(Reuters Health) - Patients undergoing major cancer surgery might reduce their risk of complications by seeing a dentist beforehand, a study from Japan suggests.

Patients who visited a dentist were slightly less likely to have post-surgery pneumonia or die within 30 days of surgery, the study authors found.

“Oral care is one option for preventing postoperative pneumonia as postoperative pneumonia can be precipitated by aspiration of oral and pharyngeal secretions,” said lead researcher Miho Ishimaru of the University of Tokyo.

Respiratory germs can grow in biofilms and microorganisms on the surface of the teeth and tongue. Dental care has been found to help reduce pneumonia for patients on ventilators, the researchers wrote in the British Journal of Surgery.

“Several studies have suggested that preoperative oral care might be associated with a decrease in postoperative pneumonia, but these were limited by small sample sizes,” Ishimaru told Reuters Health by email.

Ishimaru and colleagues analyzed national data on patients who underwent surgery for cancers of the head, neck, esophagus, stomach, lung, liver or colon and rectum at 1,600 hospitals between 2012-2015.

Of the 509,000 patients who had cancer surgery, about 81,600 received preoperative oral care.

About 15,700 patients developed postoperative pneumonia and 1,700 died within 30 days of surgery. Ultimately, preoperative oral care was linked with a half-a-percentage-point decrease in the risk of postoperative pneumonia and an eighth-of-a-percentage-point decrease in all-cause mortality.

“I think these findings are interesting. However, while statistically significant, one has to wonder how clinically relevant they are because the differences are - on an absolute scale - quite small,” said Dr. Quoc-Dien Trinh, co-director of the Dana-Farber and Brigham and Women’s Prostate Cancer Program in Boston. Trinh, who wasn’t involved with this study, has researched pneumonia after major cancer surgery.

“The authors correctly point out that unmeasured confounders may have influenced their results,” Trinh told Reuters Health by email. “For example, perhaps the surgeons/hospitals who refer patients to preoperative dental care are ‘better’ and are less likely to develop pneumonia.”

A randomized controlled trial could help researchers better understand the connections, Trinh said. Separating different types of cancers could illuminate differences, as could studying different countries.

In the U.S., “head and neck cancers almost always have a mandatory dental exam if there is any question because they get radiation often as part of their treatment,” said Dr. Sherry Wren of Stanford University and Palo Alto Veterans Hospital in California. Wren, who wasn’t involved with this study, has researched the long-term results of a postoperative pneumonia prevention program.

Wren and colleagues found that pneumonia cases at the Veterans Affairs hospital dropped 44 percent in the four years after they implemented the prevention program. The strategies include training with nursing staff about pneumonia prevention, coughing and deep-breathing exercises, twice-daily oral hygiene, head-of-bed elevation and sitting up for all meals, and good pain control.

“I think clinicians should at least consider preoperative dental care prior to a complex cancer surgery, especially given the established relationship between postoperative pneumonia and postoperative mortality,” Trinh said.

SOURCE: bit.ly/2Ns0a0H British Journal of Surgery, online August 8, 2018.