Effect of guide sleeve material, region, diameter, and number of times drills were used on the material loss from sleeves and drills used for surgical guides: An in vitro study.

STATEMENT OF PROBLEM: How material loss from sleeves and drills is affected when different guide sleeve materials and different sizes of implant drills are used for different regions of surgical guides is unclear. PURPOSE: The purpose of this in vitro study was to compare the amount of material loss from different guide sleeves (zirconia and cobalt-chromium) and drills of different diameters during osteotomy preparation in different regions. MATERIAL AND METHODS: Three tooth-supported surgical guides with sleeve holes positioned in the first premolar and second molar sites were prepared. Guide sleeves (Ø 2.20 mm, 3.40 mm, and 4.05 mm) were milled from zirconia (n=60) and cobalt-chromium (n=60) blocks. A total of 12 titanium nitride-coated stainless steel twisted drills (n=6 per sleeve material) of different diameters (Ø 2.00, 3.20, 3.85 mm) were used with corresponding sleeves during the drilling. The weight loss from the drills and the volume loss from the guide sleeves after drilling were analyzed by using multiple linear mixed effect models (α=.05). RESULTS: According to the 4-way ANOVA for volume loss from sleeves, no significant interaction was found among the 4 main effects (number of times a drill was used, region, diameter, and material), but interactions between the number of times a drill was used and diameter (P=.001) and between the number of times the drill was used and material were significant (P<.001). For weight loss from the drills, a significant interaction was detected between the number of times the drill was used and diameter (P=.024). CONCLUSIONS: Less sleeve material was lost when zirconia sleeves were used. All sleeves had more material loss in the molar region than in the premolar region. The diameter had varying effects on the amount of material loss from drills and sleeves. The sleeve material and the region did not affect the material loss from drills.

Cone Beam CT Evaluation of Maxillary Sinus Floor and Alveolar Crest Anatomy for the Safe Placement of Implants.

BACKGROUND: Alveolar bone height in the posterior maxillary region is very important and critical for dental implant planning and placement. OBJECTIVES: This study aimed to evaluate the anatomy of the maxillary sinus floor in relation to the alveolar crest and to determine variations in the vertical measurements between the maxillary sinus floor and the alveolar bone crest tip in the posterior edentulous maxilla with the use of cone beam computerized tomography. METHODS: This analysis enrolled 234 retrospectively selected patients (123 males with mean age 52.95±11.74 (range 32-76 years) and 111 females with mean age 58.14±11.92 (range 32-75 years)) with edentulous posterior maxillary regions. The maxillary sinus floor was divided into three anatomical segments (anterior, median and posterior) in relation to the transverse palatine suture. The measurements were performed on 3D surface rendered volumetric images by using rotation and translation of the views. Landmarks for measurement were specified by using a cursor driven pointer. Vertical lines were marked on the cross-sectional images between the alveolar ridge and the deepest point of the maxillary sinus floor for each of the three regions. P < 0.05 was regarded as statistically significant. RESULTS: The mean distance values between the sinus floor and the alveolar crest in the anterior, median and posterior regions were 8.74±3.97 mm, 5.37±3.23 mm and 7.06±3.28 mm, respectively. Measurements in the anterior region were found to be high in both total and gender groups compared to other regions. Also, subsinus alveolar bone heights decreased with increasing age in both genders in all three regions. CONCLUSION: This study emphasizes that the mean subsinus alveolar bone height is highest in the anterior segment of the edentulous posterior maxilla. These results may guide clinicians to make the decision of implant placement area and lead to less invasive alternative surgery methods for edentulous posterior segments.

Evaluation of the fracture resistance of root filled thin walled teeth restored with different post systems.

BACKGROUND: Restoration of the teeth with extensive root canals with different post systems is a challenge for clinicians. Evaluation of these systems is important for clinical success. The aim of this study was to compare the fracture resistance and fracture mode of endodontically treated thin-walled teeth which restored with different post systems. METHODS: Eighty extracted and endodontically treated maxillary canines were divided into 4 groups (n = 20) and the thickness of the radicular dentin walls was reduced by using diamond burs. Each root was embedded in an autopolymerizing resin with a 0.25 mm layer of vinyl polysiloxane material to simulate the periodontal ligament. The subgroups were restored with one of the following post systems: only composite resin (Group 1), cast post (Group 2), glass-fiber post (Group 3), and I-TFC post (Group 4). The samples were subjected to a gradually increasing force (0,5 mm/min). The force required to fracture was recorded, and the data were analyzed with ANOVA, Tukey test's and Chi-Square test (p < 0.05). RESULTS: The highest fracture resistance was recorded for Group 2, followed by the Group 3, Group 4, and Group 1. Differences in the fracture resistance of teeth were significant among the groups (p < 0.05). The fracture resistance of Group 4 was significantly different than the other tested post systems (p < 0.05). CONCLUSIONS: The lowest fracture resistance was recorded for Group 1, but among all post systems, Group 4 had the lowest fracture resistance. The fracture mode of the fiber posts (Radix and I-TFC posts) would permit repair of the tooth.

Marginal Adaptation of Provisional CAD/CAM Restorations Fabricated Using Various Simulated Digital Cement Space Settings.

PURPOSE: The ideal digital cement space value for the fabrication of provisional computer-aided design/computer-aided manufacturing (CAD/CAM) crowns with clinically acceptable marginal adaptation is not well known. The aim of this study was to evaluate the effect of different simulated cement space settings on the marginal fit of poly(methyl methacrylate) (PMMA) provisional CAD/CAM restorations. MATERIALS AND METHODS: An extracted premolar tooth was prepared using ceramic crown preparation guidelines and represented both natural teeth and/or custom implant abutments. The prepared tooth abutment was scanned with a three-dimensional (3D) laboratory scanner (D900, 3Shape). CAD design software was used to subsequently design a premolar crown core with three different simulated cement space settings (20 to 40 µm, 20 to 50 µm, 20 to 60 µm). PMMA blocks were used to mill the specimens (n = 9, N = 27). Using a stereo zoom microscope, a total of 36 images for each of the 3 groups (9 crowns per group, 4 sites per crown) were captured to measure the mean vertical marginal discrepancy for every group. One-way analysis of variance (ANOVA) was used to analyze the data, and the post hoc Tukey multiple comparison test was performed. RESULTS: The marginal gap values of the PMMA cores fabricated using the three cement space settings were significantly different from each other (P < .001). The marginal gap was smaller with a 20- to 60-µm setting compared with 20 to 50 µm and 20 to 40 µm, and the 20- to 50-µm setting allowed for smaller marginal gaps compared with 20 to 40 µm (P < .001). CONCLUSION: Within the limitations of this study, the marginal gaps of CAD/CAM-fabricated PMMA cores were smaller when the cement space was larger. The smallest marginal gaps were achieved when a 20- to 60-µm cement space was used (P < .001).

Influence of repeated firings on marginal, axial, axio-occlusal, and occlusal fit of metal-ceramic restorations fabricated with different techniques.

STATEMENT OF PROBLEM: Ill-fitting restorations can jeopardize dental, periodontal, and systemic health. Repeated ceramic firing may influence the fitting accuracy of restorations, but scientific information regarding this issue is lacking. PURPOSE: The purpose of this in vitro study was to assess and compare the influence of repeated firings on the marginal, axial, axio-occlusal, and occlusal fit of metal-ceramic 3-unit fixed partial dentures (FPDs) manufactured with different framework methods, including casting, fully sintered hard alloy milling (FHAM), presintered soft alloy milling (PSAM), and selective laser sintering (SLS). MATERIAL AND METHODS: A total of 60 Co-Cr metal frameworks for 3-unit FPDs were fabricated with 3 different computer-aided design and computer-aided manufacturing (CAD-CAM) techniques and conventional casting for a typodont model. The discrepancy values for premolar and molar abutments were measured by using the silicone replica technique after fabrication of the framework, second firing, fourth firing, and seventh firing. The replicas were separated into mesiodistal and buccolingual cross-sections, and digital images of the cross-sections were obtained with a stereomicroscope at ×80 magnification. The measurement points were examined to record the discrepancy values (µm) with in-built measuring software. The recorded data were subjected to repeated-measures 4-way ANOVA and the Bonferroni post hoc test (α=.05). RESULTS: For all measurement periods, the marginal, axial, axio-occlusal, and occlusal discrepancy values differed significantly among the manufacturing groups (P<.001). Moreover, the repeated firings had a statistically significant influence on the discrepancy values of PSAM, FHAM, and SLS groups (P<.05). The cast group was not significantly affected by repeated firings (P>.05). The PSAM group revealed the lowest discrepancy values at all measurement periods (P<.05), except after the second firing in the marginal and axial locations. CONCLUSIONS: The PSAM-fabricated restorations demonstrated superior fitting accuracy. All manufacturing groups were influenced by repeated firings, except the cast group. The marginal discrepancy values of all manufacturing groups were within the range of clinical acceptability (<120 µm).

Effect of fabrication stages and cementation on the marginal fit of CAD-CAM monolithic zirconia crowns.

STATEMENT OF PROBLEM: Monolithic zirconia crowns fabricated using computer-aided design and computer-aided manufacturing (CAD-CAM) technology have recently become an alternative dental prosthetic treatment. The marginal fit of monolithic zirconia crown may be affected by different stages of the fabrication procedures in the laboratory and cementation. Information regarding the accuracy of fit of monolithic zirconia crowns at different stages of fabrication and cementation is limited. PURPOSE: The purpose of this in vitro study was to evaluate the effect of different stages of fabrication and cementation on the vertical marginal discrepancy (VMD) of CAD-CAM fabricated monolithic zirconia crowns. MATERIAL AND METHODS: Six ivorine right maxillary first molar typodont teeth with standardized anatomic preparations for complete coverage ceramic crowns were scanned with a 3-dimensional laboratory scanner. Crowns were designed using CAD software and milled from presintered monolithic zirconia blocks in a 5-axis dental milling machine. A cement space of 25 µm for the margins and a 50-µm space starting 1 mm above the finish lines of the teeth were virtually set in the CAD software. A total of 144 measurements were performed on 6 specimens with 8 measurement locations in 3 different stages using stereoscopic zoom microscopy; after initial production of the crowns (post-sintering group), after glazing (post-glazing group), and after cementation (post-cementation group). The VMD values were statistically analyzed with 1-way repeated measures ANOVA and the Holm-Sidak method (α=.05). RESULTS: Different stages of fabrication and cementation significantly affected the VMD of tested crowns (P=.003). The mean VMD was 38 µm for post-sintering group, 38 µm for post-glazing group, and 60 µm for post-cementation group, with statistical differences between the post-sintering group, the post-cementation group (P<.002), and the post-glazing group and post-cementation group (P<.003); there were no statistical differences between the post-sintering group and the post-glazing group (P=.966). CONCLUSIONS: Within the limitations of this in vitro study, glazing did not significantly change the VMD of CAD-CAM monolithic zirconia crowns. Cementation significantly increased the VMD values.

Effect of Boric Acid Versus Conventional Irrigation Solutions on the Bond Strength Between Fiber Post and Root Dentin.

PURPOSE: To compare the effect of boric acid solutions of different percentages to conventional irrigation solutions on the adhesive bond strength between fiber posts and radicular dentin surface with different cement types. MATERIALS AND METHODS: One hundred fifteen extracted human incisors were endodontically instrumented to a length of 14-15 mm, and 12-mm post spaces were prepared with specific drills. Cylindrical fiber posts (Panavia Post) were luted with two different composite cements (Panavia F 2.0, Panavia SA) and cut into 1-mm-thick slices. These specimens were randomly allocated to 5 groups according to the irrigant applied: 1. control, no irrigant; 2. 10 ml of 2% chlorhexidine; 3. 10 ml of 5.25% NaOCl for 5 min and 10 ml of 17% EDTA for 3 min; 4. 10 ml of 5% boric acid solution at a temperature of 55°C for 60 s; 5. 10% boric acid solution, conditions as in group 4. Bond strength was determined using the push-out test. Microscopic assessment and SEM evaluations were performed in combination with push-out tests. RESULTS: The push-out bond strengths of cervical segments were significantly higher than for the middle and apical segments in all groups. The type of irrigation solution used significantly affected the bond strengths of the posts. The 10% boric acid solution and EDTA + NaOCl irrigation solutions provided the highest bond strengths (p < 0.005). SEM analysis showed that the dentin tubules were open and the smear layer was completely removed when EDTA/NaOCl and 10% boric acid were used as irrigation agents. CONCLUSION: Boric acid solutions, especially at a concentration of 10%, can be a viable alternative to the conventional irrigants used during endodontic treatment. The extent to which the 10% boric acid solution successfully removed the smear layer and the ease of rinsing boric acid from the root surface are advantageous.

Effect of cement space on the marginal fit of CAD-CAM-fabricated monolithic zirconia crowns.

STATEMENT OF PROBLEM: Monolithic zirconia crowns fabricated with computer-aided design and computer-aided manufacturing (CAD-CAM) have recently become a common practice for the restoration of posterior teeth. The marginal fit of monolithic zirconia crowns may be affected by different cement space parameters set in the CAD software. Information is scarce regarding the effect of cement space on the marginal fit of monolithic zirconia crowns fabricated with CAD-CAM technology. PURPOSE: The purpose of this in vitro study was to evaluate the effect of cement space on the marginal fit of CAD-CAM-fabricated monolithic zirconia crowns before cementation. MATERIAL AND METHODS: Fifteen right maxillary first molar typodont teeth with standardized anatomic preparations for complete-coverage ceramic crowns were scanned with a 3-dimensional laboratory scanner. Crowns were designed 3-dimensionally using software and then milled from presintered monolithic zirconia blocks in a computer numerical control dental milling machine. The cement space was set at 25 µm around the margins for all groups, and additional cement space starting 1 mm above the finish lines of the teeth was set at 30 µm for group 25-30, 40 µm for group 25-40, and 50 µm for group 25-50 in the CAD software. A total of 120 images (3 groups, 5 crowns per group, 8 sites per crown) were measured for vertical marginal discrepancy under a stereoscopic zoom microscope and the data were statistically analyzed with 1-way analysis of variance, followed by the Tukey honestly significant difference test (α=.05). RESULTS: The results showed that different cement space values had statistically significant effect on the mean vertical marginal discrepancy value of tested crowns (P<.001). The mean marginal discrepancy was 85 µm for group 25-30, 68 µm for group 25-40, and 53 µm for group 25-50. CONCLUSIONS: Within the limitations of this in vitro study, it was concluded that the cement space had a significant effect on the marginal fit of CAD-CAM-fabricated monolithic zirconia crowns. The marginal fit improved as the cement space decreased.

Evaluation of marginal fit of CAD/CAM restorations fabricated through cone beam computerized tomography and laboratory scanner data.

STATEMENT OF PROBLEM: Whether cone beam computed tomography (CBCT) images can be used for the fabrication of computer-aided design/computer-aided manufacturing (CAD/CAM) restorations is unknown. PURPOSE: The purpose of this in vitro study was to evaluate the marginal fit of CAD/CAM restorations fabricated by using data from CBCT scans with 3 different voxels and laser scanner images. MATERIAL AND METHODS: A crown preparation was made on an extracted premolar tooth according to ceramic crown preparation guidelines. The prepared tooth was scanned with a 3-dimensional (3D) extraoral laser scanner (D900; 3Shape), and CBCT scans were also made with an i-CAT cone beam 3D imaging system at 3 different voxel resolution settings: 0.125 mm, 0.20 mm, and 0.30 mm. The 3D images obtained from the laser scanner and CBCT scans were sent to CAD software, and a crown design was completed. Information was sent to CAM software to mill the crowns from poly(methyl methacrylate) (PMMA) blocks (n=9 from the laser scanner and 27 from 3 different CBCT scans). A total of 144 images (4 groups, 9 crowns per group, 4 sites per crown) were measured for vertical marginal discrepancy under a stereoscopic zoom microscope. One-way analysis of variance (ANOVA) was used to analyze the data. According to the assumption of homogeneity of variance, the post hoc Tukey multiple comparison test was performed (α=.05). RESULTS: The marginal gap values of crowns fabricated with an extraoral laser scanner were significantly lower than those of crowns fabricated with 0.3-, 0.2-, and 0.125-voxel CBCT images (P<.001). The marginal gap was greater when 0.3- and 0.2-voxel CBCT images were used than when 0.125-voxel CBCT images were used (P<.001). CONCLUSIONS: Crowns fabricated with the laser scanner images had lower and clinically acceptable marginal discrepancies than crowns fabricated with CBCT images in 3 different voxels. Of all the CBCT scans, only images with 0.125 voxel produced crowns with clinically acceptable marginal discrepancy.

Effect of atmospheric plasma versus conventional surface treatments on the adhesion capability between self-adhesive resin cement and titanium surface.

PURPOSE: The aim of this study was to evaluate the effects of atmospheric plasma (APL) versus conventional surface treatments on the adhesion of self-adhesive resin cement to Ti-6Al-4V alloy. MATERIALS AND METHODS: Sixty plates of machined titanium (Ti) discs were divided into five groups (n=12): 1) Untreated (CNT); 2) Sandblasted (SAB); 3) Tribochemically treated (ROC); 4) Tungsten CarbideBur (TCB); 5) APL treated (APL). SEM analysis and surface roughness (Ra) measurements were performed. Self-adhesive resin cement was bonded to the Ti surfaces and shear bond strength (SBS) tests, Ra and failure mode examinations were carried out. Data were analyzed by one-way analysis of variance and chi-squared test. RESULTS: The lowest SBS value was obtained with CNT and was significantly different from all other groups except for APL. The ROC showed the highest SBS and Ra values of all the groups. CONCLUSION: It was concluded that the effect of APL on SBS and Ra was not sufficient and it may not be a potential for promoting adhesion to titanium.

Biomechanical effects of different fixed partial denture designs planned on bicortically anchored short, graft-supported long, or 45-degree-inclined long implants in the posterior maxilla: a three-dimensional finite element analysis.

PURPOSE: The purpose of this study was to analyze the functional stresses around implants and supporting tissues placed in different combinations in the grafted and nongrafted atrophic posterior maxilla and to consider the acceptability of various fixed partial denture treatment options. MATERIALS AND METHODS: A computer model of the atrophic posterior maxilla was created from the computed tomography images of an actual patient. Three different treatment scenarios were modeled with partial denture restorations, grafted and nongrafted maxillary sinuses, and various implant inclinations. Oblique forces were applied to simulate chewing movements. Stress analyses were performed with a three-dimensional finite element analysis computer program, and the von Mises and minimum principal stresses on the implants and supporting tissues were compared. RESULTS: In all models, minimum principal (compressive) stress peak points were the highest within the crestal cortical bone (49.761 MPa), lower within sinus cortical (14.144 MPa) and trabecular bone (4.347 MPa), and lowest within grafted bone (0.049 MPa). The second molar implant in the third model (5×11-mm implant, inclined 45 degrees) showed the highest von Mises stresses (499.50 MPa), and the second molar implant in the first model (6×5-mm implant) showed the lowest (219.63 MPa) von Mises stresses. CONCLUSION: The stress absorption capacity of graft material is not sufficient and is much lower than that of other supporting tissues. For a fixed partial prosthesis, the use of short, wide implants with sinus floor bicortical fixation was found to be the most feasible approach for the atrophied posterior maxilla.

Evaluation of "all-on-four" concept and alternative designs with 3D finite element analysis method.

PURPOSE: The aim of the present study was to evaluate the effect of the forces on the implant and supporting alveolar ridge in "all on four" concept and alternative designs using finite element analysis. MATERIALS AND METHODS: Different treatment alternatives with various implant designs were performed in an edentulous mandible. In Design 1, implants were placed according to "All-on-Four" concept; Design 2, two long (13 mm long, 4 mm diameter) and two short (7 mm long, 4 mm diameter) implants; Design 3, four long and two short implants; and Design 4, two long and four short implants were placed vertically. A force of 100 N for each tooth, a total of 300 N load was applied. Finite element analysis was used to evaluate and compare the different designs. RESULTS: The stress concentration within the cortical bone was significantly higher than the trabecular bone around the neck of the implants. The maximum stress values were located around the cortical bone of the distal implant for all designs. The reduction in the number of implants did not diminish the success of the design. CONCLUSIONS: In the presence of vertically resorbed posterior mandibula, although the "all on four" concept is a feasible approach clinically, short implants had decreased the amount of force transmitted to the supporting bone.

Cone beam CT evaluation of maxillary sinus septa prevalence, height, location and morphology in children and an adult population.

OBJECTIVE: The purpose of this study was to determine the prevalence, height, location and morphology of maxillary sinus septa in dentate, partially dentate and edentulous adults as well as in mixed dentition children using cone beam computed tomography (CBCT) for maxillary sinus surgical interventions. SUBJECTS AND METHODS: Five hundred and fifty-four sides in the CBCT scans of 272 patients (30 children and 242 adults) were retrospectively analyzed. The prevalence, location and morphology were assessed in axial, sagittal, cross-sectional and panoramic 3-dimensional images. The height of septa was measured with the angle between the direction of the septum and median palatine suture. The differences among age, localization and measurements were statistically analyzed. RESULTS: The prevalence of maxillary sinus segments with septa was 58%. There were a total of 13 (3.2%) septa of completely edentulous (CE), 198 (53.9%) septa of edentate and 14 (3.8%) septa of the mixed dentition maxillary segments. The location of septa observed in all study groups demonstrated a greater prevalence (69.1%) in the middle region than in the anterior and posterior regions. No statistically significant differences were observed with regard to gender or age, for septum height (p > 0.05). However, maxillary sinus septa are higher in partially edentulous patients than edentate and CE ones (p < 0.05). CONCLUSION: Septa of various heights and courses developed in all parts of the maxillary sinus, therefore to prevent possible complications during sinus surgery, extensive evaluation with an appropriate radiographic technique was indispensable.

The effects of different adhesive agents on the shear bond strength of a self-adhesive resin cement.

PURPOSE: To compare the clinical success of a self-adhesive resin cement used in combination with different adhesive bonding systems with that of a conventional dual-cure resin cement. METHODS: The study was performed with 136 freshly extracted molars embedded in acrylic resin blocks and 136 IPS e.max Press discs. Teeth and discs were randomly divided into four equal groups and cemented together using either RelyX ARC (ARC), RelyX Unicem (Unicem), RelyX Unicem + Adper-Prompt L-pop (L-pop), or RelyX and Unicem + Total-etch (Total-etch). Shear bond strength measurements were obtained before and after thermocycling. Following bond testing, the surfaces of one sample per subgroup (thermocycled and non-thermocycled), were assessed using scanning electron microscopy (SEM). RESULTS: Among the non-thermocylced subgroups, ARC exhibited the highest bond strength values, followed by Total Etch, Unicem and L-pop. ARC also exhibited the highest bond strength values among the thermocycled subgroups, followed by Unicem, Total-etch, and L-pop. SEM analysis clearly revealed the negative effects of thermo-cycling on the mechanical properties of adhesive agents. CONCLUSIONS: RelyX Unicem may be preferable in many cases because of its simplified application and reduced technique-sensitivity.

Clinical application of stereolithographic surgical guide with a handpiece guidance apparatus: a case report.

The success of implant-supported restorations depends on the treatment planning and the transfer of planning through the surgical field. Recently, new computer-aided design and manufacturing (CAD/CAM) techniques, such as stereolithographic (SLA) rapid prototyping, have been developed to fabricate surgical guides to improve the precision of implant placement. The objective of the present case is to introduce a recently developed SLA surgical guide system into the rehabilitation of a 62-year-old male patient with mandibular edentulism. After obtaining a cone-beam computerized tomography (CBCT) scan of the mandible with a radiographic template, the images were transferred into a 3-dimensional (3D) image-based software for implant planning. The StentCad Beyond SLA surgical guide system, which is a combination of a currently used surgical template with pilot hollows and a surgical handpiece guidance apparatus, was designed to transfer a preoperatively defined implant position onto the surgical site without any drill-surgical guide contact. For the fabrication of this system, a surgical handpiece was scanned by a laser optical scanner and a mucosa-supported surgical guide was designed according to the patient's 3D model, which was attained from the CBCT images. Four dental implants were inserted through the SLA surgical guide system by a torque-controlled surgical handpiece to the interforaminal region via a flapless surgical procedure. Implants were assessed 3 months after surgery, and an implant-retained mandibular overdenture was fabricated. The present case emphasizes that CAD/CAM SLA surgical guides, along with CBCT images and scanning data, may help clinicians plan and place dental implants.