Biomechanical variables affect peri-implant bone loss in implant-supported fixed complete dentures: A methodological and prospective study.

PURPOSE: Implant-supported fixed complete dentures (IFCD) experience failures and complications related to biological and technical risk factors. This study investigated the effect of biomechanical variables of IFCD on 1-year peri-implant bone loss at the buccal, palatal/lingual, mesial, and distal implant sides. A new method was used to measure the geometric biomechanical variables of IFCD using cone beam computed tomography (CBCT). METHODS: The study sample consisted of 246 external hexagon implants supporting 48 hybrid IFCD in 44 patients. CBCT images obtained immediately (T0) and 1 year (T1) after prosthesis installation were used to measure the support polygon area, clinical crown/implant (C/I) ratio (vertical lever), anteroposterior power and resistance arms, anterior and posterior cantilevers (horizontal levers), and peri-implant bone remodeling (T1-T0). Data were analyzed using multilevel multivariable models. RESULTS: The average total bone loss in the mandible and maxilla were 0.88 mm, with a loss of 0.62 mm in the mandible and 1.08 mm in the maxilla. The C/I ratio had a significant effect on bone loss on the mesial, distal, and palatal/lingual sides (P <.05). The anterior cantilever had a protective effect on the lingual side of the anterior implant. No effect on bone loss was found for the support polygon area, posterior cantilever, resistance arm, or power arm (P >.05). CONCLUSIONS: The results suggest that the C/I ratio and anterior cantilever in IFCD affect peri-implant bone loss according to the implant side and position in the arch.

Aplicações da dentina autógena na regeneração óssea: revisão integrativa de literatura / Applications of dentine in bone regeneration: integrative literature review

A dentina e o osso alveolar apresentam muita semelhança em sua composição. Sendo assim, podemos considerar a utilização da dentina como recurso alternativo nas intervenções que buscam a regeneração tecidual óssea. Objetivo: o presente estudo realizou uma revisão integrativa da literatura sobre o uso da dentina como biomaterial para regeneração óssea. Metodologia: foi realizada uma busca por artigos, nas bases de dados Medline, via PubMed; Scielo, LILACS, BASE, Scopus e Science Direct, queavaliassem ou descrevessem o uso da dentina como biomaterial para regeneração óssea. Foram utilizados os seguintes descritores: "Dentin" AND "Bone Regeneration", sem delimitação de tempo. Os critérios de inclusão foram: estudos clínicos publicados em periódicos, oriundos de dados primários, sobre o uso de dentina como biomaterial. Os critérios de exclusão foram: revisões de literatura, estudos in vitro e em animais, estudos que não fosse possível o acesso na íntegra e estudos que associassem o uso da dentina com outros biomateriais sem que fosse possível relacionar os resultados apenas pelo uso da dentina. Resultados: vinte e três estudos foram selecionados para a presente revisão. As pesquisas demonstraram que há uma heterogenicidade relacionada ao tamanho da partícula de dentina obtida, que pode ser decorrente de diferentes métodos de processamento. Conclusão: a reutilização da dentina como biomaterial pode ser uma alternativa promissora ao enxerto autógeno. Sugere-se, então, que protocolos de processamento da partícula de dentina sejam melhor estabelecidos e estudos longitudinais precisam ser realizados para a garantia de procedimentos seguros, eficazes e práticos.

The dentin and the alveolar bone are very similar in composition, therefore, it's usage as an alternative resource in interventions that seek tissue regeneration can be considered. Objective: the aim of the present study was to carry out an integrative review of the literature on the use of dentin as a biomaterial for bone regeneration. Methodology: a search for articles was carried out in the Medline databases, via PubMed; Scielo, LILACS, BASE, Scopus and Science Direct, which evaluated or described the use of dentin as a biomaterial for bone regeneration. The following descriptors were used: "Dentin" AND "Bone Regeneration", without time limits. The inclusion criteria were: clinical studies published in journals, derived from primary data, on the use of dentin as a biomaterial. Exclusion criteria were: literature reviews, in vitro and in animal studies, studies that were not possible to be accessed in full and studies that associated the usage of dentin with other biomaterials and that it was not possible to relate the results just by using the dentin. Results: twenty-three studies were selected for the present review. Researches have shown that there is heterogeneity related to the size of the obtained dentin particle, which may be due to different processing methods. Conclusion: the reuse of dentin as a biomaterial can be a promising alternative to autogenous graft. It is suggested, then, that dentin particle processing protocols should are better established and longitudinal studies need to be carried out to the in order to ensure safe, effective and practical procedures.

Cytotoxicity assessment of Bio-C Repair Íon+: A new calcium silicate-based cement.

Background. Direct pulp capping is a method designed to preserve the exposed dental pulp. Due to good biological, physical, and mechanical properties, new versions of calcium silicate-based materials have been developed as pulp capping materials. The present study aimed to evaluate the cytotoxic effects of four calcium silicate-based pulp capping materials, of which the Bio-C Repair Íon+ is still in an experimental phase. Methods. Biodentine, MTA Repair HP, Bio-C Repair, and Bio-C Repair Íon+ cements were dispensed in a metallic matrix to produce 125-mm3 specimens, which were immersed in Dulbecco's Modified Eagle Medium (DMEM) to obtain extracts. NIH 3T3 cells were cultured and exposed to the extracts for 24 hours and seven days. Cell viability was assessed by the methyl tetrazolium test (MTT). The mean values for the experimental and control groups (without treatment) were compared by analysis of variance (ANOVA) and post hoc Tukey tests, considering a significance level of 5%. Results. All the tested materials demonstrated a reduction in cell viability (P < 0.05). According to ISO 10993-5: 2009 (E), Bio-C Repair Íon+ exhibited mild and moderate cytotoxicity in the 24- hour and 7-day analyses, respectively. Bio-C Repair and Biodentine showed mild cytotoxicity, and MTA Repair HP exhibited moderate cytotoxicity at both intervals. Conclusion. The highest cell viability was demonstrated by Biodentine, MTA, and Repair HP, in descending order. Bio-C Repair and Bio-C Repair Íon+ showed moderate cytotoxicity, similar to MTA Repair HP in the 7-day analysis.

Implant Inclination and Cantilever Length Are Not Associated with Bone Loss in Fixed Complete Dentures: A Prospective Study.

PURPOSE: To investigate whether the inclination of the most distal implant and the cantilever length influence marginal bone loss in implant-supported fixed complete dentures (ISFCDs). MATERIALS AND METHODS: A novel method using computed tomography images was developed to measure the mesiodistal implant inclination. The cantilever length was measured during ISFCD fabrication. Radiographs were obtained after ISFCD installation at 1 and 3 years after loading. RESULTS: A total of 30 subjects with 62 implants were included. Accumulated marginal bone loss was 0.35 ± 0.49 mm. No significant association was found between marginal bone loss and cantilever length or implant inclination. CONCLUSION: Implant inclination and cantilever length do not seem to affect marginal bone loss.

Risk factor model of mechanical complications in implant-supported fixed complete dentures: A prospective cohort study.

OBJECTIVES: This prospective cohort study estimated the effect of technical and clinical factors on mechanical complications in implant-supported fixed complete dentures (IFCDs). The patient's perception of the impact of oral rehabilitation on quality of life was assessed. MATERIAL AND METHODS: A non-probabilistic sample consisted of 88 consecutive patients treated with 94 screw-retained, metal-acrylic IFCDs. Data collection included sociodemographic variables, presence and intensity of bruxism, maximal occlusal force, opposing arch, design of the metallic framework, distribution of occlusal contacts, and quality of life (OHIP-14). IFCD-level data were analyzed using Kaplan-Meier survival analysis and Cox regression model. Quality of life data were analyzed by paired Student t test. RESULTS: During a mean follow-up of 35.1 ± 18.3 months, 16/94 IFCDs (17%) had repairable mechanical complications because of loosening/fracture of artificial teeth (n = 15) and screw loosening (n = 1). Framework design (retention pins <4 mm) was a significant risk factor for complications (HR = 11.038; p = 0.027) when adjusted for sex. Mechanical complications were not associated with sex, body mass index, thickness of the acrylic resin veneering, type of opposing arch, distribution of occlusal contacts and force, protrusion interference, presence/intensity of bruxism or maximal occlusal force. OHIP-14 total scores decreased after IFCD treatment for both patients with or without complications. CONCLUSIONS: Within the limitations of this study, the results suggest that clinical success is associated to framework design with retention pins equal or longer than 4 mm. Quality of life improved with IFCD treatment, even in patients with mechanical complications.

Analysis of the Marginal Fit and Dimensional Stability of Cast-to Cobalt-Chromium Implant Cylinders Cast from Different Alloys.

PURPOSE: To evaluate the influence of cobalt-chromium (Co-Cr) casting alloys' melting temperatures on the cast-to Co-Cr implant cylinders' marginal fit. MATERIALS AND METHODS: Co-Cr alloys with different melting ranges were cast into 20 Co-Cr cylinders: 10 in a high-melting temperature (HMT) group and 10 in a low-melting temperature (LMT) group. Ten cylinders were used as received as a control group. Cylinders' marginal misfit and dimensional stability were evaluated using scanning electron microscopy (×500). RESULTS AND CONCLUSION: HMT cylinders showed significant differences in marginal misfit (2.48 ± 1.07 µm2) compared to LMT (1.53 ± 0.37 µm2) and control (1.27 ± 0.57 µm2) cylinders, but there were no differences in dimensional stability. HMT Co-Cr alloys produce implant-supported prostheses with poor marginal fit.

Effect of layered manufacturing techniques, alloy powders, and layer thickness on metal-ceramic bond strength.

STATEMENT OF PROBLEM: Direct metal laser sintering (DMLS) and direct metal laser melting (DMLM) have become popular for fabricating the metal frameworks of metal-ceramic restorations. How the type of layered manufacturing device, layer thickness, and alloy powder may affect the bond strength of ceramic to metal substructure is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the bond strength of dental porcelain to metal frameworks fabricated using different layered manufacturing techniques (DMLS and DMLM), Co-Cr alloy powders, and layer thicknesses and to evaluate whether a correlation exists between the bond strength and the number of ceramic remnants on the metal surface. MATERIAL AND METHODS: A total of 75 bar-shaped metal specimens (n=15) were fabricated using either DMLS or DMLM. The powder alloys used were Keramit NP-S and EOS-Cobalt-Chrome SP-2 with layer thicknesses of 20 µm and 30 µm. After ceramic application, the metal-ceramic bond strength was evaluated with a 3-point-bend test. Three-way ANOVA followed by the Tukey honest significance difference test were used for statistical analysis (α=.05). De-bonding surface microstructure was observed with scanning electron microscopy. Energy dispersive spectroscopy analysis was conducted to evaluate the correlation between ceramic remnants on the metal surface and bond strength values. RESULTS: The mean bond strength value of DMLS was significantly higher than that of DMLM. While no statistically significant difference was found between layer thicknesses, alloy powders closely affected bond strength. Statistical comparisons revealed that the highest bond strength could be achieved with DMLS-Cobalt-Chrome SP2-20µm, and the lowest bond strength was observed in DMLS-Keramit NP-S-20µm (P≤.05). No correlation was found between porcelain remnants on the metal surface and bond strength values. CONCLUSIONS: The layered manufacturing device and the alloy powders evaluated in the current study closely affected the bond strength of dental porcelain to a metal framework. However, layer thickness did not affect the bond strength.

Multifunctional Guide for Implant Placement, Impressions, and an Occlusal Index for Fixed Complete Dentures.

This article proposes an approach to simplify the steps and reduce fabrication time for fixed implant-supported complete dentures. A multifunctional guide can function as a surgical template during implant placement and provides a framework for the definitive impression and occlusal registration. It therefore enables immediate or early loading of dental implants in full-arch rehabilitations.

Influence of ozone and paracetic acid disinfection on adhesion of resilient liners to acrylic resin.

PURPOSE: The aim of this study was to evaluate the effect of paracetic acid (PAA) and ozone disinfection on the tensile bond strength (TBS) of silicone-based resilient liners to acrylic resins. MATERIALS AND METHODS: One hundred and twenty dumbbell shaped heat-polymerized acrylic resins were prepared. From the mid segment of the specimens, 3 mm of acrylic were grinded off and separated parts were reattached by resilient liners. The specimens were divided into 2 control (control1, control7) and 4 test groups of PAA and ozone disinfection (PAA1, PAA7, ozone1 and ozone7; n=10). While control groups were immersed in distilled water for 10 min (control1) and 7 days (control7), test groups were subjected to PAA (16 g/L) or ozone rich water (4 mg/L) for 1 cycle (10 min for PAA and 60 min for ozone) per day for 7 days prior to tensile tests. Measurements of the TBS were analyzed using 3-way ANOVA and Tukey's HSD test. RESULTS: Adhesive strength of Mollosil decreased significantly by application of ozone disinfection. PAA disinfection had no negative effect on the TBS values of Mollosil and Molloplast B to acrylic resin. Single application of ozone disinfection did not have any negative effect on TBS values of Molloplast B, but prolonged exposure to ozone decreased its adhesive strength. CONCLUSION: The adhesion of resilient liners to acrylic was not adversely affected by PAA disinfection. Immersion in ozonated water significantly decreased TBS of Mollosil. Prolonged exposure to ozone negatively affects adhesion of Molloplast B to denture base materials.

Effects of postpolymerization microwave irradiation on provisional dental acrylics: physical and mechanical properties.

BACKGROUND: This study aimed to evaluate the effects of microwave irradiation on the physical and mechanical properties of poly(methyl methacrylate) (PMMA) provisional resins. METHODS: Twenty bars and 20 disc-shaped specimens were fabricated for each selected provisional restorative material (Dencor and Duralay). Test groups were subjected to microwave irradiation (3 minutes at 600 W) after polymerization. Bar specimens were subjected to a flexural strength test. Disc-shaped specimens were used to evaluate microhardness. Backscattered Raman spectroscopy was employed for each group to define the degree of conversion of the monomer/polymer. The frequency bands corresponding to C = C and C = O groups were used to determine the conversion of methyl methacrylate (MMA) monomers into polymers. Glass transition temperature was determined using a differential scanning calorimeter. RESULTS: Microwave irradiation of both tested autopolymerizing PMMA provisional materials resulted in a statistically significant increase in microhardness, degree of conversion and glass transition temperature values. Also, the results demonstrated a significant increase in flexural strength after postpolymerization microwave irradiation for the Dencor specimens. CONCLUSIONS: It is concluded that mechanical and physical properties are positively influenced by microwave irradiation.

Characterization of the interface between cast-to Co-Cr implant cylinders and cast Co-Cr alloys.

STATEMENT OF PROBLEM: The affordable Co-Cr cast alloy should provide an ideal interface with prefabricated cast-to cylinders from the same alloy family. The alloy microstructures should be maintained up to the interface, and porosities and reaction regions should be absent, and sufficient bond strength between alloys should be provided. PURPOSE: The purpose of this in vitro study was to evaluate the metallurgical interfacial compatibility between Co-Cr dental casting alloys and a prefabricated Co-Cr dental implant cast-to-cylinder. MATERIAL AND METHODS: A Co-Cr alloy was cast to Co-Cr implant cylinders. Specimens were cross-sectioned longitudinally and divided into as-cast and heat-treated groups. The microstructures of specimens were evaluated by optical and scanning electron microscopy. The elemental composition of as-received prefabricated implant cylinders and diffusion characteristics of cast interfacial regions were determined by energy dispersive x-ray spectroscopy. Vickers hardness values were defined across the interface on cast specimens and for the as-received implant cylinders. ANOVA and Tukey honest significant differences tests were used for the statistical evaluation of hardness values. RESULTS: No significant reaction regions or porosity were present in the interface. Microstructural aspect and interdiffusion indicated a metal-metal bond between the Co-Cr implant cylinder and cast alloy. Mean hardness values demonstrated a significant rise across the interface (373.5 ±12.8; 363.8 ±12.6, respectively) from the wrought cylinder (338.6 ±10.5; 329 ±9.7, respectively) to the cast alloy (399.8 ±7.4; 392.3 ±10.3, respectively) for the as-cast and heat-treated conditions, respectively. CONCLUSIONS: Co-Cr casting alloy cast on to prefabricated Co-Cr implant cylinders provided interfaces which appear to fulfill the requirements of the established criteria.

Effects of Hard Thin-Film Coatings on Adhesion of Early Colonizer Bacteria Over Titanium Surfaces.

PURPOSE: The purpose of this in vitro study was to evaluate the effect of diamond-like carbon (DLC) and titanium (Ti) nitride coatings over Ti surfaces on the adhesion of early colonizer bacteria. MATERIALS AND METHODS: Specimens were divided into 3 groups (n = 10) according to different surface modifications: titanium nitride (TiN)-coated Ti discs (experimental group 1), DLC-coated Ti discs (experimental group 2), and uncoated polished Ti discs (control group). Discs were incubated in bacterial cell suspension (Streptococcus mutans and Streptococcus sanguis) for 1 hour, and the single colonies formed by adhering bacteria were counted by fluorescence microscopy. Surface roughness and topography were examined by atomic force microscopy. RESULTS: The surface roughness of DLC was lower than TiN coating and the control group. Statistically significant reduction of the number of adherent bacteria was observed on DLC-coated surfaces. CONCLUSIONS: DLC coating over Ti surfaces strongly inhibits the adhesion of early colonizer oral bacteria.

Reabilitação protética de perda severa da dimensão vertical de oclusão e overjet extenso: relato de caso / Prosthetic reconstruction of severe loss on vertical dimension and extensive overjet: case report

Introdução: A perda da dimensão vertical associada com severa destruição dentária apresentam alterações intra e extrabucais significativas. Relato de caso: Este trabalho reporta um caso de reabilitação em paciente com severa perda de dimensão vertical resultante de desgaste dentário e inclinação vestibular dos dentes superiores. Conclusão: Casos como o apresentado neste trabalho, pela sua complexidade, necessitam de um planejamento detalhado, com o objetivo de devolver a função bucal e a integridade psicológica ao paciente

Diamondlike carbon coating as a galvanic corrosion barrier between dental implant abutments and nickel-chromium superstructures.

PURPOSE: The objectives of this study were to evaluate the galvanic corrosion behavior between titanium and nickel-chromium (Ni-Cr) alloy, to investigate the effect of diamondlike carbon (DLC) coating over titanium on galvanic corrosion behavior between titanium and Ni-Cr alloy, and to evaluate the effect of DLC coating over titanium abutments on the fit and integrity of prosthetic assemblies by scanning electron microcopy (SEM). MATERIALS AND METHODS: Five Ni-Cr and 10 titanium disks with a diameter of 5 mm and thickness of 3 mm were prepared. DLC coating was applied to five titanium disks. Electrode samples were prepared, and open circuit potential measurements, galvanic current measurements over platinum electrodes, and potentiodynamic polarization tests were carried out. For the SEM evaluation, 20 Ni-Cr alloy and 10 gold alloy superstructures were cast and prepared over 30 abutments. DLC coating was applied to 10 of the abutments. Following the fixation of prosthetic assemblies, the samples were embedded in acrylic resin and cross sectioned longitudinally. Internal fit evaluations were carried out through examination of the SEM images. RESULTS: Titanium showed more noble and electrochemically stable properties than Ni-Cr alloy. DLC coating over the cathode electrode served as an insulating film layer over the surface and prevented galvanic coupling. Results of the SEM evaluations indicated that the DLC-coated and titanium abutments showed no statistically significant difference in fit. Hence, no adverse effects on the adaptation of prosthetic components were found with the application of DLC coating over abutment surfaces. CONCLUSIONS: DLC coating might serve as a galvanic corrosion barrier between titanium abutments and Ni-Cr superstructures.

Intrapulpal heat generation during provisionalization: effect of desensitizer and matrix type.

PURPOSE: This study investigated the effect of different matrices and application of a desensitizer on pulpal temperature rise during direct provisionalization. MATERIALS AND METHODS: The apical third of a second premolar was resected and pulpal tissue was removed. Silicone heat-conducting medium was injected, and a J-type thermocouple was inserted into the pulp chamber and sealed. The tooth was embedded in acrylic resin with its cervical line 1 mm higher than the base. Addition and condensation silicone impression materials were mixed and placed inside plastic molds. Impressions were taken before tooth preparation. The tooth was then prepared with a 1.5-mm shoulder finish line. The experimental model was kept in a 36 degrees C water bath. Four provisional materials were applied in sequence onto the prepared tooth using matrices. Each provisional resin was used in combination with each matrix (n = 12). Then a dentin desensitizer was coated on the prepared tooth and provisionalizations were made in the same manner. The thermocouple was connected to the data-logger. During setting of the resins, pulp temperatures were recorded and transferred to the computer. Measurements were conducted for each test group by calculating the temperature rise as the difference between the start and highest temperature reading. RESULTS: The type of the silicone matrix used and the use of desensitizer did not affect the intrapulpal heat generation during direct provisionalization. CONCLUSION: Application of a desensitizer and different type of matrix seems to be noneffective on intrapulpal heat rise, although the type of provisional material used may be effective.

The effect of food simulants on porcelain-composite bonding.

PURPOSE: The purpose of this study was to evaluate the in vitro effects of food simulants on the bond strength of brackets to porcelain surfaces. MATERIALS AND METHODS: One hundred and eighty porcelain-fused to metal specimens were fabricated. Samples were divided into 3 groups including 60 specimens each. Different surface treatment methods were applied to each group and these were: sandblasting (SB), etching with orthophosphoric acid (OPA) and etching with hydrofluoric acid (HFA). After the surface treatments, the brackets were bonded to the center of each sample with a light-curing orthodontic composite adhesive. Then each group was divided into five test subgroups and one control subgroup each consisting of 10 specimens. The test groups were conditioned for 90 days at 37 degrees C as follows: water, 0.02N citric acid, heptane, 8% ethanol aqueous solution and 50% ethanol aqueous solution. The control specimens were stored at room temperature in air. Shear force was applied to the porcelain-bracket interface by using a universal testing machine with a crosshead speed of 1 mm/min until debonding occurred. The shear bond strength was calculated by dividing the maximum load by the cross-sectional area of the bracket to give the results in megapascals (MPa). The statistical evaluations were made by using analysis of variance. Whenever a significance was detected, Bonferroni tests were performed for post hoc analyses. RESULTS: Fifty percent ethanol conditioned specimens for all surface treatment groups showed lower shear bond strength values. HFA group showed significantly higher shear bond strength values when compared with other groups (P < 0.05). For all porcelain surface treatment groups, control groups showed statistically significant higher shear bond strength values (P < 0.05). CONCLUSION: The results of this in vitro study show that food simulants significantly decrease the bond strength between bracket and porcelain surface.

Effect of food-simulating liquids on the mechanical properties of provisional restorative materials.

OBJECTIVES: The purpose of this study was to investigate the effects of food-simulating liquids (FSL) on the mechanical properties of provisional restorative materials. METHODS: Four provisional restorative materials were selected: (1) Dentalon Plus (DP), (2) Protemp II (PII), (3) Systemp C&B (SCB) and (4) Integrity (INTG). The specimens were fabricated in customized molds and each type was randomly divided into five groups (n = 10). The test groups were conditioned for 7 days at 37 degrees C as follows: water, 0.02 N citric acid, heptane and 75% ethanol in aqueous solution. Specimens in the control group were stored at room temperature in air. After conditioning, the flexural strength (FS) values were assessed using a universal testing machine (5 mm/min crosshead speed) and the fractured specimens were used for the determination of the Knoop hardness number (KHN) using a digital micro-hardness tester (100 gf/15 s). Kruskal-Wallis and Mann-Whitney U-tests were used for statistical analysis. RESULTS: In ethanol and heptane solutions, DP specimens were totally degraded, thus, FS/KHN for DP could not be measured. For all materials, the FS/KHN values were significantly lower than their control groups after conditioning in ethanol. After heptane conditioning, the decrease in FS for SCB and KHN for PII were statistically significant. After citric acid conditioning, KHN for PII and INTG were significantly higher than the controls and the decrease in FS for SCB and INTG were statistically significant. SIGNIFICANCE: The mechanical properties of provisional restorative materials are strongly influenced by food-simulating liquids.