Strengthening of immature teeth during long-term endodontic therapy

Abstract A method to strengthen a nonvital immature maxillary central incisor during long-term endodontic therapy is described. Calcium hydroxide paste was packed into the root canal space, then removed to a level 3 mm apically to the osseous crest. A layer of IRM cement was placed over the paste to provide a bacteria-tight seal. The coronal portion of the root canal as well as the pulp chamber were acid-etched and filled with a composite resin in an attempt to strengthen the tooth. Access to the root canal was maintained by means of a vaseline-coated plastic post placed centrally in the resin. After polymerization of the resin the post was removed and the space was sealed with zinc oxide and eugenol cement. After completion of the endodontic treatment the space was filled with the composite resin.     

Fracture strength of teeth with flared root canals restored with glass fibre posts

OBJECTIVE: To investigate the fracture strength and pattern of failure of teeth with weakened roots reconstructed by different procedures. METHODS: In an in vitro study root posts were placed in 50 endodontically treated canines, divided into 5 groups (n=10) as follows: cast metallic post; glass fibre post with smaller diameter than the root canal; glass fibre post with smaller diameter than the root canal + glass fibre strips; glass fibre post with smaller diameter than the root canal + accessory glass fibre posts; anatomical post (glass fibre post with smaller diameter than the root canal, relined with low viscosity composite resin). Posts were luted with resin cement and the coronal portion of posts was constructed with composite resin. Metallic crowns were cemented on the posts. Specimens were submitted to compressive load in a universal testing machine. Fracture strength values of each group were compared. RESULTS: Fracture strength values were for Groups 1-5 respectively: 1087.06; 745.69; 775.41; 920.64; 876.12kgf, with significant differences between Groups 1 and 2 and between Groups 1 and 3 (p<0.05). Observed patterns of fracture were: Group 1 - 100% of roots fractured; Groups 2 and 4 - variable fracture modes; Group 3 - 60% of fractures occurred in the cervical root third; Group 5 - 50% of failures occurred in the coronal portion of the post. CONCLUSIONS: The fracture strength of teeth with cast metallic posts, teeth with anatomical posts or teeth with glass fibre posts combined with accessory posts was similar. All teeth restored with cast metallic posts presented fractures and were unfavourable to maintenance of the remaining tooth structure. Teeth with fibre posts (Groups 2 to 5) presented variable fracture modes; however, the maximum percentage of unfavourable fractures was 30%.     

Root canal posts — some prosthodontic aspects

Abstract Prosthodontic treatment of non-vital teeth following endodontic therapy faces problems originating from the fact that such teeth generally have damaged clinical crowns, necessitating retention beyond the remaining coronal portions of the teeth. Additional intraradicular retention can be obtained by means of root canal posts. The total need for retention shows wide variations. Each case, therefore, should be carefully analyzed before decisions arc made about post types, post designs and post dimensions. The need for retention is dependent upon intermaxillary relations, type of prosthetic appliance, position of tooth, and volume and shape of remaining tooth substance. At least 3 mm of well-sealed root canal should be left apically to the post preparation, but normally the post preparation should not extend into the apical one-third of the root. Sufficient additional retention through a post is usually achieved when the extention of the post into the root canal at least equals the difference between the mean height of the prepared coronal dentin and the height of an ideal crown preparation of the tooth.     

即刻桩腔预备对三种根管预备方法预备的直根管根尖封闭性的影响

目的 研究三种不同根管预备方法根管预备、根管充填后即刺桩腔预备对直根管根尖封闭性的影响.方法 离体直单根管上前牙124个,其中120个随机平均分为3组(n=40),A组:不锈钢根管锉常规法;B组:G 型钻根管冠部预处理 不锈钢根管锉常规法;C组:手用Pr01raper镍钛根管锉冠向下法,刺余4个随机平均分为阴性对照组和阳性对照组.所有根管均用侧方加压法充填,即刻手持垂直加压器去除部分充填材料,然后P型钻桩腔预备.用染料渗透法评价各组根尖封闭能力.结果 B组G型钻根管冠部预处理 不锈钢根管锉常规法预备的根管和C组手用ProTaper镍钛根管锉冠向下法预备的根管即刻桩腔预备后,其根尖微渗漏较A组常规法预备的轻(P<0.05).结论 大锥度根管预备,根管充填后即刻桩腔预备的根尖封闭性较好.     

Three-dimensional-guided removal and preparation of dental root posts—concept and feasibility

PatientsThis case report presents a novel method to remove glass fiber-reinforced composite root posts in a minimally invasive way while simultaneously shaping the canal for a new post-endodontic restoration. A multi-morbid, handicapped 62-year-old patient was referred with a horizontally fractured maxillary incisor presenting approximately 1 mm residual coronal tooth height. Endodontic revision was necessary, which required removal of a glass fiber-reinforced composite post. A cone-beam computed tomography (CBCT) scan was imported into conventional implant-planning software and matched to a stone cast of the intraoral situation. Position, length, and axis of the future post were planned virtually. Based on this planning, a tooth-supported splint was three-dimensionally (3D) printed. This splint allowed use of a 2.2-mm spiral drill for removal of the fractured post and shaping of the root canal for a new cast post-and-core. This metal post-and-core was adhesively cemented and prepared for a zirconia single crown veneered in the labial aspect.DiscussionThis method currently requires use of CBCT-based, ionizing 3D imaging. Additional refinements to this approach can be made regarding spiral drill design and coating as well as regarding the post-and-core workflow.Conclusions3D-guided post-endodontic management is feasible. More research is needed to balance higher radiation doses against therapeutic success.     

An in vitro study of coronal microleakage in root-canal-treated teeth restored by the post and core technique

The aims of this study were to compare coronal microleakage around cast and prefabricated post and cores and to examine the coronal seal achieved by temporary post crowns. Thirty extracted, single-rooted, human teeth were prepared chemomechanically, root filled with gutta-percha and sealer and prepared for a standard post. Three groups, each of 10 teeth, were restored with either: (i) cast post and cores cemented with zinc phosphate cement; (ii) prefabricated posts and composite cores cemented with a composite luting cement; or (iii) temporary post crowns cemented with a temporary zinc oxide-eugenol cement. The teeth were thermocycled and placed in Indian ink for 1 week, then demineralized and rendered transparent. Linear coronal dye penetration around the posts was measured and recorded. Results indicated that while cast post and cores and prefabricated posts and composite cores produced a good seal, leakage was significantly greater with temporary post crowns ( P < 0.05). It is concluded that to prevent re-infection of the root canal system, it may be preferable to restore the tooth immediately with a prefabricated post and composite system rather than place a temporary post crown and subsequently a cast post and core.     

Effect of composite post placement on bonding to root canal dentin using 1-step self-etch dual-cure adhesive with chemical activation mode

This study evaluated the effect of composite post placement and/or light-irradiation of dual-cure resin composite on adhesion to root canal dentin using the chemical activation mode of a 1-step self-etch dual-cure adhesive. Post spaces were prepared in extracted premolars. Root canal spaces were applied with Unifil Core EM Self-Etching Bond, which was chemically-polymerized, and then filled with Unifil Core EM with or without the placement of composite post. Half the specimens of each group were light-cured for 10 seconds and the other half were chemically-cured in darkness for 30 minutes. After 24 h storage, microtensile bond strengths (μTBS) at the coronal and apical regions were measured. When light-curing, placement of the composite post significantly reduced the μTBS to root canal dentin. On the other hand, when chemical-curing, there was no significant difference in μTBS between with and without placement of the composite post.     

Microcomputed tomography evaluation of contamination with endodontic obturation material remnants in teeth with different root canal anatomy after post space preparation

Statement of problemWhether the amount of the endodontic obturation material remnants in a root canal prepared for a post is related to variations in the anatomic shape of the canal or whether it varies in different parts of the post space is unclear.PurposeThe purpose of this in vitro study was to estimate the extent of root canal contamination with remnants of the obturation material after post space preparation in relation to the anatomic shape of the root canals by means of microcomputed tomography.Material and methodsFifty freshly extracted teeth were divided into 5 test groups with respect to the root anatomy of different tooth types. The root canals were shaped and obturated with gutta percha. The space for the glass fiber post was prepared with standardized drills, and all specimens were scanned by microcomputed tomography. The areas of residual obturation material on the root canal walls in the coronal and apical parts of the prepared post space were estimated by using a 3D visualization software program. Parametric and nonparametric dispersive analysis (analysis of variance and Kruskal-Wallis) and Wilcoxon tests were used for statistical data evaluation (α=.05).ResultsThe estimates of the root canal surface areas contaminated with residual obturation material after post space preparation were significantly larger in premolars (P≤.01), as compared with mandibular incisors and with the palatal roots of maxillary first molars. The contamination areas in different parts of the root canal (apical and coronal) reported significant differences within and between the test groups.ConclusionsThe extent of root canal contamination with remnants of endodontic obturation material after post space preparation was related to the anatomic shape of the roots and varied in the coronal and apical parts of the prepared post space.     

Strengthening and restoration of immature teeth with an acid-etch resin technique

Abstract Endodontic treatment with subsequent restoration of 3 immature incisors with horizontal fractures in the cervical region is described. In 1 tooth the fracture occurred supragingivally, whereas in 2 others the fracture was such that the root margins were between 1 and 2 mm subosseous. In these teeth proper access to the roots was established by means of orthodontic extrusion and/or periodontal surgery. After endodontic treatment, the gutta-percha was removed from the root canals to a level 2 to 3 mm apically to the osseous crest. The root canal dentin was acid-etched and a post to retain a crown was cemented into the canal with a composite resin. The resin will then penetrate into the dentinal tubules of the root canal walls and strengthen the root to such a degree that it becomes restorable. Semipermanent composite resin crowns and, in one instance, a more permanent porcelain crown were used to restore the teeth.     

Bonding of photo and dual-cure adhesives to root canal dentin

This study evaluated the regional tensile bond strength of a dual-cure resin composite core material to root canal dentin using photo and dual-cure adhesives and different modes of polymerization. Nineteen extracted premolars were decoronated and their root canals prepared to a depth of 8 mm and a width of 1.4 mm using Para Post drills. For the microtensile bond strength (microTBS) test, 15 roots were randomly divided into five groups and their canal walls treated with a dual-cure self-etching primer (Clearfil Liner Bond 2V Primer, Kuraray Medical Co, Japan). Adhesive resin (Clearfil Liner Bond 2V Bond A) was applied to two of the groups and light cured for 20 seconds. A dual-cure adhesive resin (Clearfil Liner Bond 2V Bond A+B, Kuraray Medical Co, Japan) was applied to the remaining three groups, one of which was light cured. The post spaces of all the groups were filled with a dual-cure resin composite (DC Core) and three were light cured for 60 seconds from a coronal direction. Chemical-cure resin composite was placed on the outer surfaces of the roots, which were then stored in water for 24 hours. They were serially sliced perpendicular to the bonded interface into eight 0.6 mm-thick slabs, then transversely sectioned into beams approximately 8 x 0.6 x 0.6 mm for the microTBS test. All of the failure modes were observed under SEM and analyzed using the Kruskal-Wallis Rank test. For Knoop hardness testing, four specimens were prepared in a similar manner, two were light-cured and the other two chemically-cured. The specimens were longitudinally sectioned into two pieces, and three indentations were made at 100 microm intervals from a coronal to an apical direction in the eight halves. Data were divided into two groups (coronal/apical halves of post space) and analyzed using two-way ANOVA and Scheffe's test (p<0.05). For each curing strategy, there were no significant differences in microTBS and Knoop hardness between the coronal and apical regions (p>0.05). Light exposure of both the adhesive resin and resin composite resulted in significantly higher microTBS than chemical-cure alone (p<0.05). Light exposure also significantly increased Knoop hardness at both the coronal and apical regions (p<0.05). When the bonding resin and dual-cure resin composite were chemically-cured, failures occurred cohesively within the resin. Photo-initiated polymerization of the adhesive resin and dual-cure resin composite was necessary to achieve good bonding to root canal dentin, which was not dependent upon region.     

Weakened anterior roots--intraradicular rehabilitation

This paper highlights the fact that many anterior teeth requiring restoration are severely weakened having wide, flared canal spaces, and thin dentinal walls that are prone to fracture. Traditionally these teeth have been restored using metal posts and are often unsuccessful because of lack of retention or root fracture. This paper describes how mineral trioxide aggregate (MTA) can be used to form an immediate apical seal rather than waiting months for apexification. Weakened roots can be reinforced using dentine bonding agents and composite resin and if insufficient coronal tooth structure is present a quartz-fibre post can be placed to retain a composite core.     

Multiple complicated crown–root fracture of a permanent incisor

Abstract –  The treatment of a transverse complicated and a vertical uncomplicated crown–root fractures with a horizontal root fracture of a maxillary right central incisor is presented. Coronal fragments were extracted atraumatically and gingivectomy was performed with electrosurgery to expose the subgingival fragment. The root canal was treated with calcium hydroxide to perform the healing at the fracture site. After the root fracture healing, a post was cemented into the canal and the coronal fragment was attached with a composite resin. Examination 18 months after treatment revealed good aesthetics and normal function.     

Fracture resistance of weakened roots restored with a transilluminating post and adhesive restorative materials

STATEMENT OF PROBLEM: The increase in wall thickness of weakened roots using composite resins may increase the root resistance to fracture. However, little is known about the recently developed methods for intraradicular reinforcement of weakened roots. PURPOSE: The purpose of this study was to determine the fracture resistance of experimentally weakened roots reinforced with composite resins, compared with conventional systems that use cast and prefabricated posts. MATERIAL AND METHODS: Forty-eight maxillary incisors were divided into 6 groups (n = 8). The control group (C) used a conventionally prepared root canal filled with cast CuAl posts. Experimental groups had the root canals overprepared to weaken them and were restored as follows: CP, cast CuAl posts; LT, light-transmitting polymerization post (Luminex) + Tetric Ceram resin + prefabricated titanium post (PTP); LF, Luminex posts + Filtek Supreme resin + PTP; LZ, Luminex posts + Z100 resin + PTP; and LR, Luminex posts + Renew resin + PTP. All posts were cemented with a resin luting agent (C & B Cement). Specimens were subjected to compressive load (N) until fracture. Data were submitted to 1-way analysis of variance and the Dunnett test (alpha = .05). RESULTS: There was significant difference (P < .01) between the conventionally prepared specimens and those filled with a cast post (C, 447.8 +/- 167.9) and the overprepared specimens and those filled with a cast post (CP, 212.8 +/- 62.4). No significant differences were found among the control specimens (447.8 +/- 167.9) and the weakened-roots filled with Luminex and composite resins LT (520.9 +/- 173.1), LF (479.9 +/- 214.9), LZ (391.6 +/- 173.6), and LR (333.0 +/- 112.2). CONCLUSION: The use of composite resins in root canals reinforced the weakened roots during fracture resistance testing.     

Endodontic management of badly broken down teeth using the canal projection system: two case reports

Aim  Teeth that have been weakened by caries and require root canal treatment to maintain their functional integrity may present with minimal coronal tooth structure and are a challenge for isolation and restoration. The aim of this clinical report is to demonstrate the management of badly broken down teeth using the Projector Endodontic Instrument Guidance System (PEIGS).
Summary  The PEIGS is an adjunct to root canal treatment designed to enhance the ease of treatment delivery. Use of this system facilitates projection of canal orifices from the floor of the pulp chamber to the cavosurface, providing direct visualization of and physical access to the projected canals. This report demonstrates the use of this novel device for the management of two badly broken down teeth.
Key learning points Use of the endodontic projection system has the following advantages:
• 'Projects' the canal orifice from the floor of the pulp chamber to the cavosurface, thereby enhancing visualization and access to the canals.
• The bonded coronal build up reduces the risk of interappointment crack initiation and coronal-radicular fracture of weakened tooth structure.
• Permits individualization of canals especially when they lie in close proximity to each other on the chamber floor.
• Isolation may be facilitated by ease of clamp retention, rendering many structurally debilitated teeth endodontically treatable.     

Resistance to fracture of restored endodontically treated teeth

Abstract Endodontically treated teeth were restored by 8 different methods. Copper rings were filled with commercial hard setting cement and the teeth were placed into the cement to the level of the cemento-enamel junction. The teeth were grouped according to restorative methods, mounted in an Instron T.T. machine and subjected to a slowly increasing compressive force until fracture occurred. The force of fracture for each tooth was recorded and the results in the various groups compared. All teeth fractured in a similar manner, irrespective of restorative method used. Preparation of a post space in the roots significantly weakened the teeth. Cementation of a steel parapost with zinc oxyphosphate cement did not significantly strengthen the teeth. Filling the post space and the access cavity with a composite resin following acid etching of the root canal and cavity walls strengthened the teeth more than other methods used to restore them. This finding may be of clinical importance, for instance in the restoration of endodontically treated young teeth with incomplete root formation and wide root canals.     

Bond Strength of Fiber Posts to Weakened Roots After Resin Restoration With Different Light-Curing Times

IntroductionThis study evaluated the bond strength of translucent fiber posts to experimentally weakened radicular dentin restored with composite resin and polymerized with different light-exposure time.MethodsRoots of 60 maxillary incisors were used. Twenty-four hours after obturation, the filling materials of root canals were removed to a depth of 12 mm, and 4 groups were randomly formed. In 3 groups, root dentin was flared to produce a space between fiber post and canal walls. In the control group, the roots were not experimentally weakened. The flared roots were bulk restored with composite resin, which was light-activated through the translucent post for 40, 80, or 120 seconds. Posts were cemented, and after 24 hours, all roots were sectioned transversely in the coronal, middle, and apical regions, producing 1-mm-thick slices. Push-out test was performed, and failure modes were observed.ResultsThe quantitative analysis showed significant statistical difference only among groups (P < .001). Comparing the weakened/restored groups, composite light-exposure time did not influence the results. Overall, adhesive failures occurred more frequently than other types of failures. Cohesive failures occurred only in the weakened/restored roots.ConclusionsIntracanal root restoration with composite resin and translucent fiber posts provided similar or higher bond strength to dentin than the control group, regardless of the light-exposure time used for polymerization.     

Structural resistance in immature teeth using root reinforcements in vitro

Abstract –  The purpose of this study was to evaluate in vitro the efficacy of root reinforcements by light-cured composite resin or zirconium fiber post in simulated immature non-vital teeth. Fifty-six bovine incisors teeth were used for this study. The crown of each tooth was removed in the medium third to obtain a standard length of 30 mm. The specimens were divided into four groups ( n  = 14): G1) the root canals were instrumented and enlarged to simulate immature non-vital teeth and were reinforced with a light-cured composite resin using a translucent curing post (Luminex system); (G2) the specimens were instrumented, enlarged and they received root reinforcement with zirconium fiber post; G3 (positive control): they received similar treatment to the G1 and G2 groups, but did not receive root reinforcement; G4 (negative control): the roots were not weakened and did not receive reinforcement. Every tooth was submitted to compressive force using an Instron testing machine with an angle of 45° at a speed of 1 mm min⁻¹ until the fracture. The results showed a markedly increased resistance to fracture in the G1 and G2 ( 122.38 and 122.08 kgf, respectively). Among the results of G1 and G2 there was not any significant difference (P > 0.05) but they were significantly different from the control groups (P < 0.05). The conclusion is that the use of root reinforcements with zirconiun fiber post or composite resin can increase significantly the structural resistance of the weakened teeth, decreasing the risk of the fracture.     

The fit of tapered posts in root canals luted with zinc phosphate cement: a histological study.

OBJECTIVES: Stress transmission to the root through passive fitting dental posts is partly influenced by the thickness of the cement layer between the post and the prepared root canal surface as well as the fit of the post in the root canal. The objective of this study was to compare the cement gap between the post surfaces and the root canals using five prefabricated, tapered, unthreaded titanium posts of different manufacturers, without and with cement. METHODS: Following the endodontic treatment with hand instruments of 100 intact anterior teeth, post spaces were prepared using opening drills of the corresponding size of post. Fifty posts were cemented with zinc phosphate cement into the roots for each system while another 50 posts were inserted into the canal without using the cement. After histological sectioning, the cement gap was measured at six sites for three times at the coronal, middle and apical regions between the root canal wall and the post surface under a light microscope before and after cementation. RESULTS: Before cementation, the highest overall cement gap was observed with the Dr Mooser post system (46 microm) and the lowest with the Velva post system and Cylindro-Conical system (30 microm). Significantly less (P<0.05) mean cement gap was observed with respect to the Erlangen post system (41 microm), the Dr Mooser post system (48 microm), the MP Pirec post system (34 microm) and Velva post system (33 microm) when compared with the Cylindro-Conical system (62 microm). The Cylindro-Conical system (79, 61 microm) and MP Pirec post system (25, 24 microm) demonstrated no significant difference (P>0.001) compared with Velva-Post (38, 20 microm) at the coronal and middle part, respectively (Mann-Whitney U-test, Boneferroni correction). Significant differences (P<0.001) were observed between the cement gap at the coronal and apical part for the Cylindro-Conical system (79, 46 microm), Dr Mooser post system (45, 56 microm) and MP Pirec post system (25, 52 microm). After cementation, the highest cement gap at the coronal part was obtained with the Cylindro-Conical system (79+/-21 microm) and the lowest with the MP Pirec post system (25+/-9 microm). However, at the apical end, the MP Pirec post system (52+/-89 microm) and Dr Mooser post system (56+/-16 microm) revealed the highest gap. SIGNIFICANCE: Form-congruence between the preparation drill and the post systems exhibited differences. The most consistent cement gap either at the coronal, middle or apical parts of the root canals was obtained with the Erlangen post system.     

An investigation into the type of union achieved between cast cores and Wiptam wire posts

The type of union formed between Wiptam wire posts and cast cores has been investigated. Scanning electron microscopy of sectioned 'as cast' specimens showed that the union between Wiptam posts and cast cores was predominantly mechanical in nature. Diffusion studies, however, using an X-ray Microanalysis Unit, revealed that there was evidence of diffusion of silver atoms into the post from the core. This suggests that the bonding between the two components is not merely a simple mechanical lock.     

超声根管清洗术对纤维桩粘接固位力的影响

目的 研究超声根管清洗术对改善纤维桩在根管内固位力的作用,为临床提供参考依据.方法 选取40颗两周内因正畸需要拔除的单根管离体牙,根冠形态完整,根长近似（≥13 mm）,经完善的根管治疗后随机分成A、B两组,于釉牙骨质界上方2 mm水平截冠并预备根管桩道.A组：不作超声根管清洗术;B组：采用超声根管清洗术.自酸蚀粘接剂把纤维桩粘接于桩道内,A、B组各15个试件在万能试验机上做拉伸粘接力测试.另在A、B组各选5个粘桩后的离体牙于根颈、根中及根尖分别切取厚1.5 mm的薄片.扫描电镜观察纤维桩与根管内壁粘接界面的显微结构.结果 拉伸粘接力试验结果表明：B组试件的纤维桩粘接力[（205.8±15.5）N]比A组试件[（151.1±13.5）N]高,（P＜0.05）.电镜观察发现：A组粘接剂与根管壁粘接界面的缝隙均较相应的B组的缝隙大.结论 使用超声根管清洗术能显著增强纤维桩与根管壁根颈处的粘接固位力.