Although several major progresses have been introduced in the field of bone regenerative medicine during the years, current therapies, such as bone grafts, still have many limitations. Moreover, and in spite of the fact that material science technology has resulted in clear improvements in the field of bone substitution medicine, no adequate bone substitute has been developed and hence large bone defects/injuries still represent a major challenge for orthopaedic and reconstructive surgeons. It is in this context that TE has been emerging as a valid approach to the current therapies for bone regeneration/substitution. In contrast to classic biomaterial approach, TE is based on the understanding of tissue formation and regeneration, and aims to induce new functional tissues, rather than just to implant new spare parts. The present review pretends to give an exhaustive overview on all components needed for making bone tissue engineering a successful therapy. It begins by giving the reader a brief background on bone biology, followed by an exhaustive description of all the relevant components on bone TE, going from materials to scaffolds and from cells to tissue engineering strategies, that will lead to "engineered" bone. Scaffolds processed by using a methodology based on extrusion with blowing agents.

/pdf/bone-tissue-engineering-state-of-the-art-and-future-trends-4x410y8eni.pdf

Bone Tissue Engineering: State of the Art and Future Trends

Objective: To study dimensional alterations of the alveolar ridge that occurred following tooth extraction as well as processes of bone modelling and remodelling associated with such change.

Material and Methods: Twelve mongrel dogs were included in the study. In both quadrants of the mandible incisions were made in the crevice region of the 3rd and 4th premolars. Minute buccal and lingual full thickness flaps were elevated. The four premolars were hemi-sected. The distal roots were removed. The extraction sites were covered with the mobilized gingival tissue. The extractions of the roots and the sacrifice of the dogs were staggered in such a manner that all dogs contributed with sockets representing 1, 2, 4 and 8 weeks of healing. The animals were sacrificed and tissue blocks containing the extraction socket were dissected, decalcified in EDTA, embedded in paraffin and cut in the buccal–lingual plane. The sections were stained in haematoxyline–eosine and examined in the microscope.

Results: It was demonstrated that marked dimensional alterations occurred during the first 8 weeks following the extraction of mandibular premolars. Thus, in this interval there was a marked osteoclastic activity resulting in resorption of the crestal region of both the buccal and the lingual bone wall. The reduction of the height of the walls was more pronounced at the buccal than at the lingual aspect of the extraction socket. The height reduction was accompanied by a “horizontal” bone loss that was caused by osteoclasts present in lacunae on the surface of both the buccal and the lingual bone wall.

Conclusions: The resorption of the buccal/lingual walls of the extraction site occurred in two overlapping phases. During phase 1, the bundle bone was resorbed and replaced with woven bone. Since the crest of the buccal bone wall was comprised solely of bundle this modelling resulted in substantial vertical reduction of the buccal crest. Phase 2 included resorption that occurred from the outer surfaces of both bone walls. The reason for this additional bone loss is presently not understood.

http://www.francescoinchingolo.it/media/JOUR_CLIN_PERIOD.pdf

Dimensional ridge alterations following tooth extraction. An experimental study in the dog

Elastomeric biomaterials for tissue engineering

The present experiment was undertaken to test the hypothesis that new connective tissue attachment may form on a previously periodontitis involved root surface provided cells originating from the periodontal ligament are enabled to repopulate the root surface during healing. A mandibular incisor with advanced periodontal disease of long standing (the distance between the cemento-enamel junction and the alveolar bone crest was 9 mm) was subjected to periodontal surgery using a technique which during healing prevented the dentogingival epithelium and the gingival connective tissue from reaching contact with the curetted root surface. Preference was hereby given to the periodontal ligament cells to repopulate the previously diseased root surface. After 3 months of healing a block biopsy containing the incisor and surrounding tissue was sampled. The histological analysis revealed that new cementum with inserting principal fibers had formed on the previously diseased root surface. This new attachment extended in coronal direction to a level 5 mm coronal to the alveolar bone crest. This finding suggests that new attachment can be achieved by cells originating from the periodontal ligament and demonstrates that the concept that the periodontitis affected root surface is a major preventive factor for new attachment is invalid.

New attachment following surgical treatment of human periodontal disease.

A link between oral health and cardiovascular disease has been proposed for more than a century. Recently, concern about possible links between periodontal disease (PD) and atherosclerotic vascular disease (ASVD) has intensified and is driving an active field of investigation into possible association and causality. The 2 disorders share several common risk factors, including cigarette smoking, age, and diabetes mellitus. Patients and providers are increasingly presented with claims that PD treatment strategies offer ASVD protection; these claims are often endorsed by professional and industrial stakeholders. The focus of this review is to assess whether available data support an independent association between ASVD and PD and whether PD treatment might modify ASVD risks or outcomes. It also presents mechanistic details of both PD and ASVD relevant to this topic. The correlation of PD with ASVD outcomes and surrogate markers is discussed, as well as the correlation of response to PD therapy with ASVD event rates. Methodological issues that complicate studies of this association are outlined, with an emphasis on the terms and metrics that would be applicable in future studies. Observational studies to date support an association between PD and ASVD independent of known confounders. They do not, however, support a causative relationship. Although periodontal interventions result in a reduction in systemic inflammation and endothelial dysfunction in short-term studies, there is no evidence that they prevent ASVD or modify its outcomes.

/pdf/periodontal-disease-and-atherosclerotic-vascular-disease-5dzvnap7v8.pdf

Periodontal Disease and Atherosclerotic Vascular Disease: Does the Evidence Support an Independent Association? A Scientific Statement From the American Heart Association

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.

Bone healing and soft tissue contour changes following single-tooth extraction: a clinical and radiographic 12-month prospective study.

Clinical Periodontology and Implant Dentistry 6ed - Libros de Medicina - Periodoncia - 252,00

Clinical Periodontology and Implant Dentistry

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 Haps 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.

New attachment formation as the result of controlled tissue regeneration

The aim of the present study was to examine if new cementum and new attachment may form during healing of a wound prepared in such a way that preference is given to periodontal ligament cells to repopulate the wound area adjacent to a root which has been surgically deprived of its periodontal ligament and cementum layer. The maxillary lateral incisors and mandibular canines in three monkeys were used for experimentation. Following elevation of a mucoperiosteal flap, the buccal and approximal alveolar bone was removed within an area extending from the mid-root level to a level 2 mm apical to the marginal bone crest. Following bone removal, the root surfaces were curetted in order to remove the cementum layer. Notches were prepared in the roots to demarcate the denuded root portion. Prior to repositioning of the tissue flap a millipore filter was placed over the treated area in order to prevent the gingival connective tissue from coming into contact with the root surface during healing. The animals were sacrificed 6 months after surgery. The jaws were removed and histological sections of the experimental teeth and surrounding periodontal tissues were produced. New cementum with inserting collagen fibers was observed on the curetted root surfaces. However, this result of healing did not consistently occur along the entire length of the curetted root portion. In the coronal part of the wound, healing was frequently characterized by connective tissue adhesion to the root surface without signs of cementum formation and fibrous attachment. The results of the experiment suggest that the periodontal ligament cells possess the ability to reestablish connective tissue attachment.

Thorkild Karring

Papers

Bone healing and soft tissue contour changes following single-tooth extraction: a clinical and radiographic 12-month prospective study.

Clinical Periodontology and Implant Dentistry

New attachment following surgical treatment of human periodontal disease.

New attachment formation as the result of controlled tissue regeneration

The regenerative potential of the periodontal ligament. An experimental study in the monkey.