Preventive prosthodontics: Maxillary denture fracture

John B. Farmer, D.M.D.* Fort Hood, Tex.

T he patient’s first complete denture experience is predominantly with the single maxillary denture. The opposing mandibular dentition is usually intact or restored by fixed partial dentures or removable partial dentures. In many instances no attempt has been made to restore a partially edentulous mandibular arch.

One of the most common prosthodontic failures encountered is the fracture and failure of the single maxillary denture (Figs. 1 and 2). This often results in continuous repair of the denture. Often, remaking the denture is the best course to follow. This article will describe the clinically related causes of maxillary complete denture fracture and propose preventive and corrective measures.

LITERATURE REVIEW

Several techniques for making single dentures have been described in the literature.lb5 These include the functionally generated path technique as well as those using centric jaw relation records and lateral and/or protrusive records. Regardless of the technique, if attention is not paid to detail, fracture and failure of the denture may occur.

Maxillary denture midline fracture has been related to deformation of the denture base during function, thereby resulting in a flexural fatique failure.6,7 Clini- cal factors related to single denture failure include: (1) improperly contoured mandibular occlusal plane, (2) high frenum attachments, (3) occlusal scheme, (4) occlusal forces, (5) the denture foundation, and (6) denture base thickness.

IMPROPERLY CONTOURED MANDIBULAR OCCLUSAL PLANE

Several authors have related the importance of restoring the occlusal plane. Ellinger et al.3 recom-

The opinions and assertions herein are those of the author and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense.

*Lieutenant Colonel, DC, USA; Chief, Removable Prosthodontics, General Dentistry Residency Program.

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Fig. 1. Maxillary denture fracture originating in mid- line labial notch region.

Fig. 2. Fracture extends through palate of denture.

mended recontouring the natural teeth to obtain an occlusal plane favorable to a maxillary denture with a balanced occlusal scheme. This includes reducing occlusal inclines by contouring to obtain shallow cusp height and narrowing the buccolingual width of the teeth. They state that the most common error in single denture construction is failure to modify the occlusal plane.

Bruce4 states that the remaining mandibular second and third molars may cause the maxillary denture to slide forward. He recommends extraction of these teeth. Bruce also recommends reshaping or crowning

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MAXILLARY DENTURE FRACTURE

Fig. 3. Mandibular occlusal plane should be con- toured to eliminate extruded cusps or incisal edges that interfere with obtaining a harmonious occlusal plane.

kig. 5. klbrotlc trenum attachments near crest or ridge interfere with an effective retentive seal. Patient had been unable to wear previous maxillary dentures. After buccal and labial frenectomies, a satisfactory denture was constructed.

Fig. 4. Attachment of maxillary labial frenum in close approximation to ridge crest results in a labial notch and subsequent weak point in maxillary labial flange. A frenectomy will eliminate this problem.

the mandibular teeth to obtain a favorable occlusal plane.

Yurkstas5 felt that modification of the existing denti- tion in relation to the foundation plane is necessary to seat rather than dislodge the dentures. Stephen? stated that “of necessity the form of the occlusal surface is influenced by the natural teeth which oppose it.” He recommends reshaping of supraerupted or tilted teeth with sharp cusps to reduce unfavorable incline planes, which would dislodge the denture anteriorly as the mandible occluded with the maxillary denture.

The reshaping and, if necessary, crowning of the mandibular dentition or replacement of missing poste- rior teeth with a removable partial denture to obtain an optimum stabiliz.ing occlusion is a prerequisite to a successful maxill.ary denture (Fig. 3).

Fig. 6. A prominent midpalatal suture line or a torus provides a fulcrum for irritation, denture instability, and subsequent fractures. Minimal relief or tori removal may be necessary.

HIGH FRENUM ATTACHMENTS

High frenum attachments result in a subsequent weak point and/or potential fracture line in the denture base. Many denture fractures are a direct result of malocclusion in combination with a maxillary denture with a deep labial notch resulting from a high frenum attachment (Figs. 4 and 5). Maxillary labial and buccal frenum attachments that closely approxi- mate or attach to the edentulous ridge crest also interfere with a satisfactory retentive seal of the maxillary denture. A labial frenectomy is recom- mended for all such patients requiring maxillary complete dentures. If possible, this can be accomplished in conjunction with the fabrication of an immediate denture.

Additional anatomic factors that, in combination

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Fig. 7. A maxillary complete denture should have no centric stops anteriorly but should have a bilateral balance of occlusal scheme in all eccentric positions.

Fig. 8. A metal base constructed of either aluminum or cobalt-chromium.

Fig. 9. A metal-based denture provides a substructure resistant to fracture for single denture patients.

Fig. 10. With continued ridge resorption, a con- toured, retained root support or a gold dome coping will become a fulcrum, resulting in instability and increased potential for denture fracture due to occlusal forces.

Fig. 11. Mandibular arch will also exhibit continued resorption, resulting in high tissue attachments and denture instability. In many instances denture base is thin adjacent to retained tooth supports. Potential for denture fracture is therefore enhanced.

with occlusal forces and ridge resorption, precipitate mucosal irritation or denture fractures are maxillary tori and prominent midpalatal suture lines (Fig. 6).

THE OCCLUSAL SCHEME

Most prosthodontists agree that a bilateral balanced occlusal scheme is ideal for maxillary denture stability. Reduction of steep, inclined planes is a key to denture stability.’ The ideal posterior occlusal form is narrow buccolingually with shallow cusp height. As shallow incisal guidance as esthetically and phonetically accept- able should be obtained. Maxillary denture fracture can result from heavy contact of the anterior teeth in centric occlusion with inadequate posterior stops. No contact is desired with the maxillary and mandibular anterior teeth in centric occlusion (Fig. 7). In the event that bilateral

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MAXILLARY DENTlJRE FRACTURE

balanced occlusion cannot be obtained, then smooth molar contacts in conjunction with incisal contacts in protrusion and lateral movements are required.

OCCLUSAL FORCES

In discussing the significance of the Frankfort- mandibular plane angle (FMA), DiPietro and Moer- geli” stated that “increased biting forces in low FMA patients (20 degrees or less) result in transmittal of more stress to the residual ridge.” They further state that shallow ridges, flat palates, decreased interridge space, and increased biting forces exist in low FMA patients. The possibility of fracture of acrylic resin bases increases in these patients. Both Bruce4 and DiPietro and Moergeli” recommended the use of metal bases in single denture construction. Aluminum-based dentures offer an excellent solution to this problem (Figs. 8 and 9).

THE DENTURE FOUNDATION

Insufficient tissue coverage by the denture base results in lack of retention and in instability of the maxillary denture. The potential for denture fracture as well as underlying tissue damage and loss of functional efficiency increases. Maximum physiologic extension of the denture base for increased tissue coverage through proper border molding and impres- sion techniques is recommended. Often, well-made overdentures fracture under occlusal forces due to resorption of the residual ridge, which results in torquing of the denture base on the retained tooth supports (Figs. 10 and 11). This can be prevented by proper patient follow-up, especially if immediate tooth-supported dentures are made. After ridge resorp- tion is stabilized <at a minimum and proper contour of the retained root supports is obtained, a metal-based denture may be of benefitlO

DENTURE BASE THICKNESS

Thin denture bases are susceptible to fracture in combination with any of the previously discussed factors. Denture bases less than 2 mm thick are prone to fracture. Metal. bases provide a rigid substructure to prevent denture base fracture.‘0“2 Further, a high- impact acrylic resin that has recently been demon-

strated as resistant to flexure fatigue may reduce the probability of denture fracture.13

SUMMARY

Factors that contribute to the fracture and failure of the single maxillary denture have been discussed. Recognition of these factors and their prevention or correction will result in a single maxillary denture that is physiologically and functionally acceptable for the patient for an extended period without chronic denture failure.

REFERENCES

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Sharry, J. J.: Complete Denture Prosthodontics, ed 3. New York, 1974, McGraw-Hill Book Co., p 273. Rudd, K. D., and Morrow, R. M.: Occlusion and the single denture. J PROSTHET DENT 30:4, 1973. Ellinger, W. E., Rayson, J. H., and Henderson, D.: Single complete dentures. J PRO~THET DENT 26~4, 1971. Bruce, R. W.: Complete dentures opposing natural teeth. J PROSTHET DENT 26~448, 197 1. Yurkstas, A. A.: The single denture. In Clark, J. W., editor: Clinical Dentistry. New York, 1980, Harper & Row, Publish- ers, vol 5, chap 16, pp l-l 6. Beyli, M. S., and von Fraunhofer, J. A.: An analysis of causes of fracture of acrylic resin dentures. J PROSTHET DENT 46:238, 1981. Tallgren, A.: The continuing reduction of the residual alveolar ridge in complete denture wearers: A mixed longitudinal study covering 25 years. J PROSTHET DENT 27~120, 1972. Stephens, A. P.: Full dentures which occlude with natural teeth. Dent Practit Dent Ret 21:37, 1970. Wiland, L.: Dentures, inclined planes, and traumatic occlusion. J PROSTHET DENT 14~892, 1964. DiPietro, G. J., and Moergeli, J. R.: Significance of the Frankfort-mandibular plane angle to prosthodontics. J PROS- THET DENT 36~624, 1976. Halperin, A. R.: The cast aluminum base. Part I: Rationale. J PROSTHET DENT 43~605, 1980. Lundquist, D. 0.: An aluminum alloy as a denture base material. J PROSTHET DENT 17~227, 1967. Johnston, E. P., Nicholls, J. I., and Smith, D. E.: Flexure fatigue of ten commonly used denture base resins. J PROSTHET DENT 46~478, 1981.

Rejmnt requests to: DR. JOHN B. FARMER U.S. ARMY DENTAC FORT Hook, TX 76544

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