Implant-supported prosthesis following Branemark protocol on electromyography of masticatory muscles

This research evaluated the effects of Branemark protocol on electromyography of the masseter and temporal muscles. The patients were divided into two groups: Group 1: patients who wore an implant-supported prosthesis in the mandibular arch following Branemark protocol, and maxillary removable complete dentures; Group II: dentate individuals (control). Electromyography was carried out at rest, right (RL) and left (LL) laterality, protrusion and maximum voluntary contraction (MVC). Data were compared by t-test. At rest, a higher electromyographic (EMG) activity was observed in Group I, and the values were significant in the right masseter and left temporal muscles. In RL, there were statistically significant differences for right masseter (P < 0.01), left masseter and temporal muscles and for the left temporal muscle in LL (P < 0.05). In protrusion, Group I presented a higher EMG activity, and there was a statistically significant difference for the right masseter muscle (RM) (P < 0.05). In MVC, the EMG values were higher in Group II (control), but significant just for the right temporal muscle (P < 0.05). In conclusion, individuals with mandibular fixed dentures supported according to the Branemark protocol and maxillary removable complete dentures showed a higher activity of masticatory muscles during the mandibular postural clinical conditions examined; however, in the MVC, Group I presented lower values when compared to dentate group. Despite presenting different EMG values in all of the clinical conditions, both groups showed similar EMG patterns of muscle activation which demonstrates that the proposed treatment can be considered as a good option for oral rehabilitation.

Assessment of linear measurements of bone for implant sites in the presence of metallic artefacts using cone beam computed tomography and multislice computed tomography

The objective was to evaluate the influence of dental metallic artefacts on implant sites using multislice and cone-beam computed tomography techniques. Ten dried human mandibles were scanned twice by each technique, with and without dental metallic artefacts. Metallic restorations were placed at the top of the alveolar ridge adjacent to the mental foramen region for the second scanning. Linear measurements (thickness and height) for each cross-section were performed by a single examiner using computer software. All mandibles were analysed at both the right and the left mental foramen regions. For the multislice technique, dental metallic artefact produced an increase of 5% in bone thickness and a reduction of 6% in bone height; no significant differences (p > 0.05) were detected when comparing measurements performed with and without metallic artefacts. With respect to the cone-beam technique, dental metallic artefact produced an increase of 6% in bone thickness and a reduction of 0.68% in bone height. No significant differences (p > 0.05) were observed when comparing measurements performed with and without metallic artefacts. The presence of dental metallic artefacts did not alter the linear measurements obtained with both techniques, although its presence made the location of the alveolar bone crest more difficult.

Microstructural and Ultrastructural Assessment of Inferior Alveolar Nerve Damage Following Nerve Lateralization and Implant Placement: An Experimental Study in Rabbits

Purpose: The present study assessed damage to the inferior alveolar nerve (IAN) following nerve lateralization and implant placement surgery through optical and transmission electron microscopy (TEM). Materials and Methods: IAN lateralization was performed in 16 adult female rabbits (Oryctolagus cuniculus). During the nerve lateralization procedure, one implant was placed through the mandibular canal, and the IAN was replaced in direct contact with the implant The implant was placed in the right mandible, and the left side was used as a control (no surgical procedure) After 8 weeks, the animals were sacrificed and samples were prepared for optical and TEM analysis of IAN structural damage Histomorphometric analysis was performed to determine the number and cross-sectional dimensions of nerve fascicles and myelin sheath thickness between experimental and control grouos. The different parameters were compared by one-way analysis of variance at the 95% significance level Results: Alterations in the perineural and endoneural regions of the IAN, with higher degrees of vascularization., were observed in the experimental group TEM showed that the majority of the myelinated nerve fibers were not affected in the experimental samples. No significant variation in the number of fascicles was observed, significantly larger fascicle height and width were observed in the control group, and significantly thicker myelin sheaths were observed in the experimental samples Conclusion: IAN lateralization resulted in substantial degrees of tissue disorganization at the microstructural level because of the presence of edema However, at the ultrastructural level, small amounts of fiber degeneration were observed. INT J ORAL MAXILLOFAC IMPLANTS 2009,24-859-865

Electrocardiographic Alterations During Endosseous Implant Placement Performed with Local Anesthetic Agents

Purpose: The purpose of this study was to analyze electrocardiographic alterations during dental implant surgeries when local anesthetic agents were used. Materials and Methods: Twenty implants were placed in 18 healthy patients. An electrocardiogram and Wincardio software were used to gather recordings from 12 static leads every 2 minutes, continuously record coronary artery (D2) derivations, and automatically measure the following electrocardiographic parameters: heart rate, duration and amplitude of the P wave, PR segment duration, ST segment deviation, QRS complex duration, and duration of the RR, QT, and corrected QT (QTc) intervals. Results: Analysis of variance of the values obtained at the different stages showed significant differences (P < .05) for the heart rate and for the duration of the RR and QT intervals. The heart rate increased during the anesthesia, incision, and bone drilling stages, reaching a peak during drilling. Duration of the RR and QT intervals decreased during the incision and drilling stages. Among the electrocardiographic parameters individually assessed, several altered values were found for the duration of the P wave, the QRS complex, and the QT and QTc intervals. Sinusal tachycardia and bradycardia, sinusal arrhythmia, supraventricular extrasystole, ventricular extrasystole, and T-wave inversion were detected. Conclusion: Dental implant placement surgery may induce electrocardiographic alterations. The most frequently found arrhythmias were extrasystole and sinusal tachycardia. The anesthesia, incision, and bone drilling stages exhibited the highest heart rate values and the shortest durations of the RR and QT intervals. INT J ORAL MAXILLOFAC IMPLANTS 2009;24:412-418

Early dental plaque formation on toothbrushed titanium implant surfaces

Purpose: To evaluate the qualitative and quantitative differences on dental plaque formation on two different roughness titanium implant surfaces, i.e. machined and titanium plasma sprayed, as well as the amount of plaque removal by regular toothbrushing after 72-hour plaque accumulation. Methods: Eight systemically healthy subjects were recruited from the patient pool of a private dental practice. All patients underwent oral hygiene instruction and full mouth prophylaxis. Subsequently, maxillary casts from all patients were obtained and removable 0.7 mm-thick acetate stents without occlusal contact points were fabricated to support four titanium specimens of 4x2x2 mm divided into two groups (machined and plasma sprayed). Subjects were instructed to wear the stents for 72 hours, full time, removing them only during regular oral hygiene. Subsequently, the appliances were immediately repositioned and then the test side was brushed for 20 seconds. At the end of the 72-hour period, the stents were removed and prepared for microbiological analysis. Results: Both machined and plasma sprayed brushed surfaces presented statistically significant fewer bacteria than non-brushed surfaces. Similarly, regarding surface roughness, machined surfaces presented a total number of bacteria significantly smaller than those presented by plasma sprayed surfaces (P< 0.05). Statistically, the non-brushed machined turned surfaces presented a greater amount of Streptoccocus sp. when compared to the brushed machined surfaces. It was concluded that rough surfaces accumulated more dental plaque than polished surfaces. Both brushed surfaces presented less plaque accumulation, however, implant brushing was more effective on machined surfaces. (Am J Dent 2008;21:318-322).

Can Fiber Posts Increase Root Stresses and Reduce Fracture?

The clinical success of fiber posts has been attributed to their lower elastic modulus. The tested hypothesis was that fiber posts could lead to lower risk of post debonding and lower risk of root fracture, despite an increase in root stresses. Stress analyses were carried out with a 3D finite element model of a premolar restored with a metallic or a fiber post. Bonded and non-bonded post/cement interface conditions were simulated. We calculated risk-of-fracture indices by determining the highest principal stress values divided by the tensile strength. Shear stresses along the post/cement interface were analyzed for the bonded models. Compared with the premolar restored with a metallic post, the fiber post generated lower stresses along the interface and higher stresses in the root. However, with the fiber post, fracture was less likely to occur in the root, since its core and post fracture indices were higher.

Effect of argon purity on mechanical properties, microstructure and fracture mode of commercially pure (cp) Ti and Ti-6Al-4V alloys for ceramometal dental prostheses

Provision of an inert gas atmosphere with high-purity argon gas is recommended for preventing titanium castings from contamination although the effects of the level of argon purity on the mechanical properties and the clinical performance of Ti castings have not yet been investigated. The purpose of this study was to evaluate the effect of argon purity on the mechanical properties and microstructure of commercially pure (cp) Ti and Ti-6Al-4V alloys. The castings were made using either high-purity and/or industrial argon gas. The ultimate tensile strength (UTS), proportional limit (PL), elongation (EL) and microhardness (VHN) at different depths were evaluated. The microstructure of the alloys was also revealed and the fracture mode was analyzed by scanning electron microscopy. The data from the mechanical tests and hardness were subjected to a two-and three-way ANOVA and Tukey`s test (alpha = 0.05). The mean values of mechanical properties were not affected by the argon gas purity. Higher UTS, PL and VHN, and lower EL were observed for Ti-6Al-4V. The microhardness was not influenced by the argon gas purity. The industrial argon gas can be used to cast cp Ti and Ti-6Al-4V.

Effect of processing induced particle alignment on the fracture toughness and fracture behavior of multiphase dental ceramics

Objective. To investigate the processing induced particle alignment on fracture behavior of four multiphase dental ceramics (one porcelain, two glass-ceramics and a glass-infiltrated-alumina composite). Methods. Disks (empty set12mm x 1.1 mm-thick) and bars (3 mm x 4 mm x 20 mm) of each material were processed according to manufacturer instructions, machined and polished. Fracture toughness (K(IC)) was determined by the indentation strength method using 3-point bending and biaxial flexure fixtures for the fracture of bars and disks, respectively. Microstructural and fractographic analyses were performed with scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Results. The isotropic microstructure of the porcelain and the leucite-based glass-ceramic resulted in similar fracture toughness values regardless of the specimen geometry. On the other hand, materials containing second-phase particles with high aspect ratio (lithium disilicate glass-ceramic and glass-infiltrated-alumina composite) showed lower fracture toughness for disk specimens compared to bars. For the lithium disilicate glass-ceramic disks, it was demonstrated that the occurrence of particle alignment during the heat-pressing procedure resulted in an unfavorable pattern that created weak microstructural paths during the biaxial test. For the glass-infiltrated-alumina composite, the microstructural analysis showed that the large alumina platelets tended to align their large surfaces perpendicularly to the direction of particle deposition during slip casting of green preforms. Significance. The fracture toughness of dental ceramics with anisotropic microstructure should be determined by means of biaxial testing, since it results in lower values. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Bis-GMA co-polymerizations: Influence on conversion, flexural properties, fracture toughness and susceptibility to ethanol degradation of experimental composites

Objectives. The aim of this study was to evaluate the influence of monomer content on fracture toughness (K(Ic)) before and after ethanol solution storage, flexural properties and degree of conversion (DC) of bisphenol A glycidyl methacrylate (Bis-GMA) co-polymers. Methods. Five formulations were tested, containing Bis-GMA (B) combined with TEGDMA (T), UDMA (U) or Bis-EMA (E), as follows (in mol%): 30B:70T; 30B:35T:35U; 30B:70U; 30B:35T:35E; 30B:70E. Bimodal filler was introduced at 80 wt%. Single-edge notched beams for fracture toughness (FT, 25 mm x 5 mm x 2.5 mm, a/w = 0.5, n = 20) and 10 mm x 2 mm x 1 mm beams for flexural strength (FS) and modulus (FM) determination (10 mm x 2 mm x 1 mm, n = 10) were built and then stored in distilled water for 24 h at 37 degrees C. All FS/FM beams and half of the FT specimens were immediately submitted to three-point bending test. The remaining FT specimens were stored in a 75%ethanol/25%water (v/v) solution for 3 months prior to testing. DC was determined with FT-Raman spectroscopy in fragments of both FT and FS/FM specimens at 24 h. Data were submitted to one-way ANOVA/Tukey test (alpha = 5%). Results. The 30B:70T composite presented the highest K(Ic) value (in MPa m(1/2)) at 24 h (1.3 +/- 0.4), statistically similar to 30B:35T:35U and 30B:70U, while 30B:70E presented the lowest value (0.5 +/- 0.1). After ethanol storage, reductions in K(Ic) ranged from 33 to 72%. The 30B:70E material presented the lowest reduction in FT and 30B:70U, the highest. DC was similar among groups (69-73%), except for 30B:70U (52 +/- 4%, p < 0.001). 30B:70U and 30B:35T:35U presented the highest FS (125 +/- 21 and 122 +/- 14 MPa, respectively), statistically different from 30B:70T or 30B:70E (92 +/- 20 and 94 +/- 16 MPa, respectively). Composites containing UDMA or Bis-EMA associated with Bis-GMA presented similar FM, statistically lower than 30B:35T:35U. Significance. Composites formulated with Bis-GMA:TEGDMA:UDMA presented the best compromise between conversion and mechanical properties. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Elastic modulus of posts and the risk of root fracture

The definition of an optimal elastic modulus for a post is controversial. This work hypothesized that the influence of the posts` elastic modulus on dentin stress concentration is dependent on the load direction. The objective was to evaluate, using finite element analysis, the maximum principal stress (sigma(max)) on the root, using posts with different elastic modulus submitted to different loading directions. Nine 3D models were built, representing the dentin root, gutta-percha, a conical post and the cortical bone. The softwares used were: MSC.PATRAN2005r2 (preprocessing) and MSC.Marc2005r2 (processing). Load of 100 N was applied, varying the directions (0 degrees, 45 degrees and 90 degrees) in relation to the post`s long axis. The magnitude and direction of the sigma(max) were recorded. At the 45 degrees and 90 degrees loading, the highest values of sigma(max) were recorded for the lowest modulus posts, on the cervical region, with a direction that suggests debonding of the post. For the 0 degrees loading, the highest values of sigma(max) were recorded for higher modulus posts, on the apical region, and the circumferential direction suggests vertical root fracture. The hypothesis was accepted: the effect of the elastic modulus on the magnitude and direction of the sigma(max) generated on the root was dependent on the loading direction.

Vertical Root Fracture in Upper Premolars with Endodontic Posts: Finite Element Analysis

Upper premolars restored with endodontic posts present a high incidence of vertical root fracture (VRF). Two hypotheses were tested: (1) the smaller mesiodistal diameter favors stress concentration in the root and (2) the lack of an effective bonding between root and post increases the risk of VRF. Using finite element analysis, maximum principal stress was analyzed in 3-dimensional intact upper second premolar models. From the intact models, new models were built including endodontic posts of different elastic modulus (E = 37 or E = 200 GPa) with circular or oval cross-section, either bonded or nonbonded to circular or oval cross-section root canals. The first hypothesis was partially confirmed because the conditions involving nonbonded, low-modulus posts showed lower tensile stress for oval canals compared to circular canals. Tensile stress peaks for the nonbonded models were approximately three times higher than for the bonded or intact models, therefore confirming the second hypothesis. (J Endod 2009;35:117-120)

Effect of Test Environment and Microstructure on the Flexural Strength of Dental Porcelains

Purpose: The objective of this study was to verify the influence of test environment on the flexural strength of dental porcelains with distinct microstructures. Material and Methods: Disk-shaped specimens from three dental porcelains with distinct leucite content (VM: zero; CE: 12; NS: 22 vol%) were manufactured and tested for biaxial flexural strength in air and immersed in artificial saliva. The results were analyzed by means of two-way ANOVA and Tukey`s test (alpha = 0.05). Results: The flexural strength (MPa) obtained for ambient air and artificial saliva environments, respectively, were: 110.0 +/- 16.0 and 81.5 +/- 10.8 for VM; 51.9 +/- 4.0 and 42.0 +/- 4.7 for CE; 72.0 +/- 11.5 and 63.6 +/- 5.8 for NS. A numerical decrease in the mean flexural strength was observed for all groups when specimens were tested under artificial saliva; however, the difference was only statistically significant for VM. Conclusions: The results indicate that the effect of water immersion on the flexural strength of dental porcelains varies according to their leucite content, as only the material without leucite in its microstructure (VM) showed significant strength degradation when tested under water.

Clinical, Histological, and Microbiological Findings in Peri-Implant Disease: A Pilot Study

Objectives: This study is intended to verify the correlation among clinical indices of the peri-implant soft tissues, the histological condition and the presence of 3 pathogens commonly associated with peri-implant diseases (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Tannerella forsythia). Materials: Four clinical indices, Gingival Index (GI), Sulcus Bleeding Index, GI modified by Mombelli, and Plaque Index modified by Mombelli (mPI) were evaluated around I dental implant of each subject (n = 10). Subgingival plaque was collected for bacterial analysis (polymerase chain reaction) and a biopsy of peri-implant soft tissues for histological analysis was harvested. The clinical indices and detected pathogens correlated with a developed histological index (HI). Results: There was no statistically significant relationship between the clinical indices (GI, Sulcus Bleeding Index, and GI modified by Mombelli) and the HI, except for the mPI on the central area of lingual aspects (r = 0.85, P = 0.0029). There was a tendency for a positive correlation between the mPI on the central area of buccal aspects and the HI (r = 0.63, P = 0.0544). The counting of lymphocytes and plasmocytes correlated positively with 111, thus suggesting the index reliability. The prevalence of A. actinomycetemcomitans, P. gingivalis, and T. forsythia did not present a significant relationship with the HI. Conclusion: Despite the small number of samples and the poor statistical significance, the mPI seems to be useful for evaluation of inflammatory severity on soft tissue around dental implants as demonstrated by its relationship with the HI. Further studies are necessary to elucidate this subject. (Implant Dent 2009;18:334-344)

Fracture resistance of Class II glass-ionomer cement restorations

Purpose: To investigate in vitro the effect of retentive grooves, GIC type and insertion method on the fracture resistance of Class II glass-ionomer cement (GIC) restorations. Methods: Premolars were divided into 12 groups (n=10) according to three variables: retentive grooves [presence (PR) or absence AR)], GICs type [Ketac-Molar (KM), Fuji VIII (F8) and RelyX Luting (RX)], and insertion method [syringe injector (SI) or spoon excavator (SE)]. The specimens were subjected to fracture resistance test. Data were submitted to three-way ANOVA and multiple comparisons were performed using a Tukey test (P < 0.05). Results: Mean fracture resistance values (Kgf) +/- standard deviations (SD) were: KM (PR+SI) 65.66 +/- 2.5; KM (PR+SE) = 62.58 +/- 2.1; KM (AR+SI) = 57.11 +/- 1.9; KM (AR+SE) = 51.94 +/- 2.3; F8 (PR+SI) = 63.05 +/- 2.1; F8 (PR+SE) = 60.12 +/- 2.3; F8 (AR+SI) = 55.11 +/- 1.9; F8(AR+SE)=49.20 +/- 1.6; RX (PR+SI)=50.99 +/- 2.4; RX (PR+SE)=48.81 +/- 2.5; RX (AR+SI)=45.53 +/- 2.6; RX (AR+SE)=41.88 +/- 3.0. Statistically significant differences were observed among all the groups tested (P=0.001). There was significant difference when pooled means for GIC type were compared with retentive grooves (P=0.01) and when pooled means for retentive grooves were compared with insertion method (P=0.01).

Silicone implant for chin augmentation mimicking a low-grade liposarcoma

The silicone implant has been widely used in facial aesthetic surgery for chin augmentation. A case of a 71-year-old woman with a lesion in the anterior mandibular region detected by radiographies and suggestive of benign soft tissue tumor is presented. The patient denied previous surgical intervention in the mental area. A biopsy was performed and initially interpreted as low-grade liposarcoma. After an immunohistochemistry study showing CD-68-positive cells and complementary information regarding a silicone implant for chin augmentation, the definitive diagnosis was silicone granuloma. This case reinforces that silicone implant in the mandibular region can be misdiagnosed as malignant tumor and the correct diagnosis is heavily dependent on close collaboration between clinician and pathologist in order to avoid unnecessary surgical intervention. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 107: e21-e23)