Seamer Michael Hogan claimed his 100th wicket of the season as Glamorgan restricted Gloucestershire on the opening day of their LV= County Championship match at the SWALEC Stadium.
Gloucestershire had reached 228 for eight in their first innings from 82.1 overs when bad light ended play at 5:30pm.
It was Glamorgan's first game since they were defeated by Nottinghamshire in Saturday's Yorkshire Bank 40 final at Lord's.
The Welsh county made three changes to their side which drew last week with Essex at Chelmsford with Jim Allenby, Graham Wagg and David Lloyd replacing Will Bragg, Andrew Salter and John Glover.
Hogan struck at the start of the seventh over to reach the landmark by bowling opener Gareth Roderick, after Glamorgan won the toss and put Gloucestershire in to bat in helpful bowling conditions.
Hogan now has 64 wickets in the championship, 28 in the YB40 and eight in the Friends Life t20 for the 2013 campaign.
But from 12 for one Gloucestershire recovered either side of lunch with Dent reaching his half-century from 77 balls shortly before the interval.
By lunch the visitors looked quite well set but in the afternoon they struggled going from 90 for one to 176 for six.
With the total on 90 Allenby bowled Alex Gidman and Dent, who had looked well set for a century, edged slow left-armer Dean Cosker into the Australian's hands at slip.
Cosker struck again next ball to have Iain Cockbain also caught at slip by Allenby from a turning delivery.
With the total on 156 Gloucestershire lost Hamish Marshall, who is 10 short of reaching 1,000 runs for the season, as he edged Wagg behind.
In the penultimate over before tea Cameron Herring was trapped lbw by Hogan and Ruaidhri Smith then struck twice in the evening session, bowling Benny Howell and then having Gidman caught behind.