Annual review of selected dental literature: report of the committee on scientific investigation of the American Academy of Restorative Dentistry.
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Dental Caries↗
Biomedical subjects
J B Summitt
Publications and source records attributed to J B Summitt.
The performance of bonded vs. pin-retained complex amalgam restorations: a five-year clinical evaluation.
BACKGROUND: The authors compared the clinical performance of complex amalgam restorations, replacing at least one cusp--retained either mechanically with self-threading pins or bonded--with a filled, 4-methacryloxyethyl trimellitate anhydride, or 4-META-based resin designed for amalgam bonding. METHODS: The authors placed 60 amalgam restorations (28 pin-retained and 32 bonded), each restoration replacing at least one cusp. They used self-threading stainless steel pins in the pin-retained group and a filled, 4-META-based bonding resin in the bonded group. For both groups, the authors left in place any retention form remaining after removal of an old restoration but did not enhance it. RESULTS: At four years, six restorations had failed. At five years, of the 40 restorations available for evaluation, three had failed, for a total of nine failed restorations; seven of those were pin-retained and two were bonded. Using the Fisher exact test to compare the groups at five years, the authors found no significant difference in failure rate, marginal adaptation, marginal discoloration, secondary caries, tooth sensitivity or tooth vitality. CONCLUSIONS: At five years, there was no difference in the performance of pin-retained amalgam restorations and bonded amalgam restorations. This study will be continued for at least a sixth year. CLINICAL IMPLICATIONS: Bonding with a filled, 4-META-based bonding resin appears to be a satisfactory method of retaining large amalgam restorations replacing cusps.
Acrylic Resins↗
Support of undermined occlusal enamel provided by restorative materials.
OBJECTIVE: The purpose of this study was to test the support of occlusal enamel by amalgam (Dispersalloy), bonded amalgam (AmalgamBond Plus adhesive system with high-performance additive powder and Dispersalloy amalgam), and a bonded resin composite (Scotchbond Multi-Purpose adhesive system and Z100 resin composite). METHOD AND MATERIALS: For each material, 16 human molars were prepared. The lingual cusps were removed, and the dentin supporting the facial cusps was cut away, leaving a shell of enamel. Each group of prepared teeth was restored using the materials according to manufacturers' instructions. All specimens were thermocycled (1,500 cycles, 6 degrees C to 60 degrees C, dwell time 30 seconds), then mounted vertically in cast stone. A separating disk, mounted horizontally, was used to create a flat horizontal surface approximately 1.5 mm wide at the tips of both remaining enamel cusps of each specimen. Specimens were loaded evenly across the cusp tips at a crosshead speed of 10 mm/min until the fracture occurred. RESULTS: Data were analyzed using analysis of variance and Tukey A post hoc analysis. No significant difference was detected among amalgam, bonded amalgam, and bonded resin composite in their ability to support occlusal enamel. Support provided for occlusal enamel by the materials, whether bonded or not, was intermediate between no support and that provided by dentin. CONCLUSION: Without further development of materials technology and evidence of efficacy, restorative materials should not be relied upon to support undermined occlusal enamel.
Analysis of Variance↗
The evaluation of subatmospheric pressure and hyperbaric oxygen in ischemic full-thickness wound healing.
We evaluated the efficacy of subatmospheric pressure and hyperbaric oxygen (HBO) as adjuncts in the treatment of hypoxic full-thickness wounds in a rabbit model. We hypothesized that subatmospheric pressure and HBO independently are effective in improving wound healing in the ischemic wound model and that when they are used in combination there is an increased positive effect on wound healing. Using a standard ischemic wound model four full-thickness wounds were created on each ear of 41 male New Zealand white rabbits (N = 82 ears). On each rabbit one ear was dressed with the vacuum-assisted closure (VAC) device and connected to suction; the other was dressed identically without the suction and suction tubing. Twenty rabbits were treated with HBO daily for 10 days at 2.0 atmospheres absolute for 90 minutes plus descent and ascent times. Necropsy on all rabbits was performed on postoperative day 10. Four ischemic wound treatment groups were evaluated: Group 1 (N = 21) VAC dressing alone; Group 2 (N = 20) VAC dressing plus HBO; Group 3 (N = 21) VAC dressing to suction alone; and Group 4 (N = 20) VAC dressing to suction and HBO. Using light microscopy a veterinary pathologist blinded to treatment groups quantified peak granulation tissue, granulation tissue gap, and epithelialization tissue gap. Data were analyzed by analysis of variance with significance indicated by P < 0.05. Statistical significance was found in a comparison of VAC dressing to suction and VAC dressing alone for peak granulation tissue and granulation tissue gap both with and without use of HBO. VAC device use appears to increase the rate of healing in a rabbit ischemic wound model. HBO therapy did not significantly affect the rate of healing in this model.
Analysis of Variance↗
Direct-placement gallium restorative alloy: a 3-year clinical evaluation.
OBJECTIVE: A pilot clinical study on a direct-placement gallium restorative alloy was initiated with nine patients who signed a consent form. METHOD AND MATERIALS: Thirty Class I restorations were placed and assessed over a 3-year period. The cavity preparations and surface of the restorations were sealed to prevent oral fluids from contacting the gallium alloy during placement and early setting of the gallium restorative material. RESULTS: The initial 18-month clinical results were encouraging. But at 21 months, one tooth had fractured, and within another year two molars were diagnosed with cracked-tooth syndrome (incomplete tooth fracture). These three fractured teeth were restored with amalgam and are symptomless at this time. There was little fracture at the margins of the gallium restorative, but tarnish and a rough surface were noted on many of the gallium restorations. The direct-placement gallium restorative alloys must be further assessed in the laboratory to correct dimensional instability. CONCLUSION: Results suggested that Galloy, used with either of two sealing resins, is not a suitable restorative material.
Dental Alloys↗
Air abrasion: an old technology reborn.
Recently, air abrasion has experienced a rebirth in restorative dentistry. Originally developed in the late 1940s, the principle of air abrasion is the imparting of kinetic energy to tiny aluminum oxide particles that are projected by a stream of compressed air or gas and expelled from a small nozzle. The force generated by the relatively hard particles striking a relatively hard surface is sufficient to cut into that surface. In the last decade, more than a dozen models of air abrasion units have been introduced into the marketplace and more are on the way. Manufacturers have developed air abrasion instruments that offer a broad range of features, from small table-top units to self-contained systems with compressors, vacuums, and curing lights. The costs range dramatically--from $1,000 to $20,000 or more--depending on the complexity of the features and attachments. Manufacturers make a variety of claims to support the value of this technology to the practicing dentist. A term often used to describe one of the benefits of air abrasion is microdentistry. The claim is that smaller, less invasive tooth preparations may be accomplished using air abrasion than with a traditional bur and air turbine. This may be true in some instances, but it would certainly depend on the operator's experience and ability to visually discern fine detail. Other claims about air abrasion are that it can be used to cut into tooth structure without local anesthesia and that it should be used on all stained grooves or fissures to determine if incipient carious lesions are present. Despite the limited number of clinical studies, the popularity of air abrasion continues to grow. To gain additional insight about these claims and to see what might be on the horizon for this technology, I spoke with three highly respected educators who are recognized for their expertise in air abrasion. What they said should give the reader a better understanding of how air abrasion might augment restorative dentistry procedures and techniques.
Air Abrasion, Dental↗
The survival of amalgam restorations.
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Dental Amalgam↗
Amalgam at the new millennium.
Dental amalgam has served as an excellent and versatile restorative material for many years, despite periods of controversy. The authors review its history, summarize the evidence in regard to its performance and offer predictions for the future of this material. For the present, amalgam should remain the material of choice for economical direct restoration of posterior teeth. When esthetic concerns are paramount, tooth-colored materials, placed meticulously, can provide an acceptable alternative.
Biocompatible Materials↗
Extension for prevention: is it relevant today?
Extension for prevention has been an integral part of dentistry for over 100 years. Because this concept advocated the removal of sound tooth structure, it was not totally accepted at the turn of the century. The advent of the gold casting catapulted extension for prevention into general acceptance. In 1883, Webb presented a concept of "prevention of extension of decay". This concept advocated a proximal cavity preparation extending toward the buccal and lingual aspects of the tooth so that contact with adjacent teeth would not be at the margins. The separation of the margins, along with proper restoration contours, was thought to promote natural cleansing of the embrasures with saliva and fluids in the diet. GV Black's 1891 idea of "extension for prevention" was to provide extension of the preparation to the facial and lingual line angles in order to bring about "self-cleansing" margins via food excursion. Black's concept also included extending preparations through fissures to allow cavosurface margins to be on non-fissured enamel. Black integrated the extension of the proximal margins with his concept of an occlusal isthmus for a Class II amalgam preparation one-third the faciolingual width of the occlusal surface. Challenges to this concept of extension for prevention were immediate; and, by the 1950's, narrower, more conservative preparations were seen by a few as being more effective in preserving teeth. Not only occlusal width was reassessed, but the need to routinely extend proximal margins to the buccal and lingual line angles was also questioned. By the mid-1960's and early 1970's a more conservative approach to amalgam preparation was advocated and was being taught in some dental schools. Today, a standardized outline form should not be used or taught as a principle of cavity preparation. In areas where fissure caries has necessitated a preparation extending into dentin, a composite resin or dental amalgam restoration should be placed, and a fissure sealant should be used to protect remaining susceptible fissures from carious attack. This current form of the concept of extension for prevention, which is supported by clinical research, preserves sound tooth structure that, using outdated concepts, would have been cut away. Placing proximal margins in sound tooth structure that just clears an adjacent tooth is also strongly advocated. Sound enamel margins in certain areas may occasionally be left in contact with adjacent teeth for amalgam preparations. For Class II preparations for composite resin, facial or lingual proximal bevels will usually suffice to separate the margins from the adjacent tooth to allow finishing and polishing at the margins. Preventing unnecessary extension and allowing sounder tooth structure to remain is one important aspect of helping patients to maintain their teeth for their lifetimes.
Dental Amalgam↗
Initial cervical exploration for parathyroidectomy is not benefited by preoperative localization studies.
Published data is controversial as to the ability of preoperative localization studies (PLS) to enhance the outcome of initial cervical exploration in patients with primary hyperparathyroidism (PHPT). One surgeon's experience was reviewed to compare surgical success, operative time, and morbidity of initial cervical exploration for PHPT in patients who had undergone PLS versus those who had not. From August 1991 to September 1997, 95 patients who had not undergone prior central cervical exploration presented for surgical management of PHPT. Sixty-seven patients underwent initial cervical exploration without any PLS having been performed (Group A). Twenty-eight patients underwent PLS, either alone or in combination, before surgical intervention (Group B). Analysis of intergroup variability was conducted upon the data available using a two-tailed t test for independent samples. In addition, the sensitivities and positive predictive values of the PLS were calculated using study reports and operative and histologic findings. There was no statistically significant difference in surgical success between those patients who had PLS and those that did not undergo PLS. Sixty-four of 67 patients (95.5%) not having PLS were cured with initial surgery, while 27 of 28 patients (96.4%) who had PLS were surgically cured. Mean postoperative calcium and intact parathormone levels were similar between the two groups, and the mean operative time did not differ. Permanent hypocalcemia occurred in one patient, and five patients had transient hoarseness. Thirty-six total PLS were obtained at an average cost of $752.68/patient, and seven patients underwent multiple tests. Overall, sestamibi scan had the highest positive predictive value (81%). For adenomatous disease alone, sestamibi scan was the most sensitive (83%). Our study shows that for matched groups limited to age, sex, and clinical diagnosis, the use of PLS did not shorten operative time, decrease complication frequency, nor alter the success of the operation as measured by postoperative calcium and parathormone levels. Therefore, routine use of preoperative localization studies before initial cervical exploration for PHPT cannot be recommended.
Adenoma↗
The effect of amalgam bonding on resistance form of Class II amalgam restorations.
OBJECTIVE: This study evaluated the load required to produce failure in Class II bonded amalgam restorations. METHOD AND MATERIALS: Five groups of 12 maxillary molars were mounted. Class II mesio-occlusal preparations were cut: group 1, extension through central grooves, without retention grooves; group 2, proximal slot preparation, without retention grooves; groups 3 and 5, slot preparation with long facial and lingual retention grooves; group 4, slot preparation without grooves, with unsupported proximal enamel allowed to remain. Groups 1 to 4 were restored with an amalgam-bonding system and amalgam; in group 5, no amalgam-bonding material was used. RESULTS: Mean (SD) failure loads: group 1, 281 (77) N; group 2, 246 (101) N; group 3, 238 (84) N; group 4, 254 (100) N; and group 5, 191 (66) N. CONCLUSION: Although there was a trend toward greater resistance to dislodgment or fracture when an amalgam-bonding technique was used, its use did not significantly increase the resistance to failure when compared to retention grooves alone.
Analysis of Variance↗
The role of research in clinical practice.
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Dental Research↗
Caries progression of white spot lesions sealed with an unfilled resin.
This study evaluated the artificial caries resistance provided to white spot lesions by sealing with an unfilled resin. Twenty extracted molar teeth were coated with an acid-resistant varnish (ARV), except for two 5 mm x 2 mm enamel windows (mesial and distal), and immersed for 5 weeks in an acidified gel brought to a pH of 4.2 with lactic acid. White spot lesions (not frank caries) were created in each window. The teeth were removed from the gel, rinsed and dried. One window was divided into two equal parts; one half was covered with the ARV (Group 1); the other half was not covered (Group 2). The other window was treated with 37% phosphoric acid for 20 sec, rinsed with water for 20 sec, dried and sealed with Prisma Universal Bond 2 Adhesive (Group 3). The teeth were reimmersed in the acidified gel for 40 days until frank caries was induced in Group 2. Specimens were then removed from the gel, rinsed, and sectioned occlusogingivally. Sections were polished to approximately 100 microns, imbibed in water, and analyzed using polarized light microscopy. Depth of demineralization was evaluated in the varnished, sealed and frankly carious areas. The mean (SD) lesion depths were as follows: Group 1 (under ARV) 366 microns (103 microns); Group 2 (frank caries) 746 microns (219 microns); Group 3 (under sealed area) 298 microns (111 microns). ANOVA and Student-Newman-Keuls procedure were used to compare group means. The mean depths of demineralization under the ARV (Group 1) and the unfilled resin sealant (Group 2) were significantly less than for the unprotected enamel (Group 2) (p > 0.0001). Results indicate the potential effectiveness of sealing white spot lesions with an unfilled resin to prevent further demineralization.
Analysis of Variance↗
2-year clinical evaluation of a gallium restorative alloy.
PURPOSE: To assess the clinical performance of 2-year old gallium alloy restorations. Parameters evaluated include: (1) fracture at the margins, (2) tarnish, (3) surface roughness, (4) tooth fracture, (5) fracture through the body of the restoration, and (6) any medical or dental conditions arising during the study. MATERIALS AND METHODS: Nine patients received 30 Class I restorations of Galloy gallium alloy. These were placed as conservatively as possible under a rubber dam. Fifteen of the preparations were lined with a Bis-GMA resin to seal the restoration from moisture. The other 15 preparations were sealed with Amalgambond. After placement of the gallium alloy, the exposed surfaces of all restorations were sealed with the Bis-GMA resin, and the occlusion was checked. The restorations were examined at 2 weeks, 3 months, 6 months, 1 year and 2 years. RESULTS: At the 2-year recall, all restorations were intact with the exception of one tooth fracture (cause unknown). Forty-five percent of the restorations exhibited tarnish and 60% had a rough surface. The fracture at the margins of these restorations was minimal, and no significant difference could be found between those using Amalgambond and those sealed with the resin system. No medical problems were reported by the patients, and postoperative sensitivity was minimal.
Bisphenol A-Glycidyl Methacrylate↗
Clinical evaluation of high-copper amalgams.
PURPOSE: To compare the clinical performance of two high-copper amalgam alloys with different compositions by evaluating marginal fracture of each restoration over a 2-year period. MATERIALS AND METHODS: Restorations of Valiant PhD and Zenith Premium alloy were placed in Class I and II cavity preparations in patients and evaluated at baseline, 1 and 2 years to determine their degree of marginal breakdown. RESULTS: After 2 years, the Zenith Premium alloy exhibited significantly less marginal breakdown than the Valiant PhD alloy with no significant additional deterioration of the Zenith restorations between the 1st and 2nd year. The data indicate that the Zenith Premium alloy exhibits less marginal deterioration than Valiant PhD so it may be predicted that it will perform better long term. A possible explanation for this better performance may be that the Zenith Premium contains zinc while the Valiant PhD includes palladium but no zinc in its formulation.
Alloys↗
The strength of Class II composite resin restorations as affected by preparation design.
This study evaluated the load, applied to the marginal ridge, required to produce failure in Class II posterior composite resin restorations with four different preparation designs. In group 1, the preparation had an extension through the occlusal groove. The other three groups employed a proximal box-only (slot) preparation. Group 2 preparations had facial and lingual retention grooves that extended from the gingival floor to the occlusal surface; group 3 preparations were slots without grooves; and group 4 preparations were slots without grooves and with unsupported proximal enamel. After the restorations were thermocycled, their marginal ridges were flattened and loaded to failure. Mean (SD) failure loads were 438 (73) N in group 1; 383 (52) N in group 2; 297 (72) N in group 3; and 281 (63) N in group 4. Mean failure loads of groups 1 and 2 were not significantly different from each other but were significantly greater than failure loads for groups 3 and 4. Mean failure loads of groups 3 and 4 were not significantly different.
Analysis of Variance↗
Effect of a resin lining and rebonding on the marginal leakage of amalgam restorations.
This in vitro study compared microleakage in Class V amalgam restorations with three different lining agents and with no lining agent, with and without resin rebonding of the margins. Eight groups of ten molars were divided into four pairs of groups. Class V preparations were cut in the facial surfaces of each molar so that the occlusal margin was in enamel and the gingival margin in dentine. The preparations in one pair of groups received no lining agent; the preparations in the remaining three pairs of groups were lined with one of the following: Copalite, Universal Bond 3 (UB3) Primer and Adhesive, or UB3 Primer only. The enamel walls of the preparations receiving the UB3 Primer and Adhesive were etched prior to applying the lining material. Amalgam was hand condensed into each preparation. In one of each pair of groups, the margins of restorations were treated with 37% phosphoric acid gel, rinsed and dried, and UB3 Adhesive was applied over amalgam and tooth margins and polymerized (rebonded). Specimens were thermocycled, stained and sectioned. Microleakage was graded using a stereomicroscope. Mean microleakage scores for occlusal and gingival margins were calculated and analysed. At enamel margins, non-rebonded Copalite and all rebonded specimens showed less microleakage than the other non-rebonded groups. The group lined with UB3 Primer only and rebonded showed significantly less (P < 0.01) microleakage at enamel margins than all the other groups except the group lined with Copalite and rebonded. At cementum/dentine margins, restorations lined with UB3 Primer and rebonded showed significantly less microleakage than the other groups.
Acid Etching, Dental↗
Cavity preparations that extend the clinical longevity of amalgam restorations.
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Dental Amalgam↗