Malocclusion is a common condition in children and adolescents with a worldwide prevalence of 56%. It is estimated that approximately 30% of Swedish children and adolescents undergo orthodontic treatment at specialist clinics under Sweden’s free comprehensive dental care for children and young patients, with crowded and displaced teeth being one of the main reasons. One of the treatments used to align teeth is placing fixed appliances with brackets on the teeth. The beneficial effects of the treatment include well-aligned teeth and healthy, stable occlusion. However, every orthodontic treatment entails a risk of adverse effects such as external root resorption and pain. In recent decades, a technique that uses passive self-ligating brackets has gained in popularity. This technique is said to generate less frictional resistance, more physiological tissue response and reduced adverse effects compared to conventional techniques. According to a Cochrane report from 2021, the current evidence is sparse regarding fixed appliance treatment in general, and specifically for the treatment effect of passive self-ligating brackets compared to conventional bracket systems in the treatment of crowded teeth in children. 

Radiographic examinations before, during and after the treatment are recommended to monitor the risk of severe external root resorption. The recommendations given in textbooks and scientific articles are contradictive as different check-up intervals and radiographic modalities are recommended. Moreover, the grounds for the recommendations are weak, and due to radiation doses and the ALADA (“as low as diagnostically acceptable”) principle, it may not be justifiable for all patients. 

The CROWDIT (Crowded Displaced Teeth) project was started to decrease knowledge gaps concerning fixed appliance treatment of adolescents with crowded and displaced teeth, from the perspective of patients, clinicians and society. The overall aim of this thesis was to present a systematic, comprehensive evaluation of external apical root resorption and pain levels across various treatment phases during the orthodontic treatment of adolescents with crowded and displaced teeth. These evaluations were based on an RCT (Randomized Clinical Trial) consisting of treatments performed without extractions using either passive self-ligating or conventional bracket systems. 

The first study of the thesis was a systematic review aimed at evaluating the scientific evidence and identifying knowledge gaps concerning external root resorption. During the preparatory work for the systematic review, no appropriate tool was found to assess the risk of bias in studies of adverse effects associated with orthodontic treatment. For this reason, a tool was designed to assess that risk of bias.

The tool and its application in a systematic review identified knowledge gaps and highlighted issues concerning the planning, conducting and reporting of studies. Based on this new knowledge, a methodological study was carried out of reliability and agreement in root length measurements, and two randomized controlled trials were conducted investigating external apical root resorption and pain.

We expect that the outcomes of this thesis and the further studies planned as part of the CROWDIT project will decrease the knowledge gaps and that the results will be integrated into the national guidelines for orthodontic treatment. We anticipate that the outcomes will thereby influence future oral healthcare so that the treatment of adolescents with crowded and displaced teeth using fixed appliances will be supported by scientific evidence.

This thesis was thus based on the following studies:

Paper I: Development of a tool for assessing the risk of bias was developed and applied in a systematic review to answer the following questions:

·          What frequencies and severities of external root resorption have been reported?

·          Is frequency and severity of external root resorption related to the patient’s age, sex, malocclusion or type of appliance?

Paper II: A methodological study that aimed to investigate:

·          The inter-rater and intra-rater reliability and agreement for measurements of the root length of all teeth from incisors to molars using multiplanar reconstruction in CBCT examinations during different phases of orthodontic treatment in adolescents with fixed appliances.

Paper III: Originated from a multi-centre RCT that aimed to investigate: 

·          The frequency and severity of external apical root resorption identified through CBCT examinations obtained before treatment, after levelling of the teeth and insertion of the first 0.019 x 0.025 stainless steel archwire, and after treatment using either passive self-ligating or conventional fixed appliance systems. A further aim was to assess the results in relation to the most affected tooth groups, the time required for levelling, the duration of the 0.019 x 0.025 stainless steel archwire, total treatment time, differences in sex and initial irregularity of teeth.

·          The relevance of intermediate radiography for the early detection of severe or extreme external apical root resorption. 

Paper IV: Originated from a multi-centre RCT that aimed to investigate:

·          Self-reported pain levels across various treatment phases for patients using passive self-ligating or conventional bracket systems.

·          Pain levels in relation to sex, initial archwire dimension, intake of analgesics, degree of displacement of the anterior teeth and impact on everyday activities.

Key findings of Paper I:

·          External root resorption of ≥ 2 mm varied across studies by between 10% and 29% for maxillary incisors. 

·          Data concerning external root resorption as related to patients’ age sex, malocclusion, and type of treatment was contradictory

·          The quality of the evidence, evaluated according to the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) approach, was low due to study limitations, imprecision and inconsistency of study results.

Key findings of Paper II

·          CBCT using MPR is a reproducible method for measuring root length during different phases of orthodontic treatment. 

·          Root shortening of ≤ 2 mm measured by CBCT using MPR, for clinical or research purposes, should be interpreted with caution as it may represent a measurement error.

Key findings of Paper III

·          The mean external apical root resorption in mm for upper incisors was 0.20 in the passive self-ligating group and 0.51 in the conventional group, while the corresponding proportion of roots with clinically relevant EARR (≥ 2 mm) was 5.0% and 7.2% respectively.

·          None of the variables treatment time, sex or initial irregularity of teeth could significantly predict the mean external apical root resorption of the upper incisors.

·          It would appear that the relevance of intermediate radiographic examination is negligible for the early detection of severe external apical root resorption.

Key findings of Paper IV

·          Pain levels of 9 to 10 on a 10-point scale were reported from 21.8% of patients in the passive self-ligating group and 30.3% in the conventional group on the most painful day (NS). 

·          Statistically significant, lower mean pain scores and a lower intake of analgesics were reported in the passive self-ligating group than in the conventional group on the first days after bonding in both arches. 

·          After the insertion of the full-size stainless steel archwire, 40% of patients reported taking analgesics.

·          It was found that girls reported lower pain scores compared to boys.

Conclusions and clinical implications:There is a low quality of scientific evidence regarding external root resorption associated with orthodontic treatment with fixed appliances. 

Measurement of root length in CBCT images ia a reproducible method for measuring root length but measured values below 2 mm should be interpreted with caution as they may contain measurement errors.

The frequency and severity of external apical root resorption was generally low and similar for patients treated with passive self-ligating and conventional bracket systems.

Intermediate radiography may be avoided in an adolescent population with crowded teeth treated without extraction, which aligns with the ALADA principle and underlines the importance of individual indications for radiographic examinations and the minimization of radiation doses.

Patients treated with passive self-ligating brackets report lower pain levels and intake of analgesics compared to those treated with conventional bracket systems after treatment initiation. In general girls reported lower pain scores compared to boys.

It is important to inform the patients and their parents before treatment that pain levels are generally substantially high after bonding as well as after insertion of a full-size stainless steel archwire. 

OBJECTIVES: To compare self-reported pain levels across various treatment phases using passive self-ligating (Damon) and conventional (Victory) standardized fixed appliance systems.

MATERIALS AND METHODS: Adolescents (12-17 years old) with crowding and displaced teeth, planned for non-extraction treatment, were recruited from four orthodontic clinics. They were randomized into stratified blocks (1:1 ratio) using concealed allocation to receive Damon Q™ (34 boys, 28 girls) or Victory™ (39 boys, 31 girls). Pain and analgesic intake were assessed on seven different occasions with validated self-report questionnaires using a 10-grade scale.

RESULTS: Of the 132 patients included, six were lost to follow up. Clinically relevant mean pain scores (≥4) were registered in both groups after bonding upper and lower arches and after insertion of 0.019 × 0.025 stainless steel archwire. The highest mean scores were reported on day two after bonding the upper arch (Damon 5.96, Victory 7.18, P = .011). In both groups, at least 40% reported taking analgesics during various treatment phases. The Damon group reported a lower intake of analgesics on days one and two (P = .042 and .037) after treatment initiation. In the entire sample, boys reported significantly higher mean pain scores than girls on the second and third days after bonding (P = .008 and .026, respectively).

CONCLUSIONS: Lower pain levels were reported from the Damon group after bonding. In general, boys reported higher pain than girls did. Clinicians and adolescents need to be aware that clinically relevant pain levels can be expected not only after bonding but also in later phases.

BACKGROUND AND AIMS: Systematic reviews (SRs) are considered to provide reliable estimates, but flaws in designs, methods of monitoring effects, and outcomes have the potential to bias results. There are several tools for assessing risk of bias (RoB), most of them designed for SRs of beneficial effects. To our knowledge, there is no tool that is adapted specifically to assess RoB in studies of adverse effects associated with orthodontic treatment. To address this, the aim of this study was first to introduce a tool for assessment of RoB in studies of adverse effects associated with orthodontic treatment and, second, to apply it in an SR of external root resorption (ERR) associated with orthodontic treatment with fixed appliance.

MATERIALS AND METHODS: The approach with domains supported by signalling questions was used for the tool. Domains and signalling questions were tailored to the review questions of the SR of studies of ERR after orthodontic treatment using periapical radiography or cone beam computed tomography. Duplicate study selection, data extraction, and RoB assessment using the tool, followed by meta-analyses, were performed.

RESULTS: Using the tool for the assessment of RoB identified shortcomings and report deficiencies of primary studies concerning the presentation of orthodontic treatment, identification of ERR, and analysis of outcomes. RoB assessment resulted in 12 of 32 studies read in full text being included. Reported severe ERR varied across studies between 2 and 14 per cent for all incisors and 10 and 29 per cent for maxillary incisors. Results of ERR related to patients' age and sex, orthodontic diagnosis, and treatment were contradictory. Quality of evidence evaluated by GRADE was low due to study limitations, imprecision, and inconsistency of study results.

CONCLUSIONS: As the tool and its application highlight important issues to consider when planning, conducting, and reporting research, the tool may have a valuable role for quality enhancement of future studies of outcomes of orthodontic treatment. The tool may also serve for authors when planning SRs. Our SR identified a need for studies that use rigorous methodology and transparent reporting.

REGISTRATION: PROSPERO (ID = CRD42018084725).

Objectives: To assess inter- and intrarater reliability and agreement for measurements of root lengths using multiplanar reconstruction (MPR) in cone beam computed tomography (CBCT) examinations.Furthermore, to determine whether using MPR from different CBCT machines was a reliable and reproduc-ible method for assessment of root length during orthodontic treatment of adolescents. Materials and methods: A total of 40 CBCT examinations obtained before, during and after orthodontic treatment of 14 adolescents, with fixed appliances from a multicentre randomised controlled trial, were used. All roots from the incisors to the first molars were measured by two independent raters and in accor-dance with a protocol preceded by a multi-step calibration. Reliability was assessed by intra class cor-relation (ICC). Agreement was assessed by measurement error according to the Dahlberg formula and Bland–Altman plot.Results: The number of repeated measurements varied from 436 to 474 for the different timepoints. Good to excellent inter- and intrarater reliability for different tooth groups and timepoints were shown. Measurement error for inter- and intrarater agreement varied between 0.41 mm and 0.77 mm. The Bland–Altman plot with 95% limits of agreement varied between +1.43 mm and −2.01 mm for different tooth groups and timepoints. Conclusions: The results of this study indicate that CBCT using MPR from different machines is a reproduc-ible method for measuring root length during different phases of orthodontic treatment. When interpret-ing root shortening measurements in CBCT using MPR for clinical or research purposes, values below 2 mm should be approached with caution, as they may contain measurement errors