Unraveling the Life History of Past Populations through Hypercementosis: Insights into Cementum Apposition Patterns and Possible Etiologies Using Micro-CT and Confocal Microscopy.

The "teeth-as-tools" hypothesis posits that Neanderthals used their anterior teeth as a tool or a third hand for non-dietary purposes. These non- or para-masticatory activities (e.g., tool-making or food preparation prior to ingestion) have also been described in other past and extant human populations, and other Primates. Cementum is the mineralized tissue that covers the tooth root surface and anchors it to the alveolar bone. Under certain conditions (e.g., mechanical stress, infection), its production becomes excessive (i.e., beyond the physiological state) and is called 'hypercementosis'. Several studies in dental anthropology have established a correlation between the teeth-as-tools and hypercementosis. The present work aims to characterize the different patterns of cementum apposition on archeological teeth and discuss their supposed etiology. Using microtomography and confocal microscopy, the patterns of cementum apposition (i.e., thickness, location, and surface characteristics) were analyzed in 35 hypercementotic teeth (Sains-en-Gohelle, France; 7th-17th c. A.D.). Four groups were identified with distinct hypercementosis patterns: (1) impacted, (2) infected, (3) hypofunctional, and (4) hyperfunctional teeth. Characterizing hypercementosis can contribute to documenting the oral health status (paleopathology) and/or masticatory activity of individuals, even from isolated teeth. This has implications for the study of fossil hominins, particularly Neanderthals, known for their use of anterior teeth as tools and frequent and substantial occurrence of hypercementosis.

Infiltrant resin and enamel infractions: two case reports of a novel and minimally invasive approach.

To date, no consensus exists regarding the management of enamel infractions (cracks and craze lines), which may be associated with sensitivity. Two clinical cases are presented on the management of enamel infractions using a modified erosion-infiltration protocol for resin infiltration. Initially indicated for the treatment of early caries lesions, Icon (DMG) low-viscosity resin infiltrant has also been used to mask unesthetic developmental defects of enamel in anterior teeth. Treatment using this modified infiltration protocol immediately eliminated tooth sensitivity associated with the enamel infractions. Resin infiltration has the potential as a minimally invasive and effective treatment for the management of sensitivity associated with enamel infractions. (Quintessence Int 2023;54:180-185; doi: 10.3290/j.qi.b3631849).

Insights into the aetiologies of hypercementosis: A systematic review and a scoring system.

OBJECTIVES: This paper aims to better define hypercementosis, investigate its described potential aetiologies, and determine whether there are different patterns of cementum apposition and if they are a function of their supposed aetiology. DESIGN: A literature review was undertaken using the Medline, DOSS, Scopus and Cochrane Library electronic databases. Two co-authors selected the published works independently, extracted the data in accordance with the PRISMA statement. RESULTS: Among 546 articles, 75 articles were finally selected. Eight different supposed aetiologies were identified: (1) intensive masticatory effort, (2) systemic disease, (3) carious lesion and apical periodontitis, (4) impaction, (5) periodontal disease, (6) concrescence, (7) super-eruption, and (8) drugs. Some of these aetiologies can be combined in the same tooth. Hypercementosis manifestations are various in nature and extent with different patterns that may be aetiology-specific. To improve the description and associated consistency in the characterisation of hypercementosis, in this review but also in future studies, we propose a new qualitative scoring system to quickly characterise hypercementosis and determine its most relevant aetiology. CONCLUSIONS: This systematic review demonstrates that hypercementosis is a complex and not yet well-defined condition. Some forms of apposition are specific to a given aetiology. The hypercementosis characterisation may contribute to document the oral condition and/or the individuals masticatory activity.

Dentine disorders and adhesive treatments: A systematic review.

OBJECTIVES: A better understanding of the microstructure and mechanical properties of enamel and dentine may enable practitioners to apply the current adhesive dentistry protocols to clinical cases involving dentine disorders (dentinogenesis imperfecta or dentine dysplasia). DATA/SOURCES: Publications (up to June 2020) investigating the microstructure of dentine disorders were browsed in a systematic search using the PubMed/Medline, Embase and Cochrane Library electronic databases. Two authors independently selected the studies, extracted the data in accordance with the PRISMA statement, and assessed the risk of bias with the Critical Appraisal Checklist. A Mann-Whitney U test was computed to compare tissues damage related to the two dentine disorders of interest. STUDY SELECTION: From an initial total of 642 studies, only 37 (n = 164 teeth) were included in the present analysis, among which 18 investigating enamel (n = 70 teeth), 15 the dentine-enamel junction (n = 62 teeth), and 35 dentine (n = 156 teeth). Dentine is damaged in cases of dentinogenesis imperfecta and osteogenesis imperfecta (p = 2.55E-21 and p = 3.99E-21, respectively). These studies highlight a reduction in mineral density, hardness, modulus of elasticity and abnormal microstructure in dentine disorders. The majority of studies report an altered dentine-enamel junction in dentinogenesis imperfecta and in osteogenesis imperfecta (p = 6.26E-09 and p = 0.001, respectively). Interestingly, enamel is also affected in cases of dentinogenesis imperfecta (p = 0.0013), unlike to osteogenesis imperfecta (p = 0.056). CONCLUSIONS: Taking into account all these observations, only a few clinical principles may be favoured in the case of adhesive cementation: (i) to preserve the residual enamel to enhance bonding, (ii) to sandblast the tooth surfaces to increase roughness, (iii) to choose a universal adhesive and reinforce enamel and dentine by means of infiltrant resins. As these recommendations are mostly based on in vitro studies, future in vivo studies should be conducted to confirm these hypotheses.

The Non-linear Electrical Properties of Silver/silver Chloride Electrodes in Sodium Chloride Solution.

An electrical measurement is non-linear when it is affected by the applied stimulus, i.e. when the measured phenomenon changes with amplitude. If pinched hysteresis loops can be observed in the voltage current representation, the underlying tissue can be classified as a memristor. Several biological memristors have been published, like human skin and apples. However, changes in the polarization impedance of electrodes may also cause pinched hysteresis loops. The question whether the reported biological memristors are real or whether the results just reflect changes in the polarization impedance arises. If the impedance of the measured object is close to or smaller than the polarization impedance of the used electrodes, the latter may dominate the measurement. In this study, we investigated the non-linear electrical properties of silver/silver chloride electrodes in a sodium chloride solution that has a similar concentration as human sweat and compared these to results from human skin. First of all, we found that silver/silver chloride electrodes in sodium chloride solution can be classified as memristors. However, the currents obtained from the sodium chloride solution are much higher than the currents recorded from human skin and there is a qualitative difference in the pinched hysteresis loops in both cases. We can conclude that the non-linear electrical measurements with silver/silver chloride on human skin are actually dominated by the skin and we can confirm that the human skin memristor really exists.