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A baby tooth falls out. You might press it into a "tooth fairy" tradition, or drop it into a keepsake box, and leave it at that. What most families don't do is record which tooth, when, and under what circumstances — and yet that information can directly influence decisions about dental care.
The transition from primary to permanent teeth typically begins around age six and continues through about 12–13 [1,2]. Over those years, a child may present with a permanent tooth erupting behind a primary tooth that hasn't fallen yet, a primary tooth falling out too early, or a permanent tooth that is late to arrive. Without a log, you cannot tell a dentist whether "this started two weeks ago" or "it's been six months."
Background: What the Transition Looks Like
Twenty primary teeth (10 per jaw) begin to emerge at around six to eight months of age and are generally complete by ages two to three. In a study that followed 70 Romanian children, the first tooth appeared at a mean of about 7 months and the full primary set was in place at a mean of about 26 months [3]. The transition to permanent teeth typically starts with the eruption: the process by which a tooth pushes through the gum and becomes visible in the mouth of the first permanent molars — the "six-year molars" — and the lower front teeth, with an average starting age of around six years, though the normal range spans roughly five to seven [1,4].
Eruption follows a broadly predictable sequence: central incisors and first molars lead, followed by lateral incisors, then canines and first premolars, then second premolars and second molars. The order of canines and first premolars often differs between the jaws (in the lower jaw the canine usually comes first; in the upper jaw, the first premolar), and it also differs somewhat between boys and girls [2,4]. Research has documented statistical associations between body mass index and dental maturity, meaning that variation in build can shift a child's schedule relative to published averages [4].
In Japan, school dental health screenings — required under the School Health and Safety Act — include items for tooth alignment and malocclusion: misalignment of the upper and lower teeth when the jaw is closed, commonly called a bad bite and for the jaw joint, alongside decay and gums [5]. Results are returned to families using codes: CO (teeth with early caries: tooth decay caused by bacterial acid dissolving the tooth's enamel under observation), GO (gingivitis: inflammation of the gums, often caused by plaque buildup, the earliest stage of gum disease under observation), and a grade for alignment and bite. Many parents receive these notices without knowing what the codes mean.
Reading the Signs of Eruption
Double rows: A permanent tooth emerging while the baby tooth in front of it is still in place — erupting on the tongue side of the primary tooth — is called retained primary tooth (late-stage primary persistence). Lower-front double rows are common. In an Iranian study that followed children aged 5 to 7.5 for two years, lower permanent incisors erupting behind the primary ones were seen in 18.4%, and among children with adequate space or only a mild shortage, about 70% lost the primary incisors without any intervention. About 15% did need the primary tooth extracted, and the authors concluded that a wait-and-see approach can be considered [9]. If the primary tooth is slow to loosen, raise it with your dentist at the next visit.
Premature loss: When a primary tooth is lost early — through decay or injury — the permanent successor may be delayed, or neighboring teeth may drift and close off the space it will need. The American Academy of Pediatric Dentistry (AAPD) advises considering a space maintainer when primary teeth are lost prematurely, while noting that evidence on how well space maintainers prevent malocclusion is still lacking [8].
Delayed or out-of-sequence eruption: Permanent eruption that departs markedly from the usual pattern — clearly uneven progress between the left and right sides, a primary tooth that stays far too long, or an unexpected reversal of order — can be a sign of local causes such as supernumerary (extra) teeth or a congenitally missing permanent successor, and occasionally of a syndrome such as ectodermal dysplasia [8]. A written log makes it easier to provide that timeline to your dentist.
Early Intervention vs. Waiting: What the Evidence Says
The question of whether to intervene orthodontically early has generated debate for decades. A 2025 systematic review found that early orthodontic treatment for Class II malocclusion: a bite pattern where the upper jaw protrudes significantly in front of the lower jaw, sometimes called an overbite started in the mixed dentition was favored in 8 of 11 comparative studies, with gains such as better upper and lower arch development [6]. The same review notes, however, that early treatment mainly corrects the bite sooner in the short term; studies have not shown that the final result stays superior to a single phase of treatment in adolescence, and individualized planning remains essential [6]. A Chinese expert consensus likewise notes that some types — such as skeletal underbite driven by mandibular overgrowth — are better treated after growth is complete, so the right timing depends on the kind of malocclusion [7]. "Earlier is always better" is not the conclusion; the answer is case-specific.
For families as a practical matter, a handful of signs are worth flagging for your next dental appointment:
- A primary tooth that stays firm even though the permanent successor is visibly coming in
- Clearly uneven progress between the left and right sides
- A school dental screening result stating that the alignment/bite needs a dentist's diagnosis [5,8]
The American Association of Orthodontists (AAO) recommends that children have a first orthodontic check-up no later than age seven. It is not a treatment decision: an early visit does not always lead to treatment, the outcome may be "follow and monitor," and treatment is recommended when it would help [10].
Recording and Using the Log at Dental Appointments
The record format doesn't need to be complicated. One entry might read: Month/Year — lower front tooth, second from center — fell out naturally — slight bleeding, healed quickly. Three fields: when, which tooth (name or rough position), how it happened. Shown to a dentist, this allows rapid assessment of whether the timeline is broadly typical or worth watching.
An app like Memori makes it easy to pair a photo with a date: the gap-toothed smile on the day of loss, or a shot showing the double row before the primary tooth fell. Photos and dates together raise the quality of information available at a first dental visit.
Similarly, photographing the annual school dental screening result slip — and placing it next to the previous year's — turns a single data point into a trend that makes it easier to judge whether a follow-up visit is worth scheduling.
Putting It into Practice
When you want to start recording, the lowest-barrier first step is to note today's date and which tooth fell out or came in this month — name unknown, position description is fine: "left lower, second from front."
When a screening notice comes home with CO, GO, or malocclusion codes, rather than filing it without decoding it, bring it to the next routine dental visit and ask: "The school noted this — can you explain what it means?"
If a primary tooth was lost early due to injury or decay, checking with a dentist about the space for the incoming permanent tooth is a reasonable proactive step.
Summary
The transition from primary to permanent teeth is a milestone built into daily life — but it acquires clinical value the moment it is recorded. "When, which tooth, and under what circumstances" takes seconds to jot down. That accumulation becomes the documentation of a process that takes seven to ten years to complete.
A child's developing dentition is best evaluated when the family and the dentist are working from the same information. The record is what enables that.
References
- Kutesa A, Nkamba EM, Muwazi L, Buwembo W, Rwenyonyi CM. Weight, height and eruption times of permanent teeth of children aged 4–15 years in Kampala, Uganda. BMC Oral Health. 2013;13:15. doi:10.1186/1472-6831-13-15. PMID: 23497340. PMC: PMC3606623.
- Fekonja A. Evaluation of the eruption of permanent teeth and their association with malocclusion. Clin Exp Dent Res. 2022;8(4):836-842. doi:10.1002/cre2.544. PMID: 35157778. PMC: PMC9382043.
- Ogodescu E, Popa M, Isac C, et al. Eruption timing and sequence of primary teeth in a sample of Romanian children. Diagnostics (Basel). 2022;12(3):606. doi:10.3390/diagnostics12030606. PMID: 35328159. PMC: PMC8947037.
- Khan AS, Nagar P, Singh P, Bharti M. Changes in the sequence of eruption of permanent teeth; correlation between chronological and dental age and effects of body mass index of 5–15-year-old schoolchildren. Int J Clin Pediatr Dent. 2020;13(4):368-380. doi:10.5005/jp-journals-10005-1797. PMID: 33149410. PMC: PMC7586486.
- Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT). Dental and oral health examinations of students (Chapter 4, Section 1), in: Promoting dental and oral health in schools to foster a "zest for living." 2011 [in Japanese]. https://www.mext.go.jp/component/a_menu/education/detail/__icsFiles/afieldfile/2011/06/23/1306939_05.pdf
- Dinu S, Igna A, Petrescu EL, et al. Timing of orthodontic intervention for pediatric Class II malocclusion: a systematic review on early vs. late treatment outcomes. Children (Basel). 2025;12(11):1533. doi:10.3390/children12111533. PMID: 41300650. PMC: PMC12651552.
- Zhou C, Duan P, He H, et al. Expert consensus on pediatric orthodontic therapies of malocclusions in children. Int J Oral Sci. 2024;16(1):32. doi:10.1038/s41368-024-00299-8. PMID: 38627388. PMC: PMC11021504.
- American Academy of Pediatric Dentistry. Management of the developing dentition and occlusion in pediatric dentistry. The Reference Manual of Pediatric Dentistry. Chicago, IL: AAPD; 2025:497-515 (latest revision 2024). https://www.aapd.org/globalassets/media/policies_guidelines/bp_developdentition.pdf
- Aminabadi NA, Farahani RM, Sohrabi A, Pouralibaba F. Lingual eruption of mandibular permanent incisors: a space correlated phenomenon? J Contemp Dent Pract. 2009;10(1):25-32. PMID: 19142253.
- American Association of Orthodontists. What are the benefits of early orthodontic treatment? https://aaoinfo.org/whats-trending/is-there-a-benefit-to-early-treatment/ (accessed 18 September 2026).