Objectives: Pit and fissure sealants are recognized as an effective preventive approach in pediatric dentistry. Composite resin is the most commonly used sealant material. Adding nanoparticles to composite resin could result in production of flowable composite with higher mechanical properties and better flowability than previous sealants. This study aimed to compare the microleakage of a flowable nanocomposite and materials conventionally used as pit and fissure sealants. Materials and Methods: A total of 185 extracted mandibular third molar teeth were selected and randomly divided into 5 groups (n=36): flowable nanocomposite, flowable composite, filled sealants, nano-filled sealants, and unfilled sealants. Five teeth were reserved for examination under a scanning electron microscope (SEM). The samples were thermocycled (5-55°C, 1-minute dwell time) for 1000 cycles and immersed in 0.2% fuchsine solution for 24 hours. Teeth were sectioned buccolingually. Microleakage was assessed qualitatively and quantitatively by means of dye penetration and SEM. Data were analyzed using chi-square, Kruskal-Wallis, and Bonferroni-corrected Mann-Whitney U tests. Results: Qualitative microleakage assessment showed that flowable composite and nanofilled flowable composite had almost no microleakage (P<0.001). Regarding quantitative scores, the nanofilled flowable composite and unfilled fissure sealant showed the lowest and the highest rate of microleakage, respectively. No statistically significant difference was found between the two flowable composites (P=0.317). Filled resin-based sealant had significantly lower microleakage than unfilled resin-based sealant (P<0.001). Conclusion: Use of flowable and nanofilled flowable composites (but not unfilled resin-based fissure sealant) is recommended for sealing of pits and fissures of molars
OBJECTIVES:Our purpose was to determine the antibacterial properties of propolis and to evaluate its use as an antibacterial mouthwash with minimal complications.MATERIALS AND METHODS:In this experimental laboratory study, an alcoholic propolis extract was prepared. The minimum inhibitory concentration (MIC) was calculated for four bacterial species including Staphylococcus aureus (S. aureus), Streptococcus mutans (S. mutans), Lactobacillus acidophilus (L. acidophilus), and Enterococcus faecalis (E. faecalis) using agar dilution. According to the MIC, a propolis antibacterial mouthwash was produced and compared to water, chlorhexidine (CHX), and Listerine using laboratory rats for clinical examination. Salivary specimens of rats were collected at 12 hours, 1 week, and 2 weeks after using the mouthwash and examined by real-time polymerase chain reaction (RT-PCR). Data were analyzed using one-way analysis of variance (ANOVA) and repeated measures ANOVA (α=0.05).RESULTS:The results of agar dilution by the number of colony-forming units showed the lowest MIC for S. aureus and the highest for L. acidophilus. Our RT-PCR findings indicated that water alone had no effect on the level of oral bacteria. Propolis mouthwash showed a significant difference with CHX and Listerine (P<0.05) in terms of the number of S. mutans, E. faecalis, and L. acidophilus colonies, while CHX and Listerine were less efficient. There was no significant difference between CHX and propolis (P=0.110) regarding S. aureus colonies, but Listerine had a lower efficacy than either (P<0.05).CONCLUSION:According to the results, propolis mouthwash was more efficient against the studied oral bacteria compared to CHX and Listerine.
OBJECTIVES:Nickel-chromium (Ni-Cr) base dental alloys with desirable properties have been employed in prosthodontics for years. Corrosion behavior of a Ni-Cr base alloy in artificial saliva with different pH values is determined in this work.MATERIALS AND METHODS:Corrosion behavior of Ni-Cr alloy was studied in artificial saliva with different pHs (2.5, 5, 7, and 9), using weight loss described by corrosion rate (CR) in mils per year (mpy) and potentiodynamic polarization described by corrosion potential (CP) in mV and current density (CD) in mA/cm2. Surface morphology was assessed using scanning electron microscopy (SEM). Statistical difference was determined using one-way ANOVA and post-hoc Tukey's honestly significant difference test with a difference significance of 95%.RESULTS:In the weight loss method, CR was 71.95±3.40, 17.26±1.03, 8.92±0.35, and 6.93±0.54 mpy at pH values of 2.5, 5, 7, and 9, respectively. Significant differences in CR were observed only at pH=2.5, while in CD, they were found at PH=2.5 and 5 (P<0.05). In the polarization method, CP values were significantly different. SEM exhibited the formation of preferential sites of corrosion attacks influenced by pH.CONCLUSION:Both techniques revealed consistent results. Corrosion resistance increases as pH increases towards less acidic conditions. In more acidic saliva, the corrosion rate is greater. The less acidic saliva leads to formation of a more stable passive film on Ni, and the dissolution of Ni decreases, leading to lower CRs.
OBJECTIVES:In this study, chitosan was introduced and used as a substitute for pulpectomy obturation against conventional materials: zinc oxide eugenol (ZOE) and iodoform-calcium hydroxide (Ca(OH)2). Efficacies of rotary versus manual instrumentations were also compared.MATERIALS AND METHODS:This preliminary study was performed on 152 intact nonresorbed root canals of primary molars divided into rotary (n=78) versus hand-instrumentation (n=74) and into ZOE (n=53), iodoform-Ca(OH)2 (n=50), and 3% nano-chitosan (n=49). Canals were cleaned/shaped using hand or rotary files. Canal spaces were measured using spiral computed tomography and obturated using the three materials. The percentages of obturation volume (POV) were estimated. Rotary and manual instrumentations were compared in terms of canal spaces before and after obturation. Three obturation materials were also compared regarding canal spaces after obturation (α=0.05).RESULTS:Average POVs of materials were 96.54% (ZOE), 97.87% (Metapex), and 74.74% (nano-chitosan; P=0.000). POV of chitosan differed from the other two (P<0.001) but the other two were similar (P=0.896). Average POVs were 91.46% (manual) and 88.51% (rotary); the difference was not significant (P=0.322). Preobturation spaces of canals for different methods were 3.89 mm 3 (manual) and 3.26 mm 3 (rotary); the difference was significant (P=0.013). Two-way ANCOVA showed a significant effect of materials (P<0.001) but not root length (P=0.585) or shaping methods (P=0.362) on POVs.CONCLUSION:Nano-chitosan showed a considerable success rate but it still needs reformulation as it was weaker than the extremely successful commercial competitors. Rotary instrumentation can provide results similar to hand-filing in terms of POV although it might yield smaller canals.
Objectives: This study aimed to compare the fracture resistance of a bulk-fill and a conventional composite and a combination of both for coronal restoration of severely damaged primary anterior teeth. Materials and Methods: In this in vitro experimental study, 45 primary anterior teeth were randomly divided into three groups. After root canal preparation, the canals were filled with Metapex paste such that after the application of 1 mm of light-cure liner, 3 mm of the coronal third of the canal remained empty for composite post fabrication. Filtek Z250 conventional composite was used in group 1, Sonic-Fill bulk-fill composite was used in group 2 and Sonic-Fill with one layer of Filtek Z250 as the veneering were used in group 3. Adper Single Bond 2 was used in all groups. The teeth were thermocycled, and fracture resistance was measured by a universal testing machine. The mode of fracture was categorized as repairable or irreparable. Data were analyzed using one-way ANOVA. Results: The mean fracture resistance was 307.00±74.72, 323.31±84.28 and 333.30±63.96 N in groups 1 to 3, respectively (P=0.55). The mean fracture strength was 14.53±2.98, 15.08±2.82 and 15.26±3.02 MPa in groups 1 to 3, respectively (P=0.77). The frequency of repairable mode of failure was 80% for the conventional, 73.6% for the bulk-fill and 80% for the bulk-fill plus conventional group, with no significant difference (P>0.05). Conclusions: Bulk-fill composites can be used for coronal reconstruction of severely damaged primary anterior teeth similar to conventional composites to decrease the treatment time in pediatric patients.
OBJECTIVES:Despite the increasing popularity of pediatric dental treatments under general anesthesia, information is scarce regarding occlusal changes in patients receiving stainless steel crowns (SSCs) under general anesthesia. This study sought to compare canine overlap before and after general anesthesia in children receiving SSCs. In case of a change, the possibility of returning to the preoperative state and the time required for this process were also evaluated.MATERIALS AND METHODS:This interventional, before-and-after study was performed on 60 children between 2 to 7 years of age requiring dental treatment under general anesthesia. The contact point of the most prominent area of the maxillary primary canine and mandibular primary canine was marked before and immediately after general anesthesia and at one and two weeks postoperatively. The change in canine overlap was analyzed using repeated measures analysis of variance (ANOVA) and linear regression test.RESULTS:Canine overlap significantly decreased immediately after general anesthesia (P<0.05). The mean bite opening was 0.51±0.22 mm at the site of the right canine and 0.50±0.185 mm at the site of the left canine. These values returned to their normal preoperative state after one week (P<0.05). Repeated measures ANOVA showed significant differences in this respect between the time points (P=0.002).CONCLUSION:The occlusion and vertical dimension of pediatric patients may change following dental treatment under general anesthesia; the magnitude of change in canine overlap may vary depending on the class of occlusion and number of SSCs placed. These changes are temporary and often resolve within a week.
OBJECTIVES:This study aimed to evaluate the effect of toothbrushing after application of 15% carbamide peroxide (CP) on the surface roughness of three types of composite resins.MATERIALS AND METHODS:Twenty samples, measuring 4 mm in height and diameter, were fabricated of three composite resins namely microfilled (MF) Heliomolar HB, nanohybrid (NH) IPS Empress Direct and microhybrid (MH) Tetric Ceram HB. After polishing, the initial surface roughness was measured with a profilometer. The tray technique was used to apply 15% CP gel for 6 hours. Then, cleaning was carried out with an Oral-B electric toothbrush for 3 minutes in a tank containing a freshly mixed toothpaste. These procedures were repeated for 21 days. Then, the surface roughness was measured again and compared with the initial values. A mixed-design ANOVA model was used for the analysis of data (P<0.05).RESULTS:The baseline roughness was significantly lower in MF compared to the NH and MH composites (P<0.001). Roughness increased in all study groups during the intervention period; however, this increase was not significant in the MH group (P=0.17). Furthermore, the increase in roughness in MF was smaller than that in NH (P<0.001) and MH (P=0.02) groups.CONCLUSION:The effect of intervention was more pronounced on NH and MH groups. Surface roughness changes were minor in MF composite resin.
Objectives: The purpose was to compare shear bond strength (SBS), pulp temperature, and adhesive remnant index (ARI) in debonding of stainless steel brackets from enamel surface using neodymium-doped yttrium aluminum garnet (Nd:YAG) laser versus the conventional debonding method. Materials and Methods: Forty-eight extracted premolars were bonded to stainless steel brackets. The samples were divided into three experimental groups and one control group. In the first three groups, Nd:YAG laser was used for debonding with the power of 1, 1.5, and 2 W, respectively, for 10 seconds. The SBS and ARI of the samples were assessed. Pulp temperature was recorded before and after irradiation. Two samples from each group were used for determining enamel morphology after debonding using scanning electron microscopy (SEM). Results: The mean SBS in the groups was 33.05, 28.69, 24.37, and 31.53 MPa, respectively, with no statistically significant differences (P=0.205). Significant differences in post-irradiation temperature were noted among the lased groups (P=0.000). Debonding mainly occurred at the adhesive-enamel interface in the 1-W laser and control groups and at the bracket-adhesive interface in the 1.5-W and 2-W laser groups. Enamel structure was amorphous and irregular following laser irradiation. Conclusions: Based on the results of this study, the use of Nd:YAG laser could not significantly affect the SBS. Therefore, this laser would not be suitable for debonding of metal brackets. The use of a 2-W laser could significantly raise the pulpal temperature. Nd:YAG laser renders a more heterogeneous enamel morphology compared to conventional debonding methods.
Objectives: This study aimed to compare the shear bond strength (SBS) of self-adhesive and conventional flowable composites and resin-modified glass-ionomer cement (RMGIC) to primary dentin. Materials and Methods: In this in vitro, experimental study, the buccal surface of 48 primary canine and first molar teeth was longitudinally sectioned to expose dentin. The teeth were randomly divided into three groups (n=16) of 37.5% phosphoric acid+ OptiBond+ Premise Flow composite (group 1), Vertise Flow composite (group 2) and RMGIC (group 3). A plastic cylindrical mold was placed on the exposed dentin and filled with restorative materials. The samples were then immersed in distilled water at 37°C for 24 hours, subjected to 1000 thermal cycles between 5-55°C and underwent SBS test. The mode of failure was determined under a stereomicroscope. Data were analyzed using one-way ANOVA and Tukey’s test. Results: A significant difference was noted in SBS of the groups (P<0.05). The SBS of conventional flowable composite was significantly higher that of RMGIC and self-adhesive flowable composite (P<0.05). The difference in SBS of RMGIC and self-adhesive flowable composite was not significant (P>0.05). Failure at the dentin-restoration interface (adhesive failure) had the highest frequency in groups 1 and 2. The frequency of adhesive failure was 100% in group 3. Conclusions: Within the limitations of this study, the conventional flowable composite yielded the highest SBS to primary dentin. Self-adhesive flowable composite and RMGIC showed the lowest SBS with no significant difference with each other.
OBJECTIVES:This study aimed to assess the microleakage of Pedo Jacket crowns compared to stainless steel crowns (SSCs) cemented with different luting cements.MATERIALS AND METHODS:In this in-vitro experimental study, 80 primary molars were randomly divided into four groups of 20 each. Groups 1 and 2 were subjected to standard tooth preparation for SSC. Crowns in group 1 were cemented with glass ionomer (GI), and crowns in group 2 were cemented with a resin-modified glass ionomer (RMGI) cement. In groups 3 and 4, minimal tooth preparation was performed for Pedo Jacket crowns, and the crowns were cemented with RMGI and Panavia resin cement, respectively. Microleakage was measured at mesial and distal surfaces in micrometers (μm), and the mean value for each tooth was calculated. Oneway analysis of variance (ANOVA) was applied to compare the microleakage of the four groups.RESULTS:Group 3 (Pedo Jacket cemented with RMGI) showed the highest microleakage (1523.83±250.32 μm) with significant differences with the remaining three groups (P<0.001). Microleakage in group 4 (Pedo Jacket cemented with Panavia) was significantly lower than that in the other three groups (301.25±219.53 μm, P<0.001). Groups 1 (SSCs cemented with GI) and 2 (SSCs cemented with RMGI) were not significantly different in terms of microleakage (P=0.49) although group 1 showed slightly higher microleakage than group 2 (598.43±260.85 μm versus 500.25±124.74 μm).CONCLUSION:Pedo Jacket crowns can serve as an acceptable esthetic alternative to SSCs if cemented with resin cements.
Objectives: The aim was to evaluate and compare pretreatment serum C-reactive protein (CRP) levels in patients with oral premalignancies and malignancies with that in healthy controls. Materials and Methods: The study sample consisted of 90 patients of both genders. The subjects were divided into three groups. Group I comprised 30 healthy controls, while group II included 30 patients with potential oral malignancies including leukoplakia, oral submucous fibrosis (OSMF), and oral lichen planus (OLP), and group III included 30 squamous cell carcinoma (SCC) patients confirmed by histopathological examination. All samples were subjected to CRP analysis. Serum CRP levels were quantitatively determined using the automated immunoturbidimetric method. Results: In group I, CRP levels were ranging from 0.1 to 18.3 mg/l with the mean ± standard deviation (SD) CRP level of 3.88±4.50 mg/l. In group II, CRP levels were ranging from 0.8 to 53.9 mg/l with the mean ± SD CRP level of 5.59±9.86 mg/l. In group III, CRP levels were ranging from 3.3 to 96 mg/l with the mean ± SD CRP level of 31.72±31.01 mg/l. Conclusions: According to the results, prediagnostic concentrations of CRP are associated with subsequent development of oral cancer and suggest that plasma CRP level is a potential marker of increased risk of cancer.
This article describes the prosthetic treatment of a patient suffering from a hemimaxillary defect after surgical resection of an adenoid cystic carcinoma (ACC) in the palate. The patient had also received therapeutic irradiation. One year after radiotherapy, three implants were placed in the remaining maxillary bone without any bone augmentation. One of the implants failed during the osseointegration period. The implant replacing the failed one also failed during prosthetic procedures. The patient was unwilling to undergo another surgical episode, and the final prosthesis was completed on the two remaining implants.
OBJECTIVES:This study aimed to evaluate the effect of oral melatonin and oral midazolam as premedication for intravenous (IV) sedation of pediatric dental patients. MATERIALS AND METHODS:This crossover, double-blind randomized clinical trial was conducted on 23 uncooperative 2-6-year-olds with definitely negative behaviors according to the Frankl's scale. Each child served as their own control. The children were randomly divided into two groups: group I received 0.5mg/kg of oral melatonin one hour before IV sedation, while group II received 0.5mg/kg of oral midazolam 30 minutes before IV sedation on their first visit. Every child received the other premedication on their second visit. The degree of sedation was judged according to the Houpt scale. Physiologic parameters including blood pressure (PB), heart rate (HR), and blood oxygen saturation (SpO2) and side effects including dizziness, nausea, vomiting, and sleepiness were assessed. The parents' and the operator's satisfaction rates were scored. Data were analyzed using paired t-test and Wilcoxon signed-rank test. RESULTS:There were significant differences in sedation scores between the two sessions (P<0.05). However, there were no significant differences in alterations of physiologic parameters between the two sessions (P>0.05). Nausea and vomiting were more common during the first two hours in the midazolam group (P=0.002). Tremors were more common in the melatonin group (P=0.013). Dizziness was more evident when melatonin was used (P<0.001). The clinician and the parents were more satisfied with the results of midazolam intake (P<0.05). CONCLUSIONS:Premedication with oral midazolam in pediatric patients is superior to that with melatonin with a higher parents' and operator's satisfaction.
Objectives: The aim of this study was to compare the efficacy of bovine bone substitute (Compact Bone B. ®) alone versus bovine bone substitute and simvastatin for human maxillary sinus augmentation. Materials and Methods: This study was conducted on 16 sinuses in eight patients. Radiographic assessments were done preoperatively (T0), immediately (T1) and at nine months after sinus grafting (T2). Alveolar bone height and density were assessed on cone beam computed tomography (CBCT) scans using Planmeca Romexis™ Imaging Software 2.2. Results: The change in alveolar bone height and density between T0, T1 and T2 was significant in both groups. Alveolar bone height (h0, h1, h2) and vertical height of the grafted bone (g1, g2) in three lines (anterior, middle and posterior) were not significantly different between groups. The grafted bone height shrinkage (%) in the anterior, middle and posterior limits of the augmented area were not significantly different between groups. The existing alveolar and grafted bone density increased significantly in both groups between T1 and T2, except for the existing alveolar bone density in the control group. There were no statistically significant differences between the alveolar bone density values obtained in TI and T2 between groups, except for the existing alveolar bone density at T1. Conclusions: This study did not show any significant positive effect for simvastatin in maxillary sinus augmentation based on radiographic examination.
Objectives: The aim of this study was to evaluate the diagnostic accuracy of different filtrations and slice thicknesses of cone-beam computed tomography (CBCT) in the detection of occlusal caries. Materials and Methods: One-hundred teeth were selected for this ex-vivo experimental study. The CBCT images of the teeth were evaluated and scored by two observers in panoramic and cross-sectional views using different slice thicknesses and filtrations. Paired t-test, repeated-measures analysis of variance (ANOVA), and the least significant difference (LSD) test were used to compare the data with the histological gold standard. Receiver operating characteristic (ROC) analysis was used to determine the diagnostic accuracy of each slice thickness and filtration (P<0.05). Results: The mean score of true caries detection in cross-sectional views was lower than that in panoramic views (P<0.05). Repeated-measures ANOVA showed a significant difference in the mean of true detections in different thicknesses of cross-sectional views, but this difference was significant only between 5 mm thickness and other thicknesses in panoramic views. On all the views, increasing the thickness decreased the accuracy of caries detection. Repeated-measures ANOVA showed a significant difference between different filtrations; on all the views, increasing the filtration increased the accuracy of caries detection. Conclusions: An increase of filtration of CBCT images increases the accuracy of occlusal caries detection; however, an increase in slice thickness results in a lower diagnostic accuracy.
Objectives: Enterococcus faecalis (E. faecalis), an infecting microorganism of the root canals, is difficult to eliminate during endodontic therapy. In this study, the effect of root canal disinfection with sodium hypochlorite (NaOCl) and chlorhexidine (CHX) was evaluated on planktonic and biofilm forms of E. faecalis in comparison with antimicrobial photodynamic therapy (aPDT) as an alternative strategy for root canal disinfection. Materials and Methods: In this study, E. faecalis (ATCC 29212) was used. The experimental procedures included aPDT with curcumin (CUR) and indocyanine green (ICG) as photosensitizers, irrigation with 5.25% NaOCl, 0.2% and 2.0% CHX solutions as traditional endodontic irrigating solutions, and the control group. The antibacterial and anti-biofilm potentials were assessed by counting the colony forming units and also using the crystal violet assay, respectively. Results: According to the results, E. faecalis biofilm was disrupted by 65.3%, 81.0% and 92.6% using 0.2% CHX, 2.0% CHX, and 5.25% NaOCl, respectively (P<0.05). In addition, CUR- and ICG-mediated aPDT displayed a significant reduction in E. faecalis count (90.2% and 82.5%, respectively) and its biofilm (83.6% and 75.2%, respectively) in comparison to the control group (P<0.05). Conclusions: APDT has a high potential for elimination of E. faecalis and is almost equivalent to NaOCl and CHX. It can be used as an adjucnt to conventional endodontic irrigating solutions.
OBJECTIVES:Temporomandibular joint (TMJ) disorders, known as TMDs, are significant public health problems and may result in pain and disability. In order to determine the prevalence of clinical/subjective TMD in rheumatoid arthritis (RA), we used the research diagnostic criteria (RDC)/TMD axes. We assessed the anti-cyclic citrullinated protein (anti-CCP)-related TMD in RA for the first time.MATERIALS AND METHODS:Fifty-two RA patients were compared to 47 healthy controls with regard to complete blood count (CBC), serology, acute phase reactants (APR), and TMJ dysfunction.RESULTS:The anti-CCP antibody showed a significant correlation with the development of clinical TMD (P=0.001, 95% confidence interval (CI)=12.4%-35.6%). A prevalence of 50% was calculated through the RDC/TMD for such disorders. In RA patients, statistically significant differences were observed between the groups with and without clinical TMD regarding psychological depression and physical symptoms.CONCLUSIONS:According to the results, a significant correlation was found between the anti-CCP antibody and TMD. Therefore, when this antibody is detected in the blood serum, the treatment must be initiated. The RDC/TMD used in this study assessed the prevalence of TMJ dysfunction in conformity with RA-associated TMJ findings previously obtained through other conventional methods.
OBJECTIVES:The use of zirconia as a framework for prosthetic restorations is increasing due to its favorable mechanical properties. Zirconia also has remarkable aesthetic properties when used as a framework and covered with a layer of cosmetic ceramic. The aim of this study was to compare the fracture toughness of three types of aesthetic ceramics, namely VITA VM®9, ceraMotion® Zr, and IPS e.max® Ceram.MATERIALS AND METHODS:Three groups of aesthetic ceramics (n=10) were subjected to three-point bending tests. The force leading to fracture was recorded for each sample to measure the impact of the ceramic type on the solidity of the framework. The type of fracture has not been studied in this work. One-way analysis of variance (ANOVA) was used to statistically analyze the results.RESULTS:The statistical analysis showed significantly different fracture toughness values among the three groups. IPS e.max® showed the lowest fracture toughness (25.42 MPa) compared to VITA VM®9 and ceraMotion® Zr (respectively 40.39 MPa; P<0.001, and 48.78 MPa; P<0.005).CONCLUSIONS:Within the limitations of the present study, it can be concluded that aesthetic ceramics play an important role in the fracture toughness of all-ceramic restorations.
OBJECTIVES:Rebonding of isolated brackets is an economic option that can be conducted using available in-office or commercial recycling methods. Nowadays, lasers are known as an efficient modality for composite removal, but there is not much information available about using lasers for removal of adhesive remnants from the ceramic bracket base.MATERIALS AND METHODS:Fifty human premolar teeth were divided into five groups. Samples in all groups were bonded to ceramic brackets. Brackets in four groups were debonded and the remaining adhesive was removed by Er:YAG laser, Er;Cr:YSGG laser, sandblasting or direct flame. After removing adhesives from the tooth surfaces by carbide bur, the recycled brackets were bonded again. in the control group, new ceramic brackets were bonded. Finally, all brackets were debonded by universal testing machine and their shear bond strength (SBS) was measured. The adhesive remnant index (ARI) was calculated under a stereomicroscope at ×10 magnification. Data were analyzed using oneway ANOVA and Tukey's test.RESULTS:SRS values showed no significant difference among the five groups (P=0.568). The highest SRS was noted in the control group (7.46±1.4 MPa), followed by Er:YAG laser group (7.40±1.24 Mpa) and the lowest was noted in the flame group (6.32±2.3 Mpa). ARI scores indicated that most of the adhesive remained on the tooth surface in all groups.CONCLUSIONS:Recycling of ceramic brackets with Er:YAG laser is an efficient in-office method which causes the least damage to the bracket base. However, all methods of bracket recycling showed acceptable SBS.
Objectives: This study aimed to analyze functional stresses around short and long implant-supported prostheses with different crown heights. Materials and Methods: Four three-dimensional (3D) models were designed with SolidWorks 2015. In models 1 (control) and 2, three dental implants (second premolar 4.1×8 mm, molars: 4.8×8 mm) were placed. In models 3 and 4, three dental implants (second premolar 4.1×4 mm, molars: 4.8×4) were placed. Residual bone height was 10 mm in groups 1 and 2 (grafted bone) models and 6 mm in groups 3 and 4. The crown heights were modeled at 11.5 mm for groups 1 to 3, and 15 mm for group 4. The applied oblique force was 220 N to simulate chewing movements. The maximum von Mises and principal stresses on the implants and the supporting tissues were compared using the 3D finite element method. Results: In all models, the highest stress value was seen within the most coronal part of bone (crestal bone), which was cortical or grafted bone. The highest stress values in the bone supporting the implant neck were seen in the premolar region of each model, especially in model 4 (291.16 MPa). The lowest stress values were demonstrated in the molar region of model 3 (48.066 MPa). The model 2 implants showed the highest von Mises stress concentrated at their neck (424.44 MPa). Conclusions: In atrophic posterior mandible with increased crown height space, short implants with wider diameter seem to be a more feasible approach compared to grafting methods.
