Application of PEEK in stomatology

Polyether ether ketone (PEEK) is a high polymer composed of one ketone bond and two ether bonds in the main chain structure, which is a special polymer material. The benzene ring in the molecular structure gives PEEK rigidity, and the ether bond has enough toughness to make PEEK have high stress resistance.

PEEK has excellent chemical stability and biocompatibility. In addition, due to its radiographic permeability, PEEK does not produce artifacts during computed tomography (CT) and magnetic resonance (MRI) imaging, and it is easy to observe bone regeneration and healing around the implant. More importantly, the elastic modulus of PEEK is comparable to that of human bone, which reduces the stress shielding effect on the surrounding bone.

PEEK materials have many excellent properties and are widely popular in the medical field. Currently, PEEK implants commonly used in clinical practice include trauma implants, spinal implants, artificial joint implants, and skull defect implants. As a dental material, PEEK also has great potential. The clinical application of PEEK materials mainly occurred in oral and maxillofacial surgery, implant department, orthodontic department and prosthodontic department.

Application of PEEK in oral frontofacial surgery

Oral and maxillofacial surgery is a discipline that mainly focuses on surgical treatment, and mainly focuses on the prevention and treatment of diseases related to oral organs (teeth, alveolar bone, lip, cheek, tongue, palate, pharynx, etc.), facial soft tissues, maxillofacial bones (maxilla, mandible, cheekbone, etc.), temporomandibular joint, salivary glands and neck. The reconstruction of oral and maxillofacial defects is a challenge for every clinician. It is a systematic project that focuses on surgery and integrates multiple specialties such as oral restoration and oral implantology, which has certain complexity and challenge.

In existing reconstruction schemes, regional soft tissue and bone flaps, as well as separate soft tissue or free flaps with bone, are usually used. All of these reconstructions require additional surgery to remove the graft and may result in different types and degrees of postoperative complications. In addition, in most cases, this restoration results in poor aesthetics. Later, a new technique was proposed for the treatment of oral defects, namely the use of polyether ether ketone (PEEK) implants. These implants are designed using computer-aided design/computer-aided manufacturing (CAD/CAM) systems to create patient-specific prostheses that restore the anatomy of the maxillofacial region and potentially achieve better aesthetic results than autologous flaps/graft materials.

Case report: A 32-year-old male soldier presented to an oral and maxillofacial surgery clinic with a severe maxillary defect. The patient was struck by a sniper shot, which entered the right zygomatic bone and exited the left, resulting in severe damage to the maxilla (alveolar bone, nasal floor, and sinus wall) (Figures 1, 2). He underwent two surgeries to graft and repair the iliac crest bone. However, both operations ended with infection at the recipient site and graft absorption. The reason may be the large size of the defect, which prevents adequate blood supply and graft integration. The patient then underwent a multi-slice spiral CT to obtain the exact bone size of the area where the implant was located.

A 3D model of the reconstructed maxilla is used to design a patient-specific shape and size PEEK implant frame. Finally, the design was sent to a PEEK reconstruction implant manufactured by the 3D Printing Lab (Limou Lab, Damascus, Syria). The healing was good at the 6-month post-operative follow-up (Figure 3). At the end of this period, four implants mounted in PEEK were exposed and the healing abutments were placed. After 2 weeks, the impression was taken with an intraoral scanner and a temporary restoration was made. Three weeks later, the final prosthesis, an acrylic bridge, was installed and the patient was monitored for six months after installation (total follow-up after PEEK implantation was approximately 13 months), with no complications recorded (Figure 4).

3D printing PEEK for maxillofacial repair can reduce the modification during surgery, thus ensuring postoperative stability and aesthetic effect. In the case of infection of the donor site or insufficiency of autologous grafts, the research advantages can not be ignored.

Application of PEEK in dental implant department

Since the 1960s, most of the implants have been pure titanium and titanium alloys (such as Ti-6Al-7Nb, Ti-6Al-4V, etc.). Although titanium implants are supported by a large number of experimental and clinical studies, there are still some problems in their clinical use. One is the potential sensitization of titanium; Second, compared with human bone tissue, titanium elastic modulus is too high, and bone tissue reconstruction or loss is easy. Third, the lack of light transmission of metal implants affects the appearance.

In 1998, the British company introduced the PEEK implant. With the advent of commercial PEEK implants, related research has gradually increased, and many companies have launched dental implant designs based on PEEK materials.

Abutment :PEEK material has a low elastic modulus, which can cushion the chewing force to a certain extent and make up for the deficiency of titanium and zirconium base. At the same time, basic experiments have shown that there is no difference in the oral microbial flora attached to PEEK abutment and titanium abutment, and the soft and hard tissues heal well. Therefore, PEEK abutment can be used as an implant abutment in aesthetic areas.

Implants: Relevant studies have shown that the elastic modulus, elastic limit and compressive strength of PEEK composite can be applied to oral implants. In addition, PEEK has a low elastic modulus, which is close to the density of human bone after adding fillers, thus effectively reducing the stress shielding effect and making up for the shortcomings of traditional titanium implants. However, compared with titanium, PEEK implants have lower mechanical stress and lower biological activity under oral conditions, which are two major problems in clinical application. Therefore, people hope that GFR-PEEK, CFR-PEEK and CS-PEEK and other modified materials to solve this problem.

Through experiments, some scholars have concluded that the fatigue limit of GFR-PEEK implant with a diameter of 4 mm is 310N (similar to the minimum fracture strength of 300N), which can meet the standard set by ISO14801 for posterior dental restoration. When the PEEK material is combined with 60% carbon fiber, the stress distribution is the same as that of the titanium alloy implant. CFR-PEEK has attracted much attention in the medical implant community due to its versatility, morphological versatility, compatibility with modern imaging techniques, excellent mechanical properties, and biocompatibility.

In terms of improving the biological activity of PEEK implants, many scholars have conducted relevant studies by adding active particles (such as carbon fiber, hydroxyapatite and TiO2) to PEEK materials to prepare composites and surface modification (such as surface foam, nitrogen plasma immersion and sulfonation), which have enhanced the osteogenic properties of PEEK to a certain extent.

There are many studies on PEEK complex, but it has not been proved that a certain PEEK complex can meet all the requirements of oral implants for materials, and it still needs some time to be applied in clinical practice.

 Application of PEEK in orthodontics

 Orthodontics is a specialized department for the treatment of dental deformities in children, adolescents and adults. The treatment range includes early treatment of malocclusion, antiocclusion, maxillary prognathism, mandibular retrognathism, malocclusion, as well as early consultation and treatment of various malocclusion and facial development asymmetry.

In orthodontics, PEEK has been used in a variety of orthodontic instruments due to its many excellent properties. Required for early childhood correction Malocclusion appliance (such as arch expander, etc.), gap retainer, orthodontic arch wire, etc.

Case report: A five-year-old child with nickel allergy was successfully expanded by 5mm using an expander made of PEEK before the eruption of the first permanent tooth due to insufficient width of the upper palate.

PEEK Malocclusion Appliance (arch expander)

Case report: The 3D printing technology of PEEK material was used to construct the interdental gap retractor for children, which was applied to 3 children. After 9 months of follow-up, it was found that it could not only maintain the interdental gap well, but also provide patients with low visibility, which made them feel comfortable and satisfied.

PEEK gap retainer

The choice of orthodontic arch wire determines the efficiency of tooth alignment to a large extent. The ideal orthodontic arch wire should have four characteristics: high strength, low stiffness, high range of motion and high wear resistance. In clinical practice, the arch wires of the existing fixed appliance are generally metal, which has poor aesthetics and affects the CT and NMR imaging.

Study evaluation: Aesthetic and frictional effects of orthodontic guides through newly designed polyetherketone (PEEK) resin tubes. The first preparation of 0.5×0.6ф and 0.8×0.9ф two kinds of standard PEEK tube, and in the tube through different arch wire. Color values are determined according to brightness and hue. Friction was assessed using different scaffold-line combinations, and surface roughness was determined by stereoscopic microscopy before and after friction was applied.

Results The color difference of PEEK tubes was almost the same as that of coating lines routinely used in clinical practice, indicating adequate aesthetics. The friction test results show that in almost all the bows tested, the friction force is greatly reduced by passing the bows through the PEEK tube. Conclusion The use of the new PEEK tube proved its good combination of aesthetics and function in orthodontic appliance.

Application of PEEK in prosthodontics

 PEEK material can be used in prosthodontic department to make removable denture brackets and restorations, fixed dentures, prostheses, etc.

Figure a:PEEK clasp

The traditional clenching ring is made of alloy, which has the advantages of good elasticity, good retention, bending and casting. However, due to the big difference between metal and natural tooth color, the metal clenching ring affects the appearance to a certain extent. The appearance of toothcolor clench to a certain extent reduces the impact of clench on the appearance of the clench, which is usually made of thermoplastic resin, PEEK is one of them.

Figure b:PEEK partial removable denture

In one case, the patient was dissatisfied with the taste, weight and color of the metal clench, so PEEK was used as the scaffold material to make the partial removable denture of the lower jaw. The doctor made the scaffold from the molten PEEK material by vacuum die-casting, and then further arranged the teeth and made the resin base.

Figure c:PEEK crown restoration

PEEK has tensile properties and elastic modulus matching enamel and dentin, high wear resistance, good polishing properties and low plaque adhesion, making it a candidate for dental crown restoration material.

The unique and excellent properties of PEEK make it expected to replace traditional metals and their alloys or zirconia in the fields of oral and facial surgery, implantology, orthodontics and prosthodontics. Although the application prospect of PEEK is good, further studies on the influence of oral environment on PEEK and its long-term application effect in clinical practice are still needed to determine the stability of its long-term performance and its feasibility in the field of stomatology.