Long-term occlusal changes and patient satisfaction in patients treated with and without extractions: 37 years after treatment


The objective of this research was to evaluate the treatment outcomes, long-term occlusal changes, and patient satisfaction after 37 years of nonextraction and extraction treatments.


Fifty-seven patients with Class I and Class II malocclusion were divided into 2 groups. Group 1 included 16 patients treated with nonextraction therapy, with mean initial (T1), final (T2), and long-term posttreatment (T3) ages of 13.2, 15.0, and 50.3 years, respectively. Mean treatment time (T2 – T1) and long-term follow-up time (T3 – T2) were 1.8 and 35.2 years, respectively. Group 2 included 41 patients treated with extraction of 4 first premolars, with mean ages at T1, T2, and T3 of 13.3, 15.6, and 53.6 years, respectively. Mean treatment (T2 – T1) and long-term follow-up (T3 – T2) times were 2.3 and 37.9 years, respectively. The Peer Assessment Rating (PAR) index and Objective Grading System (OGS) indexes were evaluated at T1, T2, and T3 stages. The subjects also answered an online questionnaire regarding esthetic and occlusal self-perception at T3. Intergroup comparison was performed with t tests.


The PAR index improved with treatment and similarly worsened at T3 for both groups. OGS scores were close to the passing score at T2 for both groups. The nonextraction group presented worse OGS scores at T3 than the extraction group. Nonextraction patients perceived more changes in alignment over time, but overall satisfaction was similar.


The PAR index improved with treatment, and the PAR and OGS scores showed a significant increase, indicating great occlusal changes in the long-term stage. The nonextraction group showed more occlusal changes and perceived more changes in their alignment over time, but overall patient satisfaction was similar in both groups.


  • Occlusal changes and patient satisfaction were evaluated 37 years after treatment.

  • Results were compared between nonextraction and extraction patients.

  • Nonextraction group showed more long-term occlusal changes 37 years after treatment.

  • Patient satisfaction was similar for both groups.

If dental professionals were asked about their orthodontic treatment goals, they might mention pleasant smiles, good occlusal function, and mainly stability of the results obtained over the years. Long-term stability of orthodontic treatment has been extensively studied and difficult to predict.

Dental occlusion is dynamic. Changes will occur regardless of the technique, appliance, and treatment protocol used. These changes can be desired by the orthodontist, called “settling of the occlusion,” or not, causing great discomfort for the clinician and the patient, the much-feared “relapse.” It is of paramount importance to determine if some traits of the orthodontic treatment might improve or worsen over time.

It is also important to highlight that relapse is defined as the return of teeth to a pretreatment position. However, long-term changes in occlusal features are also observed in untreated subjects. , A recent study compared long-term occlusal changes between treated and untreated patients and found that some long-term changes are similar in both treated and untreated patients, but changes in teeth alignment are greater in orthodontically treated patients. Therefore, it is very difficult to distinguish the relapse to the maturational changes of aging of the occlusion.

The evaluation of orthodontic treatment outcomes for a long time was subjective, so in this context, the orthodontist’s experience determined the success or failure of orthodontic treatment. The ideal parameter for orthodontic treatment finishing was based on the 6 keys to normal occlusion. The use of objective criteria is essential to quantify and measure the severity of malocclusions uniformly, the efficacy of different treatment modalities as well to assess the relapse of orthodontic treatments. Attempts have been made recently to evaluate treatments more objectively, allowing clinicians worldwide to speak the same language regarding the orthodontic treatment outcomes. In this context, the Peer Assessment Rating (PAR) index and the American Board of Orthodontics (ABO) Objective Grading System (OGS) are 2 of the most used indexes to evaluate treatment outcomes and stability.

The PAR index was developed to measure treatment outcomes in orthodontics, , and its validity was improved by weighting the scores of some components to reflect their relative importance. It evaluates tooth alignment, dental impaction, relationships of the buccal segments, overjet, overbite, and midline discrepancies. The greater the mean percentage reduction in the PAR score, the greater the finishing achieved by the orthodontic treatment.

More recently, to assess the adequacy of finished orthodontic results, ABO developed a model grading system (OGS) as an occlusal index to evaluate posttreatment dental casts. It assesses the final occlusion according to 8 different occlusal components: alignment, marginal ridges, buccolingual inclination, occlusal relationships, occlusal contacts, overjet, interproximal contacts, and root angulation. A metal gauge commercialized by the ABO is used for the measurements.

Although treatments with teeth extraction have declined in recent years, a controversy still exists regarding differences in treatment outcomes and long-term changes when patients treated with and without extractions are evaluated. Long-term posttreatment changes of patients treated with and without extraction are variable and unpredictable. , There is a lack in the orthodontic literature regarding long-term occlusal changes between treatments performed nonextraction and with extractions and patient satisfaction over time.

It was previously demonstrated extensively in the orthodontic literature that the great majority of the long-term studies is focused on the functional and esthetic parameters and some degree of deviations from the normal. Recently, researches changed their focus toward the patient perspective of the orthodontic treatment, and their correlated satisfaction and quality of life. Studies show that orthodontic treatment promotes greater psycho-emotional and social benefits. , AlQurani et al found that orthodontic treatment in adolescents, in addition to promoting health-related behavioral change, dental health, and psychosocial effects, leads to an improvement in self-confidence, self-esteem, social interactions, and social acceptance, therefore supporting the quality of life benefits of orthodontic treatment. However, there are no known studies that evaluate patient satisfaction regarding orthodontic treatment more than 35 years after retention.

The objective of this study was to evaluate the outcomes and the long-term occlusal changes in patients treated with and without extractions using the PAR and the OGS indexes, as well as long-term patient satisfaction.

Material and methods

This retrospective study was approved by the Ethics Research Committee of Bauru Dental School, University of São Paulo, Bauru, SP, Brazil (protocol no. 71629217.5.0000.5417; decision no. 2.268.347), and all subjects signed informed consent forms.

The sample size calculation was based on an alpha significance level of 5% and a beta of 20% to achieve 80% test power to detect a minimum difference of 1.5, with a standard deviation of 1.4, for the alignment component of the OGS. Thus, the sample size calculation indicated that at least 15 subjects were needed per group.

The retrospective sample was obtained from files at the Orthodontic Department at Bauru Dental School, University of São Paulo, from May 2017 to June 2019. The subjects were recalled, and dental casts and radiographs were obtained (T3).

The inclusion criteria were the following: (1) Class I or Class II malocclusion at the beginning of orthodontic treatment; (2) treatment protocol of nonextraction or with the extraction of 4 first premolars; (3) complete orthodontic treatment with full maxillary and mandibular fixed edgewise appliance (0.022 × 0.028-inch slot); (4) all permanent teeth up to the first molars erupted before the beginning of treatment; (5) no tooth agenesis or anomalies; and (6) maxillary removable appliance (Hawley plate) worn for 1 year, mandibular fixed canine-to-canine retainers worn for at least 1 year, and a maximum of 3 years after treatment, without retention at the time of follow-up.

The sample comprised 57 patients with Class I and Class II malocclusion treated with nonextraction orthodontic therapy or extraction of 4 first premolars. Dental casts and panoramic radiographs were evaluated, obtained at 3 different time points: pretreatment (T1), posttreatment (T2), and long-term follow-up (T3; an average of 37 years after treatment).

The sample was divided into 2 groups. Group 1 comprised 16 subjects (10 girls, 6 boys) who received nonextraction orthodontic treatment. Six patients presented Class I malocclusion, and 10 presented Class II malocclusions. The mean T1 age was 13.1 years (standard deviation [SD], 0.8), mean treatment time (T2 – T1) was 1.8 years (SD, 0.8), and mean long-term follow-up evaluation time (T3 – T2) was 35.2 years (SD, 6.1).

Group 2 comprised 41 subjects (26 girls, 25 boys) treated with extraction of 4 first premolars. Twenty-three presented Class I malocclusion, and 18 presented Class II malocclusion. The mean T1 age was 13.3 years (SD, 1.9), mean treatment time (T2 – T1) was 2.3 years (SD, 0.5), and long-term follow-up evaluation time (T3 – T2) was 37.9 years (SD, 4.5).

Figures 1 and 2 show the dental casts of the 3 stages (T1, T2, and T3) for a nonextraction and an extraction case presenting long-term occlusal changes.

Fig 1
Nonextraction case from pretreatment to 39 years after treatment.

Fig 2
Extraction case from pretreatment to 41 years after treatment.

The PAR index , was developed to record the malocclusion at any stage of treatment. The individual scores are summed to obtain an overall total, representing the degree to which a case deviates from normal alignment and occlusion. The dental arch is divided into 3 recording segments: left buccal, right buccal, and anterior. The following occlusal features are evaluated in both arches: buccal occlusion on the right and left sides (anteroposterior relationship, vertical, and transverse), overjet, overbite, crowding, spacing, impacted teeth and centerline. A score of 0 means that a perfect occlusion was reached; a score from 1 to 9 indicates that good dental relationships are present; a score >10 indicates the presence of a residual malocclusion; and a score >40 indicates severe malocclusion. The American PAR weighting was used; it eliminates mandibular anterior alignment. The weightings were as follows: 5 for overjet, 3 for overbite and midline discrepancy, 2 for buccal occlusion, and 1 for maxillary anterior alignment. The measurements were performed with the PAR ruler and a digital caliper (Mitutoyo America, Aurora, Ill) ( Fig 3 ).

Fig 3
PAR ruler (in the top of the dental cast) and digital caliper (right side).

The OGS was developed by the ABO to evaluate the quality of orthodontically treated occlusions. The ABO OGS contains 8 criteria: alignment, marginal ridges, buccolingual inclination, occlusal relationships, occlusal contacts, overjet, interproximal contacts, and root angulation that are evaluated using dental casts. A specific metal gauge is used to perform the measurements (ABO measuring gauge, St Louis, Mo). A score of 0 indicates ideal alignment and occlusion, whereas scores of 1 and 2 show deviations from the normal. The score for each patient indicates the relative deviations from the ideal score. The final calculation is made by adding the points award for each of the categories. The critical score for the ABO clinical examination is 30. Because OGS is used to evaluate treatment outcomes, T2, T3, and the difference between the long-term posttreatment stage and the final stage (T3 − T2) were evaluated.

All measurements were performed by 1 calibrated and blinded examiner (P.C.).

The satisfaction questionnaire was sent by WhatsApp and allowed for comments in certain occlusal traits ( Fig 4 ). Issues addressed were scored about the patients’ teeth and smile at the follow-up stage. To those who did not respond promptly, new messages were resent after 24 and 36 hours. Answers were recorded and compared.

Fig 4
Satisfaction questionnaire.

A month after the first measurement, 30% of the sample was randomly selected and remeasured by the same examiner (P.C.). Random and systematic errors were calculated according to Dahlberg’s formula and with dependent t tests, at P <0.05.

Statistical analysis

The normal distribution of the data was checked using Shapiro-Wilk test. Intragroup comparison of T1, T2, and T3 stages was performed with repeated measures analysis of variance and post-hoc Tukey test when necessary.

Intergroup comparability of sex distribution and malocclusion type was performed with the chi-square test. Intergroup comparability of initial, final, and posttreatment ages, treatment, follow-up, and retention times were performed by independent t tests. Intergroup comparison of the variables studied at the 3 stages evaluated (T1, T2, and T3) and the treatment and long-term posttreatment changes were performed with independent t tests.

All statistical analyses were performed with Statistica software (Statistica for Windows, Version 10.0, StatSoft, Tulsa, Okla) at P <0.05.


The random errors varied from 1.1 (PAR index) to 1.8 (OGS) and were within the acceptable ranges. , There was no significant systematic error ( Table I ).

Table I
Results of the error study
Variables First measurement (n = 32) Second measurement (n = 32) Dahlberg P
Mean SD Mean SD
PAR 12.1 11.4 12.5 11.7 1.1 0.244
OGS 42.4 17.9 42.6 17.8 1.8 0.593

Note. Dahlberg’s formula used for casual errors, and dependent t tests for systematic errors.

The groups were comparable regarding ages in all stages, long-term follow-up and retention times, and the distribution of sex and type of malocclusion ( Table II ). Treatment time was statistically significantly longer in the extraction than in the nonextraction group ( Table II ).

Table II
Results of intergroup comparability of the ages and treatment time, long-term follow-up evaluation and retention times, sex distribution, and type of malocclusion
Variables Group 1 nonextraction (n = 16) Group 2 extraction (n = 41) P
Age T1, y 13.2 (0.8) 13.3 (1.9) 0.841
Age T2, y 15.0 (1.1) 15.6 (2.1) 0.322
Age T3, y 50.3 (6.0) 53.6 (5.5) 0.054
Treatment time, y 1.8 (0.8) 2.3 (0.5) 0.022 ,
Long-term follow-up, y 35.2 (6.1) 37.9 (4.5) 0.071
Retention time, y 2.2 (1.1) 2.2 (1.2) 0.983
Sex 0.948
Males 6 15
Females 10 26
Malocclusion type 0.206 §
Class I 6 23
Class II 10 18

Note. Values are mean (standard deviation).

Statistically significant at P <0.05.

Independent t test.

χ 2 = 0.00, df = 1.

§ χ 2 = 1.59, df = 1.

There was a statistically significant improvement in the PAR index with treatment that significantly worsened over the years, indicating many occlusal changes at the T3 stage in both nonextraction and extraction groups ( Table III ).

Table III
Results of the intragroup comparison of the PAR index among T1, T2, and T3 for the nonextraction and extraction groups separately (repeated measures ANOVA and Tukey tests)
Variables T1 T2 T3 P
Nonextraction group (n = 16)
PAR 25.7 (9.7) a 2.8 (2.4) b 8.6 (9.7) c <0.001
Extraction group (n = 41)
PAR 23.7 (8.4) a 3.1 (1.9) b 7.5 (4.3) c <0.001

Note. Values are mean (standard deviation). Different lowercase letters in the horizontal direction indicate statistically significant differences ( P <0.05) among the stages (T1, T2, and T3) as determined by Tukey test.
ANOVA , analysis of variance.

Statistically significant at P <0.05.

The nonextraction group had a mean OGS score of 31.8 (SD, 9.4) at T2 that significantly worsened at the T3 stage (mean, 41.0; SD, 19.3) ( Table IV ). Alignment, buccolingual inclination, and occlusal relationship showed statistically significant changes toward the pretreatment position at the T3 stage. Marginal ridges significantly improved the T3 stage ( Table IV ).

Table IV
Results of the intragroup comparison of OGS index and components between T2 and T3 for the nonextraction and extraction group separately (dependent t tests)
Variables T2 (final) T3 (long-term) P
Nonextraction group (n = 16)
OGS 31.8 (9.4) 41.0 (19.3) 0.012
Alignment 5.8 (2.6) 10.3 (4.4) <0.001
Marginal ridges 5.6 (1.7) 1.8 (1.1) <0.001
Buccolingual inclination 6.9 (4.2) 9.8 (4.3) 0.024
Overjet 3.7 (2.3) 5.8 (4.4) 0.121
Occlusal contacts 3.6 (3.4) 2.5 (3.7) 0.272
Occlusal relationship 0.8 (1.8) 4.5 (6.4) 0.014
Interproximal contacts 0.8 (1.3) 1.2 (2.2) 0.587
Root angulation 4.1 (2.1) 4.8 (2.0) 0.222
Extraction group (n = 41)
OGS 31.1 (5.6) 33.8 (10.0) 0.045
Alignment 5.6 (2.8) 10.6 (4.0) <0.001
Marginal ridges 4.3 (1.5) 2.1 (1.5) <0.001
Buccolingual inclination 4.4 (2.7) 5.2 (2.9) 0.140
Overjet 4.2 (2.5) 5.3 (4.3) 0.111
Occlusal contacts 4.8 (2.7) 3.4 (3.1) 0.014
Occlusal relationship 1.8 (1.7) 2.8 (3.2) 0.047
Interproximal contacts 2.1 (2.5) 0.7 (1.7) 0.001
Root Angulation 3.6 (1.8) 3.4 (1.8) 0.698
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Jan 9, 2021 | Posted by in Orthodontics | Comments Off on Long-term occlusal changes and patient satisfaction in patients treated with and without extractions: 37 years after treatment
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