Dental and skeletal outcomes for Class II surgical-orthodontic treatment: A comparison between novice and experienced clinicians

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 .

Table I
Skeletal and dental cephalometric measures and their normative standards
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.

Table II
Means and standard deviations for skeletal and dental measures at T1 for studies 1 and 2 with ANOVA comparisons between studies
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.

Table III
Skeletal measures at T2 and T3: means, standard deviations, and significant differences between T2-T3 for Division 1 and Division 2 for each variable, and significant differences 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

Table IV
Dental measures at T2 and T3: means, standard deviations, and significant differences between T2-T3 for Division 1 and Division 2 for each variable, and significant differences between studies 1 and 2
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.

Table V
Efficacy for maxillary incisors at T1, T2, and T3: median percentages, quartile ranges, and minimum and maximum values for 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
Only gold members can continue reading. Log In or Register to continue

Apr 13, 2017 | Posted by in Orthodontics | Comments Off on Dental and skeletal outcomes for Class II surgical-orthodontic treatment: A comparison between novice and experienced clinicians
Premium Wordpress Themes by UFO Themes