Effects of ceramic type, connector dimension, and thermomechanical-aging on the fracture resistance and fit of CAD-CAM produced inlay-retained fixed partial dentures.

The purpose of the present study is to evaluate the fracture resistance and the fit of CAD-CAM produced inlay-retained fixed partial dentures. Eighteen experimental groups were generated according to different CAD-CAM ceramic materials (zirconia, lithium disilicate, and zirconia-reinforced lithium silicate), different connector dimensions (12, 14, and 16 mm2), and application of thermomechanical-aging (1,200,000 cycles of cyclic loading with simultaneous thermal cycling). Gap values of thermomechanically-aged groups were measured by using periapical radiographs. Then, the specimens were tested for fracture resistance and failure types were examined. The results were statistically analyzed (α=0.05). Higher gap values were observed after aging. Zirconia showed the highest fracture resistance values among the most of the experimental groups. In non-aged groups, the most frequent failure type was decementation in zirconia group. In the aged groups, the most frequent failure type was molar connector fracture. Thermomechanical-aging increased the gap values and decreased the fracture resistance values.

Effect of ultraviolet protective agents on maxillofacial silicone elastomer, part 1: Color stability after artificial aging.

STATEMENT OF PROBLEM: Silicone elastomers have been widely used for rehabilitation of facial defects for more than 50 years. However, color change is the most common problem limiting the service life of facial prostheses. Whether the addition of ultraviolet protectives may enhance color stability of these materials is unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of ultraviolet protectives on the color stability of maxillofacial silicones after artificial aging. MATERIAL AND METHODS: Six color groups (unpigmented, white, yellow, red, blue, and mixed) of addition-type maxillofacial silicone were prepared. Four ultraviolet protectives benzophenone-3, ethylhexyl methoxycinnamate, titanium dioxide, and ethylhexyl salicylate at 0.5% and 1% concentrations by weight were incorporated into the silicone before polymerization. The specimens were artificially aged in an accelerated weathering chamber for 300 and 600 hours and in a thermocycling device. The color change values (E) of the maxillofacial silicones were evaluated. Data were statistically analyzed by using 4-way ANOVA. The differences were compared by the Tukey honestly significant difference test (α=.05). RESULTS: Benzophenone-3 and ethylhexyl methoxycinnamate protectives did not reduce the ΔE values, and the 1% titanium dioxide groups exhibited lower ΔE values than the 0.5% titanium dioxide groups. Ethylhexyl salicylate protective generally reduced the ΔE values significantly in all color and aging groups when compared with the control groups (P<.05). In all control and ultraviolet protective groups, the highest ΔE values were seen with the red color in 300 and 600 hours of aging. Generally, no significant difference (P>.05) was seen in the ΔE values, which were clinically acceptable among the thermocycled color groups. After 600 hours of accelerated aging, the ΔE values were found to be higher than the values of 300-hour aging. CONCLUSIONS: Ethylhexyl salicylate protective incorporated into maxillofacial silicones may improve color stability.

Fracture resistance of different implant supported ceramic abutment/crown systems.

PURPOSE: The purpose of this study was to investigate the fracture resistance and failure modes of different non-aged and aged abutment/crown systems. MATERIALS AND METHODS: One hundred dental implants (diameter 4.3 mm and length 11.5 mm) were restored with five abutment/crown systems: G1: a lithium disilicate hybrid abutment crown, G2: a lithium disilicate crown cemented on a lithium disilicate hybrid abutment, G3: a lithium disilicate crown cemented on a zirconia hybrid abutment, G4: a direct veneer porcelain layering on a zirconia hybrid abutment, and G5: a lithium disilicate crown cemented on a prefabricated all-zirconia abutment. Each group was divided into two groups (n=10) as control (non-aged) and thermomechanically aged. The fracture resistance test was performed. Failures during the aging process and after the fracture resistance test were examined. RESULTS: Both of the factors (restoration type and aging) affected the fracture resistance values and there was not an interaction between the factors (p>0.05). When fracture resistance values were compared regardless of aging, the highest values were observed in G3 and G4, respectively (p<0.05). When comparing the fracture resistance values, regardless of the restoration type, the aged group showed a significant lower fracture resistance value than control group (p<0.05). CONCLUSION: A titanium base enhanced the fracture resistance of zirconia abutments. Thermomechanical aging decreased the fracture resistance of the tested ceramic abutment/crown systems. The major failure mode was the abutment fracture.

Fracture resistance of monolithic and veneered all-ceramic four-unit posterior fixed dental prostheses after artificial aging.

This study compared the fracture resistance of monolithic and veneered all-ceramic four-unit posterior fixed dental prostheses (FDPs) generated by computer-aided design/computer-aided manufacturing (CAD/CAM) after aging in a mastication simulator. Four-unit FDPs were designed from six different all-ceramic systems: 1) monolithic lithium disilicate (M-E), 2) monolithic zirconia (M-TZI), 3) veneered zirconia by conventional layering (V-L), 4) veneered zirconia by lithium disilicate pressing (V-P), 5) veneered zirconia by lithium disilicate fusing (CAD-F-E), and 6) veneered zirconia by feldspathic ceramic cementing (CAD-C-CB). The specimens were divided into control and aging groups (n = 10 per group). The aging process included both thermocycling and mechanical loading and was followed by fracture resistance testing. All specimens in the M-E, M-TZI, and V-L groups survived; however, all specimens in the V-P group were fractured during artificial aging. The highest fracture resistance values were observed in the M-TZI group. According to the fracture resistance test, connector fractures were the most frequent type of failure. M-TZI and M-E FDPs revealed no failures during aging and showed higher fracture resistance than the veneered groups. Among the veneered zirconia framework groups, V-L FDPs showed the highest success rate during aging, while the fracture resistance was similar among all the veneered zirconia groups.

Effect of Laser Etching on Glass Fiber Posts Cemented with Different Adhesive Systems.

BACKGROUND: Glass fiber-reinforced posts have been preferred frequently because of some physical properties similar to the dentin, chemically bonding to dentin, biocompatibility, and esthetics. OBJECTIVE: This study aimed to evaluate the microleakage and bond strength of glass fiber posts cemented with various adhesive systems on laser-etched root canal walls. METHODS: Roots of 120 human mandibular premolars were divided into two groups for push-out bond strength test and the microleakage test (n = 60). Erbium-doped yttrium-aluminum-garnet (Er:YAG) laser etching of the root canal walls was carried out on half of the specimens in both test groups. The laser-treated and laser-nontreated groups were divided again into three subgroups (n = 10). Glass fiber posts (everStick Post) were luted using three different resin cements: total-etch (Variolink N), self-etch (Panavia F 2.0), and self-adhesive (Rely X Unicem). Three dentin discs were obtained from each root, and the bond strength of the glass fiber posts was measured by push-out tests. The dye penetration method was used to investigate coronal microleakage. In addition, surface treatments and the bonding interfaces were observed using scanning electron microscope. RESULTS: The highest bond strengths were observed for the total-etch and self-adhesive resin cement groups with laser etching (p < 0.05), and the lowest bond strength was obtained for the self-etch resin cement group (p < 0.05). There were no statistically significant differences in terms of microleakage (p > 0.05), except for the self-adhesive resin cement group (p < 0.05). CONCLUSIONS: Er:YAG laser etching enhances the bonding strength of glass fiber posts. In addition, laser etching can reduce microleakage of self-adhesive resin cement.

Fracture strength of CAD/CAM fabricated lithium disilicate and resin nano ceramic restorations used for endodontically treated teeth.

The purpose of the present study was to evaluate and compare the fracture strength and failure modes of endocrowns, zirconia post, and fiber post supported restorations and predict the clinical outcomes of six different prostheses used for endodontically treated teeth. Sixty (n=10) maxillary central incisors were restored with zirconia post/resin-nano-ceramic crown (ZrRNC), fiber post/resinnano-ceramic crown (FbRNC), zirconia post/lithium disilicate ceramic crown (ZrLDS), fiber post/lithium disilicate ceramic crown (FbLDS), resin-nano-ceramic endocrown (EndoRNC), and lithium disilicate ceramic endocrown (EndoLDS). Fracture strength test was performed. Fracture loads and modes were determined. The EndoLDS group had the highest fracture strength, followed by ZrRNC and EndoRNC group. However the results were not significantly different among groups (p>0.05). The failure modes of the restorations changed according to the restorative materials. Endodontically treated anterior teeth might be restored with endocrowns as well as other post-core restorations, however tooth fracture failures should be considered that affect reliability of endocrowns.

Comparison of Maximum Intercuspal Contacts of Articulated Casts and Virtual Casts Requiring Posterior Fixed Partial Dentures.

PURPOSE: To evaluate the accuracy of the CEREC CAD/CAM system in reproducing the maximum intercuspal contacts of the casts, which include posterior teeth preparation for a fixed partial denture (FPD). MATERIALS AND METHODS: Ten pairs of gypsum casts were mounted in articulators in maximum intercuspal position (MIP) to serve as patient simulation models. Tooth #19 was removed from the cast. Occlusal contacts in MIP were identified with articulating paper, and digital impressions of the casts with unprepared teeth and buccal images in MIP were taken. Teeth #18 and #20 were prepared for an FPD, and full- and half-arch digital impressions of the casts with prepared teeth and buccal images from different sides were taken. In each situation, screenshot images of the virtual casts with occlusal contacts were saved as JPEG files. The proportions of congruence of virtual contacts with cast contacts were analyzed by superimposing screenshot images of the virtual casts onto the screenshot images of the casts with the indicated occlusal contacts in a transparent manner using an image-processing program. The data were statistically analyzed with a paired t-test. RESULTS: The highest percentages of virtually indicated contacts identical to the cast contacts were observed in non-prepared full-arch digital impressions. Comparison of full-arch impressions taken before and after tooth preparation showed no difference for congruence even if the buccal image was taken from the contralateral or ipsilateral side (p > 0.05). After tooth preparation, comparing full- and half-arch digital impressions revealed that half-arch impression showed significantly lower percentages of identical contacts (p < 0.05). When comparing the buccal image side, no significant difference was detected between ipsilateral and contralateral images both for non-prepared and prepared casts (p > 0.05). CONCLUSION: When there is no posterior antagonist contact following tooth preparation for an FPD, taking a full-arch digital impression and designing the restoration on full-arch virtual models can be advocated.

Analysis of the hip fracture records of a central training and research hospital by selected characteristics.

BACKGROUND/AIM: Despite the importance of hip fractures, very few studies have assessed their epidemiological characteristics in Turkey. The aim of this study was to evaluate the frequency and demography of hip fractures from the recent data of a central training and research hospital. MATERIALS AND METHODS: In this descriptive study, we identified hip fracture cases between 2009 and 2013. The age, sex, region, injury pattern, and calendar year for all patients were evaluated. RESULTS: Among the 687 patients (488 women, 199 men) described in our clinic's records, 122, 131, 144, 138, and 154 patients applied with hip fractures from the years 2009 to 2013, respectively. The mean ages of the women and men were 74.8 and 68.5 years, respectively. There were 220 patients who had femoral neck fracture (32%), 419 who had intertrochanteric fracture (61%), and 48 who had subtrochanteric fracture (7%). CONCLUSION: The female geriatric population may have an increasing and distinct hip fracture risk, mainly in the trochanteric region. Furthermore, recent studies that show variations in the frequency and demography of hip fractures highlight the importance of meticulous recording of patients' information. A nationwide survey of different categories of hospitals and various geographic regions of Turkey is also needed to inform effective prevention strategies.

Clinical and radiographic evaluation of new dental implant system: Results of a 3-year prospective study.

BACKGROUND/PURPOSE: The aim of this study was to evaluate implant survival, crestal bone level changes, and clinical parameters of IDcam dental implants over a mean follow-up period of 3 years. MATERIALS AND METHODS: Seventy-two patients, 32 females and 40 males, received 255 implants. Implant-supported metal-ceramic fixed restorations were inserted. Following completion of restorations, each patient was re-examined at 6-month intervals. Radiographic crestal bone level changes were calculated, as well as soft tissue parameters including pocket probing depth, bleeding on probing, plaque index, and gingival index. Examination results were recorded from 18 months to 42 months. Implant survival was estimated using the Kaplan-Meier method. Associations between implant survival and recorded variables were estimated using Cox proportional regression analysis. RESULTS: The Kaplan-Meier survival analysis demonstrated a cumulative survival rate of 97.6%. Three implants in three patients failed to osseointegrate at stage 2 surgery, and three implants in three patients were lost after loading. The mean marginal bone losses were 0.35 ± 0.14 mm, 0.47 ± 0.15 mm, and 0.58 ± 0.16 mm, as determined 6 months, 12 months, and 24 months after prosthetic loading, respectively. Cox proportional regression analysis revealed that the variables such as age, sex, type of the restoration, and implant region had no significant influence on implant failure (P > 0.05). Coefficients of correlation between implant survival and crestal bone loss, pocket probing depth, bleeding on probing, plaque index, and gingival index were found to be nonsignificant (P > 0.05). CONCLUSION: Survival and radiographic and clinical assessments of implants after 2 years of function demonstrated promising results for an IDcam dental implant system.

Isokinetic performance of hip muscles after revision total hip arthroplasty via previous anterolateral approach.

We investigated the isokinetic performance of hip muscles and clinical outcomes after revision total hip arthroplasty (THA) via same anterolateral approach used in primary surgery. Thirty patients who had undergone previous THA via an anterolateral approach underwent both acetabular and femoral component revision after aseptic loosening. The Harris Hip Score (HHS) was evaluated during a minimum 2-year follow-up. The isokinetic muscle strength of the operated and nonoperated hips was assessed 1 year after surgery. The HHS improved from 49.0 to 77.4. Operated and nonoperated hips exhibited similar isokinetic performance during all measurements (flexion, extension, and abduction) (p>0.05). This prospective study showed that the anterolateral approach preserves abductor strength after revision THA in aseptic cases with acceptable functional and clinical results. The main clinical relevance of this study is that the same anterolateral approach used in previous primary THA is also safe and viable for revision THA.

Effect of surface treatments on the biaxial flexural strength, phase transformation, and surface roughness of bilayered porcelain/zirconia dental ceramics.

STATEMENT OF PROBLEM: Veneered zirconia restorations are widely used in prosthetic applications. However, these restorations often fail because of chipping of the veneer porcelain. Surface treatments of zirconia core materials may affect the connection between the 2 layers. PURPOSE: The purpose of this study was to evaluate the effect of surface treatments on the biaxial flexural strength, phase transformation, and mean surface roughness of different bilayered porcelain/zirconia ceramics. MATERIAL AND METHODS: Forty disk-shaped specimens were obtained for each material (Kavo and Noritake) and divided into 4 (n=10) groups (control, airborne-particle abraded, ground, and ground and airborne-particle abraded). Airborne-particle abrasion was performed with 110-µm Al2O3 particles for 15 seconds and at 400 kPa. Diamond rotary instruments with 100-µm grain size were used for grinding. The monoclinic phase transformation and surface roughness of the specimens were measured. Then, the specimens were veneered and subjected to a biaxial flexural strength test to calculate the Weibull moduli (m values) and the stresses occurring at the layers, outer surfaces of the bilayer, and interfaces of the layers. RESULTS: The Kavo airborne-particle abraded group showed higher strength values in both layers (P<.05) than those of all experimental groups. The Kavo airborne-particle abraded group showed the lowest m values at the core and veneer layers. According to the phase analysis, significantly higher Xm values were found in the ground and airborne-particle abraded groups for both materials (P<.05). In both materials, except in the airborne-particle abraded groups, the relative monoclinic phases showed no difference (P<.05). CONCLUSION: Surface treatments affected the phase transformation, surface roughness, and biaxial flexural strength of Kavo and Noritake zirconia ceramics differently. Surface treatments increased the relative monoclinic phase content and average surface roughness.

An overview of zirconia dental implants: basic properties and clinical application of three cases.

Due to the possible aesthetic problems of titanium implants, the developments in ceramic implant materials are increasing. Natural tooth colored ceramic implants may be an alternative to overcome aesthetic problems. The purpose of this article is to give information about the basic properties of dental zirconia implants and present 3 cases treated with two-piece zirconia implants. Two-piece zirconia dental implants, 4.0 mm diameter and 11.5 mm in length, were inserted into maxillary incisor region. They were left for 6 months to osseointegrate. Panoramic and periapical radiographs were obtained and examined for bone-implant osseointegration. During the follow-up period the patients were satisfied with their prosthesis and no complication was observed.

Biaxial flexural strength and phase transformation of Ce-TZP/Al2O3 and Y-TZP core materials after thermocycling and mechanical loading.

PURPOSE: The purpose of the present study was to evaluate the effect of thermocycling and mechanical loading on the biaxial flexural strength and the phase transformation of one Ce-TZP/Al2O3 and two Y-TZP core materials. MATERIALS AND METHODS: Thirty disc-shaped specimens were obtained from each material. The specimens were randomly divided into three groups (control, thermocycled, and mechanically loaded). Thermocycling was subjected in distilled water for 10000 cycles. Mechanical loading was subjected with 200 N loads at a frequency of 2 Hz for 100000 times. The mean biaxial flexural strength and phase transformation of the specimens were tested. The Weibull modulus, characteristic strength, 10%, 5% and 1% probabilities of failure were calculated using the biaxial flexural strength data. RESULTS: The characteristic strengths of Ce-TZP/Al2O3 specimens were significantly higher in all groups compared with the other tested materials (P<.001). Statistical results of X-ray diffraction showed that thermocycling and mechanical loading did not affect the monoclinic phase content of the materials. According to Raman spectroscopy results, at the same point and the same material, mechanical loading significantly affected the phase fraction of all materials (P<.05). CONCLUSION: It was concluded that thermocycling and mechanical loading did not show negative effect on the mean biaxial strength of the tested materials.

No difference in blood loss between posterior-cruciate-ligament-retaining and posterior-cruciate-ligament-stabilized total knee arthroplasties.

PURPOSE: Posterior-cruciate-ligament-retaining (PCR) and posterior-cruciate-ligament-stabilized (PS) arthroplasties are two major common practices in total knee arthroplasty (TKA). The hypothesis of the present study was that compared with the PCR technique, the PS technique is associated with a higher amount of postoperative blood loss and greater need for blood transfusion in cemented TKA. METHODS: In this prospective, randomized study, 100 patients diagnosed with primary knee osteoarthritis were randomly assigned to either the PCR group (Group I) or the PS group (Group II). The exclusion criteria were rheumatological joint disease, previous knee surgery, anticoagulant therapy and hypertension. There were no significant differences in age, body mass index and gender, between the groups. The haemoglobin and haematocrit levels of each patient were recorded preoperatively and on postoperative days 1, 3 and 5. The postoperative suction drainage and blood transfusion volumes were also recorded. RESULTS: There were no statistically significant differences in haemoglobin or haematocrit levels between the groups on postoperative days 1, 3 and 5. There were also no statistically significant differences in the total measured blood loss volume, postoperative drainage amounts or transfusion rates between the groups. CONCLUSION: Use of the PS technique during cemented TKA does not appear to influence the amount of perioperative blood loss or the need for postoperative blood transfusion in general. The clinical relevance of this study is that the difference in blood loss between the PCR and PS techniques does not need to be considered by surgeons when performing TKA.

Finite element analysis of stress distribution with splinted and nonsplinted maxillary anterior fixed prostheses supported by zirconia or titanium implants.

PURPOSE: The aim of the present study was to evaluate the effect of splinting titanium (Ti) or zirconia (Zr) implants supporting maxillary anterior fixed prostheses on the stress levels and patterns in the implants, prostheses, and the surrounding bone; and to compare the effects of Zr and Ti implant materials on the stress distribution in splinted and nonsplinted designs via finite element modeling. MATERIALS AND METHODS: Zr and Ti dental implants and the anterior maxilla were modeled. In the nonsplinted design (D1), implants were placed into the maxillary left central incisor and canine regions, and a three-unit zirconia fixed prosthesis was modeled. In the splinted design (D2), a symmetric model of D1 was generated and the two prostheses were splinted together to create a six-unit prosthesis. Loading was applied horizontally and obliquely. Von Mises, tensile, and compressive stresses were evaluated in the implants, prostheses, and surrounding bone. RESULTS: Under both loading conditions, the stresses on the D2 implants were lower than those in the D1 implants. Stresses were concentrated on the neck of the implant and decreased through the apex. All of the stress values in cortical bone in D1 were slightly higher than in D2 for both implant materials under both loading conditions. CONCLUSION: When the implants were splinted together, stresses were reduced in the supporting bone and implants in both loading conditions, but increased stress was observed in the prostheses under oblique loading. Intense stress concentrations were found in the connector of the splinted prosthesis and the cervical region of the nonsplinted prosthesis. Zr and Ti implants showed very similar stress distributions in all materials. Under oblique loading, lower stresses occurred in implants and the prosthesis core material when Ti implants were used.

A single-tooth, two-piece zirconia implant located in the anterior maxilla: a clinical report.

It can be difficult to achieve a natural appearance in the anterior region with implant-supported restorations because metal components may show through the soft tissue. Zirconia implants, therefore, should be considered as an alternative treatment for improved esthetics. The goal of this clinical report was to evaluate a new 2-piece zirconia implant system for the maxillary anterior region. A 2-piece zirconia dental implant was placed in the maxillary left lateral incisor position and left in place for 6 months to osseointegrate. Panoramic and periapical radiographs were examined for bone-implant osseointegration. The plaque control record (PCR), bleeding on probing (BOP), and probing depth (PD) were measured after the cementation of the definitive restoration and a 6-month follow-up period. The PCR, BOP, and PD values were compared and the marginal bone level was also evaluated by making standardized periapical radiographs. The results showed that over the 6-month follow-up period, the marginal area was healthy and presented no bleeding on probing, no plaque accumulation, and no change in periimplant marginal bone level.

Quality of life of patients with implant-retained maxillofacial prostheses: a prospective and retrospective study.

STATEMENT OF PROBLEM: Clinical studies on implant-retained maxillofacial prostheses have focused on biological outcomes. An assessment of the effect of prostheses on patients' quality of life (QOL) by using specific questionnaires developed for this patient population provides important information on treatment outcomes from the patients' perspectives. PURPOSE: The purpose of this study was to report patient-based outcomes of implant-retained maxillofacial prostheses and to evaluate the effect of implant-retained maxillofacial prostheses on QOL of participants in a prospective study. MATERIAL AND METHODS: Eighty-two participants were treated with implant-retained maxillofacial prostheses. Participants were divided into 2 groups: a retrospective group (participants treated and under care) and a prospective group (participants willing to be treated). The posttreatment patient satisfaction scores for each question were statistically analyzed by 2-way ANOVA with variables of defect type and retention type. The Student-Newman-Keuls test was used to determine any significant differences among the groups. In the prospective group, mean scores before and after prosthetic treatment were compared with the paired t test (α=.05). RESULTS: The details of 54 retrospective and 28 prospective participants were reviewed. The posttreatment results of 82 patients showed that patient satisfaction with implant-retained maxillofacial prostheses was significantly different for cleaning the prostheses and recommending treatment to other people, depending on the defect and retention type. In the prospective group, participants reported significant increases in satisfaction for all questions. CONCLUSIONS: Implant-retained prostheses were considered highly satisfactory, indicating good QOL for patients with maxillofacial defects. A comparison of pretreatment and posttreatment assessments revealed that implant-retained maxillofacial prostheses increased patient QOL.

Esthetic, functional, and prosthetic outcomes with implant-retained finger prostheses.

BACKGROUND: Traumatic amputation of fingers results in a serious impairment of hand function and affects the psychological status of the patients. The implant-retained finger prostheses are an alternative treatment. The aim of this case report is to represent the use of osseointegrated implants for retention of finger prostheses in a patient with amputated thumb and index finger. CASE DESCRIPTION AND METHODS: Dental implants were placed in the residual bone of the fingers using two-stage surgery. Custom-made attachments were used to provide retention between implants and silicone prostheses. Prosthetic fingernails were made of composite resin material. FINDINGS AND OUTCOMES: After 6 months, implants were clinically successful, and the patient was satisfied with the appearance and the function of the prostheses. The complications of broken prosthetic nail and mild discoloration were observed. CONCLUSION: Reconstruction of amputated fingers with implant-retained prosthesis is a worthwhile treatment providing esthetic, functional, and psychological benefits, although some complications might be experienced. Clinical relevance Implant-retained finger prostheses are an acceptable treatment modality for patients with amputated fingers. Evaluating implant prognosis, functional results and prosthetic results of the patients are necessary to address the benefits and complications of the treatment.

Stability measurements of craniofacial implants by means of resonance frequency analysis: 1-year clinical pilot study.

PURPOSE: The purpose of this pilot study was to apply resonance frequency analysis (RFA) to measure the clinical stability of craniofacial implants and compare the RFA measurements over a 12-month period. MATERIALS AND METHODS: Patients with auricular or orbital defects were treated with prostheses retained by two or three implants. After healing periods of 3 months for auricular implants and 6 months for orbital implants, prostheses were fabricated. RFA measurements were performed immediately after implant placement, at abutment connection, and at 6 and 12 months. All stability measurements were repeated three times for each implant, and the mean value was used for analyses. For measurements performed after prosthesis delivery, connecting bars and abutments were removed prior to RFA. The stability of both types of implants was compared at different time intervals. RESULTS: Fifty-four implants were placed in 10 patients with auricular defects (26 implants) and 10 patients with orbital defects (28 implants). All auricular implants survived, and four orbital implants in four different patients failed. For auricular implants, statistically significant differences in stability values were noted between implant placement, abutment connection, and 6 months; there was no significant difference between 6 and 12 months. For orbital implants, no significant differences were found between implant placement and abutment connection, a significant increase was observed at 6 months, and no significant difference was seen between 6 and 12 months. No significant differences were found for auricular versus orbital implants between placement and abutment connection, but auricular implants showed significantly higher stability values than orbital implants at 6 and 12 months. CONCLUSIONS: The stability of surviving auricular and orbital implants increased with time according to RFA. Prior to failure, the failed implants showed RFA values that were below the mean.

Effect of fatigue on fracture toughness and phase transformation of Y-TZP ceramics by X-ray diffraction and Raman spectroscopy.

The aim of this study was to evaluate the effect of fatigue on fracture toughness and phase transformation of yttria-stabilized zirconia polycrystal materials (Cercon and Lava). The specimens were tested for indentation fracture toughness either with or without being subjected to fatigue (20,000 cycles, 2 Hz, 200 N load). X-ray diffraction (XRD) analysis was used to examine the phase composition of specimens. The indentation images were analyzed using Raman spectroscopy at indentation center (p1), indentation corner (p2), points on crack 100 µm (p3), and 200 µm (p4) away from the corner and a point ∼80 µm away from the crack (p5). Fracture toughness results were statistically analyzed by two-way analysis of variance (ANOVA); XRD and Raman spectroscopy results were analyzed by three-way ANOVA. Fracture toughness of Cercon control (CC) and fatigue (CF) groups were 6.8 and 6.9 MPa√m, respectively, with no significant difference (p > 0.01). Fracture toughness of Lava fatigue (LF; 7.3 MPa√m) was significantly higher than Lava control (LC; p < 0.01). XRD analyses showed CC and LC consisted of tetragonal zirconia, monoclinic zirconia detected after fatigue. After indentation, relative amount of monoclinic phase significantly increased in CC, CF, and LC; decreased in LF. The Raman spectroscopy results indicated that monoclinic fraction was the highest at p2, subsequently at p1 and decreased at p3, p4, and p5 for all groups. Mechanical cycling increased fracture toughness of Cercon and Lava, the second being significant. Phase transformation was also detected after fatigue, which is higher in Lava. Analysis of indentations showed that transformation was highest was at the corner, second at center.