Introduction
In the preceding chapter, we delved into the fundamentals of research and provided insights into the critical appraisal of literature. Building upon that foundation, this chapter begins by introducing readers to forest plots , a concise and visually intuitive tool for interpreting statistical analyses. Further on, we present a comprehensive overview of high-quality studies related to orthodontic treatment, focusing on carefully selected topics supported by systematic reviews or randomised controlled trials (RCTs). The aim is to provide clinicians with concise evidence that facilitates informed decision-making and enhances patient care. This chapter serves as a comprehensive resource for clinicians, synthesising current evidence to inform practice and enhance patient care in orthodontics.
Understanding forest plots
Forest plots are an essential feature of systematic reviews, offering a clear and concise visual representation of study results. They summarise findings from individual studies, facilitate comparison across studies and provide an overall estimate of the combined effect. By consolidating data in a visually accessible format, forest plots enable researchers and clinicians to quickly interpret complex analyses, aiding in evidence-based decision-making.
Orthodontic research often presents conflicting results on the same topic, making it challenging for clinicians to determine which findings are applicable to their patients. Forest plots serve as a valuable tool in such scenarios, combining data from multiple studies to calculate an overall treatment effect. This comprehensive summary helps clinicians and patients make informed decisions, grounded in the collective evidence.
The provided forest plot from literature shown in Fig. 100.1 demonstrates the effect of facemask treatment on overjet in patients with class III malocclusion, with measurements reported in millimetres. It will serve as a detailed reference to explain how to interpret forest plots. The appended text provides a summary of evidence and interpretation of studies on various aspects of clinically relevant topics.
A forest from published study is explained.
Source: Woon SC, Thiruvenkatachari B. Early orthodontic treatment for Class III malocclusion: a systematic review and meta-analysis. Am J Orthod Dentofacial Orthop 2017;151(1):28–52. doi:10.1016/j.ajodo.2016.07.017. PubMed PMID: 28024779 .
Management of class II
Early versus late treatment
Orthodontic treatment for prominent upper front teeth (Class II malocclusion) in children and adolescents:
The study aimed to evaluate the effects of orthodontic treatment for prominent upper front teeth in children aged 7–11 years (‘early treatment’ in two phases) compared to treatment in adolescence (ages 12–16 years, ‘late treatment’ in one phase), as well as the outcomes of late treatment versus no treatment and different types of orthodontic braces ( Table 100.1 ). Qualitative analysis revealed that 11 out of 17 studies had a high risk of bias, while quantitative analysis indicated that early treatment is more effective in reducing the incidence of incisal trauma compared to late treatment, although only 1 in 10 patients benefits from avoiding such trauma. Additionally, no significant benefits were found for treating patients under 10 years of age ( Figs 100.2 and 100.3 ).
TABLE 100.1
Research question using PICO format for the class II study comparing early versus late correction
| Type of studies included | All RCTs of orthodontic treatments to correct prominent upper front teeth (class II division 1 malocclusion). |
| Participant characteristics | Children and adolescents receiving orthodontic treatment to correct class II malocclusion. |
| Intervention | Early treatment with twin block appliance starting at 7 years of age for correcting class II malocclusion and as two-phase treatment. |
| Comparison | Late or adolescent treatment starting class II correction in permanent dentition as one phase. |
| Outcome | Effects of orthodontic treatment measured using cephalometric radiographs, clinical and quality of life. |
|
|
|
Outcomes for final overjet, final ANB and PAR score at the end of all treatment.
Outcomes for incidence of new incisal trauma at the end of all treatment.
Overall, there is low to moderate quality evidence suggesting that early orthodontic treatment reduces the risk of incisal trauma, but no substantial additional benefits associated with it.
Twin block versus other functional appliances
The study aimed to assess the effects of orthodontic treatment for prominent upper front teeth in adolescent patients using different types of functional appliances ( Table 100.2 ). Qualitative analysis of six trials comparing the twin block appliance to other appliances revealed three trials with unclear risk of bias, and three with high risk. Quantitative analysis showed no difference in overjet between the twin block and other removable functional appliances; however, the reduction in ANB was more favourable with twin block treatment.
TABLE 100.2
Research question using PICO format for the class II study comparing twin block versus other functional appliances
| Type of studies included | All RCTs of orthodontic treatments to correct prominent upper front teeth (Class II division 1 malocclusion). |
| Participant characteristics | Adolescents (12–16 years) receiving orthodontic treatment to correct class II malocclusion. |
| Intervention | Twin block appliance for correcting class II malocclusion treated as two phase treatment. |
| Comparison | Any other functional appliance or no treatment control group. |
| Outcome |
|
Overall, the conclusion is that the twin block appliance is significantly better than other functional appliances for skeletal correction ( Fig. 100.4 ) .
Forest plot showing effectiveness of twin block compared with other functional appliances for final overjet and final ANB measurements.
Fixed functional appliance versus removable functional appliances
The study aimed to assess the effects of orthodontic treatment for prominent upper front teeth in adolescent patients by comparing fixed versus removable functional appliances ( Table 100.3 ). Qualitative analysis identified three studies with high risk. Quantitative analysis of three trials revealed that while fixed functional appliances (FFAs) resulted in a greater reduction in overjet, removable functional appliances produced a more favourable reduction in ANB ( Fig. 100.5 ). Overall, the conclusion is that removable functional appliances lead to more skeletal changes compared to FFAs.
TABLE 100.3
Research question using PICO format for the class II study comparing fixed functional appliance versus removable functional appliances
| Type of studies included | All RCTs of orthodontic treatments to correct prominent upper front teeth (Class II division 1 malocclusion). |
| Participant characteristics | Adolescents (12–16 years) receiving orthodontic treatment to correct class II malocclusion. |
| Intervention | Fixed functional appliance for correcting class II malocclusion treated as one phase treatment. |
| Comparison | Removable functional appliance or no treatment control group. |
| Outcome |
|
Forest plot comparing fixed functional appliance and removable functional appliances.
Fixed functional appliances
The study aimed to assess the treatment effects of FFAs in treated versus untreated class II patients using lateral cephalometric radiographs ( Table 100.4 ). A total of nine articles were included, comprising one randomised controlled trial (RCT) with a high risk of bias and eight controlled clinical trials (CCTs) that averaged 22.4 points on the modified Downs and Black tool. Quantitative analysis indicated an improvement of 0.83 degrees per year in SNA measurement and 0.87 degrees per year in SNB measurement with FFAs, while the maxillomandibular difference measured by ANB showed a mean improvement of 1.74 degrees per year. However, due to the risk of bias in the studies and the small clinical effect, the overall impact of FFAs was graded as predominantly dentoalveolar ( Fig. 100.6 ). In conclusion, FFAs were effective in improving class II malocclusion in the short term, although their effects appear to be primarily dentoalveolar rather than skeletal.
TABLE 100.4
Research question using PICO format for the class II study comparing fixed functional appliance versus no treatment
| Type of studies included | RCT and CCT (prospective only) |
| Participant characteristics | Studies on human patients with class II malocclusion of any age or gender |
| Intervention | Orthodontic treatment with fixed functional appliances |
| Comparison | Untreated patients with class II malocclusion matched for age and gender |
| Outcome | Studies providing angular skeletal, dentoalveolar and soft tissue cephalometric measurements from lateral cephalometric analysis |
|
|
|
Forest plot showing the effectiveness of fixed functional appliances for SNA, SNB and ANB changes before and after treatment.
Effects of headgear
The study aimed to analyse the long-term effects of cervical headgear timing on dental arches using a RCT methodology study compared early headgear (treatment started soon after eruption of first molar) and late headgear group (18 months after eruption). The results showed that the early headgear group had a total maxillary arch length of 92.3 mm (SD 3.6) compared to 88.6 mm (SD 6.3) in the late headgear group, and similar findings were observed in the mandibular arch, with lengths of 93.7 mm (SD 4.0) in the early group and 91.9 mm (SD 3.7) in the late group, measured at 18 years of age. These results were statistically significant (P = 0.048) ( Fig. 100.7 ). However, despite the statistical significance favouring the early headgear group, the clinical significance is questionable due to the less than 2 mm difference in arch length between the two groups.
Maxillary and mandibular arch length difference between early and late headgear group measured at 18 years of age.
Class III treatment (Cochrane review)
The study analysed the effects of orthodontic treatment for prominent lower front teeth in children and adolescents ( Table 100.5 ). Qualitative analysis of 29 studies indicated all were at high risk of bias due to the lack of blinding, though seven had a low risk when this factor was omitted. Quantitative analysis showed that non-surgical treatments significantly improved overjet and ANB compared to untreated controls in the short term (6–15 months) with moderate-certainty evidence ( Figs 100.8 and 100.9 ). However, long-term follow-up (6 years post-treatment) for Class III skeletal patients revealed no significant differences in overjet and ANB. Importantly, orthodontists noted that those who received facemask treatment were 3.34 times less likely to require orthognathic surgery in adulthood ( Fig. 100.10 ). In conclusion, non-surgical orthodontic treatments improved bite and jaw relationships immediately post-treatment, while low-certainty evidence suggested surgical treatments were also effective.
TABLE 100.5
Research question using PICO format for class III treatment (Cochrane review)
| Type of studies included | RCTs |
| Participant characteristics | Children and adolescents (aged 16 years or younger) receiving orthodontic treatment to correct prominent lower front teeth (Class III malocclusion) |
| Intervention | Non-surgical orthodontic interventions |
| Comparison | No treatment, delayed treatment, another active intervention |
| Outcome | Prominence of the lower front teeth |
|
|
|
Non-surgical intervention for class III compared to untreated control measured in the short term (9–15 months): overjet.
Non-surgical intervention for class III compared to untreated control measured in the short term (9–15 months): ANB.
Forest plot showing the need for orthognathic surgery as perceived by orthodontists in adulthood (6 years after treatment).
Bone anchored maxillary protraction (BAMP)
This multicentric two-arm parallel RCT study aimed to evaluate the effectiveness of bone anchored maxillary protraction (BAMP) in managing class III skeletal malocclusion in children aged 11–14 years compared to an untreated control group, focusing on the perceived need for orthognathic surgery, skeletal and dental changes and psychological impact ( Table 100.6 ). Results showed significant improvements in overjet and ANB for the BAMP group at the 18-month follow-up, but no differences were observed at the 3-year mark ( Table 100.7 ). Notably, fewer patients in the BAMP group (48%) were perceived to need orthognathic surgery compared to 75% in the control group (P = 0.04), with an odds ratio of 0.31 (95% CI = 0.10–0.95). Ultimately, 22% of the BAMP group achieved a positive overjet, and the skeletal improvements led to a 27% reduction in the perceived need for surgery compared to the untreated group .
TABLE 100.6
Research question using PICO format for bone-anchored maxillary protraction (BAMP) treatment
| Design | A multicentre two-armed parallel randomised controlled trial. |
| Population: Adolescent patients with class III skeletal malocclusion requiring BAMP treatment at 7 years of age. | Age group: 11.5–14 years |
| Exclusion criteria: A reverse overjet greater than–6 mm, a maxillary mandibular planes angle >38 degrees, mandibular asymmetry; any medical conditions | Inclusion criteria: White Caucasian children aged 11.5–14.0 years; a class III skeletal pattern with maxillary retrusion; a reverse overjet of at least −1 mm with three or more incisors in crossbite in retruded contact position; lower permanent canines and first premolars erupted (to allow space for the lower plates after orthodontic root divergence); and dentally fit and excellent oral hygiene (to reduce the risk of post-operative infection). |
| Group 1: BAMP treatment | Group 2: No treatment control group |
| Outcomes: Overjet and skeletal measurements measured on cephalometric radiographs | Data collection: Data collection occurred at registration (DC1), 18 months (DC2) and 3 years (DC3), where skeletal and dental changes were measured. |
|
|
|
TABLE 100.7
Results of maxillary-mandibular growth during BAMP treatment compared with untreated controls
| Outcomes | BAMP group | Untreated control group | ||||
|
DCI-DC2 change
0–18 months |
DC2-DC3 change
18 months to 3 years |
P value
(BAMP vs CG) DC1-DC2 |
DCI-DC2 change
0–18 months |
DC2-DC3 change
18 months to 3 years |
P value
(BAMP vs CG) DC2-DC3 |
|
| SNA | 1.1 | 0.9 | 0.05 | 0.4 | 1.2 | 0.8 |
| SNB | 0.5 | 0.7 | 0.16 | 1.1 | 1,4 | 0.28 |
| ANB | 0.6 | 0.2 | 0.004 | −0.7 | −0.2 | 0.16 |
| Overjet | 1.4 | 0.6 | 0.002 | −0.2 | 0.1 | 0.06 |
Anchorage devices
Transpalatal arch
The study aimed to evaluate the effectiveness of the transpalatal arch (TPA) as an anchorage device in preventing the mesialisation of maxillary molars during anterior tooth retraction following premolar extraction ( Table 100.8 ). Qualitative analysis revealed that all nine RCTs had a high risk of bias, while six non-randomised studies had a moderate to high risk. Quantitative analysis indicated that groups using only the TPA experienced significant anchorage loss, with mesial molar movement ranging from 27% to 54% ( Fig. 100.11 ). In contrast, groups using combined conventional anchorage (TPA with headgear) showed a mean molar movement of 1.26–4.28 mm (20%–40% of the extraction space), while those using skeletal anchorage (TAD) had a mean loss of 0.00–2.05 mm (0%–22%). Consequently, the study concluded that TPA alone should not be recommended for maximum anchorage during anterior tooth retraction in extraction cases, based on moderate risk of bias and some certainty level.
TABLE 100.8
Research question in PICO format regarding the use of transpalatal arch as reinforcement for anchorage
| Population: | Patients with full permanent dentition undergoing fixed orthodontic treatment with upper bilateral premolar extraction and retraction of anterior teeth. |
| Intervention: | The anchorage using TPA. |
| Comparison: | Control or another retraction treatment group. |
| Outcomes: | The percentage of mesial molar crown movement at the end of the anterior retraction phase. |
|
|
|
Forest plot showing TPA alone versus TADs anchorage.
Nance button
This three-arm multicentre RCT study aimed to compare the effectiveness of Nance button, headgear and temporary anchorage devices (TADs) for anchorage supplementation in treating patients with malocclusions requiring maximum anchorage ( Table 100.9 ). Results indicated that anchorage loss among the three groups was not statistically significant, with differences of around 1 mm that may not be clinically relevant. However, peer assessment rating scores were significantly improved for TADs compared to both headgear and Nance groups. Patient questionnaires revealed similar comfort levels for TADs and the Nance appliance, while headgear was reported as more troublesome and less favoured by patients ( Table 100.10 ). In conclusion, although there was no difference in the effectiveness of anchorage support among the three groups, the quality of treatment was superior with TADs.
TABLE 100.9
Research question using PICO format for different methods of anchorage reinforcement
| Design | A multicentre three-armed parallel randomised controlled trial. |
| Population: | Adolescent patients with Class II dental malocclusion requiring maximum anchorage. |
| Inclusion criteria: | Age group between 12 and 18 years old. The operators had assessed them as needing maximum anchorage. |
| Exclusion criteria: | Requiring functional appliance or orthognathic surgery, cleft lip and palate and syndromes. |
| Age group: | 12 to 18 years |
| Groups | Group 1: TADs; Group 2: Nance; Group 3: headgear |
| Outcomes: | Mesial movement of the molars |
| Data collection: | Data collection occurred at registration (DC1), end of anchorage requirement (DC2) and end of orthodontic treatment (DC3). |
| |
