Allan Salangsang scored 16 points, pulled down nine rebounds and had a steal as he combined with Nino Gelig in that explosive Hapee windup to catch Montana at the helm at 3-1 (win-loss) mark.
The Water Force fell to 2-2.
Viva was still up, 59-57, with 6:35 remaining in the final quarter when Salangsang and Gelig took over for the Teeth Sparklers, who seized a 68-59 lead with a minute remaining.
A triple by Warren Ybañez broke Vivas silence while Jason Misolas fired another to trim the gap, 65-69, with 44 seconds to go.
But that was the closest Viva could get as the Teeth Sparklers defense held them scoreless down the stretch. Salangsang went three-of-four from the freethrow line while Eugene Tan struck a buzzer-beating basket to seal the final tally.
Earlier, Montana pounced on an erratic John-O side to pound out a 72-59 victory and assure itself of at least a playoff for the second finals slot.
Jon Dan Salvador topped with 15 points, six rebounds and three blocks as the Jewellers annexed their third semifinal win in four outings.
John-O tagged as one of the strong title contenders before the conference started, suffered its fourth consecutive semifinal setback and could only hope for a slot in the battle for third place.
John-O sank 20 of 71 attempts from the field or only 28 percentmainly because of the pale performance from Ranidel de Ocampo and Celino Cruz.