Bone Tissue Engineering (BTE) of the Craniofacial Skeleton, Part II: Translational Potential of 3D-Printed Scaffolds for Defect Repair.

Computer-aided design/computer-aided manufacturing and 3-dimensional (3D) printing techniques have revolutionized the approach to bone tissue engineering for the repair of craniomaxillofacial skeletal defects. Ample research has been performed to gain a fundamental understanding of the optimal 3D-printed scaffold design and composition to facilitate appropriate bone formation and healing. Benchtop and preclinical, small animal model testing of 3D-printed bioactive ceramic scaffolds augmented with pharmacological/biological agents have yielded promising results given their potential combined osteogenic and osteoinductive capacity. However, other factors must be evaluated before newly developed constructs may be considered analogous alternatives to the "gold standard" autologous graft for defect repair. More specifically, the 3D-printed bioactive ceramic scaffold's long-term safety profile, biocompatibility, and resorption kinetics must be studied. The ultimate goal is to successfully regenerate bone that is comparable in volume, density, histologic composition, and mechanical strength to that of native bone. In vivo studies of these newly developed bone tissue engineering in translational animal models continue to make strides toward addressing regulatory and clinically relevant topics. These include the use of skeletally immature animal models to address the challenges posed by craniomaxillofacial defect repair in pediatric patients. This manuscript reviews the most recent preclinical animal studies seeking to assess 3D-printed ceramic scaffolds for improved repair of critical-sized craniofacial bony defects.

Impact of implant thread design on insertion torque and osseointegration: a preclinical model

Background: Successful osseointegration of endosteal dental implants has been attributed to implant design, including the macro-, micro- and nano- geometric properties. Based on current literature pertaining to implant design, the resultant cellular and bone healing response is unknown when the thread thickness of the implants is increased, resulting in an increased contact area in implants designed with healing chambers. The aim of this study was to evaluate the effect of two implant designs with different thread profiles on the osseointegration parameters and implant stability at 3- and 6-weeks in vivo using a well-established preclinical dog model.Material and methods: A total of 48 type V Ti alloy implants were divided in two groups according to their thread design (D1= +0.1x/mm and D2= +0.15x/mm) and placed in an interpolated fashion into the radii of six beagles. Insertion torque was measured at time of placement, radii were extracted for histological processing following 3- and 6-week healing intervals. Histologic and histomorphometric analyses were performed in terms of bone to implant contact (%BIC) and bone area fraction occupancy within implant threads (%BAFO). Statistical analyses were performed through a linear mixed model with fixed factors of time and implant thread design.Results: Surface roughness analysis demonstrated no significant differences in Sa and Sq between D1 and D2 implant designs, which confirmed that both implant designs were homogenous except for their respective thread profiles. For insertion torque, statistically significant lower values were recorded for D1 in comparison to D2 (59.6 ± 11.1 and 78.9 ± 10.1 N⋅cm, respectively). Furthermore, there were no significant differences with respect to histological analysis and histomorphometric parameters, between D1 and D2 at both time points.(AU)

Bone regeneration at extraction sockets filled with leukocyte-platelet-richfibrin: An experimental pre-clinical study

Background: We aimed to histomorphometrically evaluate the effects of Leucocyte-Platelet-Rich Fibrin (L-PRF),with and without the combination of a bone grafting material, for alveolar ridge preservation using an in vivocanine model.Material and Methods: Seven dogs (Female Beagles, ~18-month-old) were acquired for the study. L-PRF wasprepared from each individual animal by drawing venous blood and spinning them through a centrifuge at 408RCF-clot (IntrasSpin, Intra-Lock, Boca Raton, FL). L-PRF membranes were obtained from XPression fabrication kit (Biohorizons Implant Systems, Inc., AL, USA). A split mouth approach was adopted with the first molarmesial and distal socket defects treated in an interpolated fashion of the following study groups: 1) Empty socket (negative control); 2) OSS filled defect 3) L-PRF membrane; and 4) Mix of Bio-Oss® with L-PRF. After six weeks,samples were harvested, histologically processed, and evaluated for bone area fraction occupancy (BAFO), vertical/horizontal ridge dimensions (VRD and HRD, respectively), and area of coronal soft tissue infiltration.Results: BAFO was statistically lower for the control group in comparison to all treatment groups. Defects treatedwith Bio-Oss® were not statistically different then defects treated solely with L-PRF. Collapsed across all groups,L-PRF exhibited higher degrees of BAFO than groups without L-PRF. Defects filled with Bio-Oss® and Bio-Oss®with L-PRF demonstrated greater maintenance of VRD relative to the control group. Collapsed across all groups,Bio-Oss® maintained the VRD and resulted in less area of coronal soft tissue infiltration compared to the emptydefect. Soft tissue infiltration observed at the coronal area was not statistically different among defects filled withL-PRF, Bio-Oss®, and Bio-Oss® with L-PRF.Conclusions: Inclusion of L-PRF to particulate xenograft did not promote additional bone heading at 6 weeks invivo. ... (AU)

Implants Placed in Adolescents Followed for Up to 15.5 Years: A Retrospective Case Series.

PURPOSE: To evaluate the clinical outcomes of unsplinted implant-supported single crowns placed in adolescents, ages 10 to 19 years, and followed up from 5 to 15 years. MATERIALS AND METHODS: This retrospective case series evaluated the outcomes of implant-supported single crowns placed in adolescents between June 2002 and January 2015. The patients were treated with locking-taper connection implants under a two-stage rehabilitation technique. The variables assessed included patient identification, age and reason for implant placement, implant dimensions, follow-up time, status at follow-up, and event description. To analyze peri-implant changes, bone crest level relative to the adjacent tooth was measured from periapical radiographs taken after implantation and the latest follow-up. A paired t test was performed to determine initial and follow-up differences, and data are shown as mean and 95% confidence interval. Cumulative Kaplan-Meier survival rates for implants and prostheses were calculated. RESULTS: Twenty-one adolescent patients with ages ranging from 14 to 19 years, mainly 16 to 18 years, received a total of 37 implant-supported single crowns more frequently placed in the anterior maxilla as a result of congenital aplasia and trauma. Mean changes in bone crests were 1.99 (± 0.4) mm at the day of crown insertion and 2.23 (± 0.4) mm at the latest follow-up (average: 10 years; P = .08). No implant was lost during the follow-up period, leading to 100% implant survival. A total of 34 surviving crowns and 3 crown failures at the time of the latest follow-up led to a cumulative survival rate of 70%. The most commonly observed event was loss of proximal contacts and infraocclusion, which were handled chairside by adding resin composite. CONCLUSION: Unsplinted implant-supported single crowns placed in adolescents showed high implant and prosthesis survival rates, with a mean bone crest level increase of approximately 0.23 mm relative to the adjacent teeth.

Cementation Protocol for Bonding Zirconia Crowns to Titanium Base CAD/CAM Abutments.

PURPOSE: To establish the most effective cementation protocol for bonding zirconia crowns to Ti-Base CAD/CAM abutments in terms of abutment height, cement type, and surface pretreatment. MATERIALS AND METHODS: Zirconia crowns were designed to fit abutments of 2.5-mm (short) and 4.0-mm (tall) height. The retention of conventional resin cement with a universal adhesive (RelyX Ultimate, 3M ESPE) was compared to self-adhesive resin cement (RelyX U200, 3M ESPE) following different surface pretreatments (n = 10/group): (1) no treatment (NT); (2) Ti-Base abutment surface blasting with alumina particles (SB); (3) zirconia crown tribochemical surface blasting with silica-coated alumina particles (TBS); and (4) a combination of SB + TBS. Pull-out testing was performed in a universal testing machine. Data were statistically evaluated using a linear mixed model following least significant difference post hoc test. RESULTS: Pull-out data as a function of Ti-Base height demonstrated higher retention for tall compared to short abutments (P < .001). Ultimate outperformed U200 cement (data collapsed over height and pretreatment) (P < .001). Analysis of pretreatment depicted higher retention for SB + TBS, followed by SB, TBS, and NT (P < .04). The interaction between Ti-Base height and cement type highlighted the superior adhesive strength of Ultimate compared to U200 for both heights (P < .001). Irrespective of type of pretreatment, surface pretreatment improved the retention for U200 cement and short Ti-Base (P < .03 compared to NT). In contrast, higher retention was demonstrated for SB + TBS, followed by SB, TBS, and NT, for Ultimate cement combined with tall Ti-Base (P < .02) (data collapsed over height and cement, respectively). CONCLUSION: There was a direct relationship among Ti-Base height, micromechanical and/or chemical pretreatment, and conventional adhesive bonding in improving the retention of zirconia crowns.