Though bacterial colonization of a restored surface depends more on the nature of the material than the degree of finishing and polishing,1,2 a well-polished restoration offers definite advantages. The surface of teeth is generally smooth and shiny. Sometimes the anatomy features macroscopic crevices, but it is still shiny. Light reflection generally varies depending on the quantity and quality of anatomical details present on the tooth surface. Light distribution can be fairly uniform, but the surface may shimmer when the anatomy is very pronounced.
Once the restoration is complete, composite finishing and polishing procedures must be carefully carried out to convert the raw, roughly layered composite surface into a smooth, morphologically harmonious surface polished to the level of the original tooth.
Finishing means processing an object to achieve a definitive shape, and polishing means adding a shine to the finished shape. A well-finished and polished composite will guarantee:
- A better marginal seal3
- Good blending of the tooth-restoration complex
- A more durable restoration
- Easy-to-clean surfaces
- Reduced friction and wear
- Resistance to pigmentation4
Many systems are available for finishing and polishing composite resins (Fig 9-1). Depending on their nature, they produce surfaces of varying smoothness.5–7 Whichever method is used, the surface treatment should be performed with care and in accordance with the manufacturer’s instructions. The time taken to finish and polish is also important. The effects of polishing are longer lasting if more time is taken8 (Fig 9-2).
The surface treatment is partly responsible for the restoration’s color stability. Although the color stability of a given composite depends mainly on its nature, the degree of surface finishing is also responsible for the restoration’s intrinsic color variation.9–12
In Class 2 preparations, the initial finishing stage is performed as soon as the centripetal buildup technique (CBT) procedure is complete, defining the restoration contour by removing excess composite. Achieving a well-shaped contour before completing the occlusal reconstruction helps practitioners position the far limits of grooves and fossae correctly.
The following instruments are used:
Abrasive disks are used to remove overcontours and steps on the tooth-restoration seal, creating the transition between the proximal and occlusal surfaces (Fig 9-4a) and angling the newly constructed marginal ridge in an occlusal direction (Fig 9-4b).
Abrasive disks (Fig 9-5) work on a blue ring contra-angle handpiece at low speed without irrigation. To avoid rupturing the rubber dam, it is a good idea to practice the movements to be performed before operating the motor. This will help the operator to memorize the movement to be performed and see whether enough working space is available or if it is preferable to use smaller-diameter disks.
The medium-grit disk (see Fig 9-5a) removes any defects and blends the area in with the residual dental tissue, while the fine-grit disk (see Fig 9-5c) ensures an additional finishing level that reduces surface irregularities.13
Red ring flame bur
Properly performed CBT must not leave any steps, so the function of the red ring flame bur (see Fig 9-3b) is to remove horizontal overcontours on the buccal and lingual proximal transitions and improve the occlusal flow of the composite used to construct the marginal ridge. The red ring flame bur is operated on a red ring contra-angle handpiece (for greater control) with or without irrigation, according to the work to be performed.
If the restoration must blend in with tooth tissue, the bur is operated at medium speed with irrigation. If the work requires great care, such as on a surface that is difficult to access or with complex anatomy, it is preferable to use a low-speed flame bur with gentle irrigation assisted by an air-water syringe. In any case, before operating the motor it is always advisable to practice the movement to be performed.
Interproximal abrasive strips
Abrasive strips (Fig 9-6) are polyester strips that are abrasive on one side only. They have two working surfaces, one with a coarser grain that performs the first stage of work, and a finer-grained one used during the last interproximal step. The strips work only on the cervical seal, both on the shoulder and on the transition between the tooth’s proximal and buccolingual surfaces. To avoid abrasion and loss of seal, they must never work in the interproximal contact area. In fact, the center of the strip is free of abrasive granules to facilitate interproximal insertion without abrading the contacts. Strips of various types with different grades and widths are available. Because the strips must only work on the cervical shoulder, narrow strips are preferable as they can be easily inserted between two teeth below the contact area. The strip is inserted from a buccal to palatal direction before being taken up and pulled through with the aid of tweezers (Fig 9-7