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A systematic review of cephalometric facial soft tissue changes with the Activator and Bionator appliances in Class II division 1 subjects

Carlos Flores-Mir , Paul W. Major
DOI: http://dx.doi.org/10.1093/ejo/cjl034 586-593 First published online: 9 November 2006


The objective of the present systematic review was to evaluate, through lateral cephalograms, facial soft tissue changes after the use of the Activator and Bionator appliances in Class II division 1 malocclusion subjects.

Several electronic databases (PubMed, Medline, Medline In-Process & Other Non-Indexed Citations, Cochrane Database, Embase, Web of Sciences, and Lilacs) were searched with the assistance of a senior health sciences librarian. Abstracts, which appeared to fulfil the initial criteria, were selected by consensus. The original articles were then retrieved. Their references were also hand searched for possible missing articles. Clinical trials, which assessed facial soft tissue changes with the use of either an Activator or a Bionator appliance without any surgical intervention or syndromic characteristics, were considered. A comparable untreated control group was required to factor out normal growth changes.

Five articles using the Activator and six using the Bionator fulfilled the selection criteria and quantified facial soft tissue changes. An individual analysis of these articles was undertaken and some methodological flaws were identified.

Based on the available evidence, a significant amount of controversy regarding the soft tissue changes produced by the Activator and the Bionator exists. Soft tissue changes that were reported as being statistically significant were of questionable clinical significance. Long-term, double-blinded, prospective randomized clinical trials are needed to confirm the findings. Three-dimensional quantification is also required to overcome current limitations in our understanding of the soft tissue changes obtained with the use of removable functional appliances.


Class II division 1 malocclusions have been treated for more than a century with different removable functional appliances. A functional appliance is a removable or fixed appliance, which changes the mandible/maxilla interrelationship through forces generated by acrylic or wirework to the dentition and underlying structures. These forces are generated through stretching of muscles, fascia, and/or periosteum (Mills, 1991). Removable functional appliances can be classified into four groups (Macey-Dare and Nixon, 1999):

  1. tooth-borne passive (e.g. Activator, Bass, Bionator),

  2. tooth-borne active (e.g. Twin Block),

  3. tissue-borne (e.g. Fränkel), and

  4. combined (e.g. hybrid appliance).

These distinctive types of removable functional appliances produce changes through different mechanisms, but in essence they create a pattern of function which encourages a new morphological pattern in some of the dental and skeletal facial structures (Carels and van der Linden, 1987).

Among all the available passive tooth-borne functional appliances, the Activator and the Bionator are the most commonly used. Both appliances reposition the mandible in a more protrusive position, control the overbite, and modify dental eruption (Crokaert et al., 1989; Macey-Dare and Nixon, 1999).

Aesthetic improvement is one of the main reasons for seeking orthodontic treatment (Peck and Peck, 1995; Vig et al., 1999) and functional appliances are intended to improve occlusal relationships as well as facial profile (Pancherz and Anehus-Pancherz, 1994). Of the hundreds of reports evaluating the skeletal and dental changes produced by different removable functional appliances, only a relatively small proportion have analysed the soft tissue changes. Several individual studies have evaluated the soft tissue changes produced by the Activator or Bionator. Although some literature reviews (Bishara and Ziaja, 1989; Crokaert et al., 1989; Mills, 1991; Petrovic et al., 1991; Johnston, 1996; Barton and Cook, 1997; Rudzki-Janson and Noachtar, 1998; Macey-Dare and Nixon, 1999; Collett, 2000; McSherry and Bradley, 2000; Jacobs and Sawaengkit, 2002; Gill et al., 2005) and systematic reviews (Aelbers and Dermaut, 1996; Chen et al., 2002; Shen et al., 2005) have focused on the effect of different functional appliances on skeletal and dental structures, no systematic review has specifically focused on the evaluation of soft tissue changes produced by the Activator and Bionator appliances. Therefore, the objective of the present systematic review was to evaluate facial soft tissue changes using lateral cephalograms after the use of the Activator and Bionator appliances in Class II division 1 malocclusion subjects.

Materials and methods

A computerized search was conducted using Medline (from 1966 to week 1 of January 2006), Medline In-Process & Other Non-Indexed Citations (up to 12 January 2006), Lilacs (from 1982 to December 2005), PubMed (1966 to week 1 of January 2006), Embase (from 1988 to week 1 of 2006), Web of Science (1945 to week 1 of 2006), and all evidence-based medicine (EBM) reviews (Cochrane Database of Systematic Reviews, American College of Physicians Journal Club, database of abstracts of reviews of effects, and Cochrane database of trial registration; to the fourth quarter of 2005). The terms used in this literature search were ‘Activator’, ‘Bionator’, ‘functional appliances’, ‘soft tissue’, ‘profile changes’, and ‘facial changes’. The selection and specific use for each term in every database search were made with the help of a senior librarian specialized in health sciences database searches (Table 1).

View this table:
Table 1

Search results from different electronic databases.

The following inclusion criteria were chosen to initially select potential articles from the published abstract results:

  1. Human clinical trials,

  2. Facial soft tissue changes evaluated through lateral cephalograms,

  3. Activator and/or Bionator functional appliances to correct Class II division 1 malocclusions,

  4. No syndromic or medically compromised patients,

  5. No individual case reports or series of cases, and

  6. No surgical intervention.

No attempts were made at this stage to identify studies which did not use adequate control groups to factor out growth changes. It was considered improbable that the abstracts would report sufficient information regarding control groups. This would potentially exclude some articles.

All the article abstracts that appeared to meet the initial inclusion criteria were selected, and the articles collected. The selection process was independently made by both authors and their results compared to settle discrepancies through discussion, except for the Lilacs database which was only evaluated by one of the researchers because of language limitation. If an article abstract did not provide sufficient information to make a decision, the actual article was obtained.

The articles ultimately selected were chosen with the following additional final inclusion criteria:

  1. A comparable control group to factor out growth changes if the subjects were still growing, and

  2. Only a removable functional appliance was used.

The actual articles from the selected article abstracts were then independently evaluated by both authors. A consensus was reached regarding which articles fulfilled the final selection criteria and these were finally included in the systematic review. Studies that did not factor out growth in growing subjects were rejected at this stage and not considered further. It was considered important to factor out craniofacial growth in order to make an accurate assessment of the amount of true magnitude of the soft tissue changes. Failure to consider craniofacial growth changes would result in a potential overestimation of the amount of changes obtained. Simultaneous use of fixed appliances was considered a confounder and a reason for exclusion. Although measurement error is needed for a correct interpretation of the clinical significance of the findings, it was not considered a reason to reject an article but rather was considered in the interpretation of the data.

Recognizing that more methodologically sound studies may provide more reliable conclusions, a methodological scoring process (Table 2) was developed to identify which selected studies would be most valuable. No attempt was made to imply that this evaluation tool has been properly validated. Previous reports (Juni et al., 1999, 2001; Verhagen et al., 2001) have shown that there is no sound evidence regarding the validity of the use of quality assessment of clinical trials, and they recommend that researchers examine individually the influence of key components of methodological quality.

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Table 2

Methodological score of selected articles.

The reference lists of the retrieved articles were also hand searched for additional relevant publications that may have been missed in the database searches. When extra information was required for discussion or statistical analysis and, was not specifically stated in the article, contact with the authors was undertaken to obtain the required information.


The search results and the final number of abstracts selected according to the initial selection criteria from the various databases are provided in Table 1. Comparing the database results, Medline and PubMed showed the greatest diversity of finally selected abstracts (slightly more than 50 per cent). The same abstracts were selected from PubMed and Medline. All the abstracts selected from all EBM reviews and Web of Science were already included in Medline and PubMed. Lilacs, which included only Latin-American publications, accounted for a significant percentage (33 per cent) of the finally selected abstracts which did not appear in any other databases. None of the finally selected articles was missed in the electronic database searches.

From the 30 studies, which based on the abstracts seemed to be potentially useful, only 11 (37 per cent) actually fulfilled the final selection criteria after reading the complete article (Table 2). The remaining 19 articles were rejected due to the lack of an adequate control group to factor out expected normal growth changes (Table 3) or because they were published only as an abstract, thesis, or later as a full article (Table 4). A flow diagram of the literature search appears in Figure 1.

Figure 1

Flow diagram of the literature search.

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Table 3

Articles excluded due to a lack of a control sample to factor out normal changes.

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Table 4

Publications excluded because they were published only as an abstract, thesis, or later as a full article.

Further details concerning the methodology of the selected studies are shown in Table 5.

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Table 5

Key details about the selected articles.


Five studies (Forsberg and Odenrick, 1981; Looi and Mills, 1986; Gogen and Parlar, 1989; Mamandras et al., 1989; Cozza et al., 2004) evaluated the soft tissue changes obtained with the use of an Activator. The specific measurements are shown in Table 6.

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Table 6

Articles pertaining to Activators.

No changes in the naso-labial (SnLs SnNBt) and labio-mental (SiLi SiM′) angles were observed (Looi and Mills, 1986), but a mild protrusion (1.8 degrees) of menton was reported (Cozza et al., 2004). Neither the tip (Forsberg and Odenrick, 1981) nor the base (Looi and Mills, 1986) of the nose underwent any change. Contradictory results were found regarding the position of the upper lip, the lower lip, and menton. Some studies (Forsberg and Odenrick, 1981; Looi and Mills, 1986; Gogen and Parlar, 1989) reported upper lip retrusion (−1.1 to −3 mm) but others no change (Mamandras et al., 1989; Cozza et al., 2004). Contradictory changes in upper lip thickness and length were also reported, but no changes in the lower lip or soft tissue menton were noted (Looi and Mills, 1986).


Six studies (Lange et al., 1995; Oliveira et al., 1997; Morris et al., 1998; Almeida et al., 2001; Henriques et al., 2001; Maltagliati et al., 2004) evaluated the soft tissue changes using a Bionator. The measurements used are shown in Table 7.

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Table 7

Articles pretaining to Bionators.

Contradictory results were reported for the facial angles. One of the studies (Henriques et al., 2001) did not report any changes in facial convexity, one a diminution (−2.2 degrees; Morris et al., 1998), and one augmentation (2.7 degrees; Lange et al., 1995). Regarding the labio-mental angle, a large increase (17 degrees; Lange et al., 1995) and no change (Morris et al., 1998) were observed. No studies reported a significant naso-labial angle change (Lange et al., 1995; Oliveira et al., 1997; Almeida et al., 2001; Henriques et al., 2001). Total face height and lower face thirds were augmented (Morris et al., 1998; Henriques et al., 2001).

Contradictory results were found for the antero-posterior position of the upper lip, lower lip, and soft tissue pogonion. Retrusion of the upper lip (−0.89 to −1.4 mm; Lange et al., 1995; Almeida et al., 2001) or no change (Morris et al., 1998; Henriques et al., 2001) was reported. For the lower lip, a protrusion (2.2–4.9 mm; Almeida et al., 2001; Henriques et al., 2001) or no significant change (Lange et al., 1995; Morris et al., 1998) was observed. Finally, soft tissue pogonion was found to be more protrusive (0.9 mm; Lange et al., 1995; Henriques et al., 2001) or unchanged (Morris et al., 1998).

A vertical increase was reported for upper lip, lower lip, and soft tissue menton measurements (Lange et al., 1995). The locations of the cephalometric points are shown in Figure 2. Definitions of the cephalometric points used in this study are defined elsewhere (Athanasiou, 1995).

Figure 2

Cephalometric points (Athanasiou, 1995). S, sella; N, nasion; N′, soft tissue nasion; Tr, tragus; Or, orbitale; Prn, pronasale; Sn, subnasale; Ss, stomion superious; Ls, labrale superious; Li, labrale inferious; Si, stomion inferious; Pg′, soft tissue pogonion; M′, soft tissue menton; A, point A; B, point B; U1, tip of the upper incisor.


The present systematic review was performed to analyse the soft tissue changes produced with the use of the Activator and Bionator appliances in Class II division 1 malocclusion subjects.

A significant number (25 per cent) of the finally selected studies appeared only in the Lilacs database. This finding shows the need for comprehensive database searches for systematic reviews in all possible languages. Previous studies have also raised this issue (Sutton et al., 2000; Clarke, 2002).

Art students, dental students, and parents of orthodontic patients did not perceive any significant soft tissue differences in subjects treated with two types of removable functional appliances (Activator and Fränkel; O’Neill et al., 2000) in comparison with untreated controls. Therefore, although some statistically significant soft tissue changes were found after the use of the Activator or Bionator appliances, the clinical significance, at least from a layperson's perspective, is questionable.

Another problem found in this systematic review was that the level of evidence from the selected reports was low. Only two (Looi and Mills, 1986; Morris et al., 1998) of the final selected studies obtained a methodological score higher than 50 per cent. Only one (Morris et al., 1998) of those was an actual randomized clinical trial. More methodologically sound trials are required to attain the best possible level of evidence (double-blinded, randomized clinical trials) to understand the soft tissue changes produced by these types of functional appliances.

Although an increase of the lower facial third is associated with functional appliance treatment (Alexander et al., 1999; Bardinet et al., 2003), only one (Lange et al., 1995) of the selected studies reported soft tissue vertical changes. Skeletal vertical changes are an important component of functional appliances (Falck and Kobel, 1985; Lange et al., 1995; Morris et al., 1998); therefore, they should be discussed with the patients.

The importance of posture in assessing soft tissues cephalometrically also has to be considered. Some studies use vertical lines based on natural head position changes, while others use vertical lines from heads positioned with Frankfort parallel to the floor to evaluate soft tissue changes. This makes comparison between measurements questionable.

Reference structures used to quantify soft tissue changes have to be carefully considered. For example, the aesthetic plane is not a good reference plane to quantify changes in the lips. Simultaneous changes in soft tissue pogonion or pronasale could create the impression of lip changes that are really non-existent. One study (Nalbantgil et al., 2005) reported that if the aesthetic plane was not used and instead a linear distance to a vertical line through sella, then a significant retroposition of the upper lip was found but there was no lower lip change. If the aesthetic plane was used as a reference, then no significant antero-posterior change of the upper lip, but a significant protrusion of the lower lip, was observed.

Future studies should consider three-dimensional (3D) analysis of the soft tissue changes produced by the Activator and Bionator. Conventional orthodontic frontal and lateral cephalometric analyses do not seem capable of comprehensive evaluations of 3D changes. Use of stereophotogrammetry or a laser surface scanner will overcome the current limitations. A very limited number of studies evaluating 3D soft tissue changes after functional treatment have been published (Illing et al., 1998; Morris et al., 1998; McDonagh et al., 2001). Their main limitations were failing to use a normal non-treated control group and presenting the results as visual changes rather than actual volumetric changes.


Based on the available evidence, there is significant controversy regarding the soft tissue changes produced by the Activator and the Bionator.

For the studies that supported significant changes, the nature of reported changes was of questionable clinical significance.


Special thanks to Linda Seale for her professional assistance in the database search.


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