[Tex/LaTex] Theorem without number using mdframed

mdframedtheorems

I am working on a text that involves some theorems and I am using mdframed I want a theorem whit just the optional title 

\begin{teorema}[title desired]
 Some text
\end{teorema}

so far I've seen two options but no one does what I want

the first method I used is the next

\documentclass[12pt]{book}
\usepackage[framemethod=TikZ]{mdframed}

\mdtheorem[frametitlealignment=\center, 
frametitlerule=false,
linecolor=FireBrick,
linewidth=1pt,
innerlinewidth=1pt,
frametitlerulewidth=5pt, 
frametitlebackgroundcolor=DarkSalmon,
backgroundcolor=gray!10,
userdefinedwidth=12cm,
align=center,
frametitle={},
theoremseparator={},
]{teorema}{}

\begin{document}

\begin{teorema*}
Some text
\end{teorema*}

\end{document}

with this one there is no frame title and no number but the theorem separator appears and I don't want that and the second method is the next

\documentclass[12pt]{book}
\usepackage[framemethod=TikZ]{mdframed}

\mdtheorem[frametitlealignment=\center, 
frametitlerule=false,
linecolor=FireBrick,
linewidth=1pt,
innerlinewidth=1pt,
frametitlerulewidth=5pt, 
frametitlebackgroundcolor=DarkSalmon,
backgroundcolor=gray!10,
userdefinedwidth=12cm,
align=center,
frametitle={},
theoremseparator={},
]{teorema}{}

\begin{document}

\begin{teorema}
Some text
\end{teorema}

\end{document}

with this one I don't get the frame title and the theorem separator but the number appears. How can I solve this problem

Best Answer

The easiest way to remove the number is to remove the number:

\documentclass{article}
\newtheorem{theorem}{Theorem:}
\renewcommand{\thetheorem}{\relax}

\begin{document}

    \begin{theorem}[no number]
     Some text
    \end{theorem}

\end{document}

If you want to turn it off and on again:

\documentclass{article}
\newtheorem{theorem}{Theorem:}
\let\normaltheorem=\thetheorem

\begin{document}

    \let\thetheorem=\relax
    \begin{theorem}[no number]
     Some text
    \end{theorem}
    \let\thetheorem=\normaltheorem
    \addtocounter{theorem}{-1}% I assume you don't want a missing number

    \begin{theorem}[with number]
     Some text
    \end{theorem}

\end{document}

with and without number

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