We present a DNA library preparation method that has allowed us to reconstruct a high-coverage (30×) genome sequence of a Denisovan, an extinct relative of Neandertals. The quality of this genome allows a direct estimation of Denisovan heterozygosity indicating that genetic diversity in these archaic hominins was extremely low. It also allows tentative dating of the specimen on the basis of “missing evolution” in its genome, detailed measurements of Denisovan and Neandertal admixture into present-day human populations, and the generation of a near-complete catalog of genetic changes that swept to high frequency in modern humans since their divergence from Denisovans.

https://science.sciencemag.org/content/sci/338/6104/222.full.pdf

A high-coverage genome sequence from an archaic Denisovan individual

Root canal anatomy of the human permanent teeth.

Aim To investigate the root and canal morphology of Burmese maxillary molars using a canal staining and tooth clearing technique.Methodology Maxillary molars (239) were collected from indigenous Burmese patients and designated; first (90), second (77), third (72) molars. Following pulp tissue removal and canal system staining with Indian ink, the teeth were decalcified with 10%. nitric acid, dehydrated and cleared with methyl salicylate. The following features were evaluated: (i) number of roots and morphology; (ii) number of canals per root: (iii) root canal configuration (Vertucci's classification): (iv) number of apical foramina per root; (v) number and location of lateral canals; and (vi) the presence of intercanal communications.Results All first and second molars had three separate roots. whilst third molars had one of five different root forms, of which three separate (25%) or fused (31%) roots were most prevalent. The majority of palatal (100%) and disto-buccal (96%) roots possessed one canal (type I). The prevalence of mesio-buccal roots with two canals decreased from first to third molars (68%, 49%, 39%, respectively); type II (two orifices, one apical foramen) and IV (two orifices, two apical foramina) configurations were the most common. Single/fused rooted third molars had a range of number and type of canals. Most roots in all molars had one apical foramen, those with four apical foramina were confined to third molars. Intercanal communications were most prevalent in mesio-buccal roots and two/three fused rooted third molars. Lateral canals were most prevalent in the apical third of the roots of all molars.Conclusions The mesio-buccal roots of Burmese maxillary molars possessed a variety of canal system types. Over 50% of the first and second molars had a second mesio-buccal canal, of which over 20% had intercanal communications. The palatal and disto-buccal canals mainly had type I canals. Lateral canals were equally prevalent in all tooth types but were most common in the apical third.

Root and canal morphology of Burmese mandibular molars.

Four hundred avulsed and replanted permanent incisors were examined for pulpal and periodontal healing. In 30 teeth, root formation was incomplete at the time of injury. Two teeth were excluded from the study due to nonphysiological extraalveolar storage (i.e. homemade saline). Of the 28 remaining replanted incisors, 7 showed subsequently completed root development, 8 partially completed root development and 13 arrested root development. Completed root development subsequent to replantation was found to be significantly related to pulpal revascularization, being rare in cases with pulp necrosis (5 of 15 teeth) and frequent after pulpal healing (11 of 13 teeth) (p = 0.01). Root development was not found to be significantly related to the extraalveolar storage period; but occurred slightly more frequently when the dry storage period was less than 45 min. (p = 0.13). Ingrowth of bone and formation of an internal periodontal ligament (PDL) was found in 6 teeth and was related to arrested root formation in cases with pulpal healing. The explanatory factor for these findings appeared to be damage to the Hertwig's epithelial root sheath.

Replantation of 400 avulsed permanent incisors. 3. Factors related to root growth

Variations in the normal anatomy of the inferior dental (mandibular) canal: A retrospective study of panoramic radiographs from 3612 routine dental patients

— Variations in the form and number of root canals are greater in the mesial roots and in some specimens the mesial root was divided into two. The main variations show multiple canals with subdivisions and communications frequently with one common apical foramen. Little difference was noted between root canals in young teeth and those in heavily worn mature teeth.

Anatomy of root canals. III. Permanent mandibular molars

The demonstration of root canal anatomy

The root canal systems of the deciduous teeth have been demonstrated by the epoxy resin injection technique. A major difference is noted between the simplicity of that seen in the incisors and the molars.

Anatomy of root canals. IV deciduous teeth.

— Taurodontism is defined and discussed. Its significance is speculated upon and two cases are reported.

B. C. W. Barker

Papers

Anatomy of root canals. III. Permanent mandibular molars

The demonstration of root canal anatomy

Anatomy of root canals. IV deciduous teeth.

Taurodontism: the incidence and possible significance of the trait.

Endodontic experiments with resorbable paste