A Photoelastic Stress Analysis of Screw‐ and Cement‐Retained Implant Prostheses with Marginal Gaps
Bibliographic record
Abstract
BACKGROUND: The precise fit of an implant prosthesis is considered to be a prerequisite for the success and maintenance of osseointegration. It is unknown how much static stress can be tolerated at the implant-bone interface with ill-fitting prostheses for the two different types of retention (cement vs screw). PURPOSE: The purpose of this study was to evaluate the stress pattern and magnitude in the supporting tissues around ITI (Straumann AG, Waldenburg, Switzerland) implants with screw- or cement-retained prostheses with marginal gaps by photoelastic analysis. MATERIALS AND METHODS: A photoelastic model of a human mandible, partially edentulous distal to the canine, was made of PL-2 resin. Three ITI implants (4.1 × 10 mm, Straumann AG, Waldenburg, Switzerland) were placed in the posterior edentulous region, and screw- or cement-retained three-unit fixed partial dentures (FPDs) were fabricated. Ill-fitting prostheses were made by placing a 100-μm gap between the abutments and the superstructures on the second premolar or the first molar. A static vertical force of 134 N was applied at three loading points on each prosthesis. Photoelastic stress analysis was carried out to measure the fringe order around the implant-supporting structures. RESULTS: Even in the unloaded condition, low-level stresses were generated around the implants after screw tightening or cementing the three-unit FPDs with marginal gaps. Loading on the terminal implants developed high concentrated stresses around the loaded implant, regardless of the types of restorations or the presence of gaps. However, when the middle implant was loaded, moderate stresses were distributed to the anterior and posterior implants. CONCLUSIONS: Screw-retained FPDs with gaps exhibited a wider range of stresses on the interproximal region of adjacent implants than cement-retained FPDs. However, severe misfit in the prosthesis caused the nonaxial stress transfer to the adjacent implants in the cement-retained FPDs with gaps.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".