Retrospective Study on Immediate Functional Loading of Edentulous Maxillas and Mandibles With 690 Implants, Up to 71 Months of Follow-Up

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J Oral Maxillofac Surg67:2653-2662, 2009

Retrospective Study on ImmediateFunctional Loading of EdentulousMaxillas and Mandibles With 690

Implants, Up to 71 Months of Follow-UpWilliam Li, BDS, MDS,* James Chow, BDS, MDS, MBBS,†

Edward Hui, BDS, MDS, MBBS,‡ P.K.M. Lee, BDS, MDS,§ and

Raymond Chow, BDS, MDS�

Purpose: The aim of the present study was to describe immediate functional loading of completelyedentulous maxillas and mandibles by fixed provisional prostheses and to compare cumulative survival ratesbetween maxillas and mandibles. Contributing factors including implant diameter, system, configuration, typeof abutment connections, position of implants, and insertion torque values were investigated.

Patients and Methods: From August 2001 to March 2007, 111 patients treated at the Associated Bråne-mark Osseointegration Center, Hong Kong, who received immediate functional loading of implants by fixedcompletely edentulous provisional prostheses were reviewed. Marginal bone changes were measured.

Results: There were 48 edentulous maxillas and 85 edentulous mandibles, in total 133 arches. Twenty-twocases received simultaneous maxillary and mandibular rehabilitation. Three hundred nineteen implants wereused for the maxilla and 371 implants for the mandible, in total 690 implants. A mean of 6.65 fixtures was usedto reconstruct an edentulous maxilla and a mean of 4.36 implants for an edentulous mandible. The meanfollow-up period was 29.5 months, ranging from 11.5 to 71 months. Six hundred seventy-two of 690 implants(97.4%) had been followed up at least 1 year. Four implants failed in the maxilla and 5 implants failed in themandible. Mean marginal bone loss was 0.07 mm after 1 year. Mean failure time was 2.89 months postop-eratively (range, 2 to 5 mo). In those failed implants, maximal insertion torque values were significantly lowerthan those of successful ones. The immediate loading protocol constituted cumulative survival rates of 98.7%for the maxilla and 98.7% for the mandible, with an overall cumulative survival rate of 98.7%. There was nosignificant difference in survival rates between the maxillas and mandibles (�2 exact test, P � 1.000). Theimplant survival rate was found to be not related to implant diameter, system, configuration, type of abutmentconnections, and position of implants (P � .05).

Conclusion: The immediate loading protocol by fixed provisional prostheses proved to be an effectivemethod in restoring completely edentulous maxillas and mandibles, and the maximal insertion torquevalue may be a prognostic factor in determining success.© 2009 American Association of Oral and Maxillofacial Surgeons
J Oral Maxillofac Surg 67:2653-2662, 2009
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mmediate loading of dental implants has been showno be a viable option for restoring missing teeth in aariety of edentulous areas. Conventional treatmentequires an undisturbed healing period after implantnsertion. This is often troublesome in completelydentulous cases because the provisional removable

eceived from Oral and Maxillofacial Surgery, Associated Bråne-

ark Osseointegration Center, Hong Kong

*Specialist and Director.

†Specialist and Director.

‡Specialist and Director.

§Specialist and Director.

�Specialist.

2653

entures are usually unretentive, requiring frequenteline procedures or adjustments.

The development of transitional implants for imme-iate loading was intended to provide immediate res-oration of the dentition1,2; however, these implantsay become mobile after a few months, sometimes

Address correspondence and reprint request to Dr Li: Associ-

ted Brånemark Osseointegration Center, 1901-03, The Center, 99

ueen’s Road Central, Hong Kong; e-mail: [email protected]

2009 American Association of Oral and Maxillofacial Surgeons

278-2391/09/6712-0017$36.00/0

oi:10.1016/j.joms.2009.07.015

mailto:[email protected]

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2654 IMMEDIATE FUNCTIONAL LOADING

efore the conventional implants can be loaded. Inome situations, the provisional implants may eveneopardize the process of osseointegration if they arelaced close to the conventional implants.3 Immedi-te loading of dental implants as a concept was devel-ped to decrease the duration of treatment and theumber of visits between implant placement and con-truction of final prosthesis.4

Immediate loading of completely edentulous man-ibles had been well documented.5-9 The anteriorandible has for years been considered the most

uccessful region for immediate loading of implant-upported restorations. The good vertical and bucco-ingual dimension and the good quality of bone enablehe placement of 3 to 4 implants8,9 between theental foramina with good loading condition. How-

ver, publications on immediate loading of the max-lla are scanty. The frequently encountered difficultiesn the maxilla include severely resorbed anterior labiallate, low maxillary sinus floor, and poor quality ofone in the posterior maxilla.The aim of the present study was to describe

mmediate functional loading of the completelydentulous maxillas and mandibles by fixed provi-ional prostheses and to compare the cumulativeurvival rates (CSRs) between maxillas and mandi-les. Contributing factors including implant diame-er, system, configuration, type of abutment con-ections, position of implants, and insertion torquealues were investigated.

atients and Methods

PATIENT SAMPLE

This is a retrospective study of patients who werereated with dental implants from August 2001 toarch 2007 at the Associated Brånemark Osseointe-

ration Center, Hong Kong.Inclusion criteria were all patients who received a

xed completely edentulous provisional prosthesismmediately after the implant insertion. All caseshould have a vertical bone height of at least 7 mm,dequate buccopalatal or buccolingual dimensions athe planned implant site, and a minimum of 6 im-lants in the upper arch and 4 implants in the lowerrch. Cases with delayed loading protocol, guidedurgery, and zygoma implant cases were excluded.ruxism and smoking were not considered contrain-ications in this study.

PRESURGICAL PREPARATION

Patients were admitted for consultation and discus-ion before surgery. Initial assessment included radio-raphs (orthopantomogram and periapical x-rays; Fig
) and study models. In some cases, computed tomo- g
rams were obtained. Proposed implant sites werearked on the models. In the laboratory, the modelsere mounted on articulators. The teeth to be re-oved were trimmed away from the models and fixedrovisional bridges were constructed according tohe “Hong Kong bridge” design,10-12 which were sup-orted by a titanium framework with a “railway de-ign.” Occlusal openings were made on the bridge-ork according to the planned position of the

itanium cylinders (Fig 2).

SURGICAL PROCEDURE

All patients signed a written consent and wereedated using intravenous midazolam by titrationith pulse oximetry and blood pressure monitoring.he vertical dimension was recorded before all re-aining teeth in the related arch were removed. Sur-

ery was performed by 4 oral and maxillofacial sur-eons in the Associated Brånemark Osseointegrationenter. Infected sockets were debrided surgically.

mplants were inserted using a standard protocol ofmplant site preparation suggested by the manufac-urer Nobel Biocare AB (Göteborg, Sweden; Fig 3). Inase of soft bone, primary stability was ensured usingarious techniques such as bicortical anchorage, os-eotome technique, and adaptive drill sequence. Allaximal insertion torque values were recorded using

he manufacturer’s recommended drilling units in-luding Osseocare and Osseoset, which received reg-lar functional check and maintenance. However, noalibration of drilling units and surgical handpiecesas performed for this retrospective study. Sites withig bony defect were avoided and grafted by boneust or bone substitute. Immediate extractions and

mplantation were sometimes performed. Simulta-eous implant placement and grafting were fre-uently performed.

PROSTHETIC PROCEDURE

Definitive abutments (Multi-Unit Abutment and an-

IGURE 1. Preoperative orthopantomogram planning upper andower provisional bridge.

i et al. Immediate Functional Loading. J Oral Maxillofac Surg009.

ulated Multi-Unit Abutment, Nobel Biocare; Fig 4)

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LI ET AL 2655

ere connected to the implants and preloaded ac-ording to the manufacturer’s suggestions. Titaniumylinders (Fig 5) were connected and shortened ac-ording to the vertical dimension. The positions ofcclusal openings are adjusted to fit the position ofitanium cylinders. During the adjustment, selectiverimming of the “railway” metal framework was some-imes necessary without severely affecting the rigidityf the whole bridge. Sections of rubber dam (Fig 6)ere used to isolate the fresh wound from resinonomers. The fixed provisional bridge was then

xed to the titanium cylinders by cold cured acrylicesin (Unifast Trad, GC America Inc Alsip, IL; Fig 7).are was taken to continuously evaluate the archidline, vertical dimension, and incisal show. Occlu-

al plane determination was also important whenaxillas and mandibles were reconstructed simulta-

eously (Fig 8).

IGURE 2. Upper provisional bridge with �railway� metal frame-ork design and planned occlusal openings.


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POSTOPERATIVE CARE AND FINAL PROSTHESIS

Baseline postoperative orthopantomograms wereaken for every patient immediately after surgery (Fig 9).ll patients were given a course of analgesics, prophy-

actic antibiotics, and advised frequent irrigations be-ween meals. A soft diet was suggested during thetage of provisional prosthesis. Definitive implant im-ression at the abutment level was taken after 6eeks of soft tissue healing and the definitive pros-

heses finished within 3 months (Fig 10). The designf the prostheses will enable the patients to use an

nterdental toothbrush for oral hygiene measures.

RADIOGRAPHIC EXAMINATION

Periapical radiographs using a paralleling techniqueere taken after fitting the fixed temporary prosthe-

es, at delivery of the final prostheses, and at yearlyollow-up appointments. Marginal bone level was mea-ured from the fixture–abutment junction on the mesialnd distal aspects of each implant for each patient. Theean of the 2 readings was taken as the marginal bone

evel of that implant. This was performed on calibrated

FIGURE 3. Occlusal view immediately after implant insertion.


FIGURE 4. Multiunit abutments were connected to the implants.


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omputer software Sidexis 5.55 (Sirona Dental Systems;obel Biocare) by 2 investigators. Mean marginal bone

oss after 1 year will be documented. The assessment ofmplant survivals and failures was based on criteria sug-ested by Albrektsson and Zarb.13

In the maxilla, implants placed anterior to the ca-ine position were regarded as the “anterior maxilla”roup, otherwise as the “posterior maxilla” group.mplants used were divided into narrow platform,egular platform, and wide platform groups. To eval-ate the contributing factors of different implant di-meters, systems, configurations, and types of abut-ent connections, implants used were subdivided

nto 4 groups:

1. Brånemark System MK III, which were external-hex parallel implants.

2. Brånemark System MK IV/NobelSpeedy, whichwere external-hex parallel implants with an in-creased taper, especially designed for soft bone.

3. Replace Select taper/NobelReplace Taper Groovy,which were internal connection tapered implants.

4. Replace Select Straight/NobelReplace StraightGroovy, which were internal connection paral-lel implants.

IGURE 5. Titanium cylinders adjusted and connected to multiunitbutments.


FIGURE 6. Sections of rubber dam were used for isolation.


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Data were entered into SPSS 16.0 (SPSS Inc, Chi-ago, IL) and analyzed accordingly. CSRs were pre-ented and associations between CSRs and contribut-ng factors were analyzed using �2 exact tests. Theifference in mean maximal insertion torque betweenhe successful and failed implants was investigatedsing independent-samples t test. The level of statis-ical significance was set to 0.05.

esults

One hundred eleven patients (69 men and 42omen) with a mean age of 59 years (range, 33 to 88

rs) were included in the study. There were 48 eden-ulous maxillas and 85 edentulous mandibles, in total33 arches. Twenty-two cases received simultaneousaxilla and mandible rehabilitation. Three hundredineteen implants were used for the maxillas and 371

mplants for the mandibles, in total 690 implants. Aean of 6.65 implants was used to reconstruct an

dentulous maxilla and a mean of 4.36 implants for andentulous mandible. The mean follow-up period was

IGURE 7. Upper provisional bridge in place, connected to tita-ium cylinders.


IGURE 8. Upper and lower provisional bridge in occlusion,mmediate loading.


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9.66 months (range, 11.5 to 71 mo). Six hundred sev-nty-two of 690 implants (97.4%) had been followedp at least 1 year. Four hundred twenty-two of 690

mplants (61.2%) had been followed up at least 2ears. Two hundred three of 690 implants (29.4%)ad been followed up at least 3 years. Fifty of 690

mplants (7.2%) had been followed up at least 4 years.wenty-four of 690 implants (3.5%) had been fol-

owed up more than 5 years.Four implants failed in the maxillas and 5 implants

ailed in the mandibles in 8 patients. They all pre-ented with obvious implant loosening with surround-ng fibrous encapsulation. Twenty implants were foundo have incomplete periapical radiographic documenta-ion and were excluded. The mean marginal bone lossas found to be 0.07 mm after 1 year. A reliability testetween the 2 investigators was performed andhowed that the correlation coefficient was �0.999.he mean failure time was 2.89 months postopera-

ively (range, 2 to 5 mo). No specific factor was iden-ified to explain this relatively early failure phenomenon.he immediate loading protocol constituted CSRs of8.7% for the maxillas and 98.7% for the mandibles,ith an overall CSR of 98.7%. There was no significantifference in survival rates between the maxilla andandible (�2 exact test, P � 1.000).Maximal insertion torque values were recorded for

ach implant during surgery, ranging from 20 to ateast 50 N-cm. For the 319 implants in the maxilla, theverage maximal insertion torque was 42.87 N-cm.or the 371 implants in the mandibles, the averageaximal insertion torque was 45.38 N-cm. For the

21 implants in the anterior maxilla, the average max-mal insertion torque was 43.74 N-cm. For the 198mplants in the posterior maxilla, the average maxi-

al insertion torque was 41.45 N-cm. More than halff the implants in the maxilla and mandible wereound to have a maximal insertion torque of at least0 N-cm (50.0% in the maxilla and 61.1% in theandible). Those implants with a maximal insertion

IGURE 9. Postoperative orthopantomogram immediately afterurgery.


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orque of 20 N-cm were located mainly at the poste-ior maxilla and posterior mandible. The mean maxi-al insertion torque for successful implants was

4.29 N-cm, and that for failed implants was 38.89-cm. In those failed implants, the maximal insertion

orque values were significantly lower than those ofuccessful ones (independent-samples t test, P �048). Within the 4 failed implants in the maxillas, 2

ere from the anterior maxilla and 2 were from theosterior maxilla. There was no statistically significantifference in the survival rate between anterior andosterior maxillas (�2 exact test, P � .301).Seventy-four of 690 (10.7%) implants were narrow plat-

orm implants, 536 of 690 (77.7%) were regular plat-orm implants, and 80 of 690 (11.6%) were widelatform implants. One of 74 narrow platform im-lants failed, constituting a CSR of 98.6%. Seven of36 regular platform implants failed (CSR, 98.7%).ne of 80 wide platform implants failed (CSR, 98.8%).he survival rate of implants was not affected by thehoice of implant platform (�2 exact test, P � 1.000).

IGURE 10. Postoperative orthopantomogram after insertion ofnal prostheses, 2 months after surgery.


FIGURE 11. Frequency distribution of the 4 groups of implants.


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Three hundred twenty of 690 (46.4%) implantsere Brånemark implants and 370 of 690 (53.6%)ere Replace implants (Replace Select or NobelRe-lace Groovy). All implant surfaces documented werexidized titanium surfaces (TiUnite, Nobel Biocare).eplace Select Taper/NobelReplace Taper Groovy im-lants were the most common type of implants chosenor the maxillas and mandibles. The most commonmplant used in the maxillas was the Replace Selectaper/NobelReplace Taper Groovy 4.3 � 16 mm,

ollowed by 4.3 � 13 mm, and then the Brånemarkystem MK III regular platform 15 mm long. The mostommon implants used in the mandibles were Bråne-ark System MK III regular platform 15 mm long, fol-

owed by Replace Select Taper/NobelReplace Taperroovy 4.3 � 16 mm, and then 4.3 � 13 mm (Fig 11,ables 1 and 2). CSRs of the 4 subdivided groups were9.2%, 98.4%, 98.3%, and 100%, respectively (Table). The difference in survival rates of implants amonghe 4 groups was not statistically significant (�2 exactest, P � .826).

Table 1. DISTRIBUTION OF DIFFERENT TYPES OFIMPLANTS IN MAXILLA

Number of Implants Placed

NarrowPlatform

RegularPlatform

WidePlatform

rånemark System MK III7 mm 110 mm 2 411.5 mm 513 mm 19 315 mm 2 4318 mm 11

rånemark System MK IVor NobelSpeedy

7 mm 28.5 mm 110 mm 3 311.5 mm 3 113 mm 11 115 mm 11 218 mm 5

eplace Select Taper orNobelReplace TaperGroovy

8 mm 1 110 mm 2 17 1613 mm 7 47 1916 mm 20 47 5

eplace Select Straight orNobelReplace StraightGroovy

13 mm 115 mm 3

ii et al. Immediate Functional Loading. J Oral Maxillofac Surg009.

iscussion

MANDIBULAR IMMEDIATE LOADING

Immediate loading of fully edentulous mandiblesad been well documented.5-7,10,12,14-16 The anteriorandible has for years been considered the most

uccessful region for immediate loading of implant-upported restorations. The good vertical and bucco-ingual dimension and the good quality of bone enablehe placement of fixtures8,9 between the mental fora-ens with a good loading condition.At one extreme, Brånemark et al9 described the

echnique of Brånemark Novum using 3 implants torovide “same-day teeth” for 50 edentulous mandiblesith a total number of 150 implants. The CSR was

8% with a follow-up period of 6 months to 3 years.More recently, Maló et al8 suggested an “all-on-four”

oncept for restoring the fully edentulous mandible,ith good results. Forty-four patients with 176 imme-iately loaded implants, placed in the anterior region,upporting fixed complete-arch acrylic mandibularrostheses were reported. Five immediately loaded

Table 2. DISTRIBUTION OF DIFFERENT TYPES OFIMPLANTS IN MANDIBLE

Number of Implants Placed

NarrowPlatform

RegularPlatform

WidePlatform

rånemark System MK III7 mm 18.5 mm 2 110 mm 711.5 mm 113 mm 3 27 215 mm 7 10318 mm 12

rånemark System MK IVor NobelSpeedy

7 mm 210 mm 113 mm 1 215 mm 1418 mm 1

eplace Select Taper orNobelReplace TaperGroovy

8 mm 4 110 mm 8 1013 mm 10 33 416 mm 19 83 5

eplace Select Straight orNobelReplace StraightGroovy

10 mm 213 mm 415 mm 1


mplants were lost in 5 patients before the 6 months’

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ollow-up, for a CSR of 96.7%. Testori et al6 treated 62dentulous mandibles with immediate loading by 325sseotite implants. Two implants failed, constitutingCSR of 99.4%. Wolfinger et al7 documented the

linical results of 9 of 10 patients with immediateunctional loading of Brånemark System implants indentulous mandibles. The implant survival rate was0% after 5 years.Chow et al10 first documented the use of the “Hong

ong Bridge” technique in 27 consecutive patientsith fully edentulous mandibles. One hundred twenty-

hree Brånemark implants were installed, with a fol-ow-up period from 3 to 30 months. Two of the 115emaining implants failed, resulting in an overall im-lant survival rate of 98.3%. The present study is thextension of the indication of fixed provisional pros-heses to edentulous maxillas and to evaluate mandib-lar cases with a longer follow-up period.

MAXILLARY IMMEDIATE LOADING

Well-designed retrospective and prospective studiesn immediate loading of the maxilla are scanty. Studiesn “early loading” after 72 hours of implant installationave been published.17-19 There are also case se-ies18,20-24 with 1 to 10 patients treated successfully bymmediate loading of the edentulous maxilla.

Balshi et al25 treated 55 cases by immediate func-ional loading of Brånemark System implants follow-ng “teeth-in-a-day” protocol in the edentulous max-lla. Five hundred fifty-two implants were placed inmmediate extraction or healed sites, with only 522xtures immediately loaded. The CSR was 99%,ithin a period of 4 years 2 months. A mean numberf 10 implants were placed in each patient. Maló etl26 performed a retrospective clinical study of 32atients with 128 immediately loaded implants usinghe “all-on-four” technique. Three immediately loadedmplants were lost in 3 patients, producing a 1-yearSR of 97.6%. Later, Maló et al27 combined the com-uter-guided surgical technique and the “all-on-four”echnique in the treatment of 18 edentulous maxillas.wo implants were lost, producing a 1-year CSR of7.2%. Ostman et al28 treated 20 patients with eden-

Table 3. CUMULATIVE SURVIVAL RATE OF THE 4 GROU

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ercentage of implants used 256/690 (37.1%) 64/69umber of implants failed 3 2umulative survival rate 98.8% 96ean failure time 2 mo 2

i et al. Immediate Functional Loading. J Oral Maxillofac Surg 2

ulous maxilla by Brånemark System or Replace Select n

apered implants. One hundred twenty-three oxidizedmplants were placed. A screw-retained temporaryridge was delivered within 12 hours and a finalridge within 3 months of implant placement. One0.8%) of the 123 implants failed, with CSRs of 99.2%fter 12 months. Van Steenberghe et al29 used theteeth-in-an-hour” concept (Nobel Biocare) to treat 24atients who were followed up for 1 year and foundhat all prostheses and individual implants recordedere stable. This technique involved a computer to-ographic scan-derived customized surgical template

or flapless surgery and a prefabricated prostheticuprastructure. Cannizzaro et al30 documented thereatment of 33 patients with 202 implants by fixed oremovable prostheses using a flapless surgical ap-roach. One hundred ninety-nine implants were im-ediately loaded and 2 implants failed. Ibanez et al31

reated 26 maxillary cases, loaded the implants within8 hours, using resin provisional prostheses, metal-einforced provisional prostheses, or definitive prosthe-es (metal-crylic or metal-ceramic). All implants were followedor 12 to 74 months. The success rate reported was00%. Jaffin et al32 documented 34 patients with im-ediate loading of edentulous maxilla with 236 im-lants. The abutments and temporary restorationsere placed 48 to 72 hours postoperatively. Sixteen

mplants were lost in 11 patients, thus the CSR was3%, up to 60 months of follow-up. Capelli et al33

erformed immediate rehabilitation of 41 completelydentulous maxillas with fixed prostheses on 246mplants. Provisional full-arch restorations made of aitanium framework and acrylic resin teeth were de-ivered within 48 hours of surgery. Each patient re-eived 6 implants. The CSR was 97.59% for up to 40onths of follow-up.Alternatively, immediate loading of the completely

dentulous maxilla using a combination of zygomaNobel Biocare) and conventional implants as an al-ernative to conventional grafting options has beeneported.34-37

In studies concerning immediate loading of eden-ulous maxillas, a common finding was that usually

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fter surgery by fixed prostheses and a relatively shortollow-up period26-30 was involved. In contrast to theecent study, all implants were loaded immediatelyfter surgery, and the mean follow-up period wasomparatively longer (average, 29.5 mo, up to 71o), with 97.4% of implants having been followed up

or more than 1 year. However, a future study with allmplants past 5 years of function will be advisable.urthermore, 4 to 1025-27,33 implants were placed inhe maxillas to support a fixed prosthesis, whereashe mean number of implants used in the recent studyas 6.65 implants.

FIXED PROVISIONAL BRIDGE PROTOCOL

The use of a fixed provisional bridge protocol inhis study had several advantages:

1. Easy to learn.2. The low cost involved.3. Short planning time before surgery, usually

within 1 week.4. Immediate rigid splinting of fixtures can be avail-

able.5. Flexibility in modifying the “railway design” if

the planned implant position is changed intra-operatively.

6. Definitive abutments can be preloaded immedi-ately after the surgery, minimizing the difficul-ties in manipulating postoperative soft tissueswelling and irregularities.

7. Occlusion is immediately available.

The high implant survival rate seen in this studyuggests the fixed provisional bridge protocol is aiable option for edentulous maxillary and mandibu-ar immediate loading cases. With the availability ofhe cone-beam computer tomograph, more and moreuided surgeries can be planned using computer soft-are, with similar advantages. For guided surgeries,igher accuracy and better planning can be obtained

f the alveolar ridge is healed. However, in most cases,atients are not willing to accept all teeth be removedefore a new fixed bridge is ready. Apart from theigher cost involved, the radiographic artifact pro-uced by the remaining crown and bridgework may

eopardize the guided surgery planning and the pa-ient may not agree to remove them for the sake ofiagnosis and planning.The fixed provisional bridge protocol offers a good

ption for these patients, because surgeons can per-orm the extractions simultaneously with the implanturgery. Infected sites observed can be debrided andrafted intraoperatively and large defects can bevoided. Simultaneous implant and grafting can beerformed, with the bridge immediately available,
ith flexibility of modification intraoperatively. Also, a
he fixed provisional bridge itself can serve as a “re-erve” prosthesis if the final bridge needs any labora-ory repair or adjustment. However, compared withhe “teeth-in-an-hour” protocol, the finishing time ofhe final bridge must be considered much longer (1our vs 3 mo).

INSERTION TORQUE VALUES AND VARIOUSCONTRIBUTING FACTORS STUDIED

Documentation in the literature on insertion torquealues in relation to survival rate in immediate loadingases is scanty. It is generally agreed that improve-ent in implant primary stability will improve the

mplant survival rate.39-41 Turkyilmaz42 confirmed atrong correlation between primary stability and in-ertion torque values. Good primary stability43 en-bled micromotion to be kept under the criticalhreshold of 100 �m for healing to undergo osseointe-ration rather than fibrous repair. Ottoni et al44 sug-ested that survival rate was independent of implantength, site position, and bone quality and quantity,ut that the risk for implant failure was associatedith insertion torque. However, the result was basedn single-tooth implants. Esposito et al45 stated that aigh degree of primary stability (high value of inser-ion torque) seemed to be one of the prerequisites for

successful immediate/early loading procedure.owever, Horwitz et al46 were not able to produce a

imilar result.The present findings supported the fact that theaximal insertion torque values of failed cases were

ignificantly (P � .01) lower than those of successfulases in immediate loaded maxillas and mandibles.ence, a low insertion torque can reasonably be con-

idered a risk factor for immediate loading implants indentulous maxillae and mandibles. Tapered implantsere preferred in maxillas and mandibles by the sur-

eons in the study, most probably because of theelative ease to obtain better primary stability,47

hereas the configuration of implants, parallel versusapered ones, was found not directly related to sur-ival rate.The maximal insertion torque value was the most

onvenient way of recording primary stability. In con-rast to resonance frequency analysis, a longitudinalollow-up of stability changes cannot be made. How-ver, a strong correlation between maximal insertionorque and resonance frequency analysis has beenound.42 Some of the presented cases were performedefore the resonance frequency analysis units werevailable, so the corresponding data were found in-omplete and, hence, only the maximal insertionorque values were documented. In future studies,nclusion of resonance frequency analysis and longi-udinal follow-up of implants in a prospective design
re suggested.

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Not long ago, it had been suggested48-50 that im-lants placed in the anterior mandible had higherurvival rates than for the posterior maxillas due tohe frequently encountered poor bone quality. Theoor bone quality was a result of increased cancellousnd reduced cortical content. Recently, with im-roved understanding and surgical technique, im-lant success in the posterior maxilla became compa-able to those of the anterior mandible, even inmmediate loading cases.51-53 Glauser et al51 treated 38atients with 102 Brånemark System MK IV TiUnite

mplants (38 maxillary and 64 mandibular), most ofhich were placed in posterior regions (88%) andainly in soft bone (76%). The CSR was 97.1% and

hey concluded that the immediate loading protocolas a successful treatment alternative in regions of

oft bone. This was supported by findings in theecent study. To overcome the poor bone quality inhe posterior maxilla, primary stability can be ensuredsing different techniques such as bicortical anchor-ge,39 osteotome technique, adaptive drill sequence,54

nd use of tapered implants.47,55 In the recent study,hese measures seemed to be effective because mostnsertion torques, even in the posterior maxillas, werequal to or greater than 50 N-cm.

ummary

1. The immediate loading protocol by fixed provi-sional prostheses proved to be an effectivemethod in restoring edentulous maxillas andmandibles. There is no significant difference insurvival rates between maxillas and mandibles.

2. In failed implants, the maximal insertion torquevalues were significantly lower than those ofsuccessful implants.

3. There was no statistical significant difference inimplant survival rates between anterior and pos-terior maxillas.

4. The implant survival rate was not affected by thechoice of implant diameter, the systems used(Brånemark vs Replace System), the configura-tion of implants (parallel vs taper), and the typeof abutment connections (external vs internal).

cknowledgment

This work was supported by Dr Amy Wong, wife of Dr Williami. The authors express their deep gratitude to Miss May Wong, CM,ho is a statistician and associate professor in dental public health

t the University of Hong Kong, for her effort and patience inerifying the data in this study.

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Documents

Retrospective Study on Immediate Functional Loading of Edentulous Maxillas and Mandibles With 690 Implants, Up to 71 Months of Follow-Up