Hiroki  Ii  Private Practice, Saitama, Japan,Member of the Japan Prosthodontic Society and Japan Denture Association

A retrospective study of risk factors for suction effective mandibular complete dentures

CONCLUSIONThe results of this study suggest that careful examination and assessment of the following 6 risk factors are important for achieving mandibular complete denture suction. 1) Severely resorbed or flat alveolar ridge 2) Poor-quality or reduced amount of lingual spongy tissue 3) Inadequate retromylohyoid fossa space 4) Irregular shape of the retromolar pad 5) Strong tongue retraction during mouth opening 6) Unstable occlusion

DISCUSSIONAll 6 factors analyzed in this study were significantly correlated with suction failure. The results suggest that extremely unfavorable conditions in any one of the 6 factors may lead to the loss of border seal, making it difficult to obtain the suction effect of mandibular complete dentures.

INTRODUCTIONThe concept of eliminating the problem of denture lifting by creating an effective seal around the entire border of the denture base through suction mechanism has been spreading worldwide. This concept, developed by Jiro Abe in Japan, enhances the suction effect of mandibular complete dentures and allows for denture suction even in patients with advanced resorption of the mandibular alveolar ridge. However, mandibular complete denture suction is not always successful. It is therefore important to identify factors inhibiting denture suction in order to improve predictability of mandibular complete denture treatment.

OBJECTIVETo identify factors affecting suction and stability of mandibular complete dentures fabricated based on the suction concept established by Dr. J Abe in 1999.

MATERIALS AND METHODSA retrospective study was conducted to investigate the association between the success of denture suction and 6 potential risk factors for denture suction. The study included mandibular complete dentures fabricated between 2007 and 2014 by 13 dentists for 99 patients with fully edentulous maxillae and mandibles and 10 patients with fully edentulous mandibles. Successful denture suction (Suction) was defined as no denture dislodgement from the alveolar ridge when 11N of forward traction force was applied in the midline parallel to the occlusal plane, and suction failure (Non-suction) as denture dislodgement with the force application.

Suction Effective Mandibular Complete Dentures (SEMCDs)

The seal is broken when air leaks. The absolute requirement for successful mandibular complete denture suction is to seal all borders of the denture base without any air-leaking spot. This can be achieved through fabrication of mandibular complete dentures based on the aforementioned suction concept.

OR 95%Cl of OR p-valueLower Upper

Advanced bone resorption 16.3 5.2 51.1 < 0.001Insufficient spongy tissue in sublingual fold spongy tissue in the sublingual fold

22.2 4.9 101.9 < 0.001Insufficient retromylohyoid fossa space 16.5 5.2 52.1 < 0.001Irregular shape of retromolar pad 10.0 3.5 28.8 < 0.001Strong tongue retraction during mouth opening 59 4.6 750.4 < 0.001Unstable occlusion 8.6 3.1 24.2 < 0.001

SuctionNon Suction

Success rate of

suction

0255075100

Sufficient Insufficient

0255075100

Favorable Unfavorable0255075100

Slight Moderate Strong0255075100

Stable Unstable

SuctionNon-suction

Shape of retromolar pad Tongue retraction during

mouth opening Occlusal stability

Extent of bone resorption

ACP Class

93.5%

0255075100

Type Ⅰ,Ⅱ Type Ⅲ,Ⅳn=77 n=32

93.5 %

46.9 %

Amount of spongy tissue

in sublingual fold

0255075100

Sufficient Insufficientn=62 n=47

Volume

*p<0.001

96.8 %

57.4 %

Retromylohyoid fossa

space

RESULTSThe success rate of denture suction was significantly lower under unfavorable conditions for all 6 factors studied. The overall success rate of mandibular complete denture suction was 79.8%.

35.0 %

89.9 %

n=62 n=47

* * *

* * *

n=89 n=20 n=62 n=4 n=75 n=34

89.4 %

45.8 %

52.9 %

90.7 %

95.1%

65.1%

25.0%

n=43

REFERENCES1)Abe J, Kokubo K, Sato K. Mandibular suction-effective denture and BPS : a complete guide. Tokyo : Quintessence Publishing Co Inc, 2012. 2) Ichikawa M. A report on positioning of the denture base outline of lower complete dentures from experiments measuring the traction required to separate the denture base from the alveolar ridge :The Journal of The Academy of Clinical Dentistry Vol.32(2012)No.1-2p.57-64

SEMCDs

Investigated risk factors extent of alveolar ridge resorption (Fig 1), amount of spongy tissue in the sublingual fold region (Fig 2), retromylohyoid fossa space (Fig 3), shape of the retromolar pad (Fig 4), tongue retraction during mouth opening (Fig 5), and occlusal stability (Fig 6).

Fig1 Fig2 Fig3 Fig4 Fig5 Fig6