UCLA Fit Testing Procedure: Ensuring Accuracy and Safety in Implant Prosthodontics and Healthcare Settings

Introduction

The UCLA fit testing procedure encompasses various essential aspects, ranging from ensuring the accuracy of implant abutments in prosthodontics to safeguarding the health and safety of medical students through occupational risk training. This article aims to provide a comprehensive overview of these procedures, highlighting their significance and practical applications.

UCLA Abutments in Implant Prosthodontics: Ensuring Precise Fit

The Importance of a Precise Fit

In implant-supported restorations, osseointegration provides new treatment options for both edentulous and partially edentulous patients. A precise fit between an implant abutment and a superstructure is crucial to avoid bone tension in the absence of occlusal load, which is an important factor for the long-term success of implant-supported restorations. Implants are completely surrounded by bone, and the interface is not elastic, resulting in minimal movement due to bone deformation under loading. Therefore, stress introduced into the implant system as a result of prosthesis misfit may persist for many years because of the ankylotic nature of osseointegration.

UCLA Abutments: A Solution for Implant-Anchored Prosthesis

A widely used solution in implant-anchored prosthesis is the castable plastic patterns, known as UCLA abutments. This abutment is designed to directly engage the implant, allowing the prosthodontist to extend the porcelain subgingivally in areas with extremely limited gingival tissue height. The subgingival placement of the restoration not only improves esthetics but also helps in situations with interocclusal distance limitations. The use of such abutments allows correction in angulations for implants inserted at angles other than ideal.

Concerns and Solutions for Abutment Fit

Concerns have been raised regarding whether the use of these custom-made abutments would result in a fit of the abutment to the implant that could be comparable to that achieved with the use of premachined titanium abutments. An intermediate solution was developed, whereby premachined UCLA abutments made of noble metal alloys could be cast directly to allow integration of the restoration with the abutment. Another alternative is the use of cast rectifiers.

Evaluating the Effect of Cast Rectifiers

A study evaluated the effect of cast rectifiers on the misfit of cast UCLA abutments compared to premachined UCLA abutments. The abutments were secured to the sprues and fixated in a sprue former. A silicone-casting ring was adapted to the sprue former, and the investment was poured (Bellavest T; Bego, Bremen, Germany). The patterns were induction cast: abutments of the test group with a nickel-chromium alloy (Wiron 99; Bego, Bremen, Germany), and abutments of the control group with a palladium-silver alloy (Williams W1; Ivoclar Vivadent, Amherst, NY, USA). Castings were allowed bench cool and were then divested and cleaned with air abrasion. Fitting surfaces of the castings made with plastic patterns (test group) were milled with the cast rectifiers (Conexão Sistema de Próteses, São Paulo, SP, Brazil), by turning the tool against the abutment fitting surface twenty times in a clockwise direction. A new rectifying tool was used for every 5 components.

Methodology for Misfit Measurement

In all 20 specimens, porcelain (Omega 900; Vita, Bad Säckingen, Germany) was applied to the abutments, carved, and then baked according to the manufacturer's recommendations. Misfit measurements were performed with a light microscope (Sprint 100; RAM Optical Instrumentation, Irvine, CA, USA). Laser marks were created in the abutments and in the implant to allow positioning of the components at the same place during microscopic measurements. Three microscopic measurements at X460 magnification were made for each aspect of the hexagonal base, at reading points predetermined by laser marks on the lateral aspect of the implant platform, adding up to 18 reading points for each specimen. Marginal misfit measurements in the test group were performed before (M1) and after (M2) the use of rectifiers, and after ceramic application (M3). Data were submitted to statistical analysis by analysis of variance, and individual comparisons were done by Tukey's post-hoc test.

Results of the Study

The cast UCLA abutments (test group - M1) showed the greatest discrepancies, with a marginal misfit mean of 25.68 μm. With the use of abutment rectifiers (test group - M2), there was a significant reduction in the marginal misfit of cast UCLA abutments, from 25.68 μm to 14.83 μm. Casting of the premachined UCLA abutments (control group - M2) altered significantly the marginal misfit of these components (from 9.63 μm to 14.6 μm).

The Impact of Marginal Misfit

Several studies have demonstrated the success of Implantology. However, despite the evolution of this specialty, clinical complications are still frequent. Numerous studies have been conducted to understand and reduce occasional complications. In spite of the advances in technology, the materials and techniques employed in the fabrication of prosthetic structures are not dimensionally accurate and require further investigation and development. Distortions of such structures are inevitable, and it is impossible to achieve a perfect fit and absolute passivity at the prosthetic interfaces. Prosthesis misfit favors bacterial colonization, leading to inflammation of the periimplant soft tissues and harming osseointegration.

Alternative Solutions to Reduce Misfit

Prosthetic protocols employing machined components reduce these risks, due to the higher accuracy of fit. The use of this prosthetic option has increased even though the fit at the abutment to implant interface is not as satisfactory as the fit provided by premachined abutments. Due to this increased search for components, companies have developed alternatives to reduce misfit, such as the premachined UCLA abutments. Another option is the use of castable plastic patterns followed by a laboratory finishing of the fitting surface with a cast rectifier.

Limitations of Cast UCLA Rectifiers

There is a limitation for the use of cast UCLA rectifiers. This hand-operated device has been developed only for non-hexed cast UCLA abutments (i.e., without the antirotational device). The present study revealed high values of marginal misfit in the castings made with plastic patterns (test group M1 25.68 μm) compared to premachined abutments (9.63 μm). Similar results were described by Byrne, et al. (1998). The factors that contribute to the distortion of castings, directly impairing the marginal fit between components, include fabrication of acrylic cylinders, limitations of investment processes, and casting techniques.

Read also: Navigating Tech Breadth at UCLA

The Role of Cast Rectifiers in Reducing Misfit

The use of cast rectifiers led to a significant reduction of marginal misfit of cast UCLA abutments, with a reduction of marginal misfit means from 25.68 μm to 14.83 μm. Concerning the premachined abutments used as a reference, the mean marginal misfit after the ceramic application (M3) was 14.3 μm. Ceramic application did not change the marginal misfit in any of the groups.

Standardizing Screw Tightening

The seating force used to place the samples on the master cast has an important effect on the vertical misfit. The use of a torque driver, even with the lowest torque available (10 N/cm), may considerably narrow the vertical misfit gaps at the abutment-framework interface. Marginal misfit investigations, in which screws are hand fastened, always by the same investigator, until the first resistance is met, as suggested by Zervas, et al. (1999), allows a more real fit evaluation because no attempt is made to narrow the vertical misfit gaps. However, it seems to be a risky protocol, due to the wide variation in the ability of the clinicians to perceive torque, making difficult the standardization of the screw tightening procedure prior to microscope measurements. In the present study, a special torque driver was fabricated, reducing the torque to 5 N/cm. This way, the screw tightening was standardized with a seating force that did not considerably influence the vertical misfit gaps.

Microscopic Evaluation of Marginal Misfit

In the present investigation, microscopic evaluation of the marginal misfit was employed. The measurements were taken by positioning the specimens on the microscope so that the marginal area of connection between the abutment and the implant could be observed from a directly perpendicular perspective. Other investigators have also used this methodology. This allows measurement of the marginal discrepancy in a non-destructive manner, with multiple readings of specimens. Even though there are several three-dimensional methods for evaluating prosthetic misfit, the sophisticated equipment required for such analyses are not promptly available.

Achieving a Passive Fit

According to the currently available scientific-based evidences, despite the efficacy of contemporary dental technology employed in the fabrication of prosthetic frameworks, an absolutely passive fit cannot be achieved. That is, the concepts of passivity provide necessary theoretical ideals, yet their achievement is impossible.

Conclusions from the Study

The results of the present study allow the following conclusions:

Read also: Understanding UCLA Counselors

Use of rectifiers in cast UCLA abutments reduced significantly the marginal misfit at the implant-abutment interface.
Even with carefully performed laboratory steps, changes at the implant interface of premachined UCLA abutments occurred.

Occupational Risk Training for Medical Students at UCLA

The Importance of Safety Training

Participation in direct patient care activities can pose risks to health care professionals, particularly in terms of exposure to infectious diseases. The School of Medicine requires that all medical students participate in annual safety training that facilitates students’ anticipation, recognition, and avoidance of potential occupational risks.

Bloodborne Pathogens Exposure Protocol

Medical students (including visiting students) are covered for emergency and follow-up care after body-fluid exposures that occur in the classroom, clinical, or research settings. When an exposure (e.g., needle-stick injury) occurs, students are to immediately alert their supervisor. Source patient testing should be initiated, if feasible. For exposures that occur at UCLA (including UCLA/Santa Monica), the order requisition and instructions for source testing can be found on the Mednet Forms Portal (Form #10935, Occupational Exposure- Source Patient Requisition).

Immediate Care Procedures

Students Rotating at UCLA

The student should go immediately to UCLA Occupational Health during operating hours (Monday-Friday from 7 AM to 4 PM, excluding holidays). Occupational Health is located in room 17-240 CHS, on the first floor and in the main lobby of CHS. No appointment is necessary. If the incident occurs after hours, the student should proceed to the nearest UCLA Emergency Department (Ronald Reagan Medical Center or UCLA Santa Monica Hospital).

Students Rotating at a Remote Site

If the site has an Occupational Health or Employee Health office that is open, the student should have their initial evaluation there. Otherwise, the student should go to the nearest Emergency Department. After this initial evaluation, follow-up evaluation and care should occur at UCLA Occupational Health (location details above). The student should obtain results of their baseline lab testing, and if possible, source patient testing (if performed), so that this information is available for follow-up at UCLA Occupational Health. Following exposure, the student should contact their Society Dean, or Dr. Calmes, who in turn will communicate with leadership at Occupational Health so that they are aware of the upcoming follow-up evaluation. If the student cannot reach one of the above deans, or is a visiting student, a call should be made to the medical student emergency line at 310-825-6281 to speak with a dean on call.

Medication Prescriptions

If HIV postexposure prophylaxis (PEP) is prescribed at any location other than UCLA’s Occupational Health, a starter prescription should be written to cover medications in sufficient quantity until follow-up at UCLA Occupational Health can occur. Prescriptions written at UCLA Occupational Health must be filled at UCLA’s outpatient pharmacy, or at a pharmacy that is able to dispense medications covered under UCLA’s workers’ compensation program. Prescriptions filled under regular health insurance cannot be reimbursed.

Follow-up Care

All follow-up care must occur at UCLA Occupational Health, regardless of the location of the incident or the results of the initial evaluation. Students initially evaluated elsewhere should call UCLA Occupational Health at 310-825-6771 for an appointment to be seen the following business day between 7 AM and 4 PM. Occupational Health is located in room 17-240 CHS, on the first floor and in the main lobby of CHS. Students should notify their Student Affairs dean to be excused from class or clinical duties, if necessary.

Billing Issues

The cost of the initial evaluation and care is the financial responsibility of the institution at which the exposure occurred. While California law does not require disclosure of chronic bloodborne viral infections (such as Hepatitis B, Hepatitis C, and HIV), students with these diseases are highly advised to seek educational and career counseling through the Ashe Center. CAE and the School of Medicine will engage in the interactive process to discuss the provision of reasonable accommodations. For some conditions, students may need to consult with the Ashe Center or their own medical provider prior to returning to duty. For some conditions, if a reasonable accommodation cannot be identified by CAE, the student may be restricted from participation in some or all educational activities. This restriction may be necessary to protect the health and safety of both patients and other members of the DGSOM community.

Colorectal Cancer Screening at UCLA Health

Educational Resources for Patients

UCLA Health provides a curated list of educational resources on colorectal cancer for its patients. All of the materials provided are developed by reputable organizations and institutions to help patients learn about colorectal cancer risk and the benefits of screening.

Bowel Prep Instructions

UCLA Health offers a 5-page resource with general information on bowel prep, medication management around the time of colonoscopy, transportation, diet, and a pre-procedure checklist. Patients will learn about their bowel prep formulation when they call to schedule their procedure.

Resources from Reputable Organizations

American College of Gastroenterology (ACG)

ACG has developed a range of graphics, including powerful and informative infographics, to help in colorectal cancer (CRC) awareness efforts.

Centers for Disease Control and Prevention (CDC)

CDC offers resources to help people learn about the importance of men and women 45 years old or older getting screened for colorectal (colon) cancer regularly.

Colon Cancer Coalition

The Colon Cancer Coalition has created a library of educational materials, in various languages, that are available to download.

Improving Screening Rates

With an estimated 38% of Americans expected to be diagnosed with cancer, being able to take advantage of a screening test would seem like an obvious win to catch any disease sooner rather than later. A real-world experiment that offered screening to more than 7,700 participants found that giving people a deadline to complete an at-home test for colorectal cancer was an effective nudge that boosted testing rates.

The Role of FIT Tests

Until fairly recently, initial screening for colon cancer presented a slew of hurdles. The development of an at-home test removed some of those hurdles. A FIT test provides an initial noninvasive screening for colon cancer. If a person receives a positive test, they then must undergo a diagnostic procedure such as a colonoscopy. However, if they receive a negative test, they simply need to do the FIT again the following year.

The Impact of Deadlines on Screening Completion

A team of researchers, including UCLA Anderson’s Alicea Lieberman; UC San Diego’s Ayelet Gneezy; University of Texas Southwestern Medical Center, Fort Worth’s Emily Berry, Stacie Miller and Keith E., found that less than 5% of a study group completed the test within three weeks. An even shorter deadline proved to be a more effective nudge. A small declining financial incentive coupled with a deadline did not prove to be any more effective than the short deadline with no incentive attached. It took a bigger financial nudge to compel more uptake among this lower-income pool of participants. The researchers took a look at all study participants, regardless of whether they were in the control group or one of the nudge groups with different deadlines/incentives. The results of this study suggest that future screening campaigns might embed a short deadline. It also adds to growing research showing more generally - not just in cancer screening - deadlines are an effective nudge to get past procrastination.

tags: #UCLA #fit #testing #procedure