Mixed-methods assessment of perceptions of mandibular anterior malalignment and need for orthodontic retreatment


Postorthodontic occlusal changes may stem from true relapse or may be a consequence of characteristic temporal changes. The aims of this research were to identify occlusal discrepancies related to the mandibular labial segment prompting a decision to undergo orthodontic retreatment.


A mixed-methods assessment was undertaken comprising a qualitative analysis involving focus groups exploring the relative importance of a range of occlusal features in the decision to undergo retreatment and investigating the motives for seeking retreatment. Quantitative assessment of these occlusal discrepancies was undertaken by 50 lay and 50 professional raters.


Several themes were identified in the qualitative analysis, with dental esthetics a major motive in seeking retreatment; variations in both the perception of relapse and retainer wear were identified. Horizontal irregularities of the mandibular anterior teeth were consistently perceived as the most severe. The professionals had slightly higher odds for suggesting the need for retreatment than did the laypeople, although this did not have statistical significance (odds ratio, 1.23; 95% confidence interval, 0.52-2.19; P = 0.65).


The perception of mandibular labial segment irregularity and its influence on the need for orthodontic retreatment are complex and multifaceted. Nevertheless, horizontal discrepancies of the mandibular incisors were regarded as the most significant by both lay and professional raters.


  • Many factors contribute to an adult’s decision to undergo orthodontic retreatment.

  • Patients and clinicians are sensitive to irregularity of the mandibular anterior teeth.

  • Perceptions of mandibular anterior irregularity are consistent among lay and professionals.

  • Professionals have lower tolerance levels for occlusal discrepancies.

Orthodontists are increasingly resigned to instability associated with most tooth movements. Posttreatment changes may stem from true relapse caused by unstable tooth positioning, physiologic recovery of investing tissues, or characteristic time-related changes. Thus, the requirement for indefinite retention and occasionally the need for orthodontic retreatment when retention is unsuccessful are well established. The latter may arise from poor compliance with removable retainers, detachment or residual activity of fixed retainers, or iatrogenic changes during fixed retention.

Orthodontic relapse and maturational changes often manifest in the mandibular anterior region. Such changes may include contact point displacements, rotations, angulation or inclination changes, and vertical movements either in isolation or in combination. These changes are brought into sharper focus by increased mandibular incisor exposure and reduced maxillary incisor exposure with age. However, the decision to undergo or recommend orthodontic retreatment is arbitrary. Clinicians typically have a lower tolerance for orthodontic irregularity than do patients. Most research has focused on maxillary anterior discrepancies. Moreover, although Little’s irregularity index, the most accepted for quantifying relapse, solely accounts for horizontal displacements, there is little appreciation of the relative importance of this and other possible manifestations of malalignment.

Furthermore, little emphasis has been placed on the implications of relapse and mandibular anterior discrepancies from the patient’s perspective. Malocclusion may have sociopsychologic effects and implications on oral health-related quality of life. It is therefore important that the relationship between occlusal discrepancies, social consequences, and motives for correction are more clearly understood. The premium on appropriate retreatment decisions is intensified by the failure of previous treatment and the potential for iatrogenic damage, including root resorption, associated with potentially protracted, albeit intermittent, treatment.

Qualitative methods have been adopted relatively recently in orthodontic research to shed light on decision making in patients undergoing combined orthodontic-surgical treatment. These approaches may afford a more detailed appreciation of patient-centered factors complementing established quantitative techniques. The aims of this research were therefore to identify a threshold level of mandibular labial segment irregularity prompting a decision to undergo orthodontic retreatment among adults and to evaluate the relative importance of various mandibular anterior discrepancies in this decision. A secondary aim was to compare lay and professional opinions related to the relative importance of occlusal features on the decision to undergo orthodontic retreatment. The null hypothesis was that there is no specific occlusal feature or severity level associated with a decision to retreat an orthodontic patient for mandibular labial segment irregularity.

Material and methods

The study had a mixed-methods design incorporating a qualitative component involving layperson focus group interviews to explore opinions relating to changes affecting the mandibular anterior teeth and attitudes to occlusal discrepancies prompting a decision to undergo orthodontic retreatment in adulthood followed by a quantitative, cross-sectional analysis to determine the severity of specific occlusal discrepancies. The study was approved by the research ethics committee of Queen Mary University of London (QMREC 1330d).

Focus group interviews

Laypeople were recruited via posters circulated in boroughs neighboring the Royal London Hospital, Barts, and The London School of Medicine and Dentistry. Inclusion criteria for participants were age 18 years or older, fluent English speakers, and not professionally linked to dentistry. A maximum of 6 participants were permitted per focus group with equal numbers of men and women, when possible. Basic demographics were obtained before the interviews to facilitate participant allocation to a specific group to ensure ethnic diversity and sex balance.

A topic guide was designed as an aide-mémoire to improve the consistency of data collection during the focus group interviews and to ensure that salient issues were covered in a systematic fashion. Semistructured, open-ended focus group interviews were facilitated by an interviewer (M.K.K.) in a nonclinical setting. All interviews were recorded and continued until no further comments were proposed by the participants. The interviews were supplemented with visual aids where appropriate, including study models of aligned and malaligned dental arches, removable retainers, and photographs of dental malalignment and fixed retainers. The interviews were transcribed verbatim and evaluated using framework analysis. Framework analysis allowed an overview of the textual data from the interview transcripts, facilitating visualization and examination.

Cross-sectional analysis of study models

Fifty orthodontic professionals and 50 laypeople were invited to assess study models reflecting a range of mandibular labial segment discrepancies and to complete a corresponding questionnaire. The study models (n = 18) were fabricated from impressions of various typodont setups, with each model altered to represent 1 of 5 occlusal discrepancies of the mandibular labial segment likely to be of concern to prospective patients, reflecting opinions from the focus group interviews. The discrepancies were made manually on the typodont, with contact point displacements recorded using digital calipers, and angulation, inclination, and rotational changes measured using a protractor and acrylic jigs, with readings remeasured on separate occasions, 2 days apart, to confirm repeatability.

Duplicate models were made of certain discrepancies (n = 4) to confirm intraexaminer variability, with 1 study model fabricated to represent ideal alignment (control). A maxillary study model with ideal arch alignment was also constructed to facilitate occlusion with the mandibular study models and aid assessment, where applicable.

Initial piloting of the response questionnaires of both orthodontic professionals and laypeople and the assessment of readability using the Flesch Reading Ease scale (54.0) and the Flesch-Kincaid Grade Level (8.1) were undertaken, indicating appropriateness for a reading age of 13 years. Thereafter, the professional group was recruited at the British Orthodontic Society conference at the Edinburgh International Conference Centre (September 2014). The lay group was recruited from the orthodontic department at Whipps Cross University Hospital, London, incorporating either friends or relatives of patients at the department.

The models were divided into 3 groups of 6 ( Table I ), with participants ranking each occlusal feature in order of severity using a numeric grade of 1 to 6, with 1 representing the least severe and 6 the most severe occlusal feature. The participants were then asked to select which occlusal features required orthodontic retreatment. Higher severity ratings were associated with a greater perceived need for retreatment, and a severity score of 3 generated equal responses for need for retreatment and no need for retreatment; therefore, a severity score of 3 was selected as the threshold level above which orthodontic retreatment was indicated.

Table I
Occlusal discrepancies generated on study models (n = 18) reflecting a range of occlusal discrepancies
Occlusal feature/discrepancy Group
1 2 3
Combined: horizontal and angulation (A) 3-mm horizontal discrepancy and LR1 and LL1, 7° 3-mm horizontal discrepancy and LR1 and LL1, 10° Ideal alignment
Inclination (B) LR3 and LL3, 20° LR3 and LL3, 10° LR3 and LL3, 10°
Rotation (C) LR1 and LL1, mesiobuccal 20° LR1 and LL1, mesiolingual 20° LR1 and LL1, mesiolingual 20°
Horizontal (D) LR1 and LL1, 3 mm LR1 and LL1, 5 mm LL1, 3 mm
Horizontal (E) LR1, 5 mm LR1, 3 mm LL1, 5 mm
Vertical (F) LR1 and LL1, 1 mm LR1 and LL1, 2 mm LR1 and LL1, 1.5 mm

LR , Mandibular right; 1 , central incisor; LL , mandibular left; 3 , canine.

The completed questionnaires were coded to assist data transfer into Stata for Windows (version 13; StataCorp, College Station, Tex). To assess intraexaminer repeatability, 10 participants were invited to assess the study models and complete the questionnaire on 2 separate occasions, 2 weeks apart.

Statistical analysis

Descriptive statistics related to rater characteristics and outcome data were recorded. Intraexaminer agreement was assessed using weighted kappa values for categorical data. The need for orthodontic retreatment, based on the nature and extent of mandibular anterior irregularity and rater characteristics, was assessed using random-effects logistic regression analysis. The samples were tested for normality with a prespecified significance level of P <0.05.


Focus group interviews

Twelve subjects participated in the interviews, and 3 focus group interviews were held over a 2-week period. Of the 12 participants, 2 were 18 to 24 years, 9 were 25 to 33 years, and 1 was between 34 and 45 years of age. There were an equal numbers of male and female participants, with ethnic backgrounds including Asian-white, white, and African-Caribbean. Five participants had received previous orthodontic treatment, with 1 currently in retreatment.

The interview transcripts were analyzed line by line, and 6 key themes were identified. Each theme was then further subdivided into subthemes that characterized the main theme ( Table II ). More detailed results from the focus group interviews are given in the Supplementary Appendix .

Table II
Themes and subthemes from focus group interviews
Facial Esthetics Perception of Malalignment Orthodontic Treatment Orthodontic Retreatment Perception of Retainers Perception of Relapse
Professional impact Societal perception Personal commitment Treatment implications Compliance Degree of change
Social interactions Self-concept Self-concept Motivation for retreatment Comfort Motivation for retreatment
Self-concept Age-related changes Acceptability of treatment Influence of previous treatment Long-term implications Awareness of relapse
Cultural differences Importance of maxillary and mandibular anterior teeth Motivation for treatment Acceptability of retreatment Social impact
Social background Best and worst images Best and worst study models Maintenance

Various opinions were raised regarding the influence of facial esthetics, with some participants conscious of the impact on professional careers and social interactions: “Once we are more likeable, we tend to be more successful.” Cultural and social differences were also explored, with the idea of differing esthetic norms raised by 1 participant, who felt that perception of esthetics depended on cultural background: “some cultures don’t really worry about that type of physical aspect.” Another participant developed the topic further by stating: “American culture and western society makes you think that image is more important—clothes, make-up, hair and everything all ties in.”

Many participants believed that society plays a role in the perception of dental perfection, whereas dental appearance influences self-concept with impacts on self-confidence and conduct: “I definitely do think that people do tease and taunt at a young age, if there’s a big imperfection, I do think there’s a lot of people who do look for perfection.”

When the perception of age-related dental changes was discussed, the responses were split. Some participants believed that dental changes have an impact on facial esthetics: “It’s changing what they’re used to looking at in the mirror on a daily basis.” A participant was undergoing orthodontic retreatment “to maintain myself, because obviously, like, you always deteriorate as you get older.”

Personal commitment and effort influenced the decision to seek orthodontic treatment. Some participants preferred appliances that would not greatly affect their day-to-day appearance and lifestyle: “Something more discreet and would require less maintenance, to me that would be a big seller.” Another participant stated that she would refuse orthodontic treatment since she thought that it was less esthetically acceptable for an adult to have fixed appliances, and she related brace treatment to a younger population: “It’s more of a younger teenage thing. When you see somebody who’s in their mid-20s and they have braces, it’s quite young isn’t it?”

Conversely, some participants were interested in treatment or knew family members who were eager to have orthodontic treatment for the mandibular labial segment because of an internally driven motivation to achieve dental perfection or a lack of treatment during adolescence and the long-standing desire to correct the irregularity: “I would get ones (braces) for my lower teeth because I do think they are really crooked.”

Opinions regarding orthodontic retreatment were mixed across the focus groups, with some believing that the costs and time implications influenced the decision for retreatment: “I think the length of time is a factor. The cost may be completely unattainable and just completely unrealistic, so I think that is a big thing as well. But sometimes financial plans can’t even be achievable.” Others felt that the need for orthodontic retreatment outweighed the cost implications: “For me it is not a cost issue. I would pay £3000 if I thought it would straighten my smile.”

Previous orthodontic treatment played a role in the decision to seek retreatment; previously treated patients are “more open to get the little fix to be done again” and more conscious of slight posttreatment irregularities, thus prompting a decision to pursue retreatment. The acceptability of orthodontic retreatment was explored, and most participants thought that conventional, labial fixed appliances had a negative esthetic, professional, and social impact because “it makes you look younger as well, maybe not taken seriously in life.” Conversely, 1 person noted a change in social perception and acceptance regarding fixed appliances over time and believed that retreatment was “almost, like, acceptable… as opposed to 20 years ago, it was not, it was considered geeky whereas it’s so standard now.”

Several participants held a negative view of retainers, both removable and fixed, and believed that the commitment of wear, long-term maintenance, and potential financial costs for replacement would be inconvenient and prevent compliance with the proposed retention regimen: “We are lazy and we want convenience, I want it and I know it’s terrible to say and you want image, so you want it all with the minimum of burden.” There were conflicting opinions regarding the esthetic and social impacts of retainers, with some participants reporting embarrassment with removable retainer wear in public, whereas others were aware of friends wearing removable retainers, although they had not noticed them, since “obviously you can’t see them, they are transparent.” Other participants viewed retainers as an “investment” and were willing to accept the associated long-term commitment.

The focus groups were shown a series of photographs displaying various levels of posttreatment relapse to stimulate conversation regarding relapse. The perception of relapse correlated with the degree of posttreatment change and the severity of the original malocclusion: “If they were really wonky in the beginning I’d be quite happy with that (minor degree of relapse).”

The severity of relapse was also reported as a stimulus for retreatment, with some participants willing to accept minor changes of the mandibular anterior teeth, whereas others believed that relapse was due to poor orthodontic treatment and required further treatment to correct: “I would have been annoyed against my dentist. I would probably go to another dentist to get it fixed.” Some participants, however, were conscious of the limitations of retreatment and the risk of further relapse: “It’s almost like orthodontic treatment, it’s blasé… it’s not considered a major process now, it’s not, but there’s a lot with it, you know.”

Cross-sectional analysis of study models

One hundred participants (50 orthodontic professionals, 50 laypeople) were involved in this part of the study ( Table III ). Intraexaminer reliability was assessed using the kappa coefficient, with kappa values ranging from 0.41 to 1, indicating fair to substantial agreement.

Table III
Demographic and clinical characteristics of rater groups (n = 100)
Overall (n) Layperson (n) Professional (n)
Age (y)
18-24 2 2 0
25-33 41 8 33
34-45 34 19 15
46-55 21 20 1
55+ 2 1 1
Orthodontic status
Previous orthodontics 52 25 27
No orthodontics 48 25 23
Retreatment status
Received orthodontic retreatment 7 4 3
No orthodontic retreatment 93 46 47

Significant horizontal movements of the mandibular incisors of 5 mm were ranked as the most severe discrepancy, ranging from 34% to 71%. Conversely, rotational movements of the mandibular incisors (20°) and inclination issues associated with the mandibular canines were almost universally considered to be problems of much less significance ( Table IV ). The discrepancies typically ranked as the least severe were ideal alignment, followed by vertical displacement of the mandibular central incisors, and inclination changes (10°) associated with the canines ( Table V ). A vertical displacement of 1 mm was deemed the least severe occlusal feature (90%) in group 1. For group 2, a mandibular canine inclination change of 10° was the least severe occlusal feature (64%) followed by a 2-mm vertical discrepancy of the mandibular central incisors (21%).

Table IV
Frequency of ranking of discrepancies as the most severe
Group Occlusal feature/discrepancy Overall (n = 100) Layperson (n = 50) Professional (n = 50)
1 Horizontal LR1, 5 mm 52% 46% 58%
Inclination LR3 and LL3, 20° 25% 28% 22%
Horizontal LR1 and LL1, 3 mm 10% 8% 12%
3-mm horizontal discrepancy and LR1 and LL1, 7° 8% 10% 6%
Vertical LR1 and LL1, 1 mm 4% 6% 2%
Rotation LR1 and LL1 mesiobuccal, 20° 1% 2% 0%
2 3-mm horizontal discrepancy and LR1 and LL1, 10° 50% 64% 36%
Horizontal LR1 and LL1, 5 mm 34% 22% 46%
Horizontal LR1, 3 mm 7% 2% 12%
Vertical LR1 and LL1, 2 mm 5% 8% 2%
Inclination LR3 and LL3, 10° 4% 4% 4%
Rotation LR1 and LL1 mesiolingual, 20° 0% 0% 0%
3 Horizontal LL1, 5 mm 71% 64% 78%
Rotation LR1 and LL1 mesiolingual, 20° 8% 12% 4%
Ideal alignment 8% 8% 8%
Horizontal LL1, 3 mm 6% 6% 6%
Vertical LR1 and LL1, 1.5 mm 6% 10% 2%
Inclination LR3 and LL3, 10° 1% 0% 2%
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Apr 4, 2017 | Posted by in Orthodontics | Comments Off on Mixed-methods assessment of perceptions of mandibular anterior malalignment and need for orthodontic retreatment
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