From an anatomical standpoint, it is important for the clinician to clearly understand the anatomical landmarks of bone and the innervation points that are associated with them. This is especially true for more advanced grafting cases and sites. There are plenty of continuing education venues available....
Ideal bone support affects the health of dental implants in many ways. Not only is bone around a dental implant needed to support the implant, but the surrounding bone also supports the soft tissue, which in turn affects hygiene, aesthetics, and the overall health of the implant itself. Bone grafting, to support deficient bone for implant placement and health, is often a concurrent discipline of dentistry that goes hand in hand with implant treatment. This month’s Implants Today has an outstanding article by Dentistry Today’s implant advisory board member Dr. Randy Resnik on bone grafting for oral implantology. This article highlights the main concepts and materials related to grafting bone.
In order to be able to graft bone for implant health and support, various aspects of grafting science and adjunctive principles need to be understood.
It is important to understand bone biology, and the basic cellular process that occurs in bone. For example, through understanding the role of osteoblasts, osteoclasts, and osteocytes, the clinician can better visualize what is happening when a graft material is placed into a site and remodels into mature bone. Understanding bone biology also helps to gleam insight into how newer grafting concepts such as recombinant version of bone morphogenetic protein-2 (rhBMP-2) works. Dr. Resnik talks about this in his article and shows examples.
It is important to understand bone anatomy. Through understanding the different Misch division classifications of bone—D1, D2, D3, D4—including their respective hardness and where they are found in the mouth, many clinical decisions can be made. For instance, the posterior maxilla usually has soft D4 bone, where longer healing times and less osteotomy preparation is needed. From an anatomical standpoint, it is important for the clinician to clearly understand the anatomical landmarks of bone and the innervation points that are associated with them. This is especially true for more advanced grafting cases and sites. There are plenty of continuing education venues available covering these topics, including cadaver and grafting courses offered by the implant organizations, such as the American Academy of Implant Dentistry.
It is important to understand the available grafting materials and properties of each. There are various choices of grafting materials available and Dr. Resnik’s article spells out the choices of autografts and allografts very clearly. Every graft material choice is osteconductive, meaning it is a basic scaffold allowing bone cells to take over and grow bone. Allografts (donor bone) can be osteoinductive, meaning these help induce bone growth from surrounding bone. Only an autograft, a patient’s own bone, has osteogenic properties, meaning it can initiate bone growth on its own. Through understanding these principles, a clinician can choose the appropriate material, depending on the size of the defect. The handling properties of the various available materials have to also be taken into consideration. Whether the material is a particulate material or a putty creates a different clinical treatment for a grafting site. The handling properties of a material can also influence whether or not a membrane needs to be used. The purpose of a membrane is to exclude soft tissue and contain the graft material. For example, often times with some grafting putties, because of their rigidity and containment, a membrane is not necessary.
It is important to understand how to handle the soft tissue around a graft site and suturing techniques. An important aspect of bone grafting is getting closure of soft tissue around a graft site, and obtaining good keratinized tissue in the area. Even though bone grafting is about hard tissue, the surrounding soft tissue plays a large part of the graft’s success. Flap design, suturing techniques, and even soft tissue augmentation comes into play when grafting bone. It is beneficial for a clinician to be adept at manipulation of the soft tissue and suturing procedures, especially in more advanced bone grafting cases.
It is important for a clinician to utilize information from CBCT scanning technology. For many reasons, a CBCT comes into the picture when a bone graft is being treatment planned and done. From a medical/legal standpoint, a preoperative CBCT before grafting is done can offer ideal protection; with respect to visualizing variant anatomy, relating the graft to the prosthetic end point, and helping visualize the proposed implant position. While this may not be needed for a 5-wall extraction site defect, it becomes more important as increased walls of bone are missing. A postoperative CBCT scan done after the graft has healed is also important before placing implants so that the clinician can see the volume of bone generated, the quality of bone generated, and the final planned implant position.
This important area of implant dentistry, bone grafting, requires many considerations for success. While at first glance it appears to be a hard-tissue-focused discipline, for true success, a clinician needs to have an understanding of the following: the biology of bone; bone anatomy itself and the surrounding anatomy being grafted; the various materials that are available and properties of them; the soft tissue around the graft and how to handle the tissue and suture it; and be able to utilize CBCT scan information to tie it all together. Once these principles are combined, bone grafting becomes a real science and art for treatment success.
Last modified on Wednesday, 18 November 2015 14:13
The chemical process during the manufacture of the caramel coloring used in soft drinks such as cola produces a carcinogen that could be raising the risk of cancer to above the accepted threshold of one extra case in every 100,000 people consuming the drinks, suggests an analysis.
The coloring is not necessary for the production of soft drinks and is included purely for esthetics.
Matching laboratory tests conducted by Consumer Reports on 11 different soft drinks, first reported last year, with an analysis of average consumption by Americans, the researchers found that one can a day could be enough to expose them to potentially cancer-causing levels of the chemical known as 4-MEI (short for 4-methylimidazole).
The potential carcinogen is formed during the manufacture of the familiar caramel color that is added to many widely-consumed beverages.
A law in California requires that drinks must carry warning labels if they contain enough 4-MEI to pose an excesscancer risk of more than 1 case in every 100,000 exposed people (an exposure of 29 mcg of 4-MEI every day).
Testing on 110 samples of soda brands carried out by the Consumer Reports researchers, led by a team at the Johns Hopkins Center for a Livable Future in Baltimore, MD, found that drinks contained levels ranging from 9.5 mcg per liter (mcg/L) to 963 mcg/L.
Concentrations of 4-MEI varied considerably by soda brand and state of purchase, the researchers concluded, "but were generally consistent across lots of the same beverage purchased in the same state/area."
They add: "Routine consumption of certain beverages can result in 4-MEI exposures greater than 29 mcg a day" - the level that triggers a new case of cancer in every 100,000 people consuming the drink, toxicity that was established by previous studies in mice and rats conducted by the US National Toxicology Program.
The researchers say there was not enough data from individual drinks samples to recommend one brand over another in terms of carcinogen exposure, but suggest: "State regulatory standards appear to have been effective in reducing exposure to carcinogens in some beverages."
Lead author of the study Tyler Smith, a program officer with the Johns Hopkins Center for a Livable Future, says 4-MEI levels can "vary substantially across samples, even for the same type of beverage." Smith explains:
"For example, for diet colas, certain samples had higher or more variable levels of the compound, while other samples had very low concentrations."
In the lab sampling, Malta Goya had the highest 4-MEI concentration while Coca-Cola produced the lowest value.
California listed 4-MEI as a carcinogen in 2011, under the Safe Drinking Water and Toxic Enforcement Act of 1986 - better known as Proposition 65. The authors say their results suggest that "federal regulation of 4-MEI in caramel color may be appropriate."
Variety of cola-drinking habits
To estimate consumers' exposure to the potential carcinogen, the researchers took the laboratory readings and analyzed soft drink consumption using data from the National Health and Nutrition Examination Survey (NHANES).
The data from this survey covered overall health and nutrition patterns between 2003 and 2010 for tens of thousands of US children and adults aged between 3 and 70 years.
The authors say: "We analyzed consumption of all sodas, and further categorized soda into five mutually exclusive categories: 1) cola, 2) diet-cola, 3) root beer, 4) pepper cola and 5) other (non-diet) cola."
They found the proportion of the population consuming each type of soft drink varied, with "colas being the most popular and root beer and pepper colas being the least popular."
Adolescents and young adults consumed the most of any soft drink compared with young children and older adults. Average consumptions of any soda were:
Between 550 and 1,070 milliliters drunk each day by 16- to 20-year-olds
Between 457 and 864 milliliters drunk each day by 45- to 64-year-olds.
Lifetime cancer risks
"This study sought to answer a critical question," says Urvashi Rangan, PhD, executive director of the food safety and sustainability center of Consumer Reports: "How much soda do American consumers drink on average?"
"This new analysis underscores our belief that people consume significant amounts of soda that unnecessarily elevate their risk of cancer over the course of a lifetime," Dr. Rangan says.
She adds: "We believe beverage makers and the government should take the steps needed to protect public health."
"California has already taken an important step by setting a threshold," Dr. Rangan says.
Keeve Nachman, PhD, is a senior author of the study and director of the food production and public health program at the Johns Hopkins Center for a Livable Future.
Also an assistant professor at the Johns Hopkins Bloomberg School of Public Health, Dr. Nachman says:
"Soft drink consumers are being exposed to an avoidable and unnecessary cancer risk from an ingredient that is being added to these beverages simply for esthetic purposes.
This unnecessary exposure poses a threat to public health and raises questions about the continued use of caramel coloring in soda."