Objectives: Expansion of amalgam is hypothesized to initiate cracks in restored teeth that are occasionally observed clinically. This study investigated if amalgam restored teeth submerged in a saline solution have measurable cuspal flexure and expansion. Methods: Class II MOD preparations (4mm deep, 4mm wide) were prepared in 9 extracted human molars (IRB#15-04302-NHSR) and restored with a zinc-containing amalgam (Permite, SDI). Three sound teeth were used as controls. All teeth were scanned (baseline) using a 3D optical scanner (COMET xS, Steinbichler) before immersion in saline solution for eight weeks. The teeth were periodically re-scanned. Cumulus software was used to align all scans to their baselines. Cuspal flexure was calculated using custom CuspFlex software from the differences at the buccal and lingual surfaces between the baseline and follow-up scans, and compared between amalgam and control (t-test). Amalgam expansions on the occlusal, mesial, and distal surfaces were calculated and compared (one-way ANOVA and Student-Newman-Keuls post hoc test; α=0.05). Results: The table shows cuspal flexure and amalgam expansion (mean±SD; microns); positive values indicate outward flexure (expansion). Cuspal flexure of the amalgam-restored teeth was significantly higher than the controls. Cuspal flexure gradually increased over 8 weeks. Expansion of amalgam on the mesial and distal surfaces was significantly higher than expansion at the occlusal surface and higher than cuspal flexure values. Conclusions: Significant outward cuspal flexure and expansion of restoration surfaces were found on amalgam restored molars within 8 weeks. Physical strains (flexure) in restored teeth may induce stress distributions that contribute to initiation of cracks that are occasionally observed clinically.
Division: IADR/AADR/CADR General Session
Meeting:2017 IADR/AADR/CADR General Session (San Francisco, California) Location: San Francisco, California
Year: 2017 Final Presentation ID:2019 Abstract Category|Abstract Category(s):Dental Materials 3: Metal-based Materials and Other Materials
Authors
Danley, Brent
( University of Tennessee Health Science Center
, Memphis
, Tennessee
, United States
)
Hamilton, Bruce
( University of Tennessee Health Science Center
, Memphis
, Tennessee
, United States
)
Tantbirojn, Daranee
( University of Tennessee Health Science Center
, Memphis
, Tennessee
, United States
)
Goldstein, Ronald
( Private Practice
, Atlanta
, Georgia
, United States
)
Versluis, Antheunis
( University of Tennessee Health Science Center
, Memphis
, Tennessee
, United States
)
Support Funding Agency/Grant Number: Supported, in part, by the University of Tennessee Health Science Center College of Dentistry Alumni Endowment Fund, the Tennessee Dental Association Foundation, and the Alpha Omega Foundation Research Fund. We thank Dr R. DeLong, University of Minnesota,
Financial Interest Disclosure: none
SESSION INFORMATION
Poster Session
Prosthodontics, Implants, Surface Coating, Tissue Reaction to Metal, Fitting, Fatigue Resistance and Other Testing - Orthodontics, Wires and Cements - Amalgam
Friday,
03/24/2017
, 11:00AM - 12:15PM
TABLES
Cuspal Flexure and Restoration Expansion Results
2-week
4-week
8-week
Cuspal Flexure, Amalgam
3.18±2.72*a
3.55±2.14*a
3.70±2.42a
Cuspal Flexure, Control
-0.69±1.40§
-0.44±1.21§
0.94±0.20
Amalgam expansion, occlusal
4.69±1.38a
5.05±1.37a
5.02±1.35a
Amalgam expansion, mesial
8.44±1.41b
8.26±2.17b
8.77±2.81b
Amalgam expansion, distal
8.87±2.48b
8.47±2.29b
8.03±3.29b
*,§ significantly different cuspal flexure (t-test; p<.05). Same superscript letter denotes mean value not significantly different.