Insurance · Updated 2026-09-08 · 5 min read

Do D4910 and D1110 share a frequency?

On roughly two thirds of published plans they draw on one counter. On the rest they run separate limits and one carrier deliberately interleaves them.

On most plans a periodontal maintenance visit (D4910) spends one of the cleaning slots, but this is a per-plan fact and not an industry rule. Of the carriers and public programmes whose own documents state the answer, roughly two thirds pool D1110 and D4910 into one counter and roughly a third give them separate allowances — and at two carriers the same carrier does both depending on the plan. Across the practices Kaylie serves, perio maintenance lines were refused for frequency far more often than cleanings: 8.8% at Guardian, 6.6% at Cigna and 4.7% at Delta Dental, against 1.6%, 1.0% and 0.7% for the adult cleaning at the same three carriers, measured September 2026. That gap is the shared counter showing up in the remittances.

What we measured

Every claim line for that code at that carrier, paid and refused, measured September 2026 across at least fifteen practices per cell. Perio maintenance is refused for frequency five to seven times as often as a cleaning at the same carrier, which is what a pooled counter looks like from the claim side: two cleanings already taken leave nothing for the maintenance visit.

Three carrier-level measurements say how often the pooling is even stated. On Guardian, across a census of 400 benefit checks, 201 stated the pooling by naming the codes, 101 stated it in prose only, and 44 stated no sharing at all. On Delta Dental of Kansas, of 144 benefit checks carrying both codes, 8 put the two in one benefit class with equal limits, 86 put them in different classes with equal limits, and 50 stated different limits altogether — most often two per calendar year against one every four rolling months. On Cigna, D1110 and D4910 carried the identical allowance date on 100.00% of 1,298 measured members, which is one counter reported twice.

What the carriers' own policies say

Pooled, stated by the payer: "General Policy - The time limitation for prophylaxis is established by contract. Additional prophylaxes are optional and may be charged to the patient. D4910 is counted toward the contract limitation for prophylaxis" (Delta Dental of Tennessee Dentist Handbook 2022, 2022).

Pooled, with the arithmetic spelled out: "D4910 Periodontal maintenance – Limited to 4 periodontal cleanings and 2 routine cleanings within a calendar year period; the total cannot exceed 4 in a calendar year" (OPM United Concordia FEDVIP Dental Brochure 2026, contract 02AP-14, 2026). And by subtraction: "Periodontal maintenance is limited to four times in any calendar year less the number of teeth cleanings received during such 12 month period" (MetLife Take Along Dental PPO High Plan Schedule of Benefits, form IND-DENTAL-2015-SOB-PPO-14).

Not pooled, stated four times in one product guide: "Routine Cleanings: Limited to two per year. Type III periodontal maintenance does not count toward max of two cleanings" (BCBSAZ BlueDental 2026 Employer Group Product Guide, 2026).

Not pooled, and additive — six hygiene visits a year. One state-employee dental certificate gives two cleanings per benefit period and, on a separate line, four periodontal maintenance visits, with no combined ceiling anywhere in the document.

And one design that is neither, because it deliberately staggers the two clocks so the patient is seen more often rather than less: "One D4910 per member per 6 months (may be performed in concert with D1110 so a combination results in a D1110 or D4910 every 3 months)" (Envolve Dental CP.DP.6 Non-Surgical Periodontics).

Why it depends on the plan

Six mechanisms sit behind the phrase "they share a frequency", and they behave differently for the patient. A pooled counter is one allowance several codes draw on. A replacement rule has one code consume the other's slot outright. An in lieu of rule pays the second code only as a substitute for the first. An additive rule gives the second its own allowance on top. An interleaved rule keeps two clocks deliberately offset. A negative look-back has no shared count at all and instead blocks one code for N months after another.

Two codes printing the same number are not evidence of one allowance. On one carrier both the cleaning and perio maintenance read "2 Unit(s) per Service Year" on 98 of 98 benefit checks and no combined-limit clause exists anywhere in what the carrier publishes — so nobody can tell from the benefit page whether that is one allowance or two.

The cleanest proof a shared counter is real comes from the payer's own service history rather than its wording. On one Delta member company, across 157 history tables, D1110 appeared 105 times and D4910 twelve times and the two never appeared together, where independent counters would predict about eight overlaps. Codes with genuinely separate counters co-occur freely.

What to do

• Ask the question in the carrier's own vocabulary: is the perio maintenance allowance combined with, in addition to, or in lieu of the routine cleaning?
• Ask for the number on both codes and for the combined ceiling. "Four and two" with a cap of four is a different benefit from four plus two.
• Ask for the last date of service the carrier holds under both codes. On a pooled plan one hygiene visit will be reported under both.
• Do not treat matching frequency numbers as proof of sharing, and do not treat a benefit class named for both codes as proof either — some carriers print both and still hold two counters.
• Record which of the six shapes this plan carries. The count alone will not reproduce the next estimate.
• Alternating the two codes to stretch a shared cap is an office practice, not a payer rule; only one carrier — Envolve Dental — describes an alternating schedule in writing.

Numbers last refreshed September 2026.

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