Cobalt chloride – metal found in medical products; hair dye; antiperspirant; metal-plated objects such as snaps, buttons or tools; and in cobalt blue pigment
Colophony (Rosin) – rosin, sap or sawdust typically from spruce or fir trees
Formaldehyde – preservative with multiple uses, e.g., in paper products, paints, medications, household cleaners, cosmetic products, and fabric finishes. Often released into products by the use of formaldehyde releasers such as imidazolidinyl urea, diazolidinyl urea, Quaternium-15, DMDM Hydantoin, and 2-bromo-2-nitropropane-1,3-diol. Fragrance mix – group of the eight most common fragrance allergens found in foods, cosmetic products, insecticides, antiseptics, soaps, perfumes, and dental products 
Gold (gold sodium thiosulfate) – precious metal and compound often found in jewelry and dental materials
Isothiazolinones – preservatives used in many personal care, household, and commercial products. Mercaptobenzothiazole – in rubber products, notably shoes, gloves, and car tires. Neomycin – topical antibiotic common in first aid creams and ointments, cosmetics, deodorant, soap, and pet food. Found by itself, or in Neosporin or Triple Antibiotic
Nickel (nickel sulfate hexahydrate) – has been recognized as a significant cause of allergy. This metal is frequently encountered in stainless steel cookware, jewelry and clasps or buttons on clothing. Current estimates gauge are that roughly 2.5 million US adults and 250,000 children suffer from nickel allergy, which costs an estimated $5.7 billion per year for treatment of symptoms. A significant portion of nickel allergy is preventable.
Type of DI with similar dental abnormalities usually an autosomal dominant trait with variable expressivity but can be recessive if the associated osteogenesis imperfecta is of recessive type.Recent genetic studies have identified that mutations in the genes coding for the collagen type 1 proteins, COL1A1 and COL1A2, are associated with this type of DI.Not all individuals with OI have dentinogenesis imperfecta, and the prevalence of DI varies depending on the sub-type of OI:

Higher prevalence of DI among individuals with OI type III and IV at 43-82% and 37-100%, respectively
Lower prevalence of DI among individuals with OI type I at 8-40%
No data available for other OI sub-types

Type II
DI not associated with OI. Occurs in people without other inherited disorders (i.e. Osteogenesis imperfecta). It is an autosomal dominant trait. A few families with type II have progressive hearing loss in addition to dental abnormalities. Also called hereditary opalescent dentin. Type III
Brandywine isolate. This type is rare with occurrences only in the secluded populations in Maryland, USA. Similar to DI type II, this type is also not associated with OI. Its predominant characteristic is bell-shaped crowns, especially in the permanent dentition. Unlike Types I and II, it involves teeth with shell-like appearance and multiple pulp exposures.Mutations in the gene coding for the dentine sialophosphoprotein (DSPP) are associated with DI type II and III. DSPP is a polypeptide which gives rise to 3 proteins; dentine sialoprotein (DSP), dentine glycoprotein (DGP), and dentine phosphoprotein (DPP).