Posted by in Featured Articles | 0 comments

In addition to playing a role in the biologic integration of an implant, peri-implant soft tissues play an important role in the vascularization of the bone. Without sufficient peri-implant tissues to supply nutrients, resorption of peri-implant bone and underlying bone grafts occurs. Adequate soft tissues also provide a walling off phenomenon to protect the underlying bone from oral micro-organisms.

The peri-implant soft tissue healing process has four over-lapping phases:

  • Bleeding
  • Inflammation
  • Proliferation
  • Remodeling

Bleeding Phase

The Bleeding Phase (hemostasis) is short lived, lasting 6-8 hours. The rate of bleeding significantly subsides during this phase as platelets aggregate at the wound site to form a fibrin clot. Highly vascular tissues such as muscle bleed longer than other tissues, and in highly vascular tissues, there is a greater escape of blood into the wound area. Surgical measures can be taken to reduce the rate of bleeding, if needed.

Inflammation Phase

The Inflammation Phase is an essential component of the soft tissue repair process. The onset of inflammation is rapid (a few hours) and swiftly increases in magnitude, peaking at 48-72 hours and gradually resolving over 2-3 weeks. The inflammation response to injury is a vascular response. Cellular and fluid exudates result in edema and phagocytic activation. The interaction of chemical mediators, not only stimulates inflammation, but also initiates the proliferative phase. The number of dead cells, nature of the injury and the pre-injury condition of the tissues influence the course of inflammation. Ideally the inflammatory phase of soft tissue wound healing resolves with less than critical number of cells being destroyed. This requires a meticulous handling of the soft tissues. Whenever a surgeon manages the soft tissues with a less than refined approach, the resultant trauma causes the death of the critical number of cells resulting in infection which clearly results in delayed soft tissue wound healing.

Chronic inflammation typically involves the presence of infective microorganisms with resulting suppuration. Chronic inflammation Ab Initio may be the result of local irritants, poor circulation, microorganisms, and immune disturbances. Chronic inflammation produces more fibrous material than inflammatory exudates, and frequently there is tissue destruction, inflammation and attempted healing all occurring simultaneously. Chronic inflammation is usually accompanied by fibrosis, even in the absence of significant tissue destruction.

Fibrin deposits are removed by fibrinolytic enzymes and gradually replaced by granulation tissue, which becomes organized scar tissue. The removal of fibrin allows for capillary budding and fibroblastic activity, which leads into the Proliferation Phase. Fibrotic peri-implant soft tissue healing is a contributing factor for significant implant complications.

Proliferation Phase

The Proliferation Phase (angiogenisis) overlaps with the Inflammatory phase, starting at 24-48 hours after the wound occurs. This phase involves the generation of a reparative material (collagen scar) and requires oxygen and nutrients supplied by capillaries. The peak of generation of this provisional scar occurs at 2-3 weeks and resolves over several months. The granulation tissue of this scar consists of new blood vessels, fibroblasts, inflammatory cells, endothelial cells, myofibroblasts, and the components of a hydrated extracelluar matrix (ECM)—principally fibronectin and collagen.  Growth factors (PDGF, TGF-b) encourage proliferation. Hypoxia encourages fibroblast proliferation and excretion of growth factors but too little oxygen inhibits their growth and can lead to excessive scarring.

Remodeling Phase

The Remodeling Phase overlaps with the Proliferation Phase. During the Remodeling Phase, initial-repair, weak collagen fibrils with random orientation are reabsorbed and replaced with a collagen matrix having more crosslinking and greater tensile strength. The maturing scar is dynamic and continues from 3-4 months to over a year. Understanding the timescale for peri-implant soft tissue healing is critical for the implant surgeon to properly choose the proper  time sequence between soft and hard tissue grafting procedures used for reconstruction of complex composite in preparation for subsequent implant placement.
The entire biochemical process of healing is complex and susceptible to complications for which there are many contributing factors.

 Today’s Accountability

Today’s dental implant surgeon is not only accountable for knowing how the body naturally repairs wounds, but also knowing what is possible for helping physiologic adaptation generate replacement tissue of highest quality without healing complications or poor esthetic results. At my 15th annual Comprehensive Dental Implant Surgery Course, ISTM 2013, we will examine the complications that can occur and protocols to minimize their occurrence. We will also look at advances made in tissue engineering, such as the use of platelet-derived growth factors and biocompatible matrices to promote tissue regeneration.

 Recommended Reading:

  • Schultze-Mosgau S, Blatz MB, et al. Principles and mechanisms of peri-implant soft tissue healing. Quintessence Int 2005;36:759–769.
  • Sclar, A. Soft Tissue and Esthetic Considerations in Implant Therapy. Quintessence Publishing 2003.
  • Watson T. Tissue repair. The current state of the art. SportEx-Medicine 2006;28:7-13.

 

 

Leave a Comment

Your email address will not be published. Required fields are marked *

*

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>