Effect of composite shade, increment thickness and curing light on temperature rise during photocuring.

OBJECTIVES: To examine the effect of composite shade, increment thickness and curing light characteristics on the temperature rise associated with composite photocuring. METHODS: Four shades (C2, A4, B1 and B3), four sample thicknesses (2, 3, 4 and 5 mm) of a hybrid resin composite and two curing units, one with two modes of curing, were investigated. The composite samples were packed in polytetrafluoroethylene (PTFE) moulds and cured for 40 s. Samples cured with the ramp curing mode were irradiated for only 20 s. Temperature rises on the undersurface of the curing resin composite were measured using an infrared scanning system. RESULTS: Shade C2 produced the highest maximum temperature of all shades (56.7 degrees C). Thinner samples produced greater temperature rises (2mm induced 60.9 degrees C, 5 mm induced 45.7 degrees C). Samples cured with Optilux 501 unit produced greater temperature rises (60.9 degrees C) than those cured with Dentsply unit (56.2 degrees C). CONCLUSIONS: There was a quantifiable amount of heat generated during visible light curing of resin composite. The amount of heat generated was influenced by shade selected, thickness of material and characteristics of the light curing unit.

Thermographic investigation of contemporary resin-containing dental materials.

OBJECTIVES: To measure the temperature rise induced during visible light curing of modern resin-containing dental materials and the effect of dentine sections in reducing this temperature rise. METHODS: A variety of newly introduced resin-containing materials were investigated, including flowable, packable and conventional hybrid composites, as well as a compomer and a resin modified glass ionomer material. The resin was packed into polytetrafluoroethylene (PTFE) moulds and cured for 40s. Temperature rises on the undersurface of the curing resin were measured using the Thermovision 900 infra-red scanning system. In the second part of the study, extracted, caries free teeth were sectioned into dentine disks of three thicknesses (0.7, 1.4 and 1.9 mm). Composite samples were overlaid by the disks and the insulating effect of dentine measured. RESULTS: The maximum temperature increases were: 43.1 degrees C (flowable composite), 32.8 degrees C (conventional composite), 32.8 degrees C (RMGI), 23.3 degrees C (compomer) and 22.4 degrees C (packable composite). CONCLUSIONS: There was a quantifiable amount of heat generated in resin-containing material during light curing. Dentine sections were good thermal insulators that significantly reduced temperature rises associated with resin composite photocuring.

Minocycline: stain devil?

Minocycline is the treatment of choice for acne vulgaris, the most common form of inflammatory acne, despite the increase in awareness of rare but significant side-effects. This paper discusses the undesirable side-effect of minocycline staining in permanent teeth.

Presentation, diagnosis and initial management of patients referred to a hospital tooth wear clinic.

Information on presenting complaints, diagnosis and initial management strategy was recorded on a proforma for 114 consecutive patients referred to a hospital tooth wear clinic over a two-year period. Over twice as many male patients were referred as females. Twenty percent of patients had no presenting complaint and the others shared the common complaints concerning appearance, sensitivity and their deteriorating dentitions. The assessment of aetiology identified attrition as the most common cause of tooth wear in the subject group studied. About half the group were prescribed preventative treatment only and the other half were deemed to require restorative dental treatment.

Evaluation of the 1-year clinical performance of dentin-bonded ceramic crowns and four case reports.

OBJECTIVE: Dentin-bonded crowns are a comparatively recent addition to the dentist's armamentarium. Although 1-year data cannot predict the long-term performance of restorations, it may be useful for new treatment modalities, given that it will describe early, catastrophic failures. In this study, the 1-year performance of 109 dentin-bonded crowns was assessed. METHOD AND MATERIALS: The crowns were placed in two locations (Glasgow, Scotland, and Belfast, Northern Ireland) for 27 patients. The principal reasons for crown placement were tooth substance loss, esthetic reasons, and tooth fracture. Minimal preparations were used. Ninety-eight crowns were available for review at 1 year. RESULTS: Ninety crowns were found to be intact, six had a crack visible on transillumination and two had fractured. No crowns had debonded. No secondary caries was noted. No unsatisfactory scores were recorded for marginal adaptation, adjacent gingival health, or color match. CONCLUSION: The dentin-bonded crowns placed during this study provided good overall performance at 1 year.

Effect of groove placement on the retention/resistance of resin-bonded retainers for maxillary and mandibular second molars.

STATEMENT OF PROBLEM: Lack of retention/resistance form in the clinical preparation of teeth for resin-bonded retainers may lead to clinical failure. PURPOSE: This study investigated the effect of proximal grooves on the retention/resistance of cast resin-bonded retainers for maxillary and mandibular second molar teeth. MATERIAL AND METHODS: Two ivorine teeth (a maxillary and a mandibular second molar) were prepared for resin-bonded retainers. Twenty metal replicas of the prepared teeth were made (10 for each tooth morphotype). Resin-bonded retainers 0.5 mm thick were made for the 40 replicas and luted with Panavia EX cement. Forces for dislodgment of the retainers were applied along the long axes of the teeth. Forces recorded at the time of dislodgment were analyzed with 2-way analysis of variance and the post hoc Scheffé test. RESULTS: Grooves resulted in substantial increases in debonding forces for maxillary molars (P<.001). The effect of grooves on mandibular second molars was not significant (P=.13). CONCLUSION: Grooves placed in tooth preparations of maxillary molar teeth for resin-bonded retainers had a significant effect on retention/resistance. The effect of grooves on mandibular second molars was less pronounced.

An unusual indication for root resection.

This report presents an unusual indication for root resection of a lower molar tooth and also reviews the history of root resection.

A comparison of thermocouple and infrared thermographic analysis of temperature rise on the root surface during the continuous wave of condensation technique.

AIM: This study was designed to use two methods of temperature measurement to analyse and quantify the in vitro root surface temperature changes during the initial stage of the continuous wave technique of obturation of 17 single-rooted premolar teeth with standard canal preparations. METHODOLOGY: A model was designed to allow simultaneous temperature measurement with both thermocouples and an infrared thermal imaging system. Two thermocouples were placed on the root surface, one coronally and the other near the root apex. A series of thermal images were recorded by an infrared thermal imaging camera during the downpack procedure. RESULTS: The mean temperature rises on the root surface, as measured by the two thermocouples, averaged 13.9 degrees C over the period of study, whilst the infrared thermal imaging system measured an average rise of 28.4 degrees C at the same sites. Temperatures at the more apical point were higher than those measured coronally. After the first wave of condensation, the second activation of the plugger in the canal prior to its removal always resulted in a secondary rise in temperature. The thermal imaging system detected areas of greater temperature change distant from the two selected thermocouple sites. CONCLUSIONS: The continuous wave technique of obturation may result in high temperatures on the external root surface. Infrared thermography is a useful device for mapping patterns of temperature change over a large area.

The periodontal response to cantilevered resin-bonded bridgework.

This study investigated 84 cantilevered resin-bonded bridges (CRBB) in 60 patients. These CRBB (single retainer, single pontic) had been in place for an average of 43.6 months. Periodontal health was assessed on abutment teeth and contralateral control teeth. Periodontal indices utilized were Plaque Index (PI), Gingival Index (GI), Bleeding Index (BI), Pocket Depth (PD) and mobility. The marginal adaptation, the gingival extension of the retainers and the presence or absence of caries around each retainer margin were also assessed. Information about the history of debonding was collected and a success rate of 93% was reported. PI, GI and mean PD compared statistically significantly, less favourably, with scores of the control teeth. Marginal adaptation of the retainers was of a high standard and caries did not appear to be a problem.

The provision of resin-bonded bridgework within the General Dental Services 1987-1997.

The purpose of this study was to investigate the performance of resin-bonded bridgework provided within the General Dental Services of the National Health Service. The basic procedure involved analysis of data collected from the administering authorities in England, Wales and Scotland between 1987 and 1997. These figures included the cost of the provision of such bridgework and the incidence and cost of refitting bridges which had become debonded in service. The investigation found that while the number of resin-bonded bridges provided had peaked in the early 1990s the number of claims for rebonding was still increasing at a high rate. In the most recent year of the study (1996/97) the number of claims for rebonding bridges was 50% more than the number of bridges actually fitted during that year. It was concluded that resin-bonded bridgework provided under the General Dental Services of the National Health Service was experiencing a high failure rate and that this problem was worthy of further investigation.

Immediate cantilevered resin-bonded bridgework: a case report.

Resin-bonded bridgework (RBB) is now an accepted alternative to conventional bridgework in specific cases. This article reviews the immediate replacement of two anterior teeth with the resin-bonded technique and describes the use of immediate cantilevered RBB in the aesthetic treatment of a patient with class II division II malocclusion on a moderate skeletal II base. Both maxillary lateral incisors were extracted and immediately replaced with cantilevered RBB. This simple and conservative approach produced an instant solution to a difficult aesthetic problem of proclined lateral incisors. The reported RBB continues to function successfully after 15 months.

Periodontal response to cantilevered and fixed-fixed resin bonded bridges.

The periodontal response to two types of resin bonded bridges was investigated. Cantilever or fixed-fixed resin bonded bridges which had been in service for at least two years were reviewed. Periodontal indices (plaque index, gingival index, bleeding index and pocket depth) were recorded for each bridge abutment and for matched contralateral teeth. There was no difference in the periodontal condition of the abutment teeth between cantilever and fixed-fixed resin bonded bridges, after they had been in service for at least two years. There was evidence of greater plaque accumulation and higher gingivitis levels affecting abutment teeth for both types of bridges compared with control teeth.

Bonding to molars--the effect of etch time (an in vitro study).

This study evaluated the effect of etch time on the shear bond strength obtained when bonding to the buccal enamel of first molar teeth. Recently extracted first molar teeth were etched with 37 per cent phosphoric acid gel for 15, 30 and 60 seconds. Preformed cylinders of Concise composite resin were then bonded to the buccal surfaces of the molar teeth. After storage in water for 24 hours at 37 degrees C, the specimens were debonded in a direction parallel to the buccal surface. Examination of the shear bond strengths showed significant differences in shear bond strength between 15 and 30 seconds (P < 0.01) and between 15 and 60 seconds (P < 0.001). Weibull analysis revealed that the probability of bond survival increased as etch time increased, however, the difference between 30 and 60 seconds was not statistically significant. The results indicate that, despite current recommendations of a 15-second etch for premolars, canines and anterior teeth, an etching time of at least 30 seconds should be used when bonding to the buccal surfaces of first molars. A further increase in etching time to 60 seconds produces no significant increase in bond strength.

Bond strengths of maxillary anterior base metal resin-bonded retainers with different thicknesses.

PURPOSE: This study evaluated the effect of three different thicknesses of base metal resin-bonded retainers on retention/resistance. MATERIAL AND METHODS: Three ivorine teeth, a central incisor, lateral incisor, and canine, were prepared to receive resin bonded retainers. Fifteen metal replicas of prepared teeth were made (five for each tooth morphotype). A total of 45 metal retainers were cast in three different thicknesses, 0.3, 0.5, and 0.7 mm, with 15 for each thickness. Retainers were cemented to metal die replicas with Panavia EX luting agent. After 24 hours, forces to dislodge the retainers were applied at 45 degrees to the vertical mesiodistal plane at the proximolingual line angle. RESULTS: An increase in thicknesses resulted in elevation of dislodging forces that were almost linear for the three thicknesses of canine retainers. The central incisor exhibited the greatest increase in resistance to dislodgment between retainers that were 0.3 and 0.5 mm thick, whereas increased thickness for the lateral incisor retainer resulted in minimal or no benefit.

Thermographic assessment of heat generated on the root surface during post space preparation.

The mechanical preparation of a post space in a root filled tooth is commonly carried out using rotating instruments in a slow handpiece. This procedure creates frictional heat which may be transferred to the root surface. In this investigation, the temperature changes on the root surface of 12 root filled, extracted human premolar teeth during preparation of post spaces were analysed using an infrared thermal imaging camera. A rotational speed of 8000 r.p.m. was used and the teeth were prepared with size 2 and 3 Peeso reamers and a red Parapost drill to the optimal length. The results indicate that very large temperatures are generated on the root surface and that this is greatest during the Parapost preparation stage. The long-term clinical effects of post space preparation by engine driven drills would warrant further investigation.

Thermographic assessment of root canal obturation using thermomechanical compaction.

The temperature changes on the root surface of 30 extracted human premolar teeth during thermomechanical root canal obturation with gutta-percha were determined using an infrared thermal imaging camera. Three handpiece rotational speeds of 8, 12 and 16 x 10(3) r.p.m. were used, in conjunction with a Gutta Condensor. On completion of the procedure, the quality of tooth canal obturation was examined radiographically. Under the conditions of this experiment, surface root temperature rises of > 97 degrees C were recorded during all three speed settings. The radiographic quality of obturation between the groups appeared not to be significantly different. The clinical relevance of these findings is uncertain, but the temperatures reported are of a magnitude to be of biological importance.

The clinical performance of cantilevered resin-bonded bridgework.

OBJECTIVES: The technique of resin-bonded bridgework is a well-accepted clinical technique to replace missing teeth. This study assesses the clinical performance of cantilevered resin-bonded bridgework provided in a university teaching hospital environment. METHODS: One-hundred and twelve patients who had a total of 142 cantilevered bridges were either examined or completed a questionnaire regarding their bridgework. The following data were recorded for each resin-bonded bridge: gender of patient, age at bridge cementation, date of initial cementation, tooth replaced, abutment(s) involved, and grade of clinician responsible for the provision of the bridge. Details of the incidence of debonding with date(s) and the subsequent treatment in relation to the debonded resin-bonded bridge were recorded. The subjects examined indicated their degree of satisfaction with their bridgework on a visual analogue scale. RESULTS: There were 112 patients with a total of 142 bridges, 116 (82%) maxillary and 26 (18%) mandibular. The mean length of clinical service was 36.2 months (s.d. 17.2 months). Only single pontics were included in the bridges, with almost half (49%) replacing a lateral incisor. Of the cantilever resin-bonded bridges studied, 88% remained bonded over the period of the study. A success rate of 94% is reported. CONCLUSION: This study confirms the clinical success of cantilever resin-bonded bridges particularly in the replacement of maxillary lateral incisors, maxillary premolar and permanent mandibular teeth.

Temperature changes in bovine mandibular bone during implant site preparation: an assessment using infra-red thermography.

OBJECTIVES: Changes in bone temperature during the sequence of drilling for implant site preparation using the Branemark technique were monitored using infra-red thermography. METHODS: Bovine mandibles were used to provide cortical bone of a similar quality to human mandibular bone. To ensure the consistency in the drilling procedure, one operator used a conventional dental handpiece with a motor provided by Nobelpharma. The manufacturer's specifications were followed during the implant site preparation, except that no irrigation was employed since infra-red radiation does not transmit through water. Thermal images were recorded using the Thermovision 900 system. A sequence of images was recorded during implant site preparation. Three drills were examined in terms of temperature changes during drilling over the entire area involved. The three drills used were a round bur, which determines the site of the fixture, a spiral drill (2 mm twist drill) which establishes the direction of the implant and finally a pilot drill (3 mm) which progressively increases the diameter of the site. RESULTS: Average values (n = 10 drill sequences) for maximum recorded temperature (Max T degrees C), change in temperature (delta T degrees C) from baseline and the area of involvement (mm2) for each drill in the 10 drill sequences were as follows: round, spiral (2 mm) and pilot (3 mm) drills gave maximum temperatures of 82.7 degrees C, 130.1 degrees C and 126.3 degrees C, respectively. The changes in temperature, delta T degrees C, were 45.7 degrees C, 79.0 degrees C and 78.9 degrees C for the round, 2 mm twist and 3 mm pilot drill, respectively. The average areas recorded for the round, spiral and pilot drills were 49 mm2, 140.1 mm2 and 273.0 mm2, respectively. CONCLUSIONS: It is concluded that the methodology employed accurately recorded temperature changes at and around the dental implant site, and provided preliminary baseline data against which the cooling efficacy of different irrigant systems may be compared.

The effect of etch duration on the microstructure of molar enamel: an in vitro study.

This in vitro study evaluated the influence of varying etch time on the microstructure of molar buccal enamel. The buccal surfaces of four groups of extracted first molar teeth were etched for 15, 30, 45, and 60 seconds. The etch patterns obtained were photographed with a scanning electron microscope and rated with a 3-grade scale. The 15-second etch time failed to produce any optimal etch patterns. The best etch patterns were found in molars etched for 60 seconds.

Thermographic measurement of temperature change during resin composite polymerization in vivo.

OBJECTIVES: To use the technique of infrared thermography for non-invasive monitoring of temperature changes during polymerization of resin composite by measuring the infra-red emission from the surfaces of resin composite restorations during photocuring. METHODS: In this study 10 patient volunteers had resin composite restorations placed in upper incisor teeth and during photocuring the temperature rise within the composite was measured using the Thermovision 900 infra-red scanning system. RESULTS: The results demonstrate that the exotherm is almost instantaneous, occurring as soon as the light source is activated and rising to a peak at approximately 30 s before levelling off. The measurements suggest that a maximum temperature increase of 12 degrees C could occur, although this may only be for a short period (< 15 s). CONCLUSION: The range of temperature rise measured in this study (mean 5.4 degree C +/- 2.5 degree C) would suggest that the pulp may be endangered by the temperature rise which occurs during resin composite polymerization in vivo.