treatment effects of r-appliance and fränkel-2 in...

17 EuropEan Journal of paEdiatric dEntistry vol. 14/1-2013

R. Showkatbakhsh*, M.I. Castaldo**,A. Jamilian***, G. Padricelli**,M. Fahimi Hanzayi****, S. Cappabianca*****L. Perillo******

* Department of Orthodontics,

Shahid Beheshti University of Medical Sciences, Tehran, Iran

** Departments of Orthodontics, Second University of Naples,

Naples, Italy

*** Department of Orthodontics, Dental Branch,

Center of Craniofacial Research, Islamic Azad University,

Tehran, Iran

**** Department of Orthodontics, Dental Branch, Islamic Azad

University, Tehran, Iran

***** Department of Radiology, Second University of Naples,

Naples, Italy

****** Department of Orthodontics, S

econd University of Naples, Naples, Italy

e-mail: [email protected]

Keywords Class II Division 1; Fränkel 2; Functional Appliance; Mandibular deficiency; R-appliance.

abstract

Aim The purpose of this study was to compare the effects of a differently designed functional appliance (the R-appliance) with Fränkel-2.Study Design Twenty-seven patients (16 girls and 11 boys) with a mean age of 9.8 (SD 1.6) years were treated with the R-appliance for 15.4 (SD 0.4) months and twenty-seven (15 girls and 12 boys) patients with a mean age of 9.1 (SD 1.1) years were treated with a Fränkel-2 appliance for 19 (SD 5.6) months. All patients had Class II division 1 malocclusions due to mandibular deficiency and all of them had prepubertal stages of skeletal development. Lateral cephalograms obtained at the beginning (T1) and at the end (T2) of the study were analysed.Results Paired t-tests showed that SNB significantly increased in both groups. The incisor mandibular plane angle (IMPA) was reduced in the R-appliance group by 2.2 (SD 4.9) degrees (P < 0.03) but increased by 2.2 (SD 2.6) degrees (P < 0.001) in the Fränkel-2 group. The SNA

in the R-appliance group showed an increase of 0.2 (SD 2) degrees (P < 0.6), while it was decreased by 0.4 (SD 0.5) degrees (P < 0.6) in the Fränkel-2 group.Conclusions Both treatment modalities were successful in moving the mandible forward. However, with the R-appliance, this was achieved without proclination of the lower incisors.

Treatment effectsof R-Applianceand Fränkel-2in Class II division 1 malocclusions

Introduction

Class II division 1 malocclusion due to mandibular deficiency is a commonly observed clinical problem [Brunelle et al., 1996; Tausche et al., 2004; Perillo et al., 2010] and it has been extensively studied for skeletal and dental characteristics [McNamara, 1981; Perillo et al., 2012]. Different functional appliances have been used to treat this malocclusion [Clark, 1988; Tulloch et al., 1997; Ghafari et al., 1998; Ehmer et al., 1999; Wheeler et al., 2002; O'Brien et al., 2003]. The Fränkel-2 (FR-2) is one of the most popular functional appliances used today. Rolf Fränkel developed this appliance nearly 50 years ago as an orthopaedic exercise device designed to reprogramme the neuromuscular system of the orofacial complex [Fränkel, 1966; Fränkel and Frankel, 1989].

A recent meta-analysis [Perillo et al., 2011a] reported that the FR-2 appliance had a statistically significant impact on the size of the mandible in treated patients versus untreated controls. Nevertheless, it has been observed that restriction of dento-maxillary growth and proclination of lower incisors are common findings in FR-2 treatment [Owen, 1983a; Owen, 1983b; Creekmore and Radney, 1983; Perillo et al., 1996; Rushforth et al., 1999; Janson et al., 2003; Perillo et al., 2011b]. Generally, these are the main disadvantages of most functional appliances [Toth and McNamara, 1999; Pangrazio-Kulbersh et al., 2003]. To avoid these side effects, the R-appliance was designed [Jamilian et al., 2009; Jamilian et al., 2011].

The aim of this study was to evaluate the dentoskeletal changes achieved with the R-appliance in comparison with the FR-2 in Class II division 1 growing patients with mandibular deficiency.

Materials and methods

This non-randomised retrospective study consisted of 54 patients from two different countries. Twenty-seven subjects were selected from patients treated with the R-appliance (Fig. 1A) at the SHB University

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EuropEan Journal of paEdiatric dEntistry vol. 14/1-201318

Twenty-seven (16 girls, 11 boys) patients were treated with the R-appliance in the experimental group (Fig. 2A). Their mean age was 9.8 (SD 1.6) years and the average treatment time was 15.4 (SD 0.4) months. The patients were instructed to wear the appliances full-time except for eating, contact sports and tooth brushing.

The R-appliance (Fig, 1A, 2A) is a tooth and tissue borne appliance. It consists of buccal and lingual shields, which are connected to each other through the occlusal clearance during bite construction. These shields are extended to the distal of the first permanent molars and cover the buccal and lingual regions and the depth of the vestibule. The lingual shield should be fabricated with minimal undercut relieve. The left and right lower lingual shields are connected and reinforced with a heavy archwire (1 mm diameter) to withstand the load of muscular activity. A heavy wire (1 mm diameter), which acts as a tongue bow, is positioned posteriorly to connect the right and left acrylic parts on the palatal aspect in order to reinforce the appliance. The labial bow is constructed of 0.7 mm stainless steel wire and extends from canine to canine with vertical loops in the canine region. In this group, the construction bites were taken with the upper and lower anterior teeth in an edge to edge occlusion with 2 to 3 mm posterior clearance. Lateral cephalograms of the experimental group were taken in centric occlusion at the start (T1) and completion (T2) of functional treatment.

The control group consisted of 27 patients (15 girls, 12 boys) with the mean age of 9.1 (SD 1.1) years, who were treated with the FR-2 appliance (Fig. 1B, 2B). The

of Medical Sciences and twenty-seven subjects were selected from patients treated with the FR-2 appliance (Fig. 1B) at the Second University of Naples.

A pilot study was done on 12 patients (6 in each group) and the SNB was chosen as the primary outcome. The sample size for the present study was calculated based on a significance level of .05, 95% confidence level, and a power of 90% to detect a minimum clinically significant difference of 2.1° in the SNB. Using a two-tailed paired t-test (PASS 2011, NCSS software, Kaysville, Utah) 27 samples were required in each group.

At the beginning of treatment, all patients were in prepubertal stages of skeletal development (CS1 or CS2), according to the recently improved version of cervical vertebral maturation (CVM) method described by Baccetti et al. [2005].

All patients were informed of the procedures involved and they gave written consent to the study procedure. The procedures were carried out according to the criteria of the local Ethics Commission and the Helsinki Declaration.

All subjects met the following inclusion criteria.1. ANB > 4°, SNB < 78°, overjet > 4 mm at the initial

lateral cephalograms. 2. No syndromic or medically compromised patients. 3. No previous surgical intervention.4. No use of other appliances before or during the

period of functional treatment.5. A normal mandibular growth pattern; neither

horizontal or vertical.6. No skeletal asymmetry.

fig. 1 The R-appliance (A)and the Fränkel 2(B).

fig. 2 The R-appliance (A)and the Fränkel 2(B) in situ.


TreaTmenT effecTs of r-appliance and fränkel-2

EuropEan Journal of paEdiatric dEntistry vol. 14/1-2013 19

treatment time was 19 (SD 5.6) months. The FR-2 was used according to the following protocol: full time wear with a gradual increase in wearing time and light activations of no more than 2 to 3 mm every six months. The appliances were constructed according to the design recommended by Fränkel and featured a mandibular advancement that did not exceed 2 to 3 mm [Fränkel and Fränkel, 1989]. Lateral cephalograms of the control group were taken in centric occlusion at the beginning (T´1) and at the end of treatment (T´2).

Each film was traced by one investigator on 0.003-inch frosted acetate with a 0.3 mm lead pencil and checked by another investigator to verify the accuracy of the anatomical landmark placement. Images of bilateral structures were bisected. Measurements were taken to the nearest 0.5 mm or degrees. Disagreements were resolved by retracing the landmark or the structure until they were satisfactory for both observers.

SNA, SNB, ANB, 1 to SN (angle between long axis upper central incisor and anterior cranial base), IMPA (angle between the long axis of the lower central incisor and mandibular plane), interincisal angle (angle between upper and lower incisors), Jarabak index (the ratio between posterior and anterior face heights; S–Go/N–Me), SN-ML (angle between SN and mandibular plane), SN-OP (angle between SN and occlusal plane), SN-PP (angle between SN and palatal plane), Ptm-ANS (distance between pterygomaxillary fissure and anterior nasal spine), CoGn (distance from condyle to gnathion), Co-Go-Me (angle between condyle, gonion and mentom), Ar-Pog (distance from articular to pogonion representing mandibular length), facial angle (angle formed by the intersection of the Frankfort plane with the nasion-pogonion line), and the overjet were measured on T1, T2, T´1 and T´2 radiographs (Figure 3).

Four weeks after the first measurements of the R-appliance, the tracings and measurements were repeated by two blinded dentists on 10 cephalograms at the beginning and end of the treatment. The standard deviation of error of each measurement was calculated by Dahlberg's formula [Dahlberg, 1940] (√ SD2 /2N), where D is the difference between the first and second measurements and N = 10 which is the number of double determinations. Values of error study ranged from 0.33 and 0.52 and were within acceptable limits.

The reliability of FR-2 measurements was determined by randomly selecting 10 cephalograms at the beginning and at the end of the treatment. Cephalograms were remeasured by 2 other blinded investigators. The method error was calculated using Dahlberg's formula. Values of error study ranged from 0.21 and 0.64, indicating that there was a good reliability of measurements.

The Kolmogorov-Smirnov normality test was applied to the cephalometric data. Statistical significance was set at P<0.05. The magnification factor of the cephalograms was standardised at 8%. The Statistical

Package for Social Sciences, Version 20 (SPSS Inc. Chicago, Illinois, USA) was used to analyse the data. Paired T-tests were used for intra group evaluation if the distribution was normal; otherwise, Wilcoxon test was used. T-test was used to compare the data between the two groups if the distribution was normal; otherwise, Mann-Whitney test was used.

Results

The R-appliance sample was selected from 58 patients treated at the SHB University of Medical Sciences. Twenty-nine patients were excluded because they did not meet the inclusion criteria. Two patients dropped out because they could not meet the appointments due to personal reasons. The FRl-2 sample was selected from 99 patients treated at the Second University of Naples. Seventy-two patients were excluded because they did not meet the inclusion criteria. T-test showed that there was no statistically significant difference between the mean age of the two groups (P=0.06).

All patients were treated until a favourable overjet was achieved before discontinuing treatment. At the end of the treatment all patients were at CS2 or CS3 stages.

Intra group comparisonIn the R-appliance group, paired T-tests showed

significant ANB decrease of 2 (SD 1.2) degrees (P<0.001) and SNB increase of 2.2 (SD 1.5) degrees (P<0.001). Overjet significantly decreased from 8.3 (SD 2.4) mm to 3.5 (SD 1.5) mm. IMPA significantly decreased by 2.2 (SD 4.9) degrees (P<0.03). Co-Gn significantly increased from 105.3 (SD 5.1) mm to 110.1 (SD 5) mm (Table 1).

fig. 3 Cephalometric landmarks used in this study.




tabLE 1 Pre and post treatment measurements of the R-appliance and Frankel 2.

CephalometriCmeasurements

Groupspre-treatment mean (sD)

post-treatment mean (sD)

p Value

SNa (°) R-applianceFrankel 2

79.1 (3.5)80.7 (2.4)

79.3 (3.3)80.3 (2.3)

0.60.6

SNb (°) R-applianceFrankel 2

72.4 (3.3)74.5 (2.3)

74.6 (3.5)75.8 (2.4)

0.001*0.001*

aNb (°) R-applianceFrankel 2

6.7 (1.8)6.2 (0.8)

4.7 (1.6)4.5 (0.9)

0.001*0.001*

1 to SN (°) R-applianceFrankel 2

106.5 (8.1)107.2 (4.2)

97.3 (7.6)102.7 (3.9)

0.001*0.001*

iMPa (°) R-applianceFrankel 2

102.8 (6)97.7 (5.5)

100.6 (5.9)99.9 (4.8)

0.03*0.001*

interincisal angle (°) R-applianceFrankel 2

115.6 (7.4)121.6 (7.1)

126.9 (7.5)123.6 (7.3)

0.001*0.09

Jarabak index R-applianceFrankel 2

61.9 (4.4)63.6 (1.6)

61.9 (4.9)64 (1.7)

0.90.01*

SN-ML (°) R-applianceFrankel 2

35.4 (6.2)34.2 (2.2)

36.3 (6.6)34 (2.1)

0.090.2

SN-OP (°) R-applianceFrankel 2

22.1 (4.5)19.8 (2.6)

21.6 (5)20 (2.8)

0.60.5

SN-PP (°) R-applianceFrankel 2

7.2 (3.1)8.2 (3)

7.9 (2.7)8.9 (2.8)

0.10.009*

Co-gn (mm) R-applianceFrankel 2

105.3 (5.1)104.4 (5)

110.1 (5)108.2 (5.6)

0.001*0.001*

Co-go-Me (°) R-applianceFrankel 2

123.3 (3.5)124.7 (4)

124 (3.2)124.4 (4)

0.001*0.05*

Ptm-aNS (mm) R-applianceFrankel 2

51.7 (3.8)54.3 (2.9)

53.4 (3.6)55.6 (3.1)

0.001*0.001*

ar-Pog (mm) R-applianceFrankel 2

98.1 (7.2)97.4 (5.6)

103.1 (6.3)101.2 (6)

0.001*0.001*

facial angle (°) R-applianceFrankel 2

81.7 (4.7)85.9 (2.1)

83.7 (4.7)86.9 (2)

0.003*0.001*

Overjet (mm) R-applianceFrankel 2

8.3 (2.4)6.8 (0.7)

3.5 (1.5)4.2 (0.7)

0.001*0.001*

*Statistical significance was set at P<0.05

tabLE 2 Comparison of the R-appliance and the Frankel 2 measurements.

CephalometriC measurements r-applianCe mean (sD) Frankel 2 mean (sD) p ValueSNa (°) 0.2 (2) -0.4 (0.5) 0.007*

SNb (°) 2.2 (1.5) 1.3 (0.6) 0.02*

aNb (°) -2 (1.2) -1.7 (0.5) 0.3

1 to SN (°) -9.2 (8.3) -4.5 (3.8) 0.01*

iMPa (°) -2.2 (4.9) 2.2 (2.6) 0.001*

interincisal angle (°) 11.3 (8.8) 2 (2.6) 0.001*

Jarabak index 0 (1.9) 0.4 (0.9) 0.2

SN-ML (°) 0.9 (2.7) -0.2 (1.6) 0.04*

SN-OP (°) -0.5 (4.8) 0.2 (1.6) 0.5

SN-PP (°) 0.7 (2.4) 0.7 (1.2) 0.9

Co-gn (mm) 4.7 (2.3) 3.7 (1.6) 0.07

Co-go-Me (°) 0.7 (0.8) -0.3 (0.7) 0.001*

Ptm-aNS (mm) 1.7 (2.3) 1.2 (1) 0.2

ar-Pog (mm) 5 (4.4) 3.8 (1.6) 0.2

facial angle (°) 2.1 (3.4) 1 (0.5) 0.2

Overjet (mm) -4.8 (2.5) -2.6 (0.8) 0.001*

*Statistical significance was set at P<0.05


TreaTmenT effecTs of r-appliance and fränkel-2

EuropEan Journal of paEdiatric dEntistry vol. 14/1-2013 21

In the FR-2 group, ANB significantly decreased by 1.7 (SD 0.5) degrees (P<0.001), and SNB significantly increased from 74.5 (SD 2.3) to 75.8 (SD 2.4) degrees (P<0.001). Overjet also showed a significant decrease from 6.8 (SD 0.7) to 4.2 (SD 0.7) mm (P<0.001). IMPA significantly increased from 97.7 (SD 5.5) to 99.9 (SD 4.8) degrees (P<0.001). Co-Gn significantly increased from 104.4 (SD 5) mm to 108.2 (SD 5.6) mm (Table 1).

Inter group comparisonSNB showed greater increase in the R-appliance

group (P<0.02). Inter group evaluation also showed that SNA was slightly increased (mean 0.2; SD 2) with the R-appliance but slightly reduced (mean -0.4; SD 0.5) with the FR-2 and the difference between the two groups was statistically significant (P=0.007). Moreover, 1 to SN decreased more in the R-appliance group; whereas IMPA decreased with R-appliance by 2.2 (SD 4.9) degrees and increased by 2.2 (SD 2.6) degrees (P<0.001) with FR-2 (Table 2).

Discussion The aim of the present investigation was to

evaluate the dentoskeletal effects of the R-appliance in comparison with the Fränkel-2 treatment in Class II division 1 growing patients with mandibular deficiency. At baseline comparison (Table 1) all patients had prepubertal stages of skeletal development and normal growth pattern. The findings of this study showed that both the R-appliance and the FR-2 can successfully reduce the intermaxillary discrepancy in Class II malocclusions (Fig. 4). The decrease of ANB and overjet was associated with significant increase of SNB and total mandibular length (Co-Gn) in both groups. Therefore, these results are in agreement with previous studies [Perillo et al., 1996; de Almeida et al., 2002; Cozza et al., 2006; Marsico et al., 2011; Perillo et al. 2011a; Silvestrini-Biavati et al., 2012] where functional appliances determined significant changes in mandibular growth. According to Fränkel the FR-2 acts by changing the biomechanical environment of the developing dentition [Fränkel, 1966; Fränkel and

Fränkel, 1989]. The FR-2 features projecting vestibular shields and lower labial pads that expand the orofacial capsule and cause an anterior functional shift of the mandible. This bodily translation takes place through a modification of the immature muscular pattern. Nevertheless, in agreement with many previous studies [Owen, 1983a; Owen, 1983b; Creekmore and Radney, 1983; de Almeida et al., 2002; Freeman et al., 2009; Janson et al., 2003; Rushforth et al., 1999; Perillo et al., 2011b; Perillo et al., 1996] lower incisors slightly proclined, probably because the lower labial pads of FR-2 change the lip posture and reduce the soft tissue pressure on the lower incisors. The lower incisor inclination (IMPA) decreased in the R-appliance (Table 1, 2). In the R-appliance group the mandible was positioned anteriorly for construction bite. The lingual shield of the R-appliance was fabricated with less undercut relief. The undercut relief should be reduced to the extent that it does not irritate the patient; however, it should be reduced enough to cause mild trauma. To avoid this trauma all patients were recurrently instructed to posture the mandible forward. This posturing became habitual as patients naturally adopted a comfortable position. In addition, the discomfort caused by reduced relief changed patient's compliance into an unconscious one in the long run. Since the patient moves the mandible forward the protractor muscles are activated and retractor muscles are deactivated. The activation of protractor muscles would keep mandible forward while the retractor muscles would not have any significant role to pull it back. This active protrusion has a favourable effect on the growth and remodeling of the mandible. In addition, this activation prevents headgear effect on maxillary complex and flaring of the lower incisors. Lack of reflex of retractor muscles on the mandible would cause a slight uprighting of the lower incisors. Retrusion and palatal tipping of the maxillary incisors were seen in both groups. Previous studies have also reported lingual inclination and retraction of the upper incisors after treatment with FR-2 [Janson et al., 2003; de Almeida et al., 2002; Perillo et al. 2011b].

This study was somewhat limited by the observational design. Second, the small sample size can be explained

fig. 4 Pre (A)and post-treatment (B)photos of a patient treated with the R-appliance.




with the very restrictive inclusion criteria. Third, all patients were in the pre-pubertal stages of skeletal development before (T1) and after (T2) the treatment period. According to previous data [Baccetti et al., 2001; Cozza et al. 2006] the amount of supplementary mandibular growth appears to be significantly larger if the functional treatment is performed at the pubertal peak in skeletal maturation. Therefore, the early timing can influence the results lessening the treatment effects. However, as suggested by Fränkel and Fränkel [1989], a functional treatment during pre-pubertal stages may remove the environmental factors that inhibit the mandibular growth process which can then continue favorably to the end of the growth.

Moreover, the subjects were selected from two different countries, therefore environmental and ethnic differences might affect the results.

Conclusions

1. Both the R-appliance and the Fränkel-2 in Class II growing patients with mandibular deficiency can improve the intermaxillary discrepancy with skeletal mandibular effects.

2. Retrusion and palatal tipping of the maxillary incisors were seen in both groups.

3. In the R-appliance treatment, compared to Fränkel-2, no proclination of the mandibular incisors was observed.

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