Clinical Paper

Dental Implants

Int. J. Oral Maxillofac. Surg. 2016; 45: 526–534http://dx.doi.org/10.1016/j.ijom.2015.12.001, available online at http://www.sciencedirect.com

Immediate loading of implantsinserted in edentulous archesusing multiple mucosa-supported stereolithographicsurgical templates: a 10-yearprospective cohort studyM. Cassetta: Immediate loading of implants inserted in edentulous arches usingmultiple mucosa-supported stereolithographic surgical templates: a 10-yearprospective cohort study. Int. J. Oral Maxillofac. Surg. 2016; 45: 526–534. # 2015International Association of Oral and Maxillofacial Surgeons. Published by ElsevierLtd. All rights reserved.

Abstract. The purpose of this prospective study was to evaluate survival and marginalbone loss at 10-year follow-up of implants inserted in completely edentulous archesand immediately loaded using multiple mucosa-supported stereolithographicsurgical templates. The influence on marginal bone loss of the following variableswas evaluated: sex, smoking habit, arch, implant position, implant diameter, andimplant length. Prosthesis survival and success were also determined. STROBEguidelines were followed. One hundred and eighty-eight implants were inserted in16 consecutively selected patients using a prefabricated metal-reinforced full-archprovisional acrylic restoration. The definitive metal–ceramic full-arch prosthesiswas delivered within 2 weeks. Kappa statistics, two-way analysis of variance(ANOVA) with Bonferroni adjusted post hoc test, one-way ANOVA with Tukey’srange test, and unpaired Student t-tests were used for the analysis. Four implantsfailed during the first year of function (maxilla 3, mandible 1), leading to a 10-yearsurvival rate of 97.9%. The mean marginal bone loss after 10 years was 0.76 mm.The marginal bone changes were found not to be influenced significantly by thevariables evaluated (P > 0.05). The prosthetic success rate was 66.7%; noprosthesis failures occurred. In conclusion the technique described is a predictabletreatment option with high survival in the long-term follow-up.

0901-5027/040526 + 09 # 2015 International Association of Oral and Maxillofacial Surge

M. CassettaDepartment of Oral and MaxillofacialSciences, School of Dentistry, ‘‘Sapienza’’University of Rome, Rome, Italy

Key words: dental implants; dental prosthesis;implant-supported; immediate dental implantloading; stereolithographic surgical template;computer-aided implantology; prospectivestudies.

Accepted for publication 2 December 2015Available online 29 December 2015

ons. Published by Elsevier Ltd. All rights reserved.

Stereolithographic surgical templates for implants 527

Immediate loading of dental implants hasproven to be a viable option for restoringmissing teeth in a variety of edentulousareas, decreasing the duration of treatmentand the number of visits between implantplacement and construction of the finalprosthesis.1,2 Historically, implant place-ment has been performed based only onavailable residual bone; more recently theidea of ‘prosthesis-driven implant dentist-ry’ was introduced to consider not only theexisting bone structure but also the posi-tion of the planned teeth.3 The use ofsoftware programs for implant planningand rapid prototyping, which allow thelayer by layer development of three-dimensional (3D) physical models directlyfrom a computer-aided design (CAD)model, has enabled the construction ofcustom-made stereolithographic surgicalguides to transfer the plan to the patient– the so called ‘image-guided templates’or stereolithographic surgical templates.4,5

There are few clinical reports on theoutcomes of implants inserted usingstereolithographic surgical templates de-spite their large-scale introduction overthe last decade. Studies on the combineduse of stereolithographic guides for im-plant placement and the construction of afixed restoration before implant placementto immediately load the implants are stillscarce.6,7

The purpose of the present prospectivestudy was to evaluate survival and mar-ginal bone loss clinically at 10-year fol-low-up of implants inserted using multiplemucosa-supported stereolithographic sur-gical templates and loaded immediatelywith a provisional restoration manufac-tured before surgery (main outcome).The influence on peri-implant bone remo-delling of various biologically relevant(sex and smoking habit), anatomical (archand implant location), and implant-relatedvariables (implant lengths and diameters)was also evaluated (secondary outcomes).

It was hypothesized that this techniqueis effective, with a high implant survivalrate and low marginal bone loss. It wasalso hypothesized that there would be atleast one variable with a statistically sig-nificant influence on marginal bone loss.

Materials and methods

Study setting and patient selection

This prospective cohort study was con-ducted at the department of oral and max-illofacial sciences of the study university inRome. The period of recruitment was fromNovember 2001 to January 2002. Patientswere selected consecutively and treated

from February 2002 to December 2003.After delivery of the definitive restorations,all patients were monitored annually andreceived supportive periodontal therapy.The patients were observed until July2014. The STROBE (Strengthening theReporting of Observational Studies in Epi-demiology) guidelines for prospective co-hort studies were followed. This clinicalinvestigation was conducted in accordancewith the ethical principles of the WorldMedical Association Declaration of Hel-sinki and was undertaken after informingthe patients of the content, risks, and ben-efits of the study; written consent wasobtained from each participant. The inves-tigation was reviewed and approved by thelocal ethics committee.

The main inclusion criteria were that thepatient be systemically healthy, totallyedentate, and in need of an implant-pros-thetic rehabilitation. A vertical boneheight of at least 10 mm, adequate bucco-palatal or buccolingual dimensions at theplanned implant site, and a minimum ofsix implants planned in the upper arch orfive implants planned in the lower archwere also required criteria. The patientswere in a stable occlusal relationship withno parafunctional habits (clenching and/orbruxing) and the implant sites were free ofinfection and/or tooth remnants.

Exclusion criteria were alcohol or drugabuse and general health conditions thatdid not permit a surgical procedure. Localcontraindications were, for example,tumours and ulcers. In addition, reasonto believe that the treatment might havea negative effect on the patient’s psycho-logical situation was also considered anexclusion criterion. A smoking habit wasnot considered a contraindication and wasdefined as smoking more than 10 cigar-ettes per day. The same operator (M.C.)performed the virtual surgical planningand surgical procedures. The treating cli-nician was an expert in implant dentistryand in immediate loading, but not in theuse of multiple stereolithographic surgicaltemplates.

Procedures (surgical and prosthetic

phases)

The protocol employed in this clinicalstudy consisted of an integrated treatmentsequence that included the steps outlinedbelow.

(1) Creation of a radiopaque diagnostictemplate, a ‘scanno-guide’. Thisrepresented an exact replica of a tem-porary removable complete denturethat was accepted by the patient and

fulfilled the aesthetic and functionalrequirements.

(2) Computed tomography (CT) scan ofthe patient’s arch. This was obtainedwith a spiral CT device (AsteionMulti; Toshiba Medical Systems,Rome, Italy). The scanno-guide wasworn to integrate the anatomical datawith the functional and aestheticrequirements. The CT examinationwas performed at least 1 month afterthe last tooth extraction.

(3) Digital 3D CT-based surgical plan-ning. The computer program employedin this study was SimPlant (MaterialiseDental, Leuven, Belgium). Using thissoftware, the implants were placed vir-tually, according to the bone anatomyand prosthetic designs. The potentialreceptor sites were located, and afterevaluating the volume of availablebone, the implants were placed withtheir corresponding abutment exten-sions. In the planning phase, disparal-lelism between abutments greater than208 was avoided in order to reduce thetechnical difficulties in the laboratoryphase. Each potential implant site wasalso evaluated for bone density usingthe Hounsfield scale (Hounsfield Units,HU) to assess its potential for immedi-ate loading.

(4) Development of a CAD design of thestereolithographic surgical template.This was performed by the clinician,in accordance with the patient’s pros-thetic and anatomical needs.

(5) Computer-aided manufacturing(CAM) of multiple stereolithographicsurgical templates (SurgiGuide; Ma-terialise Dental, Leuven, Belgium) totransfer the digital plan to the surgicalenvironment. The surgical guideswere employed in each patient to ac-commodate the three specified drillsof increasing diameter used for osteot-omy preparation. Therefore, threetemplates were created, characterizedby 5-mm-high stainless steel tubes0.2 mm wider than each drill. A fourthtemplate was ordered with 5-mm-highstainless steel tubes 0.2 mm widerthan the diameter of correspondingplanned implant mounting devices.

(6) Construction of a virtual plaster cast.Once the series of templates had beenreceived, the fourth template was usedto prepare the working cast, whichwas then used to create the temporaryprosthesis. The plaster cast was char-acterized by the presence of the ana-logues of the implants included in thecast. The mucosa-supported template

528 Cassetta

faithfully replicated the patient’sedentulous arch. SimPlant softwareallowed the thickness of the mucosacorresponding to each implant site tobe known. The mounting devices wereplaced in the template’s steel tube,emerging from the tube with a dis-tance corresponding to the thicknessof the mucosa. The mounting devicewas locked with adhesive wax and theimplant analogues were screwed intothe mounting devices that were placedthrough the template. Plaster waspoured into the template and theresulting internally hexed implant rep-lica was placed into the plaster castin a 3D position similar to that pro-grammed virtually. To facilitate theprosthetic phase and to synchronizethe position of the abutment within theanalogue/implant, the flat side of theinternal hex was rotated to the facialsurface. Then, a plaster cast with theimplants inserted was obtained beforethe computer-guided surgery: a so-called ‘virtual plaster cast’. Transferof the intermaxillary relationships wasobtained using the scan template(‘scanno-guide’). After mounting theplaster casts in the articulator, a newdiagnostic wax-up was performed, thetitanium abutments were milled, andthe metal-reinforced full-arch provi-sional acrylic restorations manufac-tured (Fig. 1A–D). The mucosa-supported guides did not require a flapreflection, but employed a flapless/transmucosal approach. Once the pre-operative laboratory phase was com-pleted, the patient was scheduled forsurgery.

(7) Computer-aided surgery. This was ex-ecuted in accordance with the proto-cols of the implant system used. Onehundred and eighty-eight cylindricalimplants (Premium; Sweden and Mar-tina, Due Carrare, Padova, Italy) withan internal hexagon (diameters rangingfrom 3.5 mm to 5.0 mm and lengthsfrom 10.0 mm to 18.0 mm) wereinserted in completely edentulouspatients, using multiple mucosa-sup-ported stereolithographic templates.The multiple mucosa-supportedstereolithographic templates allowedthe implant site preparation to be con-trolled, without depth control (Fig. 1Eand F). Once the drilling sequencehad been completed, the implants wereplaced into each osteotomy and rotatedto the final depth, with the flat sideof the hex positioned facially.

(8) Immediate loading. The primary im-plant stability of the inserted implants

was determined by evaluating theinsertion torque using a manual cali-brated torque gauge ratchet (Swedenand Martina, Due Carrare, Padova,Italy) and by resonance frequencyanalysis (RFA) (Osstell, IntegrationDiagnostics, Savadaled, Sweden).Implants characterized by an inser-tion torque of at least 30 N�cm and byan implant stability quotient (ISQ)value of �60 were immediately load-ed (Fig. 1F). The abutments werepositioned properly. Baseline postop-erative peri-apical radiographs weretaken for every patient immediatelyafter abutment positioning to controlthe reciprocal fixture–abutment adap-tation, which cannot be assessed di-rectly. Using a flapless technique,the interposition of soft tissue mayprevent the proper implant–abutmentfit and lead to difficulty adaptingthe temporary prosthesis, with a sub-sequent error in the construction ofthe final restoration. Abutment paral-lelism was assessed and the abut-ments milled when necessary(Fig. 1G). During the adjustment,selective trimming of the temporaryprosthesis was sometimes necessary,without severely affecting the rigidi-ty of the whole bridge. The provision-al restoration was then adapted tothe titanium abutments with cold-cured acrylic resin (Fig. 1H). Carewas taken to evaluate the arch mid-line, vertical dimension, and incisalshow continuously. Determinationof the occlusal plane was also impor-tant when the maxilla and mandiblewere reconstructed simultaneously.After completing and polishing thetemporary prosthesis, an impressionwas taken at the abutment level formanufacturing of the definitive pros-thesis. Further attention was given toavoiding the retention of impressionmaterial between the threads of theflapless inserted implants. The tem-porary restoration was seated andadjusted to remove any lateral, pro-trusive, and occlusal interferences.Centric and lateral contacts wereassessed with articulating paperuntil light occlusal contacts, uniform-ly distributed on the entire prostheticarch, were obtained. The prosthesiswas cemented and remained inplace for approximately 2 weeks –the time taken to delivery of thedefinitive metal–ceramic, cement-retained, full-arch prosthesis. A softdiet was suggested during the provi-sional prosthesis stage.

Assessment of marginal bone

The marginal bone level was recorded bytaking standardized peri-apical radio-graphs, obtained with the use of the long-cone parallel technique and a Rinn XCPfilm holding system (Rinn XCP; DentsplyRinn, Elgin, IL, USA). Care was taken toalign the X-ray film in the film holderparallel to the long axis of the implants.Digital radiographs were stored using adigital intraoral imaging system (DenOptixQST Digital X-ray Phosphor Plate System;Gendex, Hatfield, PA, USA). The storedimages were displayed on a monitor anddirect measurements were performed usingthe software VixWin PRO (Gendex, Hat-field, PA, USA). Linear measurementsfrom the fixture–abutment junction to crest-al bone level were obtained mesially anddistally using the software programme toanalyze each image. Measurements takenfrom the radiographs obtained at the time ofimplant placement (T0) were used as base-line values. Baseline measurements (T0)were used to determine the amount ofcrestal bone remodelling at the 10-yearfollow-up (T1). To make calibrated mea-surements, an object of known size wasused, e.g. the known length of the implant.Two researchers evaluated the radiographsindependently; these researchers were notinvolved in the clinical part of the investi-gation. Inter-examiner and intra-examinerreliability was determined. Kappa statisticswere used to compute intra- and inter-ex-aminer reliability. The intra-examiner kap-pa coefficients were 0.84 and 0.88. Theinter-examiner kappa coefficient was 0.78.

Implant survival criteria

Survival of the inserted implants wasassessed at the 10-year follow-up. Theassessment of implant survival and failurewas based on the criteria suggested byBuser et al.8 and Cochran et al.9

Prosthesis success and survival

The prosthesis survival and success rateswere evaluated at the 10-year follow-up.Prosthesis success was evaluated usingmodified evaluation criteria suggestedby the California Dental Association anddescribed by Pozzi et al.7 A ‘survivingprosthesis’ was considered a prostheticreconstruction that was stable and in goodfunction.7

Study variables

The predictor variables, i.e. clinical expo-sures or clinical risk factors considered to

Stereolithographic surgical templates for implants 529

Fig. 1. Images from a male 49-year-old smoker affected by periodontal disease and requiring an implant-prosthetic rehabilitation. (A)Preoperative panoramic radiograph. All teeth were extracted and the patient was rehabilitated with upper and lower complete temporarydentures. After the extractions, the temporary dentures were relined and duplicated using barium sulphate. (B) A stereolithographic surgicaltemplate was used to manufacture the ‘virtual plaster cast’; the mounting devices and the analogues of implants fixed through the template steeltubes are shown. (C) A virtual plaster cast and the milled abutments. (D) The provisional restorations. (E) The insertion of 12 implants in the upperarch, and (F) 10 implants in the lower arch, and evaluation of primary stability using resonance frequency analysis (RFA). (G) Abutment millingand (H) delivery of the provisional restorations.

influence marginal bone loss, weregrouped into the following categories:(1) biologically relevant variables: (a)sex (male or female), (b) smoking habit(smoker or non-smoker); a smoker wasdefined as a patient who smoked morethan 10 cigarettes per day. (2) Anatomicalvariables: (a) arch (maxilla or mandible),(b) implant location (anterior (incisor andcanine area) or posterior (premolar and

molar area)). (3) Implant-related vari-ables: (a) implant length (10.0, 11.5,13.0, 15.0, or 18.0 mm), (b) implant di-ameter (3.5, 4.2, or 5.0 mm).

Minimization of potential sources of bias

In order to reduce potential sources ofbias, the same operator performed thevirtual surgical planning and the surgical

and prosthetic treatments (M.C.). Thesame operator, expert in implantologyand prosthodontics, completed all thefollow-up assessments.

Statistical analysis

Statistical analyses were performed usingIBM SPSS Statistics version 20.0 soft-ware (IBM Corp., Armonk, NY, USA).

530 Cassetta

Table 1. Implants and treatment characteristics (n = 188).

Mean Number of implants %

Age, years 58.28Sex

Male 148 78.7%Female 40 21.3%

Smoking habitSmoker 92 48.9%Non-smoker 96 51.1%

ArchMaxilla 118 62.8%Mandible 70 37.2%

Implant locationAnterior 94 50.0%Posterior 94 50.0%

Implant length, mm10.0 12 6.4%11.5 12 6.4%13.0 28 14.9%15.0 112 59.6%18.0 24 12.8%

Implant diameter, mm3.5 80 42.6%4.2 92 48.9%5.0 16 8.5%

Descriptive statistics, including meanvalues and standard deviations, were usedfor the presentation of demographic studyvariables. The statistical analysis was per-formed at the implant level. Two-wayanalysis of variance (ANOVA) with Bon-ferroni adjusted post hoc test was used toevaluate the influence of different vari-ables on the crestal bone levels. If any ofthe interaction terms was significant inthe two-way ANOVA, then one-wayANOVA with Tukey’s range test wasused to analyze the significant variableswith more than two clusters. The unpairedStudent t-test was used to analyze thesignificant variables with only two clus-ters. For all the tests performed, the sig-nificance level was set at P < 0.05.

Results

Thirty-six patients were assessed for eli-gibility. Eighteen patients were not eligi-ble as they did not meet the inclusioncriteria and two patients did not provideconsent. Thus a total of 16 patients wereenrolled consecutively in this prospectivestudy. No patient was removed from thesample during the follow-up.

The average age of the patients was58.28 years (range 48–69 years); the maleto female ratio was 3:1. Of the 16 patients,eight were current smokers (>10 cigar-ettes a day). The total number of implantsinserted using multiple mucosa-supportedstereolithographic surgical templates was188. All inserted implants were loadedimmediately. Implant characteristics aresummarized in Table 1. Eight cases re-ceived simultaneous maxilla and mandiblerehabilitation. A mean of 7.37 implantswere used to reconstruct an edentulousmaxilla and a mean of 5.83 implants foran edentulous mandible. All patients com-pleted the 10-year follow-up.

Implant survival and marginal bone loss

Four implants failed during the first yearof function – three in the maxilla and onein the mandible (Fig. 2). The mean time tofailure was 27 days postoperative. The 10-year survival rate was 97.9%. Mean mar-ginal bone loss was 0.76 mm after 10 years(Table 2). The marginal bone loss wasfound not to be significantly influencedby the variables evaluated (P > 0.05).

Prosthetic outcome

All patients received the provisional res-toration immediately after implant place-ment. The surgical and prosthetic phasestook approximately 2 h per arch. The

definitive prosthesis was delivered within20 days in all cases. In three cases, due toearly implant failure, the final prosthesiswas modified after delivery. Pink porce-lain was used to adjust the prosthesis,based on the volume of missing hardand soft tissues and the length of the teeth(Fig. 2). At the 10-year follow-up, allprostheses were structurally intact, stable,and in good function. No fracture of themetal structure and no other mechanicalcomplications such as screw loosening orfracture had occurred during the entirefollow-up period, leading to a prosthesissurvival rate of 100%. At the 10-yearfollow-up, fractures of the porcelainsurface without metal exposure werefrequent, occurring in 8/24 restorations,giving a prosthetic success rate of66.7%. Considering the dental unit, 38/298 dental units experienced porcelainfracture without metal exposure, yieldinga cumulative prosthetic success rate of87.2% at the unit level.

Discussion

The first hypothesis of the present studywas confirmed by the results. The tech-nique described was found to be effective,with a high survival rate and low marginalbone loss at the 10-year follow-up. Thesecond hypothesis was not confirmed. Theresults of the present study demonstratedthat no variable significantly influencedmarginal bone loss.

In terms of the limitations of this study,standardized digital peri-apical radio-graphs were used to evaluate marginal

bone level changes. As stated by De Smetet al.,10 absolute and corrected radiograph-ic measurements of mean bone level dif-ferences around implants taken fromdigital and conventional intraoral filmsare within a range of 0.2 mm, indicatingthat standardized peri-apical radiographsare precise. However, only mesial anddistal bone levels were assessed on theintraoral radiographs; no assessment wasmade of the facial or lingual sites. This isan intrinsic limitation in interpreting peri-apical films, but this method is commonlyused for bone level evaluation aroundteeth and implants. A further limitationof the study was that no customized radio-graphic jig was used to take reproducibleradiographs.

There is a tendency in implantology toreduce the treatment time and simplify thetreatment procedures in order to increasepatient compliance while maintaininglong-term predictability of treatment out-comes.11,12 With regard to the treatmentoutcomes of implants inserted using amucosa-supported stereolithographic sur-gical template and loaded immediatelywith a prefabricated fixed restoration, dataavailable are scarce and related to a shortfollow-up. Komiyama et al. evaluated theoutcome of immediately loaded implantsinserted in edentulous jaws followingcomputer-assisted virtual treatment plan-ning combined with flapless surgery.6 Inthat study, 176 fixtures were installed tosupport 21 maxillary and 10 mandibularreconstructions. Patients were followedfor up to 44 months. Nineteen out of176 fixtures were lost between 2 and

Stereolithographic surgical templates for implants 531

Fig. 2. Images from a female 65-year-old non-smoker affected by periodontal disease. (A) Preoperative panoramic radiograph. The patient wassubjected to the extraction of all the teeth of the upper arch, including the impacted canine. A few days later, the immediate upper complete denturewas duplicated using barium sulphate and the patient underwent computed tomography. Images were imported into SimPlant 8.33 software and theinsertion of fixtures was planned. (B) On the 3D image, the site of the extracted impacted canine, evaluated using the SimPlant software densitytool, showed low bone density values corresponding to the planned implant sites (bone density values of the implant sites between 250 and300 HU). Although the site corresponding to the impacted tooth was considered at risk, the insertion of two implants was planned. These implantswere lost during the first month of immediate loading. (C) The insertion of the nine fixtures with the flapless technique. (D) The abutmentspositioned and adapted for the provisional restoration; the fixtures were then loaded. At the time of implant placement, the impression for theconstruction of the definitive prosthesis was also taken. (E–G) The correct fit between fixture and abutment and the initial marginal bone level weredetermined using peri-apical radiographs. (H, I) 10-year follow-up peri-apical radiographs highlighted a moderate marginal bone loss, and (J, K)clinical examination showed a moderate marginal inflammation of the soft tissues with an increased probing depth.

18 months after installation. The fixturesurvival rate was 89% (92% maxilla, 83%mandible). In a recent review on implantloading protocols for edentulous patientswith fixed prostheses, four of the 45 in-cluded studies implemented guided flap-less surgery with the Teeth-In-An-Hourprotocol (NobelGuide), which involvesimmediate loading with prefabricated de-finitive and/or provisional prosthesesmade of titanium and resin or full acryl-ic.12 It was found that when immediateloading was combined with guided flap-less implant placement, the implant sur-vival rate ranged from 90% to 99.4%(range of follow-up 12–51 months). Inthe present study, a prefabricated provi-sional restoration was used to immediately

load the implants rather than a definitiverestoration.

Although a number of studies haveshown acceptable accuracy of computer-assisted implant surgery, deviations be-tween the virtual and actual implant posi-tion clearly prevent the fabrication of theimplant-supported definitive restorationprior to surgery.4,5,13 Hence, if immediateloading of implants is pursued, only ametal-reinforced provisional restorationcan be manufactured before the surgery.As stated by Landazuri-Del Barrio et al.,14

the fabrication of a final prosthesis shouldbe based on the actual impression of theimplants at the time of surgery and not ontheir virtual position. In the present study,the impression for the final prosthesis was

taken at the abutment level at the time ofimplant insertion to compensate for thedeviation between the planned and actualimplant positions.4 In this study, the suc-cess and survival rates at 10 years offollow-up were found to be similar tothose reported in the literature, and thefailures were limited to the first month ofloading. The immediate splinting of theinserted implants with a full-arch metal-reinforced provisional acrylic restorationmanufactured before surgery and the de-livery of the definitive prosthesis within 20days probably determined this low failurerate by limiting the micromotion duringthe early stages of healing.

Primary stability, advocated as one ofthe most important factors for the success

532 Cassetta

Table 2. The mean, maximum, minimum, and standard deviation values of marginal bone loss(n = 188).

10-year follow-up

Mean Max. Min. SD

SexMale �0.8 �5.15 1.05 1.24Female �0.61 �1.05 �0.15 0.27

Smoking habitSmoker �0.93 �5.15 0.7 1.14Non-smoker �0.59 �3.3 1.05 1.11

ArchMaxilla �0.79 �5.15 1.05 1.20Mandible �0.72 �3.3 0.6 1.03

Implant locationAnterior �0.87 �5.15 1.05 1.44Posterior �0.66 �2 0.6 0.72

Implant diameter, mm3.5 �1.16 �5.15 0.7 1.374.2 �0.43 �1.65 1.05 0.775.0 �0.53 �1.75 0.45 0.84

Implant length, mm10.0 �0.12 �0.4 0.45 0.4411.5 �0.2 �1.75 0.7 1.2113.0 �0.76 �1.65 1.05 0.9215.0 �0.86 �5.15 0.95 1.2418.0 �0.96 �2.2 0.7 1.00

SD, standard deviation.

of immediate loading, can be determinedat the time of implant insertion by evalu-ating the insertion torque and/or using theRFA.15 An insertion torque of at least30 N cm and an ISQ value �60 are con-sidered prerequisites for immediate load-ing.12 Although the protocol used in thepresent study was designed 10 years ago,the current statements and clinical recom-mendations for immediate implant loadingwere met.12,15 In fact, in the present studyan insertion torque of at least 30 N�cm andan ISQ value of �60 were chosen as theinclusion criteria for immediate loading.All of the implants inserted satisfied thisprerequisite and were loaded immediately.The four implants lost (three in the maxillaand one in the mandible) presented inser-tion torque between 30 and 35 N�cm at thetime of insertion and loading, and ISQbetween 65 and 68. It is hypothesized thatthe relatively low density values of thebone corresponding to the planned implantsites (Fig. 2), evaluated using the SimPlantsoftware density tool (bone density valuesof the implant sites between 250 and300 HU), or overheating during implantsite preparation caused the implant losses.

Regarding the implant surface, Papas-pyridakos et al.12 highlighted that theuse of surface-modified implants playsan important role in the success of imme-diate loading. The importance of theimplant surface has also been highlightedby Gallucci et al.15 On evaluating the

existing literature, these authors stated thatimmediate loading of microtextured den-tal implants with a one-piece fixed interimprosthesis in both the edentulous mandibleand maxilla is as predictable as earlyand conventional loading.15 In the presentstudy, surface-modified implants wereused, characterized by a machined neckand by an implant body with a sandblastedand acid-etched implant surface (SLA) inthe coronal portion and a titanium plasmaspray surface (TPS) in the middle andapical thirds.

In a review of the literature, the numberof implants per patient used in the imme-diate loading protocol has varied betweenresearch groups, ranging from 4 to 12implants per arch for the edentulous max-illa, and from 2 to 10 for the edentulousmandible.12 In the present study, assuminga greater risk inherent to the protocol used,the highest possible number of implantswas inserted to easily compensate for thepossible loss of some implants.

Regarding the complications of imme-diately loaded implants (using a prefabri-cated fixed implant prosthesis) installedin edentulous jaws following computer-assisted virtual treatment planning andflapless surgery, Komiyama et al.6 statedthat surgical or technical complicationsoccurred in 42% of treated cases. Theauthors concluded that compared to con-ventional protocols, the occurrences ofsurgical and technical complications were

higher, and thus this method must still beregarded as in an exploratory phase.6

Complications are frequent and usuallycaused by a misfit between the implantsinstalled and the prefabricated prosthe-sis.16 It is difficult to achieve a passivefit of a prefabricated metal framework onthe inserted implants.16 The absence of apassive fit may further lead to mechanical(screw loosening) and biological (margin-al bone loss) complications.16 In the pres-ent study, awareness that a deviationbetween the planned and the actual im-plant position is always present, promptedthe use of a pre-fabricated provisionalrestoration rather than a pre-fabricateddefinitive prosthesis.17 Using multiplestereolithographic surgical guides, im-plant placement is quick, but the position-ing of the abutment and the matching ofimplant and analogue hex are difficult. Tofacilitate the prosthetic phase and to syn-chronize the position of the abutmentwithin the analogue/implant, the flat sideof the internal hex was rotated to the facialsurface. Using the technique described inthe present study, it was possible to com-pensate for the discrepancy between theplanned and the actual implant positionafter implant placement and abutmentconnection. In fact no complications relat-ed to a misfit between the pre-fabricatedprosthesis and abutments were recorded.The removal of all of the possible dispar-allelism, taking the impression for thedefinitive prosthesis at the time of implantplacement, with the delivery of the defini-tive prosthesis within 20 days, allowedrigid splinting of the implants, which isessential for the immediate loading proto-cols, with a reduction in prosthetic com-plications.

Better results can now be achievedusing a single stereolithographic surgicalguide and methods aimed at reducing themechanical error (intrinsic error) causedby the cylinder–burr gap.18,19 Limiting theerror that originates from mechanicalcomponents, the total error (deviation be-tween the planned implant position andthe actual implant position) can be re-duced significantly, making the adaptationof a prefabricated prosthesis easier.20 Inthe present study, no immediate prostheticcomplications were recorded, but only latecomplications, limited to the fracture ofthe porcelain; no prosthesis replacementswere required, and no mechanical compli-cations (screw loosening or fracture ofthe metal structure) occurred during thefollow-up.

D’Haese et al.,21 evaluating factors thatinfluence the survival of implants placedusing stereolithographic surgical guides

Stereolithographic surgical templates for implants 533

and loaded immediately, found that theloading protocol, sex, jaw location,and implant length did not influence im-plant survival. Regarding the variablesevaluated in the present study, noneseemed to affect the marginal bone loss,although these results could have beeninfluenced by the limited number ofimplants.

In conclusion, when a multiple stereo-lithographic surgical guide is used, there isalways a deviation between the plannedand actual implant positions. The coronaldeviation of the inserted implant mayhamper the correct fit of a prefabricatedprosthesis and require adaptation of fit andocclusion.4 Using the technique describedin the present study, it was possible tocompensate for this discrepancy betweenthe planned and actual implant positionsafter implant placement and abutmentconnection. The immediate use of a met-al-reinforced prefabricated full-arch pro-visional acrylic restoration and thedelivery of a definitive metal–ceramic,cement-retained, full-arch prosthesis with-in 20 days allowed rigid splinting of theimplants, reducing the prosthetic compli-cations and achieving high survival andsuccess rates in the long-term follow-up.However, the limited sample size of thisstudy did not allow the impact on marginalbone loss of the various biologically rele-vant, anatomical, and implant-related vari-ables to be confirmed. Further prospectivestudies with larger samples are needed toconfirm the impact of systemic and/orlocal factors on the treatment outcomesof immediately loaded implants placedusing the technique described, but the highsurvival, low marginal bone loss, andabsence of surgical and prosthetic compli-cations confirm that this is a predictabletreatment option.

Funding

None.

Competing interests

None.

Ethical approval

The local ethics committee approved thestudy (Umberto I Policlinico di Roma; Rif.1872/08.04.10).

Patient consent

Required and obtained.

Acknowledgements. The author thanks DrAlfonso Di Mambro and Dr Matteo Gian-santi for their valuable assistance in themeasurement of marginal bone levels andin the statistical analysis of the data. Theauthor also thanks Carlo Basilici, dentaltechnician at the Department of Oral andMaxillofacial Sciences of ‘‘Sapienza’’University of Rome.

References

1. Li W, Chow J, Hui E, Lee PK, Chow R.

Retrospective study on immediate functional

loading of edentulous maxillas and mand-

ibles with 690 implants, up to 71 months of

follow-up. J Oral Maxillofac Surg 2009;67:

2653–62.

2. Chee W, Jivraj S. Efficiency of immediate

loaded mandibular full arch implant restora-

tions. Clin Implant Dent Relat Res 2003;5:

52–6.

3. Kopp KC, Koslow AH, Abdo OS. Predict-

able implant placement with a diagnostic/

surgical template and advanced radiographic

imaging. J Prosthet Dent 2003;89:611–5.

4. Cassetta M, Stefanelli LV, Giansanti M,

Calasso S. Accuracy of implant placement

with a stereolithographic surgical template.

Int J Oral Maxillofac Implants 2012;27:

655–63.

5. Cassetta M, Di Mambro A, Giansanti M,

Stefanelli LV, Barbato E. How does an error

in positioning the template affect the accu-

racy of implants inserted using a single fixed

mucosa-supported stereolithographic surgi-

cal guide. Int J Oral Maxillofac Surg

2014;43:85–92.

6. Komiyama A, Klinge B, Hultin M. Treat-

ment outcome of immediately loaded

implants installed in edentulous jaws follow-

ing computer-assisted virtual treatment plan-

ning and flapless surgery. Clin Oral Implants

Res 2008;19:677–85.

7. Pozzi A, Holst S, Fabbri G, Tallarico M.

Clinical reliability of CAD/CAM cross-arch

zirconia bridges on immediately loaded

implants placed with computer-assisted/

template-guided surgery: a retrospective

study with a follow-up between 3 and 5

years. Clin Implant Dent Relat Res

2015;17(Suppl. 1):e86–96.

8. Buser D, Mericske-Stern R, Bernard JP,

Behneke A, Behneke N, Hirt HP, et al.

Long-term evaluation of nonsubmerged ITI

implants. Part 1: 8-year life table analysis of

a prospective multi-center study with 2359

implants. Clin Oral Implants Res 1997;8:

161–72.

9. Cochran DL, Buser D, ten Bruggenkate C,

Wiengart D, Taylor T, Bernard JP, et al. The

use of reduced healing times on ITI implants

with a sandblasted and etched (SLA) sur-

face: early results from clinical trials on ITI

SLA implants. Clin Oral Implants Res

2002;13:144–53.

10. De Smet E, Jacobs R, Gijbels F, Naert I. The

accuracy and reliability of radiographic

methods for the assessment of marginal bone

level around oral implants. Dentomaxillofac

Radiol 2002;31:176–81.

11. Sanna AM, Molly L, van Steenberghe D.

Immediately loaded CAD–CAM manufac-

tured fixed complete dentures using flapless

implant placement procedures: a cohort

study of consecutive patients. J Prosthet

Dent 2007;97:331–9.

12. Papaspyridakos P, Chen CJ, Chuang SK,

Weber HP. Implant loading protocols for

edentulous patients with fixed prostheses:

a systematic review and meta-analysis. Int

J Oral Maxillofac Implants 2014;29(Suppl.):

256–70.

13. Cassetta M, Giansanti M, Di Mambro A,

Calasso S, Barbato E. Accuracy of two

stereolithographic surgical templates: a ret-

rospective study. Clin Implant Dent Relat

Res 2013;15:448–59.

14. Landazuri-Del Barrio RA, Cosyn J, De Paula

WN, De Bruyn H, Marcantonio Jr E. A

prospective study on implants installed with

flapless-guided surgery using the all-on-four

concept in the mandible. Clin Oral Implants

Res 2013;24:428–33.

15. Gallucci GO, Benic GI, Eckert SE, Papas-

pyridakos P, Schimmel M, Schrott A,

et al. Consensus statements and clinical

recommendations for implant loading pro-

tocols. Int J Oral Maxillofac Implants

2014;29(Suppl.):287–90.

16. D’Haese J, Van De Velde T, Komiyama A,

Hultin M, De Bruyn H. Accuracy and com-

plications using computer-designed stereo-

lithographic surgical guides for oral

rehabilitation by means of dental implants:

a review of the literature. Clin Implant Dent

Relat Res 2012;14:321–35.

17. Cassetta M, Giansanti M, Di Mambro A,

Stefanelli LV. Accuracy of positioning of

implants inserted using a mucosa-sup-

ported stereolithographic surgical guide

in the edentulous maxilla and mandible.

Int J Oral Maxillofac Implants 2014;29:

1071–8.

18. Cassetta M, Di Mambro A, Giansanti M,

Stefanelli LV, Barbato E. Is it possible to

improve the accuracy of implants inserted

with a stereolithographic surgical guide by

reducing the tolerance between mechanical

components. Int J Oral Maxillofac Surg

2013;42:887–90.

19. Cassetta M, Di Mambro A, Di Giorgio G,

Stefanelli LV, Barbato E. The influence of

the tolerance between mechanical compo-

nents on the accuracy of implants inserted

with a stereolithographic surgical guide: a

retrospective clinical study. Clin Implant

Dent Relat Res 2015;17:580–8.

20. Cassetta M, Di Mambro A, Giansanti M,

Stefanelli LV, Cavallini C. The intrinsic error

of a stereolithographic surgical template in

implant guided surgery. Int J Oral Maxillo-

fac Surg 2013;42:264–75.

534 Cassetta

21. D’Haese J, Vervaeke S, Verbanck N, De

Bruyn H. Clinical and radiographic outcome

of implants placed using stereolithographic

guided surgery: a prospective monocenter

study. Int J Oral Maxillofac Implants

2013;28:205–15.

Address:Michele CassettaDepartment of Oral and MaxillofacialSciencesSchool of Dentistry‘‘Sapienza’’ University of Rome

V. le Cesare Pavese8500144 RomeItalyTel: +39 33 37067075; Fax: +39 06 5016612E-mail: michele.cassetta@uniroma1.it