Bond strengths of porcelain to cobalt-chromium alloys made by casting, milling, and selective laser melting.

STATEMENT OF PROBLEM: Cobalt-chromium (Co-Cr) alloys have been widely used for metal-ceramic fixed prostheses and can be fabricated using conventionally cast or new computer-aided technology. However, the effect of different manufacturing methods on the metal-ceramic bond strength needs further evaluation. PURPOSE: The purpose of this in vitro study was to evaluate the metal-ceramic bond strength of a Co-Cr alloy made by casting, milling, and selective laser melting (SLM). MATERIAL AND METHODS: Co-Cr specimens (25×3×0.5 mm) were prepared using a cast, milled, or SLM method and layered with ceramic (8×3×1.1 mm). Metal-ceramic bond strength was measured by a 3-point bend test according to ISO9693. The area fraction of adherence porcelain (AFAP) was determined by measuring the Si content of the specimens with scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). The metal-ceramic bond strength and AFAP results were analyzed using 1-way analysis of variance and the Bonferroni post hoc test (α=.05). SEM/EDS and metallurgic microscopy were also used to study the specimens' morphology, elemental composition, and metallurgic structure. RESULTS: No significant differences (P>.05) were found for the bond strength among cast, milled, and SLM Co-Cr alloys. The milled and SLM groups showed significantly more porcelain adherence than the cast group (P<.001). The surface morphologies and oxidation characters of cast, milled, and SLM Co-Cr alloys were similar, whereas the metallurgic structures were different. CONCLUSIONS: The bond strength between ceramics and Co-Cr alloys is independent of the manufacturing method. However, milling- and SLM-produced alloys had better porcelain adherence.

The Effect of Reading Aloud Exercises for Complete Denture Patients during the Functional Rehabilitation Period.

PURPOSE: The focus of this study was to evaluate the effect of reading aloud on masticatory performance and patient satisfaction of patients rehabilitated with conventional complete dentures for the first time. MATERIALS AND METHODS: Sixty-two edentulous patients who received conventional complete denture treatment for the first time were randomly divided into two equal groups. After insertion of the dentures, patients in group I were asked to read a news report three times per day for 4 weeks, while those in group II did not read. The reading duration increased by 5 minutes per week, from 5 minutes in the first week to 20 minutes in the fourth week. The patients' mouth opening during reading aloud was advised to gradually increase throughout the training project. Two and four weeks after insertion of the dentures, masticatory performance was assessed using the sieving method, and patient satisfaction was measured using a visual analogue scale, which combined the patient's perceptions in relation to comfort, esthetics, stability, ability to talk, and ability to chew. RESULTS: There were significant improvements in masticatory performance with reading aloud exercises after the insertion of complete dentures (p < 0.001) at the 2- and 4-week follow-up visits. Masticatory performance also showed significant improvement within each group in the follow-up periods (p < 0.001). No significant differences were found between the two groups in patient satisfaction (p > 0.05) at 2 weeks, but at 4 weeks, patient satisfaction regarding stability, ability to talk, and ability to chew was significantly higher for group I (p < 0.001). CONCLUSIONS: The results of this study suggest that reading aloud exercises significantly improved early masticatory performance and patient satisfaction for denture wearers who were treated with conventional complete dentures for the first time, and may be a useful clinical application for more effective denture treatment.

Effect of silica coating on the bond strength of milled pure titanium to dental porcelain.

The creation of a high bond strength between machined computer-manufactured pure titanium and porcelain remains problematic, and the effects of a silica coating on the bond strength of milled pure titanium bonded to dental porcelain require further investigation. The objective of this study was to evaluate the bond strength of machined pure titanium, with an intermediate coating of silica, to dental porcelain. In this work, 24 specimens of milled pure titanium were prepared and randomly divided into test and control groups, in which the test group was coated with silica using the sol-gel dipping technique. The metal-ceramic bond strength was evaluated, according to ISO 9693 standards, using the three-point bending test, and scanning electron microscopy and energy-dispersive spectroscopy were used to study the microstructure and elemental composition of the specimens. The bonding strength of the silica-coated group was significantly higher than that of the control group, and more residual porcelain on the metal surface could be observed in the silica-coated group. Therefore, the application of a silica intermediate coating produced using the sol-gel method could significantly improve the bond strength between machined pure titanium and porcelain.

Virtual Surgical Planning in Precise Maxillary Reconstruction With Vascularized Fibular Graft After Tumor Ablation.

PURPOSE: Reconstruction of maxillary and midfacial defects due to tumor ablation is challenging to conventional operation. The purposes of this study are to evaluate the precise 3-dimensional position of the fibular flap in reconstruction of maxillary defects assisted by virtual surgical planning and to assess the postoperative outcomes compared with conventional surgery. MATERIALS AND METHODS: We retrospectively reviewed 18 consecutive patients who underwent maxillary reconstruction with a vascularized fibular flap assisted by virtual surgical planning after maxillary or midfacial tumor ablation. Conventional surgery was performed in another 15 patients. Proplan CMF surgical planning (Materialise, Leuven, Belgium) was performed preoperatively in the virtual planning group. Fibular flaps were harvested and underwent osteotomy assisted by prefabricated cutting guides, and the maxilla and midface were resected and reconstructed assisted by the prefabricated cutting guides and templates in the virtual planning group. The operative time and fibular flap positions were evaluated in the 2 groups. Postoperative fibular positions of the maxillary reconstruction were compared with virtual plans in the virtual planning group. The postoperative facial appearance and occlusal function were assessed. RESULTS: The operations were performed successfully without complications. The ischemia time and total operative time were shorter in the virtual planning group than those in the conventional surgery group (P < .05). High precision of the cutting guides and templates was found on both the fibula and maxilla in the virtual planning group. The positions of the fibular flaps, including the vertical and horizontal positions, were more accurate in the virtual planning group than those in the conventional surgery group (P < .05). Bone-to-bone contact between the maxilla and fibular segments was more precise in the virtual planning group (P < .05). Postoperative computed tomography scans showed excellent contour of the fibular flap segments in accordance with the virtual plans in the virtual planning group. All patients were alive with no evidence of disease. Functional mandibular range of motion, good occlusion, and an ideal facial appearance were observed in the virtual planning group. CONCLUSIONS: Virtual surgical planning appears to achieve precise maxillary reconstruction with a vascularized fibular flap after tumor ablation, as well as an ideal facial appearance and function after dental rehabilitation. The use of prefabricated cutting guides and plates eases fibular flap molding and placement, minimizes operating time, and improves clinical outcomes.

Effect of oxidation heat treatment on the bond strength between a ceramic and cast and milled cobalt-chromium alloys.

There is a dearth of dental scientific literature on the effect of different oxidation heat treatments (OHTs) (as surface pretreatments) on the bonding performance of cast and milled cobalt-chromium (CoCr) alloys. The objective of this study was to evaluate the effect of different OHTs on the bond strength between a ceramic and cast and milled CoCr alloys. Cobalt-chromium metallic specimens were prepared using either a cast or a milled method. Specimens were subjected to four different OHT methods: without OHT; OHT under normal atmospheric pressure; OHT under vacuum; and OHT under vacuum followed by sandblasting. The metal-ceramic bond strength was evaluated using a three-point bending test according to ISO9693. Scanning electron microscopy and energy-dispersive spectroscopy were used to study the specimens' microstructure and elemental composition. The bond strength was not affected by the CoCr manufacturing method. Oxidation heat treatment performed under normal atmospheric pressure resulted in the highest bond strength. The concentration of oxygen on the alloy surfaces varied with the different pretreatment methods in the following order: OHT under normal atmospheric pressure > OHT under vacuum > without OHT ≈ OHT under vacuum followed by sandblasting.

Effect of heating palladium-silver alloys on ceramic bond strength.

STATEMENT OF PROBLEM: The effects of different heat treatments on the internal oxidation and metal-ceramic bond in Pd-Ag alloys with different trace elements require further documentation. PURPOSE: The purpose of this in vitro study was to determine whether heat treatment affects the metal-ceramic bond strength of 2 Pd-Ag alloys containing different trace elements. MATERIAL AND METHODS: Thirteen cast specimens (25×3×0.5 mm) from each of 2 Pd-Ag alloy groups (W-1 and Argelite 61+3) were allocated to heat treatments before porcelain application: heating under reduced atmospheric pressure of 0.0014 MPa and 0.0026 MPa and heating under normal atmospheric pressure. Bond strengths were evaluated using a 3-point bending test according to ISO9693. Results were analyzed using 2-way ANOVA and Tukey HSD test (α=.05). Visual observation was used to determine the failure types of the fractured specimens. Scanning electron microscopy and energy dispersive spectroscopy were used to study morphologies, elemental compositions, and distributions in the specimens. RESULTS: The W-1 group had a mean bond strength significantly higher than that of Argelite 61+3 (P<.001). Heating under reduced atmospheric pressures of 0.0014 MPa and 0.0026 MPa resulted in similar bond strengths (P=.331), and both pressures had significantly higher bond strengths than that of heating under normal atmospheric pressure (P=.002, P<.001). Heating under different air pressures resulted in Pd-Ag alloys that contained either Sn or In and Ga, with various degrees of internal oxidation and different quantities of metallic nodules. CONCLUSIONS: Heating under reduced atmospheric pressure effectively improved the bond strength of the ceramic-to-Pd-Ag alloys.

Effect of titanium preoxidation on wrought pure titanium to ceramic bond strength.

STATEMENT OF PROBLEM: The creation of high bond strength between machined computer-manufactured pure titanium and porcelain remains a problem. However, machined titanium does not form the thick titanium oxide film found in cast titanium. PURPOSE: The purpose of this study was to investigate the effects of different preoxidation treatments on the bond strength of a machined pure titanium ceramic system. MATERIAL AND METHODS: Specimens of commercially pure titanium (25 × 3 × 0.5 mm) were divided equally into 6 groups (n=8), which received different preoxidation treatments (3 hour natural oxidation; 600°C, 650°C, 700°C, 750°C, and 800°C for 3 minutes). Bond strengths were evaluated by using a 3-point bend test. The results were analyzed by using 1-way ANOVA and the least significant difference test. Twelve additional specimens of commercially pure titanium (15 × 3 × 0.5 mm) were cut for interface observation and divided equally into 6 groups that received the preoxidation treatments described previously. Scanning electron microscopy and energy dispersive spectrum were used to observe microscopic features of the interface between Ti and ceramic. RESULTS: The bond strength values of the 6 groups ranged from 23.72 ±2.53 MPa to 36.99 ±3.92 MPa, with significant differences (P<.05). The specimen that received 750°C preoxidation had the highest bond strength. The main interface elements of the 6 groups were O, Si, Ti, Sn, Al, Na, and K. Ti showed a sigmoidal diffusion curve in each group, and Si showed a sigmoidal diffusion curve in most groups. Sn was enriched in each group's interface. CONCLUSIONS: Preoxidation under vacuum before porcelain firing can effectively improve the bond strength of machined pure titanium-porcelain systems.

Maxillary functional reconstruction using a reverse facial artery-submental artery mandibular osteomuscular flap with dental implants.

PURPOSE: This clinical study assessed the reverse facial artery-submental artery mandibular osteomuscular flap with titanium dental implants for the functional reconstruction of maxillary defects. PATIENTS AND METHODS: Class 2a defects in 5 patients were repaired with a reverse facial artery-submental artery mandibular osteomuscular flap with titanium dental implants (n = 21). All patients received a fixed partial denture after a 3- to 6-month healing period. RESULTS: All lesions were widely excised in an area extending to the maxilla. Of the implants, 20 (95.2%) were loaded and 1 was lost before loading. Reconstruction with a fixed partial denture was successful in all patients. The patients were followed up for 12 to 20 months (mean, 15.8 months), and no recurrence was observed. CONCLUSION: The reverse facial artery-submental artery mandibular osteomuscular flap with titanium dental implants is safe, quick, and simple to elevate and is reliable for the functional reconstruction of maxillary defects.

[Study on preparation of ampelopsin liposomes].

OBJECTIVE: To study the formulation and preparation of ampelopsin liposomes and evaluate their quality. METHOD: The liposomes were prepared by a film-ultrasonic dispersion technique. Served as quota with the entrapment ratio and appearance and diameter of the liposomes, the optimal formulation and preparation were selected by means of an uniform design test. The appearance of liposomes was observed by micrography. The diameter and electric charge of surface were determined by granularity mensuration instrument. The entrapment ratio and the leakage rate of ampelopsin liposome were determined by means of dialyze. The content of ampelopsin was determined by UV. RESULT: The result of electron micrography and the size distribution showed that the liposomes were similar to spherical small unilamellar vesicles. The mean diameter was (258.2 +/- 51.2) nm and the electric charge of surface is 19.0 mV. The entrapment ratio of ampelopsin liposomes was 62. 3% and the lecithoid oxidative rate was 0.83% (n = 3). CONCLUSION: The selected formulation and preparation of ampelopsin liposomes is efficient and practicable.

Synchronous reconstruction of bilateral osteoradionecrosis of the mandible using a single fibular osteocutaneous flap in patients with nasopharyngeal carcinoma.

BACKGROUND: The reconstruction of bilateral osteoradionecrosis (ORN) of mandibular defects using a single free bone flap is rarely performed because extensively radiated neck tissue with severe fibrosis is usually unsuitable for vascularized reconstruction. METHODS: Thirty-one patients with nasopharyngeal carcinoma (NPC) underwent bilateral reconstruction of advanced ORN in the mandible using a single fibular osteocutaneous flap. Clinical factors associated with the operation were assessed, including classification of mandible defects, types of recipient vessels, perioperative complications, and postoperative outcomes. RESULTS: All of the fibular osteocutaneous flaps survived completely, with the exception of 1 inner skin paddle that presented partial necrosis in a reconstruction of through-and-through defects. All patients experienced an improvement in cosmetic results 6 months after the reconstruction, whereas 23 patients experienced improved mouth opening compared to the preoperative condition. CONCLUSION: Advanced bilateral ORN in patients with NPC could be synchronously reconstructed with a single fibular osteocutaneous flap. © 2015 Wiley Periodicals, Inc. Head Neck 38: E-E, 2016.

Analysis on the stress of the bone surrounding mini-implant with different diameters and lengths under torque.

The purpose of this study is to compare the stress of the bone around the mini-implant under the two kinds of force: the composite force which contains torque and traditional single force. There were 96 finite element models formed by the combination of mini-implant and bone, with diameters of 1.2 mm, 1.6 mm, 2.0 mm and corresponding length being 6 mm, 8 mm, 10 mm, 12 mm, respectively. Each size corresponded to 8 models. Group SF (each size n=4) was loaded with 200 g single force, while Group CF (each size n=4) was loaded with composite force which contained 6N mm torque and 200 g single force. The maximum equivalent stress (Max EQS) of the bone surrounding mini implant with different loading directions was calculated, and the relationship of force direction, diameter and length was also evaluated. The Max EQS of Group CF was higher than that of Group SF. The effect of force direction on the stress was related to the diameter of mini implant, but had nothing to do with its length. The Max EQS of the cortical bone around mini implant in Group CF was higher (P<0.05) than that in Group SF. In contrast, there was no significant difference (P>0.05) between Group SF and Group CF in terms of bone stress when the diameter of mini implant was 1.6 mm or 2.0 mm. In our study, it is demonstrated that the diameter of mini-implant is better to be larger than 1.2 mm when a mini-implant is used in a torque control of tooth. The impact of this feature in the clinical setting needs to be verified.

Finite Element Analysis of Bone Stress around Micro-Implants of Different Diameters and Lengths with Application of a Single or Composite Torque Force.

BACKGROUND: Stress on the bone surrounding dental micro-implants affects implant success. PURPOSE: To compare the stress on the bone surrounding a micro-implant after application of a single force (SF) of 200 g or a composite force (CF) of 200 g and 6 N.mm torque. MATERIALS AND METHODS: Finite element models were developed for micro-implant diameters of 1.2, 1.6, and 2.0 mm, and lengths of 6, 8, 10, and 12 mm and either a SF or CF was applied. The maximum equivalent stress (Max EQS) of the bone surrounding the micro-implant was determined, and the relationships among type of force, diameter, and length were evaluated. RESULTS: The Max EQS of the CF exceeded that of the SF (P< 0.05). The effect of force on stress was related to implant diameter, but not to implant length. The larger CF led to greater instability of the micro-implant and the effect was most pronounced at an implant diameter of 1.2 mm. The use of implant diameters of 1.6 mm and 2.0 mm produced no significant difference in implant stability when either a CF or SF was applied. CONCLUSION: When considering the use of an implant to perform three-dimensional control on the teeth, the implant diameter chosen should be > 1.2 mm.

Effect of pretreatments on the metal-ceramic bonding strength of a Pd-Ag alloy.

OBJECTIVES: The purpose of this study was to evaluate the efficacy of surface treatments on the bonding properties between a metal and ceramic. METHODS: Sixty metal specimens were divided equally into four groups of 15 samples each. These groups received different treatments (Gr1: 250µm Al2O3+preoxidation; Gr2: 250µm Al2O3+degassing; Gr3: 120µm Al2O3+preoxidation; Gr4: 120µm Al2O3+degassing). Bond strengths were evaluated using a three-point bending test. The results were analyzed using 2-way ANOVA and Tukey's test. Scanning electron microscopy and energy dispersive spectroscopy were used to observe the microscopic features, elemental compositions and distributions, and diffusion in the specimens. Mechanical profiler was used to measure the roughness of metal surface. RESULTS: The bond strengths of the four groups ranged from 45.00±3.63MPa to 51.61±5.91MPa, with significant differences (P<.05). The specimen that received the pretreatment of 250µm Al2O3 air-particle abrasion+degassing had the highest bond strength. Heating under different oxygen partial pressures caused the final Pd-Ag alloys to have varying degrees of internal oxidation and different quantities of metallic nodules. None of the elements in either the ceramic or the Pd-Ag alloy layer diffused into the other layer. CONCLUSIONS: The metal-ceramic specimen subjected to air-particle abrasion with 250µm Al2O3 and degassed before porcelain firing had significantly higher bond strength than specimens treated differently.

[Effect of different heat treatment on the bonding strength of porcelain and Co-Cr alloy].

PURPOSE: To investigate and compare the effect of different heat treatment on the metal- ceramic bonding strength and the interfacial microstructure of the Co-Cr alloy. METHODS: Thirty specimens were made according to ISO 9693,and then divided into 3 groups (n=10) through the measurements .Group A(degassed 60s):degassed and then maintained 60s in 980 degrees centigrade Group B(degassed 60s and preoxidation 60s): degassed and maintained 60s in 980 degrees centigrade, then were maintained continuously for 60s in 980 degrees centigrade after re-gassed,Group C(degassed 120s): degassed and maintained 120s in 980 degrees centigrade. The bonding strengths of the three groups were evaluated through three point bending test. Six specimens divided into 3 group were made in the same method to observe the metal-ceramic interface through scanning electronic microscope(SEM) and energy dispersive spectrum(EDS).The bonding strength data were analyzed using ANOVA and Bonferroni's test by SPSS13.0 software package. RESULTS: The mean value of bonding strength was (39.03±2.70)MPa for group A, (34.43±2.36)MPa for group B, (31.65±1.49)MPa for group C, respectively. There were significant difference between every two groups (P<0.05). SEM demonstrated that the width of interfacial transition layer was 12.3-16.4µm in group A, 15.2-21.8µm in group B and 26.3-32.2µm in group C. CONCLUSIONS: Higher metal-ceramic bonding strength for Co-Cr alloy will be formed under the situation of degassed,and maintained 60s in 980 degrees centigrade ; while extending degassed time, prolonging the heat maintained time and preoxidation after degassing will reduce metal-ceramic bonding strength.

A multidisciplinary approach to treating maxillofacial arteriovenous malformations in children.

OBJECTIVE: Congenital arteriovenous malformations (AVMs) in the maxillofacial region are rare, potentially life-threatening, vascular lesions. This study reviewed our experience with a multidisciplinary approach to treating maxillofacial AVMs in children. STUDY DESIGN: Thirteen patients (10 boys and 3 girls) with AVMs involving the facial soft tissues or jaws were treated using a multidisciplinary approach that included: 1) superselective intra-arterial embolization (SIAE); 2) bone wax packing (BWP) of the bone cavity and curettage; and 3) compartmentalization and sclerotherapy. RESULTS: The mean follow-up was 13.5 months, with a range of 6-22 months. The following outcomes were obtained: 9 lesions (69.2%) were completely involuted, 3 lesions (23.1%) were mostly involuted, and 1 lesion (7.7%) was partially involuted. The rates of completely and mostly involuted AVMs involving the jaws treated using SIAE, BWP, and curettage were 80% and 20%, respectively. The rates of completely, mostly, and partially involuted AVMs involving soft tissues treated by compartmentalization and sclerotherapy were 60%, 30%, and 10%, respectively. CONCLUSION: SIAE was reliable for controlling bleeding and as adjunctive treatment for maxillofacial AVMs in children. SIAE followed by BWP of the bone cavity and curettage was a simple, safe, and effective method for treating AVMs of the jaws; SIAE followed by compartmentalization and the injection of OK-432 and pingyangmycin was a reliable alternative treatment for AVMs of the soft tissues in the maxillofacial region.

Reverse facial artery-submental artery mandibular osteomuscular flap for the reconstruction of maxillary defects following the removal of benign tumors.

BACKGROUND: Functional and aesthetic restoration in maxillary reconstruction remains a challenge. Although many free flap procedures have become popular in maxillary reconstruction, these microsurgical methods have certain limitations and risks. This study assessed the reliability of the reverse facial artery-submental artery mandibular osteomuscular flap for reconstructing maxillary defects. METHODS: Eight maxillary defects following benign tumor ablation were repaired with reverse facial artery-submental artery mandibular osteomuscular flaps. The patients ranged in age from 16 to 33 years; 5 were male and 3 were female. Maxillary odontogenic myxoma was present in 3 cases, maxillary fibrous dysplasia and ameloblastoma in 2 cases each, and chondromyxoid fibroma in 1 case. The defects were classified as class 2a. RESULTS: Primary reconstruction of the maxilla was carried out using a pedicled mandibular osteomuscular flap. No flap failures occurred. Dental reconstruction was successful in all patients. Proper aesthetics and complete functionality were obtained, and there were no donor-site problems. The patients were followed for 12 to 24 months, with an average of 18.6 months, and no recurrence was encountered. CONCLUSION: The reverse facial artery-submental artery mandibular osteomuscular flap is safe, quick, and simple to elevate. The flap can be used reliably for reconstructing maxillary defects.