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Preservation of alveolar bone volume following tooth extraction facilitates subsequent placement of dental implants and leads to an improved esthetic and functional prosthodontic result. The aim of the present study was to assess bone formation in the alveolus and the contour changes of the alveolar process following tooth extraction. The tissue changes after removal of a premolar or molar in 46 patients were evaluated in a 12-month period by means of measurements on study casts, linear radiographic analyses, and subtraction radiography. The results demonstrated that major changes of an extraction site occurred during 1 year after tooth extraction.

The present study was designed to examine whether new attachment forms on root surfaces previously exposed to plaque by preventing the oral epithelium and the gingival connective tissue from participating in the process of healing following treatment. 4 roots in each of 3 monkeys were used as test units while the roots of contralateral teeth served as controls. A surgical procedure was first used to expose the coronal half of the buccal root surfaces. Plaque was allowed to accumulate on the exposed surfaces for a period of 6 months. Subsequently, soft tissue flaps were raised and the root surfaces were carefully scaled and planed. The crowns of the test and control teeth were resected and the mucosal flaps were repositioned and sutured in such a way that the roots were properly covered. Immediately prior to suturing, membranes (Millipore filter or Gore-tex membrane) were placed over the denuded root surfaces of the test teeth in order to prevent granulation tissue from the soft tissue flaps from reaching the roots during healing. The monkeys were sacrificed 3 months later. The jaws were removed and histological sections of test and control roots including their periodontal tissues were produced. New cementum with inserting collagen fibers was observed on the previously exposed surfaces of both test and control roots. However, the test surfaces exhibited considerably more new attachment than the control surfaces, indicating that the placement of the membrane favoured repopulation of the wound area adjacent to the roots by cells originating from the periodontal ligament.

The aim of the present investigation was to examine if a new connective tissue attachment can be established on a previously periodontitis involved root surface, located in contract with gingival connective tissue during healing. A total of 28 teeth in one dog (beagle) and two monkeys (Macaca cynomolgus) were subjected to experimental periodontal tissue breakdown by placing cotton floss ligatures or orthodontic elastics around the teeth. The ligatures were left in situ until about 50% of the supporting tissues had been lost. Following resection of the crowns, the teeth were root filled and the exposed parts of the roots thoroughly scaled and planed. Each root was extracted and implanted into grooves prepared in edentulous areas of the jaws in such a way that the root was embedded to half its circumference in bone, leaving the remaining part to be covered by the gingival connective tissue of the repositioned flap of the recipient site. Root implantation and sacrifice of the animals were scheduled to allow for observation periods of 2 and 3 months of healing. An analysis of histologic specimens, obtained from biopsies of the recipient site tissues, disclosed that a new fibrous attachment failed to form on a previously "exposed" root surface located in contact with gingival connective tissue. In areas of the roots where the periodontal ligament tissue was preserved prior to transplantation, a fibrous reattachment occurred between the root and the adjacent gingival tissue. The results indicate that gingival connective tissue does not possess the ability to establish conditions which enable the formation of a new connective tissue attachment.

Free grafts of connective tissue, without epithelium, were transplanted from either the keratinized gingiva or the non-keratinized alveolar mucosa (controls) into areas of the alveolar mucosa in seven monkeys. The grafts were placed in pouches created in the connective tissue as close as possible to the overlying epithelium. After 3-4 weeks, the transplants were exposed by removal of the overlying tissue in order to allow epithelialization from the surrounding non-keratinized alveolar mucosa. The transplants were examined clinically and histologically at time peiods between 1 and 12 months. The gingival connective tissue grafts became covered with keratinized epithelium displaying the same characteristics as those of normal gingival epithelium. The alveolar mucosa transplants were covered with non-keratinized epithelium. This indicated that gingival connective tissue is capable of inducing the formation of a keratinized gingival epithelium.

It has been shown that the connective tissue base determines the epithelial surface characteristics. Although there is no apparent difference between the connective tissues underlying the subcular and the surface gingival epithelium, the sulcular epithelium is not keratinized as is the gingival surface. The influence of the sulcular environment in determination of keratinization was explored in three adult Rhesus monkeys. Twenty-four intrasulcular mucoperiosteal flaps were elevated beyond the buccal mucogingival border, were turned inside out and sutured to leave the sulcular epithelium exposed on the surface. Short term speciments (1 hour to 7 days) were obtained from one monkey which received H3 thymidine 1 hour prior to sacrifice. Biopsies were obtained from the other two monkeys covering intervals of 1 week to 2 months. The findings indicate that the sulcular epithelium has potential for keratinization. The contact to the tooth appears to determine the lack of keratinization of the sulcular epithelium.

One hundred and thirty eight male white albino rats were used in this study. Serial sections were prepared of the palate, tongue, gingiva and ear and were stained with hematoxylin and eosin. The experiment utilized one group of rats aged 3 months and another at 15 months, at 3 hour intervals during a 24 hour period 3 rats from each group received an injection of colchicine and were sacrificed 3½ hours later. Counts of arrested metaphases demonstrated that the mitotic activity of young and old animals were similar or tended to decrease with age. in 2,3,6,15 and 25 month old rats no relationship was found between the number of nucleated cells in the various epithelia and the age of the animals. Using colchicinized rats and non-treated rats the duration of the mitotic phase was estimated in tongue epithelium of young and old animals. The result of this experiment indicated that the duration of the process of cell division tends to increase with age. The results of this study favour the opinion that mitotic activity decreases with increasing age. [ABSTRACT FROM AUTHOR]

A study was conducted on a free and attached gingiva of man and monkey. The study was conducted in three-dimensional models produced from serial sections of gingival biopsies. Both in the attached and free marginal gingiva the individual connective tissue papillae were arranged in rows running predominately parallel to the gingival margin. The possible relationship between elevations and depressions in the outer surface of the epithelium and the pattern of the underlying structures was also studied.