Case report of soft tissue crown lengthening
The case report that will be presented below was realized with a 980 nm diode laser. Diode laser is one of the most popular lasers because of its compact size, light weight, portable unit and relatively reduced cost while remaining efficient with beneficial effects.
Its active medium is a solid state, composed from semi-conductor crystal combining Indium, Gallium and Arsenide (InGaAs) that transform the electric current into light energy. It is a modern device with the foundation of modern electronics.
Depending on the clinical situation, the diode laser can be used in contact mode or non-contact mode (PBM, bleaching, desensitizing.).
Cutting tissue by diode lasers occurs through photothermolysis: Chromophores in the target tissue absorb the light energy rapidly, immediate rise in temperature with subsequent denaturation of tissue protein, as well as fragmentation and vaporization of the melanin, followed by vaporization of water content. So, it is temperature rise that causes soft tissue disruption. Depending on the temperature level reached at the surgical site, soft tissue are subjected to warming, welding, coagulation, protein denaturation, drying, ablation then vaporization or carbonization10.
Power settings of the diode laser device are adjustable, and the laser beam may be delivered in a constant continuous mode or in gated mode:
A) With continuous mode, there is a gradual increase in the temperature then heat generation gets much faster; there is tremendous risk to get uncontrolled damage (the amount of heat generated is translated directly into the amount of collateral damage)
B) With gated continuous mode, when using gated mode, there is still a rise in temperature, but the tissue has time to cool down during the thermal relaxation time, which leads to controlled collateral damage & lower thermal rise. This explains the general recommendation for laser use at low power and in gated mode for soft tissue procedures
Before surgery with the diode laser, the ultra-thin lasing fiber could be initiated. This process allows capturing most of the energy (60% of the energy or more) at the end of the laser fiber and the incision is faster.
This is done by tapping the laser fiber on articulating paper while the laser is energized. Usually a 300µm tip is selected for surgical gingival cutting rather than a 200µm tip, because this latter is more fragile and breakable
Before cutting gingival tissue, the depth of the sulcus should be measured with a periodontal probe. The bone level should be sounded and a biological width of 2-3mm should be respected in order to avoid any further periodontal damage.
During surgery, the 300µm fiber tip is placed in contact with the tissue. This gives the clinician the essential tactile feedback which is absent with some other lasers such as CO2 lasers. Excision is performed with gentle sweeping brush motions. It is important to emphasize that the laser tip does not cut like a blade, but it vaporizes tissue layer by layer at the fiber end and not on the sides, since these latter areas are protected by the collimation cladding so the energy cannot be transmitted through the sides. The correct technique is to avoid pressing on the fiber, but to simply guide it along the precise route desired, using light brush stroke to “paint away“ the amount of tissue to cut, and to let the highly directed laser energy do the work. Water irrigation with a syringe is helpful to reduce the charred layers and to cool down the tissue; high aspiration removes the dangerous laser plume.