Faculty Bibliography

Achieving the appropriate primary stability for immediate or early loading in areas with low-density bone, such as the posterior maxilla, is challenging. A three-dimensional (3D) stabilization implant design featuring a tapered body with continuous cutting flutes along the length of the external thread form, with a combination of curved and linear geometric surfaces on the thread's crest, has the capacity to enhance early biomechanical and osseointegration outcomes compared to implants with traditional buttressed thread profiles. Commercially available implants with a buttress thread design (TP), and an experimental implant that incorporated the 3D stabilization trimmed-thread design (TP 3DS) were used in this study. Six osteotomies were surgically created in the ilium of adult sheep (N = 14). Osteotomy sites were randomized to receive either the TP or TP 3DS implant to reduce site bias. Subjects were allowed to heal for either 3 or 12 weeks (N = 7 sheep/time point), after which samples were collected en bloc (including the implants and surrounding bone) and implants were either subjected to bench-top biomechanical testing (e.g., lateral loading), histological/histomorphometric analysis, or nanoindentation testing. Both implant designs yielded high insertion torque (ITV ≥ 30 N⋅cm) and implant stability quotient (ISQ ≥ 70) values, indicative of high primary stability. Qualitative histomorphological analysis revealed that the TP 3DS group exhibited a continuous bone-implant interface along the threaded region, in contrast to the TP group at the early, 3-week, healing time point. Furthermore, TP 3DS's cutting flutes along the entire length of the implant permitted the distribution of autologous bone chips within the healing chambers. Histological evaluation at 12 weeks revealed an increase in woven bone containing a greater presence of lacunae within the healing chambers in both groups, consistent with an intramembranous-like healing pattern and absence of bone dieback. The TP 3DS macrogeometry yielded a ~66% increase in average lateral load during pushout testing at baseline (T = 0 weeks, p = 0.036) and significantly higher bone-to-implant contact (BIC) values at 3 weeks post-implantation (p = 0.006), relative to the traditional TP implant. In a low-density (Type IV) bone model, the TP 3DS implant demonstrated improved performance compared to the conventional TP, as evidenced by an increase in baseline lateral loading capacity and increased BIC during the early stages of osseointegration. These findings indicate that the modified implant configuration of the TP 3DS facilitates more favorable biomechanical integration and may promote more rapid and stable bone anchorage under compromised bone quality conditions. Therefore, such improvements could have important clinical implications for the success and longevity of dental implants placed in regions with low bone density.

The aim of the study was to assess the effect of bulk material on the reliability and failure modes of narrow-diameter implants. Narrow implants (Ø3.5 × 10 mm - 11° internal conical connection) were manufactured from three different bulk materials: commercially pure titanium grade-IV (CP4), cold-worked titanium (CW), and 4Titude (4Ti), and were evaluated under fatigue testing. Eighteen samples per group were tested under step-stress accelerated life testing through 30° off-axis load application in mild, moderate, and aggressive loading profiles. The number of cycles and load at failure were used to calculate use-level probability curves and reliability for missions of 100,000 cycles up to 200 N, followed by fractographic analyses. Beta values suggested that damage accumulation dictated failures. Reliability analyses at 80, 120, and 150 N evidenced high reliability for narrow implants independent of bulk material. At 200 N, a decrease in reliability was observed for all groups (∼46%). Failure mode analysis depicted similar failures for all groups and comprised implant fracture, abutment fracture, and implant + abutment fractures. Narrow implants presented high reliability for physiologic masticatory forces in the anterior region. Characteristic strength, reliability, and failure modes were similar regardless of bulk material, suggesting that fatigue damage accumulation at thin wall implants dictated failure over bulk material strength.

To evaluate the effect of silanized filler particles and blue light-sensitive photoinitiator system on the internal and marginal fit of 3D printed resin crowns as well as the volume of provisional cement space. This study evaluated three commercially available 3D-printing resins (Smart Print Temp/SP, Resilab 3D Temp/RL, and Cosmos Temp/CT). The experimental groups consisted of the addition of 30% by weight (30 wt%) of silanized filler particles and a blue light-sensitive Ternary Photoinitiator System (TPS). Samples were printed for each group (n = 10) and evaluated for internal and marginal fit and volume of cement space using a micro-computed tomography (μCT). The obtained data were analyzed by Generalized Linear Models (α = 0.05). The incorporation of TPS and filler particles to the 3D printing resins altered the internal fit and the marginal fit, increasing the cement space at the occlusal face and decreasing the cement space of the axial walls for all tested materials. The volume was significantly affected too, especially for RL and CT. Internal misfit was significantly higher with the addition of TPS, and marginal misfit with the addition of filler particles. In general, the incorporation of TPS and 30 wt% of filler particles promoted an increase in the volume of cement space, as well as an increase in occlusal space and marginal space and a decrease in the axial walls' spaces.

Guided bone regeneration (GBR) procedures have been indicated to enhance bone response, reliably regenerate lost tissue, and create an anatomically pleasing ridge contour for biomechanically favorable and prosthetically driven implant placement. The aim of the current study was to evaluate and compare the bone regenerative performance of deproteinized bovine bone (DBB) and deproteinized porcine bone (DPB) grafts in a beagle mandibular model for the purposes of GBR. Four bilateral defects of 10 mm × 10 mm were induced through the mandibular thickness in each of the 10 adult beagle dogs being studied. Two of the defects were filled with DPB, while the other two were filled with DBB, after which they were covered with collagen-based membranes to allow compartmentalized healing. Animals were euthanized after 6, 12, 24, or 48 weeks postoperatively. Bone regenerative capacity was evaluated by qualitative histological and quantitative microtomographic analyses. Microcomputed tomography data of the bone (%), graft (%), and space (%) were compared using a mixed model analysis. Qualitatively, no histomorphological differences in healing were observed between the DBB and DPB grafts at any time point. By 48 weeks, the xenografts (DBB and DPB) were observed to have osseointegrated with regenerating spongy bone and a close resemblance to native bone morphology. Quantitatively, a higher amount of bone (%) and a corresponding reduction in empty space (space (%)) were observed in defects treated by DBB and DPB grafts over time. However, no statistically significant differences in bone (%)were observed between DBB (71.04 ± 8.41 at 48 weeks) and DPB grafts (68.38 ± 10.30 at 48 weeks) (p > 0.05). GBR with DBB and DPB showed no signs of adverse immune response and led to similar trends in bone regeneration over 48 weeks of permitted healing.

Hearing loss affects approximately 70 % of individuals with osteogenesis imperfecta (OI), a genetic connective tissue disorder characterized by bone fragility and deformities. No effective treatments exist for OI hearing loss, and its etiology is unknown limiting the development of new targeted therapies. This work investigates the impact of OI type I collagen mutations on the ossicle bone properties in the homozygous oim mouse model of severe OI, which is known to exhibit hearing loss. The morphology and porosity of the ossicles of 14-week-old oim and wild-type mice were analyzed using high-resolution synchrotron radiation microtomography. Additionally, the collagen fibers structure, bone tissue composition and mechanical properties were evaluated through second harmonic generation microscopy, Raman spectroscopy, and nanoindentation. The results demonstrated that oim ossicles are small, highly porous with an elevated lacunar number density, a flat stapes footplate and a small malleal processus brevis. One-in-two oim ossicles had incudomalleal joint abnormalities, exhibiting either a localized fracture in the incus head or a joint space widening. No differences were observed in collagen fibers structure, bone tissue composition and mechanical properties. These findings suggest that bone fractures observed in the oim incus may contribute to their reported hearing loss. However, the underlying mechanism for these fracture development remains to be investigated, as they do not appear to result from changes in bone tissue properties (collagen fibers organization, tissue composition or mechanical properties). Instead, they may be associated with joint space widening, and possibly altered ossicle chain kinematics.

BACKGROUND:Implant's primary stability is determined by the intimate and immediate contact between the implant and osteotomy wall, whereas secondary stability is primarily influenced by healing chambers that facilitate the bone formation and remodeling processes following placement. Therefore, modifications to macro-geometric parameters are essential to elicit the desired in vivo response and to ensure successful osseointegration. Three-dimensional (3D) stabilization thread forms comprise both curved and linear geometric surfaces across the thread's crest maximizing retention forces while constraining lateral movement under load relative to conventional buttress-threaded implants. METHODS:This study utilized Ti-6Al-4V ELI implants with (i) a buttress thread design [Tapered Pro, BioHorizons®, Birmingham, AL, USA] (TP - control) compared to (ii) a novel, patented, 3D stabilization trimmed-thread design (TP 3DS - experimental). Implants were placed in the mandible of sheep (N = 14 sheep, 6 implants per group per sheep) and allowed to heal for 3- and 12-weeks (N = 7 sheep per time point). During implant placement (T = 0 weeks), the maximum insertion torque value (ITV) and implant stability quotient (ISQ) were measured by torque-in testing and resonance frequency analysis, respectively. After the healing periods, subjects were euthanized, and samples harvested en bloc for biomechanical evaluation via lateral loading tests in addition to histomorphometric and nanoindentation analysis. RESULTS:ITV values were significantly lower in the TP 3DS group compared to TP (p < 0.001). Both groups presented ISQ values ≥ 70, indicating high primary stability. Relative to the TP group, TP 3DS exhibited a significant (∼1.85-fold) increase in lateral load at 3 weeks (p = 0.029) and comparable load values at 12 weeks (p > 0.05). No quantitative differences in percentage of bone-to-implant contact (BIC) and bone-area-fraction-occupancy (BAFO) were observed at either time points between the two thread designs (p > 0.05). Similarly, no differences in bone's mechanical properties (Young's modulus (E) and Hardness (H)) between TP and TP 3DS were observed at 3- and 12- weeks (p > 0.05). Qualitatively, scattered microcracks were apparent at the outer threads of the implant, particularly within the TP group, whereas small bone chips were interspersed between threads of the 3DS implant serving as additional nucleation sites for bone formation. CONCLUSION/CONCLUSIONS:The TP 3DS design reduced insertion torque, improved lateral loading competence, and resulted in a healing pattern, that are beneficial during early stages of osseointegration compared to TP implants.

This preclinical, in vivo study aimed to histologically and histomorphometrically evaluate the effect of implant design features on bone healing during the early stages of osseointegration. Three different implant macrogeometries and surface treatments were evaluated: (1) trapezoidal threads with decompressing vertical chambers and blasted acid-etched surface (Maestro/Blasted+AE); (2) large thread pitch implant with deep and wide threads, with TiUnite surface (RS/TiUnite); and (3) progressive buttress threads with SLActive surface (BL/SLActive). Implant surfaces were characterized by scanning electron microscopy, profilometry, and energy-dispersive X-ray spectroscopy. Implants were placed in the iliac bone of 12 female sheep (~65 kg and 2 years old). Following healing times of 3- and 6- weeks, samples were harvested and subjected to qualitative and quantitative histological/histomorphometric evaluations. Percentages of bone-to-implant contact (%BIC) along the implant's perimeter and bone area fraction occupancy (%BAFO) within implant threads were measured, and results were analyzed using a linear mixed model analysis. All implants, irrespective of differences in macrogeometry and surface treatment, at both healing times demonstrated successful osseointegration. Evaluations of %BIC yielded no statistically significant differences among groups at 3 and 6 weeks (p > 0.052). While no significant differences were detected among groups for %BAFO at 3 weeks (p > 0.249), Maestro/Blasted+AE yielded significantly higher degrees of bone formation within implant threads relative to RS/TiUnite (p = 0.043) and BL/SLActive group (p = 0.032) at the 6-week time point. Qualitative histological analyses depicted different osseointegration features for the different implants. While Maestro/Blasted+AE portrayed evidence of an intramembranous-like osseointegration pathway in the healing chambers and interfacial remodeling at thread tips, BL/SLActive and RS/TiUnite groups predominantly presented an interfacial bone remodeling healing pathway. Implant design features influenced the osseointegration pathway, where implants with decompressing vertical chambers enhanced bone formation between implant threads.

OBJECTIVE:To synthesize bilayer zirconia systems based on commercial or recycled 3Y-TZP obtained from non-milled remnants and to compare their optical and mechanical properties before and after aging. METHODS:Bilayer zirconia samples were fabricated using either recycled 3Y-TZP (3Y-R/4Y and 3Y-R/5Y) or commercial powders (3Y/4Y and 3Y/5Y). Microstructure and phase composition were analyzed using ScanningElectronMicroscopy (SEM) and X-Ray Diffraction (XRD). Optical and mechanical properties were assessed via reflectance and biaxial flexural strength tests (BFS), followed by fractographic analysis. Optical properties and BFS data were analyzed using two-way ANOVA and Tukey test, and Weibull statistics, respectively. RESULTS:Recycled powder exhibited particle sizes < 2.07μm. SEM micrographs depicted dense surfaces with largest grains in the 5Y, followed by recycled-3Y, 4Y, and commercial-3Y. XRD analysis revealed tetragonal peaks in commercial and recycled 3Y-TZPs, and tetragonal and cubic phases in the 4Y and 5Y surfaces. Aging induced significant phase transformation in 4Y (∼40 %), commercial- (58 %) and recycled-3Y (53 %), with no effect in 5Y surfaces. Commercial bilayers exhibited higher translucency and strength (∼1130 MPa) compared to recycled bilayers (∼935 MPa), with no significant differences within commercial, nor within recycled groups. Aging decreased contrast ratio for recycled groups and increased the strength of all groups. While all groups presented high reliability up to 500MPa, commercial bilayers outperformed recycled systems at 800-MPa. SIGNIFICANCE/CONCLUSIONS:The synthesis of bilayered systems using recycled-3Y was successful, resulting in high reliability in missions up to 500MPa. Bilayers based on commercial powder demonstrated superior translucency, strength, and reliability at 800MPa compared to their recycled counterparts.

OBJECTIVES/OBJECTIVE:To characterize two experimental zirconia bilayer materials compared to their monolithic controls, before and after hydrothermal aging. METHODS:Commercial zirconia powders were utilized to fabricate two bilayer materials: 3Y-TZP+ 5Y-PSZ (3Y+5Y/BI) and 4Y-PSZ+ 5Y-PSZ (4Y+5Y/BI), alongside control groups 3Y-TZP (3Y/C), 4Y-PSZ (4Y/C), and 5Y-PSZ (5Y/C). Compacted specimens were sintered (1550 °C- 2 h, 3 °C/min), and half of them underwent hydrothermal aging (134 °C-20h, 2.2 bar). Characterizations were performed through scanning-electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, reflectance tests and biaxial flexural strength test (ISO:6872). Weibull statistics were applied to determine the characteristic strength and Weibull modulus. Grain size and optical properties were analyzed using two-way ANOVA followed by the Tukey test. RESULTS:Degradation regions and monoclinic phase were observed at aged 3Y-TZP and 4Y-PSZ surfaces. Significant differences were observed in the evaluation of optical properties between the bilayer and control groups. The bilayer materials presented intermediate characteristic strength values compared to their controls and aging significantly increased the strength of some groups. SIGNIFICANCE/CONCLUSIONS:Experimental bilayer materials presented lower mechanical properties than monolithic controls, 3Y/C and 4Y/C. Hydrothermal aging increased the characteristic strength of bilayered and monolithic controls, except for 5Y-PSZ. Both experimental bilayer systems, as well as monolithic controls, met the ISO 6872:2015 requirements for single-unit crowns (100 MPa), 3-unit fixed dental prostheses (FDPs) up to premolars (300 MPa), and 3-unit FDPs involving molars (500 MPa). However, for FDPs with four or more units, only monolithic 3Y-TZP and 4Y-PSZ, and bilayered 3Y+5Y met the required minimum flexural strength (≥800 MPa).

BACKGROUND:The preservation of the alveolar ridge following tooth extraction is crucial to prevent atrophy and maintain structural integrity, facilitating future dental rehabilitations. This study compared the use of two different polymeric, resorbable membranes: polylactic acid (PLA), and 5% polylactic acid + 95% polycaprolactone (PLA/PCL), relative to unassisted socket healing (negative control). MATERIAL AND METHODS/METHODS:A preclinical model involving healthy, skeletally mature beagles (n=7) were used in this study. Surface topography and thermal degradation of the membranes were assessed, followed by in vivo evaluation of socket preservation in extracted maxillary premolars. Histomorphometric analysis was employed to measure bone formation and total socket area. Data was analyzed through linear mixed models with fixed factor of treatment following a post-hoc comparison by the Tukey test. Ranked data of residual membrane presence and inflammatory infiltrate were analyzed through Kruskal-Wallis non-parametric test. All analyses were conducted with statistical significance set at p-value ≤ 0.05. RESULTS:Surface topography depicted a distinctive fibrous network structure for PLA membrane relative to PLA/PCL which exhibited a more porous architecture. Thermal degradation behavior/profile, observed through TGA and DSC, for both membranes was similar. Histomorphometric analysis of bone formation within the induced socket yielded 36.1 ±7.7%, 35.6 ±7.2% and 32.8 ±7.7% for control, PLA and PLA/PCL groups, respectively, with no statistically significant differences between groups (p = 0.796). Analysis of total socket area (mean ± 95% confidence intervals) yielded significantly higher values for experimental groups, PLA (8.95 ± 1.7 mm2) and PLA/PCL (8.8 ± 1.76 mm2), relative to control (6.7 ± 1.8 mm2) (p = 0.041). Residual membrane, along with mild inflammatory infiltrate was observed after the healing period irrespective of membrane type utilized. CONCLUSIONS:Guided bone regeneration (GBR) with PLA and PLA/PCL membranes did not yield higher bone formation within the socket relative to the control group. However, an improvement in the preservation of the socket's architecture was observed.