Letter U










233
Glossary ofDental Implantology, First Edition. KhalidAlmas, FawadJaved andStephSmith.
© 2018 John Wiley & Sons, Inc. Published 2018 by John Wiley & Sons, Inc.
UCLA abutment: Prosthetic implant com-
ponent developed as a plastic castable pattern
that can be modified by adding wax for cus-
tom shape and dimensions. This is a founda-
tion for creating a cast‐to‐custom option. The
component is screw retained directly into the
implant, which circumvents the attachment
screw. See: Castable abutment.
UCLA abutment substand: An informal
term used to describe a screw‐retained dental
crown that is screwed directly into the implant
body without an intervening abutment.
ulcer, ulceration: A lesion on the surface of
the skin or mucosa characterized by discon-
tinuation of the epithelium, deeper than ero-
sion; exhibits gradual tissue disintegration
and necrosis, usually with inflammation.
ultimate strength: The maximum stress
a material can withstand at its point of
rupture. Also known as ultimate tensile
strength.
ultrasonic bone surgery: See: Piezoelectric
bone surgery.
ultrasonic scaler: An instrument vibrating
in the ultrasonic range (approximately
25000–30 000 cps) which, accompanied by a
stream of water, can be used to remove
adherent deposits from teeth.
ultrasound stimulation: Treatment modal-
ity traditionally used in physiotherapy to
treat soft tissue disorders by deep heating
tissues. It has been used with good results in
treatment of fractures or delayed union and/
or nonunions in extremities via a pulse sound
wave at 1.5 MHz with an intensity of 30 mW
per square cm. It does not seem to stimulate
healing of either defects or vertical distraction
of the mandible.
ultrastructure: The detailed structure of a
biological specimen that is beyond the reso-
lution power of the light microscope, e.g., it
may be observable using electron micro-
scopes or technologies that provide greater
resolution.
ultraviolet: A wavelength of electromag-
netic radiation that is shorter than the violet
end of the visible spectrum but longer than
that of X‐rays. Normally, it refers to wave-
lengths <380 nm.
uncovery: Popular term for the act of surgi-
cally exposing a submerged dental implant,
following healing from stage one surgery.
See: Stage two surgery.
undercut: 1. The portion of the surface of
an object that is below the height of contour
in relationship to the path of placement.
2.The contour of a cross‐sectional portion of
a residual ridge or dental arch that prevents
the insertion of a dental prosthesis. 3. Any
irregularity in the wall of a prepared tooth
that prevents the withdrawal or seating of a
wax pattern or casting.
underwood cleft: See: Maxillary sinus septum.
underwood septum: See: Maxillary sinus
septum, Septum.
undulate: Having an irregular, wavy border;
used of a colony of microorganisms.
uniform color space: If a color space is per-
ceptually uniform, it means a change of
length x in any direction of the color space
would be perceived by a human as the same
or an equal change.
U

unilateral
234
unilateral: Confined or relating to only one
side; one sided.
unilateral subperiosteal implant: An
eposteal dental implant that provides for one
or more abutments and that supports and/or
retains a removable or fixed dental prosthesis
on one side of a partially edentulous dental
arch. See: Subperiosteal implant.
uninterrupted suture: See: Continuous suture.
unit load: The part of the total load on a
bone, carried by a square unit of its cross‐
section or surface, that causes a correspond-
ing strain and stress. It is arithmetically equal
to the total load divided by the cross‐section
area of the bone carrying it. Also load calcu-
lated as being applied to an individual
implant within a multiple‐implant restora-
tion. Also, part of the total load on bone
imposed by an endosseous implant. Unit
compression load usually equals the unit
compression stress.
upright: The vertical or normal position of a
tooth.
uprighting: Tipping inclined teeth to a
more normal vertical axial inclination.
urticaria: A vascular reaction of the skin
that presents with pale red, raised, and itchy
bumps. Commonly referred to as hives and
may be associated with the sensation of
burning or stinging. It often occurs in
response to an allergic reaction but it can be
induced by nonallergic conditions. Allergic‐
induced reactions usually last less than
6 weeks and are called acute urticaria.
Nonallergic reactions usually last longer than
6 weeks and are called chronic urticaria.

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233Glossary ofDental Implantology, First Edition. KhalidAlmas, FawadJaved andStephSmith. © 2018 John Wiley & Sons, Inc. Published 2018 by John Wiley & Sons, Inc. UCLA abutment: Prosthetic implant com-ponent developed as a plastic castable pattern that can be modified by adding wax for cus-tom shape and dimensions. This is a founda-tion for creating a cast‐to‐custom option. The component is screw retained directly into the implant, which circumvents the attachment screw. See: Castable abutment. UCLA abutment substand: An informal term used to describe a screw‐retained dental crown that is screwed directly into the implant body without an intervening abutment. ulcer, ulceration: A lesion on the surface of the skin or mucosa characterized by discon-tinuation of the epithelium, deeper than ero-sion; exhibits gradual tissue disintegration and necrosis, usually with inflammation. ultimate strength: The maximum stress a material can withstand at its point of rupture. Also known as ultimate tensile strength. ultrasonic bone surgery: See: Piezoelectric bone surgery. ultrasonic scaler: An instrument vibrating in the ultrasonic range (approximately 25000–30 000 cps) which, accompanied by a stream of water, can be used to remove adherent deposits from teeth. ultrasound stimulation: Treatment modal-ity traditionally used in physiotherapy to treat soft tissue disorders by deep heating tissues. It has been used with good results in treatment of fractures or delayed union and/or nonunions in extremities via a pulse sound wave at 1.5 MHz with an intensity of 30 mW per square cm. It does not seem to stimulate healing of either defects or vertical distraction of the mandible. ultrastructure: The detailed structure of a biological specimen that is beyond the reso-lution power of the light microscope, e.g., it may be observable using electron micro-scopes or technologies that provide greater resolution. ultraviolet: A wavelength of electromag-netic radiation that is shorter than the violet end of the visible spectrum but longer than that of X‐rays. Normally, it refers to wave-lengths <380 nm. uncovery: Popular term for the act of surgi-cally exposing a submerged dental implant, following healing from stage one surgery. See: Stage two surgery. undercut: 1. The portion of the surface of an object that is below the height of contour in relationship to the path of placement. 2.The contour of a cross‐sectional portion of a residual ridge or dental arch that prevents the insertion of a dental prosthesis. 3. Any irregularity in the wall of a prepared tooth that prevents the withdrawal or seating of a wax pattern or casting. underwood cleft: See: Maxillary sinus septum. underwood septum: See: Maxillary sinus septum, Septum. undulate: Having an irregular, wavy border; used of a colony of microorganisms. uniform color space: If a color space is per-ceptually uniform, it means a change of length x in any direction of the color space would be perceived by a human as the same or an equal change.U unilateral234 unilateral: Confined or relating to only one side; one sided. unilateral subperiosteal implant: An eposteal dental implant that provides for one or more abutments and that supports and/or retains a removable or fixed dental prosthesis on one side of a partially edentulous dental arch. See: Subperiosteal implant. uninterrupted suture: See: Continuous suture. unit load: The part of the total load on a bone, carried by a square unit of its cross‐section or surface, that causes a correspond-ing strain and stress. It is arithmetically equal to the total load divided by the cross‐section area of the bone carrying it. Also load calcu-lated as being applied to an individual implant within a multiple‐implant restora-tion. Also, part of the total load on bone imposed by an endosseous implant. Unit compression load usually equals the unit compression stress. upright: The vertical or normal position of a tooth. uprighting: Tipping inclined teeth to a more normal vertical axial inclination. urticaria: A vascular reaction of the skin that presents with pale red, raised, and itchy bumps. Commonly referred to as hives and may be associated with the sensation of burning or stinging. It often occurs in response to an allergic reaction but it can be induced by nonallergic conditions. Allergic‐induced reactions usually last less than 6 weeks and are called acute urticaria. Nonallergic reactions usually last longer than 6 weeks and are called chronic urticaria.

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