Stress Over Implants of One-Piece Cast Frameworks Made With Different Materials

Implant-Prosthetic Rehabilitation of a Patient with Squamous Cell Carcinoma: A Case Report

Patients who have undergone maxillary resection procedures are rehabilitated with dental obturators or microvascular reconstruction. This case report describes implant-supported prosthetic rehabilitation of a patient who underwent maxillary resection due to squamous cell carcinoma. After maxillectomy surgery, the patient was rehabilitated using a surgical obturator for one week followed by an interim obturator until the surgical field was completely healed. For definitive prosthesis, different treatment options were presented from which the patient selected an implant-supported maxillofacial prosthesis and a removable mandibular partial prosthesis. Under general anesthesia, two zygomatic implants and four conventional implants to the posterior maxilla were inserted. After a healing period, the bar-retained maxillofacial prosthesis and removable mandibular partial denture were fabricated. The patient was satisfied with regard to function, esthetics, speech, and swallowing. No problems, except slight discoloration of the prosthesis were noted at the 6-month follow-up. Implant-supported maxillofacial prostheses are a valuable treatment option to improve   quality of life after maxillary resection.

A modified protocol for restorative implant abutment selection by using computer-aided design and computer-aided manufacturing technology

STATEMENT OF PROBLEM

Implant abutment selection is complex because of the numerous factors involved. Computer-aided design (CAD) technology allows for the virtual selection and placement of abutments after all parameters have been precisely measured. The outcome of this new protocol should be validated.

PURPOSE

The purpose of this in vitro study was to validate a new digital protocol in which abutment selection is made through a CAD software program, the abutments are virtually placed, and the restoration is then designed based on the virtual abutments to fit the actual abutments when delivered to the implants intraorally.

MATERIAL AND METHODS

A cast with 2 parallel implants was scanned 10 times. Then, 2 abutments were placed and scanned 10 times. Twenty identical superstructures were designed and manufactured to simulate the clinical situation of a 3-unit fixed partial denture, screw-retained to 2 implants. These were divided into 2 groups-A, real abutment and B, virtual abutment-and then compared by means of digital and optical measurements.

RESULTS

No significant differences were detected for the measurements between the control and test groups in either the x-axis or y-axis; significant differences were found for the median value of the measurements obtained from both groups regarding the z-axis (P=.046). The mean gap in the virtual abutment group was 50 μm and 35 μm in the real abutment group.

CONCLUSIONS

Superstructures produced after the virtual selection and placement of intermediate restorative abutments compared favorably with those produced after the digitalization of actual abutments and placement in the implant model, thus validating the proposed digital protocol for virtual abutment selection and placement.

Evaluation of Marginal Misfit of Metal Frameworks Welded by Gas-Torch, Laser, and Tungsten Inert Gas Methods

Purpose

The objective of this study was to evaluate the marginal fit and the flexural resistance of nickel-chromium frameworks welded by different techniques, gas-torch, laser, and tungsten inert gas (TIG), compared with that of frameworks made via one-piece casting.

Methods

To evaluate the marginal fit, a master model was fabricated simulating four implants. Transfers and replicas were used to transfer the positions of the implants to the model, using a silicone matrix. The bars were waxed up and casted. Three assessments of misfit were performed for each implant using a stereomicroscope before and after welding in two predetermined regions, totaling six readings for each implant. To evaluate the flexural resistance, one group was made casting the specimens in one piece. Other 3 groups using gas-torch, laser, and TIG welding techniques were made after sectioned transversally. The data showed normal distribution and two-way ANOVA for marginal fit and one-way ANOVA for flexural resistance, and Tukey's posttest (α=0.05) was performed.

Results

For the marginal fit, the three welding methods presented similar results and were different from one-piece casting. For the flexural resistance, significant differences were observed among the studied groups (p < 0.001), and the one-piece group presented higher resistance compared to the three welding techniques.

Conclusions

Within the limits of this study, the three welding techniques yielded similar misfit results, and the laser and TIG techniques presented similar flexural resistance but lower than gas-torch and one-piece casting.