Complete Arch Site Classification for All-On-4 Immediate Function

Complete arch site classification for all-on-4 immediate function

Ole T. Jensen, DDS, MS Greenwood Village, Colo

Complete arch immediate function of dental implants requires a treatment protocol that takes advantage of residual areas of cortical bone for the apical fixation of implants. A site and jaw bone classification is proposed that has been in use since 2006 for all stages of atrophy for both jaws. The use of the classification is strictly for immediate function based on specific cortical bone sites in the facial skeleton to assist practitioners in diagnosis, treatment planning, and interdisciplinary communication, as well as to reduce human error in patient management. A recent series of 100 consecutive arches that were treated ac- cording to this classification is presented. (J Prosthet Dent 2014;112:741-751)

The first published site classifica- presence or absence of bone. A second The proposed edentulous jaw clas- tion for osseointegrated implants was divergence from previously described sification for immediate function based on vertical bone support for a classifications is the near abandon- implant placement is as follows. 10-mm-long implant.1 The basis of the ment of vertical implant placement, classification was that only 10 mm of which is often problematic in late-stage Class A mandible osseointegration was needed for a atrophy. The reason is that cortical single-tooth implant restoration, a bone can usually be engaged apically The Class A mandible has sufficient theory since validated by several recent with the use of nonaxial implants vertical bone in the posterior to place studies showing that 10 mm or less can placed at a 30-degree angle from the implants above the inferior alveolar be effective.2-8 However, a site classifi- implant entry point.11 By placing im- nerve canal in first molar positions, af- cation for immediate function must be plants in this way, the anterior- ter vertical bone reduction to satisfy entirely different from a site classifica- posterior spread is increased for prosthodontic requirements for inter- tion based on establishing osseointe- improved prosthesis stability. These 2 arch space.15 An anatomic variant of gration via staged implant placement. principles, the presence of cortical the nerve deflecting down toward the The reason is that immediate function bone and an angled implant placement inferior border of the mandible may is concerned primarily with mechanical strategy, strongly suggest a need for exist such that even if the mental fora- fixation, not how much vertical bone is reinterpreting previously published site men area is high, an implant can easily present or how much bone graft classifications of edentulous jaw bone be placed posterior to the foramen. augmentation is needed to optimize morphology. The overarching reason Anterior implants are usually placed osseointgeration.1,9-12 Therefore, site for this is that a classification for im- into canine extraction site locations. classification criteria based on the mediate function must be based on The 4 vertically placed implants are implant length or millimeters of avail- mechanical engineering principles spaced 20 mm or more apart around able bone are not as relevant. For more than on biological (osseointe- the arch (Fig. 1)16 so that the interim- example, a jaw could have abundant gration) principles.13,14 plant arch span exceeds 60 mm. A but low-quality bone incapable of A complete arch site classification cantilevered prosthesis is not necessary establishing primary stability for im- for immediate function implant place- when posterior implants are placed in plants. In contrast, a patient with se- ment with such strict parameters has the first molar locations. vere bone atrophy might still retain not been proposed previously. Howev- small areas of cortical bone able to fix er, it is now important to address the Class B mandible implants for immediate loading. high level of interest in complete arch Therefore, an immediate loading site dental implant reconstruction. The The Class B mandible has several classification is primarily concerned purpose of this article is to propose and millimeters of bone above the inferior with the presence of load bearing bone report on the use of a site classification alveolar nerve canal. This amount of that can mechanically fixanimplant for complete arch immediate function bone allows implant placement slightly and is not merely descriptive of the using 4 implants. posterior to the foramen by angling the

Private practice, Greenwood Village, Colo. Jensen 742 Volume 112 Issue 4

are adequate for immediate function in the Class D mandible (Appendix [available online]).

Class A maxilla

The Class A maxilla, after bone reduction, will have an anatomic variant with a thick palatal wall of bone available 1 Class A: Implants placed in first molar locations as well as medialtothefirst molar extraction site, canine locations for favorable anterior posterior spread. usually just anterior to the palatal root socket. This entry point, angling forward at 30 degrees, will enable implant implant forward to miss the nerve, but midline and extend apically just short of placement into the cortical bone of the not enough for placement of vertical the inferior border in a V formation, palatal wall, avoiding the immediately implants posterior to the foramen. termed the V-4 (Fig. 3).17 The anterior/ adjacent sinus cavity (Fig. 5A,B).25,26 Assuming a 1-mm anterior loopethe posterior (A/P) spread is typically Anterior implants are placed 20 mm or most anterior projection of the inferior reduced to between 10 and 12 mm.17 more forward in the arch but alveolar nerve designated N pointethe The interimplant span of the 4 im- angled back to create an M-shaped implant entry point should be the plants is typically between 30 and 40 patternwhenviewedonapanographic same distance as the bone height above mm. Because the bone is usually highly radiograph.27-29 This implant placement the foramen at N point extending pos- dense, the use of “all-on-3” placement pattern is designated M-4 with all 4 im- teriorly less than 1 to 2 mm to miss the is an option that will slightly increase plants angled at 30 degrees and loop as the implant angles forward at a the A/P spread.22,23 establishes support for a restoration 30-degree angle (Fig. 2A).17-20 (The so- requiring little or no cantilever and with called anterior loop measures 0 to 1 Class D mandible an anterior posterior spread approxi- mm more than 90% of the time.)20 This mating 20 mm and an interimplant arch usually allows for implant placement in The Class D mandible is less than 10 span greater than 60 mm. All implants the second premolar zone for a planned mm in vertical height and corresponds engage the M point, the location of 10-mm cantilever.20 The 2 anterior im- to Cawood Howell Class V-VI atrophy.24 maximum bone mass at the lateral pyri- plants can be placed perpendicular to Three well-spaced implants are used form rim above the nasal fossa.2 When the ridge spaced equidistant. The 4 with the posterior implants angled to- the posterior implant entry point is near implants are spaced up to 15 mm apart ward the midline. The inferior alveolar the first molar apical fixation is often with typical interimplant spans of be- nerve is commonly dehisced and is found in the palatal wall itself as the tween 40 and 45 mm (Fig. 2A). In some usually on top of the ridge, where it can implant body can be placed in parallel patients, buccal to lingual transalveolar easily be reflected with a little manipu- with the palatal wall. The anterior implant placement at a 30-degree angle lation.17 The implant site preparation implant then angles posteriopalatally will be successful posterior to the fora- can then begin in the foramen concavity instead of buccally to fix into this same men in the first molar location. How- itself to improve the A/P spread.17 location within the palatal wall. The net ever, at least 5 mm of vertical bone Screw-tapped implants often perforate effect is that the M point is not engaged should remain above the nerve, and the inferior border.17 A single central as the maximum cortical bone mass but care should be taken not to perforate implant placed vertically completes the 0 is found palatally (designated M point) the lingual wall (Fig. 2B).21 V-3 strategy (Fig. 4). The cantilever in such that implants do not need to tra- the definitive restoration should be verse palatal to buccal to engage the Class C mandible limited to 10 mm, as the A/P spread cortex of the pyriform rim (Fig. 5C). This will likely be between 8 and 12 mm. morphology is only found in robust in- The Class C mandible has little or no The interimplant span varies between dividuals, usually men, but is also a vertical bone above the foramen, and the 25 and 35 mm. The surgeon and general finding of Class A and sometimes angled implant entry point is forward of prosthodontic team should under- Class B sites.7-29 the foramen in the first premolar zone.21 standthatasarchlengthdecreasesin This suggests a 10-mm cantilever the presence of decreased vertical bone without an entire first molar in the height, the risk of implant placement Class B maxilla definitive restoration.22 Anterior im- increases, and a lower number of implants are spread at equal distances but plants is required to satisfy load The Class B maxilla has moderate also angled at 30 degrees toward the biomechanics.16 Therefore, 3 implants atrophy and prominent sinus cavities The Journal of Prosthetic Dentistry Jensen October 2014 743

Class C maxilla

The Class C maxilla is one in which the alveolar process is absent, the si- nuses project anteriorly and transsinus implant placement is required to obtain an adequate A/P spread.28,29 Some- times implants can be placed at the second premolar area, more often in the first premolar zone. Transsinus implants with minimal fixation can be dependably grafted within the sinus with bone morphogenetic protein-2 delivered on absorbable collagen sponge (BMP-2/ACS) for immediate function (Fig. 7A,B).28 The M-point bone mass is generally reduced in volume such that only the posterior implants can obtain fixation there. Therefore, anterior implants must engage midline bone at what is designated the V point, which is the point of maximum bone mass at the most superior aspect of the midline within the nasal crest near the junction of the vomer.29-32 The anterior implants are angled 30 degrees forward from the lateral or canine entry points into the nasal crest and converge at the V point.31 These are commonly called vomer implants.29,30,32 Treatment for the Class C maxilla is designated V-4 placement, as all implants converge toward the midline in an upside down V formation to include 2 transsinus grafted implants posterior and 2 vomer implants anterior.33 Immediate function in this setting is highly reliant on 2 A, B, Class B: Posterior implants placed in second anterior implant fixation.29 The A/P premolar locations angled forward of foramen even though spread can be up to 15 mm when entry point is behind foramen. C, Class B sites can sometimes transsinus implants are well placed, be treated with buccal to lingual transalveolar placement in approximating the Class B A/P spread. fi rst molar locations with implant angled 30 degrees to Sometimes, however, the A/P spread is buccal but engaging into lingual plate. about 10 mm, suggesting a need for sinus grafting for additional implants. A with a relatively thin palatal wall grafting is not needed.30,31 Anterior typical interimplant arch span is be- requiring an entry point for the place- implant entry points are just anterior to tween 40 and 45 mm.29 ment of the implants in front of the the canine extraction sockets. The sinus cavities. Posterior implants usu- anterior implants then angle back to Class D maxilla ally enter in the second premolar zone the M point. The 4 implants are spaced before angling forward at a 30-degree equidistant in an M-4 distribution, 15 The Class D maxilla typically has V angle to gain primary stability at the mm or more apart with an A/P spread point bone but no M point bone mass M point. The implants may pass approximating 15 mm (Fig. 6). The and corresponds to Cawood Howell through a portion of the sinus, but if interimplant arch span is between 45 Class V-VI atrophy.24 There is often there is secure bicortical fixation, sinus and 55 mm. capability for bilateral vomer implant Jensen 744 Volume 112 Issue 4

(n¼2), suggesting an incidence of truly severe maxillary atrophy of about 2%. Every single arch was immediately loaded on the basis of sufficient insertion torque of implants placed into remnant cortical bone. The overarching significance of this short-term retro- 3 Four Class C implants are placed in front of foramen spective analysis was that all cases shortening anterior/posterior spread as 2 anterior implants could be immediately loaded as are placed near lateral incisor locations. implant insertion torque was obtained by engaging cortical bone. All patients were treated with first placement but little or no bone posterior contrast, lack of sufficient bone mass in molar occlusion, but cantilevers were such that zygomatic implants are pre- the paranasal zone of a flat edentulous variable. The longest cantilever was scribed (Fig. 8A).30,33 If zygomatic im- maxilla is the best indication for bilat- 10 mm, with the average cantilever plants are not elected, transsinus eral sinus grafting and delayed implant being 5.4 mm. Insertion torque values placement with BMP-2 grafting can be placement (Fig. 8D).34-37 Not every were commonly over 150 Ncm with a done as long as there is no confluence implant should be immediately loaded, composite average of 166.2 Ncm. between the sinus and nasal cavities and particularly when opposing natural There was a high frequency of 200 vertical stability of the implant can be dentition or parafunction occur.38 Ncm composite insertion torque obtained.29,33 Transsinus implants in which occurred in 48% of patients. this setting have little or no insertion Classification data On the other hand, there were 24 torque, which means that anterior im- maxillas with 120 Ncm or less of plants must have mechanical stability to From January 2, 2013, to April 9, composite insertion torque. One- to share the load.29 Occasionally, pterygoid 2013, 100 consecutive arches were 3-year data to determine osseointe- implants are used in a 6-implant scheme classified after bone reduction and gration were not our subject, but (Fig. 8B; Appendix [available online]).30 then treated with all-on-4 immediate rather the ability to prosthetically In general, many Class D maxillary function. After bone reduction osteo- load an interim prosthesis using this situations can be treated with a V-4 plasty, each arch was classified by the implant insertion techniques on the approach by using transsinus implants all-on-4 site classification. All patients basis of this classification. Data are instead of zygomatic implants, but the received 4 implants (Nobleactive; detailed in Table I. sum of the insertion torques must be at Nobelbiocare Inc) with all implants 29 least 120 Ncm to permit loading. This placed into function on the day of DISCUSSION means that the 2 anterior implants surgery. Of the arches treated, 83.3% must have high insertion torque values. were either Class A or B in the maxilla, Complete arch implant placement When this is not possible, zygomatic whereas in the mandible, 78.2% were patterns have come to be known by implants should be used or a delayed Class B or C treatment. Class D treat- common terms descriptive of the loading strategy. ment was relatively infrequent in either number and angulations of the im- When little or no bone mass is arch (3% in mandible and 2% in plants. The short form nomenclature of available at either the V point or M maxilla). M-4, V-4, and V-3 are meant to desig- point, quad zygomatic implants are The protocol suggested by this nate optimal apical fixation sites as well indicated if immediate function is classification led to infrequent need as simplify communication.23,27,32,34 absolutely necessary (Fig. 8C). In for zygomatic implants in the maxilla The M-4 is the most commonly used approach for the maxilla; these implants placed, in an M shape when viewed with panoramic radiography, can be done in the majority of maxillas (Fig. 9).27 M-4 implants are fixed into the pyriform rim. The V-4 designation indicates implants placed in a V formation in both the maxilla and 4 Class D mandible posterior implants placed through mandible, even though for the maxilla foramen with nerve being retracted. In this setting, 3 implants the pattern is actually an upside-down are placed angling toward midline in V formation, V, as the V-4 term also designates termed V-3. vomer implant placement (Fig. 10A). The Journal of Prosthetic Dentistry Jensen October 2014 745

midline to reduce the chance of implant convergence with the risk of mandibular fracture. The V-4, although less commonly used, is a critical technique when immediate function is desirable in the presence of severely reduced bone stock.33 Implant angulation has many ad- vantages, including increased implant length, apical cortical fixation, secondary stabilization from the sides of the implants, and most importantly increased A/P spread.16,29,38 Implants placed in the maxilla without angulation but with good A/P spread can be short and relatively unstable, usually requiring a delayed placement strategy as illustrated in Figure 11.30,36,37 Ideally, the M-4 and V-4 patterns will lead to a 15 mm or greater A/P spread, with posterior implant abutments emerging at the second premolar or molar locations, thereby minimizing the need for cantilever. Normally, no great advantage can be had in using vertical implants unless substantial vertical bone is available (10 mm or more after bone reduction), as in a Class A mandible (Fig. 12). Preoperative radiographic evaluation alone may be misleading, as in patients with alveolar hypertrophy. What may appear to be abundant vertical bone stock usually requires height reduction for prosthetic reasons, once again suggesting implant angulation to avoid nerve injury or pneumatizations.15,30 5 A, Class A maxilla entry point for posterior implants angle After extensive surgical experience forward hugging palatal wall to engage cortical bone aimed treating patients with Cawood Class I- apically toward canine fossa but not extending to lateral VI edentulous situations, a system for nasal rim. B, Class A maxilla after bone reduction maintains implant placement has been developed cortical palatal wall, a favorable entry point angling forward that is most favorable for each stage of buccally toward M point. C, Implants can sometimes be atrophy. As bone is lost, the remaining fi con ned to palatal wall in robust individuals with thick residual cortex bone becomes most fi palatal walls to x into maximum available cortical bone important and can be used for apical mass (designated M’ point) at palatal wall/palatal wall fixation for immediate loading. Even junction. when there is ample alveolar bone available, these cortical areas remain V-4 situations are prescribed for severe available bone creating a relative state the best aiming point for consistent bone atrophy directing all 4 implants of marked bone deficiency and which is implant fixation. Essentially the same toward the midline (Fig. 10B). For the especially evident in short-faced in- surgical technique is used for all eden- maxilla, the need for the V-4 may not dividuals.30 For the mandible, the V-4 is tulous patients, no matter the severity become evident until after alveolar used when bone loss occurs to such an of bone loss, modified from the original bone reduction, which can deplete extent that implants are angled to the angled implant placement approach

Jensen 746 Volume 112 Issue 4

either with regard to jaw bone reconstruction or for vertical implant placement generally without regard to immediate function. This new classification applies specifically to the potential for apical cortical fixation for immediate function. The classification, used since 2006, has been applied strictly for implants angled at specific landmarks, no matter the extent of jaw 6 Class B maxilla has thin palatal wall and more prominent sinus such that posterior implant entry point is second bone atrophy. fi premolar location angling forward to M point. Anterior A new classi cation is needed is to implants angle back to enter into M point bone mass, formally establish a treatment planning creating M-shaped distribution pattern when viewed with protocol that encompasses all of the panography. various stages of atrophy when immediate function is specifically intended. This charge is significantly different from past classification schemes that most often suggest alveolar reconstruction for delayed implant placement or do not specifically describe how treatment should proceed for immediate loading stability. In addition, this effort to stan- dardize optimal all-on-4 treatment ac- cording to available bone is needed because the majority of clinicians remain relatively inexperienced with complete arch immediate function. One way to consider this new classification is not to look at bone anat- omy per se but at the 4 compartments that affect implant placement potential. These are the sinus cavity, the nasal fossa, the inferior alveolar nerve canal, and inferior border of the mandible. All of these locations can lead to complications when transgressed, but typically they only need to be addressed directly in greater stages of atrophy. For example, in Cawood Class V and VI 7 A, Class C maxilla very prominent sinus cavities can be atrophy, nerve manipulation, penetra- fl membrane re ected for transsinus placement with entry tion through the inferior border, trans- points first or second premolar and apical fixation at M sinus placement including zygomatic point. Anterior implants angle back to M point and often placement, and nasal floor entrance touch posterior implants, but more often they angle forward may be needed in order for immediate into midline bone at V point. B, Transsinus implant 17,19,21,28,29 placement should be grafted with BMP-2 if implant is function to proceed. One fi not well fixed way to look at the classi cation is in terms of managing these areas, with complete avoidance of pneumatized first described by Mattsson et al and classification of treatment similar to the space in mild to moderate atrophy later Krekmanov and colleagues, then Cawood Howell description but based to planned modification or spatial standardized by Malo et al.39-43 The key on remaining bone, not on specifying manipulation in cases of severe to to immediate function treatment is sites for apical fixation for immediate extreme atrophy. apical fixation, not the amount of bone function. Other single-site or jaw bone This jaw bone site classification is not remaining. Malo et al44 described a classifications describe general atrophy specifically quantitative in that it only The Journal of Prosthetic Dentistry Jensen October 2014 747

situation, where only a few millimeters of vertical bone are available for all-on-4 treatment. Instead of millimeters, though, it may be better to think in terms of descriptive function, for example, M- 4, V-4, and zygoma placement, than trying to predict a specify quantity of periimplant bone in an angled implant setting. From an anatomic standpoint, subtracting everything but cortical bone in the maxilla reveals the dilemma for the surgeon, that is, the expectation of high function from limited load-bearing bone stock. If the surgeon envisions inserting the implants into cortical bone, it quickly becomes obvious that in late-stage atrophy, the paranasal bone is often the only available cortex 29 8 A, Class D maxilla is M point bone and V point bone mass for the maxilla other than the palate. deficient. Implant fixation is zygoma, pterygoid plate, and Much of the strategy of immediate sometimes nasal crest. B, Use of pterygoid implants function implant insertion for the requires 6-implant scheme, usually 2 pterygoids, 2 zygomatics, maxilla is based on engaging the palatal and 2 vomers. C, Use of quad zygomatics, 2 zygomatic wall, including angled palatal wall implants on each side, is alternative for immediate function. placement (implant stays within the Sinus graft for delayed alveolar implant placement can be palatal wall), transsinus placement considered. (palatal wall to nasal wall), and bicortical transalveolar (palatal to generally conforms to the previously re- measure of cortical bone quantity is, buccal) placement.27,28,31 If the palatal ported single-tooth 10-mm implant site however, by necessity an intraoperative wall is atrophic or thin from long-term classification in terms of available finding for angled implant placement denture use, paranasal bone, which is cortical bone for immediate loading. In and therefore somewhat impractical in almost always present in all stages of the single-implant classification, a Class delineating a quantitative classification atrophy, may serve as the final remnant A site is described as having 10 mm or preoperatively. In one sense, a classifi- of maxillofacial cortex in the extremes more of periimplant bone anchorage, a cation designation is definitively estab- of maxillary atrophy.24,29 Class B site 7 to 9 mm, a Class C site 4 to lished after completion of implant Although the alveolar crestal cortex 6 mm, and a Class D site 1 to 3 mm. This surgery. Perhaps these 2 classifications may be engaged, no matter how thin, single tooth site nomenclature is in fairly are close enough not to confuse in that the alveolar crest is generally removed close correlation with the immediate an immediate function designation of 10 to form the all-on-4 bone shelf in function classification for the maxilla mm or more of bone for each implant Cawood Class I-III situations and is and the posterior mandible, although site is basically a Class A situation, and largely absent in Cawood Class IV-VI not for the anterior mandible. The direct so on down the line to a Class D situations.15,18,24

Table I. Study data for 100 consecutive all-on-4 treatments Maxilla Average No. of Mandible Average No. of Immediate Class (n[54) Implants (4.00) (n[46) Implants (3.96) Function

A 26 4 8 4 100% B 19 4 23 4 100% C 7 4 13 4 100% D 2 4 2 3 100%

In maxilla, 83.3% were either Class A or Class B treatment, whereas in mandible, 78.2% were Class B or Class C treatment. Class D treatment was relatively infrequent in either arch (3% in mandible and 2% in maxilla). Jensen 748 Volume 112 Issue 4

This new jaw morphology classification is not based on preoperative osteology but on intraoperative findings after surgical preparation. It is not only descriptive but also functional-descriptive, and it takes loading capability into account, ending the long heuristic development of immediate function prosthodontics. In highly atrophic patients, implant support becomes more anterior, resulting in diminished A/P spread and Panoramic radiograph made on day of loading showing 9 excess posterior cantilever. Periimplant M-4 implant placement pattern in Class A maxilla. bone support can tolerate long canti- This all-on-4 jaw classification is typically 5 mm or more less A/P levers, but despite a recommended 44 implicitly establishes favorable biome- spread in the mandible than in the mm titanium bar, the prosthesis may chanics, including the use of longer maxilla primarily because of the posi- not because a linear relationship exists angled implants for intraosseous sec- tion of the inferior alveolar nerve after between cantilever length and anterior ondary stabilization (side loading of bone reduction. posterior spread related to screw loos- implants), a greater interimplant arch Unlike other classifications that ening. Added stress to the prosthesis span resulting in a substantial increase are based on available bone, this pro- leads to increased maintenance. Canti- of A/P spread, and favorable prosthesis posed taxonomy is derived from intra- levers, therefore, should be short (10 support from cross-arch splinting operative findings after bone reduction mm or less) to optimize support for the (extraosseous secondary stabiliza- to create the all-on-4 bone shelf. prosthesis, particularly if the A/P spread tion).38 A desirable A/P spread is The bone shelf is the basis for deter- is 10 mm or less. This means shorter generally 15 mm or more for each jaw mining implant distribution, implant restorations are likely in Cawood Class but is difficult to achieve in every pa- platform level, abutment height, and V-VI situations. When this is not tient. Potential A/P spread decreases as interarch space for the prosthesis.15,18 acceptable in the maxilla, zygomatic vertical bone loss progresses, especially The bone shelf also establishes the implants should be placed to establish in the lower jaw.24 This is illustrated in optimal trajectory of angled implants molar support for immediate func- Figure 13 A,B and is confirmed clini- into cortical anchorage and helps to tion.33 However, for the atrophic cally. In 2-jaw all-on-4 treatments, there maximize anterior posterior spread. mandible, nerve transposition should

10 A, Postsurgical radiograph of V-4 placement in Class C maxilla. B, Postsurgical radiograph of V-4 placement in Class C maxilla and Class B treatment in mandible. The Journal of Prosthetic Dentistry Jensen October 2014 749

the sum of the implant insertion torque of the 4 implants and the anterior posterior spread, with the latter being the more important. The minimum suggested sum of the insertion torque values is 120 Ncm, allowing a maximum of 50 Ncm for any 1 implant.29,38 It is more important for anterior fixtures to be stable than posterior fixtures, especially in the maxilla.29,38 11 Angled implant placement as opposed to vertical The minimum A/P spread acceptable for implant placement leads to increased implant length, better immediate loading has not been estab- implant fixation, and secondary stabilization from angled lished, but 10 mm is recommended, sides of implants for immediate function because of greater assuming the implant spacing is implant resistance form within bone. optimal.15,18,29,38 In the mandible, the A/P spread is locked into place because of nerve po- sition, so unless nerve manipulation is done, the A/P spread diminishes greatly with atrophy. With profound atrophy, the necessity for a fourth implant is much reduced because the distance around the arch from mental foramen to mental foramen is diminished and fewer implants are needed to span the available arch length. Also, because the 12 Class A mandible can be treated with vertical implants 2 implants are close, they are inter- when sufficient bone height is available, as shown in preted biomechanically as a single panoramic image. implant support. By using an all-on-3 approach, the A/P spread is usually increased slightly while still satisfying not be done except at the foramen to A/P spread may not be enough and the necessary load bearing capacity.13 avoid dysesthesia and increased po- additional implants should be placed The use of a rational classification tential for jaw fracture at the corpus.19 to increasing the total number to 6 or system helps not only to establish a Parafunction leads to a high inci- more; sometimes a delayed placement treatment plan but also implies treat- dence of implant loss from immediate strategy is necessary. ment difficulty to help prepare for sur- function.38 Should the clinical setting The decision to delay loading or in- gical workflow, such as the need for be compounded by bruxism, a wide crease the implant number is based on zygomatic implants. This classification

13 A, B, Mandibular and maxillary color-schematic showing Class A through Class C bone loss levels with associated implants. As vertical bone loss progresses, implant length decreases and interimplant arch span and anterior posterior spread decrease. Jensen 750 Volume 112 Issue 4

can help to reduce human error when 7. Felice P, Checchi V. Bone augmentation 22. Oliva J, Oliva X, Oliva JD. All on three implant surgeons use all-on-4 surgery versus 5-mm dental implants in posterior delayed implant loading concept for the atrophic jaws. Four-month post-loading completely edentulous maxilla and mandible: a without a clear understanding of the results from a randomized controlled clin- retrospective 5 year follow-up study. Int J Oral underlying consequences. ical trial. Eur J Oral Implantol 2009;2: Maxillofac Implants 2012;27:1584-92. 267-81. 23. Dekok IJ, Chang KH, Lu TS, Cooper LF. 8. Maló P, de Araújo Nobre M. Short implants Comparison of three-implant-supported SUMMARY placed one-stage in maxillae and mandibles: fixed dentures and two-implant-retained over a retrospective clinical study with 1 to 9 years dentures in the edentulous mandible: a pilot This functional-descriptive complete of follow-up. Clin Implant Dent Relat Res study of treatment efficacy and patient arch edentulous jaw bone classification 2007;9:15-21. satisfaction. Int J Oral Maxillofac Implants 9. Elias CN, Rocha FA, Nascimento AL, 2011;26:415-26. is a departure from single tooth implant Coelho PG. Influence of implant shape, sur- 24. Cawood JI, Howell RA. A classification of the site classifications, which essentially face morphology, surgical technique and edentulous jaws. Int J Oral Maxillofac Surg impose a requirement for osseous bone quality on the primary stability of 1988;17:232-6. fi dental implants. J Mech Behav Biomed Mater 25. Peterson J, Wang Q, Dechow PC. Material modi cation, as in the 10-mm implant 2012;16:169-80. properties of the dentate maxilla. Anat 1 formula. Hundreds of different opera- 10. Makary C, Rebaudi A, Sammartino G, Rec A Discov Mol Evol Biol 2006;288:962-72. tive procedures are used to recover Naaman N. Implant primary stability 26. Suresh S, Sumathy G, Banu MR, Kamakshi K, determined by resonance frequency anala- missing bone based on classifications Prakash S. Morphological analysis of the ysis: comparison with insertion torque, maxillary arch and hard palate in edentulous of axial implant placement. However, histological bone volume and torsional maxilla of South Indian dry skulls. Surg hard tissue loss need not be recovered stability at 6 weeks. Implant Dent 2012; Radiol Anat 2012;34:609-17. at all when an angled implant strategy 21:474-80. 27. Jensen OT, Adams MW. The maxillary M-4: a 11. Romanos GE, Cionei G, Jucan A, 33 technical and biomechanical note for all on is used. The surgeon must therefore Malmstrom H, Gupta B. In vitro assessment four management of severe atrophy-report of visualize fixation points for cortical of primary stability of Straumann implant three cases. J Oral Maxillofac Surg 2009;67: bone as described by this classification designs. Clin Implant Dent Relat Res 1739-44. 2014;16:89-95. 28. Jensen OT, Cottam J, Ringeman J, for angled implant placement, which, 12. Norton MR. The influence of insertion torque Adams M. Transsinus dental implants, although contrary to the common on the survival of immediately placed and bone morphogenetic protein 2 and imme- practice of axial implant placement, are restored single tooth implants. Int J Oral diate function for all on four treatment of Maxillofac Implants 2011;26:1333-43. much more favorable for immediate severe maxillary atrophy. J Oral Maxillofac 13. Brunski JB. In vivo bone response to Surg 2012;70:141-8. loading. This new classification shows biomechanical loading at the bone/dental 29. Jensen OT, Adams MW, Smith E. Paranasal not only that grafting can be mostly implant interface. Adv Dent Res 1999;13: bone: the prime factor affecting the decision to avoided but that enough cortical 99-119. use transsinus vs. zygomatic implants for 14. Thaliji G, Cooper LF. Molecular assessment fi biomechanical support for immediate function implant xation can be obtained in the of osseointegration in vitro: a review of cur- inmaxillary dental implantreconstruction. Oral majority of patients to proceed with rent literature. Oral Craniofac Tissue Eng and Craniofac Tissue Eng 2012;2:198-206. immediate function. 2012:221-50. 30. Graves S, Mahler BA, Javid B, Armellini D, 15. Jensen OT, Adams MW, Cottam JR, Jensen OT. Maxillary all on four therapy using Parel S, Phillips W. The All-on-four shelf: angled implants: a 16 month clinical study of REFERENCES maxilla. J Oral Maxillofac Surg 2010;68: 1110 implants in 276 jaws. Dent Clin North 2520-7. Am 2011;55:779-9. 1. Jensen OT. Site classification for the 16. Brunski J. Biomechanics in Osseointegration 31. Jensen OT, Cottam JR, Ringeman JL, osseointegrated implant. J Prosthet Dent in Dentistry: An Overview. 2nd ed.Chicago: Graves S, Beatty L, Adams MW. Angled 1989;61:228-34. Quintessence; 2003. p. 49-83. dental implant placement into the vomer/ 2. Yi YS, Emanuel KM, Chuang SK. Short 17. Jensen OT, Adams MW. All on four treat- nasal crest of atrophic maxillae for all on four (5.05.0 mm) implant placements and ment of highly atrophic mandible with immediate function: a 2 year clinical study of restoration with integrated abutment mandibular V-4; report of 2 cases. J Oral 100 consecutive patients. Oral Craniofac crowns. Implant Dent 2011;20:125-30. Maxillofac Surg 2009;657:1503-9. Tissue Eng 2012;2:66-71. 3. Blanes RJ. To what extent does the crown- 18. Jensen OT, Adams MW, Cottam JR, 32. Bedrossian E, Rangert B, Stumped L, implant ratio affect the survival and compli- Parel SM, Phillips WR. The all on four shelf Indresano T. Immediate function with the cations of implant-supported mandible. J Oral Maxillofac Surg 2011;69: zygomatic implant: a graft less solution for the reconstructions? A systematic review. Clin 175. patient with mild to advanced atrophy of the Oral Implants Res 2009;20(suppl):67-72. 19. Jensen OT, Cottam JR, Ringeman JL. Avoid- maxilla. In J Oral Maxillofac Implants 4. Sun HL, Huang C, Wu YR, Shi B. Failure rates ance of the mandibular nerve with implant 2006;21:937-42. of short (10 mm) dental implants and placement: a new mental loop. J Oral Max- 33. Jensen OT, Adams MW. Secondary stabi- factors influencing their failure: a systematic illofac Surg 2011;69:1540-3. lization of maxillary M-4 treatment with review. Int J Oral Maxillofac Implants 20. Benninger B, Miller D, Maharathi A, unstable implants for immediate function: 2011;26:816-25. Carter W. Dental implant placement investi- biomechanical considerations and 5. Kotsovilis S, Fourmosis I, Karoussis IK, gation: is the anterior loop of the mental report of 10 cases one year in function. Bamia C. A systematic review and meta- nerve clinically relevant? J Oral Maxillofac Oral Craniofacial Tissue Eng 2013;2: analysis on the effect of implant length on Surg 2011;69:182-5. 294-302. the survival of rough-surface dental implants. 21. Jensen OT, Cottam JR, Adams MW, 34. Tail G, Marla M. Sinus floor elevation using a J Periodontol 2009;80:1700-18. Adams S. Buccal to lingual transalveolar bovine bone mineral with or without the 6. Anitua E, Orive G. Short implants in maxillae implant placement for all on four immediate concomitant use of a bilayered collagen and mandibles: a retrospective study with 1 function in posterior mandible: report of 10 barrier: a clinical report of immediate and to 8 years of follow-up. J Periodontol cases. J Oral Maxillofac Surg 2011;69: delayed implant placement. Int J Oral Max- 2010;81:819-26. 1919-22. illofac Implants 2001;16:713-21. The Journal of Prosthetic Dentistry Jensen October 2014 751

35. Williamson RA. Rehabilitation of the resor- 39. Mattsson T, Köndell PA, Gynther GW, 43. Malo P, de Araujo Nobre M, Lopes A, bed maxilla and mandible using autogenous Fredholm U, Bolin A. Implant treatment Francischone C, Rigolizzo M. All on four bone grafts and osseointegrated implants. Int without grafting in severely resorbed maxillae. immediate function concept for completely J Oral Maxillofacial Implants 1996;11: J Oral Maxillofac Surg 1999;57:281-7. edentulous maxillae: a clinical report on the 476-88. 40. Krekmanov L, Kahn M, Rangert B, medium (3 years) and long term (5 years) 36. Cricchio G, Sennerby L, Lundgren S. Sinus Lindstrom H. Tilting of posterior mandibular outcomes. Clin Implant Dent Relat Res bone formation and implant survival after and maxillary implants for improved pros- 2012;14(suppl 1):e139-50. sinus membrane elevation and implant thesis support. In J Oral Maxillofac Implants 44. Malo P, Nobre M, Lopes A. The rehabilita- placement: a 1-6 year follow-up study. Clin 2000;15:405-14. tion of completely edentulous maxillae with Oral Implant Res 2011;22:1200-12. 41. Krekmanov L. Placement of posterior different degrees of resorption with four 37. Esposito M, Pellegrino G, Pistilli R, Felice P. mandibular and maxillary implants in pa- or more immediately loaded implants: a Rehabilitation of posterior edentulous jaws: tients with severe bone deficiency: a clinical 5 year retrospective study and a new prostheses supported by 5 mm short im- report of procedure. Int J Oral Maxillofac classification. Eur J Oral Implatol 2011;4: plants or by longer implants in augmented Implants 2000;15:722-30. 227-43. bone? One year results from a pilot ran- 42. Malo P, Rangert B, Nobre M. All on 4 im- domized clinical trial. Eur J Oral Implantol mediate function concept with Branemark Corresponding author: 2011;4:21-30. system implants for completely edentulous Dr Ole T. Jensen 38. Parel SM, Phillips WR. A risk assessment maxillae: a 1 year retrospective clinical study. 8200 E Belleview Avenue treatment planning protocol for the four Clin Implant Dent Relat Res 2005;7(suppl 1): Suite 520/ East Tower implant immediately loaded maxilla: pre- S88-94. fi Greenwood Village, CO 80111 liminary ndings. J Prosthet Dent 2011; E-mail: [email protected] 106:359-66. Copyright ª 2014 by the Editorial Council for The Journal of Prosthetic Dentistry.

Jensen 751.e1 Volume 112 Issue 4

fi APPENDIX between the front 2 and back 2 im- superior to the rst bicuspid medial root plants, then a midline perpendicular extraction site. Anterior implants then Definition of terms and acronyms measure is made going posterior off insert in about the lateral incisor posi- the front line to intersect the back line. tion, angle towards the palatal bone ’ All-on-4: A 4-implant scheme used in This distance is the anterior posterior and converge at M point as well. The either arch, usually for immediate spread. For the maxilla, 15 mm or pattern is still an M shape when viewed function. The complete arch is eden- more is desirable. on panoramic x-ray. This approach fi tulous or edentulated in conjunction usually allows for rst molar placement M-4: The designation of M-4 is based with implant placement. Typically im- of the posterior implants which elimi- on the use of 4 implants in the maxilla, plants are placed at 30 degree angles in nates cantilevers and can often avoid all placed at 30 degree angles and with the posterior to avoid the sinus in the the sinus cavity even when present in the front 2 implants tilting back to miss maxilla or the nerve in the mandible. the molar second premolar zone. The the nasal fossa and the back 2 implants Anterior implants are placed variably technique can be used more than half tilting forward to miss the sinus cav- but most often angled at 30 degrees. the time for fully dentate patients ities. The implants are aimed toward All-on-4 treatment can be used for the undergoing edentulation for all-on-four the maximum available bone mass vast majority of patients, except those therapy. lateral and superior to the base of the with gross parafunction and partial nasal fossa. When viewed with pano- V-4: The designation of V-4 is based on maxillary or mandibulectomy. ramic radiography, the 4-implant the use of 4 implants in the maxilla, all All-on-3: A 3-implant scheme used in pattern has an M shape, thus the placed at 30 degree angles with all 4 the highly atrophic mandible. The designation M-4. M-4 treatment can be implants angled forward in an upside technique includes placement of 2 done in more than 80% of all maxillary down V formation when viewed with posterior implants inserted into the cases treated and takes advantage of panoramic radiography. Posterior im- mental nerve fossa after nerve reflection cortical bone for anchorage for imme- plants are aimed at the maximum posteriorly. Because of reduced arch diate function. available bone mass at the lateral pyr- length, a single vertical implant is iform rim above the nasal fossa, while M Point: M point is the surgical aim- placed in the midline. This will usually the anterior 2 implants are directed ing point for implant placement in the allow for a 10-12 mm anterior poste- from about the lateral incisor positions maxilla when the treatment involves a rior spread. The all-on-3 mandible is forward into the nasal crest at the 4 implant scheme. M point is the point usually 10 mm or less in vertical height midline of the maxilla. V-4 treatment of maximum bone mass above the with a much reduced arch length. can be done in almost any patient but nasal fossa at the lateral pyriform rim. is required in cases of severe maxillary All-on-4 Bone Shelf: All-on-4 bone More than 80% of the time, enough atrophy when lateral nasal bone sock is reduction should be done by prosthetic bone mass is available for both reduced or a confluence of the maxil- prescription by using a denture-guide the anterior and posterior implants lary sinus and nasal fossa occurs. V-4 is in such a way that a new alveolar to gain fixation into cortical bone. used about 20% of the time to facilitate plane is established, optimal implant When only enough bone for 1 implant cortical anchorage for immediate sites can be identified, and vital struc- is available, the posterior implant function. tures more easily avoided. The bone is anchored there, and the anterior shelf should parallel the inter-pupillary implant is anchored into midline V Point: V point is the surgical aiming line. Implant bodies should be placed bone. point for implant placement in the flush to the bone shelf, allowing the maxilla when the treatment plan in- ’ ’ abutments and the prosthesis to be M Point: M point is the surgical aim- volves a 4-implant scheme in the pres- placed on top of the shelf. The bone ing point for implant placement in the ence of reduced bone stock at the shelf is made for both arches with maxilla when treatment involves a four lateral pyriform rim. V point is the a recommended 1- mm space from implant scheme and there is robust point of maximum bone mass in the the incisal edge of the prosthesis bone available usually in a dentate pa- midline of the maxilla, typically above to the bone shelf to allow for a 4 x tient undergoing complete dental ex- the base of the nasal fossa within the ’ 4 mm titanium bar-supported final tractions for all-on -our treatment. M nasal crest near the junction of the prosthesis. point differs from M point in that due to vomer. The nasal crest is present in the a wide palatal wall and abundance of vast majority of patients even in late A/P spread: An acronym for anterior cortical bone the posterior implant stage atrophy. The 2 implants are posterior spread: The distance between placement aiming point is palatal with directed at 30 degree angles from the the front 2 implants and the back 2 apical fixation usually found at the lateral incisor positions toward the implants is measured by drawing lines palatal wall/palatal vault junction midline with the implants anchoring

The Journal of Prosthetic Dentistry Jensen October 2014 751.e2 apically into the cortical bone of the or less). N point is a radiographic- posterior implant support when bone nasal crest above the nasal floor and based location used as an aiming is not available in the molar and sometimes extending to the nasal crest- point, usually 2 mm anterior to the sometimes premolar sites. vomer junction. N point when placing 30 degree Angled implants that angled posterior fixtures in a 4- implant Vomer Implant: Most anterior deflection of pass into the nasal crest of the anterior N Point: scheme used for immediate function. the inferior alveolar nerve within the midline maxilla, sometimes extending bone as the nerve emerges from the Pterygoid Implant: An implant placed superiorly into the vomer junction. The mental foramen. Based on human into the pterygomaxillary suture at the term vomer implants is a misnomer as cadaver studies, little or no anterior posterior maxilla and angled forward the implants are actually apically loop can be found within bone (1mm about 30 degrees to provide for anchored to nasal crest.

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