This results in a normal occlusion without permanent alterations in the dentition ... The purpose of treatment of an anterior open bite malocclusion is to correct the.
Radboud University Nijmegen Medical Centre Department of Orthodontics and Oral Biology
A systematic review on the stability of treatment results of the anterior open bite malocclusion
Researchers: H.W.M. van Asseldonk N.C.A. van Dijk
Supervisors: Dr. T. Bartzela Prof. Dr. C. Katsaros
Index
1. Title
3
2. Aim of the study
3
3. Project management 3.1 Project organization
3
3.2 Project team
4
3.3 Location
4
4. Systematic review 4.1 Background
5
4.2 Material and Methods
13
4.3 Results
18
4.4 Discussion
26
4.5 Determinants for treatment outcome and stability
32
4.6 Conclusion
36
5. References
37
2
Research Systematic review Department:
Project number:
Orthodontics and Oral Biology Radboud
Composition
University
date:
Nijmegen
Written by:
Date:
Signature:
Medical Centre Approved by:
1.
TITLE “A systematic review on the stability of treatment results of the anterior open bite malocclusion”
2.
AIM OF THE STUDY
Aim of this study was to describe determinants for treatment outcome and stability of anterior open bite malocclusion by performing a systematic review on the literature.
3.
PROJECT MANAGEMENT
3.1
Project organization
Research supervisors Dr. T. Bartzela Prof. Dr. C. Katsaros
3
Assigned examiners H.W.M. van Asseldonk N.C.A. van Dijk
3.2
3.3
Project team
Name:
Discipline:
Task:
H.W.M. van Asseldonk
Dental student
Researcher
N.C.A. van Dijk
Dental student
Researcher
Dr. T. Bartzela
Orthodontics
Supervisor
Prof. Dr. C. Katsaros
Orthodontics
Supervisor
Location
Radboud University Nijmegen Medical Centre, Department of Orthodontics and Oral Biology
4
4.
SYSTEMATIC REVIEW
4.1
Background
Definition
There are many different definitions of anterior open bite malocclusion in the literature. “Anterior open bite is the absence of vertical overlap of the incisal edges of the maxillary and mandibular incisors relative to the occlusal plane” (Fig. 1) (Katsaros et al. 2001).
Fig. 1 Patient with anterior open bite.
Prevalence
Open bite malocclusion has a rather low prevalence. A survey of health care problems and needs in the USA gave epidemiological data on malocclusion. The study was based on 7000 individuals and was statistically designed to provide weighted estimates for approximately 150 million persons. It showed that 3.6% of 8-11-year-olds (whites, blacks and Mexican-Americans) had anterior open bite (> 3mm in 0.9% of cases). Among 12-17-year-olds the prevalence was 3.5% (> 3mm in 0.7% of cases), and among adults (18-50 years old) 3.3% (> 3mm in 0.5% of cases) (Proffit et al. 1998). Kalsbeek performed a study on the prevalence and treatment of orthodontic malocclusions from 1987 to 1999 among Dutch children with a health insurance. The prevalence of a vertical open
5
bite in 5-year-olds (n: ±1.250) was 17%, 11-year-olds (n: ±1.450) 4%, 17-yearolds (n: ±1.400) 3% and 23-year-olds (n: ±1.150) 4% (Kalsbeek et al. 2002).
Classification
Anterior open bite is usually classified as dentoalveolar and/or skeletal. Dentoalveolar open bite is caused by vertical underdevelopment of the anterior dentoalveolar process, usually due to various types of functional disturbances. Skeletal open bite is associated with a general distortion of growth (Katsaros et al. 2001), which is characterized by an enlarged lower face height and a steep inclined mandibular plane (Lopez- Gavito et al. 1985). Elements of both dentoalveolar and skeletal dysplasia are apparent in most open bite cases, this makes differentiation between dentoalveolar and skeletal open bite quite difficult (Cangialosi 1984).
Aetiology
Vertical malocclusion is a result of the interaction of many different aetiologic factors including thumb and finger sucking, lip and tongue habits, airway obstruction, and true skeletal growth abnormalities. Successful identification of the aetiology improves the chances of treatment success. Long-term clinical outcomes are needed to determine treatment effectiveness. Clinicians should consider the cost-effectiveness of this early initiated treatment (Ngan and Fields 1997).
Chronic disturbance in nasal breathing, or habitual mouth breathing are primarily associated with impeded maxillary growth. This maldevelopment of the maxilla results in a narrow jaw with a high palate and dental crowding as well as retrognathism or prognathism of the mandible. The lack of maxillary growth is due to the position of the tongue in mouth breathers. The tongue is displaced downward and the muscular forces acting on the maxilla are no longer balanced. The functional hyperactivity, especially of the buccinator, impedes the transversal development of the maxilla (Rakosi 1993).
6
The following is a list of open bite cephalometric characteristics: 1. Excessive gonial, mandibular, and occlusal plane angles (Ar-Go-Me, SNMP, SN-OP) 2. Decreased palatal plane angle (SN-PP) 3. Small mandibular body and ramus (Go-Me, Ar-Go) 4. Increased lower/decreased upper anterior facial height (LAFH/UAFH) 5. Increased anterior/decreased posterior facial height (TAFH/TPFH) 6. Shorter nasion-basion distance (N-Ba) 7. Retrusive mandible (SNB) 8. Class II tendency (ANB) 9. Divergent palatal-mandibular angle (PP-MP) 10. Steep anterior cranial base (SN-MP) (Lopez-Gavito et al. 1985)
Aim of treatment
The aim of treatment of the anterior open bite is to correct the morphological deviation as well as to improve: 1. masticatory efficiency: to create a sufficient biting performance 2. speech: to solve the problem of lisping and/or speech distortion 3. temporomandibular dysfunction: a higher incidence of open bite is reported in symptomatic TMD patients (Williamson 1977, Mohlin and Kopp 1978). (Even though there is no evidence in the literature that orthodontic treatment can prevent or cure TMD. (McNamara andTürp 1997). 4. aesthetics: to create facial harmony, to solve gummy smile problems or to correct incompetent lip relation (Katsaros et al. 2001).
7
Treatment
Treatment of open bite ranges from simple habit control to complex surgical procedures.
1. Ending of the sucking habit: The majority of the children stop their sucking habit by the age of 6 (Larsson 1985). This results in a normal occlusion without permanent alterations in the dentition. If the ending of the habit is not achieved, the indication to start a therapeutic intervention is on eruption of the permanent incisors. Anterior vertical dentoalveolar development is expected during eruption of the incisors. The child’s cooperation with the appropriate psychological support from the family is an important factor in the intervention to stop a sucking habit (Katsaros et al. 2001). The cooperation has to be ascertained, because the appliance often works as a reminder for the termination of the sucking activity. 2. Control of tongue posture and activity: The open bite malocclusion postpones the transition to the mature swallowing pattern. The tongue activity in combination with a forward resting position of the tongue can influence the tooth position and delay the therapeutic intervention or be a reason for a further relapse (Proffit 2000). 3. Achievement of normal nasal respiration: In an anterior open bite malocclusion a consultation of an ENT specialist is indicated. Habitual mouth breathing or anatomic airway obstruction can be differentiated and therapeutic intervention should be considered. However, it must always be kept in mind that impaired nasal respiration may contribute to the development of long-face appearance but may not be the sole or the major cause (Proffit 2000). 4. Control of the posterior vertical dimension in growing patients: Anterior open bite malocclusion can be corrected by prevention of eruption or intrusion of the posterior teeth (Woodside and Linder-Aronson 1979, Subtelny 1988). Extraction of premolars is the treatment of choice in many cases. The vertical posterior dimension can be controlled with various orthodontic treatment approaches: 8
-
high pull headgear to the upper molars
-
high palatal bar
-
(magnetic) bite-blocks
-
vertical chin-cup
-
masticatory muscle training
-
functional appliance (Fränkel’s function regulator (FR-4))
-
extraction of posterior teeth
5. Elongation of the anterior teeth: In cases where the exposure of the anterior upper teeth at rest or while smiling is reduced, stimulation of the vertical development of the anterior teeth can be the method of choice. The stimulation can be achieved with an edgewise appliance and vertical elastics (Fig. 2) or extrusion arch wires. In cases where the upper teeth are exposed averagely it might be advisable to elongate only the lower incisors, thereby increasing the curve of Spee in the lower arch (Proffit 2000).
a
b Fig. 2
c a: Pretreatment situation. b: During treatment. Vertical elastics were used to assist in the closure of the anterior open bite. c: Post-treatment situation. (From Katsaros et al. 2000)
9
6. Surgical treatment: This method of treatment uses surgical interventions to correct the malocclusion. The most common surgical treatment is a total or segmental maxillary osteotomy for the superior repositioning of the maxilla or its posterior part. Upward and forward mandibular autorotation is produced in these maxillary osteotomies (Proffit and White 1991). Mandibular surgery is mainly used additionally to maxillary surgery for further correction of any sagittal, transversal or local dentoalveolar discrepancies (Katsaros et al. 2001) (Fig. 3).
a
b
Fig. 3 Anterior open bite in an adult patient treated with combined surgical-orthodontic approach. a: Pretreatment situation. b: Situation 2 years after surgery. (From Katsaros et al. 2001)
Stability of treatment results
The purpose of treatment of an anterior open bite malocclusion is to correct the vertical deviation. In many cases treatment results remain stable several years after treatment, but in other cases despite a successful treatment, relapse can occur in the follow-up period (Fig. 4, 5). Several factors can be the reason for relapse. Active habits can produce intrusive forces on the incisors, while at the same time the posture of the mandible is altered, allowing posterior teeth to erupt. Tongue habits, particularly the tongue-thrust swallowing pattern, are often blamed for
10
relapse into open bite. However, the evidence to support this statement is not convincing (Katsaros et al. 2001). Since vertical growth is the last dimension to be completed, treatment may appear to be successful at one point and fail later. Nemeth and Isaacson (1974) found that the amount of vertical growth after treatment in the posterior part of the facial skeleton was a decisive factor in the stability of orthodontic treatment results of anterior open bite. Open bite relapse was associated with a significant posterior rotation of the mandible. Vertical facial growth extends into postadolescent years (Behrents 1985). Even if growth has been modified successfully during the mixed or early permanent dentition period, active retention is likely to be necessary for a number of years.
a
b
c
Fig. 4 a: Pretreatment situation (15.4 years of age). b: End of retention ( 18.0 years of age). c: 8 years postretention (26 years of age).
11
Basis for the study “Successful treatment of anterior open bite malocclusion is considered one of the most challenging areas in orthodontics” (Kim et al. 2000). However, relatively few studies have thoroughly evaluated the stability of open bite treatment (Shapiro 2002) (Table 2).
Orthodontic treatment Although the aetiology, orofacial morphology and different forms of treatment of the open bite malocclusion are often seen in the literature, there are few studies concerning the treatment of open bite and its stability. “It would be desirable for the clinician to have reliable pretreatment determinants for open bite stability” (Lopez-Gavito et al. 1985). The fact that current studies (Janson et al. 2003, Janson et al. 2006, de Freitas et al. 2004) show less stability than previous studies (Huang et al. 1990, Katsaros and Berg 1993) makes a systematic review on the literature interesting. The question is which determinants might play a role in this difference. The lack of a sufficient amount of patients included in the studies, makes it difficult to draw reliable conclusions. Well-designed studies are needed for better understanding of the effectiveness and stability of orthodontic therapy as well as the mechanism for relapse. In many current studies there is selection bias and they have small samples (Huang 2002). Studies with increased sample size, will create results with greater statistical power (Huang 2002). Prospective studies would be desirable but are time consuming.
12
4.2
Material and methods
Search strategy
All the studies that examined the relationship between open bite treatment and stability have been identified. A literature survey was done by using the Pubmed database (Entrez Pubmed, www.ncbi.nim.nih.gov). The survey covered the period 1966 to June 2006. OLDMEDLINE records are included in Pubmed. OLDMEDLINE covered the period from 1950 till 1965. Pubmed was searched by using the following search terms:
Electronic search:
Pubmed / Cochrane Library #1
“open bite” and “stability”
#2
“open bite” and “treatment outcome”
#3
“open bite” and “recurrence”
#4
“open bite” and “retention”
#5
“open bite” and “follow up”
#6
“open bite” and “relapse”
In addition to this search the following Medical Subject Headings (MeSH) terms were used:
#7
“open bite/therapy” [MeSH] “stability”
#8
“open bite/therapy” [MeSH] and “treatment outcome”
Hand search: #9
reference lists of selected articles
13
The Pubmed search resulted in 32 studies. No additional articles were found by applying the Cochrane Library. The abstracts were reviewed and studies that were not relevant to this study were eliminated. From the selected abstracts, original articles were retrieved, and their references were hand searched for missing articles.
Study selection criteria
Inclusion and exclusion criteria are listed in Table 1. The criterion for inclusion was the presence of data on stability of nonsurgical treatment of human subjects. Exclusion criteria consisted of surgical treatment of the anterior open bite. Case reports and reviews were excluded. No restrictions were set for sample size. There was no language restriction.
TABLE 1: Exclusion/Inclusion criteria
Exclusion criteria
Inclusion criteria
Case reports
Arithmetic data on stability
Reviews
Human subject
Surgical treatment
Nonsurgical treatment
14
Figure 6 shows the flow diagram which illustrates the search that is performed to come to the included studies.
Electronic Search PubMed / Cochrane N = 32
Excluded studies Reason: did not met the inclusion criteria N = 23
Studies retrieved for more detailed analyses N=9
Hand Search N = 14
Excluded studies Reason: case reports and reviews N=5
Excluded studies Reason: did not met the inclusion criteria N=8 Potentially appropriate to be included N=6
Potentially appropriate to be included N=4
Included N = 10
Fig. 6 Search strategy.
Data collection Two investigators participated in the study. The two researchers independently carried out the screening of the articles that met the inclusion criteria. The evaluation consisted of extracting relevant data from each study. Data were retrieved from tables, figures and text in the publications. The inter-examiner conflicts were resolved by consensus review. The evaluation of individual studies was done objectively to minimize introduction of bias.
15
The data of the studies will be summarized in five tables. The following data were extracted:
Total number subjects
Study design
Growing/nongrowing
Males/females
Control group
Mean age and standard deviation of groups
Cephalometric measurements
Skeletal classification
Angle classification
Treatment approach
Extraction/non extraction
Treatment period
Retention
Overbite measurements
Follow-up period
Stability
Table 2 shows the list of articles on orthodontic treatment of the anterior open bite, which were selected applying the selection criteria.
16
TABLE 2: Selected publications on orthodontic treatment of the anterior open bite malocclusion
Article №
Reference No*/
Year of
First Author
Publication
1.
1 / Beckmann
2002
2.
4 / de Freitas
2004
3.
7 / Huang
1990
4.
8 / Janson
2003
5.
9 / Janson
2006
6.
11 / Katsaros
1993
7.
14/ Kim
2000
8.
15 / Küçükkeleş
1999
9.
17 / Lopez-Gavito
1985
10.
28 / Sugawara
2002
* Reference No. corresponds with the number of this article in the reference list.
17
4.3
Results
Of the 46 articles retrieved by applying the databases 10 of them met the inclusion- and exclusion-criteria.
Subjects and Study design The sample sizes of the reviewed studies are rather small. Only Beckmann and Segner used a group of 83 subjects (Beckmann and Segner 2002). Some studies discussed the treatment of two separate groups, based on the age of the subjects (growing/growing subjects) (Huang et al. 1990, Kim et al. 2000). Janson et al. separated the groups based on the treatment approach (Janson et al. 2006). The study design of the ten studies is shown in Table 3. No Randomized Clinical Trials had been performed. All studies were retrospective and longitudinal. Three studies used a study design with a control group (de Freitas et al. 2004, Janson et al. 2003, Katsaros and Berg 1993). De Freitas et al. used two untreated control groups. Control group 1 consisted of 15 female subjects with a mean age of 13.0 years. The selection criteria were randomized occlusions and no previous orthodontic treatment. The control group was used to characterize the experimental group pretreatment. Control group 2 consisted of 21 patients, 9 males and 12 females, with normal occlusion and an initial mean age of 14.6 years. This group was followed longitudinally for a period comparable to the follow-up period of the experimental group and was used to compare cephalometric changes (de Freitas et al. 2004). Janson et al. used one control group (Janson et al. 2003). Katsaros and Berg used a control group for the comparison of pretreatment cephalometric values. The control group consisted of thirty 12-year-old Norwegians with ideal occlusion (Katsaros and Berg 1993). All studies defined the amount of males and females in their sample. However, separation of the groups is never based on the gender of the subjects. In three studies the amount of subjects in the initial subset was reduced during the different treatment periods (Katsaros and Berg 1993, Kim et al. 2000 and Küçükkeleş et al. 1999). In the study by Kim et al. the initial sample of the growing group consisted of 29 patients, among which only 17 had complete records. The initial sample of the nongrowing group consisted of 26 patients of
18
which only 10 had complete records (Kim et al. 2000). The reason for the dropout of the patients in the study by Katsaros and Berg (Katsaros and Berg 1993) and the study by Küçükkeleş et al. (Küçükkeleş et al. 1999) was not clarified (Table 6).
TABLE 3: Subjects and Study design Total subjects
Study design
Growing / nongrowing
Beckmann 2002
83
R, L
growing
32
de Freitas 2004
31
R, L, UC
growing
8
Huang 1990
26
R, L
growing
Janson 2003
21
R,L, UC
Janson 2006
21
R, L
Article material
7
Katsaros 1993
20
R, L
Kim 2000
29
R, L
26
Control group
Mean age of groups
SD
51
no
12.11
4.8
23
yes
13.22
no
9.58
5
28
growing
5
16
yes
12.40
growing
5
16
no
12.40
growing
8
23
growing
3
17
yes
11.80
2.5
growing
8
21
no
13.42
1.08
nongrowing
5
21
26.08
5.83
nongrowing
31
Males Females
20.83
13.22
Küçükkeleş 1999
17
R, L
nongrowing
5
12
no
19.35
Lopez-Gavito 1985
41
R, L
growing
12
29
no
12.42 *
Sugawara 2002
9
R, L
nongrowing
2
7
no
19.30
NOTE: Study Design:
R = Retrospective L = Longitudinal UC = Untreated control group RCT = Randomized Clinical Trial
* Median
Cephalometric measurements / Angle Classification
The skeletal measurements collected in Table 4 give an indication of the growth pattern and skeletal classification of the subjects. The skeletal classification was obtained based on the ANB angle. Huang et al. did not report the lower anterior facial height and the ANB angle (Huang et al. 1990). In the study by Katsaros and Berg the groups were separated according to the Angle classification. The Angle classification of the treated subjects was mentioned in seven articles (de Freitas et al. 2004, Huang et al. 1990, Janson et al. 2003, Janson et al. 2006, Katsaros and Berg 1993, Lopez-Gavito et al. 1985, Küçükkeleş et al. 1999).
19
TABLE 4: Cephalometric measurements / Angle Classification
Article material
Beckmann 2002 de Freitas 2004
LAFH (mm)
Divergency
ANB
Skeletal classification based on ANB
treatment success 59.97 SD 6.69 treatment failure 65.94 SD 7.43
treatment success 36.13 SD 5.24 (ML-NSL) treatment failure 41.90 SD 5.04 (ML-NSL)
T1 treatment success 5.72 SD 2.71 T1 treatment failure 5.15 SD 3.21
II II
69.08 SD 5.20
39.10 SD 4.10 (SN.GoGn)
3.74 SD 2.10
I
I I
37.4 (SN-MP)
Huang 1990
41.5 (SN-MP) Janson 2003
67.75 SD 5.28
36.94 SD 5.66 (SN.GoGn)
2.87 SD 2.32
Janson 2006
67.75 SD 5.28
36.94 SD 5.66 (SN.GoGn)
2.87 SD 2.32
Katsaros 1993 Kim 2000
Küçükkeleş 1999 Lopez-Gavito 1985 Sugawara 2002
3.74 SD 2.18
I
30.66 SD 4.61(FH-MP)
3.79 SD 2.30
I
32.73 SD6.45 (FH-MP)
3.94 SD 2.56
I
69.08 SD 5.22
39.10 SD 4.16 (SN.GoGn)
66.70 SD 6.80
39.0 SD 5.8 (ML/NSL)
72.62 SD 6.64 79.69 SD 6.53 75.02 SD 6.47
40.47 SD 5.81 (SN-MP)
2.64 SD 2.42
I
69.20 SD 2.30
34.10 SD 5.3 (SN-MP)
5.30 SD 2.80
II
76.10 SD 5.80
33.10 SD 2.1 ( FH to MP)
4.50 SD 2.00
I
Angle Cl
16 Class I 15 Class II Class I or Class II Class I or Class II Class I Class I 16 Class I 15 Class II Class II tendency
Dental relationship Class I or mild Class II Class I or Class II div I
Treatment
Different treatment approaches have been performed. Beckmann and Segner give records of patients treated with removable and fixed appliances (Beckmann and Segner 2002). Six studies evaluated the treatment of open bite malocclusion with fixed appliances (de Freitas et al. 2004, Janson et al. 2003, Janson et al. 2006, Katsaros and Berg 1993, Küçükkeleş et al. 1999, Lopez-Gavito et al. 1985). In four of these studies, some patients got additional therapy with headgear, intermaxillary elastics, functional appliances and palatal expansion (Beckmann and Segner 2002, de Freitas et al. 2004, Janson et al. 2003, Janson et al. 2006). In the study by Katsaros and Berg one patient was treated with functional appliances (Katsaros and Berg 1993). Multiloop Edgewise Arch Wire therapy and intermaxillary elastics were used by Kim et al.. In the study by Lopez-Gavito et al. all subjects were treated with fixed appliances and headgear (Lopez-Gavito et al. 1985). Küçükkeleş et al. treated all patients with fixed
20
appliances in combination with intermaxillary elastics (Küçükkeleş et al. 1999). The treatment with a Skeletal Anchorage System (SAS) in combination with fixed appliances was studied by Sugawara et al. (Sugawara et al. 2002). Extraction was part of the therapy in four studies (de Freitas et al. 2004, Janson et al. 2006, Katsaros and Berg 1993, Kim et al. 2000). In the study by Katsaros and Berg only 16 subjects were treated with extractions (Katsaros and Berg 1993). In the study by Kim et al. anterior and/or posterior crowding was relieved by extraction of permanent teeth (Kim et al. 2000). Janson et al. treated one of his two groups with extractions (Janson et al. 2006). In the study by de Freitas et al. 24 patients were treated with extractions (de Freitas et al. 2004). The duration of treatment in the different studies is shown in Table 5. The treatment period of the nongrowing subset of Kim et al. (Kim et al. 2000) and the subset of Küçükkeleş et al. (Küçükkeleş et al. 1999) is significantly shorter than the treatment period of the growing subsets of the remaining studies (Table 5). The standard deviation of the treatment period was only mentioned in two studies (Beckmann and Segner 2002, Kim et al. 2000). The use of retention was described in seven studies (Beckmann and Segner 2002, de Freitas et al. 2004, Janson et al. 2003, Janson et al. 2006, Katsaros and Berg 1993, Kim et al. 2000, Küçükkeleş et al. 1999). In the other studies retention was not mentioned. The retention period varies from 6 weeks to 8.35 years (Kim et al. 2000, de Freitas et al. 2004). In the maxilla the most common used retainer was the Hawley appliance, while in the mandible it was the 3 x 3 retainer.
21
TABLE 5: Treatment
Total subjects
Treatment approach
Extraction/ Non extraction
Treatment period (years)
SD
Retention
Beckmann 2002
83
44 RA/ 39FiA (+HG +FuA)
Non extraction
5.58 *
2.33
Yes
de Freitas 2004
31
FiA (+HG)
Extraction
2.46
Yes
Huang 1990
26
Crib (+FiA +HG +PE)
Non extraction
1.17 (crib)
Not declared
7
Crib + FiA (+HG)
Non extraction
1.08 (crib)
Not declared
Article material
Janson 2003
21
FiA (+IE)
Non extraction
2.40
Yes
Janson 2006
21
FiA (+IE +PE)
Non extraction
2.40
Yes
31
FiA (+IE +PE)
Extraction
2.46
Yes
3.80 (incl. retention)
Yes
Katsaros 1993
20
19FiA 1HG+FuA
29
MEAW + IE
26
MEAW +IE
Kim 2000
4 patients treated with extractions Extraction of permanent teeth was required for some patients to relieve anterior and/or posterior crowding
2.25
0.92
Yes
1.42
0.75
Not declared
Küçükkeleş 1999
17
FiA +IE
Non extraction
1.33
Yes
Lopez-Gavito 1985
41
FiA + HG
Non extraction
2.08 (Retention period )
Not declared
Sugawara 2002
9
SAS + FiA
Not reported
2.58 (SAS 1.24)
Not declared
Abbreviations: RA, Removable appliances; FiA, Fixed Appliances; HG, Headgear; FuA, Functional Appliances; PE, Palatal Expanding; IE, Intermaxillary Elastics; MEAW, Multiloop Edgewise Arch Wire; SAS, Skeletal Anchorage System * total observation time
Overbite measurements
The overbite measurements were taken after different time periods; pretreatment, immediately after treatment and after follow-up (Table 6). In all studies the overbite was negative at the pretreatment stage. At the posttreatment stage all measurements but one were positive. It is important to mention that different registration methods of the overbite are used. Katsaros and Berg measured the amount of overbite on lateral cephalograms as the distance between the perpendiculars from the incisal edges of the upper and lower incisors to the N-Me line (Katsaros and Berg 1993). The overbite measurement in the study by De Freitas et al. was calculated as the distance between incisal edges of maxillary and mandibular central incisors, perpendicular to functional occlusal plane (de Freitas et al. 2004). In the study by Lopez-Gavito et al. the open bite was measured as the lineair distance from the incisal edge of the most anterior mandibular incisor to the contact point of the opposing hard tissue structure projected along the long axis of the mandibular 22
incisor (Lopez-Gavito et al. 1985). Lopez-Gavito et al. reported a posttreatment overbite of –2.2 mm. No improvement in the open bite correction was observed during the posttreatment/follow-up interval when the sample was analyzed as a whole. However, when the groups were subdivided into relapse (n=15, 36.5%) and stable (n=26, 63.5%), the relapse group demonstrated an average of 4.5±0.45mm open bite at the follow-up period. The pretreatment open bite values were similar in the stable and the relapse group. Both groups showed a similar improvement of open bite as a result of treatment (Lopez-Gavito et al. 1985). Huang et al. (Huang et al. 1990) and Lopez-Gavito et al. (Lopez-Gavito et al. 1985) did not mention the standard deviations of the measured mean overbites. Beckmann and Segner did not report the posttreatment overbite for the initial sample (83 patients). The difference in overbite between end of retention and pretreatment was noted (Beckmann and Segner 2002).
TABLE 6: Overbite measurements
Overbite pretreatment
Article material
Total subjects
Total Overbite
SD
Overbite after follow up
Overbite posttreatment
sample
Follow-up sample
SD
SD
Beckmann 2002
83
treatment success treatment (n=53) success -2.15 SD 1.36 treatment treatment failure failure (n=30) SD 1.73 -2.99
de Freitas 2004
31
-2.73 (n=31)
Huang 1990
26
-2.88 (n=26)
1.82
1.82
7
-2.71 (n=7)
1.49
2.29
Janson 2003
21
-1.75 (n=21)
0.66
1.43
0.62
0.50
0.07
0.62
Janson 2006
21
-1.75 (n=21)
0.66
1.43
0.62
0.50
0.07
0.62
1.80
1.09
1.62
0.94
treatment success 1.72, treatment failure -2.15
treatment success SD 1.17, treatment failure SD 2.05
1.02
1.62
31
-2.73 (n=31)
1.80
1.09
1.62
0.94
1.02
1.62
Katsaros 1993
20
-1.90 (n=20)
1.80
1.20 (n=20)
1.80 (n=18)
2.0
1.20 (n=18)
1.80 (n=18)
Kim 2000
29
-2.27 (n=29)
2.10
1.58
1.01 (n=17)
0.81 (1.18 n=17) 1.18 (n=17)
1.01 (n=17)
1.09 (n=10)
0.84 (0.57 n=10) 1.55 (n=10)
1.09 (n=10)
26
-2.23 (n=26)
2.10
1.78
Küçükkeleş 1999
17
-4.05 (n=17)
2.92
1.32
Lopez-Gavito 1985
41
-5.05 (n=41)
Sugawara 2002
9
-2.80 (n=9)
1.80
1.11 (1.16 n=10) 0.50 (n=10)
-2.2
0.80
2.10
1.76
0.80 0.80
1.20
1.76
23
Stability of overbite
The follow-up rates vary from 1 year to 11 years and 6 months (Sugawara et al. 2002 / Küçükkeleş et al. 1999, Lopez-Gavito et al. 1985). Beckmann and Segner noted the total observation period, which includes treatment and retention. The treatment period in the study by Beckman and Segner was not separated from the retention period (Beckmann and Segner 2002). Lopez-Gavito et al. reported no significant change in the openbite measurements between posttreatment and follow-up (Lopez-Gavito et al. 1985). Katsaros and Berg (Katsaros and Berg 1993) reported the overbite measurement for an initial sample of 20 subjects. This sample is reduced during the different stages, which makes it impossible to calculate a difference between the observation periods. In the study by Kim et al. only 10 of the initial sample of 26 patients in the nongrowing sample had complete records. In the growing sample there are 12 dropouts of the initial sample of 29 patients (Kim et al. 2000). The column ‘overbite follow up – posttreatment’ gives the relapse values during the follow-up period. The stability rates, if available in the studies, ranged from 61.9% to 100% (Table 7).
24
TABLE 7: Stability of overbite
Article material Total subjects
Follow-up period
Overbite Overbite follow up – Posttreatmentposttreatment pretreatment T1-T3 (pretreatment-end of retention) treatment success overbite 3.88 SD 1.74, T1-T3 treatment failure overbite 0.84 SD 2.22 3.82 -0.07
Stability
Beckmann 2002
83
Total observation period 5 years 7 months (SD: 2-4)
de Freitas 2004
31
8.35 years (range, 5.35-23.67)
Huang 1990
26
5-8 (range, 1-0 to 14-0)
4.70
0.00
82.6%
7
3-5 (range, 1-1 to 8-11)
4.20
0.80
100%
Janson 2003
21
5 years
3.18
-1.36
61.9%
Janson 2006
21
5.22 years (range, 3.08-9.33 years)
3.18
-1.36
61.9%
-0.06
74.2%
74.2%
31
8.35 years (range, 5.25-23.67 years)
3.82
Katsaros 1993
20
2.20 years
3.10
Kim 2000
29
35 months (SD, 17 months)
3.85
-0.23 (n=17)
94,1% 90%
100%
26
28 months (SD, 4 months)
4.01
-0.35 (n=10)
Küçükkeleş 1999
17
1 year follow-up
5.37
-1.25 (n=10)
Lopez-Gavito 1985
41
2.85
Sugawara 2002
9
Postretention period median 11-6 (yr-mo) range 9-6 to 18-0 1 year after debonding
No significant change reported -0.90
4.90
63.5% ± 70%
25
4.4
Discussion
In order to perform a meta-analysis, standardized information and complete records are required. A meta-analysis of the existing studies would give us more grounded conclusions. The lack of a precise documentation of the different components of the research makes the assemblance difficult. Instead of a quantitative analysis a systematic review on the literature was performed.
In this systematic review the data of 10 articles related to stability of the open bite treatment were used (Table 2). Heterogenous data make combination of the data difficult.
The possibility of combining data of these retrospective studies demands a similar selection procedure to produce comparable patient groups. In the collected studies different selection criteria were used. Most of the used criteria were the presence of a pretreatment open bite of 1 mm or more and all maxillary and mandibular teeth up to the second molars. Additional to the criteria mentioned above, the patients of de Freitas et al. were screened on extraction treatment with the edgewise appliance, associated with anterior vertical elastics (de Freitas et al. 2004). Pretreatment open bite of 3 mm or more was a criterion for the sample selection of Lopez-Gavito et al., when measured as the linear distance from the incisal edge of the most anterior mandibular incisor to the contact point of the opposing hard tissue structure projected along the long axis of the mandibular incisor (Lopez-Gavito et al. 1985). This situation can also be found in deep bite cases with a large sagittal discrepancy, therefore this measurement is not always a reliable indicator of the presence of an open bite malocclusion (Katsaros and Berg 1993). Katsaros and Berg used the absence of incisal contacts in habitual occlusion as well as following forward movement of the lower dental cast, keeping always at least two occlusal contacts on the posterior teeth bilaterally in the sagittal plane as an definition for open bite. The amount of the overbite was measured on the lateral cephalograms as the distance between the perpendiculars from the incisal edges of the upper and lower incisors to the N-Me line (Katsaros and Berg 1993). Küçükkeleş et al. used
26
a high angle skeletal pattern (SN.GoMe > 37°) as an additional criterion to select their sample (Küçükkeleş et al. 1999). Three out of ten studies used a ‘control group’ (de Freitas et al. 2004, Janson et al. 2003, Katsaros and Berg 1993). These control groups were used to characterize the experimental group rather than to make comparisons with the experimental groups. In a review by Huang it is mentioned that comparison between different types or combinations of orthodontic therapies in cohort or randomized designs is more important than including an untreated control group. This can be explained by the fact that these subjects usually do not improve without therapy, especially after the eruption of the permanent incisors (Huang 2002).
The growth pattern is an important factor in the aetiology, treatment and stability of the open bite case in the growing individuals. No unequivocality is found in the studies in the use of measured angles. Although the difference might be neglectable similar measurements are recommended. Kim et al. reported on stability of the treatment with the MEAW in growing and nongrowing subjects. Growing and nongrowing patients with an open bite tendency had an increased mandibular plane angle, increased lower facial height, low ODI (overbite depth indicator), and obtuse gonial angle. For the growing group they noted some significant changes in the skeletal variables during the active treatment period. In this study no control group for this age was available and it was difficult to ascertain whether the skeletal changes observed were due to growth alone or to growth in combination with treatment (Kim et al. 2000). In the sample description the amount of males and females is noted in all the studies, however, this distinction is not made in the results. The different growth pattern between males and females can be expected to have influence on the stability of the open bite treatment.
In the studies reviewed the treatment approach was described. In some studies additional therapy was used. The appliances used were: headgear, functional appliances, fixed appliance, palatal expansion, intermaxillary elastics or a combination of these appliances. The differentiation of the appliances used, is in 27
some studies not made in the results (Table 5) (Beckmann and Segner 2002, de Freitas et al. 2004, Huang et al. 1990, Janson et al. 2003, Janson et al. 2006). De Freitas et al. concluded that the palatal expansion procedure does not seem to have affected the stability of the open bite correction, but they stated that further investigation is still needed (de Freitas et al. 2004). Janson et al. speculated that the significant increase in maxillary molar dentoalveolar height during treatment could be a consequence of the rapid palatal expansion. However, the extrusion of the maxillary posterior teeth that usually occurs after rapid palatal expansion was noticeable only immediately after the procedure. At the end of the complete fixed appliance treatment period, extrusion of these teeth was similar to that of the control group (Janson et al. 2003).
Myofunctional therapy is usually recommended after orthodontic treatment to minimize the open bite relapse. Janson et al. concluded that relapse is possibly explained by the lack of tongue adaptation. The treatment protocol of the groups included myofunctional therapy after treatment. However, because this was a retrospective study, it could not be ascertained from the clinical charts that all patients in both groups followed the recommendations and underwent such therapy (Janson et al. 2006). The study of Huang et al. evaluated the stability of anterior open bite treated with crib therapy. They concluded that patients who achieved a positive overbite with crib therapy have a good chance of maintaining the positive overbite after orthodontic treatment is completed. This statement appeared to be true for both growing and nongrowing patients. The reason for this increased stability may be due to a modification of tongue position or posture (Huang et al. 1990).
Complete documentation of the patient group must include the Angle and skeletal classification. Almost all studies reported the skeletal classification (ANB). Striking is the fact that the standard deviation is large relative to the ANB angle. This makes classification of the patient group difficult. In five out of ten studies there was no differentiation between the different Angle classifications. In the study by Janson et al. group 2 included 15 Angle Class II malocclusions and group 1 included 21 Angle Class I patients. Janson et al. discussed that behavior of the overbite was similar in both malocclusions with time. In addition there was 28
no evidence that stability of open bite correction in Class I occlusions was different than in Class II malocclusions (Janson et al. 2006).
The conventional treatment of open bite consisted of extrusion of anterior teeth or by the inhibition of molar eruption in growing patients (Sugawara et al. 2002). The stability of all of these treatment options remains questionable, because the anterior teeth of skeletal open bite are usually over erupted due to the dentoalveolar compensatory mechanism for excessive anterior facial height. Predictable intrusion of molars can be achieved with application of SAS. The counterclockwise rotation of the mandible resulted in the reduction of lower facial height and the large interlabial gap. The skeletal profiles of the treated patients did not change 1 year after debonding, although the relapse rate of the intruded molars was approximately 30%. It must be noted that the follow-up period is relatively short. The relapse of the intruded molars was not directly related either to the skeletal changes or to the recurrence of open bite. Intrusion of the molars was also achieved with application of MEAW in adult patients. However, the molar intrusion according to this method has been found to be minimal (Sugawara et al. 2002). In the study of Küçükkeleş et al. was noted that although the arch wires forced the molars to be both intruded and uprighted, no molar intrusion took place. Instead, the molars were extruded while being uprighted (Küçükkeleş et al. 1999) The follow-up period of this study was only 1 year. In the study by Kim et al. (2000) the open bite correction in the growing group was obtained by increased dentoalveolar heights in upper and lower anterior teeth, uprighting movement of posterior teeth, retraction of anterior teeth and changes in occlusal planes (Kim et al. 2000). Extrusion of the upper incisors during treatment could increase the maxillary gingival display of the patients when smiling. Therefore it is very important to exclude those individuals who already show a “gummy smile” at the beginning of treatment (Küçükkeleş et al. 1999).
In most of the studies examined, the experimental groups were not divided into patients treated with or without extraction. It has been suggested that extraction treatment of the anterior open bite might provide more stable results (Janson et al. 2003). Extraction versus non extraction treatment was only performed by Janson et al. (2006). They reported better stability on the treatment of Class II 29
patients treated with extraction, although they had the greatest tendency for relapse of the open bite. In the conclusion they made a distinction between extraction and non extraction treatment. Katsaros and Berg noted extraction of certain teeth but they did not mention this in the remaining part of the article. Kim et al. used extraction of permanent teeth to relieve anterior and/or posterior crowding in some patients. The distinction in extraction versus non extraction was not made in the results. Kim et al. argued that the treatment effects are influenced by the extractions. Proper diagnosis of an open bite malocclusion includes evaluation of anterior and/or posterior crowding. If necessary, extraction of permanent teeth was an important aspect of the MEAW therapy, and Kim et al. stated that this did not present bias in the interpretation of the treatment effects (Kim et al. 2000). In the study by De Freitas et al. was stated that although treatment of open bite with extractions seemed to provide a better prognosis for correction stability, some patients might still show relapse of the open bite in the long term. Procedures designed to prevent relapse of the anterior open bite were overcorrection, active retention with bite-blocks, and speech therapy (de Freitas et al. 2004). Janson et al. concluded that extraction treatment of open bite patients has greater stability of the overbite than open-bite nonextraction treatment (Janson et al. 2006).
The observation time after debonding ranged from 1 year up till 9 years and 6 months (Sugawara et al. 2002, Lopez-Gavito et al. 1985). Short follow-up periods in growing patients were not of great value because relapse can occur even after 5 years (de Freitas et al. 2004). Katsaros and Berg raised the question whether the post-retention period was sufficient, although their study showed a high degree of stability (Katsaros and Berg 1993). It is known that the greater the follow-up period, the greater the tendency for relapse of orthodontic corrections and especially the greater the tendency for open bite relapse (Janson et al. 2006).
Stability of treatment effects is probably the most important criterion when deciding on a treatment method for open bite correction. Posterior mandibular rotation resulting from growth after treatment or extrusion of posterior teeth during treatment has been reported as an important factor for open bite relapse. 30
Relapse of anterior open bite can occur by depression of the incisors and/or elongation of the molars (Küçükkeleş et al. 1999). In patients without a habit of placing an object between their front teeth, open bite relapse is usually a result of elongation of the posterior teeth, with no apparent intrusion of incisors (Proffit 1993). Vertical growth and eruption of posterior teeth may continue until late teen years or early twenties, making the open bite tendency quite difficult to control. Thus, retention in open bite patients should be long term and involve strict control of eruption of the posterior teeth (Küçükkeleş et al. 1999). The problem of open bite relapse resulting from growth after treatment in comparison to the high degree of stability in the study by Katsaros and Berg raised the question of the correct treatment initiation of an open bite malocclusion. An early intervention may provide better possibilities for functional and skeletal changes, but may also imply a considerable risk for unfavorable growth after treatment, leading to relapse (Katsaros and Berg 1993). Stability can be classified as ‘statistically significant’ or ‘clinically significant’. De Freitas et al. discussed the term ‘statistically significant’ and stated that although this mathematic jargon could be very useful and understandable to the researchers, it is not to the clinician (de Freitas et al. 2004). This makes comparison of the stability rates difficult. Different evaluation methods have been used to measure the stability of the anterior open bite correction in the long term. Lopez-Gavito et al. defined relapse in their sample as a cephalometric distance of more than 3 mm from the tip of the lower incisor to the nearest hard tissue measured along the long axis of the lower incisor (Lopez-Gavito et al. 1985).
31
4.5
Determinants for treatment outcome and stability
As stated by Lopez-Gavito et al. it would be desirable for the clinician to have reliable pretreatment determinants for open bite stability (Lopez-Gavito 1985). The following text will describe the determinants for treatment outcome and stability that are mentioned in the current literature.
Beckmann and Segner found that retrusion of the maxillary incisors during treatment led to a more stable overbite during the retention period. This was seem first in the study by Katsaros and Berg (Katsaros and Berg 1993). That confirmed the ‘Drawbridge principle’ described by Subtelny (Subtelny 1988). Vertical lengthening of the symphysis relative to the increase in lower face height seemed to enhance bite opening during retention. If a re-evaluation takes place during active treatment, prediction of the overbite may be reliable. They noted that the angle NTGoGn (R = 0.46) had substantial predictive value for the posttreatment overbite. Retrusion of the maxillary incisors and growth of the symphisis can result in a stable overbite at the end of treatment. Deeping of the bite can be diminished by an increase in lower facial height during treatment. An excessive increase in vertical height of the symphysis must be prevented, because it may enhance relapse after active treatment. For prediction of the posttreatment overbite, the angle NTGoGn may be used although a reevaluation during treatment is recommended (Beckmann and Segner 2002).
De Freitas et al. concluded that there was no statistically significant decrease of the anterior overbite at the end of the follow-up period. Normal vertical development of the maxillary and mandibular incisors, smaller vertical development of the mandibular molars, and consequent smaller increase in lower anterior facial height were the primary factors that contributed to the nonsignificant decrease of the overbite. Their results were compared with the control group in the long term (de Freitas et al. 2004). The pretreatment Angle classification, the extractions, the use of headgear and the retention period have not been mentioned as possible determinants for treatment outcome and stability of the anterior open bite.
32
In the study by Huang et al. there was a significant increase in overbite for both groups during treatment. During the follow-up period, 17.4% of the growing sample and 0% of the nongrowing sample showed a relapse of the open bite. However, all patients who achieved a positive overbite during treatment maintained a positive overbite posttreatment. Remarkable is the fact that the nongrowing group also showed a significant increase in overbite during the follow-up period. Growth pattern, Angle classification, additional treatment to crib therapy and the use of retention has not been seen as predictable determinants for the treatment outcome and stability (Huang et al. 1990).
In the study by Janson et al. a statistically significant decrease of the obtained anterior overbite at the end of the postretention period was demonstrated. The smaller vertical development of the maxillary and mandibular incisors in the postretention period was the primary factor that played a role in the overbite decrease. Neither the initial anterior open bite nor the magnitude of correction was associated with the long-term overbite decrease (Janson et al. 2003).
Janson et al. mentioned a statistically greater stability of the overbite in the extraction group in the follow-up period. No statistically significant difference in patients with clinically significant relapse of the open bite between the groups could be demonstrated. It was concluded that open bite extraction treatment has greater stability of the overbite than open bite non extraction treatment (Janson et al. 2006).
In the study by Katsaros and Berg none of the successfully treated patients had a negative overbite at the follow-up period. The high rate of stability in this study makes the duration of the follow-up period questionable. Although this might be the fact, minimal further growth changes were expected after the follow-up period, because 17 out of the 20 patients were females and the mean age at the follow-up control was 17 years and 10 months. Uprighting of the incisors in cases with an increased facial convexity, seemed to have a favorable treatment prognosis. (Katsaros and Berg 1993).
33
Kim et al. analyzed the posttreatment and follow-up cephalometric radiographs and proved that the treatment results obtained by the MEAW therapy were very stable. It must be noted that 50% of the sample was lost during the follow-up period. The changes in overbite during the two year follow-up period were not significant. There were some significant changes in the skeletal variables for the growing group during the active treatment period. It was difficult to ascertain whether the skeletal changes observed were due to growth alone or growth in combination with treatment, because this study did not include a control group for this age group (Kim et al. 2000). Küçükkeleş et al. assessed lateral cephalograms of only 10 patients after a relatively short period of 1 year postretention in order to evaluate relapse changes. Position of the upper and lower incisors and the inclination of the occlusal plane remained stable during the follow-up period. However, extrusion of upper and lower molar teeth resulted in a reduction in overbite. As a result of upper and lower molar extrusion, total anterior and lower anterior face heights were increased. The difficulty in controlling the open bite tendency is the continuing vertical growth and eruption of posterior teeth until late teen years or early twenties. Thus, retention in open bite patients should be long-term and involve strict control of eruption of the posterior teeth (Küçükkeleş et al. 1999).
An analysis of subgroups was reviewed by Lopez-Gavito et al. to compare dentoalveolar and skeletal relationships of both stable and relapse groups. More than 35% of the treated open bite patients relapsed. Relapse was defined as a postretention open bite of more than 3 mm. This definition of relapse differs strongly from definitions in other studies. The relapse subgroup demonstrated less mandibular anterior dental height, less upper anterior facial height, greater lower anterior facial height, and less posterior facial height. The reliable prediction of posttreatment stability of the open bite was neither proved by the magnitude of pretreatment open bite, mandibular plane angle, nor any other single parameter of dentofacial form (Lopez-Gavito et al. 1985).
34
In the study of Sugawara et al. the short-term stability of SAS was indicated following the intrusion of molars. Although the relapse rate was approximately 30%, the skeletal profiles of the treated patients were stable 1 year after debonding. This suggests that relapse of the intruded molars was not directly related to the skeletal changes or the recurrence of the open bite. Sugawara suggests that overcorrection may be necessary (Sugawara et al. 2002).
35
4.6
Conclusion
This article has attempted to describe determinants for treatment outcome and stability of anterior open bite malocclusion by performing a review on the literature. The majority of the reviewed studies have a problem of lack of power because of small sample sizes and the potential for selection bias. Most of the current studies do not conclude which determinants play a role in the stability of the open bite treatment. The lack of a precise documentation and heterogenous data makes assemblance of the studies difficult, so evidence based conclusions could not be drawn. Future studies with homogenous data and complete documentation are needed to obtain reliable scientific evidence of which determinants influence the treatment outcome and stability of the anterior open bite malocclusion.
36
5.
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