Comparison of surgical and non-surgical orthodontic treatment approaches on occlusal and cephalometric outcomes in patients with Class II Division I malocclusions

Class II Division I malocclusions typically manifest with increased overjet and retrognathic mandibles. Of Class II malocclusions, there are two subcategories: Division I (characterized by increased overjet and a retrognathic mandible) and Division II (in which maxillary lateral incisors or canines are proclined relative to the central incisors). Class II Division I malocclusions are the more common of the two in the European population [1]. National estimates in the USA indicate that 23% of children, 15% of youths, and 13% of adults have a discrepancy of 5 mm or more in overjet alone, thereby signifying a Class II Division I malocclusion [1]. Left untreated, Class II malocclusions can pose a variety of complications both present and future including those in the functional, psychological, and sociological realms [2, 3].

Treatment options for Class II Division 1 malocclusions are three-pronged: orthopedic growth modification, masking with extractions of premolars, and orthognathic surgery. Each option has been proven to be an effective means of treatment [4–17]. The decision as to which path to take depends on a variety of factors: time (as in, age of patient) and magnitude (amount of discrepancy: mild, moderate, or severe) [18]. A significant skeletal component is usually present in severe Class II Division 1 malocclusions. In these cases, the ideal method of treatment is orthodontic treatment in conjunction with orthognathic surgery as this is the only treatment which addresses the skeletal base discrepancy. However, due to finances or personal preference, patients are not always accepting of this option. In these situations, one of the other modes of treatment may be attempted in lieu of orthognathic surgery. In a younger patient, many orthopedic options achieve good facial harmony. However, while a masking treatment can address occlusal discrepancies, it will not improve skeletal position and therefore profile esthetics [17, 19–26].

Depending on the type of Class II corrector used (for example: Herbst, Twin Block, Headgear, or Forsus appliances), the end of treatment skeletal outcomes could vary [27–31]. Despite the fact that, especially in the USA, Class II malocclusions are possibly the most common malocclusions encountered by practitioners in private practice and in residency programs, there is little agreement on the best practice modality. This could be because treatment is multi-factorial, depending on age, timing of treatment, and patient concerns and desires. There is a paucity of studies that have compared outcomes of surgical versus non-surgical treatment of adolescent patients [32]. This is an important age to assess treatment outcomes because it is one of the most common ages for orthodontic treatment and treatment options might be confined depending on completion of the pubertal growth spurt.

The objective of the present study is to examine end-of-treatment cast-based and cepaholometric outcomes in patients with Class II Division I malocclusions treated orthodontically in conjunction with orthognathic surgery or without any orthognathic surgery. The study tests the hypothesis that end-of-treatment outcomes differ between the two treatment approaches.

After the records were gathered, 60 patients were identified which fulfilled the inclusion criteria: 40 non-surgical and 20 surgical cases were included in the study. The study cohort was comprised of 28 female patients (21 in the non-surgical group and 7 in the surgical group) and 32 male patients (19 in the non-surgical group and 13 in the surgical group). Two patients were identified as Hispanic and two as multi-racial (Caucasian-African American). The remaining 56 patients were Caucasian. The mean age of the surgical group at the start of treatment was 14.8 years (compared to 12.9 years in the non-surgical group) [p < 0.001]. The mean age of the surgical group at the end of treatment was 17.4 years (compared to 15.4 years in the non-surgical group) [p < 0.001]. The duration of treatment for the surgical group was 2.6 years (compared to 2.5 years in the non-surgical group).

Both groups utilized TADs or HG for anchorage purposes. The breakdown in each group was as follows: non-surgical group—headgear (n = 29), headgear and TADs (1), TADs with no headgear (n = 3), and neither headgear nor TADs (n = 7)—and surgical group—headgear (n = 3), TADs in the lower arch only (n = 1), neither headgear nor TADs (n = 16).

In the non-surgical group, the retention options delivered were as follows: fixed (bonded) retainers on the lingual aspect of maxillary central incisors along with Hawley retainers (n = 2), Hawley retainers only (2), Hawley retainer and bonded lower retainer (2), Hawley retainers only (33), and tooth positioner followed by Hawley retainers (1). In the surgical group, the retention protocols included the following: Hawley retainers only (17), tooth positioner and Hawley retainers (2), and one patient was given a tooth positioner and never returned for the Hawley retainer.

Consent deband, indicating premature treatment completion, was tracked in each group. Of the non-surgical patients, 32 did not have a consent deband. The remaining 8 patients opted for consent deband: 1 finished with a crossbite, 1 consent debanded due to patient burnout, 1 decided to stop treatment as correction could not be achieved and would consider surgery or extractions at a later time point, and 5 consent debanded with no reason indicated. In the surgical group, 15 did not consent deband and the remaining 5 did. Consent deband with no reason indicated was done in 4 patients and 1 with the reason being that they did not want to wear their elastics anymore.

The present study is a retrospective analysis of consecutively treated patients with Class II Division I malocclusions. The goal of our study was to compare the end-of-treatment outcomes in patients with Class II Division I malocclusions who were treated surgically or non-surgically. Our findings showed that the cast-grading outcomes were similar between the surgical and the non-surgical treatment groups and certain end-of-treatment cephalometric values differed between the two groups. Our results showed that after adjustment for all available patient level covariates, the final mean ABO-COGS deband score in the surgical group was 0.854 points lower than that in the non-surgical group. The deband ANB angle in the surgical group was 2.24° lower than that in the non-surgical group. This indicates that the maxilla/mandible relationship improved in the surgical group to a greater extent. This can be expected since skeletal positions change with a surgical treatment. Both FMIA and IMPA angle give information about lower incisor position. The deband FMIA angle and the IMPA angle indicate the position of the mandibular incisors. Our study results showed that the FMIA angle was not significantly different between the two treatment groups. The deband IMPA was significantly higher for the non-surgical group (100.4°) compared to the surgical group (92.3°). However, this difference became statistically non-significant once age, gender initial discrepancy index, and other cephalometric variables were adjusted in the regression models. Following adjusting for all confounders, those treated surgically had 3.3° lower IMPA compared to those treated non-surgically. This indicates that the mandibular incisors were more upright at the end of treatment in the surgical group. We would expect these values to change according to which treatment plan, surgical or non-surgical, was chosen. For instance, if lower premolars were extracted before a mandibular advancement, we would expect some uprighting of the lower incisors during space closure. Also, initial crowding would have an effect on incisor position. If no extractions were done, the way to gain arch length to resolve lower anterior crowding is to procline the lower incisors. The deband upper incisors to SN plane angle, a measurement of upper incisor position, was shown to be 10.56° higher in the surgical treatment group (p = 0.001) after adjustment of all covariates in the regression model. We expected this finding because, if a surgical option cannot be entertained, a masking approach by extracting upper premolars is most likely considered instead. During space closure, there will be uprighting of the upper incisors, thereby leading to a decreased upper incisor to SN plane angle. This finding could also be explained in that for a surgical treatment option where teeth might not need to be extracted, if there is an existing upper anterior crowding, incisors will be proclined to gain space for alignment. Deband cephalometric overbite was found to be 0.606 mm lower in the surgical group while deband cephalometric overjet was shown to be 0.188 mm higher in the non-surgical treatment group after adjustment for all covariates in the regression models and these were not statistically significant.

One of the first pieces of literature analyzing need for orthognathic surgery based on severity was put forth by Proffit et al. in 1992 [22]. When reviewing an adolescent population treated non-surgically (through camouflage treatment) or surgically, Proffit et al. identified certain parameters which might be useful when deciding treatment. They evaluated cephalometric and cast measurement before and after treatment to determine efficacy of treatment. Our study found end-of-treatment occlusion to be similar in both groups. This was supported by work of Proffit et al. as well. Our study showed that overjet was slightly higher in the surgical group, which was not seen in the study by Proffit et al. This could be attributed to differing practitioners’ approach to treatment or variability in the success of the surgical treatment in respective surgical populations.

Mihalik et al. performed a long-term follow-up of Class II adults treated with camouflage treatment or surgical treatment and analyzed post-deband results [19]. Patients in this population were recalled 12 years after treatment. This group found that both groups showed acceptable correction of the malocclusion. This was echoed by our study which found ABO cast grading outcomes at the end of treatment was not significantly different between the surgical and non-surgical groups. At recall, Mahalik et al. reported that in both populations, overbite increased to a small extent and overjet increased in the surgical group by 10–20% [19]. Our study found that deband cephalometric overbite was lower in the surgical group (compared to non-surgical) and overjet was increased compared to the non-surgical group, although neither value was statistically significant. This might be expected because with camouflage treatment, as the upper incisors are retracted, overbite increases.

In an adolescent population (less than 20 years of age), Tulloch et al. discussed the difficulty in treatment planning as these patients might still be undergoing growth. This study emphasized that in severe cases, surgical treatment is most likely the best option [35]. They examined 500 patients in a study with similar inclusion criteria as ours. Patients were treated non-surgically or surgically and end-of-treatment outcomes were reviewed based on division into three categories: orthodontic success, orthodontic failure, and surgical success. This study assessed success of treatment through reduction in overjet to less than 4 mm [35]. Cephalometric radiographs were reviewed and patients were placed into two sub-groups based on gender. Initial ANB in this study was about 6°, similar to that in our study, but the initial overjet measurement is that both groups were significantly more (7.8 and 8.6 mm) when compared to our population (2.9 versus 3.1 mm). This study found that 98% of patients in their entire population did not meet their criteria for correction of overjet [35]. Since our study evaluated ANB change as a measure of AP correction, we were able to focus exclusively on skeletal position instead of tooth position. Tulloch concluded that neither gender nor age were associated with success of correction of overjet and concluded that more factors go into a “successful” or “unsuccessful” case than practitioners might think. Since these factors were held constant in our linear regression models, we were able to analyze differing variables without the risk of bias.

Kinzinger et al. studied outcomes in patients with Class II Division I malocclusions where in 60 young adults were evaluated after a surgical or non-surgical treatment [20]. Their results showed changes in all skeletal categories, as can be presumed because with this method of treatment, the skeletal base is being influenced directly. Each group in this study achieved a reduction in overjet. The surgical group was found to have significant protrusion of upper incisors, as did our research. This might be attributed to the biomechanical differences in treating a surgical case versus a non-surgical case. One might imagine that not only will a camouflage treatment increase overbite as incisors are retracted, but they will also upright. If a surgical patient has minimal crowding, it might not be outside the realm of possibility that the practitioner might choose to procline the upper incisors to allow for the alignment of the teeth before the patient is sent for surgery.

The findings of our study should be interpreted keeping the inherent limitations of retrospective studies in perspective. What we found is an association and not a true causal effect. Our analysis was limited to the variables we could gather from the treatment chart notes. The population in our study was relatively homogenous considering the location of the dental school and the population it serves. Consequently, our study results cannot be generalized to all Class II Division I malocclusions.

We can conclude that amongst Class II Division I cases identified in this study, there were some differences in deband outcomes between non-surgical and surgical populations. Those treated surgically had a significantly larger reduction in ANB angle and increased maxillary incisor proclination compared to those treated non-surgically. Further information should be gathered at other institutions to compile a more diverse picture of successful treatment options in the Class II Division I population.