maxillary and mandibular segmental alveolar growth with maxillary teeth exhibiting supraeruption and tipping while mandibular premolars show distal drift. Note mandibular second and third molars remain perpendicular to alveolar segment that supports them; alveolar segment has arced mesially.

after tooth extraction and the development of toothbearing alveolar segments. SUMMARY Difting, tipping, supraeruption, and segmentalalveolar bone growth are the four major forms of nonorthodontic intraoral tooth movement. They may occur separately but usually occur in combination (Fig. 6). They can occur at any age but tend to be most devastating in their effects on the dentition of the young adult and the elderly. They may represent nonrestorableocclusalsituations if combined and present in both arches. Clear diagnosisis therefore essentialprior to the formulation of a treatment plan.

and

movement of a posterior tooth-bearing alveolar segment, the resorption of alveolar processafter the extraction of a tooth is of extreme importance. The resorption of alveolar bone causes a decreasein resistance to the mesialgrowth of a segmentof alveolar bone at the same time as it strips bony support

from under

the incoming

alveolar segment.Little has been done to determine the effects of the interface between resorbing alveolar bone

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