Occlusal contacts with different retention procedures in 1-year follow-up period

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Occlusal contacts with different retention procedures in 1-year follow-up period
  ORIGINAL ARTICLE Occlusal contacts with different retentionprocedures in 1-year follow-up period Faruk Ayhan Bas¸çiftçi, a Tancan Uysal, b Zafer Sari, a and Ozgur Inan c Konya and Kayseri, Turkey Introduction:  The aim of this follow-up study was to evaluate the number of contacts in centric occlusionduring a 1-year retention period in patients treated with 2 retention procedures and in a control sample. Methods:  Twenty patients received modified wraparound Hawley retainers, and 20 received maxillaryJensen plates with mandibular fixed retainers. These retention patients were compared with a control groupof 20 subjects with normal occlusions. Silicone-based impression bites were used to record occlusalcontacts. Paired and independent-sample  t   tests were used to evaluate intragroup and intergroupdifferences. Results: Contacts increased in the total arch and the posterior combined (actual/near) during theretention period compared with the control group. In the Hawley retainer group, actual contacts on thesecond molars (  P   .05), near contacts on the premolars (  P   .05), and total contacts on the first molars(  P   .05) and premolars (  P   .01) had statistically significant increases. In the maxillary Jensen plate andmandibular fixed lingual retainer group, the number of actual contacts on the posterior segment increased. Actual contacts on the first molars (  P   .01), second molars (  P   .01), premolars (  P   .05), and canines(  P   .05), and total contacts on the first (  P   .05) and second (  P   .05) molars had statistically significantincreases. During the observation period, some slight occlusal changes were seen in the control sample,presumably from growth and development. At the end of the study, during the 1-year follow-up period, nostatistically significant occlusal contact differences were observed in the 3 groups.  Conclusions:  Retentionprocedures carried out in this study allowed relative vertical movement of the posterior teeth. (Am J OrthodDentofacial Orthop 2007;131:357-62) T he occlusal table that is reestablished by orth-odontic treatment might be related to the healthof the temporomandibular joint and the masti-catory muscles, 1  and also could play a significant rolein the stability of the orthodontic treatment. 2  Relativemovements in the vertical direction of the posteriorteeth after orthodontic repositioning are called settling.With settling, the number of occlusal contacts in-creases, improving the fit of the teeth during retention. 3 The best retention device would be one that allowssettling but prevents relapse. The retainer provides, atleast, a safety margin and reduces the tendency towardrelapse when it is most likely for deterioration of theattained correction to occur.Maximizing tooth contacts in centric occlusionminimizes the stresses on the teeth and periodontaltissues; ideally located centric contacts cause verticallydirected forces parallel to the long axes of the teeth. 4 For that reason, occlusal therapy can be an importantadjunct in the treatment of periodontal disease. 5,6  Thus,more ideal occlusal contacts are important factors forthe maintenance of healthy periodontal status.Begg and Kesling 7  suggested that intercuspal rela-tionships are essential for coordinated facial growth andguided eruption of the permanent dentition. Ostyn et al 8 indicated that interdigitation plays a significant role inthe control of anteroposterior and vertical facialgrowth, and is an important factor in jaw relation-ships. It was suggested that good occlusal contacts andintercuspation might be the keys to stable orthodonticresults. 9,10 Commonly prescribed retainers include Hawley,wraparound, fixed, clear overlay, and tooth position-ers. 3  Their designs differ, particularly in the extent of retainer-tooth contacts. For example, the Hawley re-tainer fits against the lingual surfaces and, in somecases, the labial surfaces of the teeth, whereas the clearoverlay retainer covers most coronal surfaces. Lingualor palatal fixed retainers are generally bonded toanterior teeth and cover no surfaces of the posterior a Associate professor, Department of Orthodontics, Faculty of Dentistry, Selcuk University, Konya, Turkey. b Associate professor and chair, Department of Orthodontics, Faculty of Dentistry, Erciyes University, Kayseri, Turkey. c Professor, Department of Prosthodontics, Faculty of Dentistry, Selcuk Uni-versity, Konya, Turkey.This project was supported by Selcuk University Scientific Research ProjectCoordination.Reprint requests to: Tancan Uysal, Erciyes Universitesi Dis Hekimligi Fakul-tesi, Ortodonti A. D., Melikgazi, 38039, Kampüs, Kayseri, Turkey; e-mail,tancanuysal@yahoo.com.Submitted, December 2004; revised and accepted, May 2005.0889-5406/$32.00Copyright © 2007 by the American Association of Orthodontists.doi:10.1016/j.ajodo.2005.05.052 357  teeth. Because of these differences in retainer design,characteristic changes in tooth position with their usecan be expected in the retention phase.We found few studies in a review of the literaturethat evaluated changes in tooth contacts after orthodon-tic treatment with various retention devices, and mostcompared conventional retainers with tooth positionersor clear overlay retainers. 3,11-13  Unfortunately, the ef-fectiveness of fixed retainers combined with upperretention plates compared with Hawley retainers wasnot adequately documented. Therefore, our aim in thisfollow-up study was to evaluate the number of contactsin centric occlusion during the 12-month retentionperiod with 2 retention procedures and compare themwith a control sample. MATERIAL AND METHODS After full orthodontic treatment, 40 patients fromthe postgraduate orthodontic clinic at Selcuk Universityin Konya, Turkey, and 20 subjects with normal occlu-sions who did not receive orthodontic treatment wereincluded in the study.The following patient selection and rejection crite-ria were taken from Durbin and Sadowsky. 13  Thepatients were treated with fixed banded or bondededgewise appliances with or without auxiliary appli-ances. They must have been treated to an optimumocclusion with the treatment objectives satisfied, usu-ally involving overcorrection; patients whose treatmentwas discontinued before completion because of poorcompliance were not included. Patients requiring pros-thetic treatment of missing teeth were not included, andthey had to be available at the 12-month follow-up.A control group was formed of graduate dentistrystudents with normal occlusions, all teeth present ex-cept third molars, no history of orthodontic or prosth-odontic treatment, and no symptoms of temporomandib-ular joint disorders. Criteria for enrollment in this studywere informed consent and willingness to participatebefore occlusal records were taken. Their mean age was16 years with a standard deviation of 3 years 1 month.Twenty patients (9 male, 11 female) received max-illary and mandibular wraparound modified Hawleyretainers (Fig 1), and 20 patients (5 male, 15 female) received maxillary Jensen plates (Fig 2) with mandib- ular canine-to-canine fixed lingual retainers. All pa-tients had been in orthodontic treatment for at least 15months.Some clinicians in the postgraduate clinic preferredone or the other retention procedure. For that reason,the study groups were organized and assigned to the 2retention groups.In the maxillary and mandibular Hawley retainergroup (group 1), 11 patients had Class I malocclusions,7 had Class II Division 1 malocclusions, and 2 hadClass III malocclusions before treatment. This sample Fig 1.  Maxillary and mandibular modified wraparoundHawley retainers (removable palatal plate incorporates Adams clasps on first molars and continuous outer bowwith adjustment loops from molar to molar fixed on Adams clasps). Fig 2.  Maxillary Jensen plate (removable palatal plateincorporates C clasps on second molars and charac-teristic outer bow between lateral incisors).  American Journal of Orthodontics and Dentofacial Orthopedics March 2007  358  Bas¸çiftçi et al  included 5 patients who had 4 first premolar extrac-tions, 14 patients treated without extractions, and 1patient with congenitally missing maxillary lateral in-cisors. Their mean age was 15 years 3 months with astandard deviation of 2 years 2 months.In the maxillary Jensen plate and mandibular fixedlingual retainer group (group 2), 9 patients had Class Imalocclusions, 7 had Class II Division 1 malocclusions,and 4 had Class III malocclusions before treatment.This sample included 4 patients with 4 first premolarextractions and 16 patients treated without extractions.Their mean age was 16 years 1 month with a standarddeviation of 3 years 4 months.Patients in both groups were instructed to wear theirretainers full time, except during meals, for 6 monthsand only at night for the next 6 months.Occlusal records were gathered from all patientsand the control sample at 2 time points. In groups 1 and2, the first records were gathered within 2 hours afterremoval of the orthodontic appliances (T1); the secondset was obtained during the retention period approxi-mately 14 months (   1.5 month) later (T2). In thecontrol sample, 2 sets of occlusal records wereobtained approximately 12 months (   1.5 month)apart.Occlusal records were taken by a method similar tothat described by Razdolsky et al. 5  The records in-cluded alginate impressions for study models to evalu-ate the occlusal contacts. After the removal of fixedappliances, the occlusal records were taken with Zeta-plus (Zhermack, Badia Polesine, Italy), a soft silicone-based impression material. With the patient seatedupright in the dental chair, impression material wasinjected onto the occlusal surfaces of all mandibularteeth, and the patient was asked to bite the materialfirmly with the back teeth for approximately 1 minute.Fifteen minutes later, the procedure was carried outagain to compare with the first registration for repro-ducibility. Two registrations of patients appeared sim-ilar, so we had no need to taken third registrations.The interocclusal registration was viewed by hold-ing it to the light box; perforations in the interocclusalregistrations that let the light through were identified asactual contacts, and very thin transparent sectionswithout perforations were recorded as near contacts.After we scored these contacts, they were transferred tothe maxillary model. The midpoints of the near-contactareas were transferred to the study models with amarker.The following variables were recorded from themaxillary and mandibular study models at each of the 2time points: total number of contacts (actual and nearcontacts combined); number of actual contacts onsecond molars, first molars, premolars, canines, andincisors; and number of near contacts on second mo-lars, first molars, premolars, canines, and incisors.Unchanged contacts were not used in the statisticalevaluation. Because the first premolars had been ex-tracted in some patients in the experimental groups,first premolar contacts were not considered in thenonextraction patients and the control group.All statistical analyses were performed with asoftware package (SPSS for Windows, version 10.0.1,SPSS, Chicago, Ill). The distributions of occlusal con-tact areas and model measurements were first analyzedfor skewness and kurtosis. Because the data werenormally distributed, means and standard deviationswere used for descriptions; paired  t   tests were used toassess differences between the means at T1 and T2. Tocompare the changes in the subgroups, an independent-sample  t   test was performed. The level of significancefor measurements was set at  P   .05 and for otheranalyses at  P   .003 because of the Bonferroniadjustment.For 10 randomly selected patients, the 2 similarocclusal registrations obtained at the clinical examina-tion were analyzed to determine methodological error.A paired  t   test analysis was also used and showed nostatistically significant differences in the mean numberof contacts recorded by using the 2 sets of occlusalregistrations. RESULTS Table I shows the changes in the mean numbers of combined (actual and near) contacts of the 3 groups onthe anterior, posterior, and total segments.In group 1, the mean number of combined contactsincreased from 13.93 to 17.09; this was statistically Table I . Changes in mean numbers of combined (actualand near) contacts in anterior, posterior, and totalsegments Combined contacts T1 T2 DifferencePaired samples t  test  Group 1 Total 13.93 17.09 3.16 *(n  20) Posterior 10.93 13.95 3.02 *Anterior 3.00 3.14 0.14 NSGroup 2 Total 12.36 16.52 4.16 † (n  20) Posterior 10.64 14.21 3.57 † Anterior 1.71 2.30 0.59 NSControl group Total 38.40 39.87 1.47 NS(n  20) Posterior 31.65 33.10 1.45 NSAnterior 6.75 6.77 0.02 NST1, After treatment; T2, after retention.  NS,  Not significant; * P  .05; † P  .01.  American Journal of Orthodontics and Dentofacial OrthopedicsVolume  131,  Number   3  Bas¸çiftçi et al  359  significant ( P   .05). The number of teeth in contactincreased by an average of 3.02 in the posterior( P  .05) and 0.14 in the anterior ( P  .05) segments.In group 2, the mean number of combined contactsincreased by an average of 4.16 ( P   .01). The meannumbers of posterior ( P   .01) and anterior ( P   .05)contacts increased from 10.64 to 14.21 and from 1.71 to2.30, respectively.The increased occurrence of combined contacts onthe anterior, posterior, and total segments of the controlsample was not statistically significant.Table II shows the means, differences, and statisti-cal comparisons of all investigated teeth during reten-tion in group 1. Actual contacts on the second molars( P  .05), near contacts on the premolars ( P  .05), andtotal contacts on the first molars ( P  .05) and premo-lars ( P  .01) showed statistically significant increases.No other variables in this group had statistically signif-icant changes.In group 2, actual contacts on the first molars ( P  .01),second molars ( P  .01), premolars ( P  .05), and canines( P   .05), and total contacts on the first ( P   .05) andsecond ( P  .05) molars had increases that were statis-tically significant (Table II). No statistically significant changes were observed on near contacts.In the control group, no statistically significantdifferences were found in the anterior, posterior, andtotal segments during the observation period (Table II).According to the independent-samples  t   test, nostatistically significant differences were found in totalcontacts of anterior and posterior teeth in the groupstested (Table II). Similarly, no statistically significant differences were found in actual and near contacts of allteeth. DISCUSSION There have been few studies on the number of occlusal contacts after active orthodontic treatment. Inprevious reports, investigators compared Hawley re-tainers, clear overlay retainers, and tooth positioners byanalyzing dental casts at debonding and after retentionperiods. 3,11-13  Unfortunately, the effectiveness of fixedretainers used in at least 1 arch compared with conven-tional maxillary and mandibular Hawley retainers wasnot sufficiently reported. Therefore, this study has notbeen carried out to evaluate the number of contacts incentric occlusion during the retention period withseveral retention procedures and compare them with thecontrol sample.Berry and Singh 14  reported variations in occlusalcontacts in the morning compared with the evening.Because of the diurnal variations in occlusal contacts, 14 and to standardize the procedure, the patients’ occlusalrecords were taken only during the afternoon in thatstudy. Similarly with Sauget et al, 3  we believe that ourresults are reliable because of the minimal number of confounders. Groups 1 and 2 were matched favorablyfor size, age, Angle classification, and number of patients with teeth extracted.Diagnosis of the interarch occlusal relationship Table II . Pre- and postretention mean values and standard deviations of occlusal contacts for each tooth in each groupand results of statistical comparisons Group 1 (n  20) Group 2 (n  20)OcclusalcontactsT1 T2 Difference(T2-T1)Paired samples t  test   P  valueT1 T2 Difference(T2-T1)Paired samples t  test   P  valuen  60 Mean SD Mean SD Mean SD Mean SD Second molar Actual 2.00 1.62 2.79 1.85 0.79 .043* 2.00 1.47 3.07 1.14 1.07 .008 † Near 1.07 1.21 1.21 1.12 0.14 NS 1.14 1.17 1.57 0.76 0.43 NSTotal 3.07 2.06 4.00 2.72 0.93 NS 3.14 1.56 4.64 1.22 1.50 .001 † First molar Actual 2.86 1.51 3.42 1.28 0.56 NS 2.14 1.29 2.93 1.27 0.79 .001 † Near 1.29 1.07 1.93 1.21 0.64 NS 1.57 1.02 2.07 1.07 0.50 NSTotal 4.14 1.88 5.35 1.91 1.21 .015* 3.71 1.94 5.00 1.66 1.29 .002 † Premolar Actual 2.50 1.61 2.60 1.65 0.10 NS 1.86 1.51 2.71 1.59 0.86 .047*Near 1.21 0.98 2.00 1.11 0.79 .010* 1.93 1.07 1.86 1.17 –0.07 NSTotal 3.71 1.59 4.60 2.02 0.89 .009 † 3.79 1.85 4.57 2.31 0.79 NSCanine Actual 0.93 1.00 0.85 1.03   0.08 NS 0.14 0.36 0.43 0.65 0.29 .040*Near 0.64 0.50 0.50 0.65   0.14 NS 1.07 0.73 1.07 0.62 0.00 NSTotal 1.57 0.85 1.35 1.08   0.22 NS 1.21 0.89 1.50 1.02 0.29 NSIncisor Actual 0.21 0.43 0.50 0.65 0.29 NS 0.14 0.13 0.16 0.27 0.02 NSNear 1.21 1.25 1.29 1.14 0.07 NS 0.36 0.63 0.64 0.93 0.29 NSTotal 1.43 1.22 1.79 1.25 0.36 NS 0.50 0.63 0.80 1.07 0.30 NST1, After treatment; T2, after retention.  NS,  Not significant; * P  .05; † P  .01.  American Journal of Orthodontics and Dentofacial Orthopedics March 2007  360  Bas¸çiftçi et al  intraorally or on a study model does not properly showthe numbers and the locations of occlusal contacts. Ourtechnique for recording occlusal contacts was highlyreproducible, and it was shown to be reliable inprevious studies. 5,11,13 The total mean numbers of contacts after activeorthodontic treatment were 13.93 in group 1 and 12.36in group 2; these values were much less than that of thecontrol group (38.40). After the 1-year retention period,slight increases were observed in both patient groups.This increase was significant and entirely due to thedevelopment of more contacts in the posterior segments(premolars and molars). Increases in posterior contactssupport previous studies. It was also reported byRazdolsky et al 5  that relative vertical movements cancontinue up to 21 months.Studies showed that overbite has a tendency toincrease after treatment and might result in increasedanterior occlusal contacts. 15,16  Durbin and Sadowsky 13 indicated that anterior contacts did not increase overtime, but this could have been caused by incompleteClass II correction resulting in excessive overjets or byfactors related to retainer interferences. Anterior occlu-sal contact findings in our study are similar to those of Durbin and Sadowsky, 13  and the development of con-tacts in the incisors and canines was not statisticallysignificant. This result supports the idea that an idealocclusion has 0.0005-in near contacts between theincisors in centric relation. 17 Dincer et al 12  stated that the number of actualcontacts was greater than the number of near contacts atthe end of retention. They thought that this could be theresult of continued mobility of the teeth during reten-tion and eruption of teeth that was possible because of the Hawley device. Sauget et al 3  found statisticallysignificant increases in the number of total contactsafter 3 months of retention with Hawley retainers.Haydar et al 11  found statistically significant increases inactual contacts only on the second premolars after a3-month retention period. In our study, actual contactson the second molars; near contacts on the premolars,and total contacts on the first molars and premolars hadstatistically significant increases in the Hawley retainergroup. These results were greater than the findings of Haydar et al, 11  and this was presumably the result of our longer follow-up period.In the literature, we did not find any study aboutpatients’ occlusal changes during retention with fixedlingual retainers. In accordance with the results of Dincer et al 12  with the Hawley retainer, we found moreactual contacts than near contacts after retention in thisgroup. Actual contacts on the first molars, secondmolars, premolars, and canines, and total contacts onthe first and second molars showed statistically signif-icant increases in group 2. The labial wire of the Jensenplate passed through the distal margin of the lateralincisors. The labial wire could not hold the canines, andthus the actual contacts of the canines increased signif-icantly.In an ideal occlusion, Ricketts 18  found 48 occlusal Table II . Continued Control group (n  20) Independent samples  t  test   P  valueT1 T2 Difference(T2-T1)Paired samples t  test   P  valueGroup 1 vsgroup 2 (T2-T1)Group 1 vscontrol (T2-T1)Group 2 vscontrol (T2-T1) Mean SD Mean SD 5.40 1.42 5.10 1.25   0.30 NS NS NS NS5.00 1.80 6.10 2.01 1.10 NS NS NS NS10.40 2.20 11.20 1.67 0.80 NS NS NS NS6.30 3.10 6.00 0.54   0.30 NS NS NS NS5.80 1.34 6.20 0.96 0.40 NS NS NS NS12.10 1.54 12.20 1.78 0.10 NS NS NS NS4.75 2.10 5.20 2.08 0.45 NS NS NS NS4.40 1.76 4.50 2.10 0.10 NS NS NS NS9.15 1.62 9.70 1.76 0.55 NS NS NS NS1.50 1.22 1.00 1.99   0.50 NS NS NS NS2.05 0.56 1.90 1.05   0.15 NS NS NS NS3.55 2.10 2.90 1.49   0.65 NS NS NS NS1.00 0.88 1.30 2.00 0.30 NS NS NS NS2.20 0.43 2.57 2.12 0.37 NS NS NS NS3.20 1.65 3.87 0.43 0.67 NS NS NS NS  American Journal of Orthodontics and Dentofacial OrthopedicsVolume  131,  Number   3  Bas¸çiftçi et al  361
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