Why Dental Temps & Prototypes Break: Common Causes of Restoration
A Broken Temp Is Often a Symptom, Not the Problem.
From an imbalanced bite to insufficient MUA angulation, improper torque, uneven seating, long spans, distal cantilevers, or patient bruxism, there are several biomechanical factors that can put excessive stress on a temporary prosthesis. The good news? Many of these factors can be identified and addressed before they lead to a breakage.
Imbalanced Bite
Imbalanced occlusion causes heavier biting on certain areas, which commonly causes breakages. Ensure a balanced bite is achieved post-operatively before a prototype.
Insufficient MUA Angles
Sharp angles create biomechanical leverage. When a patient bites down, vertical force is converted into high lateral and shear stresses. This concentrates twisting forces at the connection points, leading to screw loosening, microfractures in the prosthesis. Assess the angles of the multi-unit abutments to ensure secure screw channels.
Loose MUAs
Improperly torqued multi-unit abutments fail to generate the necessary clamping force to keep the system rigid. This lack of tension causes micro-movements, which lead to severe stress concentration, fatigue, and catastrophic screw or framework fractures over time. Make sure to retorque all multi-unit abutments before scanning & inserting prototype.
Loose Prosthesis
Uneven torque creates concentrated pressure points on the resin material, causing it to micro-fracture and eventually break. Torque the screws to 15µm, wait ~5 minutes, and then retighten the screws to ensure the prototype is evenly seated. Make sure the screws are properly torqued and engaged evenly across the arch.
Distal Cantilevers
Large spans in between implants (2+ teeth) or distal cantilevers often cause breakages. In this case, a split bar workflow is recommended. Split bars consist of a titanium substructure with full contour zirconia sleeved over the bar, offering more strength and stability in long spans and distal cantilevers. Although prototypes may break in the interim, recognizing that the final will require a split bar will alleviate worries of final prosthesis breakages.
Bruxism
A patient who grinds their teeth can easily break a full arch temporary because of the immense, unnatural pressure. Temporary materials are inherently weaker than permanent ones. Grinding exerts extreme lateral forces and crushing loads that can cause the acrylic or composite resin to crack, snap, or dislodge. Have your patient wear a nightguard with their prototype, which can be added to your cases.
Broken Temp or Prototype? We’ve Got Your Reprint Covered.
Prototypes & temps can break, but the beauty of a digital workflow allows us to reprint provisionals as needed.
Temporaries
Temporary prostheses are warrantied through Acqua-Dent for 6 months after surgery for up to 2 reprints at no additional charge. All other reprints and redesigns will be billed accordingly.
Prototypes
Prototypes are warrantied through Acqua-Dent for 2 months after the insert of the first prototype. One reprint is provided at no additional charge. All other reprints and redesigns will be billed accordingly.