The Use of Laser Technology (Er;Cr:YSGG) and Stereolithography to Aid in the Placement of a Subperiosteal Implant: Case Study

The subperiosteal implant is a custom-fabricated titanium framework. It is designed to rest on top of the mandibular bone, under the periosteum, and it is stabilized by a combination of fibrous tissue and bone support.1 Permucosal extensions provide for support and attachment of the prosthesis.

For stabilizing removable dentures, use of the subperiosteal implant has declined in recent years in favor endosseous dental implants. In some cases, however, the use of endosseous implants may be rejected by patients because of increased cost, time of treatment, postoperative pain, and the introduction of multiple invasive procedures (eg, hip grafting), ie, simply to gain stability and to increase function of masticatory function of a lower denture. Recently, techniques have been developed for making subperiosteal titanium frameworks based on models of the jaws made via computerized tomography (CT) scan and CAD/CAM technology. Hjorting-Hansen et al2 reported the osseointegration of such an individually manufactured cast titanium implant framework placed on the surface of bone. More bone-to-implant contact occurs on endosseous implants.3 This observed level of osseontegration is possible because the substructure of the complete subperiosteal implant has evolved greatly over the past 50 years.

Today, this previously unpredictable implant has become highly predictable, is less invasive, involves fewer surgical procedures, and is not as technique sensitive as it was in the past. The current design transfers forces to the substructure through the 4 permucosal posts, which are anterior to the mental nerve, in the retromolar pad area, and connected to a continuous mesobar.

This article describes the use of the erbium; chromium: yttrium-scandium-gallium-garnet (Er;Cr:YSGG) laser (Biolase Technology, Irvine, Calif) in the placement of a subperiosteal implant.

A 70-year-old woman presented with a request to gain function on mastication. The patient's diet had been predominantly soft foods for a number of years, thus causing digestive problems and ulcerations on the mandibular tissue. Her main complaint was that poor, ill-fitting dentures were causing jaw pain and headaches. She also disliked her dentofacial appearance. On clinical examination, angular cheilosis on the corners of her mouth and ulcerations on her gingival tissues (Figure 1) were seen. The patient could not tolerate wearing dentures. Her last dentures had been made less than 5 years ago.

The patient's medical condition included degenerative disc disease, systemic lupus, diabetes controlled by medication, anemia, arthritis, high blood pressure, and allergies to numerous medications. On discussion with her physician, it was determined that an overdenture supported entirely by implants would be the treatment of choice. With lupus, her long-term prognosis would be continued jaw pain and decreased bone density. Other restorative modalities had been exhausted and were less medically desirable.

The patient had been a denture wearer for approximately 15 years. She had approximately 12 mm of bone height in the anterior symposis and poor occlusal vertical dimension that caused her temporal mandibular disorder (TMD) problems. The muscles of mastication were tender to palpation, and soreness was noted upon opening and closing her mouth.

The dental records obtained included a panorex film, upper and lower Aquasil impressions, and a CT scan that was reformatted to read on a computer as a 3-dimensional (3D) image (3D Diagnostix Inc, Brighton, Mass).

Treatment determined to solve the patient's problems would be the fabrication of a cast titanium subperiosteal implant fabricated by CAD/CAM technology. Due to the patient's extensive medical problems, it was decided that treatment should be performed in a surgical center. After being informed about all treatment options, the patient opted for a mandibular overdenture supported by a subperiosteal implant and an opposing maxillary denture with myoplast liner.

A CT scan was e-mailed to a service agency (ProtoMED, Arvada, CO) to create a 3D computer model using medical imaging software. Stereolithography was used to fabricate precise anatomical models of the patient's jaws using lasers and epoxy resin. Stereolithography is a highly accurate process in which computer-driven lasers take the data from the 3D computer model and photovoltaically cure an epoxy resin layer by layer until the model is complete. Within 3 days, the case was returned to the author's office for the design of the mandibular subperiosteal implant (Figure 2). This allowed the author to eliminate a preliminary surgery to make a model of the patient's mandible.

Once the design of the subperiosteal implant was completed, it was delivered to a dental laboratory (Creative Custom Services, San Diego, CA) for fabrication of the cast framework. The casting was polished, sandblasted, etched, passivated, sterilized, and delivered to the office in approximately 4 weeks.

At the surgical appointment, the patient was sedated via general anesthesia and intubated by nasal approach, and the oral cavity was swabbed with chlorhexidine gluconate 12% (Zila, Inc, Phoenix, AZ) for 30 seconds. An oral pack was placed; local anesthetic used 4.0 mL of 20 mg of lidocaine with 10 μg of epinephrine to aid in hemostasis. Flap reflection from the retromolar pad of the patient's left side to the retromolar pad of the patient's right side (Figure 3) was accomplished with the use of a YSGG laser, using the setting of 1.25 W 30 Hz 7/14 in the hard tissue mode. A 1-cm vertical releasing incision was made distal to the retromolar pads (Figure 5) bilaterally and in the center of the symphysis (Figure 4). Soft tissues were reflected by elevators (Figures 6 and 7). The subperiosteal implant was seated on the patient's jaw. Fit was excellent on the patient, as shown in Figures 8 and 9. The YSGG laser was used to decorticate (Figure 12) the mandible (3.5 W 30 Hz 30/60 in hard tissue mode) to gain more fibroblasts with the hope of osseointegration. The laser was also used to initiate primary access for the bone screw (Figure 10), which was followed by using a surgical hand piece (Figure 11) to tactilely determine how deep the preparation was made. The struts of the implant were grafted with beta-tricalcium phosphate (Cerasorb M, Cursan AG, Kleinostheim, Germany) and the patient's blood (Figures 13 and 14) and then covered with a membrane (Figure 15). Soft tissues were approximated, and primary closure was achieved with 4.0 vicryl because of the elastic effect the tissue maintains with the use of the laser (Figures 16 and 17). The YSGG laser was used at a low level (0.75 W 0/14 20 Hz) to tissue weld and stimulate angiogenesis (Figure 18). The final step was to use local anesthetic of 4.0 mL of 0.5% marcaine with 1 : 200 000 epinephrine for pain control. The patient was also administered 8 mg of dexamethasone to decrease postoperative swelling. The analgesic order for postoperative pain control was TENS unit and maxodone 16 tablets every 4 to 6 hours as needed for dental pain.

Postoperative care included records to complete a mandibular overdenture and full maxillary denture. Biostimulation (Laser Smile, Biolase, Irvine, CA) was performed in the area 3 times within a 2-week period to help cells repair themselves quickly and reduce histamine release. Biostimulation reportedly energizes the mitochondria within the cells to produce this effect.4 The patient was pleased with the results for surgical postoperative pain (Figures 19 and 20) and how the dentures fit. All symptoms of headaches, tissue irritation, and TMD tenderness were gone. The patient is now able to eat most food, allowing for a coarser diet and thus alleviating her digestive problems.

The acronym LASER stands for light amplification by stimulated emission of radiation. Since Maimon5 developed the ruby laser in 1960, lasers have slowly integrated into the dental world. Today, lasers have approval by the Food and Drug Administration for cutting bone, enamel, dentin, and soft tissue. Lasers have been approved and used for endodontics, periodontics, oral surgery, restorations, lesion removal, and desensitization. Advantages of the laser with soft tissues include reduction in bleeding, reduction of postoperative pain, reduction of edema, and precise coagulation and cutting. The advantages in cutting bone with a laser include being gentler than bone saws or high-speed drills, less postoperative pain and swelling, less necrosis of surrounding tissue, minimal trauma due to heat transfer, and minimal trauma to the periosteum when removing bone for grafting.6,^–8 In endodontics, advantages of laser use are disinfection of canals9 (more than 1000 um), leaving open dentinal tubules, and reduction of postoperative pain and swelling.

There are certain advantages to using this technology in the placement of a subperiosteal implant. The laser can seal blood vessels, lymphatic vessels, and nerve fibers. This technology can reduce mechanical trauma and bacterial counts.10 A laser is a more precise tool than a surgical hand piece, has antisepsis qualities, and reduces trauma during the procedure.

Laser energy from the Er;Cr:YSGG laser is in the infrared-wave spectrum. The laser beam is directed at a target tissue with a fiber-optic delivery system attached to a hand piece, which is then emitted in pulses. In this laser, the photon amplification occurs through a medium of heterogeneous crystal (YSGG). This laser emits photons at 2780-nm wavelengths and has a pulse duration of 140 microseconds in the repetition rate that can vary from 10 Hz to 50 Hz. During surgical procedures, the power output for alveolar bone is 3.5 W 30 Hz, and the power output for gingival tissue is 1.25 W 30 Hz. The sapphire end-cutting tip has a diameter of 750 μm and is approximately 2 mm from target tissue during surgical procedures.

Cutting hard/soft tissue is a complex interaction of laser energy with water and tissues (hydrophotonics).11 When tissues interact with laser energy, the effect is influenced by emission wavelengths, tissue optical properties, time of exposure, laser energy, and absorption of the laser energy into the tissues. The absorptive effect is the key to how the target tissue's atoms and molecules convert laser light energy into heat, chemical, acoustic, or nonlaser light energy. Thus, the amount of laser energy needed to produce desired results varies depending on the tissue involved.

It has been shown that the YSGG laser device is selectively absorbed in the target tissue and may result in either a direct tissue cut (cold cut) or vaporization of the water within a cell. This vaporization causes a rupture (thermal cut), a process known as thermal-mechanical tissue ablation.12 The thermal-mechanical tissue ablation limits the amount of collagen damage to as little as 5 um (approximately 2 cell widths), leaving the extracellular collagen matrix less affected.

There is also reportedly less histamine release in tissues treated with a laser device, which accounts for the lessening or absence of intraoperative and postoperative pain and inflammation. Furthermore, there has been virtually no scarring and minimal tissue shrinkage on crestal, sulcular incisions. The major benefits for using the laser in this case are (1) when cutting the tissue with a laser, the tissue maintains its elastic effect, meaning primary closure is easy to maintain, without having to release tissue around the flap; (2) the ability to promote faster blood supply to the flap, thus getting faster healing than traditional methods (using the laser in a defocused mode with low-level radiation on the surgical site); (3) creating multiple decortications into the alveolar bone (starting regional acceleratory phenomenon), which brings more fibroblasts into the area, allowing a better chance to actually get a bone-to-implant fit (osseointegration); (4) less pain and swelling than traditional methods.13,^–16 

In the case described, the YSGG laser was used as a surgical modality to change the effects of subperiosteal implant placement. Technology is changing the way dentists are able to treat patients for the better. Patient experience less pain, less swelling, and faster recovery time. Benefits to the clinician include improved patient-doctor relationship and quicker case completion.17 This patient rated the pain for this procedure at a 3 on a scale ranging from 0 to 10 (0 = no pain and 10 = the most extreme pain). The author was able to use 1 device to cut tissue, decorticate bone, cut osteotomy, and stimulate cell regrowth. Implant dentistry has allowed the author to change patient's lives, and laser dentistry has given the word surgery a gentler meaning for the patient.

The patient gained increased function to masticate food without causing pain, and the overdenture was stable and totally implant supported, thus eliminating mandibular tissue irritation. Use of laser technology resulted in faster healing, less pain, and increased bone-to-implant contact than by using conventional methods.

This author lectures for Biolase but is not funded in research and does not receive any monetary remuneration.

The author would like to thank Kirk Brink from Biolase Technologies for calibrating the laser, Judy Pastrano and Kristi Meyer for organizing the procedure, and Amanda Kusek for aid with this article.