Niek Johannes Opdam

Information about the long-term clinical survival of large amalgam and composite restorations is still lacking. This retrospective study compares the longevity of three- and four-/five-surface amalgam and composite restorations relative to patients’ caries risk. Patient records from a general practice were used for data collection. We evaluated 1949 large class II restorations (1202 amalgam/747 composite). Dates of placement, replacement, and failure were recorded, and caries risk of patients was assessed. Survival was calculated from Kaplan-Meier statistics. After 12 years, 293 amalgam and 114 composite restorations had failed. Large composite restorations showed a higher survival in the combined population and in the low-risk group. For three-surface restorations in high-risk patients, amalgam showed better survival.

To investigate longevity and reasons for failure of Class II posterior composite restorations (PCRs) placed with or without a lining of glass-ionomer cement. Four hundred fifty-eight Class II PCR placed in 248 patients (110 male, 138 female, age 18 to 80) by two dentists in a general practice between 1988 and 1997 were retrospectively examined from the patient files. The restorations were placed either with a total-etch technique or with a resin-modified glass-ionomer lining placed on the dentin. Items recorded were date of placement, date of last check-up visit, tooth number, and restored surfaces. Date of replacement and reason for failure of the PCR was recorded. A restoration was clinically acceptable when still in function and acceptable at the last check-up visit. Additionally, the caries risk for each patient was estimated by the treating clinician. Life tables and Kaplan-Meier curves were used to express survival rates. A Cox regression was applied to assess the influence of variables on survival. Three hundred seventy-six total-etch PCRs and 82 PCRs with a lining were investigated. After 9 years, survival percentages of 88.1% for total-etch restorations and 70.5% for restorations with a resin-modified glass-ionomer lining were found. The most important reasons for failure were fracture and caries. Predominantly, failures started occurring after 3 to 4 years of clinical service. Results of the Cox regression show that the presence of a lining and high risk for caries significantly increased the failure rate of the restorations. PCRs placed with a resin-modified glass-ionomer lining clinically showed more frequent fractures than PCRs placed with a total-etch technique.

To investigate the influence of composite resin consistency and placement technique on proximal contact tightness of Class II composite resin restorations. A manikin model (KaVo Dental) was used with an artificial first molar in which a standardized MO preparation was ground. This preparation was duplicated 360 times. Cavities were restored using Clearfil Photo Bond (Kuraray) combined with one of three composite resins of different consistencies: a low-viscosity (X-Flow, Dentsply), a medium-viscosity (Clearfil AP-X, Kuraray) and a high-viscosity composite (Tetric Ceram HB, Ivoclar Vivadent). Each composite was combined with 6 different matrix systems and separation techniques (n = 20). Groups 1 and 2: precontoured metal circumferential matrix (KerrHawe 1101-c) in a Tofflemire retainer combined either with hand instrument (OptraContact, Ivoclar Vivadent) or separation ring (Composi-Tight Gold, Garrison Dental Solutions). Group 3: pre-contoured metal sectional matrix (Lite-Flex, Danville Materials) with separation ring. Groups 4 and 5: pre-contoured metal circumferential dead-soft matrix (Adapt SuperCap, KerrHawe) with or without separation ring. Group 6: flat metal circumferential matrix (OptraMatrix, Ivoclar Vivadent) in a Tofflemire-retainer with hand instrument (OptraContact). Proximal contact tightness was measured using the Tooth Pressure Meter (University of Technology, Delft). To determine the effect of experimental variables on the proximal contact tightness, a multiple linear regression model was constructed. Measurements in group 6 were not possible; therefore, this group was excluded. The use of medium- or high-viscosity instead of a low-viscosity composite resin resulted in statistically significantly tighter proximal contacts (p < 0.01). The use of a separation ring resulted in a large, statistically significant increase (p < 0.001) in contact tightness, while the use of a hand instrument resulted in a small, statistically significant increase of contact tightness (p = 0.017). No statistically significant differences were found when a dead-soft matrix or a sectional matrix was used instead of a Tofflemire (p = 0.159, p = 0.261, resp.). Use of a separation ring when restoring a Class II composite resin restoration has a greater influence on the obtained proximal contact tightness compared to the influence of the consistency of the composite resin.

This paper is a comment on 'The enigma of dental amalgam' by Carl Leinfelder published in 2004 in the Journal of Esthetic and Restorative Dentistry. In that paper a warning is stated against a too abrupt change from amalgam towards resin composite, because this will bring a lot of clinical problems due to the limited skills of todays' dentists in placing posterior composite resin restorations. However, the situation in The Netherlands is different since a gradual changeover from amalgam towards resin composites has taken place during the last decades and dental schools have skipped training in placing amalgam restorations out of the curriculum. Clinical studies on the longevity of amalgam and resin composite restorations placed by dental students and dentists who are experienced in both composite resin and amalgam placement show a comparable and acceptable annual failure rate for those restorations. It is concluded that a gradual changeover from amalgam towards composite resin is preferred to avoid clinical problems.