Abstract: We included five studies that evaluated three comparisons. Four studies compared crowns with fillings; two of them compared conventional PMCs with open sandwich restorations, and two compared PMCs fitted using the Hall Technique with fillings. One of these studies included a third arm, which allowed the comparison of PMCs (fitted using the Hall Technique) versus non-restorative caries treatment. In the two studies using crowns fitted using the conventional method, all teeth had undergone pulpotomy prior to the crown being placed. The final study compared two different types of crowns: PMCs versus aesthetic stainless steel crowns with white veneers. No RCT evidence was found that compared different methods of fitting preformed metal crowns (i.e. Hall Technique versus conventional technique). We considered outcomes reported at the dental appointment or within 24 hours of it, and in the short term (less than 12 months) or long term (12 months or more). Some of our outcomes of interest were not measured in the studies: time to restoration failure or retreatment, patient satisfaction and costs. Crowns versus fillings All studies in this comparison used PMCs. One study reported outcomes in the short term and found no reports of major failure or pain in either group. There was moderate quality evidence that the risk of major failure was lower in the crowns group in the long term (risk ratio (RR) 0.18, 95% confidence interval (CI) 0.06 to 0.56; 346 teeth in three studies, one conventional and two using Hall Technique). Similarly, there was moderate quality evidence that the risk of pain was lower in the long term for the crown group (RR 0.15, 95% CI 0.04 to 0.67; 312 teeth in two studies). Discomfort associated with the procedure was lower for crowns fitted using the Hall Technique than for fillings (RR 0.56, 95% CI 0.36 to 0.87; 381 teeth) (moderate quality evidence). It is uncertain whether there is a clinically important difference in the risk of gingival bleeding when using crowns rather than fillings, either in the short term (RR 1.69, 95% CI 0.61 to 4.66; 226 teeth) or long term (RR 1.74, 95% CI 0.99 to 3.06; 195 teeth, two studies using PMCs with conventional technique at 12 months) (low quality evidence). Crowns versus non-restorative caries treatment Only one study compared PMCs (fitted with the Hall Technique) with non-restorative caries treatment; the evidence quality was very low and we are therefore we are uncertain about the estimates. Metal crowns versus aesthetic crowns One split-mouth study (11 participants) compared PMCs versus aesthetic crowns (stainless steel with white veneers). It provided very low quality evidence so no conclusions could be drawn. Crowns placed on primary molar teeth with carious lesions, or following pulp treatment, are likely to reduce the risk of major failure or pain in the long term compared to fillings. Crowns fitted using the Hall Technique may reduce discomfort at the time of treatment compared to fillings. The amount and quality of evidence for crowns compared to non-restorative caries, and for metal compared with aesthetic crowns, is very low. There are no RCTs comparing crowns fitted conventionally versus using the Hall Technique.

Plain-language summary: We searched medical and dental sources for studies up to 21 January 2015. We identified five relevant studies. They were at high risk of bias because the participants knew which treatment they received and so did the people who treated them. Four studies compared crowns with fillings. Two of them compared metal crowns fitted using the conventional method with fillings and two compared metal crowns fitted using the Hall Technique with fillings. One of the studies also compared the Hall Technique with 'non-restorative caries treatment' (not using either a filling or crown but opening the cavity to make it possible to clean with a toothbrush, sealing with fluoride varnish and encouraging toothbrushing). The final study compared crowns made of two different materials (stainless steel versus stainless steel with a white covering). We looked at what happened for each treatment at the time of the dental appointment or within 24 hours of treatment, in the short term (less than 12 months) and long term (12 months to 48 months). Teeth restored with preformed crowns are less likely to develop problems (e.g. abscess) or cause pain in the long term, compared to fillings. Crowns fitted using the Hall Technique (no injections or tooth trimming) gave less discomfort at the time of the appointment, when compared with fillings. Crowns may increase the risk of gingival bleeding but this result was unclear. Only one small study compared crowns with non-restorative caries treatment and one small study compared metal and white crowns, and we could draw no reliable conclusions from these. Some of our outcomes of interest were not measured in any of the studies: these included time to restoration failure or retreatment, patient satisfaction and costs. There is moderate quality evidence that crowns are more effective than fillings for managing decay in primary molar teeth. There is moderate quality evidence that crowns fitted using the Hall Technique are less likely to cause abscesses and pain than fillings. The evidence comparing preformed crowns with non-restorative caries management, and comparing preformed metal crowns with preformed white crowns, is very low quality so we do not know which is better. Crowns placed on primary molar teeth with decay, or that have had pulp treatment, are likely to reduce the risk of major failure or pain in the long term compared to fillings. Crowns fitted using the Hall Technique may reduce discomfort at the time of treatment compared to fillings.