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Zygomatic Implants For The Rehabilitation Of The Severely Atrophic Maxilla A Case Series


November 20, 2015
by Peter Gioulos, DDS, MSc, FRCD(C); Allan Vescan, MD, MSc, FRCD(C); Steven Bongard, DDS

ABSTRACT:
Implant rehabilitation of the severely atrophic maxilla presents a surgical and prosthetic challenge to even the most experienced clinician. The “graft-less” approach with the use of zygomatic implants is gaining acceptance. The purpose of this case series is to present the successful protocols employed in our Toronto clinic for the management of severe maxillary atrophy using a graft-less approach.


INTRODUCTION
Implant restoration of missing teeth has become common place in North America and the developed world. Standard (alveolar) implant placement and restoration are now a part of most dental specialties and some general dental training programs. Treatment of the majority of implant cases is now considered routine. However, the presence of atrophy of the alveolar ridge often requires hard and/or soft tissue augmentation, which can reduce case acceptance and complicate management. Rehabilitation of the severely atrophic fully edentulous maxilla can present a significant challenge to even the most experienced clinician. The purpose of this case series is to present the successful protocols employed in our Toronto clinic for the management of severe maxillary atrophy using a “graft-less” approach.

There is no denying the need for sound protocols in managing this patient population. While the incidence of complete edentulism is on the decline [Slade et al., 2014], this medical burden remains significant. In 2010, the prevalence of U.S. edentulism was projected at 12.2 million and future projected prevalence of edentulism for the U.S. population by 2050 is 8.6 million adults [Slade et al., 2014].

Those with edentulism are and should be considered amputees. The dental amputee possesses a unique problem: ongoing and progressive loss of anatomy due to the process of residual ridge resorption (RRR). This catabolic change in the alveolus that occurs subsequent to tooth loss has been well described and classified (Nakamato, 1968; Atwood, 1971; Lekholm & Zarb, 1985; Cawood and Howell, 1988; Farina et al., 2011). Bone changes associated with RRR are most significant within the first three to six months, (Atwood, 1963; Schropp et al., 2003; Farina and Trombelli, 2011). Unfortunately, RRR continues indefinitely. These dimensional changes seem to be dependent on number of extrinsic (smoking, number of teeth removed) and intrinsic (location in the mouth, individual) factors (Saldanha et al., 2006; Farina and Trombelli, 2011; Pramstraller et al., 2011; Pietrokovski, 1975; Schropp et. al., 2003). The most widely used classifications systems for alveolar atrophy are those of Lekholm & Zarb (1985) and Cawood & Howell (1988). In our clinic, we classify individuals using clinical and radiographic evaluation and stratify patients based on the latter (Fig. 1) along with the “zones of the maxilla” classification system (Bedrossian, 2011; Fig. 2).

FIGURE 1. Classification of Residual Ridge (from Cawood & Howell, 1988): Class I: dentate. Class II: immediately post extraction. Class III: well-rounded ridge form, adequate in height and width. Class IV: knife-edge ridge form, adequate in height and inadequate in width. Class V: flat ridge form, inadequate in height and width. Class VI: depressed ridge form, with some basilar loss evident.


 

 

 

 

 

 

 

 

 

 

 

 

FIGURE 2.Classification of Bone Volumes in the Maxilla (adapted from Bedrossian, 2011): Red lines indicate sinus floor/anterior wall and nasal floor/lateral wall. Zone 1: Intercanine Region. Zone 2: Premolar Region. Zone 3: Molar Region.

FIGURE 2.Classification of Bone Volumes in the Maxilla (adapted from Bedrossian, 2011): Red lines indicate sinus floor/anterior wall and nasal floor/lateral wall. Zone 1: Intercanine Region. Zone 2: Premolar Region. Zone 3: Molar Region.

Fixed implant-supported rehabilitation of the maxillary arch must take into account prosthetic and surgical considerations. In this type of solution, the support, stability, and retention of the prosthetic is provided solely by the implant fixtures. When implants are placed soon after dental extraction and early in the resorptive phase, the need for grafting can be reduced, if not eliminated. Classically, longstanding edentulism of the maxilla was associated with the need for staged rehabilitation involving extensive autogenous grafting and placement of eight or more implants. More recently long-term predictability has been shown with a minimum of four implant fixtures when rehabilitating the completely edentulous maxilla with a fixed prosthetic (Maló et al., 2011). When planning implant placement, it is of particular importance to ensure fixture placement allows for control and management (reduction but not necessarily elimination) of the prosthetic cantilever forces (Krekmanov et al., 2000). Posterior alveolar atrophy with pneumatisation of the maxillary sinus often limits the ability to spread implant placement posteriorly. Proposed options for implant placement in the presence of maxillary alveolar atrophy include the use of short and/or narrow implants (Maló et al., 2015), reconstruction (Clayman, 2006; Chiapasco et al., 2007; De Santis et al., 2012; Pieri et al., 2012) or a graft-less approach utilizing tilted alveolar implants or specialized / basilar bone implant placement such as zygomatic (Brånemark et al, 2004; Malo et al., 2014; Maló et al., 2015) or pterygoid (Graves, 1994; Balshi et al., 2013; Curi et al., 2015) implants. Rather than reconstruct resorbed alveolar bone, zygomatic and pterygoid implants anchor into local craniofacial bone. This graft-less approach proceeds to anaplastically replace the composite (dental, hard and soft tissue) defect. To date, there is no direct randomized trial to evaluate the options available. However, when assessing the literature individually, zygomatic implants have a level of predictability in the short- and long-term comparable with that of staged reconstruction with delayed standard (alveolar) implant placement. When taking into account the benefits of immediate function and return to esthetics, comfort, reduced morbidity, and reduced cost, zygomatic implant placement is the preferred approach for these authors when faced with inadequate bone volumes for alveolar implant placement in the completely edentulous individual.

The patient workup includes a complete medical history, clinical evaluation (intra- and extra-oral), and radiographic evaluation. The radiograph of choice is the orthopantomogram (OPG), which serves as a screening image. When the degree of horizontal atrophy is in question, or when zygomatic implant placement is planned, a cone-beam CT (CBCT) is considered mandatory. For individuals that will require zygomatic implant placement, the evaluation and screening of the sinuses for pathology is critical. Any indication of sinus pathology (on history, clinically, or radiographically) must initiate a referral to an Otolaryngology – Head & Neck Surgeon and management of the osteomeatal complex must be completed prior to proceeding with zygomatic implant placement.

Proper management of severe maxillary atrophy requires a highly skilled team with open communication and a close working relationship. Our team is comprised of an oral and maxillofacial surgeon, otolaryngologist, restorative dental practitioner and laboratory technician. When compared to alveolar implants, the surgical skill involved in the placement of zygomatic implants requires a high level of understanding of the local anatomy and specialized surgical training. While risks with zygomatic implant placement are uncommon, should one develop it can carry significant consequence for the patient. Risks described can occur intraoperatively (surgical misadventure into the orbit or infratemporal fossa, bleeding, labial laceration, poor primary stability, zygomatic fracture), and postoperatively (hematoma, paresthesia, pain and tenderness to palpation, sinusitis, dehiscence/thread exposure, oral-antral fistula, implant failure, zygomatic-cutaneous fistula, zygomatic implant fracture (Aparicio et al., 2012).

In our clinic, individuals with inadequate bone volume for standard implant placement are managed using one of three graft-less techniques: 1) the angled (“All-on-4”®) implant technique; 2) a combination of two to four anterior alveolar implants with a single zygomatic and/or pterygoid implant placement in the posterior region; or 3) four zygomatic implants alone (“Quad Zygoma”). Below we outline the treatment of three patients that have undergone zygomatic implant placement in our clinic.

Case #1:
Placement of a unilateral zygomatic implant in addition to alveolar and pterygoid implants to replace a terminal dentition
A 67-year-old non-smoking female presented seeking options to restore her maxillary and mandibular arches. The medical history was significant for hypothyroidism, rheumatoid arthritis and depression. Daily medications included Synthroid, Wellbutrin as well as vitamin supplements (vitamin D, calcium and magnesium). Clinical and radiographic examination confirmed a terminal dentition with moderate to severe generalized horizontal bone loss (Figs. 3 and 4). The remaining maxillary alveolus displayed advanced horizontal and vertical atrophy. More detailed radiographic imaging with CBCT (Figs. 5 and 6) confirmed advanced atrophy with Cawood & Howell class VI at the posterior and Cawood & Howell class III at the anterior maxilla. The maxillary sinus displayed bilateral pneumatisation and significant anterior extension. There was inadequate zone 2 and 3 bone for standard implant placement. The osteomeatal complex appeared unobstructed (Fig. 7) and, with the exception of mucosal thickening (Fig. 5), no other significant sinus pathology was noted. The patient was presented with the treatment options and elected to proceed with an implant supported maxillary and mandibular fixed prosthesis. The patient was given a preoperative prescription for Amoxicillin 500mg (q8h for 8 days, beginning 1 day prior to surgery), Chlorhexidine oral rinse (0.12%, BID, rinse for 60 sec., NPO for ½ hour after) and Naproxen (250mg q12h for five days, beginning two hours prior to surgery). Under IV sedation and local anaesthetic, all remaining maxillary and mandibular teeth were extracted. Four standard implants (Nobel Biocare®, NobelSpeedy™, Regular Platform) were placed in the mandible following the angled (All-on-4®) implant technique. In the maxilla two standard implants were immediately positioned in the anterior region (Nobel Biocare®, NobelSpeedy™, Regular Platform) and the left pterygoid plate (Nobel Biocare®, NobelActive™, Regular Platform). In the right maxilla a zygomatic implant (Nobel Biocare®, Brånemark System® Zygoma, TiUnite™ surface) was placed. All implants achieved an initial insertion torque of more than 35 Ncm. Multi-unit abutments (Nobel Biocare®) were selected and positioned and torqued to manufacturer recommendations. An all-acrylic transitional full arch prosthesis consisting of 12 teeth was immediately secured onto the abutments and the implants were immediate loaded with a fixed prosthesis. The transitional prosthesis was maintained for the duration of the healing phase (six months). A modified soft diet was recommended during this period. ISQ (Osstell) measurements were taken at time of placement and at follow-up. After six months, integration was confirmed clinically, radiographically, and with ISQ. The final titanium-reinforced acrylic profile prosthetic was fabricated and inserted (Figs. 8 and 9). Continued follow-up occurs at six-month intervals.

FIGURE 3. Preoperative Clinical Photograph: Retracted frontal view.

 

 

 

 

 

 

 

FIGURE 4. Preoperative Orthopantomogram (OPG): Advanced generalized periodontal bone loss and maxillary sinus pneumatisation with signficant anterior extension displayed.

 

FIGURE 5. Preoperative cone-beam CT (CBCT) — Coronal View: Coronal view at the level of the frist molar. Blue arrow identifies minmal mucosal thickening.

 


 

FIGURE 6. Preoperative cone-beam CT (CBCT) — Tangential View: Tangential view at the level of the central-lateral incisor.

 

FIGURE 7. Preoperative cone-beam CT (CBCT) – Coronal View of Osteomeatal Complex: Patent osteomeatal complex noted with blue arrows.

 

FIGURE 8. Postoperative Orthopantomogram (OPG): Taken at the time of delivery of the final prosthesis. Note titanum milled bar within the prosthesis.

 

FIGURE 9. Final Prosthesis: Frontal high-smile view.


Case #2:

Placement of 4 Zygomatic Implants (“Quad-Zygoma”) in a patient with complete maxillary edentulism
A 64-year-old non-smoking female presented seeking treatment for her edentulous maxillary arch with the expectation for a fixed prosthesis. The mandibular arch was previously restored with a removable partial denture. Her medical history was significant for controlled diabetes (type II), hypertension, irritable bowel syndrome, osteoarthritis, chronic pain and depression. Daily medications include Pantoprazole, Decetel, Domperidone, Oxycodone, Ramipril, Ezetrol, Metformin, Trazadone, Celebrex, Lactulose and Cymbalta. Clinical and radiographic (OPG and CBCT) evaluation revealed advanced acquired maxillary atrophy with bilateral maxillary sinus pneumatisation (Figs. 10, 11 and 12). Classification for this patient was (Cawood & Howell VI) in the anterior and (Cawood & Howell V) in the posterior maxilla with inadequate zone 1, 2, or 3 bone (Bedrossian, 2011) for alveolar implant placement. The anterior maxillary residual ridge had developed idiopathic hyperplasia due to combination syndrome. The osteomeatal complex was patent and no other sig sinus pathology was noted. The patient was given a preoperative prescription for Amoxicillin 500mg (q8h for eight days, beginning one-day prior to surgery) and Chlorhexidine oral rinse (0.12%, BID, rinse for 60 sec., NPO for ½ hour after). Surgical treatment took place under deep intravenous sedation with administration of local anaesthesia. Due to the lack of anterior maxillary bone volume, four zygomatic implants (Nobel Biocare®, Brånemark System® Zygoma, TiUnite™ surface) were placed. Implant placement followed the ZAGA (Aparicio, 2011) technique (Fig. 13). In this particular case, platelet-rich fibrin (PRF) was placed on the exposed threads (Boora et al., 2015) (Fig. 14). The incision location allowed for a flap design that maintains a labial cuff of keratinized mucosa (Figs. 13 and 15). Primary tissue closure was achieved with 3-0 chromic gut suture. All implants obtained an initial insertion torque of more than 45 Ncm. Fixtures were fitted with zygomatic multi-unit abutments (Nobel Biocare®). An OPG was taken once the patient was stable (Fig. 16) to ensure full seating of the zygomatic multi-unit abutments. An all-acrylic transitional full arch prosthesis consisting of 12 teeth was immediately secured onto the abutments (Figs. 17 and 18) and the implants were placed in immediate load with a fixed prosthesis. A soft diet was recommended during the healing period. At two weeks, the patient returned for follow-up where tissues and the prosthesis were evaluated and a T-scan (Tekscan, Inc.) was used for occlusal equilibration (Fig. 19). A soft tissue complication of dehiscence of the suture line was noted at the two-week re-evaluation. This was resolved with the suture re-approximation. No further complications have occurred to date.


FIGURE 10. Preoperative Worms-Eye View: Advanced atrophy evidenced by the position of the incisive papilla on labial surface of residual ridge.

 

FIGURE 11. Preoperative Orthopantomogram (OPG): Inadequate bone volume in zones 1, 2 & 3.

 

FIGURE 12. Preoperative cone-beam CT (CBCT)–Coronal view: Section is at the level of the first molar. Advanced alveolar atrophy is noted (Cawood & Howell VI). There is no noted sinus pathology.



FIGURE 13. Intraoperative Photograph: Placement of zygomatic implant fixtures displayed. The palatal tissue has been repositioned. Note that the zygomatic multi-unit abutments and temporary cylinders have been placed.

 

FIGURE 14. Application of Platelet Rich Fibrin (PRF): Intraoperative photograph displaying use of platelet rich fibrin (PRF) to overlay exposed zygomatic implant threads. Note the visible zygomatic multi-unit abutments.

 

FIGURE 15. Placement of “Comfort Caps”: Intraoperative photograph displaying buccal keratinized cuff of tissue. Comfort caps (Nobel Biocare®) are present on the zygomatic multi-unit abutments (Nobel Biocare®, not visible in this view).

 

FIGURE 16. Postoperative Orthopantomogram (OPG): Four maxillary zygomatic implants (“Quad Zygoma”) placed.



FIGURE 17. Occlusal Surface of Fixed Transitional Prosthetic: The screw access holes are in ideal location (on the palatal of the occlusal table). Note: the second molar was removed prior to delivery.

 

 

FIGURE 18. Intaglio Surface of Fixed Transitional Prosthetic: High polish tissue surface noted.

 

 

FIGURE 19. T-scan (Tekscan, Inc.): Occlusal equilibration at two weeks postoperatively.

FIGURE 19. T-scan (Tekscan, Inc.): Occlusal equilibration at two weeks postoperatively.

Case #3:
Placement of four zygomatic implants to replace failing implant-supported maxillary full arch prosthesis
A 63-year-old non-smoking female presented with a late failure of a full arch prosthesis using the angled (All-on-4®) implant technique. The medical history was significant for Hypothyroid, Lymphedema, and ADHD. Medications included Thyroxin and Adderall. Clinical Evaluation revealed three failed maxillary implants. Radiographic analysis (OPG and CBCT) confirmed a severely atrophic maxillary anterior and posterior ridge (Cawood & Howell class IV anterior and class VI posterior) with inadequate bone in zones 1, 2 and 3 (Bedrossian, 2011) for alveolar implant placement (Figs. 20 and 21). The failed implants had caused significant destruction of the remaining alveolus in the premaxilla (Fig. 21). Possible pathology was noted in the right maxillary sinus (Fig. 22). The osteomeatal complex appeared unobstructed. Consultation with an Otolaryngologist was arranged preoperatively and no preparatory treatment was indicated. The patient was given a preoperative prescription for Clavulin 500mg (q8h for 8 days, beginning one-day prior to surgery) and Chlorhexidine oral rinse (0.12%, BID, rinse for 60 sec., NPO for half-hour after). Surgical treatment took place under deep intravenous sedation with administration of local anaesthesia. The three existing maxillary implants were removed and four zygomatic implants (Nobel Biocare®, Brånemark System® Zygoma, TiUnite™ surface) were placed following the ZAGA (Aparicio, 2011) technique (Figure 23). Flap design and suturing were done at the labial aspect to preserve keratinized mucosa. All implants achieved an initial insertion torque of more than 35 Ncm and were fitted with zygomatic multi-unit abutments (Nobel Biocare®). An all-acrylic transitional full arch prosthesis consisting of 12 teeth was immediately secured onto these implants for the patient to wear during the healing phase. A modified soft diet was recommended during the six-month healing period. Evaluation at three months shows excellent soft tissue adaptation (Fig. 23).

FIGURE 20. Preoperative Orthopantomogram (OPG): Late failure of the maxillary fixed prosthesis.

 

 

FIGURE 21. Preoperative Cone-beam CT: Sagittal view: Blue arrow indicates alveolar defect from previous failed implant.

 

FIGURE 22. Preoperative cone-beam CT (CBCT): Coronal view displays opacification of the right maxillary sinus (blue arrow) indicating mucosal thickening or sinusitis. The osteomeatal complex seems patent.

FIGURE 22. Preoperative cone-beam CT (CBCT): Coronal view displays opacification of the right maxillary sinus (blue arrow) indicating mucosal thickening or sinusitis. The osteomeatal complex seems patent.


FIGURE 23. Postoperative Orthopantomogram (OPG): Four zygomatic Implants shown.

 

FIGURE 24. 3-Month Postoperative Photograph: Favourable implant position and soft tissue. Note maintenance of keratinized tissue on labial/buccal aspect of the multiunit abutment. Minor irritation in the anterior second quadrant was due to food impaction.

 

CONCLUSION:
To date, we have managed 42 patients with a total of 80 zygomatic implants. Our experiences have been favorable. More importantly our patients report a high level of satisfaction. Prosthetic success rates are 100 percent. Complications encountered include: dehiscence (4%), oral antral fistula (2.5%), sinusitis (2.5%) and implant failure (1.3%).
The use of zygomatic implants for the rehabilitation of complete and partial maxillary edentulism is a predictable treatment modality with minimal morbidity. The execution, however, requires a multi-disciplined team and a high level of surgical and prosthetic expertise.OH


 

Dr. Peter Gioulos is a board certified Oral & Maxillofacial Surgeon practicing in two private practice clinics: Crescent Oral Surgery (Richmond Hill, Aurora & Toronto; www.crescentoralsurgery.com) and Chrysalis Dental Centre (Toronto; www.ChrysalisCanada.com). He maintains a hospital appointment at Rouge Valley Health System–Centenary Site. While he practices the full scope of his specialty, his clinical focus is immediate implant placement and restoration and zygomatic implant placement.

Dr. Allan Vescan is a board certified Otolaryngology — Head and Neck Surgeon with subspecialty expertise in Rhinology and Skull Base Surgery. He practices at Mount Sinai Hospital, University Health Network — Toronto Western Site and Centric Health — Don Mills Surgical Center. He received his Medical Doctorate (MD) in 2001 from the University of Western Ontario, followed by the completion of his Otolaryngology residency program in 2006 from the University of Toronto. He received his Oncologic Skull Base Fellowship from the University of Pittsburgh in 2007. He also holds a Master’s of Science from the Institute of Medical Science, University of Toronto.

Dr. Steven Bongard obtained his DDS degree from The University of Toronto Faculty of Dentistry in 1986. He is the founder and clinical head of Chrysalis Dental Centres in Toronto Canada (www.ChrysalisCanada.com) and United Smiles Centres in London UK (www.unitedsmilecentres.co.uk) both of which are implant only facilities focused on “same day” dental implant solutions. Dr. Bongard has extensive experience in implant placement, bone grafting procedures, as well as the prosthetic component of implant restoration. He has published and lectured both nationally and internationally on implant placement, All-on-4®, “Guided” implant surgery, single tooth, and alternative implant solutions. Clinically, his recent focus has been on developing innovative implant solutions for predictable same-day treatment of the severely atrophic edentulous patient.
Oral Health welcomes this original article.

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