An alternative method to treat a case with a severe maxillary ...
An alternative method to treat a case with a severe maxillary atrophy by theuse of tilted implants and a removable overdenture, instead of complicatedaugmentation procedures: a case report H.Bilhan*, M. Ateş*** Dr.med.dent., Istanbul University, Faculty of Dentistry, Department of Removable Prosthodontics, 2nd floor, 34390 Capa-Istanbul, Turkey** Prof. Dr. med.dent., Istanbul University, Faculty of Dentistry, Department of Removable Prosthodontics, 2nd floor, 34390 Capa-Istanbul, TurkeyCorespondence address:Dr. med.dent. Hakan Bilhan, Istanbul University, Faculty of Dentistry, Department ofRemovable Prosthodontics, 2nd floor, 34390 Capa-Istanbul, TurkeyFax: +90-212-525 35 85e-mail: email@example.comProf.Dr. Muzaffer Ateş Dr. Hakan Bilhan
An alternative method to treat a case with a severe maxillaryatrophy by the use of tilted implants and a removableoverdenture, instead of complicated augmentation procedures: acase report
AbstractBackground: Several treatment options with implants have been describedfor maxillary edentulous patients. Maxillary implant-supported overdentureshave been shown to be a predictable, accepted treatment option for theedentulous maxilla. Patients with severe bone resorption present additionaldifficulties and implant treatment in the atrophic maxilla represents achallenge. Methods: Anatomical limitations and patient desires in this casehas forced the treatment to be four tilted implants supporting an upperoverdenture. Since conventional single retention mechanisms such as ball(O-ring), locator or telescopes would transfer too much force to theimplants, especially due to their angulation, an individual bar wasfabricated. Results: One year follow-up of the case showed a stableperiimplant condition on bone as well as soft tissue level.Conclusions: Although further follow-up and higher case numbers will givemore information about this treatment modality, the actual result isencouraging and can be recommended for similar cases.Key Words: Tilted implants, severely atrophied maxilla, individual bar,implant overdenture, Marius Bridge
Introduction Several treatment options with implants have been described formaxillary edentulous patients. 1, 2, 3, 4, 5 Maxillary implant-supportedoverdentures have been shown to be a predictable, accepted treatmentoption for the edentulous maxilla. 6, 7 Patients with moderate to severe bone resorption and thin ridgespresent additional difficulties because of inadequate bone volume andmissing soft-tissue support, thus due to mechanical and anatomicdrawbacks, implant treatment in the atrophic maxilla represents achallenge. The maxillary sinus floor augmentation procedure is still notuniversally accepted because of its complexity and its unpredictability.Additionally, patients showing that kind of maxillary resorption aregenerally very old and poor in their health status. Serious and complexsurgical procedures could be contraindicated in these patients. Results of investigative studies indicate that the use of tiltedimplants is an effective and safe alternative to maxillary sinus flooraugmentation procedures, 8 because longer implants can be inserted inthis way. The use of reduced-diameter implants as an alternative to bonegrafting for treatment of patients with severely resorbed maxillae wasevaluated.9 As a conclusion implant anchorage without bone grafting wasshown to work well, alhough it is expected that patients with severelyresorbed maxillae have an increased risk of implant failure in comparisonto patients with good bone quantity and quality. In another study withpatients having severely resorbed maxillae bone grafting and implantplacement was compared to modified implant placement but no bonegrafting. The cumulative success rates were 83% in the graft group and96% in the trial group and a substantial reduction of the grafted bone,especially of the onlay grafts, occurred in many patients.10 According tothese results, modified implant placement, in our case tilted implantpositioning to be able to use longer implants, seems to be a predictabletherapy alternative.Case Description and Results A 63-year old female edentulous patient applied to the Departmentof Removable Dentures in the Dental School of Istanbul University withthe complaint of not being able to use any dentures because of strongchoke reflex. It was obvious that the only choice of treatment could be adenture without palatal coverage. Clinical and radiological assessment
showed a severely atrophied maxilla, with bilateral large sinuses and verylittle amount of bone, making a conventional implant planning impossible.After information and discussion about treatment alternatives, the patientrejected the sinus floor or any other augmentation procedures. The onlybone available for implantation was in the region of the premaxilla andtuber maxilla and even there limited in height. An overdenture attached to four implants and open palatal surfacewas planned. Because of lacking bone height, all four Astratech implantswith a TiO-blast surface were inserted in a tilted manner. Two implantswere inserted in the premaxillary region and one each in the tuber maxillaeregion bilaterally (figure 1). Implant number 22 was lost after 2 months andsubstituted with a new implant following a 6 week healing time (figure 2).This loss caused a delay of the prosthetic treatment. 8 months after the firstimplant insertion the first impressions were taken. Because of the variousimplant angulations, an open individualized tray was used for theimpression of the upper jaw. The impression tray borders were mouldedwith functional silicone (Bisico Fuction, Germany) and the final impressionwas taken with a high viscosity poliether impression material (Impregumsoft, Germany). Before removing the impression from the mouth, byopening the screws of the transfer posts, the open parts of the tray werestrenghtened by the use of a pattern resin (GC Pattern Resin, America) inorder to avoid even a slight movement of the posts, which would make themodel useless. Then the impression of the lower jaw was taken first withalginate and then with a custom tray by border moulding and ZnO Eugenolpaste. After wax rim try-in, determination of vertical dimension and centricrelation, a facebow recording was done. The tooth setup was done on thearticulator and then controlled in the patient. After correction of esthetic andfunctional determinants, the planning of the attachment system could bedone. Since we were convinced that conventional single retentionmechanisms such as ball (O-ring), locator or telescopes would transfer toomuch force to the implants, especially due to their angulation, an individualbar was fabricated. In this manner, the force applied for removal of thedenture was shared by the implants (figure 3). The bar try-in was passive and well-fitting (figure 4), so the denturewas finished and delivered to the patient (figure 5 & 6). The patient wasvery satisfied with the result.
The follow-up controls in the 6th (figure 7) and 12th months (figure 8)after denture insertion showed clinically and radiologically in comparison tothe beginning situation a stable situation around the implants. Clinicalmeasurements at control sessions included plaque score, gingival index,sulcus bleeding and pocket probing depth. Additionally, the occlusion,retention and stability of the dentures were examined. The implants wereevaluated following the success criteria of Albrektsson. 11 Mesial and distalmarginal bone levels were measured on panoramic radiographies.Discussion Patients seeking replacement of their upper denture with an implant-supported restoration are generally interested in a fixed restoration, but itis not always possible. Accompanying the loss of supporting alveolarstructure due to resorption, the lip support is lost and can only beprovided by a denture flange. Attempts to provide a fixed restoration canresult in compromises to oral hygiene based on designs with ridge laps.An alternative has been an overdenture prosthesis, which provides lipsupport but has extensions on to the palate, but still gives the patient thecomfort having a free palate. On the other hand, the amount of bone doesnot always allow to insert the necessary number of implants for fixedrestorations. Severely resorbed jaws provided with overdentures werereported as the most demanding cases. 12 The Marius bridge was developed as a fixed bridge alternativeoffering lip support that is removable by the patient for hygiene purposes,with no palatal extension beyond normal crown-alveolar contours. Thereduction or elimination of palatal coverage with maxillary implant-supported overdentures may be perceived as advantageous to patientsby providing greater comfort through reduction of tissue coverage. 13 TheMarius bridge is a complete-arch, double-structure prosthesis for maxillaethat is removable by the patient for oral hygiene. Satisfactory medium-term results of survival and patient satisfaction show that the Mariusbridge can be recommended for implant dentistry. The technique mayreduce the need for grafting, because it allows for longer implants to beplaced with improved bone anchorage and prostheses support. 14 An important disadvantage of the Marius Bridge seems to be thelacking support of the palatal gum tissue. It is shown that the uncoveringof the palate increases the forces transferred to the implants andespecially to the crestal bone. 13
Overdentures supported and retained by endosteal implants dependupon mechanical components to provide retention. In general, an implantis loaded via axial and horizontal forces. Besides this, moment loadingcan also occur.15 The clinician may be able to make empirical decisionson attachment selection, depending on the amount of retention desiredand the specific clinical situation,16 but the force transfer to the implantsshould always be respected. Different overdenture attachments are found to effect the stressdistribution in the maxillary bone surrounding the overdenture implants 17and for different loading locations, significant differences were foundamong the different overdenture attachment systems, 18 since everyattachment type has different retention characteristics. 19 Ball attachments are frequently described because of simplicity andlow cost, but retentive capacity of these components may be altered by alack of implant parallelism.20 Divergent implants in the maxilla can makerestoration with removable prosthetics difficult when the implants will notbe splinted with a superstructure. Attachments to be used with individualimplants require that the implants be within 10 degrees of divergence. 21Additionally, primary splinting of fixtures with bar attachments has provedto be clinically effective for overdentures on osseointegrated implants,because there is a tendency for better axial load sharing with bars. 22 Studies of maxillary overdentures supported by endosseousimplants often show a high implant failure rate.23 In a study, where allpatients who needed an overdenture and could only be provided with aminimum number of bilaterally-placed implants, the patients receivedeither a round 2-mm-diameter bar with clips or ball attachments as aretentive system. The cumulative implant survival rates after 7 years ofloading were 75.4% in the maxillae and 100% in the mandibles. Therewas no difference in implant survival rate between the attachmentsystems. Patients with implant losses were characterized by severelyresorbed maxillary ridges and inferior bone quality, together withunfavorable loading circumstances such as short implants combined withlong leverages. 24 For these reasons we have chosen to use longerimplants in spite of the lack of available bone, inserting them in angulatedposition. Additionally, we have chosen a retention system which will nottraumatize the implants during taking away or inserting the denture.
The results of an investigation showed that practically all implantlosses occurred during the first 2 years, whereupon a steady stateseemed to follow for up to 5 years after loading (25). We already know thatthe first year is the most critical one for implant failure and also for crestalbone resorption.26, 27, 28,29, 30, 31 This case showed in spite ofdisadvantageous loading conditions and poor bone quality and quantity astable situation around the implants. Although further follow-up and higher case numbers will give moreinformation about this treatment modality, the actual result is encouragingand can be recommended for similar cases.
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