Failing Four-Unit Bridge in a Bruxist With a Limited Implant Site
A 67-year-old man presents with a loose 4-unit metal–ceramic bridge from the maxillary right second premolar to the second molar, replacing the first molar. The bridge has been in place 14 years. The premolar abutment has 2 mm of ferrule, a cast post and core, and a 5-mm palatal pocket with bleeding; the molar abutment has recurrent caries and a fracture of the distobuccal cusp. The opposing mandibular arch has a three-unit bridge and generalised 2-mm attrition. He has a history of bruxism, uses a night guard inconsistently, and has a 40-mm mouth opening. Cone-beam CT shows 8 mm of bone height below the maxillary sinus and 6 mm width at the first molar site. He is a non-smoker, well controlled type 2 diabetic, and wants a fixed solution with no removable prosthesis.
1. How would you assess the restorability and periodontal prognosis of the two abutment teeth before deciding on a new prosthesis?
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Tooth 15: the cast post and core plus only 2 mm of ferrule is a warning sign. A 5-mm palatal pocket with bleeding suggests periodontal involvement; I would record probing depths, mobility, furcation, and radiographic bone level, and assess whether the post can be removed without root fracture. If the post is failing or the pocket does not respond to hygiene therapy, the long-term prognosis is guarded.
Tooth 17: recurrent caries and a fractured distobuccal cusp require caries removal and assessment of remaining tooth structure. I would check endodontic status, ferrule, and whether crown lengthening is needed. A fracture below the crest or a poor ferrule worsens the prognosis.
Overall: before designing anything, remove the bridge, excavate caries, test vitality and percussion, take periapical views, and complete initial periodontal therapy. The decision is not “which bridge material” but whether both abutments can be maintained. If 15 is periodontally unstable or the post cannot be safely replaced, a new 15–17 fixed prosthesis is built on a weak foundation. I would also assess the opposing arch and occlusal scheme, because the existing attrition and bruxism affect long-term survival.
2. Compare a replacement fixed dental prosthesis, an implant-supported restoration at 16, and a removable option. Which do you recommend and why?
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Replacement 15–17 FPD: simple and fixed, but it depends on 15 and 17. It requires a new post/core on 15, a crown on 17, and splinting of two abutments with different prognoses. Cantilever designs should be avoided in a bruxist.
Implant at 16 with individual crowns on 15 and 17: CBCT shows 8 mm bone height and 6 mm width. That may allow a short implant or an implant with simultaneous sinus floor elevation, depending on residual crest and sinus anatomy. Advantages: avoids a long-span bridge and replaces the missing tooth independently; disadvantages: surgery, healing time, cost, and the need to restore 15 and 17 separately.
Removable partial denture: avoids further preparation, but the patient expressly wants fixed treatment, and a clasped RPD in a bruxist with a shortened arch may accelerate abutment loss.
Recommendation: proceed with a diagnostic phase-periodontal treatment, caries control, and assessment of 15. If 15 is retainable, place an implant at 16 and restore 15, 16, and 17 as individual units. If 15 is not retainable, plan implants at 15 and 16 or a carefully designed short-span FPD, depending on bone and cost. I would not simply repeat the 15–17 bridge.
3. How would you manage the bruxism and occlusal vertical dimension in the definitive restoration?
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Bruxism: confirm with history, wear facets, and appliance wear; consider sleep study if there is snoring or suspected obstructive sleep apnoea. Provide a well-adjusted stabilization splint for night use, but do not rely on it alone.
Occlusal vertical dimension: do not increase it permanently without a clear indication such as insufficient restorative space or documented loss of vertical dimension. If more space is needed, use a trial removable appliance or provisional restorations at the proposed vertical dimension for several weeks and assess speech, comfort, esthetics, and tooth wear before finalizing.
Material and design: use monolithic zirconia or a similarly wear-resistant material with adequate occlusal thickness; design contacts to share load, avoid unsupported porcelain, and provide canine guidance or group function compatible with the opposing arch. Keep margins supragingival where possible.
Review: schedule early occlusal review, reinforce splint use, and monitor the implant and abutments. Document that bruxism is a risk factor for chipping, fracture, and implant overload, and that the patient’s inconsistent night-guard use affects prognosis.