IPR (interproximal reduction) is one of the most misunderstood parts of aligner treatment. This guide explains what teeth shaving for aligners actually involves, how much enamel is removed, whether it hurts, and why clinicians use it.
If you've been researching clear aligners, you may have come across the term "IPR" — or seen it described more alarmingly as "teeth shaving" or "teeth filing." These phrases can sound unsettling, and it's natural to have questions. The reality is far less dramatic than the name suggests: IPR is a routine, conservative dental procedure that's been used safely in orthodontics for decades. This guide explains exactly what IPR dental treatment involves, why it may be part of your aligner plan, and what the evidence says about its safety.
📌 TL;DR
IPR (interproximal reduction) — sometimes called teeth shaving for aligners — involves removing tiny amounts of enamel (typically 0.1–0.5mm) from between teeth to create space for alignment. It's a routine part of many aligner treatments, is generally well-tolerated without anaesthetic, and is considered safe when performed by a trained clinician. The amount removed is a small fraction of total enamel thickness and does not weaken teeth when done correctly.
Who This Guide Is For
This article is for UK patients who have been told they need IPR as part of their aligner treatment — or who've encountered the term while researching and want to understand what it means. It may be particularly relevant if you:
- Have seen "teeth shaving" mentioned online and want the facts without the scare tactics
- Have been given a treatment plan that includes interproximal reduction and want to understand why
- Are considering invisible braces and want to know everything the treatment may involve
- Are nervous about having any enamel removed and want evidence-based reassurance
- Want to understand how IPR fits into the broader aligner treatment process
Important: This guide provides general information about IPR. Whether IPR is appropriate for your specific case can only be determined by a qualified clinician following a thorough assessment, including X-rays and a 3D scan of your teeth.
Key Definitions in Plain English
What Is IPR?
IPR stands for interproximal reduction. In plain English, it means carefully removing a very thin layer of enamel from between two adjacent teeth. The term "interproximal" simply refers to the space between teeth. You may also see it called tooth slenderising, enamel reduction, or — less helpfully — teeth shaving or teeth filing.
The amounts involved are tiny: typically between 0.1mm and 0.5mm per contact point. To put that in perspective, a human hair is approximately 0.07mm thick, so we're talking about removing the equivalent of one to seven hair-widths of enamel.
What Is Enamel?
Enamel is the hard, protective outer layer of your teeth. It's the hardest substance in the human body — harder than bone. Average enamel thickness on the sides of teeth (the interproximal surfaces where IPR is performed) is approximately 1.0–1.5mm, though this varies between teeth and between individuals. IPR removes only a small fraction of this total thickness.
Other Terms You May Encounter
- Attachments: Small tooth-coloured composite bumps bonded to specific teeth during aligner treatment. They help the trays grip teeth for more controlled movements.
- Refinements: Additional sets of aligner trays produced after the initial series to fine-tune the result. Most cases need at least one round of refinements.
- Retainers: Custom-made devices worn after treatment to hold teeth in their new positions.
- Tracking: How well teeth are following the planned movement sequence during aligner treatment.
- 3D scan: A digital impression of your teeth using an intraoral scanner, forming the basis for treatment planning.
- Crowding: When teeth overlap or are rotated because there isn't enough room in the jaw for them to sit straight.
Why IPR Is Needed: What Creates the Problem
The fundamental reason IPR exists is that aligner treatment (or any orthodontic treatment) often needs space to move teeth into better positions. Without space, teeth simply can't move to where they need to go. There are three main ways to create this space:
1. Arch Expansion
Widening the dental arch slightly to create room. This has limits — the bone and gum tissue can only accommodate so much expansion safely.
2. Tooth Extraction
Removing teeth (usually premolars) to create significant space. This is effective but more invasive and irreversible, and is typically reserved for more severe crowding.
3. IPR (Interproximal Reduction)
Removing small amounts of enamel from between teeth to create space without extracting any teeth. This is the most conservative option and is often preferred in mild to moderate crowding cases.
In many clear aligner cases, a combination of arch expansion and IPR provides enough space to resolve crowding without the need for extractions. This is one of the reasons IPR has become such a standard part of modern orthodontics — it allows clinicians to avoid more invasive alternatives.
What IPR Actually Is (and What It Isn't)
The term "teeth shaving" conjures images of aggressive grinding. The reality is far more conservative and controlled.
What IPR Is
- A precise, measured removal of enamel from the sides of teeth — only at the contact points between adjacent teeth
- Performed using either a thin diamond-coated strip (pulled back and forth between teeth) or a very fine rotating disc
- Carried out in controlled increments, typically 0.1mm at a time, with measurements checked as the clinician works
- A well-established technique that has been used in orthodontics since the 1940s, with extensive research supporting its safety
- Usually completed in minutes, often during a routine aligner appointment
What IPR Is Not
- Not aggressive: The amounts are microscopic — fractions of a millimetre. Your clinician is not reshaping or significantly altering your teeth.
- Not the same as a dental drill: The instruments used are much finer and less invasive than those used for fillings or crowns.
- Not usually painful: Most patients report feeling pressure, vibration, or nothing at all. Anaesthetic is rarely needed. Some patients experience brief, mild sensitivity.
- Not cosmetically damaging: The reduction is between the teeth at the contact points — not on the visible front surfaces. It does not change the appearance of your teeth.
- Not weakening your teeth: When performed within safe limits (which your clinician calculates), the remaining enamel continues to protect the tooth fully.
💡 Putting It in Perspective
Normal daily activities like eating, brushing with abrasive toothpaste, or grinding your teeth at night cause enamel wear over a lifetime. The amount of enamel removed during IPR is comparable to — and often less than — natural wear that occurs between teeth over several years. The key difference is that IPR is planned, measured, and controlled.
How Much Enamel Is Actually Removed?
This is the question most patients want answered, so here are the numbers:
The amount of IPR planned for each tooth is determined digitally during treatment planning, based on your 3D scan and the movements required. Your clinician knows exactly where and how much enamel to remove before they begin — it's not estimated on the day.
How Clinicians Control the Amount
- Digital planning: The treatment plan specifies IPR amounts to 0.1mm precision for each contact point
- Thickness gauges: Thin metal strips of known thickness are used to check that the correct amount has been removed
- Incremental approach: Enamel is removed gradually, with checks between passes — never all at once
- Clinical judgement: If enamel appears thinner than expected (for example, due to natural variation), the clinician may reduce or skip IPR at that site
How Clinicians Minimise Risk
IPR is not simply "filing teeth down." When performed by a trained clinician following established protocols, several steps are taken to ensure safety and comfort.
Before IPR
- Assessment: X-rays and clinical examination confirm that enamel thickness is adequate at the planned sites
- Planning: IPR amounts are calculated digitally as part of the overall aligner treatment plan — not improvised
- Consent: Your clinician should explain what IPR involves, why it's recommended, and answer any questions before proceeding
During IPR
- Precise instruments: Diamond-coated strips or fine oscillating discs — much thinner and less aggressive than standard dental instruments
- Water cooling: When motorised instruments are used, water spray prevents heat build-up
- Measurement checks: Thickness gauges verify the amount removed matches the plan
- Incremental removal: Small amounts at a time, with pauses to assess
After IPR
- Polishing: The treated surfaces are smoothed and polished to reduce roughness. A smooth surface is less likely to trap plaque.
- Fluoride application: Many clinicians apply topical fluoride to the treated surfaces to support enamel remineralisation
- Monitoring: The sites are checked at subsequent appointments to ensure there are no issues
📊 What the Research Says
Multiple long-term studies have investigated whether IPR increases the risk of cavities, sensitivity, or gum problems. The consistent finding is that when performed correctly and within recommended limits, IPR does not increase cavity risk, does not cause long-term sensitivity, and teeth that have undergone IPR remain healthy. The enamel surface remineralises and hardens after treatment, particularly with good oral hygiene and fluoride use.
What Clear Aligners Can Do (and What They Can't)
Understanding where IPR fits in helps you see the bigger picture of aligner treatment.
What Clear Aligners Can Typically Address
- Mild to moderate crowding and spacing
- Many cases of overbite, overjet, and mild to moderate crossbite
- Tooth rotations (with attachments)
- Arch alignment and levelling
- Relapse from previous orthodontic treatment
What Clear Aligners May Struggle With
- Severe skeletal jaw discrepancies
- Very large tooth movements requiring significant extraction space
- Severe rotations of certain tooth shapes
- Complex multi-directional bite corrections
IPR supports aligner treatment by creating the space needed for tooth movements without resorting to extractions. In many cases, it's what makes a non-extraction aligner plan possible.
Step by Step: How IPR Fits into Your Aligner Treatment
🦷 IPR in the Clear Aligner Treatment Process
When Is IPR Performed During Treatment?
The timing of IPR varies depending on the treatment plan. Common approaches include:
- At the start: All IPR performed at the fitting appointment before aligner wear begins. This is common for straightforward cases.
- Staged throughout treatment: IPR is split across several appointments — for example, some at fitting, some midway through, and some during refinements. This is common for more complex cases where space is needed gradually.
- During refinements: Additional IPR may be planned if a refinement round requires further space creation.
Your treatment plan will specify exactly when IPR is scheduled. It's not a surprise procedure — you'll know in advance.
Suitability Checklist: Understanding IPR in Your Treatment
IPR isn't something you choose independently — it's recommended by your clinician as part of a treatment plan. However, understanding when it's typically used can help you feel more informed.
✅ IPR Is Commonly Used When:
- There's mild to moderate crowding that needs space for alignment
- The clinician wants to avoid tooth extractions
- Teeth have certain shapes (triangular or tapered) that would leave "black triangles" (dark gaps at the gumline) after straightening — IPR reshapes the contact points to allow teeth to sit closer together
- The treatment plan requires specific, controlled space at particular sites
- The patient has adequate enamel thickness confirmed on assessment
🚩 IPR May Not Be Appropriate If:
- Enamel is already unusually thin (due to erosion, bruxism, or genetic factors)
- There is active decay between the teeth at the planned sites
- The patient has significant dentine hypersensitivity at the planned sites
- The amount of space needed is too large for IPR alone — extractions may be more appropriate
- There are existing restorations (fillings, crowns) at the contact points that would be affected
Your clinician will assess enamel thickness, dental health, and treatment needs before recommending IPR. If you have concerns, discuss them at your consultation — it's your right to understand every aspect of your treatment plan.
When to Seek Advice
IPR is part of a broader orthodontic treatment, so the decision to have it will be made during your treatment planning. However, you should speak with your clinician if:
- You have concerns about enamel thickness or existing sensitivity and want reassurance before IPR is performed
- You experience unusual sensitivity, sharp edges, or discomfort at IPR sites after the procedure
- You notice any roughness between teeth that doesn't feel smooth — this may indicate the surface needs additional polishing
- You have a history of enamel erosion, acid reflux, or bruxism (teeth grinding) that might affect enamel thickness
- You simply want a fuller explanation of why IPR is recommended for your case — a good clinician will be happy to explain
Risks, Side Effects, and Limitations
Like any dental procedure, IPR has potential risks and limitations. Being informed helps you make confident decisions.
Potential Side Effects (Usually Minor and Temporary)
- Brief sensitivity: Some patients notice mild sensitivity to cold at IPR sites for a few days. This typically resolves quickly, especially with fluoride toothpaste.
- Temporary roughness: If the surface isn't polished thoroughly, it may feel slightly rough to the tongue. This can be smoothed at a follow-up appointment.
- Mild pressure or vibration during the procedure: Not painful for most patients, but some find the sensation unusual.
Potential Risks (Rare When Performed Correctly)
- Over-reduction: Removing more enamel than planned could theoretically increase cavity risk or sensitivity. This is prevented by careful measurement and incremental technique.
- Damage to adjacent soft tissue: Very rare, but the gum between teeth could be nicked by the instrument. This heals quickly and is more of a discomfort than a risk.
- Enamel cracking: Extremely rare with modern techniques and appropriate instruments. More of a historical concern from older methods.
Limitations
- IPR is irreversible: Enamel does not regenerate. Once removed, it cannot grow back. However, the amounts are small enough that this is not clinically significant in the vast majority of cases.
- Limited space creation: IPR can only create a certain amount of space. Severely crowded cases may still need extractions.
- Not suitable for all teeth: If enamel is already compromised, IPR may not be appropriate at certain sites.
How Long Treatment May Take
IPR itself is quick — it typically takes 5–15 minutes per session, depending on how many sites are being treated. It doesn't add significantly to the overall treatment timeline. The aligner treatment duration depends on case complexity.
What Affects Overall Treatment Time?
- Case complexity: More severe crowding or bite issues take longer regardless of whether IPR is involved
- Compliance: Wearing aligners approximately 22 hours per day is essential for staying on schedule
- Refinements: Most cases need one or two rounds of refinement trays, each adding 2–5 months
- Biology: Individual variation in how quickly teeth respond to orthodontic forces
- Staging of IPR: If IPR is spread across multiple appointments, this may affect when certain tooth movements can begin, but rarely adds significant time
Costs in the UK: What Drives Price
IPR is almost always included in the overall aligner treatment fee — it's not typically charged as a separate procedure. The figures below relate to aligner treatment costs more broadly.
For a detailed breakdown of what affects aligner pricing, see our guide on invisible braces costs in London.
💡 Cost Tip
When comparing aligner quotes, check whether IPR, attachments, refinements, retainers, and monitoring appointments are included. A lower headline price that excludes these can end up costing significantly more overall. Ask for a written breakdown of what's included before committing.
How to Keep Results: Retention and Aftercare
After treatment — whether or not IPR was part of it — retention is essential to prevent teeth from shifting back.
Retention After IPR
A common concern is whether IPR-treated teeth need special retention. The answer is that retention after IPR is the same as for any aligner case:
- Fixed retainers: A thin bonded wire behind your front teeth provides continuous passive retention
- Removable retainers: Clear plastic trays worn nightly to maintain tooth positions
- Combination: Many clinicians recommend both for maximum stability
The spaces created by IPR close as teeth move together during treatment — they don't remain as gaps. Once the teeth are in their final positions and retained, the contact points are re-established.
Aftercare Tips for Teeth That Have Had IPR
- Use fluoride toothpaste: This supports enamel remineralisation and helps protect the treated surfaces
- Clean between teeth daily: Floss or interdental brushes help keep the contact points clean and healthy
- Avoid excessive acidic foods/drinks: Acid erosion affects all enamel, but being mindful is good practice after any enamel reduction
- Attend regular dental check-ups: Your dentist can monitor the health of IPR-treated surfaces at routine appointments
- Wear your retainers as prescribed: Consistent retainer wear is the single most important factor in maintaining your result
- Report any persistent sensitivity: If sensitivity at IPR sites doesn't resolve within a few days, mention it at your next appointment
Frequently Asked Questions
Does IPR hurt?
Most patients report that IPR is not painful. The most common sensations are pressure and vibration. Some patients feel nothing at all. Anaesthetic is rarely needed. Occasionally, patients experience brief, mild sensitivity during or immediately after the procedure, but this typically resolves within a few days. If you're anxious about discomfort, discuss this with your clinician beforehand.
Is teeth shaving for aligners safe?
Yes, when performed by a trained clinician within recommended limits, interproximal reduction is considered safe. It has been used in orthodontics since the 1940s, and long-term research shows no increased risk of cavities, sensitivity, or gum problems when done correctly. The key is that only a small fraction of the total enamel thickness is removed, and the surfaces are polished and may receive fluoride afterwards.
Does enamel grow back after IPR?
No — enamel does not regenerate once removed. This is why IPR is performed conservatively and in precisely measured amounts. However, the outer surface of enamel can remineralise (harden and strengthen) after treatment, particularly with good oral hygiene and fluoride use. The amounts removed during IPR are small enough that the remaining enamel continues to protect the tooth effectively.
How much enamel is removed during IPR?
Typically 0.1–0.3mm per contact point, with a maximum of approximately 0.5mm in most cases. To put this in context, the enamel on the sides of your teeth is approximately 1.0–1.5mm thick. IPR removes a fraction of this — roughly 10–25% at the treated sites. The total space created across a full arch is usually 2–6mm.
Can I refuse IPR?
You always have the right to refuse any dental procedure. However, if IPR is part of your treatment plan, declining it may mean that the planned tooth movements can't be achieved — your clinician would need to redesign the plan, potentially using alternative methods to create space (like extractions or more arch expansion) or accepting a compromise in the final result. Discuss your concerns with your clinician so they can explain the alternatives.
Does IPR increase the risk of cavities?
Research consistently shows that IPR performed within recommended limits does not increase cavity risk. The treated enamel surfaces remain smooth (especially after polishing), and the enamel remineralises over time. Good oral hygiene and fluoride use further protect the treated surfaces. Studies following patients for years after IPR have not found higher rates of decay at treated sites.
Will I have gaps between my teeth after IPR?
You may notice small gaps temporarily — the spaces created by IPR are there so your teeth can move into better positions. As treatment progresses, these gaps close as the teeth align. By the time treatment is complete, the teeth should be in contact again. If any small spaces remain, your clinician can address them during refinement stages.
Is IPR done at every aligner appointment?
No. IPR is only performed at specific appointments as outlined in your treatment plan. Some patients have all their IPR done at the fitting appointment; others have it staged across several visits. The timing and locations are planned digitally in advance. You won't have IPR at every check-up.
Can IPR be done without aligners?
IPR can be used with any orthodontic treatment — including fixed braces and aligners — or occasionally as a standalone procedure for minor cosmetic improvements (such as reducing slightly triangular teeth to improve contact points). However, it's most commonly used as part of a broader treatment plan rather than in isolation.
How do I care for my teeth after IPR?
Use fluoride toothpaste, clean between your teeth daily with floss or interdental brushes, avoid excessive consumption of highly acidic foods and drinks, and attend regular dental check-ups. These are good practices for everyone, but they're particularly worthwhile after any enamel reduction to support long-term tooth health.
Is IPR the same as filing teeth for veneers?
No. Tooth preparation for veneers involves removing enamel from the visible front surface of the tooth and typically removes significantly more enamel than IPR. IPR removes tiny amounts from between teeth — at the contact points — and doesn't change the visible appearance of your teeth. The two procedures are quite different in purpose, technique, and amount of enamel involved.
Why is IPR sometimes called "teeth shaving"?
The term "teeth shaving" is an informal (and somewhat misleading) description that has become common online. It sounds more dramatic than the procedure actually is. The clinical term — interproximal reduction — more accurately describes what happens: a controlled, measured reduction of enamel at the interproximal (between-tooth) surfaces. The phrase "teeth shaving" can cause unnecessary anxiety, which is one of the reasons we've written this guide.
📚 References and Further Reading
- NHS — Orthodontics Overview
- British Orthodontic Society — Patient Information and Resources
- Zachrisson BU, et al. — Dental health assessed after interproximal enamel reduction: caries risk in posterior teeth, American Journal of Orthodontics and Dentofacial Orthopedics (2011)
- Jarjoura K, C Grondin — Interproximal reduction: a safe and effective alternative to tooth extraction?, Journal of Clinical Orthodontics (2009)
- Rossini G, et al. — Efficacy of clear aligners in controlling orthodontic tooth movement: a systematic review, The Angle Orthodontist (2015)
- Zhong M, et al. — Does interproximal enamel reduction increase the risk of caries? A systematic review, Journal of Dental Research (2020)
- GDC — Guidance on Advertising
Have Questions About IPR or Clear Aligners?
If you'd like to understand whether IPR would be part of your treatment — and what your aligner plan would look like — book a consultation with our team. We'll explain everything clearly, answer your questions honestly, and make sure you're fully informed before any decisions are made.
Book Your ConsultationDisclaimer: This article is for general information only and does not constitute dental or medical advice. Treatment needs, timelines, and costs vary by individual case. All cost figures are approximate UK ranges for reference and are not quotations. Whether IPR is appropriate for your case can only be determined through an in-person clinical assessment by a GDC-registered dental professional.
Written by Pro Aligners Team
Medically reviewed by Pro Aligners Team • GDC: 195843