An alternative method to treat a case with a severe maxillary atrophy by the

use of tilted implants and a removable overdenture, instead of complicated

augmentation 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, Turkey

Corespondence address:

Dr. med.dent. Hakan Bilhan, Istanbul University, Faculty of Dentistry, Department of

Removable Prosthodontics, 2nd floor, 34390 Capa-Istanbul, Turkey

Fax: +90-212-525 35 85

e-mail: bilhan@istanbul.edu.tr

Prof.Dr. Muzaffer Ateş Dr. Hakan Bilhan

An alternative method to treat a case with a severe maxillary

atrophy by the use of tilted implants and a removable

overdenture, instead of complicated augmentation procedures: a

case report

Abstract

Background: Several treatment options with implants have been described

for maxillary edentulous patients. Maxillary implant-supported overdentures

have been shown to be a predictable, accepted treatment option for the

edentulous maxilla. Patients with severe bone resorption present additional

difficulties and implant treatment in the atrophic maxilla represents a

challenge. Methods: Anatomical limitations and patient desires in this case

has forced the treatment to be four tilted implants supporting an upper

overdenture. Since conventional single retention mechanisms such as ball

(O-ring), locator or telescopes would transfer too much force to the

implants, especially due to their angulation, an individual bar was

fabricated. Results: One year follow-up of the case showed a stable

periimplant condition on bone as well as soft tissue level.

Conclusions: Although further follow-up and higher case numbers will give

more information about this treatment modality, the actual result is

encouraging 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 for

maxillary edentulous patients. 1, 2, 3, 4, 5 Maxillary implant-supported

overdentures have been shown to be a predictable, accepted treatment

option for the edentulous maxilla. 6, 7

Patients with moderate to severe bone resorption and thin ridges

present additional difficulties because of inadequate bone volume and

missing soft-tissue support, thus due to mechanical and anatomic

drawbacks, implant treatment in the atrophic maxilla represents a

challenge. The maxillary sinus floor augmentation procedure is still not

universally accepted because of its complexity and its unpredictability.

Additionally, patients showing that kind of maxillary resorption are

generally very old and poor in their health status. Serious and complex

surgical procedures could be contraindicated in these patients.

Results of investigative studies indicate that the use of tilted

implants is an effective and safe alternative to maxillary sinus floor

augmentation procedures, 8 because longer implants can be inserted in

this way. The use of reduced-diameter implants as an alternative to bone

grafting for treatment of patients with severely resorbed maxillae was

evaluated.9 As a conclusion implant anchorage without bone grafting was

shown to work well, alhough it is expected that patients with severely

resorbed maxillae have an increased risk of implant failure in comparison

to patients with good bone quantity and quality. In another study with

patients having severely resorbed maxillae bone grafting and implant

placement was compared to modified implant placement but no bone

grafting. The cumulative success rates were 83% in the graft group and

96% in the trial group and a substantial reduction of the grafted bone,

especially of the onlay grafts, occurred in many patients.10 According to

these results, modified implant placement, in our case tilted implant

positioning to be able to use longer implants, seems to be a predictable

therapy alternative.

Case Description and Results

A 63-year old female edentulous patient applied to the Department

of Removable Dentures in the Dental School of Istanbul University with

the complaint of not being able to use any dentures because of strong

choke reflex. It was obvious that the only choice of treatment could be a

denture without palatal coverage. Clinical and radiological assessment

showed a severely atrophied maxilla, with bilateral large sinuses and very

little amount of bone, making a conventional implant planning impossible.

After information and discussion about treatment alternatives, the patient

rejected the sinus floor or any other augmentation procedures. The only

bone available for implantation was in the region of the premaxilla and

tuber maxilla and even there limited in height.

An overdenture attached to four implants and open palatal surface

was planned. Because of lacking bone height, all four Astratech implants

with a TiO-blast surface were inserted in a tilted manner. Two implants

were inserted in the premaxillary region and one each in the tuber maxillae

region bilaterally (figure 1). Implant number 22 was lost after 2 months and

substituted 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 first

implant insertion the first impressions were taken. Because of the various

implant angulations, an open individualized tray was used for the

impression of the upper jaw. The impression tray borders were moulded

with functional silicone (Bisico Fuction, Germany) and the final impression

was taken with a high viscosity poliether impression material (Impregum

soft, Germany). Before removing the impression from the mouth, by

opening the screws of the transfer posts, the open parts of the tray were

strenghtened by the use of a pattern resin (GC Pattern Resin, America) in

order to avoid even a slight movement of the posts, which would make the

model useless. Then the impression of the lower jaw was taken first with

alginate and then with a custom tray by border moulding and ZnO Eugenol

paste. After wax rim try-in, determination of vertical dimension and centric

relation, a facebow recording was done. The tooth setup was done on the

articulator and then controlled in the patient. After correction of esthetic and

functional determinants, the planning of the attachment system could be

done. Since we were convinced that conventional single retention

mechanisms such as ball (O-ring), locator or telescopes would transfer too

much force to the implants, especially due to their angulation, an individual

bar was fabricated. In this manner, the force applied for removal of the

denture was shared by the implants (figure 3).

The bar try-in was passive and well-fitting (figure 4), so the denture

was finished and delivered to the patient (figure 5 & 6). The patient was

very 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 to

the beginning situation a stable situation around the implants. Clinical

measurements 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 were

evaluated following the success criteria of Albrektsson. 11 Mesial and distal

marginal 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 it

is not always possible. Accompanying the loss of supporting alveolar

structure due to resorption, the lip support is lost and can only be

provided by a denture flange. Attempts to provide a fixed restoration can

result in compromises to oral hygiene based on designs with ridge laps.

An alternative has been an overdenture prosthesis, which provides lip

support but has extensions on to the palate, but still gives the patient the

comfort having a free palate. On the other hand, the amount of bone does

not always allow to insert the necessary number of implants for fixed

restorations. Severely resorbed jaws provided with overdentures were

reported as the most demanding cases. 12

The Marius bridge was developed as a fixed bridge alternative

offering lip support that is removable by the patient for hygiene purposes,

with no palatal extension beyond normal crown-alveolar contours. The

reduction or elimination of palatal coverage with maxillary implant-

supported overdentures may be perceived as advantageous to patients

by providing greater comfort through reduction of tissue coverage. 13 The

Marius bridge is a complete-arch, double-structure prosthesis for maxillae

that is removable by the patient for oral hygiene. Satisfactory medium-

term results of survival and patient satisfaction show that the Marius

bridge can be recommended for implant dentistry. The technique may

reduce the need for grafting, because it allows for longer implants to be

placed with improved bone anchorage and prostheses support. 14

An important disadvantage of the Marius Bridge seems to be the

lacking support of the palatal gum tissue. It is shown that the uncovering

of the palate increases the forces transferred to the implants and

especially to the crestal bone. 13

Overdentures supported and retained by endosteal implants depend

upon mechanical components to provide retention. In general, an implant

is loaded via axial and horizontal forces. Besides this, moment loading

can also occur.15 The clinician may be able to make empirical decisions

on attachment selection, depending on the amount of retention desired

and the specific clinical situation,16 but the force transfer to the implants

should always be respected.

Different overdenture attachments are found to effect the stress

distribution in the maxillary bone surrounding the overdenture implants 17

and for different loading locations, significant differences were found

among the different overdenture attachment systems, 18 since every

attachment type has different retention characteristics. 19

Ball attachments are frequently described because of simplicity and

low cost, but retentive capacity of these components may be altered by a

lack of implant parallelism.20 Divergent implants in the maxilla can make

restoration with removable prosthetics difficult when the implants will not

be splinted with a superstructure. Attachments to be used with individual

implants require that the implants be within 10 degrees of divergence. 21

Additionally, primary splinting of fixtures with bar attachments has proved

to 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 endosseous

implants often show a high implant failure rate.23 In a study, where all

patients who needed an overdenture and could only be provided with a

minimum number of bilaterally-placed implants, the patients received

either a round 2-mm-diameter bar with clips or ball attachments as a

retentive system. The cumulative implant survival rates after 7 years of

loading were 75.4% in the maxillae and 100% in the mandibles. There

was no difference in implant survival rate between the attachment

systems. Patients with implant losses were characterized by severely

resorbed maxillary ridges and inferior bone quality, together with

unfavorable loading circumstances such as short implants combined with

long leverages. 24 For these reasons we have chosen to use longer

implants in spite of the lack of available bone, inserting them in angulated

position. Additionally, we have chosen a retention system which will not

traumatize the implants during taking away or inserting the denture.

The results of an investigation showed that practically all implant

losses occurred during the first 2 years, whereupon a steady state

seemed to follow for up to 5 years after loading (25). We already know that

the first year is the most critical one for implant failure and also for crestal

bone resorption.26, 27, 28,29, 30, 31 This case showed in spite of

disadvantageous loading conditions and poor bone quality and quantity a

stable situation around the implants.

Although further follow-up and higher case numbers will give more

information about this treatment modality, the actual result is encouraging

and can be recommended for similar cases.

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Legend of Figures:

Figure 1: The implants introrally with healing abutments

Figure 2: Radiographic view of mouth after implant insertion

Figure 3: Try-in of the individual bar

Figure 4: The metal framework and bar

Figure 5: The finished denture

Figure 6: The denture in place

Figure 7: Radiographic view after 6th months

Figure 8: Radiographic view after 12th months

Fig 1

Fig 2

Fig 3

Fig 4

Fig 5

Fig 6

Fig 7

Fig 8