Zygomatic approach with single-piece implants: A technical note.

Single piece zygomatic implant, or a remote anchorage implant, is an effective tool for the rehabilitation of the atrophic/resected jaws with least postoperative complications such as screw loosening, screw fractures, bone loss, mucositis, and peri implantitis. The aim of this paper was to summarize a technique for the use of a zygomatic approach for single piece implants. We used the key-words 'single piece implants" and the search revealed 700 papers in the PubMed database. After screening through the abstracts, we selected 50 articles that we finally reviewed. Zygomatic fixtures avoid the grafting procedures and cantilever situation, restoration of atrophic or postablative jaws are completed with immediate loading. It is advisable placement of zygomatic implant flapless with surgical guide, but the author believes more on the tactile perception and when the splint is at mucosal or bone level, a small change in orientation will lead the dramatic error in desired angulation leading to unwanted complication. Copyright:

INTRODUCTION

Dental implants are nowadays an established treatment modality for the functional rehabilitation of lost stomatognathic structure. Historical evidence dated back of 600 AD for the replacement of incisor with ivory by the Egyptians. With age and losing functional units like tooth which may also due to trauma postablative situation, unrestorable caries and diseases such as periodontitis, atrophy results of the jaws, both upper and lower. The classification of edentulous jaws proposed by Cawood and Howell[1] concluded in general, changes of shape of the alveolar bone follow a predictable pattern. Alveolar bone changes the shape of the anterior and posterior maxilla and mandible significantly in both the horizontal and vertical axis. Maxillary rehabilitation is always challenging as of deficient alveolar bone both qualitatively and quantitatively which makes the long-term prognosis of the fixture questionable; Schnitman et al.[2] demonstrated that the posterior maxilla was the least successful area for osseointegration with merely a 72% success rate. Augmentation procedures such as onlay grafting, inlay grafting for maxillary antrum and nasal floor, Le Forte 1 osteotomy with interpositional grafting, and distraction osteogenesis are some of the methods to reconstruct atrophic jaws before implant placement for the implant-supported rehabilitation.[3456789101112] Widmark et al.[13] found out that maxillary implants placed in the native bone had a greater success rate than implants placed into grafted bone. Other than the alveolar bone which houses the teeth along with periodontal apparatus and is prone for resorption, both upper and lower jaws lined by corticals and buttress; horizontal, transverse and vertical; that form protective frame around the different craniofacial cavities, which are mineralized as of functional reparative osteogenesis owing to facial muscular attachments, being resistant to resorption.[14] The upper jaw consists of series of frontomaxillary and frontozygomatic as anterior buttress and pterygomaxillary as posterior buttress ideal for the implant anchorage.[15]

Any ideal treatment modality aimed for the patient should be least traumatic, preferably flapless, less time-consuming, most economical without any comorbidities, and painful procedure such as grafting avoiding immediate and delayed complications postoperatively. Implant surgeons aim for immediate functional rehabilitation whenever possible, fixtures are placed with the support of highly mineralized cortical and buttress and avoiding grafting procedures. The history of intraosseous implantology begins with the introduction of the Formiggini screw. Single-piece implants were subsequently derived from the titanium bars. The intrinsic function of the emerging stump was immediate loading. The great stability of the implant in the bone thus demanded was eventually achieved by means of the self-tapping screw and bicortical support.[16] There has been a switch from sunken two-stage to single-stage implants in view of the usefulness of immediate loading.[17] Corticobasal implants are single-piece smooth surface implants which are osseo-fixated in cortical bone/buttress with the intention to use them in an immediate loading protocol.[18]

Zygoma implants were first introduced in 1998 by Per Ingvar Branemark widely acknowledged as the “Father of Dental Implantology.”[19] After Branemark, Malevez et al. described zygomatic implants as self-tapping screws in commercially pure titanium with a well-defined machined surface available in length 30–52.5 mm and a unique 45° angulated head to compensate for the angulation between maxilla and zygoma.[20] Original technique was the two-stage delayed loading protocol, Chow et al.,[21] Bedrossian et al.,[22] and Migliorança et al.[23] presented the favorable results and conclusions regarding the immediate loading of zygomatic implants.

A single-piece zygomatic implant is a smooth surface Toulouse lag screw-like fixture with different length available in the range from 35 to 55 mm length, having core diameter of 2.2 mm and apical thread diameter of 4.6 mm for primary anchorage with zygomatic bone, approached through palatal/crestal aspect of resorbed maxilla, having bendable zone to compensate for angulation variation between the maxilla and zygoma and achieving desired position of the abutment prosthetically. ZDI® implant (Simpladent GMBH, Ihde dental, Switzerland) is among the family of corticobasal implants.

Advantage and indication for single-piece zygomatic implants:

Prosthetic rehabilitation of atrophic maxilla, fixed or removable

Rehabilitation of postresection cases or congenital diseases for fixed or removable obturators

Anchorage for extraoral episthesis

Avoiding cantilever situation

Achieving staggered installation of implant restoration resisting offset loading

As a rescue implant

Immediate loading and graftless protocol

Relatively economical

Minimal Armamentarium

Unfavorable sagittal relationship of the maxilla to mandible

Avoidance of delayed complication such as abutment screw fracture, loosening, and peri-implantitis.

The disadvantage and contraindications for single-piece zygomatic implants:

Acute sinus infection and pathology, uncontrolled systemic disease

Limited mouth opening

Active intravascular bisphosphonate therapy

Active or recent therapeutic radiotherapy, chemotherapy, and blood dyscrasias that directly affects bone metabolism

Technique demanding, surgeon need to be fairly experienced

Always to be used along with anterior or posterior implants been splinted, Quad zygoma is always option when inability to achieve supporting implants, anterior or posterior in condition such as postresection surgery.

The author presents the technique of zygomatic engagement with single-piece implants having emphasis on unique flapless approach following the concept of Primum non nocere or ”First, do no harm,” and the related surgical anatomical consideration. The Ethical clearance obtained from Maharaja Vinayak Global University, Jaipur with reference no. MVGU/ADM/2020/437 and dated 24/09/2020.

Applied anatomy

The zygomatic bones are a pair diamond-shaped, irregularly-shaped bones that protrude laterally and forms the prominence of the cheeks, a portion of the lateral wall, the orbit floor, and some portions of the temporal fossa and infratemporal fossa. The zygomatic bone can withstand the forces of mastication and transmitting reactionary forces from the maxilla. It gives rise to the masseter muscle, which is the major jaw adductor in mammals. Each zygomatic bone has three surfaces (orbital, temporal, and lateral), four borders (orbital or antero-superior, maxillary or antero-inferior, temporal or postero-superior, zygomatic, or postero-inferior), and three processes (frontal, temporal, and maxillary). The bone houses the zygomatic canal leading to openings on the temporal (zygomaticotemporal foramen) and the facial surfaces (zygomaticofacial foramen) of the zygomatic bone. The zygomatic nerve, main nerve supply for the zygomatic bone which is branch of maxillary nerve, dividing into the branches and the zygomatic blood vessels pass through it; zygomaticofacial foramen is of clinical significance of the approach in discussion [Figure 1]. The two anthropological reference point: The Jugale (Ju) at the most concave point between the lateral margin of the zygomatic bone and the zygomatic arch and the Zygomaxillare (Zm) at the lowermost point of the zygomaticomaxillary suture is of clinical significance as trabeculae at Ju region is the thickest and Zm region containing fewer and thinner trabeculae elements making Ju region ideal for the fixture engagement [Figure 2]. The concavity between the frontal and temporal process of the zygomatic bone facilitates the 90° approach for the fixture engagement through the palatal approach,[24] which makes the perfect zygomatic fixation with transsinus approach.

Figure 1

Zygomatic complex; Shaded areas are site for implant

Figure 2

Jugale (Ju) and Zygomaxillare (Zm) (Kato et al. Internal Structure of Zygomatic Bone. J Maxillofac Surg 2005)

Infraorbital foramen located medially to zygomaticomaxillary suture and inferior to infraorbital rim houses infraorbital nerve and vessels, care to be taken in flap reflection for the zygomatic approach.

The vessels of clinical significance for the zygomatic approach include transverse facial, branch of superficial temporal artery, and facial artery. The transverse facial artery originates from the superficial temporal artery within the parotid gland and courses anteriorly to the cheek, over the zygomatic bone. Occasionally, it formed an anastomosis with the facial artery. The facial artery, branch of external carotid artery, travels to and curves around the inferior border of the mandible just anterior to the prominent masseter muscle. The facial artery is the main artery of the check providing several arterial branches to neighboring structures, including the skin areas of the chin, lips, and nose. The main arterial supply over the zygomatic bone is from arterial perforators originating from the transverse facial artery and facial artery. Facial vein drains from the infraorbital vein courses on average 15 mm posterior to the facial artery, being inferior to crista zygomaticoalveolaris.[25] The determination of the zygomatic bone showed a medio-lateral thickness of 7.60 ± 1.45 mm for the females and 8.00 ± 2.26 mm for the male specimens,[26] the mean length in this region is 14 mm[27] which is sufficient for two zygomatic fixture placement. The palatal mucosa around the premolars and molar is around 5 mm thick which is of clinical importance keeping the abutment margin supragingival avoiding soft-tissue reaction.

Anatomical structures explained above are of clinical importance for the zygomatic implant approach, better understanding is utmost important to avoid intra-operatory mishaps and manage complications with or without flap technique for zygomatic implant fixation.

Technique

The techniques common for zygomatic approach mainly are intra-sinus technique by Branemark (1998), sinus-slot technique from Stella and Warner (2000), extramaxillary Approach by Miglioranca et al.(2006) [Figure 3]. There was a shift from Branemark intrasinus with palatal emergence technique toward the placement technique having acceptable abutment position at the alveolar crest to achieve comfortable prosthetic solution and minimizing the cantilever by keeping the implant emergence intraorally toward first molar. Emphasis was made to have maximum contact with the anterior wall of the maxilla creating more bone to implant contact as been proposed by Stella and Warner and followed by Aparicio.

Figure 3

Zygomatic approaches

With single-piece zygomatic implant, concavity of the anterior wall of the maxilla and the alveolar ridge height defines the technique to be trans-sinus or extra-sinus approach. Here, the foremost aim is to keep the abutment emergence close to the alveolar ridge for the functionally acceptable prosthesis and least traumatic for patient keeping flapless if possible.

Presurgical evaluation

Maxillary sinus evaluation is done regarding the position of the zygomatic bone with respect to the maxillary ridge with computer tomogram, para-nasal-sinus view, orthopantomogram. Master cast is needed for planning the acceptable abutment emergence position. Routine pathological test mandatory as for the surgical protocol keeping the parameters acceptable and patient consent form to be acquired.

Armamentarium

Single-piece implant system (Simpladent and Ihde dental, Switzerland) 2.2 mm twist drill of length 50 mm and 55 mm. Implant placement aid and Hand grip Torque controlled ratchet Contra-angle 1:1 reduction Handpiece Physio-dispenser Routine surgical instruments for flap reflection and sutures.

Surgical technique

The main advantage with single-piece zygomatic implant is the freedom of placement in respect to the abutment emergence for the desired prosthetic placement because of bendable zone available in the fixture. Here, the placement is purely tactile based and the experience and anatomical knowledge of the surgeon is demanded when flapless intrasinus technique is approached. Almost all the zygomatic placement is done on routine dental setup under local anesthesia.

We broadly classify the zygomatic implant placement technique with single piece into (a) transsinus technique and (b) extrasinus approach.

The height of alveolar bone at premolars and molar available, the zygomatic bone in relation of maxilla are the important landmarks to be evaluated for trans-sinus or extramaxillary zygomatic approach. Infraorbital block, posterior superior nerve block, and greater palatine nerve block along with local infiltration at the lateral surface of zygomatic bone are done for both trans-sinus and extra-sinus technique.

Extra-sinus approach

It is also an open-flap approach. This technique is inspired from the techniques by Stella and Warner (2000) and Aparicio C (2011). Whenever an operator is in doubt always reflect the flap. This technique is preferred when simultaneously pathology or the foreign body from the maxillary sinus is to be excavated [Figure 4]. This technique is convenient to approach zygomatic bone for fixture engagement when there is available alveolar bone height at premolar and molar, the situation is present when zygomatic fixture is done as a rescue to reinforce the ailing implant system present [Figure 5].

Figure 4

Extra-sinus approach with flap in conjunction with sinus pathology removal

Figure 5

Extra-sinus Approach as rescue implant

Full-thickness flap is reflected exposing the infra-orbital foramen and cresta zygomaticoalveolaris, the extend of the flap depends upon the unilateral or bilateral zygomatic fixture placement. When unilateral, releasing vertical incision is made at maxillary midline or at piriform aperture and distal to the 1st molar extending till posterior of the zygomatic bone. When bilateral zygomatic fixture is demanded releasing incision is made distal of zygomatic bone bilaterally keeping the horizontal incision palatal to alveolar crest, degloving incision is also an ideal choice. Flap reflection is kept conservative when compared to conventional zygomatic approach where till the lateral orbital rim is exposed. Premolar site is the point of purchase from the alveolar bone directed toward the Jugale region ideally for osteotomy. Either the slot is made at anterior wall of maxilla lateralizing the Schinederian membrane or the osteotomy is just parallel to the anterior wall of the maxilla depending upon the concavity of anterior wall, extent of resorbed maxillary alveolar bone or the exteriorized zygomatic bone in relation to maxilla. Point of purchase is kept at the palatal margin of the alveolar crest or 6 mm toward palatal bone depending upon the available alveolar bone height and the concavity of anterior maxillary wall. 6 mm inferior to cresta zygomaticoalveolaris osteotomy is made to extend till the posterior of lateral surface of Zygoma, drill is exteriorized and is felt on the finger kept at the lateral surface and at jugale region. Length of the implant is determined observing the marked dimension on the osteotomy drill, from the exteriorized point till the point of purchase. This 6 mm minimal rule is very important according to the author for a zygomatic fixture of 4.6 mm diameter otherwise the threads of the single-piece zygomatic fixture will slip toward the lateral surface of zygoma or the alveolar crest making the correction difficult later on. Ideal zygomatic fixture placement is when the abutment emergence is on the palatal aspect of alveolar crest and apically engaged at the Jugale region, after bending abutment is repositioned on the alveolar crest. Zygomatic fixture is placed with the insertion tool attached with handgrip till the desired length. Zygomatic fixture is exteriorized till 1 mm or is engaged till the border of zygomatic bone. This hold true for zygomatic implant placement in high atrophy postresection case [Figure 6]. It is advisable to lateralize the Schinederian membrane and maintain its patency but if the rupture happens, it is of less clinical significance provided flap closure is achieved.

Figure 6

Extra-sinus Approach for post resection cases

Trans-sinus approach

It is the least traumatic but high skill demanding approach as being flapless. This technique is inspired from the Branemark (1998) technique. The purchase point of the osteotomy at alveolar crest depends upon the extent of maxillary resorption, concavity of anterior maxilla, or the exteriorized zygoma in relation to the maxilla. With flat anterior wall and moderately resorbed maxilla, the flapless approach is the easiest, but in the case of severe maxillary resorption or with profound concavity of anterior maxilla, this approach is very skillful demanding [Figure 7]. Depending upon the extent of concave anterior maxilla or alveolar bone height available, point of osteotomy is at the palatal aspect of alveolar crest or toward the palatal bone; more the height and concavity more palatal is the point of osteotomy [Figure 8]. With transsinus technique, an operator always achieves the ideal engagement of zygomatic fixture at jugale or confluence of frontal and zygomatic process, the angulation achieved is almost perpendicular to the targeted bone by the fixture. Length of the zygomatic implant corresponds to the osteotomy drill marking from alveolar palatal crest to the exteriorized at zygomatic bone felt from the finger. It is important to note that any angulation <45° in relation to the palatal plane will lead the osteotomy drill slipping toward infratemporal fossa and vertically more than 50° will lead toward the orbit. When the osteotomy is done at or distal to upper 1st molar, it is more than 50° angulated vertically, and it reaches close or at orbital floor, thus the care is utmost. In ultra-resorbed maxilla, after zygomatic implant placed at one side its not advisable to bent the abutment till the contralateral side fixture is placed as when the abutment is upright, it interfere in the contralateral approach with the hand grip.

Figure 7

Figure presenting intra and extrasinus approach

Figure 8

Trans-sinus approach in high alveolar condition

When more than one zygomatic fixture is placed, always the anterior which is lengthier is placed first and should be engaged cranially at zygomatic bone so that the posterior is engaged inferior to anterior at zygomatic bone, the osteotomy approach is at least 6 mm distal to the anterior at alveolar crest or palatal aspect [Figure 9].

Figure 9

Flapless double zygomatic approach

It is advisable placement of zygomatic implant flapless with surgical guide, but the author believes more on the tactile perception and when the splint is at mucosal or bone level, a small change in orientation will lead the dramatic error in desired angulation leading to unwanted complication.

DISCUSSION

Immediate loading is the key and advantage with single-piece smooth surface implantology such as ZDI®. Delayed complications such as abutment screw loosening, abutment screw fracture, peri-implantitis, and palatal emergence of the abutment jeopardizing the prosthetic system are avoided with the technique. There is enough evidence and studies in support of immediate loading (Buser et al. 1988; Piatelli et al. 1993; Henry and Rosenberg 1994; Salama et al. 1995; Bijlani and Lozada 1996; Chiapasco et al. 1997; Tarnow et al. 1997; Randow et al. 1999; Scortecci 1999; Ericsson et al. 2003; Malo et al. 2000; and Ihde 2009; Shan et al. 2013).[2829] When primary stability is achieved and a proper prosthetic treatment plan is followed, immediate functional loading is a feasible concept. Clinically, the host bone density plays an important role in determining the predictability of the immediate loading success. Trabecular density of edentulous zygomatic is higher in the jugale region and consists of plate-like structure. Stresses caused by muscles are concentrated in the jugale region of edentulous zygomatic bone because of the adherence of the masseter muscles and fascia temporalis to zygomatic bone. Osteocytes in the bone matrix act as pressure sensors and that there is a pressure sensory network among osteocytes, osteoblast, and osteoclasts. The stress caused by the associated muscles prevents the generation of osteocytes and increases the activation of osteoblasts in the zygomatic bone of edentulous maxillae making it ideal for immediate loading for fixtures.[3031] The screw shape design of the single-piece ZDI® not only minimizes micromotion but also improves the initial stability, the principle requirement for immediate loading success. Primary stability can be enhanced when cross-arch implant splinting is performed and is recommended in immediate implant loading.[32333435363738] There seems to be sufficient evidence emerging to support a one-stage nonsubmerged protocol which can achieve success rate comparable to implants placed in two-staged submerged procedure.[3940414243] Osteotomy when made for zygomatic fixture with or without flap is devoid of irrigation. It has been shown that a temperature over 47°C for 1 min causes “heat necrosis” in the bone.[44] However, increasing both the speed and the load together allowed for more efficient cutting with no significant increase in the temperature.[45] Thus, the speed around 40 thousand rpm with 1:1 reduction handpiece is advisable for the cortical osteotomy.

The emergence of the smooth surface single-piece zygomatic fixture at palatal aspect does not create adverse tissue reaction, leading to mucositis, crestal bone loss, and peri-implantitis as thickness of the keratinized tissue is around 5 mm, in severe atrophic cases, the buccinator muscle attachment is present at the vestibular aspect. The supragingival abutment level is always advantageous. Biofilm is a micobial-derived sessile community, characterized by the cells that are irreversibly attached to a substratum or interface to each other, embedded in a matrix of extracellular polymeric substance produced by microbes. The biofilm attracts the plaque and so does the bacterial colonization that clinically manifests as reversible mucositis and irreversible peri implantitis which is one of the most common cause of osseointegrated surface treated implant failures and late complications.[46] The biological seal that is formed by the mucosa surrounding smooth surface dental implants is established to provide protection against the microbial invasion.[47] The trans-sinus implants placement does not lead to delayed postoperative complication. Immediate complication such as nasal bleeding, paresthesia, and burns of the skin or labial mucosa is manageable. Zhong et al.[48] in their study observed the direct attachment of sinus membrane to the implant, forming the barrier to the sinus cavity. Petruson[49] used sinuscopy of the maxillary sinuses of 14 patients with machined surface zygomatic implants, placed with no particular care regarding whether or not membrane disruption occurred and found no signs of adverse reactions. Petruson[49] concluded to have no increased risk of inflammatory reactions in the normal nasal and maxillary mucosa in the regions where titanium implant passes through the mucosa. The nitric oxide produced in the maxillary sinuses may therefore be another important explanation of why no infections are found around titanium implants.[505152]

It is assumed that the only stability of the zygomatic implant is derived from the zygomatic bone. The stress caused by occlusal forces is supported mainly through the zygoma. The stress from these forces is transferred predominantly through the infra-zygomatic crest and divided to the frontal and temporal process of the zygomatic bone. The remainder of the implant along with the abutment constitutes a considerable cantilever. These implants are never intend to be free-standing pillars, immediate, rigid, cross arch stabilization is recommended to prevent micromotion. Brunski[5354] and Meredith[55] suggested in their studies that cross arch stabilization with rigid splinting appears to effectively reduce mechanical stress on the implants by reducing their movement. Thus, the zygomatic implant when rigidly cross arch splinted with anterior and posterior implants such as premaxillary implants and pterygoids, effectively transfer the masticatory load to anterior and posterior implants and resisting lateral/offset loading.[38] Additional implants placement to avoid cantilever extension significantly lower the stress values.[5657] Posterior cantilever on implant prosthesis produce complications, including screw fractures, prosthesis fractures, bone loss, and loss of osseointegration.[58] Improving biomechanical stability and load distribution by means of noncantilevered, bone anchored restorations should enhance the long-term prognosis of implant restorations in the posterior maxilla.[5960] The rationale for placement of 8 or more implants to support a fixed complete arch prosthesis in the maxilla is supported by Kopp's analysis of various studies on implant restorative predictabilities.[61] Bahat recommended placement of a sufficient number of implants to support the occlusal load in a way that avoids nonaxial loading.[62]

One of the most serious and prevalent problems associated with the restorative aspect of dental implants is loosening and fracturing of the screws. McGlumphy et al.[63] defined the screw joint as two parts tightened together by a screw, such as an abutment and implant being held together by a screw. Screw preload, clamping force, joint-separating force, and settling effect are the factors maintaining the dynamics of screw connection. When the settling effect is greater than the elastic elongation of the screw, the screw work loses because there is no longer any contact to hold it in place. The initial surface roughness of the screw, surface hardness, and magnitude of loading forces (offset forces and cantilever situation) are the factors affecting the stability of the connection.[64] With single-piece implants such delayed complications can be avoided with cross arch fixation and maintaining strategic occlusion[38] [Figure 10].

Figure 10

Tripodization achieved from zygomatic fixture

There are surgical advantages to both the single-stage guided surgery and single-stage free hand approaches. The freehand techniques allow the ability to adjust or re-angle the osteotomy site based on what the surgeon encounters. In addition, the free-hand technique offers better firsthand visualization of the surgical site and the opportunity to alter bone or soft tissue while the mucosa is reflected when necessary.[65] Moon et al.[66] calculated the mean angular errors between the preoperative planned and postoperative placed implant was 3.84 ± 1.49 degree, Di Giacomo et al.[67] calculated an angular error of 7.25 ± 2.67 degrees. Particularly, for an angular error, the utilization of surgical guides as a tooth support was reported to result in a smaller angular error than that of bone support and a mucosa support. The longer implants such as zygomatic fixtures with such angular error may lead to apical deviation missing the intended anchorage site, the author prefer the free hand placement based on tactile perception rather than the computerized tomogram guided surgical guide, but it is the individual's preference based on the experience.

Single-piece implantology after wide spread diffusion in the second half of the last century saw its application significantly reduced by dental implantologists. The main reason of a progressive reduction was the Branemark concept of implant osseointegration, although now the most recent knowledge allows reducing the timing on implant loading.[68] Garbaccio,[16] Scortecci,[69] and Ihde[1829387071] with their work have successfully reestablished single-piece implantology. Awadalkreem et al.[72] have shown in their work patient's satisfaction with comfort, mastication, speech, and esthetics significantly improved with the new basal implants, single-piece smooth surface implants.

SUMMARY

Single piece zygomatic implant, or a remote anchorage implant, is an effective tool for rehabilitation of the atrophic/resected jaws with least postoperative complications such as screw loosening, screw fractures, bone loss, mucositis, and peri-implantitis. Zygomatic fixtures avoid the grafting procedures and cantilever situation, restoration of atrophic or postablative jaws are completed with immediate loading. The author has presented in this article simplified and practical free-hand approach for the implant placement in zygomatic bone which he has learned by improvising after each zygomatic implant surgery completed successfully. With respect to the advantages of the single-piece zygomatic implant discussed above, it has an effective role in resection cases rehabilitation and thus rightly termed as oncology implant.[73]

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.