Functional Appliances Effectiveness and Stability of Treating Class II Skeletal Malocclusion: A Systematic Review

Nancy Ajwa^*

^*Correspondence: Dr. Nancy Ajwa, Department of Preventive Dentistry, Riyadh Elm University, Riyadh, Saudi Arabia, Email:

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Introduction

Face defects have many negative effects on the life of any person, however its very regular birth defects that occur in all socialites. One of these defects that found in all cultures is dental malocclusion. Dental malocclusion's prevalence not the same in all part of world as many factors as ethnic, environmental and genetic can affect and cause malocclusion. According to WHO, malocclusions are the third in the list of the highest conditions among oral pathologies after tooth decay and periodontal diseases and consider the third worldwide public health dental disease priorities.

Malocclusion is consisting of (mal) and (occlusion); occlusion is the relationship between maxillary and mandibular teeth when they are in functional contact. Consequently, malocclusion is the deviation from the normal occlusion movement. Angle's classification is the most popular method to classify malocclusion which divided according to this classification into three divisions; class I, II and II. Class II, which is the most, frequent condition presenting in orthodontic practice is a distal relationship of mandibular teeth compared with maxillary ones. However, the high prevalence of class 2 malocclusion, its cause for most cases is unknown. Although many factors may contribute with the condition as distortion of maxillary, mandibular development or both as it have a significant effect on positioning, alignment and health of normal teeth. Considering that, most cases of class 2 malocclusion were related to mandibular retrognathism rather than maxillary prognathism.

Depending on axial inclination of upper anterior, class 2 malocclusion is classified in two different types each called division and have number of 1 and 2. Division 1 is most frequent one, while division 2 is rare. The division one occurs when proclined upper central incisors is present with a significant increase in overjet. In division two, upper central incisors are retroclined and lateral one may be proclined or normally inclined with slightly or minimal overjet.

All children should be regularly checked for malocclusion, so if dentist see any problem in jaw or teeth alignment, he will suggest further visit to an orthodontist who in his turn will ask about child's past health, check the mouth and teeth and may also ask for taking X- rays and photos of face and teeth for more accurate diagnosis. For photting the teeth, dental casts, intra and extra oral photographs, radiographic images are used for this purpose. Nowadays, there are modern technologies used for imaging the face and teeth that replace the older ones as digitized dental models and three dimensional imaging.

Division 2 shows different triad feathers from division 1 which include; deep bite, retroclined maxillary incisors and posteriorly positioned mandibular dental arch. In addition, division 2 has different skeletal components as decreased lower face height, decreased gonial angle, hypo divergent pattern and low mandibular plane angle.

Skeletal malocclusion is a serious condition, which has many complications that affect oral health as causing dental trauma and mastication difficulties. In addition, untreated malocclusion is related to many other conditions as sleep related breathing disorders.

There many strategies for correction of class 2 malocclusion in growing age including the use of functional appliance with growing modification. Functional appliance aims to modify the position of mandible sagittally and vertically and to induce lengthening of mandible by increasing the growth at condylar cartilage. Therefore, these appliances have the maximum effect when applies early while jaw is still growing. Functional appliance may be removable appliance as activators, bionator, headgear and twin block appliances. In addition, fixed appliances as herbst, orthodontic camouflage and forsus appliance. Dissimilar to removable functional appliances, fixed functional devices have the benefit of not requiring patient compliance and they can be applied alongside with brackets. Each appliance has its advantages and disadvantages and many studies have been made to evaluate each appliance on the development of skeletal and dental correlation, however little studies have been done to compare between fixed and removable appliance in skeletal, dento alveolar and soft tissue correction, including clinical and lateral cephalometric measurements and the duration of treatment.

The current review aimed to systematically assess the literature on the effectiveness of fixed and removable functional appliances and determines its stability results among growing patients with skeletal class II malocclusion [1].

Literature Review

A systematic review was conducted where clinical trials were analyzed and published up to 2020, respecting years of seniority. Studies that have been evaluated are linked to functional appliances effectiveness and stability of treating class II skeletal malocclusion. The current systematic review of literature is carried out in view of the most important points of the report for systematic reviews [2]. To prepare and organize the systematic review, the search question was developed using the format: Comparison, OR: Result.

Search methods for identification of studies

Eligibility criteria and study selection: A comprehensive electronic search with time and language restrictions were is done. Several known databases were being included eg., “Google scholar, PubMed, the Cochrane library, web of science” from 2014 to 2020 following certain eligibility criteria (Table 1).

Table 1: Inclusion and exclusion criteria.

Data analysis

In several known database were searched eg., Google scholar, PubMed, the Cochrane library, web of science. Combine the search terms and limited the study to the English language. Depending on PRISMA checklist duplicates were removed, articles were screened based on title, abstract and full text.

Quality synthesis: One particular reviewer assessed methodological quality of the studies after final assessment of the full text (n=10) independently. Accordingly, 10 final articles were individually applied for qualitative and quantitative assessments. Quality assessment of the 10 final articles was appraised for risk of bias using a well-formulated quality assessment tool. Sampling bias was appraised by assessing and evaluating the sample selection, performance, detection of outcome assessors, attrition and reporting. The overall assessment provided range from low to moderate risk of bias; the main methodological points of these studies are summarized in Table 2.

Table 2: Criteria for judging risk of bias in the ‘risk of bias’ assessment tool reproduced from the Cochrane tool.

Search methods for identification study the following search engine where are used:

• Medline (PubMed)
• Google scholar
• Cochrane database of systematic reviews
• Trip medical database
• Cambridge libguides
• NHS evidence
• Elsevier

In order to avoid omission of relevant studies, a broad search strategy was undertaken that covered the whole spectrum of treatment strategies of malocclusion and was then carefully restricted on functional appliances. The searched studies were concluded to orthodontic studies that deal with treatment of malocclusion type two of two divisions using functional appliances. The reference lists of the trials eligible for inclusion and systematic reviews concerning Class II malocclusion treatment were also checked [3].

Malocclusion types two, functional appliances, herbst, Forsus appliance, twin block, bionator, skeletal are the most keyword used. In addition, the reference lists of the included articles as well as of relative reviews were searched for the identification of possibly relevant studies. For studies published in more than one language, the English version is used. After choosing studies, each article was tested for reliability of authors, publisher and university where study conducted.

Criteria of judgment following low, high or unclear risk were judge based on the following:

Random sequence generation: Selection bias (biased allocation to interventions) due to inadequate generation of a randomized sequence.

Allocation concealment: Selection bias (biased allocation to interventions) due to inadequate concealment of allocations prior to assignment.

Blinding of participants and personnel: Performance bias due to knowledge of the allocated interventions by participants and personnel during the study.

Blinding of outcome assessment: Detection bias due to knowledge of the allocated interventions by outcome assessors.

Incomplete outcome data: Attrition bias due to amount, nature or handling of incomplete outcome data.

Selective reporting: Reporting bias due to selective outcome reporting.

Discussion

Manual searches resulted in 9052 hits, which were reduced to 5639 after the removal of duplicates. Following the sequential elimination of 5376 studies on the basis of title and abstract, 263 full texts were considered eligible for further evaluation. From the latter, 253 were excluded for various reasons and finally 10 articles were included in the qualitative synthesis of the present review [4]. After removing the duplicated studies, each study was tested for inclusion and exclusion criteria. Only studies of randomized or non-randomized controlled clinical trials that included treatment of children less than 16 years old with skeletal class II malocclusion and overjet greater than 5 mm and treated with any type of fixed or removable functional appliances were included. The primary outcomes were measures of skeletal, dento alveolar and soft tissue correction, including clinical and lateral cephalometric measurements and the duration of treatment. Exclusion criteria included Trials involving patients with craniofacial syndromes and/or cleft lip or palate excluded, retrospective designs, animal studies, treatment with extractions and/or orthognathic surgery, unsupported opinion of expert, replies to the author/ editor and books’/conferences’ abstracts. In the remaining articles, we examined it on the basis of title, abstract and full text [5].

General results

The general characteristics of the ten included articles are presented in brief in Tables 3 and 4. Four studies were retrospective study, three were prospective study, one was randomized clinical trial, one was case report and the last study was cross sectional study. The whole studies reporting 471 cases, 244 of them were male (51.8%) and 227 were female (48.2%). 224 patients were entering intervention group. Among the 10 studies reporting age, the average patient age was 12 (mean ages within each study ranging between 10 and 13.6 years). The majority of these studies took place in university settings in different countries (Bauru, Italy, Iran, Germany, Pakistan, USA, Brazil and Australia) whereas one of them were performed in private practices and had been published as journal papers and/or dissertations in English between 2014 and 2019 [6].

Most patients had malocclusion class two divisions one while 3 in three studies, patients had malocclusion class two of the two division. Four studies had control group of no treatment while 4 groups had another group that treated with another appliance and 2 cases without any comparable groups. Five studies studied the effect of removable appliance, three studied effect of fixed appliance and the two study try to compare between the two types of appliances [7].

Most of studies measure skeletal and dental change throughout the treatment program except in two studies which depend on measuring differences in soft tissue. A wide variety of removable or fixed functional appliances were used that include bionator, forsus nitinol flat spring, herbst, headgear and twin block. Regarding treatment modalities, twin block was the most appliance used in the studies (4 studies in that 3 studies deal with herbst appliance, two studies of head gear, three studies studied forsus appliance and two studies deal with bionator (Tables 3 and 4).

Table 3: General characteristics of the chosen studies including design, setting and number of participate.

Results of individual studies

Results of each study indicated simply in Table 4. Patients treated with Twin Block (TB) appliance showed significantly more protruded and buccally inclined mandibular incisors in comparison to the control group.

Table 4: The complete of general characteristics of the chosen studies including type of malocclusion, detailed information about participates and intervention used.

In addition, they presented significantly smaller molar relationship, greater increase in mandibular length Co-Gn and significantly greater increase in Sn-Ocl in comparison to the control group. Moreover, they presented greater and significant lingual inclination and retrusion of maxillary incisors and greater and significant buccal inclination and protrusion of mandibular incisors in comparison to the control group [8]. In addition to analysis of dental relationships, the TB group exhibited significantly greater reduction in overjet and molar relationship when compared to the control group 3. Patient with Twin block showed more significant decrease in H angle and significant increase in both (VRLSi) and VRL-Pog than shown in patients treated with Herbst appliance as the difference 2.32 ± 1.69 mm in mean H angle for TB patients and difference 2.12 ± 1.88 mm in mean H angle for Herbst patients, difference of 6.60 ± 0.09 mm in VRL-Si in Twin block treated group and no significant reported difference for herbst treated group while difference of 6.04 ± 1.48 mm of VRL-Pog in Twin block treated group compared to no significant reported difference for herbst treated group 1. Further comparison of twin block appliance against forsus Fatigue Resistant Device (FRD) showed that both devices had the same rate of success. However, TB patients exhibited significantly greater mandibular than the (FRD) and control groups [9]. In addition, TB group showed significantly greater decreases in the ANB angle, greater increments in total mandibular length Co-Gn, greater decreases in overjet, greater increments of change in molar relationships, significantly greater amount of retroclination of the maxillary incisors and lower amount of mandibular incisor proclination when compared with (FRD) treated patients (20.8 mm, 2.0 mm, 23 mm, 1.5 mm, 26.5 u and 2.9 u respectively) and when compared with controlled group (20.2 u, 3.4 mm, 23.0 mm, 27.9 mm, 4.8 mm, 26.3 u and 5.6 u respectively. Moreover, when twin block appliance compared with another removable appliance as bionator, significant difference in the changes they made in ANB (A point Nasion B point) angle, NA-Pog (CONVEXITY angle), basal and gonial angles (p< 0.1). In addition, patients treated with bionator appliance showed increase in Lafh and (Co-Gn) compared with control group (0.96 mm and 1.15 mm respectively) and decreases in ANB and WITS by 0.89° and 2.06 mm in comparison to control group respectively. In addition, the OJ and OB decreased 3.12 mm and 1.22 mm in the treated group in comparison to controlled group, respectively. The IsIi and L6-Mp increased 4.33° and 0.76 mm in treated group in comparison to controlled group, respectively [10].

Head gear appliance is another removable appliance used to resolve malocclusion problem. The main result of usage of head gear in 10 years old child ended in facial aesthetic improvement with an obvious correction of the position and the relationship between the upper and lower lip with overjet reduction from 9 mm to 2 mm and normalization of overbite. In comparing with control group, patients with headgear appliance showed more negative changes (reduction) in the SNA angle. However, no significant difference in SNB changes, horizontal changes in B-point or Pogonion, nor were there significant changes in the angle FH-NPog between the study and control groups. In addition, there were no significant differences in vertical changes of ANS and PNS between study and controls [11].

Herbst appliance is one of the fixed appliances used in controlling malocclusion. It showed significant difference (P=0.01) in the change in vertical position of ANS compared to control group. In addition, there was a significant difference (P=0.03) in the vertical position of B-point in the Herbst group compared with the Class II control group with increases in right and left mandibular lengths during phase 1. However, there was a statistically significant (P=0.02) closure of the right gonial angle in the herbst group (-1.59°) compared with the control group. In compare with Functional Mandibular Advancer (FMA), no significant difference had been established except for the distance between dorsal condyle margin and pterygoid vertical (Co(dorsal)-PTV) which decreased in FMA patients and increased in herbst appliance patients.

This systematic review summarizes evidence from clinical studies on the effect of functional appliance treatment on malocclusion class 2 and the difference between fixed and removable appliance. Even though functional appliances have been used for many decades to treat class II malocclusion, only 10 studies with 471 cases were identified and found eligible for inclusion in this review [12].

The key differences between fixed and removable devices relates to the ability of fixed types to secure compliance and produce significant bite advancement with limited vertical bite opening. However, these appliances may be associated with high rate of breakages and more emergency visits. Conversely, removable appliances may be associated with excessive vertical bite opening and interference with normal functions and mandibular movement, precluding their full time use.

Clinical and radiographic findings: Various cephalometric parameters were used in the included studies; the most common measures included the anterior posterior skeletal discrepancy, mandibular length, vertical face height and overjet. Overall there was inconsistency between authors in adopting these parameters and also in the method of intervention. The functional devices regardless of their type successfully reduced the overjet to within normal limits with similar proportional correction in terms of skeletal and dental effects in the sagittal plane [13].

Dento skeletal changes are concerned; some evidence indicated that patients treated with functional appliances differed from untreated patients. Meta-analysis of 5 studies indicated the positive and effective usage of generally functional appliance to treat patients with skeletal malocclusion.

Maxillary changes: Investigations into the actual dento skeletal changes obtained with the twin block appliance in the first treatment stage did not reveal any restriction of anterior maxillary displacement while the sagittal skeletal correction of class II relationships in the FRD group was due mainly to a significant restriction of maxillary growth. In addition, use of headgear restrained forward growth of the maxilla (decreases in SNA) when used in a phase of treatment prior to and separate from, edgewise therapy. Moreover, bionator appliance was effective in reducing sagittal inter maxillary relationship however, as twin block, both appliances do not actually restrict maxillary growth because maxillary length in both groups increased after treatment however this increase was less in twin block group. In forsus appliance, it seems that the device causes significant decrease in SNA indicating the appliance promoted limitation of the anterior displacement of the maxilla. In addition, as TB, in herbst and FML appliance, no growth inhibiting effect, nor a treatment related change in maxillary length happened.

Mandibular changes: In consider of mandibular growth, in twin block treatment, revealed a statistically significant increase of from 2.0 mm to 4.17 mm in the mandibular length (Co-Gn) which is greater than what happened in FRD treated patients. With headgear, the mandibular effects ranged from no significant difference in length or SNB angle change compared to controls to enhanced mandibular growth greater than controls and comparable to that of a bionator which showed small mean increase in SNB which is correlated with the minimal mandibular skeletal growth during prepubertal period. However, in most studies TB affect mandibular growth greater than bionator except in one study where mandibular length changes were greater in bionator group 7. In forsus treated patients, Co-Gn presented a statistically significant increase which cause increase in mandibular length soon after removal of the forsus appliance.

Maxillo mandibular relation changes: Evaluation of the maxilla mandibular relationship component in twin block treated patients revealed that mandibular growth and/or repositioning did not promote significant changes in ANB and wits variables with consequent reduction in skeletal discrepancy between jaws in individuals in the experimental group. However, the TB induced a more favorable correction in inter maxillary sagittal relationships than did the FRD or what occurred in the controls. In bionator patients, ANB angle was decreased after treatment but twin block resulted in more decrease and this was statistically significant. Forsus appliance result in significantly decreasing in ANB indicating a remarkable improvement in the maxilla mandibular relation [14].

Vertical changes: The height of lower facial third was increased in both TB and bionator treated patients. However, there was no statistically significant difference between two appliances, bionator resulted in more increase. In addition, TB induced a significant posterior rotation of the mandible with respect to the control sample while the FRD group did not show any significant difference in angular measurements compared with the control group. In addition, high pull headgear treatment followed by fixed edgewise appliances did not affect vertical development of the face. In Forsus appliance, there was a mandibular rotation counterclockwise, with decrease of SN.GoMe, of FMA and more increase in postero inferior facial height than in antero inferior facial height [15].

Soft tissue analysis: Unfortunately, only two studies deal with change in soft tissue changes due to usage of functional appliance. Decrease in soft tissue convexity was reported after herbst and twin block therapies; however, this is greater in herbst. Soft tissue profile is improved with use of both Twin block and Herbst appliance but greater advancement of soft tissue pogonion and lower lip were observed in Twin Block (TB) groups as compared to herbst group (Table 5).

Table 5: Parameters and abbreviations.

Conclusion

Functional appliances have a great positive effect in treatment of malocclusion class two whatever fixed or removable appliance. Fixed appliances have a greater restriction on Maxillary development while removable appliance has a greater effect on mandibular development. Both type of appliances have positive effect on reducing overjet without any preference. However, removable appliances are more preferred for patients due to higher comfort level, patients’ speech is normal and immediately improvement in patient appearance.

References

1. van Vlijmen OJ, Kuijpers MA, Berge SJ, et al. Evidence supporting the use of cone beam computed tomography in orthodontics. J Am Dent Assoc 2012; 143:241-252.

   [Crossref] [Google Scholar] [PubMed]

2. Bendgude V, Akkareddy B, Panse A, et al. Correlation between dental traumatic injuries and overjet among 11 to 17 years Indian girls with angle's class I molar relation. J Contemp Dent Pract 2012; 13:142-146.

   [Crossref] [Google Scholar] [PubMed]

3. Blair ES. A Cephalometric roentgenographic appraisal of the skeletal morphology of class I, class II, div. 1 and class II, div. 2 (angle) malocclusions. Angle Orthod 1954; 24:106-119.

   [Google Scholar]

4. Dodda KK, Prasad SE, Kanuru RK, et al. Diagnostic features of angle's class II div 2 malocclusion. Int Soc Prev Community Dent 2015; 5:513.

   [Crossref] [Google Scholar] [PubMed]

5.  Frankel R. The treatment of class II, division 1 malocclusion with functional correctors. Am J Orthod 1969; 55:265-275.

   [Crossref] [Google Scholar] [PubMed]

6. Daskalogiannakis J. Glossary of Orthodontic Terms. 1st edition, Publisher: 4. Quintessence, London, 2000.
7. Johnson LE. Orthodontics: State of the art, essence of the science. St Louis: C V. Mosby, New York, 1986, pp. 88-99.

   [Google scholar]

8. Joshi N, Hamdan AM, Fakhouri WD. Skeletal malocclusion: A developmental disorder with a lifelong morbidity. J Clin Med Res 2014; 6:399.

   [Crossref] [Google Scholar] [PubMed]

9.  Masood Y, Masood M, Zainul NN, et al. Impact of malocclusion on oral health related quality of life in young people. Health Qual Life Outcomes 2013; 11:1-6.

   [Crossref] [Google Scholar] [PubMed]

10. McNamara Jr JA. Components of Class II malocclusion in children 8-10 years of age. Ang Orthodon 1981; 51:177-202.

    [Crossref] [Google Scholar] [PubMed]

11. Moss ML, Salentijn L. The primary role of functional matrices in facial growth. Am J Orthod 1969; 55:566-577.

    [Crossref] [Google Scholar] [PubMed]

12. O’Brien K, Wright J, Conboy F, et al. Effectiveness of early orthodontic treatment with the twin block appliance: A multicenter, randomized, controlled trial. Part 1: Dental and skeletal effects. Am J Orthod Dentofac Orthop 2003; 124:234-243.

    [Crossref] [Google Scholar] [PubMed]

13. Sauer C, Schluter B, Hinz R, et al. Childhood obstructive sleep apnea syndrome: An interdisciplinary approach. J Orofac Orthop 2012; 73.

    [Crossref] [Google Scholar] [PubMed]

14. Trenouth MJ. Proportional changes in cephalometric distances during twin block appliance therapy. Eur J Orthod 2002; 24:485-491.

    [Crossref] [Google Scholar] [PubMed]

15. Wieslander L, Lagerstrom L. The effect of activator treatment on class II malocclusions. Am J Orthod 1979; 75:20-26.

    [Crossref] [Google Scholar] [PubMed]