Interproximal Reduction, When, Why, and How | 9 MINUTE SUMMARY

In this episode, I dive into the fundamentals of interproximal reduction(IPR) when to use it, why it matters, and how to do it effectively.

We’ll cover how much IPR can safely be carried out, compare differentclinical protocols and their pros and cons, and take a critical look at howaligner software plans IPR (and where it may fall short).

This summary is based on Dr. Flavia Artese’s insightful lecture at therecent American Association of Orthodontists Annual Session in Philadelphia,along with insights from my own clinical research and experience.

How much IPR is possible?

Recommended amount ½ to 1/3 of outer enamel

Estimate with periapical radiographs are inaccurate, under-estimateas well as over estimate Meredith 2017 Brine 2001

Quantity of the enamel each interproximal surface Kailasam2021 systematic review, with an excellent table created by Bosio in 2022 highlightingthe enamel present and hypothetical safe reduction, ranging from 0.3-0.7mm,with 5-10% greater enamel on the distal surfaces

Can all teeth have IPR?

·     Triangular teeth are ideal

o  Large interradicular distance, roots canapproximate with no issue

·     Square shaped teeth not ideal

o  Reduced interradicular distance, rootapproximation of 0.8mm = loss of crestal bone Taera 2008

Are we accurate with IPR? Johner 2013 AJODO

·     Manual strips Vs rotary disc Vs oscillatingstrips = all underperformed IPR by up to 0.1mm

Protocols:

Small Vs Large

·     0.1-0.2mm manual strips

·     0.3mm+ larger reduction

·     Polishing required – If not = 25 um furrows retainplaque Jack Sheridan1989

Separation posterior region

·     Separator – Requires measuring of premolarbefore and after

·     Bur – needle bur

o  Parallel occlusal plane

o  Recontour tooth surface to create contact point

·     No separator -  requires contact point to be broken, advantageis the measurement of the IPR site is accurate

Bolton’s analysis

·     Based on excess, rather than tooth removal

Proportionality

·     Width

o  Canine 90% of central incisor

o  Lateral 70% of central incisor

IPR planning

Bolton’s discrepancy + Tooth proportionality

= whento add or remove tooth structure

However

·     “Don't do pre-emptive stripping for balancingtooth mass ratios between arches. Chances are it will work out just fine” Jack Sheradin 2007 JCO

Method of use for 4 mm of IPR:

·     Posterior to anterior – Jack Sheridan

o  Posterior IPR first, followed by distalisation,e.g. 4-5 first, distalise 4

o  Maintain arch length with stops etc, maintainanchorage

·     Anterior to posterior – Farooq

o  Anchorage preserving

o  Tony Weir 2021 the most common site in clinicalpractice was the lower anterior segment

IPR on overlapping teeth

·     Not possible to achieve ideal anatomy withmotorised IPR instruments

·     Posterior IPR first, distalise, followed byanterior alignment and IPR – Flavia

·     Use of handstrips is possible on overlappingteeth - Farooq

Limits of IPR

·     4-5mm, although Sheridan described possible 8.9mm,technically challenging

·     IPR is not a possibility for sagittaldiscrepancy:

Greater Bolton’s discrepancies in class 3 and class 2malocclusions, SR 53 studies Machado 2020, greater in class 2 and 3 casesalbeit a small difference of 0.3-0.8%

Retained primary 2nd molars

·     Idealise occlusion

·     Consider root morphology divergence, as post IPRspace may not close

o  If divergence greater than crown, reconsider asspace closure unlikely

Why do we need to use IPR with aligners? Dahhas 2024

·     Alogrythm reduces the number of aligners

·     More IPR rather than saggital correction

·     IPR staged inappropriately with large IPR whilstcontact point overlap, which is difficult to perform adequate anatomicalreduction

Join me for a summary of CBCT use inorthodontics, where I look into the current risk of cancer with CBCT use, the differenceit can make to treatment planning, and the 3 most common incidental findingsorthodontists should be aware of. This was one my highlight lectures from lastyears British Orthodontic Conference by Consultant Dental Radiologist, SimonHarvey. 

How much radiation comes from dentalCBCT, medicine?

Effective dose of modern machines:

·      Dose from full DPT with adigital system = 20-25µSv

·      KAVO, MoritaX800 4 x 4cm =16uSv

·      FDA values of CT scans acrossthe boy from Lubar 1500uSv – Heart 16000uSv

FACT 1 – effective dose in dental imagingare far below the rest of medicine

Background radiation

·      Terrestrial radiation

·      Cosmic radiation

o  Flight London – New York 56uSv– cancer UK ‘does not effect risk of cancer, even for frequent flyers’, 4uSvper hour

o  Pilots do not have an increasedrisk of cancer

UK 3000 uSv annually

FACT 2 – EFFECTIVE DOSES IN DENTAL IMAGINGARE FAR BELOW THE NATURAL BACKGROUND RADIATION

American Association of Physicist inMedicine AAPM

“evidence supporting increased cancerincidence or mortality from radiation doeses below 100mSv is inconclusive” –cancer incidence and mortality from the use of diagnostic imaging are highlyspeculative, discourage these prediction of hypothetical harm

FACT 3 EFFECTIVE DOSES IN DENTAL IMAGINGARE SO LOW, THEY DO NOT CAUSE CANCER

Clinicians improved confidence andconsistency in treatment planning decisions.

Impacted canine:

·      3 radiographs -  namely occlusal view, opg , periapical  = still not confident about prognosis.

·      CBCT = clear follicle and impactedcanine proximity to adjacent tooth, = easily make up the decision estimatingprognosis

o  22%-44% change of plans Hodges 2013 Stoustrup 2024  change in treatment plans ofimpacted teeth. The majority related to change in planning, with approximately10-20% a change in exposure Vs extraction. Keener 2023  

·      Cleft – quantification of bonedefect volume for grafting and localisation of ectopic teeth

·      Surgery – location of importantanatomical structures

3 Commonincidental findings for orthodontists

·      Dense bone island-

o  Radiopacity with no radiolucenthalo

o  Mandibular premolar region

o  Harmless, may resorb roots ifcontact it

·      Sinus mucosal thickening

o  Antrum floor intact

o  Only concern if 5mm+

·      Trabecular pattern

o  Around inferior dento-alveolarcanal

o  No corticated boarder

o  normal in children, technicalreason is physiologic response as more RBC’s are developing surrounding thatarea.

Pregnant women –yes as not irridating pelvic reason, CBCT beam is horizontal so no risk

Conclusion

1.    CBCT superior for resorption,material change to treatment plans and improve confidence of the orthodontists

2.    No recommendation for takingfull mouth CBCT instead of DPT ahead of starting every orthodontic treatment asroutine and x rays should never go hand in hand

3.    Small volume CBCT does is solow it doesn’t cause cancer

Orthodontics In Interview: Aligners, Limited or Just Misunderstood? tommaso castroflorio

“The biggest difference in overcoming the limitation (of aligners) is to understand how to control aligner deformation”

“We need to improve the available knowledge about aligners, because we need to control the companies, we do not need companies controlling us”

“I think you can treat also complex cases, in my practice I treat extraction cases”

“There are limitations in every technique, I think that the good orthodontist understands how to manage the limitation and how to overcome them”

“Large mass 3D printing will represent an important evolution in orthodontics, aligners and braces”

Tommaso explores the current understanding ofaligners, there limitations in terms of an appliance and scientific research. We explored the debate of aligners treating complex cases, why attachment designs still have limitations, and the role of aligners as functional appliances. We discuss emerging concerns of micro and nano-plastic toxicity andenvironmental concerns of aligners.

TIMELINE

00:00:00 Introduction of Dr Tomasso Castroflorio

00:00:51 Tomasso's Early Experiences with Aligners

00:08:21 What are the Limitations of Aligners?

00:11:24 How do we Overcome Limitations with Aligners?

00:17:59 Should Aligners be Restricted to Mild to Moderate Cases?

00:20:22 Research IndicatesAligners Only Tip Teeth into Extraction Sites, Do you Agree? 00:25:50 Importance of Visualization in Orthodontics?

00:29:27 Are Functional Appliance Aligners Advantageous over Conventional Functional Appliances?

00:35:08 Has There Been Over-emphasis on Attachment Design?

00:44:18 What are the Consequences of Microplastics and Aligners?

00:50:32 What is the Future of Aligners?

00:53:54 Who do you Admire the Most in Orthodontics

00:55:36 Advice from Tomasso to all Orthodontists

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Farooq Ahmed

Join me for a summary of recent long-term research of resorbed teeth due to impacted canines. This podcast is based on an excellent lecture by Julia Naoumova delivered at last year’s British Orthodontic Conference. Part 2 with focus on the prognosis of resorbed teeth from impacted canines, and follows on from part 1 with explored outcomes of open Vs closed exposures of impacted canines – see here for part 1.  

Root resorption of incisors reported at 19-67% Erikson 2000 Walker 2005, Mitsea 2022

Anna Dahlén and Julia Naoumova 2024 retrospective CBCT study n =27 incisors

Mean   Follow-up average 9 years (5.5-14.6)

Patient reported outcomes

• Survival 100%

• Horizontal grade 3 moderate resorption n=17  (resorption inner dentine not involve pulp moderate)

• Horizontal grade 4 severe resorption n=12 (pulp exposed severe)

• Vertical grade 3+ severe resorption n=7 (resorption 2mm-1/3rd moderate)o

• Vertical grade 4 extreme resorption n = 1  (resorption 1/3rd +)

• No significant difference in any grade of resorption long term of the following:

• Symptoms 

• Mobility and ankylosis

• Discolouration

• Increase gingival pocketing but not clinically significant 

• RR horizontal changes with time 

• No change 81%

• Worse 4%

• Improve 15%

• RR vertical changes  with time

• No change 43%

• Worsen 57%

• Expected as had orthodontic treatment as well

Previous research 

• 1-23 years Survival 93-100% Falahat 2008 , Bjerklin 2011, Becker 2005, Jönsson 2007

• Jönsson 2007 showed grade 1 mobility when root length < 10mm 

Conclusion:

Extraction of asymptomatic based purely on root resorption should be routinely performed

Paper by Anna Dahlén and Julia Naoumova 2024 

Longitudinal study of root resorption on incisors caused by impacted maxillary canines—a clinical and cone beam CT assessment 

https://doi.org/10.1093/ejo/cjae052

Join me for a summary of the management of impacted canines, the latest evidence regarding different techniques for alignment. This podcast is based on an excellent lecture by Julia Naoumova delivered at last year’s British Orthodontic Conference. 

Part 1 will focus on recent findings of a modified open exposure technique Vs closed exposure, in terms of duration but also other key outcomes, health, pain, use of analgesics,  time absent from school and costs. The next episode, part 2, will look at the prognosis of resorbed incisors related to impacted canines long term. 

Previous research  no difference between closed Vs open exposure for alignment, aesthetics, treatment time, surgical success, treatment times. Limited to 2D views Parkin 2017, Sampaziotis 2018, Cassina 2018. 

Questionnaire of current decision making of open Vs closed: n=48 orthodontists = current clinical decision making by orthodontists based on preference Naoumova 2018

Multicentre RCT Margitha Björksved 2018, 2021

• Modified open exposure with Glass ionomer OPen Exposure, first described by Nordenval 1999

• 6/12 of spontaneous eruption

• Traction with orthodontic appliances

Results

• Total time: no difference 26 months (95% CI −3.2 to 2.9, P = 0.93)

• Canine eruption time: Open exposure quicker by 3 months 8.5 months Vs 11.5 months (95% CI 1.1 to 4.9, P = 0.002). With no traction in open exposure group 

• No difference in periodontal status, root resorption, surgery time, complications, 

• Pain:  greater in closed group

• Greater pain with bilateral open exposure

• Closed exposure more painful applying traction 

• Analgesics use (preliminary data):

• Day 1 nearly all patients use

• Day 5 drops to less than 50% of patients use

• Day 10 most have stopped taking analgesics

• Costs: – no difference 

• €3,400  healthcare costs

• €6,300 including patient costs

• Missed days of school (preliminary data)

• Day 1 -  76% open Vs 65% closed exposure 

• Day 2 -  3% open Vs 6% closed exposure

Open exposure with GOPEX Not appropriate for:

• Close to adjacent tooth, to avoid material on adjacent teeth

• Very high canine position 

• Older patient – start traction straight away, probability of ankylosis increases Cernochova 2024

• 1% at age 15

• 4% at age 20

• 14% at age 25

• 97% at age 45

Conclusion:

• Both open and closed techniques are viable, however with open exposure of GOPEX technique the canine erupts spontaneously and quicker

• Less pain with open exposure unless bilateral

• Most patient will miss 1-2 days from school 

• Pain relief common for the first 5 days, but maybe used until day 10

Papers

Open vs closed surgical exposure of palatally displaced canines: a comparison of clinical and patient-reported outcomes—a multicentre, randomized controlled trial 

Margitha Björksved

Open and closed surgical exposure of palatally displaced canines: a cost-minimization analysis of a multicentre, randomized controlled trial 

Margitha Björksved

Join me for a summary looking at remote monitoring in orthodontic clinical practice, and if it can improve, quicken and enhance orthodontic clinical practice. This podcast is based on an excellent webinar by Jonathan Sandler and Juan Carlos Varela, as part of the Angle-net webinar series. I discuss how Dental Monitoring works, the proposed advantages and a review of the emerging research on this innovation in orthodontics. 

What is Dental Monitoring?

How does it work?

What do patients think of it?

Patients attitudes to remote monitoring

Does it reduce appointments and make treatment quicker? Sangalli 2024

Are treatment outcome better (aligners)? 

Is oral health better? 

Other innovations with remote monitoring?

Remote STL files

Is Dental Monitoring accurate? Ferlito 2022

Conclusion

Areas which are of concern

Other ways to reduce time?

“We do not accept the weaknesses of out appliances as absolutes, but rather we adjust out treatment mechanics to account for them Mazyar Moshiri,

“it's a platform for mass customization”

“I think Lightforce system has more friction than it should right now.”

“We operationalize great outcomes.”

“People that need to have a Cochrane review to prove to themselves the sky is blue, those are not the people that should be using Lightforce right now”

Alfred and I discuss his digital bonding system, Lightforce, we explore the product as well as the strength of the claims around it. Alfred replies to criticisms of the product as we explore the emerging evidence of his digital bonding system. 

Alfred gives his opinion on the digital evolution within orthodontics, we have a candid discussion on the use of digital orthodontics and where there are still areas of significant improvement needed.

Join me for a look at CBCT and its use in the diagnosis of the transverse problem, and if it offers the solution to the debated topic. The podcast is based on a lecture by Chun Hsi Chung at this year’s AAO and appraises established methods of assessment, the Curve of Wilson and the WALA ridge line through the lens of a CBCT, as well as how to use a CBCT to assess the maxilla and mandible, which although revealed an ideal measurement, may not be telling the full story.

What is ideal?

inclination 

Curve of Wilson – CBCT study 

Andrews WALA ridge 2000

Normal width  CBCT

CBCT age 13 N = 79 Miner 2012

CBCT Age 22.7 years Koo 2017

CBCT 56 adults normal occlusion  Lee 2022 PENN STUDY

Without cbct can transverse diagnosis occur?

Issue with CBCT for diagnosis

Issue with study model transverse analysis from 4mm at the gingiva

Join me for a summary looking into the increasingly popular

OSA - Defined upper airway dysfunction causing complete or

Sleep = Slow wave sleep – constructive phase of sleep

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Outcomes to paediatric patients of SDB: (AASM)

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First line medical treatment – adenotonsillectomy 

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Effect palatal expansion

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b.       

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a.       

Expansion other outcomes -  school performance  Bariani 2024

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Mandibular advancement

Move mandible forwards and open space behind the tongue – oropharynx

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Orofacial features in children with obstructive sleep

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AADSM 2024 – consensus statement

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More about OSA?

To hear more about OSA, please check out the last interview

Interview