Daniel de Moraes Telles

Resins-based denture soft lining materials modified by chlorhexidine salt incorporation: An in vitro analysis of antifungal activity, drug release and hardness

OBJECTIVES To evaluate the in vitro growth inhibition of Candida albicans, the rate of chlorhexidine release and shore A hardness from resins-based denture soft lining materials modified by chlorhexidine diacetate (CDA) or chlorhexidine hydrochloride (CHC) incorporation. METHODS Resin discs were prepared from soft denture liners based on poly (methyl methacrylate) (PMMA) or poly (ethyl methacrylate) (PEMA) containing 0.5, 1.0 and 2.0 wt.% of CDA or CHC. For antifungal activity resin discs were placed on agar plates inoculated with C. albicans, after 48 h at 37°C the diameters of inhibition zones were measured. For the chlorhexidine release, discs were immersed into distilled water at 37°C, and spectral measurements were made after 48 h. Shore A hardness was evaluated at the baseline, 2 and 7 days, using 6mm thick rectangular specimens also immersed into distilled water at 37°C. Data were statistically processed by SigmaStat software using ANOVA and all pairwise multiple comparison procedures was done using the Holm-Sidak method, with α=0.05 (p<0.001). RESULTS CDA added to PMMA soft liner and PEMA soft liner had a dose-related inhibitory effect on C. albicans and on chlorhexidine release rate (p<0.001). The PMMA and PEMA hardness increased statistically by time but not for the different CDA concentrations. CHC had no inhibitory effect on C. albicans. SIGNIFICANCE Chlorhexidine diacetate released from resins-based soft lining materials can be convenient to reduce the biofilm development on the material surface and treat denture stomatitis, without depending on patient compliance.

Torque removal evaluation of prosthetic screws after tightening and loosening cycles: an in vitro study.

OBJECTIVES The aim of this study was to evaluate the variation in removal torque of implant prosthetic abutment screws after successive tightening and loosening cycles, in addition to evaluating the influence of the hexagon at the abutment base on screw removal torque. MATERIAL AND METHODS Twenty hexagonal abutments were tightened to 20 regular external hex implants with a titanium alloy screw, with an insertion torque of 32 N cm, measured with a digital torque gauge. The implant/abutment/screw assemblies were divided into two groups: (1) abutments without hexagon at the base and (2) abutments with a hexagon at the base. Each assembly received a provisional restoration and was submitted to mechanical loading cycles. After this, the screws were removed and the removal torque was measured. This sequence was repeated 10 times, then the screw was replaced by a new one, and another cycle was performed. Linear regression analysis was performed. RESULTS Removal torque values tended to decrease as the number of insertion/removal cycles increased, for both groups. Comparisons of the slopes and the intercepts between groups showed no statistical difference. There was no significant difference between the mean values of last five cycles and the 11th cycle. Within the limitations of this in vitro study, it was concluded that (1) repeated insertion/removal cycles promoted gradual reduction in removal torque of screws, (2) replacing the screw with a new one after 10 cycles did not increase resistance to loosening, and (3) removal of the hexagon from the abutment base had no effect on the removal torque of the screws.

The use of CAD/CAM technology to fabricate a custom ceramic implant abutment: A clinical report

Well-placed dental implants are a prerequisite of functional and esthetically successful dental implant-supported crowns. The presence of soft tissue is essential for excellent esthetics because the dental implant or titanium abutment may become visible if the soft-tissue contour is not acceptable. This clinical report describes the use of a custom ceramic implant abutment designed with computer-aided design and computer-aided manufacturing (CAD/CAM) technology by milling a zirconia framework that was cemented extraorally to a prefabricated titanium abutment with a reduced diameter. This ceramic abutment has the strength and precise fit of a titanium interface and also the esthetic advantages of shaded custom-milled zirconia, with no visible metal.

Edentulism in Brazil: trends, projections and expectations until 2040

The aim of this study was to examine the edentulism rates in Brazil and make projections for the next years. Data were collected from three national oral health surveys. The percentage of edentulous jaws was calculated. Projections were made for the years 2020, 2030 and 2040, assuming that edentulism follows a logistic function. Population projections were also performed. Annual change in proportion of edentulous jaws was -0.04% for teenagers, -0.96% for adults and 0.76% for the elderly. By 2040, edentulous jaws will be virtually zero among teenagers, 1.77% among adults and 85.96% among the elderly. Teenagers will slightly decrease in number; adults will increase and subsequently decrease; the elderly will continue to increase. In teenagers and adults, the number of edentulous jaws will decrease, being approximately 616,000 in 2040. In the elderly, it will increase alarmingly, reaching over 64 million in 2040. Edentulism is declining in Brazil among teenagers and middle-aged adults, but is still increasing and will continue to increase for the next decades among the elderly.

Dimensional changes in gypsum fragments bonded with cyanoacrylate.

PURPOSE Accidental fractures may occur during manipulation and transportation of plaster casts. In clinical practice, plaster fragments may be bonded without harming the accuracy of the final denture, provided that the bonding agent does not cause dimensional alterations. Cyanoacrylate could be a good material because of its ease of use, quick set, wide availability, and low cost. The aim of this study was to assess the dimensional alteration of Type IV plaster fragments bonded with a cyanoacrylate-based adhesive. MATERIALS AND METHODS Ten hexagonal regular prisms were made of Type IV plaster, with two reference marks on one of the faces. The distance between the marks was measured under a comparison microscope. After this, the prisms were fractured so that the fracture line would be between the two reference marks, bonded with a cyanoacrylate-based universal adhesive and measured again. RESULTS The mean difference between the measurements performed before and after fracture and bonding of the fragments was 0.0194 mm. At a level of significance of 0.05, there was no statistically significant difference between the measurements before and after fracture and bonding of the dies (p = 0.1582). CONCLUSION It may be concluded that bonding of Type IV plaster fragments with a cyanoacrylate-based adhesive did not cause significant dimensional alterations.

A rationale method for evaluating unscrewing torque values of prosthetic screws in dental implants

Objectives Previous studies that evaluated the torque needed for removing dental implant screws have not considered the manner of transfer of the occlusal loads in clinical settings. Instead, the torque used for removal was applied directly to the screw, and most of them omitted the possibility that the hexagon could limit the action of the occlusal load in the loosening of the screws. The present study proposes a method for evaluating the screw removal torque in an anti-rotational device independent way, creating an unscrewing load transfer to the entire assembly, not only to the screw. Material and methods Twenty hexagonal abutments without the hexagon in their bases were fixed with a screw to 20 dental implants. They were divided into two groups: Group 1 used titanium screws and Group 2 used titanium screws covered with a solid lubricant. A torque of 32 Ncm was applied to the screw and then a custom-made wrench was used for rotating the abutment counterclockwise, to loosen the screw. A digital torque meter recorded the torque required to loosen the abutment. Results There was a significant difference between the means of Group 1 (38.62±6.43 Ncm) and Group 2 (48.47±5.04 Ncm), with p=0.001. Conclusion This methodology was effective in comparing unscrewing torque values of the implant-abutment junction even with a limited sample size. It confirmed a previously shown significant difference between two types of screws.

Does the retention system influence the stability of implant-supported maxillary overdentures? A comparison with fixed and conventional dentures

PURPOSE The purpose of this in vitro study was to compare the stability of removable implant-supported maxillary overdentures with fixed complete dentures and conventional dentures. METHODS Four types of complete dentures were tested: conventional complete dentures; overdentures retained by a male resilient attachment system; overdentures retained by a combination of clip bar and attachment system; and fixed complete dentures. Each group was placed in the posterior and anterior region and the stability was recorded by measuring the vertical displacement of the prosthesis. RESULTS There was a difference in the vertical movement of the prosthesis according to the type of system. The results showed that the behavior of the overdenture retained by a combination of a clip bar and attachment system is comparable with the stabilization of an implant-retained fixed complete denture. CONCLUSIONS Overdentures retained by a combination of a clip bar and attachment presented better stability and retention capacity under our experimental conditions, close to that of the positive control (fixed complete denture), with the advantages of removable overdentures.

Chlorhexidine incorporated into the prosthesis as a treatment strategy for denture stomatitis

Objective: to perform a literature review on the denture stomatitis (DS) treatment, in order to propose the incorporation of chlorhexidine into the denture as a treatment strategy for DS. Material and Methods: an advanced search was undertaken in MEDLINE/PubMed baseline from 1976 to 2016. Sixty-five papers were retrieved using the following keywords: chlorhexidine, denture stomatitis, denture relining. Of those, 35 papers were directly related to the subject and were therefore selected for a narrative review. Results: DS is an inflammatory reaction of multifactorial etiology, usually associated with Candida albicans and often observed in complete denture wearers. Most treatments rely on patient cooperation. Chlorhexidine (CHX) has antifungal activity and can be incorporated into denture lining materials without causing significant alterations in denture resin structure and without depending on patient compliance. Conclusion: according to the results of in vitro studies, CHX released from denture relining materials may be convenient to reduce denture biofilms and treat DS, but further in vivo studies are necessary to recommend clinical use.

Osseointegrated implants placed at supracrestal level may harbour higher counts of A. gerencseriae and S. constellatus - a randomized, controlled pilot study.

Purpose This study aimed at evaluating the bacterial colonization in dental implants inserted in the crestal or supracrestal position and correlated it to radiographic bone measurements. Methods Thirty-five implants with regular platform in nine patients (mean age 62.4±11.2 years) were inserted either at the bone crest level (control group) or at a suprecrestal level (test group). Radiographic examination was performed at baseline (implant installation) and after 6 months. Clinical and microbiological data were collected after 6 months. Digital radiography was used to assess bone remodeling (marginal bone loss and optical alveolar density). Bacterial profile was analyzed by checkerboard DNA–DNA hybridization, including a panel of 40 bacterial species. Results After 6 months, there were significantly higher counts of Actinomyces gerencseriae (p=0.009) and Streptococcus constellatus (p=0.05) in the test group. No significant differences between test and control groups were observed for marginal bone loss (p=0.725) and optical alveolar density (p=0.975). Probing depth was similar in both groups. Conclusion Significantly higher counts of A. gerencseriae and S. constellatus were found in implants placed at the supracrestal level compared to the ones placed at the bone level. No relation was found between the installation level of dental implants and peri-implant bone remodeling.

Planning and treatment in oral rehabilitation with implant-supported prostheses using cephalometric analysis

There are growing prosthetic and esthetic demands for Oral Rehabilitations on osseointegratable implants, requiring precise prosthetic-surgical planning. In edentulous patients planning may be done using cephalometric analysis to determine the position of the teeth in the dental prosthesis, and consequently, those of the implants. In this clinical case, the planning and treatment of an oral implant-supported rehabilitation is described, using cephalometry to optimize prosthetic success and patient comfort. The patient presented complete mandibular and partial maxillary edentulism, with unsatisfactory esthetics and function of the anterior teeth, with accentuated vestibular inclination. In order to determine the correct position of maxillary teeth it was necessary to use a Steiner cephalometric tracing to position the maxillary central incisor in the diagnostic wax-up. Therefore, the maxillary anterior teeth were extracted, osseointegratable implants were placed (Neodent(r), Curitiba, Brazil), and an immediate temporary fixed denture was inserted. After 30 days, surgery was performed for the placement of 4 osseointegratable implants (Neodent(r), Curitiba, Brazil) in the inter-mentonian region, on which a complete, temporary, implant-supported denture was placed. After the period of osseointegration, the definitive implant-supported dental prosthesis were fabricated.