Cementum

In this review we discuss the historical perspective of stem cell populations from oral tissues in light of our current understanding of stem cell biology. Stem cells and their niches have been identified in the periodontium starting from the late 1970s. Applying new criteria for the identification and characterization reveals that oral tissues comprise a multipotent primitive neural crest-like stem cell population capable of differentiating into neural crest derived cell lineages of the cranial-facial zone. This population supplies cells to a more restricted stem cell type with tissue specific epigenetic memory that differentiates into cell lineages characteristic of their tissue origin. We believe that the microenvironment plays an essential role in maintaining stem cell populations and directing their migration and differentiation, and that this factor needs to be considered for utilization of stem cell-based therapy for periodontal regeneration and regenerative dental medicine.

Progressive replacement resorption following delayed replantation of avulsed teeth has proved to be an intractable clinical problem. A wide variety of therapeutic approaches have failed to result in the predictable arrest of resorption, with a good long-term prognosis for tooth survival. Bisphosphonates are used in the medical management of a range of bone disorders and topically applied bisphosphonate has been reported to inhibit root resorption in dogs. This study evaluated the effectiveness of a bisphosphonate (etidronate disodium) as an intracanal medicament in the root canals of avulsed monkey teeth, placed before replantation after 1 h of extraoral dry storage. Incisors of six Macaca fascicularis monkeys were extracted and stored dry for 1 h. Teeth were then replanted after canal contamination with dental plaque (negative control) or after root canal debridement and placement of etidronate sealed in the canal space. A positive control of calcium hydroxide placed 8-9 days after replantation was also included. All monkeys were sacrificed 8 weeks later and block sections were prepared for histomorphometric assessment of root resorption and periodontal ligament status. Untreated teeth showed the greatest extent of root resorption (46 of the root surface), which was predominantly inflammatory in nature. Calcium hydroxide treated teeth showed the lowest overall level of resorption (<30 of the root surface), while the bisphosphonate-treated group was intermediate (39). Ankylosis, defined as the extent of the root surface demonstrating direct bony union to both intact and resorbed root surface, was the lowest in the untreated control group (15 of the root surface), intermediate in the calcium hydroxide group (27) and the highest in the bisphosphonate group (41). Bony attachment to the tooth root was divided approximately equally between attachment to intact cementum and to previously resorbed dentin. Overall, bisphosphonate resulted in a worse outcome than calcium hydroxide in terms of both root resorption and ankylosis.

Abstract

The objective of this literature review was to critically review the evidence available in the literature regarding the expediency of erbium family of lasers for root bio modification as a part of periodontal therapy. The literature search was performed on the Pubmed using MeSH words such as "lasers/therapeutic use, scaling, dental calculus, tooth root/anatomy and histology, ultrasonic therapy". The studies were screened and were grouped as follows: those evaluating a) efficacy for calculus removal with the Erbium family of laser b) root surface changes following Er YAG and Er Cr YSGG application c) comparative studies of the Er YAG, Er Cr YSGG lasers versus conventional methods of root surface modification d) Bio compatibility of root surface following Erbium laser treatment e) Studies on the combined efficacy of laser root modification with conventional methods towards root surface bio-modification f) Studies on effectiveness of root surface bio-modification prior to root coverage procedures. In conclusion, the erbium family has a proven anti-bacterial action, predictable calculus removal, minimal root substance removal, and appears to favor cell attachment. The Erbium family of lasers appears to be a useful adjunct for the management of periodontal disease.

Cementum increment analysis has been applied with success in mammals since several decades for both current wildlife studies and studies of fauna from archaeological sites. This method provides estimations about the age and the season at death of ungulates recovered at archaeological sites and can be used to explore important issues such as hunting or herding strategies, settlement patterns and mobility. Over the past 30 years cementum studies have expanded the range of mammalian species for which the method can be applied in archaeology. However, very few data are today available about the guanaco (Lama guanicoe) which was the dominant large ungulate in South America in prehistoric and historical times. The purpose of our project is to develop and improve the cementum increment analysis for this species using modern reference data sets before its application to archaeological assemblages. The present paper presents the preliminary results obtained from the study of canines and incisors of modern specimens and will discuss the potentiality and limitations of the technique.

High citrate concentration is a major component in the structure of craniofacial bone, teeth and periodontal tissues of humans and other osteovertebrates. It is now established that citrate incorporation into the apatite/collagen complex of bone is essential for the manifestation of the important biomechanical properties of bone; such as stability, strength, and resistance to fracture. The osteoblasts are specialized citrate-producing cells that provide the citrate incorporated in bone during osteogenic stem cell differentiation for production of new bone; “citration” that occurs in concert with mineralization. Dentin and cementum contain high citrate levels; as contrasted with low citrate in enamel. There exists no information regarding the status and source of incorporated citrate in dentin or in cementum. These are important issues relating to oral, periodontal, craniofacial structures. For example, repair of defects should include new tissue that exhibits the composition, structure, and biomechanical properties of the “normal” tissue; which cannot be achieved in the absence of citrate incorporation in the new tissues. Unfortunately, the presence and role of citrate in these tissues have been largely ignored and unrecognized over the past about 40 years by the dental and medical community. The intent of this review is to re-establish the interest and research regarding the important citrate relationships and issues; with focus on related interests in dentistry.

The aim of the present study was to evaluate the effect of different staining techniques on applicability and accuracy of tooth cementum annulation (TCA) method. Nine decalcination techniques, 8 dehydration protocols and 8 different tech niques were applied in 3 teeth from the persons of a known age. Black and white, and color images of histological sections were captur ed. An xray was taken of each tooth and they were photographed. Researchers were asked to observe both black/white and color images of histological sections. Researchers were divided into two groups. The first group analyzed histological images only, and the sec o group had photos of teeth and X-rays. In the first group of observers (without X ray) the differences in age estimation between real and observed age were significant for 2 younger patients, but not for the oldest patient, where the observed and real values matche d. Of the 6 raters, the assesments of the last 3 (that used x-ray images together with histolo...

We investigated the effects of cellular aging on the expression of cementum and mineralization-specific proteins in human periodontal ligament (PDL) cells, since this is not well studied. Previously, we showed that STRO-1-and cementum protein 1 (CEMP1)-positive PDL cells behave like cementoblasts, since they can be directed toward cementogenesis. However, the mineralization characteristics of these cells during aging have not been examined. Thus, we examined mineralization and expression of the mineralization-related proteins, CEMP1, collagen I (COL I) and osteopontin (OPN) in STRO-1 positive selected and unselected human PDL cells, control human cementoblastoma cells, and human mesenchymal stem cells (hMSC). Early (young) and late (aged) passage cells were compared. Aged STRO-1 positive cells exhibited the highest level of miner-alization as assessed by Alizarin red staining and energy dispersive x-ray spectroscopy. Aged STRO-1 positive PDL cells also exhibited high levels of CEMP1, OPN, and COL I expression at two weeks compared to all other cells. At earlier time points, osteogenic induction significantly enhanced CEMP1 expression in aged STRO-1 positive and parental PDL cells. In contrast, STRO-1 negative cells exhibited high CEMP1 expression only in young cells. High CEMP1 expression was also present in young cells derived from cementoblastoma cells and hMSC. Expression of OPN and COL I varied for STRO-1 negative PDL, cementoblastoma, and hMSC cells. In summary, cellular aging significantly promotes mineralization and expression of CEMP1, OPN, and COL I in STRO-1 positive PDL cells. These findings may impact periodontal tissue function and regen-eration in the context of aging tissues.