Pulp reactions to different preparation techniques on teeth exhibiting periodontal disease

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Journal of Oral Rehabilitation 2000 27; 93102Pulp reactions to different preparation techniques on teethexhibiting periodontal diseaseA. ZO8 LLNER* & P. GAENGLER *Department of Prosthodontics, and the Department of Conservative Dentistry, Schoolof Dental Medicine, University of Witten:Herdecke, Alfred Herrhausen Str. 50, 58448 Witten, GermanySUMMARY To evaluate the histopathological out-pathologically rated according to the BRD criteriacome of two preparation techniques (featheredgepreparation:shoulder preparation) on teeth ex- comprising the parameters (i) Bacterial invasion, (ii)hibiting pulp reactions due to age and periodontal Regenerative parameters, (iii) Degenerativeparameters. Degenerative reactions were more cor-disease, 11 teeth were prepared for full veneerrelated with tooth preparation than with advancedcrowns. Laboratory made resin crowns were fixedwith a zinc phosphate cement for a period of 90 periodontal disease. The severity of endondontalreactions depends more on remaining dentin thick-days. After extraction, adjacent pulpal areas wereness than on the type of preparation.histo-IntroductionPulp reactions to preparation techniques are still amajor concern in restorative and prosthodontic den-tistry. According to many longitudinal investigationsthere is a high rate of primarily vital teeth exhibitingtypical signs of endodontal complications followingdental restorations. According to Bergenholtz and Ny-man (1984), up to 15% of teeth showed negativeresults to sensitivity testing, including periapical infl-ammatory lesions, 413 years after crown preparation.Different factors may accumulate and lead to thesedramatic changes of the endodontium, including age,abrasion:attrition, periodontal disease, carious lesionsas natural occurring phenomena and pulp damagecaused by dental procedures and materials. Therefore,it was the aim of the present investigation to comparethe influence of different preparation techniques, likeshoulder preparation and featheredge preparation, toinvestigate further the reactions to bacterial invasion,to characterize the reactions of the pulp in correlationto the remaining dentin thickness, taking into accountthe already predamaged pulp, and finally to concludeclinical recommendations concerning pulpdegeneration.Material and methodsEleven teeth with positive reactions to sensitivity test-ing, no or minimal carious lesions, advanced periodon-tal destruction, and therefore scheduled for extraction,were prepared for full veneer crowns with the pa-tients consent using two different preparation tech-niques. The featheredge preparation, limited to theenamel:dentin junction, was used in experimentalgroup 1, including 13 sites. The shoulder preparation,extended deep into the dentin, was used in experi-mental group 2, including nine sites. Either one orboth preparation techniques were applied. The controlgroup 3 with no experimental preparations consistedof four teeth of the same patient with the same levelof periodontal destruction. Detailed information con-cerning the results of the clinical investigation and thetype of preparation is summarized in Table 1. Labora-tory made crowns (Visio Gem*) were fixed with zincphosphate cement (Harvard). The frequent clinicalcontrol included sensitivity testing, percussion testing* Espe, Am Griesberg 2, 82229 Seefeld, Germany. Richter & Hoffmann Harvard Dental, Johannisberger Str. 24,14197 Berlin, Germany. 2000 Blackwell Science Ltd 9394 A . Z O8 L L N E R & P . G A E N G L E RTable 1. Overview: clinical documentation of prepared teeth and control groupProbing depth Recession Attachment lossAge(mm)Tooth (mm)Sex (mm)(years) Site Preparation technique3 2 511 Female 50 Buccal Featheredge preparation633Oral Featheredge preparation4 112 5Female 50 Control5112 Male 462 Buccal Featheredge preparation4 1Oral 5Featheredge preparation6213 Female 450 Mesial Featheredge preparation4 2 6Distal Featheredge preparation717 3Male 462 Buccal Shoulder preparation3Oral Shoulder preparation 4 76321 Female 350 Buccal Shoulder preparation2Oral Featheredge preparation 3 5221 Male 62 Buccal Shoulder preparation 3 52 53Oral Shoulder preparation5 222 Female 750 Control6223 Female 450 Buccal Shoulder preparation4 3 7Oral Featheredge preparation625 0Female 650 Control3 225 5Male 62 Buccal Shoulder preparation523Oral Featheredge preparation3 432 7Male 62 Buccal Featheredge preparation743Oral Shoulder preparation434 Male 62 Buccal Featheredge preparation 3 1413Oral Featheredge preparation4 637 10Male 62 Control642 3Male 362 Buccal Featheredge preparation6Oral Shoulder preparation 3 3and pain history. The teeth were carefully extractedafter 90 days under local anesthesia and the rootswere cut off under permanent water cooling for rapidpenetration of 5% buffered, neutral formalin. Thespecimens were then decalcified in HNO3, embeddedin paraffin, serially sectioned at 5 mm and stained withhaematoxilineosin, azan and according to J. Hopkinsfor the detection of bacteria. Adjacent pulpal areas ofeach section were histopathologically rated (micro-scope: DMRM) according to the BRD criteria (Table 2)comprising the parameters (i) Bacterial invasion, (ii)Regenerative parameters, (iii) Degenerative parame-ters. The endodontal reactions localized in the crown,in the root or adjacent to the prepared margin wereseparately rated. The quantitative measurement ofvideo-based pictures of each section (screen: KX-14P1; camera: CF11:1) included the width of theshoulder (Fig. 1) and the thickness of the remainingdentin (Fig. 2) at three different levels: D1inner partof the margin, shortest distance to the pulp; D2in-ner margin, following the direction of the dentintubules to the pulp and D3end of the preparation,following the direction of the dentin tubules to thepulp.ResultsThe mean extension of the shoulder preparation intothe dentin was 0.8 mm. Table 3 demonstrates the corre-lation of bacteria in dentin tubules and the type ofpreparation. Bacterial invasion occurs in both types:featheredge preparation and shoulder preparation (Fig.3). The correlation of grade of bacterial invasion toirritation dentin (Table 4) as an example for the en-dodontal reactions shows no significant results. Thehistopathological changes of the endodontal areas adja-cent to the rating points D1D3 are summarized in Leica, Lilienthalstr. 3945, 64625 Bensheim, Germany. Sony, 7-35 Kitashinagawa 6-chome, Shinagawa-ku, Tokyo 141,Japan. Kappa, Kleines Feld, 37130 Gleichen, Germany. 2000 Blackwell Science Ltd, Journal of Oral Rehabilitation 27; 93102P U L P R E A C T I O N S T O C R O W N P R E P A R A T I O N S 95Table 2. BRD coding criteriaI Bacterial invasionGrade 0: No signs of bacterial invasionModerate bacterial invasion along prepared marginsGrade 1:Moderate invasion in isolated dentin tubulesGrade 2:Grade 3: Severe invasion in most dentin tubulesInfection of necrotic pulp areasGrade 4:II Regenerative paramenters of the endodontium1. Regular irritation dentinNo signs of irritation dentinGrade 0:Grade 1: Regular irritation dentin, localized in defined areas, no tendency to obliteration, well marked zone of uncalcifieddentin (predentin)Regular irritation dentin, circumpulpal, no tendency to obliteration, well marked zone of uncalcified dentin (pre-Grade 2:dentin)Grade 3: Regular irritation dentin, tendency to obliteration, reduction or absence of uncalcified dentin (predentin)2. Transient inflammation cells in pulpal tissueGrade 0: No signs of inflammation cellsIsolated chronical and:or acute inflammation cells, fibroblast rich connective tissue (mesenchymal character)Grade 1:Grade 2: Isolated chronical and:or acute inflammation cells, collagen rich connective tissue (loss of mesechymal character,reduction of pulpoblasts and fibroblasts, isolated denticles)III Degenerative parameters of the endodontium1. Irregular irritation dentinNo signs of irregular irritation dentinGrade 0:Irregular direction of dentin tubules, moderate numeric reduction of odontoblast processes, localizedGrade 1:Grade 2: Increase of irregular direction of dentin tubules, severe numeric reduction of odontoblast processes, localizedGrade 3: Severe irregularities in the direction of dentin tubules and:or loss of odontoblast processes, localized or circumpulpalMainly osteodentin, circumpulpalGrade 4:Grade 5: Only osteodentin with inclusion of tissue, circumpulpalTendency to obliteration with areas of homogenous mineralisation, circumpulpalGrade 6:2. Tissue necrosisNo signs of tissue necrosisGrade 0:Isolated areas of tissue necrosis, localized and:or included by hard tissueGrade 1:Grade 2: Extensive tissue necrosis (crown pulp)Tissue necrosis reaching:including root pulpGrade 3:3. Dentin resorptionGrade 0: No signs of dentin resorptionIsolated dentin resorption in crown dentinGrade 1:Isolated dentin resorption in root dentinGrade 2:Grade 3: Severe dentin resorption (internal granuloma)4. DenticlesNo signs of denticlesGrade 0:Fibrodenticles, isolatedGrade 1:Cellular fibrodenticles, isolatedGrade 2:Severe amount of denticles (free and:or attached), localised in crown pulpGrade 3:Grade 4: Severe amount of denticles (free and:or attached), reaching the root pulp5. InflammationNo signs of inflammation cellsGrade 0:Isolated infiltration of chronical and:or acute inflammation cellsGrade 1:Infiltration of large areas of the pulp, tendency of demarcationGrade 2:Severe infiltration without demarcationGrade 3:Isolated abscessesGrade 4:Large abcess (for example crown pulp)Grade 5: 2000 Blackwell Science Ltd, Journal of Oral Rehabilitation 27; 9310296 A . Z O8 L L N E R & P . G A E N G L E RFig. 1. Quantitative measurement: width of the shoulder (s).Fig. 2. Quantitative measurement: remaining dentin thickness atrating point D1, D2, D3.Table 5. The most severe degenerative changes occurin the area next to the rating point D2. The irregularirritation dentin formation is characterized by grade 3(out of 6): severe irregularities in the course of dentintubules and:or loss of odontoblastic processes. Themean grade for the featheredge preparation is 1.6(Fig. 4) and for the shoulder preparation 1.8 (Fig. 5).More pronounced pathological changes like osteo-dentin formation were not observed. Because of thisreaction pattern, Tables 69 refer only to this pulparea adjacent to rating point D2. The correlation ofthe two preparation techniques and the control group(Table 6) clearly documents that regular irritationdentin formation is less pronounced both in group 1(featheredge preparation, mean BRD grading 0.5) andin group 2 (shoulder preparation, mean BRD grading0.4) compared with the control group 3 (mean BRDgrading 1.2). In contrast to this, the irregular irritationdentin is more pronounced in group 1 and group 2compared with control group 3. A significant differen-tiation between the two techniques was not possible.Comparing pulp reactions and the remaining dentinthickness (Table 7), three groups were formed: up to2 mm, between 2.1 and 2.5 mm and more than2.5 mm. Especially, the endodontal reactions to lessremaining dentin thickness are characterized bysevere irregular irritation dentin formation and totalabsence of regular irritation dentin formation. This isin sharp contrast to less pathological changes in casesof thicker remaining dentin. The mean ratings of 0.6and 1.1 demonstrate very normal regular irritationdentin formation and only moderate irregular irrita-tion dentin formation. Taking first the featheredgepreparation, Table 8 shows the rating of endodontalreactions in different areas of the pulp: crown pulp, 2000 Blackwell Science Ltd, Journal of Oral Rehabilitation 27; 93102P U L P R E A C T I O N S T O C R O W N P R E P A R A T I O N S 97tion (crown pulp, area of the margin at point D2) 1.8(Fig. 6)DiscussionEarlier methodological prospective in vivo studiesused graded classifications for the estimation of(pathological) pulpal changes, including the parame-ters of inflammatory cell response, soft tissue organi-zation, dentin bridge formation and bacterial staining,as already suggested by Langeland et al. (1966),slightly modified and confirmed for recent studies byPameijer & Stanley (1995). Warfinge (1986) triedto introduce morphometric methods for the evalua-tion of inflammatory responses. As a consequence,pathological degenerative reactions are well definedfor teeth primarily exhibiting no pathological changesof the endodont, like in short-term biocompatibilitytesting for dental materials and methods defined inTable 3. Bacterial invasion into dentin tubules and type ofpreparationBRD gradingMaximumMinimumMean1.3Group 1 (featheredge 0 3preparation)Group 2 (shoulder prepa- 1.0 0 3ration)margin (D2) and root pulp. The most severe degener-ative reactions occurred in the crown pulp (irregularirritation dentin, mean BRD grading 1.5) and in thearea of the margin at point D2 (mean BRD grading1.6). The results for the shoulder preparation (Table9) document the same tendency with slightly differentmean BRD gradings: irregular irritation dentin forma-Fig. 3. J. Hopkins stain (320), isolatedbacteria in dentin tubules (BRD grade 2).BRD gradingBacterial invasion Grade 0 Grade 1 Grade 2 Grade 30.0:0:00.0:0:00.7:0:10.0:0:0Regular irritation dentin (mean:min:max)Irregular irritation dentin (mean:min:max) 2.0:1:3 1.3:0:3 2.3:1:3 2.5:2:3Table 4. Bacterial invasioninto dentin tubules andirritation dentin formation 2000 Blackwell Science Ltd, Journal of Oral Rehabilitation 27; 9310298 A . Z O8 L L N E R & P . G A E N G L E RFig. 4. Azan stain (1), featheredge preparation, overview.ISO:EN 7405 (1997). The suggested semi-quantitativeclassification proposes to consider the cumulative effectcaused by longstanding marginal periodontitis and dif-ferent preparation techniques. It takes into accountthat pulp changes are mainly localized and stronglycorrelated to the place of origin of the causing irritantin agreement with the design for human pulp studiesdescribed by Stanley (1968). Therefore, the feath-eredge preparation and the shoulder preparation wereinvestigated on one tooth, this experimental approachenables the direct comparison of the histopathologicaloutcome of these techniques on the predamaged pulp.The criteria used for the evaluation of the sections arebased on well-defined terms in general pathology (Un-derwood, 1982) concerning degeneration and regen-eration, including especially, pulp tissue changes owingto the physiological ageing process (Schroeder,1993a,b). 2000 Blackwell Science Ltd, Journal of Oral Rehabilitation 27; 93102Table5.IrritationdentinformationatpulpareasadjacenttoD1,D2,D3(seeFig.2)BRDgradingAreaD1AreaD2AreaD3Group1Group2Group1Group1Group2Group2(shoulderpreparation)(featheredgepreparation)(featheredgepreparation)(shoulderpreparation)(shoulderpreparation)(featheredgepreparation)Regularirritationdentin0.5:0:10.3:0:10.5:0:10.4:0:10.6:0:10.4:0:1(mean:min:max)1.8:0:31.2:0:31.8:0:31.6:0:31.3:0:31.3:0:3Irregularirritationdentin(mean:min:max)P U L P R E A C T I O N S T O C R O W N P R E P A R A T I O N S 99The regular irritation dentin formation is anatural phenomenon and a typical feature in earlycarious lesions (Gangler, 1996) and following mildphysiological abrasion and attrition (Schwarz & Gan-gler, 1998). In contrast to regular irritation dentin,the irregular irritation dentin formation representsthe numeric reduction or even loss of odondoblasts,and therefore fewer cells and their processes are re-sponsible for dentin formation (Langeland et al.,1975). This is the first sign of degeneration followedby the formation of fibrodenticles, osteodentin forma-tion and:or dentin resorption by activation of odonto-clasts. Finally, the tissue necrosis of smaller or largerpulp areas is the degenerative result of crossingthe point of no return of cell reactivity. Withoutdoubt, isolated or confluenting abcesses (grade 4:5)are signs of inflammation and they represent at leasta sublethal trauma of the pulp tissue. In contrastto these undoubted degenerative features, isolatedinfiltration of chronic and:or acute inflammation cellsdoes not characterize per se a degenerative pro-cess. In general pathology, the reversibility of acuteand:or chronic inflammation is well described (Un-derwood, 1982) and a prerequisite of a normalhealing process. However, this regenerative poten-tial of connective tissue is limited in inflammatorypulp responses. This is why the appearance of inflam-matory cells to local irritants even in short-termbiocompatibility testing as defined in ISO:EN 7405(1997) is classified as a potentially degenerativeprocess.Concerning the interpretation of the BRD gradings,the results of the control group are in agreementwith those of a previous investigation (Zoellner etal., 1997) on incisors exhibiting periodontal diseaseand occlusal attrition. Pulp reactions due to severemarginal periodontitis are mainly characterized byextensive regular irritation dentin formation withsome tendency to reduced numbers of odonto-blasts. Therefore, pulp responses to different prepara-tion techniques were clearly distinguished concerningthe area as well as the intensity of degenerativechanges.These degenerative reactions my be caused bybacterial infection due to microleakage occurring un-der crowns fixed with zinc phosphate cement (Gold-man et al., 1992). However, the influence of bacteriaas the main irritant is controversially disputed(Brannstrom & Nyborg, 1971; Mjor, 1974). Tron-stad & Langeland (1971) proved that bacterial inva-sion into opened dentin tubules in omnivorousteeth via abrasion is a natural occurring phe-nomenon. The results of both groups in this studyexploiting different preparation techniques con-firm experimental studies in pigs, where pulp reac-tions correlate better with the material toxicity andthe remaining dentin thickness of dentin thanwith the microbial invasion into dentin tubules(Schwarz & Gangler, 1998). Because of the non-correlation of presence and absence of bacteria withthe pulp reactions in both groups, other factorsare responsible for the intensity of degenerativechanges.The results document that the remaining dentinthickness is strictly correlated to the severity ofdegenerative parameters while different preparationtechniques do not demonstrate clearly differentendodontal reactions. According to the conclusionsof Smulson & Sieraski (1989), it is confirmed thatthe amount of 2 mm and more remaining dentinseems to be the critical factor in determining thedegree of pulp response. However, in contradiction totheir statement, that the shortest distance betweenthe prepared dentin margin and the pulp is decisivefor the severity of inflammatory reactions (Smulson& Sieraski 1989), it is demonstrated in this study thatthe critical remaining thickness of dentin follows thedirection of dentin tubules. From the experi-mental and control results presented it is concludedthat pulp changes due to periodontal disease aresuperimposed by typical mainly degenerative re-sponses following crown preparation. Different pre-paration techniques and various bacterial invasionlevels do not correlate with the severity of histo-pathological changes. From a clinical point of view,the remaining dentin thickness is the most importantfactor of the cumulative effects including period-ontal disease or type of preparation technique leadingto possible endodontal complications after crownpreparation. The application of different preparationtechniques on one tooth considering not only techni-cal requirements for the crown fabrication but pri-marily general and individual morphological toothcharacteristics like enamel and dentin thickness isrecommended. 2000 Blackwell Science Ltd, Journal of Oral Rehabilitation 27; 93102.100 A . Z O E L L N E R & P . G A E N G L E RFig. 5. Azan stain (64),magnification from Fig. 4, irregularirritation dentin formation (BRD grade2) at rating point D2.Table 6. Pulp reactions to different preparation techniquesBRD gradingGroup 1 (featheredge preparation) Group 2 (shoulder preparation) Group 3 (control group)(mean:min:max) (mean:min:max)(mean:min:max)Regular irritation dentin 0.5:0:1 0.4:0:1 1.2:1:21.6:0:3Irregular irritation dentin 1.8:0:3 0.8:0:1Resorption 0.1:0:1 0.0:0:0 0.0:0:00.5:0:30.1:0:10.1:0:1DenticlesInflammation 0.1:0:1 0.0:0:00.0:0:0Table 7. Pulp reactions and remaining dentin thicknessBRD gradingControl group\2.5 mm22.5 mmB2 mm(mean:min:max) (mean:min:max)(mean:min:max) (mean:min:max)Regular irritation dentin 0.0:0:0 0.5:0:1 0.6:0:1 1.1: 0:11.2:0:32.8:2:3 1.4:0:3Irregular irritation dentin 0.8:0:1Resorption 0.2:0:1 0.0:0:0 0.0:0:0 0.0:0:00.0:0:0 0.1:0:1 0.1:0:1 0.5:0:3DenticlesInflammation 0.0:0:0 0.0:0:0 0.1:0:1 0.0:0:0BRD gradingRootMargin (D2)Crown(mean:min:max) (mean:min:max) (mean:min:max)0.4:0:10.6:0:1Regular irritation dentin 0.9:0:1Irregular irritation dentin 1.5:0:3 1.6:0:3 0.7:0:20.0:0:00.1:0:10.0:0:0Resorptions0.0:0:00.1:0:1Denticles 0.0:0:00.0:0:00.1:0:1Inflammation 0.0:0:0Table 8. Pulp reactions indifferent areas: featheredgepreparation 2000 Blackwell Science Ltd, Journal of Oral Rehabilitation 27; 93102P U L P R E A C T I O N S T O C R O WN P R E P AR A T I O N S 101BRD gradingRootMargin (D2)Crown(mean:min:max)(mean:min:max)(mean:min:max)0.4:0:1 0.6:0:1Regular irritation dentin 0.5:0:11.8:0:3 1.0:0:2Irregular irritation dentin 1.8:0:30.0:0:0 0.0:0:0Resorptions 0.0:0:00.0:0:0 0.1:0:1 0.0:0:0DenticlesInflammation 0.0:0:0 0.0:0:0 0.0:0:0Table 9. Pulp reactions indifferent areas: shoulderpreparationFig. 6. Azan stain (6.25), shoulderpreparation, overview showing a mes-enchymal pulp tissue with irregularirritation dentin formation (BRDgrade 1) at rating point D2.ReferencesBERGENHOLTZ, G. & NYMAN, S. (1984) Endodontic complicationsfollowing periodontal and prosthetic treatment of patients withadvanced periodontal disease. Journal Periodontology, 55, 63.BRANNSTROM, M. & NYBORG, H. 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E-mail: dagmark@uni-wh.de 2000 Blackwell Science Ltd, Journal of Oral Rehabilitation 27; 93102