Abano Healthcare is alleging former director and disaffected shareholder Peter Hutson and another shareholder James Reeves are conducting a misleading communications campaign.
In a letter to shareholders, the company said Mr Hutson and Mr Reeves were also conducting a personal attack on members of Abano's board, including chairman Trevor Janes.
Mr Hutson and Mr Reeves, who own 18.5 percent of Abano between them, have requisitioned a special meeting to vote on removing Mr Janes.
Abano said the meeting would be held soon, and its board remained unanimous in supporting Mr Janes.
Managing director Alan Clarke said the company had written to shareholders about the matter because it felt it needed to add balance to public comments on the issue.
"The campaign that really started last year was based on analysis that they had carried out around the performance and operations of the business, primarily our dental business, where they had laid claims to underperformance, poor management and, basically, that the Abano model was flawed and that other companies in the sector were performing far better," Mr Clarke said.
"There are different models involved in dentistry, and it's very important to understand the differences between the companies. We have a high-growth model. We see an enormous market opportunity but we are also very cognisant of the fact that assimilating health professionals into a corporate structure with a common brand requires great care, intelligence and careful investment."
Abano believed that investment in winning hearts and minds, and getting people to understand what it was trying to achieve and build, was in the long-term interests of its shareholders."
The company's share price had firmed during the process, despite ongoing criticism of the performance of the company by Mr Hutson and Mr Reeves, Mr Clarke said.
Neither Mr Hutson nor Mr Reeves were available to comment.