Orthodontic treatment for crowded teeth in children Thesis submitted in accordance with the requirements of the University of Liverpool for the degree of Doctorate of Dental Science by Fyeza Janjua Sharif January 2017 1 Contents Orthodontic treatment for crowded teeth in children ...........................................................................1 1.ABSTRACT ...............................................................................................................................................5 1.INTRODUCTION......................................................................................................................................6 2. LITERATURE REVIEW .........................................................................................................................7 2.1 The Need for Systematic Reviews ...............................................................................................7 2.2 Cochrane Reviews ...........................................................................................................................9 2.3 Crowding ......................................................................................................................................... 11 2.3.1 Definition of crowding ........................................................................................................... 11 2.3.2 Incidence and prevalence of crowding ............................................................................. 12 2.3.3 Factors which influence crowding...................................................................................... 14 2.4 The impact of crowding on patients .......................................................................................... 17 2.5 Options for addressing crowding ............................................................................................... 17 2.5.1 Prevention ............................................................................................................................... 17 2.5.2 Treatment ................................................................................................................................ 20 3. AIMS, OBJECTIVES AND NULL HYPOTHESIS ......................................................................... 23 3.1: Aims................................................................................................................................................. 23 3.2: Objectives ...................................................................................................................................... 23 3.3: Null hypothesis ............................................................................................................................. 23 4. METHODS............................................................................................................................................. 24 4.1 Criteria for considering studies for this review ....................................................................... 24 4.1.1 Types of studies ..................................................................................................................... 24 4.1.2 Types of participants............................................................................................................. 24 4.1.3 Types of interventions .......................................................................................................... 24 4.1.4 Types of outcome measures .............................................................................................. 25 4.2 Search methods for identification of studies ........................................................................... 26 4.2.1 Electronic searching.............................................................................................................. 26 4.2.2 Databases searched ............................................................................................................. 26 4.2.3 Searching other resources .................................................................................................. 26 4.2.4 Language................................................................................................................................. 27 4.2.5 Unpublished studies.............................................................................................................. 28 4.3 Data collection and analysis ....................................................................................................... 28 4.3.1 Management of records produced by the searches...................................................... 28 4.3.2 Selection of studies ............................................................................................................... 28 2 4.3.3. Data extraction and management .................................................................................... 29 4.3.4 Assessment of risk of bias in included studies ............................................................... 29 4.3.5 Measure of treatment effect ................................................................................................ 34 4.3.6 Unit of analysis issues .......................................................................................................... 35 4.3.7 Dealing with missing data .................................................................................................... 35 4.3.8 Assessment of heterogeneity ............................................................................................. 35 4.3.9 Assessment of reporting bias ............................................................................................. 35 4.3.10 Data synthesis ..................................................................................................................... 36 4.3.11 Subgroup analysis and investigation of heterogeneity............................................... 36 4.3.12 Sensitivity analysis .............................................................................................................. 36 4.3.13 Cross-over trials .................................................................................................................. 36 5: RESULTS .............................................................................................................................................. 37 5.1: Description of studies .................................................................................................................. 37 5.1.1: Results of the search ........................................................................................................... 37 5.1.2: Included studies .................................................................................................................... 39 5.1.3: Characteristics of the trial designs and settings ........................................................... 39 5.1.4: Characteristics of the participants .................................................................................... 40 5.1.6: Characteristics of the interventions and comparisons ................................................. 41 5.1.7: Characteristics of the outcomes ....................................................................................... 42 5.1.8: Excluded Studies .................................................................................................................. 45 5.2: Risk of bias in included studies................................................................................................. 45 5.2.1: Allocation ................................................................................................................................ 45 5.2.2: Blinding ................................................................................................................................... 46 5.2.3: Incomplete outcome data ................................................................................................... 47 5.2.4: Selective reporting ............................................................................................................... 47 5.2.5: Other potential sources of bias ......................................................................................... 47 5.2.6: Overall risk of bias................................................................................................................ 48 5.3: Effects of interventions ............................................................................................................... 51 5.3.1: Comparison 1: Cervical pull headgear versus control ................................................. 51 5.3.2: Comparison 2: Extraction of lower deciduous canines versus control .................... 64 5.3.3: Comparison 3: Schwarz versus control .......................................................................... 71 5.3.4: Comparison 4: Eruption Guidance appliance versus control..................................... 81 5.3.5: Comparison: Lower Lingual Arch versus control .......................................................... 89 5.3.6: Comparison: Lower Lip Bumper versus control ............................................................ 95 3 5.3.7: Comparison: Self-ligating brackets versus conventional brackets ......................... 102 5.3.8: Comparison: Active versus passive self-ligating brackets........................................ 112 5.3.9: Comparison: Copper nickel-titanium versus nickel-titanium archwires ................