Stresses in ultrasonically assisted bone cutting

Surface quality and pullout strength of ultrasonically-assisted drilling cortical bone

Bone surgery is a complex process involving sustainable and healthy human recuperation, but poor surface quality and loose implant fixtures can affect the recovery time of orthopedic patients. However, it has been demonstrated that the application of ultrasonic vibration during drilling procedures can improve the success of bone remediation procedures. The focus of the present paper was on the investigation of surface quality and pullout strength of drilled holes. After analyzing the special kinematic characteristics of the ultrasonically-assisted drilling (UAD), UAD testing using fresh cortical bone was carried out and compared with the results obtained after conventional drilling (CD) procedures. Surface roughness measurements and microscope examination were used to evaluate surface quality, and an electro-mechanical tensile machine was used to measure pullout resistance. The test findings indicated that surface roughness was reduced by 17-68.7% when using UAD; the axial pullout strength of screws inserted into UAD holes was significantly increased by 4.28-30.1% compared to that of CD. It was found also that low spindle speeds and high feed rates reduced surface quality and the stability of the inserted cortical screws. The findings demonstrated that UAD produced better surface quality and higher pullout strengths, which could provide greater stability for implants and improved post-operative recovery.

Dynamics of implant site preparation affecting the quality of osseointegrated implants in the maxillary aesthetic zone

PURPOSE

This study compared piezoelectric (PE) and conventional drills (CD) for maxillary aesthetic zone implant insertion.

MATERIAL AND METHODS

This was a prospective split-mouth study. Implants were divided into two groups. Beds were prepared with CDs in group I and PE in group II. The implant stability quotient (ISQ) of the mechanical implant stability (MIS) was measured intraoperatively. The ISQ of the biological implant stability (BIS) was recorded at postoperative second and fourth months. Marginal bone loss (MBL) and bone density (BMD) were measured in the first and second years after prosthetic loading. The osteotomy time was also documented for both techniques. P values <0.05 were considered significant.

RESULTS

Sixty implants in 30 patients were included. PE provided a significantly higher ISQ. All values were above 70 throughout the follow-up period. The mean of the ISQ for MIS was 63.78 ± 1.03 and 73.89 ± 1.05 in group I and group II, respectively (p = 0.003). PE needed significantly longer osteotomy time with a mean of 11.99 ± 0.839 min. The BIS quality had high stability in group II and medium stability in group I throughout the study period. Its values decreased in both groups. Group II had a lesser percentage of decrease. However, it was significant only at time intervals between intraoperative and two months' postoperative (p = 0.004). MBL and BMD demonstrated insignificant results.

CONCLUSION

The implant site preparation with PE devices should be preferred to CDs whenever possible, because they seem to enhance implant stability and osseointegration, especially at the initial stages of healing.

Analysis of Forces and Temperatures in Conventional and Ultrasonically-Assisted Cutting of Bone

Bone cutting is a frequently used procedure in orthopaedic and neuro surgeries. Current research on bone cutting is concerned with the efforts to decrease the forces generated during cutting the bone as well as temperature to avoid mechanical and thermal damage (bone necrosis) induced by surgical tools. The paper presents results of finite-element simulations of conventional cutting (CC) and ultrasonically-assisted cutting (UAC) of bone in order to understand thermomechanics of the process. The study was aimed at investigating the levels of tool-penetration force and temperatures induced in the bone when a hard cutting tool penetrates into it in both types of cutting. The models allow the quantitative analysis of forces and temperatures produced during the cutting process. The use of UAC reduces the tool penetration force and temperature in the cutting region