Presentation Title: Comparison of Surface Roughness and Bacterial Colonization of Recently used Dental Ceramics

Speaker:  Amr Abouzaid

Purpose: To assess the effect on surface roughness of a liquid ceramic on 3-Y_TZP compared with polished 3-Y_TZP before and after thermocycling.

Methodology: Three groups; Group PM (3-Y_TZP, MiYO colored, polished). Group PZ (3-Y _TZP, polished). Group M (3-Y_TZP & MiYO colored). Surface roughness was measured before and after artificial aging. Defined amount of bacteria were added. Ra and CFU count values were compared among groups.

Findings: Group PZ showed the lowest CFU followed by roup PM. Surface roughness and CFU count were correlated. Thermocycling increased surface roughness.

Dr. Abouzeid is originally from Egypt, he received his BDS from the Faculty of Dentistry, Tanta University in 2014, and after that, he joined the Egyptian military for 14 months before he started his general dentistry private practice. 

In 2016 he started his journey teaching photography and esthetic dentistry courses. In 2021, he joined the graduate prosthodontics residency program at the University of Washington. In January 2024 he completed his research project and presented his master's thesis at U.W.  After graduation, Dr. Abouzeid is planning to continue his academic journey by joining a faculty position in the U.S.

Presentation Title: Effect of Fabrication Method on Fracture Strength of Interim Implant-Connecting Bars

Speaker:  Andre Cataluna

Comfort and function are critical for quality of life in post-maxillectomy patients. Immediate implant placement and early loaded implant-connecting bars are utilized to address these objectives, improving retention and stability of interim obturators while simultaneously splinting and minimizing implant movement. While several fabrication methods have been employed, there is a lack of research comparing their fracture resistance in the setting of maxillofacial prosthetics. The purpose of the present study is to compare the fracture resistance of interim implant bars fabricated via three methods: heat processed polymethyl methacrylate (PMMA), milled PMMA, and printed resin.

In maxillectomy patients, initial delivery of an interim obturator can often be met with challenges related to retention and stability during the early phases of healing. The comfort and functionality of these prosthetic devices are paramount for enhancing quality of life post-maxillectomy. To tackle these challenges, immediate implant placement and early loading of implant-connecting bars are employed to enhance the retention and stability of interim obturators. Furthermore, interim bars serve to splint and immobilize implants, mitigating the risk of individual implant movement. Despite various manufacturing methods for these bars, no prior research has investigated their susceptibility to fracture within this clinical context.

The purpose of the present study is to compare the fracture resistance of interim implant bars fabricated with three methods: heat processed polymethyl methacrylate (PMMA), milled PMMA, and printed resin (SprintRay OnX). To conduct this study, a stone master cast with two Nobel external hex implant analogs was fabricated. Analogs were spaced 14mm apart from center to center and an implant-connecting bar measuring 6mm in height and 5mm in width was waxed up. The bar was then scanned, and from this design, 20 uniform specimens were fabricated using milled PMMA (N = 10) and 3D-printed resin (N = 10). Specimens from the two groups were luted to titanium cylinders using self-cured PMMA and flowable composite resin, respectively. A transfer jig fabricated from the master cast was then utilized to fabricated 10 working casts. 10 wax pattern bars were milled, luted to titanium cylinders on the working casts, invested, and boiled out. Heat processed PMMA bars (N = 10) were then fabricated directly onto titanium cylinders. All implant bars were connected to the master cast and new abutment screws were torqued to 35Ncm. The bars were subjected to mechanical testing using the Instron at a crosshead speed of 0.5mm/min to assess load to fracture. The null hypothesis states bars fabricated from all three materials will fracture at the same load.

Dr. Andre Cataluna was raised in Carson, California. After high school, he attended the University of California, Los Angeles (UCLA), earning his Bachelor of Science in biology. Dr. Cataluna continued his training at UCLA, earning both his DDS and certificate in Advanced Prosthodontics. After completing residency, he remained at UCLA, where he is a current Maxillofacial Prosthetics fellow.

Presentation Title: Overcoming Silicone Cure Inhibition on Printed Resin Molds

Speaker:  Chen Chen

Material jetting technologies have the potential to facilitate the efficient fabrication of facial prostheses for patients with maxillofacial defects. A serious issue of silicone cure inhibition exists, however, between the 3D printed resin materials and room temperature vulcanizing (RTV) silicone and this remains unresolved. One hypothesized solution to this dilemma is by the use of platinum-containing silicone primers, which accelerate the reaction to completion before the surface resin has a chance to interfere with the silicone setting. Platinum primers, however, cause silicone adhesion to the mold surface, preventing its retrieval without tear and distortion. Thus, a silicone releasing agent is required on the mold surface to facilitate separation of the silicone from the mold at devesting. Three industry formulated platinum-containing silicone primers were tested (A-304 platinum primer, A-306 platinum plus primer, A-317 platinum accelerator, Factor II) each with increasing platinum content, in combination with three silicone releasing agents (A-501 zinc stearate, A-503 silicone mold release, A-515 Ease Release 200, Factor II). Nine identical CAD/CAM fabricated resin molds for a partial nasal prosthesis were printed with a photopolymerising printed resin material (Vero™, Stratasys) using a material jetting 3D printer (J750, Stratasys). Following application of the various combinations of primer and releasing agents, a medical grade intrinisically colored RTV silicone (VST-50, Factor II) was packed into the resin molds, clamped under 500 psi of pressure and allowed to benchtop cure for 8 hours, then immersed in boiling water for 30 mins before retrieval. Analysis of silicone cure was both qualitative and quantitative. The mold surface was qualitatively observed for presence of a film of unset silicone at the margins, a stickiness or tackiness to the touch and the absence of z-lines on the surface under 5x magnification. Quantitatively, each silicone prosthesis was measured at two set points from the bulk of the prosthesis to the margin, overlayed on a 1x1mm grid paper. Deficiency in the dimensions of the prosthesis indicated the degree of unset silicone, most pronounced at the feather margins. Finally, using the most effective combination of primer and releasing agent (A-317 and A-503), an implant-retained nasal prosthesis was successfully fabricated for a patient with full rhinectomy as proof of concept.

Dr. Chen Chen received her BDS degree from the University of Queensland, Australia in 2008. After graduating, she worked with the Royal Flying Doctors Service, servicing the rural and remote Aboriginal and Indigenous communities of Cape York Peninsula, Queensland, before entering private practice for a few years. In 2015, she completed a Graduate Diploma in Implantology from the University of Melbourne, and worked a few more years in private practice, before finally embarking on specializing in the US. In 2023, she completed her Advanced Prosthodontics Certificate at University of Southern California, and is a current Maxillofacial Prosthetics fellow at UCLA. In her spare time, she enjoys cycling, multi-day hikes and trail running, and hopes to put a few more Ultra-marathons under her belt before she grows old in her bones.

Presentation Title: Debulking and Vestibuloplasty

Speaker:  Alisa Pham

Osteomyocutaneous free tissue transfer is the primary method for surgically restoring a composite mandibular defect. Subsequent maxillofacial rehabilitation following mandibular resections demands meticulous pre-prosthetic soft tissue surgery for optimal mandibular resection prosthesis (MRP) function. The primary goals include establishing thin attached tissue suitable for denture bearing surfaces, creating space for MRP placement, and optimizing peri-implant tissue cuff when implants are utilized. Because the skin flap harvested from the leg exceeds 10 mm, significant debulking and vestibuloplasty (DBVP) is required and is achieved with the aid of a custom-fabricated stent. This report details a technique for planning and fabricating a 3D printed DBVP stent.

Using post reconstruction computer tomography, a 4 mm digital space from the osseous graft, and 4 mm from reconstruction hardware. This allows space for the periosteum and split thickness (0.3 mm) skin graft (STSG), the outline extends to just beyond the first molar. The borders are designed to be rounded with a 2.5 mm radius, and overall stent thickness of 5 - 6mm. Three screw holes are designed with a tripod distribution simultaneously guiding the twist drills to engage the fibula mono-cortically. The splint is printed in a material FDA cleared for 4 weeks of contact with mucosa.

At the time of surgery, the skin paddle is fully elevated leaving the periosteum and avoiding the vasculature pedicle. Tissue bulk may be used to line the lip or cheek on the buccal or facial side to preserve tongue bulk in situations of glossectomy. The prepared raw osseous trough is lined with the STSG and sutured to the periosteum creating a 8-12mm band along the neo-ridge. The splint is relined with soft denture liner then secured with mono cortical screws and left bolstering the graft for 4 weeks. Unpacking of the DBVP stent is combined with delivery or relining of an existing interim MRP to maintain the tissues as it matures.

Dr. Alisa Pham, originally from Westminster, California, pursued higher education across various institutions in the state. Following her high school graduation, she enrolled at California State University, Long Beach (CSULB), where she earned her Bachelor of Science in Biology. Dr. Pham then relocated to San Francisco to pursue her Doctorate of Dental Surgery at the University of California, San Francisco (UCSF). Returning to Southern California, she completed her residency, obtaining a certificate in Advanced Prosthodontics from West Los Angeles VA. Subsequently, Dr. Pham undertook a Fellowship at UCLA, where she currently serves as a Maxillofacial Prosthetics fellow.