Jon Bon Jovi admits he has seen better days. But after a quarter century of non-stop hits, stadium tours and large-haired sexiness, what do you do for an encore? On the eve of his Auckland show, Polly Vernon caught up with the 48-year-old rock god in Brazil.

Jon Bon Jovi - long serving rock god, philanthropist, ageing-yet-viable pin-up - has truly stupendous teeth. They are white and they are straight and there are lots of them. They are semi-threatening when bared, but blindingly, staggeringly glamorous otherwise. They work brilliantly onstage. Bon Jovi deploys them (quite knowingly, I am sure) to amazing effect. He'll unleash them on you with no warning; smiling suddenly and broadly (maybe with irony, maybe flirtatiously, maybe just because he's tickled by something), and you'll find yourself mesmerised by the beauty of the man's gnashers. He's got superstar teeth, no question.

This is lucky, because from where I'm standing, the rest of him looks a bit like a crumpled middle-aged man in a lumberjack shirt.

I meet him in the conference room of an expensive chain hotel located in the midst of Sao Paulo's endless urban sprawl. It's early October, the night before Bon Jovi - the band Jon named, fronts and owns in any meaningful sense - will perform a sell-out stadium gig for 60,000 Brazilian fans. I have been ushered into the long, anonymous, overly air-conditioned room, past swathes of security guards dressed in seven shades of stern.

It's all quite portentous. I'd expected to be confronted by barely suppressed tension and leather-clad, pouty-mouthed, large-haired sexiness. But once inside, I see nothing but a nondescript man in a chair. It's not until the man tells the stern security guards that they should leave ("I'll be more comfortable without you"), turns around and unleashes the full power of his teeth upon me, that I recognise him as Jon Bon Jovi at all.

Bon Jovi are two weeks into the South American leg of a lengthy world tour. The Circle tour (named after the band's 2009 album) began in May of last year and has rolled on ever since, through North America and into Europe, back to North America again before this South American section (the band's first visit in 15 years).

It's scheduled to carry on long into next year, via Japan, New Zealand, Australia and back to North America with possibly a few more dates in Europe. So Bon Jovi is ragged with travelling. He's only just flown into Sao Paulo and doesn't make much sense for the first few minutes of our interview. His sentences start and trail off into nonsense, and he blames this on me.

"But no, no! Let's start over! I don't want to do it like this! Go back to the start, go back to where you say: How are you doing? And I'll say: I'm tired! That's what I'll say."

He was born John Francis Bongiovi in 1962 in Perth Amboy, New Jersey to a Marine-turned-hairdresser father and a Marine-turned-florist mother. His childhood was all very blue-collar and secure, and Bongiovi grew up safe in the conviction that he would inevitably be a rock god.

You never thought it wouldn't happen to you?

"Never for a minute did I doubt that it wasn't going to."

Why were you so sure?

"Naivete of youth."

As a teenager he sang and played in local bands and revelled in his physical proximity to Bruce Springsteen and singer-songwriter Southside Johnny.

"These guys were 25 minutes away and doing it, literally doing it. You know, they were sitting, literally, on that boardwalk in Ashbridge Park. There wasn't a day gone by that you didn't stumble into one of them."

At 21 he formed Bon Jovi with guitarist Richie Sambora, keyboard player David Bryan and drummer Tico Torres. Three years later, in 1986, their third album, Slippery When Wet, featuring career-defining single Livin' on a Prayer, turned Jon Bon Jovi into a superstar.

In the intervening 24 years the group has never faltered, never split up, never stopped writing, recording or touring.

They've released 11 studio albums together, albums which have sold somewhere in the region of 120 million copies worldwide. Bon Jovi have performed more than 2700 concerts in 50-something countries for some 35 million fans. They were the best-selling touring act of 2008. Now, only U2 and the Rolling Stones are capable of outselling Bon Jovi on tour.

The group's leader is giving this interview to promote a forthcoming Greatest Hits album, the second the band have produced.

Why now? Is it a creative pause, an opportunity for reflection, a celebration of the past 25 years?

"A commitment," he says dryly. "Nothing more than a commitment."

Two-and-a-half years ago he cut a deal with Lucian Grainge, the chief executive of Universal, his record company. Grainge allowed him to make a somewhat self-indulgent country album in Nashville.

"I rang him and said 'I want to do this'. There was silence on the phone, and then 'I guess at this point you can do whatever you please, but ... would you do me a favour when you lose all my money and give me a Greatest Hits?' I said, 'You got it - that's a deal'."

The country album, 2007's Lost Highway, ended up selling more than either Bon Jovi or Grainge had anticipated, but still, Bon Jovi had agreed to the Greatest Hits album, released this month.

Is commercial success important to Bon Jovi?

"No. But it allows you to continue to do it. And it also becomes a platform for so many other things that have become a part of my life. I don't know that I would have had the same entree to presidential politics had I not been as successful in my day job."

Was I surprised to learn the singer is a political activist? Kind of.

Deep-held political conviction and unapologetic party bias do seem to contrast with his inoffensive, edge-free variant of rock.

But he is deeply politicised, a card-carrying Democrat. In 2004 he toured extensively on behalf of John Kerry, performing duets with Richie Sambora at rallies. In 2009 he campaigned hard on behalf of Obama, holding a fundraiser for the then-presidential candidate at his own home. After Obama was elected, Jon Bon Jovi performed live at his inauguration ceremony.

He says his politicisation began in his teens.

"You were born in the Kennedy era and you came of age and Uncle Ronnie's telling us that everything was going to be okay, because Gorbachev tore down those walls... It was a romantic time, politically."

You believed in it? "I believed in the 1980s, sure!"

But what about Uncle Ronnie, Ronald Reagan?

"I voted for him, 1980. First time I could vote."

You voted for Reagan?

"Sure, I was 18 and how could you not be impressed?"

But you're a raging Democrat.

"I woke up. I got educated. Got out of school, started to see the world, started looking at things a little differently. And with time, and experience, comes ..." he falters, "More experience. I almost dared to say 'wisdom'."

You don't think you're wise?

"Oh. I don't know about that."

Now, as a consequence of the work he has done on the US President's behalf, he is said to be friends with the Obamas.

"Friends? No. I don't want to say I'm friends with 'em. That's too strong a word. I have met a lot of them."

Bon Jovi denies, repeatedly, that he has any political ambition. He's said in the past that he wouldn't want political office, because sooner or later you have to give the private jet and the apartment back. If you're a rock star, you're allowed to keep them. Now he says: "It's a thankless job. It's a really shitty job. And I tip my hat to the pure conviction of the people who do it. Some of them do have such purity of conviction."

But you seem to have purity of conviction, I say. You believe in the Democratic Party. You believe in social justice. Four years ago you launched the Jon Bon Jovi Soul Foundation, a non-profit organisation dedicated to tackling poverty in the US, and you have spent significant time making sure it ticked over ever since.

Does he feel obliged to do good work, as a rich and privileged man?

"I don't know if I'm fully committed to that," he says (showing how versed he is in the semantics of politics). "But I think that when you come to terms with who you are, regardless of your economic status, taking the time to help others in whatever way moves you can really be fulfilling for the soul."

Is he constantly looking for ways to fulfil his soul?

"Not necessarily. I think I'm doing a pretty good job of it."

Bon Jovi would make a natural politician - not least because he is a very bossy man. He is certainly the boss of Bon Jovi the band. His bandmates describe him in those terms in the course of interviews for the 2009 film When We Were Beautiful, a documentary that follows the group as they tour Lost Highway. Jon Bon Jovi described himself as the "CEO of this major corporation".

You make it happen, don't you? I say. You make the phone calls and compile the set lists and break the balls.

"Oh yeah. Oh yeah."

Does it grate on him that the others are less involved, less responsible, more passive? According to several sequences in When We Were Beautiful, they spend significant time lounging on yachts and rolling round golf courses. Isn't that annoying?

"No. And you know why? There's a number of reasons why. When you look up at the marquee: whose name is on it? And I was willing to accept that reward, with that payment.

"I was that kid with the report card that said 'doesn't play well with others'." He laughs. "I couldn't be in a situation where someone else was controlling my destiny. I'm probably not really a candidate to be in the army. Or working at the factory. I have to sink or swim on my own merits."

I wonder if he's team leader of his domestic situation, too. Bon Jovi has been married to his wife Dorothea since 1989.They met while they were still at school. They live in Manhattan with their four children: Stephanie Rose, 17, Jesse James, 15, Jacob, 8, and Romeo, 6. Bon Jovi wears silver dog tag-like pendants inscribed with their names on a chain around his neck. So is he the boss at home?

"I am wise enough to realise that women are much smarter than any man, and that women control the world."

You really believe that?

"I know that."

He's made references to marital meanderings in the past. He has said: "I've not been a saint. I have had my lapses." Now, when I ask him what sort of a husband he is, he says, "One that runs away a lot more often than not. Ha ha! Not the perfect one, trust me. Not on any level."

We talk about fame, about the pitfalls of celebrity. He tells me he was always careful to avoid "getting sucked into that LA scene, the Hollywood scene, from supermodel to actress to get my photograph taken. It was a shallow pool to swim in. I am not a fame junkie - I have never been a fame junkie."

And we talk about ageing. Bon Jovi is 48 years old. As a young man, he was absurdly good looking. How aware was he of that then?

"In as much as you would say I was cute. Uh-huh."

You still are cute, I say - and I mean it. As crumpled as Bon Jovi looked when I first met him, through the course of our interview he has woken up and sort of re-engaged with his own face. He still has significant cheekbones, handsome features, those teeth...

He giggles. "Well, I think your eyesight's going."

Did you enjoy being a pin-up in your youth? I ask.

"Now I can say 'thank you - that's a wonderful compliment'. At 26, 27, I was pissed off about it. Because I thought 'Goddammit! I'm working so hard, I'm trying so hard, I'm trying to do what I want to do, while I'm trying to please you."

And all we could talk about was how handsome you were?


Are you a vain man?

"I'm vain in as much as I think I'm terribly out of shape right now. If you want to be perfectly honest, I'm [5kg]overweight, I'm drinking too much and I'm bored to tears."

You look okay, I say again.

"You're very kind. Okay, I'm not the fat Elvis. At 48, I look okay. But you know, I'm coming to real good terms with getting older."

What are the advantages of age?

"You become that thing that you looked at your parents and the older people in your life, and said 'no, I don't want to live to be that old'. But it's actually much better than dying. And there are too many people that are my age that are dying. That would be awful. You can see why people get fat, grow old, give up. Because every day is: get up, do the same mundane shit. When you don't know anything more and you're not willing to open up your eyes and take a step in another direction, that treadmill would make any young man old."

It sounds like he's quoting his lyrics.

Twenty-four hours later, Jon Bon Jovi stands on stage at the Morumbi Stadium in Sao Paulo and delivers three and a quarter hours of roaring, supremely commercial rock for a crowd of rapturous, teary Brazilians.

All evidence of the crumpled middle-aged man has left him. He looks truly rock god now: all leather and upper-arm definition and bouffant hair, though of course it's his teeth that steal the show. They are more compelling even than his rock-star strut or the cheap, vast rhetoric of his lyrics (sample: "With an iron-clad fist, I wake up and French kiss the morning." Can one French kiss with a fist, iron-clad or otherwise?) It's a deft and practised performance, and never mind that the band didn't soundcheck (they don't these days) or that the set list wasn't decided upon until the very last minute (Jon Bon Jovi had asked the Brazilian press for suggestions during the conference held shortly before the opening number was performed).

He attempts to finish with Livin' on a Prayer as the encore, but the crowd demands more, so he throws in Bed of Roses for good measure. He makes great use of strategic pauses, dewy eyed, head-noddy moments in which he surveys the crowd with a sort of entitled awe and exchanges meaningful looks with Sambora, Bryan and Tico.

But I don't really buy it. There is nothing technically wrong with Bon Jovi's show, nothing at all. It doesn't flag, it's utterly slick, no one falters. And I'd forgotten how much I like a lot of these songs. Yet I get a sense that Jon Bon Jovi is going through the motions. He emanated much more conviction, sincerity and engagement when we talked politics the evening before. I think politics is where his true passion lies these days. I think he might even be a little wasted on the rock. Furthermore, if it ever came to it, I'm pretty sure I'd vote Jon Bon Jovi.

Bon Jovi play Auckland's Vector Arena on December 4. The band's Greatest Hits album is on sale now.