5^th Consensus on Treatment Modalities and Corrective Interventions with Basal Dental Implants in Connection with the Maxillary Sinus.

(Version 2, July 2015)

Foreword

The human body consists of bones, soft tissues and liquids. Inside the body between those  three constituents no permanent empty space is left. Only in the oral cavity and in the respiratory system  we find such permanent spaces. Even there the tendency to fill those spaces with various soft tissues is observed.

Definition

Lateral basal jaw implants transmit masticatory forces into the cortical bone below and above horizontal rings or disk-plates.
Basal screw implants (e.g. bicortical screw, BCS) belong to the group of basal implants if they are anchored in the 2nd or 3rd cortical and into resorption-free bone areas.

Active biological “osseo-integration” along the vertical axis of the implants is not essential for the functioning of these implants.

This consensus relates only to basal implants with fully polished/machined surfaces, even though combination implants are mentioned and defined in this consensus.

Scope of use

Lateral basal implants require splinting through a bar or a fixed bridge. Secondary splinting through a removeable denture and e.g. telescopic crowns is contra-indicated.

Introduction

Treatments with dental implants in the space which is pre-operatively occupied by the «Maxillary Sinus» are frequently performed today.
In general three different treatment strategies are used if a reduced amount of  vertical bone between the crestal cortical of the distal maxilla and the basal cortical of the sinus is given:

• «Sinus-Lift»-Operations include an opening of the vestibular wall of the maxillary sinus, the lifting of the schneiderian membrane, and the interposition of bone substitute material between the Schneiderian Membrane and the bony floor of the sinus.

This operation may be performed at the same time when dental implants are placed, or as a separate intervention. If the intervention is performed without simultaneous implant placement, the waiting time between the «sinus-lift» operation and installation of conventional implant is between 3 and 5 months. Typically 2-stage implants are used after sinus-lifts, i.e. large-diameter implants with rough endosseous surfaces.

• As an alternative to «sinus-lifts» with bone stubstitute material, also a bone-block interposition is possible. This variant of treatment must be considered to have higher invasiveness, because it requires harvesting of a bone block and this leads to additional risks and morbidity at the donor site. Installing  implants simultaneously with the graft procedure is state of the art today, however immediate loading is typically not possible, in order to avoid immediate post-operative penetration of implant parts into the oral cavity. Typically 2-stage implants are used for this purpose, i.e. large-diameter implants with rough endosseous surfaces.
• Placement of conventional dental implants with rough surface into the maxillary sinus leads in many cases to a local polyposis and may trigger a generalized granulation or polyposis within the maxillary sinus. This polyposis may not have clinical effects, it may remain unnoticed.
• The usage of basal implants has offered in the last decades an alternative to conventional dental implantology. The protocol of this treatment requires purely cortical anchorage of implants in the corticals («2nd corticals», «3rd corticals»), and one of these corticals may be the bony floor of the maxillary sinus.  Basal implants feature a thin and polished core and apical retention areas, they are one-piece (single-stage) designs, and they require basal cortical anchorage. The implants are osseo-fixated trans-cortically.

In past years a strong shift towards avoiding  «sinus-lift» treatments  and to immediate-loading protocols have been observed and this has changed dental implantology. Patients do not tolerate unnecessary bone augmentations. They are typically not ready to bear a the long «healing»/treatment time, additional risks and the additional costs. 

Classification of basal implants and consequences for a trans-cortical therapy with basal implants

For the questions raised here, it is important  to differentiate between three designs:

• Lateral basal implants  (e.g. BOI, Diskos, Diskimplant) undergo a dual modus of integration. Hence woven bone formation is necessary inside the  vertical and horizontal cortical slots. If any infection should prevent this formation of woven bone, the integration of the implant into the cortical will presumably be prevented and unwanted fibrous integration occurs. Hence installation of these designs into or through maxillary sinuses holding a chronic, proliferative or acute infection is contra-indicated. Therefore pre-operative diagnosis of the status of the maxillary sinus is mandatory and eventual problems must be solved later when implants are installed.
• Screwable basal implants (e.g. BCS, GBC) and combination implants are trans-cortically osseofixated and no woven bone formation or even any response of the cortical nor the spongeous bone is necessary or desired. Therefore,- provided that retrograde influx of pus into the osteotomy is prevented, such implants may be used in cases, where a thickening of the Schneiderian Membrane, polyposis, granulation, and other soft tissue proliferation within the maxillary sinus are diagnosed[1].

Morbidity and Therapy in connection with the Maxillary Sinus

The prevalence of problems with the maxillary sinus in the population is significant, however in many cases symptoms are passing, they stem from nasal infections, and may be treated without surgical intervention. If the symptoms from the maxillary sinus  persist and influence the quality of life of the patients significantly, a surgical revision of the maxillary sinus is the therapy of the first choice. Today open sinus revisions («Caldwell Luc», carried out in different techniques) and revisions with access through the nose (closed technique, carried out with endoscopes incl. a variety of  accessory instruments for dissection and removal of the contents) are performed.

• Aims of the Caldwell-Luc procedure  is the removal of the undesired contents of the sinus (residual filling materials, root filling materials, roots, mucocelae, cysts, polyps, incurable mucosa alterations, disease in the anterior ethmoid or frontal sinus, resistant organisms, maxillary osteitis [2]) and establishing of a continious ventilation in the maxillary sinus, either through the hiatus semilunaris or through artificial communication between the nose and the maxillary sinus.
• Aim of endoscopic therapy through the nose is an enlarging of the natural ostium and the removal of uncinate process, thereby creating optimum ventilation and allowing  gradual self-healing.
• As an alternative an additional opening in the lower pathway of the nose towards the maxillary sinus may be created. These additional openings have a strong tendency to close by themselve. It has been reported, that such additional openings may lead to circulation between both openings without creating ventilation for the rest of the maxillary sinus.

Which precautions are necessary if the dental implant treatment plan includes installation of cortical implants in the basal or palatal/lateral corticals of the maxillary sinus?

There is a broad variety of possible impairment of the patient`s health through infections in the maxillary sinus:

• a considerable percentage of the population show clinically signs of a recurrent infection of  the maxillary sinus (e.g. every autumn/winter and in spring due to allergic effects of super-infected allergies).  Treatment is usually done through antibiotics and local ointments to prevent swelling. A significant number of patients will not decide on a surgical revision of the situation,  as long as their QOL is not affected signifficantly by a recurrent or permanent infection.  
• During the exacerbations the Schneiderian Membrane appears to be thickened and the lumen of the maxillary sinus may be partially or totally filled.  
• The total thickness of the Schneiderian Membrane is usually  less than 12 mm. Thicker membranes indicate presence of polyposis. The swelling of intra-sinusal soft tissue may obstruct the natural ostium and the maxillary sinus may fill with pus.

Installation of 2-stage dental implants inside the maxillary sinus (except Summers-sinus-lift, open sinus-lifts)  in the acute phase of the infection must be avoided.

Particles from dental treatments (fillings, root-canal filling materials, roots, endodontic instruments or parts of them) are frequently found inside the maxillary sinus. They are then encapsulated by granulation tissue and this tissue persists over years, typically for ever. Without (radical) surgical intervention it cannot be expected that the Schneiderian Membrane will shrink or the polyposis will heal.

Are there maxillary sinus-related absolute contra-indications for placement of basal implant?

Experience has shown that a surgical revision of  the maxillary sinus (i.e. Caldwell Luc; or an enlarging of the natural ostium) are successful and may be performed at any time later if the necessity occurs. Hence the implant installation can take place even in these slightly unfavourable pre-conditions with screwable basal implants or combination designs. Care must be taken not to position rough implant surfaces trans-cortically into the maxillary sinus becasue this may trigger a retro-grade peri-implantits.

The patient should be informed that the treatment rationale for traditional screwable basal implants and combination designs differs from the approach for 2-stage-implants for good reasons and that not all (future) treatment providers know about the above mentioned specifics.

It is known that many patients would rather live with recurrent or even chronic infections of the maxillary sinus and that they want to avoid the operation. As in the case of  screwable basal implant-installation eventual problems inside the maxillary sinus are to be considered to be separate, they presumably have nothing to do with the implants, and granulations, polyposis and soft tissue alterations can be treated without taking the implants out. It is considered unethical to deny basal implant treatment in the upper jaw to this group of patients only because they refuse surgery of the maxillary sinus.

Is the mobility of a basal dental implant an indication for the removal of the implant, if the implant is in connection with the Maxillary Sinus?

Cortically anchored dental implants are routinely placed into the lower/basal cortical of the maxillary sinus and therefore automtically a part of the implant, the apex and often also a part of the tread, are inside the maxillary sinus.  The same situation is found after orthopaedic or trauma surgery.

Mobility of conventional crestal implants with rough endosseous surfaces and large diameter of their body is typically a clear indication for their removal, because the surface of the implant may allow propagation of intra-oral bacterial into the sinus, and because re-osseo-integration of the implant is unlikely. Such implants will not participate in load transmission.
Likewise the development of bony craters around the apex of the implant (i.e. signs of a retro-grade peri-implantits, diagnosed on CT or on other radiographic pictures) indicates that  its removal is necessary. It may be difficult to differentiate between a retro-grade peri-implantitis and a natural, post-operative expansion of the maxillary sinus as a result of osteonal remodelling.

For basal implants implants in general the «Konsensus on BOI»  (1999[3], 2006[4], 2015iii) should be considered to determine the necessity of implant removal.  Lateral mobility and rotation of a basal implant are no indications for removal. Vertical mobility indicated, that the removal may be necessary.
The decision for removal of an implant is easier to take if no prosthetic workpieces are mounted (cemented). It seems problematic, that treatment providers tend to remove implants without indication after they have removed the bridge. They do this probably in order not to have to admit that the removal of the bridge was not indicated.

Trained basal implantologists get specific training during their product-specific, post-graduate education. Therefore decisions in critical treatment phases should be left to them, rather than to traditional implantologists or to laryngologists.

Method of immediate Implant placement  of lateral basal implants in case of purulent infections in the maxillary sinus

Patients with known recurrent or chronic infections of the maxillary sinus should be advised to cure this disease prior to implant placement or simultaneously. It is difficult to asses if this treatment was really done, or done in an adequate way, or if the treatment will be successful on medium and long term.

The placement of large and rough 2-stage-implants into the  maxillary sinus (incl. penetration of the Schneiderian Membrane and without sinus-lift) is contra-indicated if recurrent or chronic infections of the maxillary sinus are present or known.

Radical approach

• If lateral basal implants are used for equipping the distal maxilly an a trans-sinusal approach, the simultaneous radical operation of the maxillary sinus is the method of the first choice. As an alternative endoscopic surgery may be performed well before the placement of the implants and the result of this intervention (i.e. the normalisation of the intra-sinusal soft-tissues, absence of pus, good ventilation) must be controlled.
  
  It should be considered that  all remnants from dental therapy (root filling materials,  fillings, roots, instruments) may support a chronic infection even if the maxillary sinus is sufficiently ventilated.
• If  a radical intervention is chosen, the treatment plan aims at the removal of the cause of the problem. Hence through a lateral access (Caldwell Luc) all affected soft tissues (granulations, polyposis, remnants of dental therapy) are removed completely and  in addition a sufficient ventilation through the natural ostium is established. This ventilation is one of the central aims of the intervention. Immediately after this the lateral basal implants are placed. The hole (surgical defect) in the vestibular sinus wall is closed with the help of a titanium net. This therapy is done under antibiotic protection (i.e. Dalacin, Avelox) and additionally local disinfectants are used (i.e. Betadine).  

Conservative approach

• A more conservative approach is possible if screwable basal implants and combination designs are installed.
• The procedure includes trans-cortical osseo-fixation under local disinfection coverage (i.e. Betadine).  As problems within the maxillary sinus are not treated through this therapy (except for  a minimal instillation of Betaline 5% into the cavity), the recurrent or chronic maxillary sinusitis will persist in many the cases.
• Should this disease exacerbate later on, surgical therapy must be discussed with  the patient once again. In this case the therapy of the 1st choice is however either
  • the endoscopic enlarging of the natural ostium under endoscopic control or
  • the preparation of an additional opening towards the maxillary sinus on the lower pathway of the nose.

d.) Both therapies do not include the removal of eventual remnants of dental therapy,   however they will allow ventilation and drainage, and in approx 95% of the cases the disease will heal within 2-6 weeks without any further therapy.

e.) Whichever therapy is chosen the basal implants will not be affected through an intervention aiming  at the intra-sinusal soft tissues.  Integrated or rigidly osseo-fixated polished implants are not considered to be the cause of the problem unless other findings (like i.e.retro-grade peri-implantitis on CT-scans or x-rays or vertical mobility of the implants) is identified.

If the conservative approach is chosen, the patient must  be informed in detail about eventual future treatment necessary regarding the maxillary sinus, and that ENT-specalist may not be aware about the different dental implant treatment modalities and specifics of basal implant therapy.

Consequences of potential Expansion of the Maxillary Sinus

Throughout life the maxillary sinuses show a tendency to increase in size. This process of atrophy must be considered to be a result of Wolff`s Law which stated, that bone optimizes its shape and its volume and reacts to function.
In the area of the lower maxillary sinus this process is described traditionally as «sinusal expansion» . Any surgery in this region potentially triggers a new wave of remodelling and resorption of the bone with the result that the maxillary sinus «expands» even more. Hence we have to expect that post implantation more atrophy occurs and that this may even lead to a state where the basal border of the maxillary sinus expands so much, that the former trans-cortically installed threads of the screwable basal implants are not in contact with the basal cortical  of the maxillary sinus (2nd  cortical) any more. Hence these implants do not participate any more in the load transmission. They may be removed (without removing the bridge) or screwed backwards into the cortical (if the bridge can be taken out or prosthetics allows this).

Technique, use of systemic antibiotics and local disinfectants

When the implant-path for the installation of trans-cortical implants is drilled out, care must be taken to avoid displacing  loose bone particles into the maxillary sinus.  Rinsing the intra-osseous path with Betadine 5% prior to implant placement is as useful step.

The use of systemic (i.e. oral) antibiotics as a prophylactic precaution in combination with implant placements is up untill today not a proven method of increasing implant success or preventing inflammation within the maxillary sinus.

In traumatology and orthopaedic surgery local disinfectants  (i.e. Betadine) are used routinely to prevent local infection. This strategy is recommended for the work with basal jaw implants also.

Conclusion

• The indication for surgery on  or within the maxillary sinus stems from the maxillary sinus itself or from remnants of dental therapy inside the cavity.
• Placement of screwable basal dental implants  with trans-cortical osseo-fixation in the cortical walls of the maxillary sinus is a state-of-the-art treatment, even if iside the maxillary sinus on or several of the following pathologies is/are given:
• Thickening of Schneiderian mebrane
• Polyposis
• Mucocelae
• Residual parts of filling and root-filling material
• Before lateral basal implants may be placed trans-sinusally, the maxillary sinus must be proven to be non-infected and granulation, polyposis and remnants must be absent. Removal of granulations, polyps, mucocelae, cysts and remnants of dental implant therapy or remnants of endodontic therapy is performed through a Caldwell-Luc approach, often simultaneously with new (basal) implant placement. Also this radical approach is state-of-the-art.
• Placement of conventional  2-stage dental implants (large diameter, rough endosseous surface in the apical/transcortical region of the implant) in connection with the maxillary sinus in patients with recurrent, chronic or acute infections within the maxillary sinus is contra-indicated.