Progressive recovery of osseoperception as a function of the combination of implant-supported prostheses

The extraction of teeth involves the elimination of extremely sensitive periodontal mechanoreceptors, which play an important role in oral sensory perception. Objectives: The aim of this study was to evaluate the recovery of interocclusal sensory perception for micro-thickness in individuals with different types of implant-supported prostheses. Materials and Methods: Wearers of complete dentures (CDs) comprised the negative control group (group A, n=17). The experimental group consisted of wearers of prostheses supported by osseointegrated implants (Group B, n=29), which was subsequently divided into 4 subgroups: B(1) (n=5) - implant supported overdentures (ISO) occluding with CD; B(2) (n=6) - implant-supported fixed prostheses (ISFP) occluding with CD; B3 (n=8) - wearers of maxillary and mandibular ISFP, and B(4) (n=10) - ISFP occluding with natural dentition (ND). Individuals with ND represented the positive control group (Group C, n=24). Aluminum foils measuring 10 mu m, 24 mu m, 30 mu m, 50 mu m, 80 mu m, and 104 mu m thickness were placed within the premolar area, adding up to 120 tests for each individual. Results: The mean tactile thresholds of groups A, B(1), B(2), B(3), B(4), and C were 92 mu m, 27 mu m, 27 mu m, 14 mu m, 10 mu m, and 10 mu m, respectively. [Correction added after publication online 18 April 2008: in the preceding sentence 92 mu m, 27 mu m, 14 mu m, 10 mu m and 10 mu m, was corrected to 92 mu m, 27 mu m, 27 mu m, 14 mu m, 10 mu m and 10 mu m.] The Kruskal-Wallis test revealed significant difference among groups (P < 0.05). The Dunn test revealed that group A was statistically different from groups C, B(3), and B(4), and that B(1) and B(2) were statistically different from group C. Conclusion: Progressive recovery of osseoperception as a function of the combination of implant-supported prostheses could be observed. Moreover, ISO and/or ISFP combinations may similarly maximize the recovery of osseoperception.

Mechanical Testing of Indirect Composite Materials Directly Applied on Implant Abutments

Purpose: To test the strength to failure and fracture mode of three indirect composite materials directly applied onto Ti-6Al-4V implant abutments vs cemented standard porcelain-fused-to-metal (PFM) crowns. Materials and Methods: Sixty-four locking taper abutments were randomly allocated to four groups and were cleaned in ethanol in an ultrasonic bath for 5 min. After drying under ambient conditions, the abutments were grit blasted and a custom 4-cusp molar crown mold was utilized to produce identical crowns (n = 16 per group) of Tescera (Bisco), Ceramage (Shofu), and Diamond Crown (DRM) according to the manufacturer`s instructions. The porcelain-fused-to-metal crowns were fabricated by conventional means involving the construction and a wax pattern and casting of a metallic coping followed by sintering of increasing layers of porcelain. All crowns were loaded to failure by an indenter placed at one of the cusp tips at a 1 mm/min rate. Subsequently, fracture analysis was performed by means of stereomicroscopy and scanning electron microscopy. One-way ANOVA at 95% level of significance was utilized for statistical analysis. Results: The single load to failure (+/- SD) results were: Tescera (1130 +/- 239 N), Ceramage (1099 +/- 257 N), Diamond Crown (1155 +/- 284 N), and PFM (1081 +/- 243 N). Stereomicroscopy analysis showed two distinct failure modes, where the loaded cusp failed either with or without abutment/metallic coping exposure. SEM analysis of the fractures showed multiple crack propagation towards the cervical region of the crown below a region of plastic deformation at the indenter contact region. Conclusion: The three indirect composites and PFM systems fractured at loads higher than those typically associated with normal occlusal function. Although each material had a different composition and handling technique, no significant differences were found concerning their single load to fracture resistance among composite systems and PFM.

Cleft Palate Obturation With Branemark Protocol Implant-Supported Fixed Denture and Removable Obturator

A 41-year-old man with cleft palate presented with a wide dehiscence and missing teeth. Six implants had been placed for fabrication of an overdenture, which was unsatisfactory. A bar was waxed and cast for connection to the implants; precision attachments were placed laterally for retention. A fixed partial denture was fabricated, and milled crowns were fabricated at the molar region to provide a guiding plane for insertion of a removable palatal obturator. Good swallowing and speech outcomes were achieved. This technique provided functional and esthetic benefits, enhanced oral hygiene, and improved the psychological condition of the patient.

Clinical feasibility of mandibular implant overdenture retainers submitted to immediate load

Clinical feasibility of mandibular implant overdenture retainers submitted to immediate load Introduction: Millions of people around the world do not have access to the benefits of osseointegration. Treatments involving oral rehabilitation with overdentures have been widely used by specialists in the oral medicine field. This is an alternative therapy for retention and stability achievement in total prosthesis with conventional treatment, and two implants are enough to establish a satisfactory overdenture. Objective: The objectives of the study were to evaluate 16 patients of both sexes, with an average age of 47.4 +/- 4 years, using electromyographic analysis of masseter and temporal muscles and analyse the increase of incisive and molar maximal bite force with their existing complete dentures and following mandibular implant overdenture therapy to assess the benefits of this treatment. Materials and methods: For these tests, the Myosystem-BR1 electromyograph and the IDDK Kratos dynamometer were used. Statistical analysis was performed using the repeated measures test (SPSS 17.0). Results: A decrease in electromyographic activity during the rest, lateral and protrusion movements and increase of the maximal incisive and molar bite force after 15 months with a mandibular implant overdenture was observed. Conclusion: All the patients in this study reported a considerable improvement in the masticatory function and prostheses stability following treatment. It is possible to propose that the use of mandibular implants overdenture should become the selected treatment for totally edentulous patients to facilitate oral function and quality of life.

In Vitro Evaluation of Bacterial Leakage Along the Implant-Abutment Interface of an External-Hex Implant After Saliva Incubation

The aim of this in vitro study was to evaluate bacterial leakage along the implant-abutment interface under unloaded conditions. Twelve premachined abutments with plastic sleeves and 12 dental implants were used in this study. Prior to tests of bacterial leakage, samples from the inner parts of the implants were collected with sterile microbrushes to serve as negative controls for contamination. After casting, the abutments were tightened to 32 Ncm on the implants. The assemblies were immersed in 2.0 mL of human saliva and incubated for 7 days. After this period, possible contamination of the internal parts of the implants was evaluated using the DNA Checkerboard method. Microorganisms were found in the internal surfaces of all the implants evaluated. Aggregatibacter actinomycetemcomitans and Capnocytophaga gingivalis were the most incident species. No microorganisms were found in the samples recovered from the implants before contamination testing (negative control). Bacterial species from human saliva may penetrate the implant-abutment interface under unloaded conditions. INT J ORAL MAXILLOFAC IMPLANTS 2011;26:782-787

Effect of simulated masticatory loading on the retention of stud attachments for implant overdentures

P>This study assessed the effect of simulated mastication on the retention of two stud attachment systems for 2-implants overdentures. Sixteen specimens, each simulating an edentulous ridge with implants and an overdenture were divided into two groups, according to the attachment system: Group I (Nobel Biocare ball-socket attachments) and Group II (Locator attachments). Retention forces were measured before and after 400 000 simulated masticatory loads in a customised device. Data were compared by two-way anova followed by Bonferroni test (alpha = 0 center dot 05). Group I presented significantly lower retention forces (Newtons) than Group II at baseline (10 center dot 6 +/- 3 center dot 6 and 66 center dot 4 +/- 16 center dot 0, respectively). However, differences were not significant after 400 000 loads (7 center dot 9 +/- 4 center dot 3 and 21 center dot 6 +/- 17 center dot 0). The number of cycles did not influence the measurements in Group I, whereas a non-linear descending curve was found for Group II. It was concluded that simulated mastication resulted in minor changes for the ball attachment tested. Nevertheless, it reduced the retention of Locator attachments to 40% of the baseline values, what suggests that mastication is a major factor associated with maintenance needs for this system.

Influence of interimplant distances and placement depth on peri-implant bone remodeling of adjacent and immediately loaded Morse cone connection implants: a histomorphometric study in dogs

Objectives The aim of this study was to histomorphometrically evaluate the influence of interimplant distances (ID) and implant placement depth on bone remodeling around contiguous Morse cone connection implants with `platform-shifting` in a dog model. Material and methods Bilateral mandibular premolars of six dogs were extracted, and after 12 weeks, each dog received 8 implants, four placed 1.5 mm subcrestally (SCL) on one side of the mandible and four placed equicrestally (ECL) on the other side, alternating the ID of 2 and 3 mm. The experimental groups were SCL with IDs of 2 mm (2 SCL) and 3 mm (3 SCL) and ECL with IDs of 2 mm (2 ECL) and 3 mm (3 ECL). Metallic crowns were immediately installed. After 8 weeks, the animals were euthanized and histomorphometric analyses were performed to compare bone remodeling in the groups. Results The SCL groups` indices of crestal bone resorption were significantly lower than those of ECL groups. In addition, the vertical bone resorption around the implants was also numerically inferior in the SCL groups, but without statistical significance. No differences were obtained between the different IDs. All the groups presented similar good levels of bone-to-implant contact and histological bone density. Conclusion The subcrestal placement of contiguous Morse cone connection implants with `platform shifting` was more efficient in preserving the interimplant crestal bone. The IDs of 2 and 3 mm did not affect the bone remodeling significantly under the present conditions. To cite this article:Barros RRM, Novaes AB Jr., Muglia VA, Iezzi G, Piattelli A. Influence of interimplant distances and placement depth on peri-implant bone remodeling of adjacent and immediately loaded Morse cone connection implants: a histomorphometric study in dogs.Clin. Oral Impl. Res. 21, 2010; 371-378.doi: 10.1111/j.1600-0501.2009.01860.x.

Testing the retention of attachments for implant overdentures - validation of an original force measurement system

P>The aim of this study was to validate an original portable device to measure attachment retention of implant overdentures both in the lab and in clinical settings. The device was built with a digital force measurement gauge (Imada) secured to a vertical wheel stand associated with a customized support to hold and position the denture in adjustable angulations. Sixteen matrix and patrix cylindrical stud attachments (Locator (R)) were randomly assigned as in vitro test specimens. Attachment abutments were secured in an implant analogue hung to the digital force gauge or to the load cell of a traction machine used as the gold standard (Instron Universal Testing Machine). Matrices were secured in a denture duplicate attached to the customized support, permitting reproducibility of their position on both pulling devices. Attachment retention in the axial direction was evaluated by measuring maximum dislodging force or peak load during five consecutive linear dislodgments of each attachment on both devices. After a wear simulation, retention was measured again at several time periods. The peak load measurements with the customized Imada device were similar to those obtained with the gold standard Instron machine. These findings suggest that the proposed portable device can provide accurate information on the retentive properties of attachment systems for removable dental prostheses.

Influence of repeated screw tightening on bacterial leakage along the implant-abutment interface

Objectives Bacterial penetration along the implant-abutment interface as a consequence of abutment screw loosening has been reported in a number of recent studies. The aim of this in vitro study was to investigate the influence of repeated tightening of the abutment screw on leakage of Streptococcus mutans along the interface between implants and pre-machined abutments. Materials and methods Twenty pre-machined abutments with a plastic sleeve were used. The abutment screws were tightened to 32 N cm in group 1 (n=10 - control) and to 32 N cm, loosened and re-tightened with the same torque twice in group 2 (n=10). The assemblies were completely immersed in 5 ml of Tryptic Soy Broth medium inoculated with S. mutans and incubated for 14 days. After this period, contamination of the implant internal threaded chamber was evaluated using the DNA Checkerboard method. Results Microorganisms were found on the internal surfaces of both groups evaluated. However, bacterial counts in group 2 were significantly higher than that in the control group (P < 0.05). Conclusion These results suggest that bacterial leakage between implants and abutments occurs even under unloaded conditions and at a higher intensity when the abutment screw is tightened and loosened repeatedly. To cite this article:do Nascimento C, Pedrazzi V, Kirsten Miani P, Daher Moreira L, de Albuquerque Junior RF. Influence of repeated screw tightening on bacterial leakage along the implant-abutment interface.Clin. Oral Impl. Res. 20, 2009; 1394-1397.doi: 10.1111/j.1600-0501.2009.01769.x.

Fracture Resistance of the Implant-Abutment Connection in Implants with Internal Hex and Internal Conical Connections Under Oblique Compressive Loading: An In Vitro Study

The objective of this study was to verify if differences in the design of internal hex (IH) and internal conical (IC) connection implant systems influence fracture resistance under oblique compressive forces. Twenty implant-abutment assemblies were utilized: 10 with IH connections and 10 with IC connections. Maximum deformation force for IC implants (90.58 +/- 6.72 kgf) was statistically higher than that for IH implants (83.73 +/- 4.94 kgf) (P = .0182). Fracture force for the IH implants was 79.86 +/- 4.77 kgf. None of the IC implants fractured. The friction-locking mechanics and the solid design of the IC abutments provided greater resistance to deformation and fracture under oblique compressive loading when compared to the IH abutments. Int J Prosthodont 2009;22:283-286.

An Alternative Section Method for Casting and Posterior Laser Welding of Metallic Frameworks for an Implant-Supported Prosthesis

Purpose: The aim of this study was to compare the accuracy of fit of three types of implant-supported frameworks cast in Ni-Cr alloy: specifically, a framework cast as one piece compared to frameworks cast separately in sections to the transverse or the diagonal axis, and later laser welded. Materials and Methods: Three sets of similar implant-supported frameworks were constructed. The first group of six 3-unit implant-supported frameworks were cast as one piece, the second group of six were sectioned in the transverse axis of the pontic region prior to casting, and the last group of six were sectioned in the diagonal axis of the pontic region prior to casting. The sectioned frameworks were positioned in the matrix (10 N(.)cm torque) and laser welded. To evaluate passive fit, readings were made with an optical microscope with both screws tightened and with only one-screw tightened. Data were submitted to ANOVA and Tukey-Kramer`s test (p < 0.05). Results: When both screws were tightened, no differences were found between the three groups (p > 0.05). In the single-screw-tightened test, with readings made opposite to the tightened side, the group cast as one piece (57.02 +/- 33.48 mu m) was significantly different (p < 0.05) from the group sectioned diagonally (18.92 +/- 4.75 mu m) but no different (p > 0.05) from the group transversally sectioned (31.42 +/- 20.68 mu m). On the tightened side, no significant differences were found between the groups (p > 0.05). Conclusions: Results of this study showed that casting diagonally sectioned frameworks lowers misfit levels of prosthetic implant-supported frameworks and also improves the levels of passivity to the same frameworks when compared to structures cast as one piece.

Comparative analysis of the fit of 3-unit implant-supported frameworks cast in nickel-chromium and cobalt-chromium alloys and commercially pure titanium after casting, laser welding, and simulated porcelain firings

This study compared the vertical misfit of 3-unit implant-supported nickel-chromium (Ni-Cr) and cobalt-chromium (Co-Cr) alloy and commercially pure titanium (cpTi) frameworks after casting as 1 piece, after sectioning and laser welding, and after simulated porcelain firings. The results on the tightened side showed no statistically significant differences. On the opposite side, statistically significant differences were found for Co-Cr alloy (118.64 mu m [SD: 91.48] to 39.90 mu m [SD: 27.13]) and cpTi (118.56 mu m [51.35] to 27.87 mu m [12.71]) when comparing 1-piece to laser-welded frameworks. With both sides tightened, only Co-Cr alloy showed statistically significant differences after laser welding. Ni-Cr alloy showed the lowest misfit values, though the differences were not statistically significantly different. Simulated porcelain firings revealed no significant differences.

Digital image correlation analysis of the load transfer by implant-supported restorations

This study compared splinted and non-splinted implant-supported prosthesis with and without a distal proximal contact using a digital image correlation method. An epoxy resin model was made with acrylic resin replicas of a mandibular first premolar and second molar and with threaded implants replacing the second premolar and first molar. Splinted and non-splinted metal-ceramic screw-retained crowns were fabricated and loaded with and without the presence of the second molar. A single-camera measuring system was used to record the in-plane deformation on the model surface at a frequency of 1.0 Hz under a load from 0 to 250 N. The images were then analyzed with specialist software to determine the direct (horizontal) and shear strains along the model. Not splinting the crowns resulted in higher stress transfer to the supporting implants when the second molar replica was absent. The presence of a second molar and an effective interproximal contact contributed to lower stress transfer to the supporting structures even for non-splinted restorations. Shear strains were higher in the region between the molars when the second molar was absent, regardless of splinting. The opposite was found for the region between the implants, which had higher shear strain values when the second molar was present. When an effective distal contact is absent, non-splinted implant-supported restorations introduce higher direct strains to the supporting structures under loading. Shear strains appear to be dependent also on the region within the model, with different regions showing different trends in strain changes in the absence of an effective distal contact. (C) 2011 Elsevier Ltd. All rights reserved.

Influence of implant positioning in extraction sockets on osseointegration: histomorphometric analyses in dogs

Aim To evaluate the influence of implant positioning into extraction sockets on osseointegration. Material and methods Implants were installed immediately into extraction sockets in the mandibles of six Labrador dogs. In the control sites, the implants were positioned in the center of the alveolus, while in the test sites, the implants were positioned 0.8 mm deeper and more lingually. After 4 months of healing, the resorptive patterns of the alveolar crest were evaluated histomorphometrically. Results All implants were integrated in mineralized bone, mainly composed of mature lamellar bone. The alveolar crest underwent resorption at the control as well as at the test sites. After 4 months of healing, at the buccal aspects of the control and test sites, the location of the implant rough/smooth limit to the alveolar crest was 2 +/- 0.9 mm and 0.6 +/- 0.9 mm, respectively (P < 0.05). At the lingual aspect, the bony crest was located 0.4 mm apically and 0.2 mm coronally to the implant rough/smooth limit at the control and test sites, respectively (NS). Conclusions From a clinical point of view, implants installed into extraction sockets should be positioned approximately 1 mm deeper than the level of the buccal alveolar crest and in a lingual position in relation to the center of the alveolus in order to reduce or eliminate the exposure above the alveolar crest of the endosseous (rough) portion of the implant. To cite this article:Caneva M, Salata LA, de Souza SS, Baffone G, Lang NP, Botticelli D. Influence of implant positioning in extraction sockets on osseointegration: histomorphometric analyses in dogs.Clin. Oral Impl. Res. 21, 2010; 43-49.

Osteocyte Density in the Peri-Implant Bone of Immediately Loaded and Submerged Dental Implants

Background: The role of osteocytes in bone structure and function remains partially unresolved. Their participation in mechanotransduction, i.e., the conversion of a physical stimulus into a cellular response, has been hypothesized. The present study was an evaluation of the osteocyte density in the peri-implant bone of immediately loaded and submerged dental implants. Methods: Fourteen male patients were included in the study; all of them were partially edentulous and needed a posterior mandibular restoration. Implants were inserted in these areas; half of the sample was loaded immediately (included in a fixed provisional prosthesis on the same day as implant surgery), whereas the other half was left to heal submerged. Fourteen implants (seven immediately loaded and seven unloaded) were retrieved with a trephine after a healing period of 8 weeks. The specimens were treated to obtain thin ground sections, and histomorphometry was used to evaluate the osteocyte index in the peri-implant bone. Results: A higher and statistically significant number of osteocytes was found in the peri-implant bone around immediately loaded implants (P=0.0081). A correlation between the percentage of bone-implant contact and osteocyte density was found for immediately loaded implants (P=0.0480) but not for submerged implants (P=0.2667). Conclusion: The higher number of osteocytes in the peri-implant bone around immediately loaded implants could be related to the functional adaptation required by the loading stimulus, which also explains the hypothesized involvement of the osteocytes in the maintenance of the bone matrix. J Periodontol 2009;80:499-504.