Integers are like
letters: alone they are meaningless. But when integrated into therapeutic endeavors,
they provide a relevant basis for procedural planning and
execution of therapy. Tarnow’s e-book presents lists
of numbers which clinicians should be acquainted with when performing implant
dentistry — numeric parameters and guidelines for the treatment of teeth,
placement of implants, consideration of esthetics, the prevention and
resolution of surgical complications, treatment of edentulous ridges, and more.
Some of the numbers are means and are not intended to represent
all responses that clinicians may
experience when treating patients.
When interpreting probing measurements around teeth and implants, the following explanations should be considered.
Teeth: Probing depths of 1mm to 3mm are normal. A probing depth
4mm reflects the gray zone. At 5mm,
there is concern, but not over concern
if tissues are pink, there is no bleeding
on probing, and the probing depths
are not getting deeper. At ≥6mm,
surgical intervention may be necessary
if a patient persistently manifests
inflammation or increased pocketing,
despite conservative therapy.
Implants: Desirable probing depths
around dental implants are 2.5mm to
4mm, but deeper assessments can be
associated with healthy peri-implant
mucosa. In general, probing evaluations
may be greater around implants than
teeth, because there are no connective
tissue fibers inserting into implants, and
connective tissue adhesions adjacent
to implants do not impede probe
penetration similar to the connective
tissue attachment to teeth.
Predicting Tooth and Implant Survival Based on the Amount Of Alveolar Bone
Teeth: Despite periodontitis, teeth
with 50 percent bone loss are not a
clinical challenge to treat and retain.
This argument is supported by
numerous studies which addressed
long-term retention of teeth with
advanced bone resorption that were
successfully treated.
Implants: It has been suggested
that if an implant manifests ≥ 50
percent bone lossit should be
removed before additional bone
resorption occurs.
However, this threshold is not sacrosanct and therapy may be considered even if there is less than 50 percent bone diminishment around an implant.
Incidence of Tooth Non-Vitality After Crowns Are prepared
Post-periodontal surgery studies over a three- to 30-year period show 13.3 percent of teeth restored with crowns can become non-vital. Among patients with advanced periodontal disease, nine percent of crowned, and two percent of uncrowned teeth, may develop nonvitality after periodontal surgery.
Esthetics
Assessing the clinical smile line and its relationship to papillary display is critical when planning anterior restorations. In an older population, when patients are maximally smiling, display of midfacial gingival tissues and interdental papillae are seen as follows: • 1.72 percent of individuals have a low smile line (do not reveal midfacial gingival tissues). • 28 percent have a high smile line (demonstrate midfacial gingiva). • 2.91 percent of all patients show their papillae when smiling.
Teeth Dimensions In the Esthetic Zone
The length of a maxillary central
incisor is usually 10mm to 12mm.
Women’s incisors are typically shorter than men’s by 1mm.
Maxillary lateral incisors are 1mm
shorter cervically and incisally than
central incisors. Canines are at the
same level as central incisors
cervically and incisally.
Among the maxillary anterior
dentition, the width of central
incisors ranges from 7mm to 10mm
(mean 8.5mm), lateral incisors vary
from 5.5mm to 8mm (mean 6.5mm),
and canines range from 6.5mm to
9mm (mean 7.5mm).
The three types of front teeth
(central and lateral incisors, canine)
manifest the “golden ratio” with
respect to their height and width.
The width of maxillary anterior
teeth is about 81 percent of their
height.
Mean dimensions of proximal
contact areas between maxillary
anterior teeth are as follows: central
incisors, 4.2mm; central and lateral
incisors, 2.9mm; lateral incisors
and canines, 2mm; and canines and
first premolars, 1.5mm.
Radiographs
A radiograph is a snapshot of one moment in time. Multiple films are required to demonstrate ongoing disease activity, and past bone resorption is not a sensitive indicator of future bone loss. Radiographs underestimate the magnitude of bone resorption by nine percent to 20 percent.
4mm of clinical attachment loss occurs before bone deterioration is detected around teeth on radiographs. A 30 percent to 40 percent decrease in bone mineralization occurs before alterations in bone density are detected on an X-ray.
Implant Measurements
Implant Diameter: Increasing the diameter of an implant one size (eg, from 3.3mm to 4.1mm) increases the implant’s surface area approximately 30 percent. This is equivalent to extending the implant’s length by 3mm. Implant Length: Short textured implants can reliably support posterior prostheses. Nevertheless, implants less than 8mm long (4mm to 7mm) should be used cautiously, because they demonstrate greater failure risks compared to standard implants.
Tooth Extraction Issues
Management of Perforations Into
the Maxillary Sinus When Extracting
Teeth: After an extraction, if a small
hole into the sinus (≤2mm) is present at
the apical or lateral end of the socket, it
can be ignored, because a clot will
usually form and heal uneventfully.
If a perforation is >2mm, a resorbable
barrier should be placed over the
puncture before bone grafting over it.
Bone Resorption After Extractions:
Six months after tooth removal that
includes flap elevation, sockets
manifest a mean 1.24mm vertical bone
loss (range 0.9mm to 3.6mm), and
there is approximately 3.79mm less
horizontal bone (range 2.46mm to
4.56mm).
In contrast, after a flapless extraction,
there is approximately 1mm vertical
and horizontal bone loss.
Dry Sockets: A small percentage of
extraction sites (3.2 percent) develop a
local osteitis after tooth removal. This
occurs most often in mandibular molar
areas. Pain frequently manifests three
days after an extraction. Patients may
need to be medicated with a dry socket
paste for three to ten days to eliminate
discomfort.
Platform Switching
A systematic review indicated that platform switching (abutment narrower than implant platform) results in less vertical bone loss around implants (0.055mm to 0.99mm) than implants restored without platform switching (0.19mm to 1.67mm).
Proper Distances Between Teeth and Implants And Between Implants
Span Between a Tooth and an Implant: This span should be at least 1.5mm to 2mm for non-platformswitched implants. Bone loss is inversely proportional to how close an implant is to a tooth.
Minimum Space Between Two
Implants: To maintain interproximal
bone height for non-platform-switched
implants, 3mm is needed between the
implants. If the expanse is ≤3mm, the
mean vertical bone decrease is
1.04mm, and if the inter-implant space
is >3mm, the expected vertical bone
resorption is 0.45mm. Platformswitched
implants can be placed
slightly closer together — at a 1mm
distance. The mean vertical bone
decrease is 0.43mm.
Space Required for a 4mm
Diameter Implant: To place a 4mm
diameter implant, a span of 7mm
mesiodistally is needed between
adjacent teeth at the coronal region.
Numbers Associated With Prosthetic Issues
Abutment Height: A 5mm tall
abutment is desired for retention of a
cementable implant crown. The
minimum abutment heights necessary
to provide adequate retention for
narrow-platform (3.5mm), and wide
platform (5mm), implants restored with
single cement-retained restorations are
respectively, 3mm and 4mm. A 2mm
increase in abutment height amplifies
retention by 40 percent.
Occlusal Clearance Necessary for
Different Restorative Materials:At
least 2mm of space is required to
provide room for porcelain-fused-tometal
(PFM) occlusal materials
(opaque, 0.3mm; metal, 0.5mm; and
porcelain, 1mm). Monolithic zirconia
or lithium disilicate crowns (press or
CAD/CAM) require less vertical space
than PFM crowns. Restorations made
with these materials need as little as
1mm occlusal clearance, because
no space is required for metal
understructures.
Crown Margin Placement: It is
difficult to remove subgingival cement
entirely around a crown placed deeper
than 1mm into the sulcus. Therefore,
implant margins of cementable crowns
should not be placed more than 1mm
subgingivally. Ideally, margins should
be placed as follows:
- Posterior implants, 0.5mm subgingivally on the mid-buccal, mesio-buccal, and mesio-lingual; 0mm at other locations.
- Anterior implants, 1mm subgingivally mid-bucally, 0.5mm subgingivally mesio and disto-buccally, and 0mm lingually.
Papillae
Return of Papillary Height After Crown Placement on an Implant: After a transitional partial restoration is worn and a crown is initially placed,
90 percent of the time there is an open area under the contact point between the crown and adjacent tooth. Within one year, about 80 percent of papillae rebound and fill the interproximalspace due to reformation of the gingival col under the contact area.
Papillary Tallness Between
Implants: Average height of a papilla
between two implants is 3.4mm, and
more than 50 percent of papillae
between implants are ≤3mm high.
Papillary Size Between an Implant
and a Tooth: The mean distance from
osseous bony crest to the papilla tip is
3.85mm to 4.2mm.
Interproximal Papillary Recession
After Implant Surgery: When thick
and thin periodontal phenotypes are
compared with respect to alterations of
papillary and facial tissue height after
single-tooth implant placement which
included flap surgery, the thin
phenotype demonstrates shorter
papillae by approximately 0.7mm.
Facial tissue height is also about
0.4mm less than tissues associated
with a thick phenotype.
Papilla Dimensions for Tooth to
Pontic and Implant to Pontic:
Although not included in the e-book,
other researchers have found the
following tissue heights are needed
from the contact point to the alveolar
crestal bone level in order to maintain
100 per cent papillae appearance:
- Implant to implant, 3.5mm
- Tooth to implant, 4.5mm
- Tooth to Tooth, 5mm
- Implant to pontic, 5.5mm
- Tooth to pontic, 6.5mm
Open Contact Between Teeth and Dental Implants
After an implant restoration is inserted next to a natural tooth, an interproximal gap develops 34 percent to 66 percent of the time. This event often occurs on the mesial aspect of an implant restoration due to mesial migration of teeth, and this happens as early as three months after prosthetic rehabilitation.
Peri-Implantitis
A systematic review indicated that 18.8 percent of patients with implants (9.6 percent of the implants) develop peri-implantitis. However, this number varies in the literature, because it depends on the quantity of bone loss used to define peri-implantitis.
Implant Failure Rates
About two to three percent of implants are lost prior to prosthetic loading, and another two to three percent that supported fixed partial dentures failed within five years. A systematic review retrospectively evaluated ten long-term studies of less than 15 years each, and it was noted that implant survival rates among these studies ranged from 70 to 100 percent. Nevertheless, eight of the ten studies indicated implant survival rates were less than 90 percent.
Conclusion
When applying numbers addressed in this primer, the following axioms should be observed: always adhere to sound biologic principles; keep the therapeutic plan as simple as possible; be prepared to improvise; maintain a standard of excellence, and, finally treat patients the way you would like to be treated.
