Time Recession Research Articles

Evaluation of the Safety and Efficacy of Periodontal Applications of a Living Tissue‐Engineered Human Fibroblast‐Derived Dermal Substitute. I. Comparison to the Gingival Autograft: A Randomized Controlled Pilot Study

Periodontists have found the gingival autograft to be an effective and predictable technique to increase the amount of attached gingiva around teeth, but this technique requires the surgeon to harvest donor tissue from a remote surgical site. The present study seeks to evaluate the safety and effectiveness of a tissue-engineered skin equivalent, a living human fibroblast-derived dermal substitute (HF-DDS), compared to a gingival autograft (GA) consisting of donor tissue harvested from the patient's palate in a procedure designed to increase the amount of keratinized tissue around teeth that do not require root coverage. Twenty-five patients with insufficient attached gingiva associated with at least two teeth in contralateral quadrants of the same jaw were treated. One tooth in each patient was randomized to receive either a GA (control) or a HF-DDS graft (test). Clinical parameters measured at baseline and 3, 5, 7, 9, and 12 months included recession, clinical attachment level, keratinized tissue height, and plaque index. Probing depth was measured at 7, 9, and 12 months. Inflammation of each site was scored and texture and color of the grafted tissue were compared to the surrounding tissue. Resistance to muscle pull was evaluated and a questionnaire was used to determine patient preference. Surgical position of the graft and alveolar bone level were recorded at the surgical visit and patients were evaluated weekly for the first 4 weeks at which time recession and level of oral hygiene were measured. Biopsies and persistence studies were performed on a subset of the patients. Results for both test and control groups were similar for all measured clinical parameters with the exception of amount of keratinized tissue and percent shrinkage of keratinized tissue. The control group exhibited an average of 1.0 to 1.2 mm more keratinized tissue over time than the test group (P <0.001) and the control group had about half as much shrinkage as the test group over time (P <0.001). Test sites demonstrated significantly better color match over time compared to control sites. Similarly, tissue texture for test sites was significantly better than control sites over time. Based on the results of this investigation, the tissue engineered HF-DDS graft was safe and capable of generating keratinized tissue without the morbidity and potential clinical difficulties associated with donor site surgery. The GA generated more keratinized tissue and shrank less than the HF-DDS graft, but the test graft generated tissue that appeared more natural.

A genetic reconstruction of the history of the population of the Iberian Peninsula

The genetic patterns detectable in human populations of the Iberian Peninsula are shown by means of 'synthetic genetic maps', i.e. geographic maps of the highest principal components (PC) of gene frequencies. This method of analysis separates independent patterns of the genetic landscape, which hopefully represents different, major evolutionary events of the past. Among these are clines established by ancient important migrations, and local differentiations of populations due to barriers responsible for relative isolation. Only events of some magnitude from a demographic point of view, involving populations having initially definite genetic differences are detectable by the method. For this to be true, the genetic consequences of these events must not have been entirely smoothed out by later, prolonged genetic exchange between neighbours; but simulations have shown that long clines produced by major migrations can be rather stable in time. The first synthetic map, corresponding to the first PC, shows that the major difference in the Iberian Peninsula is that between people originally of Basque and non-Basque descent. The recession in time of the boundaries of the Basque-speaking area seems correlated with the progressive genetic dilution of the Basque genotype in modern populations, as we move away from the centre of the Basque area. Clearly there must have been a close relationship in the progressive loss of the Basque language and increasing genetic admixture with neighbours. Most probably, Basques represent descendants of Paleolithic and/or Mesolithic populations and non-Basques later arrivals, beginning with the Neolithic. The second synthetic map is correlated with early Neolithic infiltrations from the eastern edge of the Pyrenees. It has been shown by archaeologists that, in some areas, early Neolithics lived side by side at overlapping dates with well developed Mesolithics. The demographic impact of Neolithic farmers versus Mesolithics, and therefore their genetic influence was thus less important in the Iberian Peninsula than in Central Europe. The third synthetic map shows a correlation with the linguistic and historical duality between the Atlantic and Mediterranean fringes, which developed in the first millennium B.C. and was probably determined, to some extent, by infiltrations through the Pyrenees of the Urnfield cultural elements as well as by several other later events.