Tissue effects in vessel sealing and transection from an ultrasonic device with more intelligent control of energy delivery.

BACKGROUND: Ultrasonic surgical devices have been demonstrated to provide excellent hemostasis, efficient transection, minimal lateral thermal damage, low smoke generation, and no risk of electrical current passage to the patient. These benefits originate from the inherent characteristics of the ultrasonic mechanism, but further improvements were thought possible through optimization of the energy delivery during application. The study reported here compared a new ultrasonic device, Harmonic ACE®+ Shears with Adaptive Tissue Technology, with a commercial predicate device, Harmonic ACE® Shears (both Ethicon Endo-Surgery, Inc., Cincinnati, OH, USA). METHODS: Devices were evaluated in an in vivo porcine model intraoperatively and after a 30-day survival period. Both devices were used to seal a variety of vessels 1-5 mm in diameter, and compared for hemostasis, histological thermal damage, and adhesion formation. Sealed vessels were evaluated ex vivo for burst pressure, and visual obstruction caused by plumage from device application was assessed quantitatively. RESULTS: ACE+ produced significantly less thermal damage, had fewer adhesions, offered faster transection, involved less visual obstruction, and had higher burst pressures than the predicate device. All vessel seals, evaluated over the course of a 30-day survival period in pigs, remained intact. CONCLUSION: The new Adaptive Tissue Technology algorithm assists the surgeon in achieving better control of energy delivery to the tissue, sealing vessels with supra-physiological burst pressures, and low thermal damage. These preclinical results with Harmonic ACE+ may translate into meaningful clinical benefits, providing greater precision along with more efficient and effective cutting and coagulation in open or laparoscopic procedures.

Crown-to-implant ratios of short-length implants.

Excessive crown-implant ratios have been cited in the literature as being detrimental to long-term implant survival. However, unfavorable crown-implant ratios have not yet been established. The primary aim of this study was to determine the crown-implant ratios of single-tooth implant-supported restorations on short-length implants in a clinical practice, and to evaluate the health of these implants via mesial and distal first bone-to-implant contact levels. Additionally, the relationship between crown-implant ratios and proximal first bone-to-implant contact levels will be evaluated. In this retrospective cohort study, the cohort was composed of 194 patients who possessed at least 1 single 5.7 mm or 6 mm length plateau design implant-supported restoration that had been surgically placed between February 1997 and December 2005. A chart review was performed to acquire the most recent radiographs in which both the entire crown and the implant were visible. The length of the crown and implant was measured directly from the radiographs using consistent magnification to calculate the crown-implant ratio. Mesial and distal first bone-to-implant contact levels were measured using 3 times magnification and were mathematically corrected for distortion. The last available radiograph was used to measure bone levels. Follow-up time was calculated from the day of implant placement to the date of the last available radiograph. Statistical analyses with analysis of variance mixed models were used. Data from 309 single implant-supported fixed restorations were tabulated and included in the study. The mean (SD) follow-up time was 20.9 (23.2) months, with a range of 15.6 to 122.8 months. The mean crown length (SD) was 13.4 (2.6) mm, with a range of 6.2 to 21.7 mm. The mean (SD) crown-implant ratio was 2.0 (0.4) and ranged from 0.9 to 3.2. The average mesial and distal first bone-to-implant contact levels (SD) measured from the radiographs were -0.2 (0.7) mm and -0.2 (0.9) mm, respectively. No statistically significant relationship was observed between increasing crown-implant ratios and decreasing mesial and distal first bone-to-implant contact levels around the implant with P values of .94 and .57, respectively. In this investigation, mesial and distal first bone-to-implant contact levels on short-length implants fall within the established guidelines for success. Also, there are no associations between crown-implant ratios and first bone-to-implant contact levels.

Fractures related to occlusal overload with single posterior implants: a clinical report.

This clinical report describes 2 patient situations in which fractures related to occlusal overload occurred with a single posterior implants. The initial clinical presentation of both patients appeared to be screw loosening, but upon further examination, implant and abutment fractures were identified. Several factors are described that have been implicated in the etiology of implant fractures, including occlusal overload, implant location, inadequate fit of the prosthesis, design of the prosthesis, progressive bone loss, metal fatigue, implant diameter, manufacturing defects, and galvanic activity. This article describes the management of implant and abutment fractures and discusses possible mechanisms of failure for the patient situations presented. Careful treatment planning and execution of implant therapy is necessary to minimize the risk of implant and component fractures.

Crown-to-implant ratios of single tooth implant-supported restorations.

STATEMENT OF PROBLEM: The crown-root ratio guidelines used to establish a prognosis for teeth serving as abutments are commonly applied to a dental implant-supported restoration or potential implant site. These guidelines are generally empirical and therefore lack scientific validation. PURPOSE: The purpose of this study was to first determine the crown-implant ratios of single tooth implant-supported restorations, and then to compare the crown-implant ratios to the guidelines established for the crown-root ratios of natural teeth. MATERIAL AND METHODS: A retrospective cohort study design was used. The cohort was composed of subjects (n=294) having 1 or more single tooth implants (Bicon) placed between May 1992 and April 2004. A chart review was conducted to obtain radiographs in which the entire crown and implant were visible. The length of the crown and implant were measured directly from the radiographs using magnification to calculate the crown-to-implant ratio. The length of the crown was divided by the length of the implant to determine the crown-implant ratio. Calculations were made to within 0.1 mm. Implant failure was recorded and defined as removal of the implant for any reason. Data were analyzed with descriptive statistics. RESULTS: A total of 889 single tooth implants from 294 patients were measured and included in the study. The mean (SD) follow-up time was 2.3 (1.7) years, with a range of 0.1 to 7.4 years. Sixteen failures were recorded for a survival rate of 98.2%. The crown-implant ratios ranged from 0.5:1 to 3:1. The mean (SD) crown-implant ratio of implants in function was 1.3:1 (0.34). The mean crown-to-implant ratio of failed implants was 1.4:1 (2.5). CONCLUSIONS: The results of this study suggest that the crown-to-root ratio guidelines associated with natural teeth should not be applied to a potential implant site or existing implant restoration. The crown-to-implant ratios of those implants that were in function were similar to those implants that failed.