Arch-Length Discrepancies and Serial Extraction

Do you use the Peck analysis? If so, how do you use it?

Only one respondent used the Peck analy­sis. He felt it made a valuable contribution to his diagnosis and treatment planning, with emphasis on the estimation of post-treatment stability. In his opinion, if the ratio of the faciolingual and mesiodistal dimensions of the mandibular anteri­or teeth (MD/FL) is greater than .9, a reduction in the mesiodistal dimension of anterior teeth would be advisable, after checking the amount of available enamel by x-ray.

Do you use any other tooth-size analysis? If so, how?

The vast majority (91%) did not use any tooth-size analysis other than the Bolton analy­sis. Those who did rely on other analyses tended to use a setup when they were suspicious of an impending tooth-size problem. Ten percent said they felt confident enough in their experience to rely on visual appraisal of crowding.

Do you strip anterior teeth? When and why?

All respondents stripped anterior teeth either routinely or occasionally. The predomi­nant reason was to alleviate mild-to-moderate crowding. Other reasons, in descending order of frequency, were:

• To achieve better incisal relationships.
• To improve stability and reduce the tendency for relapse, due to the altered morphology of the stripped proximal surfaces.
• To reshape malformed teeth and unusual prox­imal surfaces to a more normal morphology.
• To correct slightly deviated midlines.
• To reduce or eliminate triangular interproximal spaces.
• To avoid extractions in selected cases, usually adult.

Representative comments included:

• "With screwdriver-shaped maxillary anterior teeth, I reduce the mesiodistal dimension at the gingival one-third to allow space to bring the incisal one-third together."
• "Stripping anterior teeth helps correct discrep­ancy cases at the end of treatment. It also flattens the contact points of the incisors, and this, I believe, is beneficial for retention."
• "I find this very helpful to create space for post-treatment movement of incisors when retainers are not worn as directed. Also for lower anterior crowding when I have achieved Class I cuspids with acceptable incisal relationships."
• "I strip anterior teeth when there is a mandibu­lar excess due to microdontia of the upper later­al incisors. I can't get Class I cuspid relationships without doing this."

Do you strip posterior teeth? When and why?

Although 78% of the clinicians said they stripped posterior teeth, most of these added the qualifier "occasionally", "sometimes", or "sel­dom". The primary reason for posterior stripping (mentioned by 71%) was to gain arch length in crowded cases, with strong emphasis on trying to avoid extractions in adults. The air-rotor strip­ping technique advocated by Sheridan was fre­quently involved. Additional reasons for poste­rior stripping, in descending order of frequency, were: to reduce oversize posterior teeth, espe­cially second premolars; to achieve better buccal and incisal relationships; to simplify the mechan­ics; and to achieve treatment goals more quickly, especially in adults. Some interesting replies:

• "This is an invaluable tool in treating mild-to-­moderate crowding in my adult patients. I find extractions in adults inevitably result in opening of post-treatment extraction spaces. Stripping substantially shortens treatment time, and that is an important factor when treating adults."
• "I strip posterior teeth less frequently than mandibular anterior teeth. I use this treatment option to gain arch length in a borderline extrac­tion case that I am treating on a nonextraction basis."

Are stripped teeth stable?

All the respondents thought stripped teeth were stable, although modifiers such as "usual­ly", "more", and "probably" were often added. The most common rationale was that the flat­tened proximal surfaces of the incisors promoted a more stable environment. Typical comments were:

• "After stripping, the anterior teeth are probably more stable. The posterior teeth should be equili­brated after stripping to preclude the possibility of space opening."
• "Answering this question is difficult because there are so many variables associated with sta­bility. I believe that stripping can improve stabil­ity, but it is certainly not a major element in the overall picture. It's probably just an aid, but I'll settle for what I can get."

How do you treat an arch-length discrepancy of less than 5mm?

The majority of respondents (81%) used a combination of techniques. By far the most pre­valent involved stripping and slight expansion. Twelve percent opted for the extraction of either bicuspids or a lower incisor. Less common tech­niques, in descending order of frequency, were: holding leeway and "E" space in the mixed den­tition, headgear, lip bumper, selective torquing, and settling for a compromised result. Individual comments included:

• "This depends on multiple factors. One formu­la that I use is: 5mm of crowding + incisor pro­trusion (cephalometric discrepancy) + lip incom­petence = extractions."
• "I will strip interproximally with possibly some anterior flaring if the lower incisors are behind or at the facial line (Na to Po)."

Do you use serial extraction, and, if so, what is your usual regimen?

Seventy-two percent of the respondents oc­casionally used one form or another of serial extraction; 12% used it frequently, and 18% reported that they never used serial extraction procedures.

Nearly half of the clinicians who used seri­al extraction followed the classical sequence of deciduous cuspids, deciduous first molars, and permanent first premolars. Eight percent favored extraction of only deciduous first molars and first bicuspids, while an equal percentage extracted only deciduous cuspids. Another 28% used vari­ous sequences of deciduous and permanent tooth removal, but the permanent teeth were always first premolars. The remaining 8% had no set protocol, but extracted teeth "to the demands of the situation and as the case developed".

There was a general tendency to use lingual arches in conjunction with serial extraction and to monitor space requirements throughout the sequence. Several clinicians noted that their pur­pose in initiating serial extraction was to resolve an impending crowding situation and to encour­age the premolars to erupt prior to the permanent cuspids. Some individual comments were:

• "I can't imagine a contemporary orthodontist not having a serial extraction program among their applicable treatment plans."
• "I think it terribly important to constantly monitor the serial extraction case and to initiate in-course alterations whenever it becomes obvi­ous that the initially projected outcomes will not come about."

What are your criteria for extracting permanent teeth?

While all respondents listed multiple crite­ria for removing permanent teeth, 92% indicated that two factors--the degree of crowding and the degree to which protrusion affected the profile--were the most important. Additionally, 18% said they would extract teeth due to extant or poten­tial pathology if there were faulty restorations, obvious decay, or periodontal involvement with certain teeth. A surprising number of other rea­sons were listed, including, in descending order of frequency:

• To obtain the necessary room for Class II or III correction.
• To position the mandibular incisors more favorably.
• To gain a favorable periodontal environment.
• To resolve subdivision cases.
• To avoid second molar impaction.
• To improve the vertical dimension, especially in open-bite cases.
• To avoid excessive expansion in adolescent patients.
• To assist in midline correction.
• To avoid expansion in adult patients.
• To correct lip incompetence.
• As an alternative in borderline uncooperative patients.

One thoughtful response:

• "The days of thinking that the extraction of permanent teeth would eventually lead to a stom­atognathic crisis are thankfully over. This rea­soning was supported by a bridge of anecdotes that proved to be too flimsy and insubstantial to support the heavy traffic of data and observa­tion."

What are your criteria for the choice of teeth to be extracted?

The general guidelines for the majority of clinicians were:

• Four first bicuspids in Class I crowded cases.
• Maxillary first bicuspids and mandibular sec­ond bicuspids in Class II crowded cases.
• Maxillary second bicuspids and mandibular first bicuspids in Class III cases.
• Maxillary first bicuspids in Class II patients with good mandibular archform and maxillary protrusion.

A few orthodontists felt that extractions would increase post-treatment stability, and that the removal of one incisor might be the best way to achieve acceptable anterior arch alignment, especially in adults. Some individual comments:

• "I would extract a second bicuspid with a large amalgam in lieu of a perfectly good first bicus­pid."
• "I believe no tooth is sacred. At one time or another I have probably ordered the extraction of every tooth in the dental arch. It all depends on the demands of the case. This is especially true with adult orthodontics, where accepted tooth­ removing formulas may not be in the best inter­est of the patient."

Do you ever extract second molars, and, if so, how do you proceed?

Two-thirds of the respondents indicated that they never extracted second molars. The re­mainder of the respondents did so "rarely" or "infrequently". These clinicians said they removed second molars when they were impact­ed, had large restorations of doubtful longevity, or were periodontally involved.

About one-quarter of those who extracted second molars did so only in the maxillary arch, for the purpose of distalizing the first molars into the created space using compressed-coil springs or headgear. A frequently mentioned criterion was the presence of acceptable third molars that could be identified on radiograph or had actually erupted in older patients. Comments of interest were:

• "Occasionally I extract second molars if they are impacted, decayed, or malformed, or if there is no opposing tooth and it's supererupted."
• "I extract maxillary second molars only, and infrequently. I do this in instances where there is a mild Class II with moderate overjet, there is lit­tle remaining mandibular growth, and the upper third molars are in good position."
• "I have extracted second molars, and always with apprehension--lots and lots of apprehen­sion."

When and why would you extract only second bicuspids?

Most clinicians gave multiple reasons for extracting second bicuspids, the most prevalent being mild-to-moderate lower crowding coupled with mild-to-moderate protrusion. Other purpos­es were as an aid in correcting an open bite or a Class II molar relationship, or as an alternative treatment plan for the uncooperative patient. The majority of respondents extracted mandibular second bicuspids in Class I and II cases, while maxillary second bicuspids were generally removed in Class III cases to obtain an accept­able molar shift into a Class I relationship.

Do you believe in the extraction of third molar tooth buds? If so, how do you decide, and if not, what are your main objections to enucleating third molar buds?

More than 80% of the respondents did not endorse the extraction of third molar tooth buds, and of those who did, it was only on a selective basis. In these cases, the clinicians believed they would eventually cause more severe problems than simple impaction--for example, the third molars were going to develop on top of the sec­ond molars or could impact the second molars.

The most common objection to removing third molar tooth buds was that there is no way to predict the eventual fate of the buds, so why try to second-guess the dentoalveolar development process? Closely following this was a concern about submitting a young patient to a potentially traumatic surgical procedure.

A few clinicians preferred to wait until there was some definite root development of the third molars prior to extraction, and several men­tioned the lack of supporting data for the proce­dure. Some individual comments were:

• "Third molar enucleation is usually performed quite early, and not all third molars are a prob­lem. In some cases third molars can provide an additional "ace in the hole" if posterior teeth are lost due to trauma, caries, or periodontal prob­lems."
• "When I ordered enucleation of third molar buds, I observed too many dental cysts or bits of teeth forming in the removal sites. I believe this resulted from inadequate enucleation. I don't do this any more."

Do third molars contribute to mandibular anteri­or crowding?

Nearly three-fourths of the clinicians did not believe this to be so, but many of them com­mented that third molars were just one of many factors that contribute to lower anterior crowd­ing. About 20% thought third molars did con­tribute to anterior crowding, and the remainder said they didn't know. Again, many respondents noted that there is no definitive data to substanti­ate the relationship of third molars to mandibular anterior crowding. Interesting replies included:

• "It's possible for third molars to play a part in lower anterior crowding. However, this can be used as a convenient excuse for the faulty mechanics that was the real reason for post-treat­ment incisor relapse."
• "I still believe they do contribute, in spite of the lack of supportive data."

If you start treatment before the eruption of the second molars, do you strap them up later?

Seventy percent of the respondents said they banded or bonded the second molars before finishing a case. Of these, however, 62% did so on an "as needed" basis. Many clinicians indi­cated that they were more likely to band or bond mandibular second molars than maxillary second molars. One comment was:

• "I have heard it said that good orthodontists always strap up the second molars. I don't think that's true. I believe good orthodontists strap up second molars when they need to be strapped up."

JCO would like to thank the following contributors to this month's column:
Dr. Michael D. Adkins, Jasper, IN
Dr. John P. Anderson, Atascadero, CA
Drs. R. Scott Anderson and Richard H. Portalupi, Vacaville, CA
Dr. Kevin J. Andrews, Sparks, NV
Dr. Lisa Angelici, Huntington Beach, CA
Drs. James G. Barrer and Warne H. White, West Reading, PA
Dr. William Barton, San Diego, CA
Drs. Paul J. Batastini, Paul F. Batastini, and Frank R. Batastini, Cherry Hill, NJ
Drs. Raymond T. Bedette and Robert DeWitt, Auburn, ME
Dr. Bartley H. Benson, Hermitage, TN
Drs. Jackie Berkowitz and Ewa Byczek, Columbus, OH
Dr. Steven P. Billings, Parkville, MO
Dr. Joel F. Brodsky, Lakewood, CA
Dr. D. Gregory Brooks, Dunn, NC
Dr. Robert D. Callahan, Camillus, NY
Dr. George M. Ciavola, Rutland, VT
Dr. Dennis B. Claridge, Lincoln, NE
Drs. Stanley S. Conner and Albert J. Apicella, Mechanicsburg, PA
Dr. William E. DeVries, Jenison, MI
Dr. Dawes Edwards, Orangeburg, SC
Dr. Joel Elfman, Voorhees, NJ
Dr. Richard A. Farmer, Liberal, KS
Dr. John T. Forrester, Aberdeen, WA
Dr. Myron D. Guymon, Logan, UT
Dr. William E. Harrell, Jr., Alexander City, AL
Dr. Paul C. Hermanson, Marshalltown, IA
Drs. James R. Hugg and Teresa Salino-Hugg, Burlington, IA
Dr. Greg Jorgensen, Rio Rancho, NM
Dr. Michael G. Kelley, Indianapolis, IN
Dr. William R. Koplin, Franklin, MA
Dr. Matthew F. Linaker, Tucson, AZ
Dr. John T. Lockard, Broken Arrow, OK
Dr. Hector R. Maldonado, Metairie, LA
Dr. David E. Massignan, Bay City, MI
Dr. Christopher J. Matthews, Grants Pass, OR
Dr. James R. Mayfield, Bremerton, WA
Dr. Kathleen R. McDermott, Sugar Land, TX
Dr. Robert Merrill, East Wenatchee, WA
Dr. Donald E. Mills, San Antonio, TX
Dr. Robert B. Moss, Jr., Albany, GA
Dr. Michael L. Ovens, Phoenix, AZ
Dr. Carlyn S. Phucas, Marlton, NJ
Dr. Timothy D. Poppell, Orange City, FL
Dr. Robert H. Rappaport, Longmeadow, MA
Dr. Neil D. Ross, Los Altos, CA
Dr. David M. Schneeweiss, Wesley Hills, NY
Dr. Jesse N. Schroeder, Colleyville, TX
Dr. James A. Sciaretta, Billerica, MA
Dr. Chester E. Spencer, Jr., Grand Prairie, TX
Dr. Michael G. Steinberg, Millburn, NJ
Dr. Goodwin G. Thomas, Jr., Rock Hill, SC
Drs. Don J. Thompson, Jeffrey J. Thompson, and Douglas J. Thompson, Overland Park, KS