Terry Zaniol1*, Tiziano Testori2 and Stephen Wallace3
1Private Practitioner, Crocetta del Montello, Italy
2IRCCS Orthopedic Institute Galeazzi, Dental Clinic, Section of Implant Dentistry and Oral Rehabilitation, Milan, Italy; Department of Biomedical, Surgical and Dental Sciences, Università degli Studi di Milano, Milan, Italy; Adjunct Clinical Associate Professor, Department of Periodontics and Oral Medicine, University of Michigan, School of Dentistry.
2Department of Periodontics, Columbia University College of Dental Medicine, New York, New York, USA.
Submission: January 01, 2022; Published: January 17, 2022
*Corresponding author: Terry Zaniol, Studio Dentistico Zaniol, Crocetta del Montello, Italy
How to cite this article: Zaniol T, Testori T, Wallace S. Low Window Technique: A Technical Note. Adv Dent & Oral Health. 2022; 15(2): 555906.
This article describes a technique for performing lateral antrostomy when performing lateral sinus augmentation using a rational approach. Based on a CBCT scan, a surgical guide is designed and manufactured to allow the surgeon to draw the antrostomy flush with the anterior sinus wall and floor, with its height not exceeding 6 mm. The distal antrostomy line is placed in relation to the position of the most distal fixture. This technique facilitates sinus membrane detachment and reduces flap elevation to approximately 10 mm, and potentially prevents intraoperative and postoperative complications saving the patient from later discomfort. The technique is easily reproducible and because it involves a series of standardized steps, it reduces the likelihood of intraoperative errors.
Keywords:Lateral approach; CAD-CAM surgical technique; Membrane perforation; Guided surgery
In lateral sinus augmentation, the design and position of the antrostomy determine the degree of elevation of the mucoperiosteal flap, and the width, height, shape, and distance of the window from the sinus floor may restrict the angles at which sinus membrane elevation instruments must operate in order to separate the membrane from the sinus floor. This may affect the likelihood of membrane perforation, the most common complication of sinus augmentation [1-6]. Currently, the position of the window seems to be chosen by surgeons mainly on the basis of personal habits [7-16]. Some authors suggest placing the inferior antrostomy line flush with the sinus floor, others prefer a position up to 2-3 mm higher, as in Simplified Antrostomy Design (S.A.D.), a planned fenestration technique that starts at the medial sinus wall and extends distally 3 mm above the sinus floor [10-17]. Standardized approaches to window preparation should be preferred because they entail fewer surgical errors, a faster learning curve, and greater reproducibility. To this end, based on rational considerations and observations, the authors have recently proposed a technique for designing the lateral window and performing window antrostomy that takes advantage of the tremendous accuracy that can be achieved with modern CAD-CAM fabrication systems. The purpose of this article is to describe this technique, termed the Low Window Sinus Lift [18,19], taking a rational approach to the steps involved.
In the Low Window antrostomy design, the window is positioned as low and mesial as possible (Figure 1). The inferior osteotomy line is always placed flush with the sinus floor and the mesial line is always flush with the anterior sinus wall. In addition, the height of the window never exceeds 6 mm to avoid intraosseous anastomosis. The distal osteotomy is positioned to correspond to the most distally planned implant. The reason for creating a low window in as coronal and mesial a position as possible is that the more apical and distal the window, the more difficult the surgical access to the sinus. Additionally, the position of this osteotomy design provides specific surgical advantages. Placement of the lower horizontal osteotomy flush with the sinus floor eliminates any residual bone wall that could hinder detachment of the sinus membrane. The position of the distal osteotomy line is optimized according to the position of the most distal implant; extending it more distally provides no advantage and may result in elevation of a wider mucoperiosteal flap.
Placing it more distally forces the surgeon to detach a portion
of the membrane in a “blind” condition, with no reference points.
The position of the mesial osteotomy line, flush with the anterior
sinus wall, allows easier access to the anterior sinus recess, i.e. the
zone where detaching the sinus membrane is usually most difficult.
A window height of 6 mm is the minimum that allows easy access
to membrane elevators. A lower height would be an obstacle to
membrane elevation, while a greater height would not confer any
appreciable advantage but would require the elevation of a wider mucoperiosteal flap . Low Window design may also reduce
the risk of sinus membrane perforation when the A and D angles
of the patient’s sinus are narrow (i.e., when A < 30°, a condition
with increased risk of membrane tearing during detachment ).
In fact, because the inferior osteotomy line is placed flush with
the sinus floor, the modified surgical ALW and DLW approach
angles will always be larger than their corresponding anatomic
A and D counterparts (Figure 2), reducing the risk of membrane
Based on a CT or a CBCT scan, the surgeon first plans the
implant positions using guided surgery software (Figure 3) and
then reads the .STL file corresponding to the maxilla and maxillary
sinuses to visualize their anatomy. Using the same software, the surgeon then draws the window according to the Low Window
design (Figure 4). Finally, to design the surgical guide, a “raw”.
STL object is superimposed to the alveolar process and its portion
corresponding to the Low Window antrostomy removed (Figure
5). The .STL file of the guide is then 3D-printed to manufacture the
The patient is anesthetized locally according to standard
protocols. Given the advanced and low position of the antrostomy,
tissue retraction is achieved using a flexible aid (Optragate, Ivoclar
Vivadent AG, Schaan, Liechtenstein). Its size is chosen according to
the size of the patient’s mouth. This usually eliminates the need for
the dental assistant to pull back the patient’s cheeks and lips. The
incision lines are drawn using a dermographic pen. The crestal line
is medial to the ridge, with no release incisions. It should be moved
1-2 mm more palatal if the buccal attached gingiva is minimal. If
a residual distal tooth is present, a paramarginal line is drawn at 3-4 mm at least from the marginal gingiva, starting from its distal
papilla. The attached gingiva is incised along the crestal line. A fullthickness
incision is performed, going from the distal aspect of the
most distal residual tooth to the tuberosity. The incision at the
most distal residual tooth is a full-thickness one, up to its mesial
aspect, and preserves the papilla. The flap is raised from mesial to
distal, not more than 10 mm, leaving intact the attached gingiva
at the most distal residual tooth. The antrostomy is first carried
out using a tungsten carbide spherical blur, the surgical template
acting as a guide; when the sinus membrane begins to appear, one
can switch to using a piezoelectric handpiece, with appropriate
The sinus membrane is detached according to the same
procedures used in the traditional approach; the detachment may
be carried out using an appropriate piezoelectric insert first, to
mobilize the membrane, and then using manual sinus elevators or
curettes. As will be explained later, the position of the inferior line
flush with the sinus floor and the mesial line flush with the anterior
sinus wall facilitate detachment. This is especially true for the
anterior sinus recess, a part of the sinus in which the detachment
of the membrane is notoriously troublesome and difficult. The
sinus is grafted according to standard procedures, using either autogenous bone and/or a bone substitute. The authors usually
place a collagen membrane under the sinus membrane to protect
it and graft an equine-derived xenograft. They place a collagen or
equine-derived cortical bone membrane to protect the antrostomy
(the latter being stabilized using taps or screws). External-internal
suturing  using non-resorbable suture material is followed
by suturing of the mucoperiosteal flaps using non-resorbable
suture material. A complete clinical case is shown in Figures 6-10.
Informed consent was obtained from patients.
The Low Window Technique involves a series of standardized
surgical steps and is therefore easy to learn, repeatable, and less
error-prone than the traditional freehand method. Because it
involves the use of digital software to create a surgical template,
it helps the surgeon perform osteotomies with precision [18-21].
The Low Window Technique allows easier access to the sinus
and reduces invasiveness. Detachment of the sinus membrane
is facilitated and because the mesial osteotomy line is flush with
the anterior sinus wall and the inferior border is flush with the
sinus floor, the movements the surgeon makes with the elevators
to detach the membrane are smooth and linear as they first
run parallel to the anterior wall and sinus floor and then move
upwards. Membrane detachment is facilitated, especially in the
area of the anterior recess. This potentially reduces the risk of
rupture of the membrane, a known complication of intraoperative
sinus augmentation [1-6,22-25]. In the Low Window Technique,
incisions are limited to a linear incision. No release incisions
are made, and the flap is elevated a maximum of 10 mm. This is
expected to result in a better postoperative course characterized
by less pain, hematoma, and swelling than the traditional method.
In addition, because of the low window height and minimal flap
elevation, a flexible lip and cheek retraction device can be used,
saving the patient intraoperative and postoperative discomfort. In
the authors’ experience, the low-window sinus lift technique does
not affect other important sinus augmentation variables, such as
the volume of biomaterial required or the length of implants to be
placed, and it does not preclude the possibility of simultaneous
vertical/horizontal ridge augmentation through guided bone regeneration, if required.
Published evidence on the Low Window Technique is currently
limited to an anecdotal case report  and a retrospective
case series  analyzing the records of 28 surgeries involving
22 patients who received 79 implants and were followed-up
for 38.4 ± 13.2 months. There were no cases of intraoperative
perforation of the sinus membrane or other complications, and
patients reported a high level of satisfaction. At final followup,
all prostheses and implants were successful. Retrospective
data analyses are currently being performed to assess the longterm
bone gain achieved by the Low Window Technique, as well
as immediate postoperative discomfort, pain, hematoma and
bruising. Prospective split-mouth studies are also being planned
to compare the Low Window Technique with more traditional,
freehand procedures. Overall, the Low Window Technique
saves chair time during clinical procedures because it consists
of a series of standardized surgical steps that reduce the risk of
intraoperative and postoperative complications as well as the
patient’s postoperative discomfort. It is easy to learn, repeat, and
less error-prone than traditional, freehand methods and reduces
the level of difficulty associated with lateral wall techniques .
Testori T, Wallace S, Monteverdi R, Baj A, Giannì AB (2009) Complications: diagnosis and management In: Testori T, Del Fabbro M, Weinstein R, Wallace S (Editors.), Maxillary Sinus Surgery and Alternatives in Treatment. Quintessence, London pp. 312-323.