Determination and validation of criteria to define hypercementosis in two medieval samples from France (Sains-en-Gohelle, AD 7th–17th century; Jau-Dignac-et-Loirac, AD 7th–8th century)

Highlights

• Hypercementosis is an excessive production of cementum which has rarely been studied.

• Our study establish for the first time reproductible criteria to define hypercementosis.

• Hypercementosis exist in different forms, diffuse and focal which can be moderate or marked.

• Hypercementosis is not a systematic major enlargement of the apical part of a root.

• Our definition criteria will provide a better assessment of hypercementosis frequency while it has the potential to be used to further investigate its aetiologies.

Abstract

Objective

The main aim of this article was to develop different visual criteria allowing for an objective definition of hypercementosis (cementum hyperplasia). This preliminary study must notably show how to better understand at a later stage the significance of its frequency as well as its aetiologies, especially in past populations.

Materials and methods

we set up a study protocol (macroscopic and photographic observations) on material consisting of 2 medieval samples from France (1) Sains-en-Gohelle sample-SG (AD 7th–17th century; 407 individuals; 5756 teeth observed, 319 with hypercementosis) which was used to develop the different criteria for defining hypercementosis (2) Jau-Dignac-et-Loirac sample-JDL (AD 7th-8th century; 55 individuals; 709 teeth observed, 24 with hypercementosis) which was used to test the reproducibility of the criteria.

Results

From our observations we formulated different inclusion criteria with which to define hypercementosis objectively (k intraobserver ≥ 0.96; k interobserver ≥ 0.63). We were able to distinguish moderate (1m) and marked (1M) forms of diffuse hypercementosis, focal hypercementosis in the form of small knots (2m) or large nodules (2M), or excrescences in the form of ridges (3m) or spurs (3M). Different exclusion criteria were also determined.

Conclusion

The definition that we propose in this study are based on various statistically validated inclusion and exclusion criteria. It is hoped that this will improve the significance of hypercementosis. More generally, this would also give a better understanding of the dynamics of cementum apposition.

Introduction

The teeth are an ideal medium for transmitting information on the evolution, lifestyle, social behaviour, culture, diet and activities of populations, especially those from the past. The general health of an individual or a group can also be assessed by studying dental caries, tooth wear, linear enamel hypoplasias, dental calculus, periodontal disease, periapical lesions and ante mortem tooth loss.1, 2 All these changes concern the enamel, the dentin, the alveolar bone and the cementum. However, structural changes in this last tissue are barely discernible and are much less studied than changes in other tissues.

Under certain conditions, the production of certain varieties of cementum becomes “excessive”. The term “hypercementosis”, initially called exostosis,³ hyperostosis,⁴ or excementosis,⁵ is then used in the literature. This hypercementosis exists in different forms. First, the diffuse form, which is described most frequently, though often briefly (e.g. Refs. 6, 7, 8, 9, 10, 11, 12, 13, 14, 15). The main feature is a large deposit of cementum which gives the root a distinctive appearance in the form of a “club”, a “drumstick”, or a “bulb” shape. Certain focal forms, although less common and less documented do also exist. They are actually very minute in substance and not at all prominent. It presents with small circumscribed knots, nodules, spike-like projections or spurs on the lateral and interradicular root surfaces.16, 17

In histological terms, all these distinctive anatomical features consist of an overproduction of acellular extrinsic fibre cementum (AEFC) or cellular intrinsic fibre cementum (CIFC) alone, but usually they consist of cellular mixed stratified cementum (CMSC),16, 17, 18, 19, 20 which is a tissue with alternating layers of AEFC and CIFC²¹ (Fig. 1). More generally, AEFC is found mainly on the cervical and middle root portions, but may extend further apically in anterior teeth.²² It plays a major role for tooth anchorage to the surrounding bone through Sharpey's fibres.²³ When observed macroscopically it has a smooth surface, although small cracks are often present on archaeological material.¹ It is transparent and very thin (100–200 μm in adults) so that the colour of the underlying dentin can usually be seen.¹⁶ CIFC, on the other hand, is located mainly at the apex of the dental root and when examined visually is seen to have a much less regular surface than AEFC.16, 17 It is not involved directly in attaching the tooth but does have considerable plasticity, which enables it to adapt its structure quickly to maintain occlusal relationships, repair external root resorptions and protect the dental pulp.²³ Like AEFC, the origin and nature of the cells responsible for its synthesis are not yet entirely understood.22, 24

The first classifications of hypercementosis based on visual examination of isolated teeth were developed towards the end of the 19th century.4, 25 The diffuse and nodular forms were identified in this period and several conclusions concerning their aetiologies were offered. These data were not followed up and it was not until the end of the 20th century that Consolaro et al.²⁶ offered a newer, simplified classification. This was then slightly adapted by Pinheiro²⁷ and then by Pinheiro et al.²⁸ culminating in a classification distinguishing a diffuse form ranked by level of apposition of cementum across the length of the root (mild, moderate, severe), a focal form (large nodule) and a last one, in the shape of a “shirt sleeve cuff” (circular cementum hyperplasia hypercementosis), identical to the collar-shaped hypercementosis previously described by Pindborg.²⁹ Small circumscribed knots, spike-like projections or spurs, however, were not taken into account in these classifications. On the other hand, Weinburger³⁰ then Kim et al.³¹ offered classifications based on radiological examination of teeth in order to associate some type of hypercementosis to some pathologies. Only the diffuse form was taken into account and as for the visual classifications, no statistically validated inclusion and exclusion criteria were used.

The frequency of hypercementosis is seldom mentioned in the literature and it fluctuates considerably from one study to another. It is reported in relation to a number of individuals or a number of teeth. Concerning individuals, frequency is low (1.2–8.2%) in samples from current populations whose teeth were observed radiologically,32, 33, 34, 35 and high (16.8–89.4%) in samples from populations from the past whose teeth were observed grossly.36, 37 Concerning teeth, the frequency of hypercementosis calculated in large samples (n ≥ 10,000) varies between 0.12% and 3.94%.26, 35, 38, 39 These results, obtained from teeth of extant humans, give much lower values than the 61.57% obtained by Martín-Francés et al.⁴⁰ in a group of teeth from Homo heidelbergensis in the Middle Pleistocene (Atapuerca – Sima de los Huesos), or in the sample of 95 Neanderthal teeth observed by Le Cabec et al.⁴¹ which virtually all showed the presence of hypercementosis. However, no interpretation has yet been given about the variability of these frequencies obtained with different methods, on different samples.

In terms of aetiology, although listed in the 10th version of the International Classification of Diseases (ICD10: K03.4), hypercementosis is more often considered to be the result of a general and/or local pathology. There are also some forms that are hereditary,42, 43, 44 idiopathic,29, 31, 45, 46 or linked with ageing.6, 31, 32, 47 In extant humans, the link with some general pathologies is based on numerous case reports and just a few controlled studies. Thus

hypercementosis is often found in individuals suffering from goitre,6, 9, 45, 48 Paget's disease,30, 49, 50, 51, 52, 53 or an acromegaly.6, 30, 54 It is also associated, to a lesser degree, with fluoride55, 56, 57 or lead37, 58, 59 contamination. The presence of hypercementosis affecting many or all the teeth (generalised hypercementosis) has also been reported in individuals suffering from rare diseases such as Pendred syndrome,⁶⁰ Gardner syndrome,⁶¹ enamel dysplasia with hamartomatous atypical follicular hyperplasia (EDHFH),⁶² enamel renal syndrome (ERS),⁶³ calcinosis,⁶⁴ chronic sclerosing osteomyelitis,⁶⁵ renal osteodystrophy,⁶⁶ pycnodysostosis⁶⁷ and idiopathic hypoparathyroidism (IHP).⁶⁸ The link with certain specific pathologies or local conditions has also been described, but again, mainly through case reports. Those most often blamed are apical periodontitis caused by dental caries, occlusal wear or traumas,6, 14, 18, 26, 27, 29, 33, 43, 46, 69, 70, 71, 72, 73, 74 also overloading and occlusal traumas,5, 30, 31, 36, 40, 41, 71, 72, 73, 74, 75 continuous eruption being linked with the ante mortem loss of antagonistic teeth or occlusal wear,16, 26, 27, 31, 46, 70, 71, 72, 73, 74, 76 periodontal disease,13, 15, 25, 36, 37, 60, 77, 78, 79, 80, 81 impaction,7, 29, 31, 70, 71, 73, 82, 83 and to a lesser extent, arrested dental eruption,43, 44 and dilaceration.⁸⁴ The potential aetiologies of hypercementosis are therefore numerous, sometimes contradictory (e.g. hyper- or hypofunction) and mainly documented through case reports concerning a single tooth in an individual (localised hypercementosis).

From this literature review, different problems emerge. Hypercementosis is above all most often defined only briefly. None of its classifications globally encompasses the morphological variability and none of them is formed from statistically validated criteria. The frequency of hypercementosis also varies greatly between different groups of individuals, according to their time period, their taxon, and/or method of teeth observation, but this has not yet been interpreted. Nevertheless, this frequency could be linked to the frequencies of certain bucco-dental pathologies or from their consequences, which would give a general indicator of the bucco-dental health of a sample, especially in past populations. Finally, the aetiologies of hypercementosis are numerous and sometimes contradictory, but there again no real explanation has been given. Furthermore, in order to be able to respond at a later stage to these different issues and even though for some authors72, 85 it may be difficult to determine the moment when a tooth can be said to present with hypercementosis, the main objective of this preliminary article is to determine and validate certain criteria to define it objectively.