IPR planning with tooth-by-tooth documentation

IPR is limited by the enamel available at the contact, and that varies more than the arithmetic of a space analysis suggests. Mandibular incisors carry the least interproximal enamel in the arch, commonly reported in the region of 0.7 to 1.0 mm per surface, while premolars and molars carry appreciably more. Because a contact has two surfaces, the reduction figure for a contact is shared between the two adjoining teeth, which is why a plan quotes the contact and not the tooth.

The conventional working rule taught in restorative and orthodontic practice is to remove no more than about half of the interproximal enamel at a contact and to leave enamel on both surfaces, which in the anterior segment usually means keeping individual reductions at the lower end of the 0.2 to 0.5 mm range and treating anything above that as a decision requiring a specific reason. These are the ranges in general use rather than a figure this service guarantees for any patient.

Restorations change the arithmetic completely. A composite, veneer or crown margin at a contact means there may be no enamel to reduce, and stripping into a restoration or a cervical dentine exposure is a different clinical event from stripping enamel. Contacts with existing restorative work are flagged for your decision rather than included silently in an arch total.

IPR suits mild to moderate crowding, particularly in the anterior segments, where the space needed is a few millimetres and the incisors are already at an acceptable inclination. It is also useful for reshaping triangular crowns to close black triangles, for correcting a Bolton tooth size discrepancy, and for creating a small amount of space to allow derotation without proclining the labial segment.

It is the wrong answer when the arch is genuinely constricted, when the incisors are retroclined and would benefit from proclination, or when the space requirement is large enough that meeting it by stripping would take multiple contacts past sensible limits. In those cases expansion of the posterior segments, controlled proclination of the labial segment, or a decision about extraction is the honest alternative, and each has its own cost: expansion depends on the buccal bone and the periodontal biotype, proclination depends on the labial bone plate and the lip support you are willing to change, and extraction is a decision only the treating clinician makes.

The plan sets these out as a comparison rather than a recommendation dressed as arithmetic. Where a contact could take stripping but the case would be better served by another route, that is written into the notes so you can weigh it.

The timing of IPR is as consequential as the amount. Reduction performed too early, before the teeth have separated, is difficult to execute accurately: the strip cannot reach the contact perpendicular to the enamel surface, and reduction taken at an angle removes enamel where it was not intended and leaves a ledge. Reduction performed too late leaves a tooth without the space it was staged to move into, and the aligner stops tracking.

The usual sequence is to allow the early stages to unravel the crowding enough for access, place the reduction at the stage immediately before the space is consumed, and keep each visit's reduction to a small number of contacts so the chairside step is short and controllable. Where several contacts in one segment need reduction, they are spread across stages rather than performed together, which also keeps the contacts from opening all at once.

The chart is written to be used in this order. Each line names the two teeth in FDI notation, the amount in tenths of a millimetre, and the stage, so at any given visit the clinician reads only the lines due at that stage rather than reconstructing the sequence from an arch total.

An IPR plan that lives only inside a 3D viewer is hard to execute. The deliverable is therefore a printable chart in arch order, with a column for the amount planned and a column for the amount actually performed, because the two diverge and the record of what was really removed is what matters at the next review or at a refinement.

Recording actual reduction has a direct effect on later planning. If a refinement is planned from a new scan, the residual space and the enamel already removed are both relevant, and a case with an accurate IPR record can be replanned without repeating reduction at a contact that has already been stripped close to its limit.

The chart does not prescribe the instrument or the technique, which are matters for the treating clinician and for the burs, strips or discs in the surgery. It records the plan: which contact, how much, at which stage, and which contacts were deliberately left alone.