Load-induced stresses in photoelastic primary canines with facial restorations.
OBJECTIVE
The purpose of this study was to photoelastically compare the stresses generated by loads on primary canines with facial restorations of different stiffness.


METHODS
Composite photoelastic models of a typical maxillary primary canine were fabricated using individual simulant materials for enamel, dentin, periodontal ligament, and alveolar bone. Models were made with identical facial preparations included either near the cementoenamel junction or at 2 mm incisally. The model teeth were restored using the following materials of disparate elastic moduli: (1) high modulus, hybrid composite (Herculite XRV); and (2) lower modulus compomer (Dyract). Three replications of each type of restored tooth were fabricated. Simulated masticatory forces were applied on the cusp tip and the cingulum of each tooth model. The resulting stress patterns were observed and recorded photographically in the field of a circular polariscope.


RESULTS
Prior to load application, similar low-level, polymerization-induced shrinkage stresses were localized at the preparation margins of all models. Under both incisal and cingular loading, the higher modulus hybrid composite tended to concentrate stress along the gingival and proximal margins more than did the lower modulus compomer. This effect was more pronounced with cingular than with incisal loading. For both preparations and restoratives, higher stresses were produced by the cingulum loading. No significant differences were observed within each group of replicated restored models.


CONCLUSIONS
These results suggest that, regardless of preparation height, lower modulus compomer restoration of facial lesions in primary maxillary canines may reduce stress production by occlusal forces.
Rabitz
Greg K
GK
UCLA School of Dentistry, Los Angeles, Calif, USA.
Berson
Robert
R
Caputo
Angelo A
AA
Franklin
Ryan J
RJ
Del Fierro
Dino B
DB
D000539:Alveolar Process / Q000033:anatomy & histology / Q000502:physiology; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D001732:Bite Force; D020770:Compomers / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003481:Cuspid / Q000033:anatomy & histology / Q000502:physiology*; D001840:Dental Bonding; D003737:Dental Cavity Preparation / Q000145:classification; D003743:Dental Enamel / Q000033:anatomy & histology / Q000502:physiology; D003764:Dental Materials / Q000737:chemistry*; D003793:Dental Restoration, Permanent / Q000145:classification; D003804:Dentin / Q000033:anatomy & histology / Q000502:physiology; D017220:Dentin-Bonding Agents / Q000737:chemistry; D004548:Elasticity; D006801:Humans; D008953:Models, Anatomic; D010513:Periodontal Ligament / Q000033:anatomy & histology / Q000502:physiology; D011108:Polymers / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D014094:Tooth, Deciduous / Q000033:anatomy & histology / Q000502:physiology*
D020770:Compomers; D003188:Composite Resins; D003764:Dental Materials; D017220:Dentin-Bonding Agents; C088486:Dyract; D011108:Polymers; D019279:Resin Cements; C115612:single bond; C065770:Herculite XR; D017438:Bisphenol A-Glycidyl Methacrylate