Classification system for conventional crown and fixed partial denture failures

Anomaly detection of retention loss in fixed partial dentures using resonance frequency analysis and machine learning: An in vitro study

PURPOSE

This study aimed to determine the usefulness of machine learning techniques, specifically supervised and unsupervised learning, for assessing the cementation condition between a fixed partial denture (FPD) and its abutment using a resonance frequency analysis (RFA) system.

METHODS

An in vitro mandibular model was used with a single crown and three-unit bridge made of a high-gold alloy. Two cementation conditions for the single crown and its abutment were set: cemented and uncemented. Four cementation conditions were set for the bridge and abutments: both crowns were firmly cemented, only the premolar crown was cemented, only the molar crown was cemented, and both crowns were uncemented. For RFA under cementation conditions, 16 impulsive forces were directly applied to the buccal side of the tested tooth at a frequency of 4 Hz using a Periotest device. Frequency responses were measured using a 3D accelerometer mounted on the occlusal surface of the tested tooth. Both supervised and unsupervised learning methods were used to analyze the datasets.

RESULTS

Using supervised learning, the fully cemented condition had the highest feature importance scores at approximately 3000 Hz; the partially cemented condition had the highest scores between 1000 and 2000 Hz; and the highest scores for the uncemented condition were observed between 0 and 500 Hz. Using unsupervised learning, the uncemented and partially cemented conditions exhibited the highest anomaly scores.

CONCLUSIONS

Machine learning combined with RFA exhibits good potential to assess the cementation condition of an FPD and hence facilitate the early diagnosis of FPD retention loss.

Assessment of failure rate of fixed partial dentures: A clinical study

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Materials and Methods:

Results:

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Clinical and Radiographic Assessment of Reasons for Replacement of Metal- Ceramic Fixed Dental Prostheses in Patients Referring to Dental School

Background

The expected length of service and reasons for fixed dental prostheses (FDPs) replacement are a frequent inquiry by patients while the answers were mainly based on studies reports that was conducted outside the middle east region. This clinical and radiographic survey was constructed to assess and survey clinically and radiographically the reasons of replacement of metal-ceramic fixed dental prostheses, amongst patients reporting at dental school in Taibah University.

Material and Methods

Between January and May 2016, 151 patients were recruited for this study. Interview (include questions pertained to the length of service of the prosthesis, the nature of complaint as told by patient in her own words), clinical examination, intra-oral photographs, and periapical radiographs, were done by the researchers. The parameters assessed were secondary caries, open margins, loss of retention, failure of endodontic treatment of the abutment and periodontal diseases.

Results

A total number of 249 failed fixed dental prostheses were evaluated. Of which 180 (39.7%) were single crowns, 159 (35.0%) were retainers and 117 (25.8%) were pontics in 69 fixed partial denture. The most common reason for replacement of fixed restorations was periodontal diseases affecting 92.8% of all types’ restorations, followed by defective margin in 90.4% of examined restoration, poor aesthetic in 88% of restorations, while periapical involvement was found in 85.5% of fixed dental prosthesis. The survival rates of fixed prostheses were not predictable, and no association was found between number of years in service and the number of restorations.

Conclusions

The most common reasons for replacing single unit fixed dental prostheses are periodontal diseases and periapical involvement, while defective margins and poor aesthetic mainly associated with multi-unit fixed dental prostheses.

Key words:Failure, Fixed dental prosthesis, Survival, Replacement.

Common Post-fitting Complications in Tooth-supported Fixed-Fixed Design Metal-Ceramic Fixed Dental Prostheses

Objectives: To report the frequency of common complications and their levels in metal-ceramic fixed dental prostheses (MC-FDPs).

Methods: A Descriptive Cross-sectional study was conducted at the Prosthodontics Department, Khyber College of Dentistry Peshawar from January 2011 to October 2012. Using a structured proforma, data from 139 subjects fulfilling the inclusion and exclusion criteria for the study and reporting complications in their MC- FDPs were collected using the method of interview, clinical & radiographic examination.

Results: Of 139 subjects (Mean age = 34+ 6.4 Years), 81 (58.3%) were males and 58 (41.7%) were females with a male to female ratio of 1.4:1. De-cementation was the most common complication (41.7%). Least common complication was secondary caries (6.5%). Level-1 complications were more prevalent (77.7%) than level-2 complications (22.3%). In 91.4% cases, complications occurred before the FDP completed their fifth-years’ service life with 25.2% of these occurring within the first years’ service life.

Conclusion: Irrespective of the type of complications, level-1 complications were more common with de-cementation being the most common complication. One-quarter of all the complications occurred within the first-year service life of the FDPs highlighting concern over the quality of the provided MC-FDPs. .