To study the effects of different concentrated sulfuric acid etching durations on the shear bond strength between polyether-ketone-ketone (PEKK) and dentin, providing a scientific basis for the clinical bonding procedures of PEKK prosthesis.

Forty-four PEKK specimens were prepared and randomly divided into four groups: group A was the control group, which was only polished with abrasive papers, group B, group C and group D were experimental groups, which were etched by 98% concentrated sulfuric acid for 5 s, 30 s and 60 s, respectively. In addition, one sample was randomly selected from each group, and the profile was prepared by a slow cutting machine. The surface morphology of the profile was observed under SEM. After the four groups of specimens and dentin were bonded by resin, they were soaked in distilled water at 37 ℃ for 24 h. After the shear bonding strengths were measured, the fracture interfaces of the specimens were examined by the scanning electron microscopy and stereomicroscopy, and failure models of bonding were analyzed.

After acid etching treatments, the cross-sectional images in group B presented uniform spongy shapes, while the cross-sectional images in group C and group D showed destructive pore structures. The shear bond strengths of group B (16.84 ± 1.84) MPa, group C (12.33 ± 1.22) MPa and group D (6.44 ± 1.18) MPa were higher than that of group A (3.99 ± 1.06) MPa (P ＜ 0.05). The highest shear bond strength was observed in group B (16.84 ± 1.84) MPa.

The surface treatment of 98% sulfuric acid etching for 5 s manifested the best bond strength between PEKK and dentin.

To investigate the effect of a metal occlusal surface and stress interruption design on minimally invasive prosthodontics for patients with distal extension absence and insufficient occlusal gingival distance.

We retrospectively studied the case of minimally invasive prosthodontic (Vitallium 2000) combined with a metal occlusal surface for distal extension absence in a patient with insufficient occlusal gingival distance; the stress breaking design and pressure impression technology are examined, and relevant articles are reviewd.

The design effectively solves the problems of insufficient occlusal gingival distance, large occlusal force and easy denture fracture. Reviewing the relevant literature, stress interruption design can effectively protect abutment teeth, but the behavior of stress interruption design and stress conduction phenomena in the mouths of patients has not been reported. The T-scan test results of this study showed that before and after wearing the denture, the occlusal force distribution ratio of the patient changed from 77.5% on the left and 22.5% on the right to 61.3% on the left and 38.7% on the right. The occlusal force distribution ratio of the right dentition to the total occlusal force increased by 16.2%, and the occlusal force became better distributed. Further analysis showed that the occlusal forces on the left and right sides were nearly the same in the initial occlusion stage. As the occlusal force was further increased, the proportion of the occlusal force on the right side decreased in the middle of the occlusion stage and further decreased in the final occlusion stage until it reached a dynamic balance. The above T-scan test and literature review results suggest that this dynamic balance phenomenon of bite force is related to the stress interruption design and the stress conduction effect of the split framework.

The composite of stress interruption design and metal occlusal surface allows for minimally invasive prosthodontics for the treatment of distal extension absence in patients with insufficient occlusal gingival distance.