|Year : 2014 | Volume
| Issue : 3 | Page : 156-158
Correction of misaligned implants - UCLA abutment
Navjot Singh1, Charanpreet Singh Jatana2
1 Dental Surgeon, ?Government of Haryana, General Hospital, Naraingarh, Ambala, India
2 B.R.S. Dental College and Hospital, Sultanpur, Panchkula, Haryana, India
|Date of Web Publication||18-Dec-2014|
Dental Surgeon, ?Government of Haryana, General Hospital, Naraingarh, Ambala
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Owing to anatomic considerations, implants could be inadvertently placed in less than ideal positions. These misaligned Implants in partially edentulous arches can be difficult to restore with conventional abutments and may necessitate implant removal in severe angulations. We present a case restored with a UCLA abutment due to buccal angulation of implant fixture in the posterior mandible and emphasize the need for adequate running room in such cases.
Clinical Relevance To Interdisciplinary Dentistry
- UCLA abutments offer a way of the prosthetic correction of inadvertent surgical placement of dental implants.
- Provision of adequate running room by the surgeon at the time of placement makes prosthetic rehabilitation easier.
- Adequate running room also decreases the periodontal procedures that might be required.
Keywords: Abutments, implants angulation, running room, UCLA abutment
|How to cite this article:|
Singh N, Jatana CS. Correction of misaligned implants - UCLA abutment. J Interdiscip Dentistry 2014;4:156-8
| Introduction|| |
The osseointegrated implant has long been used as a safe and useful tool in prosthetic dentistry.  When the osseointegration concept was first introduced to dentistry, the object for treatment was limited only to restoring the masticatory function of edentulous patients.  Now, with a high success rate of osseointegration, implants are widely used to restore the partial edentulism and single tooth missing.  In single-tooth restorations, a widely used solution is the UCLA abutment.  This abutment is designed to directly engage the implant and undergoes casting procedure. The cast abutment has advantages of overcoming angulation problems and esthetic problems. 
| Case report|| |
A 40-year-old female patient reported to the dental department of G.H. Naraingarh in 2009 to get her missing 36 replaced which she had lost to failed endodontic treatment 4 years previously. There was adequate apicocoronal and mesiodistal dimension, but the buccolingual width was about 5 mm making it a category B ridge according to Misch's classification.  It was decided to insert a narrower 3.75 mm diameter tapered implant of 11.5 mm length (Alpha Bio Spiral SPI™) in a two-stage protocol [Figure 1] and [Figure 2]. Due to a prominent submandibular fossa implant angulation was kept more toward the buccal so as to avoid an inadvertent perforation which resulted in a less than ideal position. After 4 months stage 2 surgery was performed, and adequate gingival healing was obtained. On inserting impression copings the incorrect angulation was clearly seen [Figure 3] and it was decided to use a UCLA Abutment with a hex engaging titanium base on which the definitive restoration was fabricated and inserted [Figure 4]. The patient was kept on yearly recall for the 1 st year and later was called annually, 4 th year post restoration radiograph show maintained implant bone levels with acceptable bone loss and a good result overall [Figure 5].
|Figure 1: Implant Alpha Bio™ Spiral SPI diameter 3.75 and 11.5 mm length placed in site 36|
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|Figure 4: Screw retained final restoration placed and access hole blocked with composite|
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| Discussion|| |
On the internal surface of the mandibular body, the main concern during implant placement is the sublingual fossa, which supports a salivary gland of the same name. The sublingual fossa is located along the mylohyoid line, which extends posteriorly from the mental spines on each side of the symphysis. Superior to the anterior part of this line is a smooth, triangular sublingual fossa, and inferior to the posterior part of the line are the oval, submandibular fossae.  During implant surgery, the clinician must keep these structures in mind to avoid accidentally perforating them as a result of angulation of the burs that may cause life-threatening hemorrhage.  The implant may be placed in the correct position, but its trajectory may be misaligned. This may result in a minor misangulation (0-15°) or a severe misangulation (>25°). Misangulations up to 15° are easy to manage. Most prefabricated abutments are available in 0-15° configurations. Components can be custom cast to correct more extreme implant angulation issues (e.g., 25°, 35°). Correcting angulation issues becomes more difficult when parallelism between multiple abutments must be achieved. A major concern pertaining to correction of buccolingual angulation issues is the amount of available running room. Angulated components require additional crevicular space (running room) to allow them to correct the angulation issue before the abutment continues coronally to retain the prosthesis. If the implant is not placed apically enough (not enough running room), the metal is likely to be visible, creating an esthetic problem.
An abutment-crown combination, colloquially described as a UCLA abutment and introduced by Lewis et al.,  facilitated the fabrication of implant-supported crowns with a more natural appearance. The original design for the UCLA abutment was a plastic burnout pattern. The dental laboratory technician modified the burnout pattern with wax to develop the contour for the metal substructure of the artificial crown. The combination plastic-wax pattern then was invested and cast. The UCLA abutment has been used over the past 24 years  in the restoration of osseointegrated implants. The design of the abutment allows fabrication of the restoration directly to the implant fixture, bypassing the transmucosal abutment cylinder. This technique is valuable in overcoming problems of limited interocclusal distance, interproximal distance, implant angulation, and soft tissue response. Another major advantage with the UCLA abutment is that of improved esthetics. UCLA system has a subgingival margin allowing this abutment to be used in cases with a minimal interocclusal clearance with proper esthetics.  With this advantage, many systems were developed following this concept. A high success rate was reported (4 years: 95.8%).  In this system, two kinds of materials are used for the abutment screw, gold alloy and titanium alloy. When titanium alloy is used, because its material property is stronger than the titanium fixture, the fixture can be damaged before the abutment screw. Thus, gold abutment screws have come into favor due to their fail-safe characteristics. 
| Conclusion|| |
In the opinion of the authors during the surgical placement of an implant, if it is deemed necessary to accept an angulation that is 15-25° (off vertical), then additional sink depth will provide more running room and permit fabrication of a restoration with proper tooth contours (no ridge laps). Such cases can be restored by customized abutments such as the UCLA with good results, but proper training in their use and an understanding of their limitations is imperative to ensure optimal success.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]