Endocrown fixed partial denture: Is it possible?

STATEMENT OF PROBLEM: Whether the replacement of a missing tooth with a fixed partial denture supported by an endodontically treated abutment could be improved with endocrowns is unclear. PURPOSE: The purpose of the study was to evaluate the mechanical behavior of a fixed partial denture (FPD) according to the preparation of the abutment teeth (endocrown or complete crown) in terms of stress magnitude in the prosthesis, cement layer, and tooth. MATERIAL AND METHODS: A posterior model with 2 abutment teeth (first molar and first premolar) was modeled with a computer-aided design (CAD) software program for conducting a 3-dimensional finite element analysis (FEA). To replace the missing second premolar, the model was replicated in different possible FPDs according to the abutment preparation design (complete crown [Conventional], 2 endocrowns [EC]) or an endocrown on one of the abutment teeth (first molar [ECM] and first premolar [ECP]) for a total of 4 designs. All FPDs were in lithium disilicate. The solids were imported to an analysis software program (ANSYS 19.2) in the standard for the exchange of product data (STEP) format. The mechanical properties were considered isotropic and the materials to show linear elastic and homogeneous behavior. An axial load (300 N) was applied at the occlusal surface of the pontic. The results were evaluated by colorimetric stress maps of von Mises and maximum principal stress in the prosthesis, maximum principal stress and shear stresses on the cement layer, and maximum principal stress in the abutment teeth. RESULTS: The von Mises stresses revealed that all FPD designs behaved similarly and that, considering the maximum principal stress criteria, the pontic was the most stressed region. For the cement layer, the combined designs presented an intermediate behavior, with the ECM more suitable to reducing the stress peak. The conventional preparation allowed less stress concentration in both teeth, and higher stress concentration in the premolar was observed with an endocrown. The endocrown decreased the risk of fracture failure. Considering the risk of debonding failure for the prosthesis, the endocrown preparation was only able to decrease the failure risk when the EC design was used and when only the shear stress was considered. CONCLUSIONS: Performing endocrown preparations to retain a 3-unit lithium disilicate FPD is an alternative to conventional complete crown preparations.

A rapid, non-invasive tool for periodontitis screening in a medical care setting.

BACKGROUND: Since periodontitis is bi-directionally associated with several systemic diseases, such as diabetes mellitus and cardiovascular diseases, it is important for medical professionals in a non-dental setting to be able examine their patients for symptoms of periodontitis, and urge them to visit a dentist if necessary. However, they often lack the time, knowledge and resources to do so. We aim to develop and assess "quick and easy" screening tools for periodontitis, based on self-reported oral health (SROH), demographics and/or salivary biomarkers, intended for use by medical professionals in a non-dental setting. METHODS: Consecutive, new patients from our outpatient clinic were recruited. A SROH questionnaire (8 questions) was conducted, followed by a 30 s oral rinse sampling protocol. A complete clinical periodontal examination provided the golden standard periodontitis classification: no/mild, moderate or severe periodontitis. Total periodontitis was defined as having either moderate or severe. Albumin and matrix metalloproteinase-8 concentrations, and chitinase and protease activities were measured in the oral rinses. Binary logistic regression analyses with backward elimination were used to create prediction models for both total and severe periodontitis. Model 1 included SROH, demographics and biomarkers. The biomarkers were omitted in the analysis for model 2, while model 3 only included the SROH questionnaire. The area under the receiver operating characteristic curves (AUROCC) provided the accuracy of each model. The regression equations were used to create scoring algorithms, composed of the remaining predictors, each with its own weight. RESULTS: Of the 156 patients participating in this study, 67% were classified with total periodontitis and 33% had severe periodontitis. The models for total periodontitis achieved an AUROCC of 0.91 for model 1, 0.88 for model 2 and 0.81 for model 3. For severe periodontitis, this was 0.89 for model 1, 0.82 for model 2 and 0.78 for model 3. The algorithm for total periodontitis (model 2), which we consider valid for the Dutch population, was applied to create a freely accessible, web-based screening tool. CONCLUSIONS: The prediction models for total and severe periodontitis proved to be feasible and accurate, resulting in easily applicable screening tools, intended for a non-dental setting.

Titanium: a review on exposure, release, penetration, allergy, epidemiology, and clinical reactivity.

Exposure to titanium (Ti) from implants and from personal care products as nanoparticles (NPs) is common. This article reviews exposure sources, ion release, skin penetration, allergenic effects, and diagnostic possibilities. We conclude that human exposure to Ti mainly derives from dental and medical implants, personal care products, and foods. Despite being considered to be highly biocompatible relative to other metals, Ti is released in the presence of biological fluids and tissue, especially under certain circumstances, which seem to be more likely with regard to dental implants. Although most of the studies reviewed have important limitations, Ti seems not to penetrate a competent skin barrier, either as pure Ti, alloy, or as Ti oxide NPs. However, there are some indications of Ti penetration through the oral mucosa. We conclude that patch testing with the available Ti preparations for detection of type IV hypersensitivity is currently inadequate for Ti. Although several other methods for contact allergy detection have been suggested, including lymphocyte stimulation tests, none has yet been generally accepted, and the diagnosis of Ti allergy is therefore still based primarily on clinical evaluation. Reports on clinical allergy and adverse events have rarely been published. Whether this is because of unawareness of possible adverse reactions to this specific metal, difficulties in detection methods, or the metal actually being relatively safe to use, is still unresolved.

In vitro cytotoxicity of metallic ions released from dental alloys.

The cytotoxicity of a dental alloy depends on, but is not limited to, the extent of its corrosion behavior. Individual ions may have effects on cell viability that are different from metals interacting within the alloy structure. We aimed to investigate the cytotoxicity of individual metal ions in concentrations similar to those reported to be released from Pd-based dental alloys on mouse fibroblast cells. Metal salts were used to prepare seven solutions (concentration range 100 ppm-1 ppb) of the transition metals, such as Ni(II), Pd(II), Cu(II), and Ag(I), and the metals, such as Ga(III), In(III), and Sn(II). Cytotoxicity on mouse fibroblasts L929 was evaluated using the MTT assay. Ni, Cu, and Ag are cytotoxic at 10 ppm, Pd and Ga at 100 ppm. Sn and In were not able to induce cytotoxicity at the tested concentrations. Transition metals were able to induce cytotoxic effects in concentrations similar to those reported to be released from Pd-based dental alloys. Ni, Cu, and Ag were the most cytotoxic followed by Pd and Ga; Sn and In were not cytotoxic. Cytotoxic reactions might be considered in the etiopathogenesis of clinically observed local adverse reactions.

Sensitization to palladium and nickel in Europe and the relationship with oral disease and dental alloys.

BACKGROUND: The role of palladium and nickel sensitization in oral disease and dermatitis is not fully understood. OBJECTIVES: To investigate whether sensitization to these metals was associated with exposure to dental alloys and oral and skin complaints/symptoms in a European multicentre study. METHODS: In six dermatology clinics, patch tests with palladium (3% Na2 PdCl4 ; Pd = 102.0 µmol/g) and nickel (5% NiSO4 .6H2 O; Ni = 190.2 µmol/g) were performed in consecutive patients, and patients' characteristics were collected with a questionnaire and a clinical investigation. RESULTS: In total, 906 patients were included, of whom 24.3% reacted to palladium and 25.2% to nickel. The rate of monosensitization was 6-7% for both metals. Palladium sensitization (as opposed to no sensitization to both metals) was associated with exposure to dental crowns [odds ratio (OR) 2.0], skin reactivity to metals (OR 2.8), oral lichenoid lesions (OR 4.7), xerostomia (OR 7.3), and metal taste (OR 20.7), but not with eczema, stomatitis, or oral burning sensation. Additionally, xerostomia (OR 8.7) and metal taste (OR 4.6) were associated with sensitization to both metals. CONCLUSIONS: Clinically, it is important for palladium-sensitized patients to undergo an oral examination, with particular attention to the presence of/exposure to dental crowns. In the case of metal contact allergy, exposure to dental crowns could play a role.

Sensitization to palladium in Europe.

BACKGROUND: Recently, sodium tetrachloropalladate (Na2 PdCl4 ) was found to be a more sensitive palladium patch test allergen than palladium dichloride (PdCl2 ). OBJECTIVES: To determine the optimal test concentration of Na2 PdCl4 , to evaluate the prevalence of palladium sensitization with Na2 PdCl4 and PdCl2 , and to compare the results with nickel sensitization in a European multicentre study. MATERIALS AND METHODS: In addition to the European or national baseline series including NiSO4 ·6H2 0 5% pet., consecutive patients were tested with PdCl2 and Na2 PdCl4 2%, 3% and 4% pet. in eight European dermatology clinics. The age and sex distributions were also evaluated in patients sensitized to nickel and palladium. RESULTS: In total, 1651 patients were tested. Relative to 3% Na2 PdCl4 , 4% Na2 PdCl4 did not add any information. Two per cent Na2 PdCl4 resulted in more doubtful reactions and showed suboptimal reactivity. The prevalence of palladium sensitization doubled with Na2 PdCl4 and was similar to that of nickel. Interestingly, in contrast to nickel sensitization, palladium sensitization was not related to female sex. CONCLUSIONS: Three per cent Na2 PdCl4 pet. is the most suitable patch test concentration. Sensitization to palladium is almost as prevalent as sensitization to nickel. The sex distribution is different between nickel-sensitized and palladium-sensitized patients, suggesting different sources of exposure.

Palladium-based dental alloys are associated with oral disease and palladium-induced immune responses.

BACKGROUND: Palladium (Pd) and gold (Au) based dental alloys have been associated with oral disease. OBJECTIVES: This study was designed to explore possible associations between the presence of Au-based and Pd-based dental alloys, and oral lesions, systemic complaints, and specific in vivo and in vitro immune responses. METHODS: The investigated population consisted of three groups: 26 non-metal-allergic volunteers, 25 metal-allergic patients, and 20 oral disease patients. Medical histories were taken, oral examinations were carried out, and compositions of all dental alloys were determined. Then, Au and Pd patch tests and in vitro assays were performed, revealing cytokine production by peripheral blood mononuclear cells [T helper (Th)1, interferon-γ; Th2, interleukin (IL)-5 and IL-13] and lymphocyte proliferation (LTT-MELISA(®) ). RESULTS: Non-plaque-related gingivitis was associated with the presence of Pd-based dental alloys, and Pd-positive patch tests and in vitro assays. Collectively, participants with Pd-based dental alloys showed increased Pd patch test reactivity (p < 0.05) and lymphoproliferation (p < 0.05). In contrast, oral lichenoid lesions were associated with Au-based alloys (p < 0.05), but this was not reflected by Au-specific immunoreactivity. CONCLUSIONS: Oral lesions and Pd-induced immune responses are associated with the presence of dental alloys. However, most oral disease patients did not show positive patch test results or in vitro signs of specific immunoreactivity, suggesting local toxic reactions or the involvement of innate immune responses.

Transition metal sensing by Toll-like receptor-4: next to nickel, cobalt and palladium are potent human dendritic cell stimulators.

BACKGROUND: Nickel was recently identified as a potent activator of dendritic cells through ligating with human Toll-like receptor (TLR)-4. OBJECTIVES: Here, we studied an extended panel of transition metals neighbouring nickel in the periodic table of elements, for their capacity to activate human monocyte-derived dendritic cells (MoDCs). METHODS: The panel included chromium, cobalt, and palladium, all of which are known to be frequent clinical sensitizers. MoDC activation was monitored by assessment of release of the pro-inflammatory mediator interleukin (IL)-8, a major downstream result of TLR ligation. Results The data obtained in the present study show that cobalt and palladium also have potent MoDC-activating capacities, whereas copper and zinc, but not iron and chromium, have low but distinct MoDC-activating potential. Involvement of endotoxin contamination in MoDC activation was excluded by Limulus assays and consistent stimulation in the presence of polymyxin B. The critical role of TLR4 in nickel-induced, cobalt-induced and palladium-induced activation was confirmed by essentially similar stimulatory patterns obtained in an HEK293 TLR4/MD2 transfectant cell line. CONCLUSIONS: Given the adjuvant role of costimulatory danger signals, the development of contact allergies to the stimulatory metals may be facilitated by signals from direct TLR4 ligation, whereas other metal sensitizers, such as chromium, may rather depend on microbial or tissue-derived cofactors to induce clinical sensitization.

Sodium tetrachloropalladate for diagnosing palladium sensitization.

BACKGROUND: Exposure to palladium (Pd) may lead to clinical allergic reactions. With frequent nickel (Ni) exposure and cross-reactivity between Ni and Pd at the T cell recognition level, positive Pd reactions on patch testing are surprisingly uncommon. PdCl(2) is often used for epicutaneous patch testing. OBJECTIVES: To compare the sensitivity and specificity of sodium tetrachloropalladate (Na(2) PdCl(4)) and PdCl(2) for Pd patch testing in metal-allergic patients and non-allergic controls. METHODS: Twenty-six metal-allergic patients and 26 non-allergic controls were selected on the basis of detailed medical histories. Patch test results were used to determine the diagnostic performance of the two Pd salts as compared with NiSO(4). RESULTS: With three outliers in both groups, the sensitivity/specificity were calculated to be 42%/96% for PdCl(2), 65%/92% for Na(2) PdCl(4) , and 77%/92% for NiSO(4). Furthermore, of all (n = 19) Na(2) PdCl(4) reactors, 17 (89%) also showed positive reactions to NiSO(4). Conversely, of all (n = 22) NiSO(4) reactors, 17 (77%) showed concomitant positive reactions to Na(2) PdCl(4) . CONCLUSIONS: Positive test reactions to Na(2) PdCl(4) are confirmed by large-scale concordant reactions to PdCl(2) and NiSO(4). Although statistical significance was not reached, the increased sensitivity has important clinical relevance, as false-positive results are rare. Incorporation of Na(2) PdCl(4) into standard and/or dental screening patch test series is suggested.

Sodium tetrachloropalladate (Na2[PdCl4]) as an improved test salt for palladium allergy patch testing.

BACKGROUND: In the last decades, palladium is widely used in dentistry. Allergic reactions to palladium are rarely diagnosed with patch testing, even when positive results would be expected. Palladium tends to cross-react with nickel, which should give rise to more positive reactions to palladium dichloride (standard test salt). OBJECTIVE: The aim of the study was to test whether or not mono-nuclear sodium tetrachloropalladate (Na(2)[PdCl(4)]) in petrolatum is a better test salt for diagnosing palladium allergy. Positive reactions to the investigated test salt are compared not only with PdCl(2(aq.)), but also to NiSO(4(aq.)) and NiSO(4(pet.)). PATIENTS/METHODS: Concentration series of Na(2)[PdCl(4)] were carried out. 164 consecutive patients were patch tested. RESULTS: 3% of Na(2)[PdCl(4)]((pet.)) was found to be the highest non-irritative concentration. The results show (n = 164) that Na(2)[PdCl(4)] covers all reactions to PdCl(2) (1.8%) and provokes more positive reactions (14%). From the 164 patients, 18.3% reacted positively to at least 1 of the nickel salts. CONCLUSION: The sensitivity of patch testing with Na(2)[PdCl(4)] is increased compared with the PdCl(2) salt. Therefore, it can be concluded that Na(2)[PdCl(4)] is to be a better test salt for diagnosing palladium allergy with patch testing.

Micro analysis of metals in dental restorations as part of a diagnostic approach in metal allergies.

In dentistry, a variety of potentially allergenic metals are used, such as mercury, palladium, nickel, gold, chromium, cobalt and other metals. This paper describes a diagnostic approach from a dentist's point of view, which enables analysis of metals in a patient's oral cavity. If metal allergy is suspected, a micro analysis can be used to determine which metals are present in the restorations. When the exact composition of the dental materials is known, the patient can be tested in vivo (patch test) and/or in vitro (lymphocyte proliferation test) to reveal sensitization. Two patients with nickel allergy are described where removal of nickel-containing materials (bridge and orthodontic wire) resulted in the marked alleviation of symptoms and improvement of health. Finally, if allergy to specific metals has been established, the restorations containing the implicated metals should be removed to discontinue the exposure and thus facilitate the patient's health.

Influence of shape and finishing on the corrosion of palladium-based dental alloys.

PURPOSE: The purpose of this study was to evaluate the effects of the surface treatment and shape of the dental alloy on the composition of the prosthetic work and its metallic ion release in a corrosive medium after casting. MATERIALS AND METHODS: Orion Argos (Pd-Ag) and Orion Vesta (Pd-Cu) were used to cast two crowns and two disks. One of each was polished while the other was not. Two as-received alloys were also studied making a total of 5 specimens per alloy type. The specimens were submersed for 7 days in a lactic acid/sodium chloride solution (ISO standard 10271) and evaluated for surface structure characterization using SEM/EDAX. The solutions were quantitatively analysed for the presence of metal ions using ICP-MS and the results were statistically analysed with one-way ANOVA and a Tukey post-hoc test. RESULTS: Palladium is released from all specimens studied (range 0.06-7.08 µg·cm(-2)·week(-1)), with the Pd-Cu alloy releasing the highest amounts. For both types of alloys, ion release of both disk and crown pairs were statistically different from the as-received alloy except for the Pd-Ag polished crown (P>.05). For both alloy type, disk-shaped pairs and unpolished specimens released the highest amounts of Pd ions (range 0.34-7.08 µg·cm(-2)·week(-1)). Interestingly, in solutions submerged with cast alloys trace amounts of unexpected elements were measured. CONCLUSION: Shape and surface treatment influence ion release from dental alloys; polishing is a determinant factor. The release rate of cast and polished Pd alloys is between 0.06-0.69 µg·cm(-2)·week(-1), which is close to or exceeding the EU Nickel Directive 94/27/EC compensated for the molecular mass of Pd (0.4 µg·cm(-2)·week(-1)). The composition of the alloy does not represent the element release, therefore we recommend manufacturers to report element release after ISO standard corrosion tests beside the original composition.

Continuing the quest for autoimmunity due to oral metal exposure.

AIM: The role of metal exposure in the development of autoimmune disease (AID) is still controversial. Here, we studied the relationship between oral metal exposure, metal allergy and autoimmunity. METHODS: A mixed population (n = 78) of non-allergic volunteers, metal-allergic patients and patients with oral problems putatively due to metal alloys was evaluated for oral Ni, Pd, Au and Hg exposure and skin hypersensitivity. Clinical autoimmune parameters were based on medical histories; additionally, serum levels of the four most common autoantibodies were measured. RESULTS: Skin hypersensitivity, as seen mainly for Ni and/or Pd, was not positively associated with autoimmune parameters. In contrast, metal hypersensitive individuals showed an extremely low frequency of thyroid autoantibodies (3% vs 20% in non-hypersensitive controls). Next, the relation between metal exposure and autoimmunity was evaluated in individuals >35 years (n = 58), since from that age on metal exposure had plateaued and was not correlated with age. In this subgroup, oral Ni exposure was associated (p < 0.01) with self-reported AID, irrespective of autoantibody levels. These unexpected findings warrant further confirmation in a larger test group. Of note, oral Pd, Au or Hg contacts were not associated with any of the clinical or serological autoimmune phenomena tested. CONCLUSION: The results of this study support the view that development of metal contact allergies may prevent autoimmune activation, and, second, that oral exposure to Pd, Au or Hg does not facilitate the development of AID.

Nickel release from orthodontic retention wires-the action of mechanical loading and pH.

UNLABELLED: Nickel (Ni) is a potent sensitizer and may induce innate and adaptive immune responses. Ni is an important component of orthodontic appliances (8-50 wt%). Due to chemical and mechanical factors in the oral environment, Ni is released from these appliances. Retention wires are in situ for a long period of time. OBJECTIVES: To quantitatively evaluate the influence of mechanical loading and pH on the nickel release from orthodontic retention wires. METHODS: Five different types of multi-stranded wires (Original Wildcat, Noninium, Lingual retainer, Dentaflex 3-s, Dentaflex 6-s), were submersed for 24 h in either 10 ml of distilled water or lactic acid, both submitted to cyclic loading in a 3-point bending test (0×, 1000×, 10,000×). The solutions were analyzed by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS), and the data was statistically analyzed (ANOVA, p<0.05). RESULTS: Mechanical loading has a strong effect on the Ni release from orthodontic retention wires, especially in distilled water. Acidity has more impact on Ni release when compared to mechanical loading. Manganese-steel "Ni-free" wires released quantifiable amounts of Ni due to trace elements of Ni within the wire. SIGNIFICANCE: All investigated wires release considerable amounts of Ni to which exposure may have biological implications.