Fracture Resistance of Internal Conical and External Hexagon: Regular and Narrow Implant-Abutment Assemblies.

PURPOSE: The aim of this study was to compare the maximum load on the elastic limit of internal conical (IC) implants with regular external hexagon (REH) and narrow external hexagon (NEH) implants. MATERIALS AND METHODS: Thirty cylindrical implants were divided in 3 groups (n = 10): REH (3.75 mm); NEH (3.3 mm); IC (3.5 mm). The implants were evaluated by means of cantilever bending loads using a mechanical testing machine. A strain qualitative analysis and the corresponding angles were analyzed. Using single factor analysis of variance with Tukey Test and Friedman Test (P < 0.05) the statistical analysis for data were performed. RESULTS: REH (294.37 N) and IC (294.37 N) groups presented statistically greater Fle than NEH (189.16 N). Regarding to the strain, there were no significant differences among groups. However, there were a greater number of fissures and more fractures present on NEH group. CONCLUSION: The IC implant with smaller diameter did not result in reduction of elastic limit when compared with the REH implants. Nevertheless, the reduction of 0.45 mm of the hexagonal connection implant's diameter has significantly diminished the elastic limit.

Microcomputed tomography marginal fit evaluation of computer-aided design/computer-aided manufacturing crowns with different methods of virtual model acquisition.

This in vitro study used microcomputed tomography to evaluate the marginal fit of crowns fabricated using a chairside computer-aided design/computer-aided manufacturing (CAD/CAM) system with different methods of virtual model acquisition. Crowns were fabricated to fit in a cast containing a single human premolar. Four methods of virtual model acquisition were used: Group 1 (control), digital impressioning of a typodont; Group 2, digital impressioning of a powdered typodont; Group 3, digital impressioning of a regular impression; and Group 4, digital impressioning of a master cast. Statistically significant differences were found between the marginal gap of Group 2 and the other groups (P < 0.05); no differences were found among Groups 1, 3, and 4. The results showed that crowns fabricated using the chairside CAD/CAM system exhibited significantly smaller vertical misfit when a thin layer of powder was applied over the typodont before digital impressioning.

Assessment of skeletal stability after counterclockwise rotation of the maxillomandibular complex in patients with long-face pattern subjected to orthognathic surgery.

BACKGROUND: The aim of this study was to evaluate the long-term skeletal stability of counterclockwise maxillomandibular complex rotation in patients undergoing orthognathic surgery for long-face pattern. METHODS: This retrospective study consisted of 10 patients who underwent the procedure between September 2002 and April 2008. To assess the skeletal stability, 30 preoperative (T1), recent postoperative (T2), and late postoperative (T3) cephalometric radiographs of the 10 patients were digitized and traced. To measure the stability in the occlusal plane and mandibular plane, the cephalometric points and planes were determined 3 times. RESULTS: In the long term, on average, the A-point moved 0.21 mm backward (AYT3-AYT2), the B-point moved 0.57 mm backward (BYT3-BYT2), and the posterior nasal spine moved 0.31 mm backward (PNSYT3-PNSYT2). On average, the anterior maxillary area (A-point) moved 0.14 mm downward (AXT3-AXT2), the mandible (B-point) moved 0.07 mm downward (BXT3-BXT2), and the posterior nasal spine moved approximately 0.18 mm upward (PNSXT3-PNSXT2). The occlusal plane increased by 0.75 degrees (OPT3-OPT2), and the mandibular plane increased by 0.45 degrees (MPT3-MPT2). CONCLUSIONS: It was observed that the counterclockwise rotation of the maxillomandibular complex produces stable results in patients with long-face pattern undergoing orthognathic surgery.

Influence of abutment screw design and surface coating on the bending flexural strength of the implant set.

The purpose of this study was to analyze the influence of the setting and the presence of solid lubricant on the abutment screw surface on the flexural strength of the joint implant/abutment/screw. Forty abutments were connected to external hex implants, divided into 4 groups (n = 10): FE (titanium alloy screw threaded in the extremity), LE (titanium alloy screw with solid lubricant and thread in the extremity), FT (titanium alloy screw with threaded in all its length), and LT (titanium alloy screw with solid lubricant and thread in all its length). Through the mechanical flexural test, the implant/abutment resistance was evaluated with load applied perpendicular to the long axis in a mechanical testing machine (EMIC) under a speed of 0.5 mm/min. Data were submitted to a statistics test, and results showed statistically significant differences between the FE group and the other groups, and the FE group showed the lowest values. The LE group showed greater values than the LT group, and the values were statistically significant. According to the methodology used, it can be concluded that within noncoated titanium screws, a screw threaded along its entire length provided greater rigidity to the implant set, while with the screw containing solid lubricant, the screw threaded in all its length provided less rigidity of the implant set than screws with the thread only on the end. Among screws with the same geometry, those with the solid lubricant are statistically higher than those which do not have threads just at the end, but those with threads along their entire length do not show statistically significant differences.

Assessment of the epidemiological profile of patients with dentofacial deformities who underwent orthognathic surgery.

The present study aimed to establish the profile of patients who underwent orthognathic surgery in a private clinic by evaluating their demographic characteristics, their facial types, and aspects related to the surgical procedures that were performed. The sample consisted of 419 medical records from male and female patients aged 15 to 62 years who underwent orthognathic surgery between 2001 and 2011. A single examiner collected data by evaluating a database of information extracted from medical records, particularly radiographic and photographic analyses. The following criteria were evaluated: gender, age, skin color, type of orthognathic surgery, type of associated temporomandibular joint (TMJ) surgery, complications, and recurrences. Seventeen patients were rejected because they had incomplete records. The average age of the patients was 28.5 years old; most were females (255 patients) and faioderm (295 patients). The most prevalent facial pattern was Pattern III (n = 166, 41.3%). Orthognathic surgery that affected the maxilla, jaw, and chin was the most prevalent type (n = 199, 49.5% of cases). A genioplasty was performed concurrently with combined surgeries and single-jaw surgery in 76.86% of patients (n = 309). TMJ surgery was performed concomitantly with orthognathic surgery in 4% of cases (n = 16). The most common postoperative complication was infection/inflammation (n = 12). We concluded that there was a higher frequency of orthognathic surgery among women and young people, the brunette skin phenotype was prevalent, and most patients had a combination of maxillary and mandibular problems.

Gingival conditioning in an implant-supported prosthesis: a clinical report.

The loss of gingival volume is a major challenge for dental surgeons with implant-supported fixed prosthesis manufactures, particularly from an aesthetics perspective in patients with a high smile line. Gingival tissue remodeling can help in papillae formation to avoid soft tissue surgery by reestablishing the appropriate shape and gingival contour of the tissues. This improves not only the aesthetics, but also the phonetics of the patient. This paper describes a clinical case of gingival conditioning obtained with interim implant-supported fixed partial dentures via incremental addition and adjustment of acrylic resin. The purpose of the gingival conditioning was to obtain improved aesthetics. Gingival conditioning by gradual pressure application is presented as an easy, non-traumatic technique that improves gingival aesthetics.

Computer-Aided Design/Computer-Aided Manufacturing of Customized Abutment for Rehabilitating a Malpositioned Implant Using Digital Flow: A Case Report.

This study presented a rehabilitation option for malpositioned implants; this involved obtaining their position and inclination through intraoral scanning, and producing a customized abutment with CAD/CAM technology. The patient in this case report presented a root fracture in tooth 21 and was subjected to extraction, implant installation, and immediate provisional prosthesis. The implant was installed with a distal inclination due to anatomical limitations. After osseointegration, an intraoral scanning transfer provided a digital model (file extension .stl), which reproduced the implant's position and inclination. Then, the file was sent so that a customized abutment (CAD/CAM) could be manufactured, promoting the final rehabilitation of the case; this allowed for good hygiene, load distribution in the dynamic interocclusal relationship, and favorable esthetics, whereas many would otherwise recommend implant removal. The result presented lower costs, a shorter time frame, and a lower morbidity for the patient.

Overdenture with immediate load: mastication and nutrition.

Lower conventional complete dentures were converted to overdentures retained by two implants with an immediately loaded bar-clip system (n 16). The masticatory performance test was carried out using 'Optocal' after forty chewing strokes. Nutritional condition was evaluated by means of a Mini-Nutritional-Assessment questionnaire. No individual was classified as malnourished. The masticatory performance test demonstrated a statistically significant difference before conversion (baseline) and 3 and 6 months after conversion of the lower conventional complete denture to an implant-retained overdenture (paired-samples t test; P < 0·05). A statistically significant difference before and after 6 months of conversion for nutritional condition (Wilcoxon test; P < 0·05) was also observed. The association between masticatory performance and nutritional assessment demonstrated that a statistically significant difference between masticatory performance of the subgroups classified at baseline as nourished (22·43 %) and those at risk of malnutrition (3·9 %) was only evidenced before conversion (P = 0·006). After the conversion from a lower conventional complete denture to an implant-retained overdenture, at 3 months, the risk of malnutrition and nourished at baseline did not present significant differences in masticatory performance. Nonetheless, the mean masticatory performance potential was 19·86 and 31·98 % for subgroups classified at baseline as at risk of malnutrition and nourished, respectively (P = 0·187). The results before conversion were less favourable for masticatory performance and nutritional condition. The increased retention of the mandibular prosthesis allowed improvement in masticatory performance and nutritional condition.

Influence of different tightening forces before laser welding to the implant/framework fit.

PURPOSE: The aim of the present study was to evaluate the influence of abutment screw tightening force before laser welding procedures on the vertical fit of metal frameworks over four implants. MATERIALS AND METHODS: To construct the frameworks, prefabricated titanium abutments and cylindrical titanium bars were joined by laser welding to compose three groups: group of manual torque (GMT), GT10 and GT20. Before welding, manual torque simulating routine laboratory procedure was applied to GTM. In GT10 and GT20, the abutment screws received 10 and 20 Ncm torque, respectively. After welding, the implant/framework interfaces were assessed by optical comparator microscope using two methods. First, the single screw test (SST) was used, in which the interfaces of the screwed and non-screwed abutments were assessed, considering only the abutments at the framework extremities. Second, the interfaces of all the abutments were evaluated when they were screwed. RESULTS: In the SST, intergroup analysis (Kruskal Wallis) showed no significant difference among the three conditions of tightening force; that is, the different tightening force before welding did not guarantee smaller distortions. Intragroup analysis (Wilcoxon) showed that for all groups, the interfaces of the non-screwed abutments were statistically greater than the interfaces of the screwed abutments, evidencing distortions in all the frameworks. ANOVA was applied for the comparison of interfaces when all the abutments were screwed and showed no significant difference among the groups. CONCLUSIONS: Under the conditions of this study, pre-welding tightness on abutment screws did not influence the vertical fit of implant-supported metal frameworks.

Effect of chlorhexidine application on microtensile bond strength to dentin.

This study evaluated the effect on microtensile bond strength (microTBS) of chlorhexidine application to dentin at different times during an indirect restoration luting procedure. Sixty bovine incisors had their superficial dentin subjected to 0.12% and 2% chlorhexidine solutions for 15 seconds before, during and after 37% phosphoric acid etching, resulting in six groups (n=10): 1) 0.12% chlorhexidine + etching; 2) 2% chlorhexidine + etching; 3) etching + 0.12% chlorhexidine; 4) etching + 2% chlorhexidine; 5) etching with 2% chlorhexidine; 6) etching without chlorhexidine (control). An adhesive system (Adper Single Bond 2) was applied and an indirect resin composite restoration (Filtek Z250) was luted using dual cured resin cement (Rely X ARC). After 24 hours of water storage, the specimens were tested by microtensile bond test (microTBS) at 0.5 mm/minute in a universal testing machine. The data were analyzed by one-way ANOVA (alpha=0.05), demonstrating no significant differences among the groups. The microTBS values in MPa were: 6: 22.83+/-3.53; 5: 22.4+/-3.52; 2: 21.62+/-2.5; 1: 21.28+/-3.17; 3: 19.62+/-2.05; 4: 19.55+/-2.34. The use of chlorhexidine at concentrations of 0.12% and 2% before, after or associated with acid etching did not significantly affect the microTBS values to dentin.

Effect of cavity preparation design and ceramic type on the stress distribution, strain and fracture resistance of CAD/CAM onlays in molars.

Objective This study aimed to evaluate the effect of the cavity preparation and ceramic type on the stress distribution, tooth strain, fracture resistance and fracture mode of human molar teeth restored with onlays. Material and Methods Forty-eight molars were divided into four groups (n=12) with assorted combinations of two study factors: BL- conventional onlay preparation with boxes made from leucite ceramic (IPS-Empress CAD, Ivoclar Vivadent); NBL- conservative onlay preparation without boxes made from leucite ceramic; BD- conventional onlay preparation with boxes made from lithium disilicate glass ceramic (IPS e.max CAD, Ivoclar Vivadent); NBL- conservative onlay preparation with boxes made from lithium disilicate glass ceramic cuspal deformation (µS) was measured at 100 N and at maximum fracture load using strain gauge. Fracture resistance (N) was measured using a compression test, and the fracture mode was recorded. Finite element analysis was used to evaluate the stress distribution by modified von Mises stress criteria. The tooth strain and fracture resistance data were analyzed using the Tukey test and two-way ANOVA, and the fracture mode was analyzed by the chi-square test (α=0.05). Results The leucite ceramic resulted in higher tooth deformation at 100 N and lower tooth deformation at the maximum fracture load than the lithium disilicate ceramic (P<0.001). The lithium disilicate ceramic exhibited higher fracture resistance than the leucite ceramic (P<0.001). The conservative onlay resulted in higher fracture strength for lithium disilicate ceramic. Finite element analysis results showed the conventional cavity preparation resulted in higher stress concentration in the ceramic restoration and remaining tooth than the conservative onlay preparation. The conservative onlays exhibited increased fracture resistance, reduced stress concentration and more favorable fracture modes. Conclusion Molars restored with lithium disilicate CAD-CAM ceramic onlays exhibited higher fracture resistance than molars restored with leucite CAD-CAM ceramic onlays.

Influence of Hemostatic Solution on Bond Strength and Physicochemical Properties of Resin Cement.

The aim of this study was to evaluate the degree of conversion, color stability, chemical composition, and bond strength of a light-cured resin cement contaminated with three different hemostatic solutions. Specimens were prepared for the control (uncontaminated resin cement) and experimental groups (resin cement contaminated with one of the hemostatic solutions) according to the tests. For degree of conversion, DC (n = 5) and color analyses (n = 10), specimens (3 mm in diameter and 2 mm thick) were evaluated by Fourier transform infrared spectroscopy (FTIR) and CIELAB spectrophotometry (L*, a*, b*), respectively. For elemental chemical analysis (n = 1), specimens (2 mm thick and 6 mm in diameter) were evaluated by x-ray energy-dispersive spectroscopy (EDS). The bond strengths of the groups were assessed by the microshear test (n = 20) in a leucite-reinforced glass ceramic substrate, followed by failure mode analysis by scanning electron microscopy (SEM). The mean values, except for the elemental chemical evaluation and failure mode, were evaluated by ANOVA and Tukey's HSD test. The color stability was influenced by storage time (p<0.001) and interaction between contamination and storage time (p<0.001). Hemostop and Viscostat Clear contamination did not affect the DC, however Viscostat increased the DC. Bond strength of the resin cement to ceramic was negatively affected by the contaminants (p<0.001). Contamination by hemostatic agents affected the bond strength, degree of conversion, and color stability of the light-cured resin cement tested.

Short implants--an analysis of longitudinal studies.

PURPOSE: The purpose of this study was to consider the therapeutic decision whether to use advanced surgery or short implants based on data concerning the use of these implants found in follow-up studies. MATERIALS AND METHODS: The MEDLINE database was consulted for follow-up studies published between the years 1980 and 2004. For those studies that met the inclusion and exclusion criteria, data concerning the number of implants 7, 8.5, or 10 mm long placed and lost, the time at which the failure occurred, and related risk factors were gathered for 33 studies arranged in tables and subjected to analysis. The studies included 16,344 implant placements with 786 failures (4.8%). Implants were analyzed according to the time of failure (i.e., before or after prosthesis seating) and risk factors implicated in the failures. RESULTS: The total rate of failures was 4.8%. Implants 3.75 mm wide and 7 mm long failed at a rate of 9.7%, compared to 6.3% for 3.75 x 10-mm implants. It was found that 54.9% of failures occurred before the prosthesis connection. Finally, 66.7% of all failures were attributed to poor bone quality, 45.4% to the location (maxilla or mandible), 27.2% to occlusal overload, 24.2% to location within the jaw, and 15.1% to infections (an implant could be associated with multiple risk factors). DISCUSSION: The analysis revealed that among the risk factors, poor bone quality in association with short implants seemed to be relevant to failure. The use of implants 4 mm in diameter appeared to minimize failure in these situations. The 3.75 x 7-mm implant presented the highest failure rate (9.7%) of 1894 implants analyzed (excluding implant designs with higher failure rates but few total implants). CONCLUSION: Short implants should be considered as an alternative to advanced bone augmentation surgeries, since surgeries can involve higher morbidity, require extended clinical periods, and involve higher costs to the patient.

Permeability of remaining endodontic obturation after post preparation.

This study assessed the correlation between leakage from the cervix to the apex and from the apex to the cervix for different post preparation techniques. Sixty roots were obturated with gutta-percha lateral condensation and AH Plus sealer and divided into two groups of 30 roots each. Immediate post preparation was used for one group and delayed preparation was used for the other. Two subgroups of 15 roots each were formed to investigate leakage from cervix-to-apex and from apex-to-cervix. The extent of leakage was determined using a dye, India ink, and a clearing technique that rendered the teeth transparent. Linear measurement of the dye penetration was recorded and examined with a stereomicroscope. Eight teeth were used as positive and negative controls. Leakage was observed in all samples. No statistically significant differences were found between the immediate and delayed post preparation techniques regarding apex-to-cervix leakage; however, the values of cervix-to-apex leakage were significantly lower for the immediate technique than for the delayed technique.

Three-dimensional evaluation of superior airway space after orthognathic surgery with counterclockwise rotation and advancement of the maxillomandibular complex in Class II patients.

OBJECTIVE: The aim of this study was to assess changes in the superior airway space (SAS) in Class II patients undergoing orthognathic surgery with counterclockwise rotation of the maxillomandibular complex (MMC). STUDY DESIGN: A total of 23 patients (15 females and 8 males; mean age, 33 years) with symptoms of respiratory disease (mouth breathing) were studied. The patients were subjected to computed tomography analyses at two time intervals: T1 (preoperatively) and T2 (postoperative minimum of 6 months). The computed tomography images were exported to Dolphin Imaging 11.5 software to measure the surface area, minimum axial area, and volume of the SAS. RESULTS: The surgery (including a median mandibular advancement of 14 mm with an average rotation of 8 degrees) significantly increased the static SAS, with mean postoperative increases of 178 mm(2) in SA, 76.67 mm(2) in minimum axial area, and 10118.5 mm(3) in volume. A significant increase was also observed in the three-dimensional airspace following orthognathic surgery, which provided a greater permeability of the SAS in Class II patients. CONCLUSIONS: This confirmed the efficacy of this technique in the treatment of respiratory disorders.

Skeletal stability in orthognathic surgery: evaluation of methods of rigid internal fixation after counterclockwise rotation in patients with class II deformities.

Our aim was to assess the influence of internal fixation in skeletal stability on patients who had had counterclockwise rotation of the maxillomandibular complex and mandibular advancement procedures. We studied 60 records of 20 patients (14 female, 6 male), mean (range) age at operation 29 (16-50) years. The mean (range) postoperative follow-up was 15 (8-24) months. Sixty standard lateral cephalometric radiographs were randomly traced and digitised by one senior radiologist to estimate surgical and postoperative changes. Patients were divided into two groups, the first group (n=10) of which had fixation with only 2.0 system plates (2 plates with monocortical screws alone) and the second (n=10) of which had hybrid fixation (1 plate with monocortical screws and 2 or 3 bicortical bone screws). During operation the change in the mean occlusal plane with counterclockwise rotation was 9.4° (range -17.3 to -2.5mm). The maxilla moved forward and upward. All the anterior mandibular measurements had advanced horizontally, the mean (range) being 17 (6.4 to 9.9) mm for the pogonion, and 17.6 (6.0 to 30.7) mm for the menton. At the longest follow-up period, there were significant long-term changes, but these were clinically acceptable (<2mm). There was no significant difference between the two groups in postoperative stability or in the magnitude of the advancement and stability.

Immediate loading implants with mandibular overdenture: a 48-month prospective follow-up study.

The aim of this prospective clinical study was to evaluate patient rehabilitation with two immediately loaded implants and bar-retained mandibular overdentures after 48 months of follow-up. Twenty patients were treated with two implants each; of these, 17 patients were re-evaluated for comparison. Gender, age, plaque index, gingival inflammation, keratinized mucosa, probing depth, bleeding, and implant loss data were recorded, and periapical radiographs were obtained for measurement of marginal bone loss. The results were statistically analyzed with one-way analysis of variance (ANOVA) followed by Student's t-test and Pearson's correlation test. To compare the data at baseline and after 48 months, a Wilcoxon Signed Rank Test was performed (α = 0.05). One implant failed (2.9%) during the first year and was replaced. A total of 35 implants were evaluated. Bone loss values were 0.52-2.89 mm (mean, 1.46 mm). Probing depth was 1.75-3.75 mm (mean, 2.22 mm). Correlations were found between bone loss and plaque index and between bone loss and gender, but bone loss did not correlate with gingival inflammation, keratinized mucosa, probing depth, or age. The overall survival rate of the implants was 97.1%. Based on these results, the use of two immediately loaded splinted interforaminal implants to retain an overdenture with a bar attachment is a clinically viable option with a high survival rate.

Micrometric precision of prosthetic dental crowns obtained by optical scanning and computer-aided designing/computer-aided manufacturing system.

The current study evaluated prosthetic dental crowns obtained by optical scanning and a computer-aided designing/computer-aided manufacturing system using micro-computed tomography to compare the marginal fit. The virtual models were obtained with four different scanning surfaces: typodont (T), regular impressions (RI), master casts (MC), and powdered master casts (PMC). Five virtual models were obtained for each group. For each model, a crown was designed on the software and milled from feldspathic ceramic blocks. Micro-CT images were obtained for marginal gap measurements and the data were statistically analyzed by one-way analysis of variance followed by Tukey's test. The mean vertical misfit was T = 62.6 ± 65.2 µm ; MC = 60.4 ± 38.4 µm; PMC = 58.1 ± 38.0 µm, and RI = 89.8 ± 62.8 µm. Considering a percentage of vertical marginal gap of up to 75 µm, the results were T = 71.5%, RI = 49.2%, MC = 69.6%, and PMC = 71.2%. The percentages of horizontal overextension were T = 8.5%, RI = 0%, MC = 0.8%, and PMC = 3.8%. Based on the results, virtual model acquisition by scanning the typodont (simulated mouth) or MC, with or without powder, showed acceptable values for the marginal gap. The higher result of marginal gap of the RI group suggests that it is preferable to scan this directly from the mouth or from MC.

Microtensile bond strength of methacrylate and silorane resins to enamel and dentin.

The aim of this study was to evaluate the microtensile bond strength (µTBS) of two substrates (enamel and dentin) considering two study factors: type of composite resin [methacrylate-based (Filtek Supreme) or silorane-based (Filtek LS)] and aging time (24 h or 3 months). Twenty human molars were selected and divided into 2 groups (n=10) considering two dental substrates, enamel or dentin. The enamel and dentin of each tooth was divided into two halves separated by a glass plate. Each tooth was restored using both tested composite resins following the manufacturer's instructions. The samples were sectioned, producing 4 sticks for each composite resin. Half of them were tested after 24 h and half after 3 months. µTBS testing was carried out at 0.05 mm/s. Data were analyzed by three-way ANOVA and Tukey's HSD tests at α=0.05. Significant differences between composite resins and substrates were found (p<0.05), but no statistically significant difference was found for aging time and interactions among study factors. The methacrylate-based resin showed higher µTBS than the silorane-based resin. The µTBS for enamel was significantly higher than for dentin, irrespective of the composite resin and storage time. Three months of storage was not sufficient time to cause degradation of the bonding interaction of either of the composite resins to enamel and dentin.