Any time a prosthesis is removable by the patient, one of the risks dentists and their patients need to be aware of is damage to the prosthesis from being dropped.
Dropping a removable prosthesis may result in chipped or broken teeth but very often results in a fractured denture base. And, while dropping the prosthesis is a common cause of fractured denture bases it is not the only cause. As a patient's arches resorb, it is not uncommon to see denture bases fracture due to stress concentrating in areas that haven't resorbed – the maxillary mid-palatal suture, for example.
As a result, fractured denture bases are a fairly common occurrence with this group of patients and, regardless of the cause, a fractured denture base can be an urgent concern for the patient. In many cases, the damaged prosthesis can be sent to the dental laboratory for repair, but what if the lab isn't available? In this article I want to share a case presentation for a patient in just this predicament.
A 91-year-old female in good general health was referred for urgent repair of her existing lower denture. The patient had implants placed and both arches restored with implant-retained overdentures about seven years prior to this appointment. She is unsure about the last time she had the prostheses evaluated or adjusted. She notes they are “fitting loose.” Additionally, the patient reports two previous attempts by another dentist to repair the broken denture (Figure 1). When asked what she was doing when the denture broke? She is unsure and/or can't remember. Upon inspection, the mandibular prosthesis is a two-implant overdenture that has fractured right through the area of one of the attachment housings.
Clinically, the mandibular arch is significantly resorbed and two implant abutments are present, but the surface appears worn. While you may not recognize these abutments, the design concept with the mandibular prosthesis is the same as a two-implant Locator overdenture (Figure 2).
According to both the patient and the referring dentist, both the upper and lower arches were treated approximately seven years prior. Additionally, the patient confesses to wearing both dentures at night to help prevent wrinkles from forming. In the maxilla, two abutments similar to the mandibular abutments are present in the anterior while the posterior two abutments appear to be angle corrected and custom fabricated Locators (Figure 3). Despite the age of the case and the damage to the lower prosthesis, the maxillary prosthesis has managed to maintain its esthetics (Figure 4). Neither prosthesis has any type of metal reinforcement.
Looking occlusally at the maxillary prosthesis, significant wear to the denture teeth is present. At seven years, this finding is not unexpected for conventional dentures and certainly to be expected with implant-retained overdentures (Figure 5 left, Figure 6). Interestingly, the maxillary overdenture had lost one of the retentive elements entirely and the remaining three retentive clips are not providing much retentive value (Figure 5 right).
From a treatment planning perspective, this patient presents with two challenges. The first challenge is how to manage the urgent problem of the fractured denture base. The second challenge is determining options for her definitive care. Understandably, additional information will be required to come up with the definitive plan, but the patient is unwilling to go without a lower prosthesis while that plan is developed. In order to move forward, it is important for the patient to know that the repair to the lower overdenture will leave the denture weaker than it was originally and any factors that contributed to the denture base fracturing, such as stress concentration around the implant abutments, could compromise the weakened denture further.
In this case, the patient desires strongly to have the lower denture repaired. For this particular repair, there are two distinct parts. Part one is to repair the fractured denture base and part two is to connect the attachment to the repaired denture base. The first step is to accurately reposition the denture base fragments (Figures 7 and 8). This step is critical as an error here could create problems with fit of the denture base to the ridge and occlusal discrepancies.
The next step is to fabricate some sort of a matrix to maintain the orientation of the fragments while the repair is being made. In this case, a remount cast is fabricated for this purpose (Figures 9 and 10).
With the remount cast fabricated, the mandibular prosthesis is then carefully removed and the surface prepared for the repair material. In this case, the repair material selected is an autopolymerizing acrylic resin (Jet Acrylic, Lang) so the surface is roughened with a carbide bur and air abraded with 50 micron particles of aluminum oxide. (Figures 11, 12 and 13).
With the denture base repaired, part two of the procedure is ready to begin; the chairside pick up (Figures 14 and 15).
The prosthesis is finished with carbide burs and polished using flour of pumice and denture polish on a rag wheel and lathe (Figure 16). Alternatively, a silicone polishing system could have been utilized.
The final result is then inserted (Figure 17).
Denture base fracture is not an uncommon occurrence in practices who treat edentulous patients. While sending the prosthesis to the dental laboratory for repair is often a great option, there may be clinical circumstances that won't allow that to occur in a timely manner. In this article I've demonstrated one way to solve this problem, but there are countless other variations. I hope this helps next time you encounter this clinical problem.
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