Maxillary tuberosity reconstruction with transport distraction osteogenesis.

Severe bone loss due to pathology in the maxillary tuberosity region is a challenging problem both surgically and prosthetically. Large bone grafts have a poor survival rate due to the delicate bony architecture in this area and presence of the maxillary sinus. Our case presentation describes a new technique for reconstructing severe bony defect in the maxillary tuberosity with horizontal distraction osteogenesis in a 45-year-old man. A 4 × 6 × 3 cm cyst was discovered in the left maxillary molar region and enucleated. Three months postoperatively, the area had a severe bone defect extending to the zygomatic buttress superiorly and hamular notch posteriorly. Three months later, a bone segment including the right upper second premolar was osteotomised and distracted horizontally. The bone segment was distracted 15 mm distally. After consolidation, implants were placed when the distractor was removed. A fixed denture was loaded over the implants after 3 months. Complete alveolar bone loss extending to the cranial base can be reconstructed with transport distraction osteogenesis. Distalisation of the alveolar bone segment adjacent to the bony defect is an easy method for reconstructing such severe defects.

Shear bond strengths of saliva contaminated 'one-bottle' adhesives.

The aim of this study was to investigate the effect of saliva contamination on the bond strengths of three one-bottle bonding systems. The dentin of 90 recently extracted, non-carious human molar teeth was exposed and ground wet on 500 grit silicon carbide (SIC) paper to establish a bonding surface in superficial dentin. Specimens were randomly assigned to nine groups of 10 teeth each. Three testing conditions are: (i) contamination with fresh saliva (pH 5.5) after acid etching, (ii) contamination with fresh saliva after bonding application, and (iii) no contamination. Three adhesive systems are: syntac single component, prime & bond NT, and gluma one bond. Cylinders of composite were applied via PTFE (polytetrafluroethylene) split mould and light cured to the dentin surfaces. All specimens were thermocycled (5000 cycles) between baths of 5 and 55 degrees C. Shear bond strengths were measured using an Instron Universal testing machine at a crosshead speed of 1 mm min-1. Two-way ANOVA was used to analyse the data. The results of this study indicated that the saliva contamination of dentin has no adverse effect on the bonding efficiency of one-bottle adhesive systems (P > 0.05). No statistically significant differences were found between the shear bond strengths of tested adhesives.

The effect of thermocycling on peel strength of six soft lining materials.

The bond strength of two heat-cured and four cold-cured soft lining materials was compared using a peeling test method before and after thermocycling. Tested soft lining materials were Molloplast B, Mollosil, Ufigel P, Ufigel C, Permaquick and Permaflex. Six specimens, 6.5 x 2 x 0.3 cm, for each group were prepared according to the manufacturers' instructions. Control groups were stored in a humidor for 24 h, whereas the others were thermocycled in a water bath between the 5 and 55 degrees C for 5000 cycles. Peel strength of samples were measured using an Instron Universal testing machine at a cross-head speed of 5 mm min-1. The types of failure were observed using an electron microscope. The highest peel bond strength values were calculated for Permaflex and Permaquick before and after thermocycling, respectively. Molloplast B, Mollosil, Ufigel P and Permaquick demonstrated an increase in peel strength after thermocycling, with Permaquick lining material having statistically significant increase. However, decrease in peel strength was observed for Ufigel C and Permaflex after thermocycling. Failure mode within the control groups was cohesive for Molloplast B, Permaquick and Permaflex, whereas adhesive for Ufigel P and Ufigel C. Mollosil demonstrated a mixed mode of failure for both thermocycled and control groups.

Finite element analysis study of the effect of superstructure material on stress distribution in an implant-supported fixed prosthesis.

This study used three-dimensional finite element analysis to investigate the effect of three different occlusal surface materials (resin, resin composite, and porcelain) and four different framework materials (gold, silver-palladium, cobalt-chromium, titanium alloys) on the stress distribution in a six-implant-supported mandibular fixed prosthesis and surrounding bone. A total of 172 N vertical load was distributed over the entire occlusal surface of the finite element model. Generated stress values were calculated in the occlusal surface material, framework, prosthesis retaining screws, implants, and surrounding cortical and spongy bones. The results obtained demonstrated that using a prosthesis superstructure material with a lower elastic modulus (1) did not lead to substantial differences in stress patterns nor in values at the cortical and spongy bones surrounding the implants; and (2) concentrated stresses in the retaining screws for the prosthesis and thus increased the potential risk of prosthesis failure. For the single loading condition investigated, the optimal combination of materials was found to be cobalt-chromium for the framework and porcelain for the occlusal surface.

In vivo and in vitro evaluation of marginal integrity in ceramic inlays.

The marginal integrity is an important factor for the long-term success of ceramic inlays. The long term clinical performance of porcelain inlays depends on a number of factors of which the marginal adaptation is of significant interest. The aim of this study was to determine the margin quality of adhesively luted sintered porcelain inlays both in vivo and in vitro. MOD cavities without bevels were prepared on 10 extracted human mandibular molar teeth. Using the Ducera inlay system, inlays were fired on refractory dies and luted with a dual-curing composite resin. After polishing, each, tooth was sectioned in buccal/lingual and mesial/distal directions and marginal adaptation was assessed microscopically. The mean marginal gap of 78.77 +/- 14.85 microns recorded for occlusal margins was significantly smaller than that of 128.85 +/- 34.34 microns seen at the approximal margins. For in vivo evaluation, 25 fired porcelain inlays, including 7 onlays, were placed in Class II cavities. The assessment of the marginal adaptation of inlays was made according to the scaling system used by Aberg et al. (Acta Odontol Scand 1994; 52:140-149). In 19 of the clinical cases, the restoration was contiguous with the existing anatomic form. Both in vivo and in vitro evaluations showed the margin quality of porcelain inlays to be high.

Finite element analysis of the effect of cantilever and implant length on stress distribution in an implant-supported fixed prosthesis.

This study investigated the stress distribution at the bone/implant interface with a three-dimensional finite element stress analysis by using three different cantilever and implant lengths in an implant-supported fixed partial denture. Simulation models were created as a bilateral distal cantilever fixed partial denture supported with six implants embedded in a model of the mandibular bone. Nine different simulation models had three different cantilevers (7, 14, and 28 mm) and implant lengths (7, 15, and 20 mm). Vertical forces of 75 N and horizontal forces of 25 N were applied to the distal end of the cantilever. Analysis of the von Mises stresses for the bone/implant interfaces revealed that the maximum stresses occurred at the most distal bone/ implant interface located on the loaded side and significantly increased with the length of the cantilever. However, there was no statistically significant change associated with the length of implants.

Luting composite thickness of two ceramic inlay systems.

The purpose of this in vitro study was to evaluate the luting composite thickness of two ceramic inlay systems, a direct chairside ceramic inlay system (Cerec, CAD/CAM), and an indirect laboratory inlay system (IPS Empress). The luting composite thicknesses were measured at the approximal margin, at the inner axial wall and at th occlusal cavosurface area. The luting composite thickness at occlusal margins and inner axial walls were found to be smaller in Empress inlays. However, the fit of inlays was poorer in Empress inlays at distal proximal margins, which most probably resulted from displacement of Cerec inlays during cementation due to inaccurate inner fit.