With regard to dental fillings, there have been advancements in materials and technology recently. During the time of Rav Shlomo Zalman, fillings were made of silver, or amalgam in dental terms, and gold. Nowadays (since thirty years ago) there are white fillings, or composites, instead of the earlier types of dental implants. At first glance, it would appear that composite fillings would have the status of plastic, as they are made out of inorganic polymers, much like plastic. However, a closer look may allow us to establish composites as halachically equivalent to glass, rather than plastic. Composites, in general terms, can be divided into two parts: the matrix and the filler. The matrix is the frame which hardens and bonds to the tooth structure. The matrix is filled up with a filler material, and the filler particles bind to the matrix. The matrix is made out of polymers, or plastic, but the fillers are glass-like materials, like leucite, quartz, or even actual glass. The majority of the composite is the filler, and the lesser portion is the matrix. Perhaps one can say based on the principle of Rov, majority, that the classification and categorization of composite will follow glass, as the glassy filler is the majority of the implant. If this is the case, white fillings will not pose any problems for Sepharadim, but Ashkenazim will have to utilize the same leniencies explained in Parts I-III of this series. However, perhaps we cannot follow Rov, because the matrix could be a Ma’amid, something that is essential to the whole; without it, the material would fall apart and fail to function properly, because the matrix is what binds the filling to the tooth. A Ma’amid is not halachically considered null and void even when it is a minority component, but rather is considered the main part of the item. Therefore, perhaps the implant must be viewed as a plastic, which, as explained previously, is subject to a major debate among the Poskim, and even the Sephardim would need to rely on the leniencies mentioned earlier by our discussion of plastic dentures.
However, there is one relatively new filling material whose matrix component is made out of glass, namely silicone dioxide. This material may be gaining popularity and is currently being used in many dental offices. For Sepharadim, this material would be beneficial, but for the Ashkenazim the same leniencies as before would need to be utilized.
In conclusion, the new materials used in dental crowns, dentures, and dental fillings may help alleviate the concerns of Beli’ot (absorption of Chametz into the dental work) in the mouth due to the fact that the new fillings and the new crowns may be viewed as glass. In that case, Sephardic Jews may be able to avoid Beli’ot of crowns and fillings by always making sure that the fillings and crowns used are all ceramic and the fillings are the composite fillings that are all glass based. For the Ashkenazim, perhaps they can be lenient and follow the Mishnah Berurah that BeDi’eved (or in a She’at HaDeChak, such as our situation of dental implants), if Rov Tashmisho (the majority of its usage) is with cold food and drink, then one does not have to kasher glass, coupled with the opinion of the Taz, who holds that the BeDi’eved of the Darchei Moshe means that one does not have to kasher glass. In addition, since this case is a She’at HaDechak, maybe Ashkenazim can rely on the Peri Chadash, who holds like the Shulchan Aruch, against the Rama, that glass does not absorb. At the very least, it could be another Senif for the Ashkenazim to be lenient, as perhaps these materials are glass and are not able to absorb any taste.
Both Ashkenazim and Sepharadim who are not diligent to make sure that everything permanent in their mouth is glass, as well as for people who already have fillings and crowns from previous generations of dentistry, would still need to rely on the approach of Rav Shlomo Zalman that one should not eat hot food within twenty-four hours of Pesach. Furthermore, if one must eat a Davar Charif on Pesach, then he or she would need to rely on Rav Shlomo Zalman’s novel idea that saliva and heat corrode the Beli’ot of Chameitz completely. Additionally, we should kasher our mouths the way that Rav Shlomo Zalman suggested: one should drink water heated to the maximum temperature that one can handle. By the Zechut of following these halachot diligently, may we see the fulfillment of our fervent hope for the Ge’ulah, expressed in the ultimate line of the Haggadah: LeShanah HaBa’ah BeYerushalayim HaBenuyah.