The Debonding of Teeth from Removable Dentures Accounts for 22% to 30% of Denture Repairs
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Multilithic Denture Teeth Promising Choice in Fabrication of Removable Dentures A Comparison of Acrylic and Multilithic Teeth Bond Strengths to Acrylic Denture Base Material. Mosharraf R, Abed-Haghighi M: J Contemp Dent Pract 2009; 10 (September): 1-6 There is not a significant difference in the bonding strength to acrylic-base dentures between the acrylic brands of teeth and the newer type of multilithic acrylic resin-composite denture teeth. Background: The debonding of teeth from removable dentures accounts for 22% to 30% of denture repairs. Acrylic resin teeth bond to denture bases, but have poor wear resistance. On the other hand, all composite resin denture teeth were shown clinically to achieve poor bonding to denture bases and greater wear resistance. This paper compares 3 groups of denture teeth--2 acrylic resin and 1 multilithic. The latter consists of an acrylic gingival ridge lap and a composite outer layer. The tests conducted sought to ascertain whether this type of "hybrid" would be successful in reducing the number of fractures at the tooth-denture base interface. Objective: To compare bond strengths of a composite-acrylic denture tooth with an all-acrylic resin tooth. Data were analyzed to see if combining the properties of composites with acrylic would result in a more fracture- and abrasion-resistant tooth with superior retentive properties. Methods: 3 types of denture teeth were used: 1 multilithic (Yaghoot) and 2 conventional acrylic teeth (Super Brilian and Major). All ridge laps were lightly ground, and the teeth were bonded to the denture base by heat polymerization. After curing and deflasking, a universal testing machine applied forces to the teeth until fracture occurred. A shear compressive force at an angle of 130° was applied to lingual surfaces of the teeth, simulating the average contact angle of Class I occlusion. Fracture sites were analyzed, and mean bond strengths recorded. Results: Although the highest bond strength and lowest number of adhesive fractures was found in the Yaghoot (multilithic) tooth group, the difference among the 3 groups was not significant. More than 65% of fractures occurred at the tooth-denture base resin junction. The grinding of the ridge lap in all specimens resulted in all bonding surfaces being in acrylic. Conclusions: The multilithic acrylic resin-composite tooth and the 2 types of acrylic resin teeth exhibited similar bond strengths to the denture resin base, as well as having the same location of the fracture sites. Reviewer's Comments: Presently, the fracture of denture teeth is a common occurrence. In this study, all had an acrylic ridge lap, which accounts for the similarity in the data of the fractures. The effect of the composite surface layer on the multilithic tooth did not appear to make any difference in this area. The author attributes this tooth's slightly higher bond strength and lower adhesive fracture rate to "better ridge lap area properties in this tooth." More information about that ridge lap difference would have been helpful to enable the practitioner to utilize those properties and increase the bond strength of the teeth to the denture base. (Reviewer-Edward N. Friedman, DDS). © 2009, Oakstone Medical Publishing Keywords: Acrylic Resins, Composite Dental Resins, Denture Bases, Bonding Print Tag: Refer to original journal article SBA Technique Mimics Native Bone, Promotes Regeneration Sandwich Bone Augmentation for Predictable Horizontal Bone Augmentation. Lee A, Brown D, Wang HL: Implant Dent 2009; 18 (August): 282-290 The sandwich bone augmentation technique, a type of guided bone regeneration procedure, can improve implant prognosis by achieving bone fill around dental implants. Background: Numerous techniques have been proposed to promote guided bone regeneration (GBR) using different types of bone grafting materials and membranes. This study discusses a protocol called sandwich bone augmentation (SBA), which stresses the creation of an environment similar to that of native bone in order to promote regeneration. Objective: To demonstrate the success of the sandwich bone augmentation technique resulting in stable implants due to successful bone fill around the implants. The regeneration of this native bone is best demonstrated by promoting successful bone fill simply by reproducing an environment favorable to native bone regeneration while inserting a variety of grafting materials. Participants/Methods: SBA was chosen in order to achieve both vertical and horizontal bone augmentation. After initial incisions and a full-thickness flap, a Tapered Screw Vent implant was placed using a surgical guide. A buccal fenestration was present. Autogenous cancellous bone was applied as the first layer of the bone graft over the implant surface. Cortical bone graft was then placed as the second external layer. This layer serves to create and maintain the space needed for regeneration. The barrier membrane is then placed to cover the bone grafts and exclude soft tissue. The increase in the number of bone forming cells is critical to attaining bone fill. Radiographs at the time of second-stage surgery in 5 to 6 months demonstrated adequate bone level and no pathology. The restoration of the implant with a ceramic crown was then commenced. Results/Conclusions: This guided bone regeneration technique has proven to be predictable and successful using several types of bone graft materials. The data show that they were as successful as other implants that did not need additional bone regeneration procedures. The most frequently reported complication of the GBR is that of membrane exposure. This complication would compromise the amount of bone regenerated, allowing contamination into the area around the implant. The SBA technique helps prevent this occurrence, since the use of bone grafts may prevent membrane collapse. Reviewer's Comments: This study presents a good review of this technique of guided bone regeneration. Dr Lee stresses the basic principles of healing that apply to any type of surgical situation, and goes one step further with her use of the SBA technique. Along with a flexible approach that employs the use of different materials, this article provides the practitioner with another method to achieve and improve the amount of bone fill, ultimately enhancing the long-term prognosis of the implants. (Reviewer-Edward N. Friedman, DDS). © 2009, Oakstone Medical Publishing Keywords: Implants, Guided Bone Regeneration, Membrane, Sandwich Print Tag: Refer to original journal article Reduce Microleakage With Silorane-Based Materials Comparing Microleakage and the Layering Methods of Silorane-Based Resin Composite in Wide Class II MOD Cavities. Bagis YH, Baltacioglu IH, Kahyaogullari S: Oper Dent 2009; 34 (September-October): 578-585 Microleakage can be reduced by using silorane-based materials, using either the vertical or oblique layering technique, rather than methacrylate-based composites. Background: One of the disadvantages of composite restorations has been the presence of microleakage due to the lack of complete marginal sealing. The volumetric shrinkage resulting from polymerization contraction can lead to hypersensitivity and recurrent decay. This study reviews 2 factors related to this microleakage--the type of layering technique and the different monomer-based composites used. Objective: To evaluate layering techniques with each of 2 different monomer systems to ascertain which combination of factors will better achieve a completed restoration with minimal or no marginal microleakage. Design/Methods: An in vitro study was used, and 32 third molars were prepared with wide MOD cavity preparations. The 32 teeth were divided into 4 groups of 8. Half of the specimens were etched, bonded, and restored with a methacrylate-based nanohybrid composite, and the other half with a silorane-based microhybrid composite. Each of these 2 groups was further subdivided according to the layering technique--16 were restored with the vertical, and 16 with the oblique. After completing the restorations, the specimens were immersed in a fuchsin dye solution for 24 hours. Then they were sectioned and examined under a stereo microscope at 10x magnification to quantify the amount of marginal microleakage. Results: The specimens restored with the silorane-based composite showed no microleakage. This result was present both in those teeth restored with the vertical as well as the oblique layering technique. However, the specimens restored with the methacrylate-based composite did show significant microleakage. There also was a difference with the layering technique used. There was less microleakage at the enamel margins on those teeth that were filled with the vertical layering technique than with the oblique. Conclusions: These in vitro results provide validity to what would result in the oral cavity. The minimizing of contraction stress and polymerization shrinkage is significant in preventing open margins and leakage. Methacrylate-based restorative materials have higher polymerization shrinkage stresses than do silorane- based resin systems. The increased contraction forces in the cavity result in a deficient marginal seal. This study concludes that microleakage can be reduced by using silorane-based materials rather than methacrylate-based composites. Reviewer's Comments: This is a relevant study that explains why postoperative sensitivity after composite placement is such a widely observed phenomena. Two variables involved when restoring teeth with composites