[Decoronation: treatment protocol for ankylotic root resorption as a consequence of dental trauma]

Severe dental traumatic injuries, such as the complete displacement of a tooth from its socket (Avulsion) or the displacement of a tooth within its socket (Intrusive Luxation), may result in extensive injury to the root surface. As a result, the root surface injury heals without cementum and there is fusion between the alveolar bone and the exposed dentin or anorganic exposed cementum, without any attachment apparatus between them. This phenomenon is known as "dento-alveolar ankylosis" and is accompanied by ankylotic resorption of the root. In a process that results subsequent to the ankylosis, the root surface resorbs, and this is part of the remodeling of the alveolar bone (ankylotic resorption). When the traumatic injury occurs at a young age, lateral and apical growth of the alveolar bone continues without continued physiological eruption of the tooth. As a result, the position of the ankylotic tooth does not change, and with time thetooth appears infra-occluded resulting in severe esthetic and functional consequences. Extraction of the ankylotic tooth is difficult and sometimes even impossible due to the rigid fusion between the bone and the tooth. In addition, attempted extraction of the ankylotic tooth may lead to fracture of the buccal plate and resorption of the alveolar bone. Retention of the ankylotic tooth may lead to damage in bone deposition in the verticaldimension, leading to difficulties in future prosthodonticrehabilitation, research-based information has been incorporated

[Endodontal and periodontal aspects of root perforations]

The purpose of treatment of perforations is to achieve a tight and permanent seal that will prevent bacteria and their by-products in the root canal from entering into the surrounding periodontal tissues. It is important to consider the type of perforation according to the classification for selection of the proper material and technique for each case. Modern techniques for treatment of perforations by orthograde and surgical approach result in prolonged survival of the tooth.

[Endodontal and periodontal aspects of root perforations]

Root perforation is an artificial communication between the root canal system to supporting tooth tissues or to the oral cavity. The etiology of the perforation can be mechanical errors during dental procedures or pathological processes. Infection of the perforation site affects the prognosis of the treated root perforation, which is influenced by time between occurrence of the perforation and appropriate treatment, size, and location of the perforation. Careful treatment planning and operative techniques are imperative to prevent root perforations.

[Dental trauma protocol--treatment of avulsion and luxation injury]

The goal of this protocol is to provide clear instructions which simplify the process of decision making and treatment of Luxation and Avulsion. In teeth with a closed apex, one should perform root canal therapy at the second appointment in teeth with injuries of luxation and avulsion (except for injuries of subluxation and concussion). The tooth should be reimplanted at site of accident if it possible. For avulsed teeth, the preferred storage medium is milk. One should condition the roots of teeth which have been avulsed. In teeth which have not finished development, the preferred treatment is to allow the continued development of the root.

[Endodontic surgery (apicoectomy)--success rate of more than 90% using dental operating microscope and ultrasonic tips]

The main cause of root canal treatment failure is presence of bacteria in the root canal. Surgical endodontic retreatment is indicated as a valuable treatment choice for failed endodontic treatment. The aim of the article is to describe the advantages of a new technique for apicoectomy using dental operating microscope and ultrasonic tips in comparison to the traditional technique. Precise root end resection with minimal or no bevel and accurate preparation of the root end cavity to the depth of 3-4 mm allows minimal bone removal and reduces procedural accidents such as perforation of the lingual canal wall. Zink oxide eugenol based materials allow sealing of the retrograde preparation adequately to prevent bacteria and toxins to penetrate the periradicular tissues. Literature review demonstrates success rate to above 90% when employing dental operating microscope and ultrasonic tips for retrograde cavity preparation.

Comparison of procedural errors resulting during root canal preparations completed by junior dental students in patients using an '8-step method' versus 'serial step-back technique.'

AIM

To compare procedural errors occurring during preparation of root canals by junior dental students in patients using a new '8-step method' versus traditional 'serial step-back technique.

METHODOLOGY

Junior dental students treated 291 root canals of maxillary and mandibular teeth in patients. A new '8-step method' was used to prepare 149 canals, whilst the traditional 'serial step-back technique' was used for 142 root canals. Instrumentation was carried out in both techniques using standardized stainless steel K-files and coronal flaring with Gates-Glidden reamers. In the apical one-third, a filing motion was used in the traditional technique: with the '8-step method,' reaming or filing motions were used in sizes up to 25 and only reaming in sizes larger than 25. All root canals were obturated with gutta-percha points and AH26 using a lateral condensation technique. Pre- and postoperative radiographs were made of each tooth. Procedural errors were recorded and statistically analysed using a binomic test for comparison of proportion.

RESULTS

Significantly (P < (1.0001) more root canals maintained their original shape with no deviation (91%) with the'8-step method' compared to the traditional 'serial step-back technique' (61%). The procedural errors detected with the'8-step method' consisted of 10 canals with transportation (5%) and five with root perforations (2%); there were no canal obstructions. With the 'serial step-back technique: significantly (P < 0.0001) more errors occurred: 28 canals were transported (17%), 10 had root perforations (7%), and 16 canals were obstructed (6%). The differences in maintaining the original root canal shape between the two methods were significantly greater in molar versus anterior teeth.

CONCLUSIONS

The new '8-step method' resulted in fewer procedural errors than the traditional 'serial step-back technique' when junior students prepared root canals in patients.

A laboratory study of the effect of calcium hydroxide mixed with iodine or electrophoretically activated copper on bacterial viability in dentinal tubules

AIM

The aim of this laboratory study was to evaluate the ability of calcium hydroxide (CH), CH/iodine-potassium iodide (IKI) and electrophoretically activated copper to kill bacteria in dentinal tubules.

METHODOLOGY

In an in vitro model of dentinal tubule infection, 42 cylindrical root specimens, prepared from freshly extracted bovine teeth were used. After removal of the smear layer, intracanal dentinal tubules were infected with Enterococcus faecalis for 3 weeks. CH alone or preparations of CH with copper or IKI were placed in the root canal for 1 week. In specimens containing copper/CH, an electrophoretic current(5 mA/5 min) was applied using two electrodes follow-ing placement of the medicament in the canal. Powder dentine samples obtained from the canal wall using ISO sizes: 025, 027, 029, 031 and 033 burs were examined for the presence of viable bacteria by inoculating agar plates and counting colony forming units (cfu).

RESULTS

A significant difference was found between the experimental groups and the positive control group. CH and CH/IKI significantly (P < 0.001)reduced bacterial viability in dentinal tubules to a depth of 200 microm. Specimens with CH/IKI had significantly fewer viable bacteria than CH alone in tubules between the depths of 200-500 microm. Treatment with CH/copper and electrophoresis was most effective: specimens showed no viable bacteria in dentinal tubules to a depth of 500 microm from the root-canal space.

CONCLUSIONS

IKI or electrophoretically activated copper additives can significantly improve the antibacterial properties of CH in dentinal tubules.

Bacterial penetration and proliferation in root canal dentinal tubules after applying dentin adhesives in vitro

Endodontic treatment is aimed at eliminating infection and preventing bacterial regrowth in the root canal and dentinal tubules. In the present study the ability of two dentin adhesives to prevent bacterial penetration and subsequent proliferation in dentinal tubules was evaluated. Cylindrical root specimens prepared from freshly extracted bovine teeth were used in an in vitro model of dentinal tubule infection. After removal of the smear layer the intracanal dentinal tubules of the specimens were acid-etched and treated with either Gluma or EBS. Untreated specimens served as controls. Specimens were infected with Enterococcus faecalis and incubated in Brain Heart Infusion for 21 days. Powder dentin samples obtained from within the canal lumina, using ISO 025 to 033 burs, were examined for the presence of vital bacteria by inoculating on agar plates and counting colony-forming units. A significant difference was found between the experimental groups and the untreated group. After application with Gluma specimens showed the least viable bacteria in dentinal tubules. Data suggested that dentin adhesives reduced bacterial invasion into dentin and therefore have a potential role in endodontic treatment.

The unpredictability of seal after post space preparation: a fluid transport study

A root canal filling remaining after post space preparation is commonly expected to provide adequate seal. Coronal leakage of 30 endodontically treated teeth was measured before post space preparation using a fluid transport assay. In 10 of these teeth post space was prepared, using a two-step procedure, first to a remaining filling of 6 mm and then to 3 mm, with the leakage studied after each step. In 10 teeth the removal was done in one step to a remaining length of 3 mm. The other 10 teeth, with intact root canal fillings, served as controls and were tested twice for leakage. A significant difference was found between the sealing ability of intact fillings and that of partially removed ones (p < 0.05). The difference between the sealing ability of 3 and 6 mm remaining length group was not statistically significant. The lack of statistical differences between the 6 mm and 3 mm fillings was due to a great variability which existed among the 3 mm remaining fillings. These results suggest that 3 to 6 mm fillings provided a seal inferior to that of intact root canal fillings. Reduction of the fillings to 3 mm resulted in an unpredictable seal.

An evaluation of endodontically treated vertical root fractured teeth: impact of operative procedures

Vertical root fractures of endodontically treated teeth are a frustrating complication that leads to extraction. The aim of the current survey was to evaluate the role of operative procedures in the etiology of this complication. A total of 154 endodontically treated vertical root fractured teeth were cleaned and washed after extraction and maintained in individual vials. Periapical radiographs before extraction, clinical findings and previous operative procedures were recorded. A post was observed in 95 teeth (61.7%), with 66 of these ending at the coronal third of the root. Most were screw posts of the Dentatus type (n = 64) and tapered cast posts (n = 14). A full crown was observed in 118 teeth, and 65 of these (55%) were extracted between 1 to 5 yr after final restoration. In 24 crowned teeth extraction was conducted within 1 yr after restoration and in 28 teeth after >5 years. It was concluded that post placement and root canal treatment are the major etiological factors for root fractures. Because signs and symptoms can appear years after the operative procedures in the root have been completed, coronal restorations would not interfere with the correct clinical diagnosis of vertical root fractures. Frequent recalls are recommended to diagnose vertical root fractures early, especially in susceptible teeth, such as premolars and mesial roots of mandibular molars.

Effect of various mixing ratios on antibacterial properties and hardness of endodontic sealers

Most chemically cured two-component dental materials, including endodontic sealers, are marketed with mixing instructions but with no strict mixing ratios. The present study evaluated the antibacterial properties and hardness of three endodontic sealers: Roth's cement (RC), CRCS, and AH26, mixed to four controlled consistencies within the range of the manufacturer recommendations. Using Enterococcus faecalis as the test microorganism, antibacterial activity was evaluated by agar diffusion and direct contact test. Surface hardness of sealers with the same consistency was evaluated on week-old specimens by the Knoop Hardness Number tester. In the agar diffusion test, light consistency of RC showed larger zones of inhibition than heavier consistency, whereas no significant differences were found with AH26 or CRCS. In the direct contact test, RC and CRCS exhibited complete inhibition of bacterial growth at all consistencies, whereas AH26 with the heavier consistencies did not inhibit bacterial growth at 24 h samples. The hardness of AH26 and CRCS was significantly lower with lighter consistencies. It is concluded that endodontic sealers possess different antibacterial and physical properties according to their mixing consistencies.

Pattern of bone resorption in vertically fractured, endodontically treated teeth

PURPOSE

To evaluate the clinical pattern of alveolar bone resorption associated with vertically fractured, endodontically treated teeth in correlation to clinical symptoms.

MATERIAL AND METHODS

The pattern of bone resorption was evaluated in 66 maxillary premolars, 13 mandibular premolars, and 31 mesial roots of mandibular molars extracted during an 18-month period because of vertical root fractures. Type and duration of symptoms were recorded and correlated to the pattern of bone resorption.

RESULTS

A V-shaped pattern osseous defect (dehiscence) was typical (91%) to the buccal plate rather than a U-shaped shallow, rounded, slow grade resorption in the palatal or lingual plate. Fenestration of the buccal plate was observed in 10 patients (9%). A positive correlation between type of symptoms and amount of buccal bone resorption was found (P <.0001). The resorptive defect was always facing the fracture line.

CONCLUSIONS

A typical pattern of bone resorption in vertical root fracture cases as shown in this study can be helpful to the clinician in diagnosing vertical root fracture when an exploratory full flap surgical procedure is performed.

Sealing furcation perforations with silver glass ionomer cement: an in vitro evaluation

Furcation perforations sealed with silver glass ionomer cement (Chelon Silver) were evaluated in vitro compared with amalgam. Access cavities were prepared in 25 extracted human molar teeth. The coronal orifices of the root canals were sealed with amalgam and varnish. Naturally occurring coronal leakage through the intact pulp chamber floor was determined quantitatively for each tooth, using a modified fluid transport model, under pressure of 1.2 Atm. Each tooth was then disconnected from the system, perforated at the furcation, and the perforation sealed with either Chelon Silver (10 teeth) or amalgam (10 teeth); five remaining teeth served as a negative control. After incubation for 24 h at 37 degrees C in 100% humidity, teeth were reconnected to the modified fluid transport system, and coronal leakage under pressure was evaluated at 1, 2, 6, 15, and 24 h. Leakage through each tooth was compared with that of its own intact pulp chamber floor before perforation and the groups compared with each other. No significant difference was found between the mean leakage of the intact pulp chamber floors of the two groups. Chelon Silver had a significantly better sealing ability than amalgam (p < 0.01): leakage rate of 0.007 and 0.017 microliter/min, respectively. It is concluded that Chelon Silver could be an adequate sealer for furcation perforations.

Radiographic features of vertically fractured, endodontically treated maxillary premolars

OBJECTIVE

The purpose of this study was to evaluate the most frequent radiographic appearance of bony lesions associated with vertically fractured roots of endodontically treated maxillary premolars.

STUDY DESIGN

The radiographic features of 102 endodontically treated teeth and their periradicular areas (51 with and 51 without vertically fractured roots) were evaluated and compared.

RESULTS

The predominant appearance of the periradicular area in the teeth with vertically fractured roots was the "halo" lesion (57%); by contrast, in the non-vertically fractured roots group, a "periapical" radiolucent lesion was most frequently found (55%). Angular bone loss (14%) and periodontal radiolucency (14%) were also typical radiolucent lesions in the vertically fractured teeth.

CONCLUSIONS

"Halo" lesion, perilateral radiolucency, and angular resorption of the crestal bone, combined with diffuse or defined but not corticated borders, indicated a high probability of vertical root fracture in maxillary premolars.

Prevalence of vertical root fractures in extracted endodontically treated teeth

AIM

The aim of this study was to evaluate the prevalence of vertical root fractures (VRF) in extracted endodontically treated teeth and to correlate the findings to previous studies and surveys.

METHODOLOGY

Root-canal-treated teeth were referred for extraction from a public dental clinic. The endodontic therapy had been completed by a variety of dentists. Each tooth was evaluated following extraction by the oral surgeon who performed the procedure: the exact aetiology for the clinical diagnosis that led to the extraction was recorded.

RESULTS

The major reasons for extraction were restorative (43.5%) and endodontic (21.1%), followed by vertical root fractures (10.9%).

CONCLUSIONS

The relatively high prevalence of vertical root fractures in this survey compared with previous clinical and radiographic surveys was probably related to the difficulties in making a clinical diagnosis of vertical fractures before extraction.

An evaluation of endodontically treated vertically fractured teeth

For this survey, 92 vertically fractured endodontically treated teeth were evaluated clinically and radiographically before and after extraction. The maxillary second premolars (27.2%) and mesial roots of the mandibular molars (24%) were the most fractured teeth. In 67.4% of the teeth, a solitary buccal pocket was present; in 34.8%, a fistula frequently appeared closer to the gingival margin than to the apical area. A lateral radiolucency or a combination of lateral and periapical radiolucency was found in more than half of the cases. The general practitioners correctly diagnosed vertical root fracture in only one-third of the 92 fractured teeth in this survey.

Antibacterial activity of calcium hydroxide-containing endodontic sealers on Enterococcus faecalis in vitro

Antimicrobial activity of endodontic sealers is an important factor in the prognosis of root canal treatment. The aim of this study was to analyse the antimicrobial activity of calcium hydroxide-containing endodontic sealers, Sealapex (SA) and CRCS compared to a ZOE-containing sealer, Roth's cement. The sealers were mixed and placed on the side wall of microtitre plate wells. A 10 microL suspension of Enterococcus faecalis was added to the surface of the sealers 1 h, 24 h, or 7 days after mixture. Bacteria were allowed to come into contact with the sealers for 1 h at 37 degrees C. Fresh media was then added and bacterial growth was measured every 30 min for 16 h. The results showed that in 1-hour-old mixture, CRCS and Roth's cement had a significantly better antimicrobial effect than SA. In 24-hour-old mixtures, ZOE-based sealer showed a more potent antimicrobial activity than calcium hydroxide-containing sealers, whereas SA showed a significantly better antimicrobial effect in the 7-day-old mixture. The antimicrobial activity of each tested sealer changes differently with the time interval between mixing and testing, suggesting different physicochemical properties and potentially diverse clinical applications.

Effect of intended treatment on anxiety and on reaction to electric pulp stimulation in dental patients

Fear and anxiety are common emotional concomitants of acute pain that increase the perception of noxious events as painful. In the present study, 92 patients who were about to undergo various dental treatments (calculus removal, filling, root canal treatment, and extraction) were evaluated comparing the level of their dental anxiety and pain expectation from the intended treatment to their reaction to electric pulp stimulation. The data indicate that patients differ significantly in their dental anxiety levels and in their expectation to experience pain according to the following hierarchy (in descending order): extraction, root canal treatment, filling, and calculus removal. Anxiety and amount of pain expected from treatment correlated significantly with each other, but no simple correlations were found between anxiety and actual pain measures recorded after pulp stimulation.

Reliability of different electronic apex locators to detect root perforations in vitro

The aim of this study was to evaluate the accuracy of the electronic apex locator Root ZX compared to the Sono Explorer Mark II Junior and Apit III in detecting root perforations. Extracted human teeth (n = 30) were perforated artificially in the middle third of the root and embedded in a box containing alginate. Detection of all perforations were carried out with K-files attached to the apex locators tested. The teeth were radiographed after each electronic measurement. The actual location of the tip of the file in relation to the external root surface and the radiographic determination of the perforations were carried out using a stereomicroscope. The mean distance of the tip of the file from the external outline of the root surface was short for all instruments and clinically acceptable (0.06-0.25 mm). There was no clinically significant difference between the morphometric measurements and the radiographic measurements. No statistical significance was found between large perforations (0.55-0.60 mm) and small perforations (0.25-0.40 mm). Under the conditions of this study, all electronic apex locators tested were acceptable clinical tools in the detection of root perforations.

In vitro antibacterial activity of a glass ionomer endodontic sealer

The aim of this study was to evaluate the antibacterial activity of a recently introduced glass ionomer endodontic sealer, Ketac Endo (KE), compared to a commonly used ZOE-based endodontic sealer, Roth's cement (RC). With the use of E. faecalis as a test organism, the agar diffusion test (ADT) and direct contact test (DCT) were performed. For the DCT, the sealers were mixed and placed on the side wall of microtiter plate wells. A 10 microL bacterial suspension was placed on the tested material samples 20 min, 24 h, and 7 days after mixing. Bacteria were allowed to directly contact the sealers for 1 h at 37 degrees C. Fresh media was then added and bacterial growth was measured every 30 min over 15 h. The results showed that in the ADT, freshly mixed KE exhibited a twofold greater inhibition zone than RC (p < 0.05); in the DCT, freshly mixed KE and RC completely inhibited bacterial growth. The 24-h and 7-day samples of KE showed no antibacterial activity, whereas RC continued to exhibit a strong effect with similar samples. It has been concluded that KE possesses a short-acting very potent and diffusable antibacterial activity, whereas RC extends its effect over 7 days after setting.

Root perforations: classification and treatment choices based on prognostic factors

Root perforations are common complications of endodontic treatment or post preparation and often lead to tooth extraction. Successful treatment depends mainly on immediate sealing of the perforation and prevention of infection. Several factors affect the achievement of these goals, most important of which are: time of occurrence, size, and location of the perforation. A classification of root perforations, based on the above factors, is presented to assist the clinician in the choice of the treatment protocol which will give the best possible results when a perforation is diagnosed.

Determination of location of root perforations by electronic apex locators

OBJECTIVES

This study was conducted to evaluate the accuracy of two electronic apex locators, the Sono Explorer Mark 2 Junior (Hakusui, Osaka, Japan) and Apit 2 (Osada, Tokyo, Japan) in detecting root perforations. The adequacy of radiographs for identifying root perforations was also assessed.

STUDY DESIGN

Thirty-two extracted human teeth were perforated in the middle third of the root and embedded in alginate. Determination of all perforations were carried out with K-files no. 25 attached to the apex locators tested. Two radiographs were taken at two angulations after each electronic measurement. The actual location of the file tip in relation to the perforation was determined with a stereomicroscope. A total of 512 radiographs were evaluated to attempt to identify root perforations.

RESULTS

The mean distance of the file tip from the external outline of the root surface was short for both instruments. A statistical difference (p < 0.05) was found between the two apex locators in dry canals or if saline solution was present. There was no significant difference between the two instruments in the presence of sodium hypochlorite. Evaluators radiographically identified 45% of the root perforations when located in buccal-lingual directions.

CONCLUSION

Under the in vitro conditions of this study, both devices determined the location of the perforations in an acceptable clinical range short of the root surface. Radiographs were found to be less reliable in identification of perforation locations.

Assessment of antibacterial activity of endodontic sealers by a direct contact test

It is recognized that endodontic success depends on bacterial elimination from the root and root canal system. Antibacterial activity of endodontic sealers can improve the success rate of endodontic treatment, provided the physical properties are not compromised. The aim of this study was to evaluate the antimicrobial properties of two endodontic sealers (AH26 and Endoflas) using a direct contact test (DCT) which was designed for this purpose. The DCT is based on measuring the effect of close contact between test bacteria and the tested material on the kinetics of bacterial outgrowth using a temperature controlled microplate spectrophotometer (THERMOmax). For comparison, the agar diffusion test (ADT) was performed for both materials. The results of the DCT showed that Endoflas was a significantly more potent bacterial growth inhibitor than AH26, whereas when assessed with the ADT, AH26 was capable of producing a larger inhibition zone than Endoflas. The DCT, by being quantitative and virtually independent of solubility and diffusion, was found more suitable to assay solid surfaces. The results demonstrated the added value of DCT in the study of the antimicrobial properties of endodontic sealers.

Intracanal pH changes of calcium hydroxide pastes exposed to carbon dioxide in vitro

It has been suggested that the main benefit of using calcium hydroxide as an intracanal medicament lies in its bactericidal effect, provided that the pH of the paste is above 12.5. The purpose of this study was to measure changes in the pH of several calcium hydroxide pastes sealed in root canals for 30 days. Sixty-two extracted, single-rooted human teeth were endodontically prepared using K-files up to size 60. The teeth were separated at random into six equal groups to be filled with either Calxyl, Hydrocalcium, or a paste made by mixing calcium hydroxide powder with either distilled water, camphorated p-monochlorophenol, local anesthetic solution, or Solvidont. Cavidentin was used to seal the coronal orifice of the teeth that were placed individually in vials containing 10 mL distilled water. Five vials of each group were exposed to air at room temperature, whereas the other five vials were exposed to carbon dioxide in a closed container. The pH of the paste in the root canal was measured after 30 days. There was no significant (p > 0.01) change in the pH (mean 13.11) of the pastes placed in teeth before and after exposure to air, whereas the pH of the pastes in teeth exposed to carbon dioxide was significantly (p < 0.01) reduced (mean 12.54). There was no significant difference in pH between the six preparations. After 30 days of exposure to carbon dioxide, they still maintained a purportedly bactericidal pH within the root canal.

Tubular permeability to calcium hydroxide and to bleaching agents

Recent reports of clinical cases suggest that cervical root resorption may follow bleaching of endodontically treated teeth. Inflammatory root resorption may be arrested by placement of calcium hydroxide into the root canal. The dentinal tubules are assumed to be a possible route of action for both agents. pH Values of the medium surrounding the tooth after placement of bleaching agents and calcium hydroxide within the root canals were determined in this study. Thirty extracted single-rooted human teeth were divided into three equal groups. The pulp cavity of the experimental teeth was filled with either bleaching agents or calcium hydroxide. In the control group it was left empty. Dipping in paraffin sealed the access cavity and the apical foramina and isolated the teeth except at the cervical root surface. The teeth were placed in vials containing distilled water and the pH of the medium was measured after 1 h, 3 days, and 7 days following renewal of the medium. The level of the pH in the first group increased, indicating that the bleaching agents leaked from the root canal to the medium surrounding the teeth. The pH in other two groups did not change noticeably. The results suggest that bleaching agents may leak from the root canal toward the periodontal tissues but calcium hydroxide does not alkalinize the medium surrounding the teeth. Leakage of the bleaching agents through dentin may, therefore, be considered as a possible etiological factor that initiates an inflammatory process around the teeth that may be followed by cervical root resorption.

Reflectance spectra of composite resins on liners

The reflectance spectra of two types of composite resins were determined on various backgrounds. It was found that the shade differences caused by different "whitish" liners were perceptible only for thin resin specimens and were smaller than those caused by varying the resin type and thickness. Employing a light brown liner gave rise to a difference in shade which was also perceptible on resin specimens of 2.5 mm thickness. Shade differences due to varying the thickness of the specimens were more pronounced on white than on black backgrounds. The clinical significance and the qualitative physical interpretation of the results were discussed.