Tooth Preparation for Ball Attachment, Locator (LOCATOR Root) Attachment, and Zest Anchor for Tooth-Supported Overdenture

General Pre-requisites (All Three Systems)

• Tooth is endodontically treated (root canal therapy completed)
• Minimum crown-to-root ratio of 1:2
• At least 5 mm of alveolar bone support surrounding the root (confirmed radiographically)
• Healthy periodontium with no active pathology
• Root width at the prepared surface must be at least 4 mm minimum
• Post-preparation to be kept at least 4-5 mm short of the root apex to preserve apical seal

1. Ball Attachment (Stud/Ball-and-Socket Type)

Step 1 - Endodontic Treatment & Decoronation

• Complete root canal therapy
• Decoronate the root, trimming it to 1 mm above the gingival tissue (supragingival)
• Finish the root face in a slightly convex dome/hemisphere shape to allow drainage and facilitate seating of the nylon cap
• The root surface is rounded and smoothed in all dimensions

Step 2 - Post Space Preparation

• Remove gutta-percha to a depth 4-5 mm short of the apex (to maintain apical seal)
• Use the manufacturer's pilot drill to create the post hole
• Post hole diameter depends on post size selected:
  • Post #1 (red): canal diameter ~1.20 mm
  • Post #2 (blue): canal diameter ~1.45 mm
  • Post #3 (green): canal diameter ~1.70 mm
• Total shaft length of post: 9.5-13.5 mm (select appropriate size based on root length)

Step 3 - Countersink / Root Face Preparation

• Use the countersink drill (root facer bur) to create a flat, recessed seat on the root face - this acts as the anti-rotation seat for the post flange
• The second tier (coronal flare) is prepared in the coronal post hole using a secondary drill to seat the flange and second tier of the post flush
• The ball head protrudes 2.70 mm above the root surface; total height with cap is approximately 4 mm

Step 4 - Post Cementation

• Post is cemented with glass ionomer or zinc phosphate cement
• The nylon cap (female/socket component) is either:
  • Processed directly into the overdenture at chairside, OR
  • Incorporated indirectly in the lab

Space Requirements (Ball Attachment)

2. LOCATOR Root Attachment (Zest Dental Solutions)

Tooth Preparation - Standard LOCATOR Root Abutment (Direct Screw-In)

• Complete root canal therapy
• Decoronate root and finish contouring
• Final root surface height: 1 mm supragingival
• Minimum root width at prepared surface: 4 mm

• Radiograph the root to measure available length and determine proper post angle (0°, 10°, or 20°)
• Determine the canal alignment relative to the occlusal plane - use angled abutments for non-parallel roots

• Hold the LOCATOR Abutment next to the Pilot Drill and set the plastic Depth Reference Ring on the pilot drill to match the screw thread length
• The screw threads can be shortened if needed for shorter roots
• Drill into the canal using the Pilot Drill, stopping at the depth ring
• Caution: Danger of root perforation if the full drill length is used without the depth stop

• Use the Spotface Diamond Bur to create a recessed countersink seat on the root face
• Drill until a full 360° recessed seat first appears on the occlusal surface of the root
• On divergent roots: create the minimum possible recessed seat on the shallow side
• The spotface seat: ensures flush seating of the abutment base and anti-rotation
• Drilling depth for direct pick-up: 4.5 mm

• Seat the appropriate angled LOCATOR Root Abutment into the canal
• The abutment self-aligns to compensate for up to 40° total divergence between roots
• Tighten to manufacturer's specified torque

Tooth Preparation - LOCATOR Cast-To Coping Version

1. Decoronate and complete endodontic treatment
2. Final root reduction: 1 mm supragingival
3. Prepare a margin using a beveled shoulder or chamfer type margin preparation
4. Remove gutta-percha to desired depth following standard procedures
5. Size the canal using the Pilot Drill (depth reference ring set to slightly exceed the Cast-To Coping thread length)
6. Seat the Cast-To LOCATOR Abutment and wax/cast the coping around it
7. Important: The outer surface of the base of the Cast-To Abutment must remain above the coping level to allow the Denture Cap to snap on without interference

LOCATOR Root Attachment Space Requirements

3. Zest Anchor (Original ERA / Direct Anchor - Zest Anchors)

Tooth Preparation

• Complete root canal therapy
• Decoronate root; reduce to 1 mm supragingival
• Round and smooth the root face in a dome/convex contour

• Use the sequence of drills provided in the Zest Anchor kit
• Standard drill sequence: pilot drill → final drill
• Post space depth: 4 mm short of apex (preserves apical seal)
• Standard Zest Anchor - post diameter: 1.7 mm (9 mm post length)
• Mini Zest Anchor - post diameter: 1.3 mm (9 mm post length)

• Female (titanium housing with ball) is cemented into the prepared canal using zinc phosphate or glass ionomer cement
• Color-coded nylon males (white, orange, grey for standard; white collar males for mini) are retained in the overdenture

Zest Anchor Space Requirements

Comparative Summary Table

Key References

1. LOCATOR Root Attachment System Technique Manual, Rev A - Zest Dental Solutions (L8101-TM RevA). Available at: zestdent.com
2. LOCATOR Attachment System Technique Manual, Rev D - Zest Dental Solutions (L8030-TM). Available at: zestdent.com
3. Sterngold Dental Attachment Catalog (666269-I). Sterngold Dental LLC, South Hackensack, NJ. Available at: sterngold.com
4. Flexi-Overdenture Technique Manual - Essential Dental Systems. Available at: edsdental.com
5. Patel J, Hafeez F. Tooth Supported Overdenture Retained with Custom Attachments: A Case Report. J Clin Diagn Res. 2015; PMC4502008. - Confirms dome-shaped preparation 3-4 mm supragingival (custom attachment case); post space 4 mm short of apex.
6. Oraljournal.com Case Report (2019). Tooth supported overdenture - imperative treatment modality. Vol 5, Issue 4. Available at: oraljournal.com - Confirms decoronation to 1 mm supragingival; post space preparation 4 mm short of apex with locator attachment using pilot drill sequence.
7. Laney WR, Gibilisco JA. Diagnosis and Treatment in Prosthodontics. Lea & Febiger, Philadelphia, 1983.
8. Preiskel HW. Overdentures Made Easy: A Guide to Implant and Root Supported Prostheses. Quintessence Publishing, 1996.
9. Fenton AH. The decade of overdentures. J Prosthet Dent. 1998; 79(1):31-36. - Reviews overdenture abutment selection and preparation principles.

Clinical Notes

• The root surface should always be at least 1 mm above the gingival crest - this prevents gingival tissue from invading the attachment space and allows maintenance of hygiene.
• A dome/convex root surface contour (not flat) is preferred for all stud attachments - it facilitates self-cleansing and reduces plaque accumulation.
• Radiographic verification of post space depth is mandatory before cementation to confirm the 4-5 mm apical seal is maintained.
• For the LOCATOR system specifically, the spotface preparation must achieve a complete 360° recessed seat - an incomplete seat leads to abutment rocking and early failure.
• For divergent roots, the LOCATOR's angled abutments (10° or 20°) are used and can correct up to 40° of total divergence between bilateral abutments without requiring additional tooth modification.