Treatment time for missing laterals.

Missing teeth or ‘Hypodontia’ is very common in the permanent dentition. Genes play a crucial role. The upper lateral incisors are mostly affected, and the time taken for treatment averages 20.2 months according to a 2016 meta-analysis. A majority of these patients seek treatment for the purpose of improving their esthetics. Time delays between diagnosis, treatment and restorative procedures leave them anxious and dissatisfied.

Dissatisfaction is mostly caused by increased duration of treatment and a lack of proper communication.

The article that will be discussed in today’s post is as follows Space closure versus space opening for bilateral absent upper lateral incisors: what is the duration of orthodontic treatment?

By Jadbinder Seehra, Anwar Al- Ali, Nikolaos Pandis and Martyn T. Coubourne

About the authors

Jadbinder Seehra works in the Department of Craniofacial Development and Orthodontics in Kings College, London. He has 75 publications and 691 citations to his credit with areas of expertise being Oral and Maxillofacial surgery, Orthodontic treatment and appliance design.

Anwar Al-Ali is also affiliated to the same university.

Nikolaos Pandis is a Diplomate of the American Board of Orthodontics and an Associate Editor of the American Journal of Orthodontics and Dentofacial Orthopedics.

He is an Associate Professor at Universität Bern with over 300 publications and 4.500 citations. Areas of expertise include clinical trials, systematic reviews, longitudinal studies and evidence based medicine.

Martyn T. Coubourne is a Professor of Orthodontics in the Department of Craniofacial Development and Orthodontics in Kings College, London.

He has over 200 publications and 4000 citations. He is the author of two successful orthodontic textbooks, the Handbook of Orthodontics (Elsevier) and Clinical Cases in Orthodontics (Wiley).

What this study intended to do?

The primary aim was to assess the time taken for treatment of patients with bilaterally missing upper lateral incisors using conventional fixed appliances. So, the goals of treatment were either space closure and substitution of the upper canine into lateral incisor position or creation of space for prosthetic rehabilitation of lateral incisors.

The secondary aim was to determine the factors that influenced this treatment duration.

What methods were used?

Sample size was calculated

Patients were identified from clinic day lists, log books and orthodontic- restorative joint clinics within the orthodontic department at Kings College Hospital.

If they had a confirmed diagnosis of bilaterally missing upper lateral incisors , they were included in the study.

Ten variables were collected from the patients’ records.

These included age (at the start of treatment), gender, grade of clinician treating the patient, occlusal variables before treatment, the treatment plan- whether space was going to be opened or closed, the type of restorative prosthesis that had been planned, the number of orthodontic breakages, orthodontic appointments and the treatment duration.

The overall treatment duration was defined as the time between the date of placement of fixed appliances and the date when the fixed appliances were removed.

What were the results obtained?

Out of the 52 patients who were finally included- 29 formed part of the ‘space closure’ (SC) group and 29 were part of the ‘space opening’(SO)

Let’s go over the list of variables. Overall, the sample included more females than males and the mean age in the SO group was slightly greater.

When it came to the occlusal variables, most patients had a Class I incisor relationship, the SC group has a higher mean overjet, higher percentage of asymmetric molar relationship and the highest amount of lower arch crowding. The mean spacing of the upper arch was greater in the SO group.

The mean number of clinicians involved in both groups was similar. A non- extraction treatment plan was most commonly involved and for a majority of the cases (78 %) the restorative prosthesis planned was a resin bonded bridge. The total number of orthodontic breakages were the same and the number of appointments were greater in the SO group.

 of orthodontic treatment was greater in the SO group, but this was not significant statistically.

It was found that the overall treatment duration was shorter if an extraction approach was employed, but it increased as the amount of lower arch crowding increased per unit.


The authors conclude, by saying that there is no difference in the overall treatment duration between both treatment approaches.

The overall treatment duration of cases of bilateral absent upper lateral incisors treated either by space closure or redistribution of space for prosthetic replacement reduces if extractions are undertaken and increases with increase in lower arch crowding.

Critical Appraisal

Strengths of this study

Patient-based outcomes- The study set out to demonstrate any differences in treatment duration using two different techniques for the same problem- bilaterally missing lateral incisors. Orthodontic treatment outcomes, that are patient centred like treatment duration are often neglected in research. This information is extremely important in order to make informed decisions and consider the patients’ point of view while formulating evidence based treatment plans.

Predictors of treatment outcome- Variables that could possibly predict the outcome were also included and assessed using regression models. If a variable was found to be a significant predictor with a univariable analysis it was put to test using a multivariable analysis as well.

The treatment plan for fixed appliance therapy was clearly categorized into the extraction and non-extraction plan. It is interesting that while previous evidence points to increased treatment duration following extraction, in this study, an extraction plan was associated with a shorter treatment duration.

The authors included consecutively treated patients which resulted in reduced selection bias.

Lastly, the authors have also discussed the flaws of this retrospective study in detail and have provided suggestions for future research.

So, what were these limitations?

The study was performed retrospectively and the sample size was calculated only based on treatment duration.

Patients were recruited from a single centre, which questions the representability of the results. While the treatment plan was categorized as extraction and non-extraction, the anchorage requirements and the plan to manage the same were not included. The authors mention that the relationship of Temporary Anchorage Devices could have been explored.

Skeletal patterns were assessed in the sagittal plane, but not in the vertical.

Occlusal variables in the transverse direction such as intermolar and inter canine width could have been included. Expansion could potentially affect the treatment duration as well. Orthodontic treatment was carried out by post graduate students under supervision, which may have influenced time, despite the fact that duration was within acceptable limits. The grade of the clinician who was responsible for the restorative prosthesis has not been mentioned – this could have played a role as well.


A number of opportunities have been listed by the authors themselves. What we could do is calculate sample from studies that have evaluated treatment outcomes with multidisciplinary treatment including restorative care and orthodontics. A prospective study could be considered with 2 groups. Group 1 could have participants with missing lateral incisors to be treated with space closure and Group 2 with space opening. T0- Placement of fixed appliance T1- Removal of fixed appliance T2- Completion of prosthetic rehabilitation The following data could be collected and matched.

1. Age, gender

2. Variables could be categorised into sagittal, vertical and transverse.




Skeletal base, overjet

Growth pattern, Overbite

Arch width, inter canine and intermolar width

3. Treatment Plan – Space Closure or Space Opening Mechanics. – Extraction and Non extraction – Anchorage: Type A, B or C

4. Planned restorative prosthesis

5. Number of orthodontic bracket breakages.

6. Time taken from T0-T1 and T1-T2.

7. Pre-treatment and post treatment quality of life with a questionnaire. Standardisation – The treating physician’s qualification could be standardised by years of experience Regression models could be used to associate the variables with treatment duration.

Challenges: A prospective study by itself would be extremely challenging in this case, even if it eliminates the limitation of incomplete records with retrospective studies.

The duration of the entire study would have to increase in order to obtain an adequate sample size.

Contributors : Dr Hita

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