The Quebec Liberals on Sunday dusted off an old promise to expand free dental coverage should they be re-elected come Oct. 1 — this time to include children up to age 16 as well as low-income seniors.

Liberal Leader Philippe Couillard made the pledge while campaigning on Day 4 in the Saguenay—Lac-Saint Jean region, reviving a promise made in part under former leader Jean Charest to beef up coverage for teens.

About 620,000 Quebecers currently qualify for free basic coverage, including children up to age 10 and people on social assistance.

With the proposed changes, nearly 1.2 million more Quebecers would qualify under the plan, Couillard said. That includes seniors 65 and older who meet the financial threshold — single seniors earning less than $18,096 a year or couples getting less than $24,000.

"Dental health is also a major factor (for seniors) because it's very painful," Couillard said from the region north of Quebec City, which includes his home riding of Roberval.

"At some point, seniors stop eating and that's a major health issue if you're already frail, very old, and you stop eating because you just can't do it."

The new measure would cost the government $150 million, but Couillard said the province's improved financial situation makes it possible.

The left-leaning Quebec solidaire party has advocated for universal dental care, but Couillard dismissed that as far too costly.

The Liberal announcement comes amid an ongoing conflict with the province's dentists, who threatened to quit the public system over a contract dispute before the province intervened by decree to block the move.

"It's not to punish dentists, it's to protect Quebecers," Couillard said Sunday of the decree, adding he was certain negotiations with the association representing 4,300 members, who have been without a contract since 2015, would be fruitful in the end.

Also on Sunday, Coalition Avenir Quebec vowed to harmonize school taxes to 10 cents per $100 of evaluation over four years if they take power.

Coalition Leader Francois Legault said school taxes have gone up 25 per cent in the past four years alone and because of variable tax rates, homeowners pay vastly different rates according to the school board to which they pay taxes.

Campaigning on Montreal's North Shore on Sunday, Legault used the example of two homes behind him at a stop in Terrebonne, where one neighbour paid $269 to one board while another next door paid $690.

Legault defended harmonizing as opposed to abolishing school taxes as the Coalition had previously championed, noting much had changed since the previous campaign.

Harmonizing the taxes would cost $700 million over that same time frame, Legault said, assuring all of his party's promises will be costed.

"We will table our financial forecast and you'll see that it is balanced," Legault said. "I have someone with me that's keeping track of that — don't worry, we have a strong management team."

For its part, Quebec solidaire called for free education, from daycare right through to university.

Party spokespeople Gabriel Nadeau-Dubois and Manon Masse made the announcement in Sherbrooke, stating the promise would cost the province $2.45 billion to implement.

The Parti Quebecois didn't make any announcements on Sunday, with Leader Jean-Francois Lisee declining to criticize his rivals when pressed by journalists.

Lisee said he didn't want to repeat mistakes from the 2014 campaign, which saw the PQ under former leader Pauline Marois go from front-runner to second place.

Lisee said he has a small book he carries with him with lessons learned from the previous campaign, but he declined to detail those problems on Sunday.

"It's a small book, but there's a lot of things in it," Lisee said, as he and deputy leader Veronique Hivon were formally named PQ candidates in their respective ridings of Rosemont and Joliette, where they were uncontested.

— with files from Patrice Bergeron in Saguenay and Caroline Plante in Terrebonne, Que.