Pulpal and periodontal effects of electrosurgery involving cervical metallic restorations.

The pulpal and periodontal effects of electrosurgery involving teeth restored with Class V cervical amalgams and nonrestored teeth were evaluated in three cynomolgus monkeys. Electrosurgical current was delivered for 1 second with a fully rectified unit at an output intensity consistent with normal clinical usage. Experimental conditions included electrosurgery involving restored teeth, electrosurgery involving unrestored enamel, restored teeth not subjected to electrosurgery, and teeth which were neither restored nor subjected to electrosurgery. No pulpal or periodontal tissue changes were observed in the latter three groups of teeth. Electrosurgery involving cervical restorations consistently resulted in coagulation necrosis of the pulp and extensive resorption of cementum, dentin, and interradicular bone in the furcation area of multirooted teeth. The results suggest that inadvertent contact with cervical restorations during electrosurgical procedures may endanger both the pulp and the periodontal attachment apparatus.     

Effect of restorations on pulpal blood flow in molars measured by laser Doppler flowmetry

Aim  To: (i) compare laser Doppler pulpal blood flow (PBF) signals from restored and unrestored first molar teeth, (ii) investigate PBF in teeth with large and small restorations, and (iii) to relate PBF to pulp chamber dimensions on radiographs.
Methodology  Bitewing radiographs of young adults with restored first molars were obtained and pulp chamber dimensions measured. Subjects were divided into 2 groups: group A with a restored tooth and an unrestored contralateral (43 subjects) and group B, those with a molar with a small (usually occlusal) restoration whilst the contralateral tooth had an extensive occlusal restoration (or restorations) or restored proximal surface(s) and/or cuspal overlay (31 subjects). The 148 teeth responded to electric pulp testing, and their PBF was recorded using a laser Doppler flowmeter. Data were analysed using Student's t -test.
Results  In group A the PBF in the restored teeth was significantly lower than in unrestored contralaterals ( P  =   0.028) and the total pulp chamber area and that in the clinical crown were smaller ( P  =   0.039 and 0.021 respectively). The group B molars with large restorations had significantly lower PBF than contralaterals with small restorations ( P  =   0.001), and their total pulp chamber area and pulp chamber width at cervix were reduced significantly ( P  =   0.003 and 0.032 respectively).
Conclusions  In molars the size of the pulp chamber was influenced by the presence of restorations and the PBF was reduced when restorations were present. Size and extent of restorations had a significant effect on PBF.     

The role of cavity preparation and conditioning in the leakage of restorations

PURPOSE: Restoration microleakage is thought to be determined by the method and location of cavity preparation, enamel etching, and dentin conditioning, as well as the restorative material. This study compared the microleakage of composite restorations placed in preparations cut with carbide and diamond burs and those treated with different bonding/conditioning agents. MATERIALS AND METHODS: Class V preparations (3 x 2 x 2 mm) were cut wholly in enamel or in enamel and cementum in 100 human premolars. Twenty teeth were prepared with carbide burs and the preparations etched and conditioned with Prime&Bond NT but not restored. A second set of 20 teeth had enamel-only preparations cut with carbides (n = 10) or diamonds (n = 10), and the preparations etched, conditioned (Prime&Bond NT) and restored with Prisma TPH. The other 60 teeth were divided into 3 groups of 20 teeth each with enamel-only (n = 10) or enamel/cementum preparations (n = 10). The 3 groups of teeth were conditioned with Optibond Solo, Clearfil SE Bond or Prompt-L-Pop prior to restoration with Prisma TPH. Two mm of root was resected from all teeth, pulpal tissue removed, and insulated copper wires inserted via the root canals to contact with the pulp chamber roof before the tooth-wire interfaces and root surfaces were sealed. The teeth were immersed in 0.9% NaCl and leakage assessed over 30 d by iR drop across a resistor in series with a DC source and stainless-steel counter electrode. RESULTS: Differences (p < 0.05) in leakage were found for enamel preparations cut with carbides and diamonds, and the relationship of leakage vs time was linear. Enamel/cementum preparations showed greater leakage, and the relationship of leakage vs time was sigmoidal. Conditioned-only preparations showed the same leakage as those conditioned and restored, while preparation leakage varied with the conditioning agent. CONCLUSION: Cavity preparation location, method of cutting, and the conditioning agent markedly affect leakage behavior.     

Immediate and delayed direct pulp capping with the use of a new visible light-cured calcium hydroxide preparation

The pulpal response to mechanical exposure and capping either immediately or after 24 hours was investigated in 64 teeth of four cynomolgus monkeys with the use of Dycal, VLC Dycal, or Prisma-Bond. All overlying amalgam restorations were surface-sealed with zinc oxide-eugenol cement. After 2 months the teeth were removed and prepared for histologic examination; dentine bridges were present in almost all teeth filled with Dycal or VLC Dycal, and pulpal inflammation was observed in only one tooth that showed evidence of infection. Dentine bridges were usually incomplete when Prisma-Bond was used, although pulpal inflammation was only observed in 2 of 22 teeth. The success rate of pulp capping delayed for 24 hours was as high as that for immediate capping.     

Laser light passage through restored and carious posterior teeth

Laser Doppler flowmetry (LDF) has been used to investigate pulpal blood flow as a means of pulp vitality testing. Transmission of laser light from the tooth surface to the pulp space may be influenced by caries and restorations. One hundred and twenty‐two first and second molars that had caries into dentine, restorations or significant loss of coronal tissue were sectioned in half axio‐bucco‐lingually. The two sections were illuminated with a laser from their buccal and lingual aspects 2 mm coronal to the amelocemental junction. Light reaching the pulp space was recorded. Buccal and lingual illumination sites were equally effective for 67 teeth (55%). Buccal sites alone were effective for 35 teeth (29%), despite over one‐third of these surfaces being restored or featuring enamel or dentine caries. A lingual position alone was effective for 20 teeth (16%). Caries affected light transmission, but for over half the teeth, the pulp could be illuminated from all four probe positions. No effect was found when the influence of mesial and distal restorations on transmission into the corresponding tooth section was examined. The pulp spaces of most (84%) restored, and carious posterior teeth could be illuminated by laser light from their buccal aspect and these teeth could potentially be vitality tested using LDF.     

Histological evaluation of electrosurgery and formocresol pulpotomy techniques in primary teeth in dogs.

The purpose of this study was to compare pulpal and periapical tissue reactions to electrosurgery versus formocresol pulpotomy techniques in the primary teeth of dogs. The study was conducted on 33 primary teeth of three mongrel dogs between the ages of one to three months. Each dog had three teeth treated by Formocresol Pulpotomy with Mechanical Coronal Pulp Removal (FC), three teeth treated by Electrosurgery Pulpotomy with Mechanical Coronal Pulp Removal (ES/MCPR), three teeth treated by Electrosurgery Pulpotomy with Electrosurgical Coronal Pulp Removal (ES/ECPR), and two teeth serving as untreated Controls. Dogs one, two and three were sacrificed performing the pulpotomies at two, four and six weeks, respectively. The pulp, periapical tissue and after surrounding bone were submitted to histological examination and the histological reaction was recorded. The results were fourteen out of 18 unfavorable and zero out of three favorable histological reactions occurred in the FC treated teeth. Six out of 18 unfavorable and one out of three favorable histological reactions occurred in the ES/MCPR treated teeth. Nine out of 18 unfavorable and two out of three favorable histological reactions occurred in the ES/ECPR treated teeth. One out of 18 unfavorable and zero out of three favorable histological reactions occurred in the untreated Control teeth. The conclusion of this study is that of the three experimental groups, the teeth treated by Electrosurgery Pulpotomy with either Mechanical or Electrosurgical Coronal Pulp Removal exhibited less histopathological reaction than the teeth treated by Formocresol Pulpotomy.     

Fracture resistance of teeth restored with Class II composite restorations

Teeth with large mesio-occlusal-distal cavity preparations fracture more easily than intact teeth. An intracoronal restoration capable of increasing tooth fracture resistance is desired. This in vitro study compared the fracture resistance of maxillary premolars restored with enamel bonding and dentin bonding. The effects of the type of curing system (chemical or photochemical) and marginal preparation (beveled or not) were also evaluated. Premolars restored with large MOD composite resin restorations were approximately twice as strong as the unrestored prepared tooth. However, all restored teeth were no more than half as strong as the intact tooth. Dentin bonded restorations were not significantly stronger than enamel bonded restorations.     

Marginal leakage of class II glass ionomer-composite resin restorations: an in vitro study.

This in vitro study assessed the sealing properties of two metal-reinforced glass ionomer cements, used as "extended bases" in glass ionomer-composite resin restorations. Two class II cavities were prepared in the proximal surfaces of 30 molars. The gingival margin of one was prepared in enamel and the other in cementum/dentin. Fifteen teeth (30 cavities) were restored with Ketac Silver material used as an extended base (group A). In the remaining 15 teeth (30 cavities), the extended base was in Miracle Mix material (group B). All occlusal surfaces were restored with Estilux Posterior Material. The restored teeth were thermocycled, immersed in fuchsin, washed in water, embedded, sectioned, and examined under a dissecting microscope. All restorations with margins in cementum/dentin of group A (Ketac Silver) leaked. No microleakage occurred in 12 of the 30 restorations with margins in cementum/dentin of group B (Miracle Mix). In addition, severe microleakage was present in 24 teeth of group A, as opposed to three in group B. It was concluded that the sealing properties of Miracle Mix material are superior to those of Ketac Silver material, in vitro.     

Microleakage and cusp fracture resistance of heat-treated composite resin inlays

The purpose of this study was to examine the microleakage and cusp fracture resistance of heat-treated composite resin inlays. One hundred and twenty extracted human bicuspid teeth were prepared with MOD Class II preparations and divided into 12 experimental groups. Ten extracted human teeth were kept sound as positive controls and 10 of the prepared teeth were left unrestored as negative controls for the cusp fracture resistance experiment. The remaining prepared teeth were grouped and restored with the following restorations: bulk or incremental placement, light-cured inlays, heat-treated inlays "cemented" with enamel bonding agent, enamel bonding agent/glass ionomer "sandwich", or a dentinal bonding agent. Heat-treated inlays showed significantly (P less than 0.05) less microleakage than all other groups. The cusp fracture resistance of the heat-treated inlays was in the same magnitude as that of the traditionally placed composite resin restoration. All restorations were significantly (P less than 0.05) lower in cusp fracture resistance than sound non-carious teeth.     

Effect of a copal varnish, ZOE or glass ionomer cement bases on microleakage of amalgam restorations

The purpose of this study was to evaluate the sealing ability of four cavity preparation treatment modalities under amalgam restorations. Class V cavity preparations were placed in 20 extracted teeth and randomly divided into four groups of five teeth each (10 restorations for each group): 1) no liner; 2) two applications of Copalite; 3) a base of IRM; and 4) a base of Chelon-Silver. After assigned cavity preparation treatment was accomplished, the teeth were restored with amalgam. The restored teeth were subjected to thermocycling and subsequently stained with basic fuchsin. The teeth were longitudinally sectioned and dye penetration recorded. Amalgam restorations with a Copalite or Chelon-Silver base exhibited significantly less microleakage than those amalgam restorations with an IRM base or no cavity preparation treatment. With the Copalite varnish, microleakage extended beyond the axial wall (toward the pulp chamber through the dentinal tubules) while with the Chelon-Silver base, microleakage was limited to the restoration-tooth interface.     

The effects on pulp tissue of microleakage in resin composite restorations

The purpose of this study was to evaluate histopathologically the effect on pulp tissue of microleakage in resin composite restorations. Seventy-two class V cavities were prepared on buccal surfaces of monkeys and divided into 3 groups, F, O, and S. Every cavity was etched with 37% phosphoric acid. In group F cavities, each cavity was restored with photo-curable composite without any dentin adhesives. In group O, the cavities were left unfilled. In group S, each cavity was treated with a dentin adhesive system and restored with a restorative composite. After 3, 30, or 90 days, animals were sacrificed and the subjected teeth were immediately removed, then fixed and decalcified. Following sectioning and staining with hematoxylin and eosin or Taylor's modified bacteria staining, each sample was examined with a light microscope. In most teeth with group S cavities, bacterial invasion was not found indicating excellent marginal sealing. The pulpal reaction was much less than that in other groups. In group F as well as in group O, bacteria were frequently observed in the cavity; however, bacteria penetrated into dentinal tubules more in group F than in group O at 30 and 90 days. A correlation between the presence of bacteria and pulpal inflammation was strongly indicated. It was suggested that a leaky restoration was more harmful to the pulp than an open prepared cavity without restoration.     

Human caries vulnerability: Is this affected by restorations or cavities at adjacent surfaces?

Silicate restorations contain fluoride. A sound enamel surface on one tooth, adjacent to a silicate restoration on another, might be expected, therefore, to receive some measure of protection from attacks of caries. We test this “protection hypothesis”. An unrestored cavity forms a zone of stagnation. Hence, an initially sound enamel surface on one tooth, adjacent to an unrestored cavity on another, should be rendered especially vulnerable to caries attack. This “stagnation hypothesis” is also tested. The relative frequencies of sound, decayed and filled sites are determined, by age, at adjacent mesial and distal surfaces on maxillary incisor teeth. In addition, the relative frequency with which a sound surface faces: (a) an adjacent restored site, (b) an adjacent unrestored site, is also determined in relation to age. Data from the North East of England and from Gloucestershire are analysed separately. They fail to verify the predictions of both “protection” and “stagnation” hypotheses. The implications of the findings to the aetiology and pathogenesis of dental caries are discussed.     

Reprint of: Relationship Between Surface and Inflammatory Resorption and Changes in the Pulp After Replantation of Permanent Incisors in Monkeys

The etiology of surface and inflammatory root resorption after the replantation of incisors was examined in green vervet monkeys. The teeth were examined histologically and histobacteriologically for pulpal healing and root resorption 2 and 8 weeks after replantation. In contrast to surface resorption, inflammatory resorption was related to infected necrotic tissue or an infected leukocyte zone in the root canal. The following theory for surface and inflammatory resorption is presented. Damaged periodontal ligament areas and damaged parts of the root surface are attacked by a resorption process whereby resorption of cementum and dentin may occur. Inflammatory resorption or surface resorption will then occur depending on the pulpal status and the depth of the resorption cavity. If the resorption cavity penetrates the intermediate layer of cementum and contacts dentinal tubules that are in communication with infected necrotic pulp tissue or an infected leukocyte zone, then inflammatory resorption will take place as a result of the diffusion of toxic elements from the pulp canal to the resorption cavity. However, if the resorption cavity is shallow and does not penetrate the intermediate layer of cementum, a tooth that displays similar pulpal changes will elicit only surface resorption because the intermediate layer of cementum will tend to arrest the diffusion of toxic elements. Finally, if the pulp contains vital, inflamed, or noninflamed tissue or if root canal treatment has been performed, surface resorption will occur regardless of the depth of the cavity.     

Pulpal response to a new visible light-cured composite restorative material: Fotofil.

A new visible light-cured composite resin, Fotofil, has been developed for the esthetic restoration of anterior teeth. The pulpal responses elicited by this material in unlined cavities and cavities lined with Dycal were compared with those elicited by a negative control consisting of modified zinc oxide-eugenol cement Notebec and a silicate cement Syntrex. The pulpal responses were evaluated in the permanent maxillary and mandibular incisors in vervet monkeys using labial Claterial in each monkey. Groups of 10 monkeys were killed at intervals of 2 days, and 2 and 8 weeks after restoration of the teeth. The most severe pulpal responses were elicited by the unlined Fotofil and Syntrex restorations at all three time intervals. The Dycal lined Fotofil restorations elicited a milder pulp response than the Nobetec at 2 days and 2 weeks. No pulpal response was elicited by the latter two materials at 8 weeks. These results clearly showed that Fotofil and Syntrex are irritant to the dental pulp up to 8 weeks. The placement of a Dycal liner beneath Fotofil restorations reduced the pulpal irritation elicited by this material to levels which were lower than those elicited by the Nobetec control at 2 days and 2 weeks.     

Penetration of the pulp chamber by bleaching agents in teeth restored with various restorative materials

It is thought that externally applied bleaching agents may penetrate into the pulp chamber. This study was conducted to evaluate the diffusion of peroxide bleaching agents into the pulp chamber of teeth restored with various restorative materials. Sixty-five human extracted anterior maxillary teeth were separated into the 13 groups containing 5 teeth. Five teeth (control group) were not subjected to any cavity preparation and restoration. Standardized class V cavities were prepared in the other 60 teeth and restored using composite resin (Charisma), polyacid modified composite resin (Dyract), or resin-modified glass ionomer cement (Vitremer). All teeth were sectioned 3 mm apical to the cementoenamel junction to remove the intracoronal pulp tissue, and the pulp chamber was filled with acetate buffer to absorb and stabilize any peroxide that might penetrate. Vestibular crown surfaces of teeth in the experimental groups were subjected to four different bleaching agents for 30 min at 37 degrees C, whereas the teeth in the control groups were exposed only to distilled water. Then the acetate buffer solution in the pulp chamber of each tooth was removed, and the pulp chamber of each tooth was rinsed with 100 ml of distilled water twice. Leukocrystal violet and enzyme horseradish peroxidase were added to the mixture of the acetate buffer and rinse water. The optical density of the resulting blue solution was determined spectrophotometrically and converted into microgram equivalents of hydrogen peroxide. Higher hydrogen peroxide concentrations resulted in a higher pulpal peroxide penetration. The highest pulpal peroxide penetration was found in resin-modified glass ionomer cement groups, whereas composite resin groups showed the lowest pulpal peroxide penetration.     

Traumatic crown fractures in permanent incisors with immature roots: a follow-up study

Abstract – A follow-up study of crown fractured permanent incisors with incomplete root formation was carried out in a group of patients, aged 6–12 years, over a 5-year-period in the Dental Clinic of the University of Verona, Italy. The number of injured patients was 55, representing 84 injured incisors. All patients were followed clinically and radiographically using a standardized follow-up protocol. The most common type of trauma was fracture of enamel and dentine without pulpal exposure (80%) and the most common type of treatment was restoration with the acid-etch composite resin technique (46%). Bonding of the crown fragment was performed in 10 instances (12%). At the 5-year-control all teeth with fracture of the enamel had no pulp complications. Four of 67 teeth (6%) with fracture of the enamel and dentine without pulpal involvement showed pulp necrosis and 1 tooth showed pulp obliteration (1.5%). Eight of 14 teeth (57%) with fractures of the enamel and dentine with pulp involvement showed pulp necrosis. Aesthetically 36 of the restored teeth were deemed satisfactory (43%). In 9 teeth the bonded fragment had to be rebonded. 14 teeth were considered unsatisfactorily restored due to wear of the composite (17%). 34 restored teeth had to be retreated because of a new trauma (40%). In one tooth a previous bonded fragment had to be rebonded. These results confirmed that crown fractures without pulp involvement in permanent incisors with incomplete root formation have a low percentage of pulp complications, while 60% of the teeth with crown fractures with pulp involvement had pulp complications.     

基于MICRO-CT的乳前牙三维模型重建

目的：利用Micro-CT对离体乳切牙和乳尖牙进行扫描和三维重建。方法：运用Micro-CT对标本牙进行扫描,结合Amira软件进行三维重建,获得标本牙不同结构的牙齿三维模型和数字图像。结果：用此方法成功构建出标本乳切牙和乳尖牙的三维模型,清晰展示出标本牙不同结构在整体中的位置、层次和形态特点,摸索出一套对乳牙行之有效、快捷、准确的建模方法。结论：对乳牙多个牙位尤其是乳前牙的三维模型开展研究,填补了乳牙内部解剖资料稀缺的空白,为临床治疗提供了参考。     

Human pulpal response to composite resin restorations

Abstract Composite resin restorations were placed in experimentally prepared cavities in human teeth. Various antibacterial regimens were used and the pulpal responses were studied and correlated with presence of bacteria on the cavity walls. Presence of bacteria seemed to be an important, but not the only reason for harmful pulpal responses. Good pulp protection was obtained by using a calcium hydroxide-containing base material after acid etching of cavities was carried out. The present results were compared with those from an identical study in monkeys, and good correlation was found.     

An in vitro comparison of marginal microleakage of alternative restorative treatment and conventional glass ionomer restorations in extracted permanent molars

PURPOSE: The objective of this study was to compare the marginal leakage of cervical restorations made using alternative restorative treatment (ART) and conventional glass ionomer restorations. METHODS: Sixteen permanent maxillary and mandibular first and second molars extracted for periodontal reasons with Class V carious dentin on the buccal surfaces were prepared using ART while a second set of 29 noncarious molars had Class V preparations made with a high-speed handpiece. The occlusal margin was located in the enamel, and the gingival margin was located in the dentin/cementum. All teeth were restored with glass ionomer cement (GIC). The teeth were thermally stressed for 300 cycles and stained with methylene blue. Samples were sectioned and evaluated for microleakage. RESULTS: One-way analysis of variance on ranks revealed no significant difference in leakage at both the dentin and enamel margins between the conventional and ART groups. The microleakage at the dentin margin, however, was significantly greater (P < .001) than at the enamel margins in the conventional group. CONCLUSION: Alternative restorative treatment with GIC provides enamel and dentin margins that show comparable marginal leakage to conventionally restored permanent teeth. For the conventional restorations, leakage at the dentin margins occurs to a significantly higher extent than at the enamel margins.     

Enamel matrix, cementum development and regeneration

Abstract Studies during the last 20 years have indicated that enamel-related proteins are involved in the formation of cementum. In the present article, this relation is further explored. Attention is called to the fact that coronal a cellular extrinsic fiber cementum is formed on the enamel surface in a number of species. The composition of the enamel matrix proteins and the expression of these proteins during root formation are briefly reviewed. The dominating constituent of the enamel matrix, amelogenin, is shown by means of immunohistochemistry to be expressed in human teeth during root formation. Amelogenin was also found to be present in Tomes' granular layer of human teeth. When mesenchymal cells of the dental follicle were exposed to the enamel matrix a non-cellular hard tissue matrix was formed at the enamel surface. Application of porcine enamel matrix in experimental cavities in the roots of incisors of monkeys induced formation of a cellular cementum that was well attached to the dentin. In control cavities without enamel matrix, a cellular, poorly attached hard tissue was formed. The present studies provide additional support to the idea that enamel matrix proteins are involved in the formation of a cellular cementum and also that they have the potential to induce regeneration of the same type of cementum.