João Malta Barbosa

Volumetric shrinkage and film thickness of cementation materials for veneers: An in vitro 3D microcomputed tomography analysis

Statement of problem Few studies have investigated the volumetric polymerization shrinkage and film thickness of the different cementation techniques used to cement veneers. Purpose The purpose of this in vitro study was to evaluate the volumetric polymerization shrinkage (VS) and film thickness (FT) of various cementation techniques through 3‐dimensional (3D) microcomputed tomography (&mgr;CT). Material and methods Forty‐eight artificial plastic maxillary central incisors with standard preparations for veneers were provided by a mannequin manufacturer (P‐Oclusal) and used as testing models with the manufacturer’s plastic veneers. They were divided into 8 groups (n=6): RelyX Veneer + Scotchbond Universal (RV+SBU); Variolink Esthetic LC+Adhese Universal (VE+ADU); Filtek Supreme Ultra Flowable + Scotchbond Universal (FF+SBU); IPS Empress Direct Flow + Adhese Universal (IEF+ADU); Filtek Supreme Ultra Universal + Scotchbond Universal (FS+SBU); IPS Empress Direct + Adhese Universal (IED+ADU); Preheated Filtek Supreme Ultra Universal + Scotchbond Universal (PHF+SBU); and Preheated IPS Empress Direct + Adhese Universal (PHI+ADU). Specimens were scanned before and after polymerization using a &mgr;CT apparatus (mCT 40; Scanco Medical AG), and the resulting files were imported and analyzed with 3D rendering software to calculate the VS and FT. Collected data from both the VS and FT were submitted to 1‐way ANOVA (&agr;=.05). Results VE+ADU had the lowest volumetric shrinkage (1.03%), which was not significantly different from RV+SBU, FF+SBU or IEF+ADU (P>.05). The highest volumetric shrinkage was observed for FS+SBU (2.44%), which was not significantly different from RV+SBU, IED+ADU, PHF+SBU, or PHI+ADU (P>.05). Group RV+SBU did not differ statistically from the remaining groups (P>.05). Film thickness evaluation revealed the lowest values for RV+SBU, VE+ADU, FF+SBU, and IEF+ADU, with an average between groups of 0.17 mm; these groups were significantly different from FS+SBU, IED+ADU, PHF+SBU, and PHI+ADU (P>.05), with an average of 0.31 mm. Conclusions Both the VS and the FT of direct restorative composite resins were higher than those of veneer cements and flowable composite resins, whether preheated or not preheated.

Histomorphological and Histomorphometric Analyses of Grade IV Commercially Pure Titanium and Grade V Ti-6Al-4V Titanium Alloy Implant Substrates: An In Vivo Study in Dogs.

Purpose:To evaluate the bone response to grade IV commercially pure titanium (G4) relative to Ti-6Al-4V (G5). Materials and Methods:Implant surface topography was characterized by optical interferometry and scanning electron microscopy (SEM). Thirty-six implants (Signo Vinces, n = 18 per group) were installed in the radius of 18 dogs. The animals were killed at 1, 3, and 6 weeks, resulting in 6 implants per group and time in vivo for bone morphology, bone-to-implant contact (BIC), and bone area fraction occupancy (BAFO) evaluation. Results:SEM depicted a more uniform topography of G4 than G5. Surfaces were statistically homogeneous for Sa, Sq, and Sdr. At 1 week, new bone formation was observed within the healing connective tissue in contact with the implant surface. At 3 weeks, new bone in direct contact with the implant surface was observed at all bone regions. At 6 weeks, the healing chambers filled with woven bone depicted an onset of replacement by lamellar bone. No significant effect of substrate was detected. Time presented an effect on BIC and BAFO (P < 0.001). Conclusion:Both titanium substrates were biocompatible and osseoconductive at the bone tissue level.

The cotton driver: an alternative technique for removing fractured screw fragments.

Screw fractures in implant-supported restorations may compromise the viability of both the implant and the prosthesis if not adequately addressed. Although a low incidence of screw loosening or fracture has been reported, the resolution of such problems is time consuming, sometimes requiring multiple appointments. The depth and the possibility of having the screw fragment wedged in a damaged area of the implant internal

Scan-layered reconstructions: A pilot study of a nondestructive dental histoanatomical analysis method and digital workflow to create restorations driven by natural dentin and enamel morphology

OBJECTIVE This work aims to present a pilot study of a non-destructive dental histo-anatomical analysis technique as well as to push the boundaries of the presently available restorative workflows for the fabrication of highly customized ceramic restorations. MATERIALS AND METHODS An extracted human maxillary central incisor was subject to a micro computed tomography scan and the acquired data was transferred into a workstation, reconstructed, segmented, evaluated and later imported into a Computer-Aided Design/Computer-Aided Manufacturing software for the fabrication of a ceramic resin-bonded prosthesis. RESULTS The obtained prosthesis presented an encouraging optical behavior and was used clinically as final restoration. CONCLUSION The digitally layered restorative replication of natural tooth morphology presents today as a clear possibility. New clinical and laboratory-fabricated, biologically inspired digital restorative protocols are to be expected in the near future. CLINICAL SIGNIFICANCE The digitally layered restorative replication of natural tooth morphology presents today as a clear possibility. This pilot study may represent a stimulus for future research and applications of digital imaging as well as digital restorative workflows in service of esthetic dentistry.

Guidelines for clinical management of laser-etched (Laser-Lok) abutments in two different clinical scenarios: A preclinical laboratory soft tissue assessment study

One-stage implants were placed in the mandibles of eight beagle dogs with laser-etched (LL) and machined abutments. After 4 weeks, half of the LL abutments were disconnected and reconnected after 10 minutes of saline storage, and the other half were replaced with a new LL abutment (impression simulation) with or without sulcus de-epithelialization. After abutment change, systems remained in vivo for 3 weeks. Results showed that LL abutments can be reconnected and that sulcus scoring prior to LL placement of one-stage implants receiving machined abutments may be beneficial.

Thickness evaluation of articulating papers and foils

Articulation and occlusion test materials are tools used in daily prosthodontic and restorative procedures that aid the clinicians in the evaluation of adjacent and opposing natural and/or artificial tooth contacts. A precision micrometer (Series 293, Mitutoyo, Japan) with a resolution of 0.001 mm was used to measure the thickness of five articulating papers and six articulation foils. Four of the articulating foils tested presented thicknesses inferior or equal to 21 μm, confirming their adequacy for the evaluation of natural dentitions. Clinicians and researchers should be aware that some labeled and actual papers/foils thicknesses are not in accordance. CLINICAL SIGNIFICANCE The thickness of articulating papers and foils reported by some manufacturers is not accurate. The information provided in this article may aid clinicians and researchers to better select the most appropriate materials for the evaluation of static and dynamic occlusion.

Quality assurance of ceramic dental restorations by photographic transillumination

Figure 1. Metal ceramic restoration, right side lighting. No detectable flaws. Quality assurance of indirect restorations should be performed by the dental laboratory before delivering the prosthetic parts to the clinician. Ultimately, it is the clinician’s responsibility to inspect and ensure, within the limits of clinically available technical and technological means, the quality of the prosthesis prior to insertion. Transillumination techniques in dentistry have been described as an aid in diagnosis as well as during the execution of various clinical procedures, including those for interproximal caries detection, endodontic visualization of dentinal defects, surgical localization of retained roots, location of the maxillary sinus floor and septa during sinus augmentation procedures, diagnosis of occult submucous cleft palate, and as a facilitator during arthroscopic puncture. In the specialty of prosthodontics, transillumination has been described thus far in the detection of microcracks in ceramic materials, based on the principle that subsurface cracks and flaws redirect light, resulting in darker shadows. Beck et al compared the sensitivity of transillumination with the fluorescent penetrant method (FPM). This technique consists of ceramic evaluation under fluorescent light after specimen immersion into a fluorescent liquid able to penetrate microscopic cracks. The technique can be used to detect microcracks in zirconia and feldspathic ceramic materials. The transillumination technique allowed a minimum crack length detection of 33 mm for feldspathic ceramic and 55 mm for zirconia ceramic. The FPM minimum crack detection was 17 mm for feldspathic and 18 mm for zirconia ceramics. Despite the increased sensitivity, the authors

The Effect of Laser-Etched Surface Design on Soft Tissue Healing of Two Different Implant Abutment Systems : An Experimental Study in Dogs

This study describes the early soft tissue morphology around two different implant systems that received either smooth or laser-etched abutments in a beagle dog model. Implants were placed in the healed mandibular molar region of eight beagle dogs and allowed to heal for 7 weeks. When the most apical aspect of the junctional epithelium (JE) was above or within the upper half of the laser-etched region, fibers were oriented perpendicular to the abutment surface. In contrast, JE positioned within the lower half of the laser-etched region or within or below the implant-abutment gap level presented fibers oriented parallel to the abutment surface.

The lamp die: an additional capacity of the alveolar model

The alveolar model, a technique that allows interchangeability of multiple removable dies on a common Type IV gypsum dentogingival cast, described by Michel Magne et al, 1 in 2008, allows an unchanged dentogingival relationship during the fabrication of restorations and has advantages over other definitive casts for making fixed restorations. Further advantages of this technique are the possibility of fabricating multiple restorations from differing restorative materials and techniques on the same cast. It also can be used with scanners in computer-aided design/computer-assisted manufacture systems because it accurately records the position, surface area, margins of the prepared teeth, margins of soft tissue, and adjacent teeth without the need for trimming, with its subsequent loss of information. 1 When used to fabricate restorations in the esthetic region, 2 the alveolar model may also allow for the assessment of the restoration’s translucency by using the technique described in this article. This additional capacity of the alveolar model may allow for the simultaneous assessment of multiple restorations and restorative materials with respect to their ability to transmit light and the improvement of the documentation of esthetic clinical treatments.