Introduction to Interproximal Reduction
Interproximal reduction (IPR) is a procedure used in orthodontics to create space between teeth for better alignment. It involves selectively reshaping the contact areas between teeth to reduce width. IPR is commonly performed in clear aligner treatment to help teeth fit properly within the aligners.
With clear aligners, IPR creates space needed for teeth movement. Aligners can only apply light forces, so if teeth are too crowded, IPR facilitates alignment by opening up space between the teeth first. This allows the aligners to then move teeth more effectively into the desired positions.
IPR offers several benefits in clear aligner treatment:
Creates space needed for desired tooth movements that may not be possible otherwise due to crowding. This helps achieve proper alignment with the clear aligner treatment plan.
Shortens clear aligner treatment time. With strategically opened up space, the teeth can move more quickly into the planned positions.
Reduces need for extraction. In some cases, IPR minimises crowding enough to prevent pulling teeth for space creation. This leads to less invasive treatment.
Improves results. With room to move, the teeth are better guided into proper alignment with clear aligner trays.
Enhances interproximal contacts. Reshaping contact areas allows for more ideal contacts between teeth after treatment.
Provides a more stable result. IPR helps alleviate crowding that could otherwise relapse after treatment.
Overall, IPR is an important complement to clear aligner treatment for creating space, facilitating tooth movements, reducing treatment time, enhancing alignment and stability, and preventing extractions.
When to Perform IPR
Interproximal reduction (IPR) is an important part of clear aligner treatment planning and should be performed at specific times during treatment for optimal results. Determining when to reduce depends on the initial malocclusion, attachment placement, desired tooth movements, and treatment staging.
Timing During Treatment
IPR should be performed just prior to placing the aligners that will initiate interproximal tooth movements. This allows the reduction space to be utilised immediately by the pending aligner geometry.
Multi-step IPR divided over several aligners is recommended for large reductions (>0.5mm). This allows progressive space opening without causing damage to the gingiva or patient discomfort.
Minor IPR can be done when required at any point during treatment to assist desired tooth movements.
Amount to Reduce
Up to 0.5mm of enamel can be safely reduced in healthy teeth without risk of damage. This corresponds to the thickness of one aligner.
0.3-0.4mm of IPR is commonly performed between most teeth being aligned. Molars may require more due to their broad mesial-distal width.
Excessive reduction (>0.8mm) in a single step can traumatise the gingiva and should be avoided.
Which Teeth to Reduce
IPR should be focused only on teeth being actively aligned. Do not reduce stable teeth.
Molars and premolars often require the most reduction due to their broad shape.
Carefully evaluate radiographs to ensure no overlapping of roots prior to IPR between specific teeth.
Contraindications
Severe crowding or spacing may require orthodontic treatment prior to clear aligners.
Patients with thin enamel or recession should use caution with IPR.
Medical conditions causing enlarged gingiva or poor healing may contraindicate IPR.
Methods of Interproximal Reduction
Interproximal reduction can be performed using manual or mechanical techniques. When choosing between hand stripping or mechanical stripping, there are a few key factors to consider:
a. Hand Stripping Techniques
Uses abrasive strips or discs that the provider holds by hand and applies interproximally
Gives the provider maximum tactile control and visibility
Allows for a more conservative and gradual reduction, with real-time patient feedback
Risk of hand fatigue, slower process
Strips or discs can be difficult to insert interproximally, especially in posterior teeth
b. Mechanical Stripping Techniques
Uses oscillating diamond strips in a slow-speed handpiece or automated precision scaler
Faster removal and more efficient, less hand fatigue
Can be more aggressive, harder to control depth of reduction
Risk of over-reducing or damaging adjacent teeth
Limited visibility and tactile feedback compared to hand techniques
Automated tools allow easier interproximal access
c. Safety Considerations
Avoid heat generation and pulpal damage
Use water spray/air coolant
Take care near CEJ to avoid root exposure
Start conservatively and check depth frequently
Ensure patient comfort and give time between stripping
Protect adjacent teeth
In summary, hand stripping allows for maximum control but can be slower and more fatiguing. Mechanical stripping is faster but the provider has less precision. For both techniques, care should be taken to maintain patient comfort, avoid pulpal irritation, and protect adjacent teeth.
Hand Stripping Techniques
Hand stripping can be performed using specialised dental instruments such as safe-sided finishing strips or diamond-coated interproximal reduction burs. Here are the key steps when performing IPR using hand instruments:
Isolate the contact point properly. Use cotton rolls, bite blocks, dental floss or special index strips. This protects the gingiva and cheek tissue.
Select an appropriate hand instrument. Finishing strips or diamond burs work well. The instrument should be narrow to target the contact point.
Stabilise your fingers on adjacent teeth. This provides control and avoids slipping.
Make light sweeping strokes directed incisally or occlusally across the contact point. Apply minimal pressure.
Assess reduction by flossing through the contact. If tight, continue gentle sweeping motions until the floss slides through cleanly.
Avoid creating sharp edges or grooves. Maintain contours for gingival health.
Polish treated areas using polishing strips once desired space is created. This smooths rough edges.
Check interproximal areas regularly as treatment progresses. Perform touch up stripping as needed.
With good isolation and instrumentation technique, hand stripping allows selective IPR without removing excess tooth structure. It offers tactile feedback to preserve anatomy. Using light force and many repetitive strokes is key for patient comfort.
Mechanical Stripping Techniques
Mechanical stripping techniques utilise specialised dental instruments to reduce interproximal enamel. This can help streamline the stripping process compared to hand techniques. Here are some key steps when using mechanical stripping:
Select the appropriate stripping disc or strip based on the desired amount of reduction. Coarse grits remove more enamel than fine grits.
Insert the stripping disc or strip into the handpiece. Ensure it is securely in place.
Set the handpiece to the lowest speed to avoid generating excess heat.
Apply light pressure to the interproximal contact, allowing the grit on the disc or strip to abrade the enamel.
Use intermittent pressure, rather than constant pressure, to allow cooling between passes.
Continue passes until the desired amount of space is created.
Avoid overheating the tooth surface. Pause between passes to allow cooling.
If reducing multiple teeth, move methodically from one site to the next.
Rinse away debris between teeth as you work.
Popular stripping instruments include abrasive discs, diamond impregnated strips, and tungsten carbide burs. Select an instrument based on the amount of enamel to be removed and patient comfort considerations. Maintain light force and intermittent pressure with mechanical stripping to preserve tooth integrity and minimise patient sensitivity.
Patient Comfort During IPR
Performing interproximal reduction can cause discomfort for some patients. There are several techniques that can help improve patient comfort during the IPR procedure:
a. Anaesthesia
Applying topical anaesthetic gels or solutions to the contact areas prior to stripping can help numb any sensation. This is especially useful for apprehensive patients or when performing extensive reductions. Some common topical anaesthetics used are benzocaine, lidocaine, or prilocaine gels.
b. Vibrations
Using an electric handpiece or mechanical stripper that vibrates can help mask sensations during stripping. The vibrations stimulate sensory receptors and decrease sensitivity to the grinding sensation. High-speed handpieces with air-rotor or electric micromotor create sufficient vibrations for this effect.
c. Patient Communication
Explain the entire process to patients beforehand so they know what to expect. Make sure to communicate before you begin stripping each tooth contact to avoid startling them with an unfamiliar sensation. Ask for feedback from the patient during the process. Check if they are comfortable or need more anaesthetic at any point. Offer breaks as needed if performing extensive IPR over multiple teeth. Breaking up the process into shorter segments can improve tolerance. Provide positive reinforcement on how well they are doing during the procedure. A calm and reassuring manner helps patients stay relaxed.
Contouring Considerations
Proper contouring technique is essential for maintaining ideal dental anatomy and aesthetics when performing interproximal reduction. The goal should be to reshape the contact points and embrasures while preserving natural tooth contours and papillae.
a. Tooth Anatomy
When contouring teeth, it's important to understand the anatomy of anterior and posterior teeth. Anterior teeth have rounded embrasures and contact areas while premolars and molars have more rectangular contours. Contouring anterior teeth requires a gentle curve while posterior teeth need straighter line angles.
b. Contact Points
Contact points should be rounded and continuous, with no sharp edges or notches after contouring. Posterior contact points are generally wider mesiodistally than anterior contacts. Care must be taken to not overly flatten or widen the contact during IPR.
c. Embrasures
Embrasures are the spaces between two adjacent teeth. Proximal embrasures should maintain a natural, curved shape from the contact point toward the gingiva after contouring. The depth of curvature will depend on the tooth type. Avoid leaving any sharp line angles in the embrasures.
d. Interdental Papilla
The papilla is the gum tissue between two teeth. When contouring for IPR, reshape the contact point but avoid recontouring the embrasure near the papilla. Over-reducing could lead to compromised papillae and black triangles between teeth. The interdental papilla height should be maintained after contouring.
Troubleshooting Guide
Interproximal reduction (IPR) is a key process in aligner treatment planning, but it can present challenges if not performed properly. Here are some common troubleshooting tips for IPR:
a. Uneven Stripping
Stripping too much enamel on one tooth compared to its neighbor is a common issue. Be sure to evaluate progress frequently and stop if stripping becomes uneven. Use a more controlled technique like hand stripping to even out discrepancies. Slow, methodical stripping helps prevent this.
b. Patient Discomfort
Some patients may experience sensitivity or pain during or after IPR. Be sure patients are using desensitising toothpaste and products. Numbing gel can be applied if hand stripping. Slow down stripping and spread it over multiple appointments if needed. Prescribe OTC pain relievers as appropriate.
c. Insufficient Stripping
Not removing enough interproximal enamel can lead to suboptimal aligner fit and treatment progress. Carefully evaluate how much enamel needs to be reduced before starting. Use a fine-tipped dental probe to measure reduction amount against initial IPR plan. Be thorough in hard-to-see areas.
d. Recontouring Issues
Improper contouring after stripping can leave sharp edges or uneven embrasures. Use contouring strips or specialty burs to smooth stripping areas and create natural embrasure shapes. Avoid over-contouring near the contact point. Evaluate contouring from both the occlusal and facial/lingual directions.
e. Poor Aligner Fit
Residual crowding, improper stripping, or recontouring can prevent optimal aligner fit. Have the patient wear previous aligners to identify problem areas. Refine IPR and contouring as needed. Additional aligner refinement may be required in difficult cases. Be sure to communicate issues to the treating orthodontist.
Comentarios