Magnetic-cap over Mini-implant Abutment

        Applied in the U-shaped Maxillary Overdenture – Case Report

Chen, Tien-Kuan*, DDS

DDS, Kaohsiung Medical University, Taiwan

Chief, Roma Dental Clinic, Taichung Taiwan

Abstract::

Patients afraid of severe invasive implant surgery yet with less residual maxillary natural teeth sometimes choose overdentures as a way of rehabilitation and somehow magnetic abutments are considered as one way of supporting elements for retention. If the abutments of natural teeth are located ideally, an U-shaped maxillary denture base can be a comfortable choice instead of the one that covers the palatal side. However, if the arch is distally free end edentulous, the retention is going to be endangered and the denture base inevitably has to cover more so the U-shaped one may be given up. Mini-implants are generally less invasive due to small wounds, less bleeding, no suturing, and being often painless after surgery so that they are more acceptable for sensitive patients. But it is well known that mini-implants are not so stable as normal implants under the long term bite force. This one year followed case report is to demonstrate a design invented by Dr. Tien-Kuan Chen, the reporter of this case, to help form an U-shaped denture base for a distal edentulous maxilla. It is a simple magnetic-cap cemented to the head of a mini-implant put at the distal free end spot and serves as a magnetic abutment just as it is done by a natural tooth. Magnetic abutments are usually made short to get less horizontal forces, always as hazard forces, so that the abutments are less forced mobile and their lives are longer. If the major function of a mini-implant is merely as a magnetic abutment, it will gain the same benefits as well. In comparison with the traditional big size implants for maxillary rehabilitation, magnetic-cap over mini-implant abutments offer another simple option in ways of shorter treatment time, longer abutment lives, being less invasive and more acceptable by sensitive patients.



Chief complaint & clinical examination

The patient, 59-year-old female, complains of being forceless and painful on maxillary teeth as eating. She asks for the most non-invasive way to rebuild her maxillary teeth and no coverage of her palate if a movable denture is necessary. There is a long 14-units-in-one-piece porcelain crown-bridge with abutments of #17, 13, 23, 25 and 27 on maxilla and all mobile (from GI to GIII: #17- GIII, #13- GI, #23- GI, #25- GIII, #27- GII). From panoramic film it shows bone absorption around all maxillary tooth roots more or less.

               
fig. 01:maxillary right molar root exposure
fig. 02: gum swelling at maxillary left posterior buccal side
fig. 03:maxillary occlusal view shows a long 14-units-in-one-piece porcelain crown-bridge
fig. 04: The removed maxillary bridge shows severe inflammation around #17 (#27 crown is separated and still left inside the mouth for  vertical dimension taking. Later it will be cut short as well and transformed into a magnetic abutment.)
　

fig. 05: pre-treatment panoramic film, taken in April. 21. 2005



Treatment plan

An U-shaped magnetic overdenture for maxilla with natural teeth (#13, 23, 25, 27) as magnetic abutments and a magnetic-cap over mini-implant abutment put at the right distally edentulous site of maxilla itself



Treatment procedure (all in two weeks)


               
fig. 06: Natural teeth (#13, 23, 25, 27) as magnetic abutments and a magnetic-cap over mini-implant abutment put at the right distally     edentulous site of maxilla (Implant is set at approximately the original site of #16, but #17 is extracted meanwhile due to no bone support.)
fig. 07: the denture with magnets buried inside its tissue surface which possesses magnetic retention
fig. 08: the U-shaped magnetic overdenture for maxilla, tissue surface view
fig. 09: the U-shaped magnetic overdenture for maxilla, occlusal surface view

               
fig. 10: the U-shaped magnetic overdenture on maxilla
fig. 11: central occlusion, right side view
fig. 12: central occlusion,left side view
fig. 13: central occlusion, frontal view
　

           
fig. 14: natural smiling
fig. 15: natural big smiling
fig. 16: rest expression
fig. 17: laugh brightly
　

fig. 18: post-treatment panoramic film, taken in May. 5. 2005

　

Magnetic-cap over mini-implant abutment design & placement

（Fig.19-24 demonstrated are from the other patient.）


           
fig. 19: mini-implant with carved concave square head, 10 mm in length, 1.8 mm in diameter
fig. 20: mini-implant put inside maxillary alveolar bone directly and photographed instantaneously; small wound, no suturing, and almost     no bleeding all the way
fig. 21: magnetic-cap, magnetic surface


           

fig. 22: magnetic-cap, cement surface with a major hole and multiple smaller holes inside
fig. 23: filling cement into the cement hole of the magnetic-cap
fig. 24: magnetic-cap cemented to the head of the mini-implant put at maxilla for immediate loading

         
fig. 25 : a widened chamber for the magnetic-cap in tissue surface of the denture to avoid horizontal hazard force as eating



fig. 26: remove the adjacent resin a little bit around the magnetic-cap to avoid horizontal hazard force as eating

After fourteen months from the delivery day

◎ Chief impression from the patient
Rather good in condition, easy to eat, the denture in stable position while eating, satisfied of the appearance as talking and laughing, more convenient to take care of oral hygiene then the


◎ Clinical examination

           
fig. 27: stable U-shaped maxillary denture in oral cavity
fig. 28:magnets in good shape
fig. 29: magnetic power check separately for every single magnet, all good


       

fig. 30: all magnetic-caps and roots in good condition, no inflammation and no
mobility（except for #25 in GI mobility, but better then it was in GIII mobility 14 months ago）
fig. 31: satisfied of the appearance by the patient as talking
fig. 32: satisfied of the appearance by the patient as laughing
　

           
fig. 33: The magnetic-cap of the mini-implant abutment gets well combined to the gingiva of the ridge and no inflammation is found. In the past 14 months, it was just roughly brushed for 30 seconds two times a day by the electrical tooth brush, and no dental flossing was done for itself.

fig. 34: The panoramic film taken in Aug. 4. 2006 shows the bone around the maxillary roots stops getting worse. Moreover, the bone around the mini-implant is getting denser then it was 14 months ago (fig.18) which indicates this mini-implant is going to have a stable future in the oral cavity and ensures the U-shaped maxillary denture base can be maintained.



Discussion & Conclusion

1. An overdenture presses both on alveolar bone and residual roots. If residual roots get reduced to keep a tiny space from the tissue surface of the denture and also able to supply retention, the overdenture is going to be steadier as eating and gets a longer life because the residual roots get no harm from the occlusal force. Magnets can release their attractive power to magnetic metals from distance and instantaneously not to be touched by the metals themselves. A magnetic overdenture uses magnetic abutments for retention and the abutments can be designed as no touch to the denture, therefore better stability and a longer life are both gained

2. Mini-implants are now regularly applied in orthodontic treatment and generally get good results. They provide long term maintained small forces to shorten the treatment time yet seldom get themselves lost from oral cavities. It shows generally the long time stand under small forces is acceptable by alveolar bone even it is done by a mini-implant. In this case report, the magnetic-cap over mini-implant abutment only executes the magnetic power to the denture but gets fewer forces as eating. Horizontally, the magnetic-cap chamber of the denture is widened (fig. 25 & 26) to avoid the grinding force of eating, usually a hazard force. Vertically, the magnetic-cap chamber base is reduced a very little bit (fig.35,36& 26) to avoid sudden hard forces while chopping. In this way, there is no apparent force to threaten the abutment and it will easily stay well in the oral cavity for a long time.

fig.35: The vertical cushion between the magnet and magnetic-cap can be done by a piece of tinfoil when a magnet is set into the denture.
fig.36: Then remove the tinfoil sticker from the magnet to create a cushion space.

3. Traditionally, an implant needs time to get integration with bone around so no early loading is helpful. This kind of long time waiting is not adored by patients so immediate loading implant techniques are advanced but they are also challenged by hard force damages in the early time after implant surgeries. Magnetic-cap over mini-implant abutments, as the above-mentioned, get little forces as biting so they integrate more easily with bone even when they are loaded immediately by the magnetic power after being implanted. This design, therefore, reduces the possibility of failure and saves more time for patients.

4. Clinically, there are some sensitive patients who are afraid of or even subjectively refuse invasive treatments. In some cases, the patients complain of constantly dropping of their upper complete dentures as talking because of gravity but actually it is due to severe absorption of the alveolar ridges of complete maxillae. Magnetic-cap over mini-implant abutments, under such circumstances, are more smoothly accepted by patients themselves to help rebuild their maxillary occlusions according to small wounds, no suturing, less bleeding, and being painless after surgeries in comparison with normal big size implant ones. Furthermore, this design may help form an U-shaped maxillary denture base in a fast and easy way for patients who have less or even no teeth left. Consequently, suffering from poor retention and less sense of taste due to the maxillary complete denture with a big base are both no longer annoying problems.

　

References

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