Background: Cardiopulmonary resuscitation (CPR) requires immediate start of manual chest compression (MCC) and defibrillation as soon as possible. During dental surgery, CPR could be started in the dental chair considering difficulty to move the patient from the dental chair to the floor. However, all types of dental chairs are not stable for MCC. We previously developed a procedure to stabilize a dental chair by using a stool. EUROPEAN RESUSCITATION COUNCIL (ERC) guideline 2015 adopted our procedure when cardiac arrest during dental surgery. The objective of this study was to verify the efficacy of a stool as a stabilizer in different types of dental chairs. Methods: Three health care providers participated in this study, and 8 kinds of dental chairs were examined. MCC were performed on a manikin that was laid on the backrest of a dental chair. A stool was placed under the backrest to stabilize the dental chair. The vertical displacement of the backrest by MCC was recorded by a camcorder and measured by millimeter. Next, the vertical displacement of the backrest by MCC were compared between with and without a stool. Results: In all 8 dental chairs, the method by using a stool significantly reduced the vertical displacements of the backrest by during MCC. The reduction ratio (mean [interquartile range]) varied between nearly 27  and 87  %. In the largest stabilization case, the displacement was 3.5 [0.5] mm with a stool versus 26 [5.5] mm without a stool (p < 0.001).