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Determining the Dental Age of a Patient

Published: March 2018

Bulletin #75 March 2018

Determining the Dental Age of a Patient

I have just returned from the 2018 AAO/AAPD Joint Winter Conference in Scottsdale, Arizona, which was most enjoyable. For the most part, the individual lectures were of a high standard and the participants were in their places in the lecture hall for virtually the whole time. My own presentation was entitled “What to do when all the teeth are impacted: the challenge of CCD”. One of the most crucial points that I raised in the lecture was the timing of surgical exposure of the teeth and the application of extrusive traction according to the patient’s dental age. The issue of dental age drew a large number of questions from the audience, both at the time and in the corridors thereafter. Several of the questioners told me that they had never been taught how to assess dental age nor to differentiate it from chronologic age (date of birth) of a patient. This surprised me, since the audience comprised orthodontists and pediatric dentists spanning the full gamut of experience from residency to retirement, whom I would have thought would have benefitted to use this in their everyday practice. Accordingly, I have devoted this bulletin to the presentation of a method that I have used over the years, which is directly clinically relevant to our sphere of activity, rather than simply presenting my readers with a chart that shows calcification diagrams of the various tooth groups as illustrated in the classic works of Schour and Massler,1 Moorrees et al.,2 Nolla,3 Demerjian et al.,4 Koyoumdjisky-Kaye et al. 5 and others.

Normal and healthy tooth buds develop at a given rate from initial calcification to root apex closure. For each of the groups of teeth individually i.e. incisors, canines, premolars, 1st, 2nd and 3rd molars, in the mandible and in the maxilla, in males and in females, there is a specific time at which they reach the various developmental stages. These stages are empirically defined in each of the above classic works. Schour and Massler1 produced an atlas consisting of 21 consecutive drawings from intra utero to adulthood, which featured annual schemes till age 12 and 3 more till age 35 years. The method of Nolla3 used a radiographic assessment of tooth development at 10 different developmental levels from presence of crypt through to apical end of root completed.

While the normal eruption times of the individual teeth is well known among both orthodontists and pediatric dentists, initiation or completion of crown calcification and fractions of root development are not remembered. Therefore, the established methods oblige us to apply the calcification criteria in a given case using these drawings and charts. This is cumbersome, confusing, difficult to handle in the clinical context and it compels us to make the charts readily available in the office.

Basic principles that relate to the eruption of permanent teeth

1. The age at which teeth normally erupt must be at every orthodontists’ fingertips and must be memorized

2. Permanent teeth normally erupt when 1/2 to 2/3 of the final root length has developed.

3. The remainder of the root reaches apexification approximately 2½-3 years later.

4. Determining the closed apex of the tooth on a radiograph is usually an easy and accurate parameter to diagnose.

5. Determining the degree of partial calcification of the root of a tooth is not an accurate diagnosis, because there is considerable variability among practitioners in determining what comprises 1/3, 1/2 or 2/3 of development of a root whose final length is unknown. It puts this assessment in the realm of “informed eyeballed guesswork”.

From this we may conclude that a mandibular incisor or first permanent molar, which erupts at age 6 years, will sport 1/2-2/3 of its final root length and its apex will close at age 9 years. We have now determined the dental age of that specific tooth.

However, what if the eruption of that tooth only occurs at age 8 years, with the same 1/2-2/3 of its final root length? The verdict for this 8 year old child is a dental age of 6 years for that specific tooth, which represents a 2 year delay in its dental development. Apexification will not take place before he/she reaches the age of 11 years. In other words, this delay remains constant in the further development of that particular tooth. It is emphasized, however, that this does not mean that the tooth is in any way defective or abnormal.

Can these principles that we have applied to a single tooth be applied to the patient’s other permanent teeth, so that we may arrive at a dental age for the permanent dentition as a whole and not just to individual teeth? With a couple of important reservations this method may be applied to all the teeth. This renders the method valuable in terms of deciding when to treat a patient in general, but it is of crucial importance in relation to the treatment of impacted teeth, in particular.

Determining dental age in the clinical setting – the Jerusalem method

By and large, the patients for whom orthodontists need to evaluate dental age are in the 7-13 chronological age range. The sole diagnostic requirement is that the examining practitioner needs to be in possession of a recent periapical survey or panoramic film of the patient’s teeth. The only factor that he/she must know is the expected age at which a specific tooth would normally erupt in the particular population sample to which the patient belongs.

As has just been pointed out, the most accurate, quantitative and determinable parameter that may be diagnosed as a means of evaluating root development is the closure of the root apex of a given tooth. The first permanent teeth to achieve apexification are the mandibular incisors and the first molars and, for most populations, these teeth normally erupt at dental age 6, completing apex closure at age 9 years.

The first task, therefore, is to examine these teeth on the radiographs for root closure. An open apex is characterized by the presence of a dental papilla indicating an active Hertwig’s root sheath. This disappears at apexification, to be replaced by a contiguous and integral lamina dura. There are sometimes minor differences in the apexification times of the incisors and molars within each tooth group and between the groups, but these are not generally significant.

The age of 9 years is, therefore, an important cut-off point from which to start the evaluation of dental age. If there is mandibular incisor or molar root closure, then the tentative diagnosis is that the patient has a dental age of at least 9 years. If not, then he/she is dentally less developed. It should be clearly understood that, whether or not the incisor or molar has erupted is entirely irrelevant, because the exercise is aimed at ranking the child’s dental development, not his/her eruption time. 75 Age 9 Fig. 1_1

Fig. 1. This child shows closed apices of the first molars, the mandibular central incisor and the right maxillary central incisor and a dental age of 9-9.5 years.

Step #1

So, step #1 in the method is to study the radiograph and check the root apices of the mandibular incisors and the first permanent molar teeth (Fig. 1). A positive apexification determination ranks dental age to be at least 9 years and then leads the practitioner to the next tooth that is scheduled to erupt.

Step #2

The maxillary central incisor erupts at age 7 years and completes its apex by age 10 years. So, this is the next evaluation that needs to be made. If the apex is closed, then the tentative dental age has now been upgraded to 10 years.

Step #3

The next tooth in line is the maxillary lateral incisor – eruption time 7½-8 years, apex closure – 10½-11 years.

The maxillary lateral incisors and the mandibular second premolars must be assessed with great care, because these are very variable teeth. They are frequently missing, often small or even rudimentary in shape and they may develop extremely late and out of the normal developmental sequence. These teeth are never developmentally ahead of their normal calcification times. They may be normal or late, but never early. Accordingly, they are excluded from the overall assessment, unless their development is in line with the overall developmental sequence seen in the other teeth.

75_age_10.5_Fig._2

Fig. 2. This child with closed apices on each of the incisors and first molars. The developing root ends feature a dental papilla on each of the canines and premolars. The dental age is 11 years.

Steps #4-6

The mandibular first premolars and canines and the maxillary first premolars have an eruption time of 9-10 years (Fig. 2) and apex closure at 12-13 years. The maxillary canines normally erupt at 11-12 years and the second molars at 12-13 years, with commensurate apexification times.

By progressing steadily up this development time scale, from incisors and molars to premolars and canines and on to second molars, the dental age is determined at the point where one group of teeth exhibits open apices. At each stage, conformation of closed apices adds confirmatory evidence to convert the tentative into a more certain diagnosis.

The very young patient

For a case in the early mixed dentition period, all the erupted incisors and molars have open root apices and we have less reliable evidence at our disposal. Here, there is no choice but to examine the length of the roots of the erupted incisors and molars and see how much root had developed in excess of the 1/2-2/3 that was present at the time of eruption. We would then need to seek verification from the level of development of the crowns and roots of the unerupted permanent teeth.

In a child with a full deciduous dentition, root development may not have started for a number of the teeth and the practitioner will be left with ascertaining dental age relying on his/her own assessment of initiation of calcification within the follicle and the subsequent degree of completion of the crown of the teeth and the degree of root development. At this very young age, the pediatric dentist may occasionally be called upon to do this, although the orthodontist is unlikely to be involved.

Tooth eruption age

We have defined the developmental stage at which teeth usually erupt. Nevertheless, a word must be said about situations in which a tooth or teeth may erupt earlier or later than this desired age because of specific general or local factors. The figures given in all the above studies represent a mean within a particular patient sample. However, the range in dental age versus chronologic age may sometimes be quite large. The early extraction of a deciduous tooth due to caries may cause the permanent successor to erupt earlier than would otherwise be expected, particularly if the deciduous tooth had been non-vital and abscessed. Alternatively, loss of space may occur following the extraction or there may be generalized severe crowding in a healthy mouth, which may block the eruption of the permanent tooth. The process of resorption of the roots and shedding of the deciduous teeth may sometimes be altered with no immediate or obvious answer to why this happens. None of these factors will usually alter the normal development of the successor teeth and we can still use this system to evaluate dental age.

A clinically-oriented nomenclature for unerupted teeth

75_age_6_Fig._3

Fig. 3. At the age of 8 years, this patient shows no closed apices in any of the permanent teeth. The incisors and molars are erupting. The dental age of this patient is 6 years, which lags behind his chronologic age by 2 years.

Late dental age.

This describes a condition of normal development in which the permanent teeth are relatively underdeveloped in relation to the child’s chronologic (birth date) age. An example would be that the unerupted mandibular incisors and/or molars are unerupted in an 8 year old child, because the roots are less than 1/2 completed (Fig. 3). This late development usually affects all this child’s teeth.

Implications: ignore the fact that the child is 8 year’s old and await eruption in accordance with root length.

Retained deciduous tooth

A single deciduous tooth is not expected to shed if it is in association with a permanent successor which exhibits less than 2/3 of its root length and an open apex or in the absence of the tooth. this is a retained deciduous tooth.

Implications: no treatment advised.

75_Fig._4_Over_retained_deciduous._Fig._4

Fig. 4. This patient was mistakenly diagnosed initially as having a late dental age of 9 years because 12 deciduous teeth were still present. However, the radiographs show almost full length roots on all the premolars and canines, with second molars showing half their root formation. The dental age of this patient is 11.5 years. Extraction of the deciduous teeth with space maintenance consideration is advised.

Over-retained deciduous tooth

A single deciduous tooth has not shed despite the fact that the permanent successor exhibits more than 2/3 of its root length (Fig. 4).

Implications: extraction of the deciduous tooth is recommended

Permanent tooth with delayed eruption

An unerupted permanent tooth whose root has developed in excess of 2/3 of its usual length, but its natural eruption is expected in a reasonable time.

Implications: re-evaluate in a year or so.

Impacted tooth

An unerupted permanent tooth whose root has developed in excess of 2/3 of its usual length, but its natural eruption is not expected in a reasonable time (Fig. 4).

Implications: create space for the tooth and wait to see if the tooth responds. In the absence of progress, expose, bond an attachment and apply traction to resolve the impaction.

References

1. Schour I, Massler M. The development of the human dentition. J Am

Dent Assoc 1941; 28: 1153–1160

2. Moorrees CFA, Fanning EA, Grøn A-M, Lebret L. The timing of orthodontic

treatment in relation to tooth formation. Trans Eur Orthod Soc

1962; 38: 1–14.

3. Nolla CM. The development of permanent teeth. J Dent Child 1960;

27: 254–266.

4. Demerjian A, Goldstein H, Tanner JM. A new system of dental age

assessment. Hum Biol 1973; 45: 211–227.

5. Koyoumdjisky-Kaye E, Baras M, Grover NB. Stages in the emergence of the dentition: an improved classification and its application to Israeli children. Growth 1977; 41: 285–296.