Photoelastic Analysis of Biomechanical Behavior of Single and Multiple Fixed Partial Prostheses With Different Prosthetic Connections

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Clinical and radiographic changes around dental implants inserted in different levels in relation to the crestal bone, under different restoration protocols, in the dog model

Background: The aim of the present study was to evaluate clinical and radiographic changes that occur around dental implants inserted in different levels in relation to crestal bone under different restoration protocols.Methods: Thirty-six implants were inserted in the edentulous mandible of six mongrel dogs. Each implant was assigned to an experimental group according to the distance from the top of the implant to the crestal bone: Bone Level (at crestal bone level), Minus 1 (1 mm below crestal bone), or Minus 2 (2 mm below crestal bone). Each hemimandible was submitted to a restoration protocol: conventional (prosthesis was installed 120 days after implant placement, including 30 days with healing cap) or immediate (prosthesis was installed 24 hours after implant placement). Fixed partial prostheses were installed bilaterally in the same day. After 90 days, clinical and radiographic parameters were evaluated.Results: As long as the implants were inserted in more apical positions, the first bone-to-implant contact (fBIC) was positioned more apically (P<0.05). However, the apical positioning of the implants did not influence the ridge loss or the position of the soft tissue margin (PSTM) (P>0.05). In addition, in immediately restored sites, the PSTM was located significantly more coronally than that in conventionally restored sites (P=0.02).Conclusions: Despite the more apical positioning of the fBIC, the height of the peri-implant soft tissues and ridge was not jeopardized. Moreover, the immediate restoration protocol was beneficial to the maintenance of the PSTM. Further studies are suggested to evaluate the significance of these results in longer healing periods.

Evaluation of mechanical properties of dental feldsphatic porcelains for metal and zirconia core

Studies has been reported a significant incidence of chipping of the feldspathic porcelain veneer in zirconia-based restorations. The purpose of this study was to compare the three-point flexural strength (MPa), Weibull parameters, Vickers hardness (VHN) and Vickers indentation fracture toughness (MPa/mm(1/2)) in feldspatic porcelains for metal and for zirconia frameworks. Bar specimens were made with the porcelains e.MaxCeram (EM) and VitaVM9 (V9) for zirconia core, and Duceragold (DG) and VitaVMK95 (VK) for metal core (n = 15). Kruskal-Wallis and Dun test were used for statistical analysis. There was no significant difference (p=0.31) among the porcelains in the flexural strength (Median = 73.2; 74.6; 74.5; 74.4). Weibull calculation presented highest reliability for VK (10.8) followed by em (7.1), V9 (5.7) and DG (5.6). Vickers hardness test showed that em (536.3), V9 (579.9) and VK (522.1) had no difference and DG (489.6) had the lowest value (p<.001). The highest fracture toughness was to VK (1.77), DG (1.58) had an intermediate value while V9 (1.33) and em (1.18) had the lowest values (p<.001). Despite of the suitable flexural strength, reliability and high hardness, the porcelains used to zirconia-based fixed dental prostheses showed lower fracture toughness values.

Atypical dento-alveolar fracture fixed with screws: a technical note

Dento-alveolar process fracture is an important and common event in the dental office practice usually managed under the well-established protocols, but sometimes this kind of lesion is evaluated in the hospital emergency rooms without attention to the dental injuries. In this type of trauma, the time between the injury and the definitive resolution is essential for the treatment success, usually 1 h in cases of dento-alveolar fractures (tooth and alveolar bone). This paper describes the management of a patient with unusual dento-alveolar fracture caused by gunshot and treated using screw fixation.

Comparative scanning electron microscopic study of the effect of different dental conditioners on dentin micromorphology

This study evaluated comparatively by scanning electron microscopy (SEM) the effect of different dental conditioners on dentin micromorphology, when used according to the same protocol. Forty dentin sticks were obtained from 20 caries-free third human molars and were assigned to 4 groups corresponding to 3 conditioners (phosphoric acid 37%, Clearfil SE Bond and iBond) and an untreated control group. After application of the conditioners, the specimens were immersed in 50% ethanol solution during 10 s, chemically fixed and dehydrated to prepare them to SEM analysis. In the control group, dentin surface was completely covered by smear layer and all dentinal tubules were occluded. In the phosphoric acid-etched group, dentin surface was completely clean and presented exposed dentinal tubule openings; this was the only group in which the tubules exhibited the funnel-shaped aspect. In the groups conditioned with Clearfil SE Bond primer and iBond, which are less acidic than phosphoric acid, tubule openings were occluded or partially occluded, though smear layer removal was observed. SE Bond was more efficient in removing the smear layer than iBond. In the Clearfil SE Bond group, the cuff-like aspect of peritubular dentin was more evident. It may be concluded all tested conditioners were able to change dentin morphology. However, it cannot be stated that the agent aggressiveness was the only cause of the micromorphological alterations because a single morphological pattern was not established for each group, but rather an association of different aspects, according to the aggressiveness of the tested conditioner.

A longitudinal study of quality of life of elderly with mandibular implant-supported fixed prostheses

Objectives: To verify the consequences of implant-supported fixed oral rehabilitation on the quality of life (QL) of elderly individuals.Material and methods: Fifteen patients were studied, being 10 females and five males; all were aged > 60 years, were completely edentulous, wore removable dentures on both arches, and were treated with implant-supported fixed dentures. Three QL questionnaires were applied, two related to the oral conditions (Oral Impact on Daily Performance - OIDP - and Oral Health Impact Profile, short version - OHIP-14) and one dealing with global aspects (World Health Organization Quality of Life - WHOQOL-BREF), before 3, 6, and 18 months after surgical placement of implants.Results: Scores in the OIDP and OHIP-14 questionnaires were better after dental treatment. The WHOQOL-BREF was less sensitive, confirming the higher reliability of specific questionnaires (focal) compared with general questions in such situations.Conclusion: Treatment with implant-supported fixed prostheses improved QL in the elderly; these effects are better detected by specific instruments focused on the subject.

Effect of axial loads on implanted-supported partial fixed prostheses by strain gauge analysis

Objectives: The present study used strain gauge analysis to perform an in vitro evaluation of the effect of axial loading on 3 elements of implant-supported partial fixed prostheses, varying the type of prosthetic cylinder and the loading points. Material and methods: Three internal hexagon implants were linearly embedded in a polyurethane block. Microunit abutments were connected to the implants applying a torque of 20 Ncm, and prefabricated Co-Cr cylinders and plastic prosthetic cylinders were screwed onto the abutments, which received standard patterns cast in Co-Cr alloy (n=5). Four strain gauges (SG) were bonded onto the surface of the block tangentially to the implants, SG 01 mesially to implant 1, SG 02 and SG 03 mesially and distally to implant 2, respectively, and SG 04 distally to implant 3. Each metallic structure was screwed onto the abutments with a 10 Ncm torque and an axial load of 30 kg was applied at five predetermined points (A, B, C, D, E). The data obtained from the strain gauge analyses were analyzed statistically by RM ANOVA and Tukey's test, with a level of significance of p<0.05. Results: There was a significant difference for the loading point (p=0.0001), with point B generating the smallest microdeformation (239.49 mu epsilon) and point D the highest (442.77 mu epsilon). No significant difference was found for the cylinder type (p=0.748). Conclusions: It was concluded that the type of cylinder did not affect in the magnitude of microdeformation, but the axial loading location influenced this magnitude.

Design of dental implants, influence on the osteogenesis and fixation

The fixation and the bone ingrowth at the interface of porous cylindrical implants (total porosity of 37% and average pores diameter of 480 mu m) were compared in vivo to rough cylindrical implants (R-a = 5.3 mu m), both of commercially pure titanium, made by powder metallurgy. The implants were inserted into the tibias of 20 rabbits and the animals were sacrificed 4 and 8 weeks after surgery. The percentage of bone-implant contact observed in porous implant was significantly larger than in the rough ones for all of sacrifice periods, respectively, 57% vs. 46% after 4 weeks, and 59% vs. 50% after 8 weeks. The mechanical tests showed a significant increase in the shear strength of the porous implants for the two analyzed periods, 4 and 8 weeks (14 and 20 MPa), when compared with rough ones (4 and 13 MPa). These results suggest that porous implants improve the contact at the implant-bone interface and increase the fixation to the bone, improving the osseointegration. Thus, the porous implant might be an alternative to dental implant in less favorable conditions, and appear to be better fixed to bone, offering promising alternatives.

Deposition of SiOx Thin Films on Y-TZP by Reactive Magnetron Sputtering: Influence of Plasma Parameters on the Adhesion Properties Between Y-TZP and Resin Cement for Application in Dental Prosthesis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)