Impact of immediate loading onearly bone healing at two-pieceimplants placed in freshextraction sockets: anexperimental study in thebeagle dogBlanco J, Mareque S, Linares A, Perez J, Munoz F, Ramos I. Impact of immediateloading on early bone healing at two-piece implants placed in fresh extractionsockets: An experimental study in the beagle dog. J Clin Periodontol 2013; doi:10.1111/jcpe.12070.
AbstractObjective: To study early bone healing of immediately loaded implants placed infresh extraction sockets versus immediate implants without occlusal loading in thedog.Materials and methods: A total of 48 implants were placed in the distal socketsof Pm3 and Pm4 in the lower jaw of 12 Beagle dogs immediately after toothextraction. In the control group, no loading was applied. In the test group, animmediate loading restoration with occlusal contacts was performed. Dogs weresacrificed at 2, 4 and 8 weeks for histological analysis.Results: At the end of the study, there was a 100% implant and prosthesissurvival. Similar results for test and control groups were observed for bone-to-implant contact (%) and peri-implant bone area. Inter-thread bone area tendedto decrease in the control and increase in the test. With respect to ridge altera-tions, bone resorption was more pronounced on the buccal aspect and wasobserved in both groups.Conclusion: Immediate loading did not impair early stages of bone healing andcrestal bone modelling at two-piece implants in fresh extraction sockets in thebeagle dog; however, bone resorption occurred in all specimens in both groups.
Juan Blanco1, Santiaqo Mareque1,Antonio Linares1, Javier Perez1,
Fernando Munoz2 and Isabel Ramos1
1Department of Stomatology, University of
Santiago de Compostela, Santiago de
Compostela, Spain; 2School of Veterinary,
University of Santiago de Compostela,
Santiago de Compostela, Spain
Key words: bone healing; immediate
implants; immediate loading
Accepted for publication 9 January 2013
There has been a growing interest inimmediate implant placement overthe last few years. A number ofstudies have reported that the sur-vival rate of implants placed immedi-ately after tooth extraction is similarto that of implants placed with a
delayed protocol (Polizzi et al. 2000,Evian et al. 2004, Chen et al. 2004).However, a number of experimentalstudies have also shown that imme-diate placement does not preventbone modelling that takes place aftertooth extraction (Ara�ujo & Lindhe
Conflict of interest and source of
funding statement
The authors declare that they have noconflict of interest in this study. Thiswork was funded by Straumann(Basel, Switzerland).
2005, Ara�ujo et al. 2006a, b, Vigno-letti et al. 2009b, Caneva et al.2010a,b). This may result in a dimin-ished dimension of the ridge (Blancoet al. 2011a) and lead to unaestheticresults in certain situations (Evans &Chen 2008, Kan et al. 2011). Thus, anumber of techniques have beendescribed to try to minimize boneloss after tooth extraction, but still ahorizontal and vertical reduction ofthe ridge occurs, although only to alimited extent (Darby et al. 2009).
On the other hand, some authorshave suggested that immediate load-ing may stimulate bone formationand thus may influence the earlystages of osseointegration (Piattelliet al. 1998, Romanos et al. 2002,2003, Degidi et al. 2005).
Recently, several studies haveshown a high survival rate of imme-diate implants with immediate load-ing (Crespi et al. 2007, 2008, Alveset al. 2010, Gillot et al. 2011, 2012).
On the other hand, a systematicreview by Atieh et al. (2009) showeda significantly higher risk of failurefor immediately loaded single toothimplants placed in extraction socketscompared with immediately restored/loaded implants placed in healedridges.
Recently, a clinical and histologi-cal intra-individually controlledstudy in humans by Donati et al.(2012) has shown that immediateloading does not influence the pro-cess of formation of new bone incontact with implants placed inhealed ridges after 1 and 3 monthsof healing. However, there is a lackof information regarding the possibleinfluence of immediate loading onhealing around immediately placedimplants and its impact on bonemodelling/remodelling after toothextraction. Pre-clinical in vivo modelsallow a systematic evaluation ofhealing processes that mimic a par-ticular clinical condition such as anextraction socket, and try to relate itto human biology. Although clinicaltrials are needed to validate resultsfrom pre-clinical studies, this modelprovides the opportunity to studyproof-of-principle concepts in com-promised biological systems (Bergl-undh & Stavropoulos 2012).
Thus, the objective of this investi-gation was to assess the influence ofimmediate loading on the osseointe-gration process and modelling/remod-
elling of the alveolar ridge onimplants placed in fresh extractionsockets in the beagle dog model.
Material and methods
Twelve female adult Beagle dogs(mean age 22 months, mean weight14.5 kg) (Isoquimen, Barcelona,Spain) were used. The animals weremaintained in individual kennels in a12:12-light/dark cycle (lights on at07:00 hours) and 22–21°C. The Ethi-cal Committee Rof Codina Founda-tion approved the study protocol.All animals were subjected to sur-gery and housed in the AnimalExperimentation Service Facility atthe Veterinary Teaching HospitalRof Codina of Lugo (Spain) duringthe year 2009. The procedures wereperformed according to Spanish andEuropean Union regulations aboutcare and use of research animalsand this article has been writtenfollowing the ARRIVE guidelines(Kilkenny et al. 2011). The dogswere monitored daily during theentire experimental procedure by aveterinarian accredited and trainedin laboratory animal science.
All surgical procedures were per-formed under general anaesthesiausing propofol (2 mg/kg/i.v., Propo-vet, Abbott Laboratories, Kent,UK), and maintained on a concen-tration of 2.5–4% of isoflurane(Isoba-vet, Schering-Plough, Madrid,Spain). The animals were pre-medi-cated with acepromazine (0.05 mg/kg/i.m., Calmo Neosan, Pfizer,Madrid, Spain) and the pain wascontrolled with the administration ofmorphine (0.3 mg/kg/i.m., MorfinaBraun 2%, B. Braun Medical, Barce-lona, Spain). During anaesthesia, theanimals were continuously moni-tored by a veterinarian, controllingelectrocardiography, capnography,pulsioxymetry and non-invasiveblood pressure.
On both sides, premolars (Pm)were then hemisected by means of afissure bur and extracted using for-ceps without raising a flap. Immedi-ately after extraction, implants witha hydrophilic and sandblasted acid-etched surface (modSLA) wereinserted into the sockets of the distalroots of the extracted teeth with aflapless approach (Straumann SLAc-tive� Bone Level implant; 3.3 mm indiameter and 8 mm long; Strau-
mann� Dental Implant System,Basel, Switzerland), according to theguidelines provided by the manufac-turer. The implants were placed sothat the shoulder of the implant wasflush with the buccal bone crest. Toachieve this, the height of the buccalsoft tissue was measured with aperiodontal probe immediately beforeimplant placement.
Once the implants were placed,implant stability was measured interms of ISQ values (Implant Stabil-ity Quotient) for each one of theimplants. Multi-Base abutments(Straumann� Dental Implant Sys-tem) of 1 mm height were connectedto the implants. After abutment con-nection, the test group was allocatedto one side of the mandible by open-ing an envelope where it was writtenif the right or left side of the mandi-ble of each dog would be the testgroup. In the test group (immediateloading group), a resin-based tempo-rary prosthesis was relined at thetime of surgery. The prosthesis hadbeen performed by means of studycasts taken previously. Occlusionwas checked to make sure there wereocclusal contacts in all cases. On thecontrol side, Multi-Base abutments(Straumann) were screwed, and thenhealing abutments were connected toallow for non-submerged healing.This produced two study groupswith 24 test implants (12 test pros-thesis) and 24 control implants(Fig. 1).
Post-operative care
Post-operative pain was controlledwith morphine (0.3 mg/kg/i.m.) dur-ing the first 24 h and meloxicam(0.1 mg/kg/s.i.d/p.o., Metacam,Boehringer Ingelheim Espa~na, Barce-lona, Spain) as analgesic during thenext 3 days. Antibiotic prophylaxiswas administrated during the firstweek with amoxicillin (22 mg/kg/s.i.d./s.c., Amoxoil retard, Syva, Le�on,Spain). The dogs’ diet throughoutthe trial period was granulated dogfeed and they had free access todrinking water. The animals wereenrolled in a plaque control pro-gramme consisting of cleaning theteeth and the implants three times aweek with gauzes embedded in clorh-exidine oral rinse 0.12% during thefirst 2 weeks, and then a brush andtoothpaste until sacrifice.
The dogs were divided into threegroups (four animals per group) andwere sacrificed at 2, 4 and 8 weeksby an overdose of sodium pentobar-bital (40–60 mg/kg/i.v., Dolethal,Vetoquinol, France) previously sed-ated with medetomidine (30 micro-grams/kg/i.m., Esteve, Barcelona,Spain).
Histological processing
The lower jaw was removed andimmersed in buffered formalin for1 week. The four implants and thesurrounding tissue were separatedfrom each mandible using a dia-mond saw (Exakt, Apparatebau,Norderstedt, Germany). The biopsieswere processed for ground sectioningin conformity with the method
described by Donath & Breuner(1982). The samples were dehydratedusing ascending grades of alcoholand embedded in a glycol methacry-late resin (Technovit 7200 VLC,Heraus-Kulzer GmbH, Werheim,Germany). Sections of implants wereglued to silanized glass slides andgrinded to 40 microns. All the slideswere stained with Levai–Laczko.From each implant, the most centralbuccal–lingual section was preparedfor the histomorphometric analysis.
Implants were histologically andhistometrically analysed using a lightmicroscope (BX51, Olympus, Tokyo,Japan). Using a colour camera (DP71,Olympus, Tokyo, Japan) the imageswere captured and transferred to acomputer. One calibrated maskedexaminer (F.M.) performed all the his-tomorphometric measurements using
a PC-based image analysis program(Microimage 4.0, Media Cybernetics,Silver Springs, MD, USA).
The analysis was performed toevaluate the following variables oneach group (Fig. 2a):
• Bone-to-implant contact (%)(BIC%)
• Bone area (Inter-thread and peri-implant bone area)
The BIC (%) was defined as thesurface of bone in direct contactwith the implant divided by the totallength of the implant, starting fromits shoulder, and multiplied by 100.The inter-thread bone area was cal-culated measuring the area occupiedby bone compared with the totalarea of tissue inside the threads. The
(a) (b) (c)
(d) (e) (f)
(g) (h) (i)
Fig. 1. Implant surgery. (a) Hemisected premolar. (b) Pm4 immediately after tooth extraction. (c, d) Flapless implant placement inthe distal sockets of teeth. (e, f) Multi-base abutments were placed on both test and control sides. (g) Control side. Healing abut-ments in place. (h) Test side. Immediate restoration in place. Notice occlusal contact verification. (i) Occlusal view. Control (left)and the test (right) sides.
peri-implant bone area is a similarparameter, but calculated in thebone from the tip of the thread to a300-microns distance.
Also, the following landmarkswere identified (Fig. 2b):
• M – Margin of the prostheticabutment
• BIC – First bone-to-implantcontact
• BC – Bone crest (B, buccal; L,Lingual)
The margin of the prostheticabutment was chosen as a referencelandmark to avoid the use of nega-tive values to make results morecomprehensive, as the implantshoulder was located below the crestof bone on the lingual side, andflush with the buccal crest. Dis-tances between landmarks were mea-sured and expressed in millimetres.The distances measured were asfollows:
• M – BIC: Distance from themargin of the prosthetic abut-ment to the first bone-to-implantcontact in both the buccal andlingual sides.
• M – BC: Distance from the mar-gin of the prosthetic abutment tothe most coronal point of thebone crest in both the buccal andlingual sides.
• BC (B) – BC (L): Vertical distancefrom the most coronal point ofthe buccal crest to the most coro-nal point of the lingual crest.
Soft-tissue findings will bereported in a subsequent publication.
Statistical analysis
The dog was used as the unit foranalysis. Average results across simi-larly treated implants in the samedog were calculated and then com-pared. A power analysis was per-formed assuming a=0.05, n = 4, adifference of the means between testand control groups of 2.88% and acommon SD = 6.31, The analysisperformed showed that thePower = 9,4%. Thus, only descrip-tive statistics was produced for eachvariable (mean values, standard devi-ation, median). Confidence intervalsfor the differences of the means witha confidence level of 95% were pre-sented. Statistical analysis was per-formed using SPSS 17.0 forWindows (SPSS Inc., Chicago, IL,USA).
Results
A total of 48 implants were placedin 12 dogs. Mean ISQ values were69.73 (SD 2.68) in the test and 71.26(SD 2.35) in the control group. ISQvalues were higher than 65 in allcases (minimum of 65.25, maximumof 74.25 in the test and minimum of67 maximum of 75.75 in the controlgroup). At the end of the experimen-tal period, there was a 100% pros-theses and implant survival rate.Occlusion was carefully checked toconfirm occlusal contacts remainedat the time of sacrifice, whichoccurred in all the bridges. However,occlusal wear could be detected inall of the prostheses during examina-tion. No adverse events could beobserved related to the surgical orprosthetic protocol in any of the
specimens in neither the test nor thecontrol group. Thus, no modificationfrom the original experimental pro-tocol was necessary. No health prob-lems occurred to any of the animalsuntil the time of sacrifice.
Histological observations
Similar observations were observedfor test and control implants at allthe studied periods. Thus, findingsare reported together for the loadedand unloaded groups to simplifypresentation of the results.
Two weeks
A scaffold of woven bone wasobserved surrounding the implant,and in direct contact with the implantsurface. The old alveolar region andapical portion of the screw were par-tially occupied by woven bone in dif-ferent degrees depending on theanimal analysed. In the central threadspaces, a blood clot and necrotic anddislocated bone produced during sitepreparation were still evident, inconjunction with the presence ofabundant new blood vessels andosteoblastic-like cells.
At 4 weeks
At 4 weeks, bone modelling andremodelling was extensive around allthe implants, although some isolatedparticles of necrotic bone derivedfrom drilling during the osteotomypersisted in the thread spacesobserved. Host bone lateral to themiddle region of the implant wasbeing replaced by woven bone. Newblood vessels and osteoblasts depos-iting new bone could be observed.Bone around the apical and coronalcompartment was composed of amixture of woven bone and an ori-ented-fibre bone. Bone remodellingaround the mature lamellar bonesurrounding the alveolar bony wallswas observed. The buccal crestconsisted of lamellar bone, wovenbone in minor quantity and, occa-sionally, remnants of bundle bone.Osteoclastic activity was still evident.
At 8 weeks
After 8 weeks of healing, the bonecompartment represented a mixtureof woven and parallel fibred bone as
(a) (b)
Fig. 2. Histomorphometric analysis. (a) Diagram illustrating the areas included in theanalysis. BIC (%), inter-thread (red) and peri-implant bone area (yellow). (b) Land-marks used for histometric measurements; M, prosthetic margin of the abutment; BC,top of the bone crest; BIC, most coronal bone-to-implant contact.
well as mature lamellar bone. Boneremodelling around the bone creststill persisted with the presence ofsome osteoclasts, although corticalbone in the newly formed crest wasalready observed and the old alveo-lar borders were diffusely identifiedin both groups.
Histomorphometric analysis.
Bone-to-implant contact
The histomorphometric analysisshowed that the BIC tended toincrease progressively from week 2to week 8 in both groups. Similarpercentages were observed for boththe loaded and unloaded groups inall the studied periods (Table 1 andFig. 3a).
Inter-thread bone area
Interestingly, inter-thread bone areatended to decrease from week 2 toweek 8 in the control group, whereasvalues tended to increase in the testgroup from week 2 to week 4 and
from week 4 to week 8. Despite inter-tread bone area being higher at2 weeks in the control group(80.78%) compared with the testgroup (70.32%), this values decreasedto 72.26% at 4 weeks and 72.87% at8 weeks in the control group, andincreased to 75.39% at 4 weeks and76.05% at 8 weeks in the test group.(Table 1 and Fig. 3b).
Peri-implant bone area
In general, no major differences wereobserved between results obtainedfor the control and test groups.Values tended to remain stablethroughout the study, althoughresults were slightly lower at week 8compared with week 2 for bothgroups. (Table 1 and Fig. 3c).
Ridge alterations
M-BC (Table 2 and Fig. 4a)
Mean distance from the margin ofthe prosthetic abutment to the bone
crest was always higher on the buc-cal side compared with the lingualside.
This distance tended to increasefrom week 2 to week 8 in the buccalside in both groups, although alower value was observed at 8 weeksin the control group, compared withthe 4-week healing period. The testgroup showed a progressive increasefrom week 2 to week 8. A similaramount of bone resorption seemedto occur in both groups after8 weeks of healing.
With respect to the lingual side,M-BC distance slightly increasedfrom week 2 to week 4, and slightlydecreased from week 4 to week 8 inboth groups. Thus, a slight boneresorption seemed to occur on thelingual side of the crest from week 2to week 4, followed by bone deposi-tion from week 4 to week 8. How-ever, only a 0.15 and 0.14 differencefor the control and test groups,respectively, was observed fromweek 2 to week 8. Thus, in general,values tended to remain stable forM-BC on the lingual side, whereasbone resorption seemed to occur onthe buccal side from week 2 to week8 in both groups.
M-BIC (Table 2 and Fig. 4b)
With respect to M-BIC, this distancedecreased from week 2 to week 8 inthe buccal side of the control group(0.95-mm difference), correspondingto bone deposition occurring in thegap between the bone wall and theimplant surface, whereas it remainedstable in the test group (0.07-mmincrease from week 2 to week 8).This fact could be explained by theslightly higher bone resorptionobserved in the buccal side of the
Table 1. BIC (%), inter-thread and peri-implant bone area
On the lingual side, M-BIC pro-gressively decreased in both groupsfrom week 2 to week 8, correspond-ing to bone deposition occurring inthe gap between the bone wall andthe implant surface.
B (BC) -L (BC) (Table 2 and Fig. 5)
The distance L (BC) to B (BC)increased progressively in bothgroups from week 2 to week 8,which indicates that a greateramount of vertical bone resorptiontook place on the buccal crest, com-pared with the lingual crest. Therewas a 0.43-mm increase in the con-trol group and a 0.98-mm increasein the test group, from week 2 toweek 8.
Discussion
This investigation assessed theimpact of immediate loading on thedynamics of bone healing ofimplants placed in fresh extractionsockets. The results showed thatimmediate loading did not impairthe osseointegration process ofimmediately placed two-pieceimplants. Moreover, immediate load-ing did not seem to alter the model-ling process of the ridge that tookplace after tooth extraction in thisexperiment. It must be kept in mindthat some load could have beentransferred to the control implantsas a non-submerged approach wasused. However, this is often thechoice selected in clinical practice asone of the advantages of immediateimplant placement is a reduced num-ber of surgeries for the patient, andsubmerged healing is often avoidedwhenever possible. Moreover, it hasbeen reported that survival of sub-merged and non-submerged implantsplaced in fresh extraction sockets issimilar (Cordaro et al. 2009).
Results from previous pre-clinicalstudies showed that immediateimplants with immediate loading hadno significantly different BIC (%),inter-thread and peri-implant bonearea compared with immediatelyplaced submerged (Mangano et al.2009) and non-submerged implants(Blanco et al. 2010), after 3 monthsof healing. The present results fur-ther support these findings. How-ever, inter-thread bone area tended
Table 2. Results of histometric measurements describing distances between landmarks(mm)
M, margin of the abutment; BC, bone crest; BIC, most coronal bone-to-implant contact;B, buccal; L, lingual; SD, standard deviation; CI, confidence interval for the differences ofthe means.
(a)
(c) (d)
(b)
4.0
3.5
3.0
2.5
2.0
1.5M-B
C (B
)M
-BIC
(B)
Time
1.0
0.5
0.0
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
2 weeks 4 weeks 8 weeks
Time2 weeks 4 weeks 8 weeks
Time2 weeks 4 weeks 8 weeks
Time2 weeks 4 weeks 8 weeks
1.75
1.50
1.25
1.00M-B
C (L
)M
-BIC
(L)
0.75
0.50
Group
Control
Test
GroupControl
Test
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
Fig. 4. Boxplots illustrating distances between landmarks used for histometric mea-surements; M, prosthetic margin of the abutment; BC, top of the bone crest; BIC,most coronal bone-to-implant contact; B, buccal; L, lingual.
to increase from week 2 to week 4 inthe test implants, whereas it tendedto decrease in the control implantsin this study. This finding might sug-gest that loading may have an effecton bone mineralization aroundimmediately placed implants duringthe early stages of healing in thebeagle dog. Similarly, Sato et al.(2011) have recently shown thatimmediate loading after implantplacement following tooth extractionupregulates cellular activity in thedog mandible after 1 and 2 weeks ofhealing. This fact may partiallyexplain the present findings, whichare in agreement with those presentedby Romanos et al. (2002), who sug-gested that “immediate loading mayhave the potential to increase ossifica-tion of the alveolar bone around en-dosseous dental implants”.
With respect to the impact ofimmediate loading on ridge altera-tions, our results are in agreementwith those presented previously byBlanco et al. (2011b), where immedi-ately loaded/immediate implants(test) were compared with unloadednon-submerged immediate implants
(control) after 3 months of healing.Results with respect to buccal boneresorption were 0.86 mm (test) and1.3 mm (control) similarly to the M-BC (buccal) distance of 1.17 mm(test) and 0.69 mm (control)obtained in this experiment, if wesubtract the 1 mm corresponding tothe prosthetic abutment. Our resultsare also somewhat similar to thosereported by Li~nares et al. (2011)(0.7-mm and 0.8-mm buccal boneloss for the control and test implantsrespectively), where immediateimplants with immediate loadingwere compared with immediateimplants with delayed loading.
On the other hand, it must bekept in mind that implants wereplaced flapless in this experiment.Despite careful bone sounding priorto implant placement, implant posi-tioning may not be as accurate, andthis fact may have an impact on theresults obtained in this experiment,especially with respect to ridge alter-ations evaluation. Implant position-ing has been demonstrated to have aclear effect on ridge alterations(Caneva et al. 2010a).
Also, 1-mm abutments are ratherlow in height, and it should be con-sidered that the “tulip” shape of theabutment may have had an effect onbone resorption, and hence this maybe a limitation of this study. Thisphenomenon has been recentlydescribed by others (Vignoletti et al.2012). Nevertheless, our results arealso in agreement with Vignolettiet al. (2009), who reported a buccalbone crest resorption of 0.73 mmafter 8 weeks of healing for controland test implants, similar to the 0.69-mm (control) and 1.17-mm (test) buc-cal bone resorption observed in thisstudy. On the other hand, less buccalresorption was found in this experi-ment compared with previous reports(Ara�ujo & Lindhe 2005, Ara�ujo et al.2006a,b). This may be partiallyexplained by the difference in implantdiameter, as this factor has also beenshown to have an effect on bone mod-elling (Caneva et al. 2010b).
With respect to the distance fromthe shoulder of the implant to BIC,our results are also similar to thosereported by Vignoletti et al. (2009),where this distance was 1.36 mm in
the buccal side of the implants, com-pared with a distance of 1.16 mmfor the control and 1.54 mm for thetest implants in this study, after8 weeks of healing in both studies.
With respect to the amount ofbone modelling taking place in thelingual side of the socket, it is notpossible to precisely calculate thisparameter in the present material, asimplant positioning was performedwith respect to the buccal bone, andit is known that the lingual bone ispositioned at a more coronal levelcompared with the buccal bone(Vignoletti et al. 2012)
Despite similarity of the results withthose of previous studies, this experi-ment presents some differences withrespect to study design, such as animalmodel (Mangano et al. 2009), healingintervals studied (Blanco et al. 2010,2011b, Li~nares et al. 2011), implantdesign (Mangano et al. 2009, Blancoet al. 2010, 2011b, Li~nares et al. 2011)and implant surface (Mangano et al.2009, Blanco et al. 2010, 2011b).
With respect to implant design, arecent histological human study hasshown that platform switchingseems to maintain better peri-implant bone levels compared withnon-mismatched implants (Canulloet al. 2011). However, other authorshave found no difference betweenseveral one- and two-piece implantsystems placed in fresh extractionsockets with respect to bone model-ling (de Sanctis et al. 2009, Vigno-letti et al. 2012). Results from thisexperiment are in agreement withstudies with a similar experimentaldesign, but with one-piece implants(Blanco et al. 2011b, Li~nares et al.2011). Nevertheless, results shouldbe interpreted with caution becauseno control one-piece implant wasused in this study, as this was notone of the aims of this study.Another confounding factor couldbe related to implant surface.Recently, Calvo-Guirado et al.(2010) have also shown greater boneapposition and less crestal boneresorption on immediately placedimplants with a conditioned chemi-cally modified surface comparedwith a non-conditioned surface.These findings suggest that implantsurface may have an effect onbone modelling/remodelling aroundimmediate implants. In the study byCalvo-Guirado et al. (2010), dogs
were sacrificed at 2, 4 and12 weeks, and a progressive increasewith respect to BIC could beobserved in both groups, similar tothis study. However, the possibleeffect of immediate loading was nottested in the latter experiment. Thetype of surface used in this experi-ment has been shown to induce fas-ter bone apposition compared withcontrol SLA surface implants inhealed ridges in pre-clinical (Buseret al. 2004, Bornstein et al. 2008,Lai et al. 2009) and histologicalclinical studies (Lang et al. 2011).Moreover, this type of surface hasalso shown an improved adhesionand stabilization of the blood cloton day 1, and higher BIC (%) onday 14 after implant placementcompared with a non-modified SLAsurface (Schwarz et al. 2007). Also,additional bone fill has been showncompared with implants with a sur-face coated with discrete crystallinedeposits of calcium phosphate(DCD/Ca) in dehiscence-type defects(Schwarz et al. 2010). Nonetheless,results from the present experimentare similar to those reported inother studies with a similar experi-mental design using either the samemodified implant surface (Li~nareset al. 2011) or a non-modifiedsurface (Blanco et al. 2011b). Onthe contrary, Vignoletti et al. (2009)found less buccal bone resorptionfor immediate implants with aDCD/Ca-coated surface comparedwith dual acid-etched implants,although comparative statistics werenot presented in the latter studywith respect to those data. Notwith-standing, it must be kept in mindthat no control implant surface wasused in this experiment, makingcomparisons difficult. Moreover,these findings should be interpretedwith caution as results obtained inpre-clinical studies should be vali-dated in humans. In summary, theconclusions of the present investiga-tion are:
• Implant osseointegration can beachieved in the same manner inimplants placed in post-extrac-tion sockets with or withoutimmediate loading.
• Alveolar bone resorption didalways occur irrespective of theloading protocol applied to theimmediately placed implants.
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Address:Santiago MarequeFacultad de odontolog�ıa Universidad deSantiago de CompostelaC/San Francisco s/n.Santiago de Compostela, SpainE-mail: [email protected]
Clinical Relevance
Scientific rationale for the study:Immediate implant placement hasbecome a common procedure inimplant dentistry. Immediate load-ing of implants is also a frequenttechnique used in daily practice,and it has been suggested to influ-ence bone remodelling during the
early stages of osseointegration. Theaim of this study was to evaluate theinfluence of immediate loading onbone healing around immediateimplants.Principal findings: Immediate loadingof immediately placed implants didnot influence bone remodelling after
tooth extraction in this animalexperimental model.Practical implications: Immediateloading did not have a deleteriouseffect on osseointegration of imme-diate implants and might be aviable treatment option in clinicalpractice.
