The Effects of Colored Pigments on the Translucency of Experimental Dental Resin Composites.

OBJECTIVE: Colored pigments are incorporated into dental resin composites to produce clinically acceptable shades for restorative materials but studies on their effects on translucency are rare. The aim of this study was to examine the effects of the addition of different colored pigments on the translucency of experimental dental resin composites. MATERIALS AND METHODS: 12 types of experimental dental resin composites containing different concentrations of red and yellow iron oxide pigments were formulated and light-cured. Total and diffuse translucency as well as CIE L*a*b* values were measured and the color differences were calculated. RESULTS: There was a statistically significant difference in the translucency values between the composites with no pigments and the composites with increasing concentrations of the pigments (p<0.05). The translucency decreased as the concentration of the pigments increased. However at pigment concentrations greater than 0.02%, the translucency of the composites reached a plateau and ceased to be influenced by the addition of the pigments (p⟨0.05). All color differences were in the range of 3.62-16.00 ΔE*ab unit. CONCLUSIONS: The pigments used in this study can influence the translucency of the experimental resin composites and should be considered as an important factor by clinicians to achieve optimal esthetic restorative outcome.

The Evolution of Dental Materials over the Past Century: Silver and Gold to Tooth Color and Beyond.

The field of dental materials has undergone more of a revolution than an evolution over the past 100 y. The development of new products, especially in the past half century, has occurred at a staggering pace, and their introduction to the market has been equally impressive. The movement has mostly come in the area of improved esthetics, marked by the gradual replacement of dental amalgam with dental composite and all-metal and porcelain-fused-to-metal indirect restorations with reinforced dental ceramics, all made possible by the rapid improvements in dental adhesive materials. This article covers the time course of dental materials development over the past century in which the Journal of Dental Research has been published. While there have been advances in nearly all materials used in the field, this article focuses on several areas, including dental amalgam, dental composites and light curing, dental adhesives and dental cements, ceramics, and new functional repair materials. A few short statements on future advances will be included at the end.

ADM guidance-ceramics: Fatigue principles and testing.

BACKGROUND: Clinical failure of dental ceramics is usually reported as partial fracture of the restoration (chipping) or as catastrophic fracture of the whole structure. In contrast to metals, ceramics are linear-elastic, brittle materials exhibiting extremely low damage tolerance to failure. Well documented clinical and lab reports have shown this fracture event often occurs at loads far below their fracture strength due to intrinsic fatigue degradation via slow crack growth or cyclic fatigue mechanisms. The presence and development of surface flaws have a dominant role in damage accumulation and lifetime reduction of ceramic structures. AIMS: This ADM guidance document aims to summarize the aspects related to fatigue degradation of dental ceramics, reviewing the concepts of fatigue testing and furthermore aims to provide practical guidance to young scientists entering into fatigue related research. The description of fatigue strength is always accompanied by a clear understanding of the underlying fracture mechanisms.

Direct metal laser sintering titanium dental implants: a review of the current literature.

Statement of Problem. Direct metal laser sintering (DMLS) is a technology that allows fabrication of complex-shaped objects from powder-based materials, according to a three-dimensional (3D) computer model. With DMLS, it is possible to fabricate titanium dental implants with an inherently porous surface, a key property required of implantation devices. Objective. The aim of this review was to evaluate the evidence for the reliability of DMLS titanium dental implants and their clinical and histologic/histomorphometric outcomes, as well as their mechanical properties. Materials and Methods. Electronic database searches were performed. Inclusion criteria were clinical and radiographic studies, histologic/histomorphometric studies in humans and animals, mechanical evaluations, and in vitro cell culture studies on DMLS titanium implants. Meta-analysis could be performed only for randomized controlled trials (RCTs); to evaluate the methodological quality of observational human studies, the Newcastle-Ottawa scale (NOS) was used. Results. Twenty-seven studies were included in this review. No RCTs were found, and meta-analysis could not be performed. The outcomes of observational human studies were assessed using the NOS: these studies showed medium methodological quality. Conclusions. Several studies have demonstrated the potential for the use of DMLS titanium implants. However, further studies that demonstrate the benefits of DMLS implants over conventional implants are needed.

Contour analysis of an implant--soft tissue interface.

BACKGROUND AND OBJECTIVE: Studies of peri-implant soft tissue on in vivo models are commonly based on histological sections prepared using undecalcified or 'fracture' techniques. These techniques require the cutting or removal of implant during the specimen preparation process. The aim of this study is to explore a new impression technique that does not require any cutting or removal of implant for contour analysis of soft tissue around four types of titanium (Ti) surface roughness using an in vitro three-dimensional oral mucosal model (3D OMM). METHODS: The 3D OMM was constructed by co-culturing a keratinocyte cell line TR146 and human oral fibroblasts on to an acellular dermis scaffold. On the fourth day, a Ti disk was placed into the model. Four types of Ti surface topographies, i.e. polished, machined, sandblasted and anodized were tested. After 10 d of culture, the specimens were processed based on undecalcified (ground sectioning), electropolishing and impression techniques for contour analysis of the implant-soft tissue interface. RESULTS: Under light microscopic examination of the ground and electropolishing sections, it was found that the cell line-based oral mucosa formed a peri-implant-like epithelium attachment on to all four types of Ti surfaces. In contour analysis, the most common contour observed between the cell line-based oral mucosa and Ti surface was at an angle ranging between 45° and 90°. CONCLUSION: The in vitro cell line-based 3D OMM formed a peri-implant-like epithelium at the implant-soft tissue interface. The contour of the implant-soft tissue interface for the four types of Ti surface was not significantly different.

A review of histomorphometric analysis techniques for assessing implant-soft tissue interface.

The success of dental implant treatment depends on the healing of both hard and soft tissues. While osseointegration provides initial success, the biological seal of the peri-implant soft tissue is crucial for maintaining the long term success of implants. Most studies of the biological seal of peri-implant tissues are based on animal or monolayer cell culture models. To understand the mechanisms of soft tissue attachment and the factors affecting the integrity of the soft tissue around the implants, it is essential to obtain good quality histological sections for microscopic examination. The nature of the specimens, however, which consist of both metal implant and soft peri-implant tissues, poses difficulties in preparing the specimens for histomorphometric analysis of the implant-soft tissue interface. We review various methods that have been used for the implant-tissue interface investigation with particular focus on the soft tissue. The different methods are classified and the advantages and limitations of the different techniques are highlighted.

Development, optimization and characterization of a full-thickness tissue engineered human oral mucosal model for biological assessment of dental biomaterials.

Restorative dental materials and oral health care products come into direct contact with oral mucosa and can cause adverse reactions. In order to obtain an accurate risk assessment, the in vitro test model must reflect the clinical situation as closely as possible. The aim of this study was to develop and optimize a three-dimensional full-thickness engineered human oral mucosal model, which can be used for biological assessment of dental materials. In this study human oral fibroblasts and keratinocytes were isolated from patients and seeded onto a number of collagen-based and synthetic scaffolds using a variety of cell seeding techniques and grown at the air/liquid interface to construct human oral mucosa equivalents. Suitability of 10 different scaffolds for engineering human oral mucosa was evaluated in terms of biocompatibility, biostability, porosity, and the ability to mimic normal human oral mucosa morphology. Finally an optimized full-thickness engineered human oral mucosa was developed and characterized using transmission electron microscopy and immunostaining. The oral mucosa reconstruct resembled native human oral mucosa and it has the potential to be used as an accurate and reproducible test model in mucotoxicity and biocompatibility evaluation of dental materials.

Minimal preparation designs for single posterior indirect prostheses with the use of the Cerec system.

The advantages of minimally invasive dentistry are well established, especially for direct restorations. However, when it comes to indirect restorations traditional tooth preparation designs are still advised by most manufacturers. The purpose of this in vitro study was to investigate the ability of a CAD/CAM machine (Cerec) to produce minimal preparation designs and identify limiting parameters. Crown preparations based on the proposed minimal design were made using phantom teeth. Gauged burs (Intensiv SA; Meissinger, Germany) and a paralleling device were used to standardize preparations. Cerec Scan/Cerec 3D was used for scanning and designing. The materials tested were a resin composite (Paradigm MZ100, 3M ESPE) and two ceramic materials (ProCAD, Ivoclar Vivadent, and VITA Mark II, Vita). The morphology, marginal integrity, and materials' integrity were examined. The design was subjected to an interactive process as material property limitations and constraints imposed by the system became apparent. SEM, optical microscopy, and transillumination were used for the qualitative control of the crowns. The results of this study showed that only the composite material produced acceptable crowns with intact margins for the minimal design initially proposed. The ceramic materials required a wider preparation design in order to produce acceptable crowns. Within the limitations of this study, the null hypothesis was partially rejected as it was found that only the composite material could produce acceptable crowns based on the proposed minimal design. It was also found that the materials' properties, the milling mode, and cutting instruments are determining factors in establishing the extent of the minimal preparation.

Tissue-engineered oral mucosa: a review of the scientific literature.

Tissue-engineered oral mucosal equivalents have been developed for clinical applications and also for in vitro studies of biocompatibility, mucosal irritation, disease, and other basic oral biology phenomena. This paper reviews different tissue-engineering strategies used for the production of human oral mucosal equivalents, their relative advantages and drawbacks, and their applications. Techniques used for skin tissue engineering that may possibly be used for in vitro reconstruction of human oral mucosa are also discussed.

HPLC analysis of components released from dental composites with different resin compositions using different extraction media.

Components released from dental composite resins are essential factors in the assessment of biocompatibility of these materials. The effect of different extraction media on monomer release from composite resins based on different monomer types was evaluated. Three types of visible light cured composite resins were formulated based on the following monomers: triethylene glycol dimethacrylate (TEGDMA), bisphenol A glycerolate dimethacrylate (BisGMA), and urethane dimethacrylate (UDMA). Seventy-five composite resin discs were fabricated and light cured for 1 min in the absence of oxygen. Extraction media used were: distilled water, saline solution, artificial saliva, serum-free culture medium, and culture medium with 10% fetal calf serum. The analysis of extracts from the composite resins was carried out by High Performance Liquid Chromatography (HPLC). Quantifiable amounts of TEGDMA were released into the aqueous media. However, BisGMA and UDMA were not detectable in any of the extracts from the composite resins. Statistical analysis by one-way ANOVA followed by Tukey's test showed that there was a significant difference in TEGDMA release between culture media and other media (p < 0.05). From the results of this experiment it can be concluded that TEGDMA-based composite resins can release a high quantity of monomer into aqueous environments. The type of extraction medium may have a significant effect on monomer release from composite resins.

Scale of protection and the various types of sports mouthguard.

OBJECTIVES: To present a grading system of the protection offered by various types of mouthguard, together with an indication of associated risks, in order to make athletes aware of the consequences of improper or no mouth protection. METHODS: A review of the literature on mouthguards, mouthguard materials, and novel laminates for mouthguards was carried out as it was apparent that information on mouthguards was lacking. Studies on stock (or unfitted) mouthguards, mouth formed (boil and bite) mouthguards, and custom mouthguards are reviewed. RESULTS: A scale of protection offered by various mouthguards and novel laminates has been produced, where 0 indicates no mouthguard and 10 indicates a custom made mouthguard offering excellent protection. CONCLUSIONS: From work carried out on laminates and the manufacturing processes of mouthguards, it became apparent that information was lacking to enable athletes make informed decisions about the best oral protection for their chosen sport.

The national survey of adverse reactions to dental materials in the UK: a preliminary study by the UK Adverse Reactions Reporting Project.

OBJECTIVE: Dental treatment involves the use of a wide range of materials. Many of the dental materials or their components pose a potential risk to the patient and member of the dental team. Pre-market biocompatibility testing cannot guarantee absolute safety, making monitoring of materials likely to cause an adverse reaction essential. The prevalence of adverse reactions to dental materials amongst dental patients and staff has not been systematically monitored in the UK. This project aims to develop a systematic approach to the evaluation and monitoring of the extent and severity of adverse reactions to dental materials in the UK. METHOD: Through the distribution of reporting forms to dental surgeries and laboratories in the UK, the ARRP has received 1,075 complete reports relating to adverse reactions seen or experienced by dental staff and patients. RESULTS: The main findings were that different materials cause adverse reactions to different groups of people. The largest proportion of patient related adverse reactions were reported to be due to metals (n = 175). These were mainly amalgam associated oral lichenoid reactions (n = 124). Dental technicians reported acrylic resin as the causal factor of hand dermatitis in 61% (44 out of a total 72) of cases reported. Finally, dental surgery staff reported gloves as causing hand dermatitis in 75% of cases (398 out of a total 531). CONCLUSIONS: Different dental materials affect different person groups depending on their exposure to the material. Dental staff are most at risk from an adverse reaction to latex gloves, whereas most reported reactions for patients were due to metals. For dental technicians the biggest danger of an adverse reaction was from acrylic resins. There is a need to continue to raise the awareness among dental professionals of the existence of the Adverse Reactions Reporting Project so as to overcome problems of under-reporting.

The effect of investment material and ceramming regime on the surface roughness of two castable glass-ceramic materials.

OBJECTIVE: To assess the surface roughness (R(a)) of two castable glass-ceramic materials, cast using four different investment materials and employing different ceramming regimes. METHODS: Forty discs, each 12 mm diameter and 2 mm thick were produced from two castable glass-ceramic materials, one a glass ionomer derivative based on 1.5SiO(2)-1Al(2)O(3)-0.53P(2)O(5)-1CaO-0.67CaF(2) (LG112), the other a fluorcanasite material based on 0.60SiO(2)-0.05K(2)O-0.10Na(2)O-0.15CaO-0.10CaF(2) (SG3). The discs were made using four dental investments, two gypsum-bonded (Whip-Mix Cristobalite (WMC), Degussa California (DC)) and two phosphate-bonded (Fujivest Super (FS), Techceram Glass (TG)). A Ni-Cr metal/ceramic alloy (Wiron 99) was also used as a control. Each investment was used to produce 10 discs for each glass-ceramic material, five left in the as-cast, glass state, the other five cerammed. Ceramming was carried out either within the investment mold or after de-vesting from the investment mold. The discs had their surface roughness values measured using a stylus, surface contact measuring instrument. RESULTS: For the Ni-Cr alloy the phosphate-bonded investments produced discs significantly smoother than those produced by the two gypsum-bonded investments (p<0.05). The FS investment produced the smoothest discs (p<0.05), but there was no significant difference between the discs produced by the two gypsum-bonded investments (p>0.05). For the SG3 material no significant differences were seen between the as-cast glass and cerammed discs (p>0.05), with the WMC investment producing the smoothest discs (p<0.05), and the TG investment the roughest (p<0.05). The LG112 material showed a significant difference between glass and cerammed discs for the gypsum-bonded investments (p<0.05) but not when using phosphate-bonded investments (p>0.05). With LG112 the WMC investment produced smoother discs than the DC and TG investments (p<0.05). The DC investment produced rougher discs than the two phosphate-bonded investments (p<0.05). SIGNIFICANCE: The selection of investment material can have a significant effect on the as-cast surface finish of castable glass-ceramic materials. A gypsum-bonded investment material gave smoother surface finishes compared to phosphate-bonded investments. The ceramming process significantly increases surface roughness.

Adverse reactions to protective gloves used in the dental profession: experience of the UK Adverse Reaction Reporting Project.

The Adverse Reaction Reporting Project (ARRP) was set up to measure the extent and severity of adverse reactions to dental materials in the UK. Further analysis into the use of protective gloves has been carried out to establish the degree to which gloves are having a deleterious effect on the dental profession. In addition the survey aimed to establish the techniques used to manage adverse reactions and their effectiveness. In a 23-month period, 369 reports were received concerning adverse reactions to protective gloves used in dental practices. Reporters were contacted for further information, and a 92% response rate was achieved. The 330 reports analysed showed dentists to be the largest group to report adverse reactions, whilst dental technicians reported the fewest. The referral rate for staff and patients was similar with a third of adverse reactions being referred (n=110) to a specialist for diagnosis. A confirmed diagnosis was received in 65% of referred cases (n=72), but the symptoms reported suggested a larger degree of Type I reactions occurring than diagnosed. The use of non-powdered gloves appeared to be favoured over powdered gloves in 42% of glove changes, and nitrile gloves were used as an alternative to latex in 39% of changes. In conclusion, the results from this survey showed that wearing gloves in dental practices in the UK caused a range of adverse reactions. In 79% (n=330) of cases reported and analysed, these reactions were readily resolved or improved by self-medication, prescribed medication and/or changing to a different type of protective glove.

In vivo bone tissue response to a canasite glass-ceramic.

The aim of this study was to determine the biocompatibility and osteoconductive potential of a high-strength canasite glass ceramic. Glass-ceramic rods were produced using the lost-wax casting technique and implanted in the mid-shafts rabbit femurs. Implants were harvested at 4, 13 and 22 weeks and prepared for light and electron microscopy. Hydroxyapatite was used as a control material. Hydroxyapatite implants were surrounded by new mineralised bone tissue after 4 weeks of implantation. The amount of bone surrounding the implant increased slightly at 13 weeks. In contrast, canasite glass and glass ceramic implants were almost entirely surrounded by soft tissue during all the time periods. Close contact between bone and canasite glass-ceramic implant without the intervening fibrous tissue was observed in only a few regions. The canasite formulation evaluated was not osteoconductive and appeared to degrade in the biological environment. It was therefore concluded that the canasite formulation used was unsuitable for use as implant. Further work is required to improve the biocompatibility of these materials with bone tissue. It is possible that this could be achieved by reducing the solubility of the glass and glass ceramic.

Osseointegration and osseoconductivity of hydroxyapatite of different microporosities.

The aim of this study was to determine the relationship between changes in microporosity and the osseointegration and the osseoconductivity of hydroxyapatite (HAp). HAp cylinders were manufactured by a combination of uniaxial powder pressing and different sintering conditions, with different percentages of microporosity: HAp-I with 3.96+/-0.75% microporosity, HAp-II with 15.66+/-1.60% microporosity, and HAp-III with 29.72+/-0.69% microporosity. These HAp cylinders were surgically implanted in rabbit femurs. After 8 and 12 weeks, the femurs were removed, fixed, sectioned, ground, and stained by Stevenel's blue/Van Gieson for light microscopy and histomorphometry. Some ground sections were routinely processed for SEM. The osseointegration and the osseoconductivity were determined by means of image analysis and the data were submitted to ANOVA. In all cases the cortical bone was repaired and the HAp facing the medullary canal was lined with endosteum, which in some areas exhibited thin bone tissue formation. SEM observations showed no differences in the morphology of tissue-HAp interfaces for the three different porosities of HAp. There were no statistical differences between the groups related to either osseointegration or osseoconductivity. These results suggest that neither osseointegration nor osseoconductivity of HAp are influenced by changes in HAp microporosity.

XPS analysis of the surface of leucite-reinforced feldspathic ceramics.

OBJECTIVE: The bond of a silane-coupling agent to a ceramic surface is expected to be influenced by the composition and chemical state of the ceramic surface. The purpose of this study was to determine the variation in the composition and the chemical states of the surfaces of a range of leucite-reinforced feldspathic (LRF) ceramics using X-ray photoelectron spectroscopy (XPS). METHODS: Five LRF ceramic discs (IPS Empress,Optec HSP,VMK 68, Mirage, and a modified Mirage) were produced and polished to a 1 microm finish. A further nine discs of the modified Mirage were produced. The discs were stored for 48h in a vacuum oven at 110 degrees C to remove absorbed water. The surfaces of these discs were analysed by XPS. Survey scans at 30 degrees take-off angle were taken and surface composition (in at%) was calculated from the narrow scans for Si 2p, O 1s, Al 2p, Mg 2s, K 2p, Na 1s, Ca 2p and N 1s. RESULTS: Atomic concentration of elements (after exclusion of C) for the five LRF ceramics were in the range: O, 45.0-51.6%; Si, 26.7-35.6%; Al, 6.3-9.7%; Mg, 4.9-8.8%; K, 0.5-2.2%; N, 0.9-2.9% and less than 1% of Na and Ca. The shapes of the O 1s and Si 2p narrow scan core lines of the five LRF ceramics were virtually identical. SIGNIFICANCE: All five LRF ceramics were found to have a silica-rich surface layer due to a reduction in K and Na relative to the bulk composition. Both the composition and chemical states of the surfaces for the five LRF ceramics were very similar.

Effect of furnace type and ceramming heat treatment conditions on the biaxial flexural strength of a canasite glass-ceramic.

OBJECTIVE: To assess the effect of different heat treatment conditions when using two different furnace types on the biaxial flexural strength (BFS) of a fluorcanasite castable glass-ceramic. METHODS: Two furnace types, one a programmable furnace (PF), the other a dental laboratory burnout furnace (DLF), were used with various ceramming times to determine their effect on the BFS of a fluorcanasite castable glass-ceramic. The glass-ceramic material was cast to produce discs of 12 mm diameter and 2 mm thickness using the lost wax casting process (n = 80). After casting, both furnace types were used to ceram the discs. Half the discs were not de-vested from the casting ring before ceramming but cerammed in situ (DLF) and half were de-vested before ceramming (PF). All the discs were given a nucleation heat treatment at 520 degrees C for 1 h and then cerammed at 860 degrees C using four heat soak times (0.5, 1, 2 and 3 h). The DLF furnace had a rate of climb of 13 degrees C/min and the PF furnace had a rate of climb of 5 degrees C/min to 520 degrees C and 3 degrees C/min to 860 degrees C. After ceramming the discs were de-vested and the BFS determined using a Lloyd 2000R tester. RESULTS: The maximum BFS values seen for both furnace types were almost identical (280 MPa), but were achieved at different heat soak times (1 h DLF, and 2 h PF). The only significant differences in BFS values for the two furnaces were between the 0.5 and 2 h heat soak times (p < or = 0.05). Individual differences were seen between results obtained from each furnace type/heat soak times evaluated (p < or = 0.05). SIGNIFICANCE: Already available dental laboratory burnout furnaces can be used to ceram fluorcanasite glass-ceramic castings to the same BFS values as more expensive and slower specialist programmable furnaces.

Dental materials: 1997 literature review.

This review of the published literature on dental materials for the year 1997 has been compiled by the Dental Materials Panel of UK. It continues a series of annual reviews started in 1973. Emphasis has been placed upon publications, which report upon the materials science or clinical performance of the materials. The review has been divided by accepted materials classifications (fissure sealants, glass polyalkenoate cements, dentine bonding, dental amalgam, endodontic materials, casting alloys, ceramometallic restorations and resin-bonded bridges, ceramics, denture base resins and soft lining materials, impression materials, dental implant materials, orthodontic materials, biomechanics and image processing, resin composites, and casting investment materials and waxes). Three hundred and thirty three articles have been reviewed.

Bonding procedures for intraoral repair of exposed metal with resin composite.

PURPOSE: To determine if tin plating can be recommended for intraoral repair of ceramic veneered cast restorations where metal of unknown composition is exposed by loss of ceramic. This study investigated the effectiveness of surface treatments incorporating tin plating and unfilled resin to enhance the tensile bond strength of a resin composite restorative to three different metal ceramic casting alloys. MATERIALS AND METHODS: Gold-platinum, palladium-tin and nickel-chromium alloys were used to fabricate 120 rods of each alloy, 4 x 15 mm. The end of each rod was ground perpendicular on 600-grit SiC paper and grit blasted with 50-micron alumina. Rods from each alloy were divided into four groups of 30 to receive one of the following treatments before bonding pairs end to end with a visible light-polymerized resin composite (Herculite XRV): 1) direct bonding with the resin composite; 2) tin plating (Micro-Tin) and bonding; 3) application of unfilled resin (Chameleon) and bonding; 4) tin plated, application of unfilled resin and bonding. The bonded samples were stored in distilled water, incubated at 37 degrees C for 24 hours and tested for tensile bond strength at a crosshead speed of 1 mm/min in a Lloyd 1000R machine. The mode of failure was examined using a stereo zoom microscope. RESULTS: A statistically significant increase in tensile bond strength was demonstrated between the control (group 1) and both the gold and palladium alloy treated with tin plating and unfilled resin (group 4). Tin plating, or tin plating with the application of unfilled resin had no statistically significant effect on the tensile bond strength of resin composite to the nickel-chromium alloy. CONCLUSION: The results demonstrate that tin plating, in conjunction with the application of a low-viscosity unfilled resin, optimizes the tensile bond of a resin composite to the three alloys used in the study. This procedure can be recommended for intraoral repair of exposed metal when the type of alloy belongs to one of the investigated alloy groups.