Tuned aperture computed tomography (TACT) for cross-sectional implant site assessment in the posterior mandible.

PURPOSE: This study was designed to optimize a new radiographic modality known as tuned aperture computed tomography (TACT) for cross-sectional imaging of implant sites in human dry mandibles. MATERIALS AND METHODS: Five imaging modalities were compared for image quality and measurement accuracy: (1) conventional hypocycloidal tomograms, (2) TACT images reconstructed using the average method produced using a linear x-ray source movement, (3) TACT images reconstructed using the average method produced using a multidirectional x-ray source movement, (4) minimally reconstructed TACT images without a fiducial marker at the site of interest, and (5) minimally reconstructed TACT images with a fiducial marker at the site of interest. RESULTS: The extended Mantel-Haenszel mean score statistic was used to investigate the influence of modality on subjective image quality. A statistically significant difference for certain types of TACT images and multidirectional tomography (P < 0.0001) was observed. Linear TACT and multmin TACT were rated as significantly better than other image modalities (P < 0.0009), whereas multidirectional tomography was rated as being significantly worse than other radiographic modalities (P < 0.0001). For the quantitative assessment, data were normalized and analyzed statistically through a paired-comparisons t test. For each modality, the accuracy for maximum height and height was significantly different from ground truth (P < 0.05). CONCLUSION: The qualitative data suggest that visibility of structures important to the choice of implant location and dimension were seen better with certain TACT methods. Quantitative differences from ground truth (actual measurements of the bone-absolute truth) were clinically negligible. TACT appears to offer the potential of superior image quality over the status quo.

Prosthetic complications in an implant-retained mandibular overdenture population: initial analysis of a prospective study.

STATEMENT OF PROBLEM: The clinical success of implant-retained, tissue-supported mandibular overdenture prostheses has been documented. However, few studies have evaluated the return visits and associated cost required to maintain these prostheses. PURPOSE: The purpose of this investigation was to evaluate the amount of maintenance required to provide acceptable and satisfactory implant-retained mandibular overdentures in a prospective clinical trial. MATERIAL AND METHODS: Fifty-eight patients received new maxillary and mandibular complete dentures followed by placement of microthreaded/TiOBlast implants in the mandibular left and right canine regions. At 3 months, ball abutments were placed, and the mandibular prostheses were relined to receive Dalla Bona-type ball housings (baseline). Prostheses were prospectively evaluated, and adjustments were made at 3-, 6-, 12-, 24-, and 36-month recall visits and at nonscheduled visits for 9 types of prosthetic complications. RESULTS: Of 58 patients, 6 required no adjustments. The remaining 52 patients made 327 return visits (including 194 nonscheduled visits) for prosthesis and/or abutment adjustments. One hundred and fifteen practitioner hours were required to provide prosthetic solutions to patient concerns at the return visits. The total estimated cost for all professional and laboratory services was $12,624.00 ($218.00 per patient). CONCLUSION: Although mandibular implant-supported overdentures with Dalla Bona-type ball attachments are an acceptable treatment option for edentulous patients, routine maintenance is required to ensure successful long-term outcomes.