ORIGINAL ARTICLE Relapse of anterior crowding in patients treated with extraction and nonextraction of premolars Aslıhan Ertan Erdinc,a Ram S. Nanda,b and Erdal Is¸ ıksalc Izmir, Turkey, and Oklahoma City, Okla Introduction: The purpose of this study was to evaluate long-term stability of incisor crowding in orthodontic patients treated with and without premolar extractions. Methods: Dental casts and cephalometric records of 98 patients were evaluated before treatment (T1), at posttreatment (T2), and at postretention (T3). Half of the patients had been treated with extractions, and half were treated nonextraction. Results: Irregularity, as measured by the irregularity index, decreased 5.51 mm in the extraction group and 2.38 mm in the nonextraction group. Mandibular incisor irregularity increased 0.97 mm in the extraction group and 0.99 mm in the nonextraction group, respectively, in the postretention period. Maxillary incisor irregularity relapse was smaller than mandibular incisor relapse for both groups. Intercanine width expanded during treatment. At T3, mandibular intercanine width decreased in both groups, but the differences were not statistically significant. At T3, intermolar width was stable, arch depth decreased, overbite and overjet slightly increased, SN mandibular plane angle decreased, and incisor positions in both groups tended to return to T1 values. Clinically acceptable stability was obtained. Conclusions: With the exception of the interincisal angle, no statistically significant differences were recorded between the extraction and nonextraction groups from T2 to T3. No statistically significant correlations were found between any variables studied and mandibular incisor irregularity at T1, T2, and T3. (Am J Orthod Dentofacial Orthop 2006;129:775-84) major goal of orthodontic treatment is to arises as to which treatment procedure is most helpful achieve long-term stability of posttreatment in achieving long-term stability. Aocclusion. Several investigators have evaluated Previous long-term studies on relapse of anterior treatment results and long-term posttreatment stability of crowding have most often evaluated patients treated orthodonticallytreatedmalocclusions.1-5Thestabilityof withextractions.2,3,7-11Differentresultsmightbeseen aligned teeth is variable and largely unpredictable. This in the relapse patterns of patients treated without variability might be due to severity and type of malocclu- extractions12-19orbycomparingextractionandnonex- sion, treatment approach, patient cooperation, or growth tractiongroups.4,20-27 6 andadaptabilityofthehardandsofttissues. Many theories have been proposed and controver- Premolar extraction to permit alignment of crowded sies exist about the cause of relapse. Protrusion and teeth has been an accepted procedure for decades and final position of the mandibular incisors might influ- continues to be a common treatment modality for ence the stability of orthodontic treatment. The pre- patients with crowded arches. However, mandibular treatment position of the mandibular incisors is the best incisors suffer from relapse and crowding despite their guidefortheirlabiolingualpositionofstability.7,28 retraction during extraction treatment. Because of Nance29assertedthatflaringthemandibularincisorsis changing concepts of facial soft-tissue profile esthetics neverasuccessfultreatmenttechnique.Brodie30stud- and late growth changes, the trend in orthodontics has iednonextractionorthodonticpatients,andCole31stud- been toward nonextraction treatment. The question thus ied extraction patients; both concluded that the axial aResearch fellow, Department of Orthodontics, Faculty of Dentistry, University inclination of teeth disturbed by orthodontic treatment of Ege, Izmir, Turkey. tends to return to pretreatment conditions. Weinberg bProfessor and Endowed Chair, Department Orthodontics, University of andSadowsky16reportedthattheprotrusionofman- Oklahoma College of Dentistry, Oklahoma City. cProfessor and chairman, Department Orthodontics, Faculty of Dentistry, dibular incisors can predispose them to relapse. On the University of Ege, Izmir, Turkey. otherhand,Freitasetal19reportedthatfinalmandibular Reprint requests to: Dr Ram S. Nanda, Department of Orthodontics, University incisor inclination and linear protrusion do not influ- of Oklahoma, College of Dentistry, P.O. Box 26901, 1001 Stanton L. Young 32 Blvd, Oklahoma City, OK 73190; e-mail, [email protected]. encecrowdingrelapse.Schulafetal reportedthatthe Submitted, September 2004; revised and accepted, February 2006. mandibular incisor anteroposterior position relative to 0889-5406/$32.00 Copyright © 2006 by the American Association of Orthodontists. various cephalometric values had no relationship to doi:10.1016/j.ajodo.2006.02.022 postretention crowding of mandibular incisors. 775 776 Erdinc, Nanda, and Is¸ıksal American Journal of Orthodontics and Dentofacial Orthopedics June 2006 3 time periods: pretreatment (T1), at the end of active treatment (T2), and at postretention (T3). The group was equally divided into nonextraction and extraction groups. The nonextraction group (n ϭ 49) included 19 males and 30 females, mean ages 14 years 1 month at T1, 16 years 3 months at T2, and 20 years 11 months at T3. The mean treatment time was 1 year 9 months, and the mean postretention time was 4 years 8 months. The extraction group (n ϭ 49) also included 19 males and 30 females, with mean ages of 12 years 11 months at T1, 14 years 8 months at T2, and 19 years 7 months at T3. The mean treatment time was 2 years 2 months, and the mean postretention time was 4 years 11 months. In the extraction group, the maxillary and mandib- ular first premolars were extracted. All patients evalu- ated in this study had pretreatment malocclusions of Angle Class I or Class II Division 1. There were 28 Class I and 21 Class II Division 1 patients in each group. All patients were treated with edgewise mechanics and achieved acceptable posttreatment results, both maxillary and mandibular arches were retained with Hawley retain- Fig 1. Cast measurements. ers; the postretention period was at least 2 years. None of the subjects had congenitally missing permanent teeth or was treated with rapid palatal expansion. Investigators found that the most frequent cause of mandibular incisor instability was expansion of inter- Analysis of dental casts caninewidthduringtreatment.18,23,25Ithasbeenre- Dental casts were measured by 1 investigator ported that stable results can be gained only when (A.E.E.) on the mandibular and maxillary dental casts, mandibularintercaninewidthismaintained.14,25,33Yet to the nearest 0.01 mm with a digital caliper. The it has also been shown that maintenance of the pretreat- following measurements were obtained for each set of ment intercanine distance during treatment does not casts. All measurements were linear. guarantee stability of the mandibular incisors’ align- ment.19,21Arch-lengthdecreaseinthepostretention 1. Incisor irregularity: the sum, in millimeters, of the stagemightcauseincisorcrowding.Kahl-Niekeetal22 5 distances between the anatomic contacts from the andÅrtunetal23reportedthatarch-lengthincreaseis mesial aspect of the left canine through the mesial associated with crowding relapse. aspect of the right canine according to the method Another factor might be that postadolescent growth describedbyLittle.35 of the jaws affects stability and influences orthodontic 2. Canine-canine width: distance between crown tips treatmentresultsoverthelongterm.Sampson34and of the right and left canines. In some cases, this Vadenetal10reportedthatgrowthrotationisgreaterin value could not be measured at T1 because the the mandible than in the maxilla, and that might be a permanentcanineswerenotyeterupted(Fig1,A). factor in the higher incidence of mandibular crowding. In the extraction group, 46 maxillary intercanine Evidence from the literature indicates many vari- widths and 48 mandibular intercanine widths and, ables and conflicting points of view. The intent of this in the nonextraction group, 47 maxillary interca- study was to search for associations between cephalo- nine widths and 49 mandibular intercanine widths metric and dental-cast parameters that might be clini- were measured. In the extraction group, intercanine cally useful predictors of posttreatment alignment of widths of only 4 patients and, in the nonextraction incisors. patients group, intercanine widths of only 2 patients were not measured. MATERIAL AND METHODS 3. First premolar-first premolar width: distance be- The sample consisted of complete records (dental tween the central fossae of the first premolars in casts and cephalometric radiographs) of 98 patients from bothjaws(Fig1,B). American Journal of Orthodontics and Dentofacial Orthopedics Erdinc, Nanda, and Is¸ıksal 777 Volume 129, Number 6 Fig 3. Linear and angular measurements. Fig 2. Cephalometric landmarks. The cephalometric landmarks were 1, porion; 2, 4. Second premolar-second premolar width: distance sella; 3, nasion; 4, orbitale; 5, A-point; 6, M-point; 7, between the central fossae of the second premolars posterior nasal spine; 8, maxillary incisor apex point; 9, inbothjaws(Fig1,C). maxillary incisor tip point; 10, mandibular incisor tip 5. First molar-first molar width: distance between point; 11, mandibular incisor apex point; 12, B-point; the central fossae of the first molars in both jaws 13, pogonion; 14, menton; 15, gonion; and 16, articu- (Fig1,D). lare. 6. Arch depth: perpendicular length from the midpoint MaxillaryPointM,36representingthemidpointof