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The main objective of this narrative review was to provide an overview of DEFS (Diagnostic Esthetic Functional Splint), namely CAD/CAM manufactured, “snap-retained”, tooth-colored splints available by materials exhibiting a certain degree of elasticity (like polycarbonates or acetal resins) for restoring function, esthetics and occlusion in several clinical situations, before or as an intermediate alternative to undergoing the final treatment. The search strategy included all papers dealing with snap-retained prosthetic systems and was based on a literature review of papers available in electronic databases (Pubmed/Medline, Evidence-Based Dentistry, BMJ Evidence-Based Medicine, Dynamed, Embase, BMJ Clinical Evidence, Web of Science, Scientific reports); eligible papers were researched on Opengreyand a manual search was performed, as well. From the electronic databases emerged 13,199 records, many of which were duplicates. The grey literature and the manual research did not produce any eligible article. After duplicates removal, 7690 records were obtained. Titles, abstracts and keywords were analyzed. The studies concerning the topic of interest were examined by the reviewers and discussed. Although no evidence-based data were found in the literature, according to the authors’ clinical experience, the DEFS (Diagnostic Esthetic Functional Splint) is a very promising solution in multiple clinical situations, due to its diagnostic, therapeutical, functional and esthetic versatility.

Aim: to assess the fracture resistance of maxillary molars restored using lithium disilicate glass-ceramic (LDG) table-top restorations fabricated with two different production protocols. Methods: sixteen maxillary molars were randomly assigned to two groups (n = 8). The teeth received a preparation for a full-coverage table-top restoration with a 90° rounded shoulder margin. Restorations were fabricated using monolithic LDG blocks milled via Cerec 3 CAD/CAM System in group 1 (G1) and heat-pressed LDG in group 2 (G2). All table-tops were luted with Variolink II cement. The specimens were loaded to fracture after thermomechanical aging (1 250 000 cycles). A qualitative analysis on the type of fracture was conducted. Collected data were statistically analyzed with non-parametric test (Mann Whitney U-test). Results: the mean load to fracture was 2395.01 ± 150.96 N in G1 and 1796.58 ± 307.27 N in G2; the difference was statistically significant (p < 0.05). The majority of the specimens showed restorable fractures (6 specimens in G1 and 6 specimens in G2). Conclusion: the milled CAD/CAM LDG table-top restorations withstood higher load before fracturing than the restorations made with the heat-pressed LDG production protocol.

Objectives: the purpose of the present prospective trial was to evaluate the clinical performance of posterior 3-unit zirconia-based fixed dental prostheses (FDPs) after 14 years of clinical function. Methods: thirty-seven patients needing to replace either premolars or molars were involved and 48 FDPs were fabricated (Procera Zirconia, Nobel Biocare AB). Frameworks with a9 mm2 cross section of the connectors and 0.6 mm minimum thickness of the retainers were made by means of Procera Forte CAD-CAM System (Nobel Biocare AB). The patients were recalled after 6 and 12 months and then yearly up to a total follow-up of 14 years. Two independent survival curves for patients wearing 1 or 2 FDPs were calculated by means of Kaplan-Meier analysis and a log-rank test was performed in order to compare these curves. The United States Public Health Service criteria were used to examine technical and esthetic outcomes. The biological examination was performed evaluating plaque control, pocket depth, attachment level, bleeding on probing at both abutments and contralateral teeth and evaluated by means of the Wilcoxon test (p < 0.05) between the baseline and the 14-year follow-up. Results: descriptive statistics resulted in 91 % and 99 % cumulative survival rates for patients wearing 1 and 2 FDPs, respectively. There were no significant differences in periodontal parameters between control and test teeth. Both function and esthetic results were successful for FDPs over a 14-year follow-up period. Conclusions: the results of this prospective clinical study confirmed the effectiveness of zirconia as a clinical option to fabricate short-span posterior FDPs. Clinical significance: within the limitations of the present prospective clinical study, zirconia-based three-unit fixed dental prostheses perform satisfactorily on long term, in posterior areas and in patients with standard biomechanical conditions.

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Aim: To investigate in vitro the fracture resistance of two different post systems, a conventional one with post space preparation using a drill and an alternative one adapted to the canal shape. Methodology: After sample size calculation, the crowns of 26 single-rooted freshly-extracted teeth were removed with a disc 1 mm coronal to the cemento-enamel junction. The canals were shaped with Mtwo rotary files up to size 40, 0.06 tpaer and filled with the continuous wave of condensation technique leaving the coronal 9 mm of the canal unfilled. After the post space preparation by a dedicated drill, double-tapered fibre posts (DT Light-Post) were cemented in half of the roots (G1, n = 13). 0.06 tapered fibre posts (Tech S Endoshape) were trimmed to fit the canal of the remaining roots (G2, n = 13) and then cemented without post space preparation. A self- adhesive cement (RelyX Unicem) was used in both groups. The posts were cut 5 mm from the root coronal surface. The specimens were embedded in acrylic resin and the top of the post was loaded under continuous compressive force (45°, 0.75 mm/min) to measure the maximum breaking load (N). Data were statistically analyzed by using a Student’s t-test (α = 0.05). Results: The mean maximum breaking loads ±SD were G1 = 164.07 ±21.54 and G2 = 151.22 ±14.69. The difference was not statistically significant (P = 0.093). Only post fractures were detected, with all the roots remaining intact. Conclusions: Within the limitation of the study, conservative posts without post space preparation performed similarly to conventional ones. In order to avoid procedural errors during the post space preparation and to spare tooth structure a conservative approach seems advisable.

Objectives: The present in vitro study aimed at evaluating the influence of a novel nanocomposite material on implant primary stability by means of periimplants scaffolds. Methods: Thirty-two titanium implants (Winsix, Biosafin) with an innovative design were modified with three-dimensional bioactive scaffolds made up of a new hybrid ceramo-polymeric material. The biomimetic nanocomposite material was designed to promote the precipitation of hydroxyapatite nanoinclusions in periimplant bone. The scaffolds were fabricated as a foamed hydrogel covering the coronal area of the implants; the material was characterized by swelling in contact with biological fluids, with a polymerization kinetic of 0.1 mm/hour. The modified implants were inserted in freshly explanted tibiae of minipigs; 16 standard implants were used as control. Then, the tibiae were kept hydrated in physiological solution and the implants removed after 1, 6, 12 and 24 hours. An electronic device was used to measure the removal torque and the data were statistically analyzed. Results: Insertion torque values ranging between 37 and 56 Ncm were recorded. Mean removal torque values of 61, 67, 79 and 86 were evidenced after 1, 6, 12 and 24 hours respectively. The ANOVA showed statistically significant differences between removal torque values (p

Objectives: The present in vivo animal study aimed at evaluating the osseointegration of biomimetic bone scaffolds made up of an innovative nanocomposite material. Methods: A novel nanocomposite hybrid ceramo-polymeric material was designed and produced to interact with bone tissue at nanoscale interfaces. The chemical, physical and mechanical properties of the material were analyzed and characterized. The highly bioactive material was designed to fabricate three-dimensional bone scaffolds in order to promote osseointegration through the precipitation of hydroxyapatite nanoinclusions in periimplant bone. The biomimetic nanocomposite was fabricated as a foamed hydrogel swelling in contact with biological fluids. The biofidelity of the scaffolded implant system was simulated in a digital environment and the stress and strain distributions assessed using three-dimensional Finite Element Analysis. The biomimetic properties of the nanocomposite material were validated in vivo in an animal model, using three-dimensional scaffolds around dental implants inserted in tibiae of minipigs. After explantation, such tibiae were subjected to micro-computed tomography scannings to evaluate bone-to-implant and bone-to- scaffold contact. Results: The chemical, physical and mechanical laboratory tests showed high biomimetic properties for the innovative hybrid material. Stress and strain distributions within the physiological range of trabecular adaptive organization (2000-3000 με) were noticed in periimplant bone with the Finite Element Analysis. The micro-CT scannings showed comparable percentages of bone contact at level of both the scaffolds and the titanium of the implants. Conclusions: The innovative hybrid ceramo-polymeric nanomaterial proved to promote accelerated osseointegration in post-surgical early healing phases.

PURPOSE: To assess under load the biomechanical behavior of the cementing system of feldspathic vs alumina porcelain veneers.MATERIALS AND METHODS: A 3D model of a maxillary central incisor, the periodontal ligament (PDL) and the alveolar bone was generated. Incisors restored with alumina and feldspathic porcelain veneers were compared to a natural sound tooth. Enamel, cementum, cancellous and cortical bone were considered isotropic elastic materials; conversely, dentin was designated as orthotropic. The nonlinear visco-elatic behavior of the PDL was considered. The adhesive layers were modelled using spring elements. A 50-N load at a 60-degree angle to the tooth's longitudinal axis was applied and validated. Stress concentration in the interfacial volumes of the main models was identified and submodelled in a new environment.RESULTS: Regarding tooth structure, strain concentrations were observed in the root dentin below the CEJ. As to the cement layer, tensile stresses concentrated in the palatal margin of the adhesive complex.CONCLUSION: Despite the effects on tooth deformation, the rigidity of the veneer did not affect the stress distributions in the cement layer or in the adhesive layers. In both cases, the palatal and cervical margins seemed to be the most stressed areas.

Objectives: Stresses produced during the fabrication of copings and by chewing activity can induce a tetragonal-to-monoclinic (t&ndash, m) transformation of zirconia. As a consequence, in the m-phase, the material is not able to hinder possible cracks by the favorable mechanism known as &ldquo, transformation toughening&rdquo, This study aimed at evaluating if different marginal preparations of zirconia copings can cause a premature phase transformation immediately after manufacturing milling and after chewing simulation. Methods: Ninety copings using three commercial zirconia ceramics (Nobel Procera Zirconia, Nobel Biocare Management AG, Lava Classic, 3M ESPE, Lava Plus, 3M ESPE) were prepared with deep-chamfer, slight-chamfer, or feather-edge finish lines (n = 10). Specimens were tested in a chewing simulator (CS-4.4, SD Mechatronik) under cyclic occlusal loads simulating one year of clinical service. Raman spectra were acquired and analyzed for each specimen along the finish lines and at the top of each coping before and after chewing simulation, respectively. Results: Raman analysis did not show any t&ndash, m transformation both before and after chewing simulation, as the typical monoclinic bands at 181 cm&minus, 1 and 192 cm&minus, 1 were not detected in any of the tested specimens. Conclusions: After a one-year simulation of chewing activity, irrespective of preparation geometry, zirconia copings did not show any sign of t&ndash, m transformation, either in the load application areas or at the margins. Consequently, manufacturing milling even in thin thickness did not cause any structural modification of zirconia ceramics &ldquo, as received by manufacturers&rdquo, both before and after chewing simulation.

Background: To assess the quantity of dentin exposure detected by 3 operators with different clinical expertise for 2 designs of tooth preparation for laminate veneers: window (WI) and butt joint (BJ). Methods: 20 intact maxillary central incisors were collected and then prepared for laminate veneers to a depth of 0.6 mm, with a cervical mini-chamfer finish line of 0.3 mm. Each prepared tooth was analyzed by 3 operators with different expertise: undergraduate student (ST), general practitioner (GP), and prosthodontist (PR), at sight under magnification. Besides descriptive statistics (CI 95%), 2-way ANOVA and Games–Howell tests were used to analyze differences among groups (α = 0.05). Results: The means of percentage and area of detected dentin exposure were WI = 30.48%, 21.57 mm2; BJ = 30.99%, 21.97 mm2; ST/WI = 22.82%, 16.44 mm2; GP/WI = 58.05%, 40.64 mm2; PR/WI = 10.55%, 7.63 mm2; ST/BJ = 28.99%, 20.83 mm2; GP/BJ = 40.56%, 28.32 mm2; PR/BJ = 23.42%, 16.75 mm2. Significant differences were found between ST/WI vs. GP/WI (p = 0.005) and GP/WI vs. PR/WI (p < 0.001). Conclusions: There was no difference in detection of exposed dentin among operators with different expertise for BJ preparation, whereas differences were found between the general practitioner and the other 2 operators in WI. Moreover, the quantity of exposed dentin was not related to different tooth preparation designs.

Background Amelogenesis Imperfecta (AI) is a syndromic entity comprising several clinical conditions, mostly genetic- based, affecting quality and quantity of enamel. The use of digital tools can be advantageous to enhance communication between the dental team and patients. Moreover, a full digital approach would allow to check each single clinical step according to the treatment plan with a backward approach. The aim of this case report is to describe a multidisciplinary treatment program of a young patient with severe open bite and amelogenesis imperfecta, whose restorative rehabilitation was planned in a full-digital workflow, from the initial communication phase up to the final prosthodontic rehabilitation. Case report An 8-year old female patient was diagnosed with a Class II division 1 malocclusion, severe open bite and AI. The treatment plan included 3 phases: the elimination of the tongue interposition habit and the anterior open bite, the orthodontic correction of dental deviation and leveling of both dental arches and a prosthetic rehabilitation. The extraction of the four first molars corrected the canine and molar Angle Class II relationships, deviation of the midline and repositioning of the maxillary incisors on the sagittal plane. Feldspathic ceramics was used in anterior sites to enhance the esthetic outcome. CAD/CAM hybrid ceramo-polymeric restorative material (PICN) was chosen for posterior regions. Conclusion The outcomes of the present case report proved that the planned objectives were satisfactorily obtained thanks to proper treatment planning, full digital workflow and the patient’s optimal compliance with the extraoral device.

Objectives This paper aimed to provide a literature review of the mechanical and biological properties of zirconia-reinforced lithium silicate glass-ceramics (ZLS) in Computer-aided design / Computer-aided manufacturing (CAD/CAM) systems. Data/Sources An extensive search of the literature for papers related to ZLS was made on the databases of PubMed/Medline, Scopus, Embase, Google Scholar, Dynamed, and Open Grey. The papers were selected by 3 independent calibrated reviewers. Study selection The search strategy produced 937 records. After the removal of duplicates and the exclusion of papers that did not meet the inclusion criteria, 71 papers were included. Conclusions After reviewing the included records, it was found that two types of ZLS (Vita Suprinity PC; Vita Zahnfabrik and Celtra Duo; Dentsply Sirona) are nowadays available on the market for CAD/CAM systems, similar in their chemical composition, microstructure, and biological-mechanical properties. ZLS is reported to be a biocompatible material, whose fracture resistance can withstand physiological chewing loads. The firing process influences the improvements of strength and fatigue failure load, with a volumetric shrinkage. To date, ZLS can be considered a viable alternative to other glass-ceramics for fixed single restorations. Clinical Significance . As to biocompatibility and mechanical properties of ZLS, data are still scarce, often controversial and limited to short-term observational periods. These promising ceramics require further in vitro/in vivo studies to accurately define mechanical and biological properties, mainly in the long-term performance of restorations produced with such materials.

Aim: The use of all-ceramic conservative occlusal veneers is becoming more popular in the clinical setting thanks to the recent improvement of the mechanical and esthetical properties of the restorative materials. Furthermore, the option of CAD/CAM fabrication may constitute a further advantage for both clinicians and patients. Since little is known about the influence of the occlusal veneer preparation design on the marginal fit of the final restoration, the present study compared the marginal fit of two preparation designs. Methods: Sixteen maxillary molars were selected from a pool of freshly extracted teeth and received 1-mm cusp reduction by using silicon indexes as reference. The teeth were randomly divided into two groups identified by the preparation design: conservative full-coverage occlusal veneer with a 90° rounded shoulder margin (n=8) and marginal chamfer (n=8). At the end of the preparation process, the exposed dentine surfaces were immediately sealed with a self etch adhesive system. Lithium disilicate restorations (IPS e.max CAD) were produced with the Cerec 3 CAD/CAM system. The intaglio surface of the occlusal veneers was conditioned with hydrofluoric acid and silane, while the tooth surface underwent silicatization, enamel etching, and adhesive system application. The occlusal veneers were luted with Variolink II cement. The specimens were embedded into acrylic resin simulating the periodontal ligament with a layer of vinyl polysiloxane; then, they were chewing machine (1,250,000 cycles, 1 Hz, 5-55°C). A quantitative marginal fit evaluation was performed observing at the scanning electron microscope resin replicas of the specimens obtained before and after the thermomechanical aging simulation. For each replica, a single trained blinded operator measured the marginal gap along 120 equidistant points of the adhesive interface. Collected data were tested for the assumptions for using parametric tests. The marginal fit measured at different experimental time points was compared within the same group with a paired sample t-test, while the two groups were compared at the same time point with an independent-sample t-test (p

Objectives The objective of this randomized controlled trial was to assess the influence of use of posts as well as the type of posterior tooth (premolars vs molars) for the treatment with lithium disilicate (LS2) partial crowns. Materials and methods A total of 60 patients were treated with posterior LS2 partial crowns. Two groups (n = 60) were made based on the type of restored tooth: Group 1, premolars and Group 2, molars. The samples of each group were divided into 2 subgroups (n = 30): Subgroup A restored with fiber posts and Subgroup B without them. Clinical and intraoral radiographic examinations were assessed during each recall (6 months and, 1, 2, and 3 years). Kaplan-Meier log-rank test and Cox regression analysis (Pp Results Three subgroups showed 100% of survival while group 2 A exhibited the lowest performance (93.3%). The Cox regression analysis showed that the presence of the post was not a significant factor for survival time (Hazard Ratio HR = 0388; CI95% Confidence Interval for H R = 0,1- to 1,5; pp = 017). Tooth type had an influence on survival time that was at the limit of statistical significance (Hazard Ratio HR = 0123; CI95% Confidence Interval for HR = 0 0015- to 0997; p = 005). Particularly, failure risk was greater for premolars. ‘Post by tooth type’ interactions were not statistically significant (p = 0126). Conclusions over a 3-year observation period, the clinical performance of endodontically treated teeth restored with lithium disilicate partial crowns was not significantly affected by the use of a fiber post and by the type of tooth (premolars or molars).

cited By 3; International audience; Objectives: The dental market moves towards high-translucency monolithic zirconia dental crowns, which are usually placed either with – or without – a thin glaze layer. The microstructural features and the mechanical performances of these materials are still controversial, as well as their susceptibility to aging. This paper aims at studying these aspects in the current generation of zirconia dental crowns showing different degrees of translucency. Methods: Four different commercial zirconia materials were investigated, including one standard ‘full-strength’ 3Y-TZP and three grades with improved translucency. The microstructural features (phase composition and assemblage, grain size) were carefully studied, as well as mechanical properties (biaxial bending strength and indentation toughness), translucency and aging behavior (in autoclave at 134 °C). Aging was conducted on crowns with and without glaze to better represent clinical uses. Results: Important differences are found in terms of microstructures among the materials in terms of cubic phase content and yttria in the tetragonal phase, leading to different optical, mechanical and aging resistance properties. We show that higher cubic phase content leads to better translucency and stability in water steam, but at the expense of strength and toughness. A compromise is always inevitable between translucency and aging resistance on one side and mechanical properties on the other side. Significance: - Even so called ‘high translucent’ zirconia ceramics tested in this work should be considered as medium translucency materials.- Aging occurs in standard state-of-the-art dental zirconia and glazing does not fully avoid this issue. However, aging did not compromise strength even after prolonged duration.- Aging is null in the ‘highly translucent’ zirconia grades but at the expense of strength, which is then comparable to glass-ceramics. © 2018 The Academy of Dental Materials

SUMMARY The present in vitro study aimed to assess the effects of root surface mechanical instrumentation on the marginal integrity and adaptation of resin composite crowns. The following null hypotheses were tested: no differences exist between finish line and 1) marginal gap or 2) marginal microleakage before and after manual mechanical periodontal maintenance. A total of 56 intact human mandibular molars were randomly distributed into four groups and subjected to standardized tooth preparations for indirect composite crowns with different marginal finish lines (90° shoulder, beveled 90° shoulder, feather edge, chamfer). One-half of the specimens was used as a control and remained untreated, and the remaining half was subjected to root surface procedures simulating five years of semestral mechanical supportive periodontal treatment. The marginal gap and microleakage were evaluated and statistically analyzed. The specimens used as controls showed lower mean marginal gaps than those subjected to the simulated periodontal treatment, whereas the latter showed lower microleakage than the control crowns. Statistically significant differences were recorded for both the experimental variables. The root surface procedures resulted in altered surfaces of the composite crowns. The marginal gap increased after the treatment, whereas the marginal microleakage was reduced. The 90° shoulder and the chamfer preparation could be considered a viable option to fabricate composite crowns, but the beveled 90° shoulder and the feather edge should not be recommended.

PURPOSE: The purpose of this study was to evaluate the effectiveness of the platform-switching technique to prevent crestal bone loss following the restoration of dental implants. MATERIALS AND METHODS: This randomized prospective multicenter trial analyzed 60 partially edentulous adults recruited at 12 professional dental centers. Subjects were randomly selected to receive either platform-enlarged or control cylindric implants in three different surgical procedures: conventional nonsubmerged, submerged, and submerged with a reduced abutment. The primary outcome measure was the change in crestal bone level assessed radiographically 12 and 24 months following placement. Nonparametric analysis of variance for repeated measures (the Friedman test) was used to assess the overall significance over time of the differences among implants in changes in crestal bone levels. Comparisons among and between groups of implants were performed by the nonparametric Friedman and Wilcoxon tests, respectively. In all the analyses an alpha = .05 was considered significant. RESULTS: A total of 360 implants were placed (60 for each group). Three control implants failed during the 2nd year following placement. All submerged and 92% of nonsubmerged platform-enlarged implants exhibited no bone loss. Control implants with an abutment as large as the implant platform exhibited more bone loss than their platform-enlarged counterparts (P < .001) or control implants with a reduced abutment (P < .001). Submerged implants with an enlarged platform showed better crestal bone preservation than submerged control implants with a reduced abutment (P = .06). CONCLUSIONS: The findings of the current trial indicated that the use of implants with an enlarged platform can result in better preservation of crestal bone as compared with conventional cylindric implants when a reduced abutment is mounted.

Objectives: This 3D-FEA aimed at evaluating the biomechanical response of bone and implant-supported prostheses in the presence of axial and tilted implants. Methods: Four numerical models of human mandible with different implant-supported prostheses configurations were set up. The cortical bone was considered orthotropic according to an indipendent mechanical characterization performed on fresh human dentate mandibles. Jaw-closing muscular forces were simulated. The spongy bone was considered isotropic while the temporo-mandibular disc was considered hyperelastic. Contact pairs elements were generated at the fixture-bone interfaces. Failure criteria were based on ultimate normal and shear stresses computed in in vivo. The strain fields in the periimplant bone were compared to Frost's biomechanical relation. The bone remodelling stimuli were computed as the strain energy density variations. Results: EPTO1=FIRST PRINCIPAL STRAIN EPTO3=THIRD PRINCIPAL STRAIN STRAIGHT IMPLANTS. PERI-IMPLANT STRAIN FIELDS. POSTERIOR IMPLANTS, EPTO1 2000 TO 8000, EPTO3 -1500 TO -8000. ANTERIOR IMPLANT, EPTO1 667 TO 4667, EPTO3 -667 TO -3340. STRAIN STATE ON EXTERIOR CORTEX BETWEEN IMPLANTS, EPTO1 100 TO 1000, EPTO 3 -100 TO -1000. STRAIN STATE IN SPONGY BONE BETWEEN IMPLANTS, EPTO1 100 TO 500, EPTO3 -100 TO -500. TILTED IMPLANTS. PERI-IMPLANT STRAIN FIELDS. POSTERIOR IMPLANTS, EPTO1 333 TO 4330, EPTO3 -667 TO -3333. ANTERIOR IMPLANT, COMPARABLE TO STRAIGHT CONFIGURATION. STRAIN STATE ON EXTERIOR CORTEX BETWEEN IMPLANTS, COMPARALE TO STREISHT CONFIGURATION. STRAIN STATE IN SPONGY BONE BETWEEN IMPLANTS, COMPARABLE TO STRAIGHT CONFIGURATION. Conclusions: Bone strain fields were scarcely influenced by implant orientation but significantly influenced by the rigidity of the restorative material.

Objectives: This clinical report describes a single-tooth implant restoration in a fresh extraction socket in the anterior maxilla, with immediate provisionalization and CAD-CAM zirconia final prosthesis. Methods and Materials: Due to a traumatic injury, an esthetically concerned 40 year-old female patient was treated with an atraumatic extraction of a maxillary central incisor, which was immediately substituted with a single implant. Immediate provisionalization was performed using a screw-retained resin crown. Two months after surgery, the patient was fitted with a final all-ceramic single crown cemented on a CAD-CAM customized zirconia abutment. Results: Healing was predictable, with the implant neither showing mobility nor presenting pain. The zirconia crown was undamaged. The patient was pleased with treatment time and esthetic result. Discussion: Implant treatment with immediate provisionalization offers several advantages: optimal esthetics is achievable as bone and soft tissue architecture is maintained; patients are provided with a fixed temporary restoration at the time of surgery; treatment time is shortened, as second stage surgery is eliminated. Furthermore, the fresh extraction socket is a metabolically active region with good potential for bone repair and successful implant placement. Conclusions: Optimal mechanical performances and excellent esthetics were achieved in the anterior sites by means of a CAD-CAM zirconia customized abutment and crown.

Objectives The present comparative analysis aimed at evaluating which combination of restorative materials resulted in the most homogeneous stress and strain distributions. Methods A three-dimensional finite element analysis was performed. All the nodes on the external surface of the root were constrained in all directions. Eighteen experimental models with different material properties and configurations were simulated. An arbitrary load of 10 N was applied at 60° angle with tooth longitudinal axis on the palatal surface of the crown. Von Mises (equivalent stresses) energetic criterion was chosen. Results In all the models the values of both strain and stress recorded at the middle third of the buccal aspect of the root surface were at their maxima. On the contrary, the minimum values were noticed at level of both the apical portion of the post and the root apex. The maximum stresses were evidenced at level of the cemento–enamel junction (CEJ) on both the buccal and palatal aspects of root cement and dentin. Stress progressively decreased from the outer to the inner part of the root and from the CEJ towards the incisal margin of the crown as well. Significance The results of the present study would allow clinicians to make an informed choice from among available materials to restore endodontically treated teeth.

STATEMENT OF PROBLEM: There is little agreement regarding a palatal extension of the preparation for porcelain veneers, as it represents a more invasive technique than a preparation limited to the facial surface of a tooth. PURPOSE: The purpose of this study was to detect the stress in maxillary anterior teeth restored with porcelain veneers and compare the resistance to fracture of porcelain veneers prepared using different preparation designs. MATERIAL AND METHODS: Forty-five maxillary anterior teeth were restored with porcelain veneers and divided into 9 groups as follows: Ca, canines with no preparation; Ca-Ch, canines with palatal chamfer preparation; Ca-W, canines with window preparation; LI, lateral incisors with no preparation; LI-Ch, lateral incisors with palatal chamfer preparation; LI-W, lateral incisors with window preparation; CI, central incisors with no preparation; CI-Ch, central incisors with palatal chamfer preparation; CI-W, central incisors with window preparation. Shear-flexural fracture tests were performed. The fractured specimens were subjected to scanning electron microscope (SEM) analysis. Data were statistically analyzed with univariate analysis of variance and the Tukey post hoc test for multiple comparisons (alpha=.05). RESULTS: The following mean fracture load values (N) were recorded: Ca, 395 +/- 6; Ca-Ch, 310 +/- 8; Ca-W, 322 +/- 8; LI, 309 +/- 8; LI-Ch, 242 +/- 6; LI-W, 225 +/- 8; CI, 298 +/- 8; CI-Ch, 255 +/- 8; CI-W, 221 +/- 6. The SEM analysis showed that both adhesive and cohesive fractures were primarily concentrated at the cervical region. Statistical analysis showed that both the type of tooth and the design of the preparation significantly influenced the resistance to fracture of the restored teeth (P