The Efficacy of the Prefabricated T4F
TMMyofunctional Appliance
in Comparison to Twin Block Appliance for Class II Division 1
Malocclusion Treatment: A Randomized Clinical Trial
by
Abdulfatah Abdulrazak Hanoun
Thesis Submitted in Fulfillment of the Requirements for the Degree of
Master of Science (Dentistry)
UNIVERSITI SAINS MALAYSIA
April 2010
ii ACKNOWLEDGEMENT
First of all, I thank Allah (S.W) for giving me the strength and courage to preserve throughout the duration of this research project and made all of this and everything possible.
I wish to express my sincere gratitude to my main supervisor Dr. Norehan Mokhtar for continued encouragement, unceasing efforts, persistent motivation, understanding, support, continual advice, great knowledge of clinical work, clinical teaching and supervision and leadership throughout my research project. I am also indebted to my co-supervisors Dr. Mohd Fadhli Khamis for his kindness, statistical analysis supervision, reading my numerous revisions with much patience and tolerance and inspiration continually received. My thanks also go to my co- supervisor Dr. Noor Hayati Abdul Razak.
I extend my gratitude to Associate Prof. Dr. Hj Abdul Rashid Hj Ismail, Prof.
Rusli Nordin, Prof. Dr. Hj Zulkifli Ahmad, Associate Prof. Dr. Mohd Ayub Sadiq for his workshops and lecture notes that made statistics easy and enjoyable;
Prof. Syed Hatim Noor for his useful explanations and valuable comments, and Dr.
Basarudin. My thanks and appreciation also go to all orthodontics lecturers in our school, Dr. Rozita Hassan for her valuable comments on my methodology and for her clinical supervision, Dr. Ahmad Burhanuddin who suggested a local clinical study about prefabricated functional appliances for his encouragement, kindness, essential great and continuous support during this study, Dr. Akbar Sham Hussin and Dr. Rafeah for their teaching, and explanations during my attendance at orthodontic clinic and for their clinical supervision.
I also extend my grateful appreciation and thanks to my dental surgery assistant Norihan Nawi at KRK who played an essential role during patients' recruitment, to Firdaus Bin Daud, Syaharudin Shaari, Siti Akirah, Yanti, Tuan Rodziah, Hakim, Suhaila, Haizan, Azlin, Aziz, dental technicians, and to the staff of Orthodontic Dental Clinic, Kota Bharu for their kind cooperation throughout my study.
iii
I would like to offer my sincere thanks to all my colleagues at the School of Dental Sciences for their friendship and continuous support over these three years of my study. My thanks and appreciation is extended to my senior Dr. Osama Baha for his assistance during proposal writing, and to my senior Dr. Saifuddin Abo Asaab.My sincere thanks go to my brother and friend Dr. Maen Zreaqat for years of a sincere brotherhood and friendship at Al-Madina Al-Munawara and then in Malaysia.
To all named and unnamed helpers and friends, I again extend my thanks.
Abdulfatah Abdulrazak Hanoun
iv
TABLE OF CONTENTSAcknowledgment ………... ii
Table of Contents ………. iv
List of Tables ………. x
List of Figures ……… xi
List of Abbreviations ………. xii
Abstrak ……….. xiv
Abstract ………. xvi
Chapter 1 – Introduction 1.0 Introduction ……….. 1
1.1 Statement of the Problem ………. 5
1.2 Justification of the Study ……….. 6
1.3 Objectives ……….………… 6
1.3.1 General Objective ………... 6
1.3.2 Specific Objectives ………... 7
1.4 Research Hypothesis ……… 7
1.4.1 Null Hypothesis ………. 7
Chapter Two -Literature Review 2.1 Introduction ……….. 8
2.2 Definition and Classification of Class II Malocclusions ….……...….. 8
2.3 Aetiology of Class II Division1 Malocclusion ……….……….... 11
2.4 Prevalence of Class II Division 1 Malocclusion ……….………….. 13
v
2.5 Dental Characteristics of Class II Division 1 Malocclusion ………….… 14
2.6 Skeletal Characteristics of Class II Division 1 Malocclusions ………... 15
2.7 Cephalometric Characteristics of the Class II Division 1 Malocclusion .. 15
2.8 Perioral Functional Characteristics of Class II Division 1 Malocclusion . 16 2.9 Racial Differences ………. 16
2.10 Class II Management ……….. 17
2.10.1 Extra-oral Traction ………... 17
2.10.2 Functional Orthodontic Treatment ………. 18
2.10.2.1 History of Functional Appliances ………. 19
2.10.2.2 Types of Functional Appliances for Class II Division 1 Treatment ……… 20
2.10.2.2.1 The Andersen Appliance ………... 21
2.10.2.2.2 The Harvold Activator ………... 21
2.10.2.2.3 The Bionator Appliance ………. …... 22
2.10.2.2.4 The Frankel Appliance ………..…… 22
2.10.2.2.5 The Herbst appliance ………. 23
2.10.2.2.6 The Twin Block Appliance ……… 24
2.10.2.2.7 Prefabricated Myofunctional Appliance T4FTM …. 25 2.11 Twin Block Appliance Studies ………... 26
2.11.1 Clinical Investigation on Twin Block Appliance Therapy... 27
2.11.1.1 Retrospective Studies... 27
2.11.1.2 Prospective Studies... 31
2.11.1.3 Randomized Clinical Trials... 34
2.11.2 Investigations on the Influence of Twin Block Appliance Design 37 2.11.3 Incremental Versus Maximum Bite Advancement .………... 39
vi
2.11.4 Treatment Timing of Twin Block Appliance ………... 39
2.12 Skeletal Versus Dentoalveolar Changes During Functional Appliance Therapy ………...……… 40
2.13 Factors Related to the Successful Response to the Functional Appliance Therapy ……….. 41
Chapter 3- Materials and Methods 3.1 Study Design ………. 44
3.2 Population and Sample ………. 44
3.2.1 Source of Population ……….. 44
3.2.2 Sampling Frame ……….. 44
3.2.2.1 Inclusion Criteria ……….. 44
3.2.2.2 Exclusion Criteria ………. 45
3.2.3 Sample Size Calculation ………. 46
3.2.4 Sampling Methods ………. 47
3.2.5 Randomization ……… 47
3.3.0 Data Collection ……….. 48
3.3.1 Clinical Assessment Records ……….. 48
3.3.2 Lateral Cephalometric Radiographs ……… 49
3.3.3 The Prefabricated Myofunctional Appliance T4F™ ………. 50
3.3.3.1 Customization of Prefabricated Myofunctional Appliance T4FTM ……….. 53
3.3.3.2 Fitting the Prefabricated Myofunctional Appliance T4FTM in the Mouth and Delivering the Appliance ………. 53
3.3.4 Twin Block Appliance Design ……… 55
vii
3.3.4.1 Construction of Bite Registration for Twin BlockAppliance ………. 55
3.3.4.2 Fitting and Delivering the Twin Block Appliance ………... 58
3.3.5.0 Observation Period for Both Groups ………. 58
3.3.5.1 Post treatment Data Collection ……… 59
3.4 Research Tools ………. 60
3.4.1 Landmarks, Reference Lines, and Angular and Linear Measurements ……… 60
3.4.1.1 Landmarks Used in the Cephalometric Analysis …………. 60
3.4.1.2 Vertical Reference Line Used in the Cephalometric Analysis for Horizontal Linear Dental and Skeletal measurements 61 3.4.1.3 The Lines Used for Angular Measurements …………..….. 63
3.4.2 Variables ………... 65
3.4.2.1 Clinical Measurement ……… 65
3.4.2.2 Cephalometric Angular Measurements ………..…. 65
3.4.2.3 Cephalometric Linear Measurements ………..… 68
3.4.3 Lateral Cephalometric Radiographs Tracing ……….. 72
3.5 Reliability of Cephalometric Measurements ……….... 73
3.5.1 Inter-examiner Reliability ………...……….... 73
3.5.2 Intra-examiner Reliability ………..….……….... 73
3.6 Data Analyses ………. 74
3.6.1 Reliability of the Measurements ………. 74
3.6.2 Pre-treatment Baseline Equivalence ………. 74
3.6.3 Comparison of the Changes during Treatment ………. 74
3.7 Ethical Consideration ……….. 76
viii
3.8 Flow Chart of the Study ……….. 77
Chapter 4- Results 4.1 Profile of the Study Groups... 78
4.2 Inter- and Intra-examiner Reliability... 78
4.3 Drop out ………...………. 80
4.4 Pre-treatment Baseline Data ………..………... 80
4.5.0 Within Group Comparisons of Overjet and Cephalometric Measurements... 82
4.5.1 Pre- and Post-treatment Comparisons for T4FTM Group ……….... 82
4.5.1.1 Overjet ………...……….. 82
4.5.1.2 Cephalometric Measurements ………….……….….. 82
4.5.2. Pre- and Post-treatment Comparisons for Twin Block Group …... 84
4.5.2.1 Overjet ………….………... 84
4.5.2.2 Cephalometric Measurements ………….………... 84
4.6 Comparison between T4FTM Group and Twin Block Group in terms of the Overjet and Cephalometric Changes During the Observation Period ….. 87
4.6.1 Overjet ………... 87
4.6.2 Cephalometric Measurements ……..………. 87
Chapter 5- Discussion 5.1 Reliability ………. 89
5.2 Pre-treatment Baseline Data ……… 89
5.3 Skeletal and Dentoalveolar Changes during the Treatment Period …….. 90
5.3.1 Skeletal Changes in T4FTM Group and Twin Block Group ... 90
ix
5.3.1.1 Anterior Posterior Changes ………. 90
5.3.1.2 Vertical Changes... 92
5.3.2 Dentoalveolar Changes in T4FTM and Twin Block Groups... 93
5.3.2.1 Anterior Posterior Changes... 93
5.3.2.1.1 Upper Incisors Retroclination ……… 93
5.3.2.1.2 Lower Incisors Proclination ……… 96
5.3.2.1.3 Linear Dental Measurements ………... 98
5.3.2.1.4 Overjet Correction ………. 100
5.3.2.1.5 Overjet Correction: Skeletal vs. Dentoalveolar …….. 104
5.3.2.2 Vertical Changes (Overbite) ………. 107
5.4 Limitations of the Study ……….. 108
Chapter 6 – Conclusions and Recommendations 6.1 Conclusions ……….. 109
6.2 Recommendations ………. 110
6.2.1 Future Studies ………... 110
6.2.3 Clinical Recommendations ………... 111
References ………. 113
Appendices ………. 123
x LIST OF TABLES
Table 4.1 Inter- and Intra- examiner reliability ………. 79 Table 4.2 Descriptive baseline data of patients who were lost to
follow up ………... 80
Table 4.3 Pre-treatment baseline equivalence between T4FTM and Twin Block appliance groups…………...… 81 Table 4.4 Pre- and Post-treatment measurements of Prefabricated
mouldable functional appliance T4FTM group …….……. 83 Table 4.5 Pre- and Post-treatment measurements of Twin Block
Appliance group ………..………... 86 Table 4.6 Table 4.6: Between group differences ……….. 88
xi LIST OF FIGURES
Figure 3.1 T4FTM appliance ………. 52
Figure 3.2 Twin Block appliance ………. 57
Figure 3.3 Landmarks & Vertical Reference line ……… 62
Figure 3.4 Lines used for angular measurements ………. 64
Figure 3.5 Angular measurements ……… 67
Figure 3.6 Linear Measurement ………... 70
Figure 3.7 Horizontal and Vertical Linear Measurement ………. 71
Figure 3.8 The Flow Chart of the Study ……….. 77
Figure 5.1 Dentoalveolar and skeletal changes in relation to Sv line (T4FTM group) ………. 106
Figure 5.2 Dentoalveolar and skeletal changes in relation to Sv line (TB group) ……….. 106
xii LIST OF ABBREVIATIONS
ai Apex inferior
ANB A point-Nasion-B point ANS Anterior nasal spine Ar Articulare
Ar_A Articulare- A point Ar_B Articulare-B point Ar_Pg Articulare-Pogonion as Apex superior
BSI British Standards Institution Co Condylion
Div.1 Division 1 Gn Gnathion
Go Gonion
HUSM Hospital Universiti Sains Malaysia ICC Intra-class Correlation Coefficient test ii Incision inferius
IIA Inter-incisal angle is Incision superius
is_ii Incision superius - incision inferius L@TAFH Facial proportion (LAFH / TAFH) LAFH Lower anterior facial height Li Lower Incisor
Li_Man Lower incisor mandibular plane angle
xiii
Man MandibleMe Menton
MMPA Maxillary mandibular plane angle
Mx Maxilla
N Nasion
OB Overbite OJ Overjet
PNS Posterior nasal spine Pog Pogonion
S Sella
SN Sella-Nasion
SN_Man Sella-Nasion Mandibular plane angle SNA Sella-Nasion-A point
SNB Sella-Nasion-B point Sv Sella vertical
Sv_A Sella vertical – A point
Sv_ii Sella vertical - incision inferius Sv_is Sella vertical - incision superius Sv_Pog Selaa vertical – Pogonion
T4FTM Prefabricated re-mouldable customizable functional appliance TAFH Total anterior facial height
TB Twin Block Ui Upper incisor
Ui_Mx Upper incisor maxillary plane angle
xiv Perbandingan Antara Keberkesanan Alat Pasang Siap T4F
TMMiofungsi Dengan Alat Blok Berkembar Untuk Rawatan Maloklusi
Kelas II Bahagian 1: Satu Kajian Percubaan Klinikal Secara Rambang
Abstrak
Alat fungsian telah digunakan secara meluas untuk merawat maloklusi Kelas II Bahagian 1. Tiada kajian terdahulu diterbitkan mengenai kesan-kesan penggunaan alat fungsian jenis pasang siap dan boleh-dibentuk-semula (T4FTM) untuk maloklusi Kelas II Bahagian 1) ke atas subjek yang mempunyai bentuk kerangka Kelas II.
Tujuan kajian ini adalah untuk membandingkan perubahan dalam struktur kerangka dan dentoalveolar pada pesakit Melayu (praremaja) yang dirawat dengan menggunakan peralatan miofungsi boleh-dibentuk-semula prafabrikasi (T4FTM), dan peralatan Blok Berkembar (TB). Satu percubaan klinikal secara rambang telah dilakukan ke atas 43 subjek (22 lelaki + 21 perempuan) Kedua-dua kumpulan ini dikenali sebagai kumpulan kawalan aktif (TB) dan kumpulan ujikaji (T4FTM). Pada akhir tempoh kajian iaitu selama enam bulan, beberapa subjek telah menarik diri, yang menyebabkan kumpulan TB terdiri daripada 17 subjek (8 lelaki & 9 perempuan), sementara kumpulan T4FTM hanya tinggal 16 subjek (9 lelaki & 7 perempuan). Min umur bagi kumpulan T4FTM adalah 13 tahun (0.7), manakala bagi kumpulan TB pula adalah 13.2 tahun (0.8). Radiograf sefalometri lateral sebelum dan selepas rawatan dilakukan ke atas setiap subjek dan overjet dinilai secara klinikal. Dua puluh satu ukuran sudut dan linear dipilih dan diukur secara berasingan, sebelum dan selepas radiograf sefalometri lateral. Perubahan yang berlaku sepanjang tempoh kajian dikira dengan membandingkan ukuran sebelum dan selepas rawatan pada setiap kumpulan. Kedua-dua kumpulan tersebut dibandingkan dari segi perubahan yang berlaku sepanjang tempoh kajian. Ujian Pekali Korelasi intra kelas (ICC) digunakan untuk menguji kesamaan di antara interpenguji dan intrapenguji daripada ukuran sefalometri. Hasil ICC asdalah dalam lingkungan 0.91 ke 0.99, yang dianggap suatu tahap ralat yang boleh diterima. Ujian t bebas digunakan untuk membandingkan perubahan di antara kedua-dua kumpulan tersebut.
Perbandingan di anatara kedua-dua kumpulan dari segi perubahan semasa rawatan menunjukkan perbezaan yang signifikan di dalam overjet, kedudukan mandibular anterior-posterior dan kerangka, serta ketaksamaan dentoalveolar yang lebih baik
xv
dalam kumpulan TB. Pengurangan overjet dalam kumpulan TB adalah dua kali lebih banyak dengan perbezaan min sebanyak 2.1mm (p<0.01). Sudut titik Sella-Nasion-B semakin meningkat di dalam kumpulan TB dengan perbezaan min sebanyak 1.25°(p<0.05). Manakala sudut titik A-Nasion-B berkurangan sebanyak 0.8° (0.9) bagi kumpulan T4FTM dan 1.6° (1.1) bagi kumpulan TB dengan perbezaan min sebanyak 0.8° (p<0.05). Perbezaan di antara Pogomon dan garis rujukan menegak (Sv_Pog) adalah lebih baik di dalam kumpulan TB dengan perbezaan min sebanyak 1.83mm (p<0.05). Perbezaan di antara pinggir insisor bawah dan garis rujukan menegak (Sv_ii) adalah lebih baik di dalam kumpulan TB dengan perbezaan min sebanyak 2.55mm (p<0.01). Perbezaan di antara bucu insisor atas dan bucu insisor bawah (is ii) adalah berkurangan dua kali di dalam kumpulan TB dibandingkan dengan kumpulan T4FTM, dengan perbezaan min sebanyak 1.83mm (p<0.05). Kedua-dua kumpulan tersebut menunjukkan perubahan yang baik dari segi pembetulan kerangka sagital dan ketaksamaan dentoalveolar semasa tempoh rawatan. Jumlah perbezaan adalah signifikan di antara kedua-dua kumpulan dengan lebih pembetulan dari segi skeletal sagital dan ketaksamaan dentoalveolar diperhatikan dalam kumpulan TB.
Pembetulan skeletal secara keseluruhannya adalah disebabkan oleh perubahan mandibel tanpa perubahan yang signifikan dari segi kedudukan sagital maksila di dalam kedua-dua kumpulan. Sumbangan bidang pergigian dalam kedua-dua kumpulan sehinggalah ke akhir pembetulan overjet telah menghasilkan kombinasi antara retroklinasi insisor atas dan retroklinasi insisor bawah. Min proklinasi insisor bawah yang menyumbang kepada pembetulan overjet adalah lebih tinggi daripada min retroklinasi insisor atas di dalam kumpulan TB. Sementara itu, di dalam kumpulan T4FTM, perubahan min insisor atas sama dengan insisor bawah. Sebagai kesimpulan, peralatan T4FTM adalah suatu alat yang efektif untuk pengurusan molaklusi BSI Bahagian 1 Kelas II ke atas pola kerangka Kelas II.
xvi
The Efficacy of the Prefabricated T4FTM Myofunctional Appliance in Comparison to Twin Block Appliance for Class II Division 1 Malocclusion Treatment: A Randomized
Clinical Trial
Abstract
Functional appliances are widely used to treat Class II Division 1 malocclusion. No previous studies were published about the effects of prefabricated re-mouldable functional appliance (T4FTM) for Class II Division 1 malocclusion on Class II skeletal pattern subjects. The aim of this study was to compare the changes in the skeletal and dentoalveolar structures in growing Malay patients (pre-adolescent) with Class II Division 1 malocclusion treated by Prefabricated Re-mouldable Myofunctional appliance T4FTM and Twin Block appliance (TB). A randomized clinical trial was carried out with a sample of 43 subjects (22 males + 21 females) randomly assigned to active control group (Twin Block group) and experimental group (T4FTM appliance group). At the end of six months study period and due to the drop out, TB group consisted of 17 subjects (8 males + 9 females), while T4FTM group consisted of 16 subjects (9 males + 7 females). Mean age was 13 years (0.7) in T4FTM group, and 13.2 years (0.8) in Twin Block group. Pre- and post-treatment lateral cephalometric radiographs were taken for each subject and the overjet was clinically measured pre- and post- the six months treatment period. Twenty one angular and linear measurements were chosen and measured separately on the pre- and post-treatment lateral cephalometric radiographs. The changes during the study period were calculated by comparing pre- and post-treatment measurements in each group. The two groups were then compared in terms of the changes that occurred during the study period. Intra-class Correlation Coefficient test was used to test inter- and intra-examiner agreement of cephalometric measurements. (ICC) results ranged from 0.91 to 0.99 which were considered acceptable level of errors. Independent t test was used to compare the changes between the two groups. The between groups comparison in terms of the changes during treatment period showed significant difference in overjet, anterior posterior mandibular position and skeletal and dentoalveolar discrepancies which were changed more favourably in TB group.
Overjet reduction was found to be two times more in TB group with a mean difference of 2.1mm (p <0.01). Sella-Nasion-B point angle was more increased in TB group with a mean difference of 1.25 ° (p <0.05). A point–Nasion-B point angle was
xvii
decreased by 0.8° (0.9) and 1.6° (1.1) in T4FTM and TB groups respectively with a mean difference of 0.8 ° (p <0.05). The distance between Pogonion and the vertical reference line (Sv_Pog) was more favourably changed in TB group with a mean difference of 1.83mm (p <0.05). The distance between the lower incisal edge and the vertical reference line (Sv_ii) was also more favourably increased in TB group with a mean difference of 2.55mm (p <0.01). The distance between the upper and the lower incisal edges (is_ii) was decreased in TB group as two times as in T4FTM group with a mean difference of 1.8mm (p <0.05). The correction of the sagittal skeletal and dentoalveolar discrepancies was favourable for both groups. The amount of changes differed significantly between the two groups with more favourable correction in terms of the sagittal skeletal and dentoalveolar discrepancy was observed in TB group. The skeletal correction was due to the mandibular changes with no significant change in terms of sagittal position of maxilla in both groups. The dental contribution in both groups to the final overjet correction was a result of combination of upper incisor retroclination and lower incisor proclination. The mean lower incisor proclination that contributed to the overjet correction was higher than the mean upper incisor retroclination in Twin Block group; while in T4FTM group, the mean upper incisor inclination change was similar with the mean lower incisor inclination change. In conclusion, T4FTM appliance is an effective appliance for the management of BSI Class II Division 1 malocclusion on Class II skeletal pattern.1 Chapter One
Introduction
1.0 Introduction
Over the years, numerous studies have investigated the possibility of growth modification. Clinical experience and research supported our knowledge and improved our understanding on the influence of intra- and extra-oral appliances used for that, particularly in skeletal Class II patients.
Class II malocclusions are of interest to the practicing orthodontists because they constitute a significant percentage of their cases and Class II Div.1 malocclusion is among the most common (Tulloch et al., 1990). In individuals with normal occlusion and skeletal relationship, the amount of maxillary and mandibular growth is synchronized resulting in a well-balanced and aesthetically pleasing profile. In individuals with Class II malocclusions, there is an anteroposterior discrepancy between the maxillary and mandibular dentitions, which may or may not be accompanied with a skeletal discrepancy. In growing individuals, the success of treatment is dependent, to a great extent, on the ability of the clinician to influence the relative growth changes in the maxilla and mandible (Bishara, 2006).
The incidence of Class II Division 1 malocclusion has been reported to be high among Western population (Jones and Oliver, 2000). Angle Class II incidence was found to be 23% among Swedish adults (Salonen et al., 1992), while it was higher among adult Dutch population with about 28% (Burgersdijk et al., 1991). The
2 incidence of Class II Division 1 incisor relationship in Caucasian population in general is 15-20 % (Mitchell et al., 2001).
Approximately 15 % of American children and youths have Class II Angle's malocclusion. The malocclusion characteristics vary between countries and are due to the differences in racial and ethnic composition. It is clear that Class II is most prevalent in Northern European descent. For instance, in Denmark 25% of children are reported to have Class II malocclusion (Proffit and Fields, 2000).
A substantial number of approaches and appliances had been developed for Class II malocclusion treatment (Kim et al., 1999). Class II Div.1 malocclusion can be treated with removable appliances, functional appliances, fixed appliances and orthognathic surgery. Functional appliances have been used for a long time in the treatment of malocclusion, particularly in Class II Division 1 malocclusions. It was stated that although some clinicians reject the clinical efficacy of these appliances, proof of their growth modifying effect remains elusive for some authors (Toth and McNamara, 1999).
These appliances that were designed aiming to influence the growth can be divided into removable and fixed functional appliances. Many types of removable functional appliances have been developed to treat Class II malocclusion such as Frankel appliance which is also known as a functional regulator (McNamara et al., 1985;
McNamara et al., 1990; Toth and McNamara, 1999), Bionator (Mamandras and Allen, 1990; Illing et al., 1998; Jena et al., 2006), Activator (Harvold, 1974;
Wieslander and Lagerstrom, 1979; Vargervik and Harvold, 1985; Baltromejus et al.,
3 2002), Twin Block appliance (Toth and McNamara, 1999; O'Brien et al., 2003b), and prefabricated myofunctional appliances (www.myoresearch.com). A fixed functional appliance known as Herbst appliance was also used effectively for Class II Division 1 malocclusion treatment (Pancherz, 1982; Pancherz, 1985; Pancherz et al., 1997; Pancherz et al., 1998; Pancherz et al., 1999; Toth and McNamara, 1999;
Baltromejus et al., 2002).
The prefabricated myofunctional appliances are a series of prefabricated functional appliances produced by myoresearch company, Queensland, Australia which are also known as "TrainerTM". These include T4K,T4CII, and T4FTM appliances. The T4K appliance was designed for young children (Usumez et al., 2004;
www.myoresearch.com, 2007), while the T4CII is used in corporate with a fixed orthodontic appliance (www.myoresearch.com, 2007).
The T4FTM appliance is also a prefabricated appliance but re-mouldable when immersed in very hot water so it can be customized to accommodate the patient's dentition in the mouth and increase the retention. The prefabricated re-mouldable customizable functional appliance "T4FTM"was suggested to be effective for Class II Division 1 malocclusion treatment (www.myoresearch.com, 2007).
All other previously known types such as Activator, Bionator and Frankel appliances are not prefabricated but it is individually customized for each patient depending on his individual dental case. The idea of prefabricated functional appliance was recently introduced to the orthodontic field and it becomes more practical with the new customizable functional appliance T4FTM. This new
4 functional appliance has the advantage of the immediate issuing and the direct fitting of the appliance in the patient's mouth and it is also a better choice in terms of the cost for the private practitioners.
Twin Block appliance has been widely used for functional orthodontic treatment in most orthodontic private and public clinics in many countries. The TrainerTM with its different types including T4FTM was recently introduced to the field and became quickly in the usage in Malaysia and other countries (Burhanuddin et al., 2005).
Even though the philosophy of prefabricated myofunctional appliance T4FTM appliance is similar to that of known functional appliances in term of forwarding the lower jaw, the need for scientific clinical evidence about its effects on skeletal and dentoalveolar structures in Class II Div. 1 treatment is essential. Moreover, the expert orthodontic committee of the Ministry of Health of Malaysia has recommended to conduct a clinical research in Malaysian population (Burhanuddin et al., 2005).
Therefore this study will evaluate the effectiveness of the prefabricated myofunctional appliance T4FTM in comparison with Twin Block appliance for the treatment of Class II Div.1 malocclusion as defined by British Standards Institution (BSI) on Class II skeletal pattern.
5 1.1 Statement of the Problem
No study has been published about functional orthodontic treatment in Class II Div.
1 Malay growing patients, so the effects of functional orthodontic treatment on Class II patients need to be investigated.
One of the functional appliances recently used in Malaysia is the prefabricated T4FTM myofunctional appliance, but there is no study about their effectiveness in Class II Div. 1 patients. There is insufficient evidence on the clinical effectiveness of this appliance particularly on Malay, consequently there is a need for local clinical research to be done on the efficacy and effectiveness of this prefabricated myofunctional appliance for orthodontic treatment.
Twin Block appliance is the most widely used functional appliance in public and private orthodontic clinics in Malaysia. Twin Block appliance was also the preferred functional appliance in the UK whereby more than 75% of British Orthodontic Society members claimed that it is their first choice (Chadwick et al., 1998). The Twin Block appliance is commonly used to correct Class II dentoskeletal disharmony (Schaefer et al., 2004). It has been found to be clinically useful (Mills and McCulloch, 1998), and its effectiveness was comparable to Herbst appliance which is known as the most effective functional appliance (Trenouth, 2000a). Due to its popularity and proved effectiveness, Twin Block appliance was chosen as an active control.
6 1.2 Justification of the Study
T4FTM appliance was designed to be worn at night time beside few hours only during day time while the Twin Block appliance is worn for full time. T4FTM appliance would be an appliance of choice for the patients who are not willing to wear a full time functional appliance; therefore it should be investigated whether it is as effective as Twin Block appliance.
A randomized clinical trial is required to provide an evidence about the efficacy of prefabricated myofunctional appliances T4FTM. It is valuable though to investigate the effects of treatment with the prefabricated myofunctional appliances T4FTM as it has recently been gaining popularity and claimed to show some good clinical results in the functional phase of the treatment for Class II Div.1 patients.
This study will emphasize on the skeletal and dentoalveolar changes following functional appliance therapy. Investigating the changes that occur as the immediate effects of treatment will increase understanding of the mode of action of this appliance in the treatment of Class II Div.1 patients.
1.3 Objectives
1.3.1 General Objective
To evaluate the efficacy of treatment with prefabricated myofunctional appliance T4FTM in comparison to Twin Block appliance for growing Malay patients with Class II Division 1 malocclusion.
7 1.3.2 Specific Objectives
To compare the linear and angular changes in the skeletal and dentoalveolar structures between two groups of Class II Div.1 Malay patients treated with Prefabricated T4FTM Myofunctional appliance and Twin Block appliance.
1.4 Research Hypothesis 1.4.1 Null Hypothesis
There is no difference in the linear and angular changes in the skeletal and dentoalveolar structures between prefabricated T4FTM myofunctional and Twin Block appliance.
