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Overcoming Pneumatization of the maxillary sinus |
by Sam Lee Introduction Due to pneumatization of the maxillary sinus, poor bone quality and quantity, treatment of posterior edentulism has been and continues to remain a challenge for dental physicians. Traditionally, these obstacles are overcome by bone condensing and grafting into the maxillary sinus beneath the Schneiderian membrane.1-18 Bone grafting into the sinus has produced predictable results enabling clinicians to place longer implants for more stable prostheses and better long term outcomes.3 Although final outcomes have proved satisfactory, sinus augmentation via lateral window grafting procedures produces substantial patient morbidity.5-7, 15, 17, 18 Because this technique involves flap elevation beyond the mucogingival junction, bruising, swelling, and pain are common postoperative complications.5-7, 15, 17, 18 An additional intraoperative complication associated with this procedure may arise from the laceration of the intraosseous branch of posterior superior artery (branch of maxillary artery).15 Finally, the technique sensitive nature of the lateral window approach carries a risk of Schneiderian membrane perforation during window preparation and membrane elevation. In an attempt to forgo the risks and complications of lateral window sinus augmentation, a number of internal (crestal) approaches to have been introduced such as osteotome5-7, reamers17, tapping drills18, piezoelectric, ISM17, and HSC.15 With most of these internal techniques for sinus augmentation, poor visibility during manipulation of the Schneiderian membrane remains a problem. While a great solution for the premolar region, use of standard diameter implants (4.0mm) in the molar region has limitations such as poor emergence profile, implant fracture, and crestal bone strain.19-21 Large platform diameter implants may overcome poor bone quality by increasing bone to implant surface contact in addition to producing superior emergence profile.21 Use of such implants in molar areas may also decrease fracture risk, crestal bone stress, and allows fabrication of a natural occlusal table.20 The purpose of this paper is to describe an innovative surgical technique that combines a crestal internal sinus lift with use of wide diameter implants. Description of Surgical Technique Flap Elevation Incision design that is at least 2mm palatal to desired implant position and flap elevation that does not extend beyond the mucogingival junction is recommended (figure 1). This incision design allows for minimal pain, unilateral flap retraction, the option of doing one or two stage implant placement without losing keratinised tissue, and the ability to treat oral antral communications in case of excessive Schneiderian membrane perforation. Location of Crestal Window When performing this technique, the lowest point of the maxillary sinus should be located by means of radiographic or cone-beam/ct options (see arrow in figure 2). It is most favorable when this position coincides with implant position. If implant placement at sites #2, 3, and 4 are anticipated with site #3 being the lowest point in the maxillary sinus floor, site #3 should be used to lift the sinus membrane. Crestal Window Preparation and Membrane Lift To perform the crestal internal sinus lift, a round window is made on the crestal bone with a set of specially designed trephine burs that have a diameter 1 mm less than the final implant size. For example, if a 6mm implant is anticipated, a 4.0mm (inner diameter) x 5.0mm (outer diameter) trephine is used. Unlike the conventional trephine techniques that require 700-1000 rpm with ample irrigation, this technique utilises lower speeds of 40-50 rpm without irrigation and is referred to as a ‘Waterless technique.’ The waterless technique has the advantage of not washing away autogenous bone filings during bone manipulation, thus allowing the surgeon to collect an increased amount of autogenous bone. Conventional trephining with precision is often challenging due to skipping or drifting of the trephine during initial bone cutting. To minimise this complication and maximise visualisation and precision of the trephine bur, a ‘pointed trephine’ is used at a speed of 50 rpm without irrigation (figure 3)... Read more 
Figure 1: Incision design that is at least 2mm palatal to desired implant position and flap elevation that does not extend beyond the mucogingival junction is recommended |  Figure 2: the lowest point of the maxillary sinus should be located by means of radiographic or conebeam/ct options | 
Figure 3: To minimize this complication and maximize visualization and precision of the trephine bur, a ‘pointed trephine’ is used at a speed of 50 rpm without irrigation |
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Harry Shiers writes about how we can stabilize complete mandibular or complete maxillary dentures
Treatment with conventional complete dentures has been shown to be reasonably successful when: The residual alveolar ridges are favorable The dentures have been well made The patient is reasonably philosophical about wearing dentures. (Fenlon et al (2000) Comm Dent Oral Epidemiology 28: 133-140)
Treatment has not been successful, however, when: The ridges are very resorbed and even well made dentures have poor support and stability Movement of dentures results in discomfort pain and ulceration Dentures are not tolerated because of emotional reasons or a strong gag reflex A single denture has poor stability because of opposing natural teeth. The worst combination is remaining maxillary teeth opposing a mandibular denture on a severely resorbed residual ridge.
How often do we see patients with unstable complete mandibular dentures? To some, they are a social embarrassment, provide difficulty with mastication, represent ageing and interfere with phonetics. There are recognised criteria for treating patients with implant-retained dentures: When the patient has experience of wearing complete denturesuntroubled for many years, but loss of residual bone or neuromuscular control limits retention of the dentures resulting in movement of one or both dentures Where a fixed prosthesis cannot compensate for the resorbed bone (and associated support) to give a satisfactory appearance Where remaining teeth have unfavorable distribution for support and retention of removable partial dentures.
Click on each thumbnail in order to view larger image.           Solutions These problems may be overcome by the use of implants to support, stabilize and retain dentures. In the mandible, the use of two implants placed in the intra-mental foramina area has been shown to be satisfactory in a multitude of studies. In the maxilla, the evidence is four implants should be used and the superstructure joined, usually by a bar between the abutments. The prosthodontic components for implant retained complete dentures vary for different implant systems but essentially there are similar methods for attaching the denture to the implants. - Ball attachments
- Bars that may be: a) ovoid, and, b) round
- Magnets
The attachments are often one-piece units that are screwed directly into the head of the implant. There is a tool associated with each implant system that allows for placement and tightening of the over-denture abutment. For the dentist who has referred out the surgery, restoring the patient with implant retained complete dentures is relatively straightforward. One can take an impression at the head of the implants or – once the appropriate abutments have been selected – an impression can be made at this level using custom-made trays, having made primary impressions in alginate. The ball abutements act as the male and the female parts are located in the fit surface of the denture. These are provided by the manufacturer and take the form of small metal adjustable spring loaded rings (flanged), which may be placed by the laboratory or picked up in the mouth using cold cure acrylic.
 Harry RBP Shiers BDS, MSc (implantdentistry), MGDS, MFDS, took his initial training in implants in 1989 with the Straumann Institute. He spent a year teaching undergraduates at The London Dental Hospital and since then has spent a year at the Eastman Dental Institute studying implants prior to completing the two-year part-time Master of Science in implant dentistry at Guy’s Hospital London. He currently runs the Harcourt House Implant Referral Centre in the west end of London where he places implants for referring GDPs.
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