Gustavo Avila-Ortiz and Pablo Galindo-Moreno...12.5 Maxillary Sinus Floor Elevation 12 247 12.5 Maxillary Sinus Floor Elevation Gustavo Avila-Ortiz and Pablo Galindo-Moreno 12.5.1

12 12.5 Maxillary Sinus Floor Elevation

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12.5 Maxillary Sinus Floor Elevation

Gustavo Avila-Ortiz and Pablo Galindo-Moreno

12.5.1 Research QuestionsMaxillary sinus floor elevation, also known as sinus augmentation, was developed by Philip J. Boyne in the 1960s as a preprosthetic surgical procedure, although this technique was first published in 1980 (Boyne and James, 1980). In this early report, a sur-gical protocol inspired by otolaryngological tech-niques, which consisted of maxillary sinus grafting via a lateral approach, was proposed using human autologous bone from the iliac crest as the sole grafting material. Since then, multiple studies describing modifications of the technique, such as the transcrestal approach (Summers, 1994; Tatum, 1986), and employing a wide array of biomaterials have shown that sinus augmentation is a predictable technique. The main goal of maxillary sinus aug-mentation is to gain bone height in posterior atrophic maxillary segments in order to allow conventional implant placement for the treatment of edentulism.

Therefore, research questions in the field of maxillary sinus floor elevation have been fre-quently related to the amount of newly formed bone achieved after grafting and the fate of implants and implant-supported prostheses placed in augmented areas, particularly in terms of sur-vival and success. According to current evidence, maxillary sinus floor elevation is associated with clinically successful outcomes, which is reflected in reported average long-term implant survival rates over 90% (Del Fabbro et al., 2008; Del Fabbro et al., 2012; Pjetursson et al., 2008; Tan et al., 2008). Besides the significance of maxillary sinus augmentation as an implant site development technique, it also represents an excellent research model for the study of healing dynamics associ-ated with different grafting materials or regenera-tive strategies in large craniofacial defects.

12.5.2 Timeline of the StudyA key logistic aspect in the preparation of any clin-ical trial involving human subjects is the establish-ment of a timeline for the conduction of the study. A timeline is essential not only for the organization and communication between members of the research team, but also for the information of study subjects. Details on the number and sequence of visits, length of each office visit, the type of procedures that will be performed and data collection or measurements that will be recorded must be provided at the screening appointment for all subjects enrolled in the study. An adequate study timeline should also consider time windows for each visit, in order to anticipate the possible protocol deviations. A number of milestones are common for the majority of studies on maxillary sinus augmentation, regardless of the surgical approach employed (i.e., lateral or trans-crestal): pre-screening, screening, baseline inter-vention (i.e., sinus augmentation surgery) and follow-up visits to assess postoperative healing and/or collect data to assess outcomes of interest. Studies involving delayed implant placement pres-ent a longer timeline compared to those in which implants are placed in a simultaneous fashion. Fig-ure 12.5-1 and Table 12.5-1 provide orientative information on the timeline sequence for studies in the field of maxillary sinus augmentation pro-cedures with delayed implant placement.

12.5.3 Inclusion and Exclusion CriteriaIdentifying local and systemic factors that may influence the course and outcomes of an investi-gation and defining the eligibility criteria for the study population on the basis of that knowledge is a fundamental research axiom. Adult healthy sub-jects able to understand and follow instructions are common eligibility criteria in oral and maxillo-facial regeneration studies. In the particular case of sinus augmentation, other complementary local and systemic factors must be considered. Table 12.5-2 depicts a list of general inclusion and exclusion criteria for studies on maxillary sinus floor elevation and delayed implant placement. It

Clinical Research Protocols for Indications in Dental Regeneration

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is worth remarking that the eligibility criteria of each individual study should be carefully estab-lished, based on the outcomes of interest and spe-cific features of the study protocol, for example: type of edentulism (i.e., partial or complete); sur-gical approach (e.g., lateral or transcrestal); timing of implant placement (i.e., simultaneous or delayed); and remaining subantral bone height (e.g., >5 mm or ≤ 5 mm).

12.5.4 Traditional EndpointsTraditional endpoints in maxillary sinus augmen-tation research can be divided into three general categories: clinical; radiographic; and histologic/histomorphometric.

Clinical EndpointsMaxillary sinus floor elevation is essentially an implant site development technique. Therefore, the most significant primary clinical endpoint is implant survival rate, typically expressed as a percentage of the total sample (Del Fabbro et al., 2004; Nkenke and Stelzle, 2009; Wallace and Froum, 2003). In long-term prospective or retrospective studies it is possible to find implant survival rate expressed in the form of Kaplan-Meier diagrams (Cho-Lee et al., 2010; Tetsch et al., 2010).

Secondary clinical endpoints may include patient-centered outcomes, implant-supported prostheses survival/success rate, and the type and incidence of complications, such as Schneiderian membrane perforation (Garbacea et al., 2012; Wallace et al., 2007), intraoperative hemorrhage (Flanagan, 2005; Zijderveld et al., 2008), postop-erative sinusitis (Barone et al., 2006; Urban et al., 2012) and implant migration into the sinus cavity (Galindo et al., 2005; Galindo-Moreno et al., 2012b).

Radiographic EndpointsThe key radiographic endpoint is variation in the dimensions of the augmented volume after sinus floor elevation. This outcome may be quantified in terms of height or volume. Height is typically measured linearly on radiographic images, deter-

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Table 12.5-1 Grid depicting a list of the visits and procedures for a hypothetical study on maxillary sinus floor elevation and delayed implant placement.

Visit 1 2 3 4+ 5 6 7+

Visit Description Screening Presurgical planning

Maxillary sinus floor elevation

Follow-up lmplant placement planning

lmplant placement

Follow-up

lnformed consent X

Update medical & dental history

X X X X X X X

Review eligibility criteria

X

Radiographie examination (ldeally CBCT images)

X Xlf required by protocol

Xlf required by protocol

Oral examination X X X X X X X

PVS/alginate impressions

X X

Photographs X X X X X X

Clinical measurements

XIf required by protocol

Xlf required by protocol

Bone biopsy X

Record adverse events

X X X X X

Length of visit (estimated)

1.5 to 2 hours

1.5 to 2 hours

2 to 3 hours

15 to 30 minutes

1.5 to 2 hours

1 to 2 hours

15 to 30 minutes

Table 12.5-2 General eligibility criteria checklist for studies on maxillary sinus augmentation and delayed implant placement.

Inclusion criteria Exclusion criteria

Subject requires sinus augmentation (e.g., Residual bone height <10 mm)

Allergies or hypersensitivities to study related materials or medications

Age: Older than 21 years Concomitant sinus pathology that contraindicates grafting

Gender: Male or Female Severe hematologic disorders (e.g., hemophilia)

ASA status I or II Uncontrolled conditions that may affect normal healing or bone metabolism

Periodontally stable Current bisphosphonate use or history of IV bisphosphonate use

Partially edentulous Pregnant women or attempting to get pregnant

Subject is able to understand and follow instructions

Smokers

Subject must understand and signthe informed consent


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mining the distance from the alveolar crest to the most zenithal point of the augmented volume, and expressed in millimeters. A variety of imaging techniques (e.g., computed tomography, pano-ramic or periapical radiographs) can be utilized to measure it (Avila et al., 2010; Hatano et al., 2004). Periapical radiographs present the limita-tions of challenging standardization and the possi-bility of not capturing all the augmented height, while panoramic radiographs have superimposi-tion of structures and a magnification factor that should be accounted for in the interpretation of the recorded measurements. Only advanced imaging, such as cone-beam computed tomogra-phy (CBCT), allows for the assessment of tridi-mensional changes of the grafted volume during the healing period or after functional loading (Kir-meier et al., 2008; Schmitt et al., 2012).

Histologic and Histomorphometric EndpointsBone biopsies of the augmented volume may be harvested laterally or crestally with a trephine in

cases of delayed implant placement (Fig 12.5-2a). Obtaining bone samples enables researchers to analyze a variety of histologic and histomor-phometric endpoints that may provide crucial information to understand healing dynamics after maxillary sinus augmentation. Core biopsies can be sectioned transversally or longitudinally (Figs 12.5-2b and 12.5-2c). The most significant endpoint in this category is the percentage of vital bone present in the sample, which is nor-mally quantified as proportion of the total area of sequential photomicrographs using histomor-phometric methods. The proportion of newly formed vital bone in a bone sample obtained from a grafted area, via histomorphometric anal-ysis, has been classically accepted as a reliable outcome to assess the consolidation of a bone substitute (Bowers et al., 1982; Feuille et al., 2003). Additionally, the percentage of non-min-eralized tissue and remaining graft particles, in cases of grafting with bone substitutes, may be quantified to further understand tissue homeo-

Fig 12.5-2 (a) Bone core biopsy obtained from a sinus augmentation site with a trephine. (b) Microphotograph of a transversal histologic section of a bone core biopsy. (c) Photomicrograph of a longitudi-nal histologic section of a bone core biopsy.

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stasis following maxillary sinus augmentation (Fig 12.5-3).

Secondary histologic and histomorphometric outcomes may include: the description of mineral-ized tissue structural organization; features of the non-mineralized tissue compartment (e.g., fibrous or adipose); integration of remaining exogenous graft particles; presence of inflammatory infiltrate and stereoscopic or semi-automated assessment of the number of osteocytes, osteoblasts and osteoclasts (Galindo-Moreno et al., 2012a); which provides crucial information relative to the healing outcomes associated with a particular biomaterial.

12.5.5 Additional Observations and Measurements

Understanding the role of local and systemic fac-tors in the process of graft consolidation follow-ing maxillary sinus augmentation is of capital importance for adequate case selection, and also to design clinical protocols associated with mini-mal incidence of complications. Hence, aside from the aforementioned primary and secondary outcomes, determining the effect of local factors such as remaining alveolar bone height, location and configuration of bony septa, presence of sinus floor convolutions, sinus mediolateral dimensions and the size of the access window on sinus augmentation outcomes, has attracted the attention of researchers (Avila et al., 2010; Avi-la-Ortiz et al., 2012a; Avila-Ortiz et al., 2012b; Gosau et al., 2009; Jang et al., 2010; Kim et al., 2006; Rios et al., 2009). The value of systemic factors that may affect bone homeostasis, such as diabetes mellitus, as risk predictors has also been investigated (Huynh-Ba et al., 2008). How-ever, this topic has not been extensively investi-gated yet, which provides a variety of opportuni-ties for further research in the oral-systemic link area. A secondary radiographic outcome that may be reported in longitudinal studies is peri-im-plant marginal bone loss on sites that received sinus augmentation (Lin et al., 2011; Mordenfeld et al., 2012) Other patient-related outcomes, such as postoperative pain and self-perceived

discomfort, provide information to understand how maxillary augmentation procedures may affect the quality of life of study subjects (Mardinger et al., 2009; Pjetursson et al., 2009). These outcomes are usually measured using visual analog scales (VAS), investigator-adminis-tered surveys or following a questionnaire.

12.5.6 Test GroupsMaxillary sinus augmentation is an excellent research model to evaluate clinical, radiographic and histologic outcomes following the use of dif-ferent implant systems, bone substitutes and/or healing enhancers, such as growth factors or bone morphogenic proteins. Hence, a common method of allocation consists of randomly assigned sub-jects to one or more groups that receive different therapies (e.g., xenograft vs autograft, implant brand A vs implant brand B, grafting vs graftless sinus augmentation) (Nedir et al., 2012; Pikdoken et al., 2011). Provided the maxillary sinus is a bilateral cranial cavity, in certain instances subjects are in need of augmentation on both sides. These subjects can be recruited for the conduction of split-mouth studies, in which two different thera-pies can be randomly assigned to either side to

Fig 12.5-3 Microphotograph of a histologic bone sample obtained from a maxillary sinus augmentation site. This image depicts the presence of vital bone (red stars) in intimate contact with remaining graft particles (yellow squares) and a minimal proportion of non-min-eralized tissue (blue triangles) [H&E 20x].


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perform comparative analyses that reduce the influence of inter-individual factors (Barone et al., 2005; Esposito et al., 2010; Galindo-Moreno et al., 2008).

12.5.7 Preoperative Care and PlanningA comprehensive medical, clinical and radio-graphic evaluation must be carried out in prepar-ation for maxillary sinus floor elevation surgery, in order to identify biologic and anatomical factors that may influence treatment outcomes or turn into surgical or prosthetic complications. Critical information includes the subject’s health status (for more details see section 12.5.3), anatomy of the maxillary sinus (e.g., residual bone height, buccopalatal shape and dimensions of the sinus cavity, location of the nasal ostium, Schneiderian membrane adhesions, sinus floor convolutions or septa) and presence of sinusal pathology or oro-antral communications. Additionally, it is impor-tant to examine keratinized mucosa width, vestib-ulum depth and interocclusal space of the surgical sites. Finally, plaque control should be optimal prior to the indication of maxillary sinus floor ele-vation.

Although certain information (e.g., remaining subantral bone height) may be obtained through the analysis of conventional radiographs (e.g., panoramic), critical diagnostic elements are likely to go unnoticed if clinicians rely exclusively on these diagnostic tools (Benavides et al., 2012). Therefore, the use of advanced imaging tech-niques, such as CBCT, is strongly recommended. CBCT scans enable clinicians to precisely assess in a tridimensional fashion the characteristics of the maxillary sinus and adjacent structures, as well as the presence of concomitant pathology. Further-more, CBCT scans are a valuable source of infor-mation for the measurement of research out-comes (e.g., augmented height) and anatomical measurements that may be used as independent variables or predictive factors. Patients must be referred for an otorhinolaryngological consulta-tion in cases of abnormal thickening of the Sch-neiderian membrane, or in those instances where

intrasinusal cystic/tumoral pathology is suspected. Only the maxilla and maxillary sinuses should be scanned to minimize radiation exposure, unless the inclusion of the mandible or other cranial structures is required for other diagnostic pur-poses. The conventional field of view (FOV) used to capture the maxilla and maxillary sinuses is approximately 6 cm, while the standard FOV for the entire head is 13 cm.

If there is no medical contraindication, the pre-scription of oral corticosteroids (dexamethasone 8 mg, once daily (QD), 24 h prior to surgical inter-vention) is recommended to control postoperative swelling and discomfort. Although there is a cur-rent trend in favor of the indication of antibiotic prophylaxis prior to maxillary sinus augmentation, clinicians must be aware that there is no solid evi-dence that supports the therapeutic benefit of those preventive protocols (Testori et al., 2012). Finally, intravenous or oral conscious sedation is elective. However, it should be utilized whenever possible due to the length of maxillary sinus aug-mentation procedures, particularly in cases where an intraoperative complication develops, and to effectively manage subjects who exhibit signifi-cant anxiety.

12.5.8 Surgical ProcedureSince the introduction of maxillary sinus aug-mentation, numerous modifications of the tech-nique have been proposed to facilitate the per-formance of the surgical intervention, to increase its predictability and to decrease the incidence of complications (Wallace et al., 2012). In general, maxillary sinus floor elevation can be executed via two different approaches: lateral (also known as direct or lateral window approach) or crestal (also known as indirect, percrestal or transalveo-lar). Both techniques present advantages and disadvantages (Table 12.5-3.). The indication of either approach is usually dictated by the residual bone height present at the site of augmentation (Wang and Katranji, 2008). Only the steps of maxillary sinus augmentation via the lateral approach will be described in this chapter.


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AnatomyPrior to the description of the surgical procedure, it is pertinent to review several concepts related to the anatomy of the maxillary sinus. The maxillary sinus is one of the paranasal sinuses, along with the frontal sinus, the ethmoidal sinuses and the sphe-noidal sinus (Fig 12.5-4). Paranasal sinuses are cra-nial air cavities lined by a ciliated specialized respira-tory epithelium. The functions of the paranasal sinuses may include: reduction of the total weight of the head; to humidify the inhaled air (which con-tributes to olfaction); to provide resonance to the voice (these cavities are usually more voluminous in males); to assist in the regulation of intranasal pres-sure (i.e., sudden height changes); and to secrete mucus (Watelet and Van Cauwenberge, 1999). The maxillary sinus, also known as the Highmore

antrum, is the biggest of the paranasal sinuses, with an average volume of approximately 12.5 cc, ranging from 5 to 22 cc (Gosau et al., 2009). It is a bilateral pyramid-shape cavity of irregular and asymmetrical configuration located within the maxillary bone. The tip of the pyramid is oriented towards the nasal cavity, whereas the base is located on the lateroposterior aspect of the maxilla, in the proximity of the maxillary apophisis. The boundaries of this cavity are six bony walls: anter-ior; posterior; superior; inferior; medial; and lateral. The anterior wall consists of thin, compact bone extending from the orbital rim to approximately the apex of the canine or the maxillary premolars. The posterior wall is formed by the pterygomaxil-lary region, which separates the sinus cavity from the temporal fossa. The superior wall of the sinus

Table 12.5-3 Main differences between the lateral and crestal approaches.

Lateral approach Crestal approach

Technical difficulty Demanding Less demanding

Visibility Direct visualization Blind approach

lnvasiveness More Less

lncidence of complications Higher Lower

Predictability (lmplant Survival) Comparable Comparable

+

+

+

+

–

–

–

–

~ ~

Maxillary sinuses

Frontal sinuses

Ethmoid sinuses

Sphenoid sinus

Fig 12.5-4 Illustration of the locations of the paranasal sinuses in coronal (left) and sagittal (right) views.


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corresponds to the orbital floor. The inferior wall is configured in function of the position of the apices of the maxillary molars and premolars. The medial wall consists of thick cortical bone from the palatal aspect of the alveolar process and the bony wall of the nasal cavity in an apical direction. Areas of the zygomatic process and the posterior aspect of the maxillary bone form the lateral wall. The vascular supply of the maxillary sinuses is provided by the greater palatine artery, the sphenopalatine artery, the infraorbital artery and the posterior superior alveolar artery (Solar et al., 1999). The posterior superior alveolar artery runs laterally to the antral cavity and it may have important implications in the surgical performance of maxillary sinus floor elevation via a lateral approach, due to the risk of an intrasurgical hemorrhage. Therefore, its location in tomographic sections should always be attempted to avoid this complication.

The maxillary sinuses are innervated by branches of the maxillary nerve [V2], specifically the greater palatine and the infraorbital nerve (Dargaud et al., 2001). However, these neural structures are rarely damaged in the performance of maxillary sinus augmentation. Septa, or Underwood’s septa, are intrasinusal bony walls of variable dimension that may appear during the development of the sinus cavity (primary septa) or as the result of functional adaptation or pathologies (secondary septa). The presence of septa ranges between 21.5% to 46.4%, although its prevalence and location var-ies significantly between different populations (Gosau et al., 2009; Kim et al., 2006; Koymen et al., 2009; Krennmair et al., 1999; Shibli et al., 2007; Velasquez-Plata et al., 2002). A septum can divide the sinus cavity into more than one differ-ent space. Identification and evaluation of this anatomical variation is essential prior to sinus aug-mentation, mainly to minimize the risk of perfor-ation of the epithelial lining of the maxillary sinus cavity, also known as Schneiderian membrane.

Surgical InterventionFollowing isolation of the surgical field, subjects are asked to rinse with an antimicrobial solution

(e.g., chlorhexidine 0.12% or 0.2% for 30 s) and perioral cutaneous surfaces are disinfected (e.g., wiping with iodine solution, unless contraindi-cated due to allergy). Local infiltrative anesthesia is administered to block the posterior superior alveolar nerve and the greater palatine nerve. Additional infiltrations along the mucogingival junction and the palatal mucosa using an anes-thetic containing epinephrine may be done to reduce intrasurgical bleeding (Fig 12.5-5a). First, a straight mid-crestal or slightly palatal incision, when keratinized mucosa is limited, is drawn on the edentulous space. This initial crestal incision typically extends between the remaining teeth, in cases of partial edentulism, or from the canine or premolar area to the tuberosity, in cases of eden-tulous distal extension (Fig 12.5-5b). In the instance of partial edentulism, mesial and distal intrasulcular incisions should be done to increase the flap area.

A mesial and distal vertical divergent releasing incision, passing the mucogingival junction to approximately the base of the vestibulum, must be done to gain appropriate access and maximize visibility through generous reflection, a key aspect in this technique. It is important to place the verti-cal incisions at a safe distance (e.g., 5 mm) from the boundaries of the lateral window to minimize the potential impact of a premature wound open-ing on the healing of the grafted area. A full-thick-ness mucoperiosteal flap is elevated to expose the lateral wall of the maxillary sinus. Elevation of the palatal mucosa is usually unnecessary in this surgi-cal procedure (Fig 12.5-5c). Then, the lateral win-dow is delineated using instruments such as a round diamond bur attached to a high-speed rotary handpiece, piezoelectric equipment, a bone scraper or a combination of them (Galin-do-Moreno et al., 2007; Peleg et al., 2004; Ver-cellotti et al., 2001). The use of piezoelectric equipment is useful to avoid damaging soft tissue structures, such as the posterior superior alveolar artery and the Schneiderian membrane (Fig 12.5-5d). Analysis of CBCT sections is essential for pre-cise presurgical planning of the position of the


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window boundaries and identification of anatom-ical elements, such as intrasinusal septa.

To facilitate the elevation of the Schneiderian membrane, the most coronal boundary of the window should be placed at approximately 2 to 3 mm apical to the floor of the sinus. The position of the mesial and distal window boundaries is dic-tated by the presence of adjacent teeth, by the location of the anterior and posterior maxillary sinus wall, and by the mesiodistal length of the edentulous span. When adjacent teeth are pres-ent, the window should be delineated approxi-mately 2 mm away from the root contour. In cases of complete edentulism or distal edentulous end, the mesial and distal boundaries should be placed 2 to 3 mm from the anterior sinus wall and at a variable distance from the posterior wall, since it is usually not necessary to graft up to the most pos-terior aspect of the cavity (Fig 12.5-6). The most apical boundary should be placed between 14 to 16 mm from the bony crest, to create a substrate that permits the placement of standard length

implants (i.e., between 10 and 14 mm), account-ing for a typical resorption rate of 20 to 30% of the original graft height (Kirmeier et al., 2008; Schmitt et al., 2012). When a septum is detected on the floor of the antral cavity, the outline of the window may require additional modifications to avoid them. In cases where the septa are high (i.e., approximately > 2.5 mm), creating two or more separate windows is recommended, in order to avoid membrane perforations (Beretta et al., 2012). Once exposed, careful elevation of the Schneiderian membrane may be performed using sinus membrane elevators and a blunt piezoelec-tric elevator (Fig 12.5-5e). The ideal sequence of elevation of the Schneiderian membrane varies between different clinical scenarios, although it is generally recommended to start releasing the areas of tension and favorable access.

Another useful tip is to always apply careful and gentle pressure when the membrane elevators are used, feeling the bony structure in order to pre-vent the occurrence of a perforation. Complete

Fig 12.5-5a to d Clinical photographs showing the sequence of a maxillary sinus augmentation procedure by a lateral approach. (a) Surgical areas after administration of local infiltrative anesthesia. Note the points of infiltration at the mucogingival junction (white arrows). (b) Incision line. (c) Lateral wall exposed following full-thickness flap elevation. (d) Outline of the lateral window. Note the presence of the posterior superior alveolar artery (white arrows)(e) to (i) See page 256.

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elevation of the sinus membrane at the medial wall is essential to ensure homogeneous distribu-tion of the grafting material and promote ade-quate angiogenesis from the bony walls (Wallace

et al., 2012). In order to avoid occlusion of the nasal meatus following grafting and a subsequent complication, the Schneiderian membrane should never be lifted beyond the ostium (Maksoud,

Fig 12.5-5e to i Clinical photographs showing the sequence of a maxillary sinus augmentation procedure by a lateral approach. (e) Aspect of the site after elevation of the Schneiderian membrane. (f) Initial graft placement. It should be packed against the mesial and medial wall. (g) Bone grafting is complete. (h) An absorbable barrier membrane is placed over the lateral window. (i) Sutures are placed to achieve primary closure.

Fig 12.5-6 Schematic representation of a lateral window design considering the distance to the anterior wall and the floor of the maxillary sinus (yellow line), a distal adjacent tooth (grey outline) and the crestal bone.

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2001). The location of this conduct is highly vari-able (May et al., 1990; Sikand, 2011), hence it should be identified preoperatively in CBCT images. In cases of Schneiderian membrane per-foration, an absorbable membrane should be placed over the perforation to prevent extravasa-tion of the grafting material into the sinus cavity, which may lead to a severe complication (Fig 12.5-7). It is generally recommended to abort the graft-ing procedure when perforations of the mem-brane are so large that they cannot be sealed intrasurgically (Vlassis and Fugazzotto, 1999). Complete repair of the Schneiderian membrane after trauma may take up to 4 months (Huang et al., 2006).

Although some authors advocate a graftless approach (Rasmusson et al., 2012; Riben and Thor, 2012), maxillary sinus floor elevation is usu-ally performed using a particulate bone substitute alone (xenograft, allograft or alloplast) or in com-bination with other substitutes, autologous bone or healing enhancers. The amount of grafting material that is required for adequate implant site development differs between cases based on the dimensions of the sinus cavity, the residual bone height and the mesiodistal length of the edentu-lous span. Therefore, as much grafting material as necessary should be employed in order to obtain a minimum height of 14 to 16 mm from the alveo-lar crest, and to completely fill up to the borders of

the lateral window, without blocking the nasal ostium (Figs 12.5-5f and 12.5-5g).

The indication of delayed or simultaneous implant placement is normally dictated by the study protocol and/or the residual bone height, under-standing that there must be a minimum amount of bone to achieve implant primary stability. If simul-taneous implant placement is performed, the implant osteotomy should be done prior to bone grafting in order to avoid disorganization of the graft volume. It is also convenient to place an initial graft volume in the medial aspect of the sinus, fol-lowed by placement of the implant(s) and subse-quent grafting of the lateral aspect. This sequence allows for improved visibility and reduces the chance of leaving a void medial to the implant(s). Based on current evidence, it is recommended to cover the lateral window with an absorbable barrier (e.g., collagen) in order to minimize soft tissue invasion into the grafted area (Tarnow et al., 2000; Tawil and Mawla, 2001). The barrier should extend a minimum of 3 mm beyond the boundaries of the lateral window (Fig 12.5-5h). The flaps are then reapproximated and sutured to achieve primary closure (Fig 12.5-5i).

Periosteal releasing incisions or additional meas-ures to ensure primary closure are generally not necessary in maxillary sinus augmentation, unless simultaneous horizontal or vertical ridge augmen-tation is performed.

Fig 12.5-7 (a) A small perforation occurred during the preparation of the lateral window (white arrow). (b) A second larger perforation (blue arrow) occurred during elevation of the Schneiderian membrane due to the presence of a subantral bone defect (yellow arrows). (c) An absorbable membrane was placed over the perforations to seal the defects.

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12.5.9 Postoperative CareSubjects should receive written and verbal general postoperative instructions. Additionally specific instructions regarding maxillary sinus augmenta-tion must be provided: strenuous physical activity such as swimming, aerobics or running should be avoided for the next 3 to 4 weeks; do not use a straw to drink; try to avoid sudden pressure changes; if blowing your nose or sneezing is inev-itable, try to do it gently and with your mouth open. To prevent the occurrence of a postsurgical infection it is generally recommended that sub-jects initiate or continue antibiotic therapy on the

day of the surgical procedure (e.g., amoxicillin 500 mg three times a day (TID) for 7 days; or clin-damycin 300 mg TID for 10 days, starting 2 days prior to the surgery, in case of allergies to penicil-lins). Non-steroidal anti-inflammatory medication or opioid analgesics may be also prescribed. Patients who had preoperative oral corticosteroids must be instructed to take additional decreasing daily doses starting the day of the surgery (e.g., dexamethasone 6 mg QD the day of the surgery, 4 mg QD the day after the intervention and 2 mg QD 2 days after the surgical procedure). Subjects should return between 10 and 14 days after the

Fig 12.5-8 Follow-up sequence of case from Fig 12.5-5. (a) At 2 weeks postoperatively, immediately after suture removal. (b) At 4-week follow-up. (c) At 20-week follow-up. (d) Surgical re-entry for implant placement at 24 weeks. (e) Implants placed. (f) Periapical radiographs showing the position of the implants in the grafted area.

2 weeks 4 weeks

24 weeks20 weeks

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c

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b

d

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References

intervention for suture removal and reinforcement of postoperative instructions. Thereafter, subjects may be followed-up at intervals of variable length depending on the study protocol and/or the esti-mated graft consolidation time prior to implant placement (Fig 12.5-8).

12.5.10 Case NumberInterestingly, the vast majority of clinical studies on human subjects published in the field of max-illary sinus augmentation do not report having performed a sample size calculation, which is a fundamental aspect of proper study design. Sample size calculations must be based on the primary outcome of interest to ensure that the study has sufficient power to be able to reject the null hypothesis when it is false and accept the study hypothesis when it is true, within reasona-ble probability. The assumptions for type I and type II error are typically set at 5% and 80%, respectively. However, identification of well-es-tablished outcomes is essential for the estimation of the effect size that is expected to be clinically significant. As mentioned in section 12.5.4, pri-mary outcomes of interest in maxillary sinus aug-mentation research include implant survival rate, radiographic changes of augmented height or volume, and amount of vital bone in histologic sections.

Regarding implant survival rate, long-term val-ues associated with single implants placed in pris-tine bone are typically around 95% (Buser et al., 1997). Therefore, a 5 to 10% variance could be considered clinically significant for implants placed in areas that underwent maxillary sinus augmen-tation. Variations in the dimensions of the aug-mented volume can be measured using either lin-ear or volumetric radiographic methods. It can be assumed that a given percentage loss from time point A to time point B (e.g., 10 to 20%) is clini-cally significant in order to perform the sample size calculation. However, it is important to remark that the clinical significance of the established per-centage is tightly related to the length of the observation period and the original augmentation

height achieved. For example, the clinical implica-tions when a loss of 4 mm of height occurs in a case where the original height was 12 mm, com-pared to a case where it was 20 mm, are substan-tially different. Finally, the significance of the pro-portion of vital bone and remaining graft particles present in bone samples obtained from the aug-mented site, particularly in studies focused on understanding healing patterns after the use of biomaterials, is unquestionable. However, the minimum amount of vital bone and maximum proportion of remaining graft required to consider a maxillary sinus augmentation procedure as suc-cessful has not been established. As a matter of fact, multiple studies reporting remarkably varia-ble percentages of vital bone following maxillary sinus augmentation also report comparable implant survival rates above 90% (Pjetursson et al., 2008). Therefore, sample size calculation based on the effect size of vital bone or remaining graft proportion is not recommended.

Acknowledgments Dr. Gustavo Avila-Ortiz would like to give special thanks to the American Academy of Periodontol-ogy Foundation (AAPF) for the support provided to pursue an academic career in periodontics. Dr. Pablo Galindo-Moreno has received lecture fees from Geistlich Pharma. Dr. Gustavo Avila-Ortiz declares no conflict of interest related to the infor-mation enclosed in this text.

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