Introduction
The information that details dental changes accompanying presurgical and postsurgical orthodontic treatment during orthognathic surgery treatment is disappointing and results in less than ideal surgical change, but it is largely derived from university clinic samples with patients treated by residents (clinical novices). In this study, we examined similar treatments performed by experienced practitioners and compared them with the novices’ results.
Methods
A sample of 72 Class II subjects treated by practitioners with a mean of 26.7 years of experience was selected. Inclusion criteria were consecutively treated surgical-orthodontic patients with mandibular advancement, rigid fixation, and good-quality lateral cephalograms. Pretreatment skeletal and dental variables were compared with those from a sample treated by novices in a previous study. Presurgical and final analyses were performed with analysis of covariance (ANCOVA), with pretreatment values as the covariate. An efficacy analyses for treatment phase and study comparisons was the final component.
Results
The novices treated patients with significantly more severe Class II skeletal problems. For both studies, there were significant positive changes in the position of the mandible. The ANCOVA analysis showed that the experienced practitioners managed the bodily position of the maxillary incisors more effectively. The efficacy analysis showed no statistically significant differences between novices and experienced practitioners. For both novices and experienced practitioners, according to the ANB changes, nonideal incisor decompensation led to less than ideal final mandibular positions.
Conclusions
The dental and skeletal mean changes and efficacy analysis for both novices and experienced practitioners showed that presurgical orthodontic treatment often does not fully decompensate the incisors; this then limits the surgical outcome.
An important goal of orthognathic surgery for Class II patients is to maximize or optimize the skeletal changes after reducing the pretreatment dental compensations to improve facial esthetics, function, and posttreatment stability. There is a growing body of literature that indicates that this goal is not realized. These studies also showed that evaluating only mean values for treatment changes of incisors in Class II malocclusion can be misleading when Class II Division 1 and Division 2 patients are combined. In samples with both divisions of Class II malocclusion, the opposing pretreatment incisor positions and movements during the presurgical decompensation tend to cancel each other and appear to indicate no mean treatment changes. The concept of treatment “efficacy” as the outcome of choice describes the percentage of change attained toward a treatment goal.
Potts et al investigated a sample of Class II surgical-orthodontic patients from the Ohio State University graduate orthodontic clinic treated by residents (clinical novices), under faculty supervision, to determine the dental and skeletal changes in surgical-orthodontic treatment. They refined the previously described analysis of Proffit et al by grouping the subjects as proclined, retroclined, protrusive, and retrusive for the maxillary and mandibular incisors at each treatment stage against ideal values. The results indicated that the presurgical orthodontic objectives of decompensation were not achieved because some incisors were not decompensated, and others were overcorrected. Patients with retrusive incisors initially were more ideally treated than those with protrusive incisors. The surgical correction achieved only 51.4% of the skeletal ideal measured by ANB angle change. Since the scope of the skeletal correction depends on dental decompensation during presurgical orthodontics, this finding was not surprising. Without adequate incisor decompensation, the surgical advancement was limited by the amount of overjet so that the postsurgical phase of orthodontic treatment “camouflaged” the less than ideal surgical outcome by dental compensation.
Attempts to identify meaningful treatment variables that might have complicated or enhanced the practitioner’s ability to achieve a better result such as extractions, elastic usage, patient compliance, and bracket slot-archwire differential failed to show any clinically meaningful associations.
Several investigations focused on the incisor and skeletal positions as the index of success because the stated goal of orthognathic surgery is to correct the malocclusion by decompensating and gaining the optimal skeletal change for normalization, not to obtain a variation of camouflage. Patients might be satisfied with many types of treatment, but to undergo orthognathic surgery for a minimal or modest morphologic change is usually considered unreasonable when weighing the costs, risks, and benefits.
The studies cited above 1,4 were conducted in the Ohio State University graduate orthodontic clinic, with patient care provided by supervised novice clinicians, and it may be that the results were less than optimal. This point was raised in the editor’s online discussion of the article by Potts et al. Therefore, in this study, we compared the incisor and skeletal changes that occurred before and after surgery in that study with a sample treated by experienced practitioners in private orthodontic practices.
Material and methods
After approval was obtained from the institutional review board, a sample of 72 Class II subjects treated by practitioners with a mean of 26.7 years of experience was selected. Inclusion criteria were consecutively treated, white surgical-orthodontic patients with mandibular advancement, rigid fixation, cervical vertebrae maturation of stage 4 or 5 before treatment (indicating a postgrowth spurt status), and good-quality lateral cephalograms at pretreatment (T1), presurgery (T2), and postsurgery or final (T3). The patients were treated at 7 private orthodontic practices throughout the United States. Thirty of these subjects (42%) were classified as Class II Division 1, exhibiting proclined maxillary incisors (incisor position in degrees greater than ideal as measured by maxillary central incisor to NA), and 42 were Class II Division 2, exhibiting retroclined maxillary incisors (incisor position less than ideal in degrees as measured by maxillary central incisor to NA). Sixty-nine percent were female. These criteria were also used in the study of Potts et al (study 1) and resulted in a sample of 18 Class II Division 1 patients (53%) and 16 Division 2 patients. Sixty-two percent were female. The subjects in study 1 were treated by novice practitioners with 3 or fewer years of experience and were supervised by experienced clinicians.
Digital tracings of lateral cephalograms were performed with Dolphin Imaging software (version 10.5, Dolphin Imaging and Management Solutions, Chatsworth, Calif). Nondigital lateral cephalograms were scanned into Dolphin by using a Professional Scanner (model 1600, Epson America, Long Beach, Calif), and the images were digitized. Because serial radiographs were analyzed, all lateral cephalograms of 1 subject were traced on the same occasion to reduce the error variance in each subject. Magnification was controlled by using the Dolphin calibrated fiduciary points. Selected cephalometric measures were chosen to demonstrate anteroposterior and vertical skeletal and dental characteristics. All measures are shown with their referenced normative standards in Table I .
| Variable and type of measure | Male norm | Female norm | Reference |
|---|---|---|---|
| Anteroposterior skeletal measures | |||
| SNA ( o ) | 82 | 82 | Steiner |
| A-point to N perp (mm) | 1 | 1 | McNamara |
| SNB ( o ) | 80 | 80 | Steiner |
| Pg to N perp (mm) | −0.3 | −1.8 | McNamara |
| ANB ( o ) | 2 | 2 | Steiner |
| Incisor overjet (mm) | 2 | 2 | ABO standards |
| Vertical skeletal measures | |||
| SN to GoGn ( o ) | 32 | 32 | Steiner |
| Mandibular plane angle ( o ) | 26 | 26 | Ricketts |
| Face height ratio (%) | 54 | 54 | Isaacson et al |
| Dental measures | |||
| Upper 1 to Na ( o ) | 22 | 22 | Steiner |
| Upper 1 to NA (mm) | 4 | 4 | Steiner |
| Upper 1 to SN ( o ) | 104 | 104 | Bell et al |
| Lower 1 to NB ( o ) | 25 | 25 | Steiner |
| Lower 1 to NB (mm) | 4 | 4 | Steiner |
| Lower 1 to MP ( o ) | 95 | 95 | Bell et al |
To verify intraexaminer reliability, 20 cephalometric radiographs were randomly selected, redigitized, and remeasured a minimum of 3 weeks later.
Statistical analysis
Intraclass correlation coefficient (ICC) and 95% CI statistics were used to test the reliability of the linear and angular cephalometric measurements.
An analysis of variance (ANOVA) for T1 with study and division as the independent factors was completed to assess differences in the dental and skeletal variables between the Class II divisions and the data for this study (study 2) and the previous study of novice clinicians. Post-hoc testing for multiple comparisons was done by using the Tukey-Kramer method. The α value of 0.05 was set for all analyses.
Significant differences were apparent between the studies; therefore, a repeated measures analysis of covariance (ANCOVA) was calculated to determine adjusted means for T2 and T3, with T1 as the covariate. Again, post-hoc testing for multiple comparisons was done by using the Tukey-Kramer method.
A modified efficacy examination based on the method of Potts et al (originally adapted from Proffit et al ) was completed to summarize the changes in incisor inclination and bodily position. This allowed for examination of the dynamics and changes in the incisors masked by summary statistics. The subjects were compared with ideal values and grouped as proclined, retroclined, protrusive, and retrusive for the maxillary and mandibular incisors at each treatment stage. This method addressed the well-demonstrated problem of having the summary statistics of the central tendency masking changes for the Class II Division 1 and Division 2 patients (initially proclined vs retroclined incisor groups). The treatment efficacy was calculated by measuring the incisor changes between time points (T1-T2, T1-T3, and T2-T3), expressed as percentages of change needed to reach the ideal value. These groups were further subdivided into those that moved in the correct direction (toward the ideal) and those that moved in the opposite direction (away from the ideal). The closer the percentage was to 100%, the more successful the treatment. Any value over 100% was corrected beyond the ideal. Negative values indicated change away from the ideal. The percentage of ideal was determined by calculating the median percentage change of the subjects per group. The efficacy of the skeletal change was also calculated in a similar manner. The results of study 1 were compared with study 2 by using the multiple nonparametric randomization tests with all P values adjusted by using the step-down Bonferroni method of Holm.
Results
Twenty lateral cephalograms were retraced and measured to assess intrarater reliability. The ICC values and their upper and lower 95% CI boundaries for the linear and angular cephalometric measures were 0.995 mm (0.989-0.998 mm) and 1.00 (0.999°-1.00°), respectively.
The means and standard deviations for the skeletal and dental measures at T1 are shown in Table II along with comparisons for studies 1 and 2.
| Study 1 | Study 2 | ||||
|---|---|---|---|---|---|
| Variable | Mean | SD | Mean | SD | P value study 1-study 2 |
| SNA ( o ) | |||||
| Div 1 | 81.4333 | 2.9201 | 81.0600 | 2.9110 | 0.9794 |
| Div 2 | 82.3313 | 4.4740 | 81.1095 | 3.0807 | 0.5633 |
| A-point to N perp (mm) | |||||
| Div 1 | 0.2055 | 3.0833 | −1.2033 | 2.7622 | 0.0604 |
| Div 2 | 0.6938 | 4.1921 | −0.5381 | 2.3186 | 0.9520 |
| SNB ( o ) | |||||
| Div 1 | 74.4888 | 3.1312 | 75.9000 | 3.7335 | 0.1221 |
| Div 2 | 74.3563 | 4.3072 | 74.9381 | 3.6519 | 0.8259 |
| Pg to N perp (mm) | |||||
| Div 1 | −10.0056 | 6.1865 | −8.4133 | 6.3966 | 0.5194 |
| Div 2 | 11.4313 | 9.0085 | −10.2667 | 6.3590 | 0.7718 |
| ANB ( o ) | |||||
| Div 1 | 6.9667 | 2.2226 | 5.1567 | 2.1599 | <0.0001 |
| Div 2 | 7.9875 | 2.1960 | 6.1714 | 1.6178 | 0.0396 |
| Incisor overjet (mm) | |||||
| Div 1 | 9.3111 | 4.0243 | 8.0900 | 2.5198 | 0.6768 |
| Div 2 | 5.2125 | 1.9117 | 4.8500 | 1.8224 | 0.9999 |
| SN to GoGN ( o ) | |||||
| Div 1 | 34.9722 | 7.6683 | 30.0000 | 8.3087 | 0.0245 |
| Div 2 | 33.1938 | 8.4523 | 31.7690 | 8.2998 | 0.7006 |
| Mandibular plane angle ( o ) | |||||
| Div 1 | 28.2111 | 8.5212 | 25.2267 | 8.0244 | 0.2398 |
| Div 2 | 26.3500 | 9.5150 | 26.7310 | 7.8410 | 0.8009 |
| Face height ratio (%) | |||||
| Div 1 | 56.7889 | 2.7267 | 54.5933 | 2.8798 | <0.0001 |
| Div 2 | 56.8938 | 1.8208 | 54.7214 | 2.3913 | 0.0010 |
| U1 to NA ( o ) | |||||
| Div 1 | 29.2667 | 7.4514 | 29.7667 | 5.9864 | 0.3194 |
| Div 2 | 12.4875 | 9.4349 | 11.1286 | 8.0306 | 0.9734 |
| U1 to NA (mm) | |||||
| Div 1 | 5.7722 | 2.9947 | 6.7733 | 1.9945 | <0.0001 |
| Div 2 | 0.26875 | 3.5381 | 3.5071 | 2.3853 | <0.0001 |
| U1 to SN ( o ) | |||||
| Div 1 | 110.7278 | 6.9245 | 110.8200 | 7.2755 | 0.6193 |
| Div 2 | 94.8188 | 10.6753 | 92.2262 | 8.5006 | 0.9999 |
| L1 to NB ( o ) | |||||
| Div 1 | 26.9056 | 7.1891 | 26.6400 | 6.5459 | 0.8429 |
| Div 2 | 26.5000 | 8.3451 | 25.8286 | 8.1665 | 0.5122 |
| L1 to NB (mm) | |||||
| Div 1 | 5.4944 | 2.8587 | 5.5333 | 1.9293 | 0.9923 |
| Div 2 | 5.2313 | 2.7818 | 5.3167 | 2.0487 | 0.8218 |
| L1 to MP ( o ) | |||||
| Div 1 | 95.4333 | 8.2765 | 100.7400 | 6.7489 | 0.0495 |
| Div 2 | 97.3063 | 10.8400 | 99.1262 | 7.2731 | 0.9465 |
In this sample, the Class II surgical patients had normal maxillary cephalometric values but a sagittal mandibular deficiency before treatment in both studies 1 and 2. The ANB angle indicated that the study 1 subjects were significantly more Class II. Study 1 also had significantly greater percentages of lower face height for both Class II Division 1 and Division 2 subjects, and a significantly greater Sn to GoGn angle in the Division 1 group.
Maxillary incisor inclination was comparable in both studies. There were significant differences for incisor bodily position in both Class II divisions; the study 1 sample had significantly less protrusion of the incisors.
The mandibular incisors were similar in inclination and bodily position when compared to the NB plane. The incisors in the study 2 subjects of Division 1 were significantly more proclined relative to the mandibular plane.
The means and standard deviations for the skeletal and dental measures at T2 and T3 for studies 1 and 2 are shown in Tables III and IV , along with the ANCOVA comparisons for each division from T2 to T3. The means and changes were also compared between studies 1 and 2.
| Skeletal ANCOVA Results for the adjusted values | |||||
|---|---|---|---|---|---|
| Study 1 | Study 2 | ||||
| Variable | Mean | SD | Mean | SD | P value study 1-study 2 |
| SNA ( o ) | |||||
| Div 1 | |||||
| T2 | 81.8432 | 3.5926 | 81.2485 | 3.6012 | 0.9900 |
| T3 | 82.0154 | 3.7826 | 81.6118 | 4.1641 | 0.9991 |
| P value T2-T3 | 1.0000 | 0.9932 | |||
| Div 2 | |||||
| T2 | 80.6312 | 4.4034 | 80.7993 | 3.4071 | 1.0000 |
| T3 | 80.8562 | 3.3879 | 82.5207 | 4.1696 | 0.2591 |
| P value T2-T3 | 1.0000 | 0.0006 | |||
| A-point to N perp (mm) | |||||
| Div 1 | |||||
| T2 | 0.1167 | 3.7809 | −0.3641 | 3.3864 | 0.9989 |
| T3 | 0.3000 | 3.8259 | 0.0792 | 4.0032 | 1.0000 |
| P value T2-T3 | 1.0000 | 0.9922 | |||
| Div 2 | |||||
| T2 | −1.2365 | 4.0298 | −0.9927 | 2.5150 | 1.0000 |
| T3 | −1.2740 | 4.4459 | 0.7573 | 3.5304 | 0.1816 |
| P value T2-T3 | 1.0000 | 0.0061 | |||
| SNB ( o ) | |||||
| Div 1 | |||||
| T2 | 74.8693 | 3.2206 | 74.5797 | 4.1178 | 0.9996 |
| T3 | 77.3026 | 3.0488 | 78.2463 | 4.6242 | 0.7172 |
| P value T2-T3 | <0.0001 | <0.0001 | |||
| Div 2 | |||||
| T2 | 74.9173 | 3.9786 | 74.6997 | 3.7028 | 0.9999 |
| T3 | 78.0985 | 3.8293 | 78.4473 | 4.0573 | 0.9985 |
| P value T2-T3 | <0.0001 | <0.0001 | |||
| Pg to N perp (mm) | |||||
| Div 1 | |||||
| T2 | −10.1977 | 6.4841 | −10.0106 | 6.5909 | 1.0000 |
| T3 | −3.8865 | 6.2444 | −2.9173 | 6.7558 | 0.9945 |
| P value T2-T3 | <0.0001 | <0.0001 | |||
| Div 2 | |||||
| T2 | −9.7451 | 9.9962 | −10.7286 | 6.3072 | 0.9934 |
| T3 | −4.3264 | 8.5689 | −2.7119 | 6.8425 | 0.8988 |
| P value T2-T3 | 0.0012 | <0.0001 | |||
| ANB ( o ) | |||||
| Div 1 | |||||
| T2 | 7.0977 | 3.7256 | 6.4478 | 2.3251 | 0.9408 |
| T3 | 4.8422 | 3.2772 | 3.1212 | 2.7065 | 0.0526 |
| P value T2-T3 | 0.0020 | <0.0001 | |||
| Div 2 | |||||
| T2 | 6.0623 | 2.0113 | 6.0717 | 1.6157 | 1.0000 |
| T3 | 3.0998 | 2.8720 | 4.0645 | 1.9864 | 0.6557 |
| P value T2-T3 | <0.0001 | <0.0001 | |||
| Incisor overjet (mm) | |||||
| Div 1 | |||||
| T2 | 7.2583 | 2.0561 | 7.4746 | 2.9990 | 0.9999 |
| T3 | 2.9361 | 1.0279 | 2.5880 | 0.7270 | 0.9974 |
| P value T2-T3 | <0.0001 | <0.0001 | |||
| Div 2 | |||||
| T2 | 6.8987 | 1.4336 | 7.0460 | 2.2981 | 1.0000 |
| T3 | 2.8675 | 0.5579 | 3.0746 | 0.7474 | 0.9999 |
| P value T2-T3 | <0.0001 | <0.0001 | |||
| SN to GoGN ( o ) | |||||
| Div 1 | |||||
| T2 | 32.3406 | 7.8319 | 32.8218 | 9.1533 | 0.9993 |
| T3 | 31.6517 | 8.0754 | 33.5018 | 7.3442 | 0.4034 |
| P value T2-T3 | 0.9911 | 0.9643 | |||
| Div 2 | |||||
| T2 | 32.6173 | 8.1237 | 32.6462 | 8.5387 | 1.0000 |
| T3 | 32.8860 | 7.4056 | 32.4914 | 7.2481 | 0.9998 |
| P value T2-T3 | 1.0000 | 1.0000 | |||
| Mandibular plane angle ( o ) | |||||
| Div 1 | |||||
| T2 | 27.2588 | 9.0998 | 27.0440 | 7.9565 | 1.0000 |
| T3 | 27.1088 | 7.9992 | 27.8406 | 6.1303 | 0.9955 |
| P value T2-T3 | 1.0000 | 0.9650 | |||
| Div 2 | |||||
| T2 | 26.2688 | 10.1429 | 27.0672 | 8.0706 | 0.9914 |
| T3 | 25.0438 | 10.2199 | 26.8720 | 6.8747 | 0.5642 |
| P value T2-T3 | 0.9356 | 1.0000 | |||
| Face height ratio (%) | |||||
| Div 1 | |||||
| T2 | 58.0673 | 2.7133 | 54.7649 | 3.2680 | 0.0010 |
| T3 | 57.4229 | 2.6465 | 55.1815 | 3.1179 | 0.0787 |
| P value T2-T3 | 0.3902 | 0.6246 | |||
| Div 2 | |||||
| T2 | 56.4940 | 1.9022 | 54.6247 | 2.5236 | 0.2264 |
| T3 | 56.4815 | 1.9132 | 55.5581 | 2.1824 | 0.9262 |
| P value T2-T3 | 1.0000 | 0.0002 | |||
| Dental ANCOVA Results for the adjusted values | |||||
|---|---|---|---|---|---|
| Study 1 | Study 2 | ||||
| Mean | SD | Mean | SD | P value study 1-study 2 | |
| U1 to NA ( o ) | |||||
| Div 1 | |||||
| T2 | 19.1398 | 11.0299 | 23.6690 | 9.5983 | 0.5547 |
| T3 | 19.8231 | 9.7982 | 22.2957 | 9.6150 | 0.9676 |
| P value T2-T3 | 0.9998 | 0.9351 | |||
| Div 2 | |||||
| T2 | 19.8371 | 7.6327 | 23.1481 | 5.8082 | 0.8520 |
| T3 | 22.0558 | 8.1604 | 22.6933 | 6.9587 | 1.0000 |
| P value T2-T3 | 0.8573 | 0.9998 | |||
| U1 to NA (mm) | |||||
| Div 1 | |||||
| T2 | 2.3251 | 3.5488 | 4.7782 | 2.1612 | 0.0051 |
| T3 | 2.0696 | 3.2390 | 4.7316 | 2.4459 | 0.0016 |
| P value T2-T3 | 0.9995 | 1.0000 | |||
| Div 2 | |||||
| T2 | 3.2465 | 2.5884 | 5.0776 | 1.6684 | 0.1216 |
| T3 | 4.1215 | 2.8152 | 4.3680 | 1.3057 | 1.0000 |
| P value T2-T3 | 0.6759 | 0.3279 | |||
| U1 to SN ( o ) | |||||
| Div 1 | |||||
| T2 | 99.9264 | 9.4320 | 103.6500 | 10.6474 | 0.7613 |
| T3 | 100.8100 | 8.3268 | 102.6300 | 10.2963 | 0.9943 |
| P value T2-T3 | 0.9973 | 0.9701 | |||
| Div 2 | |||||
| T2 | 101.6800 | 7.0671 | 104.7800 | 7.4819 | 0.8842 |
| T3 | 104.4400 | 7.2772 | 106.0700 | 7.2908 | 0.9970 |
| P value T2-T3 | 0.4749 | 0.7988 | |||
| L1 to NB ( o ) | |||||
| Div 1 | |||||
| T2 | 26.3145 | 6.9812 | 25.6638 | 7.7596 | 0.9999 |
| T3 | 30.2256 | 7.5396 | 28.3438 | 5.3034 | 0.9587 |
| P value T2-T3 | 0.0137 | 0.0458 | |||
| Div 2 | |||||
| T2 | 26.2404 | 7.2036 | 25.2137 | 7.8645 | 0.9988 |
| T3 | 30.7779 | 6.9499 | 28.0709 | 5.5366 | 0.7595 |
| P value T2-T3 | 0.0046 | 0.0036 | |||
| L1 to NB (mm) | |||||
| Div 1 | |||||
| T2 | 5.2470 | 3.0309 | 5.6385 | 2.1869 | 0.9952 |
| T3 | 6.2581 | 2.8961 | 5.4585 | 1.5635 | 0.7916 |
| P value T2-T3 | 0.0377 | 0.9957 | |||
| Div 2 | |||||
| T2 | 5.1344 | 2.7932 | 5.8607 | 2.2346 | 0.8522 |
| T3 | 5.8781 | 2.7602 | 5.9512 | 1.4274 | 1.0000 |
| P value T2-T3 | 0.3506 | 0.9999 | |||
| L1 to MP ( o ) | |||||
| Div 1 | |||||
| T2 | 96.8989 | 6.3376 | 98.2386 | 7.5990 | 0.9975 |
| T3 | 98.8434 | 6.7707 | 96.5619 | 7.4848 | 0.9949 |
| P value T2-T3 | 0.6549 | 0.5219 | |||
| Div 2 | |||||
| T2 | 98.6469 | 11.2322 | 97.7026 | 8.1324 | 0.9997 |
| T3 | 97.7594 | 11.0119 | 96.9574 | 7.65485 | 0.9999 |
| P value T2-T3 | 0.9950 | 0.9697 | |||
The ANCOVA results showed, at T3 for studies 1 and 2, no significant differences for skeletal severity and mandibular position. There was a significant difference between the Division 1 subjects of studies 1 and 2 for the face height ratio at T1 but no difference at T3. In Study 2, there was a significant anterior change in the position of the maxilla for the Division 2 patients.
There were no significant differences between studies for maxillary incisor inclination. At T2 and T3, the Division 1 patients in study 2 were more protrusive and closer to ideal. Overjet reduction was significant after surgery for both divisions and in both studies.
There were no significant differences between the studies for any mandibular incisor positions, although both groups of practitioners proclined the already proclined incisors to a position beyond ideal. The novices also significantly protruded the Division 1 mandibular incisors beyond ideal.
The efficacy analysis for the patients in this study ( Tables V-VII ) showed changes from T1 to T2, as well as from T1 to T3. The changes noted below describe the dynamics of the different treatment periods for study 2, and the results of the randomization test showed no significant differences between studies 1 and 2.
| Efficacy | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Study 1 | Study 2 | ||||||||||||
| Variable | Direction | Time period | n | Median percentage | Quartile range | Minimum | Maximum | n | Median percentage | Quartile range | Minimum | Maximum | Adjusted P value |
| Dental changes | |||||||||||||
| Retroclined maxillary incisor | |||||||||||||
| Toward ideal | 1-2 | 12 | 61 | 173 | 11 | 3100 | 37 | 95 | 81 | 12 | 937 | 1.0000 | |
| 2-3 | 11 | 109 | 169 | 37 | 500 | 18 | 57 | 264 | 7 | 917 | 1.0000 | ||
| 1-3 | 12 | 139.5 | 162.5 | 10 | 9600 | 32 | 111 | 95.5 | 4 | 750 | 1.0000 | ||
| Away from ideal | 1-2 | 4 | −170.5 | 147 | −238 | −3 | 5 | −44 | 27 | −74 | −16 | 1.0000 | |
| 2-3 | 10 | −32.5 | 109 | −472 | −3 | 14 | −66.5 | 146 | −700 | −4 | 1.0000 | ||
| 1-3 | 4 | −58.5 | 138.5 | −262 | −24 | 10 | −32 | 98 | −487 | −7 | 1.0000 | ||
| Proclined maxillary incisor | |||||||||||||
| Toward ideal | 1-2 | 15 | 136 | 442 | 12 | 14050 | 19 | 92 | 248 | 8 | 700 | 1.0000 | |
| 2-3 | 6 | 87.5 | 60 | 35 | 187 | 26 | 64 | 148 | 5 | 1029 | 1.0000 | ||
| 1-3 | 16 | 139.5 | 283 | 30 | 4000 | 19 | 183 | 308 | 16 | 2550 | 1.0000 | ||
| Away from ideal | 1-2 | 3 | −264 | 1150 | −1238 | −88 | 11 | −49 | 97 | −4000 | −7 | 1.0000 | |
| 2-3 | 7 | −35 | 206 | −235 | −3 | 13 | −61 | 324 | −8400 | −2 | 1.0000 | ||
| 1-3 | 2 | −809 | 618 | −1118 | −500 | 10 | −34 | 67 | −2100 | −1 | 1.0000 | ||
| Retrusive maxillary incisor | |||||||||||||
| Toward ideal | 1-2 | 10 | 73.5 | 77 | 18 | 171 | 19 | 90 | 68 | 4 | 400 | 1.0000 | |
| 2-3 | 15 | 53 | 79 | 28 | 371 | 14 | 100 | 129 | 6 | 480 | 1.0000 | ||
| 1-3 | 12 | 90 | 115 | 19 | 786 | 18 | 107 | 64 | 4 | 2000 | 1.0000 | ||
| Away from ideal | 1-2 | 8 | −189.5 | 150.5 | −400 | −13 | 3 | −400 | 613 | −700 | −87 | 1.0000 | |
| 2-3 | 7 | −23 | 235 | −2600 | −5 | 7 | −90 | 91 | −400 | −12 | 1.0000 | ||
| 1-3 | 6 | −69 | 111 | −425 | −42 | 4 | −686.5 | 1459.5 | −2900 | −8 | 1.0000 | ||
| Protrusive maxillary incisor | |||||||||||||
| Toward ideal | 1-2 | 13 | 197 | 214 | 52 | 365 | 26 | 75.5 | 95 | 6 | 1700 | 1.0000 | |
| 2-3 | 7 | 347 | 272 | 27 | 588 | 34 | 59 | 84 | 4 | 1100 | 1.0000 | ||
| 1-3 | 15 | 190 | 166 | 45 | 672 | 32 | 90.5 | 121.5 | 2 | 1600 | 1.0000 | ||
| Away from ideal | 1-2 | 3 | −271 | 311 | −328 | −17 | 22 | −87.5 | 135 | −1306 | −2 | 1.0000 | |
| 2-3 | 4 | −88 | 121 | −242 | −16 | 12 | −36 | 117 | −1800 | −3 | 1.0000 | ||
| 1-3 | 1 | −172 | 0 | −172 | −172 | 18 | −52 | 142 | −601 | −3 | 1.0000 | ||
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