To continue on the differences and similarities between teeth and implants, let's take a closer look to the soft tissues of the periodontium versus the peri-implant tissues. As we discussed, the lack of periodontal ligament around implants, means significant difference in terms of movement, shock absorption, and perception. It also means less vascularization, and poorer blood supply for the peri-implant tissues. Right on top of the bone, comes the zone of connective tissue for both implants and teeth. This connective tissue is highly structured around teeth, with well organized bundles of fibres, some of which are well anchored in the cementum of the teeth on one side, and the gingival tissues, or the bone on the other. The zone of connective tissue around implants is however less vascularized, and the orientation of the collagen fibres less structured. Fibres are not firmly anchored on the side of the implant, instead they are arranged around the implant like a rubber band. On top of the connective tissue zone there is a zone of epithelial cells, which constructs the junctional epithelium. These cells are attached on the tooth in the same way they attach to the implant surface, and this is the first true barrier separating the oral environment from the underlying tissues. The connective tissue zone, together with the junctional epithelium, is what we call the biological width, and this is the necessary zone of tissues that needs to be established on top of the bone at all circumstances. On top of the junctional epithelium starts the sulcus, a zone where the soft tissues are in proximity, but not attached in any way to the implant. The sulcus is a very significant difference between implants and teeth. The sulcus around teeth is defined genetically, and in healthy conditions is approximately 0.5 to 1 mm. On the other hand, the sulcus around implants is mainly determined by the height of the soft tissues, the local anatomy and the depth of placement of the implant. Therefore, especially in anterior implants where the placement is often deep in the tissues for aesthetic reasons, a sulcus of 3, 4,or even 5 mm is not uncommon. Looking closer at this implant placed in the position of a central incisor, we can see that the first couple of millimetres on top of the implant, is the only zone of attachment. This is the connective tissue and junctional epithelium. The remaining tissue all the way to the margin of the soft tissues, is epithelialized sulcus, and as you see in the mesial and distal sides, it can be several millimetres deep. The same can happen in other locations, such as for example in the posterior maxilla, as we approach areas where the soft tissues are thicker. As we can see with the dental floss, the sulcus around the central incisor does not extend deeper than a millimetre, yet, around the neighbouring implant, the sulcus is several millimetres deep. The clinical significance of the deep sulcus around implants is critical, as we need to ensure that it remains free of plaque and biofilm. The bacterial biofilm will be created in the coronal part of the sulcus, so we need to ensure that the first millimetre or two of the peri-implant sulcus is accessible to oral hygiene, and our patient can keep this critical junction clean. As we see, there are structural, anatomical, and physiological differences that make the peri-implant tissues less resistant to mechanical forces, but also more susceptible to tissue destruction when inflamed. And this will have a very important role in the diagnosis of peri-implant tissue inflammation, as we will see later in the course.
