The Effect of Ytterbium-Doped Fiber Laser with Different Parameters on Physical Properties of Zirconia Surface.

OBJECTIVE: Laser irradiation is an alternative surface treatment method for roughening zirconia surfaces. The aim of this study was to evaluate the effects of ytterbium-doped fiber laser (YbPL) on zirconia. BACKGROUND: Zirconia surfaces are resistant to many surface treatment methods, but surface roughness is crucial for adhesion of veneering materials and cements to zirconia. METHODS: The zirconia discs were prepared and divided into four groups according to the power of the laser irradiation (5, 12, 17, and 20 W). These groups were divided into five subgroups according to the frequency (25, 40, 60, 80, and 100 kHz). Surface roughness values were measured with a noncontact profilometer, and the mean Ra values were calculated. Wettability was measured with a goniometer. The surface morphology was observed with a scanning electron microscope (SEM). The changes in the surface crystalline structure were analyzed with X-ray diffractometry. RESULTS: Ra values of all groups were higher than the control group. The highest surface roughness value was at 20 W and 100 kHz. Best wettability characteristic was observed at 5 W and 60 kHz. The correlations between Ra and wettability were low but significant. SEM examination of 5 W with different frequencies showed no microcracks, however, melted areas were observed. Remaining groups had microcracks and melted layers. A significantly lower T/M-phase transformation was observed in some groups. CONCLUSIONS: YbPL irradiation was effective at roughening the zirconia surface. Although laser treatment affected zirconia surfaces and provided surface roughness, the power and frequency should be adjusted to achieve optimum results.

Effects of crown retrieval on implants and the surrounding bone: a finite element analysis.

PURPOSE: The aim of this study was to observe stress concentration in the implant, the surrounding bone, and other components under the pull-out force during the crown removal. MATERIALS AND METHODS: Two 3-dimensional models of implant-supported conventional metal ceramic crowns were digitally constructed. One model was designed as a vertically placed implant (3.7 mm × 10 mm) with a straight abutment, and the other model was designed as a 30-degree inclined implant (3.7 mm × 10 mm) with an angled abutment. A pull-out force of 40 N was applied to the crown. The stress values were calculated within the dental implant, the abutment, the abutment screw, and the surrounding bone. RESULTS: The highest stress concentration was observed at the coronal portion of the straight implant (9.29 MPa). The stress concentrations at the cortical bone were lower than at the implants, and maximum stress concentration in bone structure was 1.73 MPa. At the abutment screws, the stress concentration levels were similiar (3.09 MPa and 3.44 MPa), but the localizations were different. The stress at the angled abutment was higher than the stress at the straight abutment. CONCLUSION: The pull-out force, applied during a crown removal, did not show an evident effect in bone structure. The higher stress concentrations were mostly observed at the implant and the abutment collar. In addition, the abutment screw, which is the weakest part of an implant system, also showed stress concentrations. Implant angulation affected the stress concentration levels and localizations. CLINICAL IMPLICATIONS: These results will help clinicians understand the mechanical behavior of cement-retained implant-supported crowns during crown retrieval.

Evaluation of stress distributions in peri-implant and periodontal bone tissues in 3- and 5-unit tooth and implant-supported fixed zirconia restorations by finite elements analysis.

OBJECTIVE: In this study, it is aimed to compare the distribution of stress on periodontal and peri-implant bone tissues in 3- and 5-unit-dental and implant-supported zirconia restorations using finite element analysis. MATERIALS AND METHODS: Stress distribution formed in periodontal and peri-implant bone tissues as a result of chewing forces was analyzed in dental and implant-supported three-dimensional (3D) finite element models of zirconia restoration with 5-unit placed on the numbers of 43, 44, 45, 46, and 47 and with 3-unit placed on the number of 45, 46, and 47. Four different loading conditions were used. 200 N force was applied in 30° from the buccal inclination of number 43, 45, and 47 restorations separately and totally 850 N force was applied in 30° from the buccal inclination of whole restoration. The study was performed through static nonlinear analysis with the 3D finite element analysis method. RESULTS: Stress accumulation in bone tissues in the tooth-supported model was found less than in implant-supported models. Stress accumulation was observed in the cervical portion of the implant in implant-supported models, and stress accumulation was observed surrounding bone of roots in tooth-supported models. The highest stress values were occurred in 5 unit implant-supported model in all loadings. CONCLUSION: In posterior restorations increased in the number of supported teeth and implant can reduce the destructive forces on periodontal and peri-implant bone tissues and may allow longer period retention of the restorations in the mouth.

Evaluation and comparison of the marginal adaptation of two different substructure materials.

PURPOSE: In this study, we aimed to evaluate the amount of marginal gap with two different substructure materials using identical margin preparations. MATERIALS AND METHODS: Twenty stainless steel models with a chamfer were prepared with a CNC device. Marginal gap measurements of the galvano copings on these stainless steel models and Co-Cr copings obtained by a laser-sintering method were made with a stereomicroscope device before and after the cementation process and surface properties were evaluated by scanning electron microscopy (SEM). A dependent t-test was used to compare the mean of the two groups for normally distributed data, and two-way variance analysis was used for more than two data sets. Pearson's correlation analysis was also performed to assess relationships between variables. RESULTS: According to the results obtained, the marginal gap in the galvano copings before cementation was measured as, on average, 24.47 ± 5.82 µm before and 35.11 ± 6.52 µm after cementation; in the laser-sintered Co-Cr structure, it was, on average, 60.45 ± 8.87 µm before and 69.33 ± 9.03 µm after cementation. A highly significant difference (P<.001) was found in marginal gap measurements of galvano copings and a significant difference (P<.05) was found in marginal gap measurements of the laser-sintered Co-Cr copings. According to the SEM examination, surface properties of laser sintered Co-Cr copings showed rougher structure than galvano copings. The galvano copings showed a very smooth surface. CONCLUSION: Marginal gaps values of both groups before and after cementation were within the clinically acceptable level. The smallest marginal gaps occurred with the use of galvano copings.

An evaluation of clinical, radiological and three-dimensional dental tomography findings in ectodermal dysplasia cases.

BACKGROUND: This study aimed to review the results related to head and jaw disorders in cases of ectodermal dysplasia. The evaluation of ectodermal dysplasia cases was made by clinical examination and examination of the jaw and facial areas radiologically and on cone-beam 3-dimensional dental tomography (CBCT) images. MATERIAL AND METHODS: In the 36 cases evaluated in the study, typical clinical findings of pure hypohidrotic ectodermal displasia (HED) were seen, such as missing teeth, dry skin, hair and nail disorders. CBCT images were obtained from 12 of the 36 cases, aged 1.5- 45 years, and orthodontic analyses were made on these images. RESULTS: The clinical and radiological evaluations determined, hypodontia or oligodontia, breathing problems, sweating problems, a history of fever, sparse hair, saddle nose, skin peeling, hypopigmentation, hyperpigmentation, finger and nail deformities, conical teeth anomalies, abnormal tooth root formation, tooth resorption in the root, gingivitis, history of epilepsy, absent lachrymal canals and vision problems in the cases which included to the study. CONCLUSIONS: Ectodermal dysplasia cases have a particular place in dentistry and require a professional, multi-disciplinary approach in respect of the chewing function, orthognathic problems, growth, oral and dental health. It has been understood that with data obtained from modern technologies such as three-dimensional dental tomography and the treatments applied, the quality of life of these cases can be improved.

Long-term effects of antihypertensive medications on bone mineral density in men older than 55 years.

INTRODUCTION: In this study, we investigated the effects of long-term antihypertensive treatment with calcium channel blockers or beta blockers on the bone mineral density of maxilla, as determined by cone-beam computed tomography (CBCT). MATERIAL AND METHODS: This retrospective study was conducted on CBCT images of men older than 55 years who had received different dental indications. Data were grouped into three categories according to the antihypertensive medication history of the patients: group A included patients who had been taking beta-blocker treatment for more than 5 years, group B included patients who had been taking calcium channel blocker treatment for more than 5 years, and the control group included patients who had never used any hypertensive medications before. RESULTS: Statistically significant differences were observed between the beta blocker and calcium channel blocker groups. CONCLUSION: In hypertension treatment, beta blockers may be preferred to calcium channel blockers in patients at high risk for osteoporosis and bone resorption.

Effects of systemic zoledronic Acid administration on osseointegration of hydroxyapatite-coated and resorbable blast material surface implants in rabbit models.

PURPOSE: It is unknown whether zoledronic acid (ZA) interferes with initial bone healing at implant sites. The goal of this study was to examine the effects of systemic zoledronic acid administration on osseointegration of hydroxyapatite (HA)-coated and resorbable blast material surface (RBM) implants in rabbit models. MATERIALS AND METHODS: Twenty-eight male New Zealand rabbits (aged 6 to 12 months) were used in this study. Rabbits were randomly assigned to four groups. In group A, HA-coated implants were placed in the right tibia of seven rabbits. In group B, RBM-surface implants were placed in the right tibia of seven rabbits. In group C, HA-coated implants were placed in seven rabbits with intravenous (IV) administration of ZA. Finally, in group D, RBM-surface implants were placed in seven rabbits with IV administration of ZA. For groups C and D, IV zoledronic acid (0.1 mg/kg) was performed monthly during the entire osseointegration period. All of the rabbits were sacrificed 12 weeks after the implantation, and tibial specimens were harvested. Histomorphometric bone-to-implant contact (BIC) analysis and the data were statistically analyzed. RESULTS: The highest BIC percentage was detected in group D, with a mean value of 56.73%±1.85%, as compared with 45.80%±3.77% in group C, 35.11%±0.76% in group B, and 31.14%±1.04% in group A. CONCLUSIONS: Histomorphometric analyses showed significant improvement in the osseointegration of implants in the RBM-surface ZA group compared with the HA-coated ZA group. The results of this study suggest that systemic ZA administration may improve osseointegration of titanium implants in bone.