Use the unicode non-breaking hyphen character instead of a keyboard hyphen. This will bind the text together as a single unit.

Use:
U+2011 or ‑

e.g.
1-800-555-5555
marked up as:
1‑800‑555‑5555

<p style="font:20px/24px  Arial, Helvetica, sans-serif; Margin:0 0 15px 0; color:#000000; mso-line-height-rule:exactly;" >Lorem ipsum dolor sit amet<sup style="font-size:12px; line-height:0px; vertical-align:8px;">®</sup>, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam</p>

• Add “mso-line-height-rule:exactly” to the paragraph’s inline style attribute where you want the superscript to display.
• In the ^{tag’s style attribute, reset the line-height to 0px
• Take the font size you have set for the paragraph and reduce it by about 60%. In this example the superscript font size would be 12px when the paragraph font size is 20px.
• Now subtract that value from the font size -> 20px – 12px = 8px
• Use that amount for the vertical alignment on the superscript.
  <sup style=”font-size:12px; line-height:0px; vertical-align:8px;”>®}