The com plexity o f fra ctu red posterior teeth m akes n ecessary a differen t treatm ent approach fo r each type o f fracture. A review of the literature and treatments f o r obliquely and vertically directed com plete and incom plete fractures a re given.
Treatment rationale of fractured posterior teeth A nthony R. Silv estri, Jr., DMD Iqbal Singh, MDS, Boston
he treatment of posterior teeth with complete and incomplete fractures is different for each type of fracture that is encountered. Although several re ports have dealt with the diagnosis and description of the various types of fractures,1'8 few have de scribed in depth the treatment rationale for this dif ficult problem. The depth, degree, and direction of fractures of posterior teeth vary greatly. Con sequently, the treatment of these teeth requires the dentist to diagnose accurately the type of fracture before attempting to restore the tooth. The treatment for the most common types of fractures encountered in posterior teeth is described.
Review Gibbs1 described a condition in which only a cusp of a posterior tooth was involved. This type of incom plete cuspal fracture may involve the pulp. Gibbs called the pain resulting from incomplete cuspal fracture “cuspal fracture odontalgia.” He suggested that treatment of incomplete fractures not involving the pulp be accomplished by binding the cusps im movably together with a complete cast crown. Ritchey and others2 described the histopathology of incomplete fractures in the posterior teeth of 22 patients. Treatment ranged from root canal therapy 806 ■ JADA, Vol. 97, November 1978
to the use of cast-gold crowns or extraction. How ever, no attempt was made to correlate the treatment with the severity of the fracture. Greenstick fractures of crowns of posterior teeth, as described by Sutton,3 originate in dentin near the pulpal wall of a prepared cavity and run obliquely toward the cementoenamel junction. These frac tures do not involve the pulp. Sutton recommended the removal of the fractured tooth substance and prosthetic replacement of the missing structure with amalgam placed on a base of zinc oxide-eugenol. C a m e r o n 4 e x a m in e d 5 0 te e th w ith in c o m p le te fra c tu re s . H e te rm e d th e s ig n s a n d s y m p to m s fro m s u c h fra c tu re s “ th e c r a c k e d to o th s y n d r o m e .” T w o ty p e s o f c ra c k s w e re d e s c r ib e d : th o s e th a t a re c e n tr a lly lo c a te d , fo llo w th e lin e s o f th e d e n tin a l tu b u le s , a n d le a d to w a rd th e p u lp ; a n d th o s e th a t are m o re p e rip h e ra l a n d le a d to fr a c tu r e o f th e c u sp .
In a more recent report, Cameron5 studied 102 cracked posterior teeth. He suggested that the tooth structure that was weakened by superficial cracks be removed and replaced by a prosthesis. He also suggested that the teeth with centrally located cracks be restored with a cast-gold onlay or crown to prevent further cracking and the possibility of pul pitis. Some teeth with mild pulpitis that resulted from a crack were crowned with the use of a nonir
ritating cement. If degeneration of the pulp ensued, root canal therapy was performed through the castgold crown, thus ensuring stabilization of the frac tured segments of the tooth during root canal therapy. Incomplete fractures of the crow n and root were investigated by Hiatt6 in relation to pulpal and periodontal disease. He emphasized the progressive and irreversible nature of incom plete fractures when the lesions are not recognized and treated early. Cast-gold restorations that cover the occlusal surfaces were suggested as a treatm ent to prevent further pulpal and periodontal involvement. Snyder7 discussed the diagnosis and treatm ent of the cracked tooth syndrome and fractured cusps of posterior teeth. He said that grinding the incom plete fractured cusp out of occlusion does not perm a nently solve the problem. A restoration that binds the weakened tooth structure together is necessary. Silvestri8 described teeth that were incom pletely split and with both the crow n and the root involved. He termed the signs and symptoms from such le sions “the split root syndrom e.” Treatm ent of the reported cases involved stabilization of the frac tured tooth segments with a cast-gold onlay. A classification system for coronal fractures of posterior teeth was proposed by T alim and G ohil.9 They studied 4 0 posterior teeth that had a. variety of types of fractures and ind icated the sp ecific treat m ent for each tooth. A review of the literature shows that m any authors have reported clinical cases of fractured posterior teeth and described the treatment procedures im plemented for each case. The purpose of this article is to present a treatment rationale for the com mon types of fractured posterior teeth that are encoun tered most frequently by the clinician.
Completely fractured posterior teeth OBLIQUELY DIRECTED COMPLETE FRACTURES. Ob liquely directed complete fractures of posterior teeth are the easiest to diagnose. The oblique frac tures usually involve one cusp of a posterior tooth, extend into the dentin, and terminate at some level in an apical direction. Although it is possible for the fracture to involve the pulp, this usually does not occur. The obliquely directed complete fracture most frequently occurs on cusps that have been se verely weakened by a previous extensive amalgam restoration (Fig 1). Lateral shearing forces generated during mastication or parafunction eventually re sult in the tooth segment being sheared away com pletely. The preferred treatment for this type of frac
ture is replacem ent of the missing tooth structure with a suitable restorative material. The ideal resto ration is a cast-gold onlay or crow n that replaces the lost structure and also protects the remaining cusps from future fracture. In cases in w hich the apical termination of the fracture occurs below the attach ment apparatus, gingivectom y m ay be necessary to aid in properly placing the margin of the cast-gold preparation. Occasionally, the apical termination of the obliquely directed fracture may occur below the crest of the alveolar bone. If the crow n-root ratio is favorable, the need for construction of a cast crown is still indicated after gingivectom y and osseous recontouring immediately apical to the fracture site. An alternative treatm ent for obliquely directed complete fractures in posterior teeth is the replace ment of the missing tooth structure with amalgam. One or more pins may be necessary to retain the restoration. Although this treatment is a com promise to the preferred cast restoration, it will re main serviceable until a cast restoration can be com pleted. Care must be taken in the design of the prep aration to avoid undermining other cusps and sub jecting them to the possibility of sim ilar fracture. Occasionally, especially with m axillary premo lars, the pulp may be involved when a tooth com pletely fractures in an oblique direction. In these cases, the preferred treatment is root canal therapy followed by use of a post and core and cast crown. VERTICALLY DIRECTED COMPLETE FRACTURES. Complete vertical fractures of posterior teeth can also occur. When the fracture is com pletely through the tooth, the clinical sign is a distinct, independent mobility of one segment of the tooth and root in relation to the other segment. This type of fracture occasionally occurs in teeth that have been endodontically treated and in w hich the bifurcation extends extremely high in an occlusal direction. Root canal therapy and preparation for a post and Silvestri-Singh : TREATMENT OF FRACTURED POSTERIOR TEETH ■ 807
Fig 2 ■ Vertically directed complete fracture on tooth weakened by root canal therapy and post and core preparation. On final insertion of cast post and core, weakened tooth with high bifurcation may com pletely fracture.
Fig 3 ■ Obliquely directed incomplete fracture involving one cusp of mandibular mo lar. Extensive amalgam resto ration has undermined and weakened cusp resulting in incomplete fracture.
core w eaken the tooth. Finally, on insertion of the cast post and core, enough lateral forces are created to sp lit the tooth into two distinct sections (Fig 2). Even w hen posterior teeth are strong, caution should be taken to avoid forcefully seating a cast post and core into the prepared root to prevent split ting o f the tooth. W hen a tooth is com pletely fractured in a vertical direction, the preferred treatm ent is extraction fol lowed by prosthetic replacem ent. On very rare occa sions, it is necessary to retain one of the segm ents of a m ultirooted tooth to serve as an abutm ent for a prosthesis. In these exceptional cases, the weakest segm ent should be hem isected and the rem aining root endodontically treated before the use of the tooth for the prosthesis.
Incompletely fractured posterior teeth Incom plete fractures of posterior teeth are occurring w ith increased frequency,5,6,8 Advanced restorative techniques and procedures, such as high-speed ro tary cutting instrum ents and pins, have contributed to the increased occu rren ce.10-13 The sym ptom atol ogy associated w ith these incom plete cracks vary from sensitivity to cold, hot, sw eet, and sour stim uli. However, the overriding sym ptom shared by all pa tients is a sharp, lancinating discom fort lasting from several seconds to several m inutes when eating hard 808 ■ JADA, Vol. 97, November 1978
or crunchy foods. The hard food acts as a wedge between the cusps during chewing and causes a slight separation of the incompletely fractured seg ments. Microleakage through the crack results in inflammation of the pulp and hypersensitivity of the tooth to a wide range of stimuli.5,8,14 The variable depth and severity of the cracks explain the diverse range of symptoms. OBLIQUELY DIRECTED INCOMPLETE FRACTURES. O blique incom plete fractures of the crow n occa sionally occu r when nonaxial occlu sal forces gener ated during chew ing and parafunction exceed the capacity of the tooth to resist fracture. A n oblique crack w ill originate in enam el on the occlu sal sur face, involve one or more cusps, run into dentin in an oblique direction under the cusps, and term inate gingivally in enam el or cem entum . M ost frequently, oblique incom plete fractures occur in posterior teeth that have been previously prepared for an ex tensive am algam restoration. T he incom plete frac ture usually involves a cusp that was not removed during the cavity preparation yet was severely w eakened by the rem oval of underm ining decay. O cclusal forces create internal stresses w ith in the tooth that result in concentration of stress at the ju nction of the base of the cavity preparation and the cusp. Consequently, a m inute crack occurs in this region of the tooth (Fig 3). The preferred treatm ent is rem oval of the tooth structure threatened by the crack and restoration of the tooth w ith a cast-gold onlay or crow n. T he design of the preparation for the restoration should remove all weak tooth structure and create adequate retention w ith the use of con ventional techniques (grooves, keys, and so forth). If rem oval of the tooth structure results in exposure of the pulp, adequate therapy m ust be perform ed b e fore restoration w ith the cast gold. A lthough oblique incom plete fractures of pos terior teeth usually term inate at the cem entoenam el ju n ctio n or slightly above it, occasion ally they w ill extend into the root. Treatm ent of these frac tures w ith a cast-gold onlay or crow n can be ac com plished only after local periodontal proce dures are performed to expose the m ost apical ex tension of the fracture site. The difficulty in restor ing the tooth increases and the prognosis worsens w ith incom plete fractures that term inate below the level of the crestal bone. VERTICALLY DIRECTED INCOMPLETE FRACTURES. T he presence of vertical incom plete fractures in posterior teeth is w ell docum ented in the litera ture.4-8 U nlike the obliquely directed fractures that
I«! §■'-
Fig 4 ■ Lett, vertically directed incomplete fracture running in butcolingual direction showing mesial, occlusal, and distal step-reduction preparation. Right, vertically directed incomplete fracture running in mesiodistal direction showing buccal, occlusal, and lingual stepreduction preparation. Completed amalgam restoration for both will temporarily bind fractured segments together.
usually occur on w eakened cusps of extensively prepared teeth, incom plete vertical fractures more frequently occu r in teeth that are m inim ally restored or even in teeth w ith no restorations. T he crack may run in a m esiodistal d irection over one or both m ar ginal ridges or buccolin gually betw een cusps (Fig 4 left, right). Inherent weakness w ithin the tooth structure at the site w here the developm ental lobes coalesce during tooth form ation have been postu lated as an etiologic factor by Cam eron.5 In addition, iatrogenic factors, such as pins, restorations, and vibration from high-speed rotary instrum entation, contribute to the form ation of a crack.10"13 V ertical incom plete fractures originate in enam el and extend in to the dentin. In some cases, the crack even extends into the root.8 Hiatt6 described the progressive nature of this type of incom plete frac ture and the way the depth and severity of the crack increase in teeth that are not properly treated early. Pulpal, periapical, and periodontal involvem ent can occur in untreated teeth. In tim e, a com plete vertical fracture may occur. The segm ents o f the tooth with an incom plete vertical fracture should be tem porarily bound to gether as soon as possible. T h is prevents further cracking of the tooth and the concom itant pulpal and periodontal damage. In addition, tem porary binding allow s tim e for evaluation of the pulpal and periodontal status of the tooth before construction of the final restoration. Copper bands, arch w ires, and preformed alum inum or stainless steel crow ns may be used as a m eans of tem porarily treating the cracked tooth. A properly designed am algam restor ation w ill also bind the segm ents of the tooth to gether. For cracks running in a buccolingual d irec tion, a conventional three surface (m esial, occlusal, and distal) am algam w ill suffice. It is essential that
fim i ' MJ,' 1 Jfj
' '
i
Fig 5 ■ Cast restorations for teeth with vertically directed incomplete fractures should not have interproximal box for additional retention in re gion of fracture. Insertion of restoration in interproximal box would act as wedge and further separate fractured segments.
the cavity preparation have d istinct step reductions for both the m esial and distal boxes (Fig 4 left). T h is step reduction ensures that the am algam restoration binds and locks the fractured segm ents together. Cracks running in a m esiodistal direction over the m arginal ridges require the placem ent of an am al gam w ith a step reduction extending onto the buccal and lingual surfaces (Fig 4 right). A dditional depth of the cavity preparation is desirable to give strength to the restoration and to prevent the am algam from breaking away during subsequent preparation for the perm anent cast restoration. T h e presen ce of the intact amalgam during the preparation for the cast restoration is evidence that the in com plete fracture has not widened during the preparation. A com plete cast-gold crow n restoration is the in dicated final restoration for teeth that have incom plete vertical fractures. As the objective is to tightly and perm anently bind together the fractured seg m ents, the design of the preparation for the cast-gold restoration is crucial. Retentive intracoronal box or groove form ation should be avoided in regions that w ill tend to separate the tooth segm ents and in crease the severity of the crack. If, for exam ple, the crack runs in a m esiodistal direction, the insertion of any gold restoration that has an interproxim al box may act as a wedge and tend to separate the seg m ents rather than bind them together (Fig 5). The preparation for the cast gold restoration for a tooth w ith a crack that runs m esiod istally may have grooves on the buccal or lingual surfaces as the insertion of the gold restoration into th ese retentive devices would not tend to wedge the fractured seg m ents apart. Posterior teeth that have vertical in com plete fractures running b u ccolin gu ally should not have buccal or lingual grooves for the same reason. W hen an incom plete vertical fracture is diag nosed in a posterior tooth that has irreversible pul p itis or periodontal involvem ent as a resu lt of the Silvestri-Singh : TREATMENT OF FRACTURED POSTERIOR TEETH ■ 809
crack, the prognosis for the tooth is poor. Extraction is often the most practical treatment. However, when it is necessary to restore such a tooth, it is essential that the construction of the gold restora tion precede the root canal or periodontal therapy. As microleakage associated with the crack is a con tributing factor in pulpal or periodontal disease, control of this factor is mandatory before other treatment. The tooth with irreversible pulpitis resulting from an incomplete vertical fracture that has not previ ously been treated with a cast restoration will be severely threatened by the mechanical instrumenta tion and obturation of root canal therapy. In addi tion, fabrication of a post and core for these teeth is extremely dangerous unless the cast restoration is fabricated first as the internal stresses created by the post and core could result in a more severe crack. Consequently, root canal therapy completed with the access opening made through a permanently cemented cast crown maximizes the possibility of success.
When periodontal therapy is contemplated for a periodontal pocket that has occurred as a result of an incomplete vertical crack, fabrication and final cementation of the cast restoration should be com pleted first. The crack contributes to formation of the pocket by acting as a channel for the passage of saliva and bacteria, thereby creating communica tion between the oral environment and the deeper periodontal structures. Healing will not occur after periodontal therapy unless this communication is prevented by the placement of a properly designed, well-fitting cast restoration.
Summary The four types of fractures most frequently encoun tered in posterior teeth— obliquely directed com plete fractures, vertically directed complete frac tures, obliquely directed incomplete fractures, and vertically directed incomplete fractures— have been described. A detailed treatment approach for each type has been presented. T h e a ssista n ce o f Drs. M au ry M a ssler and S te v e n C ohen is a ck n o w l edged.
THE AUTHORS
1. G ibbs, J.W . C uspal fractu re odon talgia. D ent D ig 6 0 :1 5 8 A p ril 1 9 5 4 . 2. R itch e y , B .; M e n d e n h a ll, R .; and O rban, B. P u lp itis re su ltin g from in co m p lete to oth fractu re. O ral Su rg 1 0 :6 6 5 Ju n e 1 9 5 7 . 3. S u tto n , P.R . G ree n stick fra ctu re o f th e to o th crow n . B r D ent J 1 1 2 :3 6 2 M ay 1, 1 9 6 2 . 4 . C am eron , C .E. C racked to oth synd rom e. JAD A 6 8 :4 0 5 M arch 1 9 6 4 . 5. Cam eron, C .E. T h e cra ck ed tooth sy nd ro m e: ad d ition al fin d in g s. JA D A 9 3 :9 7 1 N ov 1 9 7 6 . 6 . H iatt, W .H. In co m p le te crow n -root fracture in p u lp al-p erio d o n tal
SILVESTRI
SINGH
Dr. S ilv e s tri and Dr. S in g h are assistant p rofesso rs, d ep artm en t of re sto rativ e d en tistry , S c h o o l o f D ental M e d icin e , T u fts U n iv ersity, O n e K n eelan d St, B o sto n , M ass 0 2 1 1 1 . A d dress req u ests fo r re p rin ts to Dr. S ilv e stri.
d isease. J P erio d o n to l 4 4 :3 6 9 Ju n e 197 3 . 7. Sn y d er, D .E. T h e cra ck ed -to o th synd rom e and fractu red p o sterio r cu sp . O ral Surg 4 1 :6 9 8 Ju n e 1 9 7 6 . 8. S ilv e s tri, A .R . T h e u n d iag n o sed sp lit-ro ot synd rom e. JAD A 9 2 :9 3 0 M ay 1 9 7 6 . 9. T a lim , S .T ., an d G o h il, K .S . M an ag em en t o f co ro n al fra ctu res of p erm an en t p o sterio r teeth . J P rosth et D ent 3 1 :1 7 2 F eb 1 9 7 4 . 10. K asloff, Z. E n am el cra ck s cau sed by rotary in stru m en ts. J P rosth et D ent 1 4 :1 0 9 Ja n -F eb 1 9 6 4 . 11. S ta n d le e, J.P .; C aputo, A .A .; and C o llard , E.W . R eten tiv e p in in s ta l la tio n stresses. D en t P ra ct D en t R e c 2 1 :4 1 7 Aug 1 9 7 1 . 12. D ilts, W .E ., and o th ers. C razin g o f tooth stru ctu re a sso cia ted w ith p la cem en t o f p in s for am algam restoration s. JA D A 8 1 :3 8 7 A ug 1 9 7 0 . 13. P a m eijer, C.H ., and S ta lla rd , R.E. E ffe ct o f self-th read in g pin s. JADA 8 5 :8 9 5 O ct 1 9 7 2 . 14. S ta n ley , H.R. T h e cra ck ed tooth synd rom e. J A m A cad G old F o il O per 1 1 :3 6 S ep t 1 9 6 8 .
8 10 ■ JADA, Vol. 97, November 1978
Treatment rationale of fractured posterior teeth A nthony R. Silv estri, Jr., DMD Iqbal Singh, MDS, Boston
he treatment of posterior teeth with complete and incomplete fractures is different for each type of fracture that is encountered. Although several re ports have dealt with the diagnosis and description of the various types of fractures,1'8 few have de scribed in depth the treatment rationale for this dif ficult problem. The depth, degree, and direction of fractures of posterior teeth vary greatly. Con sequently, the treatment of these teeth requires the dentist to diagnose accurately the type of fracture before attempting to restore the tooth. The treatment for the most common types of fractures encountered in posterior teeth is described.
Review Gibbs1 described a condition in which only a cusp of a posterior tooth was involved. This type of incom plete cuspal fracture may involve the pulp. Gibbs called the pain resulting from incomplete cuspal fracture “cuspal fracture odontalgia.” He suggested that treatment of incomplete fractures not involving the pulp be accomplished by binding the cusps im movably together with a complete cast crown. Ritchey and others2 described the histopathology of incomplete fractures in the posterior teeth of 22 patients. Treatment ranged from root canal therapy 806 ■ JADA, Vol. 97, November 1978
to the use of cast-gold crowns or extraction. How ever, no attempt was made to correlate the treatment with the severity of the fracture. Greenstick fractures of crowns of posterior teeth, as described by Sutton,3 originate in dentin near the pulpal wall of a prepared cavity and run obliquely toward the cementoenamel junction. These frac tures do not involve the pulp. Sutton recommended the removal of the fractured tooth substance and prosthetic replacement of the missing structure with amalgam placed on a base of zinc oxide-eugenol. C a m e r o n 4 e x a m in e d 5 0 te e th w ith in c o m p le te fra c tu re s . H e te rm e d th e s ig n s a n d s y m p to m s fro m s u c h fra c tu re s “ th e c r a c k e d to o th s y n d r o m e .” T w o ty p e s o f c ra c k s w e re d e s c r ib e d : th o s e th a t a re c e n tr a lly lo c a te d , fo llo w th e lin e s o f th e d e n tin a l tu b u le s , a n d le a d to w a rd th e p u lp ; a n d th o s e th a t are m o re p e rip h e ra l a n d le a d to fr a c tu r e o f th e c u sp .
In a more recent report, Cameron5 studied 102 cracked posterior teeth. He suggested that the tooth structure that was weakened by superficial cracks be removed and replaced by a prosthesis. He also suggested that the teeth with centrally located cracks be restored with a cast-gold onlay or crown to prevent further cracking and the possibility of pul pitis. Some teeth with mild pulpitis that resulted from a crack were crowned with the use of a nonir
ritating cement. If degeneration of the pulp ensued, root canal therapy was performed through the castgold crown, thus ensuring stabilization of the frac tured segments of the tooth during root canal therapy. Incomplete fractures of the crow n and root were investigated by Hiatt6 in relation to pulpal and periodontal disease. He emphasized the progressive and irreversible nature of incom plete fractures when the lesions are not recognized and treated early. Cast-gold restorations that cover the occlusal surfaces were suggested as a treatm ent to prevent further pulpal and periodontal involvement. Snyder7 discussed the diagnosis and treatm ent of the cracked tooth syndrome and fractured cusps of posterior teeth. He said that grinding the incom plete fractured cusp out of occlusion does not perm a nently solve the problem. A restoration that binds the weakened tooth structure together is necessary. Silvestri8 described teeth that were incom pletely split and with both the crow n and the root involved. He termed the signs and symptoms from such le sions “the split root syndrom e.” Treatm ent of the reported cases involved stabilization of the frac tured tooth segments with a cast-gold onlay. A classification system for coronal fractures of posterior teeth was proposed by T alim and G ohil.9 They studied 4 0 posterior teeth that had a. variety of types of fractures and ind icated the sp ecific treat m ent for each tooth. A review of the literature shows that m any authors have reported clinical cases of fractured posterior teeth and described the treatment procedures im plemented for each case. The purpose of this article is to present a treatment rationale for the com mon types of fractured posterior teeth that are encoun tered most frequently by the clinician.
Completely fractured posterior teeth OBLIQUELY DIRECTED COMPLETE FRACTURES. Ob liquely directed complete fractures of posterior teeth are the easiest to diagnose. The oblique frac tures usually involve one cusp of a posterior tooth, extend into the dentin, and terminate at some level in an apical direction. Although it is possible for the fracture to involve the pulp, this usually does not occur. The obliquely directed complete fracture most frequently occurs on cusps that have been se verely weakened by a previous extensive amalgam restoration (Fig 1). Lateral shearing forces generated during mastication or parafunction eventually re sult in the tooth segment being sheared away com pletely. The preferred treatment for this type of frac
ture is replacem ent of the missing tooth structure with a suitable restorative material. The ideal resto ration is a cast-gold onlay or crow n that replaces the lost structure and also protects the remaining cusps from future fracture. In cases in w hich the apical termination of the fracture occurs below the attach ment apparatus, gingivectom y m ay be necessary to aid in properly placing the margin of the cast-gold preparation. Occasionally, the apical termination of the obliquely directed fracture may occur below the crest of the alveolar bone. If the crow n-root ratio is favorable, the need for construction of a cast crown is still indicated after gingivectom y and osseous recontouring immediately apical to the fracture site. An alternative treatm ent for obliquely directed complete fractures in posterior teeth is the replace ment of the missing tooth structure with amalgam. One or more pins may be necessary to retain the restoration. Although this treatment is a com promise to the preferred cast restoration, it will re main serviceable until a cast restoration can be com pleted. Care must be taken in the design of the prep aration to avoid undermining other cusps and sub jecting them to the possibility of sim ilar fracture. Occasionally, especially with m axillary premo lars, the pulp may be involved when a tooth com pletely fractures in an oblique direction. In these cases, the preferred treatment is root canal therapy followed by use of a post and core and cast crown. VERTICALLY DIRECTED COMPLETE FRACTURES. Complete vertical fractures of posterior teeth can also occur. When the fracture is com pletely through the tooth, the clinical sign is a distinct, independent mobility of one segment of the tooth and root in relation to the other segment. This type of fracture occasionally occurs in teeth that have been endodontically treated and in w hich the bifurcation extends extremely high in an occlusal direction. Root canal therapy and preparation for a post and Silvestri-Singh : TREATMENT OF FRACTURED POSTERIOR TEETH ■ 807
Fig 2 ■ Vertically directed complete fracture on tooth weakened by root canal therapy and post and core preparation. On final insertion of cast post and core, weakened tooth with high bifurcation may com pletely fracture.
Fig 3 ■ Obliquely directed incomplete fracture involving one cusp of mandibular mo lar. Extensive amalgam resto ration has undermined and weakened cusp resulting in incomplete fracture.
core w eaken the tooth. Finally, on insertion of the cast post and core, enough lateral forces are created to sp lit the tooth into two distinct sections (Fig 2). Even w hen posterior teeth are strong, caution should be taken to avoid forcefully seating a cast post and core into the prepared root to prevent split ting o f the tooth. W hen a tooth is com pletely fractured in a vertical direction, the preferred treatm ent is extraction fol lowed by prosthetic replacem ent. On very rare occa sions, it is necessary to retain one of the segm ents of a m ultirooted tooth to serve as an abutm ent for a prosthesis. In these exceptional cases, the weakest segm ent should be hem isected and the rem aining root endodontically treated before the use of the tooth for the prosthesis.
Incompletely fractured posterior teeth Incom plete fractures of posterior teeth are occurring w ith increased frequency,5,6,8 Advanced restorative techniques and procedures, such as high-speed ro tary cutting instrum ents and pins, have contributed to the increased occu rren ce.10-13 The sym ptom atol ogy associated w ith these incom plete cracks vary from sensitivity to cold, hot, sw eet, and sour stim uli. However, the overriding sym ptom shared by all pa tients is a sharp, lancinating discom fort lasting from several seconds to several m inutes when eating hard 808 ■ JADA, Vol. 97, November 1978
or crunchy foods. The hard food acts as a wedge between the cusps during chewing and causes a slight separation of the incompletely fractured seg ments. Microleakage through the crack results in inflammation of the pulp and hypersensitivity of the tooth to a wide range of stimuli.5,8,14 The variable depth and severity of the cracks explain the diverse range of symptoms. OBLIQUELY DIRECTED INCOMPLETE FRACTURES. O blique incom plete fractures of the crow n occa sionally occu r when nonaxial occlu sal forces gener ated during chew ing and parafunction exceed the capacity of the tooth to resist fracture. A n oblique crack w ill originate in enam el on the occlu sal sur face, involve one or more cusps, run into dentin in an oblique direction under the cusps, and term inate gingivally in enam el or cem entum . M ost frequently, oblique incom plete fractures occur in posterior teeth that have been previously prepared for an ex tensive am algam restoration. T he incom plete frac ture usually involves a cusp that was not removed during the cavity preparation yet was severely w eakened by the rem oval of underm ining decay. O cclusal forces create internal stresses w ith in the tooth that result in concentration of stress at the ju nction of the base of the cavity preparation and the cusp. Consequently, a m inute crack occurs in this region of the tooth (Fig 3). The preferred treatm ent is rem oval of the tooth structure threatened by the crack and restoration of the tooth w ith a cast-gold onlay or crow n. T he design of the preparation for the restoration should remove all weak tooth structure and create adequate retention w ith the use of con ventional techniques (grooves, keys, and so forth). If rem oval of the tooth structure results in exposure of the pulp, adequate therapy m ust be perform ed b e fore restoration w ith the cast gold. A lthough oblique incom plete fractures of pos terior teeth usually term inate at the cem entoenam el ju n ctio n or slightly above it, occasion ally they w ill extend into the root. Treatm ent of these frac tures w ith a cast-gold onlay or crow n can be ac com plished only after local periodontal proce dures are performed to expose the m ost apical ex tension of the fracture site. The difficulty in restor ing the tooth increases and the prognosis worsens w ith incom plete fractures that term inate below the level of the crestal bone. VERTICALLY DIRECTED INCOMPLETE FRACTURES. T he presence of vertical incom plete fractures in posterior teeth is w ell docum ented in the litera ture.4-8 U nlike the obliquely directed fractures that
I«! §■'-
Fig 4 ■ Lett, vertically directed incomplete fracture running in butcolingual direction showing mesial, occlusal, and distal step-reduction preparation. Right, vertically directed incomplete fracture running in mesiodistal direction showing buccal, occlusal, and lingual stepreduction preparation. Completed amalgam restoration for both will temporarily bind fractured segments together.
usually occur on w eakened cusps of extensively prepared teeth, incom plete vertical fractures more frequently occu r in teeth that are m inim ally restored or even in teeth w ith no restorations. T he crack may run in a m esiodistal d irection over one or both m ar ginal ridges or buccolin gually betw een cusps (Fig 4 left, right). Inherent weakness w ithin the tooth structure at the site w here the developm ental lobes coalesce during tooth form ation have been postu lated as an etiologic factor by Cam eron.5 In addition, iatrogenic factors, such as pins, restorations, and vibration from high-speed rotary instrum entation, contribute to the form ation of a crack.10"13 V ertical incom plete fractures originate in enam el and extend in to the dentin. In some cases, the crack even extends into the root.8 Hiatt6 described the progressive nature of this type of incom plete frac ture and the way the depth and severity of the crack increase in teeth that are not properly treated early. Pulpal, periapical, and periodontal involvem ent can occur in untreated teeth. In tim e, a com plete vertical fracture may occur. The segm ents o f the tooth with an incom plete vertical fracture should be tem porarily bound to gether as soon as possible. T h is prevents further cracking of the tooth and the concom itant pulpal and periodontal damage. In addition, tem porary binding allow s tim e for evaluation of the pulpal and periodontal status of the tooth before construction of the final restoration. Copper bands, arch w ires, and preformed alum inum or stainless steel crow ns may be used as a m eans of tem porarily treating the cracked tooth. A properly designed am algam restor ation w ill also bind the segm ents of the tooth to gether. For cracks running in a buccolingual d irec tion, a conventional three surface (m esial, occlusal, and distal) am algam w ill suffice. It is essential that
fim i ' MJ,' 1 Jfj
' '
i
Fig 5 ■ Cast restorations for teeth with vertically directed incomplete fractures should not have interproximal box for additional retention in re gion of fracture. Insertion of restoration in interproximal box would act as wedge and further separate fractured segments.
the cavity preparation have d istinct step reductions for both the m esial and distal boxes (Fig 4 left). T h is step reduction ensures that the am algam restoration binds and locks the fractured segm ents together. Cracks running in a m esiodistal direction over the m arginal ridges require the placem ent of an am al gam w ith a step reduction extending onto the buccal and lingual surfaces (Fig 4 right). A dditional depth of the cavity preparation is desirable to give strength to the restoration and to prevent the am algam from breaking away during subsequent preparation for the perm anent cast restoration. T h e presen ce of the intact amalgam during the preparation for the cast restoration is evidence that the in com plete fracture has not widened during the preparation. A com plete cast-gold crow n restoration is the in dicated final restoration for teeth that have incom plete vertical fractures. As the objective is to tightly and perm anently bind together the fractured seg m ents, the design of the preparation for the cast-gold restoration is crucial. Retentive intracoronal box or groove form ation should be avoided in regions that w ill tend to separate the tooth segm ents and in crease the severity of the crack. If, for exam ple, the crack runs in a m esiodistal direction, the insertion of any gold restoration that has an interproxim al box may act as a wedge and tend to separate the seg m ents rather than bind them together (Fig 5). The preparation for the cast gold restoration for a tooth w ith a crack that runs m esiod istally may have grooves on the buccal or lingual surfaces as the insertion of the gold restoration into th ese retentive devices would not tend to wedge the fractured seg m ents apart. Posterior teeth that have vertical in com plete fractures running b u ccolin gu ally should not have buccal or lingual grooves for the same reason. W hen an incom plete vertical fracture is diag nosed in a posterior tooth that has irreversible pul p itis or periodontal involvem ent as a resu lt of the Silvestri-Singh : TREATMENT OF FRACTURED POSTERIOR TEETH ■ 809
crack, the prognosis for the tooth is poor. Extraction is often the most practical treatment. However, when it is necessary to restore such a tooth, it is essential that the construction of the gold restora tion precede the root canal or periodontal therapy. As microleakage associated with the crack is a con tributing factor in pulpal or periodontal disease, control of this factor is mandatory before other treatment. The tooth with irreversible pulpitis resulting from an incomplete vertical fracture that has not previ ously been treated with a cast restoration will be severely threatened by the mechanical instrumenta tion and obturation of root canal therapy. In addi tion, fabrication of a post and core for these teeth is extremely dangerous unless the cast restoration is fabricated first as the internal stresses created by the post and core could result in a more severe crack. Consequently, root canal therapy completed with the access opening made through a permanently cemented cast crown maximizes the possibility of success.
When periodontal therapy is contemplated for a periodontal pocket that has occurred as a result of an incomplete vertical crack, fabrication and final cementation of the cast restoration should be com pleted first. The crack contributes to formation of the pocket by acting as a channel for the passage of saliva and bacteria, thereby creating communica tion between the oral environment and the deeper periodontal structures. Healing will not occur after periodontal therapy unless this communication is prevented by the placement of a properly designed, well-fitting cast restoration.
Summary The four types of fractures most frequently encoun tered in posterior teeth— obliquely directed com plete fractures, vertically directed complete frac tures, obliquely directed incomplete fractures, and vertically directed incomplete fractures— have been described. A detailed treatment approach for each type has been presented. T h e a ssista n ce o f Drs. M au ry M a ssler and S te v e n C ohen is a ck n o w l edged.
THE AUTHORS
1. G ibbs, J.W . C uspal fractu re odon talgia. D ent D ig 6 0 :1 5 8 A p ril 1 9 5 4 . 2. R itch e y , B .; M e n d e n h a ll, R .; and O rban, B. P u lp itis re su ltin g from in co m p lete to oth fractu re. O ral Su rg 1 0 :6 6 5 Ju n e 1 9 5 7 . 3. S u tto n , P.R . G ree n stick fra ctu re o f th e to o th crow n . B r D ent J 1 1 2 :3 6 2 M ay 1, 1 9 6 2 . 4 . C am eron , C .E. C racked to oth synd rom e. JAD A 6 8 :4 0 5 M arch 1 9 6 4 . 5. Cam eron, C .E. T h e cra ck ed tooth sy nd ro m e: ad d ition al fin d in g s. JA D A 9 3 :9 7 1 N ov 1 9 7 6 . 6 . H iatt, W .H. In co m p le te crow n -root fracture in p u lp al-p erio d o n tal
SILVESTRI
SINGH
Dr. S ilv e s tri and Dr. S in g h are assistant p rofesso rs, d ep artm en t of re sto rativ e d en tistry , S c h o o l o f D ental M e d icin e , T u fts U n iv ersity, O n e K n eelan d St, B o sto n , M ass 0 2 1 1 1 . A d dress req u ests fo r re p rin ts to Dr. S ilv e stri.
d isease. J P erio d o n to l 4 4 :3 6 9 Ju n e 197 3 . 7. Sn y d er, D .E. T h e cra ck ed -to o th synd rom e and fractu red p o sterio r cu sp . O ral Surg 4 1 :6 9 8 Ju n e 1 9 7 6 . 8. S ilv e s tri, A .R . T h e u n d iag n o sed sp lit-ro ot synd rom e. JAD A 9 2 :9 3 0 M ay 1 9 7 6 . 9. T a lim , S .T ., an d G o h il, K .S . M an ag em en t o f co ro n al fra ctu res of p erm an en t p o sterio r teeth . J P rosth et D ent 3 1 :1 7 2 F eb 1 9 7 4 . 10. K asloff, Z. E n am el cra ck s cau sed by rotary in stru m en ts. J P rosth et D ent 1 4 :1 0 9 Ja n -F eb 1 9 6 4 . 11. S ta n d le e, J.P .; C aputo, A .A .; and C o llard , E.W . R eten tiv e p in in s ta l la tio n stresses. D en t P ra ct D en t R e c 2 1 :4 1 7 Aug 1 9 7 1 . 12. D ilts, W .E ., and o th ers. C razin g o f tooth stru ctu re a sso cia ted w ith p la cem en t o f p in s for am algam restoration s. JA D A 8 1 :3 8 7 A ug 1 9 7 0 . 13. P a m eijer, C.H ., and S ta lla rd , R.E. E ffe ct o f self-th read in g pin s. JADA 8 5 :8 9 5 O ct 1 9 7 2 . 14. S ta n ley , H.R. T h e cra ck ed tooth synd rom e. J A m A cad G old F o il O per 1 1 :3 6 S ep t 1 9 6 8 .
8 10 ■ JADA, Vol. 97, November 1978
