Art-7-Tuculescu
PROSTHETIC DENTISTRY www.stomaeduj.com
TECHNICAL COMPLICATIONS OF IMPLANT
Case Reports
RESTORATIONS: COMPONENT DEFORMATION,
FRACTURE, SEPARATION
Sorin Uram- Țuculescu1a , Pandora Keala Lee Wojnarwsky1b
Department of General Dentistry, School of Dentistry, Virginia Commonwealth University, Richmond, VA - USA
a
DDS, PhD, Professor; e-mail: suramtucules@vcu.edu; ORCIDiD: https://orcid.org/---
b
DMD, Assistant Professor; e-mail: pkwojnarwsky@vcu.edu; ORCIDiD: https://orcid.org/---
ABSTRACT https://doi.org/10.25241/stomaeduj.2021.8(2).art.7
Aim To review mechanical irreversible implant restoration complications, and discuss prevention and
troubleshooting.
Summary A variety of complications, involving different components are discussed, with clinical presen-
tation, possible causes, prevalence data and accompanying circumstances. Recovery procedures and
troubleshooting protocols are also presented.
Key learning points a. irreversible complications of implant restorations are less frequent as compared to
screw loosening, but more expensive to deal with; b. as in the case of screw loosening, most irreversible
complications may be related to the relative overload of the implant-restoration assembly; c. load control,
by careful implant placement, restoration design and execution, as well as patient commitment in wearing
an occlusal guard are paramount in preventing both reversible and irreversible mechanical implant
complications.
KEYWORDS
Technical Complication; Implant; Fracture; Prosthodontics; Deformation.
1. INTRODUCTION A loose joint favors non-uniform loads on the
components with the likelihood of accelerated wear,
With the global market for implants expected deformation, and even fracture. Driving around with
to double in the next decade [1], more general a loose ball joint in one’s suspension is just looking
practitioners are placing, restoring, and maintaining forward for the vehicle to lose control when the joint
dental implants [2]. However, follow-up care and fails. On the same reasoning, we reiterate that a loose
maintenance amounts to almost a third of the total implant screw is an emergency.
treatment costs [3], which makes servicing implant For single unit restorations, the most common
restorations and understanding failures paramount. type of wear appears as rounding of the angles of
Screw loosening, the primary complication of the hexagon of the abutment, a result of screw
screw-retained implant restorations, is considered loosening and discrete rotation of the abutment. The
a reversible complication as long as there is concurrent deformation at the receiving end of the
no significant deformation to the implant or implant can also occur. Such changes become more
superstructure connection. Other complications evident with increased lapse of time from screw
related to component wear, deformation fracture, or loosening to retightening.
separation of different materials in a heterogenous Screw deformation can occur by bending on the long
system are irreversible and may or may not be related axis, thread alteration, and head damage. Bending is
to screw loosening. This article aims to review these almost exclusively associated with off-axial overload,
other less common complications and why they before or after screw loosening. Sometimes, a
might occur.
bent screw can become lodged in the implant and
2. COMPONENT WEAR AND DEFORMATION simply break at repeated attempts to unscrew,
further complicating the retrieval procedure. Thread
Once the intimate fit of the abutment and implant alteration can be caused by significant over-torqueing,
is loosened, unintended movement occurs in the cross-threading, or presence of debris at the time of
assemblage, with resulting wear of the implant insertion. When engaging the threads of the implant,
platform and corresponding abutment surface. the advancing screw should rotate with ease.
OPEN ACCESS This is an Open Access article under the CC BY-NC 4.0 license.
Peer-Reviewed Article
Citation: Uram-Țuculescu S, Wojnarwsky PKL. Technical complications of implant restorations: Component deformation, fracture, separation. Stoma
Edu J. 2021;8(2):133-137
Received: June 14, 2021 Revised: June 22, 2021; Accepted: June 23, 2021; Published: June 25, 2021
*Corresponding author: Pandora Wojnarwsky, DMD; 521 North 11th Street, Dental Building #1, 3rd Floor, Room # 304E, Richmond, VA 23298 USA
Tel: 1-804-628-4550; Fax: 1-804-828-3151; e-mail: pkwojnarwsky@vcu.edu
Copyright: © 2020 the Editorial Council for the Stomatology Edu Journal.
Stoma Edu J. 2021;8(2):133-137 pISSN 2360-2406; eISSN 2502-0285 133
Technical complications of implant restorations
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Case Reports Resistance should only be met when the entire
length of the screw has been threaded. Resistance
Insufficient material thickness around screw access
orifices can be a risk factor for future fracture (Fig. 9).
to rotation felt from the beginning indicates un-
matched screw, cross-threading, or the presence 4. VENEERING FRACTURE AND SEPARATION OF
of debris at the site of insertion. Head damage can COMPONENTS
be caused by over-torqueing, incorrect access of
the driver bit, or using an un-matched driver bit. Veneering porcelain fracture occurs in up to 10%
Sometimes the screw access orifice is not reasonably
of the implant supported restorations [9-12] as
aligned with the implant/screw axis, and upon
torqueing, the shank of the driver binds on the opposed to the tooth-supported restorations at
lateral walls of the channel. Such a circumstance 2% [13]. The risk increases if the opposing dentition
not only creates the risk of chipping off restorative is also an implant supported restoration and the
material around the orifice, but also may prevent full patient is not wearing an occlusal guard [10].
engagement of the driver in the screw head, risking The likelihood of veneering porcelain fracture
stripping the screw. The screw head deformation is appears to be associated with the restoration size
more frequently encountered for internal hexagon [9,14], and where there is unsupported material (Fig.
heads (for example Astra Tech / Dentsply Sirona, York, 10) at the screw access orifices [15,16]. Fracture/
PA, USA; Biohorizons Dental Systems, Birmingham, chipping of the veneering porcelain covering
AL, USA), and less likely for star pattern heads (for zirconia structures is much more frequent – 14.7%
example Nobel Biocare USA, Yorba Linda, CA, USA; than monobloc fractures [8]. Localized chipping can
Straumann USA LLC, Andover, MA, USA). be especially damaging when it involves the incisal
margins, and may require full replacement, just as a
3. COMPONENT FRACTURE catastrophic fracture.
Component fracture is a more serious, but less In general, when using full contour all ceramic full
frequent complication that may render recall and arch restorations, the best results are to be expected
future appointments more time and expense for truly monolithic zirconia and partial cutback
intensive. Any component of the assembly can zirconia [17-25], as opposed to fully cutback designs
undergo fracture under uncontrolled load and/or as that are more prone to porcelain chipping [18,22,25].
a consequence of poor planning/design. Another complication that can occur in extensive
Implant fracture (Fig. 1) is rare - less than 1% at 5 year zirconia restorations is the separation of compo-
[4], however, it renders the fixture unusable. nents, when titanium cylinders dis-cement from the
Abutment screw fracture (Figs. 2, 3, 4) is relatively monolith (Fig. 11). The fracture of acrylic veneering
rare, at 0.35% at 5 years [5,6], or 3.5% over 15 years on extensive restorations is probably the most
[7]. frequent compli-cation of such structures [26],
Abutment fracture can occur as an isolated compli- representing 17% of the mechanical complications
cation (Fig. 5), or associated with a screw fracture [27]. The critical factor incriminated was poor
(Figs. 6, 7). Abutments with internal connections framework design [27], which did not provide proper
fail most frequently where the internal connection
support for the veneering material.
and the base of the abutment meet. The fractures
compromise both the ability of the joint to keep As it is, implant supported restorations do require
the abutment properly seated on implant and the maintenance and eventual repairs/replacements.
anti-rotational feature of the system. The fracture of A knowledgeable practitioner and a compliant
monolithic structures can be catastrophic in full arch patient would work together for the best achievable
restorations and occurs most of the time through prognosis of such prostheses. As techniques and
a distal screw access orifice (Fig. 8) if a long distal materials evolve, upgrading existing restorations
cantilever is designed, with a frequency of 1.4% [8]. could produce even better results.
Figure 2. Abutment screw fracture: a. radiographic view before
Figure 1. Implant fracture with platform wall separation: complication; b. restoration separated from implant with fractured
clinical (a) and radiographic (b) view. screw head; c. shank and threaded end of screw still inside the implant.
Figure 3. Double screw fracture in implant supported Figure 4. Screw fracture at transition from shank to
fixed partial denture. threaded end.
134 Stoma Edu J. 2021;8(2):133-137 pISSN 2360-2406; eISSN 2502-0285
Uram-Țuculescu, et al.
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Case Reports
Figure 5. Abutment fracture. After the fracture of the hex,
the joint lost a significant part of preload and anti-rotational Figure 6. Abutment and screw fracture: a. common screw
resistance. The screw came progressively loose inside the fracture pattern (junction of shank with head); b. fracture
crown until the restoration could be completely removed by surface of abutment, and screw (screw head remained inside
the patient: a. fractured abutment hex with screw still inside abutment)
restoration; b. corresponding fracture surfaces in abutment
and hex.
Figure 7. After repeated screw loosening episodes, the dentist Figure 8. Distal cantilever fracture in full arch zirconia implant
applied adhesive on screw threads as a fix (a). The same patient supported restoration. Please note that despite the generous
presented later on with a broken abutment and a broken screw. amount of material around the screw access orifice, a 17 mm
The fractured screw fragment and the abutment hex remained cantilever appeared to produce significant leverage to cause
stuck in the implant (b), worsening the prognosis of fragments’ the breakage (Courtesy of Dr. Bryan Limmer, Denver, CO).
removal from inside the implant.
Figure 10. Porcelain fracture at screw access orifice.
Figure 9. Full arch zirconia implant supported restoration.
Please note the reduced material thickness on lingual of screw
access orifices corresponding to #16/15 and #23 (arrows).
#16/15 area is especially prone to fracture, as it is nearest to the
distal cantilever. On the positive side, the distal cantilever is only
9 mm, with moderate leverage.
5. CONCLUSIONS Figure 11. Titanium cylinders’ separation from monolithic
zirconia full arch implant supported restoration.
Screw loosening is the primary implant complication DISCLOSURE
encountered of screw-retained restorations. Howe- The authors reviewed and approved this manuscript, have no
conflicts of interest nor off-label or investigational use in this
ver, this complication alone is often of very little manuscript. Furthermore, the authors have no financial, economic
financial and physical consequence. Component or professional interests that may have influenced the design, or
wear and deformation, component fracture, and presentation of the related information.
veneering fracture and separation of materials
ACKNOWLEDGMENTS
are more detrimental in terms of repair and/or None
replacement financially and procedurally for the
patient and the restorative dentist. The careful AUTHOR'S CONTRIBUTION
recognition of high-risk cases and diligent treatment SU, PW: agree to be accountable for the content of this work.
SU: contributed to the content and data gathering.
planning, including design of the final restoration, PW: contributed to the content and critically revised the
is important to limit or avoid these complications manuscript.
completely.
Stoma Edu J. 2021;8(2): 133-137 pISSN 2360-2406; eISSN 2502-0285 135
Technical complications of implant restorations
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-Case Reports REFERENCES
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Case Reports
Sorin URAM-ȚUCULESCU
DDS, MS, PhD, Professor
Department of General Dentistry
School of Dentistry
Virginia Commonwealth University
Richmond, VA 23298-0566 USA
CV
Dr. Sorin Uram-Tuculescu is a Professor at the Department of General Dentistry, School of Dentistry, Virginia
Commonwealth University. He is involved in pre-clinical/clinical teaching, service, and research, while maintaining
a part-time private practice. He authored/co-authored 7 textbooks, participated in the drafting of 50+ published
papers and presentations, and lectures nationally and internationally.
Questions
1. Compared to screw loosening, component fracture is:
qa. More frequent;
qb. Less frequent;
qc. About as frequent as screw loosening;
qd. More frequent in monolithic restorations.
2. The fracture of full-arch monolithic implant restorations occurs most frequently:
qa. At or near the midline;
qb. Just behind canine areas;
qc. Through a distal screw access orifice;
qd. Where the meso-structure meets the superstructure.
3. Which of the following is not true regarding veneering porcelain fracture in implant
restorations?
qa. Is more frequent that in tooth-supported restorations;
qb. Is more likely if the opposing arch is also an implant-supported restoration;
qc. Can be associated with unsupported material;
qd. Is less frequent than in tooth-supported restorations.
4. The fracture of acrylic veneering in full arch implant restorations is most likely related
to:
qa. Equilibration in group function;
qb. A restoration in the mandible;
qc. Poor metal framework design;
qd. Class III jaw relationship.
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